JPS63286570A - Thin film formation device - Google Patents

Abstract

PURPOSE:To control the crystalline orientation of a formed thin film by providing a mesh electrode for interrupting plasma to the front face of the holder for a substrate and selectively projecting neutral radicals on the substrate. CONSTITUTION:A substrate 10 is fixed on the holder 5 for a substrate and set to a manipulator 11 incorporated in a vacuum chamber 1 at a prescribed angle and the vacuum chamber 1 is exhausted at about 10<-5>-10<-7>Torr degree of vacuum. The gas contg. material elements is introduced into an electrode 2 for generating plasma from cylinders 7 and plasma is generated at about 0.1-10Torr degree of vacuum and the velocity of ions and electrons, etc., is controlled by means of a mesh electrode 3 for controlling plasma. The substrate 10 is heated with a heater 6 and a mesh electrode 4 for interrupting plasma is properly electrified and the electric potential of both this electrode 4 and the tip of the manipulator 11 is regulated to zero volt. Thereby positive ions and electrons are cut and only neutral radicals are advanced toward the substrate 10 and the neutral radicals are selectively projected on the substrate and a thin film in which crystalline orientation is controlled is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a thin film forming apparatus that can control the crystal orientation of a formed thin film.

(a) Prior Art As a method for forming a thin film on a substrate, vapor deposition, ion blating, sputtering, etc. are frequently used.

Both methods use physical vapor deposition.
This is one of the methods collectively referred to as PVD (deposition PVD).

The substrate may be a semiconductor substrate or a dielectric substrate. It may be single crystal, polycrystalline, or amorphous.

Vapor deposition is the simplest method and is mainly used to form thin metal films. Put the metal material into the crucible of the resistance heater, draw a vacuum, and energize the heater to evaporate the metal material. Alternatively, a metal material is placed in a crucible and heated with an electron beam to evaporate it.

The evaporated material hits the heated substrate and is deposited thereon.

During vapor deposition, the material is deposited in a neutral molecular state. Not ionized. There are no electrons either.

Ion blating also heats and evaporates metal materials. Not only that, but it is also ionized by gas discharge. Ionized metal particles are deposited on the substrate to form a thin film. When an inert gas is used as the ionizing gas, a thin film of the metal is formed. When a metal is ionized using nitrogen gas or oxygen gas, a thin film of a nitride or oxide of the metal can be formed.

Sputtering is a method that can be used not only for metals but also for oxide materials. After creating a vacuum, argon gas is introduced and a voltage of several hundred volts is applied between the anode and cathode, causing a glow discharge. The argon gas becomes positively ionized and collides with the cathode.

Metals and compounds scatter from the cathode. The scattered material is deposited on the substrate.

All of these are physical vapor deposition methods (PVD).

On the other hand, there is also a chemical vapor deposition method called CVD.

To form a thin film, a compound containing the constituent materials of the thin film is made into a gas and passed over the substrate.

In the thermal CVD method, the substrate is heated, and with this heat,
A thin film is formed by causing a chemical reaction on the substrate. The material is supplied in a state that can be a gas, such as a chloride or a hydride. The temperature of the substrate must be higher than the crystallization temperature. If the flow rate is insufficient with only the gas containing the material, hydrogen gas may be added as a carrier gas.

In the plasma CVD method, a high frequency electric field or a direct current electric field is applied between an anode and a cathode, a gas containing a thin film material is passed through the gas, the pressure is maintained at about 0.1 to 10 Torr, and glow discharge is caused.

A plasma is created by the glow discharge.

Plasma is a collection of positively charged ions and electrons.

In addition to plasma, many chemically active radicals are generated. Radicals are electrically neutral.

Therefore, it is sometimes called a neutral species.

When silane SiH4 gas is introduced into a plasma CVD apparatus, various ions and radicals are generated.

As an ion, SiH2+ SiH3” 12H2 12H4 etc., and as a radical, Si film Since Si film H coming H2* Si H2* Si H3* and so on.

