JP2003133579A - Ultraviolet sensing element, manufacturing method therefor and ultraviolet sensing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a further improved ultraviolet sensing element whose manufacturing process is simple, capable of front surface irradiation without being provided with a buffer layer and capable of reliable ultraviolet sensing and measurement for obtaining the ultraviolet sensing element by using a gallium nitride (GaN) semiconductor element having various merits, and to provide its manufacturing method and an ultraviolet sensing system including the ultraviolet sensing element. SOLUTION: Relating to the ultraviolet sensing element and its manufacturing method, the ultraviolet sensing element is provided with a substrate containing sapphire or silicon materials; a light absorbing layer containing the gallium nitride (GaN) epitaxially grown on the substrate; an ohmic junction layer ohmic- junctioned to a partial area of the light absorbing layer and containing one material selected from among gold (Au), aluminum (Al) and a titan/aluminum double layer; and a Schottky joining layer constituted of a nickel oxide (NiOx) by vapor-depositing nickel (Ni) separately from the ohmic junctioned layer at the upper part of the light absorbing layer and heat-treating the vapor- deposited nickel (Ni).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet sensing device, a method for manufacturing the same, and an ultraviolet sensing system including the ultraviolet sensing device, and more particularly, a Schottky device including gallium nitride (GaN).
y) An ultraviolet sensing device having a junction, a method of manufacturing the same, and an ultraviolet sensing system including the ultraviolet sensing device.

[0002]

2. Description of the Related Art Generally, ultraviolet ray sensing elements are used in commercial fields such as heat sensing sensors and flame sensing sensors, in medical fields such as sterilization sensing and ultraviolet ray sensing, and in missile guidance sensors, submarine detection, and jet engine operation. It is used in various fields such as aerospace, communication, and military fields such as sensing, and is particularly noteworthy because it can be applied to environmental fields such as nuclear power plants and earth ozone layer sensing. Is.

As such an ultraviolet sensing element, a PMT (Photomultiplier) is generally used.
A tube type device has been used, which has the advantage of less signal amplification and less noise, but its large size requires a large foot-print and has a complicated internal structure. However, the application field is limited because it has a disadvantage that a high temperature is generated when a high pressure is applied and a separate cooling device for cooling the high temperature is required.

Therefore, an ultraviolet sensing device using a semiconductor device has been developed, which enables miniaturization.
The free electrons and holes in the semiconductor are excited through the light energy applied to the semiconductor to generate an internal electric field.
After separating them along the opposite polarity by c field), they are detected as an electric signal through photoelectric conversion performed in the process of collecting them by an external electrode. The semiconductor materials usually used at this time are silicon (Si), silicon carbide (SiC), selenium (Se), etc., but such semiconductor materials have relatively low forbidden band (i).
Since it has ndirect bandgap, it has a low quantum efficiency and frequently reacts with visible light other than ultraviolet light, and thus has a problem that thermal and chemical safety are particularly lowered.

Therefore, an ultraviolet sensing device using a gallium nitride (GaN) semiconductor material having a larger forbidden band has been developed.
aN) has a very large energy bandgap of about 3.4 eV, so that it is possible to selectively detect light having a visible light wavelength and an ultraviolet light wavelength, and particularly thermal,
Al _x GaN _1-x N (3.4 to 6.n), which has very high chemical safety, can be used even in a bad environment, and can adjust the detection wavelength. 2e
It is easy to form a ternary compound such as V) and is in the spotlight as a material for a new ultraviolet sensing element. Such gallium nitride (GaN) is a substance that is usually used as a blue light emitting device, but it has characteristics that it can be applied not only to blue light emission but also to the development of an optical device that reaches the ultraviolet region due to a change in composition. , Has been actively researched and developed all over the world with the help of the development of light emitting devices using nitride semiconductors, and its application range has been expanded to light receiving devices and high temperature electronic devices.

