JP2013033806A - Semiconductor thin film manufacturing method and plasma cvd apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of forming a high quality semiconductor thin film and provide a plasma CVD apparatus achieving the manufacturing method.SOLUTION: A semiconductor thin film manufacturing method comprises: a process of decomposing a compound containing group 4 element atoms and hydrogen atoms into plasma and active species; and a process of depositing the active species on a substrate. In the decomposing process, plasma generation energy is intermittently supplied such that an idle period and a supply period is repeated, and the plasma generation energy temporarily varies in the supply period.

Description

  The present invention relates to a semiconductor thin film manufacturing method and manufacturing apparatus, and more particularly to a manufacturing method and manufacturing apparatus having a plasma enhanced chemical vapor deposition method used for manufacturing a hydrogenated amorphous silicon thin film in a silicon thin film solar cell.

  In recent years, hydrogenated amorphous silicon films have been applied to switching elements of display pixels in liquid crystal display devices, solar cells, and the like. As a method of depositing a hydrogenated amorphous silicon film, a plasma enhanced chemical vapor deposition (hereinafter referred to as “plasma CVD (chemical vapor deposition)”) is performed by decomposing a silane-based gas by performing continuous high-frequency discharge. Law is widely used.

  As a thin film forming method that is an extension of this continuous discharge plasma CVD method, a CVD method (hereinafter, referred to as intermittent discharge plasma CVD method) in which source gas is decomposed by intermittently performing high frequency discharge has been proposed.

  FIG. 9 is a diagram showing an outline of a conventional intermittent discharge plasma CVD apparatus 100. Referring to FIG. 9, intermittent discharge plasma CVD apparatus 100 includes a reaction chamber 1, a matching circuit 5, a high frequency power supply 3, and a modulation power supply 4. The high frequency power supply 3 of the intermittent discharge plasma CVD apparatus 100 uses a high frequency oscillator that can switch between an oscillation state and a stop state at a high speed by inputting a gate pulse signal.

  FIG. 10 is a diagram illustrating an output signal of the modulation power supply 4 and an output signal of the matching circuit 5. As shown in FIGS. 10A and 10B, time is shown on the horizontal axis and the amplitude of the output signal is shown on the vertical axis.

Referring to FIG. 10A, signal W1 that is an output signal (intermittent discharge waveform) of modulation power supply 4 is shown. The signal W1 is a gate pulse signal and has a period T. The amplitude of this signal W1 is in between time 0~t1 0, and outputs the _{V 1} was in between times t1 to t2 (time _{T on1).}

Referring to FIG. 10B, signal W2 that is an output signal of matching circuit 5 is shown. The amplitude of this signal W2 in accordance with the on-off state of the signal W1, in between times 0~t1 0, in between times t1 to t2 (time _{T on1)} outputs the _{V 1.}

  In the intermittent discharge plasma CVD apparatus 100, when a signal W1 having a gate pulse waveform is on (between times t1 and t2), an on state in which high-frequency power is output and discharge occurs, and when a signal W1 having a gate pulse waveform is off A hydrogenated amorphous silicon film is deposited by intermittent high-frequency discharge that repeatedly turns off the high-frequency power and turns off the discharge during the period from time 0 to t1.

  In this intermittent discharge plasma CVD method, the active radicals in the plasma, which cause dust generation, disappear in the off state where the discharge stops, so that generation of dust can be suppressed as compared with the conventional continuous discharge plasma CVD method.

  Regarding the intermittent discharge plasma CVD method, Japanese Patent Application Laid-Open No. 7-335560 (Patent Document 1) discloses that the amount of dust during discharge is reduced by two orders of magnitude due to intermittent discharge film formation modulated at several hundred to several thousand hertz. It is disclosed that there is no effect of suppressing the generation of dust in the modulation in a region other than the frequency. Furthermore, it is disclosed that the generation of dust cannot be suppressed at a low modulation frequency of 40 Hz or less, as in the case of conventional continuous discharge.

