JPH09266174A - Manufacture of amorphous semiconductor film, and manufacture device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film formation method which materializes the formation of a high-performance amorphous semiconductor film at a low temperature near the room temperature, utilizing that the high-frequency induction coupling plasma being a plasma source without occurrence of plasma under low pressure can generate low-pressure plasma equally at large area, and besides produce high-density plasma condition being excited enough, without using a high magnetic field and without using microwaves. SOLUTION: High frequency is let pass through a matching device 15 from a high frequency oscillator 14 through an induction coil 13, and it is introduced into a plasma generator 16 at least whose coil or its vicinity consists of insulating material such as a quartz tube, or the like. Monosilane (SiH4 ) or the like is introduced from a gas introduction port 17, and generated plasma reaches a substrate holder 18, and amorphous silicon can be accumulated on a substrate even if it is at low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for producing an amorphous thin film such as amorphous silicon (a-Si: H) at a relatively low temperature near room temperature.

[0002]

2. Description of the Related Art Conventionally, when forming amorphous silicon,
Direct current or alternating current (including high frequency, microwave) glow discharge plasma decomposition is performed by the so-called plasma chemical vapor deposition (CVD) method. Among them,
For example, one using ECR plasma CVD using microwave electron cyclotron resonance (ECR) is known. When a film is formed by a conventional ECR plasma CVD apparatus having a structure as shown in FIG. 6, 1 × 10 ^{−4 to} 5 ×
Even in a low pressure SiH ₄ atmosphere in the range of 10 ⁻⁴ Torr,
Plasma can be generated, and for example, when the amorphous silicon is deposited and formed at a low temperature near room temperature without heating the substrate using SiH ₄ gas, the a-Si: H thin film produced under this low-pressure atmosphere is It has been shown that good photoconductivity and light-to-dark ratio are obtained (eg Japn.J.Appl.Phys:
M. Kitagawa et.al. 26 (1987) L261).

In the apparatus configuration of FIG. 6, 61 is evacuated to a vacuum through an exhaust hole 62 in a vacuum chamber. Waveguide 63
Through the microwave oscillator 64, microwaves are introduced into the plasma generation chamber 65. At the same time, a magnetic field is applied to the plasma generation chamber 65 by the electromagnet 66. Reference numeral 67 is a gas introduction port into which monosilane (SiH ₄ ) is mainly introduced as a raw material gas. By setting the strength of the magnetic field so as to satisfy the electron cyclotron resonance condition, a plasma having a high degree of dissociation can be obtained. The generated plasma is a plasma extraction window 68.
To reach the substrate holder 69, and amorphous silicon is deposited on the holder 69.

[0004]

However, in the manufacturing method using the microwave ECR plasma CVD as described above, although the formation can be performed at a low formation temperature near room temperature, as shown in FIG.
A resonance magnetic field is required as shown in FIG. For example, in the case of 1.25 GHz microwave, a large magnetic field generator (electromagnet or the like) capable of generating a high magnetic field of 875 Gauss is required, and the size of this magnet limits the size of the plasma generation source. In addition, since the introduction of microwaves locally radiates electric power through a waveguide or a coil antenna, the deposition / area of the plasma generation region is limited, making it difficult to achieve a large area.

To avoid these problems, multiple E
A CR source is required or the substrate needs to be moved for processing, which leads to a drastic decrease in the deposition rate and eliminates the possibility of high speed formation at low temperatures. It was impeding practical application.

Further, in such a method using a conventional ECR plasma using a high magnetic field, the generated plasma moves along a magnetic field gradient, and generally, charged particles of both ions and electrons have high energy to the deposition surface. Since the irradiation is carried out with a large amount, there is a high possibility that the base or the substrate will be damaged, which further hinders the practical application of such a manufacturing method.

The present invention aims to solve such problems.

