JPH0621048A - Selective formation method of silicon nitride film - Google Patents

Abstract

PURPOSE:To greatly reduce the number of manufacturing processes and a manufacturing cost by enabling selective formation of a silicon nitride film and by adopting a method for formation of a stack capacitor. CONSTITUTION:After a silicon oxide film 1 is selectively formed in a silicon substrate 2, a polycrystalline(e silicon 3 is selectively formed on a surface of the silicon substrate 2. A silicon nitride film 4 is selectively formed on a surface of the polycrystalline silicon 3 and a polycrystalline silicon 5 is selectively formed on a surface of the silicon nitride film 4 to form a stack capacitor. Selective formation technique of the silicon nitride film 4 is to carry out reaction using hydrazine, dichlorosilane and hydrogen chloride as raw gas and to form a silicon nitride film selectively on a surface of silicon alone. It is desirable to make volume ratio of hydrazine, dichlorosilane and hydrogen chloride in a reaction tube 20 to 40%, 30 to 50% and 10 to 50%, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a silicon nitride film used as an insulating film of a stack capacitor.

[0002]

2. Description of the Related Art A stack capacitor is used in a cell portion of a dynamic random access memory.
The outline of the manufacturing process of the stack capacitor is shown in FIG. First, as shown in FIG.
The thermal oxide film 1 is selectively formed by using the OCOS) element isolation technique, and an opening for establishing conduction with the lower electrode of the stack capacitor is formed between the thermal oxide films 1. Then
As shown in FIG. 2B, the polycrystalline silicon 3 is deposited on the entire surface by the CVD method. Subsequently, as shown in FIG. 2C, the polycrystalline silicon 3 is selectively etched by a photolithography technique and a dry etching technique to form a lower electrode of the stack capacitor.

Then, as shown in FIG. 2D, a silicon nitride film 4 is deposited on the entire surface of the substrate by the CVD method. Furthermore,
As shown in FIG. 2E, after the polycrystalline silicon 5 is deposited on the entire surface of the substrate by the CVD method, the polycrystalline silicon 5 and the silicon nitride film 4 are simultaneously patterned by the photolithography technique and the dry etching technique.
The stack capacitor as shown in (f) is completed. Incidentally, in the actual manufacturing method, in addition to the photolithography technique and the dry etching technique, cleaning, resist coating, baking, exposure, dry etching, resist removal, etc. are included.

[0004]

Recently, a technique for selectively growing polycrystalline silicon has been developed so that the lower electrode of a stack capacitor can be formed by the selective polycrystalline silicon growth method. The selective growth technique for polycrystalline silicon is described in Japanese Patent Application No. 2-215544. In the selective growth technology of polycrystalline silicon, when a silicon film is formed on a substrate whose surface is made of silicon and silicon oxide under the conditions that the polycrystalline silicon grows, hydrogen chloride gas is added to the silicon oxide so that the silicon oxide is formed on the silicon oxide. The nucleated silicon is removed by etching, and a silicon film is grown only on the silicon surface.

By using this polycrystalline silicon selective growth technique, the steps of FIGS. 2B and 2C can be simplified, and the stack capacitor manufacturing step can be simplified. However, since the silicon nitride film 4 as the dielectric film cannot be selectively grown, the polycrystalline silicon electrode as the upper electrode cannot be selectively grown, and the above-described selective growth technique of polycrystalline silicon cannot be effectively used. There is a problem. That is, if the selective growth of the silicon nitride film is possible, the selective growth of the polycrystalline silicon electrode formed thereon is also possible. From the stack capacitor manufacturing process shown in FIGS. 2E and 2F to the lithography process. Therefore, the dry etching process can be simplified. An object of the present invention is to enable selective growth of a silicon nitride film, and by utilizing this method for forming a stack capacitor,
It is an object of the present invention to provide a method for selectively growing a silicon nitride film, which is capable of significantly reducing the number of manufacturing steps and the manufacturing cost.

[0006]

According to the present invention, hydrazine, dichlorosilane, and hydrogen chloride are reacted as source gases to selectively grow a silicon nitride film only on the surface of silicon. The volume ratio of hydrazine, dichlorosilane, and hydrogen chloride in the reaction tube was 20 to 40% and 30%, respectively.
-50%, 10-50%.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1A to 1C are cross-sectional views showing a process of forming a stack capacitor in the order of steps by using the selective growth technique for a silicon nitride film according to the present invention. First, as shown in FIG. 1A, a silicon oxide film 2 having a thickness of 200 nm is selectively formed on the surface of a silicon substrate 2 by a LOCOS element isolation technique. Then, as shown in FIG. 1B, the polycrystalline silicon 3 as a lower electrode of the stack capacitor having a thickness of 400 nm is selectively formed on the surface of the silicon substrate 2 between the silicon oxide films 2 by the selective polycrystalline silicon growth technique. To form.

