Device and method for aligning substrates

Abstract

A device for aligning and bringing a large-area substrate into contact with a carrier substrate comprising: a substrate holding means for attaching the substrate; a carrier substrate holding means for attaching the carrier substrate; detection means for detection of a peripheral contour of the substrate attached to the substrate holding means and detection of a peripheral contour of the carrier substrate attached to the carrier substrate holding means relative to a contact plane of the substrate with the carrier substrate; aligning means for aligning the substrate relative to the carrier substrate; and contacting means for bringing the substrate into contact with the carrier substrate.

Claims

1. A device for aligning a large-area substrate with a carrier substrate and bringing the large-area substrate into contact with the carrier substrate for the further processing of the large-area substrate, said device comprising: a substrate holding means configured to attach the large-area substrate thereto; a carrier substrate holding means configured to attach the carrier substrate thereto; detection means positioned in a contact plane of the large-area substrate with the carrier substrate, the detection means being configured to detect, relative to the contact plane, a peripheral contour of the attached large-area substrate and a peripheral contour of the attached carrier substrate; an alignment system configured to align the large-area substrate relative to the carrier substrate; controlling means configured to control the alignment system based on the detected peripheral contours; and contacting means configured to bring the large-area substrate, aligned relative to the carrier substrate, into contact with the carrier substrate, wherein the alignment system and the contacting means are further configured to continuously align the large-area substrate relative to the carrier substrate until the large-area substrate is brought into contact with the carrier substrate.

2. The device according to claim 1, wherein the alignment system further comprises at least one of: a rotational guide configured to rotate the detection means relative to at least one of the large-area substrate and the carrier substrate; and an adjustment system configured to adjust the detection means relative to at least one of the large-area substrate and the carrier substrate in at least one of an X-direction parallel to the contact plane and a Y-direction parallel to the contact plane.

3. The device according to claim 1, wherein the detection means is attached to a carrier unit that is annular in sections and that can be arranged at least in sections in the contact plane.

4. The device according to claim 3, wherein the contacting means comprises an adjustment unit configured to adjust the substrate holding means in a Z-direction, and wherein the carrier unit is attached between the carrier substrate holding means and the substrate holding means with the adjustment unit being attached at least one of there between and with a base plate attached in-between.

5. The device according to claim 4, wherein the alignment system further comprises an adjustment system configured to adjust the detection means relative to at least one of the large-area substrate and the carrier substrate in at least one of an X-direction parallel to the contact plane and a Y-direction parallel to the contact plane, the adjustment system being attached directly between the base plate and the carrier unit.

6. The device according to claim 1, wherein the detection means operates electromagnetically, and wherein the peripheral contour of the large-area substrate and the peripheral contour of the carrier substrate are detected simultaneously.

7. The device according to claim 1, wherein the detection means is positioned opposite the peripheral contours of the large-area substrate and the carrier substrate.

8. A process for aligning a large-area substrate with a carrier substrate and bringing the large-area substrate into contact with the carrier substrate for the further processing of the large-area substrate, the process comprising: attaching the large-area substrate to a substrate holding chuck; attaching the carrier substrate to a carrier substrate holding chuck; detecting, relative to a contact plane of the large-area substrate with the carrier substrate, a peripheral contour of the attached large-area substrate and a peripheral contour of the attached carrier substrate, the detecting being performed by a distance-measuring system positioned in the contact plane; aligning the large-area substrate relative to the carrier substrate via a mechanical alignment system; controlling the aligning based on the detected peripheral contours via a control system; and bringing the large-area substrate, aligned relative to the carrier substrate, into contact with the carrier substrate via a Z-direction adjustment unit, wherein the large-area substrate is continuously aligned relative to the carrier substrate until the large-areas substrate is brought into contact with the carrier substrate.

9. The process according to claim 8, wherein the detecting comprises at least one of: rotating the distance-measuring system relative to at least one of the large-area substrate and the carrier substrate via a rotational guide of the alignment system; and adjusting, via an adjustment system of the alignment system, the distance-measuring system relative to at least one of the large-area substrate and the carrier substrate in at least one of an X-direction parallel to the contact plane and a Y direction parallel to the contact plane.

10. The process according to claim 8 or 9, wherein the distance-measuring system operates electromagnetically, and wherein the peripheral contour of the large-area substrate and the peripheral contour of the carrier substrate are detected simultaneously.

