JPH11354067A - Oxygen negative ion beam implanting method and implanting apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit kinds of ions of oxygen generated to one kind, make an oxygen negative ion beam implanting apparatus instaltable in a small area at low cost and enhance its throughput by generating plasma including oxygen in a plasma chamber, and extracting an oxygen negative ion beam by an extraction electrode system composed of multiple porous electrode plates which have a hole distribution in a range wider than the diameter of a board. SOLUTION: A main discharge chamber 30 is formed continuing from an MP negative electrode 28, and the main discharge chamber 30 is filled with oxygen plasma which drifted from the MP negative electrode 28. An opening part is formed on the opposite side of the main discharge chamber 30, an accelerating electrode 36, a decelerating electrode 37 and a grounding electrode 38 formed from three sheets of porous plates, each having a hole distribution in a range wider than the diameter of a board are installed ahead of the opening part as an extraction electrode system, and negative ions are extracted from the main discharge chamber 30 as a beam. Oxygen negative ions O can be implanted into the board surface as a batch, and only negative ions can effectively be extracted by periodically turning on and off a plasma generation means and applying a voltage to the extraction electrode system after a slight delay.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and apparatus for forming an oxide film at a certain depth near the surface of a substrate by implanting oxygen ions into a semiconductor substrate, an insulator substrate, and a metal substrate. In the case of a semiconductor substrate, since an oxide (insulating film I) is formed near the surface, an S / I / S structure is obtained. In the case of metal, it has an M / I / M structure. Especially in the case of Si substrate, SO
It is called an I substrate. The abbreviation for Si-on-insulator (SOI) is referred to as such. A SOI substrate obtained by oxygen implantation is called SIMOX. The object of the oxygen implantation of the present invention is not limited to the Si substrate, but includes the SiGe substrate and the S substrate.
There is an iC substrate and the like. In that case, the insulating layer I is generated in the middle by oxygen implantation, and a layer of the same material is present on both the substrate side and the surface side. In addition, the present invention can be used to form an oxide layer at a boundary between different kinds of substances. It can also be used for hetero-epitaxial growth of GaAs on a Si substrate and implanting oxygen into the boundary to form an oxide layer. An M / I / M structure can also be obtained by injecting oxygen into a constant thickness inside the metal. It can also be used to create an oxide layer by injecting oxygen at the insulator / metal interface. The applications are listed below. 1. 1. Si substrate Si / I / Si substrate (SOI structure) 2. SiGe substrate SiGe / I / SiGe substrate (SiGe SOI structure) 3. SiC substrate SiC / I / SiC substrate (SiCSOI structure) 4. Si substrate GaAs / I / Si substrate (oxidation barrier layer) Metal film PZT / high-concentration oxygen layer / metal film These were all attempts to improve the substrate by accelerating and implanting oxygen positive ions.

[0002] An SOI substrate (silicon on insulator) is a substrate having an Si single crystal on an insulating layer in a broad sense. There is also an SOI substrate in which thin Si is placed on a thick insulator substrate (Si / insulating substrate). For example, it is formed by forming a Si thin film on sapphire. However, when hetero-grown on a heterogeneous crystal, there are many crystal defects, no cleavage, and it is expensive. There is little benefit. So SOI
Speaking of the substrate, the whole is Si and a thin insulating layer near the surface and S
It mainly has a three-layer structure of (i / insulating layer / Si substrate) where i single crystal exists. Insulating layer is SiO _2. That is, it has a three-layer structure of (Si / SiO ₂ / Si substrate). S
i-wafers are inexpensive. High quality ones are readily available. Since the SOI substrate has Si on Si, the lattice constant is the same and the number of defects is small. Cleavage is also convenient for element isolation.

[0003]

2. Description of the Related Art A Si-on-insulator substrate having a single-crystal Si semiconductor layer formed on an insulator (so-called SOI substrate)
Enables higher integration compared to normal bulk Si substrates,
It is said to be excellent in many ways, such as being able to produce low power consumption and high speed devices. Due to its superiority, it is being vigorously studied in various places. It has been studied but has not reached a practical level. This is because it is difficult to manufacture the SOI substrate, and the SOI substrate is still more expensive than the Si substrate. SO
The principle, physical properties, and electrical superiority of the I-substrate are described in, for example, the following document.

Special Issue: "Single-crystal silico
n on non-single-crystal insulators "; edited by G.
W. Cullen, Journal of Crystal Growth, vol. 63, No.
3, pp429-590 (1983)

There are two ways to make an SOI substrate. In each case, positive ions are implanted into the substrate. One is by hydrogen positive ion implantation. Implanting hydrogen positive ions into a first Si substrate having a surface oxide film to form a fragile porous layer in the Si substrate, and bonding a second Si substrate;
The first Si substrate is separated from the porous layer, and the exposed Si surface is polished to obtain a (Si / I / Si) structure. Since hydrogen positive ions are protons and can be easily generated, ion implantation itself is simple. However, the step of thinly cutting the first Si substrate with the porous layer is not easy. This is especially difficult.

Another is due to oxygen positive ions. This is simpler and implants oxygen positive ions at a certain depth in the Si substrate. Oxygen ions form silicon oxide (SiO ₂ ), resulting in a (Si / I / Si) structure. This is SIMOX (Separated by IMplanted OXyge
n). The SIMOX method of forming a buried oxide layer by oxygen ion implantation is most widely used as a method for manufacturing an SOI substrate. SOI structures on Si substrates are best known.

[0007] However, even with respect to semiconductors such as SiGe and SiC, attempts to form an oxide layer in the middle of the substrate have been made in small but minute ways. Yukari Ishikawa, Noriyuki Shibata, Susumu Fukatsu "Preparation of SiGeSOI Structure by Low Energy Oxygen Ion Implantation" Proceedings of Spring Society of Applied Physics, 29a-K-1p803 (199)
8) SiGe is a mixed crystal semiconductor. It is not Si itself. It is strange to call this SOI (silicon oninsulator). However, the reporter of the above paper uses the term SiGeSOI. Following this, here is SiGeS
OI. As a method of forming an oxide layer at a boundary between a metal and a ferroelectric, there is, for example, Japanese Patent Application Laid-Open No. 9-232517, "Dielectric Element and Method for Manufacturing Dielectric Element". A ferroelectric PZT is formed on the metal electrode, and an oxygen positive ion beam is implanted thereon at 150 keV to form an oxide film between the metal and the PZT. Furthermore, oxygen positive ion beam
The accelerating system is accelerated to 120 keV to form an oxide layer on the surface of PZT. Further, an electrode metal is provided on the oxide layer. That is, a laminated structure such as metal / oxide layer / PZT / oxide layer / metal is proposed. The purpose is to prevent fatigue of the PZT film. By applying an electric field, the ferroelectric PZT is polarized, but the polarizability gradually decreases.
This is due to a decrease in the oxygen concentration near the electrode. In order to secure a sufficient oxygen concentration, high-concentration oxygen is injected into the interface between the electrode and the PZT. The present invention relates to the improvement of a method and apparatus for manufacturing an oxide layer localized at a certain depth by implanting oxygen ion beams into a substrate or a film such as a semiconductor, a metal, or an insulator. The application to the SiSOI substrate is the most important. In the following, the problems of the prior art will be described using a Si SOI substrate (SIMOX) as an example.

