JPH0745513A - Aligner - Google Patents

Abstract

PURPOSE:To obtain an aligner capable of exposing the peripheral part of a wafer to a light flux of uniform light intensity distribution. CONSTITUTION:When a wafer 1 coated with resist is mounted on a rotary stand 2, and the resist in the peripheral part 12 of the wafer 1 is irradiated with the luminous flux from a light source 4 while the wafer 1 is rotated, a variable shielding means which partially and dynamically shields the luminous flux, a light receiving means which clamps the peripheral part 12 of the wafer 1 and is arranged at a position optically facing the variable shielding means, and a signal obtained by the light receiving means are used, thereby detecting the edge position of the wafer 1 and the shielded part of the luminous flux from the variable shielding means. Further a control means which operates as follows is installed; on the basis of the edge position information of the wafer 1, servo control is applied to the change amount of the light shielding region of the variable shielding means, and the exposure width in the direction of radius of gyration of the peripheral part 12 of the wafer 1 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly to an exposure apparatus adapted to selectively expose a peripheral portion of a circular substrate such as a wafer used for manufacturing a semiconductor integrated circuit.

[0002]

2. Description of the Related Art When manufacturing a semiconductor integrated circuit, a resist is uniformly applied as a photosensitive material in order to form a circuit pattern on the surface of a substrate such as a wafer.

At this time, the resist applied to the substrate such as a wafer is easily peeled off at the peripheral portion of the wafer through various processing steps, and the peeled resist becomes dust, which has an adverse effect on the subsequent integrated circuit manufacturing process. There was a problem of affecting.

On the other hand, Japanese Unexamined Patent Publication No. 2-56924 proposes an exposure apparatus for preventing the resist peeling in the peripheral portion of the wafer. In this publication, a light emitting portion that irradiates an exposure light flux and a light receiving portion that is opposed to the light emitting portion with a peripheral portion of the wafer interposed therebetween are integrally movable relative to the wafer.

Of the exposure light flux for exposing the peripheral portion of the wafer, a light flux corresponding to a predetermined exposure width (the length in the radial direction of the wafer) is blocked by the wafer, and the remaining light flux is sandwiched between the peripheral portions of the wafer. Light is received by a light receiving section arranged facing the exposure light source, and a servo operation is performed to keep the exposure width of the peripheral portion of the wafer constant by using a signal obtained by this light receiving section so that the peripheral portion is exposed. There is.

[0006]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2-569
In the exposure apparatus proposed in Japanese Patent No. 24, the servo operation of the wafer position is performed so that the relative positional relationship between the wafer edge and the exposure light flux becomes constant in order to make the exposure width of the peripheral portion of the wafer constant. . Therefore, there are the following problems.

(1-1) When an exposure apparatus is mounted on a semiconductor device manufacturing apparatus such as a stepper, vibration due to servo operation adversely affects the main apparatus. Especially in the case of a stepper, the alignment accuracy is lowered.

(1-2) Dust is generated in association with the vibration of the servo operation and adheres to the wafer surface, which becomes an obstacle for forming a fine circuit pattern.

(1-3) The accuracy of controlling the exposure width of the wafer depends on the tracking performance of the servo operation. In order to shorten the exposure time of the peripheral part, not only the exposure light source is strengthened to increase the rotation speed of the wafer, but also the followability of the servo operation is not improved, the accuracy of the exposure width is reduced.

(1-4) In order to realize the servo operation favorably, the entire apparatus becomes complicated.

(1-5) The exposure accuracy depends on the unevenness of the light intensity distribution due to the exposure light source and the light guide, and the change over time.

The present invention is an exposure apparatus suitable for manufacturing a semiconductor device capable of efficiently exposing a predetermined area in the radial direction of a peripheral portion of a circular substrate such as a wafer with a light flux having an appropriate light intensity distribution in time and space. For the purpose of providing.