[0008]

In order to solve the above problems, the present invention has proposed a conventional microwave ECR plasma CVD.
A low-temperature formation of a-Si: H, which had been realized only in the above, is required by using a large magnetic field generator by using an inductively coupled plasma (ICP) that does not use a high magnetic field as a plasma source instead of the microwave ECR. Instead, it was found that the SiH ₄ gas can be plasma decomposed uniformly in a large area in a low pressure region, and the above problems can be solved.

According to the conventional method, SiH ₄ gas, which has a high dissociation energy and is difficult to decompose, is generated by utilizing the resonance phenomenon (ECR) of microwave and strong magnetic field to generate low-pressure plasma having a high electron temperature. As a result, the magnetic field generator, the microwave waveguide, and the like are maneuvered so that downsizing is difficult, and a device configuration that is not suitable for upsizing is required. In the present invention, a high-frequency inductively coupled plasma, which is a plasma source that does not use a high magnetic field, does not use a microwave, and does not generate plasma under a low pressure, uniformly generates a low pressure plasma in a large area and is sufficiently excited. It was utilized that it is possible to create a high density plasma state. Therefore, it was possible to deposit without damaging the film while keeping the deposition rate sufficiently high.

The present invention provides a thin film forming method by which the high-performance amorphous semiconductor thin film can be formed at a low temperature near room temperature by the above means.

[0011]

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

(First Embodiment) FIG. 1 is a schematic view of an ICPCVD apparatus used in this embodiment. A vacuum chamber 11 is evacuated to a vacuum through an exhaust hole 12. Induction coil 13
High frequency from the high frequency oscillator 14 passes through the matching device 15, and is introduced into the plasma generation chamber 16 made of an insulating material such as a quartz tube at least near the coil. By applying a high frequency to the coil, an induction magnetic field is generated and an electromagnetic field is applied to the plasma generation chamber 16. Reference numeral 17 is a gas introduction port where monosilane (SiH ₄ ) is mainly introduced as a raw material gas, and the number of turns of the coil is set so as to satisfy the inductive coupling condition with the frequency of the high frequency to be applied, whereby plasma having a high dissociation degree is generated. can get. The frequency of the high frequency at this time is 10 to 10
The 0 MHz region is preferred. The generated plasma reaches the substrate holder 18 and amorphous silicon is deposited on the substrate on the substrate holder. For example, when methane (CH4) is mixed, amorphous silicon carbide (SiC) can be formed.

For example, as shown in FIG. 2, 100% S
When iH ₄ gas is supplied at a flow rate of 5 sccm and amorphous silicon is deposited and formed at a low temperature near room temperature without heating the substrate, a relatively good photoelectric conductivity is obtained at a SiH ₄ pressure in the range of 2 mTorr to 15 mTorr. It is preferable to form in this pressure region at this flow rate.

In FIG. 3, the pressure of SiH ₄ is kept constant at 3 mTorr,
It shows changes in photoconductivity and dark conductivity of an amorphous silicon thin film formed at room temperature when high-frequency power is changed from 100 to 1000 W. Good characteristics are shown in a relatively high power region of 500 to 1000 W.

(Embodiment 2) FIG. 4 shows a configuration in which the plasma during deposition is introduced into a spectroscope 41 through an optical fiber or the like to perform emission spectroscopy in the apparatus configuration of FIG. 1 so that a change in a predetermined emission peak can be detected. Is to have. Further, the emission intensity is monitored by the data processing device 42, and the feedback circuit 4 for the discharge pressure, discharge power, and supply flow rate is used.
By assembling 3, the flow rate regulator 44 and the pressure regulator 4
5, feedback to the high frequency power supply 14, Si, S
By controlling the emission peaks of iH and H to be a predetermined value, it is possible to stably produce a good quality amorphous thin film.

