Object carrier, system and method for back light inspection

Abstract

An object carrier, a system and a method is disclosed for the back light inspection of transparent or semitransparent objects. The carrier has a carrier base layer with photo luminescent properties which carries the transparent or semitransparent object on top of the layer. The transparent or semitransparent object could be a wafer and the object carrier could be a wafer chuck. At least one light source being arranged above the object carrier such that excitation light emitted from the at least one light source is directed through the transparent or semitransparent object to the layer with photo luminescent properties. The light returned from the layer with photo luminescent properties is collected by an objective and registered by a sensor.

Claims

1. A system for back light inspection of a transparent or semitransparent object, comprising: an object carrier with a carrier base and a layer with photo luminescent properties wherein the transparent or semitransparent object rests on the layer with photo luminescent properties; a first light source arranged above the object carrier such that first excitation light emitted from the first light source is directed through the transparent or semitransparent object to the layer with photo luminescent properties; an optical unit adapted to capture emission light emitted from the layer with photo luminescent properties and traveled through the transparent or semitransparent object; and a sensor for registering the emission light captured by the optical unit, wherein the sensor is an area scan camera or a line scan camera.

2. The system of claim 1, wherein the first excitation light emitted by the first light source has an excitation waveband of λ.sub.ex±Δλ.sub.ex.

3. The system of claim 2, wherein the sensor is configured such that a registered image is defined by an emission waveband λ.sub.em±Δλ.sub.em, and wherein λ.sub.em±Δλ.sub.em≠λ.sub.ex±Δλ.sub.ex.

4. The system of claim 1, wherein the first light source is a broadband emitting light source with at least one filter applied to for generating an excitation waveband of λ.sub.ex±Δλ.sub.ex.

5. The system of claim 4, wherein at least one optical filter is arranged in front of the sensor so that only filtered light of the emission waveband λ.sub.em±Δλ.sub.em reaches the sensor.

6. The system of claim 4, wherein the sensor is insensitive to the excitation waveband of λ.sub.ex±Δλ.sub.ex and sensitive to at least a portion of the emission waveband λ.sub.em±Δλ.sub.em.

7. The system of claim 1, wherein the sensor is a time delay integration line scan camera.

8. The system of claim 1, wherein the first excitation light emitted by the first light source travels through the optical unit to the layer with photo luminescent properties.

9. The system of claim 1, wherein the first excitation light emitted by the first light source travels outside the optical unit to the layer with photo luminescent properties.

10. The system of claim 1, further comprising a second light source emitting second excitation light, wherein: the first excitation light emitted by the first light source travels through the optical unit to the layer with photo luminescent properties; and, the second excitation light emitted by the second light source travels outside the optical unit to the layer with photo luminescent properties.

11. The system of claim 1, wherein the first light source is a lamp or a combination of lamps.

12. The system of claim 1, wherein the first light source is an LED or a combination of LEDs.

13. The system of claim 1, wherein the first light source is a laser or a combination of lasers.

14. The system of claim 1, wherein the optical unit has a microscope objective and at least one optical filter so that only light with an emission waveband of λ.sub.em±Δλ.sub.em from the layer with photo luminescent properties reaches the sensor.

15. The system of claim 14, wherein the microscope objective defines a beam path, and a dichroic beam splitter is arranged in the optical unit such that light from the at least one first light source with the excitation waveband of λ.sub.ex±Δλ.sub.ex is coupled into the beam path of the microscope objective.

16. The system of claim 14, wherein the microscope objective defines a first beam path, and light from a second light source with the excitation waveband of λ.sub.ex±Δλ.sub.ex defines an illumination beam path different from the first beam path of the microscope objective.

17. The system of claim 14, wherein: the microscope objective defines a first beam path; a dichroic beam splitter is arranged in the optical unit such that light of the excitation waveband of λ.sub.ex±Δλ.sub.ex is coupled into the first beam path of the microscope objective; and, light from a second light source with the excitation waveband of λ.sub.ex±Δλ.sub.ex defines an illumination beam path different from the first beam path of the microscope objective.

18. The system of claim 1, wherein the layer with photo luminescent properties is composed of a bulk material with photo luminescent properties coated with a reflective material.

19. The system of claim 1, wherein the layer with photo luminescent properties is composed of a transparent bulk material coated with a second material with photo luminescent properties which is coated with a reflective material.

