Two-Stage Chemical Mechanical Polishing for Semiconductor Flatness
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Solution Overview
Problem
Conventional CMP methods using abrasive grains with high non-Prestonian properties face challenges in achieving high flatness and controlling the thickness of polished films, leading to high defect densities and low polishing rates, especially after protrusions are removed, making it difficult to monitor and control the polishing process effectively.
Innovation Solution
A two-stage polishing process is employed, using a first abrasive with a high polymer additive concentration for initial flattening and a second abrasive with a lower polymer additive concentration to address the automatically stopping state, allowing for continued polishing and defect removal without excessive film removal, with the second stage having a higher polishing rate and pressure to control the final film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If abrasive grains with high non-Prestonian properties are used for CMP, then high flatness is achieved, but polishing rate suddenly lowers after protrusions are removed causing automatically stopping state
Solution Approach 1:
The polishing process is divided into two distinct stages: a first polishing process using abrasive grains with high non-Prestonian properties to achieve high flatness, and a second polishing process using abrasive grains with lower non-Prestonian properties to maintain polishing rate and remove defects. This segmentation allows each stage to optimize for its specific function without the drawbacks of the other.
Solution Approach 2:
The invention changes the parameters of the abrasive grains between polishing stages, specifically adjusting the non-Prestonian properties by selecting different abrasive materials (ceria for high non-Prestonian, silica for lower non-Prestonian). This parameter change enables transition from a polishing regime that achieves high flatness to one that maintains productivity and removes defects.
2Manufacturing precision
If abrasive grains with high non-Prestonian properties are used, then polishing automatically stops when surface is flat, but defects remain on the polished film surface
Solution Approach 1:
The polishing process is segmented into two stages where the second stage specifically addresses defect removal. The first stage focuses on achieving high flatness with automatic stopping, while the second stage continues polishing to remove defects that remained after the first stage, thereby improving reliability without sacrificing the flatness control achieved in the first stage.
Solution Approach 2:
The abrasive grain parameters are changed from high non-Prestonian properties to lower non-Prestonian properties in the second polishing stage. This parameter change allows the polishing to continue at a stable rate and effectively remove defects without the automatic stopping behavior that prevents defect removal in the first stage.
3Productivity
If high non-Prestonian abrasive grains are used, then polishing rate is high when protrusions exist, but polishing rate becomes very low after protrusions are removed
Solution Approach 1:
The polishing process is divided into two stages with different abrasive grains optimized for different conditions. The first stage uses high non-Prestonian abrasive grains to achieve high polishing rates when protrusions are present, while the second stage uses lower non-Prestonian abrasive grains to maintain adequate polishing rates and achieve high flatness after protrusions are removed.
Solution Approach 2:
The invention changes the non-Prestonian parameter of the abrasive grains between stages. The first stage uses abrasive grains with high non-Prestonian properties for rapid material removal, while the second stage transitions to abrasive grains with lower non-Prestonian properties to maintain a stable, controllable polishing rate that enables achievement of high flatness.
4Device complexity
If single-stage polishing with high non-Prestonian abrasive is used, then process is simple, but it is difficult to control the amount of polishing for each lot
Solution Approach 1:
The polishing process is segmented into two stages with different abrasive grains, each optimized for specific objectives. The first stage removes protrusions and achieves initial flatness, while the second stage fine-tunes the surface and removes defects. This segmentation enables better control of the total polishing amount for each lot by adjusting the duration and parameters of each stage independently.
Solution Approach 2:
The invention changes abrasive grain parameters between stages to enable independent optimization of each polishing stage. The first stage uses high non-Prestonian abrasive for rapid material removal, while the second stage uses lower non-Prestonian abrasive for precise control of the final polishing amount, thereby improving lot-to-lot consistency.
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 reduces defect densities and allows for precise control of the polishing process, ensuring the film is polished to a predetermined thickness without excessive polishing, improving the overall quality and consistency of the semiconductor device manufacturing.
Implementation Method 1
a first polishing process which performs a polishing process on a surface of a film to be polished using a first abrasive with non-Prestonian properties produced by mixing abrasive materials, including abrasive grains, a polymer additive and water, at a predetermined first mixture ratio
Implementation Method 2
a second polishing process which performs a polishing process on the surface of the film using a second abrasive produced by mixing the abrasive materials at a predetermined second mixture ratio different from the first mixture ratio to make a concentration of the polymer additive lower than that of the first abrasive
Implementation Method 3
mixing abrasive materials, including abrasive grains, a polymer additive and water, at a predetermined first mixture ratio
Data Source
AI summary
An interlayer insulating film is formed on a semiconductor substrate having a semiconductor element formed thereon. At this time, there are protrusions higher than surroundings thereof and non-protruding portions lower than the protrusions on the surface of the interlayer insulating film. First, a first polishing process is carried out on the surface of the interlayer insulating film with use of a first abrasive having non-Prestonian properties produced by mixing abrasive materials including abrasive grains, a polymer additive and water at a predetermined first mixture ratio. Then, after the first abrasive process shifts to an automatically stopping state, a second polishing process is carried out on the surface of the interlayer insulating film with use of a second abrasive having the concentration of polymer additive lower than that of the first abrasive and produced by mixing the abrasive materials at a second mixture ratio different from the first mixture ratio.