JPH11150111A - Method of film formation and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor device, whose element characteristics are stabilized by ensuring the controllability of the preprocessing of film formation, in the manufacturing process of a semiconductor device. SOLUTION: A preprocessing S6 is made by having the surface of a wafer arranged in prescribed atmosphere irradiated, and a film forming processing S7 is made to the surface following this preprocessing, without exposing the wafer to atmosphere. The preprocessing includes an oxidizing processing in oxidizing gaseous atmosphere, a reducing processing in a gaseous hydrogen atmosphere, and an organic combined group decomposing processing in the oxidizing gaseous atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film forming apparatus and a film forming method, and more particularly to a film forming apparatus and a film forming method suitable for forming a silicon film in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become more highly integrated and higher in performance, the state of a functional region interface within an element has had a great effect on element characteristics. FIG.
(1) is a diagram showing the relationship between the oxide film thickness between the emitter electrode and the emitter diffusion layer and the current gain factor (hfe) in the bipolar device, and FIG. 7 (2) is a diagram showing the relationship between the emitter electrode and the emitter diffusion in the bipolar device. FIG. 4 is a diagram showing a relationship between an oxide film thickness between layers and an electrode contact resistance (VBE). FIG. 8A shows the difference between the oxide film thickness between the emitter electrode and the emitter diffusion layer and the current gain rate difference (Δ) of a pair transistor in which two bipolar elements are connected.
FIG. 8 (2) is a diagram showing the relationship between the oxide film thickness between the emitter electrode and the emitter diffusion layer and the electrode contact resistance difference (ΔVBE) of the paired transistor. It is. As is apparent from these figures, it is understood that the above-described device characteristics vary depending on the thickness of the oxide film at the interface of the functional region.

[0003] Therefore, in order to obtain a semiconductor device having stable element characteristics, it is important to control the state of the film-forming base surface, that is, the interface, with good reproducibility when performing the film-forming process in the manufacturing process. It has become to.

FIG. 9 shows a process of patterning an insulating film during a manufacturing process of a semiconductor device from a CVD (Chemica) process.
FIG. 2 is a process flow chart showing a typical example up to the formation of a silicon film by a 1 Vapor Deposition method. Hereinafter, a part of the manufacturing process of the semiconductor device will be described with reference to FIG. First, in a first step S11, an insulating film on a semiconductor substrate is patterned by dry etching using a resist pattern as a mask. At this time, in order to secure the processing shape and etching selectivity,
Etching is performed while forming a sidewall protective film made of an organic compound. Next, in a second step S12, post-processing for removing damage to the surface of the semiconductor substrate due to the dry etching and removing the sidewall protective film is performed. This post-processing is performed by dry etching and in situ. In the next third step S13, after removing the resist pattern using a gas or a chemical, in the fourth step S14, the resist residue is removed by chemical cleaning.

After the openings are formed in the insulating film as described above, in the next fifth step S15, an oxide film is formed on the surface layer of the semiconductor substrate by an oxidation treatment using a chemical. The thickness of this oxide film depends on the purpose of the device characteristics.
The optimum value is set in a range of about 0.6 to 2.0 nm. Thereafter, in a sixth step S16, the semiconductor substrate is subjected to CVD.
Then, in a seventh step S17, a silicon film is formed in the CVD apparatus. The above process is performed, for example, in the case of manufacturing a bipolar element having a double polysilicon structure, forming an emitter opening in an insulating film on a base diffusion layer in a surface layer of a semiconductor substrate, and forming a silicon film connected to a bottom surface of the emitter opening. Applied to

[0006]

However, in the above-described film forming method in the process of manufacturing a semiconductor device, an oxide film is formed on a film-forming base surface by an oxidizing process using a chemical as a pretreatment. The controllability of the thickness of the oxide film cannot be obtained due to the variation in the composition due to the mixing and the aging change after the mixing, the variation in the temperature of the chemicals during the treatment, the variation in the number of times the chemicals are used, and the like. Further, between the time of performing the oxidation treatment and the time of performing the CVD treatment, the surface of the oxide film is exposed to the air, and the oxidation of the surface of the semiconductor substrate proceeds. The degree of this oxidation varies depending on the length of the standing time in the air. For this reason, if the number of wafers that can be processed at one time is different between the oxidation process and the CVD process, the above-mentioned leaving time varies depending on the wafer, and this causes a deterioration in controllability of the oxide film thickness.

