JPH0814027B2 - Method for producing silicon dioxide film containing impurities - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a silicon dioxide film containing impurities, and is particularly useful as an impurity diffusion source in semiconductor materials, an alkali metal diffusion preventive film, a surface protective film, and the like. To a method for producing a silicon dioxide film containing various impurities.

[Prior Art] It is widely practiced today to coat the surface of various materials with a silicon dioxide film containing impurities. For example,
In a semiconductor using a silicon substrate, a step of diffusing impurities is required to turn the silicon into a P-type or N-type semiconductor, and as a diffusion source of the impurities, a dioxide containing the impurities coated on the silicon substrate is used. A method using a silicon coating is known.

When an alkali metal-containing glass is used as a glass for a liquid crystal display panel or a solar cell, the surface of these glasses is coated with a silicon dioxide film in order to prevent the elution of alkali metal components from the glass. ing. In this case, it is known that the use of a silicon dioxide film containing As has a higher elution preventing ability than the use of a pure silicon dioxide film.

Moreover, in general, an AsSG (As Silicate Glass) film is used in order to make glass flow at a low temperature and obtain a flat surface.

As a method of coating silicon dioxide containing impurities as described above, methods such as a CVD method and a coating method have been widely used.

For example, in the CVD method, a silicon dioxide film containing As can be formed by the reaction of the following formula (1).

SiH ₄ + 2AsH ₃ +60 ₂ → SiO ₂ + As ₂ O + 5H ₂ O (1) It is known that these hydrides may be added in the same manner as AsH ₃ to contain Sb and Ga.

However, in the above CVD method, the substrate must be heated to 400 ° C. or higher, and it is difficult to deposit it on a large base material surface with a uniform film thickness. It was difficult to deposit at. In addition, since these hydride gases are generally harmful and toxic gases, the device or incidental equipment is expensive to ensure safety, and the cost required to coat these films is high. There was a point.

In addition, a method for producing a silicon dioxide film in which a treatment liquid containing hydrofluoric acid, which is generally in a supersaturated state of silicon dioxide, is contacted with a substrate to deposit a silicon dioxide film on the surface of the substrate (hereinafter referred to as a deposition method). (Abbreviated as)) is known. (For example, Japanese Unexamined Patent Publication No. 60-33233) It is known that the above-mentioned deposition method can form a silicon dioxide film of uniform thickness at a low temperature on the surface of a large-sized substrate having irregularities by using a simple apparatus. ing.

[Problems to be Solved by the Invention] In the present invention, it is not possible to form a film having a uniform thickness on the surface of a substrate having an uneven surface in the conventional method for producing a silicon dioxide film containing impurities. It is not possible to form a film with a uniform thickness on the surface of a large-sized substrate. A coating cannot be formed on the surface of the base material that causes adverse effects by heating. A silicon dioxide film cannot be manufactured inexpensively. It is to solve the problems such as.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a treatment liquid containing hydrofluoric acid, which is a supersaturated state of silicon dioxide.
In a method for producing a silicon dioxide film, which comprises bringing a silicon dioxide film into contact with a substrate to deposit a silicon dioxide film on the surface of the substrate, at least one impurity selected from the group consisting of As, Sb, and Ga is added to the treatment liquid. In advance, a silicon dioxide film containing the impurities is deposited.

As a source of impurities contained in the processing liquid, As, Sb,
Any raw material such as a single element such as Ga and a compound of these elements can be used.

When depositing a silicon dioxide film containing As, the As concentration in the treatment liquid is preferably 0.01 to 5.0 mol / liter. Of these, 0.1 to 2.0 mol / liter is desirable. If the concentration is less than 0.01 mol / liter, the concentration of As contained in the deposited silicon dioxide film will be low, and the effect of the present invention will not be easily exhibited. Further, if the concentration is higher than 5.0 mol / liter, As is apt to be insoluble in the treatment liquid.