A typical SIMOX manufacturing process is described below. The Si substrate is heated to about 450C to 750C.
Oxygen positive ions (O ⁺ ) having an energy between 20 keV and 220 keV are implanted into the substrate. Oxygen ions (O ⁺ ) penetrate to a certain depth from the surface of the Si substrate and stay there. The implantation depth is controlled by the acceleration energy. The surface remains Si. A typical dose in the SIMOX process is about 2 × 10 ¹⁷ atoms / cm ² or more. In an oxygen and argon atmosphere,
The substrate is heat-treated (annealed) at a temperature of 1400 ° C. Atmospheric oxygen prevents escape of oxygen atoms from the substrate. By this heat treatment, the implanted oxygen atoms react with nearby Si atoms to form a buried layer of silicon dioxide (SiO ₂ ). Thereby, a three-layer structure of (Si / SiO ₂ / Si) is formed. It is an SOI substrate.

In SIMOX, oxygen ions are directly implanted to a certain depth and converted into SiO ₂ , so that a shallower portion of Si is used as an active Si layer. Since the Si on the substrate side and the Si layer on the surface are originally part of the same Si substrate, the crystal structure is matched from the beginning. Because the internal oxide film halves the Si substrate horizontally
It is called separated by oxygen. The purpose of the oxygen implantation is to form an internal oxide film. This is a simple SOI substrate manufacturing method.

Since the surface Si is disturbed by ion implantation, the crystallinity is restored by annealing. Annealing is proposed in the following document. JP-A-8-46161 "SOI substrate and its manufacturing method" An oxygen positive ion beam is implanted into a Si substrate and annealed to form an oxide layer at a certain depth. Usually, annealing is performed in an atmosphere of Ar and oxygen. However, in the present invention, annealing is performed in a hydrogen atmosphere.

As an ion implantation method of oxygen ions, an ordinary ion implantation apparatus used for implanting dopants such as B and P into a Si substrate is often used. This is because the dose and the acceleration energy are not so different from the dopant implantation in the Si wafer process. Doping ion implanters are expensive and large.
The necessity of using expensive equipment makes the SOI substrate expensive.

The present invention addresses oxygen ion implantation. Conventionally, oxygen plasma is generated by AC or DC discharge such as microwave or high frequency, and oxygen positive ions are extracted by applying an appropriate voltage to an extraction electrode system. The oxygen ions are mass-separated by a magnetic field or an electric field to remove O ₂ ⁺ (monovalent positive ions of oxygen molecules) and the like to extract only O ⁺ (positive ions of oxygen atoms) and irradiate the substrate. Generally, the ion beam diameter is smaller than the substrate.
Since it is a thin beam, it is not possible to irradiate the substrate at once. Therefore, the beam is scanned by a scanning system using an electric or magnetic field,
Irradiate the entire substrate uniformly.

FIG. 1 shows an oxygen positive ion implanter using a typical ion implanter. This is an apparatus based on filament excitation. A filament 2 is provided in a chamber 1 that can be evacuated. The terminal of the filament 2 is taken out through the insulator 5. A DC filament power supply 3 is connected to both ends of the terminal. The chamber 1 has a gas inlet 4 through which oxygen gas is supplied. An arc power source 6 (Va) is provided between the chamber 1 and the filament 2.
k) is connected. An acceleration power supply 7 (Vacc) is provided between the negative electrode of the arc power supply 6 and ground. The potential of the chamber 1 is Vacc + Vak.

Outside the outlet 8 of the chamber 1, three perforated electrodes are provided so that the axes of the openings are common.
An acceleration electrode 9, a deceleration electrode 10, and a ground electrode 11. The positive electrode of the acceleration power supply 7 is connected to the acceleration electrode 9 via the resistor 13. A deceleration power supply 12 is connected to the deceleration power supply 10. A quadrant arc mass separation magnet 14 is provided on the extension of the opening of the chamber outlet 8 and the electrodes 9, 10, 11.
The ion beam 15 exiting from the chamber 1 enters the mass separation magnet 14 from the inlet 16 and exits from the exit 17 along a path which is curved by the magnetic field. Since the orbit is adjusted by the mass and energy, the monoatomic ion O ⁺
Through the slit plate 18. However, the diatomic ion O ₂
⁺ Draws an eccentric trajectory 27 and hits the wall or slit of the mass separation magnet 14 and disappears. Monoatomic oxygen positive ion O
⁺ Is scanned right and left by a scanning mechanism 22 including counter electrodes 19 and 20 and a variable power supply 21 through a slit plate 18. The scanning beam 23 is applied to the Si wafer on the susceptor 25.
24.

[0015]

The apparatus shown in FIG. 1 for oxygen ion implantation is the same as a conventional impurity ion implantation apparatus. B is used as a p-type dopant in a Si wafer.
Alternatively, a large-sized device for implanting P as an n-type dopant is used. Since it is for dopant implantation, the configuration of the ion implantation apparatus becomes very complicated. Moreover, it becomes an expensive device. A large installation area is required. Not only is the equipment expensive. Since the ion implantation is performed by scanning a narrow beam, the processing time per wafer becomes very long. That is, the throughput is low.

As a result, the unit price per SOI substrate becomes very high. For this reason, SOI substrates are not widely used, although the excellence of SOI substrates is widely recognized. This is the current situation. In addition to SiSOI, SOI of other metals, ferroelectrics, etc. is far from mass-produced. Despite its long research history, it is still at the research and development stage. SOI still cannot overcome the difficulties of high cost substrates.

Why are the devices expensive and large? Why low throughput? This will be described. Oxygen positive ions in oxygen plasma take various forms. Not just a single-atom ion O ⁺ . O ⁺ , O ₂ ⁺ (diatomic ion)
Or O ₃ ⁺ (triatomic ion), polyvalent ion O
Several types of ions, such as ⁺⁺ , exist in oxygen plasma.
Unless any one of them is exclusively implanted, a buried oxide film layer is formed in multiple layers. The implantation depth varies depending on the mass M of the ion beam and the acceleration energy E. The acceleration energy is the same for the same monovalent ions. Speed is proportional to the square root of the reciprocal of mass. High velocity, low mass ions reach deeper. Large mass ions stop in the shallow water.

A monovalent ion having a different mass is represented by M
If there are seeds, M peaks of implantation depth will be formed. If the implantation depth is not fixed, the oxide film of the SOI substrate can be doubled or tripled. The Si film on the surface side of the oxide film is too thin. It is also known that when a large amount of ions having a large atomic weight, such as O ₂ ⁺ and O ₃ ⁺ , are implanted, crystal defects in the surface Si layer rapidly increase. Such cannot be used as an SOI substrate. Therefore, it is absolutely necessary to exclusively implant only one atomic monovalent ion O ⁺ . It would be advantageous if there was a plasma generator that could selectively generate, for example, only O ⁺ from the beginning. But it is not.