11. The process according to claim 8 or 9, wherein the detection of the peripheral contours is carried out sequentially by the rotating the distance-measuring system relative to at least one of the large-area substrate and the carrier substrate.

12. The process according to claim 9, wherein the peripheral contours of the large-area substrate and carrier substrate are aligned equidistant or concentric with respect to one another with a gap deviation of less than 50 m.

13. The process according to claim 8 or 9, wherein the controlling of the aligning completes when a value drops below a determinable threshold value for the gap deviations.

14. The process according to claim 8, wherein the large-area substrate has a mean diameter d1 and the carrier substrate has a mean diameter d2, wherein the mean diameter d1 is greater than the mean diameter d2.

15. The process according to claim 14, wherein the mean diameter d1 is 500 m greater than the mean diameter d2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a is a schematic cross-sectional view of a device according to the invention in a first embodiment,

(2) FIG. 1b is a schematic overview of the device according to FIG. 1a,

(3) FIG. 2a is a schematic cross-sectional view of a device according to the invention in a second embodiment,

(4) FIG. 2b is a schematic overview of the device according to FIG. 2a,

(5) FIG. 3a is a schematic cross-sectional view of a process step of an embodiment of a product according to the invention (substrate-carrier substrate combination) before the bonding step,

(6) FIG. 3b is a schematic cross-sectional view of a process step of an embodiment of a product according to the invention after the bonding step,

(7) FIG. 3c is a schematic cross-sectional view of a process step of an embodiment of a product according to the invention after the back-thinning,

(8) FIG. 4a is a schematic cross-sectional view of a process step of an embodiment of a product according to the invention before the bonding step,

(9) FIG. 4b is a schematic cross-sectional view of a process step of an embodiment of a product according to the invention after the bonding step, and

(10) FIG. 4c is a schematic cross-sectional view of a process step of an embodiment of a product according to the invention after the back-thinning.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) In the figures, advantages and features of the invention are characterized with these reference numbers that are identified in each case according to embodiments of the invention, whereby components or features with the same function or components or features whose function has the same effect are characterized with identical reference numbers.

(12) The figures show a device and a process, which make it possible to align substrates 2, 5 (or substrate stacks) with respect to one another via peripheral edges 2u, 5u. The process according to the invention is a dynamic, optical scanning process with software optimization of the measured data.

(13) In FIGS. 1a and 1b, a product substrate is attached as substrate 2 to a substrate holding means 1 (chuck). The substrate holding means 1 is adjustable in the Z-direction via an adjustment unit 3 (contacting means), i.e., crosswise to a contact plane between the substrate 2 and a carrier substrate 5.

(14) Above the substrate holding means 1, there is another chuck (carrier substrate holding means 4) with the carrier substrate 5 attached thereto. The carrier substrate holding means 4 is connected to a mechanical unit (carrier unit 7) via a rotational guide (rotational means 6). This mechanical carrier unit 7 is connected to a base plate 9 via guides (adjustment system 8 for adjustment in the X- and Y-direction). This adjustment system 8 makes it possible that the mechanical carrier unit 7 can be moved in the X- and Y-direction, specifically controlled via a control system, not shown.

(15) Technically, the only important thing is producing a relative movement between the substrates 2, 5.

(16) This carrier unit 7 has an annular, preferably circular, guide element 10. A distance-measuring element 11 (detection means) is located on the guide element 10. The detection means are advantageously positioned in the contact plane of the two substrates 2, 5, and all distances are measured/detected at a specific angular range by the distance-measuring element.

(17) As a result, in this scanned angular range, a distance profile is produced that assigns the position of the substrates 2, 5 to the instantaneous position of the scanning unit (detection means).

(18) In the area of the circular guide element 10, the detection means have additional measuring means 12. The measuring means 12 define the precise position of the scanning unit 11 on the periphery of the substrates 2, 5. An evaluation unit of the measuring means 12 is advantageously integrated in the assigned distance-measuring elements. This is advantageous when several distance-measuring elements are used.

(19) In an independent embodiment according to the invention, a carrier substrate 5 is used, which has a slightly smaller diameter d2 than the diameter d1 of the product substrate 2. Thus, the carrier substrate 5, primarily the carrier substrate edge (peripheral edge 5u) is protected from additional process steps, and the carrier substrate 5 can be used preferably several times without additional purification steps. According to the invention, even very costly and complex carrier substrates 5 can thus be used many times.

