JPH0669032B2 - Plasma processing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a conductive member constituting a plasma enhanced chemical vapor deposition apparatus.

Semiconductor elements such as IC and LSI are gallium arsenide (GaA).
A single crystal substrate (wafer) made of a compound semiconductor such as s) or a single semiconductor such as silicon (Si) is used, and a semiconductor region is formed by performing heat treatment, diffusion of impurities, ion implantation, or the like. At the same time, semiconductor elements are manufactured by using thin film forming technology and photolithography technology.

That is, taking a Si semiconductor as an example, the conductor layers include aluminum (Al), tungsten (W), molybdenum (M
o) and other metals are used, thin film forming methods such as sputtering and vacuum deposition are used, and silicon nitride (Si ₃ N ₄ ) and silicon dioxide (Si) are used to form the insulating layer.
O ₂ ), phosphosilicate glass (abbreviated as PSG), etc. are used, and are made by using a chemical vapor deposition method (abbreviated as CVD) or a plasma CVD method improved from this.

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

[Conventional technology]

CVD is a reaction in which two or more types of gaseous substances are reacted at high temperature under atmospheric pressure or reduced pressure to generate new solids and gaseous substances, while plasma CVD is the reaction of two or more types of gaseous substances in plasma. Is used to form new solids and gaseous substances at a relatively low temperature by using a plasma, and the plasma can be used to lower the substrate temperature during the reaction, and the thermal damage to the thin film produced is reduced. You can hold it down.

The reason for this is that the energy of the molecules that make up the gaseous substance is relatively low, but it is equivalent to being excited by collisions with electrons in the low-temperature plasma and being placed in a thermally high temperature state, so that an effective chemical reaction even at low temperatures occurs. This is to proceed.

FIG. 1 shows the structure of a plasma CVD apparatus. A reaction container 1 made of stainless steel or aluminum (hereinafter abbreviated as aluminum) has an inlet 2 and an outlet 3 for a reaction gas. An upper electrode 4 and a lower electrode 5 made of aluminum are provided. A wafer 6 to be processed is placed on the lower electrode 5 and heated by a heater 7 provided below the lower electrode 5. It has become.

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 so that, for example, a high frequency current of 13.56 MHz is supplied.

The case of forming an insulating film made of silicon nitride on the wafer 6 made of Si will be described below.

Monosilane (SiH ₄ ) and ammonia (NH ₃ ) are introduced from the inlet 2 of the reaction vessel 1 as a reaction gas by using nitrogen (N ₂ ) or argon (Ar) gas as a carrier,
The temperature of the wafer 6 is maintained at 300 to 400 ° C. by evacuating from the exhaust port 3 to maintain the vacuum degree at 1 TORR and energizing the heater 7.

In this state, between the aluminum upper electrode 4 and the lower electrode 5,
When RF discharge is performed, the growth of silicon nitride (Si ₃ N ₄ , to be precise, Si _x N _y ) which is a reaction product on the surface of the wafer 6 proceeds, and the processing time is adjusted to a predetermined thickness. You can make an insulating layer.

The same applies to the case of forming an insulating layer such as SiO ₂ or PSG. The former case uses SiH ₄ and nitrous oxide (N) as reaction gases.
₂ O), and in the latter case SiH ₄ and phosphine (P
It can be formed by using a mixed gas with H ₃ ).

As described above, the insulating layer having a predetermined thickness can be formed on the wafer 6 by the plasma CVD method. 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 performed by the conductive member 8 provided so as to be connected to the introduction terminal 10 of the reaction container 1.

Therefore, the conductive member 8 needs to have mechanical strength and thermal strength, and is conventionally formed of a stainless plate material.

Although the insulating layer is formed by plasma CVD in this way, although deposition preferentially occurs on the heated wafer 6 due to vapor phase growth, the upper and lower electrode parts 4, 5 and the peripheral part are also formed. In order to occur, it is necessary to clean the inside of the reaction vessel 1 from time to time, and the plasma treatment method is also used for this cleaning.

That is, when Freon (CF ₄ ) gas is introduced from the reaction vessel 1 through the inlet port 2 and RF discharge is performed while exhausting to the same degree of vacuum as before the outlet port 3, CF ₃ *, CF ₂ *, CF *,
Radicals such as F * are generated, and the deposited insulator is dry-etched and cleaned.

