METHOD OF PROCESSING A SUBSTRATE AND SYSTEM FOR PROCESSING A SUBSTRATE

Abstract

A substrate having a first side and a second side opposite to the first side is processed by attaching a protective film to the first side and, after attachment, processing the substrate from the second side of the substrate. After processing from the second side, the second side is inspected for defects on the second side of the substrate. After inspection for defects, a support film is attached to the second side of the substrate. The protective film is removed from the first side of the substrate and, after removing the protective film, the first side of the substrate is inspected for defects on the first side of the substrate.

Claims

1. A method of processing a substrate, the substrate having a first side and a second side being opposite to the first side, wherein the method comprises: attaching a protective film to the first side of the substrate; after attaching the protective film to the first side of the substrate, processing the substrate from the second side of the substrate; after processing the substrate from the second side of the substrate inspecting the second side for defects from the second side of the substrate; after inspecting the second side of the substrate for defects, attaching a support film to the second side of the substrate; removing the protective film from the first side of the substrate; and after removing the protective film from the first side of the substrate, inspecting the first side of the substrate for defects from the first side of the substrate.

2. The method according to claim 1, further comprising inspecting the first side of the substrate for defects through the protective film before removing the protective film from the first side of the substrate.

3. The method according to claim 2, wherein inspecting the first side of the substrate for defects through the protective film is performed before or after attaching the support film to the second side of the substrate.

4. The method according to claim 3, wherein the substrate has on the first side a device area with a plurality of devices.

5. The method according to claim 4, further comprising: if a defect or defects is or are identified by inspecting the second side, of the substrate for defects from the second side of the substrate, determining a position or positions of the identified defect or defects, thereby obtaining first positional information, and/or if a defect or defects is or are identified by inspecting the first side of the substrate for defects from the first side of the substrate, determining a position or positions of the identified defect or defects, thereby obtaining second positional information.

6. The method according to claim 5, further comprising correlating the first positional information with the second positional information.

7. The method according to claim 6, wherein inspecting the second side of the substrate for defects from the second side of the substrate is performed using an inspection means, and the inspection means is also used for inspecting the first side of the substrate for defects from the first side of the substrate.

8. The method according to claim 7, wherein the support film is attached to the second side of the substrate so that at least a central area of a front surface of the support film is in direct contact with the second side of the substrate such that no adhesive is present between at least the central area of the front surface of the support film and the second side of the substrate.

9. The method according to claim 8, wherein the substrate is a wafer, in particular, a semiconductor wafer.

10. The method according to claim 9, wherein the protective film is attached to the first of the substrate so that at least a central area of a front surface of the protective film is in direct contact with the first side of the substrate, such that no adhesive is present between at least the central area of the front surface of the protective film and the first side of the substrate.

11. The method according to claim 10, wherein processing the substrate from the second side of the substrate consists of or comprises dividing the substrate into a plurality of separate elements from the second side of the substrate.

12. The method according to claim 11, wherein dividing the substrate into the plurality of separate elements consists of or comprises cutting the substrate along a thickness direction of the substrate, the thickness direction extending from the second side of the substrate towards the first side of the substrate.

13. The method according to claim 12, wherein cutting the substrate along the thickness direction of the substrate consists of or comprises mechanically cutting the substrate and/or laser cutting the substrate and/or plasma cutting the substrate.

14. The method according to claim 11, further comprising, after inspecting the first side of the substrate for defects from the first side of the substrate, picking up the separate elements from the support film.

15. The method according to claim 14, wherein processing the substrate from the second side of the substrate consists of or comprises thinning the substrate so as to reduce the thickness of the substrate.

16. A system for processing a substrate, the substrate having a first side and a second side being opposite to the first side wherein the system comprises: an attaching means configured to attach a protective film to the first side of the substrate; a processing means configured to process the substrate from the second side of the substrate, after attaching the protective film to the first side of the substrate; an inspection means configured to inspect the second side of the substrate for defects from the second side of the substrate, after processing the substrate from the second side of the substrate; an attaching means configured to attach a support film to the second side of the substrate, after inspecting the second side of the substrate for defects; a protective film removing means configured to remove the protective film from the first side of the substrate; and an inspection means configured to inspect the first side of the substrate for defects from the first side of the substrate, after removing the protective film from the first side of the substrate.

17. The system according to claim 16, wherein the inspection means configured to inspect the second side of the substrate and the inspection means configured to inspect the first side of the substrate are the same single inspection means.

18. The system according to claim 16, wherein the attaching means configured to attach the protective film to the first side of the substrate and the attaching means configured to attach the support film to the second side the substrate are the same single attaching means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0196] Hereinafter, non-limiting examples of the invention are explained with reference to the drawings, in which:

[0197] FIG. 1 is a perspective view showing a wafer as a substrate to be processed by methods of the present invention;

[0198] FIG. 2 is a cross-sectional view illustrating a step of attaching a protective film to a first side of the wafer in a method according to a first embodiment of the present invention;

[0199] FIG. 3 is a cross-sectional view illustrating a step of processing the wafer from a second side of the wafer in the method according to the first embodiment;

[0200] FIG. 4 is a cross-sectional view illustrating a step of inspecting the second side of the wafer for defects from the second side of the wafer in the method according to the first embodiment;

[0201] FIG. 5 is a cross-sectional view illustrating a step of cutting the protective film in the method according to the first embodiment;

[0202] FIG. 6 is a cross-sectional view illustrating a step of attaching a support film to the second side of the wafer in the method according to the first embodiment;

[0203] FIG. 7 is a cross-sectional view illustrating a step of inspecting the first side of the wafer for defects through the protective film in the method according to the first embodiment;

