JPH05135687A - Semiconductor electron-emitting element - Google Patents

Abstract

PURPOSE:To provide diamond crystal of high quality so as to provide a high electron emission characteristic by setting the crystal defect density of a diamond semiconductor layer to 10<8> pieces/cm<2> or less. CONSTITUTION:A 1mum-thick (p)-type diamond layer 102 is formed on a (p<+>) type Si substrate 101 by heat filament CVD method. An SiO<2> mask 103 is provided in a predetermined position and an (n)-type diamond layer 104 is selectively formed in only the exposed part of the diamond layer 102 of a mask opening. Next, an Ti electrode 105, a 100Angstrom -thick Ag layer 111, an SiO<2> layer 106, and a poly Si leading electrode 107 are formed into respective predetermined shapes by photomechanical technique. When a reverse-biased voltage Vb is applied between the electrodes 105, 108, injected electrons are allowed to pass through the (n)-type diamond layer 104 and the Ag layer 111 and escape into a vacuum region. The electrons can be released outside of an element by application of a leading voltage Vg to the electrodes 107, 105. During crystallization of the diamond O2 is added in the raw material so that the crystal defect density is 10<8> pieces/cm<2> or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor electron emitting device, and more particularly to a semiconductor electron emitting device using a diamond semiconductor layer.

[0002]

2. Description of the Related Art Conventionally, among semiconductor electron-emitting devices, one using avalanche amplification is a p-type semiconductor device.
There are an element in which a junction between a type semiconductor and an n-type semiconductor is formed (pn junction element), and an element in which a Schottky junction between a semiconductor layer and a metal or a metal compound is formed (Schottky junction element).

An example of a pn junction type semiconductor electron-emitting device using the avalanche amplification described above is disclosed in US Pat. No. 425.
Those described in 9678 and US Pat. No. 4,303,930 are known.

In this semiconductor electron-emitting device, a p-type semiconductor layer and an n-type semiconductor layer are formed on a semiconductor substrate, and a metal such as cesium is further attached to the surface of the n-type semiconductor layer to form an electron-emitting portion. The reverse bias voltage is applied to the diode formed of the p-type semiconductor layer and the n-type semiconductor layer to cause avalanche amplification, thereby hotening the electron and emitting the electron from the electron emitting portion.

As a Schottky junction type semiconductor electron-emitting device using the avalanche amplification, for example, a junction between a p-type semiconductor layer and a metal electrode is formed, and a reverse bias voltage is applied to this junction to perform avalanche amplification. In some cases, the electrons are made hot by causing the electrons to be emitted from the electron emitting portion.

By the way, if a large amount of electron emission current is to be obtained when electrons are emitted from the semiconductor electron emission device utilizing the avalanche amplification as in the above-mentioned conventional example, a very large amount of current must be applied to the device. Usually, in order to emit electrons from the pn junction as described above, a current density of 10,000 amperes or more is required. However, when such a large current is passed, the element generates heat and the electron emission characteristic of the element is increased. There are problems that the device becomes unstable and the life of the device is shortened.

Therefore, there has been a demand for an electron-emitting device which generates little local heat.

Further, in the conventional example of the pn junction type, a material having a low work function is used in order to lower the work function of the electron emitting portion and suppress the reverse bias voltage.

Conventionally, a material such as cesium has been used as a material having a low work function in order to emit electrons without increasing the reverse bias voltage so much. However, a material having a low work function such as cesium is chemically active. Therefore, it is difficult to expect stable operation due to the influence of local heat generation of the semiconductor layer. Therefore, an electron-emitting device that can use a relatively stable material as a work function lowering material has been desired.

Further, as the electrode material of the conventional Schottky junction type electron-emitting device, a material which can form a Schottky junction and has a low work function has been desired. However, in the conventional electron-emitting device, the electrode material easily migrates due to local heating of the semiconductor layer,
Due to the size of the energy bandgap of the semiconductor, the selection range of the electrode material is narrow, and there is a problem that the material selection for improving the stability of the device cannot be performed well. Further, when a layer of cesium or an oxide of cesium is formed on the surface of the electron emitting portion in order to lower the work function of the electron emitting portion, the same problem as in the conventional example of the pn junction type occurs.

Therefore, there has been a demand for an electron-emitting device which produces a small amount of local heat and has a wide range of materials for the Schottky electrode.

From the above viewpoints, an electron emitting device using a diamond semiconductor layer is expected. The diamond semiconductor layer has the highest thermal conductivity of the substance at room temperature,
Also, because of the wide band gap (5.4 eV), the heat resistance is strong, and the material range for the Schottky electrode is wide.

[0013]

DISCLOSURE OF THE INVENTION Diamond crystals are generally precipitated as polyhedral particles composed of {100} planes and {111} planes, and as a result of coalescence of these polyhedral grains, a film diamond is obtained. This {100} plane and {11
1}, the growth mechanism is different, and the present inventors report (Japanese Journal of Applied Physics, Vol. 29, No. 10, L1901 to L1903, 199, 199).
According to (0 years), the {111} plane has a multinuclear growth pattern,
The 0} plane is growing in a single nucleus growth mode. The electron emission characteristics of these two crystal planes are greatly different. For example, the {111} plane has a smaller amount of emitted electrons than the {100} plane, which hinders an increase in the emitted electron amount of the semiconductor electron-emitting device.

