JPH09266201A - Plasma cvd apparatus - Google Patents

Abstract

(57) Abstract: The present invention relates to a plasma C having good reproducibility of film quality and film thickness distribution of an obtained film with respect to an increase of accumulated deposition film thickness.
An object is to provide a VD device. SOLUTION: In a plasma CVD apparatus in which an inner chamber is provided in a container connected to a vacuum exhaust device, and a high frequency applying electrode having a gas inlet in the inner chamber and a substrate stand are provided, a high frequency applying electrode of the inner chamber is provided. , And the inner walls other than the substrate table are covered with an insulator, the corners of the inner chamber are covered with an insulator, or only the high-frequency applying electrode is covered with an insulator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a thin film which constitutes a semiconductor element in manufacturing a semiconductor element such as a thin film transistor for a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, in manufacturing a semiconductor device such as a thin film transistor for a liquid crystal display, a method of forming an amorphous silicon film or a silicon nitride film constituting the device is to use a raw material gas (SiH ₄ , H ₂ , NH ₃ , N ₂
Is generally used for plasma chemical vapor deposition (plasma CVD), in which the plasma is decomposed by high frequency power or microwave power and deposited on a substrate such as glass.
As an apparatus for performing this, for example, 1. 1. A parallel plate capacitively coupled plasma CVD apparatus in which a high-frequency electrode and a substrate stand are provided in a vacuum container; 2. A plasma CVD apparatus in which an inner chamber is provided in a vacuum container, a high-frequency electrode and a substrate stand are provided in the inner chamber, and a film is formed in the inner chamber. There has been a plasma CVD apparatus in which the inside of the inner chamber is covered with an insulator (Japanese Patent Laid-Open No. 7-230956: FIG. 5).

[0003]

Of the conventional techniques, one
In the case of the parallel plate capacitively coupled plasma CVD apparatus as shown in, the film deposited on the portion other than the substrate in the processing chamber is
There is a problem in that the film is peeled off during the film forming process and causes particles.

To solve this problem, a discharge chamber (inner chamber) having a double structure such as 2, 3 is used, and the substrate table and the high-frequency electrode are heated to raise the temperature of the entire inner chamber. It is possible to make the film deposited on an unnecessary portion of the inner wall of the inner chamber) dense and prevent the film from peeling off. Furthermore, by covering the inside of the inner chamber with an insulator having a lower thermal conductivity than the conductor as in 3,
It is possible to enhance the heat retaining effect of the inner chamber.

However, a discharge chamber having a double structure like 2, 3
In the case of (inner chamber) configuration, it is applied to the high frequency electrode
High-frequency power peak to peak voltage (V_PP), And high frequency
Electrode self-bias voltage (V_DC) Fluctuates. For example, 2
In the case of a plasma CVD apparatus like that shown in FIG.
U, V_PP, V_DCThe value of increases as the accumulated film thickness increases.
Absolute value decreases. In FIG. 4, V as the cumulative film thickness increases
_PPShows the change of V_DCThe same applies to changes in the absolute value of
there were. After accumulating a 2 μm thick silicon nitride film
Is 50V or more with respect to the initial value_PP, V_DCBoth strange
The movement was confirmed. As a result, plasma generated by discharge
The state and density of the mask have changed, and the film quality and film thickness distribution have changed.
There was a problem that occurred. Next, as in 3 (Fig. 5)
When the entire inner wall of chamber 1 is covered with insulators 20, 21, 22
Under the same discharge conditions as the device of No. 2 _PP, V_DCInitial value of
250V, -200V, which is relatively small,
20V or less even after depositing a 2 μm thick silicon nitride film
Can be suppressed by the fluctuation of. However, for the same input power,
There was a problem that the film formation speed was low,
The start is unstable, and the quality of the discharge and the film quality and film thickness distribution
There was a problem of poor reproducibility.

[0006]

SUMMARY OF THE INVENTION The present invention is a plasma CVD apparatus having a double structure discharge chamber (inner chamber) having a characteristic that generation of particles during film formation can be suppressed. limit may stabilize on, i.e., while maintaining the discharge initiation and discharge repeatability, as a parameter representative discharge V _DC of V _PP and the high-frequency electrode of the high frequency power, an increase in cumulative deposition thickness It is intended to provide a plasma CVD apparatus that suppresses fluctuation with respect to the film and has good reproducibility of the film quality and film thickness distribution of the obtained film.

