Alignment marks in busy pixel layouts
By forming an alignment mark of an optical structure on the uncovered area during the transfer of the micro device, the pixel array alignment problem is solved, and accurate alignment and efficient transfer of the micro device are achieved.
Patent Information
- Application Number
- CN202380040784.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-06-07
- Filing Date
- 2023-06-07
- Publication Date
- 2025-01-10
AI Technical Summary
During micro-device transfer, it is difficult for the prior art to accurately align the position of the micro-device array, especially in cases where pixel array repeatability is high and tools are difficult to use existing pixel structures as alignment marks.
By forming alignment marks of optical structures on areas not covered by micro-device, including patterning of polymer films to change the optical properties, and identifying and aligning the transfer process of micro-device using image processing.
The transfer of the micro-device accurately aligns the micro-device in a highly repeatable pixel array is realized, the alignment accuracy between the micro-device and the system substrate is improved, and the successful transfer of the micro-device and the correct position filling is ensured.
Smart Images
Figure CN119301754A_ABST
Abstract
Description
[0001] CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 349,872, filed on June 7, 2022, which is hereby incorporated by reference in its entirety.
[0003] Background and technical field
[0004] The present invention relates to the transfer and alignment of microdevices. Summary of the invention
[0005] The present invention relates to an alignment mark structure of an array of pixels or microdevices that identifies the position of a subset of an array of microdevices or pads, wherein the alignment mark structure comprises an optical structure in an area not covered by microdevice pads, wherein the optical structure changes an optical property of the area.
[0006] The present invention relates to an alignment mark structure, which includes a film formed on an area not covered by a pad or a micro device, the film is extended to more than one pixel area, and the outer edge of the film is formed into a certain shape.
[0007] The present invention relates to a method of forming alignment marks on an array of pixels (or microdevices), the method comprising: forming a polymer film on top of the array; and patterning the polymer to cover a portion of the pixel area and modify the optical properties of the area.
[0008] The present invention relates to a method for transferring microdevices from a box to a system substrate, the method comprising: for alignment, identifying the edge of a first area of the system substrate by image processing, wherein an alignment mark is formed by changing the optical properties of the first area between the microdevices; aligning the box with the first area of the system substrate using the alignment mark; transferring a first group of selected microdevices to the system substrate; and moving the box away from the system substrate.
[0009] The present invention relates to a method for aligning a microdevice using an alignment mark structure, the method comprising: forming a film formed on an area not covered by a pad or a microdevice; extending the extended film to more than one pixel area so that the outer edge of the film forms a certain shape; using image processing to identify the edge and shape of the alignment mark; and using the shape information to align a transfer head or a box with a donor substrate or a system substrate. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The foregoing and other advantages of the present disclosure will become apparent by reading the following detailed description and referring to the accompanying drawings.
[0011] Figure 1 (a) to Figure 1(f) shows an exemplary method for transferring a microdevice into a system substrate.
[0012] 2(a) and 2(b) illustrate the location of a microdevice in a donor substrate or the location of a microdevice pad (landing area) on an acceptor substrate.
[0013] 3(a) and 3(b) illustrate optical structures between microdevices on a donor substrate or between pixel regions in a system substrate for alignment marks.
[0014] FIG. 3( c ) shows a similar pattern or a different pattern used to fill the spaces between existing traces.
[0015] Figure 3(d) shows the effect of creating new fill features / patterns that create contrast that can be used as alignment marks. DETAILED DESCRIPTION
[0016] The invention disclosed herein is a structure / process for forming an alignment mark and a method for transferring a microdevice using the alignment mark.
[0017] Transferring the microdevice to a substrate can enable different applications. The microdevice can be a light emitting device, a sensor, a chiplet, or other applications.
[0018] In one case, microdevices are selectively picked up from a donor substrate and then transferred to a system substrate.
[0019] In another case, the microdevices can be transferred by offset and printing process steps in another case. Here, a selected set of microdevices is transferred from the cassette substrate to the (system) substrate. The cassette substrate or the system substrate is moved so that the cassette substrate covers another area of the system substrate. Here, another selected set of microdevices is transferred to the system substrate.
[0020] Regardless of the transfer method, there is at least one case where the microdevice and the system substrate (or the pickup head and the donor substrate) are aligned. At least one alignment mark is present on the system substrate (or the donor substrate), and at least one alignment mark is associated with the microdevice. The alignment marks are used to align the microdevice. In all transfer cases, there is still an alignment step of the system substrate with the substrate before picking up or transferring.
