Photomask Shift Patterning for Dense Semiconductor Pitch Reduction
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Solution Overview
Problem
Conventional multi-patterning processes for semiconductor devices require multiple photomasks, increasing costs and complexity, especially for achieving dense patterns with pitches smaller than lithographic resolution.
Innovation Solution
A litho-etch-litho-etch (LELE) process using a single photomask, where the photomask is shifted during the second litho-etch process to reduce the pitch of the patterned target layer, allowing for pitch reduction without the need for additional photomasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photomasks are used for multi-patterning, then pitch reduction is achieved, but manufacturing cost increases
Solution Approach 1:
The patent segments the patterning process into multiple litho-etch cycles (LELE), where a single photomask is reused across different exposure steps. By dividing the pitch reduction task across sequential processing stages rather than requiring multiple masks simultaneously, the method achieves fine pitch control while reducing mask-related costs
Solution Approach 2:
The photomask is prepared with a specific pattern configuration before the patterning process begins. The mask position and pattern are predetermined to enable the desired pitch reduction when used in the LELE sequence, allowing the single mask to perform multiple patterning functions through pre-planned positioning and exposure strategies
2Manufacturing precision
If multiple photomasks are used for multi-patterning, then dense patterns are formed, but process complexity increases
Solution Approach 1:
The complex task of forming dense patterns is segmented into manageable litho-etch cycles. Each cycle uses the same photomask but produces different pattern features through controlled exposure and etching parameters. This segmentation simplifies the overall process by reusing the mask rather than coordinating multiple different masks
Solution Approach 2:
A single photomask is designed to serve multiple functions across different exposure steps. The same mask pattern is used in the first litho-etch cycle and again in subsequent cycles, with the mask's position and exposure conditions varied to create different pattern features. This multi-functionality reduces process complexity by eliminating the need to manage multiple specialized masks
Data Source
AI summary
The embodiments of the disclosure provide a patterning method, which includes the following processes. A target layer is formed on a substrate. A hard mask layer is formed over the target layer. A first patterning process is performed on the hard mask layer by using a photomask having a first pattern with a first pitch. The photomask is shifted along a first direction by a first distance. A second patterning process is performed on the hard mask layer by using the photomask that has been shifted, so as to form a patterned hard mask. The target layer is patterned using the patterned hard mask to form a patterned target layer. The target layer has a second pattern with a second pitch less than the first pitch.