[0007]

SUMMARY OF THE INVENTION The present invention is a film forming method and a film forming apparatus made to solve the above problems. That is, in the film forming method of the present invention, the surface of a wafer placed in a predetermined atmosphere is irradiated with ultraviolet rays to perform a pre-treatment, and then the wafer is exposed to the air, and the pre-treatment is continued. Is characterized by performing a film forming process. The pretreatment is an oxidation treatment in an oxidizing gas atmosphere, a reduction treatment in a hydrogen gas atmosphere, and a decomposition treatment of an organic bonding group in an oxidizing gas atmosphere.

In the above-described film forming method, the pre-processing by ultraviolet irradiation and the subsequent film forming processing are continuously performed without affecting the wafer surface by the atmosphere. Therefore, a film forming process is performed on the wafer surface while maintaining the state of the wafer surface by the pre-processing. When the pretreatment is an oxidation treatment,
The oxidizing gas is decomposed by the ultraviolet rays to generate activated oxygen atoms having a strong oxidizing power, and the oxygen atoms oxidize the wafer surface to form an oxide film.
At this time, the formation speed of the oxide film is controlled by the oxygen partial pressure in the processing chamber and the output of the ultraviolet lamp, and an oxide film having a predetermined thickness is formed on the wafer surface. When the pretreatment is a reduction treatment, the wafer surface exposed to the hydrogen gas atmosphere is irradiated with ultraviolet rays to reduce and remove an oxide film on the wafer surface. Further, when the pretreatment is a decomposition treatment of an organic bonding group, the wafer surface exposed to the oxidizing gas atmosphere is irradiated with ultraviolet rays to decompose and remove organic substances on the wafer surface. Therefore, a film forming process is performed on the oxide film controlled to have a predetermined thickness or on the wafer surface from which the oxide film and organic substances have been removed.

Further, the film forming apparatus of the present invention is a multi-chamber type film forming apparatus having a transfer chamber and a plurality of processing chambers. In one of the processing chambers, an ultraviolet lamp is provided above a wafer mounting table disposed therein, and a gas introduction pipe for supplying an oxidizing gas or a hydrogen gas is connected. It is characterized by: The inside of each of the above chambers can be decompressed.

According to the film forming apparatus having the above structure, the oxidizing gas is supplied from the gas introduction pipe into the processing chamber provided with the ultraviolet lamp, so that the strong oxidizing gas activated by the ultraviolet light in the processing chamber. A powerful oxygen atom is generated, and the wafer surface is oxidized. Further, the organic bonding group on the wafer surface is decomposed by the irradiation of the ultraviolet ray, and an oxidizing gas is supplied to the decomposed product, whereby the decomposed product is easily removed by sublimation. Further, the formation rate of the oxide film by the above-mentioned oxidation treatment is controlled by the partial pressure of the oxidizing gas supplied into the processing chamber and the output of the ultraviolet lamp. On the other hand, by supplying hydrogen gas from the gas introduction pipe into the processing chamber, the wafer surface exposed to the hydrogen gas atmosphere is irradiated with ultraviolet rays,
The wafer surface is reduced. The wafer that has been subjected to the oxidation treatment, the reduction treatment, or the decomposition treatment of the organic bonding group as described above is transferred to another processing chamber without being exposed to the outside air, and the film formation processing is performed. Therefore, the oxidation-reduction treatment by ultraviolet irradiation, the decomposition treatment of the organic bonding group, and the film formation treatment are continuously performed without affecting the wafer surface by the atmosphere.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a film forming method and a film forming apparatus according to the present invention will be described below with reference to the drawings. FIG.
FIG. 2 is a process flow illustrating an example of a manufacturing process of a semiconductor device to which the film forming method of the present invention is applied, and FIGS. 2 and 3 are process flows illustrating the film forming process in detail. FIG. 4 is a configuration diagram illustrating an example of a film forming apparatus used in the film forming method of the present invention, and FIG. 5 is a cross-sectional view of a main part (aa ′ in FIG. 4) of the film forming apparatus. First, the configuration of the film forming apparatus will be described with reference to FIG.

