Substrate Placement on Burls to Minimize Overlay Errors
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Solution Overview
Problem
Lithographic apparatuses face challenges in achieving accurate substrate placement on substrate holders with burls, leading to overlay errors due to substrate bending and varying burl positions, which are exacerbated by the need for precise alignment for high-density pattern imaging.
Innovation Solution
A method involving the acquisition of burl positions, calculation of substrate placement data, and precise placement of substrates on substrate holders with burls to minimize overlay errors, using a computer-readable medium and a transfer system that includes a measurement unit and processor to determine optimal substrate positions based on burl positions and deformation analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If substrates are placed on substrate holders with burls to minimize contact area and reduce contamination effects, then substrate contamination is reduced, but substrate bending occurs leading to overlay errors
Solution Approach 1:
The system performs preliminary measurement of burl positions and substrate characteristics before placement. The control system calculates optimal placement positions in advance that account for substrate bending over burls, thereby pre-compensating for overlay errors before exposure occurs
Solution Approach 2:
The system measures actual burl positions and substrate response, then uses this feedback information to adjust and optimize substrate placement positions. This closed-loop approach allows the system to compensate for variations in burl positions and substrate bending to maintain overlay accuracy
2Stability of the object's composition
If substrates are clamped securely against burls using vacuum to maintain substrate stability during exposure, then substrate positioning stability is improved, but substrate bending increases causing overlay errors
Solution Approach 1:
The system determines optimal substrate placement positions before actual exposure, taking into account the expected substrate bending under vacuum clamping. This preliminary calculation allows the system to position substrates such that bending-induced shifts are minimized or compensated
Solution Approach 2:
The system varies the placement position parameters based on measured burl positions and substrate characteristics. By adjusting where substrates are placed relative to burls, the system optimizes the balance between stable clamping and minimal bending-induced overlay error
3Ease of manufacture
If burls are positioned in a fixed pattern on substrate holders to simplify manufacturing, then manufacturing complexity is reduced, but variations in burl positions cause overlay errors between different substrate holders
Solution Approach 1:
The system measures actual burl positions on each substrate holder and uses this feedback information to adjust substrate placement positions. This allows the system to compensate for manufacturing tolerances and position variations in burls while maintaining consistent overlay accuracy across different substrate holders
Solution Approach 2:
The system performs preliminary characterization of each substrate holder's burl positions and stores this information for use during substrate placement. This advance preparation allows the system to optimize placement positions for each specific substrate holder, compensating for manufacturing variations
Data Source
AI summary
A method of placing a substrate onto a surface of a substrate holder, in which the surface is provided with a plurality of burls. Substrate placement data for allowing placement of the substrate at a certain position with respect to a position of the plurality of burls on the surface of the substrate holder is calculated. The substrate is placed at the certain position in accordance with the substrate placement data. The certain position may be based on the position at which placement would result in a minimized overlay error or may be based on the position at which placement would result in minimized substrate deformation.