JPS61579A - Manufacture of thin film - Google Patents

Abstract

PURPOSE:To form an amorphous semiconductor thin film having good quality on a substrate by removing previously the adsorbed gas in a reaction chamber by discharge of gaseous NH3 when said film is formed on the substrate surface by plasma CVD method while introducing raw material gas into the reaction chamber in which the substrate is arranged. CONSTITUTION:The substrate 7 is mounted on an electrode 4 of the substrate side in a chamber 1, and an electrode 5 of raw material introducing side having a gas jetting hole 3 is arranged at the position opposing thereof. Next, the gaseous NH3 is allowed to flow into the chamber 1, 13.56MHz high frequency voltage is impressed between both electrodes 4, 5 by an electric source 6, and glow discharging is performed. Gases such as O2, H2O, CO2 adsorbed to the inner wall of the chamber, respective electrodes 4, 5, the substrate 7, etc. are removed as NOx, hydrocarbon from inside of the chamber 1. Thereafter, SiH4, Si2H6, PH3, B2H6, NH3, etc. as raw material gas is introduced from the hole 3 of the electrode 5 to glow discharge it, and the amorphous semiconductor thin film of high purity amorphous, Si, etc. is formed on the surface of the substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for manufacturing thin films such as semiconductor films by plasma CVD.

BACKGROUND OF THE INVENTION In recent years, amorphous semiconductors, specifically amorphous silicon a-SS, have been attracting attention, and there are life-size sensors, solar cells, thin film transistors, etc. that use this amorphous silicon a-3i. For this production, plasma CVD is generally used.
D (chemical vapor deposition) method is used.

The drawing schematically shows a parallel plate type plasma CVD apparatus. To explain its operation, raw material gases such as SiH4, 5izH6, PH3°B2HEI, NH3, etc. are introduced into the chamber 1 through the gas inlet 2 and the gas ejection hole 3, and the substrate side electrode 4 and the high frequency side electrode 5 are connected to each other. A high frequency voltage (for example, 13.56 MHz) is applied by the high frequency power supply 6 between
is applied to generate plasma discharge. The raw material gas is decomposed and reacted in this plasma to form an a-Si film or an insulating film on the substrate 7. During this film-forming process, excess raw material gas is removed from the exhaust port 8, and the inside of the chamber 1 is maintained at a predetermined pressure (0.02 to 3 Torr). Further, the substrate 7 is heated to a predetermined temperature (100 to 4
00°C).

At this time, the 0 adsorbed on the chamber 1 and the electrodes 4 and 5
2, H20, GO2, and other adsorbed gases decompose and react in the plasma, and are incorporated into the film as impurities, deteriorating the film quality. Specifically, in the case of an a-Si film, when 02 is mixed, the clear conductivity σD increases, the ratio σP/σ0 with the photoconductivity σp worsens, and the photodegradation of σp is accelerated. . Furthermore, if the insulating film is made of Si3N4, the dielectric strength and moisture resistance will be lowered.

Conventionally, in order to remove this kind of adsorbed gas, N2 gas or N2 gas is introduced into the chamber 1 and discharged before doping.

However, when using the N2 gas method, CO2 is removed, but 02 is reduced to N20, and remains in the chamber 1 in this N20 state. Furthermore, when using the N2 gas method, 02 is removed as NOx, but CO2 is difficult to remove. Furthermore, since the decomposition energy of N2 is high and the discharge is performed with high high frequency power, the substrate 7 or the coated element may be damaged. In particular, when creating an insulating film for passibasigon, a-3i serves as the base.

J Aflffi poles etc. are subjected to impact and their characteristics deteriorate.

Purpose The present invention was made in view of the above points, and provides a thin film manufacturing method that can reliably remove impurities such as 02 adsorbed to chambers, electrodes, etc., and can form a high-quality film. The purpose is to

Structure The present invention introduces N H3 gas into the chamber before doping and discharges the adsorbed gases 02 and N20.
．． The feature is that C'02 etc. are removed.

Here, in this embodiment, the plasma CVD apparatus shown in the drawings is used as is.

As in this example, by using N H3 gas,
First, NH3 is decomposed to produce NN ions, N ions, N ions, etc., and 02. N20 becomes NOx and CO2
becomes CY HX, 02. Both N20 and CO2 can be removed efficiently.

Furthermore, compared to N2 gas, NH3 gas has lower decomposition energy and reacts with lower power, so there is no impact on the substrate as seen in the case of N2 gas, and there is no deterioration of device characteristics. In this way, before doping, NH
By removing impurities using three gases, the performance and reliability of manufactured devices can be improved.

The discharge conditions for this NH3 gas include a NH3 gas flow rate of 10 to 11005 CC, and a chamber pressure of 0.02.
~2 Torr, which was relatively good when the high frequency power was 10-300W.

More preferably, these conditions are set to 22, respectively, in the above-mentioned order.
5-60sec, 0.1-ITorr, 2O-10
It is 0W. Also, when using NH3 gas, a-8i
:N:H (meaning a-8'i N-doped) or Si3N4 and N5:rNxOv films are particularly advantageous. In these cases, N is also used as the raw material gas during doping.
Since H3 gas is used, there is also the advantage that the gas switching operation is easy.

Incidentally, when forming the a-8i:N:H film, we compared the conventional N2 gas method and the NH3 gas method according to the present invention as discharge gas species for removing adsorbed gas, and found that the photoconductivity σP of the film properties was lower than that of the conventional N2 gas method and the NH3 gas method according to the present invention. In the method, it was 1.5Xto-4 (0 ports)-1, but 2.0XIO-3 (Ωam)-
”.Also, the dark conductivity σD was 5.0XIO-s(0cm)-' in the conventional method, but it became 2.0X10-&(0cm)-'. In addition, a coplanar cell was used to measure σP, and 10
This was carried out under 0 mW/cu (AMI) irradiation.

Effects As described above, the present invention uses NH3 gas as the discharge gas species for removing adsorbed gas, so 02°N20. C.O.
All secondary adsorbed gases can be removed efficiently.
It is possible to reduce the amount of impurities mixed into the film and improve the film properties.

Since NH3 gas reacts with low power, plasma damage to the underlying layer can be reduced, and in this respect, the properties of the film and
This can improve reliability.

[Brief explanation of drawings]

The drawing is a schematic side view showing a plasma CVD apparatus.

Claims (1)

[Claims] In a thin film manufacturing method using a plasma CVD method in which a raw material gas is introduced into a chamber and decomposed and reacted in plasma generated by high-frequency glow discharge to form a thin film on a substrate,
A thin film manufacturing method characterized by introducing NH_3 gas into a chamber and causing discharge before doping the source gas.