Semiconductor Gettering Region via Ion Implantation
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Solution Overview
Problem
Current semiconductor wafer cleaning methods are inadequate in preventing the diffusion of contaminants, such as metal atoms, into the wafer, which can affect the operation of electrical devices, particularly in power semiconductor devices like MOSFETs, leading to changes in operation voltage and potential device failure.
Innovation Solution
A method is introduced to form a gettering region in the semiconductor wafer substrate by implanting ions, specifically hydrogen or helium ions, to create intrinsic point defect complexes that decorate with hydrogen, forming a stable gettering layer effective in trapping contaminants, thereby preventing their diffusion into the device region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wafer cleaning methods are used, then the wafer surface is cleaned, but contaminants still diffuse into the wafer from solder layers, metallization layers, or bonding substrates
Solution Approach 1:
The patent applies preliminary action by forming the polysilicon gettering layer on the wafer back side before thinning and device fabrication processes. This layer is positioned to intercept contaminants before they can diffuse into the wafer bulk, preventing contamination rather than removing it after diffusion occurs.
Solution Approach 2:
The polysilicon layer serves as an intermediary gettering medium between the external environment (solder layers, metallization, bonding substrates) and the wafer interior. It captures heavy metal contaminants through segregation and trapping mechanisms, acting as a barrier that protects the wafer from direct contamination.
2Reliability
If a polysilicon layer is applied over the wafer back side for extrinsic gettering, then contaminant trapping is improved, but the polysilicon layer is prone to oxidation during processing and must be completely removed during wafer thinning
Solution Approach 1:
The patent extracts the problematic oxidation issue by removing the polysilicon layer after it has fulfilled its gettering function. The layer is deliberately designed to be temporary and removable, separating the gettering function from the final device structure. This allows the use of polysilicon for its excellent gettering properties without suffering from its oxidation vulnerability in the final product.
Solution Approach 2:
The polysilicon gettering layer is discarded after serving its purpose of capturing contaminants during processing. Its removal is intentional and necessary to prevent oxidation-related issues in the final device, while the benefits of contaminant trapping are retained in the wafer bulk where the contaminants were sequestered.
3Reliability
If a polysilicon layer is used for gettering, then heavy metal trapping is enhanced, but it is difficult to obtain suitable polysilicon layers from basic material suppliers for large diameter wafers
Solution Approach 1:
The patent replaces the mechanical/material challenge of obtaining large-diameter polysilicon layers from suppliers with an in-situ deposition process. By depositing the polysilicon layer directly on the wafer using standard semiconductor fabrication techniques, the invention bypasses the limitation of material supplier capabilities and enables the use of large-diameter wafers with effective gettering layers.
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
The gettering region effectively captures metal contaminants, reducing leakage currents and maintaining the mobility of free charge carriers, thus minimizing on-state power losses and ensuring the reliability of power semiconductor devices.
Implementation Method 1
implanting ions into the doped substrate region to form a gettering region
Implementation Method 2
form a gettering region in the doped substrate region of the semiconductor carrier
Data Source
AI summary
A method for processing a semiconductor carrier is provided, the method including: providing a semiconductor carrier including a doped substrate region and a device region disposed over a first side of the doped substrate region, the device region including at least part of one or more electrical devices; and implanting ions into the doped substrate region to form a gettering region in the doped substrate region of the semiconductor carrier.