[0013]

An exposure apparatus according to the present invention comprises: (2-1) placing a resist-coated wafer on a turntable, and rotating the wafer to remove the resist on the periphery of the wafer from a light source. When exposing with a light flux, a variable light-shielding means for partially and dynamically shielding the light flux, a light-receiving means arranged at a position optically opposed to the variable light-shielding means with the peripheral portion of the wafer interposed therebetween, and the light-receiving means The edge position of the wafer and the light-shielding portion of the light flux from the variable light-shielding means are detected by using the signal obtained in step 1, and servo control is performed on the variation amount of the light-shielding area of the variable light-shielding means based on the edge position information of the wafer. In addition, a control means for controlling the exposure width in the rotation radius direction of the peripheral portion of the wafer is provided.

In particular, the variable light-shielding means has a mechanism for continuously changing the transmittance for each minute area unit, and by continuously changing the transmittance for each minute area unit, the light emitted to the wafer is irradiated. The intensity is controlled, and the light receiving means has a mechanism for measuring the light intensity distribution of the incident light beam, and the variable light shielding means has no transmittance in each minute area unit corresponding to the light intensity distribution of the light beam. It is characterized in that the intensity of light applied to the wafer is stabilized temporally and / or spatially by changing the stage, and the variable light shielding means is constituted by a liquid crystal shutter.

(2-2) Rotating table on which a wafer coated with a resist is placed, illumination means for irradiating a rectangular light beam in the rotation radius direction of the rotating table, and light flux incident in the rotating table direction in the rotation radius direction. The variable light blocking means provided in the optical path that blocks light at an arbitrary length and the peripheral portion of the wafer are sandwiched, and the light blocking means is placed at a position optically opposed to the variable light blocking means, and the light flux passing through the variable light blocking means is received. And a control means for controlling the light-shielding area of the variable light-shielding means based on the signal obtained by the light-receiving means, so that the peripheral portion of the wafer in the radial direction of rotation is exposed. There is.

[0016]

Embodiment 1 FIG. 1 is an explanatory diagram showing a schematic configuration of an exposure apparatus according to Embodiment 1 of the present invention.

In the figure, reference numeral 1 denotes a wafer as a circular substrate, on the surface of which a resist sensitive to exposure light described later is applied. A rotary table 2 holds the wafer 1. The turntable 2 is rotated at a predetermined speed by a motor 3. Wafer 1 is a wafer transfer path (not shown)
Is conveyed to the rotary table 2 along with and is held by suction on the rotary table 2 at a position where the center thereof and the rotation center of the rotation axis of the rotary table 2 substantially coincide with each other. A light source 4 is composed of a high pressure mercury lamp or the like and supplies exposure light.

A condenser lens 5 condenses the exposure light from the light source 4 and guides it to the incident surface 6a of the light guide 6. The light guide 6 consists of a bundle of optical fibers,
The cross section (incident surface) 6a on the side of the condenser lens 5 is bundled into a substantially circular shape, and the cross section (emission surface) 6b on the opposite side is formed in a rectangular shape so that a rectangular exposure light beam can be obtained. 7
Is a light beam emitted from the emission surface 6b of the light guide 6, and has a rectangular shape.

Reference numeral 8 is a liquid crystal shutter used as a variable light-shielding means in a liquid crystal printer or the like. A liquid crystal shutter controller 9 controls the liquid crystal shutter 8 to transmit or block the incident light beam 7 in units of a small area (pixel). Reference numeral 10 denotes a light beam that has passed through the liquid crystal shutter 8, and a part of the light beam 11 exposes the peripheral portion 12 of the wafer 1. Reference numeral 13 denotes a remaining light flux of the light flux 10 which has passed through the liquid crystal shutter 8 and which has exposed the peripheral portion 12 of the wafer 1.

Reference numeral 14 denotes a linear type light receiver, which is used for the wafer 1
It is arranged at a position facing the liquid crystal shutter 8 with the peripheral portion of the light receiving portion sandwiched therebetween, and the intensity distribution of the received light is detected. Reference numeral 15 denotes a photodetector control circuit, which detects the edge of the wafer 1 or a unit (pixel) of a minute area which is transparent or shielded by the liquid crystal shutter 8 based on a photoelectric signal from the photodetector 14.
Reference numeral 16 is a CPU as a control means, which takes in the output from the light receiver control circuit 15 and controls the drive of the liquid crystal shutter controller 9.

