JPS60218826A - Formation of thin film - Google Patents

Abstract

PURPOSE:To improve a thin film formation speed and obtain a structure more similar to the stoichiometrical composition by allowing chemical vapor growth while a magnetic field which passes through a substrate to be processed is being applied on the occasion of executing chemical vapor growth by placing a substrate to be processed under the plasma ambient. CONSTITUTION:A substrate 1 to be processed is placed on a substrate pedestal 2 comprising a heater and it is wired and connected to a high frequency power supply. Meanwhile, a reaction vessel 4 is insulated from the substrate pedestal 2 through an insulator 5. The one side of such reaction vessel 2 is provided with the source supply hole 6 for plasma CVD and is connected to a gas cylinder through a gas flow meter, while the other side thereof is provided with an exhaustion hole 7 is connected to the exhaustion system and the bottom side thereof is grounded. The outside of substrate pedestal 2 provided on the reaction vessel 4 is provided with a magnet 8 (in this case, an electromagnet) and so that the line of magnetic force passes through the substrate 1 to be processed. Here, it is important that the line of magnetic force passes through the substrate 1 to be processed equally in the form of a loop and therefore a mechanism for moving in parallel the magnet 8 on a support substrate 2 is also provided to attain said objective.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to cycloidal movement of electrons or a method for forming a high-density thin film.

(b) Background of the technology Plasma refers to a state in which freely moving free radicals and positively and negatively charged particles coexist in a reduced pressure atmosphere and maintain electrical neutrality. (Plasma CVD) uses this for solid precipitation reactions.

In other words, a typical chemical vapor phase reaction (CVD) is a reaction in which two types of gas react at normal pressure or reduced pressure at high temperatures, or a reaction in which a new solid and a gas are generated by decomposition of the gas.

On the other hand, plasma CVD is a reaction in which plasma is generated at a relatively low substrate temperature, and two types of gases react or the gases are dissociated to generate a new solid and gas.

Here, the feature of the latter reaction is that by using plasma, the substrate temperature during the reaction can be lowered, and therefore thermal damage to the substrate or the thin film existing thereon can be reduced.

The present invention relates to a thin film forming method that is a further improvement on plasma CVD.

(c) Conventional technology and problems Semiconductor devices such as ICs and LSIs are formed using thin film formation technology and photolithography to form fine patterns with multilayer structures on semiconductor single crystal substrates. .

In other words, the conductor pattern is made of aluminum (AI).

Gold (Au), tungsten (W), molybdenum (M
o), and the insulating layer is silicon nitride (SiJNf), silicon oxide (SiO2
), and the semiconductor layer is formed using a single or compound semiconductor such as silicon (St 2 ).

There are various methods for forming thin films, such as vacuum evaporation and vacuum deposition, but the CVD method can deposit metals, semiconductors, and insulators by selecting the source gas. Another feature is that a thin film having a structure close to stoichiometric composition can be formed.

Furthermore, plasma CVD has the characteristic that a thin film can be formed at a relatively low temperature compared to CVD because the source gas is plasma-excited to cause a reaction to occur in an active state.

However, as the area of semiconductor substrates continues to expand and the cost of semiconductor devices continues to decrease, there is a need to increase the thin film formation rate accordingly.

Furthermore, since plasma CVD involves plasma excitation of the source gas to cause a reaction, there is a problem in that the composition of the formed thin film tends to deviate from the stoichiometric composition, which tends to cause deterioration of electrical characteristics. A solution was needed along with an improvement in the speed of thin film formation.

(d) Object of the Invention An object of the present invention is to improve the plasma CVD method to increase the thin film formation rate, and to provide a method for forming a thin film having a structure closer to the stoichiometric composition.

(e) Structure of the Invention The object of the present invention is to perform vapor phase growth by exposing a substrate to be processed to a plasma atmosphere, and to perform the vapor phase growth while applying a magnetic field that passes through the processing substrate. This can be achieved by a vapor phase growth method.

In the first aspect of the present invention, collisions with gas molecules due to cycloidal movement of electrons are utilized as a method of increasing the density of plasma near the surface of a substrate to be processed.

That is, a magnet is provided behind a substrate support stand on which a substrate to be processed is mounted, and arranged so that lines of magnetic force are transmitted through the substrate to be processed.

And as before, the substrate support stand and reaction vessel (chamber)
The radicals or molecules of the gas molecules excited by applying a high-frequency electric field between the As a result of the formation of radicals and the progress of ionization of gas molecules, the density of the plasma increases synergistically.

The radicals activated under such an environment cause a chemical reaction with each other and are deposited on the substrate to be processed.

Therefore, plasma C which takes into account the cycloidal motion of electrons
VD can greatly increase the thin film growth rate compared to simple plasma CVD.

In this way, plasma CV is applied while applying a magnetic field to the substrate to be processed.
By using method D, high-density plasma can be generated with low electric field strength, so the plasma dissociation of the source gas progresses sufficiently, and the stoichiometric composition, which is a problem with conventional CVD films, is changed. Deterioration of electrical characteristics due to misalignment can be avoided.

In addition, in this method, the electric field strength is low in spite of the high density of the plasma, and therefore the acceleration energy of the ions can be suppressed to a low level, so that damage to the substrate to be processed due to ion bombardment is reduced.

Next, what is important in the second aspect of the present invention is that by applying a high-density magnetic field, the gas pressure at which plasma discharge occurs can be lowered, thereby making it possible to confine the plasma in the magnetic field application area. The influence of impurity gas adsorbed on the inner wall of the reaction vessel can be reduced.

The relationship between the gas pressure at which plasma discharge occurs and the magnetic field is B.
1evin and Haydon have the following relationship\
Pe...Effective gas pressure under magnetic field P...Gas pressure under no magnetic field ω...Angular velocity of electrons τ...Average collision time of electrons λ...In electron plasma The mean free path B of...
・Magnetic field strength■ ... Electron acceleration voltage From this equation, if the value of B is 100 c, plasma discharge will be maintained even at 10 Torr.

Therefore, if a high magnetic field is applied and the discharge gas pressure is lowered, the plasma discharge can be contained, thereby making it possible to further suppress gas emission from the reaction vessel other than the plasma region.

As described above, applying the magnetic field according to the present invention to conventional plasma CVD not only improves the rate of thin film formation on the substrate to be processed, but also brings the composition of the product closer to the stoichiometric composition. It is possible to create thin films with less contamination of impurities.

(f) Embodiments of the Invention The configuration of an apparatus embodying the present invention and the configuration of a mass-produced apparatus will be explained below with reference to the drawings.

FIG. 1 shows an embodiment in which the substrate 1 to be processed is held upward, and FIG. 2 shows an embodiment in which the substrate 1 to be processed is held downward.

In FIG. 1, a substrate 1 to be processed is placed on a substrate support 2 having a built-in heater, and a high frequency power source 3 is connected to a high frequency power source 3 having an oscillation frequency of 13.56 MHz and an output of 0.5 to 10 KW.
wired to the power source.

On the other hand, the reaction vessel 4 is insulated from the substrate support 2 by an insulator 5, and on one side there is an injection port 6 for a source gas for plasma CVD, which communicates with a gas cylinder via a gas flow meter. The other side has an exhaust lower, which is connected to the exhaust system, and the bottom side of the reaction vessel is grounded.

Next, a magnet 8 (an electromagnet in this case) is provided on the outside of the substrate support stand 2 provided in the reaction container 4, and is configured so that lines of magnetic force pass through the substrate 1 to be processed.

What is important here is that the lines of magnetic force pass uniformly through the substrate 1 to be processed in a loop shape, and for this purpose a mechanism is provided in which the magnet 8 or the support substrate 2 moves in parallel.

In addition, the strength of the magnetic field passing through the substrate to be processed is suitably 100 G or more; if it is smaller than this, the electron trajectory is less curved and the electrons do not move cycloidally between the electrodes, so the magnetic field has no effect.

As an example, the substrate 1 to be processed is made of silicon (St),
Aluminum (AI) is added to this for wiring pattern formation.
), hydrogen (H
2) Trimethylaluminum (TMA) diluted with gas
, triisobutylaluminum (TIBA), etc. are used, and plasma CVD is performed at a reduced pressure of approximately ITorr. However, when implementing the present invention, the AI film formation rate is more than an order of magnitude faster than conventional methods (and Conventionally, the film contained about 2% carbon (C), but this content is much lower, and therefore a high-quality thin film can be obtained.

FIG. 2 shows a counter electrode 1 in which a substrate 1 to be processed has a built-in heater 9.
The structure is the same as that shown in FIG. 1 except that the reaction vessel 4 is grounded.

In this case, the distance between the substrate 1 to be processed and the magnetic pole of the magnet 8 is the first
Although the film formation rate is somewhat reduced due to the distance compared to the figure, since the potential is on the positive side during plasma discharge, the effects of ion bombardment and the impact of cycloidally moving electrons can be avoided, and furthermore, the wall surface This eliminates the problem of deposits turning into powder and falling onto the substrate to be processed.

Next, FIGS. 3 to 5 are sectional views showing a second embodiment of the present invention, and are designed to achieve high efficiency and mass production.

That is, in order to confine the plasma near the substrate to be processed by making maximum use of the magnetic field of the magnet, and to eliminate contamination from the inner wall of the container, the reaction container 11 was made into a bell shape, and a heater was built into the inner wall of the recessed part. A substrate support 12 and a substrate 13 to be processed are placed thereon, and an electromagnet 14 is provided on the outside of the recess so as to fit therein.

By arranging the magnets in this way, a magnetic field of 1000 G or more can be applied perpendicularly to the substrate to be processed.
A parallel high magnetic field can be achieved with the opposing iron core parts.

Note that the substrate to be processed 13 needs to be in contact with the substrate support 12, and it is necessary to provide a holder on the substrate support.

Further, the reaction container 11 is grounded, and a gas introduction pipe 15 is provided in the upper center of the reaction container 11 insulated from the container, and is connected to the high frequency power source 3 in a circuit.

