Polishing Head Elastic Membrane Inflation Control
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) techniques face challenges in accurately controlling pressure chambers of a polishing head, leading to excessive stress on wafers due to individual differences in the elastic membrane, material, and structural issues, which can result in wafer damage, especially as the number of pressure chambers increases.
Innovation Solution
The method involves regulating the flow rates of gas into the pressure chambers using flow-rate control valves to inflate the elastic membrane into a desired shape, allowing for precise control of the inflation speed and volume, thereby preventing excessive stress on the wafer. This is achieved by supplying gas at different flow rates into first and second pressure chambers until cumulative target flow-rate values are reached, with the system controller calculating and adjusting the flow rates to maintain consistent inflation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure control is used to inflate the elastic membrane, then the membrane can be inflated, but the inflation is not precise and excessive stress is generated on the wafer
Solution Approach 1:
The patent changes the control parameter from pressure to flow rate. By controlling the flow rate of gas supplied to each pressure chamber, the system achieves precise control over the inflation process. The flow-rate control valves regulate the amount of gas entering each chamber, allowing the elastic membrane to be inflated to a desired shape without generating excessive stress on the wafer.
2Adaptability or versatility
If the number of pressure chambers is increased to polish more regions, then more regions can be polished with different forces, but the inflation becomes more difficult to control
Solution Approach 1:
The patent divides the polishing head into multiple pressure chambers (first pressure chamber and second pressure chamber), each equipped with its own flow-rate control valve. This segmentation allows independent control of gas flow to different regions, enabling precise inflation of the elastic membrane to achieve desired shapes for polishing different wafer regions with different forces.
3Ease of operation
If pressure chambers are inflated to release the wafer, then the wafer can be released, but excessive inflation causes wafer damage
Solution Approach 1:
The system uses feedback control through flow-rate control valves that regulate the gas supply to each pressure chamber. By monitoring and adjusting the flow rate, the system can inflate the elastic membrane to the precise degree needed for wafer release without excessive inflation that would damage the wafer. The cumulative target flow-rate values provide a feedback mechanism to control the inflation 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 allows for reliable inflation of the elastic membrane into a desired shape, reducing the risk of wafer damage by controlling the amount of inflation and minimizing stress, while also reducing the amount of release gas needed, thus preventing drying of the polished wafer.
Implementation Method 1
regulating the flow rates of gas into the pressure chambers using flow-rate control valves
Implementation Method 2
the elastic membrane is curved downward, so that a gap is formed between an edge portion of the wafer W1 and the elastic membrane 110
Implementation Method 3
the system controller calculating and adjusting the flow rates to maintain consistent inflation
Data Source
AI summary
A technique is disclosed that can allow an elastic membrane to be inflated into a desired shape when a workpiece is released from a polishing head, or when the workpiece is held on the polishing head, thereby avoiding excessive stress on the workpiece. The method includes supplying a gas into a first pressure chamber and a second pressure chamber at a first flow rate and a second flow rate regulated by a first flow-rate control valve and a second flow-rate control valve to inflate an elastic membrane of a polishing head when a polished workpiece is released from the polishing head, or when a workpiece to be polished is held on the polishing head. The first pressure chamber and the second pressure chamber are formed by the elastic membrane.