However, in an existing ultraviolet sensing device using such a general gallium nitride (GaN) semiconductor device, an internal electric field is provided to separate electrons and holes generated by the ultraviolet light applied to the device. A junction having different energy levels, such as a pn junction or a Schottky junction, is required. However, in the case of a pn junction structure, it is generally difficult to grow and dope a p-type absorber layer in a broadband semiconductor. , P-type gallium nitride (GaN) has a drawback that ohmic junction is difficult and the junction resistance is large. That is, generally, if a gallium nitride (GaN) broadband semiconductor is doped with an acceptor, it is not easy to form a p-type light absorption layer such as an insulating layer without forming a p-type semiconductor. There is a drawback that a separate heat treatment process and a treatment process are required to form the type semiconductor.

The gallium nitride (GaN)
In the case of a Schottky junction structure formed by joining gold (Au), nickel (Ni), tungsten (W), or the like, which is a metal material suitable for a semiconductor, the structure or the structure is relatively larger than that of the pn junction described above. Although the manufacturing process is simple, the front irradiation method cannot be used due to the light loss due to the absorption of ultraviolet rays by these metals, and thus the back irradiation method of irradiating ultraviolet rays through the substrate is used.

On the other hand, general gallium nitride (Ga)
N) Although a sapphire has been used as a substrate for a Schottky junction UV sensing device using a semiconductor, in order to overcome the difference in thermal expansion coefficient between the sapphire substrate and the nitride semiconductor, a sapphire substrate is usually used. A buffer layer made of aluminum nitride (AlN) or gallium nitride (GaN).
layer) on which a light absorption layer for absorbing ultraviolet light, gallium nitride (GaN) or G, is formed.
Grow axAl1-xN.

This will be described with reference to the drawings.
FIG. 2 is a schematic structural diagram of an ultraviolet sensing element proposed by Han et al., showing a substrate 1 and a Ga on top of it as shown.
A buffer layer 2 made of aluminum nitride (AlN) or the like for buffering the mismatch of the thermal expansion coefficient with the xAl1-xN light absorption layer 3 is arranged, and GaxAl1- is again provided on the aluminum nitride (AlN) buffer layer 2. The xN light absorption layer 3 is grown to a thickness of about 2 μm. After that Au / Ti
An ohmic layer in which the Schottky layer 4 is joined using W / Au of 100Å / 1000Å / 5000Å, and is ohmic-joined using gold (Au) on the light absorption layer 3 so as to be separated from the Schottky layer 4. Place 5.

However, since metal such as Au / TiW / Au is used as the material of the Schottky junction layer 4 in a general ultraviolet sensing element having such a structure,
Front illuminating for UV sensing
When the ionization method is used, since the metal absorbs ultraviolet rays and precise ultraviolet ray detection is not possible, a back illumination method of irradiating ultraviolet rays through the substrate is adopted to avoid this. However, even in such a backside irradiation method, ultraviolet rays are depleted by a depletion layer near the Schottky junction layer 4.
Before reaching the edge, the light is absorbed by the light absorption layer 3 to cause an ultraviolet loss.

That is, gallium nitride (Ga)
N) Absorption coefficient (absorption co) of the light absorption layer
Efficient) is approximately 1 × 10 5 cm ⁻¹ , so that 67% of the incident light is absorbed if it passes through a light absorption layer having a thickness of 0.1 μm, and 0.2 μm is obtained.
In the case of m thickness, 86% is absorbed. After all, when the thickness of the light absorption layer is 1 μm or more, the actual amount of ultraviolet rays reaching the depletion layer near the Schottky junction layer becomes very small, and effective ultraviolet ray detection is difficult. Further, the range where the photoexcited electrons and holes are captured by the external electrode and can be converted into an electric signal is the diffusion distance (diffus) of the depletion layer and the electrons.
However, considering the fact that the electron diffusion length of gallium nitride (GaN) is about 0.2 μm, the existing backside irradiation method can eliminate most of the photoexcited free electrons and holes. There is a problem that it cannot be converted into a sufficient electric signal because it is recombined before being captured by the external electrode.

Also, when packaging the ultraviolet sensing element chip having the above-described structure, it is necessary to form a hole through which the ultraviolet ray can pass in the mount, which complicates the manufacturing process. In order to reduce the price of silicon, silicon (S
The energy band gap is 3.0 eV as in i)
When a substrate having a wavelength (λ) = 410 nm or less is used, a phenomenon in which ultraviolet rays to be sensed are mostly absorbed by the substrate and cannot serve as an ultraviolet sensing element is frequently observed. Therefore, the UV sensing device having various structures has been newly proposed, but the conventional UV sensing device including the structure proposed by Khan commonly includes a buffer layer for high-quality growth of the light absorption layer. It has a disadvantage that the process is complicated.

