JPH1012565A - Diamond semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable complete element isolation between electronic devices, by forming an insulating region containing nitrogen of specific atomic concentration, between electronic element regions composed of a P-type semiconductor diamond layer in which B is introduced. SOLUTION: In a single crystal insulating-diamond layer, B<+> ions are implanted in a pair of rectangular element regions 2a and 2b. In order to active B, heat treatment is performed at a specific temperature in a vacuum, and then heat treatment is performed at a specific temperature in the air. Thereby a graphite layer generated by the damage of ion implantation is eliminated. The element regions 2a, 2b are covered with an Au mask, and N<+> ions are implanted in the region except the part in which B<+> has been implanted. An insulating region where the atomic concentration of nitrogen is about 1×10<14> to 1×10<21> cm<-3> is formed. After heat treatment is performed at a specific temperature in a vacuum, the graphite layer on the diamond layer surface is eliminated by oxidizing process at a specific temperature in the air. Thereby element isolation between electronic element regions is realized completely, and the generation of malediction due to the interferences between elements can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond semiconductor device on which high-temperature electronic devices, high-power electronic devices, highly integrated circuits, and the like are formed, and a method of manufacturing the same. The present invention relates to a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Diamond has a band gap of 5.5.
Since it has a large eV, a high dielectric breakdown electric field, and a high thermal conductivity as compared with conventional semiconductor materials, it is expected as an electronic device that operates even in a severe environment such as a high temperature or a radiation. Further, since both the mobility of electrons and holes are high, the saturation speed of carriers is high, and the dielectric constant is low, it is also expected as a high-frequency electronic device.

[0003] As mentioned above, diamond has great potential, and since the latter half of the 1980's, diamond field effect transistors (Field Effect Transistors) have been developed.
Research and development on tor (FET) have been actively conducted, and the evaluation of characteristics in a high-temperature and high-frequency region has been advanced.

[0004] Therefore, it has been proposed to produce a logic circuit in which a plurality of diamond FETs are connected by utilizing such characteristics of the diamond FET, and the development of a diamond integrated circuit device has begun (for example, Gaien et al. Abstracts of 9th Diamond Symposium, p.136 and Ito et al.
9th Diamond Symposium Abstracts, p.13
8). In this method, diamond integrated circuits such as NOT, NAND, NOR, and RS flip-flop circuits are manufactured by connecting a plurality of metal / semiconductor junction (MES) FETs using a surface conductive layer.

[0005] The surface conduction layer of diamond can be formed by hydrogenation such as hydrogen plasma treatment, but it has been found that such a surface conduction layer disappears at a temperature of 350 ° C or more in the atmosphere. I have. Originally, high-temperature electronic devices that are expected to use diamond FETs,
When forming high power electronic devices and high integrated circuits,
Since the operating atmosphere is at a high temperature or involves a large amount of heat generation, it is difficult to use such a thermally unstable surface conductive layer as a semiconductor layer.

Further, when the surface conduction layer is formed by hydrogenation, it is impossible to control the doping concentration and the film thickness, and the doping concentration and the film thickness of the diamond semiconductor layer required for each element can be arbitrarily obtained. It is not possible.
Therefore, when fabricating a high-temperature, high-power, highly integrated electronic device using a semiconductor substrate having a diamond layer, it is necessary to use B-doped p-type semiconductor diamond.

By the way, in a diamond integrated circuit having a surface conductive layer formed by hydrogenation, Ar ⁺ ions are implanted in the fabrication process to release hydrogen, which is the conduction origin of the surface conductive layer of the diamond FET, from inside the diamond. Insulation by diamond makes it possible to isolate elements between diamond electronic devices.

[0008]

However, when Ar.sup. ⁺ Ions are implanted by the above-described method, hydrogen in the surface conductive layer can be thermally desorbed by the heating effect of the ion implantation and the surface conductive layer can be eliminated. , B-doped diamond electronic devices cannot be separated. This is because Ar injected into diamond does not work as a hole trap.

