JPH0246723A - Device for thin film formation - Google Patents

Abstract

PURPOSE:To form a thin film of good quality at a high deposition rate without generating oxidation, nitriding and the like by a method wherein the title device is provided with an inner skin container having the through hole of a reaction gas feeding means in such a way that a pair of electrodes are surrounded with the inner skin container, a vacuum container is provided with an inert gas feed opening and an exhaust vent for reaction gas fed in the inner skin container is interconnected to the vacuum container through a fine gap. CONSTITUTION:A vacuum container 1 is divided into 2 chambers of a reaction chamber 11 and an exhaust chamber 12 by an inner skin container 8, both chambers are interconnected to each other through a fine gap 10 and the pressure in the container 1 is set at a value to exceed somewhat 0.01Torr. When inert gas is sent in the chamber 12 through an inert gas feed opening 9 at a high flow velocity, the gas is made to flow in a viscous flow, whose mean free path is sufficiently short, and the gas to leak in the chamber 12 of the container 1 and free gas from the container 1 are induced by this viscous flow and are exhausted through a gas exhaust means 3 and are never made to flow backward in the chamber 11 through the fine gap 10. On the other hand, as a sufficient amount of reaction gas stays in the chamber 11 for sufficient hours, a thin film of good quality is formed on a semiconductor wafer 6 at high speed.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of a thin film forming apparatus using chemical vapor deposition (CVD), the present invention has been developed to address the issue of leakage gases such as oxygen and nitrogen, and free gases from metals constituting the apparatus. The purpose of the present invention is to provide a thin film forming apparatus that can form a high quality thin film at a high deposition rate without oxidizing or nitriding the thin film to be deposited even when the thin film is deposited. A vacuum container having a gas exhaust means and a pair of electrodes are provided inside the vacuum container, and one of the pair of electrodes surrounds the pair of electrodes in a thin film forming apparatus constituting a susceptor. , an inner shell container having a through-hole for the reaction gas supply means is provided, an inert gas supply port is provided in the vacuum container, and an outlet for the reaction gas supplied into the inner shell container is a narrow one. a ring-shaped or square loop-shaped gas injection means configured to communicate with the vacuum container through a gap, or to inject a gas flow from the periphery of one of the pair of electrodes to the periphery of the other; It is configured so that it can be set up.

[Industrial application field]

The present invention relates to an improvement in a thin film forming apparatus using chemical vapor deposition (CVD). In particular, even if gases such as oxygen or nitrogen leak into the thin film forming apparatus or become liberated from the metals that make up the apparatus, the formed thin film will not be oxidized or nitrided, and will remain of high quality. The present invention relates to an improvement in a thin film forming apparatus that makes it possible to form thin films at a high deposition rate.

[Conventional technology]

The CVD method includes a method using thermal decomposition of a reaction gas, a method using plasma decomposition of a reaction gas, and the like.

As an example, a plasma CVD apparatus according to the prior art will be explained with reference to the drawings.

The reference figure in FIG. 2 is a sectional view of the plasma CVD apparatus. The semiconductor wafer 6 is carried in through the gate valve 13, placed on the electric conductor 445 constituting the susceptor, exhausted from the gas exhaust means 3, and supplied with reaction gas from the reaction gas supply means 2 as shown by the solid arrow. , high frequency voltage of high frequency ti7 is applied to electrode 4
The reaction gas is applied between
Deposit the desired thin film on top. Note that la is an insulating sealing material and 1b is an O-ring.

By the way, in the case of a low-speed exhaust method in which the exhaust speed from the gas exhaust means 3 is slow, if there is a region in the vacuum container 1 where gas leaks, the internal pressure of the vacuum container 1 is low, so outside air will leak into the vacuum container 1. However, this leak gas reaches the semiconductor wafer 6 as shown by the broken line in the figure, and is incorporated into the thin film deposited on the semiconductor wafer 6. In addition, since the plasma spreads to the inner metal area of the vacuum vessel L, the ions that collide with the wall of the vacuum vessel L liberate contaminants such as oxygen from the wall of the vacuum vessel L, and the liberated contaminants such as oxygen are also It reaches the semiconductor wafer 6, as shown by the broken line, and is incorporated into the thin film deposited thereon. As a result, when depositing a metal film such as aluminum that is easily oxidized, the deposited film is oxidized and the resistivity becomes high.

