Selective Etch Layer for Monolithic Semiconductor Integration
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Solution Overview
Problem
Monolithic heterogeneous integration of compound semiconductors with elemental semiconductors faces challenges such as limited process control and repeatability in etching windows, impact of growth temperatures on CMOS device parameters, reliability issues due to non-native substrates, layer cross-contamination, and difficulties in CMOS to CS interconnect fabrication.
Innovation Solution
A selective etch layer, such as aluminum oxide or aluminum nitride, is introduced between the elemental semiconductor device and the compound semiconductor device, enabling precise control of the etching process to minimize additional buried oxide thickness, thereby improving vertical and lateral window etch control and reducing defects in compound semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a selective etch layer is introduced between the elemental semiconductor device and the compound semiconductor device, then vertical and lateral window etch control is improved, but device structure complexity increases
Solution Approach 1:
A selective etch layer (aluminum oxide or aluminum nitride) is introduced as an intermediary layer between the elemental semiconductor device layer and the compound semiconductor device layer. This intermediary layer provides precise control over the etching process by being selectively removable, enabling accurate definition of vertical and lateral window boundaries while managing the complexity through its specific functional role in the heteroepitaxial growth process
Solution Approach 2:
The buried oxide layer is segmented into multiple portions with different thicknesses, where a first portion remains beneath the selective etch layer and a second portion is removed to form the window. This segmentation allows differential etching control, enabling precise window formation while maintaining structural integrity in other regions, thus improving manufacturing precision without proportionally increasing overall device complexity
2Productivity
If additional buried oxide thickness is minimized, then spacing between CMOS and CS devices is reduced, but etch process control becomes more difficult
Solution Approach 1:
The buried oxide layer is divided into a first portion and a second portion, where the first portion is retained beneath the selective etch layer and the second portion is selectively removed to form the window. This segmentation enables precise control of the etching process by providing a structured approach to removing minimal oxide thickness, allowing tight device spacing while maintaining etch process control through the organized removal sequence
Solution Approach 2:
The selective etch layer serves as an intermediary that mediates between the requirement for minimal buried oxide thickness and the need for etch process control. By positioning this layer between the elemental semiconductor device and the compound semiconductor device, it enables the etching process to proceed with precise control over the minimal oxide removal, achieving both tight spacing and process control
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 enhances process control and repeatability during SOI manufacture and CS growth, reducing defects and maintaining minimal spacing between CMOS and CS devices, leading to improved reliability and performance of compound semiconductor devices.
Implementation Method 1
A selective etch layer, such as aluminum oxide or aluminum nitride, is introduced between the elemental semiconductor device and the compound semiconductor device, enabling precise control of the etching process to minimize additional buried oxide thickness
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 2A~2C
AI summary
A semiconductor structure having compound semiconductor (CS) device formed in a compound semiconductor of the structure and an elemental semiconductor device formed in an elemental semiconductor layer of the structure. The structure includes a layer having an elemental semiconductor device is disposed over a buried oxide (BOX) layer. A selective etch layer is disposed between the BOX layer and a layer for a compound semiconductor device. The selective etch layer enables selective etching of the BOX layer to thereby maximize vertical and lateral window etch process control for the compound semiconductor device grown in etched window. The selective etch layer has a lower etch rate than the etch rate of the BOX layer.