Further, when active radicals (for example, Si—H ₂ ) in the plasma are taken into the hydrogenated amorphous silicon thin film, the Si—H ₂ bond density in the film increases. However, the Si—H ₂ bond contained in the hydrogenated amorphous silicon thin film affects the film quality such as defect density, and the photoconductivity of the film and the ratio of photoconductivity to dark conductivity (hereinafter referred to as SN ratio (Signal)). to Noise Ratio))) and the performance of the optical semiconductor device is degraded.

In the intermittent discharge plasma CVD method, active radicals in the plasma are extinguished in an off state, so that active radicals (such as Si—H ₂ ) are less taken into the film than in the conventional continuous discharge plasma CVD method, resulting in high quality. It is possible to form hydrogenated amorphous silicon.

JP-A-7-335560

  In mass production processes such as switch elements for each display pixel in liquid crystal display devices and solar cells, it is important to improve the throughput of plasma CVD equipment from the viewpoint of investment cost of manufacturing equipment. Development is a problem.

  Although a satisfactory film is obtained to some extent by the intermittent discharge plasma CVD method, which is a solution to this problem, even the intermittent discharge plasma CVD method has a problem that the film quality deteriorates when the film forming speed is increased.

  Therefore, development of a method for forming a high-quality hydrogenated amorphous silicon film is desired continuously even during high-speed film formation.

  The object of the present invention was made to solve the above-mentioned problems, and a production method for forming a high-quality semiconductor thin film that suppresses generation of active radicals and can be sufficiently utilized as an optical semiconductor device such as a solar cell. And it is providing the plasma CVD apparatus which implement | achieves the manufacturing method.

  A method of manufacturing a semiconductor thin film according to an aspect of the present invention includes a step of decomposing a compound containing group 4 element atoms and hydrogen atoms into plasma and active species, and a step of depositing active species on a substrate. In the decomposition step, the plasma generation energy is intermittently supplied so as to repeat the pause period and the supply period, and the plasma generation energy fluctuates with time in the supply period.

  Preferably, the plasma generation energy is generated by a high frequency power source based on a signal obtained by combining two pulses having different voltage amplitudes.

  A plasma CVD apparatus according to another aspect of the present invention includes high-frequency power generation means and a reaction chamber that performs processing on a substrate disposed in a substrate disposition portion. A reference signal for decomposing a compound containing elemental atoms and hydrogen atoms into plasma and active species, depositing the active species on the substrate, and modulating the output of the high-frequency power generating means with different voltage amplitudes 2 It further comprises a modulation reference signal generating means for generating an intermittent signal in which two pulses are combined.

  Preferably, the modulation reference signal generation means includes a plurality of intermittent signal generation means and a signal synthesis means for synthesizing output signals output from each of the plurality of intermittent signal generation means.

  Preferably, the output signals of the plurality of intermittent signal generating means are synchronized with each other, have the same period, and have different duty ratios.

  Preferably, the output signals of the plurality of intermittent signal generating means are synchronized with each other and have a period that is an integral multiple of one period of the output signals of the plurality of intermittent signal generating means and different from each other. And the duty ratio is different.

  According to one embodiment of the present invention, a high-quality semiconductor thin film can be produced in a short time that can be sufficiently utilized as an optical semiconductor device such as a solar cell.

It is a figure which shows the structure of 100 A of capacitive coupling type plasma CVD apparatuses. It is a flowchart for demonstrating the plasma processing performed with the plasma CVD apparatus 100A of embodiment. It is a figure which shows the modulation | alteration reference signal (intermittent discharge waveform) W1A output from the signal synthetic | combination means 13, and the modulation | alteration high frequency electric power signal W2A output from the matching circuit 5. FIG. It is a figure which shows the modulation | alteration reference signal W1B output from the signal synthetic | combination means 13, and the modulation | alteration high frequency electric power signal W2B output from the matching circuit 5. It is a figure which shows the modulation | alteration reference signal W1C output from the signal synthetic | combination means 13, and the modulation | alteration high frequency electric power signal W2C output from the matching circuit 5. It is a figure for demonstrating the output signal W1A from the signal synthetic | combination means 13 of FIG. It is a figure for demonstrating the output signal W1C from the signal synthetic | combination means 13 of FIG. It is a figure which shows the table | surface which compared the characteristic of the hydrogenated amorphous silicon film formed by embodiment with the characteristic of the hydrogenated amorphous silicon film formed by the prior art example. It is a figure which shows the outline of the conventional intermittent discharge plasma CVD apparatus 100. FIG. FIG. 3 is a diagram illustrating an output signal of a modulation power supply 4 and an output signal of a matching circuit 5.

Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent part in a figure, and the description is not repeated.
[Configuration of Capacitively Coupled Plasma CVD Apparatus 100A Common to Each Embodiment]
FIG. 1 is a diagram showing a configuration of a capacitively coupled plasma CVD apparatus 100A. Referring to FIG. 1, plasma CVD apparatus 100 </ b> A includes a reaction chamber 1, a high frequency power supply 3, a modulation reference signal generating unit 4 </ b> A, and a matching circuit 5.

  The reaction chamber 1 includes a cathode electrode 2, an anode electrode 7, and a substrate 6. The reaction chamber 1 is composed of a casing that can be sealed. The substrate 6 carried into the reaction chamber 1 can be formed with a p-type layer and an n-type layer in the reaction chamber 1. The cathode electrode 2 and the anode electrode 7 are respectively installed in the reaction chamber 1 and have a parallel plate type electrode structure.

  The distance between the cathode electrode 2 and the anode electrode 7 is determined according to desired processing conditions, and is preferably 1 mm to 40 mm, for example.

  The matching circuit 5 connected to the cathode electrode 2 and the high-frequency power source 3 connected to the matching circuit 5 are respectively installed outside the reaction chamber 1. A high frequency power source 3 and a modulation power source 4 are connected to the cathode electrode 2 via a matching circuit 5. Plasma is generated between the cathode electrode 2 and the anode electrode 7 to which the substrate 6 is fixed.

  Further, in the plasma CVD apparatus 100A, a flow rate controller (not shown) introduces 10 sccm of silane gas and 130 sccm of hydrogen gas into the reaction chamber 1 while controlling the flow rate (the inlet is not shown), at a constant flow rate ratio. The pressure is evacuated and the pressure in the reaction chamber 1 is maintained at 4.0 Torr.

  The high frequency power supply 3 and the matching circuit 5 are connected, and the output signal of the high frequency power supply 3 is given to the matching circuit 5.

  The modulation reference signal generation means 4A includes intermittent signal generation sources 9 and 11, a circulator 10, an isolator 12, and a signal synthesis means 13. The modulation reference signal generating means 4A is connected to a connection node between the high frequency power supply 3 and the matching circuit 5. The output of the intermittent signal generation source 9 is given to the signal synthesis means 13 via the circulator 10, and the output from the intermittent signal generation source 11 is given to the signal synthesis means 13 via the isolator 12.

  The signal synthesizer 13 synthesizes the output signal and outputs it to the matching circuit 5. The respective signals output from the intermittent signal generation sources 9 and 11 are given to the signal synthesis means 13, and the synthesized signal is given to the input terminal of the matching circuit 5.

  The isolator 12 and the intermittent signal generation source 11 are connected in series between the signal synthesis means 13 and the ground potential. Further, the intermittent signal generation source 9 and the circulator 10 are connected in series between the signal synthesis means 13 and the ground potential.

  The signal output from the intermittent signal generation source 9 is input to the signal synthesis unit 13 via the circulator 10. The circulator 10 is a circuit means installed to prevent the reflected signal from the signal synthesizing means 13 from affecting the intermittent signal generation source 9. Note that other circuit means having the same function may be substituted. If the reflected signal in the signal synthesizing means 13 is small and does not affect the intermittent signal generation source 9, the circulator 10 may be omitted.

  On the other hand, the signal from the intermittent signal generation source 11 is input to the signal synthesis means 13 via the isolator 12. The isolator 12 is a circuit means installed so that the reflected signal in the signal synthesis means 13 does not affect the intermittent signal generation source 11, and other circuit means having the same function may be substituted. Further, the isolator 12 may be omitted if the reflected signal in the signal synthesizing means 13 is small and does not affect the intermittent signal generation source 11.

