JP2011009292A - Ultraviolet sensor and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet sensor low in cost, stable in characteristic and high in response speed.SOLUTION: The ultraviolet sensor is of the type utilizing photoconductive effect of zinc oxide and is characterized in that the zinc oxide is additive-free zinc oxide and the half bandwidth of a diffraction peak in a (002) surface is not more than 0.5 degrees in an X-ray diffraction pattern of the zinc oxide. Thus, the low-cost and high-response-speed ultraviolet sensor can be achieved.

Description

  The present invention relates to an ultraviolet sensor using a carrier generated by irradiating a sensitive film with ultraviolet rays.

  2. Description of the Related Art Conventionally, there is an ultraviolet sensor in which zinc oxide is a main component and a light sensing unit is configured by a sintered body. For example, Patent Document 1 discloses an ultraviolet sensor that is a single crystal or polycrystal having zinc oxide as a main component and uses the a-plane of zinc oxide as a light sensing portion.

  On the other hand, there is an ultraviolet sensor using a zinc oxide thin film as a light sensing part. For example, Patent Document 2 discloses an ultraviolet sensor using a thin film in which zinc oxide is doped with impurities.

Japanese Patent Laid-Open No. 10-182290 JP 2008-039665 A

  In recent years, due to the destruction of the ozone layer and the like, there has been a tendency for the amount of ultraviolet rays of sunlight reaching the surface of the earth to increase, and there is concern about the impact on the human body. Such ultraviolet rays have a very serious impact on human health, such as skin cancer and cataracts, as well as sunburn, and it is hoped that such ultraviolet rays will be easily measured and taken measures. It is rare.

  Conventional ultraviolet sensors are expensive, such as those using an optical filter or an epitaxial (single crystal) growth film of gallium nitride. In recent years, an ultraviolet sensor using zinc oxide which is relatively inexpensive and has an absorption wavelength only for ultraviolet rays has been proposed in Patent Document 1, Patent Document 2, and the like. However, the characteristics of these ultraviolet sensors are not stable because the sintered body has insufficient crystal control. Even when a thin film is used, defects are generated due to the high concentration of carriers doped with dopants, and the response speed is very slow. Therefore, it is difficult to measure the amount of ultraviolet rays easily and instantaneously.

  The present invention has been made in view of the above points, and an object thereof is to provide an ultraviolet sensor that is inexpensive, has stable characteristics, and has a high response speed.

  The ultraviolet sensor of the present invention is an ultraviolet sensor utilizing the photoconductive effect of zinc oxide, wherein the zinc oxide is made of additive-free zinc oxide, and the diffraction peak at the (002) plane in the X-ray diffraction pattern of the zinc oxide. The full width at half maximum is 0.5 degrees or less.

  According to this configuration, it is possible to obtain an ultraviolet sensor that is sensitive only to ultraviolet rays, has a high response speed, and is relatively inexpensive.

  In the ultraviolet sensor of the present invention, the zinc oxide preferably has a specific resistance of 1 Ω · cm or more and a film thickness of 100 nm or more.

  In the ultraviolet sensor of the present invention, it is preferable that an insulating protective film having a wider band gap than the zinc oxide is provided on the zinc oxide.

  In the ultraviolet sensor of the present invention, the protective film is preferably one of silicon oxide and aluminum oxide film or nitride film.

  According to these structures, the said zinc oxide can be protected from environments, such as humidity, without interrupting | blocking the ultraviolet-ray which reaches | attains the said zinc oxide film | membrane which detects an ultraviolet-ray.

  In the method for producing an ultraviolet sensor of the present invention, it is preferable that 3% or more of oxygen is added to a carrier gas that is an inert gas during the film formation of zinc oxide.

  According to this film formation method, in the additive-free zinc oxide, a film having a half-value width of the diffraction peak on the (002) plane of the X-ray diffraction pattern of 0.5 degrees or less and a specific resistance of 1 Ω · cm or more is obtained. be able to.

