JPS63299363A - Formation of polysilicon film doped with phosphorus - Google Patents

Abstract

PURPOSE:To enable the effective forming of a polysilicon film doped with phosphorus good in its particle diameter, by using a vapor growth method to form an amorphous silicon film doped with phosphorus and next using heat treatment to perform polycrystallization. CONSTITUTION:A wafer is mounted on a wafer susceptor 19, and an infrared lamp 17 is used to heat the wafer, and a carrier gas and an inactive gas are supplied inside a reaction chamber 6 from gas supply ports 10 and 24. Next, a disilane gas and a phosphine gas are supplied from the gas supply port 10, and an amorphous silicon film doped with phosphorus is made to grow and formed on the wafer. Next the wafer is projected into a diffusion furnace and provided with heat treatment under a nitrogen atmosphere. Hence, a polysilicon film doped with phosphorus good in its particle diameter can be effectively formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a phosphorus-doped polysilicon film used as a gate electrode or wiring material of a semiconductor device.

Conventional technology The polysilicon film doped with phosphorus is silicon
It has become an important technology as a gate electrode or wiring material for OS devices. First, a conventional method for forming a polysilicon film doped with phosphorous will be described below.

First, a polysilicon film is deposited by vapor phase growth.

FIG. 2 shows a schematic diagram of a commonly used vapor phase growth apparatus. A large number of semiconductor wafers 3 arranged in a quartz boat 2 are put into a reaction tube 1 made of a quartz tube, and the temperature is 0.1 to 1.
While flowing monosilane gas (StH4) from the gas inlet 4 under reduced pressure of Torr, the reaction tube 1 is heated to SOO to 660[deg.] C. by a resistance heater 6 provided around the reaction tube 1 for growth. Next, the semiconductor wafer is transferred to a diffusion furnace (having a reaction tube similar to the vapor phase growth apparatus described above) and phosphine (PH3
) and oxygen (o2) at about 1oOoC while flowing under normal pressure. A polysilicon film doped with phosphorus is formed by the process.

Problems to be Solved by the Invention However, in the above method, since the surface of the polysilicon film is oxidized, a step of removing the oxide film on the surface using an etching solution such as hydrofluoric acid is required afterwards. Additionally, in the vapor phase growth of polysilicon films, the temperature is generally set to be low on the gas inlet side of the reaction tube 1 and high on the exhaust side in order to make the film thickness uniform across the semiconductor layer. . Therefore, the produced polysilicon film has a substantially uniform film thickness on each semiconductor wafer, but the grain size differs. Furthermore, doping with phosphorus in a diffusion furnace causes an increase in grain size, resulting in the finally formed polysilicon film having large crystal grains and non-uniformity. Furthermore, etching tends to occur along crystal grains, making it difficult to form highly accurate circuits, and this is one of the challenges for applying it to devices that will continue to become smaller and more highly integrated.

Therefore, as a means to solve these problems, a method has been proposed in which phosphorus is deposited simultaneously with the vapor phase growth of a polysilicon film. However, when silane gas is used as the raw material gas, the growth rate is significantly reduced due to the addition of phosphine gas, which is a source of phosphorus. In addition, the phosphorus-doped polysilicon film formed by this method cannot be used as it is for gate electrodes due to its high resistance, so heat treatment is required as a post-process, but this causes an increase in grain size, which is a problem. remains.

Therefore, the present invention provides a method for forming a phosphorus-doped polysilicon film having a good grain size that can accommodate future miniaturization and higher integration of semiconductor devices.

Means for solving the problems and technical means of the present invention for solving the above problems are as follows:
First, a phosphorus-doped amorphous silicon film is formed by vapor phase growth using disilane gas and phosphine gas as raw material gases, and then a phosphorus-doped polysilicon film is obtained by heat treatment.

For production The effect of this technical means is K as follows.

In other words, when disilane gas is used as the raw material gas, the growth rate does not decrease even when phosphine is added, and by forming an amorphous silicon film in this vapor phase growth, the grain size remains unchanged even after subsequent heat treatment. It is possible to maintain a smaller size than in the conventional method, and to effectively form a good phosphorus-doped polysilicon film suitable for miniaturization.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the accompanying drawings. First, an amorphous silicon film doped with phosphorus is grown in a vapor phase. FIG. 1 shows a schematic diagram of the vapor phase growth apparatus used in this example.

