JP4890012B2 - Plasma CVD equipment - Google Patents

Description

  The present invention relates to a plasma CVD apparatus for forming a thin film such as a quartz film on a substrate at a low temperature by making a raw material gas into a plasma state by discharge and generating active radicals and ions.

  Thin film transistors (TFTs) are used in input / output devices such as substrate-type optical waveguides, active matrix liquid crystal display panels, and contact image sensors, and mobile phones. The gate insulating film constituting the thin film transistor is required to be formed at a low temperature. A film forming method using a plasma CVD apparatus is a method capable of forming a thin film such as a quartz film on a substrate at a low temperature, and is used, for example, for forming a gate insulating film of this thin film transistor. .

  In the film forming method using the plasma CVD apparatus, mixing of particles into the thin film becomes a big problem. When particles are mixed in the thin film, the thin film not only deteriorates in electrical characteristics and optical characteristics, but also has a problem that the manufacturing yield decreases and the manufacturing cost increases. In other words, in order to form a high-quality thin film at low cost, it is necessary to improve the manufacturing yield, that is, to reduce the amount of particles mixed into the thin film.

As a method for reducing the amount of particles mixed into the thin film, for example, in Patent Document 1, a reaction chamber in which a substrate for forming a desired thin film is arranged and a plasma forming chamber are divided by a mesh electrode. A film forming method using a plasma CVD apparatus having the above structure is disclosed.
In this film forming method using the plasma CVD apparatus, oxygen active species formed in the plasma forming chamber are transported to the reaction chamber, and a reaction gas (raw material gas) serving as a thin film material is supplied to the surface of the substrate. The reaction proceeds only on the surface of the substrate, and a thin film with a small amount of mixed particles is formed on the substrate.
Moreover, in this film-forming method using the plasma CVD apparatus, a thin film or granular deposit formed on the surface of the gas introduction pipe by arranging a gas introduction pipe for supplying the reaction gas outside the substrate. Is prevented from falling on the substrate. Therefore, mixing of particles into the thin film is suppressed.
Japanese Patent Laid-Open No. 11-106928

  However, in the method disclosed in Patent Document 1, the reaction gas is decomposed in the vicinity of the surface of the substrate. Therefore, when the RF (Radio Frequency) power used for decomposition of the reaction gas is small, the reaction gas is sufficiently large. Since it is not decomposed, there are problems that impurities are mixed into the thin film and the film forming speed is reduced. On the other hand, if the RF power is increased to promote decomposition of the reaction gas, the substrate or the thin film may be deteriorated.

Therefore, as a method for promoting the decomposition of the reaction gas to form a thin film on the substrate, for example, a method using a plasma CVD apparatus 100 as shown in FIG.
In FIG. 3, reference numeral 101 denotes a high frequency power source, 102 denotes a substrate side electrode, 103 denotes a shower head, 104 denotes a carrier gas, 105 denotes a source gas, 106 denotes a fine particle, 107 denotes a substrate, 108 denotes a quartz film, 109 denotes a container, and 110 denotes Liquid raw material, 111 is a flow meter, 112 is piping, 113 is a vacuum pump, and 114 is a film forming chamber.

In the film forming method using the plasma CVD apparatus 100, high-frequency power sources 101 such as an RF power source and a microwave power source apply high frequencies of different frequencies to the substrate-side electrode 102 and the shower head 103, respectively. As a result, the plasma density in the region between the substrate-side electrode 102 and the shower head 103 can be increased. In this region, the decomposition efficiency of the source gas 105 transferred into the film formation chamber 114 by the carrier gas 104 is increased. Can be improved.
Such a CVD apparatus that applies a high frequency to both the substrate-side electrode 102 and the shower head 103 is called an inductively coupled plasma-enhanced (CVD) -CVD apparatus. The present invention can be widely applied to fields such as device manufacturing and packaging.

