Process Chamber Pressure Control Using Variable Flow and Pump Speed
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Solution Overview
Problem
Existing semiconductor processing chamber pressure control systems face challenges with large and expensive throttle valves causing contamination, limited operational range, and thermal limit exceedance, leading to pump failure and precise control requirements.
Innovation Solution
A method and apparatus using a variable flow control device between the first and second pump units, with controlled speed of the first pump unit to increase the range of chamber pressures without exceeding thermal or motor stall limits, and incorporating a further flow control device to enhance operational range and reduce sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a throttle valve is provided between the outlet of the semiconductor processing chamber and the inlet of the first pump unit, then pressure control is achieved, but the valve is large and expensive and causes contamination requiring regular cleaning
Solution Approach 1:
The invention extracts the throttle valve from the chamber outlet position and relocates it to the inlet of the second pump unit. This removes the valve from the chamber environment, eliminating contamination risks while preserving pressure control functionality through the same variable conductance mechanism.
Solution Approach 2:
The first pump unit acts as an intermediary between the chamber and the throttle valve. By positioning the valve after the first pump unit rather than directly at the chamber outlet, the system uses the pump as a buffer that isolates the chamber from contamination while maintaining pressure control capability.
2Measurement precision
If a throttle valve is provided between the first pump unit and the second pump unit, then pressure control is achieved, but the backing pressure increases causing the pump to exceed its thermal limit
Solution Approach 1:
The invention dynamically adjusts the speed of the first pump unit based on operating conditions. By varying the pump speed, the system can maintain effective pressure control through the throttle valve without allowing backing pressure to rise to levels that would cause thermal exceedance, thus adapting the pump's operational characteristics to avoid overheating.
3Measurement precision
If a throttle valve is provided between the first pump unit and the second pump unit, then pressure control is achieved, but the operative range is limited requiring precise control
Solution Approach 1:
The invention changes the operational parameter of the first pump unit from fixed speed to variable speed. This allows the system to expand its operative range by adjusting pump speed to match different pressure control requirements, making the throttle valve effective across a broader range of chamber pressures without requiring extremely precise valve positioning.
Data Source
AI summary
A method of operating apparatus for controlling the pressure in a process chamber (10), the apparatus comprising a first pump unit (14) having an inlet in fluid connection with an outlet of said process chamber, and a second pump unit (16) having an inlet in fluid connection with an outlet of the first pump unit via a flow control unit (18) comprising a variable flow control device (20; 28) having variable conductance for controlling outlet fluid pressure at the outlet of the first pump unit, the method comprises controlling speed of the first pump unit to increase the range of chamber pressures over which control of the outlet fluid pressure produces changes in said chamber pressure without exceeding the thermal limit and/or motor stall limit of the first pump unit.