Backside Deep Implantation for CMOS Image Sensor Substrate Damage
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Solution Overview
Problem
Current CMOS image sensor manufacturing processes face challenges with high energy deep implantation regions, leading to substrate damage, current leakage, dark current phenomena, and white pixel issues, which affect image quality and increase costs.
Innovation Solution
The method involves forming shallow implantation regions on one surface and deep implantation regions on the opposite surface of the substrate, reducing energy and dose, thereby minimizing substrate damage and improving image quality, throughput, and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high energy deep implantation regions are formed from the front surface, then deep well regions can be created, but substrate damage occurs leading to current leakage and dark current phenomena
Solution Approach 1:
The patent applies inversion by performing deep implantation from the back surface of the substrate instead of the front surface. This reverse approach allows high energy ions to reach deep well regions without damaging the front surface device structure, thereby creating deep implantation regions while avoiding substrate damage that would cause current leakage and dark current phenomena.
Solution Approach 2:
The patent segments the implantation process into two separate operations: shallow implantation from the front surface and deep implantation from the back surface. This segmentation allows each implantation to be optimized independently - shallow implantation creates precise doping near the device structure while deep implantation forms deep well regions without interfering with the front surface, thus avoiding substrate damage.
2Manufacturing precision
If high energy deep implantation is performed, then deep well regions are formed, but current leakage and dark current phenomena increase
Solution Approach 1:
By inverting the implantation direction and performing deep implantation from the back surface, the patent achieves deep well region formation without the harmful effects of front surface damage. This eliminates the root cause of current leakage and dark current phenomena while maintaining the required deep well region depth for device performance.
3Manufacturing precision
If high energy implantation is used, then deep implantation regions are achieved, but manufacturing costs increase
Solution Approach 1:
The patent divides the implantation process into two lower-energy steps performed from opposite surfaces. Instead of requiring one high-energy implantation step that damages the substrate and requires costly repair processes, the segmented approach uses two moderate-energy steps that together achieve the same deep implantation depth without damage, thereby reducing manufacturing costs.
4Manufacturing precision
If high energy implantation is performed, then deep regions are reached, but substrate damage reduces throughput
Solution Approach 1:
By segmenting the implantation into two independent lower-energy steps from opposite surfaces, the patent eliminates the need for costly and time-consuming substrate repair processes. Both shallow and deep implantation can be performed efficiently without causing damage that would require rework or scrap, thereby maintaining high manufacturing throughput while achieving deep implantation capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces current leakage and dark current phenomena, enhances image quality, increases manufacturing throughput, and simplifies the formation of implantation mask layers, facilitating the scaling down of semiconductor devices.
Implementation Method 1
A first implantation process is performed on the substrate from the first surface to form a first shallow implantation region in the substrate adjacent to the first surface
Data Source
AI summary
A semiconductor device includes a substrate and a device. The substrate has a first surface and a second surface opposite to each other. The substrate includes a first well region, and the first well region includes a first shallow implantation region adjacent to the first surface and a first deep implantation region adjacent to the second surface, in which a dopant concentration of the first deep implantation region at the second surface is substantially equal to 0. The device is disposed on the first surface of the substrate and adjoins the first shallow implantation region.