The semiconductor electron-emitting device of the present invention is a semiconductor electron-emitting device using a diamond semiconductor layer, wherein the crystal defect density of the diamond semiconductor layer is set to 10 ⁸ defects / cm ² or less. Characterize.

[0014]

The function of the present invention will be described below together with the findings obtained in making the present invention.

As described above, the {111} plane is {10
The amount of emitted electrons is smaller than that of the 0} plane, which is {11
1} plane is a multi-nucleus growth mode and 10 ¹⁰ / cm ² in the plane
It is considered that a large number of such dislocations / defects occur, which impairs the electron emission efficiency when used as an electron-emitting device and causes the amount of emitted electrons to decrease.

The inventors of the present invention have conducted earnest research from this viewpoint, and as a result, have found that the crystal defect density of {111} is 10 ⁸ defects / c.
With m ^2, it found that it is possible to increase the electron emission efficiency of the semiconductor electron emitting device is one that has reached the present invention. The density of dislocations / defects of the present invention is preferably 10 ⁸ / cm ² or less, more preferably 5 × 1.
It is not more than 0 ⁷ pieces / cm ² .

The growth mode of the {111} plane is a multi-nucleus growth mode as described above, but the addition of oxygen to the source gas during diamond crystal growth reduces the nucleation rate of the multi-nucleus growth mode, It became clear that it will change to a single nuclear growth mode. Due to this change to the single nucleus growth mode, dislocations and defects found in the {111} plane are significantly reduced, and a high quality diamond crystal can be formed.
Although there are many unclear points regarding the cause of this, it is considered that the addition of oxygen, which has a large etching effect, reduces the supersaturation degree of the carbon source and reduces the nucleation rate. By using the diamond semiconductor layer having few dislocations and defects as described above, a semiconductor electron-emitting device having a large amount of emitted electrons can be obtained.
The method of reducing the dislocations and defects may be a method of adding oxygen to the raw material gas, or a method of adding another etching gas such as a gas containing fluorine and chlorine.

The semiconductor electron-emitting device used in the present invention may be any one using negative electron affinity (Negative Electron Affinity), one using electron avalanche amplification (avalanche amplification), or the like.

The present invention will be described below by taking an example using avalanche amplification. 2A and 2B are energy band diagrams in a pn junction type semiconductor electron-emitting device in which the electron avalanche inducing layer is an n-type semiconductor layer. In the figure, p represents a p-type semiconductor layer, n represents an n-type semiconductor layer, and T represents a layer of a low work function material. 2A is p
It shows a case of a pn junction between a diamond layer and an n-type diamond layer. FIG. 2B shows a case where a heterojunction of a p-type diamond layer and an n-type semiconductor layer having a band gap smaller than that of diamond is used. Unless otherwise specified, the p-type and n-type semiconductors in the present invention also mean so-called p ⁺ and n ⁺ containing impurities at a high concentration.

As shown in FIGS. 2A and 2B, by reverse biasing the junction between the p-type semiconductor layer and the n-type semiconductor layer, the vacuum level E _vac can be _calculated from the conduction band E _c of the p-type semiconductor layer. The energy level can be low, and a large energy difference ΔE (= E _c −E _vac ) can be obtained. By causing avalanche amplification in this state, a large number of electrons, which were minority carriers, can be generated in the p-type semiconductor layer, and the electron emission efficiency can be improved. Further, since the electric field in the depletion layer gives energy to the electrons, the electrons are hottened to increase the kinetic energy, and the electrons having potential energy larger than the work function of the surface of the n-type semiconductor layer cause energy loss due to scattering. It is possible to jump out of the surface without it.

In the semiconductor electron-emitting device of the present invention,
By using the diamond layer as at least the p-type semiconductor layer, the thermal conductivity is excellent, the local heat generation of the element is small due to the heat radiation, and thus stable electron emission characteristics can be obtained.

P of a diamond semiconductor as shown in FIG. 2A.
When the n-junction is used, energy band coupling at the junction interface is smooth, electron scattering is small, and good electron emission characteristics can be obtained.

FIG. 2B shows an energy band diagram when a heterojunction of a p-type diamond layer and an n-type semiconductor layer having a band gap smaller than that of diamond is used.
In the electron-emitting device using pn junction type avalanche amplification, heat generation can be further reduced by lowering the resistance value of the n-type semiconductor. In general, in the case of a material having a large band gap such as diamond, the effective state density of the conduction band is small, so that the resistivity of the semiconductor is Si, G
Like e, it is difficult to reduce to about 10 ⁻⁴ Ω · cm. Therefore, by forming an n-type semiconductor layer having a bandgap smaller than that of the p-type semiconductor layer on the p-type semiconductor layer to reduce the resistance of the n-type semiconductor layer, it is possible to further reduce heat generation and to improve stability. It is possible to obtain an electron-emitting device having high efficiency.