[0013]

SUMMARY OF THE INVENTION Therefore, according to the present invention, when a gallium nitride (GaN) semiconductor device having various advantages is used to realize an ultraviolet sensing device, front irradiation is possible without including a buffer layer. An object of the present invention is to provide an ultraviolet sensing device capable of more reliable ultraviolet sensing and measurement, a simple manufacturing process thereof, an improved ultraviolet sensing device, a method of manufacturing the same, and an ultraviolet sensing system including the ultraviolet sensing device. There is.

[0014]

The present invention has been devised in order to achieve the above-mentioned object, and a substrate made of one material selected from sapphire or a silicon substrate is used as an ultraviolet sensing element. A light absorbing layer made of a material containing gallium nitride (GaN) having a thickness of 1.5 μm to 2.5 μm epitaxially grown on the substrate; and an ohmic layer on a part of the light absorbing layer. An ohmic contact layer which is bonded and contains one material selected from gold (Au), aluminum (Al), and titanium / aluminum double layer (Ti / Al) having a thickness of 950Å to 1050Å; 15 is formed on the upper surface of the ohmic contact layer by a Schottky junction apart from the ohmic contact layer.
An ultraviolet sensing device having a Schottky junction layer having a thickness of 0Å to 300Å and a material selected from tungsten (W), nickel (Ni), and indium tin oxide (ITO).

At this time, if the ohmic contact layer is made of one material selected from gold (Au) and aluminum (Al), the thickness thereof is 950 to 1, respectively.
When the titanium / aluminum double layer is 050Å, the titanium has a thickness of 50 to 150Å, the aluminum has a thickness of 850 to 950Å, and the material of the Schottky junction layer is tungsten (W). The thickness of the Schottky junction layer is 250 to 350 Å, and the thickness of indium tin oxide (ITO) is 200 to 300 Å. Ni), depositing nickel (Ni) having a thickness of 250 to 350Å on the light absorption layer,
The deposited nickel (Ni) is heat-treated to form nickel oxide (NiOx), and indium tin oxide (ITO) is formed on the upper portion of the deposited nickel (NiOx) to reduce series resistance.
It is characterized by further including a series resistance reduction layer.

Further, according to the present invention, a substrate, a light absorbing layer epitaxially grown on the substrate, an ohmic contact layer ohmic-bonded to a partial region on the light absorbing layer, and the light absorbing layer are provided on the light absorbing layer. As a method of manufacturing an ultraviolet sensing device including a Schottky junction layer that is Schottky junction separated from an ohmic junction layer, cleaning the substrate; and epitaxially growing a light absorption layer on the cleaned substrate. Ohmic bonding a metal to a portion of the epitaxially grown light absorbing layer; and Schottky bonding a Schottky junction layer on the light absorbing layer so as to be separated from the ohmic junction layer. Provided is a method of manufacturing an ultraviolet sensing element including:

At this time, the substrate is made of one material selected from sapphire and silicon, and the light absorbing layer epitaxially grown on the substrate has a thickness of 1.5 μm to 2.5 μm gallium nitride. Ride (Ga
N), and the ohmic contact layer to be bonded on the light absorption layer is gold (Au), aluminum (Al), or titanium / aluminum double layer having a thickness of 950Å to 1050Å. The material of the Schottky junction layer, which is joined to the light absorbing layer so as to be separated from the ohmic junction layer, is 150Å to 300.
Å Tungsten (W), Nickel (N
i), one material selected from indium tin oxide (ITO), nickel (Ni) on the light absorption layer when the material of the Schottky junction layer is nickel (Ni). Is deposited, and the deposited nickel (Ni) is heat-treated to form nickel oxide (Ni
Ox) and further includes an indium tin oxide (ITO) series resistance reducing layer on the top of the structure for reducing series resistance.