Amorphous S using glow discharge of plasma CVD method
i-film is created. In this case, in the case of DC discharge, positive ions are unevenly distributed on the cathode side. Thin film formation is faster when the substrate is placed on the cathode side.

However, thin film formation also takes place on the anode side.

Even with high frequency discharges, a substantial distinction between cathode and anode occurs. The high-frequency electrode becomes a cathode because it is self-biased negatively.

In this case, the Si film is formed in the same way on both the anode and the cathode.

There are still many unknowns about the mechanism of thin film formation by plasma CVD. It can also be said that there is little we know.

The aforementioned ions are ineffective for forming thin films.

It is the neutral radicals that deposit on the substrate and become part of the thin film. The most important radical for the formation of Si film is S.
It is said to be the iH3.

Generally, in the glow discharge region, neutral radicals are numerically more dominant than ions. A radical is an excited state that is created not by the loss of an electron, but by the transition of an electron to a higher level.

High-speed electrons collide with neutral molecules. Electrons are scattered by inelastic scattering, but they are slow-moving electrons.

This energy loss excites neutral molecules and turns them into neutral radicals.

Plug 7 The CVD method is used to form thin films of SiN, 5i02, amorphous silicon a-3i, etc.

The advantage of the plasma CVD method is that the substrate heating temperature is low. In thermal CVD, material molecules must be excited by heat, so the substrate must be heated to a high temperature.

Since plasma CVD excites material molecules with high-speed electrons, the substrate heating temperature may be low.

There is an advantage.

However, the quality of thin films produced by plasma CVD is inferior to that produced by thermal CVD.

In this case, ECR-CVD (Electron Cyc
There is lotron Re5onance CVD. This is to excite and accelerate N2.02, Ar gas, etc. using microwaves and a magnetic field.

By matching the frequency of the microwave and the cyclotron frequency of the electrons determined by the magnetic field, the electrons can effectively absorb the energy of the microwave. Electrons move in a cyclotron, absorbing energy, increasing their orbital radius, and proceeding in a spiral. These electrons accelerate ions of reaction gas SiH4 and the like.

These ions hit the substrate and are deposited on the substrate. Since this method can be performed at a higher degree of vacuum than the plasma CVD method, a thin film of good quality with less impurities can be produced. Moreover, the substrate heating temperature can be lowered.

(1) Problems with the Prior Art What is formed by these CVD methods is a polycrystalline thin film. It is a polycrystalline thin film, and the directions of crystal grain boundaries are diverse. This is natural because the substrate is polycrystalline or amorphous, and the growth rate is fast.

However, the state of grain boundaries affects the physical and chemical properties of thin films.

Those with uniform crystal orientation are often physically and chemically stable.

Therefore, a method that can control crystal orientation is desired.

Furthermore, in the plasma CVD method, the plasma contains many positive ions, electrons, and neutral radicals. All of these will come into contact with the surface of the substrate. This is natural since the substrate is provided on either the anode or the cathode.

The mechanism of how thin films are formed is not clear, but it is believed that positive ions are not very effective for thin film deposition.

This is thought to be due to the small probability that positive ions will be neutralized by electrons at the cathode and at the same time cause the necessary chemical reaction.

For example, in direct current glow discharge, a dark area containing many positive ions is generated near the cathode. Since the positive ion concentration is high in this part, the voltage drop between the electrodes is unevenly distributed in the hollow part. The positive ion concentration in this dark area remains almost constant and does not contribute to chemical reactions.

It is believed that radicals contribute to the deposition reaction. If so, it would be sufficient to irradiate the substrate with only radicals. In addition, irradiation with high-energy ions causes defects and deteriorates film quality.

If only radicals were to be irradiated onto the substrate, there would be no need to provide the substrate as an electrode, as in the conventional plasma CVD method; in fact, it would be better not to provide the substrate with an electrode.

No conventional thin film forming apparatus has been designed to selectively apply only neutral radicals to a substrate.

Furthermore, there was no suitable method for aligning the crystal orientation in a thin film. Even if a substance is polycrystalline, there are substances that are physically and chemically stable if the crystal orientation is uniform.