Further, since the diamond layer is used for the p-type semiconductor layer, a large ΔE can be obtained with a small reverse bias potential because the diamond has a wide band gap. Therefore, unlike the prior art, it is not necessary to form a chemically unstable layer of a low work function material such as cesium on the surface of the n-type semiconductor layer, and a chemically stable material having a relatively high work function is used. Layers can be formed. Since the energy band gap of diamond is 5.4 eV and the activation energy of the p-type semiconductor is 0.37 eV when boron is used as an impurity, the work function of the material layer formed on the surface of the n-type semiconductor layer is 5. If it is 0 eV or less, ΔE> 0 is achieved by applying a relatively low reverse bias voltage, and electron emission becomes possible.

FIG. 5 is an energy band diagram of a Schottky junction type electron-emitting device in which the avalanche inducing layer is a Schottky electrode. In the figure, p indicates a p-type semiconductor layer, and T indicates a Schottky electrode. As shown in FIG. 5, the vacuum level E _{vac is set} to p by _{reducing the} bias between the junction between the p-type semiconductor layer and the thin film Schottky electrode.
Energy level lower than the conduction band level E _c of the type semiconductor layer, and a large energy difference ΔE (= E _c −E
_vac ) can be obtained.

By causing avalanche amplification in this state, a large number of electrons, which were minority carriers, can be generated in the p-type semiconductor layer, and the electron emission efficiency can be improved. Also, since the electric field in the depletion layer gives energy to the electrons, the electrons are hottened and the kinetic energy becomes larger than the temperature of the lattice system, and the electrons with a potential larger than the work function of the surface lose energy due to scattering. It is possible to cause electron emission without being accompanied by.

When diamond is used for the p-type layer, a good Schottky junction can be formed by forming the electrode from a material having a wide work function range because of its large band gap, and the work function of the electrode material is The tolerance range of can be made very wide. In addition, since a Schottky electrode material can be selected from materials having a wide work function range, a Schottky junction capable of stable electron emission can be formed.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For forming a diamond layer in the device of the present invention, known hot filament CVD method, microwave plasma CVD method, magnetic field microwave plasma CVD method are used.
A vapor phase synthesis method such as a method, a DC plasma CVD method, an RF plasma CVD method, or a combustion flame method can be used.

As the carbon raw material, hydrocarbon gas such as methane, ethane, ethylene, acetylene and the like, liquid organic compound such as alcohol and acetone, carbon monoxide or halogenated carbon and the like can be used, and further hydrogen, oxygen can be appropriately used. A gas containing chlorine, fluorine, can be added.

In order to reduce the dislocation / defect density to 10 ⁸ / cm ² or less, oxygen-containing gas such as O ₂ , H ₂ O and N ₂ O is added to the raw material gas. The amount added is such that the ratio of oxygen to carbon (O / C) in the source gas is 0.2 ≦ (O /
C) ≦ 2, preferably 0.5 ≦ (O / C) ≦ 1.
If it is less than 0.2, there is no effect of oxygen addition and a diamond crystal with few dislocations / defects is not formed. If it is more than 2, the practically usable diamond formation rate cannot be obtained due to the etching effect of oxygen. Because.

More detailed conditions for synthesizing diamond crystals include, for example, oxygen and carbon ratio (O / C) in the raw material gas.
In an atmosphere gas having the above range, the pressure is 1 to 100.
As 0 Torr, a diamond crystal is synthesized by the known microwave plasma CVD method, hot filament CVD method, and combustion flame method, and further, the pressure is 0.01 to 10 Torr.
For example, it can be synthesized by a known magnetic field microwave plasma CVD method within the range of r. The diamond crystal does not necessarily have to be formed on the entire surface of the substrate, and may be formed only on a desired portion by the selective deposition method of diamond based on, for example, JP-A-2-30697 of the present inventors. Further, the above-mentioned JP-A-2-306
Based on Japanese Patent No. 97, a diamond crystal having a single nucleus may be used by sufficiently reducing the nucleation site to 10 μm ² or less. However, in the case of forming a diamond crystal consisting of a single nucleus in the combustion flame method, the nucleus generation density is generally low, and if the nucleus generation site is 10 μm ² or less, precipitation is likely to occur, so that the nucleus generation site is 100%.
[mu] m ² value exceeding the following 10 [mu] m ^2, preferably 25 [mu] m ²
To 80 μm ² is preferable.

Of the above diamond crystal synthesizing methods,
The combustion flame method uses an oxygen-acetylene flame, and 0.85 ≦ O.
_By setting ₂ / C ₂ H ₂ ≦ 0.98, particularly high quality (crystal defect density of about 1 × 10 ⁷ pieces / cm ² ) diamond can be formed, and a relatively high formation rate (tens of μm / cm ² ). h
r) can be obtained. In addition, since the magnetic field microwave plasma CVD method can synthesize under a relatively low pressure compared to other methods, it is possible to form a film uniformly over a large area (for example, film thickness unevenness of ± 5% on a φ5-inch wafer). Is. As a selective deposition method of diamond, there is a method of forming a pattern of scratched portions on a substrate by using diamond abrasive grains. For example, the method disclosed in Japanese Patent Laid-Open No. 2-30697 of the present inventors can be mentioned. However, the method is not particularly limited to such a method.

