JP2001237162A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device, by which photolithograpy antireflection SiON film can be kept stable in KrF laser beam absorption characteristics after it is formed. SOLUTION: A silane compound or the like is introduced into the reaction chamber 10 of a plasma CVD device to form an antireflection SiON film on a wafer 5, and the antireflection SiON film formed on the wafer 5 is thermally treated at a required temperature in an inert gas atmosphere of nitrogen gas or the like so as to be kept stable in KrF laser beam absorption characteristics after a film forming process is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique for forming an anti-reflection film used in a lithography step of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art With the increase in the degree of integration of semiconductor devices, in recent years, two-dimensional design rules for circuit patterns and the like have been miniaturized.
Miniaturization is further advancing. In particular, a circuit pattern width of 0.22
In a device of μm or smaller, an antireflection film is required for the purpose of suppressing halation and securing a focus margin in a photolithography process for a gate wiring or the like.
anti Reflected Layer) film (hereinafter, referred to as
ARL-SiON film) is frequently used.

For example, Japanese Patent Application Laid-Open No. 8-55992 discloses that an ARL-SiON film is used as an anti-reflection film in order to pattern a channel material layer made of polysilicon on a gate electrode covered with an insulating film of a thin film transistor. Techniques are disclosed. A photoresist is formed on the ARL-SiON film, is selectively exposed using KrF laser light (wavelength: 248 nm) as exposure light, and is developed to form a photoresist pattern on the ARL-SiON film. Using this photoresist pattern as a mask, CF
₄ / CHF ₃ mixed gas for reactive ion etching (RI
E) is performed to pattern the channel material layer. AR
The L-SiON film has a function of preventing the influence of light reflected from the channel material layer when exposing the photoresist.

The mechanism by which the ARL-SiON film absorbs KrF laser light is explained as follows. A
The RL-SiON film is basically a conductive film whose structure is formed of a cluster Si film. When the KrF laser beam is applied thereto, the cluster Si is polarized, an electric field having a phase opposite to that of the KrF beam is generated in the film, and the reflected light is reduced by canceling each other. Therefore,
The reason why the ARL-SiON film functions as an anti-reflection film is its conductivity. When the ARL-SiON film loses conductivity due to, for example, oxidation, the absorption coefficient of the KrF laser light also decreases accordingly. In order to stably form the gate wiring and the like, the K required in the lithography process is required.
A very important factor is how to stably provide the absorption coefficient of the rF laser light.

[0005]

In the ARL-SiON film, the absorption coefficient of light in the wavelength region of KrF laser light (around 248 nm) is an important parameter of the film characteristics. There has been a problem that the absorption coefficient abruptly attenuates due to long standing or the number of wet treatment steps.

FIG. 5 shows the change over time in the KrF laser light absorption coefficient of the conventional ARL-SiON film when left in a clean room. FIG. 5 also shows ARL-SiON
The time-dependent change in the absorption coefficient when a protective oxide film having a thickness of about 10 nm is continuously formed on the surface of the ARL-SiON film after the film is formed is also shown. When a protective oxide film is formed on the surface of the ARL-SiON film, the decrease in the absorption coefficient of the KrF laser beam is reduced, but is still insufficient.

It is considered that the attenuation of the absorption coefficient of the KrF laser beam occurs due to the following reason. Suppose A
If the RL-SiON film has a very rough film quality having a large number of dangling bonds (unbonded hands), the RL-SiON film absorbs moisture from the clean room or absorbs moisture in a wet process.
The cluster Si is oxidized by direct adsorption of a hydroxyl group (OH) or moisture to the dangling bond of the cluster Si film forming the ARL-SiON. The decrease in the conductivity of the ARL-SiON film due to oxidation causes a decrease in the absorption coefficient of the KrF laser beam. Among the wet processes, the attenuation of the absorption coefficient is particularly remarkable in the resist stripping process. It is considered that the acid component contained in the resist stripping solution accelerates the oxidation of the cluster Si.

FIG. 6 shows the transition of the attenuation of the absorption coefficient of the KrF laser beam with the number of passes through the resist stripping step of the ARL-SiON film. Although the amount of attenuation for each pass of the resist stripping process gradually decreases, the absorption coefficient of the film itself does not saturate downward but continues to decrease. The lithography margin (focus margin) in the process of forming the gate wiring and the like is very narrow, and it is not always possible to form a wiring of a desired size by only one exposure operation. Is to peel off the resist once, apply the resist again, and repeat the exposure and development work. In such a case, depending on the number of passes through the peeling process, the AR
If the L-SiON film fluctuates, not only the KrF laser light absorption coefficient required in the lithography process cannot be guaranteed, but also the function as an antireflection film may be lost.

As described above, in the prior art, the oxidation of the ARL-SiON film causes a problem that the effect as an antireflection film is reduced or the function as an antireflection film is lost. Such an attenuation of the KrF laser light absorption coefficient of the antireflection film significantly reduces the production yield due to a decrease in the lithography margin in the gate wiring forming step and the like.