  The ultraviolet sensor according to the present invention is an ultraviolet sensor using the photoconductive effect of zinc oxide, and the zinc oxide is made of additive-free zinc oxide, and has high orientation and low crystal defects. While being inexpensive, it enables ultraviolet detection with a fast response speed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view of an ultraviolet sensor according to an embodiment of the present invention, and FIG. 2 is a plan view of the ultraviolet sensor according to the embodiment of the present invention. 1 and 2, the ultraviolet sensor 1 of the present embodiment includes a substrate 2 made of glass, silicon, plastic, or the like. On the substrate 2, a sensitive film (ultraviolet ray sensing unit) 3 for sensing ultraviolet rays is formed. Further, a protective film 4 made of silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, or the like is formed in the sensing region on the sensitive film 3. Furthermore, a pair of electrodes 5 made of aluminum, gold, platinum, or the like is formed in a region other than the sensing region on the sensitive film 3.

  The sensitive film 3 is an additive-free zinc oxide film having a half value width of a diffraction peak on the (002) plane of the X-ray diffraction pattern of 0.5 degrees or less, a specific resistance of 1 Ω · cm or more and a film thickness of about 200 nm. Is formed.

  FIG. 3 is a graph showing the relationship between the half-value width of the diffraction peak on the (002) plane of the X-ray diffraction pattern of zinc oxide and the response speed at the time of detecting ultraviolet rays, where the horizontal axis indicates the response speed and the vertical axis indicates the X-ray. The half-value width of the diffraction peak in the (002) plane of the diffraction pattern is shown. As shown in FIG. 3, the response speed increases as the half-value width of the diffraction peak on the (002) plane becomes narrower. From this tendency, the response speed can be increased by narrowing the half width of the diffraction peak on the (002) plane of zinc oxide.

  FIG. 4 is a graph showing the relationship between the specific resistance of zinc oxide and the response speed at the time of detecting ultraviolet rays. The horizontal axis shows the response speed, and the vertical axis shows the specific resistance of zinc oxide. As shown in FIG. 4, the response speed increases as the specific resistance of zinc oxide increases. From this tendency, the response speed can be increased by increasing the specific resistance of zinc oxide.

  FIG. 5 is a cross-sectional photograph of a zinc oxide crystal formed on a substrate. As shown in FIG. 5, the substrate side of the zinc oxide film grows in a microcrystalline state and becomes small crystal grains from about 50 to about 100 nm. If the thickness is greater than that, a crystal with high orientation is obtained, and therefore an ultraviolet sensor having a good response speed can be obtained by setting the film thickness to about 200 nm.

  FIG. 6 is a graph showing the ultraviolet response characteristics when additive-free zinc oxide is used as the sensitive film 3, and the horizontal axis indicates time and the vertical axis indicates output current. Irradiation of ultraviolet rays is started at 10 seconds on the horizontal axis, and irradiation of ultraviolet rays is terminated at 40 seconds. FIG. 7 is a graph showing ultraviolet response characteristics when zinc oxide doped with gallium as a dopant is used as the sensitive film 3, the horizontal axis indicates time, and the vertical axis indicates output current. Irradiation of ultraviolet rays is started at 10 seconds on the horizontal axis, and irradiation of ultraviolet rays is terminated at 40 seconds. From these, it can be confirmed that the response speed is increased by using the additive-free zinc oxide as the sensitive film 3.

  In the ultraviolet sensor having the above structure, photoelectrons are emitted by irradiating the sensitive film 3 with ultraviolet rays, and the amount of current flowing between the pair of electrodes 5 or the resistance between the pair of electrodes 5 changes. The amount of ultraviolet rays can be determined by detecting the change in the amount of current or resistance.

  8 and 9 are cross-sectional views showing manufacturing steps of the ultraviolet sensor according to the embodiment of the present invention. As shown in FIG. 8A, a sensitive film 3 is formed by forming a zinc oxide film on the substrate by sputtering or vapor deposition. At the time of film formation, for example, argon is used as a carrier gas, and oxygen is mixed with 3% or more for film formation.

  FIG. 10 is a graph showing the relationship between the amount of oxygen added during zinc oxide film formation and the half width of the diffraction peak on the (002) plane of the X-ray diffraction pattern of the zinc oxide film formed. And the vertical axis represents the half-value width of the diffraction peak on the (002) plane of the X-ray diffraction pattern. As shown in FIG. 10, by increasing the amount of oxygen added during film formation, zinc oxide having a narrow half-value width of the diffraction peak on the (002) plane of the X-ray diffraction pattern can be obtained.

  FIG. 11 is a graph showing the relationship between the amount of oxygen added during film formation of zinc oxide and the specific resistance of the formed zinc oxide, where the horizontal axis represents the amount of oxygen added during film formation, and the vertical axis represents the specific resistance. Show. As shown in FIG. 11, zinc oxide with high specific resistance can be obtained by increasing the amount of oxygen added during film formation.

