JPS6156415A - Plasma treatment equipment - Google Patents

Abstract

PURPOSE:To enable cleaning simply in a container by using a stainless material coated with aluminum as the conductor of a high frequency current holding a discharge electrode. CONSTITUTION:A top electrode 4 and a bottom electrode 5 made of aluminum for plasma discharge are provided in a reaction container 1 and a wafer 6 to be treated is placed on the bottom electrode 5 and is heated by a heater 7. The top electrode 4 and the bottom electrode 5 are connected to a high frequency power source 9 through a conductor 8. The conductor 8 which holds the electrodes 4, 5 requires mechanical strength and is made of stainless steel the surface of which is coated with thick aluminum for corrosion resistance. A screw for fixing the conductor 8 is also coated with aluminum. This enables dry etching for plasma CVD using CF4 gas and man-hours for cleaning process can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a conductive member constituting a plasma chemical vapor deposition apparatus.

Semiconductor devices such as ICs and LSIs are made of gallium arsenide (C, a
Compound semiconductors such as As ) or silicon (S
A single-crystal substrate (hereinafter referred to as a wafer) made of a single semicircle as shown in i) is used and subjected to heat treatment.

BACKGROUND OF THE INVENTION Semiconductor regions are formed by diffusion of impurities, ion implantation, etc., and semiconductor elements are manufactured using thin film formation technology and photolithography.

In other words, taking the St semiconductor as an example, the conductor layer is aluminum (AI) and Tanges+7 (W).

Metals such as molybdenum (Mo) are used, and thin film formation methods such as sputtering and vacuum evaporation are used, and silicon nitride (SiCoN4), silicon dioxide (Si 02 ), It uses phosphosilicate glass (abbreviated as PSG) and is manufactured using chemical vapor deposition method (abbreviated as CVD) or plasma CVD method, which is an improved version of this method.

The present invention relates to an improvement of a plasma CVD apparatus used for forming an insulating layer.

[Conventional technology]

CVD is a reaction in which two or more gaseous substances are reacted at high temperature under normal pressure or reduced pressure to produce a new solid and gaseous substance, while plasma CVD is a reaction in which two or more gaseous substances are reacted in a plasma. By using plasma, the substrate temperature during the reaction can be lowered and the resulting thin film can be prevented from being thermally damaged. You can hold down less.

The reason for this is that although the molecules that make up the gaseous substance have relatively low energy, they are excited by collisions with electrons in the low-temperature plasma, which is equivalent to being placed in a thermally high temperature state, and therefore effective chemical reactions occur even at low temperatures. This is to progress.

Figure 1 shows the configuration of a plasma CVD apparatus. A reaction vessel 1 made of stainless steel or aluminum (hereinafter abbreviated as aluminum) has a reaction gas inlet 2 and an outlet 3, and a plasma discharge is carried out inside the apparatus. An upper electrode 4 and a lower electrode 5 made of aluminum are provided for processing, and a wafer 6 to be processed is placed on the lower electrode 5. and is heated by a heater 7 provided under the lower electrode 5.

Here, the upper electrode 4 and the lower electrode 5 are circuit-connected to a high frequency power source 9 through a conductive member 8, for example, 13.56
1 so that a high frequency current of MHz is supplied.

Here, the case where an insulating film made of silicon nitride is formed on the wafer 6 made of Si will be explained as follows.

Inlet port 2 of reaction vessel 1. Monosilane (SiHa) and ammonia (NH3) are introduced as reaction gases from the reactor, and nitrogen (N2) or argon (Ar) gas is introduced as a carrier. Electricity is supplied to maintain the temperature of the wafer 6 at 300 to 400°C.

When RF discharge is performed between the upper electrode 4 and the lower electrode 5 made of aluminum in such a state, the growth of silicon nitride (Si3Na, to be precise, St, 4N,), which is a reaction product, progresses on the surface of the wafer 6. However, by adjusting the processing time, an insulating layer of a predetermined thickness can be formed.

The same is true when making insulating layers such as 5i02 and PSG; the former uses SiH4 and nitrous oxide (
N20), or in the latter case, Si1 and phosphine7 (
It can be formed by using a mixture of PH・) and 0.

