Exposure Apparatus Focus Control Using Master Surface Profile Data
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Solution Overview
Problem
Existing exposure apparatuses face challenges in forming patterns on masters with high accuracy due to residual focus errors caused by surface roughness, inclination, and decentering of the master, leading to increased costs from enhanced polishing requirements.
Innovation Solution
An exposure apparatus that adjusts the focus of laser light using integrated surface profile data to correct for focus errors, incorporating a control unit with an error detection unit, adder, and computing unit to generate a correction signal for precise focus control based on surface roughness, inclination, and decentering of the master.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional focus control using a four-quadrant detector is employed, then the exposure apparatus can perform basic focus adjustment, but residual focus errors remain due to surface roughness, inclination, and decentering of the master
Solution Approach 1:
The system performs preliminary measurement of the master's surface profile, inclination, and decentering before exposure. Based on these measurements, the control unit pre-calculates and applies correction values to the focus position, proactively compensating for expected focus errors before the actual exposure process begins
Solution Approach 2:
The system implements a feedback mechanism where the measured surface profile data, inclination, and decentering are continuously fed back to the control unit. The control unit dynamically adjusts the focus position based on this feedback, creating a closed-loop control system that eliminates residual focus errors
2Manufacturing precision
If enhanced polishing of the master surface is performed to reduce surface roughness, then pattern formation accuracy improves, but manufacturing costs increase significantly
Solution Approach 1:
The system replaces mechanical polishing processes with an optical measurement and electronic correction system. Instead of physically modifying the master surface through enhanced polishing, the system uses optical sensors to measure surface characteristics and electronically adjusts the focus position to compensate for surface irregularities
Solution Approach 2:
The system changes the focus position parameter dynamically based on measured surface profile data. By adjusting the focus parameter electronically rather than modifying the physical master surface, the system achieves high pattern formation accuracy without the cost of enhanced polishing
3Reliability
If the control system incorporates multiple measurement parameters (surface profile, inclination, decentering), then focus control accuracy improves, but device complexity increases
Solution Approach 1:
The control unit serves multiple functions: it processes surface profile measurements, calculates inclination, determines decentering, computes correction values, and controls the focus position. This multi-functional design consolidates what could be separate complex subsystems into a single integrated control unit
Solution Approach 2:
The system merges multiple measurement functions (surface profile measurement, inclination detection, decentering calculation) into a single integrated measurement and control system. By combining these functions, the system achieves high focus control accuracy while avoiding the complexity of multiple separate measurement and control subsystems
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 solution enables more accurate pattern formation on masters without significant increases in cost by effectively suppressing residual focus errors, thereby improving exposure accuracy.
Implementation Method 1
a laser light source 121 which outputs laser light
Implementation Method 2
The object lens 124 concentrates laser light transmitted through the polarizing beam splitter 123 and directs the light toward the master 1
Implementation Method 3
The optical sensor 13 is a sensor which receives light from the cylindrical lens 126 (reflected light from the master 1) on the active area and performs output depending on the received light
Data Source
AI summary
An exposure apparatus 10 is an exposure apparatus for forming a pattern by exposure by irradiating a set master 1 with laser light, comprising: an optical pickup 12 which is capable of adjusting the focus of laser light and a control unit 19 which adjusts the focus of laser light emitted from the optical pickup 12 using integrated surface profile data indicating the relative positional relationship between the surface of the master 1 and the optical pickup 12 according to at least one of the surface roughness of the master 1, the inclination of the master 1, and the decentering of the master 1.