JPH11176726A - Aligning method, lithographic system using the method and method for manufacturing device using the aligning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple aligning method, capable of obtaining image formation characteristic high respectively for a plurality of types of patterns, without causing sharp reduction in process speed even when a sensitive material necessary for shortening a deferment time of period is used. SOLUTION: Protective patterns 35, 36 for aligning each portion except the intrinsic patterns from reticle patterns 33R, 34R to be aligned are produced, and cyclic patterns 40, 37 are produced for prescribing a final form. Chemical amplifying type resist is first applied on a wafer of a first lot, and the protection patterns 35, 36 are aligned as patterns of a first reticle. Thereafter, the cyclic patterns 40, 37 as patterns for a second reticle with respect to a wafer of the one lot are aligned, and is developed immediately thereafter. After that, etching, etc., is performed to form circuit patterns.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method used for transferring a mask pattern onto a photosensitive substrate in a lithography process for manufacturing, for example, a semiconductor device, a liquid crystal display device, or a thin film magnetic head. The present invention relates to a method, a lithography system for performing the exposure method, and a method for manufacturing a device using the exposure method.

[0002]

2. Description of the Related Art Since the degree of integration of semiconductor elements is increasing and the patterns to be formed are becoming finer, projection exposure apparatuses of the batch exposure type (stepper etc.) or the scanning exposure type such as the step-and-scan type are used. In, there is a demand for higher resolution. In general, the resolution is proportional to the wavelength of the exposure light, and the numerical aperture (NA) of the projection optical system
Therefore, a direct method for increasing the resolution is to shorten the wavelength of the exposure light and increase the numerical aperture of the projection optical system. Therefore, recently, KrF (wavelength 248 nm) and ArF (wavelength 1) have been used as exposure light.
The use of excimer laser light (eg, 93 nm) shortens the wavelength and increases the numerical aperture (NA) of the projection optical system. Further, on the illumination optical system side, a high-resolution technique such as a modified illumination in which the shape of the aperture stop is decentered into a plurality of small apertures has been developed, and a high-resolution technique such as a phase shift reticle has been proposed for the reticle.

However, an increase in the numerical aperture decreases the depth of focus, and further shortening the wavelength of exposure light involves a problem of durability of a material used for an optical system. In addition, although the depth of focus of a periodic dense pattern increases due to the use of a deformed illumination or a phase shift reticle, the depth of focus of an isolated pattern may decrease on the contrary. Therefore, isolated patterns and periodic patterns (dense patterns) formed on the same layer
Are written on separate reticles, and an illumination method is used, such as normal illumination for the exposure of an isolated pattern, and a modified illumination for the exposure of a periodic pattern. Has also been proposed. According to this method, the line width stability of each pattern on the wafer is improved. Further, when forming an isolated pattern, a method of providing an auxiliary pattern on both sides of the isolated pattern and exposing it as a periodic pattern, and for the auxiliary pattern portion, exposing only that portion to form an isolated pattern Has also been proposed.

In recent lithography processes, chemically amplified resists have been used for short-wavelength exposure light such as KrF excimer laser for exposing fine patterns. This type of resist has the advantages of high sensitivity and good resist profile (cross-sectional shape), but has the instability of trace contaminants in the environment in which the resist is located, and especially exposure. As a result, the acid formed in the resist reacts with ammonia in the environment to lower the sensitivity.

[0005] For this reason, in a place where the environment is not sufficiently clean, if the so-called “pulling time” from the exposure of a wafer coated with a chemically amplified resist to the development thereof becomes long, the sensitivity of the resist decreases. For example, when the resist is of a positive type, there arises an inconvenience that the line width of a resist pattern formed after the development processing is increased. Therefore, conventionally, particularly when a chemically amplified resist is used, it has been considered that it is desirable to carry out development processing promptly after exposure.

[0006]

As described above, it is desirable to shift to the developing step as soon as possible after exposure. However, as described above, in order to expose a plurality of types of patterns in the same layer with a sufficient depth of focus, when performing multiple exposure by dividing a reticle pattern, it is attempted to reduce the time until development for each wafer. Then, the time required for exposing the whole wafer of one lot becomes long, and there is a disadvantage that the throughput is reduced.

In other words, in order to perform such multiple exposure and to reduce the time required for laying, a resist is applied to all the wafers in one lot and then the first pattern is exposed for each wafer. After that, the pattern to be exposed by exchanging the reticle is changed to the second pattern, and the aperture shape of the illumination system and the numerical aperture of the projection optical system are changed so as to obtain optimal imaging parameters. It is necessary to expose the pattern and move to a development step. Therefore, the exposure time for each wafer becomes longer, the exposure time for one lot of wafers becomes considerably longer, and the throughput of the exposure process decreases.