  The signal from the high frequency power source 3 is modulated by the intermittent signal from the signal synthesizing means 13 and input to the matching circuit 5. An output signal from the matching circuit 5 is input to the cathode electrode 2.

  FIG. 2 is a flowchart for explaining the plasma processing performed in plasma CVD apparatus 100A of the embodiment. With reference to FIG. 2, first, in order to perform plasma CVD processing, in step S <b> 11, a gas of a compound containing group 4 element atoms and hydrogen atoms is injected into reaction chamber 1.

  In step S12, a voltage is applied between the anode electrode 7 and the cathode electrode 2. By this treatment, the injected gas is ionized and separated into a plasma state or an active species state. The reaction chamber 1 is in a mixed state of plasma or active species.

  In step S <b> 13, the active species causes a chemical reaction on the surface of the substrate 6 and in the vicinity of the surface of the substrate 6 installed on the anode electrode, thereby generating an amorphous silicon film on the surface of the substrate 6.

In this way, it is possible to appropriately form an amorphous silicon film on the surface of the substrate 6 by setting the injected gas to a plasma state and an active species state.
[Embodiment]
FIG. 3 is a diagram showing a modulation reference signal (intermittent discharge waveform) W1A output from the signal synthesizing means 13 and a modulated high-frequency power signal W2A output from the matching circuit 5. Referring to FIG. 3, as shown in FIGS. 3A and 3B, time is shown on the horizontal axis and the amplitude of the signal is shown on the vertical axis. Here, the output signal of the modulated high-frequency power signal W2A is modulated by the on / off state of the modulation reference signal (intermittent discharge waveform) W1A.

FIG. 3A shows the modulation reference signal W1A output from the signal synthesis means 13. Referring to FIG. 3A, the modulation power supply signal W1A is a pulse signal having a two-stage pulse amplitude with a period T. Since the amplitude is 0 between time 0 and t1, no power is supplied. During this time 0 to t1, the signal W1A, which is a gate pulse signal, is in an off state. Time T1 to T12 (time _{T on1)} during the constant power amplitude _{V 1} is supplied, during the time T12～t2 (time _{T on2),} the power of the constant amplitude _{V 2 (V 2> V 1} ) Is supplied. Between times t1 and t2, the signal W1B, which is a gate pulse signal, is turned on. The signal W1A repeats the power supply as described above with a period T.

  On the other hand, the high frequency power supply 3 in FIG. 1 outputs a high frequency power signal (not shown) having an oscillation frequency of 13.56 MHz. This high frequency power signal is repeatedly switched on and off in a DC manner at regular intervals. In the embodiment, the interval on time is set to 0.5 msec, and the off time is set to 2.0 msec.

  Next, FIG. 3B is a diagram showing the modulated high-frequency power signal W2A output from the matching circuit 5. Referring to FIG. 3B, a signal W2A indicates a modulated high-frequency power signal obtained by modulating the on-state high-frequency power signal output from the high-frequency power source 3 by the modulation reference signal W1A in the matching circuit 5.

  This modulated high frequency power is supplied to the cathode electrode 2 via the matching circuit 5. As a result, a potential difference is generated in the region between the cathode electrode 2 and the anode electrode 7, and the injected gas is ionized to generate plasma. In this manner, an a-Si: H film (hydrogenated amorphous silicon film) is deposited on the surface of the substrate 6 by generating silane plasma between both electrodes.

  In the embodiment, the on / off operation of the high frequency power in a DC manner is repeated at a constant cycle. However, if plasma generation can be turned on / off without completely turning off the high frequency power for plasma generation. Good. In the embodiment, the substrate temperature is set to 200.degree.

  By using the input waveform of the embodiment, the film forming time can be shortened as described later, and a high-quality hydrogenated amorphous silicon film can be formed.