This varies depending on the purpose and substance.

In some cases, completely random is preferable.

00 Purpose When a gas containing a material is made into a plasma, positive ions, electrons, and neutral radicals are generated, but among these, ion radicals can be selectively irradiated to a substrate with arbitrary energy.
Another object of the present invention is to provide a thin film forming apparatus in which the incident angle is variable.

A second object of the present invention is to provide a thin film forming apparatus that can control the crystal orientation of a thin film deposited on a substrate.

(4) Configuration The present invention will be explained in detail with reference to FIG.

A plasma generation electrode 2 and a manipulator 11 are provided in the vacuum chamber 1 . A mesh electrode 3 for plasma control is provided between these.

The inside of the vacuum chamber 1 is evacuated by a vacuum evacuation device 20 .

The plasma generating electrode 2 is an electrode for generating plasma. Gas is supplied from a gas cylinder 7 placed outside the apparatus to the plasma generating electrode 2 via a valve 12.

This gas includes simple elements, hydrides, chlorides, etc. of elements constituting the thin film, and a carrier gas.

Although the plasma generating electrode is simply described, there is a distinction between an anode and a cathode, and a high frequency power source 8 or a DC bias power source 9 is applied between the anode and the cathode.

DC bias power supplies include positive power supplies and negative power supplies.

In other words, there are high frequency power sources, DC positive power sources, and DC negative power sources.

One of the three power sources is used alternatively.

Which one to use depends on the properties of the raw material gas and the properties of the thin film to be formed.

At the plasma generating electrode 2, positive ions, electrons, and neutral radicals are generated.

A plasma control mesh electrode 3 is provided above the plasma generation electrode 2 . A bias power source 19 is also applied to this electrode 3 . It is also possible to give a positive potential,
A negative potential can also be applied.

It can also be grounded.

Regarding the plasma control mesh electrode 3, a manipulator 11 is provided on the opposite side of the plasma generation electrode 2.

The manipulator 11 can grip the substrate holder 5. Further, a heater 6 for heating the substrate is provided at a position corresponding to the back surface of the substrate holder 5.

The substrate holder 5 and the heater 6 can be turned at any angle with respect to the main axis of the manipulator 11 by means of a turning mechanism 13. The main shaft of the manipulator can move up and down and rotate. In other words, the substrate holder 5 can be rotated, raised and lowered, and turned around.

The substrate holder 5 can be detached and attached freely. After a substrate 10 such as a semiconductor is attached to the substrate holder 5) ζ, the substrate holder 5 is placed in the vacuum chamber 1 and attached to the tip of the manipulator 11.

A plasma-blocking mesh electrode 4 is provided on the front surface of the substrate holder 5 . This electrode 4 can be freely turned by a turning mechanism 13 together with the substrate holder 5 and the heater 6 for heating the substrate.

Plasma cutoff mesh electrode 4 and manipulator 11
are electrically connected to the bias power supply 2.
9 allows direct current positive voltage and negative voltage to be applied. or,
It is also possible to ground it.

a) Fix the substrate 10 to the working substrate holder 5. This is set on the manipulator 11 inside the vacuum chamber 1. Vacuum chamber 1 is evacuated. The degree of vacuum at this time is 10-5 to 10
``We plan to pull it down to about -7 Torr.

The turning angle of the substrate holder 5 is set appropriately.

A gas containing material elements is introduced from the cylinder 7.

A part of this gas is ionized at the plasma generation electrode 2.

The degree of vacuum when plasma is generated is 0.1~1°To
It is about rr.

A positive voltage or a negative voltage (or zero voltage) is applied to the mesh electrode 3 for plasma control. As a result, ions,
Electrons are accelerated or decelerated.

The substrate heating heater 6 is energized to heat the substrate.

The voltage of the plasma shield mesh electrode 4 is also set appropriately.

By making this a negative voltage, positive ions in the plasma can be attracted. Positive ions can be removed by applying a positive voltage.

