Wafer Gettering Layer via Metal Salt Diffusion
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Solution Overview
Problem
Existing methods for forming gettering layers on wafers to capture impurities often reduce the die strength of device chips, as they require creating marks or strain on the wafer surface, which can be detrimental to chip integrity.
Innovation Solution
A method involving the application of a metal salt solution to the back side of a wafer, followed by heating to diffuse the metal salt and form a gettering layer, which captures impurities without reducing the die strength by eliminating the need for marks or strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If marks or strain are left on the wafer to capture impurities, then the gettering function is improved, but the die strength of device chips decreases
Solution Approach 1:
The invention separates the gettering function from the wafer substrate by introducing a distinct gettering layer formed through metal salt diffusion. This gettering layer acts as an independent impurity capture mechanism, allowing the wafer to maintain its structural integrity without requiring marks or strain that would compromise die strength.
Solution Approach 2:
The metal salt serves as an intermediary substance that facilitates impurity capture. By applying metal salt solution to the wafer back surface and diffusing it to form a gettering layer, the invention introduces a mediating material that performs the gettering function without directly modifying the wafer's mechanical structure.
2Strength
If marks or strain are removed by polishing or etching to maintain die strength, then the die strength is improved, but the gettering function must be re-established
Solution Approach 1:
The invention performs preliminary action by forming the gettering layer through metal salt diffusion before wafer processing steps such as polishing or etching. This ensures the gettering function is established in advance, eliminating the need to re-form marks or strain after removing the wafer surface.
Solution Approach 2:
The metal salt diffusion process introduces a chemical intermediary that creates the gettering layer without requiring mechanical marks. This chemical approach replaces the traditional mechanical marking method, allowing the gettering function to be maintained independently of surface modifications.
3Strength
If a gettering layer is formed by metal salt diffusion, then the die strength is maintained, but a new process step is added
Solution Approach 1:
The invention utilizes parameter changes by controlling the diffusion process through variables such as temperature, time, and metal salt concentration. By adjusting these parameters, the gettering layer can be formed with appropriate depth and concentration profiles, optimizing both the gettering function and process efficiency.
Solution Approach 2:
The invention replaces the mechanical system of creating marks through grinding or scratching with a chemical diffusion process. Instead of mechanically altering the wafer surface to create impurity traps, the metal salt diffusion chemically forms a gettering layer that captures impurities without mechanical damage.
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 effectively captures impurities without compromising the die strength of device chips, providing a robust and efficient method for forming gettering layers that prevents contamination from metals like copper.
Implementation Method 1
a diffusing step of heating the wafer after performing the coating step, thereby diffusing the metal salt on the back side of the wafer to form the gettering layer containing the metal salt on the back side of the wafer
Implementation Method 2
the diffusing step includes the step of applying a laser beam to the back side of the wafer, the laser beam having an absorption wavelength to the wafer, thereby heating the wafer to diffuse the metal salt
Data Source
AI summary
A gettering layer forming method includes a coating step of applying a solution of metal salt to a back side of a wafer, and a diffusing step of heating the wafer after performing the coating step, thereby diffusing the metal salt on the back side of the wafer to form a gettering layer containing the metal salt on the back side of the wafer, in which the metal salt is diffused in the gettering layer.