[Modification 1 of Embodiment]
A modification 1 of the embodiment will be described in comparison with the embodiment. In the following description, only parts different from the embodiment will be described, and parts similar to those of the embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 4 is a diagram illustrating the modulation reference signal W1B output from the signal synthesis unit 13 and the modulation high-frequency power signal W2B output from the matching circuit 5.

FIG. 4A shows the modulation reference signal W1B output from the signal synthesizing means 13. As shown in FIG. Referring to FIG. 4A, the modulation reference signal W1B is a pulse signal having a two-stage pulse amplitude with a period T. Since the amplitude is 0 between time 0 and t1, no power is supplied. Between time 0 and t1, the signal W1B, which is a gate pulse signal, is off. Time T1 to T12 (time _{T on2)} during the constant power amplitude _{V 2} is supplied, the time T12～t2 (time _{T on1)} between the power of the constant amplitude _{V 1 (V 1 <V 2} ) is Supplied. Between times t1 and t2, the signal W1B, which is a gate pulse signal, is turned on. The signal W1B repeats the power supply as described above with a period T.

  On the other hand, the high frequency power supply 3 in FIG. 1 outputs a high frequency power signal (not shown) having an oscillation frequency of 13.56 MHz. On / off switching of the high-frequency power signal is repeated in a constant cycle.

  Next, FIG. 4B is a diagram showing the modulated high-frequency power signal W2B output from the matching circuit 5. Referring to FIG. 4B, a signal W2B indicates a modulated high-frequency power signal obtained by modulating the on-state high-frequency power signal output from the high-frequency power source 3 by the modulation reference signal W1B in the matching circuit 5.

  This modulated high-frequency power is supplied to the cathode electrode 2 via the matching circuit 5. As a result, plasma is generated in the region between the cathode electrode 2 and the anode electrode 7.

  By using the input waveform of the first modification of the embodiment, the film forming time can be shortened and a high quality hydrogenated amorphous silicon film can be formed as will be described later.

[Modification 2 of Embodiment]
A modification 2 of the embodiment will be described in comparison with the embodiment. In the following description, only parts different from the embodiment will be described, and parts similar to those of the embodiment will be denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 5 is a diagram showing the modulation reference signal W1C output from the signal synthesis unit 13 and the modulation high-frequency power signal W2C output from the matching circuit 5.

FIG. 5A is a diagram showing the modulation reference signal W1C output from the signal synthesis unit 13. As shown in FIG. Referring to FIG. 5A, the modulation reference signal W1C is a pulse signal having a two-stage pulse amplitude with a period T. Since the amplitude is 0 between time 0 and tA1, no power is supplied. Between time 0 and tA1, the signal W1C, which is a gate pulse signal, is off. During time tA1 to tA12 (time T _on11 ), electric power having a constant amplitude V ₁ is supplied, and during time tA12 to tA2 (time T _on12 ), a constant amplitude V ₂ (V ₂ > V ₁ ) is supplied. Power is supplied. During this time tA1 to tA2, the signal W1C which is a gate pulse signal is turned on.

Since the amplitude is zero between the times tA2 and tA3, no power is supplied. During this time tA2 to tA3, the signal W1C, which is a gate pulse signal, is turned off. Time TA3～tA4 (time _{T ON11)} during the constant power amplitude _{V 1} is supplied. During this time tA3 to tA4 (time T _on11 + T _on12 ), the signal W1C which is a gate pulse signal is in an on state. Further signal W1C repeats power supply as described above in the period _{T 12.} Compared with waveforms W1A of the embodiment, the waveform W1B always no amplitude V2 to the ON state, the amplitude _{V 2} is output in the cycle _{T 12.}

  On the other hand, the high frequency power supply 3 in FIG. 1 outputs a high frequency power signal (not shown) having an oscillation frequency of 13.56 MHz. On / off switching of the high-frequency power signal is repeated in a constant cycle.

  FIG. 5B is a diagram showing the modulated high-frequency power signal W2C output from the matching circuit 5. Referring to FIG. 5B, the signal W2C is a signal of modulated high-frequency power obtained by modulating the on-state high-frequency power signal output from the high-frequency power supply 3 by the modulation reference signal W1C in the matching circuit 5.

