JP3430162B2 - Pattern exposure method - Google Patents

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 low frequency during exposure of a circuit pattern having a line width of 0.5 .mu.m or less. The present invention relates to a pattern exposure method suitable for superimposing lines with high accuracy and with high accuracy without being affected by vibration and the like.

[0002]

2. Description of the Related Art Since the line width of a semiconductor circuit pattern has conventionally been 0.8 .mu.m, the line width variation of the pattern is. +-. 0.08 .mu.m, and the alignment accuracy is about the same value. Was there. For this reason, conventionally, when the reticle pattern is reduced and exposed to ⅕ on the wafer while the wafer is moved by step and repeat, the exposure is started with some time after the step movement. If so, the vibration accompanying the step movement can be kept within the above accuracy, and the pattern can be exposed to a predetermined target accuracy. However, the demand for miniaturization of the pattern line width is rapidly advancing, and the age of the line width of 0.5 to 0.3 μm is about to come.

[0003]

However, if the pattern line width is reduced to 0.5 to 0.3 .mu.m, even after a considerable amount of time has passed after the step movement, the vibration isolation mechanism of the exposure apparatus is used. Even if is activated, low-frequency vibrations of a few hertz or less remain. This is the same even if the rigidity of the exposure apparatus is increased considerably,
Vibrations corresponding to the above-mentioned frequency and the resonance frequency of the structure are small but remain. Therefore, the relative positions of the mask or reticle, the projection optical system, and the wafer are:
It is changing slightly, but constantly. Therefore, even if the exposure is started after the alignment is performed, there is a problem that the relative position between the reticle image and the wafer is deviated between the alignment and the start of the exposure, and the exposure time itself is 0.2 to
Since the time is about 0.4 seconds, the exposure is performed in a state where the relative position between the reticle image and the wafer changes during the exposure, resulting in variations in pattern line width and deterioration in overlay accuracy. There is a problem that it cannot be avoided and a predetermined target accuracy cannot be obtained.

The present invention has been made in view of the above problems of the prior art.
Even if the 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 the line width of the pattern and a decrease in overlay accuracy.
An object of the present invention is to provide a pattern exposure method capable of superimposing a circuit pattern having a pattern line width of 0.5 μm or less with a high precision line width and a high precision.

[0005]

In order to achieve the above object, the pattern exposure method of the present invention irradiates a mask or reticle with exposure light and exposes the pattern on the mask or reticle through a projection optical system. The optical image has already
In a pattern exposure method for exposing a wafer having a pattern formed thereon in an overlapping manner, an alignment detection system is used to detect a relative positional deviation amount between the pattern on the wafer and the pattern on the mask or reticle, and the exposure is performed. Light the mass
Position of at least two of the stage for holding the wafer, the projection optical system, the stage for holding the mask or the reticle during irradiation of the mask or reticle, and measuring the position through the projection optical system of the pattern. to determine the displacement of the relative position due to vibration between the projection image and the wafer was the relative positional deviation amount of information of the pattern on the pattern on the wafer the mask or reticle, relative position due to the vibration correcting the relative position between the projection image and a wafer di is corrected displacement - stearyl for holding the di- and / or mask or reticle - according to the displacement amount of information and, stearyl to hold the wafer Thus , the exposure light is radiated onto the wafer on which the pattern has already been formed, and the exposure is performed in an overlapping manner.

Here, by exposing while correcting the relative position between the projected image and the wafer, the line width becomes 0.5.
A configuration in which a circuit pattern of μm or less is overlaid and exposed may be used. In addition, before using the alignment detection system
The pattern on the wafer and the mask or reticle
Detection of the relative displacement of the pattern before projection exposure
It may be configured to perform. Also, the mask
Has already been detected by the optical image of the pattern on the reticle.
After the wafer on which the
To move it to the area adjacent to the overexposed area on the wafer.
Area of the mask or pattern on the reticle
It is also possible to adopt a configuration in which imagewise exposure is performed.