FIG. 5 shows high frequency power, SiH4 flow rate, H2 and S
It shows the change in photoconductivity of various amorphous silicons produced when the flow rate ratio with iH4 or the pressure is changed. The abscissa indicates the Si observed near 400 nm to 420 nm among the emission peaks of the plasma emission spectrum near the substrate.
Emission peak from H molecule, emission peak from Si atom centered around 288 nm (280 to 290 nm), around 618 nm (610
The relative ratios Si / SiH and H / SiH of emission peaks from H atoms centered at 620 nm) are obtained. When Si> SiH and H> SiH, the photoelectric conductivity of the produced amorphous silicon thin film is relatively good.

That is, in order to obtain amorphous silicon having a good film quality at low temperature formation, the ratio of the peak intensities of Si, SiH, and H described above can be determined by observing the emission spectrum of plasma.
It can be performed by adjusting the conditions such that> SiH or H> SiH.

The film forming rate under these conditions is 5 to 30 A.
/ Sec is about the same as or higher than the case of ECR plasma CVD, and the film formation rate was sufficiently high.

In the above embodiment, the embodiment of the present invention has been described by using the solenoid coil type inductive coupling device having the external coil arrangement as shown in FIG. 1. However, for example, a spiral type coil is wound in the same plane. An inductive coupling device, an internal coil arrangement in which these coils are installed in the reaction chamber, and a device to which an auxiliary magnet is added have the same effect.

[0020]

First of all, the SiH ₄ gas, which has a high decomposition energy and is hard to decompose, has conventionally been used to generate a low-pressure plasma having a high electron temperature by utilizing a resonance phenomenon (ECR) between a microwave and a strong magnetic field. Because of this, the arrangement of the magnetic field generator, the microwave waveguide, and the like is large, and downsizing is difficult, and the device configuration is not suitable for upsizing.

To solve this problem, according to the present invention, by using an inductively coupled plasma capable of generating a low pressure plasma in a large area, it is decomposed at a low pressure and sufficiently excited at a low power. It was possible to deposit without damaging the film while maintaining a sufficiently high deposition rate. As a result, it is possible to fabricate a high-performance element without damaging the substrate or the lower layer film even when forming the thin film semiconductor device.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an inductively coupled plasma (ICP) CVD apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing changes in photoconductivity and dark conductivity of an amorphous silicon thin film.

FIG. 3 is a diagram showing changes in photoconductivity and dark conductivity of an amorphous silicon thin film.

FIG. 4 is a schematic diagram of an inductively coupled plasma (ICP) CVD apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram showing changes in photoconductivity of amorphous silicon when the mixed gas ratio is changed.

FIG. 6 is a configuration diagram of an apparatus for depositing amorphous silicon by using ECR plasma CVD as a conventional example.

[Explanation of symbols]

 11 Vacuum Chamber 12 Exhaust Port 13 Induction Coil 14 High Frequency Oscillator 15 Matching Device 16 Plasma Generation Chamber 17 Gas Inlet Port 18 Substrate Holder 41 Spectroscopic Device 42 Data Processing Device 43 Flow Rate Regulator 44 Pressure Regulator

Claims (11)

[Claims] 1. A raw material comprising a silicon element such as silane (SiH ₄ ), disilane (Si ₂ H ₆ ), methane (CH ₄ ),
At least one of a raw material containing a carbon element such as ethane (C ₂ H ₄ ), hydrogen (H ₂ ) or a mixture of these elements is used, and high frequency inductively coupled plasma (ICP: Indu) is used.
A method for producing an amorphous semiconductor thin film, which comprises depositing and forming in a chemical vapor deposition process using a ctive coupled plasma. 2. A high frequency of 100 kHz to 100 M
The method for producing an amorphous semiconductor thin film according to claim 1, wherein the frequency is set to Hz. 3. The gas pressure during the deposition of the raw material is 1 × 10.
^{-4 to} 6x10 ^-3 Torr is set, and the amorphous thin film manufacturing method according to claim 1 characterized by things. 4. An emission peak (SiH) from SiH molecules, which is observed near 400 nm to 420 nm in a plasma emission spectrum of at least the vicinity of the substrate of the high frequency inductively coupled plasma, and a gas pressure during deposition of the raw material are near 288 nm (280 to 280 nm). 290 nm) centered at the emission peak (Si) from Si atoms, H centered around 618 nm (610-620 nm)
The relative relationship between the emission peaks (H) from the atoms is (S
i)> 4.0 × (SiH), or (H)> 2.0 ×
The method for producing an amorphous semiconductor thin film according to claim 1, wherein the setting is made so as to satisfy (SiH). 5. The high frequency power is centered on the emission peak (SiH) from SiH molecules, which is seen near 400 nm to 420 nm in the plasma emission spectrum of at least the vicinity of the substrate of the high frequency inductively coupled plasma, and around 288 nm (280 to 290 nm). Emission peak (Si) from Si atom, 618nm
The relative relationship of the emission peak (H) from the H atom centered around (610 to 620 nm) is (Si)> 4.0 × (Si
2. The method for producing an amorphous semiconductor thin film according to claim 1, wherein H) or (H)> 2.0 × (SiH) is set. 6. The gas supply flow rate at the time of depositing the source gas is 400 nm to 420 nm in the plasma emission spectrum of high frequency inductively coupled plasma at least in the vicinity of the substrate.
The emission peak from the SiH molecule (Si
H), emission peak from Si atoms centered around 288 nm (280 to 290 nm) (Si), near 618 nm (610 to 620 nm)
The relative relationship of the emission peak (H) from the H atom centered at is (Si)> 4.0 × (SiH), or (H)
The method for producing an amorphous semiconductor thin film according to claim 1, wherein the setting is made so as to satisfy> 2.0 × (SiH). 7. Si as a source gas during deposition of the source
A mixed gas of H ₄ and hydrogen H ₂ was used, and the supply flow rate ratio thereof was set such that the emission peak (SiH) from SiH molecules at about 400 nm to 420 nm in the plasma emission spectrum of at least the vicinity of the substrate of the high frequency inductively coupled plasma was 288n.
The relative relationship between the emission peak (Si) from the Si atom centered around m (280 to 290 nm) and the emission peak (H) from the H atom centered around 618 nm (610 to 620 nm) is
(Si)> 4.0 × (SiH) or (H)> 2.0
The method for producing an amorphous semiconductor thin film according to claim 1, wherein mixed setting is performed so as to satisfy x (SiH). 8. A substrate holder and a silicon element such as silane (SiH ₄ ) and disilane (Si ₂ H ₆ ) and a carbon element such as methane (CH ₄ ) and ethane (C ₂ H ₄ ) in a vacuum chamber. And a raw material supply means for supplying a raw material containing at least one of hydrogen (H ₂ ) or an element obtained by mixing these, and for generating a high-frequency electric field in a region where plasma is generated in the vacuum chamber. Inductively coupled plasma (ICP: Inductive Coupled)
Plasma) apparatus for depositing and forming an amorphous semiconductor thin film, which is formed by chemical vapor deposition. 9. A high frequency of 100 kHz to 100 M
9. The apparatus for producing an amorphous semiconductor thin film according to claim 8, wherein the frequency is set to Hz. 10. The gas pressure during the deposition of the raw material is 1 × 1.
9. The amorphous thin film manufacturing apparatus according to claim 8, wherein the thickness is 0 ^{−4 to} 6 × 10 ⁻³ Torr. 11. At least one of a gas pressure, a gas supply flow rate, a gas mixing ratio and a high frequency power at the time of depositing a raw material,
An emission peak (SiH) from SiH molecules, which is seen near 400 nm to 420 nm in the plasma emission spectrum of at least the vicinity of the substrate of the high frequency inductively coupled plasma, 28
The relative relationship between the emission peak (Si) from the Si atom centered around 8 nm (280 to 290 nm) and the emission peak (H) from the H atom centered around 618 nm (610 to 620 nm) is
(Si)> 4.0 × (SiH) or (H)> 2.0
9. The apparatus for producing an amorphous semiconductor thin film according to claim 8, wherein the setting is made so as to satisfy x (SiH).