The present invention also provides, as an ultraviolet sensing system, a substrate, a light absorption layer epitaxially grown on the substrate, an ohmic contact layer ohmic-bonded to a partial region on the light absorption layer, An ultraviolet ray sensing device including a Schottky junction layer on the light absorption layer, the Schottky junction layer being spaced apart from the ohmic junction layer and performing a Schottky junction, and sensing an emitted ultraviolet ray to generate a current having a different magnitude depending on its intensity. An ultraviolet sensing system including: an element; a converter for applying a current generated by the ultraviolet sensing element to convert and amplify the voltage into different voltages; and a display for displaying a message through the voltage amplified and converted by the converter. The display unit includes a plurality of electroluminescent devices having different colors, each of which emits light through a different voltage applied by the conversion unit; Characterized in that it is a liquid crystal display device for displaying different messages through different voltages applied in parts.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

The present invention complements the disadvantage that the performance of the device is deteriorated due to the large absorption coefficient of gallium nitride (GaN) in the existing backside irradiation method by using the metal bonding material and performing the Schottky bonding. In order to provide an ultraviolet sensing device capable of front-irradiating ultraviolet rays by increasing the transmittance of ultraviolet rays by oxidizing the metal bonding material to form a metal oxide, and a method of manufacturing the same. The ultraviolet sensing element according to the present invention has a structure as shown in FIG.

FIG. 2A is a cross-sectional view showing the structure of the ultraviolet sensing element according to the present invention, which is a substrate 21 and
Light absorbing layer 2 epitaxially grown on the substrate 21
2, a Schottky junction layer 24 that is Schottky junctioned with a partial region on the light absorption layer 22, a conductive thin film layer 26 above the Schottky junction layer 24, and the Schottky junction layer 24. An ohmic contact layer 25 is formed on the absorption layer 22 to form an ohmic contact. At this time, the ohmic contact layer 2 is included.
5 may have a structure in which a Schottky junction layer 24 is placed between them as shown in FIG.

Since the ultraviolet sensing device according to the present invention does not use the p-type gallium nitride (GaN) method by utilizing the Schottky junction structure, the p-type
Type doping and ohmic contact problem of p-type gallium nitride (GaN) can be avoided, the device fabrication process can be simplified, and high quantum efficiency can be obtained because the front irradiation method is used. When the Schottky junction layer is made of an oxide, the process can be further simplified, which is advantageous in mass production.

Hereinafter, the manufacturing process of the same will be described in more detail with reference to the drawings. FIG. 3 is a flow chart showing a manufacturing sequence of the ultraviolet sensing device according to the present invention.
3 is a process diagram of a UV sensing device according to the present invention manufactured according to the sequence diagram of FIG. 3, which includes a substrate 21 and cleaning and inspecting the substrate 21 (S1).
Epitaxially growing a gallium nitride (GaN) light absorption layer 22 on the first layer (S2), and forming an ohmic junction layer 25 in a partial region on the gallium nitride (GaN) light absorption layer 22 (S2). S3), forming a Schottky junction layer 24 so as to be spaced apart therefrom (S4), forming a conductive thin film 26 on the Schottky junction layer 24 (S5), and packaging. The process is divided into a metal pad forming and physical processing step (S6) for packaging and a packaging step (S7), which will be described in order.

First, in the step of providing a substrate 21 and epitaxially growing gallium nitride (GaN) on the substrate 21 (S2), the substrate 21 is preferably made of sapphire or silicon. HVPE (Hydride Vapo) with a high epitaxial layer growth rate on a transparent sapphire or silicon substrate 21.
r Phase Epitaxy) process, preferably about 5 to 1 at a temperature of 1000 to 1100 ° C.
The gallium nitride (GaN) light absorption layer 22 is grown to a height of about 2 μm for 0 minutes.

Thereafter, such gallium nitride (G
aN) An ohmic junction layer 25 is formed on a partial area of the upper portion of the light absorption layer 22 (S3), and a photoresist having a predetermined thickness is applied on the gallium nitride (GaN) light absorption layer 22. The pattern is formed by using an electron beam evaporator or a thermal-evaporator along a photoresist pattern formed by gold (Au), aluminum (Al), titanium aluminum (aluminum). The ohmic junction layer 25 may be formed by a lift-off method after depositing one metal selected from Ti / Al). At this time, especially when a thermal evaporator is used, the basic pressure (Based-pres)
Sure) 1.0 × 10 ⁻⁵ torr, 1000 Å for gold (Au) at room temperature, 1 for aluminum (Al)
000Å, titanium / aluminum double layer is 100Å each
It is desirable to form it with a thickness of about / 900Å.