[0204] FIG. 8 is a cross-sectional view illustrating a step of inspecting the first side of the wafer for defects through the protective film and through a transparent chuck table in a method according to a modification of the first embodiment;

[0205] FIG. 9 is a cross-sectional view illustrating a step of removing the protective film from the first side of the wafer in the method according to the first embodiment;

[0206] FIG. 10 is a cross-sectional view illustrating a step of inspecting the first side of the wafer for defects from the first side of the wafer in the method according to the first embodiment;

[0207] FIG. 11 is a cross-sectional view illustrating a step of performing a stealth laser cutting process on the wafer from the first side of the wafer in a method according to a second embodiment of the present invention;

[0208] FIG. 12 is a cross-sectional view illustrating a step of performing a stealth laser cutting process on the wafer through the protective film from the first side of the wafer in a method according to a third embodiment of the present invention;

[0209] FIG. 13 is a cross-sectional view illustrating a step of performing a blade cutting process on the wafer from the second side of the wafer in a method according to a fourth embodiment of the present invention;

[0210] FIG. 14 is a cross-sectional view illustrating a step of inspecting the second side of the wafer for defects from the second side of the wafer in the method according to the fourth embodiment;

[0211] FIG. 15 is a cross-sectional view illustrating a step of attaching the support film to the second side of the wafer in the method according to the fourth embodiment;

[0212] FIG. 16 is a cross-sectional view illustrating a step of performing a stealth laser cutting process on the wafer through the protective film from the first side of the wafer in the method according to the fourth embodiment; and

[0213] FIG. 17 is a cross-sectional view illustrating a step of applying an external force to the wafer by radially expanding the support film in the method according to the fourth embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0214] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. The preferred embodiments relate to methods of processing a substrate and to substrate processing systems for performing these methods.

[0215] In the first to fourth embodiments, the processing method of the invention is performed on a wafer 2 as the substrate (see FIG. 1). The wafer 2 can be, for example, a MEMS wafer having MEMS devices formed on the surface of a first side 4, i.e., a front side, thereof. However, the wafer 2 is not limited to a MEMS wafer, but may also be a CMOS wafer having CMOS devices, preferably as solid-state imaging devices, formed on the first side 4 thereof or a wafer with other types of devices on the first side 4.

[0216] The wafer 2 may be made of a semiconductor, e.g., silicon (Si). Such a silicon wafer 2 can include devices, such as ICs (integrated circuits) and LSIs (large scale integrations), on a silicon substrate. Alternatively, the wafer 2 may be an optical device wafer configured by forming optical devices, such as LEDs (light emitting diodes), on an inorganic material substrate of, for example, ceramic, glass or sapphire. The wafer 2 is not limited to this and can be formed in any other way. Furthermore, also a combination of the above described exemplary wafer designs is possible.

[0217] The wafer 2 can have a thickness in the μm range, preferably in the range of 30 to 1000 μm.

[0218] The wafer 2 preferably exhibits a circular shape. However, the shape of the wafer 2 is not particularly limited. In other embodiments, the wafer 2 may have, for example, an oval shape, an elliptical shape or a polygonal shape, such as a rectangular shape or a square shape.

[0219] The wafer 2 is provided with a plurality of crossing division lines 6 (see FIG. 1), also termed streets, formed on the first side 4 thereof, thereby partitioning the wafer 2 into a plurality of rectangular regions where devices 8, such as those described previously, are respectively formed. These devices 8 are formed in a device area 10 of the wafer 2. In the case of a circular wafer 2, this device area 10 is preferably substantially circular and arranged concentrically with the outer circumference of the wafer 2.

[0220] The device area 10 is surrounded by an annular peripheral marginal area 12, as is schematically shown in FIG. 1. In this peripheral marginal area 12, no devices are formed. The peripheral marginal area 12 is preferably arranged concentrically to the device area 10 and/or the outer circumference of the wafer 2. The radial extension of the peripheral marginal area 12 can be in the mm range and preferably ranges from 1 to 3 mm.

[0221] The wafer 2 further has a second side 14, i.e., a back side, opposite to the first side 4 (see FIG. 1).

[0222] In the following, a first embodiment of the present invention will be described with reference to FIGS. 1 to 10.

[0223] As is shown in FIG. 2, a protective film 16 is attached to the first side 4 of the wafer 2. The protective film 16 covers the devices 8 formed in the device area 10 and thus protects the devices 8, e.g., from contamination and damage. Optionally, before attaching the protective film 16 to the first side 4 of the wafer 2, the wafer 2 may be cut from the first side 4 along part of its thickness, in particular, along the division lines 6. The thickness of the wafer 2 is the distance between the first side 4 and the second side 14. In this way, if a layer or layers is or are formed on the first side 4, such as a low-k layer or a metal layer, the layer or layers can be removed in the regions where the wafer 2 is to be divided, in particular, along the division lines 6. For example, the wafer 2 may be cut along part of its thickness by mechanical cutting, e.g., using a blade or a saw, and/or by laser cutting or laser grooving.

[0224] The protective film 16 may be made of a plastic material, such as a polymer. For example, the protective film 16 may be made of a polyolefin, such as polyethylene (PE), polypropylene (PP) or polybutylene (PB). The protective film 16 may have a thickness in the range of 5 to 500 μm, preferably 5 to 200 μm, more preferably 8 to 100 μm, even more preferably 10 to 80 μm and yet even more preferably 12 to 50 μm. In the present embodiment, the protective film 16 has a substantially circular shape in a top view thereon and a diameter which is larger than the diameter of the wafer 2.

