Stiff Base Plate Assembly for Semiconductor Overlay Alignment
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Solution Overview
Problem
The challenge of achieving consistent and accurate alignment between consecutive layers on a semiconductor substrate is hindered by variations in the clamped state of the substrate due to deformation caused by clamping processes, which are difficult to reproduce, leading to alignment errors.
Innovation Solution
A base plate is attached to the semiconductor substrate, with a thickness ranging from 50% to 200% of the substrate's thickness, to maintain its position during processing steps, reducing deformations and ensuring consistent alignment by increasing the assembly's stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate is clamped onto an object table during lithographic patterning, then the substrate can be held firmly for processing, but the clamping process causes deformation of the substrate that varies between layers, leading to poor alignment accuracy
Solution Approach 1:
A base plate is introduced as an intermediary component between the substrate and the object table. The base plate remains attached to the substrate throughout the entire multi-layer processing sequence, serving as a stable reference frame. This mediator absorbs the variability of the clamping process, preventing direct transmission of clamping-induced deformations to the substrate, thereby enabling consistent alignment across multiple layers without requiring reproducible clamping states
Solution Approach 2:
The base plate is attached to the substrate in advance, before the lithographic patterning process begins. This preliminary attachment establishes a stable reference structure that will remain fixed during all subsequent processing steps. By preparing this stable reference frame beforehand, the system eliminates the need to achieve reproducible clamping states for each layer, as the base plate already provides the necessary stability
2Ease of operation
If a thin substrate is used for semiconductor processing, then the substrate can be handled and processed, but the substrate deforms during clamping and processing, making accurate alignment difficult
Solution Approach 1:
The base plate and substrate are merged into a single assembly through permanent attachment. The base plate, being inherently stiff and stable, combines with the thin substrate to create a composite structure that maintains the ease of handling the thin substrate while adding the dimensional stability and resistance to deformation of the base plate, thereby enabling accurate alignment
Data Source
AI summary
A base plate configured to be attached to a semiconductor substrate, wherein the base plate is configured to remain attached to the semiconductor substrate during a sequence of processing steps performed on the semiconductor substrate, and the base plate is made from a material having a Young's modulus larger than 300 GPa.