  This modulated high-frequency power is supplied to the cathode electrode 2 via the matching circuit 5. As a result, plasma is generated in the region between the cathode electrode 2 and the anode electrode 7.

  As in the second modification of the embodiment, when the waveform W1C is in the ON state, it is not always necessary to provide a high and low two-stage pulse power supply, and it is only necessary to output a high amplitude V2 pulse power supply at a constant cycle.

By using the input waveform of the second modification of the embodiment, the film formation time can be shortened and a high quality hydrogenated amorphous silicon film can be formed as will be described later.
[Method for Generating Output Signal W1A from Signal Synthesizer 13 of Embodiment]
A method for generating the modulation reference signal (intermittent discharge waveform) W1A from the signal synthesis means 13 of the embodiment will be described. Note that the output signal W1B of the first modification of the embodiment can also be generated by performing the same processing as described below, and thus description thereof will not be repeated.

  FIG. 6 is a diagram for explaining the output signal W1A from the signal synthesis unit 13 of FIG. Referring to FIG. 6, in FIGS. 6A to 6C, time is shown on the horizontal axis and the amplitude of the output signal is shown on the vertical axis.

  6A shows the output signal WX1 from the intermittent signal generation source 9, FIG. 6B shows the output signal WY1 from the intermittent signal generation source 11, and FIG. The output signal W1A from the signal synthesis means 13 similar to 2 (A) is shown.

Here, the output signal WX1 in FIG. 6A and the output signal WY1 in FIG. 6B are synchronized and have the same period T. On the other hand, the amplitude (V ₂ ) of the output signal WY1 is larger than the amplitude (V ₁ ) of the output signal WX1. Moreover, the on-time of the output signal A from the intermittent signal source 9 and _{T ON1,} when the on-time of the output signal B from the intermittent signal generator 11 and _{T ON2,} the different times from _{T ON1} and _{T ON1} Have.

  1 synthesizes the output signal WX1 of FIG. 6A and the output signal WY1 of FIG. 6B to generate the output signal W1A of FIG. 6C.

The output signal W1A and the output signal W1 of the modulation power supply 4 in FIG. 10A are intermittent discharge waveforms, but the pulse fluctuations (V ₁ , V ₂ ) of high and low in the signal W1A when the signal is on. relative is located, on the time the signal W1 differ in amplitude V ₁ is no variation in the amplitude constant.

Further, the pulse frequency and the duty ratio are the same between the signal W1A and the signal W1. The duration of the high amplitude _{V 2} at the ON time in the intermittent discharge of the signal W1A is 20usec _{(T ON2),} duration 480usec _{(T ON1)} of low amplitude _{V 1} of the time on, the duration of time off 2 msec (for example, time 0 to t1). Further, it high amplitude _{V 2} of the duration of the ON state _{(T ON2)} low amplitude _{V 1} of the duration of the ON state than the _{(T ON1)} is long.

On the other hand, the duration of an amplitude _{V 1} of the time on the intermittent discharge of the signal W1 is 500Usec, the duration of the off is 2 msec.

  As shown in FIG. 6C, the modulation reference signal W1A from the signal synthesizing unit 13 in the first modification of the embodiment continues the output signal WY1 having the high amplitude V2 next to the output signal WX1 having the low amplitude V1. It is time series to do, but is not limited to this.

For example, if the modulation reference signal W1B from the signal synthesizing means 13 in the modified example 1 of the embodiment as shown in FIG. 3 (A), i.e., next to the low amplitude V ₁ of the high amplitude V2 of the output signal The same effect can be obtained even when the output signal continues.

Although not shown, when the output signal of the low amplitude V ₁ is divided before and after the output signal of the high amplitude V ₂ , that is, the output signal next to _one of the divided output signals of the low amplitude V _1. continuing output signal amplitude V ₂ is, same effects can be obtained in time series that continues other split portion of the output signal of the low-amplitude V ₁ to the following.
[Method for Generating Output Signal W1C from Signal Synthesizer 13 of Modification 2 of Embodiment]
A method for generating the modulation reference signal (intermittent discharge waveform) W1C from the signal synthesizing unit 13 according to the second modification of the embodiment will be described.

