Photomask Opening Correction for Uniform Semiconductor Pattern Transfer
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Solution Overview
Problem
In the semiconductor industry, photomasks often suffer from defects such as under-size and over-size defects, which can lead to reduced yield and scrapped wafers due to imperfections in pattern transfer during photolithography, especially as feature sizes decrease, necessitating improved methods for defect correction and pattern uniformity.
Innovation Solution
The method involves using wet etching with specific etchants and protecting layers to correct global and local under-size defects, and incorporating an adjustment mark to adjust exposure energy, ensuring feature sizes meet target requirements through a series of fabrication stages and photolithography processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional photolithography is used for pattern transfer, then the process is simple and fast, but under-size and over-size defects occur reducing yield
Solution Approach 1:
The patent applies preliminary action by performing wet etching on the photomask before photolithography to pre-correct feature size deviations. The method involves: (1) receiving a photomask with patterns, (2) performing wet etching to remove portions of the photomask and adjust feature sizes, (3) determining an adjusted exposure energy based on the etching results, and (4) performing photolithography with the adjusted energy. This preliminary correction step ensures that subsequent photolithography produces accurate feature sizes on the substrate, preventing under-size and over-size defects while maintaining production efficiency.
2Area of moving object
If feature sizes are reduced to increase device density, then more devices per unit area are achieved, but pattern transfer defects increase
Solution Approach 1:
The patent implements feedback by using the results of wet etching to determine the adjusted exposure energy for subsequent photolithography. The method: (1) performs wet etching to remove portions of the photomask, (2) measures or evaluates the etching results to determine feature size deviations, (3) calculates an adjusted exposure energy based on these deviations, and (4) applies this adjusted energy in the photolithography step. This closed-loop feedback mechanism compensates for variations introduced by reduced feature sizes, ensuring accurate pattern transfer even as device density increases.
3Ease of manufacture
If photomask imperfections are present, then manufacturing is simpler, but defects are compounded during subsequent processing
Solution Approach 1:
The patent applies preliminary action by incorporating a wet etching step before photolithography to pre-correct photomask imperfections. The method involves: (1) receiving a photomask that may contain manufacturing variations, (2) performing wet etching to remove portions and correct feature size deviations, (3) determining adjusted exposure energy based on etching results, and (4) performing photolithography with the corrected photomask and adjusted parameters. This preliminary correction prevents the compounding of defects during subsequent processing while maintaining relative manufacturing simplicity.
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 corrects defects and improves pattern uniformity, ensuring that feature sizes meet specifications, thereby enhancing the quality of photomasks and reducing wafer scrap rates by adjusting exposure energy based on defect types.
Implementation Method 1
performing a wet etching to widen the plurality of openings with an etchant
Implementation Method 2
a photolithography is performed to transfer the first opening and the second opening to a target layer
Data Source
AI summary
A method for forming a semiconductor device includes receiving a substrate having a first opening and a second opening formed thereon, wherein the first opening has a first width, and the second opening has a second width less than the first width; forming a protecting layer to cover the first opening and expose the second opening; performing a wet etching to widen the second opening with an etchant, wherein the second opening has a third width after the performing of the wet etching, and the third width of the second opening is substantially equal to the first width of the first opening; and performing a photolithography to transfer the first opening and the second opening to a target layer.