CMOS Mesa Structure for Crystallographic Orientation
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Solution Overview
Problem
Current CMOS devices face challenges in achieving enhanced performance by fabricating complementary p-FET and n-FET transistors with different semiconductor substrate channel crystallographic orientations on a single substrate, while maintaining low energy consumption and ease of fabrication.
Innovation Solution
The solution involves creating semiconductor structures with pairs of mesas within a substrate, where each mesa has a specific ratio of channel effective horizontal to vertical surface area, allowing transistors to benefit from optimized crystallographic orientations, with one mesa having a vertical orientation and the other a horizontal orientation, and using these orientations to enhance transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different crystallographic orientations are used for p-FET and n-FET channels, then charge carrier mobility and transistor performance are improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The semiconductor substrate is divided into multiple regions, each with different crystallographic orientations (e.g., <100> for n-FETs and <110> for p-FETs). This segmentation allows each transistor type to benefit from its optimal orientation while maintaining a single substrate structure, resolving the contradiction between performance improvement and device complexity.
Solution Approach 2:
Different local regions of the substrate are assigned different crystallographic orientations tailored to specific transistor types. The <100> orientation is localized to n-FET channel regions while <110> orientation is localized to p-FET channel regions, enabling locally optimized performance without requiring the entire device to be complex.
2Reliability
If multiple crystallographic orientations are integrated on a single substrate, then individually optimized performance of p-FETs and n-FETs is achieved, but manufacturing complexity increases
Solution Approach 1:
The substrate is segmented into distinct orientation domains that can be fabricated using standard CMOS processes. By dividing the substrate into <100> and <110> regions, the patent enables individually optimized transistor performance while maintaining compatibility with existing manufacturing techniques, thus improving ease of manufacture compared to requiring entirely new fabrication approaches.
Solution Approach 2:
A single semiconductor substrate performs multiple functions by accommodating different crystallographic orientations for different transistor types. The substrate simultaneously supports n-FETs with <100> orientation and p-FETs with <110> orientation, eliminating the need for separate substrates or specialized fabrication processes and thereby improving ease of manufacture.
3Reliability
If vertical crystallographic orientation is used for one device and horizontal for another, then charge carrier mobility is enhanced for each device type, but fabrication process complexity increases
Solution Approach 1:
The channel regions are segmented into vertical and horizontal crystallographic orientations based on device type. Vertical orientation (<110>) is assigned to p-FET channels while horizontal orientation (<100>) is assigned to n-FET channels, enabling enhanced charge carrier mobility for each device type while using standard segmentation techniques that do not significantly increase fabrication process complexity.
Data Source
AI summary
A complementary metal oxide semiconductor (CMOS) structure includes a semiconductor substrate having first mesa having a first ratio of channel effective horizontal surface area to channel effective vertical surface area. The CMOS structure also includes a second mesa having a second ratio of the same surface areas that is greater than the first ratio. A first device having a first polarity uses the first mesa as a channel and benefits from the enhanced vertical crystallographic orientation. A second device having a second polarity different from the first polarity uses the second mesa as a channel and benefits from the enhanced horizontal crystallographic orientation.