5 (A) and 5 (B) and FIG. 6 (A),
FIG. 6B, FIG. 7A, and FIG. 7B show the inspection results of the ohmic characteristics and the junction resistance of the ohmic junction layer 25 made of the Au, Al, or Ti / Al material described above. 5 is a graph showing the ohmic characteristics of Au, which is obtained by depositing the Au in order to examine the ohmic characteristics of Au and then examining the ohmic characteristics while changing the heat treatment temperature of the Au.
As shown in (A), the gallium nitride (GaN) junction shows a clear IV characteristic of rectification characteristics related to the characteristics of the Schottky barrier layer, and the current-voltage characteristics change linearly depending on the heat treatment temperature. Was confirmed. Especially 575
When heat-treated at ℃ for 10 minutes, Au on the GaAs substrate
It was observed that a similar appearance to the result of contacting was observed. When the heat treatment temperature was fixed at 600 ° C. and the time was changed, the time was increased to 1, 5, 10 minutes and
It can be seen that the −V curve again exhibits a rectifying characteristic tendency.

The result of measurement of the junction resistance of the Au ohmic junction layer by the TML method is shown in FIG. 5B, which shows a value of about 1.14 × 10 ⁻⁴ Ω / cm ² . .

FIGS. 6A and 6B are graphs showing the inspection results of the ohmic characteristics and the junction resistance of the Al ohmic junction layer, where Al is ohmic even if heat treatment is performed at a low temperature. And has a lower contact resistance than Au, has good adhesiveness to gallium nitride (GaN), and has a lift-off (lift-o).
ff) It has been well known that the substance is useful as an element, but it shows the lowest resistance value at a heat treatment temperature of 430 ° C., and the junction resistance value at this time is 3.45 × 10.
^It showed ⁻³ Ω / cm ² . Moreover, the temperature was raised to 480.
It shows a resistance value higher than 430 ℃ at 10 ℃ and 10 at 430 ℃.
It can be confirmed that the case of heat treatment for 5 minutes shows a higher resistance value than the case of heat treatment for 5 minutes and has a similar appearance to the case of using Au.

Further, FIGS. 7A and 7B respectively show T
3 is a graph showing ohmic characteristics and junction resistance of an i / Al ohmic junction, wherein such Ti / Al has a junction resistance value of 10 ⁻⁴ to 10 ⁻⁷ Ω / c depending on heat treatment conditions.
gallium nitride (Ga) having a low value of about m ^2.
Since it is a material that has very good bonding characteristics with N),
As shown in (A), it exhibits linear ohmic characteristics when heat-treated at 430 ° C. and 530 ° C. for 5 minutes, and the junction resistance at this time shows 2.8 × 10 ⁻⁵ Ω / cm ² value. It can be confirmed that is a lower value than when Au or Al is used. Therefore, Ti / Al has excellent bonding characteristics with gallium nitride (GaN) and can be used as a lift-off device.

After that, a photoresist pattern is formed again on the substrate 21 to form the Schottky junction layer 24, and then a metal or a metal oxide is attached using a sputter or an electron beam evaporator. (S4), the present invention is divided into several examples according to the metal material to be Schottky bonded. Therefore, the present invention will be described separately. In the present invention, tungsten having high thermal safety ( W) and indium tin oxide (IT
O) and nickel oxide (NiOx) were used.

[0031]First embodiment First of all, the metal used for the Schottky junction according to the present invention
Tungsten (W) is used.
The Schottky junction layer preferably has a basic pressure of 1.0 ×
10^-6torr, process pressure (work-pressu
re) 2.0 × 10^-3with about torr, room temperature
300 Å using a sputter device with a temperature environment of 100 degrees
A thin tungsten film having a thickness of 100 μm. like this
Dark current characteristics of a Schottky junction made of pure tungsten
10 as shown in FIG.^-8Small leakage current
(Leakage current)
I can accept it.