When Ar ⁺ ions are implanted into the diamond semiconductor layer, the surface of the diamond subjected to the ion bombardment is converted to graphite to impart conductivity because of the heavy weight of Ar. Therefore, it is impossible to completely separate the diamond electronic devices unless the graphite layer is removed.

[0010] The present invention has been made in view of the above problems, and is intended to be applied to a high-temperature electronic device, a high-power electronic device, and a semiconductor diamond layer into which B is applied, which is applied to a highly integrated circuit. A diamond semiconductor device and a method of manufacturing the same that can completely isolate elements between devices and thereby prevent a malfunction due to interference between elements when forming a plurality of element regions on the same substrate The purpose is to provide.

[0011]

According to the diamond semiconductor device of the present invention, 1 × 10 ^{14 to} 1 × 1 between the electronic element regions comprising the p-type semiconductor diamond layer into which B is introduced.
It has an insulating region containing nitrogen at an atomic concentration of 0 ²¹ cm ^-3 . This nitrogen is preferably introduced into the diamond layer by ion implantation. It is preferable that at least one type of electronic element selected from the group consisting of a transistor, a thermistor, a diode, an optical sensor, and a light emitting element is formed in the electronic element region.

The method of manufacturing a diamond semiconductor device according to the present invention is characterized in that a 1 × 10 ^{14 to} 1 × 10 ²¹ c is provided between electronic element regions formed of a p-type semiconductor diamond layer into which B is introduced.
The insulating region is formed by introducing nitrogen at an atomic concentration of m ⁻³ .

This nitrogen is preferably introduced into the diamond layer by ion implantation. After the ion implantation, it is preferable to perform a heat treatment at a temperature of 800 ° C. or more for 1 minute or more in a vacuum, and further remove the non-diamond layer on the surface of the diamond layer generated by the ion implantation. Further, the non-diamond layer can be removed by heat treatment at 500 ° C. or higher in an oxygen-containing atmosphere, acid cleaning, or oxygen plasma treatment.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When a pair of B-doped p-type semiconductor diamond layers are formed so as to be separated by a distance of 1 to several .mu.m, a region of several .mu.m sandwiched between these two p-type semiconductor diamond layers. Is an insulating diamond, when a voltage is applied between these semiconductor diamond layers, a current flows and the insulating property cannot be maintained. this is,
This is for the following reason.

FIG. 1 is a schematic diagram showing the energy bands of two B-doped semiconductor diamond layers and an insulating undoped diamond layer sandwiched between them. FIG. 1 (a)
As shown in (2), when no voltage is applied to the two semiconductor diamond layers, the undoped layer acts as a barrier to holes in the B-doped layer, and the movement of holes occurs between the two. Since there is no current, no current flows.

However, as shown in FIG.
When a voltage is applied between the two layers, the B-doped diamond layer and the undoped diamond layer have a homojunction, and there is no discontinuity in the valence band. Is implanted into the region. Then, since the holes reach the B-doped diamond layer on the opposite side, a current flows.
This is called a space charge limiting current, and its current density J can be calculated by the following equation 1.

[0017]

J = (9/8) με (V ² / L ³ ) J: Current density (A / cm ² ) μ: Mobility (cm ² / V · s) ε: Dielectric constant of material (F / cm) V: applied voltage (V) L: thickness (cm) of a region through which current flows.

For example, the mobility of holes in diamond is 1600 (cm ² / V · s) and the relative permittivity is 5.7 (that is, the permittivity ε = 5.7 × 8.85 × 10 ^-14 ( F / c
m)), assuming that the thickness of the undoped diamond layer between the B-doped semiconductor layers is 0.5 (μm) and the applied voltage is 1 V,
Leakage current (leakage current) occurs due to the space charge limited current of 7.27 × 10 ³ (A / cm ² ). The value of the current density is a current amount that cannot be neglected as a leakage current, and causes a malfunction due to interference between elements.

