An optical system for monitoring angular position of micro-mirror array based on Scheimpflug condition

Abstract

A micro-mirror array angular position monitoring optical system based on the Scheimpflug condition comprises a laser array, a micro-lens array, a multi-step flat glass, an imaging lens assembly, a micro-mirror array, a reflected light receiving lens assembly, and a position sensor, arranged in sequence along the beam propagation direction. The laser array emits an array beam with a certain numerical aperture, the micro-lens array collimates the array beam and then vertically injects it into the multi-step flat glass, and the imaging lens assembly projects the array beam emitted from the multi-step flat glass onto the micro-mirror array. The laser array, micro-mirror array, and imaging lens assembly satisfy the Scheimpflug condition, ensuring that the spot size at the micro-mirrors is smaller than the effective area of ​​the micro-mirrors. The reflected light receiving lens assembly focuses the beam reflected by the micro-mirror array onto the position sensor, which monitors the angular position of each micro-mirror in the micro-mirror array. The micro-mirror array exhibits excellent imaging quality, a simple structure, ease of assembly and adjustment, high measurement accuracy, and high monitoring efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography machines, and in particular to a micro-mirror array angular position monitoring optical system based on Scheimpflug conditions. Background Art

[0002] With the continuous development of semiconductor industry technology, the requirements for the performance of lithography machines are becoming higher and higher. In order to achieve random conversion of different illumination modes in lithography machines, free pupil illumination systems have gradually been applied to lithography machines at 28nm and below nodes.

[0003] For the free pupil illumination system, the micromirror array is its core component. By changing the two-dimensional angle of the micromirror array, an arbitrarily adjustable illumination mode can be achieved. Therefore, the stability of the micromirror array directly affects the performance of the lithography machine. Monitoring the rotation state of the micromirror array has important application value for the lithography machine illumination system.

[0004] In the patent "Micro-mirror array angular position monitoring device and method of use for lithography", the angular position monitoring unit is composed of an array laser assembly, a micro-lens array assembly, a micro-mirror array assembly, a Fourier receiving mirror group, and a position sensor. The array light beam emitted by the array laser is collimated by the micro-lens array into a parallel light beam that is incident on the corresponding array micro-mirror. After being reflected by the micro-mirror, it is imaged by the Fourier receiving mirror group to the position sensor, and the position sensor detects the angular state of the array micro-mirror. In this optical path, if the spot size of the light beam collimated by the micro-lens and propagated to the corresponding micro-mirror is larger than the effective area of ​​the micro-mirror, the light beam outside the effective area is imaged by the Fourier mirror group to the position sensor, which will interfere with the angle state of the micro-mirror to be measured, making the subsequent algorithm correction more difficult and even causing errors in the micro-mirror angle measurement. Summary of the Invention

[0005] In response to the technical problems of angular position monitoring of a micromirror array in a lithography machine, the present application provides an optical system for monitoring the angular position of a micromirror array based on the Scheimpflug condition. This optical system can reduce the spot size at the micromirror array to help improve the resolution and accuracy of the angular position measurement of the micromirror array.

[0006] The technical solutions provided by the present invention are as follows:

[0007] The present invention provides a micro-mirror array angular position monitoring optical system based on the Scheimpflug condition, which comprises a laser array, a micro-lens array, a multi-step flat glass, an imaging lens group, a micro-mirror array, a reflected light receiving lens group and a position sensor, arranged in sequence along the light beam propagation direction;

[0008] The laser array emits an array beam having a certain numerical aperture, the microlens array collimates the array beam and then vertically injects it into the multi-step flat glass, the imaging lens group projects the array beam emitted from the multi-step flat glass onto the micro-mirror array, and the laser array, micro-mirror array, and imaging lens group satisfy the Scheimpflug condition so that the spot size of the light beam propagating to the corresponding micro-mirror in the micro-mirror array is smaller than the effective area of ​​the micro-mirror;

[0009] The reflected light receiving mirror group focuses the light beam reflected by the micro-mirror array onto the position sensor, and the angular position of each micro-mirror in the micro-mirror array is monitored by the position sensor.

[0010] Further preferably, the multi-step flat glass is used to make the propagation optical paths of the emitted light beams at different positions of the laser array different, so that the laser array is arranged perpendicular to the optical axis.

[0011] Further preferably, the laser array includes several lasers, the microlens array includes several microlenses, the micromirror array includes several micromirrors, and the lasers, microlenses and micromirrors correspond to each other one by one.

[0012] Further preferably, the multi-step flat glass is used to perform optical path compensation on the light beams emitted by each laser, so that the light beams emitted by lasers at different positions propagate through different optical paths.

[0013] Further preferably, the multi-step flat glass is provided with a matching stepped flat glass corresponding to each laser, and the matching enables the stepped flat glass to compensate for the optical path of the light beam emitted by the corresponding laser.