In the method disclosed in Japanese Patent Laid-Open No. 2-30697, after the surface of the substrate is scratched, a patterned mask is formed on the substrate, etching is performed, and the mask is removed to remove scratches. Is a method for forming a pattern. Alternatively, a method may be used in which a mask member is provided in a pattern on the substrate, the surface of the substrate is scratched, and the mask member formed in a pattern by etching is removed to form the scratched portion in a pattern. Alternatively, after the surface of the substrate is scratched, a mask member having heat resistance may be formed in a pattern to form the scratched portion in a pattern.

The method of the scratch treatment using the diamond abrasive grains is not limited to a specific method, and for example, there are methods such as polishing using the diamond abrasive grains, ultrasonic treatment, or sandblasting. .. For example, 1μ
When the Si single crystal substrate is scratched by using a diamond abrasive grain of m or less and a horizontal polisher, a nucleus generation density of 10 ⁷ / cm ² or more is obtained. Also, the method of ultrasonic treatment is
Particle size 1 μm to 50 μ at a rate of 0.1 to 1 g / 10 ml
The substrate is placed in a liquid in which m abrasive particles are dispersed for 5 minutes to 4
It is carried out by applying ultrasonic waves with an ultrasonic cleaner or the like for a time, preferably 10 minutes to 2 hours. By this ultrasonic treatment method, it is possible to obtain a nucleus generation density of 10 ⁷ / cm ² or more.

An example of a method of selectively depositing diamond by forming a pattern of scratched portions on a substrate using diamond abrasive grains will be described with reference to the schematic diagrams of FIGS. 7A to 7E. First, the substrate 701 will be described. The surface is uniformly scratched using diamond abrasive grains (FIG. 7A). A mask 702 is formed on the surface of this substrate (FIG. 7B). The mask may be made of any material, and examples thereof include a resist formed in a pattern using a photolithography method (optical drawing method). Next, the substrate 70 is placed through the mask 702.
1 is etched to form a pattern on the scratched portion (FIG. 7C). The etching may be dry etching or wet etching. In the case of wet etching, etching with a mixed solution of hydrofluoric acid and nitric acid can be used. In the case of dry etching, plasma etching, ion beam etching, or the like can be given. As the etching gas for plasma etching, CF ₄ gas and CF ₄ gas to which a gas such as oxygen or argon is added can be used. As an etching gas for the ion beam etching, a rare gas such as Ar, He, Ne or oxygen,
Gases such as fluorine, hydrogen and CF ₄ are also possible. Etching depth is 100Å or more, preferably 500-1000
0Å, optimally about 800 to 2000Å is preferred. Next, when the mask 702 is removed (FIG. 7D) and diamond is formed by using the vapor phase synthesis method, the diamond 703 is selectively formed on the scratched portion (FIG. 7).
E).

FIG. 8 shows a schematic diagram of a method for synthesizing diamond by the combustion flame method. Reference numeral 801 is a burner, 802 is a substrate, 803 is an inner flame, 804 is an outer flame, and 805 is a substrate holder, which is water-cooled to cool the substrate. The source gas is oxygen and acetylene, and hydrogen gas, other hydrocarbon gas (methane, ethylene, etc.) and doping gas (containing gas such as boron, phosphorus, nitrogen, etc.) may be added thereto. Although the gas flow rate varies depending on the size of the burner, it is generally preferably about 1 liter / min to 10 liter / min. In the present invention, the flow rate ratio of oxygen and acetylene is 0.2 ≦ O ₂ / C ₂ H ₂ ≦ 2, preferably 0.85 ≦ O ₂
/ C ₂ H ₂ ≦ 0.98, more preferably 0.90 ≦
O ₂ / C ₂ H ₂ ≦ 0.95 is preferred.

Further, when the above O ₂ / C ₂ H ₂ ratio is within a desirable range (0.85 to 0.98), the difference in nucleation density between the scratched and unscratched portions tends to be large (Fig. 9). In order to carry out the selective deposition method, it is generally desirable to create regions having different nucleation densities of three digits or more, but in the combustion flame method, it is within the above range (0.85 ≦ O ₂ /
When C ₂ H ₂ ≦ 0.98), a nucleus generation density of 3 digits or more occurs. For this reason, when a semiconductor electron-emitting device using selectively deposited diamond by the combustion flame method is produced, it is desirable to perform it within the above gas flow rate range. The substrate temperature is 5
00 ° C to 1200 ° C, preferably 600 to 800 ° C is preferable.

As an impurity for forming the p-type diamond layer, an element of Group III of the periodic table such as boron can be used. As a method of adding boron, a method of adding a boron-containing compound to a raw material gas, an ion implantation method, or the like can be used.

