JPH03139824A - Depositing method for semiconductor device - Google Patents

Abstract

PURPOSE:To improve photoconductivity of a thin film, to regulate coupling hydrogen amount and to accelerate a depositing speed by supplying material gas and, as required, carrier gas to the surface of a heated substrate to deposit silicon, germanium, carbon or their mixture thin film, and supplying exciting hydrogen on the film without exposing with the atmosphere. CONSTITUTION:A quartz substrate 3 and a crystalline silicon substrate 3' are placed on a SiC coated susceptor 2, Si2H6 is mixed in H2, this material gas is supplied on the substrates, and heated by an infrared lamp 4. The pressure in a chamber is set to a predetermined pressure (e.g. 10Torr). The temperature of the substrate is set to approx. 440 deg.C, and a thin silicon film is deposited in predetermined thickness (300Angstrom or lower). Then, only the Si2H6 in the gas is stopped, a chamber is evacuated, hydrogen flow rate is regulated to a predetermined inner pressure in the chamber (e.g. 1-0.3Torr), an AC power source is turned ON by a switch SW13, and the hydrogen excited as hydrogen plasma 15 is supplied on the thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for depositing a semiconductor thin film, and more particularly to an improvement in a method for depositing a semiconductor thin film from a gas source using heat.

[Prior Art] Conventionally, as a method of depositing a silicon thin film from a gas source using heat, amorphous silicon from a silane-based gas was more than two orders of magnitude smaller than crystalline (including polycrystalline) silicon. However, on the other hand, thermal CVD amorphous silicon also had excellent properties such as less photodegradation.

[Problems to be Solved by the Invention] Therefore, a method for depositing a semiconductor thin film that takes advantage of the advantages of thermal CVD and has a high deposition rate, and a method for improving photoelectric characteristics has been desired. This problem also applies to germanium thin films and carbon-containing silicon thin films.

In the case of silicon (Si3■a), the actual film formation temperature is 400°C or higher, but at these temperatures, the deposition rate is usually about 1,000 per hour, and in practical terms it is more than 50°C.
Required high deposition temperatures. In this way, film formation at high temperatures limits the types of substrates that can be used, and in particular, glass substrates cannot be used. Furthermore, even when a thin film was formed using a film deposited using plasma, the film was taken out of the film-forming apparatus to the outside air, and then exposed to hydrogen plasma, there was almost no improvement in the light conductivity.

[Means for Solving the Problems] The present invention includes a step of supplying a raw material gas and, if necessary, a carrier gas to a heated substrate surface, and depositing a thin film of silicon, germanium, carbon, or a mixture thereof, and depositing this thin film. The method is characterized by comprising a step of supplying excited hydrogen onto the thin film without exposing it to the outside air. That is, in the present invention, a method is adopted in which the bonded hydrogen in the semiconductor thin film is adjusted through such a process.

``Adjusting bonded hydrogen'' means that even if hydrogen is already included in the thin film, it involves the process of supplying excited hydrogen and heating the substrate to release the raw material gas without exposing the substrate to the outside air. The present invention is characterized by comprising a step of supplying the thin film, thereby increasing the deposition rate of the thin film.

[Function] According to the present invention, as shown in the following examples, it is possible not only to improve the light guiding strength of the thin film and adjust the amount of bound hydrogen in the thin film, but also to increase the deposition rate several times. is also possible.

'1 In the present invention, the raw material gases for St, Ge, and carbon thin films are each silane-based (Sit(4, Si2H6, 5i3Ha
,...), german The film thickness to which this bonded hydrogen is adjusted changes depending on the temperature, but for example, at around 450°C, it is up to about 300%, so it is modified throughout the thickness direction of a thick film. In order to achieve this, it is desirable to repeat the semiconductor thin film process, which is characterized by depositing a film of 300 Å or less and then exciting it.

Furthermore, the present invention introduces hydrogen while supplying excited hydrogen onto the substrate, and forms a hydrogen plasma by applying a DC or AC voltage between two electrodes provided inside or outside the chamber. This plasma may be directed to the thin film surface or the substrate surface. Hydrogen plasma can be formed by creating a chamber made of an insulating material and coupling alternating current from that part through inductive coupling, or by introducing microwaves from the insulating material part. The plasma may be created in a space containing the substrate or in a separate space. Furthermore, hydrogen is introduced into the decompression chamber, and this hydrogen is exposed to an electron beam.
Excited hydrogen may be formed by irradiation with X-rays. Furthermore, excited hydrogen can be produced by irradiating hydrogen with deep ultraviolet rays or mixing it with excited Hg gas (in this case, normal pressure may be used instead of Z).

The signal from the thermocouple 6 is detected by a thermocouple 6 inserted into the substrate 3. The signal from the thermocouple 6 is supplied to a control device 7, and the control device 7 adjusts the power supplied to the lamp depending on the magnitude of this signal. It is designed to adjust the temperature at 3'. Further, the quartz chamber 1 is vacuum-sealed by a stainless steel flange 8, and can be reduced in pressure by a connected vacuum pump 9. A plurality of preset gases are supplied to the surface of the substrate from the gas mixing device 10 at controlled flow rates.

[Example] As an example of the present invention, a case of thermal CvD using disilane (SiJa) will be shown.

As shown in FIG. 1, the apparatus used in the experiment is such that a susceptor 2 is provided in a quartz chamber 1, a substrate 3.3' is placed on top of the susceptor 2, and the susceptor is irradiated with infrared rays from an infrared lamp 4. 2 and the substrate 3°3'. 5 is a reflecting mirror. The temperature of the substrate 3.3' causes a plasma discharge to occur around the susceptor 2.

Factor 11"1 This example shows an example in which a silicon thin film is deposited using disilane (SfJa) as a source gas. Note that hydrogen is used as a carrier gas. A quartz substrate 3 and a crystalline silicon substrate 3 are placed on top of the SiC coated susceptor 2 shown in FIG.
' (for measuring the amount of bonded hydrogen) and 8240sccr
512) 1.12 sec into the substrate, this raw material gas is supplied onto the substrate, and heated by an infrared lamp 4. The pressure inside the chamber is a specified pressure (10 Torr in this example).
r). The temperature of the substrate is set at about 440° C., and a silicon thin film is deposited to a specified thickness.

Next, only Si and H6 in the source gas are stopped, the chamber is evacuated, and the hydrogen flow rate is adjusted to a specified chamber pressure (1 to 0.3 Torr in this example).
Turn on the AC power supply with 5W13, and hydrogen plasma 15
The excited hydrogen is supplied onto the thin film.

The silicon thin film deposited through this process was hydrogenated amorphous silicon.

First, the photoconductivity of the silicon film to which no excited hydrogen was supplied was less than 10-'S/cm under light with an M1.5 spectrum and an intensity of 60 mW/cm2. However, about 6
The photoconductivity of the silicon film to which excited hydrogen was supplied for 3 minutes each time it was deposited was 4 x 10-'S/cm or more. The photoconductivity increased closer to the hydrogen plasma source. The amount of bound hydrogen also increases as it approaches the hydrogen plasma source. The amount of bound hydrogen in a portion of the silicon film far from the hydrogen plasma source (approximately 10 cm) is actually smaller than that in a film to which no excited hydrogen is supplied. Furthermore, even if hydrogen is used as a carrier gas in the F# film deposition process, a film with a large amount of bound hydrogen is not necessarily obtained. In addition, even in samples close to the hydrogen plasma source, the amount of bound hydrogen was lower than that of samples to which no excited hydrogen was supplied.

The silicon film obtained by the method of the present invention is shown in FIG.
5 to 10-'S/cm, whereas according to the method of the embodiment of the present invention, the amount of bonded hydrogen in the thermal CVD amorphous silicon film is 10-5S/cm at a level of 3 to 4 at%.
, has the potential to obtain a photoconductivity of to-'S/cm at 4 to 5 atomic %. If we improve the leakage and impurity contamination of the current equipment and increase the purity of excited hydrogen, it will be 10-'
Values up to S/cm are expected to be obtained.

In order to effectively obtain this improvement in photoconductivity, an experiment was conducted to determine how thick a thin film should be deposited before supplying excited hydrogen to the surface of the thin film. As shown in FIG. 1, the thickness of the thin film is limited by a method that does not generate plasma directly above the thin film or a method that does not accelerate excited hydrogen. In the case of real-speed excited hydrogen, the thickness of one deposition film is 3
It can be seen that when the thickness is less than 00 Å, the photoconductivity is further improved by nearly an order of magnitude. In this example, the silicon thin film was deposited on a quartz substrate at 440°C from raw material gas of Si2H612sccl+H240SCCm + carrier gas, and the excited hydrogen was generated from hydrogen plasma discharged at 40 seconds of hydrogen at 0.33 Torr and a discharge power of 30 W (13.56 MHz). supplied.

Example 3 As an example showing another aspect of the present invention, the results of measuring changes in photoconductivity by changing the thickness of a film deposited at one time in an example in which an excitation layer was used are shown.

Even if the film thickness deposited at one time exceeds 500 people, simple thermal C.
Since the photoconductivity is improved by an order of magnitude compared to the case of VD (no supply of excited hydrogen), it is not necessary to limit the film thickness, but from the results shown in Figure 3, the non-pressure is approximately 0.6T.
Adjusted to δrr. Turn on 5W13, apply AC voltage to the discharge electrode, generate hydrogen plasma with 40W AC power, and supply excited hydrogen onto the substrate for 5 minutes (at this time, the substrate is already heated to 425°C). . After that, the chamber pressure was set to 10 Torr by flowing 5i2H,
5f2H was supplied onto the substrate heated to 425°C. The deposition rate of the obtained silicon thin film was 70 to 40 persons/min, and the deposition rate varied only within the above-mentioned range from 3 minutes to 10 minutes after the supply of excited hydrogen. However, these deposition rates are 5 to 3 times lower than those obtained when performing normal thermal CVD experiments in which excited hydrogen is not supplied to the substrate in advance using the same equipment.
It was double that. 5i2 raw material gas during deposition of silicon thin film
116.12sccm 182 (carrier gas) 40s
ecm and the deposition temperature was 440° C., the deposition rate improvement rate was 1.7 to 2 times.

Bye. A thin film mainly composed of germanium can be deposited by mixing a silane-based gas with a raw material gas in which all of the hydrogen has been replaced with fluorine.

A carbon film can be deposited by a similar method using a hydrocarbon such as methane (C114) or ethane (C2Ha) as a raw material gas.

Furthermore, by mixing the raw material gases such as silane gas, germane gas, alkyl silane gas, etc., silicon,
A thin film containing germanium and carbon mixed in arbitrary proportions was prepared using monosilane (Sin4) as in the above embodiment.
, trisilane (Si3t+), other silane-based gases, and gases in which an alkyl group is bonded to silicon can also be used.

For the deposition of germanium, as described above, a germane-based (GeH4, Ge2u6...) gas and a gas in which some of the hydrogen has been replaced with fluorine are used, and as explained above, according to the present invention. For example, (1) bound hydrogen is effectively used to improve photoelectric properties (photoconductivity), (2) because there are few bound hydrogens, the optical band gap is 1.
．． (3) Photodeterioration is as small as a thermal CVO film, (4) Deposition rate is improved even at lower temperatures than conventional thermal CVD.12. -Discharge electrode, 14...AC power supply.

There is an effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of the apparatus used in the present invention; Figure 2 is a characteristic diagram showing the relationship between the degree of light guiding and the amount of bound hydrogen. 2...susceptor, 3.3”...board, 4...Infrared lamp, 6...Thermocouple, 7...control device, lO...gas mixing device, n water content - t, ((baby%) Figure 3 Figure 2

Claims (3)

[Claims] (1) A step of supplying a raw material gas and, if necessary, a carrier gas to the heated substrate surface, and depositing a thin film of silicon, germanium, carbon, or any mixture thereof, and excitation hydrogen without exposing the thin film to the outside air. A method for depositing a semiconductor thin film, comprising the step of: supplying a substance onto the thin film. (2) The method of depositing a semiconductor thin film according to claim 1, wherein the thickness of the thin film deposited before or between the steps of supplying excited hydrogen is 300 Å or less. (3) A method for depositing a semiconductor thin film, comprising a step of supplying excited hydrogen onto a substrate, and a step of heating the substrate without exposing it to the outside air and supplying a source gas.