JPH0660408B2 - Thin film manufacturing method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for producing an insulating film, a dielectric film and a protective film for semiconductor electronic devices, superconducting devices, various electronic parts, various sensors.

(Prior Art) Semiconductor electronic devices, superconducting devices, various electronic parts,
Insulating films, dielectric films, and protective films for various sensors have been tried to be formed by various methods such as thermal oxidation of a substrate material, thermal CVD on the substrate surface, sputtering, plasma assisted CVD, and spin coating. .

In recent years, as device integration or stacking progresses, a film forming method that has good coverage on the step portion or good flatness is required.

Now, as one of the methods attracting attention, CVD using tetraethoxysilane (also known as tetraethylorthosilicate, abbreviated as "TEOS" hereinafter) or diacetoxyditertiary butoxysilane (hereinafter abbreviated as "DADBS"), etc. There is technology. (Note that these TEOS and D
Although ADBS and the like are organic compounds of silicon, which is a semiconductor, such organic compounds of semiconductors will be collectively referred to as “organometallic compounds” in this specification.

For example, Ikeda et al. "Electrochemistry" Vol.56, No.7 (1988)
There are articles on the method in P.527-P.532 and the references cited therein.

Ikeda et al. Have reported a silicon oxide film (hereinafter abbreviated as “NSG film”) having a good flatness and a step coverage improved by atmospheric pressure CVD using TEOS and ozone, and a phosphorus-containing silicon oxide film (hereinafter “PSG film”). “Abbreviated as“ ”and a boron-containing silicon oxide film (hereinafter abbreviated as“ BSG film ”). In this case, ozone is used as an oxidation source, whereby an NSG film can be produced at a low temperature of 400 ° C., and OH groups in the film are reduced to obtain a good quality NSG film.
However, there is a drawback that the film forming rate is about 1400 Å / min, and it takes about 7 minutes to prepare a 1 μm NSG film, which is much lower than the film forming rate of 1 μm / min required by a single-wafer type device. It does not reach.

Also, RA Levy et al., J. Electrochem. Soc. Vol. 134, No. 7
(1987) P.1744-P.1749 and its references, oxygen and D
NSG film, PSG using ADBS or TEOS
It is introduced that a film, a BSG film, and a boron-phosphorus-containing silicon oxide film (hereinafter abbreviated as "BPSG film") were produced. In this case, although the film forming temperature is 550 ° C., which is considerably higher than the method using ozone described above, the film forming rate is slow at 300 Å / min, which is also industrially applicable. Has not reached.

Further, in Japanese Patent Application Laid-Open No. 61-7,
7695 [Vapor growth method] "and" US Pat.
Although there is a film forming method of the invention of "No. 4,060", these cannot be said to have reached a satisfactory level in terms of film forming rate and film quality.

In addition, Noguchi et al., At the 35th Joint Lecture on Applied Physics (Spring 1988) Lecture No. 29P-G-5, showed that oxygen atoms produced by microwave discharge and tetramethoxysilane (hereinafter "TMOS"). Abbreviated)
It is shown that the carbon content in the produced film is reduced as compared with the case where tetramethylsilane (hereinafter abbreviated as “TMS”) is used. However, the film made using this TMOS
From the infrared absorption spectrum, the presence of a large amount of OH groups is observed, and it is clear that the film is not always a good film. It is considered that this is because the supply amount of oxygen active species is insufficient.

Another example using an oxygen atom is described in JP-A-63-83275, "CVD apparatus", in which an NSG film,
Oxygen atoms and silane are reacted to form a PSG film or a BSG film. This reaction usually proceeds rapidly at room temperature even under a source pressure to produce powder dust of silicon oxide. Further, since they react rapidly, it is difficult to introduce and mix the two gas components into the reaction chamber, and it is difficult to form a film having good uniformity.

In order to solve the problem, in the invention of Japanese Patent Laid-Open No. 63-83275, the reaction between oxygen atoms and silane is suppressed by cooling the outflow portion of the gas, and the reaction is carried out by introducing it to the surface of the heated substrate to be treated. Is a device adapted to cause However, in the case of this method, it is necessary to cool the outflow part of the gas, the apparatus becomes complicated, and it is impossible to completely suppress the reaction in the space away from the substrate surface. There is a drawback that occurs.

