SiGe Layer Etching Uniformity via Ge Content Gradient
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Solution Overview
Problem
Current methods for selective etching of SiGe layers in multiple stacked alternating --Si--[(SiGe)--Si]u-- layers result in non-uniformity, leading to uncontrollable devices and dysfunctional circuits due to non-uniform stress distribution.
Innovation Solution
Compensating for stress effects by incrementally increasing the Ge content in successive SiGe layers to enhance etch rate uniformity, using etchants like CF4, O2, Ar, and adjusting Ge concentration to maximize selectivity and minimize mechanical stress, while employing reactive ion plasma etching or oxidizing chemistry for selective removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective etching of SiGe layers is performed using conventional methods, then SiGe layers can be removed, but non-uniformity in etching depth occurs due to non-uniform stress distribution
Solution Approach 1:
The patent applies local quality by varying the Ge content in different SiGe layers to compensate for non-uniform stress distribution. Specifically, SiGe layers with higher Ge content are placed in regions experiencing higher stress to maintain uniform etching rates across all layers, thereby achieving uniform etching depth and reliable device characteristics
Solution Approach 2:
The patent changes the compositional parameter (Ge content) of SiGe layers to control stress distribution and etching behavior. By adjusting the Ge concentration in different layers, the patent optimizes both the stress state and etch rate to achieve uniform etching depth across multiple stacked layers
2Productivity
If Ge content is increased in SiGe layers to enhance etch rate, then etching speed improves, but mechanical stress in the layer stack increases
Solution Approach 1:
The patent applies local quality by strategically varying the Ge content in different SiGe layers based on their position in the stack. Layers experiencing higher stress are assigned higher Ge content to reduce stress, while maintaining overall etch rate uniformity. This localized optimization balances etching speed and stress management
Solution Approach 2:
The patent changes the Ge content parameter across different SiGe layers to simultaneously control both etch rate and stress. By optimizing the Ge concentration gradient, the patent achieves uniform etching depth while managing mechanical stress within acceptable limits
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
Achieves uniform removal of sacrificial SiGe layers, reducing etching depth variations and ensuring functional multichannel FET devices by optimizing Ge content and etching processes, thereby improving device performance and reliability.
Implementation Method 1
selective etching of SiGe layers in multiple stacked alternating --Si--[(SiGe)--Si]u-- layers
Implementation Method 2
non-uniform stress distribution in the layer stack
Implementation Method 3
employing reactive ion plasma etching or oxidizing chemistry for selective removal
Implementation Method 4
employing reactive ion plasma etching or oxidizing chemistry for selective removal
Data Source
AI summary
An intermediate product in the manufacture of a vertical multiple-channel FET device containing alternating —Si—[(SiGe)—Si]u- stacked layers is shown, as well as a process for selectively etching the SiGe layers in such a stacked layer system, and products obtained from such selective etching. Differential Ge content is added to the successive layers to provide uniform removal of the sacrificial SiGe layers.