[0032]Second embodiment The present invention also uses conductive oxide as a Schottky junction metal.
Indium tin oxide (ITO) film is used
However, this is preferably a basic pressure of 1.0 × 10^{− 5}tor
and using an electron beam vapor deposition machine with a room temperature environment of 25
Indium tin oxide (I having a thickness of about 0Å
TO) implements a Schottky junction layer. At this time,
Indium tin oxide (ITO) Schottky junction layer
The dark current characteristics of 10 are as shown in FIG.^-3Value of degree
Show.

[0033]Third embodiment Finally, the present invention provides a metal oxide as a Schottky junction metal.
NiOx, which is a material, is used.
Electric furnace, preferably Ni at 430 ° C.
Can be obtained by exposing for 5 minutes.
The NiOx obtained through the process will be described in the first embodiment described above.
Using a sputter device, the temperature should be 100 each under the same pressure.
℃, 150 ℃, 200 ℃ controlled 150 Å, 250
Å, 350Å thickness and then the transparency and dark
The results of examining the flow characteristics are shown in FIG. 10 (A) and FIG. 10 (B).
Showed each.

On the other hand, since the transmittance of the deposited Schottky junction material is an important factor for having a structure of irradiating light from the front surface of the device in order to enhance the quantum efficiency, the deposition of the different thicknesses described above is performed. Nickel oxide (NiO
10A in which the transmittance of x) is measured, the transmittance is measured after heat treatment of vapor-deposited NiOx at 430 ° C. As a result, the thickness of 300 Å or less shows 80% or more, It was confirmed that the thickness showed a lower transmittance, and the thickness of 400 Å showed a transmittance of about 60% based on 350 nm. Further, as shown in FIG. 10B, the IV measurement showed a low dark current of about pA, confirming that the device was suitable for fabrication, but it is desirable that the transmittance is 80% or more when heat-treated. Therefore, it is advantageous to use NiOx having a thickness of 300Å whose thickness can be easily adjusted.

The Schottky junction layer 24 constructed according to each of the above embodiments is patterned by a lift-off method, and Ni used for the Schottky junction is particularly used.
In the case of Ox, the resistance value of itself is very high, so that the series resistance value is very high when applied to the device, which causes the performance of the device to be deteriorated. Deposition on NiOx is possible through the electron beam evaporator described above.

Thereafter, such a substrate is packaged, but in the case of ITO which is the conductive thin film 26, it is not shown in the drawing because the bonding property with an Au wire (wire) formed in a packaging process described later is deteriorated. However, it is desirable that Au be vapor-deposited on the ITO conductive thin film 26 to complement this, and Al can be used at this time, but since the wire bonding characteristic of Al metal is lower than that of Au, it is desirable to use Schottky. Au is vapor-deposited on the bonding layer 24 and the ohmic bonding layer 25. In particular, in the case of the ITO conductive thin film 26, it is advantageous to further include a Cr bonding layer between the ITO conductive thin film 26 and the Au bonding layer in order to assist the bonding with Au.
0 ^-5 torr, using a thermal deposition machine having a room temperature environment Au is 1000 Å, Al is 1000 Å, Ti / Al is deposited to each be of the order of 100 Å / 900 Å thick.

Thereafter, a physical processing process is performed to separate and package the ultraviolet sensing device manufactured through the above process into chips (S6). That is, to obtain a desired thickness and smoothness, a small flaw (scr
polish for removing cracks that may occur in the device during the cutting process described later by removing atch).
ping) and a cutting process for separating the chip into individual devices according to the determined size of the chip. At this time, the polishing step is preferably performed on a sapphire or silicon substrate having a thickness of about 340 μm by 100 μm or less (9
0 μm), first use diamond pellets to less than 110 μm, then use eccentric weights to adjust the smoothness and adjust the thickness and smoothness every 10 minutes to avoid overloading the element. Adjust while checking.
Further, in the subsequent cutting step, it is desirable to cut while maintaining a low cutting speed of about 0.5 to 0.7 mm / sec.

