JPH0798652B2 - Method and apparatus for producing silicon dioxide film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for producing a silicon dioxide film, and more particularly to silicofluorination utilizing the temperature dependence of the solubility of silicon dioxide in a hydrosilicofluoric acid solution. The present invention relates to an improved method and apparatus for producing a silicon dioxide film on the surface of a substrate by contacting the substrate with a supersaturated solution of hydrogen acid in silicon dioxide.

[Prior Art] As a method for forming a silicon dioxide film, in addition to vacuum vapor deposition, sputtering, CVD, and dip coating (dipping method), a method for forming a silicon dioxide film on a large substrate with a simple apparatus is available. A method of immersing a substrate in a treatment solution containing a hydrofluoric acid solution in which silicon is supersaturated to deposit a silicon dioxide film on the surface of the substrate (hereinafter referred to as a deposition method)
It has been known. (For example, Japanese Patent Laid-Open No. 60-33233) In addition, among the precipitation methods, the temperature dependence of the solubility of silicon dioxide in a hydrosilicofluoric acid solution, which has the advantage of not requiring waste liquid treatment and thus low manufacturing cost, was used. A method for immersing a substrate in a treatment solution containing a saturated solution of hydrosilicofluoric acid in silicon dioxide (JP-A-61-281047) and an apparatus for producing a silicon dioxide film suitable for the method (Shokai-63-102738) are provided. Are known.

The above-mentioned silicon dioxide film production apparatus comprises a treatment tank for immersing a base material, a treatment liquid preparation tank, and a treatment liquid preheating tank. The treatment liquid is circulated between these three tanks, and the silicon dioxide is always in a supersaturated state. By introducing the treated liquid into the treatment tank, the coating can be produced continuously and at a stable rate for a long time. Furthermore, the particles having a smooth surface can be obtained by filtering the particles with a filter provided in the middle of the route and increasing the deposition rate.

[Problems to be Solved by the Invention] However, in the above-described manufacturing apparatus, since the particles are filtered by the filter and the treatment liquid is mixed in one circulation path, the total amount of the treatment liquid circulated (the treatment liquid in the treatment tank is (3% / min or more with respect to the amount) must be once cooled to saturate and dissolve silicon dioxide, and then heated again, which has the disadvantage that the cost required for heating and cooling increases, which in turn increases the manufacturing cost of the coating. It was

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a silicon dioxide obtained by raising the solution temperature of a hydrosilicofluoric acid solution in which silicon dioxide is in a substantially saturated state. In a method and an apparatus for producing a silicon dioxide film in which a treatment solution containing a hydrofluoric acid solution in a supersaturated state is brought into contact with a substrate to deposit silicon dioxide on the surface of the substrate, the temperature of the solution is raised to raise the temperature of the solution. For the processing liquid in the processing tank that became supersaturated,
A silicon dioxide film is produced at a stable rate over a long period of time by adding a hydrosilicofluoric acid solution in which silicon dioxide is almost saturated at low temperature and keeping the silicon dioxide in the treatment liquid in the treatment tank in a supersaturated state. A method and an apparatus suitable for the method are provided.

Here, the term “substantially saturated state” is a term that includes a completely saturated state and a state almost close to saturation, and in the present invention, the substantially saturated state is preferably a fully saturated state.

In this method, in order to keep the treatment liquid in the treatment tank at a constant amount, it is necessary to discharge the same amount as the added treatment liquid from the treatment tank. In addition to the above-mentioned route for adding the treatment liquid to obtain a coating having a smooth surface, a route provided with a filter having a mesh diameter of 1.5 μm or less for filtering the treatment liquid is provided in the treatment tank per minute. It is necessary to circulate 3% or more of the treatment liquid amount.

Here, the temperature T1 of the treatment liquid added is 35 ° C. or lower,
The treatment liquid temperature T2 in the treatment tank is 70 ° C or less, and the difference (T2-T1) between the treatment liquid temperature in the treatment tank and the temperature of the added treatment liquid is
It is preferable that the temperature is 10 ° C. or higher from the viewpoint of reducing the change in concentration of the processing solution by suppressing the generation of silicon tetrafluoride vapor from the processing solution and the rate of forming a silicon dioxide film.

