JPH01266743A - Manufacture of silicon conductor - Google Patents

Abstract

PURPOSE:To enable withstand voltage of thermal oxide film to be higher by forming amorphous silicon thin film with a polycrystal silicon obtained by heat treatment. CONSTITUTION:A silicon conductor 13 consists of a polycrystal silicon obtained by allowing an amorphous silicon thin film containing impurities giving conductivity to be subjected to heat treatment. Also, it is obtained by making a mixture gas of silicon hydrogenerated object (SinH2n+2, n>=2) and group 3 or group 5 hydrogenerated object as a material gas and by building up amorphous silicon on a substrate 11 in a build-up temperature range of 400-600 deg.C. It increases gate withstand voltage of a thermal oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a silicon conductor, and particularly to a silicon conductor used for gate electrodes of semiconductor devices and a method for manufacturing the silicon conductor.

[Conventional technology]

A silicon conductor conventionally used as a gate electrode of a semiconductor device is generally made of a polycrystalline silicon film to which phosphorus is added at a high concentration by vapor phase diffusion or ion implantation.

The general method for forming silicon films for gate electrodes of semiconductor devices is as follows: (1) A polycrystalline silicon film with no added impurities is formed by low-pressure vapor phase growth using silane (SiH) gas as the main reaction gas. Later, POCL, heat treatment in a gas atmosphere,
Method of diffusing phosphorus into polycrystalline silicon (vapor phase diffusion method)
(2) After forming a polycrystalline silicon film in the same manner as in (1) above, phosphorus ions are implanted into the silicon (ion implantation method). (3) Silane (SiH4) gas and phosphine (pH 3)
) There are three methods in which phosphorus is added during film formation using gas as a reaction gas.

[Problem to be solved by the invention]

However, since the conventional polycrystalline silicon film is polycrystalline immediately after the film is formed, there is a problem in that side etching as shown in FIG. 9 tends to occur when etching the silicon film by the plasma etching method. In addition,
In FIG. 9, 1 is resist, 2 is polycrystalline silicon (
The phosphorus concentration is 1 x 1021 -3).

Further, when a thermally oxidized film of a polycrystalline silicon film is used as a gate film of a semiconductor device, there is a problem that the gate breakdown voltage decreases as the phosphorus concentration becomes high, as shown in FIG.

Further, in the method for manufacturing a polycrystalline silicon film described in (1) above,
Since it is necessary to perform heat treatment at a temperature of about 900'C to 1000C, there are problems such as the inability to lower the temperature of the gate electrode forming process and the fact that the film is polycrystalline.

Furthermore, in the method for manufacturing a polycrystalline silicon film described in (2) above,
Heat treatment at about 90°C to 1000°C is required to make the phosphorus concentration distribution in the film uniform and to activate the implanted phosphorus, making it impossible to lower the temperature of the gate electrode formation process;
Further, there is a problem that the diffusion of impurities into the gate oxide film has a negative effect on the reliability of the semiconductor device.

In addition, with the manufacturing method (3) above, there are problems such as it is difficult to form a film with a uniform thickness, the formed film is polycrystalline, and the time required for film formation is long. was there.

In addition, plasma C
VD (Chemical Vapor Deposits)
However, there is a problem in that the plasma bombardment causes deterioration of device characteristics and breakdown of the insulation film.

The present invention has been made to solve the above problems.

An object of the present invention is to provide a silicon conductor whose thermal oxide film has a high gate breakdown voltage.

Another object of the present invention is to provide gates for semiconductor devices. To provide a method for manufacturing a silicon conductor which has excellent processability by plasma etching and whose thermal oxide film has a high gate breakdown voltage at a temperature of 600° C. or lower in the manufacture of silicon conductors used in i[, etc. There is a particular thing.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve division problems]

In order to achieve the above object, the silicon conductor of the present invention has the following features:
The main feature is that it is made of polycrystalline silicon obtained by heat-treating an amorphous silicon thin film containing impurities that provide conductivity.

Further, in the method for manufacturing a silicon conductor of the present invention, a mixed gas of a silicon hydride (SinH2□2, n≧2) and a group 3 or group 5 hydride is used as a raw material gas, and the deposition temperature is 4.
The main feature is that it includes a step of depositing amorphous silicon on a substrate at a temperature in the range of 00 to 600°C.

[Effect]

According to the above means, the silicon conductor of the present invention is made of polycrystalline silicon obtained by heat-treating an amorphous silicon thin film containing impurities that impart conductivity, and therefore cannot be used in conventional semiconductor integrated circuits. The withstand voltage of the oxide film obtained by oxidizing the silicon conductor can be increased compared to that of the silicon conductor.