The film forming apparatus 1 includes a transfer chamber 11,
This is a so-called multi-chamber type having a plurality of processing chambers 12A, 12B, 12C connected to the transfer chamber 11 via an opening / closing door, and a cassette station 13. The inside of each of the chambers 11, 12A to 12C and the cassette station 13 can be individually decompressed.

A transfer robot 14 for transferring a wafer is accommodated in the transfer chamber 11. The transfer robot 14 takes out a wafer from the wafer cassette 15 stored in the cassette station 13 and mounts the wafer on a wafer mounting table (not shown) in each of the processing chambers 12A to 12C. This is for moving the wafer placed on the mounting table into the other processing chambers 12A to 12C or for storing it in the wafer cassette 15.

One of the processing chambers 12A to 12C is used as a chamber for performing a pre-process of film formation (hereinafter, referred to as a pre-processing chamber 12A), and the other processing chambers 12B and 12C are used as chambers. It is used as a chamber for performing a film forming process by the CVD method.

[0015] As shown in FIG.
The inside of 2A is vertically separated by an ultraviolet transmitting window 20, and the separated portions are pressure-independent. A wafer mounting table 21 is provided at a lower portion in the pre-processing chamber 12A separated by the ultraviolet transmitting window 20, and an ultraviolet lamp 22 is provided at an upper portion in a state of facing the mounting surface of the wafer mounting table 21. I have. As the ultraviolet lamp 22, for example, a low-pressure mercury lamp is used.

A gas inlet pipe 23 and an exhaust pipe 24 are connected to a lower portion of the pre-processing chamber 12A. The gas introduction pipe 23 is connected to the pretreatment chamber 12A at a side wall of the pretreatment chamber 12A. The gas introduction pipe 23 is for introducing a gas containing an oxidizing gas or a hydrogen gas into the pretreatment chamber 12A. The exhaust pipe 24 is connected to the preprocessing chamber 12A on the bottom surface of the preprocessing chamber 12A. The exhaust pipe 24 is connected to an exhaust pump via a gate valve and a pressure regulator (not shown). This pressure controller is 1.33 × 10 ²
Pressure control can be performed in a range of about 1.00 × 10 ⁵ Pa.

The wafer mounting table 21 has a rotating mechanism 21a for freely rotating the mounting surface. Also,
The wafer mounting table 21 has a heater 2 for heating the mounting surface.
1b is provided. The heater 21b can heat the wafer W mounted on the wafer mounting table 21 to about 600 ° C., and is embedded in, for example, the mounting surface of the wafer mounting table 21 or disposed on the mounting surface. ing.

Further, the cassette station 13
Is for accommodating a plurality of wafers W set in the wafer cassette 15. This cassette station 1
Reference numeral 3 denotes a unit capable of storing at least the number of wafers W to be processed at one time in a process preceding the process using the film forming apparatus 1.

In the film forming apparatus 1, the pretreatment chamber 12
A is connected via the transfer chamber 11 to the processing chambers 12B and 12C for performing another film forming process. For this reason, the wafer that has been subjected to the pre-processing in the pre-processing chamber 12A is transferred to the other processing chambers 12B and 12C without being exposed to the outside air, and the film is formed by CVD.

Here, by supplying an oxidizing gas from the gas introduction pipe 23 into the preprocessing chamber 12A, oxygen atoms having a strong oxidizing power activated by ultraviolet rays are generated in the preprocessing chamber 12A. Then, the surface of wafer W is oxidized. The formation rate of the oxide film by this oxidation process is controlled by the partial pressure of the oxidizing gas supplied into the pre-processing chamber 12A and the output of the ultraviolet lamp 22. Further, the organic bonding group is decomposed on the surface of the wafer W by the irradiation of the ultraviolet light, and an oxidizing gas is supplied thereto to remove the decomposed product by sublimation.