The method of generating plasma includes microwave discharge,
There are various types such as high frequency discharge and DC discharge. However, as far as the author knows, a method that can exclusively generate any one of oxygen positive ions O ⁺ , O ₂ ⁺ , O ₃ ⁺ , and O ⁺⁺ has not been found yet. Even with plasma in which electron density and electron temperature are strictly controlled, the O ⁺ / O ₂ ⁺ ratio is 80/20 to 20/20.
/ 80. It is not possible to generate plasma beyond this range. One atomic ion and two atomic ions are always mixed in the oxygen plasma. For this reason, a mass separation system is always provided in an ion implantation apparatus using an ion beam.

This is a device corresponding to the mass separation magnet 14 shown in FIG. For example, ions other than O ⁺ are removed from the beam by a mass separator, and the substrate is irradiated. Mass separation magnets are heavy, bulky magnets. In order to bend a large area beam with a magnet, a magnet having a large diameter and capable of generating a strong magnetic flux density is required. Not very usable on production machines. Mass separation of a large area ion beam with a magnet is not possible. Therefore, the beam is narrowed down to a narrow beam, and mass separation is performed using a magnet. Even if the beam is narrow, it is a high-speed beam and bends it, so a strong magnetic field is required and the magnet itself is large.

Because of the narrow beam, it is much smaller than the area of the wafer. Ions cannot be implanted into the wafer at one time. Therefore, a scanning device must be provided after the mass separation device. The scanning device uses an alternating magnetic field or an alternating electric field. The ion beam is swung right and left and back and forth by a magnetic field and an electric field, and is injected over the entire surface of the wafer. FIG. 1 shows a scanning mechanism using an alternating electric field. The scanning device itself also takes up considerable space. If the beam bending angle is small, the distance must be long.

Due to the mass separation magnet, the size is increased, the weight is increased, and the installation area is increased. One factor that makes the device expensive is the mass separation magnet. Also, scanning must be performed for mass separation, and the cost is further increased due to the scanning device. Since beam scanning takes time, the throughput is reduced. As described above, since the conventional method of manufacturing an SOI substrate using an oxygen ion beam implantation apparatus cannot limit the number of ion species to one, the apparatus is large, expensive, and has low throughput. No plasma generation method can solve this.

It is a first object of the present invention to provide a method and an apparatus for implanting oxygen ions into a semiconductor, metal, or insulator substrate, which can limit the kind of ion generated by oxygen to one kind. It is a second object of the present invention to provide an oxygen ion implanter which is inexpensive and can be installed in a small area by squeezing the generated ion species into one type, eliminating the need for mass separation. It is a third object of the present invention to provide an oxygen ion implantation apparatus which does not require scanning by narrowing the generated ions to one kind and has high throughput.

[0024]

As described above, there are several types of ionic species in the oxygen positive ion.
It is extremely difficult to generate them exclusively. The present invention does not stop there. The present invention uses oxygen negative ions O ⁻ instead of positive ions. Oxygen as the negative ions O ^- in addition to _{^{O 2 -, O 3 -,}} O 5 - and the like are known. However, negative ions of these plural atoms are extremely unlikely to be generated. Therefore, oxygen negative ions have not been used before. But,
However, in the case of oxygen negative ions, it is possible to increase O ⁻ to 90% or more by appropriately selecting the plasma parameters. Negative ions of oxygen most O ^- a. Take advantage of the excellent monopoly of O ⁻ in negative ions.
Since there is no other oxygen negative ion, mass separation and scanning become unnecessary. This is the gist of the present invention. At the opening of the ion source, there is provided an extraction electrode system comprising a plurality of porous electrode plates having a pore distribution wider than the substrate diameter. In order to extract only negative ions, a negative bias voltage is applied to the plasma chamber of the ion source, and a predetermined bias voltage is also applied to the extraction electrode system. Since the bias is biased to a negative voltage higher than the ground potential, only negative ions and electrons are extracted to the outside from the plasma. The electron current is an invalid current for the purpose of ion implantation. In order to reduce the ratio of electron current, it is necessary to increase the density of negative ions in the plasma. There are several ways to increase the proportion of negative ions in the plasma.

The generation of oxygen ions in an oxygen glow discharge is described in the literature. SVKrishna Kumar, "Mass spectrometric diagnosti
cs of Plasma-Negativeions in an oxygen glow discha
rge ", SVKrishna Kumar Journal GeologicalSociety
of India, vol.27, at pp144-153 (1986) glow discharge, increasing the gas pressure, also increases the discharge current, such as by a strong electric field, O ^- the ratio of can be increased up to 90% It is. Under optimum conditions, it can be raised to a level where other ion species cannot be detected by QMS (Quadrupole Mass Spectroscopy).

According to the present invention, a negative ion beam is extracted from oxygen plasma by the action of the extraction electrode system of the ion source and injected into a semiconductor substrate, a metal substrate, and a dielectric substrate outside the ion source. Since oxygen negative ions only have monoatomic monovalent ions O ⁻ from the beginning, mass separation is unnecessary. Large and heavy mass separation magnets are not required. This makes the device smaller. The device installation area is also reduced. Less expensive because there is no magnet.

If mass separation is not required, there is no need to narrow the beam. What is necessary is just to generate a large-area beam and implant ions into the wafer as it is. Since beam scanning is not performed, the cost of the apparatus is reduced by the amount of the scanning mechanism. Further, since a scanning mechanism is unnecessary and a scanning distance is not necessary, the installation area can be further reduced. Since the ions can be implanted at once, the implantation time can be greatly reduced. Therefore, the throughput is greatly improved. S
The manufacturing cost of a substrate having an oxide film at an intermediate depth, such as an ISOI substrate, can be reduced.

It looks like only good things. But there is a problem. Why Oxygen Negative Ions? That is the problem. In the first place, all the conventional techniques implant positive ions of oxygen because positive ions are easily generated. Negative ions are not easy. Even when boron or phosphorus is doped into Si as a dopant, these are generated in the form of positive ions, separated by mass, scanned and injected into a wafer. Since these dopants are also implanted with positive ions, they have the same problems as described herein and have not been solved yet.

First, plasma is a collection of electrons, ions, neutral radicals, neutral molecules, and atoms. The electron charge and the ionic charge cancel each other out, so that the whole should be neutral. That's it. The difference between the numbers of positive ions and negative ions is the number of electrons. If so, it is much more difficult to generate negative ions. Negative ions are always less than positive ions, and it is difficult to generate negative ions at high density.

The inventor has solved the difficult problem of negative ion generation. One is a method of temporarily increasing negative ions by rapidly annihilating electrons while maintaining neutrality in plasma. When converted to monovalent ions,
Since the number of electrons + the number of negative ions = the number of positive ions, it is possible to make the number of negative ions close to the number of positive ions by temporarily approaching the number of electrons to zero. If the plasma excitation means is shut off while the plasma is on, the electron temperature drops sharply and the low energy electrons increase.