Further, the higher the addition rate of the treatment liquid is, the more silicon dioxide dissolved in the hydrosilicofluoric acid solution is supplied into the treatment tank, so that a higher film formation rate can be obtained. However, if the amount of the treatment liquid added per minute is 1.2% or more with respect to the amount of the treatment liquid in the treatment tank, the film formation rate does not increase and the manufacturing cost only increases, which is not preferable. Although the reason for this is not well understood, it is expected that the amount of the treatment liquid in which the silicon dioxide in the treatment tank is in a supersaturated state increases as the amount of the treatment liquid added increases.

Further, the treatment liquid may be added continuously or discontinuously. However, when the treatment liquid is added discontinuously, a concentration distribution of silicon dioxide dissolved in the treatment liquid occurs, and silicon dioxide particles are generated in a high concentration portion. It is not preferable because it becomes easy.

The substantially saturated silicon dioxide solution of hydrosilicofluoric acid used in the present invention can be obtained, for example, by dissolving silicon dioxide (for example, industrial silica gel, quartz glass, etc.) in a hydrofluoric acid solution. Any concentration of hydrosilicofluoric acid can be used, but a concentration of 1 mol / mol or more is preferable because a deposition rate that is industrially usable can be obtained. When the concentration is higher than 3 mol / mol, silicon tetrafluoride vapor is generated violently and leads to a decrease in the film forming rate of the coating film, but this can be solved by controlling the gas-liquid interface.

[Operation] In the present invention, in a method and an apparatus for producing a silicon dioxide film utilizing the temperature dependence of the solubility of silicon dioxide in a hydrosilicofluoric acid solution, the silicon dioxide becomes supersaturated due to the temperature rise in the treatment tank. To the above processing solution, simply add 1.2% or less of the total amount of the processing solution in the processing tank per minute to a processing solution in which silicon dioxide is almost saturated at low temperature, and a film formation rate that is industrially usable is obtained. It was done by finding out what could be obtained.

By this method, it is possible to inexpensively produce a coating film continuously and at a stable film formation rate for a long period of time. Further, by cooling the treatment liquid discharged at the same time as the addition of the treatment liquid and saturating dissolution of silicon dioxide, the treatment liquid can be used again as a treatment liquid for addition, and the manufacturing cost can be further reduced. .

Example 1 A treatment liquid was prepared by saturating and dissolving silicon dioxide (industrial silica gel) in hydrofluoric acid of 2 mol / concentration at a temperature of −3 ° C. in the treatment liquid preparation tank (1). The whole amount of the treated liquid thus obtained was fed to the treated liquid storage tank (2) through the liquid feed pipe (11A) by the liquid feed pump (12A). At this time, the silicon dioxide particles remaining undissolved when the treatment liquid was prepared were filtered with a filtration filter (13A).

Next, the processing liquid in the processing liquid storage tank is passed through the liquid transfer pipe (11B) by the liquid transfer pump (12B) to the rectification section (9) of the processing tank (3) 1.
7 liquids were delivered. After sending the solution, the solution sending pump (12D) passes the solution sending pipe (11D) to start circulating the processing solution from the addition part (10) of the processing tank to the rectification part of the processing tank at a rate of 170 ml / min. The treatment liquid was filtered with a filter (13B or 13C) provided on the way, and the treatment liquid in the treatment tank was heated with a heater (6) to raise the temperature to 60 ° C. and hold it at that temperature.

At the same time, the processing liquid is transferred from the processing liquid storage tank by the liquid feed pump (12B) to 5, 10, 20, 30 ml / min (these are 0.3, 0.6, 1.2, 1.8% of the processing liquid amount in the processing tank, respectively). % / Mi
(corresponding to n) is added to the addition part (10) of the processing tank at the same speed, and at the same time, the processing liquid is sent from the overflow part of the immersion part of the processing tank at the same speed as each addition by the liquid supply pump (12C). It was passed through (11C) and discharged to the treatment liquid preparation tank. The discharged treatment liquid was cooled again in the treatment liquid preparation tank to saturate and dissolve silicon dioxide. The treatment liquid preparation tank, the treatment liquid storage tank, and the feeding of the treatment liquid between the treatment tanks were performed thereafter until the production of the film was completed.

A 25 mm x 25 mm silicon wafer is used as the substrate on which the silicon dioxide film is formed, and it is immersed every hour after the heating of the treatment liquid is started. The change with time of the film velocity was examined.

Table 1 shows the results of the average film formation rate of the coating film obtained by the above method for 24 hours.