[0225] The protective film 16 may be attached to the first side 4 of the wafer 2 with an adhesive. The adhesive may be present on an entire front surface 18 of the protective film 16 which comes into contact with the first side 4 of the wafer 2. For example, the protective film 16 may be a UV curable adhesive tape. Alternatively, the protective film 16 may be attached to the first side 4 of the wafer 2 so that at least a central area of the front surface 18 of the protective film 16 is in direct contact with the first side 4 of the wafer 2, such that no adhesive is present between at least the central area of the front surface 18 of the protective film 16 and the first side 4 of the wafer 2. The protective film 16 may be attached to the first side 4 of the wafer 2 so that, in the entire region where the front surface 18 of the protective film 16 is in contact with the first side 4 of the wafer 2, the front surface 18 of the protective film 16 is in direct contact with the first side 4 of the wafer 2. The entire front surface 18 of the protective film 16 may be free of adhesive.

[0226] An adhesive, e.g., an adhesive layer, may be provided only in a peripheral area of the front surface 18 of the protective film 16, as has been detailed above. The peripheral area of the front surface 18 of the protective film 16 may be arranged so as to surround the central area of the front surface 18 of the protective film 16.

[0227] A peripheral portion of the protective film 16 is attached to an annular frame 20 so that the protective film 16 closes a central opening of the annular frame 20, i.e., the area inside the inner diameter of the annular frame 20. The annular frame 20 facilitates handling of the protective film 16, in particular, in the process of attaching the protective film 16 to the first side 4 of the wafer 2.

[0228] The protective film 16 is attached to the first side 4 of the wafer 2 by a first attaching means comprising a chuck table 22 and an annular frame holder 24. The wafer 2 is supported by the chuck table 22, and the annular frame 20, having the protective film 16 attached thereto, is held by the annular frame holder 24, so that the protective film 16 can be reliably and accurately attached to the first side 4 of the wafer 2. For example, the first attaching means may be a tape laminator or a tape mounter. A vacuum chamber, a pressing roller, a pressing membrane, a pressing piece or block or a combination of these elements may be used for applying pressure to the protective film 16 so as to press the protective film 16 against the first side 4 of the wafer 2. The first attaching means forms part of a substrate processing system according to the present embodiment.

[0229] Attaching the protective film 16 to the first side 4 of the wafer 2 may comprise applying an external stimulus to the protective film 16, as has been detailed above. For this purpose, the first attaching means may further comprise an external stimulus applying means, such as a heating means, a cooling means, a vacuum applying means and/or an irradiation means.

[0230] After attaching the protective film 16 to the first side 4 of the wafer 2, the wafer 2 is processed from the second side 14 of the wafer 2, as is shown in FIG. 3. In the present embodiment, processing the wafer 2 from the second side 14 consists of cutting the wafer 2 along the division lines 6 over the entire thickness of the wafer 2. Hence, the wafer 2 is fully divided in the cutting process, thus obtaining a plurality of separate elements in the form of chips or dies 26. Each chip or die 26 comprises one of the devices 8 formed in the device area 10.

[0231] The wafer 2 is divided along the division lines 6 by a cutting means 28 (see FIG. 3). In the present embodiment, the cutting means 28 is a cutting blade configured to mechanically cut the wafer 2. The cutting means 28 forms part of the substrate processing system according to the present embodiment.

[0232] Alternatively, the wafer 2 may be cut along the division lines 6 by laser cutting and/or plasma cutting, as has been detailed above. Also, a sequence of mechanical cutting and/or laser cutting and/or plasma cutting steps may be applied.

[0233] After dividing the wafer 2 into the plurality of chips or dies 26, the second side 14 of the divided wafer 2 is inspected for defects from the second side 14 of the divided wafer 2, as is shown in FIG. 4. Possible defects to be identified when inspecting the second side 14 of the divided wafer 2 include, for example, back side chipping, delamination of layers formed on or in the wafer material, cracks, non-straight cut lines (meandering), burrs, whiskers, particles, contaminations, die shifts, i.e., undesired movement of the chips or dies 26, and die size differences, e.g., caused by an undesired slant cut or a cutting width change because of cutting blade wear. This inspection step allows for defects in the divided wafer 2 originating from the cutting process to be identified.

[0234] The second side 14 of the divided wafer 2 is inspected for defects from the second side 14 by a first inspection means 30 (see FIG. 4), in particular, a camera, such as a microscope camera for optical inspection. The first inspection means 30 forms part of the substrate processing system according to the present embodiment.

[0235] If a defect or defects is or are identified by inspecting the second side 14 of the wafer 2, a position or positions of the identified defect or defects is or are determined, thereby obtaining first positional information. The substrate processing system according to the present embodiment may comprise a position determining means configured to perform this step. The first positional information is information specifying the position of each defect on the second side 14 of the divided wafer 2. The position of each defect may be defined in a coordinate system of the wafer 2, e.g., in relation to the division lines 6 and/or the devices 8.

[0236] The first positional information can be correlated with information on the position of each chip or die 26 in the divided wafer 2, allowing for defective chips or dies 26 to be identified and traced in a particularly accurate and efficient manner without having to individually inspect each chip or die 26, as has been detailed above. The substrate processing system according to the present embodiment may comprise a control configured to perform this step. The position of each chip or die 26 in the wafer 2 may be defined in a coordinate system of the wafer 2, e.g., in relation to the division lines 6 and/or the devices 8.

[0237] The method of the present embodiment further comprises the optional step of cutting the protective film 16 after inspecting the second side 14 of the divided wafer 2 for defects from the second side 14 of the divided wafer 2, as is shown in FIG. 5. The protective film 16 is cut in a circular manner along the outer circumference of the divided wafer 2, as is indicated by a curved arrow in FIG. 5. A film cutting means 32, such as a cutting blade, is used for this cutting step. The film cutting means 32 forms part of the substrate processing system according to the present embodiment. During the cutting process, the wafer 2 is supported by the chuck table 22 of the first attaching means, and the annular frame 20 is held by the annular frame holder 24 of the first attaching means. The cut protective film 16 is shown, for example, in FIGS. 6 and 7.