The reaction chamber 6 is composed of a wall member 8 made of stainless steel and having a water cooling groove 7 therein, and a transparent quartz plate 9 provided at the top. This transparent quartz plate 9 is fixed to the wall member 8 using known gas sealing means such as an O-ring. A gas supply port 1o is provided at one end of the side wall of the reaction chamber 6, and disilane, phosphine, and nitrogen gas as a carrier gas are supplied to the gas supply port 10 at predetermined flow rates through flow meters 11, 12, and 13. A provided gas supply pipe 14 is connected. The other end of the reaction chamber 6 is provided with a gas exhaust port 15 connected to a vacuum exhaust device such as a rotary pump (not shown). Further, a heating block 16 is attached above the outside of the reaction chamber 6. This heating block 1
6 has a structure in which a plurality of infrared rungs 17 are arranged and a reflecting mirror 18 is arranged above them. Inside the reaction chamber 6, a wafer support 19 made of graphite coated with SiC is installed on which a wafer is placed. The wafer support 19 is connected to a rotation means 21 by a support post 20. Further, on the exhaust side wall of the reaction chamber 6, an inert gas supply port 24 is connected to an inert gas supply pipe 23 having a flow meter 22 disposed in the middle thereof, and has an opening near the lower surface of the transparent quartz plate 9. is formed. Further, an inert gas is supplied from the inert gas supply port 24 between the outer periphery of the inert gas supply port 24 and the lower surface of the transparent quartz plate 9, the outer periphery of which is supported by a protrusion 26 on the side wall of the reaction chamber at a position close to the bottom of the inert gas supply port 24. A partition plate 26 made of transparent quartz that forms a flow path is arranged so that the gas first flows along the lower surface of the transparent quartz plate 9 as shown by the arrow, and then turns around at the gas supply port 10 side and is ejected into the reaction chamber 6. It is a provision. This is done by blowing out an inert gas from the partition plate 26 to release disilane or phosphine gas into the transparent quartz plate 9. This is also to prevent unnecessary film adhesion by preventing contact with the partition plate 26.

A phosphorus-doped amorphous silicon film was grown using a vapor phase growth apparatus having the above configuration. First, a wafer was placed on a wafer support stand 19, and the wafer temperature was set at 650° C. using an infrared lamp 17 while being rotated by a rotating means. Next, nitrogen gas as a carrier gas is supplied to Q using the flow meter 13.
573/min.

and nitrogen gas 2 as an inert gas in the flow meter 22.
1j/min for each gas supply port 10. and is supplied into the reaction chamber e from the inert gas supply port 24, and at the same time exhausts the gas from the gas exhaust port 15 to reduce the pressure in the reaction chamber 6 to approximately 5.
It was held at Torr. Next, in this state, flowmeter 11.1
Disilane 20cc/min through 2.

Phosphine was supplied at a rate of 2.4 cc/min and growth was performed for 2 minutes. When the film formed on the wafer was confirmed by electron beam diffraction, it showed a no-row pattern and was found to be amorphous.

Next, heat treatment is applied to the circles in order to crystallize them.

The wafer was placed in the diffusion furnace described in the conventional example and processed at 1000'C for 30 minutes in a nitrogen atmosphere. As a result of comparing and evaluating the phosphorus-doped polysilicon film formed in this way with a film formed using a conventional method using a transmission electron microscope, it was found that the polysilicon film formed in this example had uniform crystal grains, It was also found to be good.

Although nitrogen was used as the carrier gas and inert gas in the above embodiments, the present invention is not limited to this, and any gas that does not cause a reaction, such as helium, can be used. Furthermore, in this example, a device using a resistance heater as the heat source was used for heat treatment, but it is expected that a heat treatment furnace that uses lamp heating would require shorter treatment time and would further enhance the effects of the present invention. .

Effects of the Invention As described above, the present invention first forms phosphorus-doped amorphous silicon by vapor phase growth, and then polycrystallizes it by heat treatment. This method can efficiently obtain a silicon film and is suitable for semiconductor devices that are becoming smaller and more highly integrated.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a vapor phase growth apparatus used in an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a vapor phase growth apparatus used for conventional vapor phase growth. 6...Reaction chamber, 17...Infrared lamp, 19...Wafer support stand.

Claims (1)

[Claims] A method for forming a phosphorus-doped polysilicon film, which comprises forming an amorphous silicon film doped with phosphorus by vapor phase growth of phosphine gas and disilane gas, and then polycrystallizing the silicon by heat treatment.