Polishing Apparatus Circumferential Film Thickness Control
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Solution Overview
Problem
Existing semiconductor polishing apparatuses face challenges in achieving uniform film thickness distribution along the circumferential direction of wafers due to variations in initial film thickness and complex structures, leading to discontinuous polishing rates and flatness issues.
Innovation Solution
A polishing apparatus with a rotating mechanism, pressure regulators, and a controller that adjusts polishing conditions such as pressure, height, and angular velocity in synchronization with the rotation angle of the polishing head to control the polishing rate and eliminate film thickness variations along the circumferential direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If divided pressing elements (pistons or pressure chambers) are arranged along the circumferential direction to control film thickness variation, then film thickness uniformity is improved, but device complexity increases
Solution Approach 1:
The polishing head is divided into multiple independent pressing elements arranged along the circumferential direction, with each element capable of independent vertical movement and pressure control. This segmentation allows differential pressure application to different circumferential regions of the wafer, enabling correction of circumferential film thickness variations while maintaining manageable system complexity through modular design
Solution Approach 2:
The pressing elements are designed with dynamic capabilities including independent vertical movement, rotational adjustment, and real-time pressure control. This dynamic design allows the system to adapt to varying film thickness conditions at different circumferential positions during the polishing process, achieving uniform film thickness without requiring an overly complex static structure
2Manufacturing precision
If divided rigid pistons are used to press the wafer along the circumferential direction, then film thickness variation is reduced, but polishing rate continuity deteriorates
Solution Approach 1:
The pressing elements transition from rigid, static pistons to dynamic components capable of independent vertical movement and rotational adjustment. This allows continuous, smooth variation in pressing force across the wafer surface during rotation, eliminating the discontinuous polishing rates that occur with rigid piston structures while maintaining film thickness uniformity
Solution Approach 2:
The system employs periodic adjustment of pressing element positions and forces synchronized with the wafer rotation cycle. This periodic action ensures that each circumferential region receives appropriate pressure at the correct phase of rotation, maintaining continuous and uniform polishing rate across the entire wafer surface
3Manufacturing precision
If divided pressure chambers are used to control pressing force, then film thickness variation is reduced, but variation in pressing force between chambers increases
Solution Approach 1:
The system incorporates sensors and control mechanisms that monitor the pressing force applied by each element in real-time, with feedback loops that adjust individual element forces to maintain consistency. This feedback control compensates for variations between chambers, ensuring uniform pressing force distribution across all circumferential regions while achieving film thickness uniformity
Solution Approach 2:
The system dynamically adjusts pressing force parameters for each element based on real-time measurements of film thickness variation and pressing force consistency. By changing pressure, position, and timing parameters adaptively, the system achieves both film thickness uniformity and pressing force consistency that cannot be obtained with fixed chamber designs
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 controls the polishing rate and uniformity of film thickness across the wafer's circumference, reducing variations and improving the yield in semiconductor manufacturing by dynamically adjusting polishing conditions based on the wafer's orientation and rotation.
Implementation Method 1
a polishing head including an elastic membrane for pressing the substrate against the polishing surface
Implementation Method 2
a retainer ring arranged so as to surround the substrate, the retainer ring being capable of contacting the polishing surface
Implementation Method 3
a process of polishing a wafer by bringing the wafer into sliding contact with a polishing surface of a polishing pad while supplying a polishing liquid containing abrasive grains
Data Source
AI summary
A polishing apparatus capable of eliminating a variation in film thickness along a circumferential direction of a substrate, such as a wafer, is disclosed. The polishing apparatus includes: a polishing head including an elastic membrane for pressing the substrate against the polishing surface and a retainer ring arranged so as to surround the substrate, the retainer ring being capable of contacting the polishing surface; a rotating mechanism configured to rotate the polishing head about its own axis; a rotation angle detector configured to detect a rotation angle of the polishing head; and a polishing controller configured to periodically change a polishing condition of the substrate in synchronization with the rotation angle of the polishing head.