On the other hand, by supplying hydrogen gas from the gas introduction pipe 23 into the pretreatment chamber 12A, the surface of the wafer W exposed to the hydrogen gas atmosphere is irradiated with ultraviolet rays, and the surface of the wafer W is reduced. You.

Therefore, in the pre-processing chamber 12A, after an oxide film having a predetermined thickness is formed on the wafer surface by irradiation of ultraviolet rays, or after removing an organic residue and a natural oxide film,
This makes it possible to perform a film forming process without exposing the wafer surface to the atmosphere.

Next, as an example of a method of manufacturing a semiconductor device to which the film forming method using the above-described film forming apparatus is applied, the steps from patterning an insulating film on a semiconductor substrate to forming a silicon film by a CVD method are shown in FIG. This will be described with reference to FIG. Note that the method shown here is merely an example, and conditions such as temperature and pressure in each process are not limited to the following numerical values.

First, from the first step S1 to the fourth step 4,
First step (S11) of the conventional technique described with reference to FIG.
To the fourth step (S14), the insulating film on the semiconductor substrate forming the wafer is patterned by dry etching using the resist pattern as a mask, and after removing the resist pattern, the resist residue is removed by chemical cleaning. Remove.

The following fifth step S5 is a characteristic step of the present invention. That is, in the fifth step S5, the wafer to be processed is transferred into the wafer station of the film forming apparatus 1. After that, in the sixth step S6, a pre-process is performed in situ prior to the film forming process in the film forming apparatus 1.
The pre-processing in the sixth step S6 is intended to process a film-forming base surface, and is performed, for example, according to the procedure shown in FIG.
4 and FIG. 5).

First, in a first step S61, each chamber of the film forming apparatus 1 is depressurized while the wafer W is housed in the wafer station 13. Thereafter, the wafer station 13 is moved by the wafer transfer robot 14.
The wafer W is inserted into the pre-processing chamber 12A and the wafer W is mounted on the wafer mounting table 21.

Thereafter, in a second step S62, the opening / closing door between the pre-processing chamber 12A and the transfer chamber 11 is closed, and the inside of the pre-processing chamber 12A is further reduced in pressure to remove the air therein. At the same time, the wafer W on the wafer mounting table 21 is heated to 400 ° C. to 500 ° C. by the heater 21b.

Next, in a third step S63, an oxidizing gas is introduced into the pretreatment chamber 12A from the gas introduction pipe 23. Here, as the oxidizing gas, for example, oxygen gas or dry air diluted with an oxygen gas or an inert gas is introduced. In this state, by irradiating ultraviolet rays from the ultraviolet lamp 22, the wafer W is irradiated under an oxidizing gas atmosphere.
Decompose the organic bonding groups on the surface.

Here, the energy E per mole of a substance that is received by irradiation of an electromagnetic wave is E = E, where Planck's constant h, Avogadro's number N, speed of light c, and wavelength λ of the electromagnetic wave are given by
h × (N / 4.2) × (c / λ). For this reason, when a low-pressure mercury lamp is used as the ultraviolet lamp 22, E = 1 for ultraviolet light having a wavelength λ = 185 nm.
E = 1 for ultraviolet light of 55 kcal and wavelength λ = 254 nm
It becomes 15 kcal.

FIG. 6 shows the binding energy of each organic binding group. From this table and the energy values calculated above, it can be seen that all the organic bonding groups shown in the above table are decomposed by the irradiation of ultraviolet rays. Therefore, by irradiating ultraviolet rays in an oxidizing gas atmosphere, the organic bonding group is decomposed, and the substance generated by this decomposition is combined with oxygen to be sublimated and removed. As described above, the organic substances that inhibit the subsequent oxidation processing and deteriorate the quality of the oxide film formed by the oxidation processing are removed from the wafer surface. This organic substance is, for example, an organic substance residue formed of a sidewall protective film and a resist pattern at the time of dry etching.

