JPH0258331A - Method for manufacturing silicon nitride thin film - Google Patents

Abstract

PURPOSE:To form a satisfactory silicon nitride thin film while easily controlling the quantity of hydrogen in the film by thermally depositing material silicon on a substrate simultaneously while irradiating it with excited nitrogen and hydrogen plasma. CONSTITUTION:A gas inlet 17 is introduced into a vacuum chamber 11 by precisely controlling the flow rate of nitrogen and hydrogen gases. The intensity of a magnetic field in a plasma generating chamber 15 is so set as to satisfy electron cyclotron resonance conditions thereby to generate a plasma having high dissociation degree. For example, when the frequency of a microwave is 2.45GHz, the electron cyclotron resonance is generated 875G of the intensity of the magnetic field. The generated plasma is passed through a plasma drawing window 18 to be radiated to a substrate 20 on a substrate holder 19. Material silicon 19 is contained in a deposition source 22, and material silicon 21 is, for example, heated to be melted by an electron beam heating method to be deposited on the substrate 20. Thus, the silicon is reacted with nitrogen on or near the substrate to form a silicon nitride thin film on the substrate 20.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing silicon nitride thin films.

BACKGROUND OF THE INVENTION Silicon nitride thin films are often used as passivation films for semiconductor devices, gate insulating films for amorphous silicon thin film transistors, etc. because of their good density, moisture resistance, and alkali ion resistance. Methods for forming silicon nitride thin films include thermal chemical vapor deposition (thermal CVD), sputtering, high-frequency plasma chemical vapor deposition (plasma CVD), and electron cyclotron resonance (EC).
R) Plasma CVD method, ion beam evaporation method, etc. are used.

Problems to be Solved by the Invention The thermal CVD method produces a very good silicon nitride thin film, but because the formation temperature is as high as around 800"C, it is difficult to form a film after A1 wiring of an integrated circuit or to form an amorphous silicon nitride film. It is difficult to use it as a silicon gate insulating film.

With sputtering, plasma CVD, and ion beam evaporation, it is possible to form a silicon nitride thin film at around 300°C. However, with the sputtering method, it is difficult to obtain a high-quality silicon nitride thin film because sputtering gas is mixed into the film, and the substrate is damaged during film formation, so it cannot be used as a passivation film or gate insulating film. .

In the ion beam evaporation method, there is damage caused by ions, so it cannot be used as a bashing film or a 1-fat film.

The plasma CVD method uses dangerous gases such as 5iHz gas, and the resulting film has incomplete bonding between Si and N, and also contains a large amount of hydrogen. Is it necessary to control the amount by controlling the substrate temperature or radiation? ■It is difficult to control the amount of hydrogen because the conditions need to be changed, and the film quality such as composition changes.

The ECR plasma CVD method can create a film without heating the substrate, and can create a high-quality nitride/recon thin film with almost no damage to the substrate. However, it uses dangerous gas such as 5iHa gas,
Furthermore, since NSiHa is used, the film contains hydrogen, and the amount of hydrogen can be controlled very easily.

Means for Solving the Problems In order to solve the following problems, the inventors have
Either a mixed gas of a nitrogen-containing gas and a hydrogen-containing gas is simultaneously excited by plasma decomposition using one microwave and electron cyclotron resonance absorption, or a nitrogen-containing gas and a hydrogen-containing gas are excited by microwave and electron excitation, respectively. The amount of hydrogen in the film can be easily controlled by independently exciting plasma decomposition using cyclotron resonance absorption and irradiating the substrate with the excited nitrogen and hydrogen plasma while simultaneously heating and vaporizing the raw material silicon. However, we have found that it is possible to form a good silicon nitride thin film.

Nitrogen gas, ammonia gas, or a mixture thereof is used as the nitrogen-containing gas, and hydrogen gas is used as the hydrogen-containing gas. It is preferable to set it so that it is maintained at 5X10-3 Torr. More preferably, the substrate is aligned at 1
It is preferable to rotate at a rotation speed of 1 to 500 revolutions per minute.

Further, by applying a DC bias voltage to the substrate, the plasma state near the substrate can be controlled, and the quality of the silicon nitride thin film can be controlled.

Effect: With this method, without using S s HJ gas,
It becomes possible to easily produce a silicon nitride thin film at low temperature with very little damage to the substrate and with controlled hydrogen (1). Also, by rotating the board,
A uniform film with good step coverage can be formed.

EXAMPLES Below, typical examples of the present invention will be shown based on the drawings. FIG. 1 shows a schematic diagram of a first device used in this example. Reference numeral 11 denotes a vacuum chamber, which is evacuated to a vacuum through an exhaust hole 12. Microwave oscillator 1 through waveguide 13
4, microwaves are introduced into the plasma generation chamber 15.

