Wafer Edge Protective Layer for Clean Photoresist Lithography
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Solution Overview
Problem
Existing resist coating methods for semiconductor wafers lead to contamination and patterning instability due to resist material accumulation at the edges and backside of the wafer, causing defects and reducing manufacturing efficiency.
Innovation Solution
A method involving the selective coating of a protective layer on the edge portion of the wafer using a chemical solution containing acid-labile groups, thermal acid generators, and a solubility control unit, which prevents resist material deposition and is removable without affecting the photoresist layer, thereby preventing contamination and maintaining patterning stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If existing resist coating method (spin coating) is used to coat resist material on the wafer, then the wafer surface is covered with resist material, but resist material accumulates at the edges and backside of the wafer causing contamination and patterning instability
Solution Approach 1:
The wafer surface is divided into two distinct regions: the front surface (where resist coating is desired) and the backside/edge regions (where resist accumulation is prevented). A protective layer is selectively applied only to the backside and edges, segmenting the wafer surface to allow different coating behaviors in different regions. This resolves the contradiction by enabling complete front surface coverage while preventing harmful edge accumulation.
Solution Approach 2:
A protective layer acts as an intermediary substance applied to the backside and edges of the wafer. This protective layer prevents resist material from adhering to the edges and backside during the coating process, while allowing the front surface to be properly coated. The protective layer mediates between the need for complete coverage and the need to prevent contamination.
2Object-affected harmful factors
If additional coating processes are applied to prevent edge bead, then contamination is reduced, but manufacturing efficiency decreases due to additional process steps
Solution Approach 1:
The protective layer is applied in advance to the backside and edges of the wafer before the resist coating process. This preliminary action prevents resist material from adhering to the edges during subsequent processing, eliminating the need for post-coating edge bead removal steps. By performing the protective action beforehand, the process achieves better edge control without adding throughput penalties.
Solution Approach 2:
The harmful edge bead formation is extracted and prevented by applying the protective layer selectively to edge regions. Instead of allowing edge bead to form and then requiring additional removal steps, the protective layer extracts the problem at its source by preventing resist adhesion to edges in the first place. This eliminates the need for subsequent edge bead rinse or removal processes.
3Object-affected harmful factors
If edge bead rinse is used to remove resist from wafer edges, then contamination is reduced, but undesired humps are created which become defect sources
Solution Approach 1:
Instead of trying to remove harmful resist material from the edges after it has accumulated, the protective layer converts the edge regions into a beneficial non-stick surface. The protective layer transforms the harmful edge regions into a controlled, predictable surface that prevents resist adhesion, thereby preventing both contamination and the formation of defective humps that would compromise patterning stability.
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 solution effectively prevents resist material accumulation at the wafer edges, reducing contamination and defects, and enhances manufacturing efficiency by ensuring clean and stable lithography processes.
Implementation Method 1
The chemical solution includes a chemical mixture of an acid labile group (ALG), a solubility control unit and a thermal acid generator (TAG). A thermal process triggers the TAG to release acid; the generated acid reacts with the ALG, causing the ALG cleaved from the monomer and the monomer to bind with the solubility control unit to form polymer.
Implementation Method 2
The spin coating apparatus includes a wafer stage designed to secure a wafer for spin coating. The wafer stage is operable to rotate around an axis such that a wafer secured thereon spins.
Data Source
AI summary
A method of manufacturing a semiconductor device includes forming a first protective layer over an edge portion of a first main surface of a semiconductor substrate. A metal-containing photoresist layer is formed over the first main surface of the semiconductor substrate. The first protective layer is removed, and the metal-containing photoresist layer is selectively exposed to actinic radiation. A second protective layer is formed over the edge portion of the first main surface of the semiconductor substrate. The selectively exposed photoresist layer is developed to form a patterned photoresist layer, and the second protective layer is removed.