Since the low energy electrons have a large cross-sectional area of collision, they easily collide with neutral atoms and molecules. When it collides with a neutral oxygen atom, it becomes monovalent O ⁻ . When it collides with a neutral oxygen molecule, it splits the molecule into two atoms and gives a charge to become a neutral atom and a negative ion O ⁻ . When the plasma is extinguished in this way, electrons decrease rapidly and negative ions increase. The number of negative ions comes to antagonize the number of positive ions. Of course, this is only temporary, after which both positive and negative ions begin to decrease. A bias voltage is applied to the extraction electrode system only for a short time to implant negative ions into the wafer. Immediately after the plasma is extinguished, a predetermined bias voltage is applied to the extraction electrode system to implant negative ions.

Since the injection is performed only for a short time, it is necessary to repeatedly and repeatedly stack. Then, the plasma is turned on and off in a pulsed manner, and a positive voltage bias is applied to the extraction electrode system in a pulsed manner after a certain time delay. Even if the amount of the negative ion implantation per one time is slight, the desired dose amount is eventually reached by repeated implantation. This method is temporarily called a negative ion beam method after the light is turned off.

There is another method of generating negative ions at high density in addition to the negative ion beam method after the light is turned off. In this method, the electron energy is reduced to increase the cross section of collision with neutral atoms and neutral molecules. This is called an energy filter method. These are to increase the negative ion density temporally and spatially and extract negative ions therefrom. However, in the case of an ion source having an extraction electrode system, only negative ions can be extracted to the ground side depending on how the ion source and the ground potential are selected. That is, a negative bias voltage is applied to the ion source,
If the ground side is grounded, only negative ions can be extracted from the plasma.

There is also a negative ion generation method utilizing the low work function of Cs. This is a well-known method. When Cs is attached to a negatively biased target and a neutral atom molecule is applied, electrons of Cs move to neutral atoms and molecules to form negative ions. Cs becomes a positive ion, but returns to neutral again because electrons come from the target. Cs skillfully uses the fact that Cs easily releases electrons (has a low work function), and Rb can be substituted.

There are several methods of plasma generation, such as arc discharge using a filament, high-frequency discharge between parallel plate electrodes, DC discharge, microwave discharge, and sputter negative ion generation. The present invention can be applied to any of them.

In the case of the glow discharge, as described above, oxygen negative ions can be generated by limiting the conditions of the glow discharge, such as increasing the gas pressure, increasing the discharge current, and increasing the voltage.

[0037]

DETAILED DESCRIPTION OF THE INVENTION The present invention is, negative oxygen ions O ^- and S
It is characterized by being injected into the i-substrate. Most oxygen negative ions are O ⁻ . Therefore, no mass separation is required. Since there is no need to narrow the beam for mass separation, a scanning device is also unnecessary. The apparatus is simplified and downsized, and the throughput is increased. How to make hard-to-make negative ions? That is a problem. The generation of negative ions will be described.

[1. Negative ion beam method after extinguishing] This is a method of injecting negative ions by pulsating plasma and applying a predetermined voltage to the extraction electrode system immediately after extinguishing.

By turning on the plasma generation means, a plasma containing oxygen is generated in the plasma generation chamber. Next, the plasma generating means is turned off. The temperature of the electrons in the plasma is increased from several tens eV to several eV within several μsec.
It drops rapidly. On the other hand, during this period, the electron and the positive / negative ion density hardly change. Low-energy electrons predominate in the plasma. Due to the dissociative attachment of the low-speed electrons and oxygen molecules, the probability of generation of oxygen negative ions sharply increases. e ⁻ + O ₂ → O ⁻ + O.
It can be simply expressed by the equation e ⁻ + O → O ⁻ . Due to such adhesion, the negative ion density sharply increases immediately after the plasma generating means is turned off. 20 to 30 μsec
At this point, the electrons are light and diffuse rapidly, disappear, and decrease in density. On the other hand, positive and negative ions hardly disappear due to their large mass. For this reason, a unique (almost no electron) plasma is formed in which the electron density is extremely low and the plasma is maintained by positive and negative ions. This phenomenon is described in the following document, for example.

"Pulse Modulated Plasma" Seiji Samukawa, Applied Physics Vol. 66, No. 6, p550-558 (1997)

MBHopkins, M.Bacal & WGGraham, "
Enhanced volume production of negative ions in the
post dischagrge of a multicusp hydrogen discharg
e ", J. Appl. Phys. 70 (4), p2009-2014 (1991)"

The above describes a plasma of chlorine or argon. Is an investigation on hydrogen plasma. No literature examining oxygen could be found.
However, a similar decrease has also occurred for oxygen plasmas in the present inventors' experiments. The above references do not say anything more. The inventor takes advantage of this. In the present invention, a predetermined pulse voltage is applied to the extraction electrode system at the moment when the unique plasma (the number of positive ions = the number of negative ions) is formed. Thereby, oxygen negative ions (O ⁻ ) are implanted into the Si substrate.

[2. Energy Filter Method] The plasma chamber is divided into two, and plasma is generated in the first plasma chamber. A wafer and a susceptor are provided in the second plasma chamber. An energy filter is provided between the two plasma chambers.
In the first plasma chamber, vigorous plasma generation is performed, and the energy of electrons is high. Energy filters prevent the passage of high energy electrons. The second plasma chamber contains many low energy electrons. Low-energy electrons have a large collision cross section with neutral molecules and atoms, and are negatively ionized.
When the number of low-energy electrons decreases in this way, the first
Low energy electrons come in from the plasma chamber. Energy filters are selective for electron energy. Neutral atoms and molecules are allowed to pass freely. It does this by creating a magnetic field of the order of a few hundred gauss. Such a magnetic field can be generated by facing permanent magnets. Alternatively, a magnetic field can be generated by passing a current through a plurality of parallel conductor bars.

[3. Cs method] This method is already widely used as a negative ion source. When Cs is adsorbed on the metal surface, it has the effect of lowering the work function of the metal surface. Since the work function is lowered, electrons are more easily emitted. Therefore, when the metal is biased negatively, the metal functions as an electron emitter. When an oxygen molecule or an oxygen positive ion strikes Cs, electrons are given to the oxygen molecule or the like to become an oxygen negative ion. Cs
Is stored in a solid state in an evaporation source, heated and vaporized, and guided to a metal surface. In addition to Cs, rubidium Rb, potassium K,
Barium Ba or the like can also be used.

[4. Glow discharge method] When a high frequency is applied between parallel plate electrodes, a glow discharge is generated at an appropriate pressure and gas type. A plasma is thereby generated, but the rate of negative ions can be increased by increasing the pressure and the electric field. This is also described above.

【Example】

Embodiment 1 (Use of Increase of Negative Ions Immediately After Plasma Is Turned Off) Embodiment 1 will be described with reference to FIG. This is an example in which a microwave is used as a plasma excitation source. Microwaves are guided from the antenna into the chamber, where plasma is generated. A coaxial cable 31 is connected to the MP cathode chamber 28 having the source gas inlet 29. An antenna 32 is fixed to the end of the coaxial cable 31. Microwaves generated by a magnetron (not shown) are transmitted through a coaxial cable and transmitted from an antenna 32 to an MP cathode chamber 2.
Go inside 8. Oxygen gas is introduced into the chamber 28.