In this plasma CVD apparatus 100, the source gas 105 is decomposed into ion species and active species in the vicinity of the shower head 103 by the high frequency applied to the shower head 103. The ionic species and active species that have passed through the pores 103a penetrating the shower head 103 are combined with each other by plasma energy or the like in the region between the substrate-side electrode 102 and the shower head 103, and have a certain size or more. Fine particles 106 are deposited on the substrate 107. The fine particles 106 deposited on the substrate 107 become particles formed in the quartz film 108.
In the plasma CVD apparatus 100, although the decomposition efficiency of the source gas 105 can be improved, as described in Patent Document 1, the source gas 105 is decomposed only near the surface of the substrate 107, and the quartz film 108 is It was not possible to prevent particles from entering.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma CVD apparatus that has high decomposition efficiency of source gas and suppresses the mixing of particles into a quartz film.

  A plasma CVD apparatus according to claim 1 of the present invention includes a film forming chamber, a first gas supply means for introducing a mixed gas composed of a first carrier gas and a source gas into the film forming chamber, and a second carrier gas. A second gas supply unit for introducing the film into the film formation chamber; and an exhaust unit for reducing the pressure in the film formation chamber. The film formation chamber includes a first space in which the mixed gas introduction unit is disposed. The second space in which the substrate-side electrode on which the substrate on which the thin film is formed is placed is disposed, and the first space and the second space are provided so as to be separated from each other. A plurality of shower heads, the second carrier gas introduction portion is provided in the gap between the shower heads, and a high frequency is applied to each of the shower head and the substrate-side electrode at least in the first stage among the shower heads. Apply It characterized by having a power supply means.

  The plasma CVD apparatus according to a second aspect of the present invention is the plasma CVD apparatus according to the first aspect, characterized in that the shower head arranged closest to the substrate side electrode is at the same potential as the film formation chamber.

  A plasma CVD apparatus according to a third aspect of the present invention is the plasma CVD apparatus according to the first aspect, wherein the introduction portion of the second carrier gas is arranged so as to introduce the second carrier gas in parallel to the gap between the shower heads. It is characterized by being.

  The plasma CVD apparatus according to a fourth aspect of the present invention is the plasma CVD apparatus according to the first aspect, wherein the introduction portion of the second carrier gas is arranged so as to introduce the second carrier gas perpendicular to the gap between the shower heads. It is characterized by being.

  The plasma CVD apparatus according to a fifth aspect of the present invention is the plasma CVD apparatus according to the first aspect, wherein the distance between the substrate and the shower head disposed closest to the substrate-side electrode is 20 mm or more and 200 mm or less. It is characterized by.

  The plasma CVD apparatus according to claim 6 of the present invention is characterized in that, in claim 1, the second carrier gas is oxygen.

  According to the plasma CVD apparatus of the present invention, the decomposition efficiency of the source gas can be increased, and the ion species and active species generated by the decomposition of the source gas are the second carrier gas on the substrate. Only a reaction can be performed to form a thin film, so that mixing of particles into the thin film can be significantly suppressed.

  Hereinafter, a plasma CVD apparatus embodying the present invention will be described in detail with reference to the drawings.

(1) First Embodiment FIG. 1 is a schematic configuration diagram showing a first embodiment of a plasma CVD apparatus according to the present invention.
In FIG. 1, reference numeral 1 is a plasma CVD apparatus, 2 is a film forming chamber, 3 is a first gas supply means, 4 is a second gas supply means, 5 is an exhaust means, 6 is a first space, and 7 is a first gas supply means. Second space, 8 is a shower head, 8A is a first shower head, 8B is a second shower head, 9 is a substrate side electrode, 10 is a power supply means, 11 is a first carrier gas, 12 is a liquid raw material, 13 is a container, 14 is a flow meter, 15 is a pipe, 16 is a mixed gas, 17 is an introduction part, 18 is a second carrier gas, 19 is a flow meter, 20 is a pipe, 21 is an introduction part, 22 is a substrate, 23 Indicates a thin film, 24 indicates a fine particle, and 25 indicates a gap.