[0007]

With the above configuration, the minute displacement amount 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 is detected by the displacement detection system. optical system, it becomes possible to measure the projected shadows during exposure with the respective wafer. 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 divided into 5: 1, both the projection optical system and the wafer are not displaced and only the reticle is displaced by ΔLr. In this case, the displacement amount of the reticle image on the wafer is -1/5 ΔLr, and the displacement amount of the reticle image on the wafer is 6/5 ΔLi when only the projection optical system is displaced by ΔLi. The total amount of displacement ΔL to be measured is given by the following formula: ΔL = ΔLw + 6 / 5ΔLi-1 / 5ΔLr (1) where ΔLw is a minute displacement with respect to the reference position (for example, the center of the chip) on the wafer. Is.

[0008] Sampling during the measurement, the row at least four times the frequency of the dominant frequency of the minute vibration remaining
By doing so, it is possible to grasp the outline of the amplitude and phase of the vibration, and it is possible to obtain a predetermined measurement accuracy. For example, when the exposure is performed after the vibration of a relatively high frequency of tens to hundreds of tens of Hz that remains immediately after the step movement of the wafer stage is sufficiently damped, the vibration removal function of the exposure apparatus also dampens it. In order to remove the influence of vibration of several Hz which cannot be completely performed, exposure is performed without waiting for complete attenuation of residual vibration after the above step movement, by performing sampling frequency of ten or more Hz which is four times or more of the several Hz. The sampling frequency is several hundreds of Hz, which is four times as large as the above several tens to several hundreds of Hz.

The relative position between the projected image and the wafer is corrected.
Exposing while correcting. For example, the sampling data
Always fine motion control means during exposure (the phase between the projection image and the wafer
Feedback to the means for correcting and controlling displacement to position)
It allows to control the residual vibration. Then, under this control state, the deviation of the wafer with respect to the reticle image, that is, the total displacement amount ΔL measured is corrected by finely moving one or both of the wafer stage and the reticle stage by the fine movement control means. With this correction, the reticle image and the wafer are accurately superimposed even if there is a relative positional change between the reticle, the projection optical system, and the wafer, which are slightly generated at all times, and the pattern of the pattern is accurately overlapped. Even if the circuit pattern has a line width of 0.5 μm or less, it is possible to perform exposure with high line width and alignment accuracy.

When finely controlling the wafer stage or the like, prediction is performed by using data of a plurality of sample points which are obtained in advance in consideration of the vibration characteristics peculiar to the mechanism of the exposure apparatus, in addition to the sampling data. By performing the control, more accurate exposure can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 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 residual vibration after a step movement and measurement / exposure timing.
It is a figure which shows the relationship with imming .

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 are provided. And a shutter function capable of ON-OFF control of the exposure light 11 for. 4 is reticle 2
The light transmitted through the wafer 5 placed on the wafer stage 6
A projection optical system including a reduction lens that performs projection exposure after reducing the size is configured to form an image of 1/5 times the pattern on the reticle 2 on the surface of the wafer 5 on which the pattern is already formed. Reference numeral 7 is an alignment detection system for detecting a relative position between the pattern formed on the wafer 5 and the pattern of the reticle 2, 8 is an alignment detection light, and the detection method is such that the relative position is an exposure position. Detectable methods such as Japanese Patent Publication No. 63-60525 and Japanese Patent Laid-Open No.
The method described in JP-A 1-220326 is used. A CCD one-dimensional image sensor is used for detection, and the detected data is AD-converted at high speed and is detected at a sampling period of several ms using a digital signal processor (DSP). Further, the alignment detection system 7 converts the alignment detection light 8 into the exposure light 1
Since the light having the same wavelength as that of No. 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 that it does not enter the wafer 5. I have to. 9
Is the reticle 2 under the exposure condition in which the shutter function is ON.
A laser length measuring device that measures the displacement amount of the relative position due to the vibration between the projected image of the projection optical system 4 of the upper pattern and the wafer 5 constitutes the displacement detection system together with the alignment detection system 7. The displacement detection system is configured to sample and measure at a sampling frequency having a frequency four times or more the main frequency of the vibration. Laser length measuring device 9
Are laser beams 31, 3 for the respective 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.
Measure through 2, 33. In FIG. 1, each displacement in one direction perpendicular to the optical axis 4a is measured. However, a detection system not shown in the figure, which is perpendicular to the plane of the paper, is incorporated in the two directions perpendicular to the optical axis 4a. About each is measured. The displacement detection position of the projection optical system 4 is a position C that internally divides between the reticle 2 and the wafer 5 into L ₁ : L ₂ = 5: 1 as shown in FIG. 10 is
It is composed of the laser length measuring device 9 and the alignment detection system 7.
Pattern on the reticle 2 which is measured by the displacement detecting system which -
One or both of the wafer 5 and the reticle 2 are finely displaced according to the change state and the amount of displacement of the relative position between the projection image of the projection optical system 4 and the wafer 5.
It is fine movement control means for correcting and controlling the relative positional displacement between the projected image and the wafer 5.