  FIG. 7 is a diagram for explaining the output signal W1C from the signal synthesis unit 13 of FIG. Referring to FIG. 7, in FIGS. 7A to 7C, time is shown on the horizontal axis of each figure, and the amplitude of the output signal is shown on the vertical axis.

  7A shows an output signal WX2 from the intermittent signal generation source 9, FIG. 5B shows an output signal WY2 from the intermittent signal generation source 11, and FIG. The output signal W1C from the signal synthesizing means 13 similar to 2 (A) is shown.

Here, the output signal WX2 in FIG. 7A and the output signal WY2 in FIG. 7B are synchronized. On the other hand, the period is different, and the period of the output signal WY2 is in an integer multiple (twice) of the period of the output signal WX2. Further, the amplitude (V ₂ ) of the output signal WY2 is larger than the amplitude (V ₁ ) of the output signal WX2. Further, if the ON time of the output signal A from the intermittent signal generation source 9 is T _ON11 and the ON time of the output signal B from the intermittent signal generation source 11 is T _ON12 , T _ON11 and T _ON12 have different times. Have.

  1 synthesizes the output signal WX2 of FIG. 7A and the output signal WY2 of FIG. 7B to generate an output signal W1C of FIG. 7C.

The output signal W1C and the output signal W1 of the modulation power source 4 in FIG. 10A are intermittent discharge waveforms, but the pulse fluctuations (V ₁ , V ₂ ) of high and low two levels when the signal W1C is on. relative is located, on the time the signal W1 differ in amplitude V ₁ is no variation in the amplitude constant.

Further, the pulse frequency and the duty ratio are the same in the signal W1C and the signal W1. The duration of the high amplitude _{V 2} at the ON time in the intermittent discharge of the signal W1C is 40usec _{(T ON12),} the total time of low amplitude _{V 1} of the time on the 960usec _{(2T ON11),} the total time during OFF 4 msec (for example, time Sum between tA2 and tA3 and between time tA4 and tA5). Further, it high amplitude _{V 2} of the duration of the ON state _{(T ON12)} low amplitude _{V 1} of the duration of the ON state than the _{(T ON11)} is long.

On the other hand, the duration of an amplitude _{V 1} of the time on the intermittent discharge of the signal W1 is 500Usec, the duration of the off is 2 msec.

When the modulation reference signal W1C from the signal synthesizing means 13 in the second modification of the embodiment as shown in FIG. 7 (C) is on, the next output signal WX2 of low amplitude V ₁ for a certain period It has become time-series that the output signal WY2 of high amplitude V ₂ continues, but is not limited thereto.

  Next, the embodiment and its modifications 1 and 2 have been described. The characteristics of the hydrogenated amorphous silicon film formed by using the configuration of the embodiment will be described while comparing with the conventional example. .

FIG. 8 is a diagram showing a table comparing the characteristics of the hydrogenated amorphous silicon film formed by the embodiment and the characteristics of the hydrogenated amorphous silicon film formed by the conventional example. Referring to FIG. 8, the items of the ratio of SiH ₂ bond to SiH bond (hereinafter abbreviated as SiH ₂ / SiH), photoconductivity (σph), and SN ratio are compared with the embodiment and the conventional example. Is done. Further, the film formation speeds of the hydrogenated amorphous silicon thin film formed by the intermittent discharge waveform W1A of FIG. 1 of the embodiment and the hydrogenated amorphous silicon thin film formed by the conventional intermittent discharge waveform W1 of FIG. Also written. The measurement conditions are the same for the conditions other than the intermittent discharge waveforms W1 and W1A that are input waveforms as described above. Conditions other than the intermittent discharge waveforms W1 and W1A that are input waveforms, for example, process conditions (gas flow rate, pressure in the reaction chamber 1, substrate temperature, etc.) are all the same.