In particular, since it is advantageous to further include a step of cleaning the substrate with an organic material at each stage, it is advantageous that particle contamination of the device can be reduced. Therefore, only a gallium nitride (GaN) semiconductor layer is preferably formed. Substrate is 100 ℃, TCE, ACE, MeOH 5 each
Minute, ultrapure water cleaning solvent (DI water) and BOE
(Buffered oxide etcher) 1
After cleaning for 0 minutes, it is blown with N ₂ gas.
To do. Lithography for forming an ohmic contact layer and a Schottky contact layer.
In step T1, without using HMDS, the PR coating was rotated at 400 RPM for 5 seconds at 3500R.
It is exposed for 35 seconds under a rotation of PM, and then baked at 110 ° C. for 30 minutes.
ing), and then apply light having an intensity of about 12 mW to 12
It is exposed for sec seconds and developed in a stock solution for 20 seconds.

At this time, as a result of examining the electrical characteristics of the ultraviolet sensing element according to the present invention, the leakage current is 10
It was confirmed that the ultraviolet sensing element according to the present invention showed a low value of about ^-12 amps, which is about 365 nm.
It was found that the light was cut-off in the wavelength band of 1, and did not react to visible light, but only to ultraviolet light.

The quantum efficiency of the device is 0.04 A / W.
The breakdown voltage is shown in the reverse direction even if it is about -40V.
Does not appear, especially when ITO is used, leakage current
10 ^-3Although it has a high value, it is 10 in the case of NiOx.
^-11Sure that you can get very low values
I was able to recognize it.

The present invention also provides an ultraviolet sensing system including an ultraviolet sensing element constructed through the above-described manufacturing method, which is characterized by having a small size and a simple structure which are particularly portable.

That is, this is as shown in FIG.
An ultraviolet sensing element 52 that applies an ultraviolet ray to convert it into a photocurrent, and a converter 5 that amplifies the photocurrent generated by the ultraviolet sensing element and converts it into a voltage.
4 and a display unit 56 to which the voltage amplified by the conversion unit 54 is applied and which outputs a predetermined message to the user.

The ultraviolet sensing system 50 according to the present invention having the above structure is driven while the ultraviolet ray including the visible ray is applied to the ultraviolet ray sensing element 52. When such light is applied, the ultraviolet ray sensing element 52 is applied. When ultraviolet rays are detected while a current of nano-amperes or less is generated by visible light, a current of about micro-amperes is generated and applied to the conversion unit 54. At this time, the conversion unit 54 selectively senses only a predetermined value or more, that is, a current of several microamperes or more, converts the current into a predetermined voltage, amplifies it, and applies it to the display unit 56.
The display unit displays a message to the user by the voltage thus amplified to a constant value. At this time, preferably, the display unit 56 is an LCD (liquid c).
The display 56a and the LED 56b, which is an electroluminescent device, are used together, and in particular, the LED 56b.
Uses three colors, green, yellow, and red, to make it easier to recognize the intensity of UV light at present, and if it is too bright, it may not be seen well by the user's eyes.
LC with character display function to solve the problem of 56b
It is advantageous to equip D56a.

[0044]

The gallium nitride (GaN) ultraviolet ray sensing device using the metal oxide thin film according to the present invention is much simpler in manufacturing process than the existing sensing device and has excellent performance. It has the advantage that power is excellent.

Further, it is an improved device having a small installation area and having a structure of an element having an optimum quantum efficiency and capable of more reliable ultraviolet ray detection. In particular, the present invention provides a gallium nitride (GaN) thin film growth technique and a bonding process technique, and has an advantage of being indirectly utilized in the development of various electronic devices using the technique. It can be applied to the development of a P-type ohmic junction forming process for a ride (GaN) optical element. In particular, the present invention has the advantage that the import substitution effect and the export increase effect can be satisfied at the same time by developing an ultraviolet sensor that currently depends on imports, and the ultraviolet detection performance is excellent even without the buffer layer. Providing a device, which is different from the conventional use of metal for Schottky junction, has an excellent light-transmitting property, and provides an ultraviolet sensing device capable of front-side irradiation as well as back-side irradiation. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a general ultraviolet sensing element using gallium nitride (GaN).

2A is a sectional view showing a structure of an ultraviolet sensing element according to the present invention, and FIG. 2B is a sectional view showing another structure of an ultraviolet sensing element according to the present invention.

