JPH03179742A - Silicon oxide film formation - Google Patents

Abstract

PURPOSE:To make it possible to form a good and fine pattern on a semiconduc tor wafer to be treated by a method wherein the wall of a tank, in which a supersaturated solution of hydrofluoric acid for dipping the wafer is housed, is forcedly cooled from the outside and the wall temperature of the tank is made lower than the mean temperature of the solution. CONSTITUTION:A silicon semiconductor wafer 11 to be treated is dipped into a film-forming solution 13 housed in a film-forming tank 12 made of PVC. Moreover, an overflow tank 14 for the overflowed film-forming solution 13 is installed adjoining the tank 12 and the solution 13 is circulated and filtered by a pump 15 and a filter 16 and is again returned to the tank 12. A plurality of circulating hole parts 17 are formed in the bottom part of the tank 12 and these hole parts 17 are coupled with the tank 14 through a capillary 18. As the tank 14 is provided with a heater 19 and a cooling tube 20, it is possible to control the solution 13 to overflow the tank 12 at 35 deg.C by a heating/cooling means. Moreover, a cooling pipe 21 is arranged on the periphery of the outside of the tank 12 and the wall temperature of the tank 12 can be cooled to 1 to 10 deg.C.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for forming a film of silicon oxide, such as silicon dioxide (hereinafter referred to as silicon dioxide), and particularly relates to a method of forming a film of silicon oxide, such as silicon dioxide (hereinafter referred to as silicon dioxide). This is suitable for forming a silicon film.

(Prior art) A method of forming a film of silicon oxide, such as silicon dioxide (hereinafter simply referred to as silicon dioxide), on the surface of a semiconductor wafer. In particular, a method using a precipitation reaction from a supersaturated solution of silicon oxide of hydrofluoric acid (L
PD method) is used as one step in the semiconductor manufacturing process. In this method, a film of silicon dioxide is also formed on the wall of the supersaturated silicon oxide solution bath of hydrofluoric acid in which the semiconductor wafer to be processed is immersed, but depending on the material of the wall of this supersaturated solution bath, the silicon dioxide on the wall surface may peel off and become coated. The phenomenon of adhesion to the surface of processed semiconductor wafers is often observed.

The following explanation will be given with reference to FIG. 1 showing a silicon dioxide film forming apparatus. A hydrofluoric acid film forming tank 1 made of vinyl chloride and containing a film forming solution 2 is provided with a plurality of flow holes 3 at the bottom. At the same time, an overflow (OverFQow) tank 4 is installed to accommodate the overflowing film forming solution 2 and place an A2 plate to be described later.

Here, a thin tube 7 in which a pump 5 and a filter 6 are arranged.
to communicate with the flow hole section 3. Therefore, film forming solution 2
is circulated and filtered and then returned to the film forming tank 1. To make the film-forming solution 2 in the film-forming tank 1 a supersaturated solution, for example, use the A2 plate 8.
It is effective to shift the equilibrium state in the direction of precipitation by immersing and dissolving the silicon dioxide layer, and a silicon dioxide layer is precipitated and formed on the semiconductor wafer 9 to be processed that is immersed in the supersaturated film forming solution 2. This silicon dioxide layer is deposited not only on the semiconductor wafer 9 to be processed but also on the inner wall of the film forming tank.

(Problem to be Solved by the Invention) When the inner wall of the film-forming tank l containing the supersaturated film-forming solution 2 is made of vinyl chloride, the deposition on the inner wall is similar to that on the semiconductor wafer 9 to be processed. The silicon dioxide layer splits and peels off. That is, the thin silicon dioxide layer splits and becomes angular silicon dioxide pieces 10 with reduced adhesion strength and, in fact, peels off and floats in the film-forming solution 2 when subjected to impact or vibration.

If such silicon dioxide pieces adhere to the semiconductor wafer 9 to be processed immersed in the film forming solution 2, they will seriously impede the subsequent formation of fine patterns. This phenomenon occurs when the film forming tank l is made of materials other than vinyl chloride such as polyvinylidene fluoride (PVDF), tetrafluoroethylene perfluorovinyl ether copolymer (PFA), polypropylene (PP), and polytetrafluoroethylene (PTFE). ) and peak materials, and changing the material of the film forming tank l is not an effective solution.

The present invention was made under these circumstances, and particularly provides a method for forming a silicon oxide film that can form a fine pattern on a semiconductor wafer.

[Structure of the invention]

(Means for Solving the Problem) When forming a silicon oxide layer on the surface of a semiconductor wafer by a precipitation reaction from a supersaturated solution of hydrofluoric acid, a tank wall containing a supersaturated solution of hydrofluoric acid in which a semiconductor wafer to be processed is immersed. A feature of the silicon oxide film forming method according to the present invention is that forced cooling is performed from the outside to lower the tank wall temperature below the average temperature of the solution.

(Operation) In the LPD method in which a silicon dioxide layer is formed on a semiconductor substrate wafer by a precipitation reaction from a supersaturated solution, precipitation begins and silicon dioxide film formation progresses by bringing the film forming solution into a supersaturated state. At this time, the degree of supersaturation of the film-forming solution depends on the temperature,
When the liquid temperature rises from the initial liquid state, the degree of supersaturation increases, and when the liquid temperature falls, the degree of supersaturation decreases. That is, as the liquid temperature increases, it becomes easier to form a film of silicon dioxide, whereas as the liquid temperature decreases, it becomes difficult to form a film. For this reason, in a silicon dioxide film forming apparatus, by cooling the film forming tank from the outside, the degree of supersaturation of the film forming liquid near the wall is reduced, and formation of a silicon oxide film can be prevented.