[0021] In some cases, the pixels in the system substrate or the microdevices in the box are packed together with other structures. Therefore, it is not practical to add sufficiently large and clear alignment marks in the pixels. In addition, the repetitiveness of the pixel array is very high, and it may be difficult for the tool to use one of the existing pixel structures as an alignment mark.
[0022] Figure 1 (a) to Figure 1(f) shows a transfer situation in which a microdevice is selectively released from a cartridge. Here, a cartridge 100 has several microdevices 102 and it is aligned with a system substrate 104 ( Figure 1 (a)). The box 100 is in contact or nearly in contact with the substrate 104 ( Figure 1 (b)), and a selected set of microdevices 106 are transferred to the system substrate 104. The cartridge and the system substrate are removed and the transferred microdevices 106 remain on the system substrate 104 ( Figure 1 (c)). Here, another alignment may be performed, or the cartridge 100 or the system substrate 104 may be moved so that the cartridge covers another portion of the system substrate 104. Figure 1 (e) and Figure 1 Repeat the previous steps in (f). And this process can continue until the micro-device on the box is completed or the expected area of the system substrate is filled. In the case of transferring an area away from the edge of the pixel array in the system substrate, the alignment mark should be present in the pixel area.
[0023] FIG. 2( a) and FIG. 2( b) show the arrangement of contact pads 202, 202-2 and 202-4 for a microdevice in a system substrate (or microdevice position 202) in a donor substrate. In FIG. 2( a), the microdevice may have a connection portion 202 on one side, and FIG. 2( b) shows an embodiment in which the microdevice has more than one pad 202-2 and 202-4 on one side to connect the device to the system substrate. The distances 204 and 206 between the pads or microdevices are set by the pixel resolution or the donor resolution. Region 200 shows the pixel area in the system substrate or the microdevice spacing area in the donor substrate. As shown in FIG. 2( a) and FIG. 2( b), the region 200 between the microdevices may be very small. In addition, other structures may exist in region 200 with respect to the system substrate or the donor substrate. Therefore, it may be difficult to detect the alignment mark.
[0024] FIG. 3( a) and FIG. 3( b) highlight an embodiment in which alignment marks are formed by changing the optical properties of the area between microdevices. FIG. 3( a) shows a pixel area 200 including a microdevice 202 (or a microdevice pad connection portion 200). In the case of a system substrate, the pad 202 will be filled with a microdevice after alignment. In the case of a donor substrate, the microdevice 202 will be picked up from the substrate after alignment. The distances 204 and 206 between the microdevices or pads may be very small. Here, the optical properties of the area 208 between one or more microdevices (or pads) 202 change. The structure that forms the optical change can be a continuation or combination of several parts. For alignment, the edge of the structure 208 is identified by image processing, and the structure and its relative position can be used to align the microdevice with the system substrate (or the pickup head with the donor substrate). It can be seen that some microdevices 210 (or pads) are outside the structure 208.
[0025] FIG3( b ) shows a structure similar to that shown in FIG3( a ). Here, the microdevice or pixel in the system substrate has more than one pad ( 202 - 2 , 202 - 4 , 210 - 2 , and 210 - 4 ). The area between two pads can also be used as part of the optical structure 208 . The rest of the structure is the same as that described in FIG3( a ).
[0026] FIG3( c ) shows another related embodiment where a similar pattern or a different pattern of optical structures 208-1, 208-2, and 208-3 is used to fill the space between existing traces 220-3. These additional features can be used together as alignment marks. The pattern can fill the space between the traces. The feature can be a layer of metal, polymer, or other form.
[0027] In another related embodiment, the effect of the new fill features / patterns 208-1, 208-2, and 208-3 shown in Figure 3(c) creates a contrast that can be used as an alignment mark 208, as shown in Figure 3(d). This contrast can be enhanced by image processing or image capture techniques (e.g., reduction, etc.).
