KR100258175B1 - Apparatus for aligning a reticle using position sensitive detector and method of aligning a reticle - Google Patents

Abstract

PURPOSE: A method and an apparatus for aligning a reticle are provided to measure the rotation of the reticle and to achieve the high accuracy of a position alignment by using a position sensing device. CONSTITUTION: A reticle aligning device comprises a semiconductor laser module(201) including a semiconductor laser(210) and a collimator lens(211) for generating a parallel laser beam(202). A prism(203) is provided to refract the parallel laser beam(202) generated from the semiconductor layer module(201) at a right angle. Slits(205) are formed in a reticle(204) to allow the refracted laser beam to pass through the reticle(204). A position sensing device(206) is provided to detect the position of the parallel laser beam which passes through the slit(205) of the reticle(204).

Description

Reticle Aligner and Reticle Alignment Method Using Position Detection Devices

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step and scan exposure apparatus using an ArF excimer laser as a light source, and in particular, a position detection using a one-dimensional semiconductor position detection element, which allows the device to be relatively simple and obtain high position accuracy. A reticle alignment apparatus and a reticle alignment method using the device.

Recently, as the integration degree of semiconductor memory devices increases, the line width of the circuit becomes smaller, and high resolution lithography equipment is required to satisfy this. In addition, in order to cope with the rapid development trend of semiconductor memory devices, technology development for micro pattern formation, which is the most important process, must be made.

The semiconductor exposure equipment used to project the electronic circuit recorded on the reticle onto the photoresist-coated wafer surface increases the minimum line width resolution as the degree of integration of semiconductors increases. KrF excimer laser light has been used. In addition, ArF excimer laser step and scan exposure equipment with a wavelength of 193nm, which will be used for high-density integrated circuits of 1GDRAM or more, will soon become practical.

The main performances of semiconductor exposure equipment include resolution, exposure area, and alignment accuracy. Especially in the semiconductor process requiring multiple pattern formation process, the semiconductor circuit pattern formed on the layer made in the previous process and the layer made successively It is very important that they form exactly overlap. The performance of the exposure equipment in this regard is the overlay accuracy of the circuit pattern, and in general, the exposure equipment requires an overlap accuracy of 1/4 or less of the minimum pattern formed in the semiconductor circuit. For example, an overlapping accuracy of 0.08 μm (3σ) is required for 64M DRAM to which 0.35 μm design rule is applied and 0.06 μm (3σ) to 256M DRAM to which 0.25 μm is applied.

The alignment of the wafer itself is important to achieve such wafer superposition accuracy, but at the same time, the alignment precision of the reticle containing the circuit pattern is also important. The alignment accuracy of the reticle alignment system is the precision that the reticle alignment system must have in order to achieve the final overlap accuracy in semiconductor device fabrication. This is defined as a value obtained by multiplying the magnification of the projection optical system by the overlapping precision, and when calculating the magnification of the projection optical system by x4, the reticle alignment precision of about 0.24 μm (3σ) is required for 256M DRAM.

In order to achieve such reticle alignment accuracy, a reticle alignment method used in conventional exposure equipment is a method of enlarging an alignment mark pre-engraved on a reticle using a microscope objective lens and manually performing alignment through a TV monitor. . As another alignment method, an intensity of the diffracted light may be used as an alignment signal using interference or diffraction effects of the aligned light diffracted by the reticle alignment mark in the form of a diffraction grating.

However, these methods are complicated by the auxiliary systems for the alignment, and the alignment accuracy is fundamentally limited by the design technique of the reticle alignment mark or the S / N ratio of the alignment signal. It is the limit.

Accordingly, the present invention solves the above-described problems, and by using three one-dimensional semiconductor position detection elements, a semiconductor laser, etc., the device is relatively simple and a high alignment position accuracy of 0.1 μm can be obtained, and at the same time, The purpose of this paper is to propose a new method and means for sorting reticles that can be extracted to the full amount.

The reticle alignment device using the position detection element of the present invention for achieving the above object is a semiconductor laser module consisting of a semiconductor laser and a collimating lens as a light source for illuminating the slit located in the reticle, and parallel light emitted from the semiconductor laser module And a position detecting element for detecting a position of the parallel light passing through the slit of the reticle, and a prism refracted at right angles, the parallel light refracted by the prism.

