JP2003124112A - Pattern exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the line width of a pattern and the superposition of patterns in accuracy. SOLUTION: A pattern exposure method comprises a first step of irradiating a mask or a reticle 2 with exposure light 11 and a second step of projecting the optical image of a pattern on the mask or the reticle 2 through the intermediary of a projection optical system 4 for exposure, and superposing it on the pattern which is already formed on a wafer 5. The positions of two or more out of a stage 6 holding a wafer in projection exposure, a projection optical system 4, and a stage 3 holding a mask or a reticle are measured so as to obtain the displacement of the relative positions of the projection image of the pattern projected through the intermediary of the projection optical system 4 and the wafer 5 due to vibrations, the stage 6 holding the wafer and/or the stage 3 holding the mask or the reticle is displaced for correction, corresponding to information as to the above displacement, by which the projection image is superposed for exposure on the wafer where patterns have been already formed as the relative positions of the projection image and the wafer 5 are corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern exposure method for exposing a fine circuit pattern, and more particularly, to a method for exposing a circuit pattern having a line width of 0.5 .mu.m or less to a low frequency pattern during exposure. The present invention relates to a pattern exposure method suitable for superimposing lines with high precision and high precision without being affected by vibrations or the like.

[0002]

2. Description of the Related Art Since the line width of a semiconductor circuit pattern has conventionally been 0.8 μm, the variation in the line width of the pattern is ± 0.08 μm, and the alignment accuracy is almost the same as this value. I was For this reason, conventionally, when the pattern of a reticle is reduced to 1/5 on a wafer while the wafer is moved in a step-and-repeat manner, the exposure is started after a short time after the step movement. Then, the vibration caused by the step movement is also within the above accuracy, and the pattern can be exposed to the predetermined target accuracy. However, the demand for a finer pattern line width is rapidly increasing, and the line width of 0.5 to 0.3 μm is approaching.

[0003]

However, when the line width of the pattern is reduced to 0.5 to 0.3 .mu.m, even after a considerable time has passed since the step movement, the vibration isolating mechanism of the exposure apparatus is required. , Low frequency vibration of several hertz or less remains. This is the same even if the rigidity of the exposure device is considerably increased,
Vibration corresponding to the frequency or the resonance frequency of the structure remains, though slightly. Therefore, the relative positions of the mask or reticle, the projection optical system, and the wafer are:
It is constantly changing, albeit slightly. Therefore, even if the exposure is started after performing the alignment, there is a problem that the relative position between the reticle image and the wafer is shifted between the alignment and the start of the exposure.
Since the exposure time is about 0.4 seconds, the exposure is performed in a state where the relative position between the reticle image and the wafer is changing during the exposure, so that the line width of the pattern varies and the overlay accuracy decreases. There is a problem that a predetermined target accuracy cannot be obtained because it cannot be avoided.

The present invention has been made in view of the above-mentioned problems of the prior art,
Even if a low-frequency vibration remains and the relative position between the reticle image and the wafer changes during exposure, it is possible to prevent variations in pattern line width and a decrease in overlay accuracy.
An object of the present invention is to provide a pattern exposure method capable of superimposing circuit patterns having a pattern line width of 0.5 μm or less with a high precision line width and at a high precision.

[0005]

In order to achieve the above object, a pattern exposure method of the present invention irradiates a mask or a reticle with exposure light, and forms a pattern on the mask or a reticle through a projection optical system. Already the pattern by the optical image
In the pattern exposure method for overlappingly exposing a wafer on which a pattern is formed, at least any two or more of a stage for holding the wafer, a projection optical system, and a stage for holding a mask or a reticle during the projection exposure. , The amount of displacement of the relative position accompanying the vibration between the wafer and the projected image of the pattern via the projection optical system is obtained, and the wafer is held in accordance with the information on the obtained amount of displacement. Stage or / and stage for holding mask or reticle
The exposure is superimposed on the wafer on which the pattern has already been formed while correcting the relative position between the projection image and the wafer by correcting and displacing the wafer.

Here, by exposing while correcting the relative position between the projection image and the wafer, the line width becomes 0.5.
A configuration in which a circuit pattern of μm or less is over-exposed may be adopted.