A magnetic field is applied to the plasma generation chamber 15 by the electromagnet 16 . Reference numeral 17 denotes a gas inlet port through which nitrogen and hydrogen gases are introduced into the vacuum chamber 11 with their flow rates precisely controlled.

Plasma with a high degree of dissociation can be generated by setting the strength of the magnetic field in the plasma generation chamber 15 so as to satisfy the electron cyclotron resonance conditions. For example, when the microwave frequency is 2.45 GHz and the magnetic field strength is 875 G, "D" occurs in the electron cyclotron. The generated plasma passes through the plasma extraction window 18 and is irradiated onto the substrate 20 on the substrate holder 19. Raw material silicon 21 is housed in a vapor deposition source 22, and the raw material silicon 21 is heated and melted by, for example, an electron beam heating method to form the substrate 20.
Steam the silicone on top. In this way, silicon and nitrogen react on the surface of the substrate or in the vicinity of the substrate, and a silicon nitride thin film is formed on the substrate 20.

The amount of gas introduced into the vacuum chamber varies depending on the pressure inside the vacuum chamber from 1X10-'Torr to 5X10Torr.
By setting the temperature to be maintained at -3 Torr, stable and highly excited plasma could be generated.

When nitrogen gas is used as the nitrogen-containing gas and hydrogen gas is used as the hydrogen-containing gas, the amount of hydrogen in the silicon nitride thin film can be varied from 0% to several 10% by changing the gas partial pressure of hydrogen.
% can be easily controlled.

Therefore, for example, as shown in FIG. 4, by changing only the gas partial pressure of hydrogen gas, it was possible to change the optical bandgap of the silicon nitride thin film. The stress in the film also changed as the amount of hydrogen changed.

By changing the partial pressure of nitrogen gas, the composition ratio N/Si of the silicon nitride thin film could be freely changed from O to 1.33.

If ammonia gas is used as the nitrogen-containing gas and hydrogen gas is used as the hydrogen-containing gas, the hydrogen n in the silicon nitride thin film cannot be changed to O, but ammonia gas is more easily excited than nitrogen gas and is Because it reacts well, it is possible to reduce the power of the microwave, and even if the partial pressure of ammonia gas is lowered, it is possible to easily obtain a film close to stoichiometry (N/5i = 1.33). Ta.

Even when a mixed gas of nitrogen gas and ammonia gas was used as the nitrogen-containing gas and hydrogen gas was used as the hydrogen-containing gas, a good silicon nitride thin film could be obtained.

When depositing a silicon nitride thin film, the substrate temperature needs to be heated to around 300"C in the normal plasma CVD method, but in this method, nitrogen and hydrogen are activated to a very high degree, so A very good silicon nitride thin film can be obtained even at a substrate temperature of 150° C. or less. Therefore, a silicon nitride thin film can also be formed on a substrate made of plastic or the like.

A good silicon nitride thin film can be formed even if the substrate is fixed, but since the nitrogen/hydrogen plasma source and silicon evaporation source are placed asymmetrically with respect to the substrate, the film thickness and In order to form a silicon nitride thin film with uniform film quality such as composition ratio and good step coverage on stepped portions, the substrate 20 is rotated by a motor 23 at a rotation speed of 1 to 500 revolutions per minute with the normal line of the substrate as an axis. It is best to rotate it with

The quality of the silicon nitride thin film differs depending on the arrangement of the substrate, silicon evaporation source, and nitrogen/hydrogen plasma source, but the arrangement of the substrate and silicon evaporation source depends on the line connecting the raw material silicon to be heated and evaporated with the substrate and the normal to the substrate. The angle between them is 60
It is desirable to keep it below 30 degrees.

The composition of the silicon nitride thin film can be changed by changing the evaporation rate of the raw material silicon, that is, the poison of silicon arriving at the substrate, the amount of nitrogen gas introduced, the degree of vacuum, the power of microwaves, etc.

The amount of hydrogen in the silicon nitride thin film can be easily controlled by changing the flow rate of hydrogen gas introduced.

In addition, as shown in FIG. 2, by applying a DC bias voltage varying between 500V and -500V to the substrate 20 using a DC power supply 24, ions and electrons flying toward the substrate can be controlled. Therefore, the quality of the silicon nitride thin film can be controlled.

FIG. 3 shows a schematic diagram of the second device used in this example. Reference numeral 11 denotes a vacuum chamber, which is evacuated to a vacuum through an exhaust hole 12. There are two plasma generation chambers, one being 1.
5 and 25, each of which is equipped with a waveguide, a microwave oscillator, and an electromagnet. Waveguide 1 each independently
Microwaves are introduced into plasma generation chambers 15.35 from microwave oscillators 14.34 through 3.33, respectively. Plasma generation chamber 15.35 by electromagnet 18.36
A magnetic field is applied to each. Reference numerals 17 and 37 are gas introduction ports, and the gases are introduced into the plasma generation chambers 15 and 35 by precisely controlling the flow rate of the gases. For example, nitrogen gas is introduced into the plasma generation chamber 15 and hydrogen gas is introduced into the plasma generation chamber 35. Plasma with a high degree of dissociation can be generated by setting the strength of the magnetic field in the plasma generation chamber 15.35 so as to satisfy the electron cyclotron resonance conditions. The generated plasma is transferred to the plasma extraction window 18.3.
8 and is irradiated onto the substrate 20 on the substrate holder 19. Raw material silicon 21 is contained in a steaming source 22,
For example, the raw material silicon 21 is heated and melted using an electron beam heating method to deposit silicon onto the substrate 20 . In this way, silicon and nitrogen react on the surface of the substrate or in the vicinity of the substrate, and a silicon nitride thin film is formed on the substrate 20.

In this method, since nitrogen plasma and hydrogen plasma can be controlled independently, the composition and hydrogen amount of the silicon nitride thin film can be controlled more precisely and easily than in the first embodiment.

Effect of the invention The effects of the present invention include the following.

5iHa gas is an explosive and extremely dangerous gas that is difficult to handle and requires a separate device to treat the exhaust gas, but the present invention does not use 5iHa gas, so it is not dangerous and pollution-free. Does not require exhaust gas treatment equipment.

Because silicon nitride thin films can be created at low temperatures near room temperature,
The stress caused by the difference in thermal expansion coefficient between the substrate and the silicon nitride thin film can be reduced, and productivity is improved because the time required to raise and lower the temperature required for heating the substrate is not required. In addition, it can be formed on organic substrates such as plastics and polycarbonates, which have low melting points or low softening points, which expands the range of uses.

Since the amount of stress in the silicon nitride film can be controlled by the amount of hydrogen present in the film, it is possible to create a film with very little stress even if the substrate is changed.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are schematic diagrams of an apparatus for producing a silicon nitride thin film according to the present invention, and Figure 4 shows the optical band gap and hydrogen content of the silicon nitride thin film produced according to the present invention. FIG. 11... Vacuum chamber 12......t
Jl° pore, 13... Waveguide, 14...
...Microwave oscillator, 15 plasma generation chamber, 16...
...Electromagnet, 17...Gas inlet, 18.
... Plasma drawer window, 19 ... Substrate holder, 20 ... Substrate, 21 ... Raw material silicon, 22 ... Evaporation source, 23. ... Motor 24 ... DC power supply 33 ...
Waveguide, 34...Microwave oscillator, 35 Plasma generation chamber, 36...Electromagnet, 37...
・Gas inlet, 38...Plasma drawer window.

Claims (7)

[Claims] (1) Simultaneously excite a mixed gas of a nitrogen-containing gas and a hydrogen-containing gas by plasma decomposition using one microwave and electron cyclotron resonance absorption, and irradiate the excited nitrogen plasma and excited hydrogen plasma onto the substrate. A method for producing a silicon nitride thin film characterized by simultaneously heating and vapor-depositing raw material silicon. (2) Excite a nitrogen-containing gas and a hydrogen-containing gas independently by plasma decomposition using microwaves and electron cyclotron resonance absorption, respectively, and simultaneously irradiate the substrate with the excited nitrogen plasma and excited hydrogen plasma. A method for producing a silicon nitride thin film, characterized by heating and vapor-depositing raw material silicon. (3) Claim 1, characterized in that nitrogen gas, ammonia gas, or a mixture thereof is used as the nitrogen-containing gas, and hydrogen gas is used as the hydrogen-containing gas.
The method for producing a silicon nitride thin film according to item 1 or 2. (4) The method for producing a silicon nitride thin film according to claim 1 or 2, wherein the deposition is carried out while holding the substrate at a temperature of 150° C. or lower. (5) The substrate is rotated at 1 to 50 times per minute with the normal line of the substrate as the axis.
3. The method for manufacturing a silicon nitride thin film according to claim 1 or 2, wherein the silicon nitride thin film is rotated at a rotational speed of 0 rotations. (6) Silicon nitride according to claim 1 or 2, characterized in that the angle formed between the line connecting the raw material silicon to be heated and evaporated and the substrate and the normal line of the substrate is 60 degrees or less Method for manufacturing thin films. (7) The method for manufacturing a silicon nitride thin film according to claim 1 or 2, characterized in that a DC bias voltage of 500V to -500V is applied to the substrate.