Refer to Figure 3 In the case of a high-speed exhaust system with a high exhaust speed, leak gas and pollutants such as oxygen released from the wall of the vacuum vessel 1 are attracted to the high-speed viscous exhaust flow and discharged, as shown by the broken line in the figure. Therefore, contaminants such as oxygen are less likely to be incorporated into the thin film deposited on the semiconductor wafer 6, and the specific resistance of the thin film is less likely to increase. However, the reaction gas
Since the residence time in the vicinity of is short, the deposition rate of the film is reduced.

[Problem to be solved by the invention]

Since the conventional plasma CVD apparatus employs a low-speed exhaust system, it has not been possible to eliminate the influence of leak gas and wall surface free gas, as shown in FIG. 2 above. Even if a high-speed exhaust system is adopted as shown in Figure 3 above in order to eliminate the effects of leak gas and wall free gas, eliminating the effects of leak gas and wall free gas is not necessarily sufficient, and furthermore, A significant drawback is that the rate of thin film deposition is reduced.

The purpose of the present invention is to eliminate this drawback, and the purpose of the present invention is to eliminate oxidation, nitridation, etc. of the thin film to be deposited even if there is a leak gas such as oxygen or nitrogen, or a free gas from the metal constituting the device. It is an object of the present invention to provide a thin film forming apparatus which enables the formation of a high quality thin film at a high deposition rate without any problems, and which makes the thickness of the deposited film uniform over the entire surface of a wafer.

[Means to solve the problem]

The above object is to provide a vacuum container (1) having a reaction gas supply means (2) and a gas exhaust means (3);
) is provided with a pair of electrodes (4, 5), and one of the pair of electrodes (4, 5) is achieved by adding any of the following means to the thin film forming device that constitutes the susceptor. be done.

The first means added is the pair of electrodes (4, 5).
an inner shell container (8) provided surrounding the reactor gas supply means (2) and provided with a through-hole through which the reaction gas supply means (2) extends; and an inert gas supply port provided in the vacuum container (1). (
9), but in this case, the outlet of the reaction gas supplied into the inner shell container (8) is communicated with the vacuum container (1) through the slit (10). This is very important.

The second means added is the pair of electrodes (4, 5).
A ring-shaped or rectangular loop-shaped gas injection means (16) that injects a gas flow (air curtain) from one periphery to the other periphery of the ring-shaped or rectangular loop-shaped gas The injection means (16) is configured such that the gas flow (air curtain) to be injected is connected to a pair of electrodes (4, 5).
It is effective to provide it from the outer circumferential end on one side toward the other outer NJ end.

[Effect]

The diagram shown in FIG. 4 shows the pumping speed and the metal The relationship between mH deposition rate and the relationship between evacuation rate and the conductivity of the deposited metal thin film.In order to increase the deposition rate, it is necessary to lower the evacuation rate, while the In order to improve the conductivity, it is necessary to increase the pumping rate, and there is an antinomic relationship between the deposition rate and the quality of the film formed. The present invention is a means to resolve this antinomic relationship.

Refer to FIG. 1a In the thin film forming apparatus according to the present invention, a vacuum vessel 1 is divided into a reaction chamber 11 and an exhaust chamber 12 by an inner shell vessel 8, and the compartments are communicated with each other through a slit 10. Since the pressure of the inert gas is assumed to be a value somewhat exceeding 0.01T o r r, when the inert gas is fed into the exhaust chamber 12 from the inert gas supply port 9 at a high flow rate, the mean free path of the inert gas is sufficient. Flows as a short viscous flow, vacuum container 1
The leak gas leaking into the exhaust chamber 12 and the free gas from the vacuum container 1 are attracted by the viscous flow of the inert gas and are discharged from the gas exhaust means 3, and flow back into the reaction chamber 11 through the slit 10. On the other hand, since a sufficient amount of reaction gas remains in the reaction chamber 11 for a sufficient period of time, the exhaust speed in the reaction chamber 11 is such that a high quality thin film is formed on the semiconductor wafer 6 at a high speed. This is because, since it is not necessary to increase the speed to eliminate the influence of leak gas, the speed can be set to an optimum speed, and the thin film deposition speed can be made sufficiently high.

