Double-Side Grinding Spindle Alignment via Torsional Coupling
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Solution Overview
Problem
Existing double-side grinding machines for semiconductor wafers lack a method to accurately correct parallelism deviation between grinding spindles, which affects the shape and nanotopology of the wafers, as previous methods fail to account for radial measured values during spindle alignment.
Innovation Solution
A method involving torsionally coupled grinding spindles with an inclinometer and distance sensors mounted between the grinding disk flanges to determine radial and axial correction values, allowing for symmetrical orientation of the spindles, and a control unit to calculate and apply horizontal and vertical corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If grinding spindles are oriented based only on axial measurements without radial measured values, then the alignment process is simpler, but the parallelism deviation between spindles cannot be accurately corrected
Solution Approach 1:
The patent transitions from one-dimensional axial measurements to three-dimensional measurements by incorporating radial measured values obtained during spindle rotation. This multi-dimensional measurement approach enables accurate determination of parallelism deviation and bearing play, resolving the contradiction between measurement simplicity and alignment accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where radial and axial measurements are continuously taken during spindle rotation, and the measured values are used to calculate correction values for spindle orientation. This closed-loop feedback system enables precise correction of parallelism deviation while maintaining a systematic and manageable alignment process.
2Manufacturing precision
If grinding spindles are tilted symmetrically to satisfy product criteria, then grinding pattern and global geometry improve, but axial alignment deviations remain uncorrected
Solution Approach 1:
The patent performs preliminary correction of axial alignment and parallelism deviation before applying symmetric tilting for grinding operations. By establishing accurate axial alignment as a preliminary step, the subsequent symmetric tilting can focus solely on optimizing grinding pattern and global geometry without compromising alignment accuracy.
Solution Approach 2:
The patent segments the spindle orientation adjustment into two independent stages: first correcting axial alignment and parallelism deviation, then applying symmetric tilting for grinding optimization. This segmentation allows each stage to address specific requirements without interfering with the other, resolving the contradiction between alignment accuracy and grinding quality.
3Measurement precision
If multiple sensors and inclinometers are mounted between grinding disk flanges to obtain radial and axial measurements, then spindle alignment accuracy improves, but device complexity increases
Solution Approach 1:
The patent designs the measurement system with multi-functional components that simultaneously perform multiple measurement tasks. The radial and axial sensors mounted on the spindle nose serve both to measure parallelism deviation and to detect bearing play, reducing the need for separate measurement systems and thereby limiting the increase in device complexity.
Solution Approach 2:
The patent combines radial and axial measurement functions into a single integrated measurement system mounted between the grinding disk flanges. By merging these measurement functions and using the data collectively to calculate correction values, the system achieves high measurement accuracy while avoiding the complexity of entirely separate measurement systems.
4Ease of operation
If grinding spindles are corrected using only axial displacement without considering radial offset, then the alignment process is simpler, but the shape and nanotopology of wafers are adversely affected
Solution Approach 1:
The patent uses feedback from both radial and axial sensors to calculate comprehensive correction values that account for parallelism deviation and bearing play. This feedback mechanism ensures that wafer shape and nanotopology quality are maintained by correcting all relevant alignment errors, not just axial displacement.
Solution Approach 2:
The patent incorporates radial measurement dimension to complement axial displacement measurement. By considering both radial offset and axial displacement in the correction calculation, the system maintains wafer quality without requiring overly complex operational procedures, as the additional radial data is integrated systematically into the correction process.
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 enables precise axial alignment measurements and corrections, resulting in significantly more symmetrical spindle orientation, improving the shape and nanotopography of ground semiconductor wafers by accounting for process forces and reducing bearing play.
Implementation Method 1
a measuring unit comprising an inclinometer and two sensors for distance measurement is mounted instead of grinding disks between the two grinding disk flanges
Implementation Method 2
two sensors for distance measurement is mounted instead of grinding disks between the two grinding disk flanges... used to determine radial and axial correction values
Implementation Method 3
the two grinding spindles, each comprising a grinding disk flange for receiving a grinding disk, are coupled torsionally by means of a coupling element
Data Source
AI summary
Correction of grinding spindle positions in double-side grinding machines for the simultaneous double-side machining of semiconductor wafers is achieved by torsionally coupling the two grinding spindles, each comprising a grinding disk flange for receiving a grinding disk, and providing a measuring unit with an inclinometer and two sensors for distance measurement, between the two grinding disk flanges such that the grinding spindles are essentially in the position they would have with mounted grinding disks during the grinding process, wherein the coupled grinding spindles are rotated while inclinometer and sensors determine radial and axial correction values of axial alignment to adjust the grinding spindles to a symmetrical orientation. The spindle positions may be corrected under the action of process forces.