JPH01223719A - Film formation of polycrystalline silicon - Google Patents

Abstract

PURPOSE:To crystallize an amorphous silicon film and to form a polycrystalline silicon film whose surface is flattened as a mirror surface, by depositing the amorphous silicon film onto a substrate by thermally decomposing a silane gas at a specific substrate temperature or lower and annealing the whole at a fixed temperature or lower. CONSTITUTION:A normal vapor growth device is used, a substrate to be film-formed 3 is placed onto a susceptor 2 in a growth chamber 1, and heated by a heater 4. A source gas is introduced to a shower 5 from a gas introducing port 1S, and fed onto the substrate to be film-formed 3. The gas in the growth chamber 1 is exhausted from an exhaust port 1D so that the inside of the growth chamber 1 is kept at specified pressure. The temperature of the substrate is elevated to 450 deg.C or less, Si2H6 is employed as the source gas, and the pressure of Si2H6 is reduced to 0.3-30Torr, and thermally decomposed on the substrate, thus growing an a-Si film. The whole is annealed at a temperature of 600 deg.C or less in nitrogen by using a normal heating furnace. Accordingly, the mirror surface-shaped polySi film, which has approximately single orientation and the surface of which is flattened, is acquired, and the breakdown resistance of an insulating film formed onto the polySi film is increased, thus improving the reliability of the device.

Description

[Detailed description of the invention] 〔overview〕 Regarding the method of forming a polySt film.

Obtaining a mirror-like poly-Si film with a flat surface with a single orientation,
The aim is to improve the breakdown resistance of the insulating film formed on top of this and make devices more reliable.

An amorphous silicon (a-5i) film is deposited on the substrate by thermal decomposition of silane gas at a substrate temperature of 450° C. or lower.

The substrate is annealed at 600° C. or lower to crystallize the amorphous silicon film to form a substantially single-oriented polycrystalline silicon film.

[Industrial application field]

The present invention relates to a method for forming a polycrystalline silicon (poly-Si) film.

Poly-Si films are often used as conductive films and the like in the formation of semiconductor devices.

[Conventional technology]

When an insulating film is formed on a poly-Si film and used as an insulating layer between the eyebrows of semiconductor devices such as non-volatile memories and highly integrated dynamic memories, problems may arise due to protrusions of the poly-Si that occur when using conventional film formation methods. The electric field concentration destroyed the nine interlayer insulating layers, reducing the reliability of the device.

In the conventional film forming method, for example, monosilane (S i t l 4) was used as a source gas, the pressure was reduced to several Torr, and poly-Si was deposited by thermal decomposition on a substrate at 620''C.

In this case, since the crystal grains of the poly-Si film formed have multi-orientation, the surface of the film does not become flat like a mirror surface.
This produces irregularities on the surface that are uniformly distributed at submicron intervals.

Therefore, the insulating film formed on such a poly-Si film has the drawback of being easily destroyed as described above.

[Problem to be solved by the invention]

An object of the present invention is to obtain a film forming method in which the surface of a poly-Si film is flattened like a mirror surface.

[Means to solve the problem]

To solve the above problem, amorphous silicon (a-5i) is formed on the substrate by thermal decomposition of silane gas at a substrate temperature of 450°C or less.
The amorphous silicon film is crystallized by depositing a film and annealing the substrate at a temperature below 600°C.

This is achieved by a film forming method characterized by forming a polycrystalline silicon film in which the crystal axes of each crystal grain have approximately a single orientation.

[Effect]

In the present invention, the surface of the poly-Si film is flattened by i-orienting the crystal axes of each crystal grain of the poly-Si film.

According to the experimental results of the present inventors, etc.

First, an a-Si film is grown on a substrate at a low temperature of 450°C or less.

It was found that a substantially single-oriented poly-Si film can be obtained by subsequent low-temperature annealing at 600° C. or lower for crystallization.

Surface irregularities due to crystal grain orientation were observed using a Nomarski differential interference microscope at a magnification of 5 μm/cm.

Figure 2 (11 to (4)) are photographs showing the experimental results of observing the surface of the poly-Si film deposited on the SiO□ layer after annealing in nitrogen (N2) at 600°C using the deposition temperature (substrate temperature) as a parameter. This is a copy of the figure.

From the figure, when the deposition temperature in FIG. 2 (1) is 450°C.

Although the surface of the poly-Si film is so flat that it cannot be seen at this magnification, it can be seen that as the deposition temperature increases, the surface irregularities become larger.

As a result, it was found that according to the film forming method of the present invention, almost no surface irregularities were observed, and a flat mirror surface was obtained.

In addition, the fact that polySi has a single orientation can be confirmed by X-ray diffraction.
It was found that the film surface was oriented in the (111) plane.

FIG. 3 is for the sample in FIG. 2 (1). FIG. 3 is a diagram showing a rocking curve of a poly-Si film.

The vertical axis shows the specific intensity of diffraction, and the horizontal axis θ° is X'fIfA
is the angle of incidence of

The solid line in the figure is the rocking curve of Si, and the 9 diffraction intensity is (1
11) has a sharp peak.

The dotted line in the figure indicates doped arsenic (As).

If the growth temperature of the a-Si film is higher than 450° C., it will crystallize as a multi-oriented polycrystalline film after annealing.

For low-temperature growth of an a-Si film, it is more advantageous to use disilane (Sizlls) as a source gas than the conventional 5it14. Alternatively, it is also possible to use a higher order silane.

Furthermore, if the crystallization annealing exceeds 600° C., nuclei having other crystal axes are generated and a single orientation is not achieved.

〔Example〕

FIG. 1 is a sectional view of an apparatus used for film formation to explain an embodiment of the present invention.

The apparatus is a normal low pressure chemical vapor deposition (LP-CVD) apparatus, and a substrate 3 to be grown is placed on a susceptor 2 in a growth chamber 1.

The growth substrate 3 is heated by a heater 4 provided within the susceptor 2 .

The source gas is led to Java 5 from the gas inlet IS,
It is supplied onto the growth substrate 3.

The exhaust port ID is installed so that the inside of the growth chamber 1 is maintained at a predetermined pressure.
More exhaust.

(11a - Growth of Si film Using the above-mentioned apparatus, the substrate temperature was set to 450°C, 5 iJb was used as the source gas, and this was heated at 0.3 to 30 Torr.
The a-Si film is grown by thermal decomposition on the substrate.

Conventional LP-CVD a-Si films are grown at 560-580°C using Sign.

(2) Crystallization Annealing Annealing is performed at 600° C. in nitrogen using a normal heating furnace.

〔Effect of the invention〕

As explained above, according to the present invention, a mirror-like poly-Si film having a substantially single orientation and a flat surface can be obtained.

The dielectric breakdown resistance of the insulating film formed thereon can be improved, and the reliability of the device can be increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus used for film formation to explain one embodiment of the present invention. Figure 2 (1) to (4) show S after annealing in nitrogen at 600°C.
FIG. 3 is a schematic diagram showing the results of an experiment in which the surface of a poly-Si film deposited on an iO□ layer was observed using the deposition temperature as a parameter. FIG. 3 is a diagram showing a rocking curve. In fig. 1 is the growth room. is is the gas inlet. ■D is the exhaust port. 2 is the susceptor. 3 is a growth substrate. 4 is a heater. 5 is a shower 6000C.
℃ Kisetsu Shiriyumi - Saitoji Komu Day Z Oral Procedures Correction Book Ceremony) 1. ' Showing 4 items 1986 Patent Application No. 049066 2 Name of the invention Method for forming a film of polycrystalline silicon 3 Relationship with the person making the amendment Patent applicant address 1015 Kamiodanaka, Nakahara-ku, Yozaki City, Kanagawa Prefecture (5
22) Masu Fujitsu Co., Ltd. 5. Date of amendment order: May 31, 1986 (shipment date) 6. Amended engraving drawing b'J', j ”y Denden x!: 450' C 000C Missing episode 5 Shikipu N2 -Annie-Luno exchange: Sn°/S, 0°550℃ May m 6500C Yo own theory, Akeburo 4 Shoki 2 Kimi Z Day

Claims (1)

[Claims] An amorphous silicon (a-Si) film is deposited on the substrate by thermal decomposition of silane gas at a substrate temperature of 450°C or lower, and the amorphous silicon film is crystallized by annealing the substrate at 600°C or lower. 1. A method for forming a polycrystalline silicon film, the method comprising: forming a polycrystalline silicon film having a substantially single orientation.