Multi-Zone Pedestal Heater Control with Shared Return Leads
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Solution Overview
Problem
Existing wafer-processing equipment struggles with achieving uniform temperature profiles across substrates, leading to yield issues and the need for advanced control techniques to fine-tune processing conditions.
Innovation Solution
A multi-zone heater control system that includes a plurality of power leads supplying voltage to different heating zones in a pedestal, with a shared return lead and switches that switch the polarity of the voltage to maintain control and prevent interference with DC chucking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple heating zones are controlled independently with separate return leads, then temperature uniformity across substrate is improved, but device complexity and current requirements increase
Solution Approach 1:
Multiple heating zones share a common return lead instead of having separate return leads for each zone. This merging of return paths reduces the number of electrical connections and simplifies the overall system architecture while maintaining independent control of each heating zone through individual power leads and switching mechanisms.
Solution Approach 2:
The heating system is divided into multiple independently controllable zones along the pedestal height, allowing differential heating control. Each zone can be adjusted to achieve optimal temperature profiles across the substrate surface, resolving the temperature uniformity issue while using a shared return lead to minimize complexity.
2Reliability
If polarity switching is implemented to prevent interference with DC chucking, then processing reliability is improved, but control system complexity increases
Solution Approach 1:
The heating elements operate with periodic polarity reversal rather than continuous DC. This AC-like operation with controlled polarity switching prevents interference with the DC chucking system that holds the substrate, while maintaining effective heating through resistive heating during both positive and negative cycles.
Solution Approach 2:
The system dynamically switches polarity based on operational requirements, transitioning between different electrical states to accommodate both heating and substrate holding functions. This dynamic control allows the same electrical infrastructure to serve multiple purposes without interference.
3Use of energy by moving object
If duty cycling is used to reduce current requirements, then electrical load is reduced, but heating efficiency decreases
Solution Approach 1:
Duty cycling implements periodic on-off operation of heating zones, activating them only during specific time intervals when heating is required. This reduces the average current draw and electrical load on the system while maintaining effective heating performance by concentrating energy delivery during active periods.
Solution Approach 2:
The system pre-cools or pre-heats zones during idle periods, and activates heating only when needed based on predicted thermal requirements. This preliminary preparation reduces peak current demands while maintaining heating efficiency through proactive thermal management.
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
The system effectively controls temperature across multiple heating zones, minimizing yield issues by ensuring uniform temperature profiles and reducing current requirements through duty cycling and shared return leads.
Implementation Method 1
a plurality of power leads configured to supply a voltage to a plurality of different heating zones in a pedestal
Implementation Method 2
a plurality of switches that are configured to switch a polarity of the voltage provided to the plurality of power leads
Data Source
AI summary
A method of providing power to a plurality of heaters in multiple zones for wafer-processing equipment may include causing a voltage to be supplied to a plurality of power leads configured to supply the voltage to a plurality of different heating zones in a pedestal, causing current to be received from the plurality of different heating zones through a return lead that is shared by the plurality of power leads, and causing a polarity of the voltage provided to the plurality of power leads to switch. The switching frequency may be configured such that a DC chucking operation can be active at the same time to hold a substrate to the pedestal. Duty cycling the heating zones that share the return lead may minimize the current through the shared return lead.