Tilted Ion Implantation Mask for Multi-Depth Substrate Doping
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Solution Overview
Problem
Conventional multistep lithography methods for achieving different implant depths in substrates are costly and result in indirect alignment of implant areas, leading to reduced device performance and increased costs, while grey-tone lithography lacks accuracy in vertical resist patterning.
Innovation Solution
A method involving a tilted implantation process using an implant mask with a first implant zone as an opening and a second implant zone as a block array, where the implant species is implanted under an angle that allows it to pass through less mask material in the block array regions than in non-structured regions, achieving different implant depths with improved accuracy and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multistep lithography is used to achieve different implant depths, then implant depth control is possible, but device area increases and performance is limited due to indirect alignment
Solution Approach 1:
The patent transitions from controlling implant depth through multiple lateral lithography steps to a single lateral step combined with vertical mask thickness variation. By patterning the resist in the vertical dimension (creating different mask thicknesses), the method achieves different implant depths through one lithography process, eliminating indirect alignment issues and reducing device area.
2Manufacturing precision
If multistep lithography is used to achieve different implant depths, then implant depth control is possible, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple lithography steps and implantation processes into a single integrated process. By using a single lithography step to create a mask with varying vertical thickness, followed by a single tilted implantation, the method eliminates the need for multiple separate lithography and implantation cycles, thereby reducing manufacturing cost while maintaining implant depth control.
3Measurement precision
If grey-tone lithography is used to reduce implant depth selectively, then alignment accuracy is improved, but vertical resist patterning accuracy is insufficient
Solution Approach 1:
The patent changes the controlling parameter from lateral resist thickness variation (grey-tone lithography) to vertical mask thickness variation. By tilting the implantation and using a mask with controlled vertical thickness differences, the method achieves precise depth control through the geometric relationship between mask thickness and implant angle, rather than relying on difficult-to-control vertical resist patterning.
4Ease of manufacture
If a single lithography step with tilted implantation and block array mask is used, then manufacturing cost is reduced, but implant depth precision must be maintained
Solution Approach 1:
The patent applies local quality by creating different mask thicknesses in different regions of the mask. The block array regions have reduced thickness compared to non-structured regions, allowing the implant species to reach different depths in different areas. This local variation in mask properties enables precise depth control while using a single lithography step.
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 allows for precise control of implant depths with reduced costs and improved device performance by eliminating the need for multiple lithography steps and enhancing the accuracy of vertical resist patterning, similar to grey-tone lithography but with better control and wider material compatibility.
Implementation Method 1
a method of implanting an implant species into a substrate at different depths
Data Source
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AI summary
A method of implanting an implant species into a substrate at different depths is described. The method includes forming an implant mask over the substrate. The implant mask includes a first implant zone designed as an opening and a second implant zone designed as a block array. The implant species is implanted through the implant mask under an implant angle tilted against a block plane. Thereby, a first implant area is formed by the implant species at a first depth in the substrate beneath the first implant zone, and a second implant area is formed by the implant species at a second depth in the substrate beneath the second implant zone. The first depth is greater than the second depth.