Micromirror Array Control via Separate Measuring Light Bundle
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Solution Overview
Problem
Existing microlithographic projection exposure systems face challenges in accurately controlling the tilting position of micromirror arrays due to intensity losses from decoupling useful light, leading to longer downtimes and complex sensor installations.
Innovation Solution
A control device that uses a separate measuring light bundle to determine the deflection of micromirrors without decoupling the projection light, allowing continuous monitoring of the optical system's alignment during operation by directing the measuring light at a different angle than the projection light, enabling precise control of the micromirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If part of the exposure beam is decoupled from the beam path to adjust mirror elements by intensity measurements, then the mirror alignment can be checked, but intensity losses occur which are undesirable for shortest exposure times
Solution Approach 1:
The patent extracts the measurement function from the main exposure beam path by using a separate measuring illumination device. This allows alignment measurement of mirror elements without decoupling useful light from the projection beam path, thereby avoiding intensity losses while maintaining measurement capability
Solution Approach 2:
The patent introduces an intermediary measuring illumination device that provides a separate light source for measurement purposes. This intermediary system enables mirror alignment checking without directly interfering with the main exposure beam, thus preventing intensity losses in the projection light
2Measurement precision
If sensors are installed on actuators to determine rotation or tilt angle of mirror elements, then precise position control is achieved, but the arrangement becomes very voluminous due to installation space required for sensors
Solution Approach 1:
The patent replaces direct mechanical sensing on each mirror actuator with an optical measurement system. By using optical reflection and detection methods, the system achieves precise tilt angle determination without requiring physical sensors mounted on each mirror element, thus reducing overall system volume and complexity
Solution Approach 2:
The patent uses optical copying principles where the position and orientation of mirror elements are determined by measuring the reflection of measuring light bundles. This indirect optical measurement approach eliminates the need for direct physical sensors on each actuator, reducing device complexity and volume
3Measurement precision
If mirror elements are checked and adjusted at times when the lens is not being used, then alignment can be verified, but longer downtimes are required which impair effective operation
Solution Approach 1:
The patent enables continuous measurement of mirror element alignment during lens operation by using a separate measuring illumination device. The measurement process occurs simultaneously with exposure operations, eliminating downtime and maintaining continuous productive action without compromising alignment verification
Solution Approach 2:
The patent implements preliminary measurement capability where the measuring illumination device is continuously active or can be quickly activated to assess mirror alignment before it deviates from required specifications. This allows for proactive adjustment during operation rather than reactive correction during downtime
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 allows for high-accuracy control of micromirrors without intensity losses, reducing downtimes and simplifying the installation of sensors, thereby enhancing the operational efficiency of microlithographic projection exposure systems.
Implementation Method 1
at least one measuring light bundle from a measuring illumination device is directed onto the beam deflection element to be examined, so that the deflection of the measuring light bundle due to the beam deflection element can be detected by a detector device
Data Source
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AI summary
The lighting system has a pupil surface and a substantially planar arrangement of beam deflecting elements (28) which is triggered in an individual manner. The beam deflecting elements are used for variably illuminating the pupil surface. Every beam deflecting element allows a projection light beam (32) that is incident afterward to be deflected in accordance with a control signal which is applied to the beam deflecting element. Independent claims are also included for the following: (1) a calibration device for measuring or correcting variables (2) a controlling unit for controlling a two-dimensional arrangement of individually controllable beam deflection elements (3) a measuring instrument for simultaneous receiving of measuring signals (4) a method for determining the deflection projection light bundle in a lighting system of a micro-lithographic projection exposure apparatus.