That is, the present invention provides a plasma CVD apparatus in which an inner chamber is provided in a container connected to a vacuum exhaust device, and a high-frequency applying electrode having a gas inlet and a substrate stand are provided in the inner chamber. The high frequency applying electrode and the inner wall other than the substrate stand are covered with an insulator, the corners of the inner chamber are covered with an insulator, or only the high frequency applying electrode is covered with an insulator. By the means, the fluctuation of V _PP and V _DC when the deposition process of the insulating film such as the silicon nitride film is continued is remarkably suppressed.
In addition to these means, the thickness of the insulator or semi-insulator provided in the inner chamber should be 5 μm or more so that V _PP of the high-frequency power applied to the high-frequency electrode and V _{DC of the} high-frequency electrode become predetermined values. In addition to this, by controlling the magnitude of the applied high frequency power, the introduction of the high frequency power into the plasma is further stabilized.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Representative embodiments of the present invention will be described below with reference to the drawings (FIGS. 1 to 6).

(Embodiment 1) FIG. 1 shows a schematic cross-sectional view of a plasma CVD apparatus in which an inner wall other than a high frequency applying electrode in an inner chamber and a substrate stand is covered with an insulator. In FIG. Vacuum container, 2 inner chamber, 3 inner chamber upper lid, 4 upper electrode (high frequency electrode), 5 heater, 6 high frequency electrode plate with gas introduction hole, 7 high frequency introduction terminal, 8 gas introduction Port, 9 is a vacuum exhaust port, 10 is a lower electrode (substrate table),
11 is a lower lid of the inner chamber, 12 is a substrate, 13 is a heater, 14
Is plasma, 15 is a substrate push-up pin, 16 is an upper lid corner portion cover, 17 is a side wall cover, and 18 is a lower lid corner portion cover.

The operation of the plasma CVD apparatus configured as described above will be described below. The vacuum container 1 is evacuated by a vacuum pump (not shown) connected to the vacuum exhaust port 9 and kept at a predetermined pressure, and an internal chamber 2 for performing a film forming process is provided in the vacuum container 1. The inner chamber 2 includes an inner chamber upper lid 3 having an upper electrode 4 serving as a high frequency electrode, and a substrate 12
It is composed of an inner chamber lower lid 11 having a lower electrode 10 which serves as a substrate table on which the substrate is placed. For loading and unloading substrates, the inner chamber lower lid 1
1 moves downward, and the substrate push-up pin 14 causes the substrate 1
2 is lifted from the substrate table 10. The plasma 14 is generated in the inner chamber by supplying a raw material gas such as SiH ₄ , H ₂ , NH ₃ , and N ₂ into the inner chamber 2 from the gas introduction port 8 through the high-frequency electrode plate 6 having the gas introduction hole. After adjusting to a predetermined flow rate and pressure, a high frequency voltage is applied to the high frequency electrode 4 from a 13.56 MHz high frequency power source (not shown) through the high frequency introducing terminal 7. Since the high-frequency electrode plate 6 and the substrate table 10 are directly exposed to plasma, it is desirable to use a material such as Al that does not easily deteriorate by cleaning with NF ₃ .

Silicon oxide, silicon nitride, boron nitride, alumina, glass,
Provide an upper lid corner portion cover 16, a side wall cover 17, and a lower lid corner portion cover 18, which are made of any one of an insulator such as ceramics, a silicon carbide, and a semi-insulating semiconductor (semi-insulator) such as diamond. There is. The thickness of the cover needs to be at least 5 μm or more, because the influence of the decrease in the thickness of the insulator due to the cleaning using NF ₃ or the like is not a problem, and if the thickness is several mm, it is sufficient for regular use. is there. Further, these covers are detachable, so that they can be easily cleaned and replaced during regular maintenance.