SUMMARY OF THE INVENTION In view of the foregoing, it is a first object of the present invention to provide a multiple exposure method capable of obtaining high imaging characteristics for a predetermined pattern including, for example, an isolated pattern. Further, the present invention provides a multiple exposure method capable of obtaining high image forming characteristics for a plurality of types of patterns without causing a significant reduction in processing speed even when using a photosensitive material that requires a shortening of the withdrawal time. It is a second object to provide a method.

It is a third object of the present invention to provide a lithography system using such an exposure method and a method for manufacturing a device.

[0010]

An exposure method according to the present invention is directed to an exposure method for exposing a predetermined pattern image onto a substrate (W) coated with a photosensitive material. Exposing an image of a first mask pattern (35, 36) for exposing the photosensitive material onto the substrate (step 104); and exposing the photosensitive material after exposing the image of the first mask pattern. And a step of exposing the image of the second mask pattern (33R, 37) for defining the image of the predetermined pattern onto the substrate before the development (Step 107).

According to the present invention, since the exposure of the image of the second mask pattern for defining the shape of the image of the pattern to be exposed is performed before the development, the image of the second mask pattern is exposed. Of the photosensitive material is reduced, and the characteristic change of the photosensitive material is reduced. Therefore, even when the pattern to be exposed includes an isolated pattern or the like,
These patterns can be exposed with high imaging characteristics (resolution, etc.). When the predetermined pattern is composed of, for example, a periodic pattern and an isolated pattern, a protection pattern (35, 36) for exposing portions other than the two types of patterns is used as the first mask pattern. As the second mask pattern, periodic patterns (33R, 37) corresponding to these two types of patterns are used. By setting the second exposure condition so that the periodic pattern can be exposed at a high resolution, the isolated pattern can also be exposed at a high resolution as a periodic pattern (37).
High resolution can be obtained for two types of patterns.

In this case, when a chemically amplified resist is used as a photosensitive material on the substrate, if the isolated convex pattern (34) is formed after developing the photosensitive material, the photosensitive material is made positive type. When an isolated concave pattern (39) is formed after developing the photosensitive material, it is desirable that the photosensitive material be negative. In order to form an isolated convex pattern (34) after development, it is necessary to gradually increase the area of the photosensitive material that dissolves after development by repeating exposure. Therefore, it is convenient to use a positive photosensitive material.

On the other hand, after development, an isolated concave pattern (39)
In order to form a photosensitive material, it is necessary to gradually reduce the area of the photosensitive material that is dissolved after development by repeating exposure. Therefore, a negative photosensitive material is convenient. In these cases, it is the exposure of the second mask pattern that defines the final shape, and the delay time from the exposure of the second mask pattern to the development can be considerably shortened. Therefore, even if the exposure wavelength is a short wavelength such as excimer laser light and a photosensitive material such as a chemically-amplified resist that requires a short resting time is used, high image formation can be achieved for two types of patterns. Characteristics are obtained.

Further, the first substrate is sequentially applied to a plurality of substrates.
After exposing the image of the mask pattern, the exposure conditions are changed before the development of the photosensitive material, and then the second mask pattern image is sequentially exposed on the plurality of substrates. desirable. At this time, the post-exposure drawing time required for shape control of the actual pattern line width and the like performed in the second time can be fixed and short, so that there is little change in the pattern shape after development. Further, since the pattern shape is not determined in the first exposure, a change in the pattern shape due to the subsequent drawing can be ignored. Furthermore, the first exposure and 2
Since an appropriate withdrawal is allowed between the first exposure and the second exposure,
A plurality of substrates that have been subjected to the first exposure are temporarily collected in a predetermined cassette, and after exchanging exposure patterns, changing illumination conditions, and changing the numerical aperture of the projection optical system, the plurality of substrates are then collected. The second mask pattern can be exposed to the substrate collectively.

For this reason, the number of times of changing the exposure condition can be reduced and the exposure time for which it is necessary to shorten the storage time can be reduced as compared with the case where the exposure is repeated with the changing operation of the exposure condition interposed between one substrate. Even when a material is used, a reduction in processing speed can be reduced as much as possible. In a lithography system according to the present invention, in a lithography system for forming a predetermined pattern on a substrate (W), a photosensitive material coating apparatus (4) for coating a photosensitive material on the substrate is provided.
1) and a first mask pattern (35, 3) for exposing the photosensitive material in a portion other than the image of the predetermined pattern.
After exposing the image of 6) on the substrate and before developing the photosensitive material, a second image for defining the image of the predetermined pattern is formed.
An exposure device (1) for superposing an image of the mask pattern (33R, 37) on the substrate and exposing the substrate, a developing device (41) for developing the photosensitive material on the substrate, and a second mask pattern The exposure time of the second mask pattern to the exposure apparatus (1) is controlled such that the retention time from the exposure of the image to the development of the photosensitive material is controlled so that the retention time falls within a predetermined allowable range. Control device (4
5).