As described above, an insulating layer of a predetermined thickness can be formed on the wafer 6 by the plasma CVD method, but what is important here is the distance between the upper electrode 4 and the lower electrode 5 and the positioning of the wafer 6. This is done by a conductive member 8 connected to the introduction terminal 10 of the reaction vessel 1.

Therefore, the conductive member 8 needs to have mechanical strength and thermal strength, and has conventionally been formed using a stainless steel plate.

In this manner, the formation of the color edge layer is performed by plasma CVD, and although the deposition occurs preferentially on the heated wafer 6 due to vapor phase growth,
This also occurs in the surrounding areas, so it is necessary to clean the inside of the reaction vessel from time to time, and plasma treatment is also used for this cleaning.

That is, when Freon (CF4) gas is introduced from the reaction vessel 1 through the inlet 2 and evacuated to the same degree of vacuum as before through the outlet 3, RF7ii electrolysis is performed, CF', *.

Radicals such as CF2*, CF*, and Flg are generated,
As a result, the precipitated insulator is dry etched and cleared.

However, at this time, the conductive member 8 was also etched,
There is a problem that poor contact occurs when plasma CVD is performed.

FIG. 2 is a perspective view showing the relationship between the upper electrode 4, the conductive member 8, and the introduction terminal IO, and the same applies to the lower electrode 5.

Here, the upper electrode 4 is made of aluminum from the viewpoint of corrosion resistance.
On the other hand, since the conductive member 8 requires corrosion resistance and mechanical strength, a plate made of stainless steel is used, and is fixed to the upper electrode 4 and the electrode 10 by screwing or the like.

When dry etching with CF4 is performed to obtain such a structure, the joints 11 such as screws are also eroded at the same time, resulting in poor contact.

Therefore, conventionally, the electrodes 4 and 5 in the reaction vessel 1 were periodically
Then, the conductive member 8 is disassembled and taken out, and heated with hot nitric acid (HNO).
Etching was performed using strong acids such as 3).

[Problem that the invention seeks to solve]

As mentioned above, when an insulating layer is formed using the plasma CVD method, it does not remain on the surface of the wafer, but also deposits on the periphery, and if left as is, it becomes dust in the carrier gas. and float, causing quality deterioration.

Therefore, it is necessary to clean the inside of the container, and although it is known that dry etching using CF4 can be done with just M, this is not possible due to corrosion of the conductive member and poor contact at the lead-in terminal. It was a problem.

[Means for solving problems]

The above problem occurs in a plasma chemical vapor deposition apparatus used to form an insulating layer of a half-gate element. This can be solved by using a product coated with

[Function] In the present invention, when performing dry etching using CF4 gas as an etchant, the discharge electrode part made of aluminum is not etched, but the introduction member made of stainless steel is etched, so the stainless steel base material is coated with aluminum. By using it as an introduction member, it provides strength and corrosion resistance.

〔Example〕

In the present invention, the conductive member 8 that holds the upper electrode 4 and the lower electrode 5 and serves for positioning is required to have mechanical strength, so it is formed of stainless steel as in the past, and its surface is thickly coated with aluminum. This method provides corrosion resistance by hot-dip aluminum plating.
Methods such as or plasma spraying are suitable.

For example, as an example, a conductive member made of conventional stainless steel is subjected to surface treatment such as degreasing and removal of a passive film, and then immersed in an aluminum bath molten at a temperature of about 1000°C for 2 minutes to form a conductive member of about 200 μm. ) can be coated with aluminum.

In this way, sufficient corrosion resistance can be imparted by using a coated aluminum as the conductive member 8 and also using a screw for threading the conductive member 8 coated with aluminum.

〔Effect of the invention〕

As described above, by carrying out the present invention, dry etching using plasma CVD using CF and gas becomes possible, and the number of steps in the cleaning process can be reduced compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of the plasma CVD apparatus. FIG. 2 is a perspective view showing the relationship between the upper electrode and the conductive member. In the figure, 1 is a reaction vessel, 4 is an upper electrode, 5 is a lower electrode, 6 is a wafer, 8 is a conductive member,
10 is an introduction terminal, and 11 is a joint portion. 1st IM

Claims (1)

[Claims] In a plasma chemical vapor deposition apparatus used for forming an insulating layer of a semiconductor element, a conductive member installed in the apparatus, which holds a discharge electrode and constitutes a high-frequency current path, is made of a stainless steel base material coated with aluminum. A plasma processing device featuring: