JP3154730B2 - Thin film processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method and an apparatus for processing a thin film.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, processes such as thin film formation and etching, and heat treatment have conventionally been performed in separate process chambers. Taking thin film formation as an example, various chemical vapor deposition methods (CVD methods) such as reduced pressure, normal pressure, or plasma, and physical vapor deposition methods (PVD methods) such as vapor deposition and sputtering, depending on the type of film to be formed. ) Is used. However, no matter which method is used to form the thin film, the properties finally required cannot be satisfied,
In most cases, heat treatment is required to improve the shape and film quality. This heat treatment step has been performed in a process chamber different from the thin film forming step. Therefore, once a thin film is formed on a semiconductor substrate in a vacuum furnace, the semiconductor substrate is carried out of the furnace and inserted into a diffusion furnace to perform heat treatment.

However, conventionally, processes such as thin film formation and heat treatment were performed in separate process chambers.
The following problems occurred.

FIG. 6 shows an interlayer insulating film formed by a conventional thin film processing method. First, as shown in FIG.
1, a polycrystalline silicon film 22 is formed as a wiring layer,
On the surface thereof, a boron phosphosilicate glass (hereinafter referred to as BPSG) film 23 is formed as an interlayer insulating film. Here, a step 22 a exists between the polycrystalline silicon film 22 and the semiconductor substrate 21. Therefore, this step portion 2
To fill in 2a and improve step coverage,
A BPSG film is used.

Here, the BPSG film 23 is formed by O2,
PH3 (phosphine), SiH4 (monosilane), B2
Atmospheric pressure CVD, TEOS using H6 (diborane), etc.
Decompression CV using an organic agent such as (tetraethoxysilane)
The D method or the plasma CVD method is used. FIG. 6A shows a case where the BSPG film 23 is formed by using the normal pressure CVD method.

In the formed BPSG film 23, a void 27 is generated at the step 22a. As shown in FIG. 6A, when the step portion 22a of the polycrystalline silicon film 23 as the base film is tapered in the forward direction, the size of the void 27 is relatively small. However, it is not easy to taper in the forward direction during patterning, and FIG.
As in the case of the polycrystalline silicon film 51, the taper tends to be formed in the opposite direction. When the taper is formed in the opposite direction, a large void 28 is generated in the BPSG film 52.

FIGS. 6C and 6D show the case where BPSG films 54 and 56 are formed by a low pressure CVD method. By using the low pressure CVD method, the step coverage is improved as compared with the normal pressure CVD method. As a result, FIG.
As shown in (c), the step portion 53a of the polycrystalline silicon film 53 is formed.
When a taper in the forward direction is provided, the generation of voids is small, and when the stepped portion 56a of the polycrystalline silicon film 56 is tapered in the reverse direction as shown in FIG. Cheap.

[0008] When a BPSG film is formed on a polycrystalline silicon film processed into a fine pattern, it is difficult to prevent the generation of voids due to the shape of the steps, and a low-pressure CVD method excellent in step coverage is used. It cannot be completely prevented.

Therefore, a heat treatment is performed on the formed BPSG film, and the BPSG film is melted, flown, and planarized. However, as shown in FIG. 7A, the generated void often remains after the heat treatment. In some cases, as shown in FIG.
It may float on the surface of the PSG film 35 and cause a defect. The existence of such voids and the deficiency of the BPSG film cause a reduction in manufacturing yield and a decrease in reliability. The problem caused by the generation of voids has become more pronounced as the miniaturization of semiconductor devices progresses.

Conventionally, there have been several methods for preventing the generation of voids as follows. A BPSG film is once formed to a thickness small enough to prevent voids from occurring, heat-treated and allowed to flow, so that the step from the base is reduced to some extent. Next, a second film formation is performed, and flow is similarly performed by heat treatment to further reduce the step. In this way,
The formation of the BPSG film and the heat treatment are performed a plurality of times in different process chambers (refer to Japanese Patent Application No. 2-9163). However, such a thin film processing method has a problem that the number of steps increases, the throughput of the manufacturing line decreases, and the manufacturing cost increases.

As another means, a BPSG film is 850 degrees Celsius.
There is a method in which the film is formed at a melting temperature on the order of degrees and is made to flow at the same time as the film formation to perform flattening. However, in this manufacturing method, the BPSG film forming reaction itself is rate-limiting. That is,
Since the temperature is high, the reaction speed is higher than the supply speed of the reaction gas, and the film is formed from the location where the reaction gas is supplied. Therefore, when performing batch processing on a large number of semiconductor wafers, it is difficult to form a BPSG film having a uniform thickness and film quality. To realize such a film, the configuration of the manufacturing apparatus becomes complicated, and the manufacturing cost increases due to an increase in the price of the apparatus. Another problem related to the formation of the BPSG film according to the prior art is the problem of moisture absorption of the BPSG film. This problem has become remarkable when the melting temperature is lowered with miniaturization of devices.

When flowing the BPSG film, it is necessary to increase the dopant concentration of the BPSG so that the BPSG film can be melted even at a low temperature. However, BPS with a high dopant concentration
The G film has high hygroscopicity. As shown in FIG. 8A, a BPSG film 43 is formed in a vacuum furnace so as to cover the polycrystalline silicon film 42 on the surface of the semiconductor substrate 41. Then, when the semiconductor substrate 41 is taken out of the furnace and left in the air to perform the heat treatment, the BPSG film 43 is formed as shown in FIG.
Absorbs moisture at the surface portion 44 of the substrate, and is deteriorated. When a heat treatment is performed in this state to cause a flow, the BP shown in FIG.
It has a shape like the SG films 43a and 44a and cannot be planarized. Even after performing the flow, if the semiconductor substrate 41 is left in the air, moisture absorption occurs at the surface portion 44a of the BPSG film 43a. As a result, when a resist is applied for patterning thereafter, the adhesion between the resist film and the surface portion 44a of the BPSG film 43a is reduced, and there has been a problem that the resist film is peeled off.

[0013] The conventional thin film method also has a problem that the formed thin film is contaminated. For example, when forming a MOS transistor, a capacitor, or the like having a gate electrode formed of polycrystalline silicon, a surface of a semiconductor substrate is oxidized to form a gate insulating film, and a polycrystalline silicon film is formed by a low-pressure CVD method. After doping with impurities such as phosphorus, the gate electrode is obtained by patterning. In this case, the semiconductor wafer is left in the air from the formation of the gate insulating film to the formation of the polycrystalline silicon film. At this time,
Impurities such as heavy metals may adhere to the gate insulating film and reduce the gate breakdown voltage. The phenomenon that the quality is deteriorated due to such contamination is caused by oxidizing a polycrystalline silicon film to obtain a gate insulating film, or by silicon nitride (Si3N4).
This also occurred when the film was used as a gate insulating film.

Further, the present invention is not limited to the formation and oxidation of a thin film.
There is also the following problem when heat treatment is performed after etching. After the etching, the semiconductor substrate is taken out and left in the air in order to move it from the etching process chamber to the heat treatment process chamber.
At this time, impurities such as moisture and heavy metals contained in the air adhere to and contaminate the surface of the substrate, resulting in a decrease in reliability.

These problems are basically caused by exposing the semiconductor substrate to the atmosphere. To solve these problems, a batch type multi-chamber apparatus having a load lock chamber has been considered. For example, it is a device in which a low-pressure CVD device, a diffusion furnace, and an etching chamber are connected by a load lock chamber.

However, when this apparatus is used, it is unavoidable to enlarge the apparatus, and since the load lock chamber is shared, while the transfer of the substrate to one chamber is performed, the other chamber operates simultaneously. Cannot be performed, and the operation rate of the apparatus is low.
This leads to an increase in equipment costs and running costs.

[0017]

As described above, conventionally, processes such as thin film formation, oxidation, etching, and the like, and heat treatment are performed in separate process chambers, so that throughput is reduced, manufacturing costs are increased, and contamination is caused. This has led to problems such as reduced reliability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and an apparatus capable of manufacturing a semiconductor device having high reliability and uniform quality at low cost.

According to the thin film processing method of the present invention, a plurality of substrates to be processed are loaded into a process chamber, and at least one substrate is transported from the process chamber to the outside inside the process chamber. And a step of performing a plurality of processes including a thin film formation process by chemical vapor deposition and at least one heat treatment at different temperatures using the same heating source.

Here, the change of the temperature in each process is as follows.
It is preferable that the temperature is raised and lowered at a rate of 50 degrees Celsius or more per minute in the process chamber to reach a predetermined temperature.

[0021]

The thin film processing apparatus according to the present invention comprises: means for placing a plurality of substrates in a process chamber in parallel; heating means for raising and lowering the temperature in the process chamber at a rate of 50 ° C. or more per minute; Means for supplying a gas necessary for performing the process into the process chamber, and vacuum evacuation means for exhausting air in the process chamber, and inside the process chamber, the substrate to be processed from the process chamber to the outside. A plurality of processes including at least one thin film formation process by a chemical vapor deposition method and at least one heat treatment are carried out at different temperatures by using the same heating means without carrying out.