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

The position shift detection by the laser length measuring device 9 is performed during the projection exposure, and the reticle 2, as shown in FIG.
For each of the projection optical system 4 and the wafer 5, the wafer 5
Projecting with respect to the reference position (e.g., center of the chip) W in
A minute displacement ΔLr in a direction perpendicular to the optical axis 4a of the shadow optical system 4 ,
ΔLi and ΔLw are obtained . In this case, the projection optical system 4
Since the displacement measurement position in is at the position C, which is the distance between the reticle 2 and the wafer 5 divided by 5: 1, both the projection optical system 4 and the wafer 5 are not displaced, and only the reticle 2 is reticle. 2 displaced from the reference position A by ΔLr
In the case of (a), the displacement amount of the reticle image on the wafer 5 is −1 / 5ΔLr from the reference position W of the wafer 5. Further, only the projection optical system 4 has a distance Δ from the reference position A of the reticle 2.
In the case of the Li displacement shown in FIG. 2B, the displacement amount of the reticle image on the wafer 5 is 6 / 5Δ from the reference position W of the wafer 5.
It becomes Li. Further, in the case of FIG. 2C in which only the wafer 5 is displaced from the reference position A of the reticle 2 by ΔLw, the displacement amount of the reticle image on the wafer 5 is the reference position W of the wafer 5.
Is also ΔLw. The positional deviation is not affected by the inclination of the projection optical system 4, and ΔL = 0 as shown in FIG.

From the above-mentioned minute displacements ΔLr, ΔLi, and ΔLw, the total displacement amount ΔL to be measured during the projection exposure is obtained from the equation (1), and one of the wafer stage 6 and the reticle stage 3 is controlled by the fine movement control means 10. Alternatively, both are slightly moved by the obtained ΔL to correct the positional deviation. Since the respective values of .DELTA.Lr, .DELTA.Li, and .DELTA.Lw are always detected during the pattern exposure, even if the exposure pattern slightly shifts on the wafer 5 due to vibration during the exposure, the wafer 5 is always .DELTA.L. It becomes possible to make fine movement corrections for the like, and it becomes possible to expose a good pattern shape to the correct alignment position. In the detection of ΔLr, ΔLi, and ΔLw, for example, when the displacement amount of the reticle 2 is so small as not to be a problem, the measurement of ΔLr is omitted, and ΔL is obtained from the detected values of ΔLi and ΔLw. -It is also possible to control the movement of the gear 6 and the like.

In the pattern exposure apparatus as shown in FIG. 1, the structure supporting each system of the apparatus has its own resonance frequencies, and residual vibrations at these frequencies occur. For example, immediately after the step movement of the wafer stage 6, a relatively high-frequency, fast-damping vibration of several tens to hundreds of tens Hz remains, but even if the vibration is damped, it is damped by the anti-vibration function of the exposure apparatus. The vibration of several Hz which cannot be completely left remains.
However, these residual vibrations are not shown in Fig. 3 (a) or (b).
Since the waveform has a basic frequency as shown by the solid line, the sampling at the time of the above measurement is more than 4 times the main frequency of the residual minute vibration, that is, the frequency of the residual vibration is the above number. In the case of Hz, a sampling frequency of ten or more Hz, which is four times or more that of Hz, and in the case of several tens to one hundred and several tens Hz, as in the case of exposure without waiting for the complete attenuation of the residual vibration after the above step movement, It is possible to grasp the approximate amplitude and phase of the vibration by performing sampling at a sampling frequency of several hundred Hz, which is four times or more that of the vibration.