FIG. 3 is a flow chart showing the manufacturing process of the ultraviolet sensing device according to the present invention in order.

FIG. 4 is a process cross-sectional view showing, in sequence, a manufacturing process of an ultraviolet sensing element according to the present invention.

FIG. 5 is a graph showing the results of measuring ohmic characteristics and junction resistance when Au is used as the ohmic junction layer of the ultraviolet sensing element according to the present invention.

FIG. 6 is a graph showing the results of measuring ohmic characteristics and junction resistance when Al is used as the ohmic junction layer of the ultraviolet sensing element according to the present invention.

FIG. 7 is a graph showing the results of measuring ohmic characteristics and junction resistance when Ti / Al was used as the ohmic junction layer of the ultraviolet sensing element according to the present invention.

FIG. 8 is a graph showing dark current characteristics that appear when tungsten (W) is used as the Schottky junction layer of the ultraviolet sensing device according to the present invention.

FIG. 9 is a graph showing dark current characteristics that appear when indium tin oxide (ITO) is used as the Schottky junction metal of the ultraviolet sensing device according to the present invention.

FIG. 10 is a graph showing a transmittance and a dark current characteristic, which appear when nickel oxide (NiOx) is used as a Schottky junction metal of the ultraviolet sensing device according to the present invention.

FIG. 11 is a block diagram showing the structure of an ultraviolet sensing system according to the present invention.

[Explanation of symbols]

21: substrate 22: Light absorbing layer 24: Schottky junction layer 25: Ohmic junction layer 26: Conductive thin film layer

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Claims (6)

[Claims] 1. A substrate made of a material selected from sapphire or a silicon substrate as an ultraviolet sensing element; and gallium nitride having a thickness of 1.5 μm to 2.5 μm epitaxially grown on the substrate. A light absorbing layer made of a material containing a ride (GaN); gold (A) having a thickness of 950Å to 1050Å which is ohmic-bonded to a partial region on the light absorbing layer;
u), aluminum (Al), and an ohmic junction layer containing one material selected from titanium / aluminum double layers; nickel having a thickness of 250Å to 350Å separated from the ohmic junction layer on the light absorption layer. (Ni) is deposited, and the deposited nickel (Ni) is deposited.
And a Schottky junction layer formed of nickel oxide (NiOx) by heat treatment. 2. The material of the ohmic contact layer is gold (A
u) or one material selected from aluminum (Al), the thickness is 950Å to 10 respectively.
The UV sensing according to claim 1, wherein the titanium has a thickness of 50Å to 150Å and the aluminum has a thickness of 850Å to 950Å when the titanium / aluminum bilayer is 50Å. element. 3. The indium tin oxide (I) for reducing series resistance is formed on the Schottky junction layer.
The ultraviolet sensing device of claim 1, further comprising a TO) series resistance reduction layer. 4. A substrate, a light absorbing layer epitaxially grown on the substrate, an ohmic contact layer ohmic-bonded to a partial region on the light absorbing layer, and the ohmic contact layer on the light absorbing layer. And a step of cleaning the substrate, the step of epitaxially growing a light absorption layer on the cleaned substrate, the method comprising: Ohmic-bonding a metal to a portion of the epitaxially grown light absorbing layer; depositing nickel (Ni) on the light absorbing layer and separating the ohmic contact layer, and depositing the deposited nickel (Ni). ) Is heat treated to obtain nickel oxide (N
and a step of performing a Schottky junction on a Schottky junction layer made of iOx). 5. The substrate is one material selected from sapphire and silicon, and the light absorption layer epitaxially grown on the substrate is 1.5 μm to 2.5 μm.
The ohmic contact layer, which is made of a material including gallium nitride (GaN) having a thickness of μm, and has a thickness of 950Å to 1050Å is gold (Au), aluminum (Al), or titanium. / A Schottky junction layer, which is a material selected from the aluminum double layer and is joined to the light absorption layer so as to be separated from the ohmic junction layer, has a thickness of 150Å to 300Å. The method for manufacturing an ultraviolet sensing element according to claim 4. 6. The indium tin oxide (I) for reducing series resistance is formed on the Schottky junction layer.
The method of claim 4, further comprising the step of joining a (TO) series resistance reduction layer.