Deep Etch Layout for Transistors With Varying Pitch
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Solution Overview
Problem
Forming large arrays of semiconductor devices with varying pitches poses challenges, as inconsistent etch depths due to differing diffusion region widths can lead to unintended performance issues and complicate back-end-of-the-line processing.
Innovation Solution
Techniques are developed to maintain substantially similar depth for epitaxial trenches between semiconductor regions, using a masking procedure to adjust the etch depth of wider diffusion regions, ensuring consistent etching across devices with different pitches, and employing dielectric materials to manage the step profile of diffusion regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single etching process is used to form diffusion regions across devices with varying pitches, then the manufacturing process is simple, but the etch depths become inconsistent causing performance issues
Solution Approach 1:
The etching process is divided into two sequential steps: a first etching process that etches wider diffusion regions to a first depth, and a second etching process that etches narrower diffusion regions to a second depth. This segmentation allows each etching step to be optimized for specific pitch ranges, achieving consistent etch depths across devices with varying pitches while maintaining process manageability.
2Ease of manufacture
If diffusion regions with different widths are etched to the same depth, then back-end processing is simplified, but wider regions experience excessive etching damage
Solution Approach 1:
Different etch depths are applied to different local regions based on their pitch characteristics. Wider diffusion regions (smaller pitch) are etched to a first depth that minimizes etch damage, while narrower diffusion regions (larger pitch) are etched to a second depth that ensures adequate exposure. This local differentiation allows each region to receive the precise etching depth it needs, reducing overall etch damage while maintaining back-end processing simplicity.
Data Source
AI summary
Techniques are provided herein to form semiconductor devices having different pitches, yet maintaining a substantially similar depth to the diffusion regions between the semiconductor regions. In an example, a row of semiconductor devices having semiconductor regions extending in a first direction can include some devices having a diffusion region with a first width in the first direction and some devices having a diffusion region with a second width in the first direction, where the second width is different from the first width. The depths of the diffusion regions having both the first and second widths may be substantially similar (e.g., within 2 nm or less of one another). In some examples, the bottom surface of at least one of the wider diffusion regions has a step profile.