According to the lithography system of the present invention, the control device (45) controls the exposure device (1) so that the time from the exposure of the image of the second mask pattern to the development thereof is as short as possible. Control. Thereby, the exposure method of the present invention can be performed. The method for manufacturing a device according to the present invention is a method for manufacturing a device for forming a predetermined pattern including an isolated pattern (34; 39) on a substrate (W), wherein a photosensitive material is coated on the substrate. And a first step for exposing the photosensitive material in a portion other than the image of the predetermined pattern.
After exposing the image of the mask pattern (35, 36) on the substrate, and before developing the photosensitive material, the second mask pattern (40, 40) for defining the image of the predetermined pattern is formed.
37) a second step (steps 103 to 107) of exposing the image on the substrate by superimposing the image, a third step (step 108) of developing the photosensitive material on the substrate, and a photosensitive step remaining in the third step. And forming a pattern on the substrate using the material as a mask (Step 109).

According to the present invention, the exposure method of the present invention is used, and the time required for the second mask pattern to be exposed to development can be shortened. It is possible to use a photosensitive material such as an amplifying type resist that requires a shortened leaving time, and to form a fine periodic pattern or an isolated pattern with a stable line width and high resolution.

In this case, the predetermined pattern includes, for example, a periodic pattern (33) in addition to the isolated pattern, and the first mask pattern includes the isolated pattern to be formed on the substrate and the periodic pattern. A pattern (35, 36) for exposing a partial area between the pattern and the pattern is included.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a lithography system used in this example. In FIG. 1, a wafer carrier 43 is movably arranged along a wafer transfer line 42. Along the transfer line 42, photoresist is applied to the wafer, and PEB (pos.
A coater / developer 41 for performing t-exposure bake and development, a wafer cassette 44 for temporarily storing a wafer before or after exposure, and a projection exposure apparatus 1 are arranged, and control a lithography process by these apparatuses. A controlling host computer 45 is also provided. A timer device 46 is also connected to the host computer 45, and the host computer 45 also manages the time for storing the photoresist from the exposure in the projection exposure apparatus 1 to the PEB and development in the coater / developer 41.

First, in the projection exposure apparatus 1, exposure light IL consisting of ultraviolet pulse light having a wavelength of 248 nm emitted from the exposure light source 1 consisting of a KrF excimer laser light source passes through a first lens 8A and a second lens 8B. The cross-sectional shape is shaped and enters the fly-eye lens 10. As the exposure light, other laser light such as ArF excimer laser light, i-line of a mercury lamp (wavelength 365 nm), and the like can be used. In this example, a chemically amplified resist is used as a photoresist corresponding to the exposure light IL.

On the exit surface of the fly-eye lens 10, an aperture stop plate 11 of an illumination system is rotatably disposed. Around the rotation axis of the aperture stop plate 11, a circular aperture stop 13A for normal illumination, a plurality of aperture stops are provided. Aperture stop 13B for deformed illumination comprising an eccentric small aperture and annular aperture stop 13 for annular illumination
A small circular aperture stop 13D for C and a small coherence factor (σ value) is formed. The main control system 2 for the projection exposure apparatus 1 is configured so that a desired illumination system aperture stop can be arranged on the exit surface of the fly-eye lens 10 by rotating the aperture stop plate 11 with a drive motor 12. I have.

A part of the exposure light IL that has passed through the aperture stop on the exit surface of the fly-eye lens 10 is
After being reflected by the, it is incident on an integrator sensor 16 composed of a photoelectric detector via a condenser lens 15. The main control system 2 indirectly monitors the illuminance (pulse energy) of the exposure light IL on the surface of the wafer W from the detection signal of the integrator sensor 16 and the integrated exposure amount on the wafer W, and from the result, the wafer W Is controlled.
The exposure light IL transmitted through the beam splitter 14 passes through a first relay lens 17A, a variable field stop (reticle blind) 18, a second relay lens 17B, a mirror 19 for bending an optical path, and a condenser lens 20 to form a pattern of a reticle R. Illuminate the surface. The arrangement surface of the variable field stop 18 and the pattern surface of the reticle R are conjugate, and the illumination area on the pattern surface is defined by the opening shape of the variable field stop 18. As an example, the pattern area of the reticle R of the present example is divided into a first pattern area 32A and a second pattern area 32B.
The pattern in B can be alternately exposed. Under the exposure light IL, the image of the pattern in the illumination area on the reticle R is formed by a photoresist at a predetermined projection magnification β (β is, for example, ４ ，, ５) through the projection optical system PL. It is projected on the coated wafer W.

