Method of fabricating image sensor dies and the like for use in assembling arrays

• US 5,219,796 A
• Filed: 11/04/1991
• Issued: 06/15/1993
• Est. Priority Date: 11/04/1991
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Quinn, Kraig A., Jedlicka, Josef E., Ormond, Brian T.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): TRINH, MICHAEL MANH
• Application Number:
  US07/787,444
• Time in Patent Office: 589 Days
• Field of Search: 437/229, 437/226, 437/227, 437/974, 437/66, 148/DIG. 135, 148/DIG. 28
• US Class Current: 438/68
• CPC Class Codes: H01L 21/304 Mechanical treatment, e.g. grinding, polishing, cutting H01L21/30625 takes precedence
• CPC Class Codes: H01L 21/78 with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y10S 148/028 Dicing

Abstract

An improved process for forming individual dies having faces that allow the dies to be assembled against other like dies to form one and/or two dimensional scanning arrays with minimal chipping and fracturing wherein the active side of a wafer is etched to form separation grooves with the wall of the grooves adjoining the die presenting a relatively wide surface to facilitate sawing, wide grooves are cut in the inactive side of the wafer opposite each separation grooves, and the wafer cut by sawing along the separation grooves, the saw being located so that the side of the saw blade facing the die is aligned with the midpoint of the wide wall so that on sawing the bottom half of the wall and the remainder of the grooves are obliterated leaving the top half of the wall to prevent cracking and chipping during sawing.

Claims

1. A method of fabricating a high resolution image sensor die from a <

100>

silicon wafer to form a precision face at each end of said die to enable said die to be abutted end-to-end with other like dies to form a longer array without image loss or distortion at the ends where said dies are abutted, comprising the steps of;

a) forming a first groove in one side of said wafer delineating where the die is to be separated from said wafer with the wall of said first groove next to the die being relatively wide and parallel to the <

111>

crystalline plane of said wafer;

b) forming a second groove in the opposite side of said wafer opposite said first groove with the axis of said second groove parallel to the axis of said first groove; and

c) sawing said wafer along said first groove with one edge of the cut made by sawing being nominally centered on said relatively wide wall of said first groove with said relatively wide wall allowing for misalignment of the cut made by sawing while providing a remaining wall section to prevent development of fractures in the die along the cut.

2. The method according to claim 1 including the step of:

forming said first groove so that said first groove is V-shaped.

3. The method according to claim 1 including the step of:

forming said first groove so that said first groove is V-shaped with said wall having substantially greater area than the remaining wall of said first groove.

4. The method according to claim 3 including the step of:

forming said first groove so that said remaining wall of said first groove is substantially perpendicular to said one side of said wafer.

5. A method of separating semiconductor image sensor dies from a larger wafer to provide dies with precision ends which enable the dies to be joined against one another end to end to form longer arrays without image loss or distortion at the points where the dies are joined, comprising the steps of:

a) forming V-shaped grooves having first and second intersecting sides on the surface of said wafer where said dies are to be separated from said wafer with said first side of said grooves bordering the die and having an area substantially larger than said second side of said grooves to facilitate cutting and separation of said dies from said wafer;

b) forming second grooves on the surface of said wafer opposite each of said first grooves, said second grooves being deeper than said first grooves and less than the thickness of said wafer, said second grooves being wider than said first grooves to facilitate assembly of said dies with other like dies; and

c) making a relatively wide cut through said wafer along said grooves with one edge of said cuts being at a point along a line substantially centered through said first side area to thereby avoid the need to exactly align said cut with a predetermined point in said grooves while producing a cut without fracturing of said wafer at said cut.

6. A method for producing photosensitive scanning dies having precisely controlled ends enabling one of the dies to be assembled against another of the dies to form a longer composite array without distortion or damage to the image scanning properties of the dies, the dies being cut from a larger <

100>

silicon wafer, comprising the steps of;

a) etching first grooves in one side of said wafer defining said die ends, the walls of said first grooves paralleling the <

111>

crystalline plane of said wafer;

b) forming relatively wide second groove in the opposite side of said wafer in association with each of said first grooves, the axis of each of said second grooves being parallel to the axis of said first groove associated therewith; and

c) cutting said dies from said wafer by sawing through said wafer at each of said first grooves with one edge of the cut made by sawing being substantially centered along the wall of said first grooves adjoining said die so that the remaining part of said wall together with the opposite wall of said first grooves are destroyed and fracturing and chipping thereof resulting from said sawing avoided so as to provide dies with uniform precise ends and without damage to active elements on said dies proximate said die ends.

7. A method for producing photosensitive scanning dies having precisely controlled ends enabling one of the dies to be assembled against another of the dies to form a longer composite array without distortion or damage to the image scanning properties of the dies, the dies being cut from a larger <

100>

silicon wafer, comprising the steps of;

a) forming first grooves in one side of said wafer defining said die ends with at least the wall of said first grooves that adjoining the dies being parallel to the <

111>

crystalline plane of said wafer;

b) forming second grooves in the opposite side of said wafer in association with each of said V-shaped grooves, the axis of each of said second grooves being parallel to the axis of said V-shaped groove associated therewith;

c) cutting said dies from said wafer by sawing through said wafer at each of said V-shaped grooves to provide a cut substantially wider than the width of said V-shaped grooves; and

d) locating said cut so that the edge of said cut closest to said dies is substantially aligned with the midpoint of said wall whereby said cut removes part of said wall together with the opposite wall of said V-shaped grooves to reduce fracturing and chipping resulting from said sawing and provide dies with uniform precise ends.

8. The method according to claim 7 including the step of:

forming said first grooves so that said wall provides a substantially larger area than said opposite wall whereby to facilitate locating said cut.

9. The method according to claim 7 including the step of:

forming said first grooves so that said opposite wall is substantially perpendicular to said one side of said wafer.

10. The method according to claim 7 including the step of:

repeating steps a-d at the opposite end of said dies.

11. A method of separating semiconductor image sensor dies from a larger wafer to provide dies with precision ends which enable the dies to be joined against one another end to end to form longer composite array without image loss or distortion at the points where the dies are joined, comprising the steps of:

a) non-mechanically forming V-shaped grooves on the surface of said wafer where said dies are to be separated from said wafer, said V-shaped grooves having first and second intersecting walls;

b) mechanically forming second grooves on the surface of said wafer opposite each of said V-shaped grooves to facilitate separating individual dies from said wafer, said second grooves being deeper than said V-shaped grooves, said second grooves being wider than said V-shaped grooves; and

c) mechanically cutting through said wafer along said V-shaped grooves with one edge of the cut being substantially aligned with the midpoint of said first wall of said V-shaped grooves,

the width of said cut being greater than the width of said V-shaped grooves whereby substantially one half of said first wall of said V-shaped grooves together with said second wall of said V-shaped grooves are removed by said cut while the remaining substantially one half of said first wall of said V-shaped grooves remains substantially intact whereby said cut separates said individual dies from said wafer with the ends of said dies being smooth and undistorted.

12. The method according to claim 11 including the step of mechanically forming said second grooves by sawing.

13. The method according to claim 11 including the step of non-mechanically forming said V-shaped grooves by anisotropic etching.

14. The method according to claim 11 including the steps of:

providing a <

100>

silicon for said wafer; and

forming at least said first wall of said V-shaped grooves so that said first wall is parallel to the <

111>

plane of said wafer.

15. The method according to claim 14 including the step of:

forming said second wall of said V-shaped grooves perpendicular to the surface of said wafer.