The flow of neutral radicals cannot be controlled by the electrode voltage. However, since the radicals have different concentrations and have long mean free paths, they fly onto the substrate 10 through the electrodes 3.4.

When trying to block ions and electrons from flying to the substrate 10, the plasma blocking mesh electrode 4 and the manipulator 1
The potential of the tip of No. 1 is set to OV.

In this way, both positive ions and electrons are cut, and the substrate 10
does not reach. Since neutral radicals are not affected by these electric fields, they proceed toward the substrate 10.

Only radicals will exist near the substrate.

In this way, a chemical reaction of the radicals occurs near the substrate.

Reaction products are deposited on the substrate.

Case) Example I The inside of the chamber was evacuated to 5×10=Torr or less.

As a film forming gas, 5iH410096 gas was used at 30 to 1
50 secM was allowed to flow into the chamber. Gas pressure is 0.1~
It was I Torr. The substrate temperature was 300°C.

A high frequency power of 5 to 150 W was applied to two plasma generation electrodes.

The plasma control mesh electrode 3 has a voltage of -150V to -1
A bias voltage was applied in the range of -150V.

To change the direction of material flow relative to the substrate, the angle of the substrate holder was changed by a diversion mechanism.

In this way, a thin silicon film could be formed on the substrate.

By changing the orientation angle, we were able to arbitrarily control the crystal orientation of the formed film.

(i) Example 2 A TiN thin film was formed on a substrate using the method of the present invention. The reactive gases are TIc14 and NH3 or N2 gas.

The angle between the direction of the flow of ions and radicals and the substrate is θ
The experiments were carried out for the case of =90° and the case of θ =45°.

The structure of this thin film was analyzed by X-ray diffraction. Figure 2 shows the results.

The horizontal axis is the diffraction angle 2θ. The vertical axis is the diffraction intensity.

The unit of diffraction intensity is an arbitrary scale.

In order to compare the cases where θ=45° and θ=95°, the O level of the diffraction intensity is shifted.

When θ=90°, that is, normal incidence, TiN has a peak. There is a weak peak at TiN(200).

In the case of θ=45°, that is, oblique incidence, TiN(111)
There is a strong diffraction peak. No peak appears for TiN (200).

Comparing the cases of θ=45° and θ=90°, θ=45°
It can be seen that TiN (111) is strongly expressed.

This means that the crystal orientation is different when θ=45° and when θ-90°.

Which thin film is preferable depends on the purpose. However, it can be seen that the crystal orientation changes depending on the angle of incidence of ions and radicals on the substrate.

(c) Effect In the plasma CVD method, it was not possible to separate neutral radicals, electrons, and ions, but in the present invention,
It becomes possible to apply only neutral radicals to the substrate.

Furthermore, the crystal orientation of the thin film can be controlled.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of a thin film forming apparatus of the present invention. FIG. 2 shows the formation of a TiN thin film using the apparatus of the present invention.
A graph showing the results of measuring diffraction intensity by X-ray diffraction. The incident angle of ions and radicals to the substrate is 45° and 9
It was set to 0°.

Claims (1)

[Claims] A vacuum chamber 1 that can be evacuated to a vacuum, a plasma generation electrode 2 that is provided in the vacuum chamber 1 and turns gas containing the constituent elements of the thin film into plasma, and a high frequency power source that applies voltage to the plasma generation electrode 2. DC bias power supply,
a manipulator 11 for holding the substrate holder 5;
A substrate heating heater 6 for heating the substrate, a turning mechanism provided on the manipulator 11 that can change the direction of the substrate holder, a mesh electrode 4 for plasma interruption provided immediately in front of the substrate, the manipulator 11 and plasma generation. a bias power supply for applying a DC bias voltage to the mesh electrode 2 for plasma control, a bias power supply for applying a DC bias voltage to the mesh electrode 4 for plasma interruption, and a DC bias voltage to the mesh electrode 4 for plasma interruption and the substrate holder 5. A thin film forming apparatus comprising: a bias power supply for applying .