JPH03222405A - Aligner and blind exposure method used therefor - Google Patents

Abstract

PURPOSE:To make it possible to use an aligner at the focal point which has been most stabilized and hence improve focussing accuracy by performing blind exposure processing prior to actual exposure processing and opening and closing a first shutter, performing the blind exposure processing at the interval identical to the on/off interval required when performing the actual exposure processing. CONSTITUTION:Under the condition where a first shutter 7 is open, an attempt is made to irradiate exposure light from an exposure light source 6 in the same way required for an actual exposure process and raise the temperature of an aligner, particularly the temperature of an exposure optical system 2 near the temperature prevailing during actual exposure process. A further attempt is made to open and close a first shutter 7 at an interval equivalent to an on/off exposure interval required during actual exposure process, which increases the temperature of the aligner, particularly the optical system 2 to the temperature prevailing during the actual exposure process and maintains the temperature so that actual exposure process may be carried out from a constant focal point which has been stabilized. It is, therefore, possible to obtain stabilized exposure accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an exposure apparatus, and particularly to a step type projection exposure apparatus for semiconductor integrated circuit devices, which can be used without being affected by temperature fluctuations in an optical system caused by exposure light. The present invention relates to an exposure apparatus that is capable of performing exposure processing from a stabilized and constant focal position, and a technique that is effective when applied to a main exposure method used therein.

[Prior Art] Semiconductor integrated circuit devices are manufactured by repeating photo-etching and thin film deposition many times. For example, the basic steps of lithography include resist coating, exposure, and development.

Furthermore, in recent patterning techniques for submicron semiconductor integrated circuit devices, the depth of focus of steppers has become shallower, and how to suppress focal fluctuations has become an important factor.

Possible causes of this focus variation include, for example, temperature variation in the optical system due to exposure light, depth of focus variation and reduction magnification variation due to changes in atmospheric pressure.

For example, regarding temperature fluctuations in the optical system, intense exposure light hits the lens element during exposure, so even a small amount of light absorption causes the temperature of the lens itself to rise.

For example, when the exposure time is set to 4 Q Qmsec and 100 wafers are exposed continuously and then paused for 60 minutes, the optimum focus position will be as shown in Figure 2. A focus change of about 0.8 μm may occur.

Because this phenomenon is highly reproducible, for example, Kogyo Chosukaikai Co., Ltd., published on November 18, 1986, "Electronic Materials Special Edition Ultra LSI! I! Manufacturing and Testing Equipment Guidebook JP78
~As described in the literature such as P83, the reticle transmittance is measured for all the reticles used, and the focus fluctuation due to temperature fluctuation of the optical system is calculated from an empirical formula, and a correction curve is created to correct the focus position. A method is adopted in which the focus position is determined in advance, a program is created that is compatible with all reticles, and the focus position is corrected for each wafer using software.

[Problems to be Solved by the Invention] However, in the prior art as described above, no consideration is given to using the exposure device in the most stable state of the focus position, and the focus accuracy is not adjusted on the software. Measures are being taken to improve it. Therefore, conventional focus position correction methods have problems in terms of time and focus position correction accuracy. Since it is necessary to create a corresponding program, it has the disadvantage that it takes a lot of time to use.

On the other hand, regarding the correction accuracy of the focus position, it is not possible to obtain sufficient correction accuracy to perform the actual exposure processing at the time when the focus fluctuation is the largest, and the adjustment of the correction coefficient is insufficient, so There is a problem that a correction of about 20 to 30% is required.

In other words, in conventional exposure equipment, a method is used to improve focus accuracy using software using a program that corresponds to all reticles. We have discovered a method that can improve focus accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an exposure apparatus and a blank exposure method used therein, which can be used with the most stable focal position regardless of the reticle used, and which can improve focal position accuracy. .

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] Among the inventions disclosed in this application, a brief overview of typical inventions is as follows.

That is, the exposure apparatus of the present invention is an exposure apparatus in which the exposure light from the exposure light source is controlled by the opening/closing operation of the first shutter, and the pattern to be exposed is projected onto the exposure target by an optical system, wherein the exposure apparatus A main exposure process is performed before the actual exposure process, and the main exposure process is performed by opening and closing the first shutter at the same intervals as the opening and closing intervals during the actual exposure process.

Further, a second shutter is interposed between the pattern to be exposed and the object to be exposed, and the second shutter is closed during the blank exposure process to prevent exposure of the object to be exposed. It is.

Furthermore, the blank exposure method used in the exposure apparatus of the present invention is as follows:
The opening/closing operation of the first shutter is controlled in two stages, and in the first stage the first shutter is kept open until the temperature approaches the temperature during the actual exposure process, and in the second stage, the opening and closing operation is controlled during the actual exposure process. The first shutter is opened and closed at the same intervals as the opening and closing intervals during the actual exposure process up to a temperature of .

