CN-122002926-A - Preparation method of back-illuminated image sensor

CN122002926ACN 122002926 ACN122002926 ACN 122002926ACN-122002926-A

Abstract

The application provides a preparation method of a backside illuminated image sensor, which is characterized in that after a first substrate is subjected to a first cutting treatment and before the first substrate and a second substrate are bonded, a step supplementing layer is formed on the side surface of a first step, the upper surface and the side surface of a second step and the upper surface of a third step in a three-level step structure of the edge of the first substrate, so that the upper surface of the step supplementing layer on the second step and the upper surface of the first step are flush, the contour and the appearance of the edge of the first substrate are optimized, and a gap is not reserved between the edge of a logic area on the first substrate and the edge of the second substrate after the first substrate and the second substrate are bonded, thereby avoiding the situation of edge breakage caused in the second cutting treatment of the first substrate, ensuring the number of effective Die of the edge of the first substrate and improving the yield of products.

Inventors

WANG RANRAN
ZHAO ZHENGYUAN
CAO MIN
ZHANG SHUO
YANG LINLIN
HUI KESHI
LI YUANHAO
TAN JUAN
LI CHUANYU
ZHANG SHOULONG

Assignees

华虹半导体(无锡)有限公司
华虹半导体制造(无锡)有限公司

Dates

Publication Date: 20260508
Application Date: 20260107

Claims (10)

1. A method for manufacturing a backside illuminated image sensor, comprising: Providing a first substrate, wherein the first substrate comprises a pixel area and a logic area positioned at the periphery of the pixel area, and at the moment, a circle of annular concave is formed at the edge of the first substrate; Performing first cutting treatment on the first substrate to remove a first substrate with partial thickness at the bottom of the annular recess, wherein the edge of the first substrate forms a three-stage step structure, the three-stage step structure comprises a first stage step, a second stage step and a third stage step, the first stage step, the second stage step and the third stage step are sequentially arranged from top to bottom, the edge of the logic area is the first stage step, the bottom wall of the annular recess is the second stage step, and the first substrate with the residual thickness at the bottom of the annular recess is the third stage step; Forming a step supplementing layer, wherein the step supplementing layer covers the side surface of a first step, the upper surface and the side surface of a second step and the upper surface of a third step in the three-step structure, and the upper surface of the step supplementing layer on the second step is flush with the upper surface of the first step; forming a first bonding layer covering the pixel region, the logic region and a step supplement layer at the edge of the first substrate on the first substrate; providing a second substrate, wherein a second bonding layer is formed on the second substrate; inverting the first substrate after forming a first bonding layer and bonding the first bonding layer with the second bonding layer on the second substrate; Thinning the first substrate from the back surface of the first substrate; and performing a second cutting process on the first substrate to remove part of the step supplementing layer and part of the first bonding layer at the edge of the first substrate from the back surface of the first substrate.
2. The method for manufacturing a backside illuminated image sensor according to claim 1, wherein the step supplement layer is made of silicon dioxide.
3. The method of manufacturing a backside illuminated image sensor according to claim 1 or 2, wherein the step-supplementing layer is formed by a plasma-enhanced chemical vapor deposition process.
4. The method for manufacturing a backside illuminated image sensor according to claim 3, wherein in the step-supplementing layer is formed by a plasma-enhanced chemical vapor deposition process, precursors are silane and N 2 O, wherein the flow rate of silane is more than 0sccm and less than or equal to 300sccm, the flow rate of N 2 O is more than 0sccm and less than or equal to 2000sccm, the process temperature is 250-350 ℃, and the process duration is 10 s-200 s.
5. The method of manufacturing a backside illuminated image sensor according to claim 1, wherein after forming the first bonding layer and before providing the second substrate, the method of manufacturing a backside illuminated image sensor further comprises: and grinding and removing the first bonding layer of partial thickness of the pixel area and the upper surface of the logic area on the first substrate so as to planarize the first bonding layer.
6. The method of manufacturing a backside illuminated image sensor according to claim 1, wherein the depth of the annular recess is not more than 2 μm and the minimum lateral dimension of the annular recess is greater than 1.3mm.
7. The method of manufacturing a backside illuminated image sensor according to claim 1, wherein a ring cut width is smaller than a minimum lateral dimension of the annular recess during the first dicing process of the first substrate, and a ring cut depth is at least 150 μm.
8. The method for manufacturing a backside-illuminated image sensor according to claim 1, the bonding layer is characterized in that the material of the first bonding layer is silicon dioxide.
9. The method for manufacturing a backside-illuminated image sensor according to claim 1, the bonding layer is characterized in that the material of the second bonding layer is silicon dioxide.
10. The method of claim 1, wherein the first bonding layer is bonded to the second bonding layer on the second substrate using a van der waals bonding process.