  After the formation of the sensitive film 3, as shown in FIG. 8B, for example, silicon oxide is formed on the sensitive film 3 by sputtering or the like, and the protective film 4 is formed. Next, as shown in FIG. 8C, a resist is applied and dried on the protective film 4 to form a resist film 6, and the resist film 6 is subjected to photolithography to form a resist film in a region corresponding to the ultraviolet light sensing portion. Patterning is performed so that 6 remains.

  Next, as shown in FIG. 9D, the silicon oxide is etched using the resist 6 as a mask. At this time, the etching may be either wet or dry etching. Next, as shown in FIG. 9E, electrode materials 5 and 51 are formed on the entire surface by sputtering or the like. Next, by removing the resist 6 with a material that dissolves the resist 6 (lift-off), an ultraviolet sensor as shown in FIG. 1 is produced. The electrode 5 may be formed by printing using a silver paste or a gold paste after removing the resist 6.

  Thus, in the ultraviolet sensor 1 of the present embodiment, the half-width of the diffraction peak on the (002) plane of the X-ray diffraction pattern is 0.5 ° or less and the specific resistance is 1 Ω · cm. By using an additive-free zinc oxide film having a thickness of about 200 nm as described above, it is possible to detect ultraviolet rays with a fast response speed.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, in the above embodiment, the electrode is formed on one surface of zinc oxide, but the electrode may be formed by sandwiching a zinc oxide film between the electrodes. Other modifications may be made as appropriate without departing from the scope of the object of the present invention.

  The present invention can be applied to measuring instruments that detect ultraviolet rays from the sun or ultraviolet rays from germicidal lamps used in industrial applications.

It is sectional drawing of the ultraviolet sensor which concerns on embodiment of this invention. It is a top view of the ultraviolet sensor of FIG. It is a graph which shows the relationship between the half value width of the diffraction peak in the (002) plane of the X-ray diffraction pattern of zinc oxide, and the response speed at the time of an ultraviolet-ray detection. It is a graph which shows the relationship between the specific resistance of zinc oxide, and the response speed at the time of ultraviolet-ray detection. It is a cross-sectional photograph of a zinc oxide crystal. It is a graph which shows an ultraviolet-ray response characteristic when additive-free zinc oxide is used as the sensitive film | membrane 3. It is a graph which shows the ultraviolet-ray response characteristic when the zinc oxide which added the gallium as a dopant is used as the sensitive film | membrane 3. FIG. (A)-(c) is a figure for demonstrating the manufacturing method of the ultraviolet sensor which concerns on embodiment of this invention. (D)-(e) is a figure for demonstrating the manufacturing method of the ultraviolet sensor which concerns on embodiment of this invention following FIG.8 (c). It is a graph which shows the relationship between the oxygen addition amount at the time of zinc oxide film-forming, and the half value width of the diffraction peak in the (002) plane of the X-ray diffraction pattern of the zinc oxide formed into a film. It is a graph which shows the relationship between the oxygen addition amount at the time of zinc oxide film-forming, and the specific resistance of the zinc oxide formed into a film.

1 UV sensor 2 Substrate 3 Sensitive film 4 Protective film 5 Electrode 6 Resist film 51 Electrode material

Claims (5)

  An ultraviolet sensor using the photoconductive effect of zinc oxide, wherein the zinc oxide is made of additive-free zinc oxide, and the half width of the diffraction peak at the (002) plane in the X-ray diffraction pattern of the zinc oxide is 0.5. An ultraviolet sensor characterized by being less than or equal to a degree.   2. The ultraviolet sensor according to claim 1, wherein the zinc oxide has a specific resistance of 1 Ω · cm or more and a film thickness of 100 nm or more.   The ultraviolet sensor according to claim 1, further comprising an insulating protective film having a wider band gap than the zinc oxide on the zinc oxide.   4. The ultraviolet sensor according to claim 3, wherein the protective film is one of silicon oxide and aluminum oxide film or nitride film.   An ultraviolet sensor using the photoconductive effect of zinc oxide, characterized in that zinc oxide is deposited on a substrate by sputtering or vapor deposition while adding 3% or more of oxygen to an inert gas carrier gas. Production method.

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