Thereafter, in a fourth step S64, the introduction of the oxidizing gas from the gas introducing pipe 23 is stopped, and the oxidizing gas in the pretreatment chamber 12A is exhausted from the exhaust pipe 24.
Next, hydrogen gas is introduced into the pretreatment chamber 12A from the gas introduction pipe 23, and ultraviolet rays are irradiated from the ultraviolet lamp 22 in this state. Thus, a reduction process is performed on the surface of the wafer W to remove a natural oxide film formed on the exposed surface of the semiconductor substrate. At this time, as an example, the heating temperature of the wafer W is 4
The temperature is kept at about 00 ° C. to 500 ° C., and the inside of the pretreatment chamber 12A is kept at almost normal pressure.

Next, in a fifth step S65, the introduction of hydrogen gas from the gas introduction pipe 23 is stopped, and the hydrogen gas in the pretreatment chamber 12A is exhausted. Thereafter, oxygen gas is introduced as an oxidizing gas from the gas introduction pipe 23 into the pretreatment chamber 12A. While the oxygen gas partial pressure in the preprocessing chamber 12A is maintained at a predetermined value, ultraviolet light of a predetermined output is irradiated from the ultraviolet lamp 22 onto the surface of the wafer W.

[0033] Thus, ultraviolet UV wavelength 185nm emitted from the lamp 22 is absorbed by the oxygen in the processing atmosphere to generate O ₃ (ozone), UV is absorbed excited state of the wavelength 254nm in the O ₃ Oxygen atom O
⁽¹ D) is generated. Furthermore, by the thermal decomposition of O ₃ ,
Oxygen atoms O ( ³ P) in the ground state are easily generated. The silicon surface can be easily oxidized at a relatively low temperature by these oxygen atoms having a strong oxidizing power. At this time, the oxidation treatment is performed while controlling the oxidation speed with high accuracy by the oxygen partial pressure and temperature in the pretreatment chamber 12A and the output of the ultraviolet lamp. As described above, an oxide film having a predetermined thickness is formed on the surface of the wafer W.

Here, in order to optimize the film forming rate, an oxygen gas may be diluted to a predetermined concentration with an inert gas such as nitrogen, helium, argon, or neon and introduced as an oxidizing gas. Air may be introduced as the oxidizing gas. Further, in order to increase the oxidation rate, the oxygen gas may be increased in concentration or ozone may be introduced.

The first steps S61 to S61 of the sixth step S6 are described above.
After an oxide film is formed on the surface of the wafer W by the preprocessing in the fifth step S65, in a seventh step S7 (FIG. 1), the opening and closing door of the preprocessing chamber 12A is opened, and the wafer W is transferred by the transfer robot in the transfer chamber 11. Is transferred to one of the processing chambers 12B and 12C for another CVD process. Next, in the processing chambers 12B and 12C, a film forming process for forming a silicon film on the wafer W on which the oxide film is formed is performed by applying the CVD method.

According to the method of manufacturing a semiconductor device, the pretreatment by ultraviolet irradiation and the subsequent film forming process are performed continuously without affecting the wafer surface by the atmosphere. The film formation process is performed while maintaining the surface state. Here, as the pretreatment, an oxide film is formed after removing the organic residue and the natural oxide film. Therefore, when this oxide film is formed, the oxidation of the semiconductor substrate surface is not hindered by the organic residue, and the natural oxide film is also removed. In addition, the film thickness can be controlled with high accuracy by controlling the output of the ultraviolet lamp. Therefore,
A film formation process can be performed on an oxide film whose film thickness is controlled with high precision.

Since the oxidation treatment in the pretreatment is performed by irradiating ultraviolet rays in an oxidizing gas atmosphere, the thickness of the oxide film is controlled to 1 nm or less by controlling the partial pressure and temperature of the oxygen gas and the output of the ultraviolet lamp. It can be controlled in the thickness range. In addition, by using energy assist by ultraviolet irradiation, a certain film forming rate can be obtained while ensuring controllability, and the productivity does not decrease.

In the semiconductor device formed as described above, the film thickness of the oxide film at the interface between the semiconductor substrate and the silicon film is controlled with high accuracy, and stable element characteristics are obtained by removing organic substances. Will have.

When there is no organic residue on the wafer surface and it is not necessary to remove the organic residue, as shown in FIG. 3, the fourth step S62 is followed by the fourth step S62.
The natural oxide film is removed by the reduction process in step S64.

[0040]

As described above, according to the film forming method of the present invention, controllability and production can be achieved by continuously performing the pre-treatment by ultraviolet irradiation and the subsequent film-forming treatment without exposing it to the atmosphere. Pretreatments such as decomposition treatment, reduction treatment, and oxidation treatment of organic bonding groups are performed on the film-forming base surface while ensuring the property, and the next film formation is performed while maintaining the state of the film-forming base surface by this pretreatment. Processing can be performed. For this reason, in the manufacturing process of the semiconductor device, it is possible to control the state of the film-forming base surface, for example, the thickness of the oxide film at the interface with high accuracy, and to manufacture a semiconductor device with stable element characteristics. become.

According to the film forming apparatus of the present invention, an ultraviolet lamp is provided in one of the processing chambers of the multi-chamber type film forming apparatus.
Pretreatment by ultraviolet irradiation such as reduction treatment and oxidation treatment and subsequent film formation treatment can be performed without exposing the wafer to the atmosphere.

[Brief description of the drawings]

FIG. 1 is a process flow showing a manufacturing process of a semiconductor device to which a film forming method of the present invention is applied.

FIG. 2 is a process flow showing an example of a pretreatment in a film forming method of the present invention.

FIG. 3 is a process flow showing another example of the pretreatment in the film forming method of the present invention.

FIG. 4 is a configuration diagram illustrating an example of a film forming apparatus of the present invention.

FIG. 5 is a sectional view of a main part of a film forming apparatus.

FIG. 6 is a table showing binding energies of organic bonding groups.

FIG. 7 is a diagram (part 1) illustrating a relationship between a natural oxide film thickness between an emitter electrode and an emitter diffusion layer and device characteristics.

FIG. 8 is a diagram (part 2) illustrating a relationship between a natural oxide film thickness between an emitter electrode and an emitter diffusion layer and device characteristics.

FIG. 9 is a process flow showing a manufacturing process of a semiconductor device to which a conventional film forming method is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Film-forming apparatus, 11 ... Transport chamber, 12A, 12B,
12C: processing chamber, 14: wafer transfer robot, 2
DESCRIPTION OF SYMBOLS 1 ... Wafer mounting table, 22 ... UV lamp, 23 ... Gas introduction pipe

Claims (5)

[Claims] 1. A method for performing a pretreatment by irradiating ultraviolet rays to a surface of a wafer placed in a predetermined atmosphere, and performing a film forming process on the surface of the wafer following the pretreatment without exposing the wafer to the atmosphere. A film forming method characterized by the above-mentioned. 2. The film forming method according to claim 1, wherein the pretreatment is an oxidation treatment in an oxidizing gas atmosphere. 3. The film forming method according to claim 1, wherein the pretreatment is a reduction treatment in a hydrogen gas atmosphere. 4. The film forming method according to claim 1, wherein the pretreatment is a process of decomposing an organic bonding group in an oxidizing gas atmosphere. 5. A film forming apparatus, comprising: a transfer chamber in which a wafer transfer robot is stored; and a plurality of processing chambers connected to the transfer chamber via an opening / closing door, wherein the transfer chamber and the inside of the processing chamber can be depressurized. In one of the treatment chambers, an ultraviolet lamp is provided above a wafer mounting table disposed therein, and a gas introduction pipe for supplying an oxidizing gas or a hydrogen gas is connected. A film forming apparatus characterized by the above-mentioned.