Here, the Z axis is taken in parallel with the optical axis AX of the projection optical system PL, and the orthogonal coordinate system of a plane perpendicular to the Z axis is represented by the X axis.
Assuming the Y axis, the reticle R is held on a reticle stage 21 for positioning in the X, Y, and rotation directions. On the other hand, the wafer W is sucked and held on the wafer holder 22, and the wafer holder 22 is fixed on the wafer stage 23. The wafer stage 23 corrects the position and the tilt angle of the wafer W in the Z direction and projects the surface of the wafer W onto the projection optical system. System PL
And the stepping and positioning of the wafer W in the X and Y directions. The positions of reticle stage 21 (reticle R) and wafer stage 23 (wafer W) are each measured with high precision by a laser interferometer (not shown), and main control system 2 controls reticle stage 21 and wafer stage based on the measurement results. 23 is controlled.

At the time of exposure, after exposure of a certain shot area on the wafer W is completed, the wafer stage 23 is stepped, and the next shot area is moved to the exposure field to perform exposure. -Each shot area on the wafer W is repeatedly exposed in the repeat mode. In addition, as the projection exposure apparatus 1,
In addition to the batch exposure type, a step-and-scan method in which exposure is performed by synchronously scanning the reticle R and the wafer W with respect to the projection optical system PL using a projection magnification as a speed ratio may be used.

A reference mark member 24 made of a glass substrate is fixed in the vicinity of the wafer holder 22 of the wafer stage 23, and, for example, cross-shaped reference marks 25A and 25B are formed on the reference mark member 24 by a chrome film or the like, and projected. On the side surface of the optical system PL, an image processing type alignment sensor 28 for detecting the position of a wafer mark attached to each shot area on the wafer W is provided. A reference mark (not shown) for the alignment sensor 28 is also formed on the reference mark member 24. The alignment marks 31A and 31B are also formed on the pattern surface of the reticle R in a positional relation obtained by converting the positional relation between the reference marks 25A and 25B by the projection magnification from the wafer to the reticle. Mirror 26
A reticle alignment microscopes 27A and 27B of an image processing method are installed via A and the like.

When aligning the reticle R,
As an example, the reference marks 25A and 25B are illuminated from the bottom side with illumination light having the same wavelength as the exposure light in a state where the centers of the reference marks 25A and 25B are set substantially at the centers of the exposure fields of the projection optical system PL. Reference marks 25A, 25
The image B is formed near the alignment marks 31A and 31B, and the reticle alignment microscope 27A detects the amount of displacement of the alignment mark 31A with respect to the image of the reference mark 25A, and the reticle alignment microscope 27B detects the alignment mark with respect to the image of the reference mark 25B. 31
By detecting the displacement amount of B and positioning the reticle stage 21 so as to correct these displacement amounts,
Positioning of reticle R with respect to wafer stage 23 is performed. At this time, by observing the corresponding reference mark with the alignment sensor 28, the alignment sensor 2
An interval (baseline amount) from the detection center 8 to the center of the pattern image of the reticle R is calculated. When performing overlay exposure on the wafer W, the alignment sensor 28
The wafer stage 23 is driven based on the position where the detection result of the reticle R is corrected by the baseline amount, so that the pattern regions 32A,
The pattern image in 32B can be exposed with high overlay accuracy.

Next, an example of an operation when a predetermined circuit pattern of a semiconductor device is formed in each shot area on the wafer W using the lithography system of the present embodiment will be described. FIG. 2 shows a circuit pattern formed in each shot area on the wafer in this example. In FIG. 2, a rectangular pattern 33a formed of a metal film of a predetermined thickness (convex) elongated in the Y direction on the wafer. At predetermined intervals 33b
Periodic (dense) arranged at a predetermined pitch in the direction
The circuit pattern 33 is formed. Further, a rectangular isolated circuit pattern 34 made of a (thick) metal film having a predetermined thickness and elongated in the Y direction is formed at a predetermined distance from the circuit pattern 33 in the X direction. When the isolated convex circuit pattern 34 is included, a positive photoresist is used as a photoresist applied on the wafer.

Then, the circuit patterns 33 and 34
FIG. 3 (a) shows an original pattern obtained by enlarging the original pattern at the projection magnification from the wafer to the reticle of the projection optical system PL in FIG.
Reticle patterns 33R and 34R. In FIG. 3A, the periodic reticle pattern 33R
Is a pattern in which five rectangular light-shielding patterns 33Ra having a length LY1 in the Y direction are arranged at a predetermined pitch over a width LX1 in the X direction with the light transmission region as a background. Less than,
Each light-shielding pattern 3 of the present example is assumed to represent the size of each part of the reticle pattern 33R by the size of a projected image on a wafer.
The width of 3Ra in the X direction is 200 nm, and the interval between them is 20 nm.
0 nm, and the length LY1 in the Y direction is set to be considerably wider than the width. Also, the reticle pattern 33
Isolated reticle pattern 34R formed next to R
Is a light-shielding pattern having a width LX2 in the X direction and a length LY1 in the Y direction, and the width LX2 is 200
nm.

