JPH06103758B2 - Method of manufacturing electronic device using diamond - Google Patents

Description

The present invention relates to a method of manufacturing an electronic device using diamond, particularly a visible light emitting device.

"Prior Art" With respect to light emitting devices, red light emission has already been achieved more than 10 years ago by using III-V compound semiconductors such as GaAs. However, this light emitting element is red, blue,
It was extremely difficult to emit green light, and it was completely impossible to emit continuous visible light such as white light using a crystalline material.

An attempt to make a light emitting device using diamond has already been shown by the present inventor, for example, it is shown in Japanese Patent Application No. 146930 in 1981 (filed on September 17, 1981).

Considering the size of the market for light-emitting devices, diamond has the advantages that it has heat resistance and is extremely chemically stable, and the raw material is an inexpensive material called carbon.
The potential for industrial mass production is enormous.

"Conventional drawbacks" However, a stable light emitting device using this diamond,
And no method of making it with high yield or the structure required for it has been shown so far.

A conventional visible light emitting device using diamond has a structure in which one electrode is provided on the lower side of the substrate and the other is provided on the upper side of the diamond to flow a current in the vertical direction. However, if the diamond has a polycrystalline structure, the current locally flows in the grain boundaries and other areas where the current is more likely to flow, and a large amount of heat is generated in the current concentration area, resulting in a sufficient visible light. We investigated the drawback of no light emission. As a result, the following facts were revealed.

The vertical flow method causes too much variation in manufacturing yield. Since the ohmic junction or the Schottky junction in the electrode portion does not have a sufficiently stable function, it is necessary to apply a voltage higher than necessary. Further, the voltage also varies in the degree of Schottky junction for each element, and high manufacturing yield cannot be expected.

Diamond is generally easy to make I-type (intrinsic) and P-type conductivity types, but it is extremely difficult to make N-type conductivity type diamond, and as a result, a PIN junction or PN junction is constructed using only diamond. It was difficult to do.

Further, no artificial control method is shown for the recombination center that constitutes the light emitting source.

"Object of the Invention" The present invention has been made to eliminate such drawbacks. That is, diamond was formed in a thin film shape on a substrate having an insulating surface, a pair of electrodes was arranged on the upper side, and a current was passed in the lateral direction to further reduce the influence of polycrystalline grain boundaries. Further, between the electrode and the diamond having a low resistance light emitting region, a semiconductor of silicon or silicon carbide having N-type or P-type conductivity was formed as a buffer layer. By embodying the N-type conductivity, which is difficult for this diamond, with silicon or silicon carbide, a PN or PIN junction was formed while the emission center was in diamond, and current injection was achieved. Further, according to the present invention, an impurity region which emits light using this semiconductor is intentionally provided by using a self-alignment process.

One of the technical ideas of the present invention is that, when an impurity is added from the outside to a region where light emission is to be performed, the electrical resistance of this region is one digit higher than that of a region in which other impurities are not intentionally added. The above has also been made small, and the physical properties that electric current concentrates and flows easily have been found, and this is actively applied to construct an electronic device. Then, a carrier (electrons or holes) is efficiently injected into the light emitting region in the diamond by applying a voltage between the pair of electrodes, and recombination is performed between emission centers, between bands (between valence band and valence band), or Luminescent center-
It is a smooth pattern between bands (conduction band or valence band).

[Structure of the Invention] The present invention relates to a method for manufacturing an electronic device for forming visible light by forming a diamond on a substrate having an insulating surface and passing a current in the lateral direction. The present invention is
Silicon carbide having P or N type on the upper surface of diamond
(SixC _1-X 0 <X <1) or a single-layer or multi-layer layer of a semiconductor such as silicon (hereinafter also referred to as a buffer layer) and a strip-shaped, comb-shaped, or donut-shaped pattern on the buffer layer. A conductor electrode is provided. Impurities are implanted into the diamond in the region having no buffer layer by ion implantation or the like by controlling the acceleration voltage in a self-aligned manner using this electrode as a mask.

The ion implantation method is a preferable method for producing a uniform concentration of emission centers, because the ion implantation can be performed regardless of the shape and morphology of diamond without causing any difference in the impurity concentration of the added impurities both in the crystal grain boundaries and in the bulk. .

A region to which this impurity is added, that is, an impurity region becomes a light emitting region. Further, another electrode is provided on the upper surface of this impurity region. When the electrode is provided here, the electrode may be provided on the buffer layer at the same time. By applying a pulse or a direct current or an alternating current between the electrodes formed on the upper side of both of the pair, visible light is generated, particularly light is emitted in the impurity region. This impurity region, that is, the light emitting region does not exist below the buffer layer. In the present invention, the buffer layer is used as a mask to ion-implant the impurity in a region where the buffer layer does not exist in a self-aligned manner. It is an impurity region. This impurity region is annealed if necessary, and another electrode is formed in a part of the impurity region. Then, only two photomasks are required to manufacture the electronic device of the present invention, and an extremely high manufacturing yield can be expected.

In the present invention, a P or N type semiconductor is used as the buffer layer, particularly silicon, silicon carbide or a semiconductor of these multilayers is formed, and as a result, the semiconductor layer is interposed on diamond and heat treatment at 500 ° C. or higher is performed. By providing a pair of electrodes capable of passing a current in the lateral direction without performing after forming a pair of electrodes, reliability under long-term actual use conditions was improved. That is, the structure is as follows: Upper electrode-P-type or N-type semiconductor (for example, silicon or silicon carbide) -Diamond having no impurity region-Diamond having an impurity region serving as a light-emitting region-Upper electrode provided on the impurity region or It was used as an upper electrode through another buffer layer. A structure in which the upper electrode and the undoped diamond are not in direct contact with each other, and the other electrodes are in close contact with the highly doped diamond, resulting in a stable bond between the diamond and the semiconductor. Is.

Further, in the present invention, in order to generate blue light emission more effectively, Zn (zinc), Cd (cadmium), which is an element of Group IIb of the Periodic Table of Elements, and an element of Group VIb are added as impurities in this diamond. An element selected from O (oxygen), S (sulfur), Se (selenium) and Te (tellurium) was added by an ion implantation method or the like. A compound of carbon and OH such as methanol (CH ₃ OH) was used for diamond synthesis.

In the semiconductor, B (boron), Al (aluminum), Ga (gallium), In (indium) which is a group IIIb element of the Periodic Table of Elements or N (nitrogen), P (phosphorus) which is a group Vb element , As (arsenic) and Sb (antimony) were added to obtain P or N type. This may be added to the diamond, but the color tended to change from blue to green.

When the ion implantation method is used, damage can be made in diamond and impurities can be simultaneously added to all parts at a uniform concentration, so that more recombination centers or emission centers can be formed.

If the impurities are added only by the diffusion method, the impurities are likely to concentrate at the crystal grain boundaries, and some of the added impurities are unevenly distributed at the grain boundaries, which reduces the activity, which is not preferable.

The region to which impurities are added by this implantation has an electric conductivity larger by one digit or more than the region to which impurities are not added. Therefore, when a voltage is applied between the pair of electrodes, the injected carriers intentionally flow in the impurity region, and electrons and holes are likely to be recombined with each other via the recombination center. Light can be emitted by this recombination process.

When this ion implantation method is used, thermal annealing is then performed, for example, in an atmosphere containing oxygen, such as oxygen, NOx, or air, for example, 200
Even if it is performed at ~ 1000 ° C, the damage remains as it is, and the strain energy in the atomic sense is only relaxed. Therefore, oxygen, which is an element of Group VIb of the Periodic Table of the Elements, is added to the impurities already implanted. In addition to the above, the luminous efficiency can be increased.

As a result, the current is prevented from being locally concentrated by flowing in the lateral direction, and the current flows in the impurity region uniformly added to the diamond by ion implantation, resulting in inter-band transition, band-recombination center or emission center. Carriers are recombined due to the transition between them or the transition between the recombination centers or between the emission centers. Visible light emission is suppressed according to the energy band interval (gap) of the recombination. In particular, the visible light can emit blue and green according to this transitional energy band width. Further, continuous light such as white light can be produced by creating an energy level of recombination centers between a plurality of bands.

The types of impurities and the conductivity type configuration that more positively emit blue light are shown.

On a substrate having an insulating surface, a group IIb impurity such as (CH ₃ ) ₂ Zn is added to diamond together with CH ₃ OH and hydrogen to form a film by a plasma vapor phase method. A semiconductor serving as a buffer layer on the upper side of the diamond is formed as an N type. The semiconductor is selectively removed, and the VIb group or IIb group of the periodic table of elements is particularly
An impurity region was formed by selectively adding a VIb group impurity, for example, S or Se. It has been excellent to provide another electrode on a part of the impurity region via another electrode or a buffer layer and apply a voltage between the pair of electrodes provided on the upper side of the substrate.

On the contrary, as a conductivity type structure and a kind of impurities, diamond doped with O, S, Se, and Te is formed on a substrate having an insulating surface. And those diamonds are H ₂ S, H ₂ S
e, H ₂ Te, (CH ₃ ) ₂ S, (CH ₃ ) ₂ Se, (CH ₃ ) ₂ Te is formed by adding CH ₃ OH and hydrogen during the diamond film formation by the plasma method. It An impurity region is formed by ion-implanting IIb group or VIb group impurities, particularly IIb group impurities such as Zn and Cd into the impurity region with the semiconductor serving as the upper buffer layer of P type. An electrode or an electrode via another buffer layer is formed on this impurity region, and an electrode is also formed on the semiconductor which is the buffer layer. A so-called reverse conductivity type may be used.

The present invention will be described below according to examples.

Example 1 In the present invention, FIG. 1 shows the manufacturing process. As shown in FIG. 1 (A), diamond (2) was produced on a substrate (1) having an insulating surface on which a silicon nitride film was formed, using the magnetic field microwave CVD apparatus shown in FIG. A method for forming a diamond film by a magnetic field microwave CVD apparatus is shown in Japanese Patent Application No. 61-292859 (a thin film forming method (filed on Dec. 8, 1986)) filed by the present inventor. The outline is shown below.

The silicon nitride film (1-2) has a thickness of 0.1 to
The silicon semiconductor (1-1) substrate having a thickness of 0.5 μm was dipped in a mixed solution containing alcohol mixed with diamond grains, and ultrasonic waves were applied for 1 minute to 1 hour. Then, a large number of minute damages can be formed on the substrate (1) having this insulating surface. This damage can be the source of nuclei for subsequent diamond formation. This substrate (1) was placed in a magnetic field microwave plasma CVD apparatus (hereinafter also simply referred to as a plasma CVD apparatus). This plasma CVD apparatus can add microwave energy with a frequency of 2.45 GHz to the reaction chamber (19) through the microwave oscillator (18), attenuator (16) and quartz window (45) up to 10 KW. In addition, the Helmholtz coil (17), (1
7 ') was added up to a maximum of 2.2 KG to construct a resonance surface of 875 Gauss. Substrate inside this coil (1)
Was placed on the holder (13) with the substrate retainer (14). In addition, the substrate position moving mechanism (42) adjusts the position in the reaction furnace,
A vacuum was drawn up to 10 ^-3 to 10 ^-6 torr. Thereafter to these, 40 to 200 vol% gas having a C-OH bond, such as methyl alcohol (CH ₃ OH) or ethyl alcohol (C ₂ H ₅ OH), for example, alcohol (22) with hydrogen (21) (100% by volume
At that time, CH ₃ OH: H ₂ = 1: 1) was added).

Dimethyl zinc (Zn (CH ₃ ) ₂ ) can be added to Zn (CH ₃ ) ₂ / CH ₃ OH
0.5 to 3% (volume%) was uniformly added from the system (23) during film formation. If you want to make this diamond P-type,
Trimethylboron (B (CH ₃ ) ₃ ) is used as a P-type impurity (2
From (3), B (CH ₃ ) ₃ / CH ₃ OH = 0.5-3% was introduced to make the diamond P-type.

