JP2000100710A - Pattern-forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a pattern-forming method wherein diffusion or deactivation of acid which is to be generated between exposures is prevented, resolution and dimension control are satisfactory and throughput is high. SOLUTION: A fine pattern is formed on a resist by charged beam exposure (21), the resist is heat treated (22), a rough pattern is formed on the resist through light exposure (23), the resist is heat treated again (24), and lastly the resist on which the rough pattern and the fine pattern are formed is developed (25).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pattern forming method for transferring a pattern to the same resist by using light exposure and charged beam exposure.

[0002]

2. Description of the Related Art In recent years, electron beam lithography has been proposed as a first candidate for post-optical lithography. Electron beam lithography is an effective technique for meeting the recent demand for finer patterns, but it has the disadvantage of low throughput, so mix-and-match has been proposed as a method to increase throughput. ing. Mix-and-match is the process of transferring a pattern to the same resist using light exposure and electron beam exposure to form a certain pattern layer in the device manufacturing process. It is a method of forming. In this mix-and-match, it is possible to increase the number of wafers that can be processed per hour by an electron beam lithography apparatus by reducing the exposure area of electron beam exposure.

However, in this mix-and-match lithography, it is necessary to correct the dimensional deviation of a pattern formed by light exposure due to backscattering of electrons generated during electron beam exposure. Until now, complicated data processing such as applying a bias to the pattern design data to correct the dimensional fluctuations caused by the backscattered electron fog due to the fogging of the backscattered electrons had to be performed on the reticle fabrication data for light exposure. was there.

[0004] In addition, a method using a phase shift mask, a method of transferring a common pattern by light, and the like have been disclosed (JP-A-4-155812, JP-A-1-293616). It is hard to say that this method satisfies both throughput and future miniaturization at the same time.

[0005] As described above, in the mix-and-match of the same layer of light and EB, which has been conventionally carried out to improve the throughput, the resolution of electron beam exposure is not sufficiently utilized, and the throughput is equal to that of the stepper. There was a problem that it did not reach by now.

In order to solve the above problem, a lithography system has been proposed in which the same resist is exposed by light and EB having both a resolving power exceeding the light of electron beam exposure and a throughput equivalent to that of a stepper (Japanese Patent Laid-Open No. Hei. 9-
No. 46683).

In this lithography system, the coating and developing apparatus applies a resist to a wafer. The wafer coated with the resist is transported from the coating and developing device to the optical stepper. In an optical stepper, the resist is exposed to light. Thereby, the rough pattern is transferred to the resist.
Next, the wafer is transferred from the optical stepper to the electron beam exposure apparatus. In this electron beam exposure apparatus, a resist is exposed by an electron beam. Thereby, a fine pattern is drawn on the resist. At this time, a cell projection method is adopted to increase the throughput.

As is well known, the throughput of electron beam exposure is lower than the throughput of light exposure. Therefore, 1
A plurality of electron beam exposure apparatuses are arranged for one optical stepper. Wafers processed by the optical stepper are processed in parallel by a plurality of electron beam exposure apparatuses. After the rough pattern and the fine pattern are drawn, the wafer is transported to a coating and developing device, where it is developed. This fixes the pattern.

[0009] Resists that can be used in such lithography systems include, for example, UV2HS and UVN-H.
It is a chemically amplified resist having high resolution such as S (shipple) and high sensitivity. Since the performance of such a chemically amplified resist deteriorates due to various chemical substances in the air, it is necessary to control the environment during transportation.

By configuring the lithography system in this manner, a device pattern including a fine pattern of the 0.1 μm rule can be formed at a high throughput.

As described above in detail, according to such a lithography system, it is possible to provide a mass production system after optical lithography having both excellent resolution exceeding the light of electron beam exposure and throughput equivalent to that of a stepper. Can be.

However, the following problems also occur in the above lithography system. This lithography process mainly includes three steps of light exposure, electron beam exposure, and heating. The chemically amplified resist used in this system is composed of a polymer material, and its exposure is 2
Process. In the first step, the resist portion irradiated with the light or the electron beam absorbs energy. If the resist type is negative type, a cross-linking reaction is caused to become insoluble. In this first step, acid is generated in the resist by irradiation with light or an electron beam. Exposure in the next step occurs when the acid causes a crosslinking reaction (negative type) or a decomposition reaction (positive type) of the polymer material as a catalyst.

During the period from exposure to heating, the acid diffuses or deactivates in the resist. This diffusion or deactivation
A dimensional error, ie, an excessively thin or thick exposure pattern.

