CMP Polishing Head Load Control for Wafer Thickness Uniformity
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Solution Overview
Problem
Conventional CMP techniques fail to uniformly polish wafers, leading to variations in film thickness along the circumferential direction, which cannot be effectively eliminated.
Innovation Solution
A polishing method and apparatus that determine areas of maximum or minimum film thickness and adjust polishing rates by varying the load or speed of the polishing head relative to the substrate, ensuring symmetrical areas are polished at different removal rates to equalize film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP techniques are used to polish wafers, then the polishing process is simple and uniform, but film thickness variation along the circumferential direction cannot be eliminated
Solution Approach 1:
The polishing head applies different loads to different areas of the wafer surface based on the measured film thickness distribution. Specifically, areas with greater thickness variation receive higher polishing loads, while areas with minimal variation receive lower loads, achieving localized quality adjustment to eliminate circumferential thickness variations
Solution Approach 2:
The polishing head dynamically adjusts its load distribution during the polishing process based on real-time or pre-measured film thickness data. The load adjustment occurs while the wafer and polishing head are rotating, enabling adaptive control of removal rates across different circumferential positions
2Productivity
If the polishing head load is increased to remove more material, then the polishing speed increases, but the film thickness distribution becomes more uneven
Solution Approach 1:
Rather than uniformly increasing the load across the entire wafer surface, the system selectively applies higher loads only to specific circumferential areas that exhibit greater film thickness variations. This localized approach maintains overall productivity while improving thickness uniformity in problematic regions
Solution Approach 2:
The system changes the load parameter spatially across the wafer surface, creating a non-uniform load distribution pattern that corresponds to the measured film thickness distribution. This parameter variation enables different removal rates in different areas, simultaneously achieving high productivity and precision
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 reduces and eliminates film thickness variations along the circumferential direction of the substrate, achieving uniformity across multiple substrates.
Implementation Method 1
A CMP process is performed by rubbing a wafer against a polishing surface while supplying slurry onto the polishing surface. A film, which has been formed on the wafer, is polished by the combined effect of the mechanical action of abrasive grains contained in the slurry
Implementation Method 2
A film, which has been formed on the wafer, is polished by the combined effect of the mechanical action of abrasive grains contained in the slurry and the chemical action of a chemical component of the slurry
Data Source
AI summary
The present invention relates to a method and an apparatus for polishing a surface of a substrate having a film whose thickness varies along a circumferential direction of the substrate. The polishing method includes: obtaining a film-thickness distribution in a circumferential direction of a substrate (W); determining a first area having a maximum or minimum film thickness based on the film-thickness distribution; rotating a polishing table (3) holding a polishing pad (2); pressing a surface of the substrate (W) against the polishing pad (2) while rotating the substrate by a polishing head (1); and polishing the first area at a removal rate different from that of a second area in the surface of the substrate (W).