On the contrary, S, Se, Te which are VIb group elements as dopants
When adding, for example, (H ₂ S or (C
_{H 3) 2 S) / CH} 3 OH = 0.1~3% may be added. For the growth of diamond, the pressure in the reaction chamber (19) was set to 0.01 to 3 torr, for example 0.26 torr by exhausting unnecessary gas from the exhaust system (25). A magnetic field of 2.2 KG (kilogauss) was applied from (17) and (17 ') so that the position of the substrate (1) or its vicinity was 875 gauss. Microwave added 4KW. In addition to this microwave energy, auxiliary heat energy is applied from the holder (13) to increase the substrate temperature to 200 to 1000 ° C, for example 800
℃ was made.

Then, the carbon in the alcohol which was decomposed by the microwave energy and turned into plasma was grown on the substrate, and a large number of single crystal diamonds could be grown in a columnar shape. At the same time, graphite components other than the diamond are also likely to be formed, but these react with oxygen and hydrogen and revaporize as carbon dioxide gas or methane gas. As a result, crystallized carbon or diamond (2) is grown on the substrate (1) with a thickness of 0.5 to 3 μm, for example, an average thickness of 1.3 μm (deposition time 2 hours), as shown in FIG. 1 (A). I was able to.

That is, in FIG. 1 (A), a diamond (2) having Zn or B added on a substrate (1) having an insulating surface.
Or undoped (state in which impurities are not intentionally added)
Diamond (2) was formed.

P type conductivity type silicon or silicon carbide (Six
C _1-X 0 <X <1) (3) was added by plasma CVD method with silane (SiH ₄ ) instead of alcohol, and IIIb group impurity gas,
For example, B ₂ H ₆ is added at the same time as P-type silicon, or a carbide gas is added to these gases, and silicon carbide (SixC _1-X 0 <X <1) having a thickness of 300Å to 0.3 μm is formed by the plasma CVD method. Formed. This formation is made by using a plasma CVD device similar to diamond.

Since impurities different from P-type and N-type are added in these film formations, a diamond chamber and a N-type semiconductor layer film-forming reaction chamber are used as a multi-chamber system to connect them to each other for mass production. That is valid.

In FIG. 1 (B), the buffer layer (3) was selectively removed by the first photomask to obtain FIG. 1 (B).

As shown in FIG. 1 (B), this photoresist (4),
(4 '), buffer layer (3), (3') as a mask
S by an ion implantation method using an acceleration voltage of 50 to 200 KeV
Alternatively, Se is 1 × 10 ^{18 to} 5 × 10 ²⁰ cm ^-3 , for example, 6 × 10 ¹⁹ cm
^-3 to form an impurity region (5). Then, as shown in FIG. 1 (C), the buffer layer (3),
The end portion (3 ′) and the end portion (20) of the impurity region (5) can be matched or substantially matched with each other. For this reason, when a current is passed through the buffer layer to the impurity region, it is possible to prevent the applied voltage from varying due to the variation in the matching accuracy among the products. Then, the photoresist on the buffer layer (3) was removed. All of these were heat-treated in oxygen or air as needed to remove lattice strain in the impurity region, and oxygen was further added to this. All of these were dipped in dilute hydrofluoric acid to remove the silicon oxide components on the buffer layers (3) and (3 ').

In the next manufacturing step of FIG. 1 (D), molybdenum and tungsten (29-1) were formed thereon as a buffer layer with a thickness of 0.05 to 0.5 μm. At this time, the same material may be formed as (9-1) in the same step. Further, aluminum (29-2), (9-2) may be formed thereon as an electrode member for wire bonding in a thickness of 0.5 to 2 μm.

After that, this electrode member is selectively removed by a photoetching method using a second photomask, and the electrode (9-
1), (9-2) or (9) and (29-1), (29-2) or (29) were formed. That is, a photoresist was selectively formed and removed by a known dry etching method using plasma.

Next, wire bonding (8), (28) was performed on the electrodes (9-2), (29-2). Further, a silicon nitride film (6) was coated on the whole as an antireflection film.

This was performed after the light emitting element was provided on the lead frame and wire bonding was performed. FIG. 1 (D) shows this structure.

Further, it is effective to mold the whole of these with a light-transmissive plastic to improve the moisture resistance and the mechanical resistance.

In the structure of FIG. 1 (D), a voltage of 10 to 200 V (DC to 100 Hz duty ratio 1), for example 50 V, was applied between a pair of electrodes, that is, (9) and (29). Then, the electric current (11) and the electrode (9) -the buffer layer (3) -the diamond (2) without the impurity region-the diamond (5) with the impurity region-the electrode (29) could be passed. Since the resistance of the impurity region (5) is smaller than that of other undoped diamonds by one digit or more, the current is not present in the undoped diamonds below this impurity region as well. A region (impurity region) (5) in which the semiconductor (3) and the electrode (9), which have a light-shielding property, do not exist (5). ) Was able to emit light to the outside (upward).

That is, it became possible to emit visible light, particularly blue light of 475 nm ± 5 nm, from the portion of the diamond centered on the impurity region (5). The strength had 17 candela / m ² .

[Example 2] In this example, a completed drawing is shown in Fig. 2 (A). The manufacturing process is the same as in Example 1 schematically shown in FIG.
That is, 0.5 to 3 μm on the substrate (1) having an insulating surface,
For example, undoped diamond was formed with an average thickness of 1.2 μm. After that, with respect to the surface of the diamond (2), a P-type silicon or silicon carbide semiconductor (3) (SixC _1-X
0 <X <1) was formed as the buffer layer (3). After that, the semiconductor was selectively removed by using a photoetching method (first mask), and the buffer layer (3) was selectively left.

Next, Zn, which is an element of Group IIb of the periodic table of elements, is ion-implanted at a concentration of 9.5 × 10 ¹⁹ cm ⁻³ on the diamond (2) using the buffer layer (3) and the photoresist thereon as a mask. , An impurity region (5) was formed.

In this example, the periodic table of elements is used as an impurity for the emission center.
An element of IIb group was used as the main component instead of VIb group.

Further, aluminum was directly provided as the electrode (29) to a thickness of 1.5 μm without providing another buffer layer in this impurity region. At the same time, the electrode (9) was also provided with a second photomask and heat-treated in the atmosphere at 400 to 500 ° C.

Aluminum is directly attached to the impurity region as a negative electrode.

The other steps were the same as in Example 1.

Also in this embodiment, the protective antireflection film (6) is formed on the impurity region (5).

A voltage of 40 V was applied between the pair of electrodes (29) and (9).

Then, blue emission with a wavelength of 480 nm could be observed from here. Its intensity was 14 candela / m ^2, which was darker than that of Example 1. However, it was possible to put it into practical use.

Example 3 This example shows a completed vertical sectional view in FIG. 2 (B). The manufacturing process is substantially the same as that of the first embodiment. A large number of electrodes were provided in a comb shape to form a large-area light emitting element.

In Example 1, diamond (2) was formed on a substrate (1) having an insulating surface while being oxidized. On top of these, N-type silicon carbide semiconductors (3), (3 '), (3 ")
Was formed.

Then, the VIb group element Se (selenium) is added to the diamond (2) by an ion implantation method at an acceleration voltage of 50 to 200 KeV to a concentration of 1 × 10 ^{19 to} 6 × 10 ²⁰ cm ⁻³ , and the impurity region is added. (5) was formed. Then, the edge of this semiconductor and the edge (20) of the impurity region could be matched or substantially matched. Further, on the impurity region (5), a P-type semiconductor (29
-1) and (29-1 ') were selectively formed as other buffer layers.

This was annealed in the atmosphere at 750 to 900 ° C, oxygen was added to the impurity region (5) at a higher concentration, and the lattice strain was eliminated to add oxygen, selenium, and two kinds of VIb group elements. .

Semiconductors (3), (3 ′), which constitute the buffer layer,
The silicon oxide components on (3 "), (29-1), and (29-1 ') were removed by dilute hydrofluoric acid. Next, aluminum was deposited to a thickness of 2 μm on these semiconductor electrodes (9), (9 '), (9 "),
(29-2) and (29-2 ').

After scribing this electronic device and bringing it into close contact with the lead frame or stem, wire bond (8),
(28) was formed.

Finally, the same silicon nitride film as in Example 1 was formed as the antireflection film (6). Since the light emitting area is large, and because the buffer layer is interposed between both electrodes and diamond,
In addition to having long-term stability, it was possible to produce a greenish blue emission with a wavelength of 490 ± 10 nm and 29 candela / m ² .

"Effects" In the light emitting device using diamond, which has been known to flow a current in the vertical direction, the temperature of the diamond becomes close to 60 ° C just by applying a voltage of 40 V to the electrode and the substrate for 10 minutes, and the upper electrode and the diamond are separated. Since they were close to each other, they reacted and deteriorated. However, in the present invention, diamond is provided on a substrate having an insulating surface, a pair of electrodes are present on the substrate, and carriers are injected laterally to the diamond into the impurity region. The structure is a self-aligned structure in which the buffer layer and the impurity region are matched or substantially matched with each other, and an impurity region for light emission is formed at a position in close contact with the semiconductor layer having a light-shielding effect.
As a result, even if a pulse voltage of 40 to 100 V is applied, in addition to achieving visible light emission, the emitted light can be emitted to the outside through the antireflection film without any obstruction, resulting in high brightness. Was fulfilled. Further, since the electrode material does not diffuse into the impurity region which is the light emitting portion, no decrease in the emission luminance was experimentally observed even after continuous application for about one month.

The present invention mainly shows the case of making one light emitting device.
However, after forming a light emitting device using a plurality of diamonds on the same substrate, forming electrodes, and then scribing and breaking to an appropriate size, it is possible to make one by one.
Alternatively, it is effective to use a light emitting device in which a large number of light emitting sources are integrated on the same substrate, for example, a light emitting device having a matrix array.

Further, in the method of the present invention, only two types of photomasks are used, and an extremely high yield can be expected. For example, when making a 0.8 mm × 0.8 mm LED on a 4-inch wafer, 10 ⁴
We were able to make one LED on one side of the same wafer.

In the present invention, diamond is mainly shown as a polycrystalline thin film. However, it goes without saying that when this diamond is a single crystal diamond, physical properties such as higher brightness and luminous efficiency can be expected.
However, it has the drawback of becoming more expensive.

In the present invention, the substrate having an insulating surface may be not only a substrate having a silicon nitride film formed on silicon but also a substrate having another insulator or silicon carbide. In addition, a crystal diamond having sufficient insulating property, which does not allow current to flow downward, can be used as a substrate for carrying out the present invention.

Including such a light emitting device, using the same diamond, and using the silicon semiconductor above or below it, the diode, the transistor, the resistor, and the capacitor are integrally formed, and it is possible to construct an integrated electronic device. It is valid.

[Brief description of drawings]

FIG. 1 shows a manufacturing process of a diamond electronic device of the present invention and a vertical sectional view thereof. FIG. 2 shows a vertical sectional view of another electronic device of the present invention. FIG. 3 shows an example of a magnetic field microwave apparatus for forming diamond on a substrate for use in the present invention. 1 ... Substrate 2 ... Diamond 3,3 ', 3 ", 29-1,29-1' ... Buffer layer 4 ... Photoresist 5 ... Impurity region 6 ... Antireflection film 7 ... Electrode 8, 28 …… bonded wire 11 …… injected current path 9,29-2,29-2 ′ …… upper electrode 13 …… holder 16 …… attenuator 17,17 ′ …… magnet 18 …… microwave oscillator 19 …… Reaction chamber 20 …… End of impurity region 21,22,23,24 …… Doping system 25 …… Exhaust system 42 …… Movement mechanism …… Photo etching process

Claims (3)

[Claims] 1. A step of selectively forming diamond on a substrate having an insulating surface and a semiconductor on the diamond,
A step of adding an impurity to the diamond in the region where the semiconductor is removed by using the semiconductor as a mask to form an impurity region; and a step of forming a pair of electrodes on the impurity region and the semiconductor. A method for manufacturing an electronic device using a characteristic diamond. 2. A method of manufacturing an electronic device using diamond according to claim 1, wherein an impurity element is added by an ion implantation method to an element of Group IIb or VIb of the Periodic Table of Elements. Method. 3. A step of selectively forming a diamond and a buffer layer on the diamond on a substrate having an insulating surface, and adding impurities to the diamond in the removed region of the buffer layer using the buffer layer as a mask. Forming an impurity region by forming an electrode on the buffer layer and forming another electrode on the impurity region or another buffer layer on the impurity layer and an electrode on the layer. A method for manufacturing an electronic device using diamond, which comprises: