Polishing Apparatus Pressure Control Switching
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Solution Overview
Problem
Existing polishing apparatuses face challenges in achieving high precision during low-pressure polishing due to the increased error ratio associated with pressure controllers having large full-scale ranges, leading to difficulties in maintaining uniform pressure distribution, especially at the wafer edge, which can result in 'edge drop' and affect the yield of semiconductor devices.
Innovation Solution
A polishing apparatus with a substrate holding device featuring an elastic film forming multiple pressure chambers, where a pressure control unit with parallel first and second pressure regulation mechanisms allows for precise pressure control by switching between them based on set threshold values, enabling stable pressure control even when the pressure fluctuates near threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pressure controller with a large full-scale range is used to cover a wide pressure range, then the adaptability is improved, but the measurement precision deteriorates due to increased error ratio
Solution Approach 1:
The pressure control system is segmented into multiple pressure controllers, each responsible for a specific pressure range. The controller selection unit divides the overall pressure range into sub-ranges and selects the appropriate controller based on the current set pressure, allowing each controller to operate within its optimal precision range while collectively covering a wide pressure spectrum.
Solution Approach 2:
The system changes the parameter of controller selection based on the set pressure value. When the set pressure exceeds a threshold, the controller selection unit switches between different pressure controllers, effectively adapting the measurement scale to match the required pressure level and maintaining high precision across the full pressure range.
2Device complexity
If a single pressure controller is used for the entire pressure range, then the device complexity is reduced, but the measurement precision deteriorates at specific pressure ranges
Solution Approach 1:
The pressure control system is made dynamic through the controller selection unit, which automatically switches between different pressure controllers based on real-time pressure conditions. This dynamic adaptation allows the system to maintain optimal precision across varying pressure ranges without requiring manual intervention or complex configuration.
Solution Approach 2:
The controller selection unit autonomously determines which pressure controller to use based on the set pressure threshold, eliminating the need for external control or complex user configuration. The system self-manages the switching between controllers, simplifying the overall control architecture while maintaining high precision.
3Device complexity
If pressure control is not switched between multiple controllers, then the device complexity is reduced, but the manufacturing precision deteriorates due to edge drop
Solution Approach 1:
The pressure control for different regions of the substrate is segmented into multiple pressure chambers with independent control. The controller selection unit applies appropriate pressure control strategies to different chambers based on their specific requirements, enabling precise control of the polishing profile and prevention of edge drop while maintaining manageable system complexity.
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 solution enables high-precision polishing across a wide range of pressures, maintaining stability and preventing 'edge drop' by using pressure controllers with smaller and larger full-scale ranges in a switching manner, thereby improving the polishing profile and yield of semiconductor devices.
Implementation Method 1
a pressure chamber formed by an elastic film is provided on the lower portion of the substrate holding device and a fluid such as, for example, air is supplied to the pressure chamber such that the wafer is pressed by the fluid pressure via the elastic film
Implementation Method 2
The substrate holding device includes an elastic film configured to form a plurality of pressure chambers to press the substrate
Data Source
AI summary
A polishing apparatus includes a polishing table for supporting a polishing pad and a substrate holding device for pressing a substrate against the polishing pad. The substrate holding device includes an elastic film to form multiple pressure chambers to press the substrate, and a pressure control unit controlling pressure of the pressure chambers. The pressure control unit includes a first flow path connected to a first pressure chamber, and first and second pressure regulation mechanisms. The pressure control unit performs switching control from first pressure regulation mechanism to second pressure regulation mechanism when a set pressure within first pressure chamber reaches a first threshold value. Then, the pressure control unit performs switching control from second pressure regulation mechanism to first pressure regulation mechanism when the set pressure within the first pressure chamber reaches a second threshold value lower than the first threshold value.