[0007]

With the above arrangement, the displacement detection system detects the minute displacement of the relative position due to the vibration between the projected image of the pattern on the mask or reticle (hereinafter simply referred to as "reticle") and the wafer. It becomes possible to measure each of the optical system and the wafer in the direction perpendicular to the optical axis of the projection optical system even during projection exposure. In this case, when the displacement measurement position in the projection optical system is set to a position where the distance between the reticle and the wafer is internally set to 5: 1, only the reticle is displaced by ΔLr without displacing both the projection optical system and the wafer. In this case, the displacement of the reticle image on the wafer is-
The displacement amount of the reticle image on the wafer when the projection optical system is displaced by ΔLi is ／ ΔLr.
Since ΔLi is obtained, the total displacement ΔL to be measured during the projection exposure is given by the following equation: ΔL = ΔLw + 6 / 5ΔLi−1 / 5ΔLr (1) where ΔLw is a reference position (for example, a chip) on the wafer. (The center of the figure).

Since the sampling at the time of the above measurement is performed at a frequency four times or more of the main frequency of the remaining minute vibration, it is possible to grasp the outline of the amplitude and phase of the vibration, and Measurement accuracy can be obtained.
For example, when exposure is performed after sufficiently high-frequency vibrations of several tens to several hundreds of Hz remaining immediately after the step movement of the wafer stage have sufficiently attenuated, exposure is also attenuated by the anti-vibration function of the exposure apparatus. When exposing without waiting for complete attenuation of residual vibration after the above-mentioned step movement, in order to remove the influence of vibration of several Hz that cannot be completed, sampling at a frequency of more than ten times more than four times the frequency of several Hz. Is performed at a sampling frequency of several hundred Hz that is four times or more of the several tens to one hundred and several tens Hz.

The above sampling data is always fed back to the fine movement control means during exposure to control the residual vibration. Then, under this control state, the deviation of the wafer with respect to the reticle image, that is, the measured total displacement ΔL is corrected by finely moving one or both of the wafer stage and the reticle stage by the fine movement control means. By this correction, the reticle image and the wafer are accurately overlapped with each other even if the relative positional change of the reticle, the projection optical system, and the wafer, which is slightly generated, is constantly generated. Even with a circuit pattern having a line width of 0.5 μm or less, exposure can be performed with a highly accurate line width and alignment accuracy.

[0010] When fine movement control of the wafer stage or the like is performed, prediction is performed using data of a plurality of sample points obtained in advance in consideration of the inherent vibration characteristics of the mechanism of the exposure apparatus in addition to the sampling data. By performing the control, exposure with higher accuracy can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 is a diagram showing a schematic configuration of a pattern exposure apparatus, FIG. 2 is a diagram showing a displacement state of each part of an exposure pattern, and FIG. 3 is a diagram showing a relationship between residual vibration after step movement and timing of measurement / exposure. .

In FIG. 1, reference numeral 1 denotes an exposure optical system including an exposure light source, in which an exposure illumination system for irradiating light emitted from the exposure light source to a reticle 2 mounted on a reticle stage 3, and a reticle 2 And a shutter function capable of ON-OFF controlling the exposure light 11 with respect to. 4 is reticle 2
The light transmitted through the wafer 5 is placed on the wafer stage 6
A projection optical system including a reduction lens for performing projection exposure by reducing the projection upward, and is configured to form an image 1/5 times the size of the pattern on the reticle 2 on the surface of the wafer 5 on which the pattern is already formed. Reference numeral 7 denotes an alignment detection system for detecting a relative position between a pattern formed on the wafer 5 and a pattern on the reticle 2, and 8 denotes an alignment detection light. Detectable methods, for example, JP-B-63-60525 and JP-A-6
The method described in JP-A-1-220326 is used. A CCD one-dimensional image sensor is used for the detection, the detected data is A / D-converted at a high speed, and is detected using a digital signal processor (DSP) at a sampling period of several ms. Further, the alignment detection system 7 outputs the exposure light 1 to the alignment detection light 8.
Since light having the same wavelength as 1 is used, if the alignment detection is performed for a long time, the resist is exposed. Therefore, the alignment detection is performed in a short time, and thereafter, the alignment detection light 8 is shielded so as not to be incident on the wafer 5. I have to. 9
Is the reticle 2 in the exposure state where the shutter function is ON.
A laser length measuring device for measuring a displacement amount of a relative position caused by vibration between the image projected by the projection optical system 4 of the upper pattern and the wafer 5, and constitutes a displacement detection system together with the alignment detection system 7. The displacement detection system is configured to measure by sampling at a sample frequency having a frequency four times or more the main frequency of the vibration. Laser length measuring device 9
Are the displacements of the reticle 2, the projection optical system 4, and the wafer 5 in the direction perpendicular to the optical axis 4a of the projection optical system 4 at the moment detected by the alignment detection system 7, respectively.
The measurement is performed via 2, 33. In FIG. 1, each displacement in one direction perpendicular to the optical axis 4a is measured. However, a detection system in a direction perpendicular to the plane of the drawing (not shown) is actually incorporated, and two directions perpendicular to the optical axis 4a are measured. Are respectively measured. The displacement detection position of the projection optical system 4 is a position C which internally divides the space between the reticle 2 and the wafer 5 into L1: L2 = 5: 1 as shown in FIG. Reference numeral 10 denotes one of the wafer 5 and the reticle 2 in accordance with the change in the relative position between the image projected by the projection optical system 4 on the reticle 2 measured by the displacement detection system and the wafer 5 and the amount of displacement. Or both are finely displaced to correct and control relative position displacement between the projection image and the wafer 5.

With the above configuration, the exposure optical system 1
The emitted exposure light 11 illuminates the circuit pattern on the reticle 2, and the light transmitted through the reticle 2 is に of the pattern on the reticle 2 on the surface of the wafer 5 by the reduction lens in the projection optical system 4. Double the image. Since it is necessary to precisely align this image with the pattern of the wafer 5 already formed and to expose the image of the reticle 2 on the wafer 5, the alignment detection system 7 controls the pattern of the wafer 5.
The relative displacement between the pattern of the reticle 2 and the pattern of the reticle 2 is detected.

As shown in FIG. 2, the detection of the above positional deviation is performed with respect to each of the reticle 2, the projection optical system 4, and the wafer 5 with respect to a reference position (for example, a center of a chip) on the wafer 5.
The minute displacements ΔLr, ΔLi, and ΔLw with respect to W are performed during projection exposure in a direction perpendicular to the optical axis 4a of the projection optical system 4. In this case, the displacement measurement position in the projection optical system 4 is a position C where the distance between the reticle 2 and the wafer 5 is internally divided into 5: 1.
In FIG. 2A in which only the reticle 2 is displaced by ΔLr from the reference position A of the reticle 2 without displacing both the projection optical system 4 and the wafer 5, the reticle image on the wafer 5 Is -1 / 位置 from the reference position W of the wafer 5.
5ΔLr. Also, only the projection optical system 4 is
In the case of FIG. 2B displaced by ΔLi from the reference position A, the amount of displacement of the reticle image on the wafer 5 is 6/5 ΔLi from the reference position W of the wafer 5. Further, only the wafer 5 is displaced by ΔLw from the reference position A of the reticle 2 in FIG.
In the case of (c), the displacement amount of the reticle image on the wafer 5 is also ΔLw from the reference position W of the wafer 5. The displacement does not affect the inclination of the projection optical system 4 and becomes ΔL = 0 as shown in FIG.

From the above-mentioned minute displacements ΔLr, ΔLi, and ΔLw, the total displacement ΔL to be measured during the projection exposure is obtained from the above equation (1), and fine movement control means 10 selects one of wafer stage 6 or reticle stage 3, Alternatively, both are finely moved by the obtained ΔL to correct the positional deviation. Since the values of .DELTA.Lr, .DELTA.Li and .DELTA.Lw are always detected even during the pattern exposure, even if the exposure pattern slightly shifts on the wafer 5 due to vibration during the exposure, the value of the wafer 5 is always .DELTA.L. And the like can be corrected for fine movement, and a good pattern shape can be exposed to a correct alignment position. In the detection of ΔLr, ΔLi, and ΔLw, for example, when the amount of displacement of the reticle 2 is small enough to cause no problem, the measurement of ΔLr is omitted, and ΔL is obtained from the detected values of ΔLi and ΔLw, and the wafer level is calculated from these values. The fine movement control of the jaws 6 and the like may be performed.

In the pattern exposure apparatus as shown in FIG. 1, the structure supporting each system of the apparatus has a unique resonance frequency, and residual vibration of these frequencies occurs. For example, immediately after the step movement of the wafer stage 6, vibrations having a relatively high frequency of several tens to several hundreds of Hz and rapidly attenuating remain, but even if the vibrations attenuate, they are attenuated by the anti-vibration function of the exposure apparatus. Unreliable vibration of several Hz remains.
However, these residual vibrations are not shown in FIG. 3 (a) or (b).
Since the waveform of the basic frequency shown by the solid line is used, the sampling at the time of the above measurement is performed at a frequency four times or more the main frequency of the remaining minute vibration, that is, the frequency of the residual vibration In the case of Hz, the sampling frequency is four times or more, more than ten and several ten Hz, and in the case of several tens to one hundred and several tens Hz, such as when exposing without waiting for complete attenuation of the residual vibration after the above step movement. By performing the sampling at a sampling frequency of several hundred Hz which is four times or more of the above, it is possible to grasp the approximate amplitude and phase of the vibration.