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

FIG. 2 is a perspective view showing the relationship among the upper electrode 4, the conductive member 8 and the introduction terminal 10, 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 is required to have corrosion resistance and mechanical strength, a plate material made of stainless steel is used and is fixed to the upper electrode 4 and the introduction terminal 10 by a method such as screwing.

When dry etching with CF ₄ is performed to take such a configuration, the joint portion 11 such as a screw stop is also eroded at the same time, and this causes contact failure.

Therefore, conventionally, the electrodes 4, 5 in the reaction vessel 1 are regularly
The conductive member 8 is disassembled and taken out, and hot nitric acid (HNO
₃ ) Etching was performed using a strong acid such as.

[Problems to be solved by the invention]

As described above, when the insulating layer is formed by using the plasma CVD method, not only the surface of the wafer but also the peripheral portion is deposited, and if it is left as it is, it becomes dust in the carrier gas. It floats and causes quality deterioration.

Therefore, it is known that the inside of the container needs to be cleaned, and dry etching using CF ₄ can be simply performed, but this cannot be performed because corrosion of the conductive member and poor contact at the introduction terminal occur. It was a problem.

[Means for solving problems]

In the plasma chemical vapor deposition apparatus used for forming the insulating layer of the semiconductor element, the above-mentioned problem is that in the growth container, only the conductive member that holds the discharge electrode and constitutes the high-frequency current path is formed on the stainless steel base material of aluminum. It can be solved by using a coated product.

[Operation] In the present invention, when dry etching is performed using CF ₄ gas as an etchant, the discharge electrode portion made of aluminum is not etched, while the introduction member made of stainless steel is etched. By using it as a lead-in member, it has strength and corrosion resistance. At this time, in order to coat the conductive member with aluminum, if the inner wall of the reaction vessel made of stainless steel is also coated with aluminum, degassing occurs from the aluminum coating when the reaction vessel is evacuated, and the reaction is evacuated. This is because it takes a long time.

Therefore, corrosion progresses to some extent on the inner wall of the stainless steel reaction vessel not coated with aluminum.

However, this corrosion product is removed at the same time when the deposits adhering to the inner wall of the reaction vessel are removed by the plasma of the fluorocarbon gas, so there is no effect.

〔Example〕

According to the present invention, the conductive member 8 that holds the upper electrode 4 and the lower electrode 5 and also serves as a positioning member needs to have mechanical strength. Therefore, the conductive member 8 is formed of stainless steel as in the prior art, and this surface is thickly coated with aluminum. Corrosion resistance is imparted by the method, and as this method, methods such as aluminum hot-dip plating and plasma spraying are suitable.

For example, as an example, after performing a surface treatment such as degreasing or removing a non-moving body film on a conventional conductive member made of stainless steel,
An aluminum coating with a thickness of about 200 μm can be performed by immersing it in a molten aluminum bath at a temperature of 1000 ° C. for 2 minutes.

As described above, the conductive member 8 is coated with aluminum, and the screw for fixing the conductive member 8 is also coated with aluminum, whereby sufficient corrosion resistance can be imparted.

〔The invention's effect〕

As described above, by carrying out the present invention, it is possible to perform dry etching in which plasma CVD is performed using CF ₄ gas, and it is possible to reduce the number of steps in the cleaning process as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a side sectional view of a 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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuhiro Tsukune 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (56) References JP-A-59-184527 (JP, A) JP-A-59- 139628 (JP, A)

Claims (2)

[Claims] 1. A lower electrode having an upper electrode (4) and a lower heater (7) inside a reaction vessel (1) having a reaction gas inlet (2) and an outlet (3) connected to an exhaust system. (5)
And the semiconductor wafer (6) are placed on the lower electrode (5), and the upper electrode (4) and the lower electrode (5) are respectively provided with conductive members (8). In a plasma processing apparatus, which is circuit-connected to a high-frequency power source (9) outside the reaction vessel (1) via an upper electrode (4) and a lower electrode made of aluminum, which are provided in the reaction vessel (1) made of stainless steel. (5)
The plasma processing apparatus is characterized in that the conductive member (8) for holding each of the above, and forming a high frequency current path is formed by coating a stainless steel base material with aluminum. 2. The plasma processing apparatus according to claim 1, wherein a screw for fixing the conductive member (8) is coated with the aluminum.