Assembly of Wafer Stacks

• US 20150115413A1
• Filed: 05/15/2013
• Published: 04/30/2015
• Est. Priority Date: 05/17/2012
• Status: Active Grant

• Current Assignee: Ams Sensors Singapore Pte. Ltd. (Ams-Osram AG)
• Original Assignee: Heptagon Micro Optics Pte Ltd
• Inventors: Rudmann, Hartmut
• Granted Patent: US 9,716,081 B2
• Time in Patent Office: Days
• US Class Current: 257/622
• CPC Class Codes: H01L 2223/54426 for alignment
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 25/162 the devices being mounted on two or more different substrates
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 27/1469 Assemblies, i.e. hybrid integration
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/12044 OLED
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H01L 2933/0058 relating to optical field-shaping elements
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

A method of forming a wafer stack includes providing a sub-stack comprising a first wafer and a second wafer. The sub-stack includes a first thermally-curable adhesive at an interface between the upper surface of the first wafer and the lower surface of the second wafer. A third wafer is placed on the upper surface of the second wafer. A second thermally-curable adhesive is present at an interface between the upper surface of the second wafer and the lower surface of the third wafer. Ultra-violet (UV) radiation is provided in a direction of the upper surface of the third wafer to cure a UV-curable adhesive in openings in the second wafer and in contact with portions of the third wafer so as to bond the third wafer to the sub-stack at discrete locations. Subsequently, the third wafer and the sub-stack are heated so to cure the first and second thermally-curable adhesives.

Claims

1. A method of forming a stack of wafers, the method comprising:

providing a sub-stack comprising a first wafer and a second wafer, each of which has a respective upper surface and lower surface, the sub-stack including a first thermally-curable adhesive at an interface between the upper surface of the first wafer and the lower surface of the second wafer;

placing a third wafer on the upper surface of the second wafer, the third wafer having an upper surface and a lower surface, wherein a second thermally-curable adhesive is present at an interface between the upper surface of the second wafer and the lower surface of the third wafer;

providing ultra-violet (UV) radiation in a direction of the upper surface of the third wafer to cure a UV-curable adhesive in openings in the second wafer and in contact with portions of the third wafer so as to bond the third wafer to the sub-stack at discrete locations; and

subsequently heating the third wafer and the sub-stack so to cure the first and second thermally-curable adhesives.

2. The method of claim 1 wherein the openings in the second wafer are located near the periphery of the second wafer.

3. The method of claim 2 wherein each of the openings in the second wafer is a through-holes that extends from the upper surface of the second wafer to its lower surface, wherein the UV-curable adhesive substantially fills the openings.

4. The method of claim 1 wherein the UV radiation reaches the UV-curable adhesive by passing through UV-transparent windows in the third wafer.

5. The method of claim 4 further including:

prior to placing the third wafer on the upper surface of the second wafer, dispensing the UV-curable adhesive into the openings of the second wafer;

subsequently moving the third wafer onto the upper surface of the second wafer, wherein the UV-transparent windows in the third wafer are substantially aligned over the openings in the second wafer containing the UV-curable adhesive; and

providing the UV radiation through the UV-transparent windows in the third wafer after moving the third wafer onto the upper surface of the second wafer.

6. The method of claim 1 wherein the third wafer includes through-holes that extend from the upper surface of the third wafer to its lower surface, the method further including:

after moving the third wafer onto the upper surface of the second wafer, dispensing the UV-curable adhesive into the openings in the second wafer through the through-holes in the third wafer; and

subsequently providing the UV radiation through the through-holes in the third wafer.

7. The method of claim 1 wherein moving the third wafer onto the upper surface of the second wafer and providing the UV radiation to cure the UV-curable adhesive are performed in a mask aligner.

8. The method of claim 7 further including removing from the mask aligner the third wafer attached to the sub-stack after providing the UV radiation to cure the UV-curable adhesive, and heating the third wafer attached to the sub-stack so to cure the first and second thermally-curable adhesives in a location other than in the mask aligner.

9. The method of claim 1 further including separating the stack of wafers into individual modules each of which includes a portion of the first, second and third wafers.

10. The method of claim 1 wherein the wafers are made of materials substantially non-transparent to UV-radiation.

11-30. -30. (canceled)

31. A wafer stack comprising:

a first wafer having an upper surface and a lower surface;

a second wafer having an upper surface and a lower surface;

a first thermally-cured adhesive at an interface between the upper surface of the first wafer and the lower surface of the second wafer;

a third wafer having an upper surface and a lower surface,

a second thermally-cured adhesive at an interface between the upper surface of the second wafer and the lower surface of the third wafer;

UV-cured adhesive disposed in the second wafer and in contact with portions of the second and third wafers, wherein the UV-cured adhesive is disposed at discrete locations near the periphery of the second wafer.

32. The wafer stack of claim 31 wherein the third wafer includes UV-transparent windows each of which is substantially aligned with a respective one of the locations in the second wafer that contains the UV-cured adhesive.

33. The wafer stack of claim 31 wherein the UV-cured adhesive also is disposed in the third wafer at locations each of which is substantially aligned with a respective one of the locations in the second wafer that contains the UV-cured adhesive.

35. The wafer stack of claim 31 wherein each of the discrete locations near the periphery of the second wafer is approximately equally spaced from adjacent ones of the discrete locations.

36. The wafer stack of claim 31 wherein the wafers are made of materials substantially non-transparent to UV-radiation.

34. (canceled)