The film-forming solution is normally used at around room temperature and is controlled to keep the room temperature constant. In the temperature range around room temperature, if the temperature of the film rises by 10°C, the film-forming rate doubles and the temperature of the film increases. 1
It has been found that the film formation rate increases by 172 times when the temperature decreases by 0°C. Therefore, it is preferable to cool the film-forming tank wall by 10° C. or more relative to the film-forming solution in order to reliably prevent silicon dioxide from forming in the film-forming tank.

(Example) An example according to the present invention will be described with reference to the drawings. Second
The figure shows the main parts of a silicon dioxide film forming apparatus, and the silicon semiconductor wafer 11 to be processed is placed in a PVC film forming tank 12.
It is immersed in a film forming solution 13 contained in a container. In addition, an overflow tank 1 for the film forming solution 13 overflowing adjacent to the film forming tank 12 is provided.
4 is installed, is circulated and filtered by a pump 15 and a filter 16, and is returned to the film forming tank 11 again. A plurality of flow holes 17 are formed at the bottom of the film forming tank 12 , and these are connected to the overflow tank 14 through a thin tube 18 . The overflow tank 14 is equipped with a heater 19 and a cooling pipe (chiller pipe) 20 that are electrically connected to a power source (not shown), so that the film forming liquid 13 overflowing from the PVC film forming tank 12 It is possible to control the temperature to 35° C. by heating and cooling means. Furthermore, a cooling pipe 21 is disposed around the outside of the PVC film-forming tank 12 to cool the wall temperature of the film-forming tank to 1 to 1O'c. Note that the materials described in the prior art section can also be applied to the film forming tank 12.

Here, by immersing and dissolving the peripheral plate 22 in the overflow tank 14, the equilibrium state of the film forming solution 13 is shifted to a supersaturated state, and silicon dioxide ( (not shown) is formed into a film. This silicon dioxide layer is applied to the semiconductor wafer 11 to be processed.
In some cases, a suitable mask material may be installed in order to deposit at a predetermined position. The deposited silicon dioxide layer can be used, for example, as an insulator layer or a passivation layer essential to the semiconductor wafer U to be processed. After the start of film formation, the silicon dioxide film forming apparatus can be used continuously with the same film forming liquid for two consecutive periods while receiving replenishment from a film forming liquid supply tank (not shown), during which time the semiconductor wafer 11- Thickness per sheet 3
A silicon dioxide layer up to 0 μm thick can be deposited in place.

However, since the wall of the film forming tank is maintained cooled to about 10° C., the supersaturation caused by the film forming liquid 13 in this vicinity becomes negligibly small, thus preventing the film forming of the silicon dioxide layer. be able to.

〔Effect of the invention〕

According to the silicon oxide film forming method according to the present invention, it is possible to form a silicon dioxide layer only on the semiconductor wafer to be processed without forming a silicon dioxide layer on the wall of the film forming tank, so that subsequent fine patterns can be formed very well. Can be formed. Table 1 shows whether or not a silicon dioxide layer is formed on the wall of the film forming tank by visual inspection.
The results were shown.

However, this data is obtained when the silicon dioxide film forming apparatus shown in FIGS. 1 and 2 is used continuously for two consecutive periods.

1st table Wall of film forming tank Elapsed time after starting film forming 1 day 7 days 14 days With cooling None Yes Yes With no cooling None None None In the silicon dioxide film forming apparatus with the cooling pipe removed as shown in Figure 2, the time elapsed since the start of film forming After 7 days, silicon dioxide was formed all over the wall of the film forming tank, and moreover, it separated into small pieces and became floating.

Figure 3 shows the amount of silicon dioxide deposited on a 0.1 μs thick silicon dioxide film formed blindly on a 5 inch diameter silicon semiconductor wafer 14 days after the start of film deposition using the silicon dioxide film deposition apparatus used in the method of the present invention. We clarified the distribution state of dust with a diameter of 0.3 tim or more, and Figure 4 shows the thickness of a mask formed 14 days after the start of film formation on a 5-inch diameter silicon semiconductor wafer using a conventional silicon dioxide film deposition system. As is clear from this figure, which shows the distribution of dust with a diameter of 0.3 μs or more attached to 0.1- silicon dioxide, the effectiveness of installing a cooling pipe around the outer periphery of the film-forming tank is clear. There is.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the main parts of a conventional silicon dioxide film forming apparatus, Figure 2 is a sectional view schematically showing a silicon dioxide film forming apparatus used in the method of the present invention, and Figures 3 and 4 are silicon dioxide film forming apparatuses. FIG. 2 is a diagram showing the state of dust attached to silicon dioxide deposited on a semiconductor wafer. 1.12... Film forming tank, 2.13... Film forming solution, 5
．． 15...Pump, 6.16...Filter 1
9... Heater, 20... Cooling pipe, 8.22.
...Surrounding plate, 9.11...Semiconductor wafer, 21.
...Cooling pipe, 10...Silicon dioxide piece. 3.17... Distribution hole section.

Claims (1)

[Claims] When forming a silicon oxide layer on the surface of a semiconductor wafer by a precipitation reaction from a supersaturated solution of hydrofluoric acid, the average of the solution is A silicon oxide film forming method characterized by lowering the tank wall temperature rather than the temperature.