Substrate Processing Pallet Cooling via Interface Pad
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Solution Overview
Problem
Substrate processing pallets face challenges in maintaining optimal temperature control during semiconductor wafer processing, leading to residual thermal stress and poor adhesion due to inadequate thermal contact and thermal expansion mismatches, which limits cooling efficiency and increases processing costs.
Innovation Solution
The use of a substrate processing pallet with an interface pad matching the substrate's thermal expansion coefficient and an electrostatic chuck with an energy storage system that allows for continuous grip without continuous power connection, combined with active backside gas cooling, enhances thermal contact and cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If processing power is increased to maintain high throughput, then productivity is improved, but substrate temperature increases causing thermal stress and poor adhesion
Solution Approach 1:
An interface pad made of material with intermediate thermal properties is introduced between the substrate and pallet. This intermediary layer facilitates heat transfer from the substrate to the pallet while allowing the substrate to maintain lower temperature during high-power processing, enabling high throughput without thermal damage
Solution Approach 2:
The thermal contact parameters are modified by changing the interface materials and their properties. The interface pad material is selected to optimize thermal conductivity and thermal expansion matching, changing the thermal transfer parameters to enable effective cooling at high processing powers
2Temperature
If processing power is reduced to control substrate temperature, then temperature is improved, but productivity decreases and processing cost increases
Solution Approach 1:
The interface pad acts as a thermal intermediary that enables efficient heat extraction from the substrate, allowing the substrate to be processed at high power while maintaining temperature control through improved thermal coupling with the cooling pallet
3Temperature
If mechanical clamps are used to increase gas pressure at the interface, then thermal contact is improved, but particles and edge exclusion problems occur
Solution Approach 1:
The mechanical clamping system is replaced with an electrostatic chuck that uses electrical fields to hold the substrate against the pallet. This substitution eliminates mechanical contact points that generate particles and cause edge exclusion, while maintaining or improving thermal contact through uniform pressure distribution
Solution Approach 2:
Gas pressure is applied to the backside of the substrate to enhance thermal contact between the substrate and pallet. This pneumatic approach distributes pressure uniformly across the substrate surface, improving thermal coupling without the localized stress and particle generation associated with mechanical clamps
4Temperature
If ceramic or semiconductor pads are bonded to metal pallets to improve surface smoothness, then thermal contact is improved, but thermal expansion mismatch causes cracking
Solution Approach 1:
The interface pad is made from a homogeneous material that matches the thermal expansion coefficient of the metal pallet. This material homogeneity in terms of thermal expansion properties prevents differential expansion and contraction that would cause cracking, while maintaining good thermal contact
Solution Approach 2:
A composite interface pad structure is used that combines materials with complementary properties. The composite is designed to match the thermal expansion of the metal pallet while providing the necessary surface smoothness and thermal conductivity, avoiding the cracking issues of simple material bonds
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 improves thermal communication between the substrate and pallet, reduces thermal stress, and increases cooling efficiency, preventing cracking and maintaining high throughput processing while reducing processing costs.
Implementation Method 1
The interface pad attaches to the base member, has substantially the same coefficient of thermal expansion as the base member, and facilitates cooling of the substrate
Implementation Method 2
an electrostatic chuck with an energy storage system that allows for continuous grip without continuous power connection
Implementation Method 3
heat transfer across a gap is primarily due to gas conduction, which is essentially a linear function of gas pressure under typical processing conditions
Data Source
AI summary
A substrate processing pallet can cool a substrate. A substrate processing pallet can include a base member; an interface pad attachable to the base member, the interface pad having substantially the same coefficient of thermal expansion as the base member and adapted to facilitate cooling of the substrate; and a surface of the base member having features for aligning a substrate on the interface pad. A substrate processing pallet can also include a base member; an interface pad attachable to the base member; an electrostatic chuck for gripping the substrate during processing; an energy storage system for storing energy to sustain the electrostatic chuck at sufficient charge to sustain grip the substrate during processing; and a conduit for transporting gas to a backside of the substrate to facilitate cooling of the substrate.