In the plasma CVD apparatus 1 of this embodiment, the film forming chamber 2, the first carrier gas 11 and the mixed gas 16 made of the raw material gas generated by vaporizing the liquid raw material 12 are introduced into the film forming chamber 2. Gas supply means 3, second gas supply means 4 for introducing the second carrier gas 18 into the film forming chamber 2, and exhaust means 5 for reducing the pressure inside the film forming chamber 2 to a predetermined pressure. ing.
The film formation chamber 2 has a first space 6 in which the introduction portion 17 of the mixed gas 16 is disposed and a second space in which the substrate side electrode 9 on which the substrate 22 on which the thin film 23 is formed is disposed. 7 and a shower head 8 composed of a first shower head 8A and a second shower head 8B, which are provided so as to be divided at a predetermined interval so as to divide the first space 6 and the second space 7. It is composed of

In addition, an introduction part 21 for the second carrier gas 18 is provided in the gap 25 between the first shower head 8A and the second shower head 8B. The introduction part 21 is connected to the first shower head 8A. It arrange | positions so that the 2nd carrier gas 18 may be introduce | transduced in parallel with respect to the gap | interval 25 of the 2nd shower head 8B.
Furthermore, the plasma CVD apparatus 1 includes a power supply unit 10 that applies a high frequency to each of the first shower head 8 </ b> A and the substrate-side electrode 9.

  In the plasma CVD apparatus 1, the second shower head 8 </ b> B arranged closest to the substrate-side electrode 9 is not connected to the power supply means 10 for applying a high frequency, and the second shower head 8 </ b> B The film forming chamber 2 is at the same potential. Thereby, abnormal discharge at the time of RF application is less likely to occur, and not only the amount of particles mixed into the thin film 23 is reduced, but also malfunction of the plasma CVD apparatus 1 is less likely to occur.

The distance between the substrate 22 placed on the substrate side electrode 9 and the second shower head 8B disposed closest to the substrate side electrode 9 is preferably 20 mm or more and 200 mm or less, and 20 mm or more. More preferably, it is 100 mm or less.
If the distance between the substrate 22 and the second shower head 8B is less than 20 mm, the in-plane uniformity of the thin film 23 formed on the substrate 22 deteriorates. On the other hand, when the distance between the substrate 22 and the second shower head 8B exceeds 200 mm, the formation of particles proceeds in the space between the substrate 22 and the second shower head 8B, and into the thin film 23. The amount of mixed particles increases.

  The second carrier gas 18 is preferably oxygen. As a result, the ion species and active species that have moved into the second space 7 react with oxygen as the second carrier gas 18 only on the substrate 22 to form the thin film 23 on the substrate 22.

  The first gas supply means 3 includes a flow meter 14 for controlling the flow rate of the first carrier gas 11 and the flow rate of the raw material gas generated by vaporizing the liquid raw material 12 contained in the container 13, The pipe 15 is connected to the flow meter 14 and the introduction unit 20, and includes a first carrier gas 11 and a pipe 15 for introducing a mixed gas 16 made of a raw material gas into the film forming chamber 2.

  The second gas supply means 4 is connected to a flow meter 19 for controlling the flow rate of the second carrier gas 18 and to the flow meter 19 and the introduction part 21, and the second carrier gas 18 is supplied to the first shower head 8 </ b> A. And a pipe 20 introduced into the gap 25 of the second shower head 8B.

  As the exhaust means 5, a vacuum pump such as a mechanical booster pump or a dry pump is used. By this evacuation means 5, the atmospheric pressure (degree of vacuum) in the film forming chamber 2 is maintained at a predetermined value.

The first shower head 8 </ b> A and the second shower head 8 </ b> B are provided with a large number of pores 8 a penetrating the shower head in a direction perpendicular to the gap 25.
The pores 8a allow ionic species and active species generated by the source gas to be decomposed by the high frequency applied to the first shower head 8A, or fine particles formed by aggregation of ionic species and active species. Is provided.