In the present embodiment, first, in the above-described structure, the following calibration operation is performed before the peripheral exposure of the wafer 1 is performed and the wafer 1 is not mounted on the rotary table 2. The exposure light from the exposure light source 4 is condensed by the condenser lens 5 and guided to the light guide 6. After passing through the light guide 6, the exposure light introduced into the light guide 6 becomes an exposure light flux having a rectangular cross section from the exit surface 6b and irradiates the liquid crystal shutter 8 with it.

Next, the CPU 16 controls the liquid crystal shutter controller 9 to change the light-transmitting area of the liquid crystal shutter 8, and at the same time, takes in the output of the linear type photodetector 14 from the photodetector control circuit 15, thereby transmitting the liquid crystal shutter 8. The relationship between the position where light is switched to light blocking and the output of the light receiver 14 is detected.

Next, after the above-mentioned calibration operation is completed, the CPU 16 once drives the liquid crystal shutter controller 9,
The entire area of the liquid crystal shutter 8 is set to the light blocking state. In this state, the wafer 1 is transferred onto the rotary table 2 along a wafer transfer path (not shown), and suction-held on the rotary table 2 at a position where the center of the wafer 1 and the rotation center of the rotation axis of the rotary table 2 are substantially coincident with each other. To do.

Next, the liquid crystal shutter 8 is sequentially switched to the translucent state in the direction from the outer periphery of the wafer 1 toward the center of the wafer 1. At this time, the output of the light receiver 14 is continuously taken in from the light receiver control circuit 15, and the point at which this output does not follow the change of the light transmitting area of the liquid crystal shutter 8 is determined to be the edge of the wafer 1.

Next, the light-transmitting region of the liquid crystal shutter 8 is widened so that the width (radial width) of the light flux 11 that exposes the peripheral portion 12 of the wafer 1 becomes a predetermined width, and the liquid crystal is further moved from the edge of the wafer 1. Servo is applied so that the position of the shutter 8 where light is switched to light is constant. In this state, the motor 3 is driven to rotate the wafer 1 on the turntable 2 so that the entire outer peripheral portion of the wafer 1 is exposed.

FIG. 2 shows the exit surface 6b of the light guide 6 of FIG.
It is explanatory drawing of the light intensity distribution of the cross section of the light beam 7 further emitted. FIG. 3 is an explanatory diagram showing the ratio of light transmission time when the liquid crystal shutter 8 is switched to execute the exposure amount control function and the illuminance unevenness correction function corresponding to the light intensity distribution of FIG.

Next, a method of executing the exposure amount control function and the illuminance unevenness correction function will be described with reference to FIGS.

First, with the wafer 1 not mounted on the turntable 2, the liquid crystal shutter 8 is set so that the entire area thereof is in a light transmitting state. At this time, generally, an intensity distribution having unevenness as shown in FIG. 2 is obtained from the light receiver 14.

In addition, the intensity distribution at this time generally changes with time, for example, in the direction of the arrow in the figure. The CPU 16 takes in the intensity distribution obtained by the photoreceiver 14 through the photoreceiver control circuit 15 so that each pixel of the liquid crystal shutter 8 is in a translucent state for a time inversely proportional to the intensity distribution as shown in FIG. The control circuit 15 is driven to drive the liquid crystal shutter 8 for switching.

As a result, the average of the intensity distribution of the light flux after passing through the liquid crystal shutter 8 is made constant.
Then, the peripheral portion of the wafer 1 is exposed using the light flux having the uniformed intensity distribution. The light receiver 14 used in this embodiment may also be used for wafer positioning.

FIG. 4 is a schematic view of the essential portions of Embodiment 2 of the present invention.

In this embodiment, the shape of the incident surface 6a of the light guide 6 is rectangular as in the case of the exit surface 6b as compared with the first embodiment shown in FIG. The difference is that the liquid crystal shutter 8 is arranged between the condenser lens 5 and the incident surface 6a of the light guide 6, and the other configurations are the same.

In this embodiment, the transmission area of the liquid crystal shutter 8 is controlled by the liquid crystal shutter controller 9 to control the shape of the light beam 10 incident on the incident surface 6a of the light guide 6. Thereby, the state of the light flux emitted from the exit surface 6b is controlled, and the same optical effect as that of the first embodiment is obtained.