A magnetic field applying means 33 generates a vertical magnetic field in the MP cathode chamber 28. This produces a microwave resonance magnetic field. The electrons emitted from the oxygen gas resonantly absorb the microwave. The movement of the electrons becomes intense and the oxygen strikes oxygen, resulting in oxygen plasma containing positive ion oxygen and electrons. A rare gas such as Ar may be added. If it is as it is, only positive ions can be formed, so it cannot be used for the purpose.

Therefore, a main discharge chamber 30 is provided following the MP cathode 28. The main discharge chamber does not have its own plasma excitation source. Oxygen plasma drifted from the MP cathode 28 fills the main discharge chamber 30. Permanent magnets 3 having different polarities such as NS, SN,.
5 are attached. This has the effect of forming a cusp magnetic field in the chamber and preventing charged particles in the plasma from colliding with the wall surface. A cusp magnetic field for confining plasma. Between the main discharge chamber 30 and the MP cathode 28,
There is an arc power supply 39 (Vex). Ve the main discharge chamber 30
It is biased by the positive voltage of x. As a result, electrons, negative ions, and the like are drawn from the electron emission port 34 into the main discharge chamber 30 from the MP cathode. The electrons provide energy for generating the main discharge plasma 57. Not only electrons but also positive ions and negative ions of oxygen move to the main discharge chamber 30.
Electrons fly through space at high speed and strike oxygen to produce positive and negative ions. When the energy is high, there is a tendency to bounce off electrons and create positive ions. When the energy is low, it is easy to enter oxygen orbitals and form negative ions.

When positive ions are formed, electrons increase. When negative ions are formed, electrons decrease. Electrons are supplied continuously from the MP cathode. Electrons lose energy by colliding with oxygen atoms and molecules. Slow electrons can combine with oxygen atoms to form negative ions. However, most of them disappear on the wall surface of the main discharge chamber. The main discharge plasma 57 contains oxygen positive ions, electrons, oxygen negative ions, neutral oxygen molecules, neutral atoms, and the like. The opposite side of the main discharge chamber 30 is an opening. At the end of the opening, electrodes 36, 37, and 38 formed of three perforated plates are provided as an extraction electrode system. These extract negative ions as beams from the main discharge chamber 30. Acceleration power supply 42 has switch 44 and resistor 41
Are connected to the accelerating electrode 36 via the. Switch 44
Is closed, the main discharge chamber 30 is biased to a negative high voltage. Difference between acceleration voltage Vacc and pull-in voltage Vex−
(Vacc-Vex). The voltage of the accelerating electrode 36 is-
Vacc. A positive voltage Vdec from the deceleration power supply 43 is applied to the deceleration electrode 37 via the switch 45.

When the second switch 44 and the third switch 45 are closed, a negative ion beam is extracted from the main discharge plasma 57 by the action of Vacc. First switch 4
When 0 is closed, electrons and negative ions are drawn into the main discharge chamber 30 from the MP cathode, and a main discharge plasma 57 containing many negative ions is generated. All switches 40, 44, 45
, The negative ions may be continuously extracted to implant oxygen negative ions into the Si wafer 58 on the susceptor 47. This is of course. Due to the negative bias of the deceleration electrode 37, only negative ions and electrons are
Not injected into 8. Even if electrons are injected, they are not impurities and may be very small.

However, if electrons and negative ions are simultaneously injected, power is lost by the amount of the electron current. I want to increase the ratio of negative ions. It is preferable to open and close the switch in a pulsed manner as shown in FIG. FIG. 3 (a)
Indicates the on / off timing of the first switch 40. Off 51, rising 48, on 49, falling 50,
It is a repetition waveform of OFF 51. FIG. 3B is a waveform showing the ON / OFF timing of the second switch 44 and the third switch 45. Off 56, rise 53, on 5
4. Falling 55 is repeated. However, the latter is slightly delayed. At the time of the fall 50 of the first switch 40, the second and third switches rise (53) with a slight delay while they remain off (52). Such a delay on / off operation is repeated indefinitely.

A delay circuit 46 controls opening and closing of the three switches 40, 44, and 45. When the first switch is closed, the main discharge plasma 57 is formed (ON 49). When the first switch 40 opens, the plasma temperature drops rapidly and the electrons lose energy. Initially, the electrons are 10e
Although the energy is about V, it becomes about 1 eV or less in a few μsec after the first switch 40 is opened. It becomes a slow electron. Slow electrons have a large collision cross section with neutral oxygen. It collides with neutral oxygen atoms and attaches to them, turning the oxygen atoms into negative ions. The negative ion density increases so as to antagonize the positive ion density. At that moment 52, the second and third switches 44 and 45 are closed. As a result, the extraction electrode systems 36, 37, and 38 extract the negative ion beam. Since the negative ion density is high, only negative ions can be efficiently extracted. Eventually, since negative ions are attached, the extraction voltage is turned off (55).
From the first switch fall 50 to the second switch rise 53, it is preferable to be about 10 μsec as described above. However, since pulse driving is repeated, 50 and 5
3 interval (delay time) τ is 10 μsec to off time To
ff.

In this way, only when the main discharge plasma has a high density of oxygen negative ions, the electrodes are negatively biased and a negative ion beam can be extracted and injected into the wafer. Although the electron current is ineffective, it can be opened and closed at such timing to reduce the electron current and extract a large current negative ion beam. In this embodiment, the switch 40,
Semiconductor switches 44 and 45 are used. In this case, the duty is 1%, and the repetition frequency is several Hz to 1
It has been confirmed that application is possible up to 0 kHz. It is also possible to use a thyratron or the like as the switching means.

The main point of the first embodiment is that the plasma is turned on / off, a large amount of O ⁻ is generated during the off period, and a predetermined bias voltage is applied to the extraction electrode system in a timely manner to convert O ⁻ into S.
Injecting into i-substrate. The present invention skillfully utilizes the phenomenon of increasing negative ions immediately after plasma is turned off.

Although a high-frequency excitation device is used here, the present invention is not limited to this. The plasma generating means may be microwave plasma or DC discharge plasma in addition to high frequency plasma. In either case, a predetermined bias voltage is applied to the extraction electrode system at the same timing as the increase of negative ions immediately after the plasma generating means is turned on and off and turned off.
The opposite is also true. In the first embodiment, the plasma generation (the first switch 40) and the extraction (the second and third switches) are performed in a pulsed manner, and the beam extraction is performed only when the oxygen negative ion density is high. This is possible. Although not explained, it is effective to delay the generation of the plasma and the extraction of the beam in any of the embodiments.

Second Embodiment (Low Energy Electrons Passed by Energy Filter) FIG. 4 shows a second embodiment. This increases the number of low energy electrons by the energy filter and promotes the generation of negative ions. Although an ECR plasma generation device is taken as an example, other excitation methods can be applied. The plasma chamber 61 has a gas inlet 62.
The magnetron 64 generates a microwave 66. Microwave 66 passes through waveguide 65, passes through dielectric window 79 and enters plasma chamber 61. The coil 67 generates a magnetic field satisfying the ECR condition. That is, if the microwave is 2.45 GHz, a magnetic flux density of 875 gauss is generated. There the electrons resonately absorb the microwaves.

A plurality of conductor rods 69 are provided in parallel in the middle of the plasma chamber 61. For this, a current is applied in the same direction. A magnetic field of several tens of gauss to about 100 gauss is generated around the conductor rod 69. A magnetic field is created in the direction of the envelope.
That is, the magnetic flux density B is generated in the horizontal direction. Electrons spiral around a horizontal magnetic field. The period of the spiral motion does not depend on the energy, but the radius is proportional to the square of the energy. Since the Faraday force is proportional to the velocity v of the electron, the Faraday force increases as the energy becomes higher. High energy electrons cannot pass through this weak magnetic field barrier. Low-energy electrons can pass through it. Therefore, the magnetic field generated by the conductor rod 69 is an energy filter that selectively transmits only low-energy electrons.

The plasma chamber 61 is divided vertically by a conductor rod 69. The upper portion is a portion that resonates and absorbs microwaves. This is referred to as a first plasma chamber 68. The lower part is a part that generates negative ions. This is referred to as a second plasma chamber 70. The lower part of the second plasma chamber 70 is open, and there are three extraction electrode systems 75, 76, 77 under the lower part. In each case, a large number of holes for extracting ion beams are formed. It is a porous electrode plate. In order to draw out the ion beam of the porous extraction electrode system 75, 76, 77 straight, the ion beam is
Holes are drilled. Si wafer 72 at the end of the electrode
Is placed on the susceptor 73. Susceptor 73 is supported by shaft 74. This is the ground voltage (ground potential). The acceleration power supply 86 (Vacc) has a positive electrode grounded and a negative electrode connected to the acceleration electrode 75 via a resistor 88. The negative electrode is also connected to the plasma chamber 61. A voltage of -Vacc is applied to the plasma chamber 61 and the acceleration electrode 75. A positive voltage is applied to the deceleration electrode 76 by the deceleration power supply 87.
The ground electrode 77 is at ground potential. Positive ions are confined in the plasma chamber 61 by the acceleration voltage Vacc. Only negative ions and electrons can pass through the acceleration electrode 75. The acceleration energy of negative ions is q (Vpz + Vac
c). This is the plasma chamber 6 as viewed from the wafer.
This means that a positive bias voltage has been applied to 1.

The positive bias voltage Vacc is applied to the Si wafer-7
It is appropriately determined according to the necessary oxygen implantation depth to the substrate 2. 2
In many cases, the implantation depth is about 0 keV to 220 keV. The negative ion beam O ⁻ emitted from the electrode groups 75, 76, 77 having a large area is injected into the Si wafer 72. The beam system is wider than the wafer diameter. Therefore, oxygen negative ions O ⁻ can be implanted at once. There is no beam scanning mechanism. The reason why scanning is unnecessary is that there is no need for mass separation. Negative oxygen ions O ^- since only one or not generated mass separation is not required.

A large number of permanent magnets 71 for confining plasma are provided on the lower half outer wall of the plasma chamber 61. The arrangement is such that the NS poles are inverted between adjacent magnets. It has the effect of generating a cusp magnetic field between adjacent magnets and confining charged particles in the center of the plasma chamber. In this example, the excitation source of the plasma is a microwave, but the present invention is not limited to this, and the plasma may be generated by high-frequency discharge or DC discharge.

The operation is as follows. Oxygen gas is introduced from inlet 62. Microwave 66 is introduced into plasma chamber 61 through dielectric window 79. The electrons resonately absorb the microwave and produce a high-density oxygen plasma in the first plasma chamber 68.
To be generated. This plasma contains positive ions, electrons, neutral atoms, and molecules. There are many electrons and few negative ions. The electron energy is as high as about 10 eV.

A magnetic field B (several tens to one hundred gauss) generated by the conductor bar 69 is at the boundary between the first and second plasma chambers 68 and 70. Charged particles, especially fast electrons, cannot escape this magnetic field barrier. Neutral atoms and molecules can pass through the magnetic field B. Even light electrons having low energy (about 1 eV or less) can pass through the magnetic field B of the conductor rod 69. The low-energy electrons are caught by the magnetic field and perform cyclotron motion, but eventually escape the influence of the magnetic field.

In the second plasma chamber 70, the plasma does not newly increase because the ECR condition is not satisfied. Only the movement from the first plasma chamber 68 exists. The plasma temperature is low. There are few high energy electrons and many low energy electrons. It is about 1 eV. Low-energy electrons dissociate and attach to neutral oxygen molecules. This produces oxygen negative ions. Almost all low-energy electrons attach to neutral atoms and molecules and disappear. High negative ion density. From such a second plasma chamber 70 to the accelerating electrode 75
A negative ion beam is extracted by the action of. The accelerating electrode 75 and the decelerating electrode 76 attract negative ions and electrons. The number of electrons is small, and the ratio of the negative ion beam is large. Even if the electrons are injected into the sample (wafer), they may not be useful, and may cause a problem of heating the substrate. Thus, the energy filter is provided at an intermediate height of the plasma chamber 61. It is also effective to add a method of forming a weak magnetic field in the extraction electrode system to remove electrons.

In the second embodiment, the oxygen gas is supplied only to the first plasma chamber 68, but this is not restrictive. Generally, the higher the oxygen gas pressure, the higher the negative ion generation efficiency. Oxygen gas may also be supplied to the second plasma chamber 68 to increase the negative ion generation efficiency. Alternatively, oxygen gas may be supplied only to the second plasma chamber 70 without supplying oxygen gas to the first plasma chamber.

In the example shown, a bias voltage is always applied to the extraction electrode systems 75 and 76. However, the invention is not limited thereto, and a switch may be interposed between the acceleration electrode and the resistor 88 and the power supplies 86 and 87. By repeatedly opening and closing the switch, the negative ion beam is intermittently extracted from the plasma.

In this embodiment, the microwave continuously oscillates and does not temporarily extinguish the plasma. However, the magnetron may be intermittently oscillated to turn on and off the plasma as shown in the timing waveform of FIG. This is because, for the same reason as in the first embodiment, the number of low-speed electrons increases at the time of off. When a voltage of + Vpd is applied to the accelerating electrode at the same timing as in FIG. 3, a negative ion beam is extracted at the moment when the negative ion density increases.

[Embodiment 3 (low energy electrons are passed by an energy filter)] FIG. 5 shows a third embodiment. This is the part of the energy filter that is not a conductor rod,
It is replaced by permanent magnets 81-84. Apart from the permanent magnet 71 that creates the cusp magnetic field, the plasma chamber 61
The permanent magnets 81 to 84 facing in the same direction are provided at the intermediate height of. A magnetic flux density B is generated in one direction between the permanent magnets 81 and 82 and the permanent magnets 83 and 84 having opposite poles. This has the effect of blocking high-speed electrons and functions as an energy filter. This has the same effect as flowing a current through the conductor rod of FIG. The lower half permanent magnet 71 is for generating a cusp magnetic field. Negative ions are extracted by an extraction electrode system including an acceleration electrode 75, a deceleration electrode 76, and a ground electrode 77. This is the same as in the second embodiment. No mass separation or beam scanning is required because the entire surface is once implanted.