In this example, as shown in FIG. 3B, the protection patterns 35 and 36 (first reticle patterns) used in the first exposure are changed from the reticle patterns 33R and 34R in FIG. As shown in FIG. 3C, the periodic patterns 40 and 37 (second reticle pattern) used in the second exposure are generated. As shown in FIG. 1, since the reticle R has two pattern areas 32A and 32B, one of the pattern areas 32A has the protection patterns 35 and 3 on it.
6 may be formed, and the periodic patterns 40 and 37 may be formed in the other pattern region 32B. However, the case where the protection patterns 35 and 36 are formed on the first reticle and the periodic patterns 40 and 37 are formed on the second reticle will be described below.

In FIG. 3B, one protection pattern 35 is a light-shielding pattern having a width LX3 in the X direction and a length LY2 in the Y direction with the light transmitting area as a background, and the width LX3 and the length LY2 are The width L of each reticle pattern 33R
It is set wider than X1 and length LY1. Further, the other protection pattern 36 has an X
This is a light shielding pattern having a width LX4 in the direction and a length LY2 in the Y direction, and the width LX4 is set wider than the width LX2 of the reticle pattern 34R. Further, the protection patterns 35 and 3
The intervals of 6 are set such that the reticle patterns 33R and 34R can be completely covered by the protection patterns 35 and 36. The protection patterns 35 and 36 are shown in FIG.
(A) is used to protect the periodic reticle pattern 33R and the isolated reticle pattern 34R, and to uniformly expose other portions.

In FIG. 3C, one periodic pattern 40 is a pattern having the same shape as the reticle pattern 33R of FIG. 3A, and a periodic pattern 37 adjacent to the reticle pattern 33R in the X direction is shown in FIG. a) Reticle pattern 34
This is a pattern in which five light shielding patterns 37a having the same shape as R are arranged in the X direction at a predetermined pitch. At this time, the width LX5 in the X direction of the two light transmitting portions sandwiching the central light-shielding pattern of the periodic pattern 37 is set wider than the width LX4 of the protection pattern 36, and the protection pattern 36 and the periodic pattern 37 overlap. Exposure is equivalent to exposing the reticle pattern 34R alone. That is, the reticle pattern 34 isolated by the exposure of the periodic pattern 37
R can be exposed, and the pattern other than the light-shielding pattern at the center of the periodic pattern 37 is a kind of auxiliary pattern.

Next, an example of the operation of forming the circuit patterns 33 and 34 of FIG. 2 using the above-described protection patterns 35 and 36 and the periodic patterns 40 and 37 will be described with reference to the flowchart of FIG. First, step 1 in FIG.
In step 01, a metal film is deposited on 25 wafers to be exposed (this is referred to as one lot) by a deposition apparatus (not shown) in step 102, and in step 102, the lottery using the coater / developer 41 of FIG. A chemically amplified positive resist is applied on the metal film of the wafer. Thereafter, in step 103, the protection patterns 35, 3 shown in FIG.
Load the first reticle on which 6 has been formed. And
The numerical aperture of the projection optical system PL is 0.60, the aperture stop of the illumination system is a circular aperture (normal illumination) having a σ value of 0.75, the defocus amount of the wafer is 0, and the exposure amount is 20 mJ / cm ^2. Set to each. In the next step 104, the pattern image of the first reticle is sequentially exposed to each shot area on the one lot of wafers using the projection exposure apparatus 1 under the exposure conditions. It is assumed that this exposure is overlay exposure, and the reticle alignment microscopes 27A and 27B and the alignment sensor 2 are used before each wafer is exposed.
The alignment between the first reticle and each shot area of the wafer is performed by using. The wafers of one lot after the exposure are temporarily stored in the wafer cassette 44 in FIG.

Thereafter, in step 106, the first reticle is returned to the reticle case (not shown) from the reticle stage 21 of the projection exposure apparatus 1 via a reticle loader system (not shown). The second reticle on which the periodic patterns 40 and 37 are formed is loaded on the reticle stage 21. Then, the numerical aperture of the projection optical system PL is set to 0.60, and the aperture stop of the illumination system is set to a ring-shaped aperture having a σ value of the outer diameter of 0.75 and an inner diameter of 2/3 of the outer diameter (so-called 2/3 wheel). In (band illumination), the defocus amount of the wafer is set to 0, and the exposure amount is set to 30 mJ / cm ² . At the same time, the host computer 45 uses the timer device 46 to reach the upper limit of the chemical amplification-type resist withdrawal time used in this example from the first exposure in step 104. Watch not to be.

In the next step 107, the host computer 45 sets the coater / developer 41 of FIG. 1 in a state of waiting for development within a range in which the elapsed time is not expected to reach the upper limit of the reserved time. At this point, an exposure start command is issued to the main control system 2 immediately. Accordingly, under the exposure condition, the pattern image of the second reticle is changed to the first reticle in the projection exposure apparatus 1.
Each shot area on a wafer in the lot is sequentially exposed.
At this time, the reticle alignment microscopes 27A, 27
B and the alignment sensor 28 are used to align the second reticle with each shot area of the wafer. Thereby, the alignment between the pattern image of the first reticle and the pattern image of the second reticle is also performed.

Each wafer immediately after the completion of the second exposure is transferred to the coater / developer 41 via the wafer transfer line 42 in step 108, where the photoresist PEB (pre-development bake), And development are performed. As a result, the reticle pattern 3 shown in FIG.
A resist pattern is formed in which only the portions 3R and 34R are left as convex patterns. Then, in step 109 using an etching apparatus (not shown), the resist pattern is used as a mask to etch the metal film on each wafer, and then the resist pattern is removed, thereby forming the convex circuit pattern 33 shown in FIG. , 34 are formed in each shot area on each wafer. Thereafter, the wafer of the one lot shifts to the step of forming the circuit pattern of the next layer.

As described above, in this embodiment, the circuit patterns to be transferred are the protection patterns 35 and 36 and the periodic patterns 40 and 3
7, exposure of the protection patterns 35 and 36 is first performed on one lot of wafers. Then, when the development preparation is completed, the periodic pattern 4 for defining the final circuit pattern dimensions for the one lot of wafers.
Exposures 0 and 37 are performed repeatedly, and development is performed on each wafer immediately after the exposure. Therefore, since the delay time from exposure to development for defining the dimensions of the final circuit pattern is extremely short, the circuit has a high resolution and a high line width stability by utilizing the original characteristics of the chemically amplified resist. A pattern is formed. To confirm this, together with the above-described embodiment, after exposing the image of the pattern of the first reticle to each wafer, the exposure conditions are switched to expose the image of the pattern of the second reticle, and then development is performed. Although an exposure method of performing the same was tried, the average value of the line width and the variation of the line width of the finally obtained circuit pattern were equivalent.

Further, in this example, when the isolated circuit pattern 34 shown in FIG. 2 is formed, the protection pattern 36 (FIG. 3 ( b)), and in the second exposure, the periodic pattern 37 (FIG. 3C) is exposed. In this case, if a periodic pattern is used, exposure can be performed at a high resolution by using annular illumination or the like. Therefore, by forming an isolated circuit pattern by exposing the periodic pattern, the isolated circuit pattern can be exposed to other elements. And a very high resolution.

In the above embodiment, a positive resist is used to form the convex isolated circuit pattern 34. On the other hand, when forming a concave isolated circuit pattern, it is desirable to use a negative resist. FIG. 5 shows an example of a concave isolated circuit pattern formed in each shot area on the wafer. In FIG. 5, a concave rectangular pattern 38a elongated in the Y direction and having a predetermined depth is formed on the base. A periodic (dense) circuit pattern 38 arranged at a predetermined pitch in the X direction at a predetermined interval 38b is formed. Further, isolated rectangular circuit patterns 39 having a predetermined depth and elongated in the Y direction are formed at predetermined intervals in the X direction with respect to the circuit patterns 38. When the concave isolated circuit pattern 39 is included as described above, for example, a chemically amplified negative resist is used as a photoresist applied on the wafer. Then, using the protection patterns 35 and 36 in FIG. 3B as the first reticle pattern and using the periodic patterns 40 and 37 in FIG. 3C as the second reticle pattern, By performing etching and the like after performing exposure and development, a periodic circuit pattern 38 and an isolated concave circuit pattern 39 in FIG. 5 can be formed.

Further, in the above embodiment, as described with reference to the flowchart of FIG. 4, first, the pattern of the first reticle is exposed to one lot of wafers, and thereafter, the exposure of the projection exposure apparatus is performed. The exposure condition is switched to expose the pattern of the second reticle to the wafer of the one lot. With this exposure method, the overall exposure time is shortened and the throughput of the exposure process is improved as compared with the case where the exposure conditions are switched for each wafer and the pattern of the two reticles is exposed. For simplicity, this will be described with reference to FIG. 6 taking as an example a case where three wafers are exposed.

FIG. 6A shows a flow of an operation for performing exposure in the same manner as in the embodiment of FIG. 4, and FIG.
The flow of operation when double exposure is performed by switching the exposure condition for each wafer is shown. The horizontal axis in these figures is time t. In FIG. 6, A is a time for setting various exposure conditions in the projection exposure apparatus, B is a time for placing and aligning the wafer on the wafer stage, and an exposure time of the pattern of the first reticle, and C is a wafer. On the wafer stage,
This is the exposure time of the alignment and the pattern of the second reticle. In the case of FIG. 6A, the start time t1
Between the time t2 and the intermediate time t2 for the three wafers.
Is performed, and the exposure of the second reticle pattern to three wafers is performed between the intermediate time point t2 and the end time point t3. On the other hand, FIG.
In the case of (b), the exposure of the two reticle patterns to the first wafer is performed from the start time t1 to the intermediate time t4, and the second reticle pattern is exposed from the intermediate time t4 to the next intermediate time t5. Of the two reticles on the third wafer (the order of exposure of the reticles is opposite to C and B), and between the intermediate time t5 and the end time t6, the two reticles on the third wafer are exposed. Exposure of the pattern is performed.

6A and 6B, when the number of wafers is assumed to be N, according to the exposure method as in the above-described embodiment, two exposure conditions are changed for each wafer. Compared to the method of exposing a reticle pattern, almost (N-1) A
It can be seen that only the exposure time is reduced. Further, FIG.
In the exposure method (b), the exposure order of the patterns of the first and second reticle is reversed for the exposure of the second wafer from the intermediate time point t4 to t5 in order to shorten the exposure time. The pattern that defines the shape of the circuit pattern is first exposed. In addition, when a plurality of wafers were exposed to light in the reverse order of exposure and the circuit pattern formed was measured, the average value of the pattern line width was increased by about 0.02 μm. Variation has also increased. From this result, it is clear that the method of performing the exposure of the pattern directly related to the line width control of the actual circuit pattern immediately before the PEB and the development processing as in the embodiment of FIG. 4 is more accurate and stable in the line width. It can be said that it is effective on both sides.

The present invention is not limited to the above-described embodiment. As shown in FIG. 1, the first exposure pattern is formed on one reticle R, for example, in the left and right pattern areas 32A and 32B. And the pattern for the second exposure may be arranged so that the variable field stop 18 exposes the left pattern the first time and the right pattern the second time. In this case, the number of wafers in one lot is N
In the exposure method shown in FIG.
While the unloading and alignment must be repeated 2N times, in the exposure method of FIG. 6B, the loading / unloading and alignment of the wafer can be performed N times. However, in the current projection exposure apparatus, the time required for loading / unloading and aligning the wafer can be shorter than the time required for changing the exposure conditions such as changing the setting of the variable field stop or the illumination system aperture stop. It can be said that the exposure method shown in FIG. 6A is generally superior including the line width accuracy of the finally obtained circuit pattern.

Further, the method of dividing the pattern to be exposed is not limited to the above-described embodiment, but the exposure of the pattern defining the actual pattern shape including the auxiliary pattern is performed for the second time, and the auxiliary pattern erasing method is performed. The present invention is applied to any case as long as the first exposure is performed. For example, when a pattern to be exposed is a pattern that is long in a predetermined direction, the pattern is divided into a first pattern that defines a shape in the longitudinal direction and a second pattern that defines a shape in the short direction. The present invention can also be applied to the case where

Further, the present invention can be applied to a case where a resist other than the chemically amplified type is used as a photoresist, and an exposure apparatus using a charged particle beam such as an electron beam or an X-ray as an exposure energy beam. The present invention can be applied to a case where a predetermined circuit pattern is exposed by using the method. As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention.

[0045]

According to the exposure method of the present invention, the exposure of the second mask pattern for defining the image of the predetermined pattern to be exposed is performed before the development of the photosensitive material. There is an advantage that the time required for the mask pattern to be exposed to development can be shortened, and that a predetermined pattern including, for example, an isolated pattern can be formed with high imaging characteristics.

When a chemically amplified resist is used as a photosensitive material on a substrate, and an isolated convex pattern is formed after developing the photosensitive material, the photosensitive material is developed using the positive material as a positive type. When an isolated concave pattern is formed later, the isolated convex or concave pattern can be formed with high line width control accuracy when the photosensitive material is made to be a negative type.

After sequentially exposing the images of the first mask pattern to the plurality of substrates, changing the exposure conditions before developing the photosensitive material, and sequentially exposing the plurality of substrates to the second mask image. In the case of exposing the image of the mask pattern in a superimposed manner, the entire exposure time is shortened as compared with the case of exposing two mask pattern images sequentially by changing the exposure condition for each substrate. Therefore, even when a photosensitive material that requires a shortened retraction time is used, there is an advantage that a high imaging characteristic can be obtained for each of a plurality of types of patterns without causing a significant reduction in processing speed (throughput).
According to the lithography system of the present invention, the exposure method of the present invention can be used. And according to the device manufacturing method of the present invention, by using the exposure method of the present invention,
Since the withdrawal time from the second exposure to the development can be shortened, a predetermined pattern including, for example, an isolated pattern can be formed with high accuracy.

At this time, the predetermined pattern includes a periodic pattern in addition to the isolated pattern, and the first mask pattern is used to expose a partial region between the isolated pattern to be formed on the substrate and the periodic pattern. In this case, the isolated pattern and the periodic pattern can be simultaneously formed with high resolution.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a lithography system used in an example of an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing an example of a convex circuit pattern to be formed in the embodiment.

3A is an enlarged plan view showing a reticle pattern corresponding to a circuit pattern to be formed, and FIG. 3B is a plan view of FIG.
3C is an enlarged plan view showing a pattern of a first reticle corresponding to the reticle pattern of FIG. 3C, and FIG. 3C is an enlarged plan view showing a pattern of a second reticle corresponding to the reticle pattern of FIG.

FIG. 4 is a flowchart illustrating a process of forming a circuit pattern according to an example of an embodiment of the present invention.

FIG. 5 is an enlarged perspective view showing an example of a concave circuit pattern to be formed in the embodiment.

FIG. 6 is a diagram for comparing and explaining a case where two reticle patterns are sequentially exposed for a plurality of wafers and a case where two reticle patterns are exposed alternately for one wafer; is there.

[Explanation of symbols]

 Reference Signs List 1 projection exposure apparatus 3 exposure light source 11 aperture stop plate 18 variable field stop R reticle PL projection optical system W wafer 23 wafer stage 34 convex isolated circuit pattern 35, 36 protection pattern 37, 40 periodic pattern 39 concave isolated circuit pattern 41 Coater / Developer 44 Wafer Cassette 45 Host Computer

Claims (6)

[Claims] 1. An exposure method for exposing an image of a predetermined pattern onto a substrate coated with a photosensitive material, the method comprising: exposing a first mask pattern for exposing a portion of the photosensitive material other than the image of the predetermined pattern; Exposing an image on the substrate; and after exposing the image of the first mask pattern and before developing the photosensitive material, an image of a second mask pattern for defining an image of the predetermined pattern. And exposing the substrate to light on the substrate. 2. The exposure method according to claim 1, wherein a chemically amplified resist is used as the photosensitive material on the substrate, and the photosensitive material is developed when an isolated convex pattern is formed after the photosensitive material is developed. An exposure method, wherein the material is a positive type, and when an isolated concave pattern is formed after developing the photosensitive material, the photosensitive material is a negative type. 3. The exposure method according to claim 1, wherein an exposure condition of the image of the first mask pattern is sequentially exposed on a plurality of the substrates and before development of the photosensitive material. And exposing the plurality of substrates to the image of the second mask pattern in sequence after exposing the plurality of substrates. 4. A lithography system for forming a predetermined pattern on a substrate, comprising: a light-sensitive material coating apparatus for coating a light-sensitive material on the substrate; and exposing the light-sensitive material in a portion other than an image of the predetermined pattern. After exposing the image of the first mask pattern on the substrate, before developing the photosensitive material, an image of the second mask pattern for defining the image of the predetermined pattern is superimposed on the substrate. An exposure device for exposing; a developing device for developing the photosensitive material on the substrate; and a storage time from exposure of the image of the second mask pattern to development of the photosensitive material. A lithography system, comprising: a controller that instructs the exposure apparatus to expose the second mask pattern so that the placement time falls within a predetermined allowable range. 5. A method of manufacturing a device for forming a predetermined pattern including an isolated pattern on a substrate, comprising: a first step of applying a photosensitive material on the substrate; and a method other than an image of the predetermined pattern. After exposing an image of a first mask pattern for exposing a portion of the photosensitive material onto the substrate and before developing the photosensitive material, a second mask pattern for defining the image of the predetermined pattern A second step of exposing the image on the substrate by superimposing an image of the third step, a third step of developing a photosensitive material on the substrate, and forming a pattern on the substrate using the photosensitive material left in the third step as a mask And a fourth step. 6. The method according to claim 5, wherein the predetermined pattern includes a periodic pattern in addition to the isolated pattern, and the first mask pattern is formed on the substrate. A method for manufacturing a device, comprising a pattern for exposing a partial region between the isolated pattern to be formed and the periodic pattern.