Next, as shown in FIG. 1C, a silicon nitride film 4 having a thickness of 10 nm is formed only on the surface of the polycrystalline silicon 3 by the selective silicon nitride film growth technique according to the present invention. This selective silicon nitride film growth technique will be described later. Next, as shown in FIG. 1 (d), the thickness of the silicon nitride film 4 is reduced only on the surface thereof by the selective polycrystalline silicon growth technique.
Polycrystalline silicon 5 is formed as an upper electrode of a stack capacitor of 00 nm to form a stack capacitor. Therefore, in this stack capacitor manufacturing method, by using the selective silicon nitride film growth description, the photolithography step and the etching step when forming the dielectric film and the upper electrode can be omitted, and the manufacturing man-hour can be reduced. .

The selective silicon nitride film growth technique is a chemical vapor deposition method using hydrazine, dichlorosilane and hydrogen chloride as source gases, and the composition of each gas is 100.
/ 400 / 500sccm, growth pressure 0.18Torr, growth temperature 800 ℃. When the concentration of dichlorosilane is 50% by volume, nucleation of silicon nitride containing a large amount of silicon occurs in the gas phase, resulting in loss of selectivity. On the other hand, if it is 30% or less, the growth rate becomes slow and the practicality is lacking. Higher concentrations of hydrazine increase the growth rate, but higher than 40% increases the risk of explosion and is not practical. When the concentration of hydrogen chloride is 10% or less, the selectivity is lost, and when it is 50% or more, the etching action is increased and the silicon nitride film does not grow.

Further, when the growth pressure is lowered, a silicon nitride film having a uniform thickness can be formed even on a surface having irregularities.
The equipment of the exhaust system becomes large and the device cost rises. Although the growth rate decreases as the growth pressure decreases,
If it was Torr or higher, a growth rate of 1 A / min or higher was obtained. Selective growth was possible with this gas composition in the range of 700-850 ° C. Above 850 ℃, the decomposition of aminosilane was promoted, and nucleation of silicon nitride occurred in the gas phase. 7
At 00 ° C or lower, the growth rate was 1 A / min or lower.

After all, when the practical growth rate is set to 5 A / min, the variation of the film thickness is 10% or less even for the uneven substrate, and the silicon nitride film is grown without losing the selectivity. For this, the gas composition shown in FIG. 3 may be used. That is, the volume ratios of hydrazine, dichlorosilane and hydrogen chloride in the reaction tube are 20 to 40%, 30 to 50% and 10 to respectively.
50%, growth pressure 0.1-1 Torr, growth temperature 7
A temperature of 50-800 ° C is desirable.

[0012]

As described above, according to the present invention, a silicon nitride film can be selectively grown on silicon. Therefore, for example, a photolithography process is performed when manufacturing a stack capacitor having a silicon nitride film as a dielectric film. Therefore, the dry etching process can be omitted. Further, the steps of cleaning, resist coating, baking, exposure, dry etching, resist removal and the like included in these steps can be omitted, and accidental accidents and reduction in non-defective product rate that occur in these steps can be reduced. This has the effect of reducing the number of man-hours and costs.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method of manufacturing a stack capacitor using a selective silicon nitride film growth technique of the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing a method of manufacturing a conventional stack capacitor in the order of steps.

FIG. 3 is a diagram showing a composition ratio of a raw material gas used in the method of the present invention.

[Explanation of symbols]

 1 silicon oxide film (thermal oxide film) 2 silicon substrate 3 polycrystalline silicon (lower electrode) 4 silicon nitride film 5 polycrystalline silicon (upper electrode)

Claims (2)

[Claims] 1. A method for forming a silicon nitride film by a chemical vapor deposition method on a substrate having a silicon oxide film and silicon on the surface thereof, wherein hydrazine, dichlorosilane and hydrogen chloride are used as source gases to react, and A method for selectively growing a silicon nitride film, which comprises selectively growing a silicon nitride film only on the surface of silicon. 2. The volume ratio of hydrazine, dichlorosilane and hydrogen chloride in the reaction tube is 20 to 40%, respectively.
The selective growth method for a silicon nitride film according to claim 1, wherein the amount is 30 to 50% and 10 to 50%.