[0028] In a related embodiment, the structure / region 208 is formed by depositing and patterning a layer on the top layer before or after forming the pad. Here, if the layer used for the structure is conductive before forming the structure layer 208, a dielectric layer can be used. In another case, the pads 202, 202-2, 202-4, 210, 210-2 and 210-4 are formed after the structure. If the pad passes through the structure, a dielectric can be used between the pad and the structure layer if the layer is conductive. Deposition can be performed by evaporation, spraying, inkjet coating, PECVD, PVD, ALD, electron beam or other deposition methods. Here, the structure can be a conductive layer, a metal layer, a polymer layer, a dielectric layer, or a combination of these layers.
[0029] In another related embodiment, the structure can be formed by modifying the surface of one of the existing layers in the pixel area. The modification can be performed by a wet or dry etching process. The modification can be surface roughening or thinning of the layer to produce optical contrast.
[0030] In another related embodiment, the structure can be removed after the microdevice is transferred into the system substrate. Here, a dry or wet etching process can be used to remove the structure.
[0031] In another related embodiment, if one of the structural layers cannot be removed, other areas in the system substrate may be covered with that layer to provide similar / comparable optical properties.
[0032] In another related embodiment, the layer properties in areas other than the structured area can be modified after the microdevice transfer is complete to have similar optical properties throughout the system substrate.
[0033] In another related embodiment, a portion of the surface of the system substrate including the area associated with the optical structure may be covered by a layer to reduce or eliminate the impact on the structure and thus produce similar optical properties for all related areas in the system substrate. The layer may be a dielectric layer, an organic layer, a metal layer, or other type of layer. The layer may be opaque or reflective.
[0034] In a related embodiment, a structure extending between patterns in a pixel or between at least two adjacent pixel regions is formed to create an alignment mark. The structure can change the optical properties of the portion it covers. The structure can be continuous or can be a possible combination of separate smaller structures.
[0035] In another related embodiment, the structure may be formed of dielectric layers, metal layers, or polymer layers, or a combination of different layers.
[0036] In another related embodiment, some microdevices are shaped differently from other microdevices. These microdevices form alignment marks. In a related embodiment, each microdevice having a different shape is an alignment mark, and in another related embodiment, a combination of more than one microdevice forms an alignment mark.
[0037] Although the present disclosure is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown in the drawings by way of example and will be described in detail herein. However, it should be understood that the present disclosure is not intended to be limited to the specific forms disclosed. On the contrary, the present disclosure will cover all modifications, equivalents and alternative forms that fall within the spirit and scope of the present invention as defined by the appended claims.
Claims
1. An alignment mark structure of an array of pixels or microdevices for identifying the position of a subset of an array of microdevices or pads, wherein the alignment mark structure comprises: An optical structure in an area not covered by a microdevice pad, wherein the optical structure changes an optical property of the area. 2 . The alignment mark structure of claim 1 , wherein the structure extends over the area of more than two pixels.
3. The alignment mark structure of claim 1, wherein the structure is made of a polymer.
4. The alignment mark structure of claim 1, wherein the structure is made of a dielectric or conductive material.
5. The alignment mark structure of claim 1, wherein the structure is made of stacked materials.
6. An alignment mark structure, comprising: Films formed on areas not covered by pads or microdevices; The film is extended to more than one pixel area; and The outer edge of the film is shaped. 7 . The alignment mark structure of claim 6 , wherein the film comprises a single layer or a multilayer.
8. The alignment mark structure of claim 6, wherein the film is a polymer, a dielectric, or a metal.
9. A method for forming an alignment mark on a pixel (or microdevice) array, the method comprising: forming a polymer film on top of the array; as well as The polymer is patterned to cover a portion of a pixel area and to modify the optical properties of the area.
10. The method of claim 9, wherein the polymer film covers areas in more than one pixel.
11. The method of claim 9, wherein the polymer film is photodefinable.
12. An alignment mark structure in an array of microdevices, wherein the alignment mark is formed based on some microdevices having different shapes. 13 . The alignment mark structure according to claim 12 , wherein the alignment mark is formed on the system substrate after the micro devices having different shapes are transferred onto the system substrate.
14. The alignment mark structure of claim 12, wherein the micro device has one connection portion on one side, or has more than one pad on one side to connect the device to the system substrate.
15. A method of transferring a microdevice from a cartridge to a system substrate, The method comprises: For alignment, identifying edges of a first region of the system substrate by image processing, wherein alignment marks are formed by changing optical properties of the first region between microdevices; aligning the cartridge with the first area of the system substrate using the alignment mark; transferring a first set of selected microdevices to the system substrate; as well as The cartridge is removed from the system baseboard.
16. The method according to claim 15, further comprising: realigning the cartridge with a second region of the system substrate, wherein another alignment mark is formed by changing an optical property of the second region between microdevices; transferring a second group of selected microdevices to the system substrate; removing the cartridge from the system baseboard; as well as The remaining expected area of the system substrate is realigned by repeating the previous steps to fill the remaining expected area of the system substrate or until the microdevice in the cartridge is completed.
17. The method of claim 15, wherein the transferring is performed on an area away from an edge of a pixel array in the system substrate, wherein alignment marks are present in the pixel area.
18. The method of claim 15, wherein the microdevice has one connection on one side.
19. The method of claim 15, wherein the microdevice has more than one pad on one side to connect the microdevice to the system substrate.
20. The method of claim 19, wherein the distance between the pads or the microdevices is set by a pixel resolution or a donor resolution.
21. The method according to claim 15, wherein the region forming the optical change is a continuation or combination of several parts.
22. The method of claim 19, wherein the pad is part of the region having the optical change.
23. The method of claim 21, wherein the optically variable region or structure is formed by a layer deposited and patterned on a top layer before or after forming the pad.
24. The method of claim 22, wherein if the layer used for the structure is conductive before forming the optically variable region, a dielectric layer is used.
25. The method of claim 22, wherein the pad is formed after the structuring.
26. The method of claim 18, wherein the pad is formed after the structuring.
27. The method of claim 25, wherein if the pad passes through the structure, a dielectric is used between the pad and the structure layer if the layer is conductive.
28. The method of claim 27, wherein the dielectric deposition is performed by evaporation, spraying, inkjet coating, PECVD, PVD, ALD or electron beam, and wherein the optically variable region is a conductive layer, a metal layer, a polymer layer, a dielectric layer or a combination of these layers.
29. The method of claim 23, wherein the structure is formed by modifying a surface of one of the existing layers in the pixel region using a wet or dry etching process.
30. The method of claim 29, wherein the modification is surface roughening or layer thinning to create optical contrast.
31. The method of claim 23, wherein the structure is removed after the microdevice is transferred into the system substrate using a dry or wet etching process.
32. The method of claim 23, wherein if one of the structural layers is non-removable, other areas in the system substrate are covered with that layer to provide similar / comparable optical properties.
33. The method of claim 23, wherein layer properties in regions other than the structure region are modified after microdevice transfer is complete to have similar optical properties throughout the system substrate.
34. A method according to claim 23, wherein a portion of the surface of the system substrate including the area associated with the optical structure is covered by a layer to reduce or eliminate the impact on the structure, thereby producing similar optical properties for all relevant areas in the system substrate, wherein the layer is one of a dielectric layer, an organic layer or a metal layer, and further wherein the layer is opaque or reflective.
35. The method of claim 23, wherein a structure extending between patterns in one pixel or between at least two adjacent pixel regions is formed to produce an alignment mark.
36. A method according to claim 35, wherein the structure changes the optical properties of the part it covers and the structure is continuous or a possible combination of separate smaller structures.
37. The method of claim 23, wherein the shape of some of the microdevices is different from other microdevices, and the microdevices form alignment marks.
38. The method of claim 37, wherein each microdevice having a different shape is an alignment mark.
39. The method of claim 37, wherein a combination of more than one microdevice forms an alignment mark.
40. A method for aligning a microdevice using an alignment mark structure, the method comprising: forming a film formed on an area not covered by a pad or a microdevice; extending the extended film to more than one pixel area; shaping the outer edge of the film; Using image processing to identify the edges and shapes of the alignment marks; and using information about the shapes to align a transfer head or cassette with a donor substrate or a system substrate.
41. The method of claim 40, wherein the inner edges form different shapes and the image processing detects the inner shapes to improve alignment accuracy.
42. The method of claim 40, wherein the film comprises a single layer or multiple layers.
43. The method of claim 40, wherein the film is a polymer, a dielectric, or a metal.
44. The method of claim 40, wherein where the film is conductive, a dielectric is deposited before or after the film to isolate it from the main pixel structure.
45. The method of claim 40, wherein a similar pattern or a different pattern of optical structures is used to fill spaces between existing traces, thereby creating alignment marks.
46. The method of claim 40, wherein the new fill pattern creates a contrast to be used as an alignment mark.