Further, the method for producing a silicon conductor of the present invention uses a mixed gas of a silicon hydride (S l nH2n+z, n≧2) and a group 3 or group 5 hydride as a raw material gas, and the deposition temperature is 400 to 600. Since the silicon film is deposited in the temperature range of 600°C, we use a silicon conductor with excellent processability in the plasma etching method and a high gate breakdown voltage of the thermal oxide film.
It can be manufactured at a heat treatment temperature of "C" or lower.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be specifically described using the drawings.

Incidentally, for the purpose of explaining the embodiments.

Components having the same function are given the same reference numerals, and repeated explanations thereof will be omitted.

FIG. 1 is an impurity distribution characteristic curve showing the impurity distribution in a film obtained by secondary ion analysis of a silicon conductor according to an embodiment of the present invention.

The silicon conductor of one embodiment of the present invention is made of polycrystalline silicon obtained by heat treating an amorphous silicon thin film containing impurities that provide conductivity. As the impurity imparting conductivity, for example, phosphorus (P) is used. The phosphorus concentration (impurity concentration) is about I x 10''(!11-'), and the impurity concentration distribution in the film is uniform.

The film quality of the silicon thin film made of polycrystalline silicon in this example was confirmed by electron diffraction, with a halo pattern in the diffraction image, and the polycrystalline silicon thin film was confirmed to be amorphous before heat treatment. It was done.

Next, an example will be described in which the thermal oxidation film of the silicon thin film (conductor) made of polycrystalline silicon of the present embodiment is applied as a gate film of a MOS diode.

FIG. 2 shows the thermal oxidation film of the silicon conductor of this example.
It is a cross-sectional view of a main part showing a schematic configuration of an example applied as a gate film of an OS diode, in which 11 is a silicon substrate, 12 is an oxide film such as Sin, 13 is a silicon conductor of this embodiment, and 14 is a silicon conductor of this embodiment. Thermal oxide film (gate film) of the silicon conductor 13 and 15 are metal or silicon conductors. The thickness of the thermal oxide film (gate film) 14 is approximately 100 mm.

Thermal oxide film (gate film) 1 of MOS diode of this example
As shown in FIG. 3, the breakdown voltage of No. 4 did not decrease at all. The reason for this is that the silicon conductor 13 of this embodiment before the oxide film is formed is amorphous.

As can be seen from the above description, according to the silicon conductor 13 of this embodiment, compared to the silicon conductor used in the conventional half-core integrated circuit, the silicon conductor 13 is obtained by thermally oxidizing the silicon conductor 13. The breakdown voltage of the thermal oxide film (Ge 1-) 14 can be increased, and the breakdown voltage does not decrease even if a large number of impurities are implanted.

Next, an embodiment of the method for manufacturing a silicon conductor film of the present invention will be described.

FIG. 4 is an explanatory diagram for explaining the schematic configuration of one embodiment of a reaction apparatus for carrying out the method of manufacturing a silicon conductor (thin film) of the present invention.

The reaction apparatus of this example is as shown in FIG.

This is a commonly used diffusion furnace type low pressure CVD device, in which 21 is a reaction tube, 22 is an electric furnace, 23 is an exhaust system,
24 is a disilane (SxzHW gas cylinder), 25 is a phosphine (PH3) gas cylinder, 26 is a carrier gas cylinder, 27 is a quartz boat, and 28 is a silicon wafer.

In FIG. 4, a silicon wafer 28 placed on a quartz boat 27 in a reaction tube 21 at a temperature of 400° C. to 600° C.
is inserted, and the inside of the reaction tube 21 is evacuated. When the temperature of the reaction tube 21 is stabilized, disilane gas and phosphine gas are introduced into the reaction tube 21 from a disilane (SxzHs) gas cylinder 24 and a phosphine (PH3) gas cylinder 25 for a desired time, and a silicon conductor containing phosphorus is placed on a silicon wafer 28. 13 films are formed.

FIG. 5 shows the relationship between the deposition rate of the silicon conductor 13 film, the phosphorus concentration in the silicon conductor 13 film, and the disilane partial pressure.

The film deposition rate of the silicon conductor 13 increases approximately in proportion to the partial pressure of disilane, and the phosphorus concentration increases approximately 2/2 of the partial pressure of disilane.
It is inversely proportional to the third power. Silicon conductor 13 before heat treatment
In order to change the crystallinity of the film to amorphous, it is necessary to lower the film deposition temperature to about 600°C or less, as described later.
As shown in FIG. 5, a practical film deposition rate can be obtained even at low temperatures.

The relationship between the phosphine partial pressure and the phosphorus concentration in the film of the silicon conductor 13 is shown in FIG. In FIG. 6, it can be seen from FIG. 6 that the phosphorus concentration in the film of the silicon conductor 13 is proportional to the phosphine partial pressure, and the concentration can be easily controlled.