[0034]

According to the present invention, by setting each element as described above, a predetermined area in the radial direction of the peripheral portion of a circular substrate such as a wafer can be temporally and spatially divided by a light flux having an appropriate light intensity distribution. It is possible to achieve an exposure apparatus suitable for manufacturing a semiconductor element, which can perform efficient exposure.

In particular, according to the present invention, the liquid crystal shutter is used to change the area for peripheral exposure, and the liquid crystal shutter is switched according to the light intensity distribution, so that the light intensity irradiated on the wafer can be changed over time. By physically and spatially stabilizing, (3-1) stable exposure can be obtained which is not affected by unevenness of the light intensity distribution due to the exposure light source or the light guide and temporal change.

(3-2) Since the servo drive for keeping the relative position of the wafer edge and the exposure light source constant is not performed, it is possible to prevent the generation of vibration and dust.

Further, since the followability of the liquid crystal shutter is faster than the servo drive for keeping the relative position of the wafer edge and the exposure light source constant, the exposure width control accuracy is improved. When the control accuracy of the exposure width is made equal to the conventional one, the exposure time can be shortened by using a stronger light source.

(3-3) The drive mechanism for keeping the relative position of the exposure light source at the wafer edge constant is not required. Further, since the mechanism is simple, it can be easily incorporated in an apparatus having a wafer rotating function. It is possible to achieve an exposure apparatus having effects such as the above.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a light intensity distribution of a light beam cross section of FIG.

FIG. 3 is an explanatory diagram showing a ratio of light transmission time when the liquid crystal shutter of FIG. 1 is switched.

FIG. 4 is a schematic view of the essential portions of Embodiment 2 of the present invention.

[Explanation of symbols]

 1 Wafer 2 Rotating Table 3 Motor 4 Light Source 5 Condenser Lens 6 Light Guide 7 Rectangular Luminous Flux 8 Liquid Crystal Shutter 9 Liquid Crystal Shutter Controller 10 Luminous Flux Transmitted by Liquid Crystal Shutter 11 Actual Flux of Wafer Exposed 12 Wafer Periphery 13 Remaining Luminous flux 14 Linear type photodetector 15 Photodetector control circuit 16 CPU

Claims (5)

[Claims] 1. A wafer coated with a resist is placed on a turntable, and while exposing the resist in the peripheral portion of the wafer with a light flux from a light source while rotating the wafer, the light flux is partially and dynamically changed. A variable light-shielding means for shielding light, a light-receiving means arranged at a position which optically opposes the variable light-shielding means with a peripheral portion of the wafer sandwiched, and a signal obtained by the light-receiving means are used to change the edge position and the variable of the wafer. The light-shielding portion of the light flux from the light-shielding means is detected, and servo control is performed on the variation amount of the light-shielding area of the variable light-shielding means based on the edge position information of the wafer,
An exposure apparatus comprising: a control unit that controls an exposure width in a rotation radius direction of a peripheral portion of the wafer. 2. The variable light-shielding means has a mechanism for continuously changing the transmittance for each minute area unit, and the light irradiated to the wafer by continuously changing the transmittance for each minute area unit. The edge exposure apparatus according to claim 1, wherein the intensity is controlled. 3. The light receiving means has a mechanism for measuring a light intensity distribution of an incident light flux, and the variable light shielding means continuously changes the transmittance of each minute area unit in accordance with the light intensity distribution of the light flux. The exposure apparatus according to claim 2, characterized in that the intensity of light applied to the wafer is stabilized temporally and / or spatially. 4. The exposure apparatus according to claim 3, wherein the variable light blocking means is composed of a liquid crystal shutter. 5. A rotating table on which a resist-coated wafer is placed, an illuminating means for irradiating a rectangular light beam in the rotation radius direction of the rotating table, and a light beam incident in the rotation table direction in an arbitrary rotation radius direction. A light receiving means which is arranged at a position optically opposed to the variable light blocking means, sandwiching the variable light blocking means provided in the optical path for blocking the length and the peripheral portion of the wafer, and which receives the light flux passing through the variable light blocking means. An exposure apparatus is characterized in that the peripheral portion of the wafer in the radial direction of rotation is exposed by using control means for controlling the light-shielding area of the variable light-shielding means based on the signal obtained by the light-receiving means. .