[0238] By cutting the protective film 16 in this way, the diameter of the protective film 16 is reduced, so that the protective film 16 has substantially the same diameter as the wafer 2, thereby facilitating the further handling of the combination of protective film 16 and wafer 2.

[0239] After cutting the protective film 16, a support film 34 is attached to the second side 14 of the divided wafer 2, as is shown in FIG. 6. The support film 34 supports the divided wafer 2 and reliably holds the chips or dies 26 in their positions also after the protective film 16 has been removed from the divided wafer 2 (see FIG. 9).

[0240] The support film 34 may be made of a plastic material, such as a polymer. For example, the support film 34 may be made of a polyolefin, such as polyethylene (PE), polypropylene (PP) or polybutylene (PB). The support film 34 may have a thickness in the range of 5 to 500 μm, preferably 5 to 200 μm, more preferably 8 to 100 μm, even more preferably 10 to 80 μm and yet even more preferably 12 to 50 μm. In the present embodiment, the support film 34 has a substantially circular shape in a top view thereon and a diameter which is larger than the diameter of the wafer 2.

[0241] The support film 34 may be attached to the second side 14 of the divided wafer 2 with an adhesive. The adhesive may be present on an entire front surface 36 of the support film 34 which comes into contact with the second side 14 of the divided wafer 2. For example, the support film 34 may be a UV curable adhesive tape. Alternatively, the support film 34 may be attached to the second side 14 of the divided wafer 2 so that at least a central area of the front surface 36 of the support film 34 is in direct contact with the second side 14 of the divided wafer 2, such that no adhesive is present between at least the central area of the front surface 36 of the support film 34 and the second side 14 of the divided wafer 2. The support film 34 may be attached to the second side 14 of the divided wafer 2 so that, in the entire region where the front surface 36 of the support film 34 is in contact with the second side 14 of the divided wafer 2, the front surface 36 of the support film 34 is in direct contact with the second side 14 of the divided wafer 2. The entire front surface 36 of the support film 34 may be free of adhesive.

[0242] An adhesive, e.g., an adhesive layer, may be provided only in a peripheral area of the front surface 36 of the support film 34, as has been detailed above. The peripheral area of the front surface 36 of the support film 34 may be arranged so as to surround the central area of the front surface 36 of the support film 34.

[0243] A peripheral portion of the support film 34 is attached to an annular frame 38 so that the support film 34 closes a central opening of the annular frame 38, i.e., the area inside the inner diameter of the annular frame 38. The annular frame 38 facilitates handling of the support film 34, in particular, in the process of attaching the support film 34 to the second side 14 of the divided wafer 2.

[0244] The support film 34 is attached to the second side 14 of the divided wafer 2 by a second attaching means comprising a chuck table 40 and an annular frame holder 42. The divided wafer 2 is supported by the chuck table 40, and the annular frame 38, having the support film 34 attached thereto, is held by the annular frame holder 42, so that the support film 34 can be reliably and accurately attached to the second side 14 of the divided wafer 2. For example, the second attaching means may be a tape laminator or a tape mounter. A vacuum chamber, a pressing roller, a pressing membrane, a pressing piece or block or a combination of these elements may be used for applying pressure to the support film 34 so as to press the support film 34 against the second side 14 of the divided wafer 2. The second attaching means forms part of the substrate processing system according to the present embodiment.

[0245] In other embodiments of the present invention, the same single attaching means may be used as the first attaching means and the second attaching means.

[0246] Attaching the support film 34 to the second side 14 of the divided wafer 2 may comprise applying an external stimulus to the support film 34, as has been detailed above. For this purpose, the second attaching means may further comprise an external stimulus applying means, such as a heating means, a cooling means, a vacuum applying means and/or an irradiation means.

[0247] In the present embodiment, after attaching the support film 34 to the second side 14 of the divided wafer 2, an optional step of inspecting the first side 4 of the divided wafer 2 for defects through the protective film 16 is performed, as is shown in FIG. 7. Possible defects to be identified when inspecting the first side 4 of the divided wafer 2 through the protective film 16 include, for example, front side chipping, delamination of layers formed on or in the wafer material, cracks, non-straight cut lines (meandering), burrs, whiskers, particles, contaminations, die shifts, i.e., undesired movement of the chips or dies 26, and die size differences, e.g., caused by an undesired slant cut or a cutting width change because of cutting blade wear. This inspection step allows for further defects in the divided wafer 2 originating from the cutting process to be identified.

[0248] The first side 4 of the divided wafer 2 is inspected for defects through the protective film 16 by a second inspection means 44 (see FIG. 7), in particular, a camera, such as a microscope camera for optical inspection. The protective film 16 is transparent for visible light. The second inspection means 44 forms part of the substrate processing system according to the present embodiment. In other embodiments of the present invention, the same single inspection means may be used as the first inspection means 30 and the second inspection means 44.

[0249] If a defect or defects is or are identified by inspecting the first side 4 of the divided wafer 2 through the protective film 16, a position or positions of the identified defect or defects is or are determined, thereby obtaining third positional information. The substrate processing system according to the present embodiment may comprise a position determining means configured to perform this step. For this purpose, the position determining means configured to obtain the first positional information or a different position determining means may be used. The third positional information is information specifying the position of each defect on the first side 4 of the divided wafer 2. The position of each defect may be defined in a coordinate system of the wafer 2, e.g., in relation to the division lines 6 and/or the devices 8.