The n-type semiconductor layer in the pn junction type element of the present invention is preferably as thin as possible. When a diamond layer is used as the n-type semiconductor layer, it can be formed by adding, to the diamond, an element of Group V of the periodic table such as nitrogen and phosphorus and lithium as an impurity.
As a method of adding these impurities, a method of adding these impurity-containing gases to the raw material gas, an ion implantation method, or the like can be used. When a semiconductor other than diamond is used for the n-type semiconductor layer, Si, Ge, In, As, P, and the like, Group II, Group III, and V of the periodic table.
Group III, Group VI semiconductor materials and combinations thereof,
Further, an amorphous material such as amorphous silicon or amorphous silicon carbide can be used. It is possible to add impurities of 1 × 10 ²⁰ atom / cm ³ or more to these materials, and the specific resistance value of the n-type semiconductor layer is 1 or less.
It can be as low as 0 ⁻⁴ Ω · cm.

The material of the Schottky electrode used in the semiconductor electron-emitting device of the present invention clearly shows Schottky characteristics with respect to the p-type diamond layer. Generally, there is a linear relationship between the work function φ _WK and the Schottky barrier height φ _Bn for an n-type semiconductor (Physic
s of Semiconductor Devices Sze 274p 76
(B) JOHN WILEY & SONS), φ _Bn decreases as the work function decreases. Further, generally, there is a relation of approximately φ _Bp + φ _Bn = E _g / q between the Schottky barrier heights φ _Bp and φ _Bn for the p-type semiconductor (q is an electric charge). The height is φ _Bp = E _g / q−φ _Bn . As described above, by using a material having a small work function, a good Schottky diode can be formed for the p-type semiconductor layer.

The material of the Schottky electrode in the Schottky junction type element of the present invention is a material that does not easily migrate even at high temperature, and is doped with an impurity element due to the wide energy band gap of diamond (5.4 eV). If a material having a work function equal to or lower than the energy obtained by subtracting the activation energy is used, the electron emission can be more efficiently performed. As a material that can be used when boron is used as an impurity,
Materials having a work function of 5.0 eV or less among elements of Group A to Group 7A and Group 2B to Group 4B, Periodic Table No. 8
Elements of Group 1 and Group 1B such as Ir, Pt, Au,
Further, lanthanoid-based elements, and a part of various metal silicides, metal borides, and metal carbides can also be used. Further, a material obtained by combining these elements and materials described above may be used.

Of these Schottky electrodes, refractory metals such as tungsten, tantalum, molybdenum, various metal silicides, metal borides, metal carbides, etc. are cesium formed on the surface of the conventional semiconductor electron-emitting device. Are chemically stable as compared with low work function materials such as Pd, Pt, Au, Ir, Ag, Cu, Rh, etc., because they have low resistance and do not easily migrate,
Electrons can be stably emitted even at a relatively low degree of vacuum (about 10 ⁻³ Torr).

The work function of these materials is 1.5 to 5.0.
It is about eV, which is a good Schottky electrode for all p-type semiconductor layers. These Schottky electrode materials can be deposited on a semiconductor with extremely good controllability by electron beam evaporation or the like, and are generated in the vicinity of the Schottky junction by depositing to a thickness of 1000 Å or less, more preferably 500 Å or less. Hot electrons can pass through the Schottky electrode without significantly losing energy, and stable electron emission can be performed.

By using the Schottky electrode described above, a good Schottky junction type semiconductor electron-emitting device can be obtained.

In the device of the present invention, as the work function lowering material formed on the electron avalanche inducing layer, the activation energy when the impurity element is doped due to the wide energy band gap of diamond (5.4 eV). It is desirable to use a material with a work function below the reduced energy. As a material that can be used when boron is used as an impurity, a material having a work function of 5.0 eV or less among elements of groups 1A to 7A of the periodic table and groups 2B to 4B of the periodic table, It can be used for elements such as Ir, Pt, and Au among the elements of Group 8 and Group 1B of the table, as well as various metal silicides, metal borides, and metal carbides.
Further, a material obtained by combining these elements and materials described above may be used.

Of these work function lowering materials, Au,
Elements such as Ir, Pd, Pt, Ag, Cu and Rh are particularly preferable because they have low resistance and go to my grade. Further, these materials are chemically stable as compared with work function lowering materials such as cesium formed on the surface of the conventional semiconductor electron-emitting device, and have a relatively low vacuum (10 ⁻³ Torr).
Electrons can be stably emitted even at about r).

These materials can be deposited on a semiconductor with excellent controllability by an electron beam evaporation method or the like.
By depositing a thickness of 100 Å or less, preferably a thickness of a monoatomic layer to a few atomic layers, hot electrons can pass through these materials having a low work function without significantly losing energy, and stable electron emission can be achieved. It can be performed.

[0048]

Embodiments of the present invention will be described below with reference to the drawings. (Example 1) This example shows a pn junction type electron-emitting device of the present invention.

FIG. 1A is a plan view, and FIG. 1B is its A-
FIG.

In the figure, 101 is a p ⁺ type semiconductor substrate, and Si (100) was used in this embodiment. 102 is a p-type diamond layer. Reference numeral 103 denotes an insulating selective deposition mask, and a SiO ₂ layer was used here. 104 is an n-type diamond layer, 105 is a titanium (Ti) electrode for ohmic contact, 106 is an insulating layer, and 107 is an extraction electrode. Reference numeral 108 denotes an ohmic contact electrode having A1 deposited on the back surface of the Si substrate 101. 109 is a power supply for applying a reverse bias voltage V _b between the electrodes 105 and 108, 1
Reference numeral 10 is a power supply for applying the extraction voltage V _g between the electrode 105 and the extraction electrode 107. 111 is Ag (work function: 4.26) as a material that lowers the work relationship.
eV) layer.

The above element was manufactured by the following method.

(1) A 1 μm thick p-type diamond layer 102 was formed on a p ⁺ -type Si substrate 101 by a hot filament CVD method. The formation condition is that the substrate temperature is 1000
C, pressure 100 Torr, gas flow H ₂ : 200S
CCM, CH ₄ : 1SCCM, O ₂ : 0.4SCCM,
100 ppm B ₂ H ₆ (diluted with hydrogen): 1 SCCM, filament temperature was 2100 ° C.

(2) Next, the SiO ₂ mask 10 is formed at a predetermined position by a resist process of photolithography.
Formed 3.

(3) Next, the n-type diamond layer 104
Was formed by the hot filament CVD method. The formation conditions are gas flow rate H ₂ : 200SCCM, CH ₄ : 1SC
CM, O ₂ : 0.4 SCCM, 100 ppm PH ₃ (hydrogen diluted): 5 SCCM except that the same as the above (1).

The n-type diamond is a SiO ₂ mask 103.
It does not deposit on the top surface of the mask and the opening (diamond layer 1
02 exposed area).

(4) Next, using a photolithography technique, the Ti electrode 105, the silver layer (100 Å thickness) 111, S
iO ₂ insulating layer 106 and polysilicon lead electrode 10
7 was formed into a predetermined shape.

When a reverse bias voltage V _b is applied between the electrodes 105 and 108 of the semiconductor electron-emitting device manufactured as described above, electrons are injected from the p-type diamond layer 102 to the n-type diamond layer 104, and the electrons are injected. The electrons pass through the n-type diamond layer 104 and the silver layer 111, exude into the vacuum region, and further, by applying the extraction voltage V _g between the extraction electrode 107 and the electrode 105, the electrons can be emitted to the outside of the element. did it.

The emission current density at this time was significantly increased to 15 times that of the device formed in the same manner as the semiconductor electron-emitting device except that the diamond layer was formed without adding oxygen. .. In addition, using a transmission electron microscope (TEM), a diamond crystal formed under the same conditions as this device was
When the crystal defect density was measured, 6 × 10 ⁷ defects / cm
It was confirmed to be ² . (Examples 2 to 6, Comparative Examples 1 and 2) A semiconductor electron-emitting device was prepared in the same manner as in Example 1 except that the amounts of oxygen and methane at the time of diamond layer formation were changed, and the amount of emitted electrons was measured. .. Table 1 shows the conditions at this time, comparison with the amount of emitted electrons of the element to which oxygen was not added when forming the diamond layer, and the defect density of the diamond crystal formed under the same conditions. The crystal defect density was measured in the same manner as in Example 1.

It can be seen that in Examples 2 to 6, good electron emission efficiency can be obtained.

[0060]

[Table 1] * Element with no oxygen added during diamond formation (Comparative Example 1)
(Embodiment 7) This embodiment shows a Schottky junction type electron-emitting device. FIG. 3A is a plan view and FIG. 3B is a sectional view taken along line AA.

In the figure, 301 is a p ⁺ type semiconductor substrate, and Si (100) was used in this embodiment. 302 is a p-type diamond layer. Reference numeral 303 denotes an insulating selective deposition mask, and a SiO ₂ layer is used here. 304 is a p ⁺ -type diamond layer, 305 is a Schottky electrode, here tungsten (work function: 4.55
eV) was used. Reference numeral 306 is an insulating layer, and 307 is a lead electrode. Reference numeral 308 is an ohmic contact electrode in which A1 is deposited on the back surface of the Si substrate 301. Three
A power source 09 applies a reverse bias voltage V _b between the Schottky electrode 305 and the electrode 308, and 310
Is a power supply for applying the extraction voltage V _g between the Schottky electrode 305 and the extraction electrode 307.

The above element was manufactured by the following method. (1) Hot filament CV on p ⁺ type Si substrate 301
A 1 μm thick p-type diamond layer 302 was formed by the D method. The formation conditions are a substrate temperature of 1000 ° C. and a pressure of 10
0 Torr, gas flow rate H ₂ : 200SCCM, CH
₄ : 1SCCM, O ₂ : 0.3SCCM, 100ppm
B ₂ H ₆ (diluted with hydrogen): 1 SCCM, filament temperature was 2100 ° C. (2) Next, a SiO ₂ mask 303 was formed at a predetermined position by a resist process of photolithography. (3) Next, the p ⁺ -type diamond layer 304 was formed to a thickness of 1000 Å by the hot filament CVD method. The formation conditions are gas flow rate H ₂ : 200SCCM, CH ₄ : 1S.
CCM, O ₂ : 0.3 SCCM, 100 ppm B ₂ H ₆
(Hydrogen dilution): Same as the above (1) except that 5 SCCM was used.