Figure 7 shows that after heat-treating the amorphous silicon of this example,
Diffraction intensity measured by line diffraction method is shown.

The heat treatment time is 30 minutes.

As can be seen from Figure 7, a silicon conductor film containing no impurities becomes polycrystalline at a temperature of about 650°C, but a silicon conductor film containing a high concentration of impurities becomes polycrystalline at a temperature of 575°C.
Polycrystallizes at ~600°C.

Therefore, the temperature at which the film of silicon conductor 13 is deposited is approximately 6
A temperature of 00°C or lower is appropriate.

Also, as a silicon hydride, trisilane (3111H211+Z) can form a film at a lower temperature than disilane.

n>2) etc. may be used. In this case, since the deposition rate is high, the film formation time can be shortened.

FIG. 8 is a characteristic diagram based on an electron micrograph showing processing characteristics when the thin film of the silicon conductor 13 according to this embodiment is processed by a dry etching method such as a plasma etching method.

When the film of the silicon conductor 13 according to this embodiment is processed by the dry etching method, as shown in FIG.
Unlike the case of conventional polycrystalline silicon as shown in the figure,
No side etching was observed. The reason for this is that the film of the silicon conductor 13 before heat treatment is amorphous, so phosphorus in the thin film is not activated. In FIG. 8, 31 is a resist, and 32 is a silicon conductor (polycrystalline silicon) produced according to this embodiment.

As can be seen from the above description, according to the method for manufacturing the silicon conductor 13 film of this embodiment, the silicon conductor 13 film contains a high concentration of impurities that impart conductivity.
Since the crystallinity of the film immediately after deposition is amorphous, it has excellent processing characteristics by dry etching of the film. In addition, hydrides such as silicon disilane (SL, H2O, 2, n≧
2) and a 3a or 5m hydride such as phosphine as the raw material gas, and the deposition temperature was 400°C to 600°C.
Since the silicon film is deposited at a temperature within the range of 600° C. or lower, a silicon conductor whose thermal oxide film has a high gate breakdown voltage can be manufactured at a temperature of 600° C. or lower (film deposition temperature).

The reason why the deposition temperature is in the range of 400°C to 600°C is because
This is because the deposition temperature differs depending on the raw material gas used.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a silicon conductor whose thermal oxide film has a high gate breakdown voltage.

In addition, a silicon conductor with excellent processing characteristics using plasma etching method and a high gate breakdown voltage of its thermal oxide film is used.
It can be produced at temperatures below 0°C.

[Brief explanation of the drawing]

FIG. 1 is an impurity distribution characteristic curve diagram showing the impurity distribution in a film obtained by secondary ion analysis of a silicon conductor according to an embodiment of the present invention. FIG. 2 is a thermal oxidation diagram of a silicon conductor according to an embodiment of the present invention. membrane, M
FIG. 3 is a sectional view of a main part showing a schematic configuration of an example applied as a gate film of an OS diode. FIG. FIG. 1 is an explanatory diagram for explaining the schematic configuration of an embodiment of a reaction apparatus for carrying out the method of manufacturing a silicon conductor film of the present invention. FIG. 5 is a diagram showing the relationship between the deposition rate of a silicon conductor film, the phosphorus concentration in the silicon conductor 13 film, and the disilane partial pressure in an embodiment of the method for manufacturing a silicon conductor of the present invention; The figure shows data showing the relationship between the phosphorus concentration in the film of the silicon conductor and the phosphine gas partial pressure in this example.
Data showing the diffraction intensity measured by the line diffraction method, FIG. The figure shows the cross-sectional shape of a conventional polycrystalline silicon film processed by plasma etching. FIG. 10 shows data showing the dielectric strength when a conventional thermal oxidation film of a polycrystalline silicon film is used as a gate film of a gate electrode of a semiconductor device. In the figure, 1...resist, 2...polycrystalline silicon, 1
1... Silicon substrate, 12... Oxide film, 13...
Silicon conductor, 14... thermal oxide film (gate film), 1
5... Metal or silicon conductor, 21... Reaction tube, 22... Electric furnace, 23... Exhaust system, 24...
... Disilane gas cylinder, 25 ... Phosphine gas cylinder, 26 ... Carrier gas cylinder, 27 ... Quartz boat, 28 ... Silicon wafer, 31 resist, 32 ... Silicon conductor.

Claims (2)

[Claims] (1) A silicon conductor characterized by being made of polycrystalline silicon obtained by heat-treating an amorphous silicon thin film containing impurities that impart conductivity. (2) Silicon hydride (Si_nH_2_n_+_
2, n≧2) and a group 3 or group 5 hydride as a raw material gas, and a step of depositing amorphous silicon on a substrate at a deposition temperature in the range of 400 to 600°C. A method for manufacturing a silicon conductor.