[0250] The third positional information can be correlated with information on the position of each chip or die 26 in the divided wafer 2, allowing for defective chips or dies 26 to be identified and traced in an even more accurate and efficient manner without having to individually inspect each chip or die 26, as has been detailed above. The control of the substrate processing system according to the present embodiment may be configured to perform this step.

[0251] The third positional information can be correlated with the first positional information, as has been detailed above. The control of the substrate processing system according to the present embodiment may be configured to perform this step. In this way, the nature of any defect or defects identified can be determined with a particularly high degree of precision. Also, the efficiency and reliability of identifying and tracing defective chips or dies 26 can be further enhanced.

[0252] FIG. 8 illustrates a step of inspecting the first side 4 of the divided wafer 2 for defects through the protective film 16 in a method according to a modification of the first embodiment. The method of this modification differs from the method of the first embodiment in that the step of inspecting the first side 4 of the divided wafer 2 for defects through the protective film 16 is performed before the step of attaching the support film 34 to the second side 14 of the wafer 2, in that the step of cutting the protective film 16 (see FIG. 5) has been omitted and in that the first side 4 of the divided wafer 2 is inspected for defects from below the wafer 2 (rather than from above the wafer 2, as is shown in FIG. 7 for the method of the first embodiment) through a chuck table 46 which is transparent for visible light.

[0253] In the modified method illustrated in FIG. 8, the first side 4 of the divided wafer 2 is inspected for defects through the protective film 16 while the wafer 2 is supported by the annular frame 20 via the protective film 16. Further, the divided wafer 2 rests on the chuck table 46. The first side 4 of the divided wafer 2 is inspected for defects by the second inspection means 44 through the protective film 16 and through the transparent chuck table 46. The second inspection means 44 is arranged underneath the transparent chuck table 46, as is illustrated in FIG. 8, so that it can inspect the first side 4 of the divided wafer 2 for defects from below the wafer 2. Third positional information can be obtained in the same manner as detailed above.

[0254] Inspecting the first side 4 of the divided wafer 2 for defects by the second inspection means 44 through the protective film 16 and through the transparent chuck table 46 offers the advantage of allowing for the first side 4 to be inspected for defects immediately after dividing the wafer 2 without having to move the wafer 2, in particular, without having to remove the wafer 2 from the chuck table 46. Hence, the inspection process can be performed in a particularly accurate and reliable manner.

[0255] If the second side 14 of the divided wafer 2 is inspected for defects from the second side 14 by the first inspection means 30 from above the wafer 2 (see FIG. 4) and the first side 4 of the divided wafer 2 is inspected for defects by the second inspection means 44 through the protective film 16 and through the transparent chuck table 46 from below the wafer 2 (see FIG. 8), these two inspection processes can be performed without having to move the wafer 2, in particular, without having to remove the wafer 2 from the chuck table 46. Hence, the processes of obtaining and correlating positional information can be performed in an especially accurate and reliable manner.

[0256] Alternatively, the same single inspection means may be used as the first inspection means 30 and the second inspection means 44, as has been detailed above.

[0257] In the modified method, after inspecting the first side 4 of the divided wafer 2 for defects through the protective film 16 and through the transparent chuck table 46, the support film 34 is attached to the second side 14 of the divided wafer 2 substantially in the same manner as detailed above for the method of the first embodiment. Also the subsequent steps, in particular, those of removing the protective film 16 from the first side 4 of the divided wafer 2 and then inspecting the first side 4 of the divided wafer 2 for defects from the first side 4 of the divided wafer 2, are substantially the same as those described below for the method of the first embodiment.

[0258] After inspecting the first side 4 of the divided wafer 2 for defects through the protective film 16 in the methods of the first embodiment and the modification of the first embodiment, the protective film 16 is removed, i.e., peeled off, from the first side 4 of the divided wafer 2, as is shown in FIG. 9.

[0259] The protective film 16 is removed from the first side 4 of the divided wafer 2 by a protective film removing means 48. The protective film removing means 48 is configured to hold the protective film 16 at a peripheral portion of the protective film 16 and to pull this portion in a direction along the first side 4 of the divided wafer 2, as is indicated by an arrow in FIG. 9, so as to remove the protective film 16 from the first side 4 of the divided wafer 2. The protective film removing means 48 forms part of the substrate processing system according to the present embodiment.

[0260] By removing the protective film 16 from the first side 4 of the divided wafer 2, particulates, such as chippings or debris, which have been separated from the wafer 2 during the cutting process, but remained on the wafer 2 due to the presence of the protective film 16, can also be removed. In particular, these particulates may adhere to the protective film 16, e.g., due to the presence of an adhesive on the protective film 16 or due to a material bond between particulates and protective film 16, so that they are removed from the divided wafer 2 together with the protective film 16. Thus, the amount of particulates present on the chips or dies 26 when they are picked up from the support film 34 is greatly reduced. The chips or dies 26 even may be substantially free of such particulates. Therefore, chips or dies 26 with a high quality are obtained and further processing, handling and/or transport of the chips or dies 26 can be rendered considerably more efficient. For example, the chips or dies 26 may be put to use, e.g., assembled into semiconductor package devices or incorporated in electronic equipment, directly after they have been picked up from the support film 34. Moreover, the accuracy and reliability of the inspection of the first side 4 of the divided wafer 2 can be further improved, as will be detailed in the following.

[0261] During and after the step of removing the protective film 16 from the first side 4 of the divided wafer 2, the chips or dies 26 are reliably held in their positions by the support film 34.

