Lithographic Substrate Loading Relaxation Method
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Solution Overview
Problem
Thermal and mechanical stresses induced in substrates during loading in lithographic apparatuses can negatively impact pattern transfer quality, and existing methods to mitigate these stresses are either complex or time-consuming.
Innovation Solution
A method involving loading a first object on a second object in a lithographic apparatus, followed by a predetermined time interval to allow temperature balance, and then performing a relaxation action such as reducing clamping force, lifting the object, applying gas pulses, or vibrating the substrate table to reduce friction and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a substrate is quickly loaded and clamped on a substrate table, then productivity is improved, but thermal and mechanical stresses are induced in the substrate which negatively influence pattern transfer quality
Solution Approach 1:
The substrate is pre-heated to the substrate table temperature before loading. This preliminary thermal conditioning prevents thermal stress induction during the quick loading process, allowing high productivity to be maintained without compromising pattern transfer quality.
Solution Approach 2:
A relaxation action is performed after loading to counteract the mechanically induced stresses. This preliminary anti-action compensates for the stress induction that occurs during rapid clamping, maintaining manufacturing precision while enabling fast loading.
2Manufacturing precision
If existing methods are used to mitigate thermal and mechanical stresses, then manufacturing precision is improved, but device complexity or process time increases
Solution Approach 1:
The substrate itself is used as the heating element through resistive heating. The substrate's own electrical conductivity is exploited to heat it to the required temperature, eliminating the need for separate external heating systems and reducing device complexity.
Solution Approach 2:
The temperature of the substrate is dynamically adjusted to match the substrate table temperature before loading. This parameter change ensures thermal compatibility and prevents stress induction without requiring complex mechanical mitigation systems.
3Manufacturing precision
If a substrate is heated to match substrate table temperature, then thermal stress is reduced, but additional heating hardware and process time are required
Solution Approach 1:
The substrate is heated using its own electrical resistance. Current is passed through the substrate to generate heat internally, eliminating the need for external heating hardware and simplifying the overall system while achieving thermal stress reduction.
Solution Approach 2:
The mechanical or thermal contact heating system is replaced with an electrical heating method. By using electrical current to heat the substrate directly, the patent eliminates complex thermal coupling mechanisms and simplifies the heating infrastructure.
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 effectively reduces thermal and mechanical stresses, improving the overlay performance and product quality without requiring additional hardware, thus being cost-efficient and easy to implement.
Implementation Method 1
waiting a predetermined time interval to allow temperature balance
Implementation Method 2
performing a relaxation action... vibrating the substrate table to reduce friction and stress
Data Source
AI summary
The invention relates to a method of loading a first object on a second object in a lithographic apparatus. The method includes: a) loading the first object on the second object, b) waiting a predetermined time interval and c) performing a relaxation action. The first object may be a substrate and the second object a substrate table. The first object may also be a substrate table and the second object a support structure, supporting the substrate table.