(Problems to be Solved by the Invention) As described above, in the conventional method, ozone + TEOS system,
Oxygen + DADBS system and oxygen + TEOS system are 1 μm / mi industrially required as a single-wafer type device.
There is a drawback that a film forming rate of about n cannot be obtained.

Further, in the oxygen atom + silane system, which can obtain this high film formation rate, the reaction rapidly occurs in the mixing portion of both substrates, so a method of suppressing the reaction by cooling the mixing portion and the gas outflow portion is required, There is a drawback in that the apparatus becomes complicated and the generation of dust due to reaction in space cannot be suppressed.

In addition, oxygen atoms produced by microwave discharge and TMA
In addition, in the method of using TMOS together, the amount of oxygen active species is insufficient. Therefore, when TMA is used, a film containing carbon-based impurities is obtained, and when TMOS is used, a film containing an OH group is obtained. However, there is a drawback in that a uniform film cannot be obtained.

(Object of the invention) The present invention solves this problem by using a large amount of oxygen active species obtained in a high temperature non-equilibrium plasma or a local thermal equilibrium plasma instead of ozone, and by replacing silane with TEOS, DADBS, which has low reactivity. To provide a method and an apparatus for producing an insulating film, a dielectric film or a protective film at a high speed and with little dust on a substrate surface set at a predetermined temperature by using an organometallic compound such as TMOS or tantalum alcoholate. To aim.

(Means for Solving the Problem) In order to achieve the above object, the present invention uses an organometallic compound and an oxygen active species produced by high temperature non-equilibrium plasma or local thermal equilibrium plasma as source gases, A thin film forming method for forming an oxide film on the surface of a substrate by using a chemical reaction, and an apparatus for realizing the same include a treatment chamber capable of keeping airtightness, a substrate installed in the treatment chamber, A substrate temperature adjusting mechanism for adjusting the temperature of the substrate, an organometallic compound introducing mechanism for introducing an organometallic compound into the front space of the substrate in the processing chamber, a high temperature non-equilibrium plasma or a local thermal equilibrium plasma generating mechanism, and And an oxygen active species introducing mechanism for introducing oxygen active species into the front space of the substrate.

(Operation) The high temperature non-equilibrium plasma or the local thermal equilibrium plasma produces much larger amount of oxygen active species than the glow plasma or the microwave plasma used in the device fabrication process. By using this oxygen active species and an organometallic compound such as TEOS, DADBS, TMOS or tantalum alcoholate, which is less reactive than silane, a chemical reaction is induced only on the surface of the substrate set to a predetermined temperature, and the film thickness An oxide film having a uniform film quality distribution can be manufactured.

(Example) In this example, Japanese Patent Application No. 61-0 filed by the applicant of the present application
A useful invention is obtained by using this as a basic technique of "Surface treatment method and apparatus" in Japanese Patent Application Laid-Open No. 62-227089 (Japanese Patent Application Laid-Open No. 62-227089) and applying it to a low temperature oxide film forming process which was not generally known at the time of the application. I was able to do it. "LTE plasma" in the specification of said patent application
Corresponds to “local thermal equilibrium plasma” in the present specification.

Fabrication of an NSG film will be described as a first embodiment of the present invention.

FIG. 1 shows a front sectional view of an apparatus for realizing the method of this embodiment. Reference numeral 21 denotes a stainless steel processing chamber, which has a structure that can be evacuated or kept airtight as necessary. Further, the structure is such that pressurization is possible. 11
Is a substrate from which a thin film is to be produced.

The substrate temperature adjusting mechanism 10 (12, 13, 14, etc.) will be described. Reference numeral 12 is a substrate holder that holds the substrate 11 and controls the temperature of the substrate. Reference numeral 13 is a heater and 14 is a thermocouple. The substrate holder 12 has a diameter of 15 cm and can raise the temperature up to about 450 ° C. The temperature of the substrate holder 12 is measured by the thermocouple 14, and P, PI, PID are obtained by using a temperature controller (not shown) and a thyristor unit together.
The temperature of the substrate holder 12 is adjusted by controlling the power applied to the heater 13 by control or ON / OFF control using a simple relay. If necessary, use a cooling mechanism such as water cooling for this part.