Fourth Embodiment FIG. 6 shows a fourth embodiment. This is a sputtering type negative ion source using cesium. A sputter-type negative ion source utilizing cesium is described in, for example, the following document. Tetsuo Tomioka, Hiroshi Tsuji, Hirotaka Toyoda, Yasuhito Goto, Junzo Ishikawa,
"Characteristics of Extracting Oxygen and Fluorine Negative Ions from RF Plasma Sputter Type Negative Heavy Ion Source" Proc. BEAMS
1995 TOKYO, pp 191-194

A conductive target 101 is provided above the plasma generation chamber 100. The axis of the target 101 is drawn out through an insulator 102 and connected to a negative bias power supply 103. Raw material gas (X
e + O ₂ ). A high-frequency coil 105 of several turns is installed inside the plasma generation chamber 100. The terminal of the high-frequency coil 105 is taken out through the insulator 106. One end is connected to a high frequency power supply 109 via a matching box 107. One end of the high-frequency power supply 109 is grounded. The other end of the coil 105 is grounded.

There is a wide opening below the plasma generation chamber 100. An extraction electrode system consisting of three perforated plates is attached to the tip of the electrode. Acceleration electrode 113, deceleration electrode 114,
This is the ground electrode 115. These have the function of extracting negative ions from the plasma generation chamber and accelerating them. A susceptor 110 (chamber not shown) and a wafer 111 are provided in a sealed space further downstream of the extraction electrode system. Shaft 112
Is the ground potential. The plasma generation chamber 100 is biased by the acceleration power supply 122 to a high negative voltage with respect to the ground. This is determined by the depth of implantation of oxygen negative ions into the substrate. It is about 20 kV to 200 kV. For example, 100
A negative voltage of kV is applied to the plasma generation chamber. The negative electrode of the acceleration power supply 122 is connected to the acceleration electrode 113 via the resistor 124. The same negative voltage as the acceleration power supply 122 is applied to the acceleration electrode 113. A positive voltage is applied to the deceleration electrode 114 by the deceleration power supply 123. The accelerating electrode 113 has the same voltage as the plasma generating chamber 100. As a result, the positive ion beam does not go outside. Only negative ions are extracted outside by the acceleration electrode 113,
It is rapidly accelerated with the deceleration electrode 114.

The oven 1 is placed outside the plasma generation chamber 100.
There are seventeen. Cesium Cs118 is accommodated in this. The oven can be heated by the surrounding heater 119. A pipe is provided on the oven 117, and a nozzle 121 at the tip of the pipe is provided toward the lower surface of the target 101. When Cs is heated by the heater 119, steam is generated and ejected from the nozzle 121 and adheres to the surface of the target 101. A gas outlet is provided downstream of the extraction electrode, from which the inside can be evacuated to a vacuum. The operation of the above configuration will be described.

The target 101 has a voltage of 300 V to 800 V
About negative voltage is applied. Cesium vapor is generated from the oven 117 and adheres to the target 101. A mixed gas of a sputtering gas such as argon Ar and xenon Xe and an oxygen gas is introduced into the plasma generation chamber 100. Some of the oxygen molecules are adsorbed on the target cesium layer.

A high-frequency voltage is applied to the high-frequency coil 105. Since the electrons in the gas vibrate up and down due to the high frequency and hit the atoms to be ionized, plasma of the mixed gas (Xe + O) is generated. Plasma means electrons, positive ions,
A collection of neutral radicals and neutral molecules.

A negative voltage is applied to the target 101.
Positive ions of the inert gas in the mixed gas, for example
Xe + ions are attracted to the target. Inert moth
Positive ions hit the target oxygen molecules and
To putter. The oxygen molecule takes an electron from Cs and decomposes
And one atom negative ion O⁻become. Cs has low electronegativity
And easily emit electrons. The electron is oxygen negative
Make on. Since Cs is used, the negative ion concentration increases.
From a plasma containing a high density of oxygen negative ions, O ⁻ion
The beam is pulled out and irradiated on the wafer 111. Ue
The O has a certain depth⁻Is injected.

This method has a problem that Cs on the Si substrate or Cs implanted shallowly must be removed later. However, there is an advantage in that the efficiency of generating negative ions is increased. Since oxygen negative ions are implanted into the wafer, the negative ion density in the plasma is reduced. However, since the plasma tries to maintain neutrality as a whole, positive ions strike the cesium-coated target and take electrons from Cs to give electrons to neutral oxygen. As a result, negative ions O ^{− for the} lost negative ions are newly generated.

High-concentration oxygen negative ions can be produced without turning on / off the high-frequency coil in a pulsed manner. An oxygen negative ion beam can be continuously implanted. However, the Cs sputter negative ion source may be intermittently driven in a pulsed manner as in the embodiments of FIGS. Example 1,
Although 2 and 3 have three extraction electrode systems, they may have two electrodes of an acceleration electrode and a ground electrode.

[0077]

According to the present invention, a buried oxide film is formed at a predetermined depth by implanting negative oxygen ions into a semiconductor substrate such as Si, SiGe, or GaAs, a dielectric substrate, or a metal substrate. The plasma is extracted as a negative ion beam by the extraction electrode system. Ion beam - beam diameter is large because negative oxygen ions O than the substrate ^- a can be injected collectively to the substrate surface.
Oxygen negative ions can be exclusively generated only for O ⁻ by adjusting the plasma parameters. O by periodically applying a predetermined pulse bias voltage to the extraction electrode system ^- only the stably, can be injected practical amount in a short time. There is no need to provide a mass separation system. Since a large-scale device for mass separation is not required, the price of the device is reduced. The area required for installation can also be reduced. Since there is no mass separation, there is no need to narrow the beam, and scanning is not required. Since the injection can be performed at once without scanning, the throughput is improved.

Further, the plasma generation means is periodically turned on / off.
When the voltage is turned off and a voltage is applied to the extraction electrode system a little later than that, only negative ions can be efficiently extracted. This makes it possible to avoid overheating of the substrate due to excessive irradiation of electrons and an increase in the capacity of the power supply of the extraction electrode system. An inexpensive, stable, small installation area ion implantation apparatus can be provided.

[Brief description of the drawings]

FIG. 1 generates oxygen positive ions, separates them by mass and scans them to form S
FIG. 7 is a schematic cross-sectional view of an apparatus according to a conventional example for injecting into an i wafer.

Fig. 2 Oxygen plasma is generated by microwave excitation and microwave resonance absorption by a coil magnetic field, temporarily interrupts the inflow of electrons from the microwave source, and applies a voltage to the extraction electrode system when negative ions increase temporarily after the interruption. FIG. 1 is a cross-sectional view of an apparatus according to a first embodiment of the present invention, in which a negative ion beam is extracted by applying a voltage and oxygen negative ions are implanted into a Si wafer.