To reduce the dimensional error, it is desired to shorten the time from exposure to heating. However, in the above system,
Since the optical stepper exposes the resist in the atmosphere and the electron beam exposure device exposes the resist in a vacuum, the transfer time from the optical stepper to the electron beam exposure device and the electron beam exposure time between the light exposure and the electron beam exposure In addition to time, evacuation time for changing the environment from an atmospheric state to a vacuum state is necessarily required. Therefore, the time from light exposure to heating cannot be reduced so much.

Therefore, in a pattern forming method in which pattern transfer to a resist formed on a substrate to be processed is performed on the same chemically amplified resist by both light exposure using a photomask and charged beam exposure. A method has been proposed in which the resist is subjected to a heat treatment both after the exposure and after the charged beam exposure. FIG. 5 shows a flowchart of the pattern forming method. As shown in FIG. 5, the resist applied on the substrate to be processed is first exposed to light using an optical stepper (51), and then subjected to a heat treatment (5).
2). Then, the substrate to be processed is transferred to the charged beam exposure device by the wafer transfer mechanism, and charged beam exposure is performed (53). After this charged beam exposure, a heat treatment is performed again (54), and then development is performed (55) to form a desired pattern.

Thus, the diffusion and deactivation of the acid generated during the exposure can be prevented so that both the light and the electron beam exposure pattern have the same resolution and dimensional controllability, and exceed the light of the electron beam exposure. It is possible to form a pattern having both excellent resolution and throughput equivalent to that of a stepper. However, even with this method, it is hard to say that a sufficient throughput can be obtained because the amount of exposure required for electron beam exposure is large.

[0017]

As described above, according to the conventional pattern forming method, the following problems occur. In other words, a chemically amplified resist that is sensitive to both light and electron beams is used. Although this chemically amplified resist has high sensitivity and high resolution, the acid generated in the resist upon exposure serves as a catalyst. Heating promotes cross-linking or decomposition of the polymer material to promote photosensitivity. When the time from the exposure to the heat treatment is increased, the acid generated in the resist is diffused or deactivated, and the resolution and dimensional control of the pattern are deteriorated.

In particular, since the lithography system uses a stepper that exposes in the atmosphere and an electron beam apparatus that exposes in a vacuum, there is a time that cannot be eliminated, such as a vacuum evacuation time between the two exposures. Therefore, the diffusion or deactivation of the acid during the evacuation time or the like is an obstacle to simultaneously forming both the light and electron beam exposure patterns with good resolution and dimensional control.

Therefore, by performing a heat treatment both after light and electron beam exposure, the diffusion or deactivation of the acid generated between the exposures is prevented, and the resolution and dimensional controllability are good.
In addition, it is possible to form a pattern with high throughput, but since the amount of exposure required for electron beam exposure is large,
It is hard to say that sufficient throughput can be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent the diffusion or deactivation of an acid generated between light exposure and charged beam exposure to prevent light and charged beam exposure. It is an object of the present invention to provide a pattern forming method with high resolution and dimensional control at the same time and high throughput.

[0021]

According to a first aspect of the present invention, there is provided a pattern forming method, wherein a first step of forming a fine pattern on a resist by charged beam exposure is provided.
A second step of heating the resist after the step, a third step of forming a rough pattern on the resist by light exposure after the second step, and heating the resist after the third step. A fourth step of developing the resist on which the rough pattern and the fine pattern are formed after the fourth step.

Preferred embodiments of the present invention are as follows. (1) The resist is a chemically amplified resist having sensitivity to both the charged beam and the light. (2) In (1), the heating time in the fourth step is a time required for substantially completing a crosslinking reaction or a decomposition reaction of a polymer material, which is caused by using an acid generated in the resist by light exposure as a catalyst. Adjusted. (3) In (2), the heating time in the second step is a time required for the cross-linking reaction or the decomposition reaction of the polymer material to be substantially completed by using an acid generated in the resist by the charged beam exposure as a catalyst. It is adjusted to. (4) The heating time in the fourth step is adjusted to be substantially the same as the heating time in the second step. (5) The heating time combining the second and fourth steps is a heating time that satisfies the resolution required for the pattern to be formed and is adjusted to a heating time that maximizes the sensitivity of the resist.

(Function) In a pattern forming method in which pattern transfer to a resist formed on a substrate to be processed is performed on the same resist by both light exposure using a photomask and charged beam exposure, the pattern is formed after light exposure. The resist is heat-treated both after and after the charged beam exposure, and the charged beam exposure is performed before the light exposure.

As a result, the resist portion exposed by the charged beam is heated twice. Double heating increases the exposure sensitivity than single heating. That is, since the exposure sensitivity of the charged beam is increased, the irradiation amount of the charged beam can be reduced. For this reason, the throughput of the charged beam can be increased. Therefore, the waiting time between light exposure and charged beam exposure is reduced, and the system throughput is increased.

Further, by adjusting the heating time of the resist after exposure with light and a charged beam to a heating time that satisfies the resolution and maximizes the sensitivity of the resist, the required resolution can be satisfied. In addition, since it is possible to perform exposure while minimizing the irradiation amount of the charged beam, the throughput of the charged beam is further increased, and the system throughput is further improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an entire configuration of a lithography system for realizing a pattern forming method according to an embodiment of the present invention. FIG. 1A is a diagram showing a basic concept of the present lithography system. b) is a diagram showing a planar arrangement of the present lithography system.

In FIG. 1, reference numeral 1 denotes a stepper such as a Deep-UV stepper using an excimer laser beam, and 2 denotes an electron beam exposure apparatus of a cell projection system, and a plurality of these are arranged. Reference numeral 3 denotes a resist coating / developing apparatus for applying a resist and developing a resist having a pattern exposed, and reference numeral 4 denotes an atmosphere controlled atmosphere between various apparatuses 1, 2, and 3 for processing the resist by an in-line process. This is a transport mechanism for transporting by. Reference numeral 5 denotes a wafer as a substrate to be processed.

Next, a pattern forming method using the lithography system configured as described above will be described with reference to the flowchart of FIG. Resist coating and developing device 3
The wafer 5 coated with the resist is transferred to the electron beam exposure apparatus 2 by the transfer mechanism 4. In the electron beam exposure apparatus 2, a pattern to be subjected to electron beam exposure is aligned. After this alignment is completed, each chip on the entire surface of the wafer 5 is sequentially exposed by the electron beam (21). Here, in order to increase the throughput of electron beam exposure, the repetitive pattern is exposed by a cell projection method. By this electron beam exposure, a pattern having a relatively small size among the patterns formed on the wafer 5 is drawn.

When the light exposure is completed, the wafer 5 is transferred by the transfer mechanism 4 to the resist coating / developing device 3, where a heat treatment (Post Exposure Bake: PEB) is performed for a predetermined time (22).

After that, the wafer 5 is transferred to the optical stepper 1 by the transfer mechanism 4. In the optical stepper 1, the reticle pattern is reduced on the entire surface of the wafer 5 and is sequentially exposed (23). By this light exposure, a pattern having a relatively large size among the patterns formed on the wafer 5 is drawn.

After all the patterns have been drawn on all the chips on the entire surface of the wafer 5, the wafer 5 is returned to the resist coating / developing device 3 by the transport mechanism 4. Then, in the resist coating / developing device 3, a heat treatment (PEB) is performed again (24), followed by development (25) to complete the pattern formation.

Further, since the throughput of the electron beam exposure apparatus 2 is generally lower than the throughput of the optical stepper 1, a plurality of electron beam exposure apparatuses 2 are arranged. By configuring the system in this manner, the wafers 5 unloaded from the plurality of electron beam exposure apparatuses 2 can be processed in parallel by the optical stepper 1, and the processing capability of the optical stepper 1 is reduced by the processing of the electron beam exposure apparatus 2. You are not limited by your abilities. Therefore, both high resolution of electron beam exposure and high throughput of the stepper are compatible.

A resist that can be used in such a lithography system is a chemically amplified resist (UV2HS or UVN-HS: Shipley) with high resolution and high sensitivity. Since the performance of the chemically amplified resist deteriorates due to various chemical substances in the air, the transport mechanism 4 is installed and the environment is controlled in the various devices 1, 2, and 3 and between the various devices 1, 2, and 3. We handle it under the environment. In this environmental control, not only chemical pollution but also physical pollution, temperature, humidity and the like are naturally controlled. This suppresses a change in the pattern dimensions before and after the exposure.

As described above, in this embodiment, the electron beam exposure is performed before the light exposure. That is, it is performed before the exposure step with a relatively low throughput and the step with a relatively high throughput. Then, a step of heating the resist is performed immediately after each exposure step.

Therefore, the fine pattern portion of the resist exposed by the electron beam having a low throughput is 2.
It is heated twice in the heat treatment steps 2 and 24.
Further, the rough pattern portion of the resist exposed to light having a relatively high throughput is one of the 24 heat treatment steps.
Will be heated only once.

FIG. 3 is a diagram showing a resist sensitivity curve (PEB1) when the resist is heated only once and a resist sensitivity curve (PEB2) when the resist is heated twice, and the horizontal axis is the exposure amount. The vertical axis represents the resist remaining film ratio.
It can be seen that the resist sensitivity when heating twice is higher than the resist sensitivity when heating only once. this is,
This means that the exposure amount of the electron beam can be reduced. Therefore, the electron beam throughput increases,
As a result, the throughput of the entire system is also improved.

FIG. 4 is a diagram showing the dependence of the exposure sensitivity and resolution of the resist on the number of times of heating (heating time).
The horizontal axis represents the number of times of heating, and the vertical axis represents sensitivity or resolution for the sensitivity curve. In FIG. 3, the resist sensitivity is higher when heating is performed twice than once.
It can be seen that the sensitivity increases as the number of EBs increases. However, as can be seen from the relationship curve between the heating time (= unit heating time per one time × the number of heating times) and the resolution, the longer the heating time, the more the resolution is degraded contrary to the sensitivity. Therefore, it is desirable to adjust the heating time so as to satisfy the required resolution, for example, shorter than the heating time corresponding to the intersection of the sensitivity curve and the resolution curve. Therefore, by performing the heating process at the heating time at the point where the sensitivity curve and the resolution curve intersect, it becomes possible to perform exposure with the minimum required dose of electron beam while satisfying the required resolution, and improve the system throughput. .

The heating time after the light exposure and the heating time after the electron beam exposure are substantially equal to each other in order to sufficiently perform the crosslinking reaction or the decomposition reaction of the resist polymer material caused by the acid generated by the exposure as a catalyst. It is desirable to adjust the same.

As described in detail above, according to the present embodiment,
By performing the low-throughput electron beam exposure prior to the high-throughput light exposure, the portion exposed to the electron beam is heated twice, thereby increasing the sensitivity to the electron beam. The higher the sensitivity, the higher the electron beam throughput, and the higher the electron beam throughput, the higher the system throughput.

The light stepper 1 is a Deep-UV
Although the case where the stepper is used has been described, it is also possible to use another wavelength band. Also, the electron beam exposure apparatus 2
Although the case where the cell projection method is used has been described, a drawing method using ordinary electron beam exposure can also be used. Furthermore, although the case of performing exposure using an electron beam has been described, any charged beam such as an ion beam may be used.

[0041]

As described above in detail, according to the present invention, a desired pattern transfer to a photosensitive material formed on a substrate to be processed is performed by both light exposure using a reticle mask and charged beam exposure. By performing the charged beam exposure with low throughput first, the resist part exposed by the charged beam will be heated twice, increasing the sensitivity of the charged beam exposure and reducing the dose of the charged beam. Can be. Therefore, it is possible to form a pattern with good resolution and dimensional control and high throughput.

[Brief description of the drawings]

FIG. 1 is a view showing a basic concept and a planar arrangement of a lithography system according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a pattern forming method according to the embodiment.

FIG. 3 is a view showing the relationship between the amount of exposure of the resist and the rate of remaining resist in the same embodiment.

FIG. 4 is a diagram showing the dependence of exposure sensitivity and resolution on the number of times a resist is heated.

FIG. 5 is a flowchart of a conventional pattern forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical stepper 2 ... Electron beam exposure apparatus 3 ... Resist coating / developing apparatus 4 ... Transport mechanism 5 ... Wafer

Claims (5)

[Claims] A first step of forming a fine pattern on the resist by charged beam exposure; a second step of heating the resist after the first step; and forming a fine pattern on the resist after the second step. A third step of forming a rough pattern by light exposure, a fourth step of heating the resist after the third step, and forming the rough pattern and the fine pattern after the fourth step And a fifth step of developing the resist. 2. The pattern forming method according to claim 1, wherein the resist is a chemically amplified resist having sensitivity to both a charged beam and light. 3. A heating time in the fourth step is adjusted to a time required for substantially completing a crosslinking reaction or a decomposition reaction of a polymer material, which is caused by using an acid generated in the resist by the light exposure as a catalyst. 3. The pattern forming method according to claim 2, wherein the method is performed. 4. The heating time in the second step is a time required for substantially completing a crosslinking reaction or a decomposition reaction of a polymer material, which is caused by an acid generated in the resist by the charged beam exposure as a catalyst. The pattern forming method according to claim 2, wherein the pattern is adjusted to: 5. The heating time combining the second and fourth steps is a heating time that satisfies the resolution required for a pattern to be formed and is adjusted to a heating time that maximizes the sensitivity of the resist. The pattern forming method according to claim 1, wherein the pattern is formed.