[0262] After removing the protective film 16 from the first side 4 of the divided wafer 2, the first side 4 of the divided wafer 2 is inspected for defects from the first side 4 of the divided wafer 2, as is shown in FIG. 10. Possible defects to be identified when inspecting the first side 4 of the divided wafer 2 include, for example, front side chipping, delamination of layers formed on or in the wafer material, cracks, non-straight cut lines (meandering), burrs, whiskers, particles, contaminations, die shifts, i.e., undesired movement of the chips or dies 26, and die size differences, e.g., caused by an undesired slant cut or a cutting width change because of cutting blade wear. This inspection step allows for defects in the divided wafer 2 originating from the cutting process to be identified with an even higher degree of accuracy. In particular, removing the protective film 16 from the first side 4 of the divided wafer 2 causes or enables removal of particulates, such as chippings or debris, which have been separated from the wafer 2 during the cutting process, as has been detailed above. This allows for the detection of defects in the divided wafer 2 which may not have been identifiable prior to removing the protective film 16.

[0263] The first side 4 of the divided wafer 2 is inspected for defects by a third inspection means 50 (see FIG. 10), in particular, a camera, such as a microscope camera for optical inspection. The third inspection means 50 forms part of the substrate processing system according to the present embodiment. In other embodiments of the present invention, the same single inspection means may be used as the first inspection means 30, the second inspection means 44 and the third inspection means 50. The same single inspection means may be used as the first inspection means 30 and the third inspection means 50.

[0264] If a defect or defects is or are identified by inspecting the first side 4 of the divided wafer 2, a position or positions of the identified defect or defects is or are determined, thereby obtaining second positional information. The substrate processing system according to the present embodiment may comprise a position determining means configured to perform this step. For this purpose, the position determining means configured to obtain the first positional information, the position determining means configured to obtain the third positional information or a different position determining means may be used. The second positional information is information specifying the position of each defect on the first side 4 of the divided wafer 2. The position of each defect may be defined in a coordinate system of the wafer 2, e.g., in relation to the division lines 6 and/or the devices 8.

[0265] The second positional information can be correlated with information on the position of each chip or die 26 in the divided wafer 2, allowing for defective chips or dies 26 to be identified and traced in an even more accurate and efficient manner without having to individually inspect each chip or die 26, as has been detailed above. The control of the substrate processing system according to the present embodiment may be configured to perform this step.

[0266] The second positional information can be correlated with the first and/or third positional information, as has been detailed above. The control of the substrate processing system according to the present embodiment may be configured to perform this step. In this way, the nature of any defect or defects identified can be determined with an even higher degree of precision. Also, the efficiency and reliability of identifying and tracing defective chips or dies 26 can be further enhanced.

[0267] After inspecting the first side 4 of the divided wafer 2 for defects from the first side 4, the chips or dies 26 are picked up from the support film 34. Since defective chips or dies 26 are reliably and accurately identified and traced by the inspection steps, as has been detailed above, such chips or dies 26 can be efficiently separated out and rejected. Those chips or dies 26 for which no defects have been detected may be put to use, e.g., assembled into semiconductor package devices or incorporated in electronic equipment, directly after they have been picked up from the support film 34, as has also been detailed above.

[0268] The substrate processing system according to the present embodiment may further comprise a pick-up means configured to pick up the chips or dies 26 from the support film 34 after inspecting the first side 4 of the divided wafer 2 for defects from the first side 4.

[0269] In the following, a second embodiment of the present invention will be described with reference to FIG. 11.

[0270] The method of the second embodiment differs from the method of the first embodiment in that a stealth laser cutting step is performed before attaching the protective film 16 to the first side 4 of the wafer 2 and in that the wafer 2 may not be cut along its entire thickness in the cutting step (see FIG. 3). The remaining steps of the method of the first embodiment are performed in the same manner in the method of the second embodiment. Hence, a repeated detailed description thereof is omitted.

[0271] In particular, in the method of the second embodiment, a stealth laser cutting step is performed from the first side 4 of the wafer 2 along the division lines 6 before attaching the protective film 16 to the first side 4, as is shown in FIG. 11. In this step, a laser beam LB having a wavelength that allows transmission of the laser beam LB through the wafer 2 is applied to the wafer 2. The laser beam LB is applied to the wafer 2 in a plurality of positions along the division lines 6 so as to form a plurality of modified regions in the wafer 2 along the division lines 6. By forming these modified regions, the strength of the wafer 2 in the areas thereof where the modified regions are formed is reduced. Hence, the division of the wafer 2 along the division lines 6 in the subsequent cutting step or in a later separation step is greatly facilitated.

[0272] The laser beam LB may be a pulsed laser beam. The pulsed laser beam may have a pulse width, for example, in the range of 1 fs to 1000 ns.

[0273] The laser beam LB is applied to the wafer 2 by a stealth laser cutting means 52 (see FIG. 11). The stealth laser cutting means 52 forms part of the substrate processing system according to the present embodiment.

[0274] In the step of cutting the wafer 2 from the second side 14 thereof, the wafer 2 may only be cut along part, e.g., half, of its thickness. For this cutting step, a cutting means 28 (see FIG. 3) in the form of a cutting blade configured to mechanically cut the wafer 2 is used. A mechanical cutting load exerted on the wafer 2 by the cutting means 28 can help cracks in the wafer 2 generated in the stealth laser cutting step to propagate to the first side 4 of the wafer 2, thus fully dividing the wafer 2 into the separate chips or dies 26.

[0275] Alternatively, in the cutting step, the wafer 2 may be cut along its entire thickness, e.g., by mechanical cutting and/or laser cutting and/or plasma cutting. In this case, the presence of the modified regions along the division lines 6 facilitates the cutting process due to the local reduction of the strength of the wafer 2.