FIG. 3 is a pulse waveform diagram showing a timing of supplying high-frequency power and a timing of applying negative and positive bias voltages to an acceleration electrode and a deceleration electrode of an extraction electrode system in the first embodiment of FIG.

FIG. 4 shows that a magnetic field is generated in the middle of a chamber by a conductor rod current by using an ECR plasma method, the plasma is divided into two, a negative ion generation rate is increased, a negative ion beam is extracted by an extraction electrode system, and oxygen negative ions are implanted into a wafer. Sectional view of the apparatus according to the second embodiment of the present invention.

FIG. 5 shows that a magnetic field is formed in the middle of a chamber by a permanent magnet magnetic field using an ECR plasma method to divide the plasma into two to increase a negative ion generation rate, extract a negative ion beam by an extraction electrode system, and implant oxygen negative ions into a wafer. Sectional view of the device according to the third embodiment of the present invention.

FIG. 6 is a sectional view showing a fourth embodiment of the present invention in which oxygen negative ions are implanted into a wafer by using a Cs-based sputtering negative ion source.

[Explanation of symbols]

 1 chamber 2 filament 3 filament power supply 4 gas inlet 5 insulator 6 arc power supply 7 acceleration power supply 8 exit 9 acceleration electrode 10 deceleration electrode 11 ground electrode 12 deceleration power supply 13 resistance 14 mass separation magnet 15 oxygen positive ion beam 16 inlet 17 Outlet 18 Slit plate 19 Electrode 20 Electrode 21 Variable power supply 22 Scanning mechanism 23 Scan beam 24 Wafer 25 Susceptor 26 Central trajectory 27 Deviant trajectory 28 MP cathode 29 Gas inlet 30 Main discharge chamber 31 Coaxial cable 32 Antenna 33 Magnetic field applying means 34 Electron emission hole 35 permanent magnet 36 acceleration electrode 37 deceleration electrode 38 ground electrode 39 arc power supply 40 first switch 41 resistor 42 acceleration power supply 43 deceleration power supply 44 second switch 45 third switch 46 delay circuit 47 susceptor 48 rise 49 on 50 fall 51 off 52 Extinction Hour 53 rise 54 on 55 fall 56 off 61 plasma chamber 62 gas inlet 64 magnetron 65 waveguide 66 microwave 67 coil 68 first plasma chamber 69 conductor bar 70 second plasma chamber 71 permanent magnet 72 wafer 73 susceptor 74 axis 75 accelerating electrode 76 decelerating electrode 77 ground electrode 79 dielectric window 81 to 84 permanent magnet 86 accelerating power supply 87 decelerating power supply 88 resistance 100 plasma generation chamber 101 target 102 insulator 103 negative bias power supply 104 gas inlet 105 coil 106 insulator 107 matching box 109 high frequency power supply 110 susceptor 111 wafer 112 axis 113 acceleration electrode 114 deceleration electrode 115 ground electrode 117 oven 118 cesium solid 119 heater 120 pipe 121 nozzle 122 acceleration power supply 123 deceleration power supply 12 Resistance

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/265 F Z

Claims (8)

[Claims] 1. A method for forming an oxide layer at a predetermined depth by injecting oxygen ions into a semiconductor substrate, an insulator substrate, or a metal substrate, wherein a plasma containing oxygen is generated in a plasma chamber by a plasma generating means, An oxygen negative ion beam is extracted from plasma by an extraction electrode system composed of a plurality of porous electrode plates having a pore distribution wider than the substrate diameter, and oxygen negative ions are implanted into a semiconductor substrate, an insulator substrate or a metal substrate to a predetermined depth. Oxygen negative ion beam implantation method. 2. A magnetic field for capturing electrons is formed in an intermediate portion in a plasma chamber for generating plasma, and a plasma is generated by a plasma generating means in a first plasma chamber on one side of the magnetic field, and a second plasma chamber is formed. An extraction electrode system is provided in the opening of the first plasma chamber to prevent high-energy electrons in the first plasma chamber from being disturbed by the magnetic field and moving to the second plasma chamber. In the second plasma chamber, collision of low-energy electrons with neutral atoms and molecules is prevented. An oxygen negative ion beam, wherein an oxygen negative ion beam is extracted from the second plasma chamber and injected into a semiconductor substrate, a metal substrate, or a dielectric substrate. Injection method. 3. Supplying Cs to a plasma chamber provided with a means for generating plasma by applying a high frequency to a high-frequency coil, depositing Cs on a surface of a conductive target set in the plasma chamber, and applying a negative pressure to the target. By applying a voltage, the target is sputtered with positive ions,
2. The oxygen negative ion beam implantation method according to claim 1, wherein an oxygen plasma having a high oxygen negative ion concentration is generated. 4. The method according to claim 1, wherein the plasma generation means is turned on / off periodically, and 10 μm after the plasma generation means is turned off.
4. The oxygen negative ion beam injection according to claim 1, wherein a direct current voltage is applied to the extraction electrode system during a period from sec to when it is turned on again to extract an oxygen negative ion beam from the plasma. Method. 5. A plasma chamber which can be evacuated and generates plasma, a plasma generating means for generating plasma in the plasma chamber, a gas inlet for introducing a gas containing oxygen atoms into the plasma chamber, A gas exhaust device for exhausting gas from the plasma chamber, a plurality of extraction electrode systems provided at the opening of the plasma chamber and having a diameter larger than the substrate diameter, and an extraction electrode system for extracting a negative ion beam from the plasma. Oxygen negative ions, comprising: a power supply for applying a negative high voltage and a positive voltage to the substrate; and a susceptor provided on the downstream side of the extraction electrode system for mounting a semiconductor substrate, an insulator substrate, or a metal substrate. Beam injection device. 6. A magnetic field forming means for forming a magnetic field in the plasma chamber is provided inside or outside the plasma chamber, the plasma chamber is divided into two, and high-energy electrons are prevented from being transmitted by the magnetic field. 6. The oxygen negative ion beam implantation apparatus according to claim 5, wherein plasma generation is performed, an extraction electrode system is provided in the other plasma chamber, and a susceptor is provided downstream of the extraction electrode system. 7. A conductive target provided in a plasma chamber provided with a means for generating plasma by applying a high frequency to a high frequency coil, a negative bias power supply for applying a negative voltage to the target, Cs, Rb, K The oxygen negative ion beam implantation apparatus according to claim 5, further comprising: an oven for generating steam such as a gas; and a nozzle for guiding the steam generated by the oven to a target. 8. A relation between a switch for turning on / off the plasma generation means, a plasma generation on / off, a switch for turning on / off a DC voltage applied to the extraction electrode system, a timing of turning on / off the plasma generation means, and a timing of turning on / off the extraction electrode system voltage. 8. A delay circuit for determining a negative voltage, wherein a DC voltage is applied to the extraction electrode system immediately after the plasma generation means is turned off to extract a negative ion beam. Oxygen negative ion beam implanter.