The p ⁺ type diamond is a SiO ₂ mask 30.
3 was not deposited, but was selectively deposited only on the openings (exposed portions of the diamond layer 302) of the mask. (4) Next, using a photolithography technique, a tungsten electrode (100 Å thickness) 305 and a SiO ₂ insulating layer 30 are formed.
6 and the polysilicon lead electrode 307 were both formed in a predetermined shape.

When a reverse bias voltage V _b is applied between the Schottky electrode 305 and the electrode 308 of the semiconductor electron-emitting device manufactured as described above, the p ⁺ type diamond layer 3 is formed.
04 and the Schottky electrode 305 cause avalanche amplification, and the generated hot electrons pass through the Schottky electrode 305 and exude into the vacuum region. Further, the extraction voltage V _g is drawn between the extraction electrode 307 and the Schottky electrode 305. The electrons could be emitted to the outside of the device by applying.

The emission current density at this time was 12 times larger than that of the element formed in the same manner as the semiconductor electron-emitting element except that the diamond layer was formed without adding oxygen. .. When the crystal defect density of the diamond crystal formed in the same manner as in this example was measured by using a TEM, it was found to be 7.5 × 10 ⁷ pieces / cm ² . (Embodiment 8) This embodiment shows a Schottky junction type electron-emitting device in which a diamond crystal having a single nucleus is formed by a selective deposition method, and its sectional view is shown in FIG. In the figure, 401 is a p ⁺ type semiconductor substrate, and Si (100) was used in this embodiment. 402 is a p-type diamond layer. 403 is an insulating selective deposition mask, and a SiO ₂ layer was used here. 404 is a p ⁺ -type diamond layer, 405 is a Schottky electrode, and here, tungsten (work function: 4.55 eV)
Was used. 406 is an insulating layer, and 407 is an extraction electrode. Reference numeral 408 is an ohmic contact electrode in which A1 is deposited on the back surface of the Si substrate 401. Reference numeral 409 is a power supply for applying a reverse bias voltage V _b between the Schottky electrode 405 and the electrode 408, and 410 is a power supply for applying the extraction voltage V _g between the Schottky electrode 405 and the extraction electrode 407. Power.

The above element was manufactured by the following method. (1) The p ⁺ type Si substrate 401 was placed in alcohol in which diamond particles having an average particle size of 25 μm were diffused, and a scratch treatment was performed using an ultrasonic cleaner. Then, a mask aligner (PLA-5 manufactured by Canon Inc.) is placed on this substrate.
00) was used to form a PMMA-based resist pattern having a diameter of 7 μm. This substrate was etched to a depth of 1000Å using an Ar ion beam etching device. The etching conditions at that time are: acceleration voltage: 1k
V, etching time: 10 minutes. Then sulfuric acid
The resist was removed with a mixed solution of hydrogen peroxide and diamond was formed by using a combustion flame method. The conditions at this time were O ₂ : 1.85 liter / min, C ₂ H ₂ : 2 liter / min, 100 ppm B ₂ H ₆ (hydrogen dilution): 5
0 SCCM, substrate temperature 750 ° C., synthesis time 15 minutes. As a result of this diamond formation, p-type diamond particles 402 of about 10 μm were selectively formed only on the portion (resist pattern forming portion) where the scratching treatment remained. (2) Next, a SiO ₂ mask 403 was formed at a predetermined position by a resist process of photolithography. (3) Next, the p ⁺ type diamond layer 404 was formed to a thickness of 1000 Å by the hot filament CVD method. The formation conditions are gas flow rate H ₂ : 200SCCM, CH ₄ : 1SC
CM, 100 ppm B ₂ H ₅ (diluted with hydrogen): ₅ SCCM
The same as (1) above except for the above.

The p ⁺ type diamond layer is a SiO ₂ mask 4
No deposit on the surface of the mask layer 03, and only on the opening portion (exposed portion of the diamond layer 402) of the mask. (4) Next, using a photolithography technique, a tungsten electrode (100 Å thickness) 405 and a SiO ₂ insulating layer 40
6 and the polysilicon lead electrode 407 were both formed in a predetermined shape. When a reverse bias V _b is applied between the Schottky electrode 405 and the electrode 408 of the semiconductor electron-emitting device manufactured as described above, avalanche amplification occurs at the interface between the p ⁺ type diamond layer 404 and the Schottky electrode 405. The generated hot electrons pass through the Schottky electrode 405, seep into the vacuum region, and are further drawn out.
By applying the extraction voltage V _g between the Schottky electrode 405 and the Schottky electrode 405, electrons could be emitted to the outside of the device.

The emission current density at this time is the same as in Example 7.
It was about 3 times higher than that of. When the crystal defect density of the diamond crystal formed in the same manner as in this example was measured by using a TEM, it was found to be 1 × 10 ⁷ pieces / cm ² . (Embodiment 9) This embodiment shows a Schottky junction type electron-emitting device in which diamond crystals are formed by using the magnetic field microwave plasma CVD apparatus shown in FIG.

In the figure, reference numeral 601 is a cavity resonator, and 602.
Is an electromagnet, and 603 is a microwave waveguide connected to a microwave oscillator (not shown). Reference numeral 604 is a microwave introduction window made of quartz glass, and 605 is a gas introduction port, which is connected to a gas cylinder and a gas flow rate regulator (not shown). Reference numeral 606 is a substrate, 607 is a substrate holder containing a heater capable of heating up to 1000 ° C., 608 is a sample chamber, 609 is an exhaust port, and a pressure adjusting valve and a vacuum pump (a turbo molecular pump and a rotary pump, not shown) are connected. 1 x 10 ^-7
A vacuum can be drawn up to Torr) is connected.

The element is formed by forming the diamond layer as shown in FIG.
Example 7 was carried out in the same manner as in Example 7 except that the magnetic field microwave plasma CVD method was used.

Of these, the p-type diamond layer 302 was formed under the following conditions. Source gas is O ₂ : 90 SCCM, C ₂
H ₂ : 100 SCCM, 100 ppm B ₂ H ₆ (hydrogen diluted) 10 SCCM, respectively. Pressure is 0.1
Torr magnetic field strength is 20 near the microwave inlet 504.
00 Gauss, and the vicinity of the substrate was adjusted to 900 Gauss. The substrate temperature was 750 ° C. and the microwave output was 1.0 kW.

The p ⁺ type diamond layer 304 has a gas flow rate of O ₂ : 90 SCCM, C ₂ H ₂ : 100 SCCM,
100 ppm B ₂ H ₆ (hydrogen diluted) 50 SCCM each was introduced to form the same as the p-type diamond layer (film thickness is 1
000Å).

The semiconductor electron-emitting device formed as described above could obtain an emission current density almost equal to that of the device of Example 7. When the crystal defect density of the diamond crystal formed in the same manner as in this example was measured by using a TEM, it was found to be 8 × 10 ⁷ pieces / cm ² .

[0074]

As described above, according to the semiconductor electron-emitting device of the present invention, high quality diamond crystals can be obtained and high electron-emitting characteristics can be obtained.

Therefore, according to the semiconductor electron-emitting device of the present invention, it is possible to provide a highly reliable display, an EB (electron beam) drawing device, a vacuum tube, an electron beam printer, a memory and the like.

[Brief description of drawings]

FIG. 1A is a plan view showing a pn junction type electron-emitting device according to a first embodiment of the present invention.

1B is a cross-sectional view taken along the line AA of FIG. 1A.

FIG. 2A is a schematic diagram of energy bands in a pn junction type semiconductor electron-emitting device composed of p-type diamond and n-type diamond.

FIG. 2B is a schematic diagram of energy bands in a hetero pn junction type semiconductor electron-emitting device.

FIG. 3A is a plan view showing a Schottky junction type electron-emitting device according to another embodiment of the present invention.

3B is a cross-sectional view taken along the line AA of FIG. 3A.

FIG. 4 is a cross-sectional view of a Schottky junction type electron emitting device using selectively deposited diamond according to still another embodiment of the present invention.

FIG. 5 is a schematic diagram of energy bands in a Schottky junction type semiconductor electron-emitting device.

FIG. 6 is a schematic view of a diamond forming apparatus used in Example 9.

FIG. 7A is a schematic diagram of a selective deposition method.

FIG. 7B is a schematic diagram of a selective deposition method.

FIG. 7C is a schematic diagram of a selective deposition method.

FIG. 7D is a schematic diagram of a selective deposition method.

FIG. 7E is a schematic view of a selective deposition method.

FIG. 8 is a schematic diagram of a combustion flame method.

FIG. 9 is a characteristic diagram showing a nucleus generation density by a combustion flame method.

[Explanation of symbols]

101 p ⁺ type semiconductor substrate, 102 p type diamond layer, 103 insulating selective deposition mask, 104
n-type diamond layer, 105 ohmic contact electrode, 106 insulating layer, 107 extraction electrode,
108 ohmic contact electrode, 109 power supply, 110 power supply, 111 work function lowering material layer,
301 p ⁺ type semiconductor substrate, 302 p type diamond layer, 303 insulating selective deposition mask, 304
p ⁺ type diamond layer, 305 Schottky electrode,
306 Insulating layer, 307 Extraction electrode, 308
Ohmic contact electrode, 309 power supply, 31
0 power source, 401 p ⁺ type semiconductor substrate, 402 p type diamond layer, 403 insulating selective deposition mask,
404 p ⁺ type diamond layer, 405 Schottky electrode, 406 insulating layer, 407 extraction electrode, 408 ohmic contact electrode, 40
9 power supply, 410 power supply, 601 cavity resonator, 6
02 Electromagnet, 603 Microwave waveguide, 604
Microwave introduction window, 605 gas introduction port, 606
Substrate, 607 substrate holder, 608 sample chamber,
609 exhaust port, 701 substrate, 702 resist,
703 diamond crystal, 801 burner, 80
2 substrate, 803 internal flame, 804 external flame, 805
Substrate holder.

Claims (1)

[Claims] 1. A semiconductor electron-emitting device using a diamond semiconductor layer, wherein the crystal defect density of the diamond semiconductor layer is 10 ⁸ defects / cm ² or less.