Method of stress relief in anti-reflective coated cap wafers for wafer level packaged infrared focal plane arrays

Patent metadata

Field	Value
Publication number	US-2016340179-A1
Application number	US-201615227181-A
Country	US
Kind code	A1
Filing date	Aug 3, 2016
Priority date	Aug 23, 2012
Publication date	Nov 24, 2016
Grant date	—

Abstract

Methods for reducing wafer bow induced by an anti-reflective coating of a cap wafer are provided. The method may utilize a shadow mask having at least one opening therein that is positioned opposite recessed regions in a cap wafer. The method may further include depositing at least one layer of an anti-reflective coating material through the shadow mask onto a planar side of a cap wafer to provide a discontinuous coating on the planar side.

First claim

What is claimed is:

1 . A method of reducing wafer bow induced by an anti-reflective coating on a cap wafer, the method comprising:
providing the cap wafer having a planar side and an opposing cavity side, the cavity side including at least one recessed region and a dividing region on either side of the at least one recessed region; and depositing a layer of an anti-reflective coating material onto the planar side of the cap wafer to provide a discontinuous coating on the planar side such that the discontinuous coating is dimensioned and configured to partially overlap the dividing region.

2 . The method of claim 1 , wherein the discontinuous coating is dimensioned and configured such that a wafer bow induced by the anti-reflective coating is less than 30 microns.

3 . The method of claim 2 , wherein the wafer bow is less than 20 microns.

4 . The method of claim 1 , wherein the discontinuous coating is dimensioned and configured to extend beyond the at least one recessed region.

5 . The method of claim 1 , wherein the discontinuous coating is dimensioned and configured to correspond to saw streets on the cap wafer.

6 . The method of claim 1 , further comprising depositing a layer of an anti-reflective coating material in the recessed regions on the cavity side of the cap wafer to provide a discontinuous coating on the cavity side.

7 . The method of claim 6 , wherein the discontinuous coating on the planar side is dimensioned and configured such that a wafer bow induced by the anti-reflective coating is less than 30 microns.

8 . The method of claim 6 , wherein the discontinuous coating on the planar side is dimensioned and configured such that a wafer bow induced by the anti-reflective coating is in balance with a wafer bow induced by the anti-reflective coating on the cavity side.

9 . The method of claim 6 , further comprising providing a device wafer onto which at least one MEMS device is formed.

10 . The method of claim 9 , further comprising:
positioning the cap wafer over the device wafer such that the cavity side of the cap wafer is facing the at least one MEMS device; aligning the cap wafer to the device wafer such that the at least one recessed region is positioned over the at least one MEMS device; and bonding the cap wafer to the device wafer to create bonding structures.

11 . The method of claim 10 , further comprising inspecting the bonding structures through inspection regions provided by the discontinuous coating on the planar side of the cap wafer.

12 . The method of claim 11 , wherein the inspection is performed using a charge-coupled device (CCD).

13 . A method of reducing wafer bow induced by an anti-reflective coating on a cap wafer, the method comprising:
providing the cap wafer having a planar side and an opposing cavity side; depositing a first discontinuous layer of anti-reflective coating material onto the cavity side of the cap wafer; and depositing a second discontinuous layer of anti-reflective coating material onto the planar side of the cap wafer such that the second discontinuous coating is dimensioned differently than the first discontinuous coating.

14 . A cap wafer, comprising:
a planar side and an opposing cavity side; a first discontinuous layer of anti-reflective coating material disposed onto the cavity side; and a second discontinuous layer of anti-reflective coating material disposed onto the planar side such that the second discontinuous layer of anti-reflective coating material is dimensioned differently than the first discontinuous coating.

15 . The cap wafer of claim 14 , wherein the cavity side of the cap wafer includes a plurality of recessed regions and the first discontinuous layer of anti-reflective coating is disposed in the plurality of recessed regions.

16 . The cap wafer of claim 14 , wherein the dimensions of the second discontinuous layer of anti-reflective coating material are larger than the dimensions of the first discontinuous layer of anti-reflective coating material.

17 . The cap wafer of claim 14 , wherein the second discontinuous layer of anti-reflective coating corresponds to saw streets on the cap wafer such that the dimensions of the anti-reflective coating material extend to the saw streets.

Assignees

• Raytheon Co

Inventors

• Gooch Roland W
• Diep Buu Q
• Black Stephen H
• Kocian Thomas A
• Kennedy Adam M

Classifications

• B81C1/00325 Primary

  for reducing stress inside of the package structure · CPC title

• B81B2201/0207

  Bolometers · CPC title

• B81B7/0067

  for controlling the passage of optical signals through the package · CPC title

• B81C2203/0118

  Bonding a wafer on the substrate, i.e. where the cap consists of another wafer · CPC title

• B05D5/061

  Special surface effect · CPC title