As the substrate side electrode 9, aluminum or stainless steel is used.
The power supply means 10 is not particularly limited as long as it can apply different electric power and high frequency with different frequencies to the first shower head 8A and the substrate-side electrode 9, respectively. A high frequency power source such as an RF power source or a microwave power source can be used.

In this embodiment, the shower head 8 has a two-stage structure including the first shower head 8A and the second shower head 8B. However, the plasma CVD apparatus of the present invention is not limited to this. Absent. In the plasma CVD apparatus of the present invention, the shower heads may be provided to be stacked in three or more stages at intervals.
Further, in the plasma CVD apparatus of the present invention, when the shower head is provided in three or more stages, the power supply means for applying a high frequency to each of the shower head and the substrate side electrode at least the first stage of the shower head is provided. What is necessary is just to provide. In the plasma CVD apparatus of the present invention, the first-stage shower head is a shower head arranged closest to the introduction portion of the source gas.

Next, a method for forming the thin film 23 on the substrate 22 using the plasma CVD apparatus 1 of this embodiment will be described.
In order to form the thin film 23 on the substrate 22 using the plasma CVD apparatus 1, the raw material liquid 12 which is the raw material of the thin film 23 accommodated in the container 13 is vaporized to be a raw material gas, and this raw material gas Is mixed with the first carrier gas 11 to form a mixed gas 16, which is introduced into the first space 6 of the film forming chamber 2 from the introduction portion 17 through the pipe 15.

At this time, the flow rates of the source gas and the first carrier gas 11 are controlled by the flow meter 14.
Further, the flow rate of the first carrier gas 11 is set to 100 sccm or more and 3000 sccm or less.
The flow rate of the raw material gas obtained by vaporizing the raw material liquid 12 is set to 5 sccm or more and 100 sccm or less.

Further, the air pressure in the film forming chamber 2 is maintained at a predetermined value by the exhaust means 5.
The atmospheric pressure in the film forming chamber 2 is set to 10 ⁻⁵ Pa to 100 Pa.

Further, the power supply means 10 applies different electric power and high frequency with different frequencies to the first shower head 8A and the substrate side electrode 9, respectively. There is a potential difference between them.
The high frequency power applied to the first shower head 8A is 5 W or more and 200 W or less, and the frequency is 10 MHz or more and 27 MHz or less.
The high frequency power applied to the substrate side electrode 9 is 100 W or more and 1000 W or less, and the frequency is 100 kHz or more and 500 kHz or less.

The source gas 16 introduced into the first space 6 is decomposed into ionic species and active species by the high frequency applied to the first shower head 8A.
Ion species and active species generated by the decomposition of the raw material gas 16 pass through the pores 8a of the first shower head 8A and move to the gap 25 between the first shower head 8A and the second shower head 8B.

The ionic species and active species that have moved into the gap 25 between the first shower head 8A and the second shower head 8B are introduced into the gap 25 in parallel to the gap 25 from the introduction portion 21 and are the first species made of oxygen. The second carrier gas 18 passes through the pores 8a of the second shower head 8B and moves to the second space 7.
The flow rate of the second carrier gas 18 is 25 sccm or more and 750 sccm or less.

The ion species and active species that have moved into the second space 7 react with oxygen as the second carrier gas 18 on the substrate 22 to form a thin film 23 on the substrate 22.
Further, in the method for forming the thin film 23 using the plasma CVD apparatus 1, the fine particles 24 in which the ion species and the active species are aggregated are much smaller than those in the conventional art. Therefore, it is possible to prevent the fine particles 24 from being deposited on the substrate 22 or the thin film 23 and mixed into the thin film 23 as particles.