Without these covers (prior art 2), large variations in V _PP as shown by the dotted line in FIG. 4 are observed. The change in absolute value of V _DC was almost the same as the change in V _PP . For example, as conditions for forming a silicon nitride film, SiH ₄ = 50 sccm, H ₂ = 200 sccm, N
H ₃ = 200 sccm, N ₂ = 300 sccm, pressure = 1
When Torr is set and the high frequency power is set to 1.5 kW, V _PP is about 600 V and _VDC is about -500 V in the initial stage,
The deposition rate is 2000Å / min, and the film thickness distribution on the substrate is ±
5% was obtained. However, as the accumulated deposited film thickness increases, the absolute values of V _PP and V _DC decrease, and the accumulated deposited film thickness becomes 2 μm.
At m, V _PP was about 550 V, V _DC was about -550 V, the film forming rate was ~ 2200 Å / min, and the film thickness distribution on the substrate was ± 20%, which means that the initial film forming characteristics were not maintained. . This is because the silicon nitride film is deposited on the inner chamber inner wall other than the substrate, and the capacity of the inner chamber fluctuates, so the application of high-frequency power to the inner chamber becomes non-uniform, and the shape of the discharge and the plasma concentration distribution It is thought that this is because the film formation rate and the film thickness distribution change as a result.

On the other hand, the inventors of the present invention have previously covered an insulator or a semi-insulating cover in the inner chamber in order to suppress the influence of the insulating film deposition in the inner chamber which causes the influence of the discharge and the variation of the film formation. It has been found that the provision of is extremely effective. That is, by newly providing an insulating or semi-insulating upper lid corner portion cover 16, side wall cover 17, and lower lid corner portion cover 18 each having a thickness of about several mm, the insulating film deposited by the film forming process other than the substrate Capacitance change is suppressed and even if the accumulated deposited film thickness increases. It is possible to realize stable high-frequency power input and discharge and film formation processing with excellent reproducibility.

The change in V _PP in this embodiment is shown by the solid line in FIG. The material of each cover was quartz. The change in the absolute value of V _DC was almost the same as the change in V _PP . As processing conditions, SiH ₄ = 50 sccm, H ₂ = 200 sc
cm, NH ₃ = 200 sccm, N ₂ = 300 sccm,
The pressure was 1 Torr and the high frequency power was 1.5 kW. Under these processing conditions, V _PP was about 300 V and _VDC was about -200 V in the initial stage, and the film formation rate of the silicon nitride film was 1700 Å / min, and the film thickness distribution on the substrate was ± 5%. On the other hand, when the accumulated deposited film thickness is 2 μm,
Both V _PP and V _DC were suppressed to fluctuations of about 5 V or less. Further, the film forming rate was ˜1700 Å / min, and the film thickness distribution on the substrate was ± 5%, which maintained the initial film forming characteristics.

(Embodiment 2) FIG. 2 shows a schematic sectional view of a plasma CVD apparatus in which a corner portion of an inner chamber is covered with an insulator. In FIG. 2, 1 is a vacuum container, 2 is an inner chamber,
3 is an upper lid of the inner chamber, 4 is an upper electrode (high frequency electrode), 5 is a heater, 6 is a high frequency electrode plate having a gas introduction hole, 7 is a high frequency introduction terminal, 8 is a gas introduction port, 9 is a vacuum exhaust port, 10
Is a lower electrode (substrate base), 11 is a lower lid of the inner chamber, 12 is a substrate, 13 is a heater, 14 is plasma, 15 is a substrate push-up pin, and 16 is an upper lid corner portion cover.

The operation of the plasma CVD apparatus constructed as above will be described below. The vacuum container 1 is evacuated by a vacuum pump (not shown) connected to the vacuum exhaust port 9 and kept at a predetermined pressure, and an internal chamber 2 for performing a film forming process is provided in the vacuum container 1. The inner chamber 2 includes an inner chamber upper lid 3 having an upper electrode 4 serving as a high frequency electrode, and a substrate 12
It is composed of an inner chamber lower lid 11 having a lower electrode 10 which serves as a substrate table on which the substrate is placed. For loading and unloading substrates, the inner chamber lower lid 1
1 moves downward, and the substrate push-up pin 14 causes the substrate 1
2 is lifted from the substrate table 10. The plasma 14 is generated in the inner chamber by supplying a raw material gas such as SiH ₄ , H ₂ , NH ₃ , and N ₂ into the inner chamber 2 from the gas introduction port 8 through the high-frequency electrode plate 6 having the gas introduction hole. After adjusting to a predetermined flow rate and pressure, a high frequency voltage is applied to the high frequency electrode 4 from a 13.56 MHz high frequency power source (not shown) through the high frequency introducing terminal 7. Since the high-frequency electrode plate 6 and the substrate table 10 are directly exposed to plasma, it is desirable to use a material such as Al that does not easily deteriorate by cleaning with NF ₃ .