(20) If the carrier substrate 5, unlike previous common practice in the semiconductor industry, is not larger but rather smaller (or within the scope of manufacturing tolerances is of equal size) than the product substrate 2, no purification process of the carrier substrate edge 5u is required, and the edge area of the carrier substrate 5 remains free of contamination, since the product substrate 2 serves as a cover for the carrier substrate 5 and/or the carrier substrate edge 5u, and this carrier substrate 5 is not exposed to the effects of the working. The carrier substrate 5 can therefore be reused without a purification step.

(21) The difference between the (mean) diameter d1 of the product substrate 2 and the (mean) diameter d2 of the carrier substrate 5 is less than 500 m, preferably less than 400 m, more preferably less than 300 m, most preferably less than 200 m, and with utmost preference less than 100 m.

(22) In the case of product substrate diameters and carrier substrate diameters of the same size and because of manufacturing tolerances, a case can also arise where the diameter d2 of the carrier substrate 5 is minimally (within the manufacturing tolerance) larger than the diameter d1 of the product substrate 2. It is important according to the invention that protection of the carrier substrate edge 5u is adequately provided by the shadowing action of the product substrate edge 2u of the, in this case, smaller product substrate 2 (not indicated).

(23) In order to achieve the required accuracy of the edge overlap, the edge agreement (edge extension of the product substrate 2) is in particular precise to within 5 m to 10 m (concentric). In other words, the distances between the peripheral edges 2u, 5u deviate from one another in the radial direction from the center of the substrates 2, 5 by at most the above-mentioned values.

(24) According to the invention, the carrier substrate 5 is smaller than the product substrate 2 by 0 m to 500 m, so that the mechanical support of the mechanically critical edge area 2u of the product substrate 2 remains adequate.

(25) For reasons of cost and production throughput, positioning on passmarks within the carrier substrate 5 is preferably not provided. Therefore, all adjustments according to the invention are made between structured product substrate and unstructured carrier substrate according to the substrate edges 2u, 5u of the substrates 2, 5.

(26) Since the substrate edges 2u, 5u of the substrates 2, 5 can be associated with considerable manufacturing tolerances, a precise positioning is especially critical, especially when very precise positionings below 20 m are required.

(27) Therefore, accuracies according to the invention of +/5 m to +/20 m and rotational accuracies of +/5/10 m equivalent on the notch (if present on the carrier substrate) or on the flat are required.

(28) The carrier substrate holding means 4 is mounted to rotate by the rotational means 6 and is connected via the carrier unit 7 to the adjustment system 8, which makes possible a translational movement of the carrier unit 7 and thus the carrier substrate holding means 4. One (or more) optical scanning unit(s) 15, 15 are located in the carrier unit 7.

(29) The scanning unit 15, 15 is able to detect, in particular to scan, the peripheral contours 2u, 5u of the two substrates 2, 5 at least in sections. The distance-measuring system 11 allows the continuous determination of the distance from the distance-measuring system 11 to the peripheral contours 2u, 5u.

(30) As a result, a gap profile is produced, which simultaneously measures/detects the outside geometry of the two substrates 2, 5. This gap profile produces both the largest outside diameter of the respective substrate 2, 5 and the distance from the peripheral contours 2u, 5u of the individual substrates 2, 5 with respect to one another. The scanning units 15, 15 preferably rotate along the guide elements 10 in the mechanical device.

(31) Because of the rotation of the scanning units 15, 15, it is possible to measure the substrate edges 2u, 5u of the two substrates 2, 5 and at the same time to determine the position of the two substrates 2, 5 relative to one another. The scanning units 15, 15 can move along a closed circle if the guide 10 is closed, or only along circular segments 10, as shown in the embodiment in FIG. 1b. For fewer precise adjustment requirements, the rotation of the scanning units 15, 15 can be eliminated. It is also possible not to rotate the scanning units 15, 15 but rather to rotate the two substrates 2, 5 in the case of stationary scanning units 15, 15, by corresponding contacting means 3 having rotational units.

