JPH04139743A - Liquid growing method for insulating film - Google Patents

Abstract

PURPOSE:To increase the deposition rate of an SiO2 to be precipitated on a wafer by adding boric acid by charging the surface of a wafer to positive charge by applying a voltage, moving SiO3<2-> ions having negative charge toward the wafer, and enhancing concentration of the ions near the wafer. CONSTITUTION:Hexafluorosilicic acid solution 3 is put in a solution tank 1, SiO2 particles are dissolved in the solution, SiO3<2-> ions are produced and held in an equilibrated state. Then, boric acid (H3BO3) solution is added to precipitate SiO2 on the surface of a wafer 3, and a voltage of several volts several tens of volts is applied from a DC power source 4 to the wafer 2 so that positive charge is particularly accumulated. Reference numeral 5 denotes a negative electrode for storing negative charge, which is formed, for example, of carbon, silicon carbide, etc., and connected to a negative electrode wiring 6 of the source 4. Thus, an insulating film (SiO2 film) can be formed not only with flatness on the wafer but also at a greater deposition rate.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for liquid phase growth of an insulating film.

[Summary of the Invention] The present invention provides an insulating film solution in which 5iOz is dissolved in a hydrosilicofluoric acid solution to generate SiO32- ions, and then a boric acid solution is added to deposit 5iOz on a wafer. In the phase growth method, a voltage is applied so that the surface of the wafer can be positively charged, and the concentration of SiO32- ions near the wafer is increased, whereby an insulating film is deposited and deposited on the wafer. It becomes possible to increase the speed and improve the film quality of this insulating film.

[Conventional technology] As the density and integration of VLSI increases, the miniaturization and multilayering of wiring have become essential. Planarization of interlayer insulating films is becoming increasingly important.

In recent years, as a method for planarizing such an interlayer insulating film, via
-ECR-CVD method, liquid phase CVD method, and liquid phase growth method are considered to be particularly effective.

Here, the bias/ECR-CVD method refers to the bias/ECR-CVD method.
This is a planarization method in which conditions are set so that deposition and etching can be performed simultaneously in ECR-CVD.

In addition, the liquid phase CVD method uses tetraethoxysilane (TEO
This method liquefies S) on the wafer surface and oxidizes it by exposing it to 0° plasma.

Furthermore, in the liquid phase growth method, as shown in FIG.
5iOz is dissolved in this solution to ionize 5iOi'- ions, and the wafer 2 is immersed in the solution.

Next, an insulating film is formed by precipitating and depositing S'rOt on the surface of the wafer 2 by adding a boric acid (Hs B O3) solution.

In particular, among the above-mentioned methods, the liquid phase growth method uses low-temperature conditions (
This method has advantages in that it is possible to form an insulating film at a temperature of ~40°C), the equipment itself is simple, and the insulating film can be grown with the resist attached to the wafer surface. (“Monthly Sem1conductor W
(See page 85 of July 1990 issue) "Problems to be Solved by the Invention" In the above liquid phase growth method, the following (A) and (B)
As shown in the chemical reaction formula, by adding boric acid (83BO8), the chemical reaction of formula (B) proceeds to the right, hydrofluoric acid (HP) is consumed, and according to Le Chatelier's law, , has a reaction mechanism in which the chemical reaction shown by formula (A) proceeds in the right direction and 5iOy is spontaneously deposited on the wafer.

HtS i F a”2 HtO→6 HF4S i
OtJ・・・(A) HsBOs+4 HF →BF, +H,0°+2H,O
+e・・・・・(B) Here, the dissolved S 10 m is 5i03 in the solution
It is thought that these ions exist as "- ions," and these Sin and To ions are naturally precipitated as 5ifts near the wafer.

In this way, in the liquid phase growth method, since the film is formed by spontaneous precipitation of 5iOp, the growth rate of the insulating film is from several 100 to several 1
000 people/hr', which was a big problem in practice.

The present invention was devised by focusing on these conventional problems, and aims to provide a liquid phase growth method for insulating films that enables high-speed film formation and is also expected to improve film quality. be.

[Means for Solving the Problem] Therefore, the present invention dissolves 5iOy in a hydrosilicofluoric acid solution to generate SiO32- ions, and then adds a boric acid solution to form 5iOy on a wafer. In the liquid phase growth method of the insulating film to be deposited, a voltage is applied so that the surface of the wafer can be positively charged, and SiO+ near the wafer is
``The solution is to increase the concentration of ions.

[Operation] When a voltage is applied and the wafer surface is positively charged, the negatively charged SiOs"- ions move toward the wafer, and the SfO,"- ion concentration near the wafer increases. Therefore, the growth rate of SiOx deposited on the wafer increases by adding boric acid.

[Example] Hereinafter, details of the liquid phase growth method of an insulating film according to the present invention will be described based on an example shown in the drawings.

(First Example) In this example, as shown in FIG. 1, a hydrosilicic acid solution 3 is placed in a solution tank I, SiOv particles are dissolved in this solution, and SiO32- ions are generated. and maintain equilibrium.