[Function] According to the exposure apparatus described above, the courtyard light process is performed before the actual exposure process by the exposure apparatus, and the first shutter is opened and closed at the same interval as the opening and closing interval during the actual exposure process during the courtyard light process. By doing so, the exposure apparatus, especially the optical system, is raised to and maintained at the temperature state during the actual exposure process, and the actual exposure process can be performed from a stabilized constant focal position.

Furthermore, in this case, a second shutter is interposed between the pattern to be exposed and the object to be exposed, and by closing this second shutter during the courtyard light processing, the influence on the exposed object during the courtyard light processing can be reduced. It can be prevented.

Furthermore, the opening/closing operation of the first shutter is controlled in two stages; in the first stage, the first shutter is kept open until the temperature approaches the temperature during actual exposure processing, and in the second stage, the opening and closing operation of the first shutter is controlled to the temperature during actual exposure processing. By opening and closing the first shutter at the same intervals as the opening and closing intervals during the actual exposure process, the temperature of the optical system can be raised to the temperature state during the actual exposure process in a short time.

[Embodiment] FIG. 1 is a schematic configuration diagram showing an exposure apparatus that is an embodiment of the present invention.

First, the configuration of the exposure apparatus of this embodiment will be explained with reference to FIG.

The exposure apparatus of this embodiment is, for example, a step-type projection exposure apparatus using a reduction projection optical system, and includes an exposure illumination system 1 that irradiates exposure light, an exposure optical system 2 that focuses and projects this exposure light, and It is composed of a reticle mounting system 3 that mounts a reticle on which a pattern to be exposed is formed, a wafer drive system 4 that mounts and drives a wafer as an exposure target, and a shutter drive system 5 that prevents exposure during blank exposure. ing.

The exposure illumination system 1 uses, for example, a filter to capture G-line (4
Exposure light such as a mercury lamp that emits a wavelength of 36 nm) #
I6 and a first shutter 7 that blocks the exposure light from the exposure light source 6, and blocks the exposure light a! ! The structure is such that the exposure time of the exposure light irradiated from 6 is controlled by a first shutter that is automatically controlled by a program.

The first shutter 7 is wiped during blank exposure and is controlled in two stages. In the first stage, it is held open to a temperature close to the temperature at the time of actual exposure, and in the second stage, the temperature at the time of actual exposure is maintained. The opening and closing operations are performed at the same intervals as the opening and closing intervals during actual exposure.

The exposure optical system 2 includes, for example, a condenser lens 8 that focuses exposure light and a reduction projection lens 9 that projects the exposure light. It has a structure in which it is projected by a lens 9.

In the reticle mounting system 3, a reticle 10 in which a circuit pattern lOa, which is a pattern to be exposed, is formed with a light-shielding film such as chromium (Cr) on a transparent quartz glass substrate, etc., is mounted on a reticle stage 10 by a chuck (not shown) or the like.
1 is removably installed.

In the wafer drive system 4, a wafer 14 is removably mounted on a wafer stage 13 that is controlled in the X and Y directions by a drive source such as a motor 12 using a chuck (not shown) or the like.

The shutter drive system 5 is automatically controlled by a program, and has a structure in which the second shutter 15 is closed during blank exposure to prevent exposure of the wafer 14.

Next, the operation of this embodiment will be explained.

For example, in the actual exposure process, the reticle IO is replaced with one having an actual circuit pattern 10a, and the wafer 14 is positioned directly under the reduction projection lens 9 by the movement of the wafer stage 13, and the exposure light source 6 is irradiates with exposure light, condensing lens 8 and reduction projection lens 9
The exposure process is performed by projecting exposure light onto a predetermined exposure location on the wafer 14, for example, a range of one chip size. Then, a method is adopted in which the wafer 14 is repeatedly stepped against the circuit pattern 10a of the reticle 100 to perform exposure processing on the entire wafer 14.

However, in the exposure mounting of this embodiment, the main exposure process is performed by the following method before the above-mentioned exposure process.

First, with the first shutter 7 open, exposure light #16 is irradiated in the same manner as in the actual exposure process, and the temperature of the exposure device, especially the exposure optical system 2, is adjusted to the temperature during the actual exposure process. Raise it in the neighborhood type. Furthermore, the first shutter 7 is opened and closed at the same intervals as the opening and closing intervals during the actual exposure process, from the temperature in the vicinity during the exposure process to the temperature during the exposure process. This two-stage control of the first shutter shortens the time it takes for the temperature of the exposure device to reach the temperature during actual exposure processing, and suppresses the drop in throughput of the exposure process due to the introduction of main exposure processing. can do.

At this time, when the wafer 14 is placed on the wafer stage 13, the second shutter 15 is kept closed until the main exposure process is completed, thereby preventing the wafer 14 from being exposed to light in the courtyard light. It is possible.