  According to the plasma CVD apparatus 1 of this embodiment, the second carrier gas made of oxygen in the gap 25 between the first shower head 8A and the second shower head 8B in parallel to the gap 25 from the introduction portion 21. 18 is introduced, so that the decomposition efficiency of the raw material gas can be increased, and the ion species and active species generated by the decomposition of the raw material gas are allowed to react only with the second carrier gas 18 on the substrate 22; A thin film 23 having a substantially uniform in-plane film thickness distribution can be formed. In addition, mixing of particles into the thin film 23 can be significantly suppressed.

(2) Second Embodiment FIG. 2 is a schematic configuration diagram showing a second embodiment of the plasma CVD apparatus according to the present invention.
In FIG. 2, the same components as those in the plasma CVD apparatus 1 shown in FIG.
The plasma CVD apparatus 30 of this embodiment is different from the plasma CVD apparatus 1 described above in that the introduction part 31 of the second carrier gas 18 is provided in the gap 25 between the first shower head 8A and the second shower head 8B. The introduction portion 31 is disposed so as to introduce the second carrier gas 18 perpendicularly to the gap 25 between the first shower head 8A and the second shower head 8B. It is.

  According to the plasma CVD apparatus 30 of this embodiment, the second carrier gas made of oxygen is perpendicular to the gap 25 from the introduction portion 31 in the gap 25 between the first shower head 8A and the second shower head 8B. 18 is introduced, so that the decomposition efficiency of the raw material gas can be increased, and the ion species and active species generated by the decomposition of the raw material gas are allowed to react only with the second carrier gas 18 on the substrate 22; It is possible to form the thin film 23 that is more excellent in the uniformity of the in-plane film thickness distribution than in the second embodiment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

Example 1
A thin film 23 made of silicon dioxide was formed on a substrate 22 made of silicon having a diameter of 100 mm using the plasma CVD apparatus 1 shown in FIG.
In Example 1, the gap 25 between the first shower head 8A and the first shower head 8B was 5 mm.
The temperature of the substrate 22 is 380 ° C., the pressure in the deposition chamber 2 is 20 Pa, the flow rate of the first carrier gas 11 is 600 sccm, the flow rate of the second carrier gas 18 is 150 sccm, and tetraethyl silicate ( The flow rate of the source gas obtained by vaporizing Si (OC ₂ H ₅ ) ₄ ) was 12.5 sccm.
The RF power applied to the first shower head 8A was 80 W, and the frequency was 13.56 MHz. The RF power applied to the substrate side electrode 9 was 600 W, and the frequency was 380 kHz.
Under the above conditions, the thickness of the thin film 23 made of silicon dioxide formed on the substrate 22 was 10.5 μm, and the film thickness distribution in the surface of the substrate 22 was ± 7%.
In addition, after cleaning the inside of the film forming chamber 2, the number of particles having a diameter of 1 μm or more present in the thin film 23 formed on the fifth substrate 22 was 30.

(Comparative Example 1)
A thin film 23 made of silicon dioxide was formed on a substrate 22 made of silicon having a diameter of 100 mm using the plasma CVD apparatus 1 shown in FIG.
In Example 1, the gap 25 between the first shower head 8A and the first shower head 8B was 5 mm.
The temperature of the substrate 22 is 380 ° C., the pressure in the deposition chamber 2 is 20 Pa, the flow rate of the first carrier gas 11 is 750 sccm, the flow rate of the second carrier gas 18 is 0 sccm, and tetraethyl silicate ( The flow rate of the source gas obtained by vaporizing Si (OC ₂ H ₅ ) ₄ ) was 12.5 sccm.
The RF power applied to the first shower head 8A was 80 W, and the frequency was 13.56 MHz. The RF power applied to the substrate side electrode 9 was 600 W, and the frequency was 380 kHz.
Under the above conditions, the thickness of the thin film 23 made of silicon dioxide formed on the substrate 22 was 10.0 μm, and the film thickness distribution in the plane of the substrate 22 was ± 6.5%.