[0023]

A plurality of processes including at least one thin film formation process by a chemical vapor deposition method and a heat treatment are performed using the same heating source without unloading the substrate to be processed in the same process chamber. By performing at temperature,
Throughput is improved, manufacturing costs are reduced, and since the semiconductor substrate is not taken out of the process chamber and exposed to the atmosphere, there is no risk of deterioration or contamination of the substrate due to moisture absorption, and reliability is improved. I do.

Here, it is important from the viewpoint of securing the throughput that each process is performed after the temperature is raised and lowered at a rate of 50 ° C. or more per minute in the process chamber to reach a predetermined temperature.

Further, the process includes a thin film formation process by a chemical vapor deposition method, and a thin film obtained by performing the thin film formation process is subjected to a heat treatment in the same process chamber, thereby making it possible to form an atmosphere. It is possible to effectively prevent deterioration of the film quality due to being left inside and contamination by impurities such as heavy metals.

Such a thin film processing can be performed by using the thin film processing apparatus of the present invention. The temperature in the process chamber where a plurality of substrates are placed in parallel is raised or lowered at the rate of 50 degrees Celsius or more per minute by the same heating source, and gas required for the process is supplied and evacuated. Accordingly, a plurality of processes including a thin film formation process by a chemical vapor deposition method and a heat treatment can be performed at different temperatures without unloading the substrate from the process chamber.

[0027]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a method of forming a thin film according to the present embodiment step by step. As shown in FIG. 1A, a polycrystalline silicon film 2 is formed on a semiconductor substrate 1, and a step portion 2a having a height of about 0.8 μm and a horizontal interval of about 0.5 μm exists. I do. The step portion 2a is flattened by forming a BSPG film as follows. As the film forming apparatus, for example, a Hot Wall type vertical reduced pressure CVD apparatus for heating the entire inside of a furnace can be used. As conditions for forming the film, for example, TEOS (tetraethoxysilane), PH3 (phosphine), TMB (trimethylborate) or the like is used as a reaction gas, the temperature is set to about 600 degrees Celsius, and the pressure is set to about 1 Torr. First, as a first film formation, a BPSG film 3 is formed on the polycrystalline silicon film 2 with a film thickness that does not cause voids in the step portion 2a.

Here, by setting the thickness of the BPSG film 3 as follows, the generation of voids can be prevented. FIG. 2 shows that when a BSPG film is formed on the surface of a polycrystalline silicon film having a height of 0.8 μm at the step portion, the horizontal interval (0.3 μm to 1.0 μm) of the step portion and the film thickness (2
(2000 to 6000 Å) is shown as a result of examining how it relates to the generation of voids. From this result, it can be seen that when the interval between the step portions is 0.5 μm, the generation of voids can be prevented if the film thickness is about 3000 Å or less.

Next, heat treatment is performed in the same furnace without taking out the semiconductor substrate 1 from the film forming apparatus. After the atmosphere inside the furnace was replaced with, for example, nitrogen gas (N2) and returned to atmospheric pressure, the temperature of the furnace was raised to, for example, 850 degrees Celsius at a rate of 50 degrees Celsius per minute. Leave for about 20 minutes. As a result, the BPSG film flows, and FIG.
The BPSG film 3a is smoothed as shown in FIG.

The temperature of the atmosphere inside the furnace was returned to 600 degrees Celsius at a temperature reduction rate of 50 degrees Celsius per minute, and the furnace was evacuated to 2 degrees.
The first film formation is performed, and a BPSG film 4 is formed as shown in FIG. The thickness of the BPSG film 4 is, for example, 5000 angstroms so that a film thickness finally required for the apparatus is obtained.

The furnace temperature is increased to 850 degrees Celsius at a rate of 50 degrees Celsius per minute. The furnace atmosphere was nitrogen (N2
) And steam and heat treating for about 15 minutes. Thereby, the flattened BPSG film 5 as shown in FIG. 1D can be formed without generating a void in the step portion 2a. Further, since the film formation and the heat treatment are performed without taking the semiconductor substrate 1 out of the furnace, the semiconductor substrate 1 is not left in the air. Therefore, the BPSG film 5 is prevented from being deteriorated due to moisture absorption.

Here, TEOS or the like is used as a reaction gas for film formation, but SiH4 (monosilane), Si2H6 (disilane), or other organic sources can also be used.
In the second heat treatment, the inside of the furnace is set to an atmosphere of nitrogen and water vapor. However, as in the first heat treatment, an atmosphere of only nitrogen may be used, or both the first and second heat treatments may be made of a water vapor atmosphere. Further, another gas such as O2 (oxygen) or Ar (argon) can be used.