The reticle alignment method using the position detection device of the present invention is to manufacture a reticle with the first and third slits in the horizontal direction and the second slit in the vertical direction on the reticle to simultaneously measure the position error and rotational error of the x and y axis of the reticle And the first, second and third corresponding in the direction perpendicular to the first, second and third slits to detect the light transmitted through the first, second and third slits. And positioning the position detecting device.

1 is a plan view showing a device of the reticle transport system applied to the present invention.

Figure 2 is a side view of the device showing the principle of the reticle alignment system to locate the reticle applied to the present invention.

3 is a circuit diagram for processing an electrical signal of the position detection device shown in FIG.

Figure 4 is a device diagram showing the position and direction of the alignment slit to be formed in the reticle according to the present invention.

FIG. 5 is an apparatus diagram showing the position and direction of a position detecting element corresponding to the alignment slit shown in FIG. 4. FIG.

FIG. 6 is a layout view of the reticle slit and the position detection device of FIGS. 4 and 5.

<Description of Signs of Major Parts of Drawings>

101: reticle handling robot 102: y-axis travel guide

103: y-axis feed guide 104: x-axis feed motor

105: feed guide in the x-axis direction 106: reticle mount

107: projection lens 108: reticle alignment system mount

109, 110 and 111: semiconductor laser module

112: reticle 113, 114, and 115: prism

201: semiconductor laser module 202: semiconductor laser light

203: Prism 204: reticle

205: slit 206: position detection element (PSD)

207: electrical signal output terminal 208: electrical signal output terminal

209: electrical signal ground or 5V terminal

301 and 302: signal input terminals 303 and 304: current-voltage conversion operational amplifier

305: subtraction circuit 306: addition circuit

307: division circuit 308: subtraction output terminal

309: output terminal 401: reticle

402: electronic circuit regions 403, 404, and 405: slit

501, 502, and 503: position detection element (PSD)

504, 505, and 506: light receiving area of the position detecting element

507: position detection element mount 601: reticle

602: circuit area 603, 604 and 605: slit

606, 607 and 608: position detecting element

609, 610, and 611: shape of light shining on the slit

1 is a plan view showing the apparatus of the reticle delivery system, the process of carrying in the reticle is as follows.

The reticle handling robot 101 removes the reticle 112 from the reticle cartridge and places the reticle 112 on the reticle mount 106 which is in the loading position. The reticle mount 106 loads the reticle 112 and moves to the exposure position located above the projection lens 107 by the x-axis anti-deflection feed motor 104. The reticle position error when the reticle handling robot 101 places the reticle 112 on the reticle mount 106 is about tens of microns in the x and y axis directions, and includes a rotation error. Therefore, before moving the reticle to the exposure position, the position of the reticle must be adjusted within the limit of the position error required by the exposure equipment. Reference numerals 102 and 103, which are not described herein, are y-axis feed guides, and reference numeral 105 is an x-axis feed guide. Reference numeral 108 is a reticle alignment system mount, reference numerals 113, 114, and 115 are prisms, and reference numerals 109, 110, and 111 are semiconductor laser modules.

Figure 2 is a side view of the device showing the principle of the reticle alignment system to locate the reticle, three independent sensors are needed to determine the x and y axis error and rotational error of the reticle for one position detection method Explain.

The semiconductor laser module 201 includes a visible light semiconductor 210 and a collimating lens 211 to emit collimated parallel light 202. The laser light 202 is bent 90 degrees by the prism 203 and directed downward, and illuminates the slit 205 carved in the bottom edge portion of the reticle 204. Light rays passing through the slit 205 enter a one-dimensional semiconductor position-sensitive device (PSD) 206 located directly below the reticle 204. The one-dimensional position detecting element 206 is commercialized as a kind of semiconductor diode photodetector. The light receiving area of the one-dimensional position detecting element 206 has a width of about 1 mm and a length of about 5 to 15 mm, and the first and second output terminals 207 and 208 are positioned at both ends along the longitudinal direction. The current from the output terminals 207 and 208 changes depending on the position of the light incident on the light receiving region, and the output current can be processed using a circuit to determine the position where the light enters.

3 is a circuit diagram of processing current from the one-dimensional position detecting element and converting the position information into position information.

When the first and second output terminals 207 and 208 of the one-dimensional position detecting element 206 are connected to the first and second input terminals 301 and 302, the first and second current-voltage conversion calculations are performed. The amplifiers 303 and 304 change the voltages V1 and V2 in proportion to the corresponding currents, respectively. The subtraction circuit 305 generates an output corresponding to the difference between V1 and V2, and the addition circuit 306 generates an output corresponding to the sum of V1 and V2. The division circuit 307 generates a signal 309 that is proportional to the value obtained by dividing the signals V1-V2 of the subtraction circuit 305 by the signals V1 + V2 of the addition circuit 307.