(Example 2)
A thin film 23 made of silicon dioxide was formed on a substrate 22 made of silicon having a diameter of 100 mm using the plasma CVD apparatus 1 shown in FIG.
In Example 1, the gap 25 between the first shower head 8A and the first shower head 8B was 5 mm.
The temperature of the substrate 22 is 380 ° C., the pressure in the deposition chamber 2 is 20 Pa, the flow rate of the first carrier gas 11 is 600 sccm, the flow rate of the second carrier gas 18 is 150 sccm, and tetraethyl silicate ( The flow rate of the source gas obtained by vaporizing Si (OC ₂ H ₅ ) ₄ ) was 12.5 sccm.
The RF power applied to the first shower head 8A was 80 W, and the frequency was 13.56 MHz. The RF power applied to the substrate side electrode 9 was 600 W, and the frequency was 380 kHz.
Under the above conditions, the thickness of the thin film 23 made of silicon dioxide formed on the substrate 22 was 10.0 μm, and the film thickness distribution in the plane of the substrate 22 was ± 3%.
Further, after the inside of the film forming chamber 2 was cleaned, the number of particles having a diameter of 1 μm or more present in the thin film 23 formed on the fifth substrate 22 was 37.

  The plasma CVD apparatus of the present invention can also be applied to the formation of insulating films and optical waveguides for semiconductor devices.

1 is a schematic configuration diagram showing a first embodiment of a plasma CVD apparatus according to the present invention. It is a schematic block diagram which shows 2nd embodiment of the plasma CVD apparatus which concerns on this invention. It is a schematic block diagram which shows the conventional plasma CVD apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plasma CVD apparatus, 2 ... Film-forming chamber, 3 ... 1st gas supply means, 4 ... 2nd gas supply means, 5 ... Exhaust means, 6 ... 1st One space, 7 ... Second space, 8 ... Shower head, 8A ... First shower head, 8B ... Second shower head, 9 ... Substrate side electrode, 10. ..Power supply means, 11 ... first carrier gas, 12 ... liquid raw material, 13 ... vessel, 14 ... flow meter, 15 ... piping, 16 ... mixed gas, 17 ... Introduction part, 18 ... Second carrier gas, 19 ... Flow meter, 20 ... Piping, 21 ... Introduction part, 22 ... Substrate, 23 ... Thin film, 24. ..Fine particles, 25... Gap, 30... Plasma CVD apparatus, 31.

Claims (6)

Deposition chamber, first gas supply means for introducing a mixed gas composed of a first carrier gas and a source gas into the film formation chamber, and second gas supply means for introducing a second carrier gas into the film formation chamber And at least an exhaust means for decompressing the film forming chamber,
The film formation chamber includes a first space in which the mixed gas introduction unit is disposed, a second space in which a substrate-side electrode on which a substrate on which a thin film is formed is disposed, and the first space. And a plurality of shower heads provided to overlap with each other so as to divide the second space,
In the gap between the shower heads, an introduction part for the second carrier gas is provided,
A plasma CVD apparatus comprising power supply means for applying a high frequency to each of at least the first shower head of the shower head and the substrate-side electrode.   2. The plasma CVD apparatus according to claim 1, wherein the shower head disposed closest to the substrate-side electrode is at the same potential as the film formation chamber.   2. The plasma CVD apparatus according to claim 1, wherein the introduction portion of the second carrier gas is arranged so as to introduce the second carrier gas in parallel to the gap between the shower heads.   2. The plasma CVD apparatus according to claim 1, wherein the introduction portion of the second carrier gas is disposed so as to introduce the second carrier gas perpendicular to the gap between the shower heads.   2. The plasma CVD apparatus according to claim 1, wherein a distance between the substrate and a shower head disposed closest to the substrate-side electrode is 20 mm or more and 200 mm or less. The plasma CVD apparatus according to claim 1, wherein the second carrier gas is oxygen.

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