In the corner portion of the inner chamber, any one of an insulator such as silicon oxide, silicon nitride, boron nitride, alumina, glass, ceramics, and a semi-insulating semiconductor (semi-insulator) such as silicon carbide or diamond is used. An upper lid corner portion cover 16 made of a material is provided. The thickness of the cover needs to be at least 5 μm or more, because the influence of the decrease in the thickness of the insulator due to the cleaning using NF ₃ or the like is not a problem, and if the thickness is several mm, it is sufficient for regular use. is there. Further, these covers are detachable, so that they can be easily cleaned and replaced during regular maintenance.

V in this embodiment_PP, V_DCFigure of fluctuation
4 is indicated by a chain line. The material of the cover was quartz. What
Oh, V_DCChange in absolute value of V_PPIs almost the same as
Was. As processing conditions, SiH_Four= 50 sccm, H_Two=
200 sccm, NH_Three= 200 sccm, N_Two= 300
sccm, pressure = 1 Torr, high frequency power 1.5
It was set to kW. Under this processing condition, V is initially_PPIs about 400
V, V_DCIs about -250 V, and a silicon nitride film is formed.
1800 Å / min as speed, film thickness distribution on the substrate is ± 5%
was gotten. On the other hand, when the accumulated film thickness is 2 μm
Is V_PP, V_DCBoth are suppressed to less than 10V fluctuation
Was. Furthermore, the film formation rate is ~ 1900Å / min, on the substrate
The film thickness distribution is ± 7%, which maintains the initial film formation characteristics.
Was. In the present embodiment, V_PP, V_DCMeasure
High frequency so that the fluctuation of the measured value is within the specified range.
By providing a mechanism for controlling the magnitude of wave power, V
_PP, V _DCBoth are suppressed to less than about 5V fluctuation, and further
The film speed is ~ 1900Å / min, the film thickness distribution on the substrate is ±
It is possible to maintain almost the initial film formation characteristics of 5%.
Came.

(Embodiment 3) FIG. 3 shows a plasma CVD apparatus in which only a high frequency applying electrode is covered with an insulator.
, 1 is a vacuum container, 2 is an inner chamber, 3 is an inner chamber upper lid,
4 is an upper electrode (high frequency electrode), 5 is a heater, 6 is a high frequency electrode plate having gas introduction holes, 7 is a high frequency introduction terminal, 8
Is a gas inlet port, 9 is a vacuum exhaust port, 10 is a lower electrode (substrate base), 11 is a lower lid of the inner chamber, 12 is a substrate, 13 is a heater, 14 is plasma, 15 is a substrate push-up pin, and 19 is a high-frequency electrode plate. It is a cover.

The operation of the plasma CVD apparatus configured as described above will be described below. The vacuum container 1 is evacuated by a vacuum pump (not shown) connected to the vacuum exhaust port 9 and kept at a predetermined pressure, and an internal chamber 2 for performing a film forming process is provided in the vacuum container 1. The inner chamber 2 includes an inner chamber upper lid 3 having an upper electrode 4 serving as a high frequency electrode, and a substrate 12
It is composed of an inner chamber lower lid 11 having a lower electrode 10 which serves as a substrate table on which the substrate is placed. For loading and unloading substrates, the inner chamber lower lid 1
1 moves downward, and the substrate push-up pin 14 causes the substrate 1
2 is lifted from the substrate table 10. The plasma 14 is generated in the inner chamber by supplying a raw material gas such as SiH ₄ , H ₂ , NH ₃ , and N ₂ into the inner chamber 2 from the gas introduction port 8 through the high-frequency electrode plate 6 having the gas introduction hole. After adjusting to a predetermined flow rate and pressure, a high frequency voltage is applied to the high frequency electrode 4 from a 13.56 MHz high frequency power source (not shown) through the high frequency introducing terminal 7. Since the high-frequency electrode plate 6 and the substrate table 10 are directly exposed to plasma, it is desirable to use a material such as Al that does not easily deteriorate by cleaning with NF ₃ .

The high-frequency electrode plate is made of any one of an insulator such as silicon oxide, silicon nitride, boron nitride, alumina, glass, ceramics, or a semi-insulating semiconductor (semi-insulator) such as silicon carbide or diamond. A high frequency electrode cover 19 is provided. By providing an insulating or semi-insulating cover on the high-frequency electrode, fluctuations in capacitance of the high-frequency electrode with respect to the inside of the inner chamber are suppressed. The thickness of the cover should be at least 5 μm because the influence of the decrease in the thickness of the insulator due to the cleaning using NF ₃ etc. does not matter.
m or more is necessary, and a thickness of several mm is sufficient for regular use. Further, these covers are detachable, so that they can be easily cleaned and replaced during regular maintenance.

The variation of V _PP and V _DC in this embodiment is shown by the solid line 3 in FIG. The material of the cover was quartz. In addition,
The change in absolute value of V _DC was almost the same as the change in V _PP .
As processing conditions, SiH ₄ = 50 sccm, H ₂ = 20
0 sccm, NH ₃ = 200 sccm, N ₂ = 300 sc
cm, pressure = 1 Torr, high frequency power 1.5 kW
And Under this processing condition, V _PP is about 300V, V
_DC was about -200 V, the film formation rate of the silicon nitride film was 1400 Å / min, and the film thickness distribution on the substrate was ± 5%. On the other hand, when the accumulated deposition film thickness is 2 μm, V
Both _PP and _VDC were suppressed to less than about 7V. Further, the film forming rate was up to 1500 Å / min, and the film thickness distribution on the substrate was ± 7%, which means that almost the initial film forming characteristics were maintained.

[0023]

As described above, according to the present invention, in addition to the feature of suppressing the generation of particles during film formation, high frequency is used as a typical discharge parameter while maintaining the start of discharge and the reproducibility of discharge. Electric power V _PP and high frequency electrode V
_It is possible to obtain an advantageous effect that the _DC is suppressed from varying with an increase in the accumulated deposition film thickness, and the film quality and the film thickness distribution of the obtained film are good.

[Brief description of drawings]

FIG. 1 is a plasma C according to a first embodiment of the present invention.
Sectional view of VD device

FIG. 2 is a plasma C according to a second embodiment of the present invention.
Sectional view of VD device

FIG. 3 is a plasma C according to a third embodiment of the present invention.
Sectional view of VD device

FIG. 4 is an increase in cumulative deposited film thickness and a change in V _{PP in} the plasma CVD apparatus according to the present invention and the prior art.

FIG. 5 is a conventional dual structure plasma CVD apparatus in which an inner wall is covered with an insulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Inner chamber 3 Inner chamber upper lid 4 Upper electrode (high frequency electrode) 5 Heater 6 High frequency electrode plate with gas introduction hole 7 High frequency introduction terminal 8 Gas introduction port 9 Vacuum exhaust port 10 Lower electrode (substrate table) 11 Inner chamber lower lid 12 Substrate 13 Heater 14 Plasma 15 Substrate push-up pin 16 Upper lid corner cover 17 Side wall cover 18 Lower lid corner cover 19 Upper electrode (high frequency electrode) cover

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichiro Ishihara 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A plasma CVD apparatus in which an inner chamber is provided in a container connected to a vacuum exhaust device, and a high frequency applying electrode having a gas inlet and a substrate stand are provided in the inner chamber. A plasma CVD apparatus characterized in that an inner wall other than the electrodes and the substrate stand is covered with an insulator or a semi-insulator. 2. A plasma CVD apparatus in which an inner chamber is provided in a container connected to a vacuum exhaust device, and a high-frequency applying electrode having a gas inlet and a substrate table are provided in the inner chamber, a corner portion of the inner chamber. Is covered with an insulator or a semi-insulator. 3. A plasma CVD apparatus in which an inner chamber is provided in a container connected to a vacuum evacuation device, and a high frequency applying electrode having a gas inlet and a substrate stand are provided in the inner chamber. A plasma CVD apparatus characterized in that only electrodes are covered with an insulator or a semi-insulator. 4. The plasma CVD apparatus according to claim 1 or 2, wherein the thickness of the insulator or semi-insulator provided in the inner chamber is 5 μm or more. 5. A voltage component (V _PP ) of the high frequency power applied to the high frequency electrode, and a self-bias voltage (V) of the high frequency electrode.
The plasma CVD apparatus according to claim 1 or 2, wherein the magnitude of the applied high-frequency power is controlled so that _DC ) becomes a predetermined value. 6. The plasma CVD apparatus according to claim 1, wherein the high frequency applying electrode in the inner chamber and the substrate table are heated.