In the embodiment, the temperature at which the BPSG film is flowed is set to 850 degrees Celsius. However, in consideration of the flowability of the BPSG film, the tolerance of the apparatus for the heat treatment, and the required flatness, etc. 800 degrees or 90 degrees Celsius
Other temperatures, such as 0 degrees, can also be set. In the embodiment, the BPSG film formation and the flow process are performed twice each, but the number is not limited to this number. In the embodiment, BPSG is used as a material for the insulating film for flattening the step portion of the base film, but PSG (phosphosilicate glass) or BSG
(Boron silicate glass) may be used.

Next, as a modification of the above embodiment, the BPS
A method for forming a silicon oxide film on the G film will be described. After flowing through the BPSG film, the temperature is set to 700 degrees Celsius, and a silicon oxide film into which impurities are not implanted is deposited to a thickness of 1000 angstroms by, for example, low pressure CVD using TEOS as a reaction gas. After that, the temperature inside the furnace was rapidly raised to 900 degrees Celsius,
Heat treatment is performed in a nitrogen atmosphere for 20 minutes. This heat treatment increases the density of the silicon oxide film, stabilizes the film quality without absorbing moisture even if the silicon oxide film is left in the air, and eliminates the possibility of peeling off even when a resist is applied. Although the process of forming a silicon oxide film and performing heat treatment using TEOS as a reaction gas has been described above, the process may be set by changing film formation conditions, film thickness, heat treatment temperature, and the like. The material to be deposited is not limited to undoped silicon oxide, but may be PSG or B doped with impurities at a low concentration.
PSG or silicon nitride may be used.

The manufacturing method of the present invention can be similarly applied to the case where the surface of a semiconductor substrate is oxidized to form an insulating film. As another embodiment of the present invention, a process for forming a MOS capacitor on a semiconductor substrate will be described with reference to FIG.

As shown in FIG. 3A, a field oxide film 12 is formed in a device isolation region on the surface of a semiconductor substrate 11 by a normal selective oxidation method. The semiconductor substrate is placed in an apparatus according to the present invention set at a temperature of 600 degrees Celsius, for example, at a temperature increase rate of 50 degrees Celsius per minute and 80 degrees Celsius.
The temperature is raised to 0 degrees, and a silicon oxide film 13 of about 100 angstroms is formed in the element formation region.

Then, the internal temperature of the furnace is lowered to, for example, 600 degrees Celsius at a temperature decreasing rate of 50 degrees Celsius per minute, and the pressure is reduced to about 0.5 Torr by vacuum evacuation. A SiH4 gas is introduced into the furnace, and a polycrystalline silicon film 14 is formed to a thickness of about 4000 angstroms as shown in FIG. afterwards,
The polycrystalline silicon film 14 is doped with phosphorus and patterned to form a polycrystalline silicon film 15 as shown in FIG. 3C, thereby obtaining a capacitor.

Here, the heat treatment step is not limited to the oxidation step, but an annealing treatment or the like can be performed in the same furnace.
Further, the present invention is applied by performing, in the same furnace, a process of depositing polycrystalline silicon while doping phosphorus during film formation and a process of performing heat treatment to activate phosphorus in the polycrystalline silicon film. You can also. Alternatively, cleaning treatment of the semiconductor substrate surface by gas etching and heat treatment may be combined. In FIG. 3, the underlying film on which the oxide film 13 is formed is the semiconductor substrate 11, but it is also possible to form a polycrystalline silicon film as the underlying film. When the gate insulating film is formed, not only the silicon oxide film but also a silicon nitride film or a combination of the silicon nitride film and the silicon oxide film can be used.

In each of the embodiments described above, it is assumed that a MOS type semiconductor device is manufactured. However, the present invention can be applied to a technical field to which thin film technology is applied, such as processing of a liquid crystal display device.