From this result, it is possible to cool the total amount of the processing liquid (3% or more of the amount of the processing liquid in the processing tank) circulated as in the conventional method and to dissolve the silicon dioxide in a saturated manner, so that the total amount of the processing liquid in the processing tank is reduced per minute. of
It can be seen that a film formation rate sufficient for industrial use can be obtained only by adding an amount of 1.2% or less.

Example 2 A silicon dioxide film was manufactured in the same manner as in Example 1. The addition of the treatment liquid was performed at a rate of 10 ml / min (0.6% / min with respect to the treatment liquid amount in the treatment tank) for 72 hours.

In the above method, the result of the film forming rate with respect to the time from the start of film production is shown in FIG.

From this result, it is understood that the method of adding the treatment liquid enables the production of the coating film without deteriorating the deposition rate for a long period of time.

EFFECTS OF THE INVENTION According to the present invention, a film is formed at a stable rate for a long time only by adding a treatment solution in a supersaturated state at a high temperature in a treatment tank to a treatment solution in a substantially saturated state at a lower temperature. be able to.

Furthermore, since the added amount is 1.2% or less of the total amount of the processing liquid in the processing tank per minute, it is possible to form a silicon dioxide film having a very low manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing a silicon dioxide film manufacturing apparatus of the present invention. FIG. 2 is a diagram showing the results of the time lapse and continuous film formation in the method for producing a silicon dioxide film according to the present invention. 1 …… Treatment liquid mixing tank, 2 …… Treatment liquid storage tank 3 …… Treatment tank, 4 …… Cooler 5 …… Stirrer, 6 …… Heater 7 …… Dip part, 8 …… Rectifier plate 9 …… Rectification Part, 10 …… Addition part 11 …… Liquid supply pipe, 12 …… Liquid supply pump 13 …… Filtration filter, 14 …… Base material 15 …… Cock (3 ways), 16 …… Cleaning liquid tank

Claims (2)

[Claims] 1. A treatment solution containing a supersaturated hydrofluoric acid solution of silicon dioxide obtained by raising the solution temperature of a hydrosilicofluoric acid solution in which silicon dioxide is substantially saturated, and a substrate. In the method for producing a silicon dioxide film in which silicon dioxide is deposited on the surface of a base material by contacting, the temperature of the treatment liquid after contacting the base material is maintained at a high temperature, and the temperature of the treatment liquid is adjusted separately at a low temperature. A method for producing a silicon dioxide film, characterized in that a silicon hydrofluoric acid solution in which silicon is substantially saturated is added to maintain silicon dioxide in the treatment liquid in a supersaturated state. 2. A treatment liquid containing a supersaturated hydrofluoric acid solution of silicon dioxide obtained by raising the solution temperature of a hydrosilicofluoric acid solution in which silicon dioxide is substantially saturated, and a substrate. An apparatus for producing a silicon dioxide film, which is brought into contact with and deposits silicon dioxide on the surface of a substrate, has a stirrer (5) for preparing a treatment liquid by dissolving silicon dioxide in a hydrosilicofluoric acid solution, A treatment liquid preparation tank (1) provided in a constant temperature bath having heating and / or cooling means for keeping the hydrous acid solution at a constant temperature, and a treatment liquid preparation bath (1) also provided in the constant temperature bath for keeping the prepared treatment liquid at a constant temperature. A treatment liquid storage tank (2), an immersion part (7) for immersing the base material to form a silicon dioxide film on the surface of the base material, and a immersion part for arranging the flow of the processing liquid flowing into the immersion part. Processing liquid from the rectifying section (9) provided in the Flow-flowing further comprises the addition part (10) to which the processing liquid is added, and has a straightening plate (8) provided at the boundary between the dipping part and the straightening part, and further raises the processing liquid temperature to a predetermined temperature. It comprises a processing tank (3) having a heating means for keeping it at a constant temperature, and further, a liquid sending pipe (11D) for circulating the processing liquid in the processing tank, and a liquid sending pump (12D) provided in the middle of the liquid sending pipe. ) And a treatment liquid filtration filter (13B and 13C), and a liquid feed pipe (11A) for feeding the treatment liquid in the treatment liquid preparation tank to the treatment liquid storage tank.
And a liquid feed pump (12A) and a liquid filtration filter (13A) provided in the middle of the liquid feed pipe, and further, the treatment liquid in the treatment liquid storage tank to the treatment tank rectification unit and the treatment tank dipping unit. Liquid transfer pipes (11B, 11B,
11C) and a liquid feed pump (12B and 12C, respectively) provided in the middle of the liquid feed pipe, for producing a silicon dioxide film.