Hydrostatic Pad Pressure Modulation for Wafer Nanotopology
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Solution Overview
Problem
Current double side grinding processes for semiconductor wafers often result in nanotopology degradation due to misalignment of clamping planes and subsequent elastic deformation, leading to undesirable features like C-marks and B-rings, which cause yield losses in IC manufacturing.
Innovation Solution
A double side grinder with hydrostatic pads and grinding wheels that adjust hydrostatic pressure stages during the grinding process, using pattern detection software to manage clamping pressure and reduce elastic deformation, thereby improving nanotopology by maintaining the wafer in a more uniform plane and reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hydrostatic pads are used to clamp the wafer during grinding, then the wafer is held without rigid physical contact reducing damage, but misalignment of clamping planes causes elastic deformation and nanotopology degradation
Solution Approach 1:
The patent applies dynamics by making the hydrostatic pad system adjustable and adaptable during the grinding process. The clamping pressure is dynamically modified through multiple stages (initial clamping, grinding stage with reduced pressure, and final clamping) to accommodate the wafer's deformation characteristics at different process phases. This dynamic adjustment resolves the contradiction by preventing both wafer damage and nanotopology degradation simultaneously.
Solution Approach 2:
The patent changes the physical parameter of hydrostatic pressure throughout the grinding process. By reducing pressure during the grinding stage and increasing it during initial and final clamping stages, the system adapts to prevent elastic deformation and nanotopology defects while maintaining wafer protection. This parameter modification resolves the technical contradiction between wafer protection and manufacturing precision.
2Reliability
If constant hydrostatic pressure is applied during grinding, then the wafer remains clamped securely, but elastic deformation occurs leading to C-marks and B-rings defects
Solution Approach 1:
The patent implements periodic action by applying hydrostatic pressure in distinct stages rather than continuously. The pressure is applied during initial clamping, reduced during the grinding operation, and reapplied during final clamping. This periodic modulation of clamping pressure prevents elastic deformation and nanotopology defects while maintaining wafer stability when needed, resolving the contradiction between clamping reliability and nanotopology uniformity.
Solution Approach 2:
The clamping system transitions from a static constant pressure approach to a dynamic staged pressure approach. The system adapts its clamping force according to the process stage, providing stability when required and reducing constraints during grinding to prevent deformation. This dynamic behavior resolves the technical contradiction.
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 solution effectively minimizes nanotopology defects such as C-marks and B-rings, leading to improved wafer flatness and parallelism, and reduces yield losses by uniformly grinding the wafer surfaces and maintaining lower nanotopology values.
Implementation Method 1
establishing a first hydrostatic pressure in the hydrostatic pads to initially clamp the wafer during a first stage of the grinding operation
Implementation Method 2
The hydrostatic pressure is reduced to a second hydrostatic pressure lower than the first pressure during grinding of the wafer in a second stage of the grinding operation
Data Source
AI summary
Systems and methods are disclosed for modulating the hydrostatic pressure in a double side wafer grinder having a pair of grinding wheels. The systems and methods use a processor to measure the amount of electrical current drawn by the grinding wheels. Pattern detection software is used to predict a grinding stage based on the measured electrical current. The hydrostatic pressure is changed by flow control valves at each stage to change the clamping pressure applied to the wafer and to thereby improve nanotopology in the processed wafer.