SOI Device Non-Oxidizing Thermal Treatment for BOX Uniformity
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Solution Overview
Problem
In semiconductor-on-insulator (SOI) devices, particularly ultra-thin body and buried oxide (UTBB) devices, the BOX layer thickness is undesirably increased during silicon germanium p-channel formation, leading to non-uniform thickness and increased threshold voltage due to oxidation protrusions, which affects device performance.
Innovation Solution
A method involving a rapid thermal anneal in a non-oxidizing atmosphere to diffuse germanium into the silicon layer, followed by a wet etch to control the depth and prevent oxidation, replacing traditional rapid thermal oxidation to minimize BOX layer oxidation and maintain a planar surface, allowing for a non-linear diffusion profile and reduced BOX thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rapid thermal oxidation is used to form silicon germanium p-channel, then germanium diffusion into silicon layer is achieved, but BOX layer thickness increases and becomes non-uniform due to oxidation protrusions
Solution Approach 1:
The patent applies an inert atmosphere (nitrogen or forming gas) during the thermal annealing process to prevent oxidation of the BOX layer. This inert environment allows germanium to diffuse into the silicon layer while forming p-channel, without causing oxidation protrusions that would increase BOX layer thickness and create non-uniformity. The inert atmosphere replaces the oxidizing environment of traditional rapid thermal oxidation, eliminating the harmful oxidation effect while maintaining the beneficial germanium diffusion.
2Reliability
If traditional rapid thermal oxidation is used, then germanium diffusion occurs, but threshold voltage increases due to increased BOX thickness
Solution Approach 1:
By using an inert atmosphere during thermal processing, the patent prevents oxidation-induced thickening of the BOX layer. This maintains the original BOX thickness and prevents the increase in threshold voltage that would otherwise occur. The inert environment decouples the germanium diffusion process from oxidation, allowing independent control of these two parameters.
Solution Approach 2:
The patent changes the atmospheric composition parameter from oxidizing to inert, which fundamentally alters the thermal processing outcome. This parameter change allows the process to achieve germanium diffusion without the side effect of BOX layer oxidation and thickening, thereby maintaining threshold voltage control.
3Manufacturing precision
If non-oxidizing thermal treatment is used, then BOX layer oxidation is reduced, but process time may increase
Solution Approach 1:
The use of inert atmosphere enables a more efficient thermal process that achieves the desired germanium diffusion and p-channel formation without the time-consuming need to control and remove oxidation protrusions. The process can proceed directly to completion without additional steps to correct oxidation damage, potentially reducing overall process time despite the different atmospheric conditions.
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 reduces BOX layer oxidation, facilitating next-generation scaling by maintaining a uniform BOX thickness and reducing threshold voltage variations, enabling improved performance and scalability for UTBB devices.
Implementation Method 1
performing a thermal treatment in a non-oxidizing atmosphere to diffuse the second semiconductor material into the first semiconductor layer
Implementation Method 2
removing the second semiconductor layer may comprise removing the second semiconductor layer using a wet etch
Implementation Method 3
performing a thermal treatment in an oxidizing atmosphere prior to removing the second semiconductor layer
Data Source
AI summary
A method for making a semiconductor device may include forming, on a first semiconductor layer of a semiconductor-on-insulator (SOI) wafer, a second semiconductor layer comprising a second semiconductor material different than a first semiconductor material of the first semiconductor layer. The method may further include performing a thermal treatment in a non-oxidizing atmosphere to diffuse the second semiconductor material into the first semiconductor layer, and removing the second semiconductor layer.