20. A system for back light inspection of a transparent or semitransparent object, comprising: an object carrier with a carrier base and a layer with photo luminescent properties; a first light source arranged above the object carrier such that first excitation light emitted from the first light source is directed through the transparent or semitransparent object to the layer with photo luminescent properties; an optical unit adapted to capture emission light emitted from the layer with photo luminescent properties and traveled through the transparent or semitransparent object; and a sensor for registering the emission light captured by the optical unit, wherein the object carrier is arranged to move the transparent or semitransparent object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:

(2) FIG. 1 is a schematic representation of a prior art arrangement for back light inspection;

(3) FIG. 2 is a schematic representation of another embodiment of a prior art arrangement for back light inspection;

(4) FIG. 3 is a schematic representation of an example embodiment of the present invention for the back light inspection of objects;

(5) FIG. 4 is a schematic representation of an example embodiment of the present invention for the back light inspection of objects;

(6) FIG. 5 is a schematic representation of an alternative for the illumination in order to achieve the back light illumination of transparent or semitransparent objects;

(7) FIG. 6 is a schematic representation of a system for back light inspection of transparent or semitransparent objects;

(8) FIG. 7 is a schematic representation of another embodiment of the system for back light inspection;

(9) FIG. 8 is a schematic representation of an implementation of the system according to one embodiment of the invention; and,

(10) FIG. 9 is a schematic representation of an implementation of the system according to a further embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(11) In the drawings, identical reference characters are used for like elements of the present invention or elements of like function. For the sake of clarity, only those elements and reference characters which are of relevance to the shown aspects of the respective embodiment of the present invention are shown repeatedly.

(12) While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspect. Also, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways and is intended to include various modifications and equivalent arrangements within the spirit and scope of the appended claims.

(13) Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims.

(14) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described.

(15) In the below description, an embodiment is an example or implementation of the invention. The various appearances of “one embodiment”, “an embodiment”, “certain embodiments” or “some embodiments” do not necessarily all refer to the same embodiments.

(16) FIG. 3 is a schematic representation of one inventive embodiment for the back light inspection of transparent or semitransparent objects 2. Object 2 rests on layer 22 with photo luminescent properties. Layer 22 is composed of bulk layer 24, having the photo luminescent properties; with reflective coating 26 at the side of layer 22 which faces carrier base 18 (see FIGS. 6-8). Opposite to the object 2, objective lens 25 is arranged. Objective lens 25 can be a microscope objective. Excitation light 30 is emitted from the at least one light source (not shown) and directed via objective lens 25 to object 2. Excitation light 30 passes through object 2 and reaches bulk layer 24 with photo luminescent properties. In bulk layer 24, emission light 32 is generated which travels through object 2 and is captured by objective lens 25.

(17) The embodiment shown in FIG. 3 has vacuum means 20, which is mounted to the porous bulk layer so that a vacuum is applied to the object through micro pores 29 of bulk layer 24. Applying a vacuum to object 2 via vacuum means 20 enables object 2 (wafer) to be in firm contact with layer 22 with photo luminescent properties. In order to facilitate the removal of object 2, layer 22 with photo luminescent properties has pin lifting holes 31 and lifting pins 34. The top of lifting pins 34 is made of the same photo luminescent material as layer 22 with photo luminescent properties to limit the disturbance of the image.

(18) FIG. 4 shows a schematic representation of an example embodiment for the back light inspection of objects 2. Here layer 22 with photo luminescent properties is composed of glass plate 27 with photo luminescent coating 28. The material of photo luminescent coating 28 could be phosphor. Photo luminescent coating 28 is covered with reflective coating 26 on the coating which faces carrier base 18 (see FIGS. 6-8). In the example embodiments shown in FIGS. 3 and 4, reflective coating 26 is made of aluminum. Excitation light 30 is emitted from the at least one light source (not shown) and directed via objective lens 25 to object 2. Excitation light 30 passes through object 2, glass plate 27 and reaches photo luminescent coating 28. With luminescent coating 28, emission light 32 is generated which travels through glass plate 27 and object 2 and is captured by objective lens 25. In the instance that luminescent coating 28 is a phosphor coating, excitation light 30 covers a waveband from ultraviolet to blue and emission light 32 covers a waveband from green to red.

(19) In FIG. 5, an additional illumination concept for layer 22 with photo luminescent properties is shown. Layer 22 with photo luminescent properties is identical with layer 22 shown in FIG. 3. Excitation light 30, having a waveband in the ultraviolet region, is emitted from the at least one light source (not shown) and directed via objective lens 25 to object 2. Excitation light 30 passes through object 2 and reaches bulk layer 24 with photo luminescent properties. Additionally, at least one further light source 60 is provided, which directs its excitation light 62 in the green waveband and/or blue waveband through object 2 to bulk layer 24 with photo luminescent properties. In bulk layer 24, emission light 32 is generated which travels through object 2 and is captured by objective lens 25.

(20) FIG. 6 is a schematic representation of an example embodiment of system 1 for back light inspection of objects 2. Object 2 is positioned on stage 9 for moving object 2 along X-coordinate direction X and Y-coordinate direction Y. Stage 9 enables the positioning of various sections of object 2 in excitation light 30 emitted by the at least one light source 6. Excitation light 30 exits light source 6 and enters optical unit 8 and from optical unit 8 excitation light 30 reaches layer 22 via microscope objective 25 (see FIGS. 3-5) and object 2. Excitation light 30 reaches layer 22 with a waveband of λ.sub.ex±Δλ.sub.ex. From layer 22 with photo luminescent properties, light 32 with an emission waveband of λ.sub.em±Δλ.sub.em reaches optical unit 8 and the associated sensor 12. Sensor 12 is configured such that a registered image is defined by an emission waveband λ.sub.em±Δλ.sub.em and wherein λ.sub.em±Δλ.sub.em≠λ.sub.ex±Δλ.sub.ex.

