Etch Stop Layer for Dual Crystal Orientation Semiconductor Devices
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Solution Overview
Problem
The existing methods for making dual orientation semiconductor devices often result in surface damage during dry etching through the buried oxide layer, leading to defects in the selective Si epitaxy process and subsequent device performance.
Innovation Solution
Incorporating a dielectric etch stop layer between the buried oxide and the substrate to act as an etch stop, allowing for selective etching that minimizes surface damage, enabling high-quality epitaxial growth with minimal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is used to etch through the BOX layer to access the bottom substrate, then the alternate Si plane is accessed, but surface damage is induced on the bottom substrate which negatively impacts selective Si epitaxy and creates dislocations
Solution Approach 1:
A new BOX layer is introduced as an intermediary between the original BOX and the substrate. This intermediate BOX layer absorbs the etching damage, preventing it from reaching the substrate surface. The new BOX layer serves as a sacrificial buffer that protects the substrate during the dry etching process while still allowing access to the alternate crystal orientation when the new BOX is selectively removed.
Solution Approach 2:
The new BOX layer is deposited beforehand as a protective cushion layer. This pre-deposited layer anticipates and prevents the harmful effects of etching damage before they can reach the substrate. By having this protective layer in place prior to etching, the substrate surface is shielded from damage that would otherwise occur during the etching process.
2Adaptability or versatility
If the bottom substrate is accessed directly by etching through BOX, then dual orientation is achieved, but defects are introduced into the channel epi reducing device performance
Solution Approach 1:
The new BOX layer acts as a mediator that enables access to the bottom substrate for dual orientation functionality while simultaneously protecting against defect formation. This intermediary layer allows the system to achieve both crystal orientations needed for device versatility without compromising the reliability of the channel epi region.
Solution Approach 2:
The BOX structure is segmented into two distinct layers: the original BOX layer and the newly deposited BOX layer. This segmentation allows selective etching of the new BOX layer to access the substrate for dual orientation, while the original BOX layer remains intact to provide continuous protection and prevent defect formation in the channel region.
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 prevents surface damage during etching, resulting in high-quality semiconductor devices with enhanced electron and hole mobility in multiple crystal orientations, improving the performance of subsequently formed devices.
Implementation Method 1
Incorporating a dielectric etch stop layer between the buried oxide and the substrate to act as an etch stop, allowing for selective etching that minimizes surface damage
Implementation Method 2
enabling high-quality epitaxial growth with minimal defects
Data Source
AI summary
A method of having transistors formed in enhanced performance crystal orientations begins with a wafer having a semiconductor substrate (12,52) of a first surface orientation, a thin etch stop layer (14,54) on the semiconductor substrate, a buried oxide layer (16,56) on the thin etch stop layer, and a semiconductor layer (18,58) of a second surface orientation on the buried oxide layer. An etch penetrates to the thin etch stop layer. Another etch, which is chosen to minimize the damage to the underlying semiconductor substrate, exposes a portion of the semiconductor substrate. An epitaxial semiconductor (28,66) is then grown from the exposed portion of the semiconductor substrate to form a semiconductor region having the first surface orientation and having few, if any, defects. The epitaxially grown semiconductor region is then used for enhancing one type of transistor while the semiconductor layer of the second surface orientation is used for enhancing a different type of transistor.