[0276] In the step of inspecting the first side 4 of the wafer 2 for defects through the protective film 16 (see FIGS. 7 and 8) and/or in the step of inspecting the first side 4 of the wafer 2 for defects from the first side 4 of the wafer 2 after removal of the protective film 16 (see FIG. 10), it can be identified whether cracks in the wafer 2 generated in the stealth laser cutting step have propagated to the first side 4 of the wafer 2.

[0277] If it is identified in one or both of these inspection steps that such cracks have not propagated to the first side 4 of the wafer 2 or that the wafer 2 has not been fully divided into the separate chips or dies 26 by crack propagation, a separation step may be performed subsequent to inspecting the first side 4 of the wafer 2 for defects from the first side 4 of the wafer 2 after removal of the protective film 16. In this separation step, an external force may be applied to the wafer 2, in particular, by expanding, e.g., radially expanding, the support film 34, i.e., by using the support film 34 as an expansion tape. In this way, the wafer 2 can be fully divided into the separate chips or dies 26 along the division lines 6. Such a step of expanding, in particular, radially expanding, the support film 34 will be explained in further detail below with reference to FIG. 17 for the method of the fourth embodiment of the present invention.

[0278] If it is identified in the step of inspecting the first side 4 of the wafer 2 for defects through the protective film 16 that cracks have not propagated to the first side 4 of the wafer 2 or that the wafer 2 has not been fully divided into the separate chips or dies 26 by crack propagation, the separation step may be performed prior to inspecting the first side 4 of the wafer 2 for defects from the first side 4 of the wafer 2 after removal of the protective film 16. In this case, any defects in the wafer 2 which may have been caused by the separation step can be reliably identified in this latter inspection step.

[0279] Optionally, before expanding the support film 34, a breaking step can be performed on the wafer 2 in order to break the wafer 2 along the division lines 6.

[0280] Also if the wafer 2 is fully divided into the chips or dies 26 in the cutting process (see FIG. 3), a step of expanding, e.g., radially expanding, the support film 34 may be carried out before or after inspecting the first side 4 of the wafer 2 for defects from the first side 4. In this way, the separated chips or dies 26 can be moved away from each other, thus increasing the distance between adjacent chips or dies 26. Increasing the die-to-die distance in this manner particularly reliably ensures that the chips or dies 26 are not damaged in the step of picking them up from the support film 34.

[0281] In the following, a third embodiment of the present invention will be described with reference to FIG. 12.

[0282] The method of the third embodiment differs from the method of the second embodiment only in the order of the steps of attaching the protective film 16 to the first side 4 of the wafer 2 and performing the stealth laser cutting step on the wafer 2. The remaining steps of the method of the second embodiment are performed in the same manner in the method of the third embodiment. Hence, a repeated detailed description thereof is omitted.

[0283] In particular, in the method of the third embodiment, the protective film 16 is attached to the first side 4 of the wafer 2 first (see FIG. 2). After this attachment step, but before cutting the wafer 2 from its second side 14 (see FIG. 3), a stealth laser cutting step is performed from the first side 4 of the wafer 2 along the division lines 6 substantially in the same manner as in the method of the second embodiment. The only difference is that the laser beam LB is applied to the wafer 2 through the protective film 16, as is shown in FIG. 12. Thus, the wavelength of the laser beam LB is chosen so that the laser beam LB is transmitted through the protective film 16, i.e., so that the protective film 16 is transparent for the laser beam LB.

[0284] In the following, a fourth embodiment of the present invention will be described with reference to FIGS. 13 to 17.

[0285] The method of the fourth embodiment differs from the method of the first embodiment in that, in the cutting step (see FIG. 3), the wafer 2 is only cut from the second side 14 along part of its thickness and in that a stealth laser cutting step is performed on the wafer 2 after attaching the support film 34 to the second side 14 of the wafer 2. The remaining steps of the method of the first embodiment are performed in the same manner in the method of the fourth embodiment. Hence, a repeated detailed description thereof is omitted.

[0286] In particular, in the method of the fourth embodiment, the protective film 16 is attached to the first side 4 of the wafer 2 as described above for the method of the first embodiment (see FIG. 2). Subsequently, the wafer 2 is cut along the division lines 6 from the second side 14 of the wafer 2 by the cutting means 28. In this step, the wafer 2 is cut only along part of its thickness so that the wafer 2 is not fully divided in the cutting process. Rather, cutting groves 54 are provided which extend from the second side 14 towards the first side 4 of the wafer 2 but do not reach the first side 4.

[0287] Alternatively, the wafer 2 may be cut along the division lines 6 along part of its thickness by laser cutting and/or plasma cutting, as has been detailed above. Also, a sequence of mechanical cutting and/or laser cutting and/or plasma cutting steps may be applied.

[0288] After cutting the wafer 2 along the division lines 6 along part of its thickness, the second side 14 of the partially cut wafer 2 is inspected for defects from the second side 14 of the wafer 2 by the first inspection means 30, as is shown in FIG. 14. This inspection step and the subsequent steps of obtaining first positional information and correlating this information with information on the position of each chip or die 26 to be obtained from the wafer 2 in the wafer 2 are performed in the same manner as described above for the method of the first embodiment.

[0289] After inspecting the second side 14 of the partially cut wafer 2 for defects from the second side 14 of the wafer 2, the optional step of cutting the protective film 16 in a circular manner along the outer circumference of the wafer 2 is carried out in the same manner as for the first embodiment (see FIG. 5). Subsequently, the support film 34 is attached to the second side 14 of the partially cut wafer 2 by the second attaching means comprising the chuck table 40 and the annular frame holder 42, as is shown in FIG. 15. Also this latter step is performed in the same manner as described above for the method of the first embodiment (see also FIG. 6).

