JPS6354216B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for forming a film.

Recently, insulating films,
Silicon nitride (hereinafter referred to as
Si ₃ N ₄ ) has attracted attention, and methods for forming its film have been actively researched.

On the other hand, amorphous silicon (hereinafter referred to as a-Si) films are attracting attention as photoreceptors for solar cells and electrophotography, and research on methods for forming the films is also being actively conducted.

Conventional methods for forming these films include (a) plasma method and (b) reactive sputtering method, but in (a), for example, SiH ₄ is decomposed by electric discharge to form a Si film. When trying to form on the substrate surface,
Si and H ions and radicals may be incorporated into the film, which has drawbacks such as the formation of pinholes and the occurrence of changes in physical properties over time due to the escape of substances that have been incorporated over a long period of time. In the case of _{the 3N4} coating, drawbacks such as the occurrence of pinholes have also been pointed out. As for (b), it has been pointed out that it is difficult to uniformly form a coating over a wide area, so it cannot be used for large drums for electrophotography or solar cells with a large area.

The present invention has been made in view of the above circumstances, and its purpose is to provide a novel method for forming a silicon nitride film that is free from pinholes and does not change over time and can be formed uniformly over a wide area. The feature is that the substrate is placed in an airtight container in which the pressure of mercury vapor is controlled within the range of 1 × 10 ^-4 to 20 mmHg, and the Radiant light intensity is 20μW/
cm ² or more, the substrate is irradiated with a discharge lamp in which the synchrotron radiation is 70% or more of the total radiation, and SiH ₄ at a pressure of 0.01 to 7 mmHg and the pressure relative to the SiH ₄ are placed in the airtight container. A silicon nitride film is formed on the surface of the substrate by flowing N ₂ H ₄ at a ratio of 30≧Pressure (N ₂ H ₄ )/Pressure (SiH ₄ )≧1. be.

The present invention will be described below with reference to examples and drawings thereof.

FIG. 1 is an explanatory diagram, partially shown in cross section, of an example of a film forming apparatus for carrying out the film forming method of the present invention, and a heating source such as a heater, a mirror, etc. are omitted. Figure 2 shows the A-
It is an explanatory view of A section.

In the figure, 1 is a quartz glass pipe, 2
is a disc member that airtightly holds the pipe 1 from both sides through elastic packing 3 made of rubber or plastic, 4 is a support column for assembling the disc member 2, and 5a and 5b are rotating shafts. ,
The tips of each are brought into contact with each other by a friction plate 6, so that when one rotates, the other also rotates, and with respect to the disc member 2, an airtight and rotatable seal is used, such as a Wilson seal, for example. is attached to. A holding member 9 for holding the base body 8 is provided on the outer periphery of one side 5b of the rotating shaft. In the illustrated example, the base 8 is a cylindrical aluminum pipe.

7 and 10 are an infrared lamp and a low-pressure mercury vapor discharge lamp that irradiate the base 8 from outside the pipe 1, and are fixed to the disc member 2 via a lamp holder 11. This lamp holder 11 may also serve as support for the mirror 12 to simplify the mechanism.

Reference numerals 13 and 14 refer to a reactive gas inlet passage and a discharge passage, respectively; 15 a mercury reservoir for controlling the mercury vapor pressure inside the pipe 1; and 16 a mercury reservoir for controlling the mercury vapor pressure inside the pipe 1, and This is an auxiliary path for supplying buffer gas. Depending on the type of reactive gas, a plurality of inlet channels 13 may be provided, or one inlet channel 13 may be sufficient if the necessary gases are mixed in advance. 19 is
This is a filter that cuts out light of 200 nm or less.

To show an example of the design of the above device, pipe 1 has an inner diameter of
120mm, the base 8 has a diameter of 45mm, a length of 990mm, an infrared lamp with an emission length of 1200mm, and a power consumption of 500W.
Low-pressure mercury vapor discharge lamp has a light emission length of 1250 mm and power consumption.
Four 500W batteries are used, and the mirror is made of mirror-finished aluminum. With this device, while rotating the rotary shaft at a speed of 10 times/min, the temperature of the outer peripheral surface of the aluminum pipe of the base 8 is maintained at approximately 100°C, the mercury vapor pressure is maintained at approximately 1 × 10 ^-3 mmHg, and SiH ₄ and N ₂ H ₄
500c.c./min (approximately 0.2mmH pressure)
g) When flowing, a layer of silicon nitride with a thickness of 1.5 μm is formed on the outer peripheral surface of the aluminum pipe in about 6 minutes. In addition, 254±10nm on the outer circumferential surface of the aluminum pipe
The intensity is approximately
It is 650μW/ ^cm2 .

The principle behind the formation of the silicon nitride layer or film is as follows: Hg254±10nm ―――――――― Hg* (activation of mercury) SiH ₄ +Hg*→Si+2H ₂ +Hg N ₂ H ₄ +Hg*→N ₂ +2H ₂ +Hg 3Si +2N ₂ →Si ₃ N ₄ (silicon nitride) Due to the deposition of Si ₃ N ₄ →Si ₃ N ₄ . The pressure ratio of N ₂ H ₄ and SiH ₄ should preferably be 30≧Pressure (N ₂ H ₄ )/Pressure (SiH ₄ )≧1; in a range larger than 30, pinholes occur, and in a range smaller than 1, Si There are drawbacks such as _a slow film formation rate for _3N4 . Hg acts as a photosensitizer, and the pressure is 1×
10 ^-4 to 20 mmHg is suitable. The reason is 1×
Below 10 ^-4 mmHg, the density of activated mercury atoms is too low, and above 20 mmHg, the influence of self-absorption of mercury becomes significant, and in both cases, the film formation rate is slow. This is because it is less practical. Similarly, if the pressure of SiH ₄ is lower than 0.01 mmHg, the film formation rate is extremely slow and impractical;
In larger areas, pinholes (in this case, the ones that look like "su") occur and the film quality is poor.
Practical and high-quality membranes for this method ranged from 0.01 mmHg to 7 mmHg.

Buffer gases introduced using the auxiliary channel 16 include Ar, N ₂ , etc., and these include 6 ³ P ₁ of Hg* and
Collisions with electrons in the 6 ¹ P ₁ orbit can bring about various positive effects without causing chemical changes. For example, Ar and N ₂ can moderately suppress the film formation rate when it is too high. I do things. Also,
As mentioned above, the filter 19 cuts out light of 200 nm or less, but the 185 ± 10 nm light emitted from a low-pressure mercury vapor discharge lamp has almost the same effect as 254 ± 10 nm, so Filter 1
If 9 is excluded, the effect of light of 185±10 nm is also added, resulting in even better results.

FIG. 3 is an explanatory diagram of a hollow support 17 for mounting and fixing an insulating substrate and an IC circuit chip (none of which are shown), which is arranged in place of the base 8 in FIG. 1. The body has a net structure 18 so that the temperature of the insulating substrate and chip can easily rise. Formation of a silicon nitride film on an insulating substrate, such as an alumina plate, can be achieved under the same conditions as in the previous example.

By the way, in the film forming method of the present invention, as will be understood from the following explanation, film formation utilizes deposition of a reaction product mainly in the vicinity of the substrate surface using a photosensitization reaction. From, on the substrate surface
The higher the intensity at 254±10nm, the better, at least
It is better to be hotter than 20μW/ ^cm2 . If it is smaller than this, the film formation rate will be slow and it will be impractical. Therefore, although the present invention uniformly irradiates a wide area with an intensity of 20 μW/cm ² or more, if a mercury lamp such as a low-pressure mercury vapor discharge lamp is used, radiation of 254 ± 10 nm can be achieved. Since it accounts for more than 70% of the omnidirectional light, it is relatively easy to design and implement, and the film formation rate can also be controlled by controlling the output of the mercury lamp or by mixing buffer gas. Since it can be easily formed, a coating without pinholes or deterioration over time can be quickly and uniformly formed over a large area.

As can be understood from the above explanation, the present invention provides a method for disposing a substrate in an airtight container in which the pressure of mercury vapor is controlled within the range of 1 x 10 ^-4 to 20 mmHg, and mercury vapor on the surface of the substrate. The radiation intensity of 254±10n is 20μW/
cm ² or more, the substrate is irradiated with a discharge lamp in which the synchrotron radiation is 70% or more of the total radiation, and SiH ₄ at a pressure of 0.01 to 7 mmHg and the pressure relative to the SiH ₄ are placed in the airtight container. A film of silicon nitride is formed on the surface of the substrate by flowing N ₂ H ₄ at a ratio of 30≧Pressure (N ₂ H ₄ )/Pressure (SiH ₄ )≧1. Because it is a coating that does not have pinholes or changes over time,
It can be formed uniformly over a wide area, and therefore the IC
Silicon nitride films can be provided that are good as surface protection films for circuit chips and other insulating films.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of an example of a film forming apparatus for carrying out the film forming method of the present invention;
The figure is an explanatory diagram of the hollow support stand, and in the figure, 5a, 5a,
5b is a rotating shaft, 8 is a base, 10 is a low-pressure mercury vapor discharge lamp, and 12 is a mirror.

Claims (1)

[Claims] 1. A substrate is placed in an airtight container in which the pressure of mercury vapor is controlled within the range of 1 × 10 ^-4 to 20 mmHg, and the intensity of radiated light at 254 ± 10 nm on the surface of the substrate is
The emitted light is 20 μW/cm ² or more so that the total emitted light is
The substrate is irradiated with a discharge lamp of 70% or more, and SiH ₄ at a pressure of 0.01 to 7 mmHg is added to the airtight container.
A silicon nitride coating is formed on the surface of the substrate by flowing N ₂ H 4 at a pressure ratio of 30≧pressure (N ₂ H ₄ )/pressure (SiH ₄ )≧1 to SiH _{4 .} A film forming method characterized by forming a film. 2. The film forming method according to item 1, wherein Ar or N ₂ is also introduced.