(32) In the embodiment according to FIGS. 2a and 2b, the scanning units can be optics 13, 13, 13, 13, whose optical axes are approximately at right angles to the substrate surface of the substrate 2. In one embodiment, the scanning units are microscopes that supply an optical image of the substrate edges and thus the peripheral contours 2u, 5u for measuring and evaluation.

(33) One or more of these optics 13, 13, 13, 13 can in turn be arranged to be movable (rotating around the standing substrates 2, 5) or stationary (with rotating substrates 2, 5).

(34) In another embodiment, at least four optics 13, 13, 13, 13 are arranged in a stationary manner on the periphery above and/or below the substrates 2, 5. Both substrate edges 2u, 5u are visible through the optics 13, 13, 13, 13 (optionally with refocusing because of the Z-distance, which could exceed the depth of focus).

(35) In this embodiment, it is advantageous when the carrier substrate 5 lies with the lower diameter d2 in the optical path between the optics 13, 13, 13, 13 and the substrate 2 with the larger diameter d1, so that for the optics 13, 13, 13, 13, both peripheral contours 2u, 5u with corresponding alignment of the two substrates 2, 5 with respect to one another are visible at the same time.

(36) Should the optics be sensitive to an electromagnetic irradiation, for which the substrates that are used are transparent, the substrate 2 with the larger diameter d1 can also be located closer to the respective optics. By way of example, silicon wafers that are transparent to infrared radiation can be mentioned.

(37) Mathematically, the adjustment of the two substrates 2, 5 with respect to one another can be done based on any adjustment calculation, preferably by the least squares method. The optics or distance-measuring systems are preferably to be designed in such a way that the recorded data are digitized and can be forwarded to a corresponding computer.

(38) Corresponding software in the computer (control system) is able to control the X- and/or Y- and/or rotational units in such a way that a continuous matching of the alignment of the two peripheral contours 2u, 5u with respect to one another is carried out specifically until the corresponding adjustment calculation of the software yields a parameter that is a measurement of the accuracy of the adjustment calculation, which value drops below a threshold value specified by the user.

(39) FIGS. 3a-3b show a shortened process for the production of a product according to the invention (substrate-carrier substrate combination) with the carrier substrate 5, whose diameter d2at least before the back-thinning process (FIGS. 3a-3b)is smaller than the diameter d1 of the substrate 2. After an alignment and bonding process according to the invention (FIG. 3b), a back-thinning process of the substrate 2 (FIG. 3c) is carried out.

(40) The substrate 2 is connected to the carrier substrate 5 by an adhesive layer 14, which is attached to the substrate 2 before the bonding, in particular to an adhesive surface with a diameter d3, which is between the diameter d2 of the carrier substrate 5 and the diameter d1 of the substrate 2, and preferably corresponds to the diameter d2 of the carrier substrate 5.

(41) In the embodiment according to FIG. 3, the carrier substrate 5 has a very small edge radius, while the substrate 2 has a very large edge radius. In the embodiment according to the invention, two advantages are thus obtained. First, the relatively small edge radius of the carrier substrate 5 contributes to the fact that a support surface 5o supporting the substrate 2 after incorporation on the carrier substrate 5 as much as possible reaches a support edge 2k of the peripheral contour 2u, which has the result of an advantageous support of the product substrate 2 by the carrier substrate 5. The adhesive layer 14 does not have a significant effect on the support; in particular, the latter has at least the diameter d3 that is equal to the diameter d2 of the carrier substrate 5.

(42) Because of the edge radius, the substrate 2 has an annular shoulder 2a on its peripheral contour at least on the contact side of the substrate 2 with the carrier substrate 5, and said shoulder has an annular width dR that corresponds to at least the difference between the diameters d2 and d1. The shoulder 2a is distinguished in this embodiment by continuous reduction of the thickness D.sub.1 of the substrate 2 in the direction of the peripheral contour 2u and/or by continuous reduction of the diameter of (at most) the mean diameter d1 up to a diameter dk on the contact side 2o. The shoulder 2a can be defined in particular by the adhesive layer 14, in particular by a diameter d3 of the adhesive layer 14.

(43) In addition, the relatively large edge radius of the product substrate 2 makes it possible that the diameter d1 of the product substrate 2 by itself is matched to the diameter d2 of the carrier substrate 5 by the back-thinning and the shape of the cross-section of the peripheral contour 2u by the looping-back being carried out up to at least the shoulder 2a. After an alignment and bonding process according to the invention (FIG. 3b), a back-thinning process of the substrate 2 (FIG. 3c) is carried out at least to above the shoulder of the peripheral contour 2u, i.e., at least up to the shoulder 2a.

(44) It would also be conceivable that the edge radius of the product substrate 2 is very small, which would increase the usable surface of the product substrate 2, primarily in the case of very large wafers, and thus would increase the yield of functional units, for example chips, 16, provided on the product substrate 2.

(45) FIGS. 4a-4b show another shortened process of a product according to the invention (substrate-carrier substrate combination) with a carrier wafer 5, whose diameter d2 is smaller than the diameter d1 of a substrate 2. The edge of the (product) substrate 2 was looped back according to the invention on the peripheral contour 2u by an annular width dR to achieve an effect similar to the effect of the larger edge radius in the embodiment according to FIGS. 3a to 3c. In this connection, an annular shoulder 2a is produced. The looping-back is produced in particular by a process that is known in the industry under the name edge-trimming.

(46) The diameter d2 of the carrier wafer 5 advantageously equals the diameter d1 of the substrate 2 reduced by the annular width dR of the circular ring. After an alignment and bonding process according to the invention (FIG. 4b), a back-thinning process of the substrate 2 is carried out (FIG. 4c) at least up to the looped-back section of the peripheral contour 2u, i.e., at least up to the shoulder 2a.

(47) Both products according to the invention have the property that after the back-thinning, the diameter d2 of the carrier wafer 5, 5 and the diameter d1 of the substrate 2, 2 have a smaller difference, approximately equal, or the diameter d1 is even smaller than the diameter d2, by the back-thinning process resulting in a reduction of the diameter d1 of the substrate 2, 2 because of the edge shape of the substrate 2, 2.

(48) The edge shapes of the substrates are determined by SEMI standards. There are substrates with different edge profiles provided for special objects. These edge profiles are produced by special machines. The shape of the edges is of importance for the chip yield. To be able to process as many chips as possible on a substrate, chips must also be produced on the outermost edge areas. Therefore, it is useful according to the invention to make the edge geometry as square as possible, or at least rounded with the smallest possible radius of curvature. As a result, preferably a wafer is produced with as large an area of use as possible.

(49) The different wafer edge profiles are defined in the SEMI standard. The different wafer edge profiles can adopt very complicated shapes and are described in the rarest cases by a single parameter. According to the invention, the edge radius is defined as a parameter that results in a significant rounding of the wafer edge profile.

(50) For an embodiment according to the invention, in which the product wafer is to have as many functional units as possible, the characteristic edge radius is less than 1 mm, preferably less than 0.5 m, more preferably less than 0.1 mm, most preferably less than 0.001 mm, and with utmost preference equal to 0 mm.

(51) For an embodiment according to the invention in which the product wafer is reduced in its thickness by processes after the bonding process, the calculation of the characteristic edge radius has to be carried out based on the end thickness of the product wafer or the diameter of the carrier substrate and/or product substrate. The characteristic edge radius is larger than 0 mm, preferably larger than 0.001 mm, more preferably larger than 0.1 mm, most preferably larger than 0.5 mm, and with utmost preference larger than 1 mm.

(52) For an embodiment according to the invention, in which the carrier wafer is optimally to support the product wafer by as large a surface as possible, the characteristic edge radius of the carrier wafer is smaller than 1 mm, preferably smaller than 0.5 mm, more preferably smaller than 0.1 mm, most preferably smaller than 0.001 mm, and with utmost preference equal to 0 mm.

REFERENCE SYMBOL LIST

(53) 1 Substrate Holding Means 2, 2 Substrate 2o Contact Side 2a, 2a Shoulder 2k, 2k Support Edge 3 Contacting Means 4 Carrier Substrate Holding Means 5, 5k Carrier Substrate 2u, 5u Peripheral Contours 5o Support Surface 6 Rotational Means 7 Carrier Unit 8 Adjustment System 9 Base Plate 10 Guide Elements 11 Distance-Measuring Elements 12 Measuring Means 13, 13, 13, 13 Optics 14 Adhesive Layer 15, 15 Scanning Unit 16 Functional Units d1, d2, d3, dk Mean Diameter dR Mean Annular Width D.sub.1 Thickness