An apparatus for performing the thin film processing method of the present invention must satisfy the following conditions. 1. It can raise and lower the temperature at a rate of 50 degrees Celsius or more per minute,
The temperature difference within the wafer surface during temperature rise and fall should be 20 degrees Celsius or less. 2. High temperature heat treatment of 850 degrees Celsius or more is possible. 3. Evacuation must be possible. 4. Having a gas supply function so that a CVD process, a heat treatment process, and an etching process can be performed. Hereinafter, a configuration of a thin film processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows a longitudinal section of a hot wall furnace type LP-CVD apparatus. The whole is covered with a quartz outer tube 61, and a quartz inner tube 62 is provided therein. Quartz inner tube 6
The substrate holder 64 is installed inside the second holder 2. The detailed structure of the substrate holder 64 is as shown in FIG. A number of ring-shaped trays 69 are provided in parallel on the inner periphery of the quartz board 68 in the vertical direction.
A semiconductor wafer 70 is mounted thereon. The ring-shaped tray 69 has an effect of suppressing an in-plane temperature difference of the semiconductor wafer 70 at the time of raising and lowering the temperature, and at the same time, making a film thickness on the surface of the wafer 70 uniform when forming a thin film by the CVD method.

The features of the device according to the present embodiment are as follows: TEOS,
PH3, TMB, CVD material gas such as O ₂ etching gas, oxidizing gas, and that can be introduced inert gas or the like, in order to uniform the film thickness between the semiconductor wafer 70 mutually, distribution nozzle injector 65 is provided, and further has an exhaust system piping 66 for making a vacuum,
It has a flange that can withstand high temperatures and has sufficient airtightness. Here, a rubber O-ring cannot be used as a sealing material for the flange, and a hollow metal O-ring seal or the like must be used.

The apparatus according to this embodiment has a vertical furnace structure. However, if it has a furnace body that can raise and lower the temperature at a rate of 50 degrees Celsius or more per minute, can perform high-temperature heat treatment at 850 degrees Celsius or more, and has the necessary process gas introduction and evacuation functions. Alternatively, an apparatus having a horizontal furnace structure may be used.

[0043]

As described above, according to the thin film processing method of the present invention, at least one chemical vapor deposition method is carried out without loading a semiconductor substrate into a process chamber and unloading the semiconductor substrate from the process chamber to the outside. By performing a plurality of processes including a thin film forming process and a heat treatment at different temperatures using the same heating source, the manufacturing time can be shortened and the cost can be reduced. There is no risk of deterioration or contamination, and improvement in reliability and yield can be achieved.

Such processing can be performed by using the thin film processing apparatus of the present invention.

[Brief description of the drawings]

FIG. 1 is a sectional view of an element in each step showing a thin film processing method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing conditions under which voids do not occur in a BPSG film.

FIG. 3 is a sectional view of an element according to a step showing a thin film processing method according to another embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a configuration of a thin film processing apparatus according to one embodiment of the present invention.

5 is an enlarged view showing the substrate holder of the apparatus shown in FIG. 4 in detail.

FIG. 6 shows a BPSG formed using a conventional thin film processing method.
FIG. 4 is a longitudinal sectional view showing a sectional shape of a film.

FIG. 7 shows a BPSG formed by using a conventional thin film processing method.
FIG. 4 is a longitudinal sectional view showing a sectional shape of a film.

FIG. 8 is a vertical cross-sectional view showing a cross-sectional shape when a BPSG film is formed by using a conventional thin film processing method and is caused to flow by hot melting.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 polycrystalline silicon film 3 BPSG film 4 BPSG film 5 BPSG film 11 semiconductor substrate 12 field oxide film 13 gate oxide film 14 polycrystalline silicon film 15 polycrystalline silicon film 61 quartz outer tube 62 quartz inner tube 63 heater 64 substrate Holder 65 Dispersion nozzle injector 66 Exhaust system piping 67 Metal hollow O-ring 68 Quartz board 69 Ring tray 70 Substrate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 H01L 21/31 H01L 21/22 C23C 16/00

Claims (3)

(57) [Claims] A step of loading a plurality of substrates into a process chamber; and performing at least one chemical vapor deposition inside the process chamber without unloading the substrates from the process chamber to the outside. Performing a plurality of processes including a thin film formation process using a heating method and at least one heat treatment at different temperatures using the same heating source. 2. The thin film processing method according to claim 1, wherein the heat treatment is performed after the temperature is raised at a rate of 50 degrees Celsius per minute or more and reaches a predetermined temperature in the process chamber. 3. A means for placing a plurality of substrates in parallel in a process chamber; a heating means for raising and lowering the temperature in the process chamber at a rate of 50 degrees Celsius per minute or more; Means for supplying a gas into the process chamber; and evacuation means for exhausting air in the process chamber, wherein the substrate to be processed is not carried out from the process chamber to the outside inside the process chamber. A thin film processing apparatus, wherein a plurality of processes including at least one thin film formation process by a chemical vapor deposition method and at least one heat treatment are performed at different temperatures by using the same heating means.