If an inert gas, reducing gas, etc. is injected toward the periphery of the electrode 5 from the gas injection means 16 provided around the electrode 4 instead of the inner shell container 8 (see FIG. 1c), the pressure inside the vacuum container 1 is 0. OI
If T o r r is slightly exceeded, the injected gas becomes a viscous flow with a short mean free path and acts as an air curtain, and as in the thin film forming apparatus having the inner shell container 8 described above, leak gas and Gas released from the wall surface is prevented from reaching the semiconductor wafer 6, and a state in which the pressure in the reaction chamber (11) is higher than that in the exhaust chamber (12) is realized, and a high quality iiwA is formed. Moreover, the deposition rate can be made sufficiently high.

Refer to FIGS. 1d and 1e. Furthermore, if the jetted gas from the gas jetting means 16 is jetted toward the outer circumferential surface of the loop-shaped insulating layer 41 at the peripheral end of the electrode 4, a metal film or the like will adhere to this region. is prevented from
A decrease in the dielectric strength of the electrode 4 can be prevented.

Note that the mean free path of gas is approximately 100n at pressure ITorr, which is sufficient to eliminate leak gas, etc.; however, the mean free path of gas is approximately 100n at pressure ITorr. Below OIT o r r, the value becomes 11 or more, which is about the same as the dimension between the wall of the vacuum container l and the semiconductor wafer 6, and there is no effect of preventing infiltration of leak gas or the like.

〔Example〕

Three embodiments of the present invention will be described below with reference to the drawings.

1. Quantification Process 1... Referring back to FIG. 1a, this is a sectional view of a plasma CVD apparatus according to a first embodiment of the present invention. 1 is a vacuum container, 2 is a reaction gas supply means, 3 is a gas exhaust means, 4 is a non-grounded side electrode, 5 is a grounded side electrode constituting a susceptor, and 6 is a thin film formed 7 is a high frequency power supply, 8 is an inner shell container, 9 is an inert gas supply port, 10 is a slit, 11 is a reaction chamber, and 12 is an exhaust chamber. , 13 is a gate valve, and 1
4 is a magnet rotated as shown by the arrow, 15 is a bellows, and 1a is an insulating sealing material.

As an example, a case will be described in which a thin film of aluminum is deposited. The semiconductor wafer 6 is placed on the electrode 5 constituting the susceptor, and while being exhausted by the gas exhaust means 3,
A reaction gas prepared by diluting trimethylaluminum with hydrogen is fed into the reaction chamber 11 from the reaction gas supply means 2.
1 pressure is 0.1~LOT o r r, exhaust chamber 1
2 is lower than this, and a high frequency voltage of 13.56 MHz and power of 0.1 to 5 W/c4 generated by the high frequency power source 7 is applied between the electrodes 4 and 5 to create a gap between the two electrodes. Plasma is generated to decompose the reactive gas, and a thin film of aluminum (not shown) is deposited on the semiconductor wafer 6. In this case, in order to activate the decomposition of trimethylaluminum, it is recommended to place a magnet 14 and deposit it while rotating it! The ff stone 14 is effective for increasing the plasma density near the semiconductor wafer 6 and increasing the reaction rate, as well as stably generating plasma when the pressure is as high as IOT o r r.

Referring to FIG. 1b, the semiconductor wafer 6 is transported out of the plasma CVD equipment.
The bellows 15 is retracted and the electrode 4 is transported.
Push up the inner shell container 8 having the gate valve 1.
3 is opened, the semiconductor wafer 6 on which the thin film has been formed is carried out, the semiconductor wafer 6 on which the thin film is newly formed is carried in, the gate valve 13 is closed, the inner shell container 8 is lowered, and the above-mentioned deposition process is carried out. Perform the process.

2 i, X2 - Referring again to FIG. 1C, this is a sectional view of a plasma CVD apparatus according to a second embodiment of the present invention. 1 is a vacuum container, 2 is a reaction gas supply means, 3 is a gas exhaust means, 4 is a non-grounded side electrode, 5 is a grounded side electrode constituting a susceptor, and 6 is a '111m A semiconductor wafer that is formed,
7 is a high frequency power supply, 11 is a reaction chamber, 12 is an exhaust chamber, 13 is a gate valve, 16 is a gas injection means, and 1a is an insulating sealing material.