The above sampling data is always fed back to the fine movement control means 10 during the exposure to control the residual vibration. FIG. 3A is an explanatory diagram of this state, and shows the relationship between the residual vibration and the measurement / exposure start time in the measurement control during exposure (that is, when the minute displacement of each section is measured except during step movement). Is shown. As can be seen from the figure, the uncontrolled residual vibration indicated by the solid line is measured and controlled immediately after the step movement, becomes flat as indicated by the dotted line, and exposure is started in a stable state. This has an effect that the process can be shortened as compared with the related art in which the exposure is started after waiting for the stabilization of the low-frequency residual vibration with slow attenuation. The displacement of the wafer 5 with respect to the reticle image under the state where the residual vibration is controlled, that is, the measured total displacement ΔL is determined by the fine movement control means 10 on the wafer stage 6.
Alternatively, one or both of the reticle stages 3 are finely moved for correction. With this correction, the reticle image and the wafer 5 are accurately superimposed even if the relative position of the reticle 2, the projection optical system 4, and the wafer 5 is slightly but constantly generated. Even with a circuit pattern having a pattern line width of 0.5 μm or less, exposure can be performed with a highly accurate line width and alignment accuracy. When the fine movement control of the wafer stage or the like is performed, predictive control is performed using data of a plurality of sample points obtained in advance in consideration of the inherent vibration characteristics of the mechanism of the exposure apparatus, in addition to the sampling data. Thereby, exposure with higher accuracy can be performed.

The fine movement control during the projection exposure of the wafer stage 6 or the like is desirably based on the current situation to be obtained from the vibration data during the exposure, but in the case where the vibration data cannot be obtained. As shown in FIG. 3 (b),
The relative position between the exposure pattern and the wafer 5 during the alignment detection performed immediately before the exposure is performed by using data detected in the above-described sampling cycle, or by using the laser length measuring device 9 for exposure. ΔLr, ΔLi, ΔL detected immediately before
The wafer stage 6 and the like may be driven using the data of w. In this case, the vibration occurring during the subsequent exposure is predicted from the detected data, and if the wafer stage 6 or the like is minutely driven based on the predicted vibration, the correct position during the exposure can be obtained as shown by the dotted line in FIG. It is possible to stably control the wafer stage 6 and the like.

As a method for measuring the relative position between the reticle image and the wafer 5, other than the above method, for example, the relative position between the pattern on the reticle 2 and the image of the pattern on the wafer 5 is directly measured. You may do it. In this case, since the measurement is performed during the exposure, it is essential that the measurement unit does not block the exposure light 11.

Although not shown, the change of the relative position is measured by projecting the pattern on the wafer 5 through the projection optical system 4 in the vicinity of the reticle 2, as opposed to the method of projecting the pattern on the reticle 2. And reticle 2
It is also possible to perform the detection by detecting the relative position with respect to the above pattern.

[0021]

As described above, according to the present invention, in the pattern exposure method, even if a low-frequency vibration remains and the relative position between the reticle image and the wafer changes during exposure, the pattern can be reduced. It is possible to prevent variations in line width and decrease in overlay accuracy, and to overlay circuit patterns with pattern line widths of 0.5 μm or less with high accuracy and high accuracy. It has the effect of being able to.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a displacement state of each part of an exposure pattern.

FIG. 3 is a diagram illustrating a relationship between residual vibration after step movement and timing of measurement and exposure according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure optical system, 2 ... Reticle, 3 ... Reticle stage, 4 ... Projection optical system, 5 ... Wafer, 6 ... Wafer stage, 7 ... Alignment detection system, 8 ... Alignment detection light, 9 ... Laser length measuring device, 10 ... Fine movement control means, 11 exposure light, 31, 32, 33 laser beam.

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[Procedure amendment]

[Submission date] September 24, 2002 (2002.9.2)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

3. Exposure light emitted from a light source of an exposure apparatus is masked.
The projection optical system of the exposure apparatus.
Of the pattern on the mask or reticle through
It is mounted on the stage of the exposure apparatus by an image
A pattern for overlapping exposure of a wafer on which a pattern has already been formed.
An exposure method, wherein the exposure apparatus
A plurality of positions in a direction perpendicular to the optical axis of the projection optical system;
Is measured in a non-contact manner through the projection optical system.
Perpendicular to the optical axis of the projection optical system between the optical image of the projector and the wafer.
The displacement amount of the relative position in the direct direction is detected, and the detected displacement
The projection between the optical image and the wafer according to quantity information
While correcting the relative position in the direction perpendicular to the optical axis of the optical system,
Note that over-exposure is performed on a wafer on which a pattern has already been formed.
A pattern exposure method.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

In order to achieve the above object, according to the present invention, a mask or a reticle is irradiated with exposure light emitted from a light source of an exposure apparatus, and the mask or the reticle is projected through a projection optical system of the exposure apparatus. Due to the optical image of the pattern above, the pattern already mounted on the stage of the exposure apparatus
In a pattern exposure method for overlappingly exposing a wafer on which a pattern is formed, at least two or more of a stage, a projection optical system, a mask or a stage for holding a reticle are positioned during the overlap exposure by using a laser length measuring device. , The amount of displacement of the relative position between the optical image and the wafer through the projection optical system of the pattern is detected at a predetermined cycle, and the displacement detected at the predetermined cycle is detected. By correcting and displacing one or both of the stage for holding the wafer and the stage for holding the mask or reticle in accordance with the information on the amount, the relative position between the optical image and the wafer is already corrected. The wafer was overexposed on the wafer on which the pattern was formed.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

In order to achieve the above object, according to the present invention, a mask or a reticle is irradiated with exposure light emitted from a light source of an exposure apparatus, and a pattern on the mask or the reticle is projected via a projection optical system of the exposure apparatus. A pattern exposure method for superposing and exposing a wafer having a pattern formed thereon, which is mounted on a stage of an exposure apparatus, by using an optical image of the pattern.
During overlay exposure, each position in a plane perpendicular to the optical axis of the projection optical system at a plurality of locations of the exposure apparatus including the stage is measured using a laser length measuring device, and the optics are projected through the projection optical system of the pattern. The amount of displacement of the relative position between the image and the wafer is detected, and the relative position in the plane perpendicular to the optical axis of the projection optical system between the optical image and the wafer is determined according to the information on the detected amount of displacement. While correcting, the wafer is over-exposed on a wafer on which a pattern has already been formed. To achieve the above object, according to the present invention, a mask or a reticle is irradiated with exposure light emitted from a light source of an exposure apparatus, and an optical pattern of the pattern on the mask or the reticle is projected through a projection optical system of the exposure apparatus. In a pattern exposure method for overlay exposure of an already patterned wafer placed on a stage of an exposure apparatus by using an image, light of a projection optical system at a plurality of positions of the exposure apparatus during the overlay exposure. The position in the direction perpendicular to the axis is measured in a non-contact manner and the displacement of the relative position in the direction perpendicular to the optical axis of the projection optical system between the optical image of the pattern via the projection optical system and the wafer is detected. Then, while correcting the relative position in the direction perpendicular to the optical axis of the projection optical system between the optical image and the wafer in accordance with the detected information on the amount of displacement, the optical image is superimposed on the wafer on which the pattern has already been formed. It was made to expose.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Makoto Murayama             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd., Production Technology Laboratory F term (reference) 5F046 AA23 BA04 CC01 CC02 CC16                       DB05 ED01 FC05

Claims (2)

[Claims] 1. A pattern for irradiating a mask or a reticle with exposure light and overlappingly exposing a wafer on which a pattern is already formed by an optical image of the pattern on the mask or the reticle via a projection optical system. A step of measuring at least two positions of a stage for holding the wafer, a projection optical system, a stage for holding a mask or a reticle during the projection exposure, and measuring the position of the pattern. The amount of displacement of the relative position accompanying the vibration between the projection image and the wafer via the projection optical system is determined, and the stage or / and mask or reticle for holding the wafer in accordance with the obtained information of the amount of displacement. By correcting and displacing the held stage to correct the relative position between the projected image and the wafer, it is possible to perform overlapping exposure on the wafer on which the pattern has already been formed. Characteristic pattern exposure method. 2. The pattern according to claim 1, wherein the exposure is performed while correcting the relative position between the projection image and the wafer so that a circuit pattern having a line width of 0.5 μm or less is overlaid. -Exposure method.