When at least one impurity selected from the group consisting of As, Sb and Ga is contained in the treatment liquid, the concentration of hydrofluoric acid in the treatment liquid is 0.1 to 2.0 mol / liter. Preferably there is. The concentration of hydrosilicofluoric acid in the treatment liquid is 2.
If the concentration is higher than 0 mol / l, the As concentration contained in the formed silicon dioxide film tends to be low, and if the concentration of hydrosilicofluoric acid in the treatment liquid is lower than 0.1 mol / l, the silicon dioxide film is formed. Is not formed at all, or a film having a uniform thickness is unlikely to be formed.

The temperature of the treatment liquid when the treatment liquid and the base material are in contact with each other is preferably 0 to 35 ° C. That is, if the temperature of the treatment liquid is higher than 35 ° C, the As concentration contained in the formed silicon dioxide film tends to be low, and if the temperature of the treatment liquid is lower than 0 ° C, the water in the treatment liquid freezes. Or
The stability of the treatment liquid itself tends to deteriorate due to precipitation of H ₂ SiF ₆ and nH ₂ O.

There is no particular limitation on the method for preparing the treatment liquid containing the hydrosilicofluoric acid aqueous solution in which silicon dioxide is supersaturated, and for example, H ₃ BO ₃ can be added to the hydrofluoric acid aqueous solution in which silicon dioxide is approximately saturated. , Al, Al (OH) _{3 and} other additives,
Also, a method of raising the temperature of the hydrosilicofluoric acid aqueous solution in which silicon dioxide is substantially saturated can be used.

The method of contacting the treatment liquid with the base material may be a contact method such as flowing the treatment liquid down the surface of the base material, but the base material is placed in a dipping tank filled with the treatment liquid. The dipping method is preferable because it is easy and a coating having a uniform thickness is easily obtained.

The substrate applied to the present invention is not limited to silicon and alkali metal-containing glass, and silica glass, alkali-free glass, various ceramics, semiconductor substrates other than silicon, and any other substrate that does not easily cause an adverse reaction with the treatment liquid. It can be applied to wood. Further, the application is not limited to the impurity diffusion source for the semiconductor element, the prevention of alkali metal diffusion, and the like, and can be used for other applications.

[Operation] According to the present invention, since precipitation from a solution is used,
A silicon dioxide film having a uniform thickness can be formed even on a substrate having an arbitrary surface shape such as an uneven surface or a large area. Also, the silicon dioxide film can be formed on a large area by using a simple dipping tank. In addition, since the heating of the base material is not required in the film formation, the film can be formed at a temperature near room temperature, and the base material has poor heat resistance (for example, a plastic molded body) or is easily deteriorated by heat (for example, impurities are diffused). Semiconductor substrate). By further changing the film forming conditions, the content of at least one impurity selected from the group consisting of As, Sb, and Ga can be arbitrarily adjusted.

[Example] Using the silicon dioxide film manufacturing apparatus shown in FIG. 1, the surface has a diameter of 1.5 μm and depths of 1.5 μm, 3.6 μm, and 5.5 μm, respectively.
A silicon dioxide film containing As was formed on a flat silicon substrate 127 mm (5 inches) in diameter having a deep groove (opening) of 1 by the following procedure.

The silicon dioxide film manufacturing apparatus comprises an outer tank (1) and an inner tank (2), and water (3) is filled between the inner tank and the outer tank. In this example, the temperature of the water was adjusted to 10 ° C by the temperature controller (4). Further, the water (3) is agitated by the agitator (5) in order to make the temperature uniform.
The inner tank consists of the front part (6), the middle part (7) and the rear part (8),
Silica gel powder was dissolved and saturated in each part, and As ₂ O ₅ was dissolved as an As compound in an amount of 0.2 mol / liter.
3 l of a hydrosilicofluoric acid aqueous solution having a concentration of 2.0 mol / l was filled as a treatment liquid.

Here, first, the circulation pump (10) is started, and the treatment liquid in the rear part (8) of the inner tank is pumped out by a fixed amount and the filter (1
The treatment liquid circulation was started in which the solution was filtered in 1) and returned to the inner tank (6). After that, 0.5 mol / liter boric acid aqueous solution (12)
Was continuously added dropwise to the rear part (8) of the inner tank at a rate of 0.2 ml / min and kept for 20 hours. In this state, the treatment liquid became a treatment liquid having an appropriate degree of SiO ₂ supersaturation.

Here, the absolute removal rate of the filter (11) was set to 1.5 μm, and the processing solution circulation rate was set to 240 ml / min (the circulation rate was about 8% / min because the total processing solution volume was 3 liters).

After that, the silicon substrate (9) is placed in the middle part (7) of the inner tank.
Under the above conditions (0.5 mol / liter boric acid aqueous solution was added at a rate of 0.2 ml / min, 8% / min was circulated, and filtration was performed with an absolute removal rate of 1.5 μm filter). Held for hours.

The film thickness of the silicon dioxide film obtained by the above treatment was about 100 nm in the flat portion of the silicon substrate. With respect to the silicon dioxide film formed on the flat portion of the silicon substrate, composition analysis was performed from the surface to the depth direction by secondary ion mass spectrometry. As a result, Si, O and As
Was detected, and the As concentration was found to be about 1 × 10 ¹⁹ atm / cm ³ . On the other hand, the cross section of the silicon dioxide film formed in the grooved portion of the silicon substrate was observed with an electron microscope. As a result, the silicon dioxide film is formed following the shape of the silicon substrate, which is the substrate.
Moreover, the film thickness was about 100 nm at the bottom of the deep hole, which was almost the same as that of the flat plate without grooves.

In this way, a silicon dioxide film containing As was deposited on a silicon substrate having a minute opening, and As was diffused from the glass layer to the silicon substrate at 900 ° C., a diffusion layer with a desired concentration was formed. It could be formed on a silicon substrate.

Similarly, when a glass layer containing Sb and Ga was deposited on a silicon substrate and diffused, a diffusion layer having a desired concentration could be formed on the silicon substrate as described above.

[Effects of the Invention] According to the present invention, as is clear from the examples, an impurity-containing silicon dioxide film having a uniform thickness can be formed on the surface of a substrate having irregularities at low cost. Further, it can be easily applied to a large area substrate.

[Brief description of drawings]

FIG. 1 is a system diagram of a silicon dioxide film manufacturing apparatus used in an embodiment of the present invention. (1) Outer tank, (2) Inner tank, (3) Water (4) Temperature controller, (5) Stirrer (6) Inner tank front part, (7) Inner tank middle part (8) Inner tank rear part, ( 9) Silicon substrate (10) Circulation pump, (11) Filter (12) Boric acid aqueous solution

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Kawahara, 4-8 Doshomachi, Higashi-ku, Osaka City, Osaka Prefecture, Japan Nihon Sheet Glass Co., Ltd. (72) Katsuya Okumura, 1 Komukai-Toshiba-cho, Kawasaki-shi, Kanagawa Prefecture Incorporated company Toshiba Research Institute (72) Inventor Toru Watanabe 72 Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Horikawa-cho Factory (72) Inventor Masami Watase 72 Horikawa-cho, Kawasaki-shi, Kanagawa (56) References: JP-A-58-199744 (JP, A) JP-A-62-20876 (JP, A) JP-B-48-41068 (JP, B1)

Claims (2)

[Claims] 1. A method for producing a silicon dioxide film, which comprises contacting a substrate with a treatment liquid containing hydrofluoric acid in a supersaturated state of silicon dioxide to deposit a silicon dioxide film on the substrate surface. At least one impurity selected from the group consisting of As, Sb, and Ga is contained in the treatment liquid, and a silicon dioxide film containing the impurities is deposited. Production method. 2. The method for producing a silicon dioxide film containing impurities according to claim 1, wherein the impurity in the treatment liquid is As, and the As concentration in the treatment liquid is 0.01 to 5.0 mol / liter. .