[0290] After attaching the support film 34 to the second side 14 of the partially cut wafer 2, a stealth laser cutting step is performed from the first side 4 of the wafer 2 along the division lines 6 through the protective film 16, as is shown in FIG. 16. In this step, which is performed substantially in the same manner as described above for the method of the third embodiment (see also FIG. 12), the laser beam LB, having a wavelength that allows transmission of the laser beam LB through the protective film 16 and through the wafer 2, is applied to the wafer 2 by the stealth laser cutting means 52. The laser beam LB is applied to the wafer 2 in a plurality of positions along the division lines 6 where the cutting groves 54 are formed (see FIG. 13), so as to form a plurality of modified regions in the wafer 2 along the division lines 6. The modified regions are formed in the remaining portions of the wafer 2 along the division lines 6 which have not been cut in the cutting step, i.e., the modified regions are formed above the cutting grooves 54 in the direction from the second side 14 towards the first side 4 of the wafer 2.

[0291] By forming these modified regions, the strength of the remaining portions of the wafer 2 is reduced. Cracks in the wafer 2 generated in the stealth laser cutting step may propagate to the first side 4 of the wafer 2 and to bottoms of the cutting grooves 54, thus fully dividing the wafer 2 into the separate chips or dies 26 (see FIG. 17). Alternatively, the wafer 2 may not be fully divided in the stealth laser cutting process.

[0292] After performing the stealth laser cutting step from the first side 4 of the wafer 2 along the division lines 6 through the protective film 16, the protective film 16 is removed, i.e., peeled off, from the first side 4 of the wafer 2 in the same manner as described above for the method of the first embodiment (see FIG. 9).

[0293] After removing the protective film 16 from the first side 4 of the wafer 2, the first side 4 of the wafer 2 is inspected for defects from the first side 4 of the wafer 2 in the same manner as described above for the method of the first embodiment (see FIG. 10). Also the subsequent steps of obtaining second positional information and correlating this information with the first positional information and with information on the position of each chip or die 26 to be obtained from the wafer 2 in the wafer 2 are performed in the same manner as described above for the method of the first embodiment.

[0294] After removing the protective film 16 from the first side 4 of the wafer 2, a separation step is carried out, as is shown in FIG. 17. The separation step may be performed before or after inspecting the first side 4 of the wafer 2 for defects from the first side 4 of the wafer 2. In this separation step, the support film 34 is radially expanded, i.e., used as an expansion tape. If the wafer 2 has not been fully divided in the stealth laser cutting step, the radial expansion of the support film 34 applies an external force to wafer 2, fully dividing the wafer 2 into the separate chips or dies 26 along the division lines 6 (see FIG. 17). If the wafer 2 has been fully divided in the stealth laser cutting step, the radial expansion of the support film 34 moves the separated chips or dies 26 away from each other, thus increasing the distance between adjacent chips or dies 26. Increasing the die-to-die distance in this manner particularly reliably ensures that the chips or dies 26 are not damaged in the subsequent step of picking them up from the support film 34.

[0295] If the separation step is performed after inspecting the first side 4 of the wafer 2 for defects from the first side 4 of the wafer 2, it can be identified in this inspection step whether cracks in the wafer 2 generated in the stealth laser cutting step have propagated to the first side 4 of the wafer 2, as has been detailed above for the method of the second embodiment.

[0296] If the separation step is performed before inspecting the first side 4 of the wafer 2 for defects from the first side 4 of the wafer 2, any defects in the wafer 2 which may have been caused by the separation step can be reliably identified in this inspection step.

[0297] The support film 34 is radially expanded by an expansion means comprising an expansion drum 56 (see FIG. 17). In the expansion process, an upper edge of the expansion drum 56 is brought into contact with a portion of the support film 34 arranged along the outer circumference of the wafer 2 from below the support film 34. Subsequently, the expansion drum 56 and the annular frame 38, having the support film 34 attached thereto, are moved relative to each other in the vertical direction, i.e., in the direction from the second side 14 towards the first side 4 of the wafer 2. In particular, the expansion drum 56 is moved upwards and/or the annular frame 38 is moved downwards, as is indicated by arrows in FIG. 17. In this way, the support film 34 is radially expanded. The expansion means forms part of the substrate processing system according to the present embodiment.

[0298] In other embodiments of the method and the system of the present invention, the support film 34 may be expanded using a different expansion means, e.g., employing expanding bars. For example, the expanding apparatus described in DE 10 2018 207 498 A1 may be used as an expansion means for expanding the support film 34.

[0299] Optionally, before expanding, e.g., radially expanding, the support film 34, a breaking step can be performed on the wafer 2 in order to break the wafer 2 along the division lines 6.

[0300] After expanding the support film 34, the chips or dies 26 are picked up from the support film 34 as described above for the method of the first embodiment.

[0301] The method of the fourth embodiment may be modified by changing the order of the steps of performing the stealth laser cutting step from the first side 4 of the wafer 2 along the division lines 6 and removing the protective film 16 from the first side 4 of the wafer 2. Specifically, in the modified method, the protective film 16 is removed from the first side 4 of the wafer 2 before carrying out the stealth laser cutting step from the first side 4 of the wafer 2. Hence, the laser beam LB is applied directly to the wafer 2, i.e., without having to pass through the protective film 16, in the same manner as described above for the method of the second embodiment (see FIG. 11). The remaining steps of the modified method are the same as those of the method according to the fourth embodiment.

[0302] The methods and systems according to the first to fourth embodiments described above may be modified by using a protective film 16 and/or a support film 34 having a cushioning layer or a cushioning layer and a base sheet attached thereto, as has been detailed above.

[0303] In the methods and systems according to the first to fourth embodiments described above, processing is performed on the back side of the substrate, i.e., the wafer 2. However, in other embodiments of the present invention, the substrate may be processed from the front side of the substrate.