The processing chamber 21 has a cylindrical shape with a diameter of about 25 cm and a height of about 30 cm, and can be evacuated to a vacuum through a valve 31 using a mechanical booster pump 32 and an oil rotary pump 33. A vacuum gauge 34 measures the pressure in the processing chamber 21. In the present embodiment, the pressure of the processing chamber 21 is kept constant by opening / closing the valve 31.

Reference numeral 22 is a gas blowing plate, which is the application of the applicant of the present application, Japanese Patent Application No. 62-254268 (JP-A-1-119674).
No.) "Distribution plate" in the specification of "Film forming apparatus and method", the structure is the same as that described in detail in the above specification, and 24 is a heater, which is a gas blowing plate 2
2 is for setting a predetermined temperature, and 23 is a diffusion plate, which is a plate having a thickness of 2 mm and a large number of holes having a diameter of about 1 mm formed densely.

The gas blowing plate 22 uniformly distributes TEOS, which is easily liquefied, to the front space of the substrate 11 and blows it out. If it is not heated here, dew condensation occurs on the TEOS and the process gas is supplied. Becomes unstable, causing problems in stability and reproducibility of film formation.

Further, as another effect of heating by the gas blowing plate 22, an intermediate product due to thermal denaturation is generated in the process gas,
It is also possible that it contributes to film formation (Japanese Patent Application No. 62-
No. 254268 “Film forming apparatus and method”). However,
At present, the mechanism has not been clarified.

Next, the mechanism 40 for introducing an organometallic compound will be described.
43 is TEOS, which is a liquid at normal temperature and pressure. The nitrogen of the carrier gas is a pressure reducing valve from a high pressure cylinder (not shown).
Delivered through the flow controller (arrow 45). Four
Reference numeral 2 is a bubbler, and TEOS 43 in a liquid state is bubbled by nitrogen introduced through a valve 44 and vaporized, and is introduced into the front space of the substrate 11 through the valve 41 and the gas blowing plate 22.

Reference numeral 46 indicates a constant temperature bath. To adjust the bubbling temperature and keep TEOS, which is easily liquefied, in a gaseous state,
Keep the valve 41 and piping warm. In this example, the bubbler 4 had a capacity of about 1 and was filled with 300 g of TEOS.

Next, another oxygen active species of the process gas produced by the high-temperature non-equilibrium plasma or the local thermal equilibrium plasma generation mechanism 50 and the oxygen active species introduction mechanism 60 for introducing the same will be described. It is a double glass tube, and it has a structure that allows water to flow between the double tubes for cooling. In this embodiment, the inner tube of the quartz glass tube has a diameter of 3 cm and a length of 53 cm. 56 and 56 'show the flow of cooling water.

Reference numeral 53 is a coil made of a copper pipe, which is also water-cooled from the inside though not shown. One of the coils 53 is grounded and the other is connected to the high frequency power supply 51 through the matching circuit 52. In this embodiment, the high frequency power source 51
A high-frequency separately excited power source having a frequency of 13.56 MHz and an output of 10 kW was used as Oxygen (arrow 57) is introduced from a high pressure cylinder (not shown) through a pressure reducing valve and a flow controller.

An oxygen active species introduction mechanism 60 for introducing oxygen active species into the processing chamber 21 includes a stainless steel pipe 63, a stainless steel flange 61 welded to the pipe 63 and having an O-ring groove formed therein, and a discharge tube 54. It is composed of a quartz glass flange 58, a rubber O-ring 59 that seals between both flanges, a normal screw (not shown) that joins both flanges, and a valve 62.

As described in Japanese Patent Application No. 61-069646, when high frequency power is injected from the high frequency power supply 51 into the coil 53, high frequency glow discharge is initially generated in the discharge tube 54. When the injection power is further increased, the coil 53
A high temperature non-equilibrium plasma or a local thermal equilibrium plasma 55 locally pinched inside is generated. (For the high-temperature non-equilibrium plasma among these, see the “vacuum” by Mito et al.
(Vol. 1, No. 4 (1988) P.271-P.278 and its references). This high temperature non-equilibrium plasma or local thermal equilibrium plasma is
The emission intensity is much higher than that of high-frequency glow discharge, and a large amount of active species are generated. Especially, there are many atomic active species.
In addition, it has a characteristic that the discharge impedance is significantly low electrically. Regarding the difference between high-temperature non-equilibrium plasma and local thermal equilibrium plasma, "High temperature non-equilibrium plasma" in the left column on page 271 of "Vacuum" is ... It is a high-temperature plasma. ”, The high-temperature plasma in which the local thermal equilibrium is achieved is called the local thermal equilibrium plasma. Although the thermal equilibrium is not achieved, it is much higher than that in the glow discharge. What is high temperature is called high temperature non-equilibrium plasma. Which plasma is formed depends on the diameter of the discharge tube 54, the electric power to be injected, and the like, and therefore cannot be determined. In addition, since the merit of producing a large amount of the active species is a phenomenon that occurs in any case, it is not so significant to strictly distinguish the two.

FIG. 2a shows an example that is usually observed in the emission spectroscopy of high-frequency or microwave glow discharge, and b is an example that is usually observed in the emission spectroscopy of high-temperature nonequilibrium plasma or local thermal equilibrium plasma. The vertical axis of FIG. 2a is magnified 4500 times as compared with the vertical axis of b. (Ie therefore
The emission intensity of b is about 4500 times stronger than that of a). Further, it is clear that the light emission of b strongly depends on the light emission from oxygen atoms, and in the high temperature non-equilibrium plasma or the local thermal equilibrium plasma, the dissociation of oxygen proceeds to generate a large amount of active species.

As an example of using the active species of the high temperature non-equilibrium plasma or the local thermal equilibrium plasma, Japanese Patent Application No. 63-163350 filed by the applicant of the present application (Japanese Patent Laid-Open No. 14801/1991).
No.) “Methods for improving oxide superconductors” and 46th Academic Meeting of Applied Physics (Autumn 1988) Lecture No. 6P-kan B
-16, Proceedings of Proceedings 1st Volume, P.131, etc., their usefulness is clear. However, there is no reference to a method for producing an oxide thin film by using a combination of an oxygen active species of high temperature non-equilibrium plasma or local thermal equilibrium plasma and an organometallic compound.

Now, the oxygen active species generated in the high temperature non-equilibrium plasma or the local thermal equilibrium plasma 55 of this embodiment is introduced into the front space of the substrate 11 through the oxygen active species introduction mechanism 60 and the gas blowing plate 22.

In this embodiment, the pressure inside the processing chamber 21 is 200 Torr,
Oxygen flow rate 10 / min, bubbling nitrogen flow rate 2 / m
In, the temperature of the constant temperature bath 46 is 80 ° C., the temperature of the gas blowing plate 22 is 80 ° C., the temperature of the substrate holder 12 is 400 ° C., and the high frequency power is 85 kW, the NSG film can be obtained at the film forming rate of about 1.2 μm / min. It was It was found that the NSG film was a good quality film in which carbon was not observed by infrared absorption spectroscopy and OH groups were small.

It is important in the factory that a good quality film can be obtained at a film forming rate of about 1.2 μm / min, and it is necessary to satisfy the film forming rate of 1 μm / min required for a single wafer processing apparatus. is there.

When oxygen active species are produced by ordinary microwave glow discharge, it is clear from the emission spectrum analysis pattern in Fig. 2 that atomic oxygen is generated in the discharge plasma, but the amount of oxygen is high temperature non-equilibrium plasma. Alternatively, the amount is much smaller than that of the local thermal equilibrium plasma. Moreover, since microwaves are absorbed by water, there is a drawback that microwave power loss is large and it is difficult to cool the discharge tube with water.

A second embodiment of the method of the present invention involves introducing the nitrogen carrier trimethyl phosphate phosphate through valve 71 of the apparatus of FIG. Phosphoric acid trimethyl ester is bubbled and transported by nitrogen whose flow rate is controlled in a bubbler (not shown). The bubbling temperature is 60 ° C. and the nitrogen flow rate is 1.5 / min. Other conditions such as pressure in the processing chamber, TEOS, etc. are the same as in the embodiment of FIG. 1, and a silicon oxide film containing phosphorus (selecting phosphorus as an element to be added), that is, a PSG film is formed on the surface of the substrate 11. It could be produced at a speed of 1.3 μm / min.

Further, as a third embodiment of the method of the present invention, a method using triethoxyboron in place of the phosphoric acid trimethyl ester of the second embodiment can be mentioned. In this case, boron can be contained by selecting boron as an element to be added to the oxide film. By bubbling temperature of triethoxyboron at 15 ° C., nitrogen flow rate of 0.2 / min, and other conditions being the same as those of the first embodiment, a BSG film is formed on the surface of the substrate 11 at a speed of 1.3 μm / min. It was made with.

In addition, as a fourth embodiment of the present invention, by using the second and third embodiments together, that is, by introducing both phosphoric acid trimethyl ester and triethoxyboron, the substrate 11
The BPSG film on the surface of which can be formed at a rate of 1.3 μm / min.

Even when DADBS was used instead of TEOS, the NSG film could be similarly prepared. When trimethyl phosphate and triethoxyboron were used together as in the case of TEOS, PSG film, BSG film and BPSG film could be produced at high speed and with good quality. When arsenic is the element to be added, arsine or triethoxyarsine may be used.

In addition, as a fifth embodiment of the present invention, tantalum alcoholate such as tantalum methylate or tantalum ethylate is used as the organometallic compound in place of TEOS of the first embodiment, a bubbling temperature of 60 to 160 ° C., and a substrate holder. If the temperature of 12 is 450 ° C., a tantalum oxide film can be formed on the surface of the substrate 11 at a rate of 300 Å / min. This tantalum oxide film is mainly used as a dielectric film of the capacitor part of the device, and the required film thickness is about 250Å. Therefore, the film formation is completed in about 1 minute and is considered to be industrially useful.

In the above-mentioned embodiments, all examples of film formation under reduced pressure are shown, but the process pressure may be normal pressure or higher. NSG film, PSG film, which attaches particular importance to flatness,
When forming a BSG film or a BPSG film, the higher the pressure, the better the flatness. However, in this case, high-temperature non-equilibrium plasma or local thermal equilibrium plasma with high discharge power is required. In the case of low power, it is necessary to reduce the inner diameter of the discharge tube.

In the case of normal pressure or higher pressure, the mechanical booster pump 32 and the oil rotary pump 33 are detached and used as necessary in each of the above drawings.

As the gas introduced by the arrow 57, nitrous oxide or oxygen containing ozone can be used in addition to oxygen.

Furthermore, regarding the amount of oxygen active species, Fujimura et al.
Semiconductor World 1988 July 1988 p.131-p.138 "and references cited therein. Similarly to those found in these documents, also in the case of the present example, addition of nitrogen or a trace amount of fluorine-based gas (nitrogen trifluoride, freon, etc.) leads to reduction of OH groups in the film, and good results are obtained. Is getting

However, regarding the stability of the electrical characteristics of the oxide film that occurs when this added gas mixes into the target oxide film,
Not clear at this time.

Another example of an apparatus used to carry out the method of the present invention is shown in FIG. The same members as those in FIG. 1 are given the same numbers.
The present embodiment mainly has a structure in which the gas blowing plate 22 of the embodiment shown in FIG. 1 is removed. With these devices,
There is a defect that the distribution of the film thickness and film quality of the produced film is deteriorated. However, since the organometallic compound and the oxygen active species can be directly introduced, higher speed film formation (about 2 μm / min) was possible. It has been found that rotating the substrate is effective for improving the film thickness and film quality distribution.

FIG. 4 shows another embodiment of the present invention. The same members as those in FIG. 1 are given the same numbers.

28 is a processing chamber of a quartz glass tube (inner diameter 30 cm, length 80 cm), from which the substrate 11 can be heated by an electric furnace (or radiated light from a halogen lamp) 81. Reference numeral 82 is a base holder made of quartz glass. Reference numeral 101 denotes a hatch, which has a structure in which the base 11 can be taken in and out together with the base holder 82 in the direction of the arrow 102.

A check valve 92 has a structure capable of discharging gas only in the direction of arrow 91. The discharge tube 54 made of quartz glass and the processing chamber 28 may be integrally configured without providing the bulb 62. In this case, the oxygen activated species introducing mechanism 40 is simple in only the welding portion or the connecting portion between the processing chamber 28 and the discharge tube 54.

This embodiment has an advantage that a large number of wafers can be processed at once. The processing chamber 28 may have a vertical structure.
In that case, there is a possibility that the temperature distribution of the substrate will be improved and a more uniform film can be produced.

Further, in the examples shown in FIGS. 1, 3, and 4, the bubbler 42 of the organometallic compound introduction mechanism 40 was used.
Instead of bubbling, the structure may be such that the vapor pressure of the organometallic compound is simply used for vaporization and the flow rate is controlled to be introduced into the processing chamber, or a vaporizer for forced vaporization may be installed. Good. When forming a film under pressure, it is particularly effective to use a vaporizer together.

Although nitrogen has been described as an example of the carrier gas for the organometallic compound, any inert gas such as argon or helium or any other gas having low reactivity may be used.

〔The invention's effect〕

By using an organometallic compound and an oxygen active species produced by high temperature non-equilibrium plasma or local thermal equilibrium plasma, a high-quality oxide film can be produced at high speed, and semiconductor electronic devices, superconducting devices, various electronic components, various sensors It can be used for the production of insulating films, dielectric films and protective films.

[Brief description of drawings]

FIG. 1 is a front sectional view of an embodiment of the present invention, FIG. 2a is an emission spectrum analysis pattern of a normal high-frequency or microwave glow discharge of oxygen, and b is an emission spectrum from a high-temperature nonequilibrium plasma or a local thermal equilibrium plasma. Analysis patterns, FIG. 3 and FIG. 4 are front sectional views of another embodiment of the present invention. 10 ... Substrate temperature adjusting mechanism, 11 ... Substrate, 12 ... Substrate holder, 21 ... Processing chamber, 22 ... Gas blowing plate, 33 ... Oil rotary pump, 40 ... Organometallic compound introduction mechanism, 42 ... … Bubbler, 50… Generation mechanism, 54…
... Discharge tube, 55 ... high-temperature non-equilibrium plasma or high-temperature equilibrium plasma, 60 ... oxygen activated species introduction mechanism, 81 ... electric furnace, 101 ... hatch.

Front page continuation (72) Inventor Noboru Nakamura 5-8-1, Yotsuya, Fuchu-shi, Tokyo Within Nichiden Anelva Co., Ltd. (56) Reference JP-A-61-248418 (JP, A)

Claims (7)

[Claims] 1. An organic metal compound and oxygen active species produced by high temperature non-equilibrium plasma or local thermal equilibrium plasma are used as source gases, and the chemical reaction thereof is used to produce an oxide film on the surface of a substrate. Characteristic thin film manufacturing method. 2. The method for producing a thin film according to claim 1, wherein the organometallic compound is tetraethoxysilane and the oxide film is a silicon oxide film. 3. The method for producing a thin film according to claim 1, wherein the organometallic compound is tantalum alcoholate, and the oxide film is a tantalum oxide film. 4. An organometallic compound, a hydride or organic compound of an element to be added, and an oxygen active species produced by high temperature non-equilibrium plasma or local thermal equilibrium plasma are used as source gases, and their chemical reaction is used to form a substrate. A method for producing a thin film, characterized in that an oxide film containing the element to be added is produced on the surface of the film. 5. The organic metal compound is tetraethoxysilane, the element to be added is phosphorus and / or boron, and the organic compound of the element to be added is trimethyl phosphate and triethoxyboron. 5. The thin film manufacturing method according to claim 4, wherein the oxide film to be manufactured is a silicon oxide film containing phosphorus and / or boron. 6. A processing chamber which can be kept airtight, a substrate installed in the processing chamber, a substrate temperature adjusting mechanism for adjusting the temperature of the substrate, and an organometallic compound for the substrate in the processing chamber. Organometallic compound introduction mechanism to be introduced into the front space, high-temperature non-equilibrium plasma or local thermal equilibrium plasma generation mechanism, and oxygen active species produced by the high-temperature non-equilibrium plasma or local thermal equilibrium plasma generation mechanism are introduced into the front space of the substrate And an oxygen activated species introducing mechanism for forming an oxide film on the surface of the substrate. 7. A temperature-controlled gas blowing plate for uniformly supplying the organometallic compound to the front space of the substrate is provided as a member for introducing the organometallic compound into the processing chamber. The thin film forming apparatus according to claim 6.