Next, a boric acid (HsBOs) solution is added and the Si
n, is deposited on the surface of the wafer 2, and a voltage of several volts to several tens of volts is applied to the wafer 2 by direct current 1ac4 so as to accumulate particularly positive charges. The figure shows a negative electrode 5 that stores negative charges, is made of carbon, silicon carbide, etc., and is connected to a negative electrode wiring 6 of the DC power source 4.

In addition, in this example, since the apparatus based on the solution tank I was a batch type, the positive electrode wiring 7 from the DC power supply 4 was
The terminal 7a is divided into a plurality of parts so as to be connected to a plurality of wafers 2. Further, the terminals 7a of these positive electrode wirings 7 are supported by clamps or susceptors relative to the wafer 2, although not shown. In this way, by accumulating positive charges on the wafer 2, the 5in3"-ions are attracted to the vicinity of the wafer 2 due to electrostatic action. Therefore, the concentration of 5iOa"-ions near the wafer 2 becomes high. There is. In this state, by adding a boric acid (H-B O3) solution, the equilibrium of the above equation (A) is shifted to the right. Since the concentration of 5i03'- ions is high near the wafer 2, the 5i03'- ions are 2. Rapidly deposits on the surface.

That is, in this embodiment, it is possible to form an insulating film (SiO film) at a high growth rate on the wafer surface, as well as having flatness. Furthermore, since there are a large number of 5in3'-ions that precipitate near the wafer and become growth seeds, there is an advantage that the initial film seeds are formed well and the film quality is improved.

Next, the process of forming an insulating film on the wafer is shown in FIGS.
Explain based on the second diagram.

As shown in FIG. 2A, after an aluminum wiring layer 9 is deposited by sputtering or the like on an insulating film 8 made of, for example, Sin, a resist pattern 10 is formed using a lithography technique. .

Next, as shown in FIG. 2B, the aluminum wiring layer 9 is anisotropically etched using the resist pattern IO as a mask to expose the lower insulating film 8.

Then, in this state, it is immersed in the solution bath l shown in FIG. 1, and the liquid phase growth method is performed based on the method described above.
An insulating film 11 of SiO is grown in a liquid phase as shown in FIG. In this case, as shown in FIG. 3C, the S j O insulating film 11 is formed to have substantially the same thickness as the aluminum wiring layer 9 .

Next, the wafer is taken out from the solution bath 1, the resist pattern IO is removed using a technique such as ashing, and then Sid!
Membrane 12 membrane type 2.

In this example, a 5-inch insulating film 11 and a S i Ov film 12 are used.
However, by forming the Sin insulating film 11 using the liquid phase growth method, it is possible to significantly improve the flatness compared to the method of depositing the insulating film using the CVD method.

(Second Embodiment) FIGS. 3A to 3E show a second embodiment in which the present invention is applied to trench formation.

First, in this embodiment, a resist is applied onto the silicon substrate I3, and a resist pattern 14 is formed using lithography technology (FIG. 3A). Using this as a mask, the silicon substrate 13 is etched to form a trench groove I5. (Figure 3B).

Next, the silicon substrate 13 (wafer) is immersed in the solution bath l shown in FIG. 1 by the same liquid phase growth method as in the first embodiment, and 5iOy is deposited in the trench groove 15 to form the trench 16. (Figure 3C). At this time, the upper surface of the trench I6 is grown to such an extent that it slightly protrudes from the surface of the silicon substrate 13.

Next, after removing the resist pattern 14, as shown in Figure 3, a film 17 of SiO, for example, is deposited by plasma CVD and etched until it becomes as shown in Figure 3E. A flat trench 16 is formed.

Above is the first part. Although the second embodiment has been described, the present invention is not limited to these embodiments, and various design changes can be made in accordance with the gist of the configuration. For example,
In the above embodiment, the solution tank L was a batch type, but
Of course, a single-wafer type may also be used.

Furthermore, in both of the above embodiments, the liquid phase growth of the insulating film was performed with the resist applied, but the growth may be performed after the resist is removed.

Furthermore, in the present invention, the solution in the solution tank may be circulated and particles may be removed using a filter.

[Effects of the Invention] In the method for forming an insulating film according to the present invention, since positive charges are stored in the wafer, the concentration of s + O3''- ions that precipitate to become 5iOy becomes high near the wafer. This has the effect of increasing the growth rate (growth rate) of the insulating film.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the first embodiment of the liquid phase growth method for an insulating film of the present invention, FIGS. FIG. E is a sectional view showing the process of the second embodiment, and FIG. 4 is an explanatory diagram of the conventional example. 2...Wafer, 3...Hydrosilicic acid solution, 4...
DC power supply, 11...5 top insulating film, I6...trench. %1 Hajime=10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000D

Claims (1)

[Claims] (1) A method of liquid phase growth of an insulating film in which SiO_2 is dissolved in a hydrosilicofluoric acid solution to generate SiO_3^2^- ions, and then a boric acid solution is added to deposit SiO_2 on the wafer. A method for liquid phase growth of an insulating film, characterized in that a voltage is applied so that the surface of the wafer can be positively charged to increase the concentration of SiO_3^2^- ions in the vicinity of the wafer.