SiH ₂ / SiH, which is a comparative item, means that the smaller the value, the less SiH ₂ contained in the hydrogenated amorphous silicon film, and the higher the quality of the hydrogenated amorphous silicon film.

  The photoconductivity (σph), which is a comparative item, means that the larger the value, the smaller the density of defects contained in the hydrogenated amorphous silicon film, indicating that the hydrogenated amorphous silicon film is of higher quality. Yes.

  Similar to the photoconductivity (σph), the SN ratio as a comparison item means that the larger the value, the smaller the density of defects contained in the amorphous silicon film, and the higher the quality of the hydrogenated amorphous silicon film. It is shown that.

In the hydrogenated amorphous silicon film formed by the intermittent discharge waveform W1A according to the embodiment, the Si—H ₂ bond is reduced compared to the hydrogenated amorphous silicon film formed by the conventional intermittent discharge waveform W1, The photoconductivity (σph) and the SN ratio are increased by about 5 times.

  In general, when the film forming speed is low, the film quality tends to be improved. However, the hydrogenated amorphous silicon film formed by the intermittent discharge waveform W1A according to the embodiment is formed by the conventional intermittent discharge waveform W1. The film quality was good in spite of the high film-forming speed of the hydrogenated amorphous silicon film.

  Therefore, according to the configuration of the embodiment, it is possible to provide a high-quality hydrogenated amorphous silicon film that can shorten the film forming time as compared with the conventional hydrogenated amorphous silicon film. The above effects can also be achieved in Modification 1 and Modification 2 of the embodiment, and a high-quality hydrogenated amorphous silicon film can be provided as in the embodiment.

  In the above embodiment, the hydrogenated amorphous silicon film has been described as an example. However, the present invention is not limited to this, and a narrow bandgap a-SiGe: H film manufactured using a group 4 hydrogen compound as a raw gas or It is also effective in increasing the speed and quality of similar elements of amorphous silicon-based alloy films such as a wide band gap a-SiC: H films.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 reaction chamber, 2 cathode electrode, 3 high frequency power supply, 4 power supply for modulation, 4A modulation reference signal generating means, 5 matching circuit, 6 substrate, 7 anode electrode, 9, 11 intermittent signal generating source, 10 circulator, 12 isolator, 13 Signal synthesis means, 100, 100A capacitively coupled plasma CVD apparatus.

Claims (6)

A method for manufacturing a semiconductor thin film, comprising:
Decomposing a compound containing a group 4 element atom and a hydrogen atom into plasma and active species;
Depositing the active species on a substrate,
In the decomposing step, the plasma generation energy is intermittently supplied so as to repeat the pause period and the supply period,
The method for producing a semiconductor thin film, wherein the plasma generation energy varies with time in the supply period.   The method of manufacturing a semiconductor thin film according to claim 1, wherein the plasma generation energy is generated by a high-frequency power source based on a signal obtained by combining two pulses having different voltage amplitudes. A plasma CVD apparatus,
High-frequency power generation means;
A reaction chamber for processing the substrate disposed in the substrate disposition portion,
The plasma CVD apparatus decomposes a compound containing a group 4 element atom and a hydrogen atom into plasma and active species in the reaction chamber, and deposits the active species on a substrate.
A plasma CVD apparatus further comprising a modulation reference signal generation means for generating an intermittent signal, which is a reference signal for modulating the output of the high-frequency power generation means and is a combination of two pulses having different voltage amplitudes. The modulation reference signal generating means includes
A plurality of intermittent signal generating means;
The plasma CVD apparatus according to claim 3, further comprising: a signal synthesizing unit that synthesizes an output signal output from each of the plurality of intermittent signal generating units.   5. The plasma CVD apparatus according to claim 4, wherein output signals of the plurality of intermittent signal generating means are synchronized with each other, have the same period, and have different duty ratios.   The output signals of the plurality of intermittent signal generation means are synchronized with each other and have a period that is an integral multiple of one period of the output signals of the plurality of intermittent signal generation means and different from each other, The plasma CVD apparatus according to claim 4, wherein the duty ratio is different.

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