Therefore, according to the exposure apparatus 11 of this embodiment, the main exposure process is performed before the actual exposure process, and in particular, the temperature of the exposure optical system 2 is kept in the same state as the temperature during the actual exposure process, and the temperature is kept in a stable state. By doing so, a fixed focus position is maintained in a stable state, and the exposure process of the wafer 14 can be performed from a stable state.

As above, the invention made by the present inventor has been specifically explained based on Examples, but it should be noted that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Not even.

For example, in the exposure apparatus of this embodiment, the exposure light source 6
Although the case where the mercury lamp emits the G-line wavelength has been described, the present invention is not limited to the above-mentioned embodiment, and can also be applied to, for example, the exposure light source 6 that emits the E-line (545 nm) wavelength. It is possible.

Furthermore, in this embodiment, a case has been described in which the exposure area for each step is carried out within the range of one chimbe size, but it is not limited to this, and can be changed by adjusting the exposure optical system 2, for example. It is.

In the above description, the invention made by the present inventor will mainly be described as a wafer 1 of a semiconductor integrated circuit device, which is the field of application of the invention.
Although the case where the present invention is applied to a step projection exposure apparatus used in 4 has been described, it is not limited to this.
For example, it is widely applicable to exposure apparatuses using other projection optical systems such as reduction projection exposure apparatuses.

[Effects of the Invention] Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

(1) In an exposure apparatus in which the exposure light from one light source is controlled by the opening/closing operation of a first shutter, and the pattern of the exposed object is projected onto the exposed object by an optical system, before the actual exposure process by the exposure apparatus. By performing main exposure processing and opening and closing the first shutter at the same intervals as the opening and closing intervals during actual exposure processing, the exposure device, especially the optical system, rises to the temperature state during actual exposure processing. Since the actual exposure process can be performed from a constant and stabilized focal position, stable exposure accuracy can be obtained.

(2) There is a second
A shutter is provided, and by closing this second shutter during main exposure processing, the projection of the exposure light onto the exposure object is blocked, so that it is possible to prevent the influence on the exposure object during the main exposure processing. can.

[3] The opening and closing operation of the first shutter is controlled in two stages, in which the first shutter is kept open until the temperature approaches the temperature during actual exposure processing in the first stage, and then in the second stage during actual exposure processing. By opening and closing the first shutter at the same intervals as the opening and closing intervals during the actual exposure process, the temperature of the optical system can be raised to the temperature state during the actual exposure process in a short time, so it is possible to introduce the main exposure process. It is possible to suppress a decrease in the throughput of the exposure process due to the exposure process.

(4) With (1) to [3] above, it is no longer necessary to measure the transmittance of all reticles and create a program that corresponds to all reticles, which is required in the past, so it takes a lot of time to use. Therefore, it is possible to obtain an exposure apparatus that does not require any additional processing.

[5] According to [1] to (3) above, the exposure apparatus itself can be used in the most stable state of the focus position without having to correct the focus position on software as in the past, which improves the focus position accuracy. It is possible to obtain an exposure apparatus in which the pattern resolution and dimensional accuracy can be improved and stabilized.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an exposure apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing focus fluctuation when no correction is made in a conventional exposure apparatus. DESCRIPTION OF SYMBOLS 1... Exposure illumination system, 2... Exposure optical system, 3... Reticle mounting system, 4... Wafer drive system, 5... Shutter drive system, 6... Exposure light source, 7...・First shutter,
8... Condenser lens, 9... Reduction projection lens, 10.
... Reticle, 10a... Circuit pattern (pattern to be exposed), 11... Reticle stage, 12...
Motor, 13... Wafer stage, 14... Wafer (exposure target), 15... Second shutter.

Claims (1)

[Scope of Claims] 1. An exposure apparatus in which exposure light from an exposure light source is controlled by opening and closing operations of a first shutter, and a pattern of an exposed object is projected onto the exposed object by an optical system, the exposure apparatus comprising: An exposure apparatus characterized in that a blank exposure process is performed before the actual exposure process, and the blank exposure process is performed by opening and closing the first shutter at the same intervals as opening and closing intervals during the actual exposure process. 2. A second shutter is interposed between the pattern to be exposed and the object to be exposed, and the second shutter is closed during the blank exposure process to prevent the object to be exposed from being exposed. The exposure apparatus according to claim 1. 3. The opening/closing operation of the first shutter is controlled in two stages, and in the first stage the first shutter is kept open until the temperature approaches the temperature during the actual exposure process, and in the second stage the actual exposure process is continued. 3. The blank exposure method for use in an exposure apparatus according to claim 1, wherein the first shutter is opened and closed at the same intervals as the opening and closing intervals during the actual exposure processing up to a temperature during processing.