[0014] Further preferably, the step thickness of the stepped flat glass is designed according to a target optical path of a corresponding laser emitted light beam.

[0015] Further preferably, the laser array, micro-mirror array and imaging lens group satisfy the Scheimpflug condition, specifically: the plane where the laser array is located, the plane where the micro-mirror array is located and the plane where the imaging lens group is located intersect at a Scheimpflug line.

[0016] The micro-mirror array angular position monitoring optical system provided by the present invention satisfies the Scheimpflug condition through the laser array, the micro-mirror array and the imaging lens group. The imaging lens group directly projects the array light spot after the collimated output of the microlens array onto the corresponding micro-mirror array, which can significantly reduce the light spot size at the micro-mirror array, and is beneficial to reducing the crosstalk of the array light points at the micro-mirror array, thereby improving the measurement accuracy and efficiency of the micro-mirror array angular position monitoring.

[0017] Furthermore, optical path compensation is performed by using multi-step flat glass to solve the problem of tilted installation of the laser array. Adding multi-step flat glass can not only help reduce the spot size at the micro-reflection mirror surface, but also reduce the difficulty of subsequent optical system installation.

[0018] The micro-mirror array angular position monitoring optical system provided by the present invention can achieve excellent imaging quality at the micro-mirror array based on the Scheimpflug condition. The micro-mirror array angular position monitoring optical system has a simple structure, is easy to assemble and adjust, has high measurement accuracy, and has high monitoring efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the optical path for angular position monitoring in the prior art;

[0020] Figure 2 This is a schematic diagram of the optical path principle of Scheimpflug's law;

[0021] Figure 3 Schematic diagram of the optical path principle of the micro-mirror array angular position monitoring optical system based on the Scheimpflug condition. DETAILED DESCRIPTION

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0023] The optical path diagram of the angular position monitoring unit system in the prior art is as follows: Figure 1 As shown, the array light beam emitted by the laser array 1 often has a certain divergence angle after being collimated by the microlens array 2. The design and processing of the microlens, as well as the alignment of the laser and the microlens, will cause the light beam emitted by the microlens array 2 to have a certain divergence angle. The divergent light beam propagates for a certain distance and is incident on the micromirror array 3. There is a risk that the spot size exceeds the effective area of ​​the micromirror, which will cause excess light beam to be incident on structural parts outside the effective reflection area of ​​the micromirror, and then be received by the Fourier receiving lens group 4 and imaged into the position sensor 5, resulting in the accuracy and efficiency of angular position monitoring being affected.

[0024] The present invention creatively introduces the Scheimpflug law into the angular position monitoring of the micro-mirror array, and uses the Scheimpflug law to project the array light beam generated by the laser array to the corresponding micro-mirror array, so that the spot size of the light beam propagating to the corresponding micro-mirror in the micro-mirror array is smaller than the effective area of ​​the micro-mirror; although the spot size at the micro-mirror array has been reduced, the laser array needs to be placed at an angle, which increases the difficulty of installation and adjustment. Furthermore, the present invention also creatively adds multi-step flat glass behind the laser array. The multi-step flat glass can meet the Scheimpflug condition and the laser array can be placed perpendicular to the optical axis, which reduces the difficulty of installation and adjustment. At the same time, angular position monitoring based on the Scheimpflug condition is conducive to further improving the accuracy and efficiency of micro-mirror array angle measurement through hardware.

[0025] In 1993, Austrian Army Captain Scheimpflug proposed the Scheimpflug Law (Scheimpflug Law), which states that when the three planes of the object plane, lens plane, and image plane in the imaging system intersect on the same straight line (Scheimpflug line), the object plane can be clearly imaged. The optical path principle diagram of the Scheimpflug Law is shown below. Figure 2 shown.

[0026] The optical path principle diagram of the micro-mirror array angular position monitoring optical system provided by the present invention is as follows: Figure 3 As shown, a laser array 1, a microlens array 2, a multi-step flat glass 6, an imaging lens group 7, a micro-mirror array 3, a reflected light receiving lens group 4 and a position sensor 5 are sequentially arranged along the light beam propagation direction;

[0027] The laser array 1 emits an array beam with a certain numerical aperture. The microlens array 2 collimates the array beam and then vertically injects it into the multi-step flat glass 6. The imaging lens group 7 projects the array beam emitted from the multi-step flat glass 6 onto the micromirror array 3. The laser array 1, the micromirror array 3, and the imaging lens group 7 meet the Scheimpflug condition so that the spot size of the light beam propagating to the corresponding micromirror in the micromirror array 3 is smaller than the effective area of ​​the micromirror.

[0028] The reflected light receiving lens group 4 focuses the light beam reflected by the micro-mirror array 3 onto the position sensor 5 , and the position sensor 5 monitors the angular position of each micro-mirror in the micro-mirror array 3 .