For example, when hydrogen is injected from the gas injection means 16 toward the periphery of the electrode 5, the pressure inside the vacuum container l becomes 0.1.
~IOT o r r, the hydrogen gas becomes a viscous flow with a sufficiently short mean free path, which has the effect of partitioning the vacuum container 1 into the reaction chamber 11 and the exhaust chamber 12, and the leak gas and wall free gas of the vacuum container 1 are The gas is removed from the gas exhaust means 3 without reaching the semiconductor wafer 6. Therefore, it is possible to eliminate leak gas and the like without increasing the gas velocity in the reaction chamber 11, so that a high-quality thin film can be deposited at a high rate.

5 is a diagram showing the relationship between the specific resistance of an aluminum thin film deposited using the plasma CVD apparatus shown in FIG. 1c and the flow rate of hydrogen gas injected from the gas injection means 16. When the pressure of the vacuum vessel 1 is 2.3 Torr, increasing the hydrogen gas injection flow rate significantly reduces the specific resistance of the deposited aluminum.

1d is an enlarged view of the electrode 4 of the plasma CVD apparatus according to a modification of the second embodiment shown in FIG. 1c. In order to insulate the electrode 4 and the vacuum vessel l, an insulator layer 41 is provided on the outer surface of the electrode 4, and a shield layer 42 is provided on the outer surface of this insulator layer 41. When the plasma reaction progresses and a metal film is deposited on the tip of the insulator Ji41,
The electrode 4 and the shield layer 42 may be short-circuited. However, the hydrogen gas injected from the gas injection means 16 is
If the metal film is sprayed along the outer periphery of the insulating layer 41 provided on the insulating layer 41 toward the end thereof, a metal film is prevented from being deposited on the insulating layer 41, and a short circuit between tJi4 and the shield layer 42 is prevented. Ru.

Refer again to FIG. 1e. Also, as shown in the figure, the tip of the insulating layer 41 is
It may be shaped like an umbrella that spreads outward, and the hydrogen gas from the gas injection means 16 may be blown onto this portion.

See Figures 6, 7, and 8. Figure 6 shows the plasma C used in the computer simulation.
It is a schematic diagram of a VD device. Figure 7 shows the gas pressure distribution inside the vacuum vessel 1 when the gas flows downward from the electrode 4 and is exhausted from the gas exhaust means 3 as shown by the arrow in the figure. The isobar diagram shown in is obtained. 7th
The figure shows only the right half of the vacuum container l, and the semiconductor wafer 6
This shows that a pressure gradient is generated near the other electrode 5, which also serves as a susceptor on which is placed. If such a pressure gradient exists, it becomes impossible to keep the plasma constant, and the S quality and thickness of the deposited film become non-uniform. On the other hand, if the thin film forming apparatus according to the present invention is used, this pressure non-uniformity can be improved, and in particular, by using a plasma CVD apparatus having a gas injection means shown in FIG. 1e, and using hydrogen as a carrier gas. When diluted trimethylaluminum gas is supplied as a reaction gas and aluminum is deposited on a silicon dioxide substrate at 100°C or less, 1
The gas pressure between the pair of electrodes 4 and 5 becomes uniform, and the formed thin film has a saw-like thickness over the entire area of the semiconductor wafer, as shown in FIG. 8, and the error range is as shown in the figure. As a result, it is generally less than ±5%, which is a marked improvement compared to the conventional technology (which varies between a few percent and 20%), and is within a sufficiently acceptable range for practical use.

In addition, the reproducibility is also good, and it has been experimentally confirmed that there is a constant tendency for the board to be somewhat thicker at the center and somewhat thinner at the periphery, and this error of ±5% is not practical. It's not a big hindrance.

What is also surprising is that when the silicon dioxide substrate on which the aluminum film was formed as described above was heat-treated for 30 minutes at a temperature of 450'C in a mixed gas of hydrogen and nitrogen, the resistivity decreased to 7 μΩ1. This is a significant decrease compared to the conventional technology. The reason for this is not necessarily clear, but it is thought to be because the amount of oxygen, etc. that enters as leak gas is reduced.

The above has described the formation of aluminum thin films, but it is also important to form metal films such as tungsten, molybdenum, silicides of these high-melting point metals, stainless steel, and insulating films such as silicon dioxide, silicon nitride, silicon oxynitride, and phosphosilicate glass. Needless to say, the present invention is effective even in this case.

