Photomask CD Correction Using DMD-Guided Laser Etching
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Solution Overview
Problem
The increasing miniaturization of semiconductor devices requires techniques for forming smaller circuit patterns, and EUV photolithography processes face challenges in effectively correcting defects in photomasks, particularly critical dimension (CD) deviations, which can be transferred to wafers.
Innovation Solution
A method involving a digital micromirror device (DMD) is used to direct a laser beam to a mirror array, converting it into a beam pattern array based on local CD correction information, which is then focused into a linear beam to apply a chemical liquid to the photomask for precise CD correction, allowing for efficient correction of CD deviations in local regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photomask correction methods are used, then manufacturing process is simple, but CD correction precision is insufficient
Solution Approach 1:
The patent segments the correction process into distinct functional modules: a DMD device for beam pattern generation, a laser source for irradiation, a chemical liquid supply system, and a scanning mechanism. This segmentation allows each component to be optimized independently while achieving high CD correction precision through coordinated operation of these modular subsystems
Solution Approach 2:
The patent replaces conventional mechanical correction methods with an optical-based system using laser irradiation controlled by a DMD device. The DMD dynamically generates beam patterns corresponding to correction target regions, substituting mechanical adjustment with optical field control to achieve precise localized CD correction
2Manufacturing precision
If local CD correction is performed, then CD uniformity is improved, but correction time increases
Solution Approach 1:
The patent employs periodic scanning action where the laser beam, directed by the DMD, systematically moves across the photomask surface in repeated cycles. This periodic irradiation pattern allows efficient coverage of multiple correction target regions while maintaining focused energy delivery to achieve uniform CD correction across the mask
Solution Approach 2:
The patent introduces chemical liquid as an intermediary medium between the laser irradiation and the photomask material. The chemical liquid enhances the etching effect of laser irradiation, allowing faster material removal and CD correction while reducing direct laser energy requirements, thus decreasing correction time
3Measurement precision
If beam pattern array is focused into linear beam, then irradiation precision is improved, but optical system complexity increases
Solution Approach 1:
The patent transforms the two-dimensional beam pattern array from the DMD into a one-dimensional linear beam through optical focusing. This dimensional reduction concentrates the optical energy along a line, enabling precise scanning-based irradiation of correction regions while using relatively simple optical focusing components rather than complex two-dimensional spatial control systems
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 method enables precise and efficient correction of CD deviations in photomasks, improving the accuracy of semiconductor device manufacturing by effectively addressing defects and ensuring uniformity of pattern dimensions on wafers.
Implementation Method 1
directing a laser beam to a mirror array of a digital micromirror device (DMD), wherein the mirror array has mirrors arranged in a plurality of rows and a plurality of columns; converting the laser beam into a beam pattern array corresponding to the mirror array by controlling on/off switching of each of the mirrors
Implementation Method 2
forming a linear beam by focusing the beam pattern array through an optical system
Implementation Method 3
performing CD correction of an area of the photomask by applying an etchant to the photomask, directing the linear beam to the photomask, and moving the linear beam to irradiate the area
Data Source
AI summary
A method of manufacturing a photomask includes forming a photomask having a plurality of pattern elements, wherein the plurality of pattern elements include correction-target pattern elements having a critical dimension (CD) deviation; acquiring local CD correction information; directing a laser beam to a mirror array of a digital micromirror device (DMD), wherein the mirror array has mirrors arranged in a plurality of rows and a plurality of columns; converting the laser beam into a beam pattern array corresponding to the mirror array by controlling on/off switching of each of the mirrors based on the local CD correction information; forming a linear beam by focusing the beam pattern array through an optical system; applying an etchant to the photomask and directing the linear beam to the photomask and moving the linear beam to irradiate the photomask.