Description

Preparation method of back-illuminated image sensor Technical Field The application relates to the technical field of semiconductor manufacturing, in particular to a preparation method of a back-illuminated image sensor. Background Conventional Image Sensors (CIS) employ a front-side illuminated (FSI) process, in which light needs to pass through metal wiring before passing through a photosensitive area. However, in the back-illuminated (BSI) process, the wafer is turned over, so that the absorption and loss of metal wiring to light are reduced, the light input amount of unit pixels is increased, the light sensing amount is increased, the light sensing capability of the CIS in a low light environment is greatly improved, and specifically, in the back-illuminated process, the device wafer and the carrier wafer are combined together through a bonding process, and the CIS is prepared through processes of ring cutting/cutting (Trim), multiple back thinning and the like. In the cutting (2 nd Trim) process after bonding of two wafers, rough areas of the edges of the device wafers after wet thinning are cut off, the quality and stability of the device wafers in the back-illuminated image sensor are improved, and the performance and reliability of the final product are ensured. However, in actual situations, the appearance/profile of the edge of the device wafer is poor, so that the edge area of the device wafer and the edge area of the carrier wafer cannot be effectively combined together during bonding, and a gap exists between the edge area of the device wafer and the edge area of the carrier wafer, so that edge breakage (chipping) is easily caused in the cutting (2 nd Trim) process after bonding of two wafers, the number of effective Die at the edge of the device wafer is affected, and the yield of products is reduced. Disclosure of Invention The application provides a preparation method of a back-illuminated image sensor, which can solve the problems that in the preparation process of the back-illuminated image sensor, edge breakage is caused in the circular cutting process after bonding of a device wafer and a carrier wafer, the number of effective Die at the edge of the device wafer is affected, and the yield of products is reduced. The embodiment of the application provides a preparation method of a back-illuminated image sensor, which comprises the following steps: Providing a first substrate, wherein the first substrate comprises a pixel area and a logic area positioned at the periphery of the pixel area, and at the moment, a circle of annular concave is formed at the edge of the first substrate; Performing first cutting treatment on the first substrate to remove a first substrate with partial thickness at the bottom of the annular recess, wherein the edge of the first substrate forms a three-stage step structure, the three-stage step structure comprises a first stage step, a second stage step and a third stage step, the first stage step, the second stage step and the third stage step are sequentially arranged from top to bottom, the edge of the logic area is the first stage step, the bottom wall of the annular recess is the second stage step, and the first substrate with the residual thickness at the bottom of the annular recess is the third stage step; Forming a step supplementing layer, wherein the step supplementing layer covers the side surface of a first step, the upper surface and the side surface of a second step and the upper surface of a third step in the three-step structure, and the upper surface of the step supplementing layer on the second step is flush with the upper surface of the first step; forming a first bonding layer covering the pixel region, the logic region and a step supplement layer at the edge of the first substrate on the first substrate; providing a second substrate, wherein a second bonding layer is formed on the second substrate; inverting the first substrate after forming a first bonding layer and bonding the first bonding layer with the second bonding layer on the second substrate; Thinning the first substrate from the back surface of the first substrate; and performing a second cutting process on the first substrate to remove part of the step supplementing layer and part of the first bonding layer at the edge of the first substrate from the back surface of the first substrate. Optionally, in the method for manufacturing a backside illuminated image sensor, the step supplementing layer is made of silicon dioxide. Optionally, in the method for manufacturing the backside illuminated image sensor, the step supplementing layer is formed by adopting a plasma enhanced chemical vapor deposition process. Optionally, in the preparation method of the back-illuminated image sensor, in the process of forming the step-supplementing layer by adopting a plasma-enhanced chemical vapor deposition process, the precursors are silane and N 2 O, wherein the flow of the silane is more than 0scc