By passing through the division circuit 307 in this manner, the output signal 309 generates a stable position signal irrespective of the intensity of light incident on the position detection element 206. In addition, the division circuit 307 may be omitted and the output 308 of the subtraction circuit 305 may be directly used in the zero search process where V1 and V2 find the same position. In this case, although the output signal depends on the intensity of the incident light, the intensity of the incident light does not matter when finding a point where V1 = V2.

4 is a plan view showing the slit shape and the position of the reticle required to detect the position of the reticle with respect to the x-axis, y-axis, and rotation using the apparatus of FIG. 2 and the circuit of FIG.

Reference numeral 401 denotes a reticle, and reference numeral 402 is a circuit region containing an electronic circuit in the reticle 401. Reference numerals 403 and 405 denote horizontal slits of the reticle and are used to detect the position in the y direction corresponding to each position. Reference numeral 404 is the vertical slit of the reticle and is used to detect the position in the x direction.

FIG. 5 is a plan view showing the position and direction of the one-dimensional position detecting element positioned under each slit of FIG. 4 and used to detect the position of light passing through the slit.

The first, second and third position detection elements 501, 502 and 503 are located immediately below the slits 404, 405 and 406 of the first, second and third reticles, respectively. The first and third light receiving regions 504 and 506 of the first and third position detecting elements 501 and 503 are in the vertical direction y, and the second light receiving of the second position detecting element 502 is performed. Region 505 is located in the horizontal direction x. Reference numeral 507 denotes a mount on which the position detecting element is placed.

FIG. 6 shows the reticle of FIG. 4 and the position detecting device of FIG. 5 together to show the correlation of x position, y position and rotation angle.

Reference numeral 601 denotes a reticle, and reference numeral 602 denotes a circuit region on the reticle. Reference numerals 603, 604, and 605 denote slits of the first, second, and third reticles, and reference numerals 606, 607, and 608 denote first, second, and third Position detection element. The first position detection element 606 detects the position y1 of the semiconductor laser light that passes down from the top through the slit 603 of the first reticle, and the third position detection element 608 is the third reticle The position y2 of the semiconductor laser light that passes through the slit 605 from the top to the bottom is detected. It is possible to find out the information rotated by the reticle from the position values of y1 and y2. By making y1 and y2 equal, it is possible to make the reticle horizontal and eliminate the rotational error, and at the same time eliminate the error in the y-axis direction. The second position detecting element 607 can detect the x direction position of the light coming down through the second reticle slit 604 to eliminate the x direction position error. The position detection area that can be detected by the apparatus is the same as the longitudinal direction of the light receiving area of the one-dimensional position detection element, and the cross-sectional shape in the slit of the semiconductor laser light shining on the slit to ensure this detection area is indicated by reference numeral 609. ), Such as 610 and 611, so as to sufficiently include the position detecting element.

As described above, according to the present invention, the following excellent effects can be obtained.

First, as a method used in a conventional reticle alignment device, a very complicated alignment system and an apparatus such as a microscope, an illumination source for alignment, a monitor, and the like were essential. However, in the present invention, a position detecting device, a prism, a light emitting diode (LED) or a semiconductor laser is essential. By using as a light source, the device can be configured relatively simply, and the space for the reticle alignment device can be reduced.

Second, since the resolution of the position detection element currently commercially available in terms of reticle alignment accuracy is usually 0.1 μm or less, more accurate position accuracy can be obtained than the conventional method, and by simultaneously measuring three slits on the reticle by reticle In addition to the position information of the reticle can also extract the amount of rotation.

Claims (2)

A semiconductor laser module comprising a semiconductor laser and a collimating lens as a light source for illuminating a slit positioned in the reticle, A prism that refracts the parallel light emitted from the semiconductor laser module at a right angle; A slit of the reticle for passing parallel light refracted by the prism, And a position detecting element for detecting a position of parallel light passing through the slit of the reticle. Forming a first and a third slit in the horizontal direction and a second slit in the vertical direction on the reticle to simultaneously measure the x and y axis position error and the rotational error of the reticle, Arranging corresponding first, second and third position detection elements in a direction perpendicular to the first, second and third slits to detect light transmitted through the first, second and third slits Reticle alignment method using a position detection device characterized in that it comprises a step.

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