[0029] The laser array 1 , the micro-mirror array 3 and the imaging lens group 7 satisfy the Scheimpflug condition, specifically: the planes of the laser array 1 , the micro-mirror array 3 and the imaging lens group 7 intersect at the Scheimpflug line.

[0030] In the present invention, the multi-step flat glass 6 is used to make the propagation optical path of the emitted light beam at different positions of the laser array 1 different, so that the laser array 1 is arranged perpendicular to the optical axis.

[0031] In the present invention, the laser array 1, the microlens array 2, the multi-step flat glass, and the micro-mirror array 3 need to correspond to each other. Specifically, the laser array 1 includes several lasers, the microlens array 2 includes several microlenses, and the micro-mirror array 3 includes several micro-mirrors. The lasers, microlenses, and micro-mirrors correspond one to one. Furthermore, the multi-step flat glass 6 is used to compensate the optical path of the light beams emitted by each laser, so that the light beams emitted by lasers at different positions propagate different optical path lengths.

[0032] Since the overall tilt of the laser array 1 at a certain angle will bring certain difficulties to the subsequent optical path adjustment, the technical solution of the present invention uses the multi-step flat glass 6 to compensate for the optical path, thereby solving the problem of the tilted installation of the laser array 1; further, the multi-step flat glass 6 is respectively provided with a matching stepped flat glass corresponding to each laser, and this matching enables the stepped flat glass to compensate for the optical path of the light beam emitted by the corresponding laser.

[0033] In the optical system, the propagation optical path of the light beam emitted by each laser is different. Furthermore, the step thickness of the step flat glass is designed according to the target optical path of the light beam emitted by the corresponding laser. Different optical paths are compensated by step flat glass of different thicknesses. The greater the thickness of the step flat glass, the longer the compensated optical path, and the smaller the thickness of the step flat glass, the shorter the compensated optical path. For example, the thickness of the step flat glass with a short light beam propagation path is smaller than the thickness of the step flat glass with a long light beam propagation path.

[0034] The micro-mirror array angular position monitoring optical system provided by the present invention can achieve excellent imaging quality at the micro-mirror array and a small spot size at the micro-mirrors based on Scheimpflug condition projection imaging. The Scheimpflug condition is realized by using multi-step flat glass to solve the problem of tilted installation of the laser array, making the laser array easy to assemble and adjust. The monitoring optical system has a compact structure, and the resolution and accuracy of the micro-mirror array angular position measurement are improved.

[0035] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A micro-mirror array angular position monitoring optical system based on Scheimpflug conditions, characterized in that: A laser array, a microlens array, a multi-step flat glass, an imaging lens group, a micro-reflector array, a reflected light receiving lens group and a position sensor are sequentially arranged along the light beam propagation direction; The laser array emits an array beam having a certain numerical aperture, the microlens array collimates the array beam and then vertically injects it into the multi-step flat glass, the imaging lens group projects the array beam emitted from the multi-step flat glass onto the micro-mirror array, and the laser array, micro-mirror array, and imaging lens group satisfy the Scheimpflug condition so that the spot size of the light beam propagating to the corresponding micro-mirror in the micro-mirror array is smaller than the effective area of ​​the micro-mirror; The reflected light receiving mirror group focuses the light beam reflected by the micro-mirror array onto the position sensor, and the angular position of each micro-mirror in the micro-mirror array is monitored by the position sensor.

2. The micro-mirror array angular position monitoring optical system according to claim 1, wherein: The multi-step flat glass is used to make the propagation optical paths of the emitted light beams at different positions of the laser array different, so that the laser array is arranged perpendicular to the optical axis.

3. The micro-mirror array angular position monitoring optical system according to claim 2, wherein: The laser array includes a plurality of lasers, the microlens array includes a plurality of microlenses, and the micromirror array includes a plurality of micromirrors. The lasers, microlenses, and micromirrors correspond to each other one by one.

4. The micro-mirror array angular position monitoring optical system according to claim 3, wherein: The multi-step flat glass is used to perform optical path compensation on the light beams emitted by each laser, so that the light beams emitted by lasers at different positions propagate through different optical paths.

5. The micro-mirror array angular position monitoring optical system according to claim 4, wherein: The multi-step flat glass is provided with a matching step flat glass corresponding to each laser, and the matching enables the step flat glass to compensate for the optical path of the light beam emitted by the corresponding laser.

6. The micro-mirror array angular position monitoring optical system according to claim 5, wherein: The step thickness of the stepped flat glass is designed according to the target optical path of the corresponding laser emitting light beam.

7. The micro-mirror array angular position monitoring optical system according to claim 1, wherein: The laser array, micro-mirror array and imaging lens group satisfy the Scheimpflug condition, specifically: the plane where the laser array is located, the plane where the micro-mirror array is located and the plane where the imaging lens group is located intersect at a Scheimpflug line.

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