JPH06103753B2 - Method of manufacturing electronic device using diamond - Google Patents

Description

The present invention relates to a method for manufacturing an electronic device using diamond,
In particular, it relates to a method for manufacturing a light emitting element.

"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 device is red, and it is extremely difficult to emit blue and green, and it is 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.

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

“Conventional Defects” The present invention has been made in order to configure a visible light emitting device using diamond, to increase the yield thereof, and to increase the light emitting efficiency.

The present inventor investigated what kind of emission center is in a conventional diamond. Then, until now, when a large current was applied to the pair of electrodes constituting the device, a large amount of heat was generated, and a defect that sufficient visible light was not emitted was investigated. As a result, the following facts were revealed.

A conventional light emitting device using diamond has a large number of crystal grain boundaries because diamond is polycrystallinely grown in a columnar shape on a substrate. The graphite component, not the diamond component, is biased in the crystal grain boundaries, and is likely to be electrically conductive.

In addition, metal ions, which tend to exist unintentionally, tend to concentrate in the crystal grain boundaries around the diamond growth process in a biased manner, and when a current is applied between a pair of electrodes to cause light emission, this current is generated Leakage current easily occurs in the field. As a result, in the structure shown in FIG.
The current that contributes to the light emission flowing in the diamond in proportion to the applied input power is extremely small.

That is, in FIG. 1, diamond (2) grows in a columnar shape on a substrate (here, a conductive substrate), has pinholes (5) and grain boundaries (4), and the upper electrode (3) is placed on the diamond. )
Is provided. Since the electrode material passes through the pinhole and reaches the lower substrate, an electrical short circuit occurs here, and at the crystal grain boundaries (4) where the graphite component is biased, the grain boundaries are electrically conductive. A leak will occur.

"Object of the Invention" The present invention has been made to eliminate such drawbacks. That is, the purpose is to cause all or most of the applied current to flow in the diamond (bulk) instead of the grain boundaries. Then, charges are efficiently injected into the light emitting source in diamond, and recombination is performed between emission centers, between bands (valence band-valence band), or between emission center-bands (conduction band or valence band). It is a neat thing.

"Structure of the Invention" The present invention relates to a method for manufacturing an electronic device in which a diamond and one or more electrodes are provided on the upper surface of the diamond on a substrate such as a semiconductor or a conductor or a substrate having an insulator surface. In the case of one electrode, the substrate is the conductor,
Visible light is generated by passing a pulse, a direct current or an alternating current between the substrate and the electrode. Further, in the case of forming a plurality of electrodes, diamond is provided on a substrate having an insulating surface, and an electronic device, for example, a visible light emitting device is provided by flowing a similar current between the plurality of electrodes on the substrate.
However, in general, diamond has a polycrystalline structure, and each diamond crystal has pinholes or recesses at the periphery thereof. Therefore, the present invention is directed to filling pinholes or recesses corresponding to these with an insulator, for example, an organic or inorganic insulator, and providing one or more electrodes on the diamond surface and the insulator surface. Regarding the method.

When diamond is formed in a columnar shape on a substrate, its crystal grain boundaries easily serve as a current path. In general, a recess or pinhole is formed on the upper surface of this crystal grain boundary. Therefore, by filling the inside of the recess or the pinhole with an insulator, for example, an organic resin insulating film or molten glass, it is possible to prevent the current from flowing intensively in the passage. Then, an electric current flows through the diamond, carrier recombination occurs due to band-to-band transition, transition between band-recombination center or emission center, or transition between recombination centers or emission centers, resulting in the recombination. The visible light emission is suppressed in accordance with the energy band interval (gap). In particular, the visible light can emit blue and green depending on between the transition bands. Further, continuous light such as white light can be produced by creating an energy level of recombination centers between a plurality of bands.

The present invention will be described below according to examples.

Example 1 In the present invention, diamond was produced on a silicon semiconductor or a metal conductor by using a magnetic field microwave CVD apparatus. A method for forming a diamond film by this 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. ing. The outline is shown below.

The semiconductor substrate having a high concentration added to the P type was immersed in a mixed solution containing diamond grains and ultrasonic waves were applied for 10 minutes to 1 hour. Then, a large number of minute damages can be formed on this semiconductor substrate. This damage can be the source of nuclei for subsequent diamond formation. This substrate was placed in a magnetic field microwave plasma CVD apparatus (hereinafter also simply referred to as a plasma CVD apparatus). This plasma CVD device is 2.4
A microwave with a frequency of 5 GHz can be applied up to 10 KW. A maximum of 2 KW was applied to the magnetic field using a Helmholtz coil to form a resonance surface of 875 Gauss. Inside the reaction furnace where the substrate inside this coil is arranged,
A vacuum was drawn up to 10 ^-3 to 10 ^-6 torr. Thereafter, an alcohol such as methyl alcohol (CH ₃ OH) or ethyl alcohol (C ₂ H ₅ OH) was diluted with hydrogen to 1 to 15% by volume and introduced into them. For example, it was introduced at a volume ratio of 5%, and the pressure was 0.01 to 50 torr, for example 0.1 torr. A magnetic field of 2KG (kilogauss) was applied so that the position of the substrate or its vicinity was 875 gauss. Microwave applied 5KW.

Then, the carbon in the alcohol decomposed into plasma by the microwave energy grows on the substrate, and a large number of single crystal diamonds can be grown in a columnar shape. At the same time, graphite components other than this diamond are easily formed, but this reacts with oxygen and hydrogen and is re-vaporized as carbon dioxide gas or methane gas. As a result, the crystallized carbon or diamond is 0.5 to 3 μm, for example, an average thickness of 1.3.
It was possible to form a film of μm / 2 hours.