Here, the source gas is introduced into the reaction vessel 1 through the gas introduction pipe 15.
1 and is configured to be ejected in the direction of the substrate to be processed 13 from a small opening provided around the tip of the gas introduction tube 15 . Further, a wafer introduction preliminary chamber 16 connected to an exhaust system is provided in the upper part of the reaction vessel 11, and is configured to load a substrate 13 to be processed.

When performing plasma CVD according to the present invention using an apparatus having the structure shown in FIG. 3, plasma containment is ensured,
Furthermore, since the lines of magnetic force are evenly distributed, the efficiency of forming a thin film is improved, and the film composition approaches the stoichiometric composition, and the uniformity of the film thickness is also improved.

That is, the source gas is supplied from the gas introduction pipe 15 and exhausted from the exhaust lower, but the magnetic lines of force from the electromagnet 14 are transmitted perpendicularly to the substrate 13 to be processed with uniform magnetic flux density. A high frequency voltage is applied between the reaction vessel 11 containing the gas inlet tube 15 and the gas introduction tube 15.

Here, the electron moves around the lines of magnetic force m v / e B where m...Mass of the electron e...Amount of charge of the electron ■...Speed of the electron B...Swirling motion with a radius equal to the strength of the magnetic field Therefore, the plasma is confined in the electrode space, but by adopting the configuration shown in Fig.
It is possible to take a magnetic field value as high as above and increase the magnetic flux density, and therefore it becomes possible to perform plasma CVD in a reduced pressure state of 10' torr or less.

Furthermore, by applying a magnetic field of 1000 G or more, the gas pressure around the plasma can be reduced to 10 Torr or less, thereby reducing contamination from the surrounding walls.

In other words, the plasma can be confined only in the vicinity of the substrate 13 to be processed, and contamination due to outgassing from the reaction container 11 can be prevented.

In order to further completely prevent contamination from the reaction vessel 11, the outside of the reaction vessel 11 is coated with a magnetic material such as iron (JE), except for the portion where the magnetic poles of the electromagnet 14 face each other in the dumbbell-shaped recess of the reaction vessel 11. It would be more effective if the lines of magnetic force were prevented from penetrating into the container except for the dumbbell part.

By adopting the structure shown in FIG. 3 as described above, plasma CVD processing can be performed on two substrates at a time.
- FIG. 4 shows only the reaction vessel 11 and the magnetic pole portion of the electromagnet 14 in four structures that enable the simultaneous growth of a larger number of structures.

The feature of this structure is that the tip of the gas introduction pipe 15 is divided into two,
A substrate support 17 is provided with a source gas ejected from each tip and a heater from the bottom of the reaction vessel.
By installing the substrate 13 to be processed at an intermediate position of the gas introduction pipe 15, it is possible to simultaneously process four substrates by plasma CVD.

Next, FIG. 5 shows a modification of FIG. 3, in which the structure shown in FIG. 3 alleviates the complexity of supplying the substrate 13 to be processed from the wafer introduction preparatory chamber 16 and loading/unloading the substrate. By tilting the support stand 12, the substrate 13 to be processed can be held more easily than in the case shown in FIG.

In this case, the tip of the gas introduction tube 15 has a T-shape, and the source gas is ejected from a plurality of ejection ports provided on the lower surface of the tube, but unlike the structure shown in FIG. The distance between the electrodes at which this occurs is long, and the magnetic field line distribution also expands, so the plasma confinement effect decreases. However, since the magnetic field and the electric field are perpendicular to each other at the center, the plasma density increases due to the cycloidal movement of the electrons.

The basic structure and mass production structure for carrying out the present invention have been described above, and by adding the magnetic field according to the present invention to conventional plasma CVD, the film growth rate can be increased and the problems of the conventional method can be solved. can.

(g) Effects of the Invention By carrying out the present invention, the problems of conventional plasma CVD, that is, the composition of the produced film tends to deviate from the stoichiometric composition, and the electrical deterioration of the thin film tends to occur, can be solved. It becomes possible to significantly increase the film formation rate compared to the conventional method.

[Brief explanation of the drawing]

FIG. 2 is a configuration diagram of a mass-produced plasma CVD apparatus. In the figure, 1.13 is the substrate to be processed, 2 and 12 are substrate support stands, 3 is a high frequency power source, 4 and 11 are reaction vessels, 8 is a magnet, 10 is a counter electrode, 14 is an electromagnet, ¥-3 and 4- wJ

Claims (1)

[Claims] (11) A thin film characterized in that when a substrate to be treated is subjected to vapor phase growth by exposing it to a plasma atmosphere, the vapor phase growth is performed while applying a magnetic field that passes through the substrate to be treated. Formation method. (2) The thin film forming method according to claim 1, characterized in that the magnetic field is provided by loop-shaped lines of magnetic force from the processing substrate, passing through the plasma space and returning to the processing substrate. ( 3) The thin film forming method according to claim 1, wherein the magnetic field is provided by a pair of ferromagnetic magnetic poles sandwiching the processing substrate.