[0010] An object of the present invention is to provide a process for recovering oxidized cluster Si in an ARL-SiON film in a process after forming the ARL-SiON film, thereby achieving Kr.
An object of the present invention is to provide a method for controlling the absorption coefficient of F laser light.

[0011]

According to the present invention, there is provided a semiconductor comprising a step of forming an ARL-SiON film on a wafer having a wiring material formed on a surface thereof and patterning the wiring material by photolithography using laser light. In the method for manufacturing an apparatus, the SiON film is formed on the wafer by a plasma CVD apparatus, and then the SiON film is heat-treated.

[0012] The heat treatment can be continuously performed in the reaction chamber of the plasma CVD apparatus immediately after the completion of the SiON film forming step.

When forming the SiON film, the lower electrode of the plasma CVD apparatus is heated, and the preferable temperature is 300 to 500 ° C.

A preferable temperature of the heat treatment after the formation of the SiON film is 650 ° C. or more, and a non-oxidizing atmosphere such as a nitrogen gas or an argon (Ar) gas is used as the heat treatment atmosphere.

According to the present invention, in a series of steps for forming an ARL-SiON film, a heat treatment is carried out,
By recovering the oxidized cluster Si in the iON film, it is possible to recover the film quality deterioration such as the attenuation of the absorption coefficient of the KrF laser light, and the necessary KrF laser light required in the subsequent photolithography process is recovered. The absorption coefficient can be supplied stably.

[0016]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an ARL for explaining an embodiment of a method of manufacturing a semiconductor device according to the present invention.
FIG. 1 is a schematic configuration diagram of a CVD apparatus for forming a SiON film.
The CVD apparatus shown in FIG. 1 is a parallel plate type plasma CVD apparatus, and an upper electrode 1 serving also as a gas dispersion plate is provided in a reaction chamber 10.
And a lower electrode 2 also serving as a wafer mounting table.
The lower electrode 2 has a heater mechanism (not shown) for heating the placed wafer 5.

For forming the ARL-SiON film, silane-based compound gas is mainly used, and N ₂ O gas or the like is used for controlling film characteristics such as absorption coefficient. An inert gas such as N ₂ is introduced as a diluent gas for stabilizing the reaction system. These gases are introduced into the reaction chamber 10 via the upper electrode 1. Further, the reaction chamber 10 is connected to an exhaust means through an exhaust port 20 so that the inside thereof can be evacuated, and the reaction gas introduced into the reaction chamber 10 from the upper electrode 1 flows through the exhaust port 20 into the reaction chamber. It is discharged out of 10.

Examples of the silane compound used in the method of the present invention include silicon hydride represented by Si _n H _{2n + 2} such as silane and disilane, and halogen silane such as chlorosilane. Is also good. Among them, silane,
Disilane, chlorosilane or a mixture thereof is desirable, and silane, disilane or a mixture thereof is particularly desirable.

Next, an embodiment of a method of manufacturing a semiconductor device using the above-described CVD apparatus will be described. First, 300 ~
After the wafer 5 on which the wiring material (not shown) is formed is placed on the lower electrode 2 maintained at 500 ° C., preferably 350 to 450 ° C., an inert gas such as N ₂ is placed in the reaction chamber 10. The gas is introduced, the degree of vacuum in the reaction chamber 10 is maintained at 200 to 400 Pa, preferably 350 to 450 Pa by a vacuum degree adjusting mechanism (not shown), and the wafer 5 inserted into the apparatus is heated.

Next, 5 g of SiH ₄ gas is supplied from the upper electrode 1.
0-300 sccm, desirably 100-200 sccc
m, N ₂ O gas is introduced at 100 to 1000 sccm, preferably 500 to 750 sccm. The flow rates of these film forming gases are controlled by a mass flow controller (not shown) installed outside the apparatus.

Under these conditions, the high-frequency power source 3 supplies 50 to 150 W between the upper electrode 1 and the lower electrode 2.
A high frequency power of 60 to 90 W is applied. As the frequency, an industrial frequency band such as 13.56 MHz can be used. The applied high-frequency power generates a plasma 4 in the reaction chamber 10, and ARL-SiO 2 is formed on the wafer 5.
An N film grows.

Thereafter, the wafer 5 is discharged out of the reaction chamber 10. When the wafer 5 is exposed to the atmosphere as described above,
Since the ARL-SiON film absorbs moisture in the clean room, the absorption coefficient of the KrF laser beam starts to decrease. This absorption coefficient attenuation is recovered by the following processing.

First, since it is necessary to restore the oxidized state of the ARL-SiON film, the processing must be performed in an atmosphere of an inert gas such as N ₂ or Ar. This is because in an atmosphere containing O ₂ , oxidation proceeds further, which is contrary to the purpose of recovery of attenuation of absorption coefficient.

Next, it is necessary to heat-treat the ARL-SiON film at a temperature of 650 ° C. or higher in order to desorb OH groups taken into the film. In the present embodiment, a vertical diffusion furnace capable of performing a process at a high temperature by introducing N ₂ is used as the heat treatment apparatus. The heat treatment conditions include N
Heat treatment at 850 ° C. was performed in _two atmospheres for 5 minutes.

FIG. 3 shows that KrF
8 for ARL-SiON film with attenuated laser light absorption coefficient
Kr after heat treatment for 5 minutes in a nitrogen atmosphere at 50 ° C
6 shows the transition of the absorption coefficient of F laser light. KrF due to moisture absorption
It can be seen that the attenuation of the laser light absorption coefficient has significantly recovered after the heat treatment. This means that the moisture in the film is desorbed by the heat treatment, and the electrical conductivity of the cluster Si constituting the ARL-SiON film is restored.

In this embodiment, the heat treatment condition of 850 ° C. for 5 minutes is selected, but by appropriately selecting the heat treatment condition, the KrF laser light absorption coefficient of the ARL-SiON film after the heat treatment is appropriately controlled. be able to.

On the other hand, it can be seen that the variation of the KrF laser light absorption coefficient of the ARL-SiON film due to moisture absorption does not occur after the recovery heat treatment as shown in FIG. This is because the dangling bond in the ARL-SiON film, which was a cause of the attenuation of the KrF laser light absorption coefficient due to the heat treatment, is recovered by the heat treatment, and no new moisture absorption or penetration of OH groups occurs. It is thought to be.

In this embodiment, ARL-SiO
The N film formation and the heat treatment under an inert gas atmosphere as the absorption coefficient recovery processing were performed in a completely different apparatus and in a separate process. However, as a second embodiment, the N 2 gas or the like was not contained in the reaction chamber 10. An annealing process at a desired temperature and time may be performed immediately after film formation by introducing an active gas. Also, as shown in FIG. 2, an annealing chamber 6 is added to the reaction chamber 10, and after the ARL-SiON film is formed, the wafer is transferred from the reaction chamber 10 to the annealing chamber 6, and the film is formed and annealed in In-Situ. Is also good. In FIG. 2, reference numeral 7 denotes a transport mechanism, and reference numeral 8 denotes a load lock.

By using the second embodiment, since the wafer 5 is not exposed to the atmosphere, not only the KrF laser light absorption coefficient can be suppressed from attenuating in the subsequent process, but also the KrF laser The control of the light absorption coefficient can be performed more reliably.

In the above embodiment of the present invention, ARL-
Although the heat treatment step after the formation of the SiON film has been described, a photolithography technique using ordinary KrF laser light can be used for the patterning method of the wiring material thereafter.

[0031]

As is clear from the above description, according to the present invention, by performing a heat treatment after the formation of the ARL-SiON film, it is possible to recover the film quality deterioration such as the attenuation of the KrF laser light absorption coefficient of the film. It is possible to stably supply a necessary absorption coefficient required in a subsequent photolithography process, and to produce a high-quality and high-reliability semiconductor device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a CVD apparatus for forming an ARL-SiON film for describing an embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a schematic configuration diagram of another CVD apparatus used in the method of manufacturing a semiconductor device according to the present invention.

FIG. 3 shows ARL-S showing the effect of heat treatment of the method of the present invention.
FIG. 4 is a diagram showing a transition of a KrF laser light absorption coefficient of an iON film.

FIG. 4 shows an ARL-SiON film formed by the method of the present invention.
FIG. 4 is a diagram showing the decay of the KrF laser light absorption coefficient of a film over time.

FIG. 5 is a diagram showing the decay of the KrF laser light absorption coefficient with time of leaving the ARL-SiON film formed by the conventional method in the air over time.

FIG. 6 is a diagram showing attenuation of a KrF laser light absorption coefficient of an ARL-SiON film with the number of times of passing through a resist stripping step in a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper electrode 2 Lower electrode 3 High frequency power supply 4 Plasma 5 Wafer 6 Annealing chamber 7 Transport mechanism 8 Load lock 10 Reaction chamber 20 Exhaust port

Claims (7)

[Claims] 1. A method of manufacturing a semiconductor device, comprising: forming a laser light antireflection film made of a SiON film on a wafer having a wiring material formed on a surface thereof; and patterning the wiring material by photolithography using laser light. In the method, after the SiON film is formed on the wafer by a plasma CVD apparatus, the SiON film is heat-treated. 2. The method according to claim 1, wherein the heat treatment is performed continuously in the reaction chamber of the plasma CVD apparatus immediately after the step of forming the SiON film. 3. The method according to claim 1, wherein the formation of the SiON film is performed using the plasma C
2. The method according to claim 1, wherein the lower electrode of the VD device is heated to a temperature of 300 to 500 [deg.] C. 4. The method for manufacturing a semiconductor device according to claim 1, wherein a mixed gas of silane gas and N ₂ O gas is used as a film forming gas for said SiON film. 5. The method according to claim 1, wherein the temperature of the heat treatment is 650 ° C. or higher. 6. The method for manufacturing a semiconductor device according to claim 1, wherein the atmosphere of the heat treatment is an atmosphere of a nitrogen gas or an argon (Ar) gas. 7. The semiconductor device according to claim 1, wherein the plasma CVD apparatus has an annealing chamber connected to the reaction chamber, and the heat treatment of the SiON film is performed in the annealing chamber. Method.