However, at the grain boundaries, this electrically conductive graphite component remains, and it is easy to form an electrical leak path. Further, because of the crystal growth, the remaining portion of the graphite component becomes a crystal grain boundary, and the concave portion is constituted by the upper surface.

This diamond has a polycrystalline structure that grows upward from the substrate. As an example thereof, in FIG. 2 (A), columnar diamond (2) can be grown on a silicon substrate (1).

However, this diamond (2) is polycrystalline and the crystals are next to each other, producing grain boundaries (4) there. Sometimes it also has a pinhole (also referred to as a hole or an opening that extends from above to the substrate) (5).

When this crystal grain boundary (4) is examined by laser Raman spectroscopy,
It was found that there are many graphite components in this area, and it is electrically conductive in a region 10 ² to 10 ⁴ times as easily as diamond (2).

For this reason, in this example, the entire surface was coated with photoresist, especially positive resist. Then, it was possible to fill the inside of the pinhole (5) with an organic substance as an insulator. In addition, the concave portion on the upper surface of the polycrystalline diamond, for example, (4 ') could be filled with the organic substance as the insulator.

Then, the upper surface of the coated organic resin can be made flat. This is a positive photoresist, such as OF
PR 800 (Adjusted by further diluting clay C and P / A)
Can be achieved by applying a spin coat method.

Further, these were subjected to known baking (80 ° C., 20 minutes) and irradiated with ultraviolet light (intensity ² mW / cm ² for 6 seconds). This irradiation time was adjusted to expose to the broken line (11). Further, the exposed region was removed by using a developing solution of (NMD-3), and the remaining resist was left as it was, or if necessary, heat-cured. Then, it becomes possible to expose the upper surface (2 ') of the diamond (2) and further fill the recesses (4') or the pinholes (5) with the insulators (4 ') and (5').

Next, an electrode member (7) was formed on the upper side by a vacuum deposition method and a sputtering method. As this electrode, translucent ITO (indium tin oxide) (7) and aluminum on it,
A metal (12) such as silver or molybdenum was formed in multiple layers. As the electrode, only aluminum or chromium or molybdenum and aluminum on it may be used as a multilayer film. Chromium or the like is a stable refractory metal, and aluminum on it is suitable for wire bonding.

Through the above steps, columnar polycrystalline diamond is formed on the substrate, its upper surface is exposed and is in close contact with the DC electrode member, and further, the recess or pinhole is filled with an insulating material, and there is an electrical leak path. It became possible to prevent.

In the structure of FIG. 2C, 10 to 200 V (DC to 100 H) is provided between a pair of electrodes, that is, the substrate (1) and the electrode (12).
z Duty ratio 1) For example, a voltage of 60V was applied. Then, after passing a current through this diamond portion, it became possible to emit visible light, particularly green light, from there. The intensity had 12 candela / m ² .

Example 2 In this example, in addition to Example 1, a substrate was provided with an insulating surface, that is, a silicon nitride film was formed to a thickness of 0.5 to 1 μm on a silicon single crystal substrate. On this, diamond was formed according to Example 1 to an average thickness of 0.5 to 3 μm, for example 1.2 μm. After that, ultrasonic waves were applied to the diamond surface in a liquid in which diamond grains were mixed at the same time as in Example 1 to damage the formed diamond surface.

Then, many recombination centers such as luminescence centers could be formed on the upper surface of the diamond.

After this, as in Example 1, the process of filling the insulator of the method of the present invention was performed.

Instead of FIG. 2 (C), a voltage of 40 V was applied between the plurality of electrodes, for example, the pair of electrodes (7) and (17) on the upper side. Then, blue emission with a wavelength of 450 nm could be observed from here. Its strength was 6 candela / m ² .

In FIG. 3, the substrate (1) is a generic term for a silicon substrate (20) and a silicon nitride coating (21). Fig. 2 (A),
The steps corresponding to (B) are omitted for simplicity. The damage given to the diamond is shown as (22).

"Effects" Until now, when a voltage of 30V was applied to the substrate for 10 minutes, the temperature of the diamond was close to 50 ° C, and the upper electrode and the diamond reacted and deteriorated. However, by adopting the structure shown in the present invention as described above, even if a voltage of 60 V is applied, visible light emission is achieved. There was no decrease in

The present invention mainly shows the case of making one light emitting device.
However, it is effective to fabricate a light emitting device using a plurality of diamonds on the same substrate, form electrodes, and then scribe and break to an appropriate size to provide a single or integrated light emitting device. Further, including the light emitting device, it is effective to use the same diamond to integrate a diode, a transistor, a resistor, and a capacitor to form a composite electronic device.

[Brief description of drawings]

FIG. 1 shows a conventional diamond light emitting device. FIG. 2 shows a manufacturing process of a diamond light emitting device of the present invention and a vertical sectional view thereof. FIG. 3 shows another example of the diamond of the present invention.

Claims (2)

[Claims] 1. A step of forming a polycrystalline diamond on a substrate, and a step of filling the pinhole or concave portion of the diamond with the organic resin by forming a light-transmitting organic resin to cover the diamond. And a step of selectively removing the organic resin to expose the upper surface of the diamond while leaving the organic resin in the pinholes or recesses, and forming one or more electrodes on the upper surface. A method for manufacturing an electronic device using diamond, which comprises steps. 2. A method for manufacturing an electronic device using diamond according to claim 1, wherein the polycrystalline silicon is formed into a columnar shape on the substrate by a plasma vapor phase reaction method.