Therefore, in order to completely separate the elements from each other and to prevent a malfunction, it is necessary to intentionally introduce a hole trap into the undoped diamond region to suppress a leakage current due to a space charge limited current. In diamond semiconductors, it has been clarified that nitrogen functions as a donor and has a function of compensating for B that functions as an acceptor. Thus, the present inventors have found that nitrogen introduced into diamond acts as a trap for holes passing through the diamond valence band. When holes flow into the region containing nitrogen from the B-doped semiconductor diamond layer side by injection, nitrogen acting as a trap captures the holes, so that the diamond semiconductor layer can be element-isolated.

Normally, the doping concentration of a B-doped semiconductor diamond layer used as a semiconductor layer is 1 × 10 ¹⁷ c
m ⁻³ or more, and the activation rate at room temperature is about 0.1%.
× 10 ¹⁴ cm ^-3 can be considered. Therefore, even if nitrogen is introduced into the element isolation region at an atomic concentration of less than 1 × 10 ¹⁴ cm ⁻³ , this region cannot function as a trap capable of completely capturing holes. On the other hand, if nitrogen is introduced into the diamond beyond the atomic concentration of 1 × 10 ²¹ cm ⁻³ , the diamond layer is graphitized and cannot exist as diamond.
Therefore, the atomic concentration of nitrogen introduced between the element regions in diamond is set to 1 × 10 ^{14 to} 1 × 10 ²¹ cm ⁻³ .

Since the insulating region for isolating the diamond semiconductor layer must be formed in a specific region, it is preferable to use an ion implantation method as a method for introducing nitrogen into diamond. . According to the ion implantation method, it becomes possible to introduce nitrogen into a fine region by using an appropriate mask material,
By controlling the acceleration energy and the dose (implantation amount), the atomic density of nitrogen in diamond and the profile in the depth direction can be arbitrarily set. In addition, a nitrogen-doped diamond region having a uniform concentration can be formed by performing ion implantation a plurality of times while changing the acceleration energy and the implantation amount.

Further, when the diamond layer is subjected to a high-temperature heat treatment in vacuum after the ion implantation, defects on the surface of the diamond layer caused by nitrogen ion implantation can be removed and nitrogen is moved to a lattice substitution position. This can increase the percentage of nitrogen acting as a trap. The temperature of this heat treatment is 80
If the temperature is lower than 0 ° C. or the heat treatment time is shorter than 1 minute, nitrogen cannot sufficiently act as a hole trap. Therefore, when nitrogen is introduced into the diamond layer by ion implantation, it is preferable to perform a high-temperature heat treatment at a temperature of 800 ° C. or more in a vacuum for 1 minute or more after the ion implantation.

Furthermore, when the ion implantation method is used, the graphite layer (non-diamond layer) near the diamond surface generated by ion bombardment has conductivity, so that the element region in the diamond layer must be separated. It is desirable to remove this graphite layer. However, since N is lighter than Ar, its ion bombardment is small and the formation of a graphite layer is small. The graphite layer generated on the diamond surface can be removed by performing heat treatment at 500 ° C. or higher in an oxidizing atmosphere, acid cleaning, or oxygen plasma treatment.

As described above, in the present invention, since the element regions can be completely insulated from each other, a diamond transistor circuit, an integrated circuit of a diamond transistor and a diamond sensor, a logic circuit using a diamond diode, a diamond light emitting diode array, etc. Can be formed in a large amount on one substrate having a semiconductor diamond layer, and a malfunction due to interference between elements does not occur.

[0025]

The results of the element separation of the semiconductor diamond layer by the method of the present invention will be described below.

