JPS6052578A - Formation of silicon nitride film - Google Patents

Abstract

PURPOSE:To form a silicon nitride film having good quality on a substrate at a low temp. with good mass productivity by bringing a gaseous mixture contg. gaseous silane and gaseous hydrazine into excitation and reaction by plasma. CONSTITUTION:A substrate 3 placed on a rotary table 4 is heated and held to and at about 300-350 deg.C by a heater 5 in a reaction vessel 2 in which about 0.1-1Torr gaseous pressure is maintained by a vacuum evacuating system 1. The reactive gas consisting of a gaseous mixture composed of gaseous SiH4 and gaseous N2H4 supplied at an adequate flow rate by controlling flow rate regulating valves 11 by a controller 12 in accordance with the information from flowmeters 10 and a pressure sensor 13 is introduced through a gas introducing part 9 into the vessel 2. A high frequency is the supplied from a high frequency power source 6 via a high frequency electrode 8 to induce a plasma reaction in a plasma generating part 7. As SiN film having a low content of H, a uniform film thickness and good denseness is thus formed on the substrate 3 at a high rate of deposition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a silicon nitride film useful as a protective film/insulating film for devices.

The silicon nitride film acts as a good barrier against Na ions,
It also has good moisture resistance and insulation properties, making it useful as a protective film and insulating film for devices. Conventionally, a thermal perforation method has been used as a method for forming a silicon nitride film, but the thermal nitridation method
Since a high temperature of 00° C. or higher is required, deformation of the impurity profile is inevitable, making it difficult to apply it to high-density integrated devices. As a countermeasure to this problem, plasma C was developed to form a silicon nitride film at a relatively low temperature (250 to 400 degrees Celsius) through a reaction using plasma.
VD technology has suddenly attracted attention and is being actively researched.

A plasma CVD apparatus usually includes a plasma generation section, a gas introduction section, a vacuum evacuation line, a power supply system, a control system, and the like. Various excitation means such as high-frequency discharge 5-electron cyclotron resonance and ion beam are used to generate plasma, but from the viewpoint of mass production, the gas pressure is set at 0.1 to 1'l'orr.
The most common method is to use high-frequency discharge.

Conventionally, in a silicon nitride film formed by plasma CVD technology, a mixed gas containing either silane gas and ammonia gas or a mixed gas containing silane gas and nitrogen gas has been used as a reaction gas. Silane gas is a general term for silicon hydrides, but generally refers to monosilane SiH4. However, attempts have also been made to use disilane Si2H6 as the silane gas.Since ammonia gas NH3 is much more reactive than nitrogen gas N2, it is better to use a 5IH4/NH8-based mixed gas because SiH4/ The deposition rate is higher than when using an Nt-based mixed gas, and it is superior in terms of mass productivity. However, when examining the film quality of the deposited film formed using an infrared absorption method, it was found that almost no N-H absorption was observed in the film made of SiH+/7% yarn, whereas SiH4/NH Very strong N--H absorption was observed in the film made using this system, and it was found that the film contained a large amount of hydrogen, ranging from 10 to 30%. In addition, for evaluation of compactness, buffered hydrofluoric acid BHF
Comparing the etch speeds of SiH4/NH!
The etch rate of the film made with the system is 2500X/order,
Etch rate of film made of SiH,/N, thread ~500A
It was found that it was about five times larger than /wR, and there was also a problem in denseness.

Therefore, an object of the present invention is to provide a method for forming a silicon nitride film that eliminates the drawbacks of these conventional silicon nitride film forming methods and can form a silicon nitride film of high quality with good mass productivity at low temperatures.

The method of the present invention is a method for forming a silicon nitride film in which a reaction gas containing nitrogen and silicon as elements is excited to cause a reaction, and a silicon nitride film is deposited on a substrate. It is characterized by using a mixed gas containing silane gas and hydrazine gas.

The present invention will be described in detail below with reference to the drawings. The figure is a block diagram showing an example of the configuration of a device for implementing the present invention.

In the figure, vacuum evacuation system 1 consists of an oil rotary pump and a mechanical booster pump connected in tandem, and reaction tank 2
It is used to reduce the internal gas pressure by 0.1 to I Torr I/C. As a protection measure for the evacuation system 1, traps, baffles, etc. are used in the evacuation system 1 to prevent damage and deterioration of the pump.

The substrate 3 is placed on a rotary table 4, and is heated to about 300 to 350° C. by a heater 5 and kept warm. The high frequency power supply 6 supplies high frequency waves of 13.56 MHz into the reaction tank 2 via the high frequency electrode 7 to ionize gas in the plasma generating section 8 and generate plasma. The reaction gas is supplied into the reaction tank 2 through the gas introduction section 9, and a plasma reaction occurs within the plasma generation section 8. In the gas introduction part 9, monosilane gas SiH4, hydrazine gas N, H
4 and nitrogen gas N2 are piped, and their flow rates and flow rate ratios are determined by the flow meter 10 and the pressure sensor 1.
Based on the information in No. 3, the controller 12 controls the flow rate adjustment valve 11 to set the optimum value.

Nitrogen gas N is used to purify the reactor.

In the above configuration, when the working pressure is 0.5 Torr, the discharge power is 1/2, the total gas amount is 2000 sec, and the mixing ratio of monosilane gas and hydrazine gas is 1=2, silicon nitride is deposited at a deposition rate of about 2000 A/m. A film was formed, and the uniformity of the film thickness was within ±5 inches between wafers when ten 5-inch diameter wafers were used.

In this invention, unlike the conventional method of forming a silicon nitride film, ammonia gas NH,
Since hydrazine gas (N, H, gas) is used instead of hydrazine gas, the hydrogen content in the formed thin film can be reduced to a factor of 5 or less, and the film quality can be significantly improved compared to the conventional method. This means that hydrazine gas N, H, ammonia gas NH,
This is thought to be largely due to the lower hydrogen content compared to .

In addition, since hydrazine gas is easily oxidized and has a strong reducing power so that it is used as rocket fuel, the airtightness of the piping must be maintained to avoid air contamination to the same extent as monosilane (Sin). It is necessary to give sufficient consideration.

In the embodiments of the present invention, an example has been shown in which the present invention is applied to a coupled type (parallel plate type) plasma CVD apparatus, but the present invention may be applied to an inductively coupled type plasma CVD apparatus instead. It goes without saying that the present invention may be applied to an electron cyclotron resonance plasma CVD device, a light-excited plasma CVD device, or the like instead of a plasma CVD device.

As the silane gas, monosilane (S
Disilane Si2H6 can also be used instead of in4).

As described above, according to the present invention, there is provided a method for forming a silicon nitride film that can be mass-produced at low temperatures, and can form a high-quality silicon nitride film.

[Brief explanation of the drawing]

The figure is a block diagram showing an example of the configuration of a device for implementing the present invention. In the figure, 1... Vacuum exhaust system 2... Reaction tank 3... Substrate 4... Rotating table 5... Heater 6... High frequency power source 7... High frequency electrode 8... Plasma generation part 9...
Gas introduction part 10... Flow meter 11... Flow rate adjustment valve 12... Controller 13... Pressure sensor. Representative Patent Attorney Fu Hakubi

Claims (1)

[Claims] A method for forming a silicon nitride film in which a mixed gas containing silane gas and hydrazine gas is excited and reacted to form a silicon nitride film on a substrate.