(21) A further embodiment of system 1 is shown in FIG. 7. Another light source 60 is arranged such that excitation light 62 emitted by light source 60 travels outside optical unit 8 via object 2 to layer 22 with photo luminescent properties. Microscope objective 25 of optical unit 8 defines beam path 25B and the light from the at least one further light source 60 with the excitation waveband λ.sub.ex±Δλ.sub.ex defines illumination beam path 60B which is different from beam path 25B of microscope objective 25 (see FIGS. 3-5). Again, sensor 12 is configured such that a registered image is defined by an emission waveband λ.sub.em±Δλ.sub.em of emission light 32 exiting layer 22 with photo luminescent properties through object 2 and wherein λ.sub.em±Δλ.sub.em≠λ.sub.ex±Δλ.sub.ex. A combination of the embodiments shown in FIGS. 6 and 7 is possible as well. Here, light 30 from light source 6 is coupled into beam path 25B and light 62 from the at least one further light source 60 is coupled with the excitation waveband of λ.sub.ex±Δλ.sub.ex in illumination beam path 60B which is different from beam path 25B.

(22) FIG. 8 is a schematic representation of an implementation of system 1 according to an example embodiment. Layer 22 with photo luminescent properties is on carrier base 26 and carrier base 26 is positioned on stage 9. Here, one light source 6 is arranged above object 2. Excitation light 30 emitted from light source 6 is directed through object 2 to layer 22 with photo luminescent properties. Again, microscope objective 25 (see FIGS. 3-5) defines beam path 25B. Dichroic beam splitter 40 is arranged in optical unit 8 such that light from light source 6 is coupled into beam path 25B with the excitation waveband of λ.sub.ex±Δλ.sub.ex. At least one optical filter 42 is arranged in front of sensor 12 so that only light 32 of the emission waveband λ.sub.em±Δλ.sub.em reaches sensor 12. In an example embodiment, sensor 12 is insensitive to light 30 of the excitation waveband of λ.sub.ex±Δλ.sub.ex and only sensitive to at least a portion of the emission waveband λ.sub.em±Δλ.sub.em.

(23) Light 32 returning from layer 22 contains the emission waveband λ.sub.em±Δλ.sub.em and light 34 returning from layer 22 also contains the excitation waveband λ.sub.ex±Δλ.sub.ex, wherein λ.sub.em±Δλ.sub.em≠λ.sub.ex±Δλ.sub.ex. Dichroic beam splitter 40 lets a portion of light 34 with the excitation waveband λ.sub.ex±Δλ.sub.ex pass and, as mentioned above, this portion is blocked by optical filter 42 so that it does not reach sensor 12. On the other hand, a portion of light 34 with the excitation waveband λ.sub.ex±Δλ.sub.ex is reflected by dichroic beam splitter 40 back into light source 6.

(24) In the case where light source 6 in FIG. 8 emits blue light with a wavelength of 460 nm, dichroic beam splitter 40 in optical unit 8 (microscope) has a cut on at the wavelength of 514 nm. Here, light 30 shines through object 2 (wafer) on layer 22 having photo luminescent properties. Layer 22 emits white light 32 which is sent to sensor 12 (camera) through dichroic beam splitter 40 and high pass filter 42, which has a cut on a wavelength of 514 nm.

(25) FIG. 9 is a schematic representation of an implementation of system 1 according to an example embodiment. Here, in addition to light source 6 (excitation light in the UV region), two further light sources 60 are provided. Light sources 60 are arranged such that excitation light 62 from the further light sources 60 travels outside optical unit 8 via object 2 to layer 22 having photo luminescent properties. The number of further light sources 60 shown in this embodiment should not be regarded as limiting the scope of the invention. It is clear for a person having ordinary skill in the art that the number of further light sources 60 can be selected according to the inspection requirements.

(26) In the case where the further light source 60 is a ring light with an excitation light in the green light region, it might be worthwhile to use a different set of filters to have the range UV-green available as excitation wavelengths. The emission filter should only transmit the red. This will block the blue response from object 2.

(27) The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described.

(28) Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention as claimed.

LIST OF REFERENCE CHARACTERS

(29) 1 System 2 Transparent or semitransparent object 4 Carrier 5 Light from light source 6 Light source 7 Portion of light 8 Optical unit 9 Stage 10 Object carrier, wafer chuck 12 Sensor 20 Vacuum means 22 Layer with photo luminescent properties 24 Bulk plate 25 Objective lens, microscope objective 25B Beam path 26 Reflective coating 27 Glass plate 28 Phosphor coating 29 Micro pores 30 Excitation light, illumination light 31 Lifting holes 32 Emission light 34 Lifting pins 40 Dichroic beam splitter 42 Optical filter 60 Further light source 60B Illumination beam path 62 Excitation light X X-coordinate direction Y Y-coordinate direction