FIG. 2 is a plan view showing the shape and size of a region for implanting B ⁺ ions into the single crystal diamond layer used in this embodiment. In this embodiment, for example,
B ⁺ ions were implanted into a 1 mm × 0.5 mm pair of rectangular element regions 2 a and 2 b in a 4 mm × 4 mm single crystal (001) insulating diamond layer (Type Ia) 1. The distance between the element region 2a and the element region 2b is 0.5 μm.
The acceleration voltage during ion implantation was 60 kV, and the dose (implanted amount) was 4 × 10 ¹⁶ cm ⁻² . As a mask for ion implantation, a gold (Au) mask formed by photolithography was used.

Next, after the Au mask is removed, 10 B is applied in a vacuum to activate B as an acceptor.
Heat treatment was performed at a temperature of 00 ° C. for one hour. Next, a heat treatment was performed at a temperature of 500 ° C. for 5 minutes in the air in order to remove a graphite layer generated by damage due to ion implantation. At this time, B in the diamond
Ion Mass Spectrometry (Secondary Ion Mass Spectrometry)
When measured by Spectroscopy (SIMS), 1 × 10 ²⁰ cm ⁻³ of B was detected in the surface layer.

[0028] Then, the region B ⁺ ions are injected (element regions 2a and 2b) is coated with Au mask, by the N ⁺ ions are implanted into a region excluding the region B ⁺ ions were implanted, an insulating An area was formed. At this time, the acceleration voltage for ion implantation was fixed at 60 kV, and the dose (injection amount) was changed to form a sample having insulating regions with different atomic densities. Then, the sample subjected to the ion implantation is subjected to a heat treatment at a temperature of 800 ° C. for 10 minutes in a vacuum, and further subjected to an oxidation treatment at a temperature of 500 ° C. for 5 minutes in the air. Then, the graphite layer on the surface of the diamond layer generated by ion implantation was removed. Table 1 below shows the nitrogen dose amount of each sample and the nitrogen atom density on the diamond layer surface measured by SIMS after the removal of the graphite layer. However, the sample No. Reference numeral 4 denotes a case where nitrogen ions were not implanted.

[0029]

[Table 1]

Thereafter, an Au / Ti laminated electrode is formed on the B-doped semiconductor diamond layer (device regions 2a and 2b) by sputtering deposition, and the current-voltage (IV)
The properties were measured.

FIG. 3 is a graph showing the current-voltage characteristics between the element regions of each sample by logarithmic values, with the vertical axis representing the current and the horizontal axis representing the voltage. The numbers in the graph indicate the sample Nos.
Is shown. As shown in FIG. Sample No. 4 in which the atomic density of nitrogen in the surface layer of the diamond layer is 4 × 10 ¹⁹ cm ⁻³ or less. Comparing 2 and 3, as the atomic concentration of nitrogen is increased, the voltage value when the leakage current is generated for the first time is also increased. That is, when a high voltage is applied, a current flows between element regions.

However, if the atomic density of nitrogen is 5 × 10
^{At 20} cm ^-3 , no leakage current occurred between the element regions even when a high voltage was applied. Thus, when nitrogen is introduced into diamond at an appropriate concentration, a semiconductor device having excellent characteristics in which element regions are completely separated from each other can be manufactured.

Next, the sample no. Under the same conditions as in 1, B
A doped semiconductor diamond layer (element region) was formed, and nitrogen ions were implanted between the element regions to form an insulating region. Then, three kinds of post-ion implantation processes shown in Table 2 below were performed on these three samples.

[0034]

[Table 2]

After these heat treatments and oxidation treatments, an Au / Ti laminated electrode is formed on the B-doped semiconductor diamond layer (element region) by sputtering deposition.
Voltage (IV) characteristics were measured.

FIG. 4 is a graph showing the current-voltage characteristics between the element regions of each sample in logarithmic values, with the vertical axis representing the current and the horizontal axis representing the voltage. The numbers in the graph indicate the sample Nos.
Is shown. As shown in FIG. In No. 5, the element regions were completely insulated from each other, and no leakage current occurred.

On the other hand, the sample No. 6 has a heat treatment temperature of 80
Since the temperature was lower than 0 ° C., it was not possible to completely insulate between the element regions. This indicates that it is necessary to perform a heat treatment at 800 ° C. or higher in order for nitrogen to function as a hole trap. Sample N
o. In No. 7, since the oxidation treatment for removing the graphite layer formed by ion implantation was not performed, insulation between the element regions could not be made, and a large leakage current occurred. This indicates that the diamond surface was converted to graphite due to the damage due to the nitrogen ion implantation, thereby providing conductivity between the element regions.

Therefore, when nitrogen is introduced by ion implantation, heat treatment is performed at an appropriate temperature, and the graphite layer formed on the surface of the diamond layer by the oxidation treatment is removed, thereby completely removing the element regions. A semiconductor device having improved characteristics can be manufactured.

[0039]

As described in detail above, according to the present invention,
Since nitrogen is introduced at an appropriate atomic concentration between the electronic element regions composed of the p-type semiconductor diamond layer into which B has been introduced, it is possible to completely isolate the electronic element regions of the diamond semiconductor device. Thus, even when a plurality of electronic elements are formed on the same substrate, it is possible to prevent a malfunction due to interference between the elements. When a transistor, a thermistor, a diode, an optical sensor, a light-emitting element, and the like are formed in this electronic element region, a high-performance diamond integrated circuit can be obtained.

According to the method of the present invention, when nitrogen is introduced between electronic element regions by ion implantation, an insulating region can be formed with a desired atomic concentration and a fine region. By performing the processing, the element regions can be completely insulated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing energy bands of two B-doped semiconductor diamond layers and an insulating undoped diamond layer sandwiched between the layers.

FIG. 2 is a plan view showing the shape and size of a region for implanting B ⁺ ions into a single crystal diamond layer used in this example.

FIG. 3 is a graph showing a current-voltage characteristic between element regions of each sample as a logarithmic value, with the vertical axis representing current and the horizontal axis representing voltage.

FIG. 4 is a graph showing current-voltage characteristics between element regions of each sample in logarithmic values, with current being plotted on the vertical axis and voltage on the horizontal axis.

[Explanation of symbols]

 1; diamond layer 2; element region

Claims (9)

[Claims] 1. An electronic device comprising a p-type semiconductor diamond layer into which B has been introduced, wherein 1 × 10 ^{14 to} 1 × 10
A diamond semiconductor device having an insulating region containing nitrogen at an atomic concentration of ²¹ cm ^-3 . 2. The diamond semiconductor device according to claim 1, wherein said nitrogen is introduced into said diamond layer by ion implantation. 3. A transistor, wherein:
3. The diamond semiconductor device according to claim 1, wherein at least one kind of electronic element selected from the group consisting of a thermistor, a diode, an optical sensor, and a light emitting element is formed. Wherein B between the electronic element regions consisting of p-type semiconductor diamond layer is introduced, 1 × 10 ¹⁴ to 1 × 10
^A method for manufacturing a diamond semiconductor device, wherein an insulating region is formed by introducing nitrogen at an atomic concentration of ²¹ cm ^-3 . 5. The method according to claim 4, wherein the nitrogen is introduced into the diamond layer by ion implantation. 6. After the ion implantation, a vacuum is applied
Heat treatment at a temperature of 00 ° C. or more for 1 minute or more,
6. The non-diamond layer on the surface of the diamond layer generated by the ion implantation is removed.
3. The method for manufacturing a diamond semiconductor device according to item 1. 7. The method according to claim 6, wherein the non-diamond layer is removed by performing a heat treatment at a temperature of 500 ° C. or more in an oxygen-containing atmosphere. 8. The method according to claim 6, wherein the non-diamond layer is removed by acid cleaning. 9. The method according to claim 6, wherein the non-diamond layer is removed by oxygen plasma processing.