The above sampling data is constantly fed back to the fine movement control means 10 during 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 displacements of the respective parts are all measured except during the step movement). Indicates. 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 and becomes flat as indicated by the dotted line, and the exposure is started in the stable state. This has the effect that the process can be shortened as compared with the conventional method in which the exposure is started after waiting for the stabilization of the low-frequency residual vibration with slow damping. The deviation of the wafer 5 with respect to the reticle image under the condition that the residual vibration is controlled, that is, the total displacement amount ΔL measured is controlled by the fine movement control means 10 by the wafer stage 6
Alternatively, one or both of the reticle stages 3 are finely moved to correct. With this correction, the reticle image and the wafer 5 are accurately superposed on each other even if there is a relative positional change between the reticle 2, the projection optical system 4, and the wafer 5 which are generated slightly but constantly. Even if the circuit pattern has a line width of 0.5 μm or less, it is possible to perform exposure with high line width and alignment accuracy. When finely controlling the wafer stage or the like, predictive control is performed by utilizing the data of a plurality of sample points obtained in advance in consideration of the characteristic vibration characteristics of the mechanism of the exposure apparatus, in addition to the sampling data. As a result, exposure with higher accuracy can be performed.

Fine movement control during projection exposure of the wafer stage 6 or the like is desired to be obtained from vibration data during the exposure, which is desirable in accordance with the current situation, but in the case where the vibration data cannot be obtained. , As shown in FIG.
The relative position between the exposure pattern and the wafer 5 when the alignment detection is performed immediately before the exposure is performed by using the data detected in the above sampling cycle, or the exposure is performed by the laser measuring device 9. The ΔLr, ΔLi, ΔL detected immediately before
The wafer stage 6 or the like may be driven by using the data of w. In this case, if the vibration occurring during the subsequent exposure is predicted from the detected data and the wafer stage 6 or the like is finely driven from this vibration prediction, 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 image on the reticle 2 and the image on the wafer 5 is directly measured. It may be done. In this case, since the measurement is performed during the exposure, it is indispensable that the measuring means does not block the exposure light 11.

Although not shown, the measurement of the change in the relative position is carried out in the vicinity of the reticle 2 through the projection optical system 4 on the pattern on the wafer 5 contrary to the method of projecting the pattern on the reticle 2. Image on the reticle 2
It is also possible to detect the relative position with the upper pattern.

[0021]

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

[Brief description of 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 showing a relationship between residual vibration after step movement and timing of measurement / exposure according to the present invention.

[Explanation 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.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Makoto Murayama               292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa               Hitachi, Ltd. Production Technology Laboratory               Within                (56) References JP-A-60-32050 (JP, A)                 JP-A-3-50819 (JP, A)                 JP-A-1-288647 (JP, A)

Claims (4)

(57) [Claims] 1. A pattern in which a mask or reticle is irradiated with exposure light, and a wafer on which a pattern is already formed is overlaid and exposed by an optical image of the pattern on the mask or reticle through a projection optical system. An exposure method, wherein an amount of relative positional deviation between the pattern on the wafer and the pattern on the mask or reticle is detected by using an alignment detection system, and the exposure light is transmitted to the mask or reticle.
Position of at least any two of the stage for holding the wafer, the projection optical system, the stage for holding the mask or the reticle during irradiation, and the projected image through the projection optical system of the pattern. and obtains the displacement of the relative position due to vibration between the wafer, the relative positional deviation amount of information of the pattern on the pattern on the wafer the mask or reticle, the displacement of the relative position due to the vibration depending of the information, stearyl holding the wafer - stearyl holds the di- and / or mask or reticle - said by correcting the relative position between the projection image and a wafer di is corrected displacement already A pattern exposure method comprising irradiating exposure light onto a wafer on which a pattern is formed to perform overlapping exposure. 2. The pattern according to claim 1, wherein the exposure is performed while correcting the relative position between the projected image and the wafer, whereby the circuit pattern having a line width of 0.5 μm or less is overlapped and exposed. Exposure method. 3. The relative positional deviation amount between the pattern on the wafer and the pattern on the mask or reticle using the alignment detection system is detected before the projection exposure. The pattern exposure method described in 1. 4. A wafer on which a pattern has already been formed is overlapped and exposed by an optical image of the pattern on the mask or reticle, and then the wafer is moved to an overlapped and exposed region on the wafer. 2. A pattern exposure method according to claim 1, wherein adjacent areas are exposed by an optical image of the pattern on the mask or reticle.