〔Effect of the invention〕

゛As explained above, the thin film forming apparatus according to the present invention includes a vacuum vessel having a reaction gas supply means and a gas exhaust means, and a pair of electrodes provided in the vacuum vessel. One of the electrodes constitutes a susceptor in the thin film forming apparatus, in which an inner shell container is provided surrounding the pair of T-shaped rods, to which the through hole of the reaction gas supply means is extended and attached. An inert gas supply means is provided between the shell container and the vacuum container, and an outlet for the reaction gas supplied to the inner shell container is communicated with the vacuum container through a slit. Alternatively, by providing a loop-shaped (ring-shaped or rectangular loop-shaped) gas injection means for injecting a gas flow from the periphery of one of the pair of electrodes to the periphery of the other electrode, the vacuum vessel is divided into a reaction chamber and an exhaust chamber by the inner shell container or injection gas, and leak gas such as oxygen and nitrogen or free gas from the wall of the vacuum chamber is exhausted from the exhaust chamber without flowing into the reaction chamber. The advantages of the high-speed evacuation method, which eliminates the harmful effects of leak gas, and the advantages of the low-speed evacuation method, which provides a high deposition rate, are combined. That is, in the thin film forming region, since a low-speed exhaust system is used, the deposited thin film is not oxidized, nitrided, etc., and a high quality yi film is formed. Moreover, since the high-speed exhaust system is used in relation to the inner wall of the vacuum container, leak gas containing contaminants is attracted to the high-speed viscous exhaust flow and exhausted, as shown by the broken line in FIG. 3 showing the prior art. It does not reach the semiconductor wafer, so contaminants such as oxygen are less likely to be incorporated into the thin film deposited on the semiconductor wafer, and the resistivity of the thin film is less likely to increase, and the quality of the deposited thin film is The quality is extremely high, and the deposited film thickness is generally uniform over the entire surface of the wafer.

[Brief explanation of the drawing]

FIG. 1a is a block diagram of a thin film forming apparatus according to a first embodiment of the present invention. FIG. 1b is a diagram showing a state in which a semiconductor wafer is loaded into and unloaded from the TRWi forming apparatus according to the first embodiment of the present invention. FIG. 1C is a configuration diagram of a thin film forming apparatus according to a second embodiment of the present invention. FIG. 1d and FIG. 1e are configuration diagrams of an electrode section of a thin film forming apparatus according to a modification of the second embodiment of the present invention. FIG. 2 is a block diagram of a thin film forming apparatus according to the prior art, and is a diagram illustrating a low-speed exhaust system. FIG. 3 is a block diagram of a thin film forming apparatus according to the prior art, and is a diagram illustrating a high-speed exhaust system. The fourth is a diagram showing the relationship between exhaust speed, deposition speed, and electrical conductivity. FIG. 5 shows the relationship between the flow rate of hydrogen gas functioning as an air curtain and the resistivity of the deposited aluminum film. FIG. 6 is a schematic diagram of a thin film forming apparatus for simulation calculation. FIG. 7 is an isobars diagram obtained by simulation calculation. FIG. 8 is a diagram showing the distribution of the film thickness and specific resistance of the thin film formed in each region within the wafer. Reaction chamber, exhaust chamber, gate pulp, magnet, bellows gas injection means, insulator layer, shield layer. 1 ・ ・ 1 a ・ 1 b ・ 2 ・ ・ 3 ・ 4, 5 6 ・ ・ 7 ・ ・ 8 ・ ・ 9 ・ 10 , gas exhaust means, ... a pair of electrodes, semiconductor wafer, high frequency IT source, inner shell container, inert gas supply port, slit,

Claims (1)

[Claims] [1] A vacuum container (1) having a reaction gas supply means (2) and a gas exhaust means (3), and a pair of electrodes (4, 5) inside the vacuum container (1). ) is provided, and one of the pair of electrodes (4, 5) constitutes a susceptor in the thin film forming apparatus. An inner shell container (8) having a through hole is provided, the vacuum container (1) is provided with an inert gas supply port (9), and the reaction gas supplied into the inner shell container (8) is discharged. A thin film forming apparatus characterized in that the outlet communicates with the vacuum container (1) through a slit (10). [2] A vacuum container (1) having a reaction gas supply means (2) and a gas exhaust means (3), and a pair of electrodes (4, 5) provided inside the vacuum container (1), In the thin film forming apparatus where one of the pair of electrodes (4, 5) constitutes a susceptor, a loop-shaped gas flow is injected from the periphery of one of the pair of electrodes (4, 5) toward the periphery of the other. Gas injection means (
16) A thin film forming apparatus comprising: