TW447004B - Process for preparing a hydrogen sensor - Google Patents

Abstract

This invention provides a preparation method for a hydrogen sensor, which includes: (a) n-type or p-type semiconductor film is formed on a semiconductor substrate, (b) a patterned first metal electrode is formed on the film and thus an ohmic contact is formed between the first metal electrode and the film, and (c) on the semiconductor film, a second metal electrode is formed and is separated from the first metal electrode. A Schottky contact is formed between the second metal electrode and the film. The material and thickness of the second metal electrode allow the decrease of the Schottky barrier of the Schottky contact when hydrogen is in contact with the second metal electrode. The second metal electrode can be formed from the application of physical vapor deposition or electroless plating.

Description

447004 progress, and the danger of hydrogen sensing with the air confirms that the volume is large. The additional hydrogenation is set to the silicon half (the research of the metameter is to change the polarization of adsorption and diffusion through the requirements. Is the conductor technology 1-ox i de-causes a metal with a good surface after the generation of hydrogen, it will be made, and therefore in the preparation of a metal-semiconductor hydrogen sensor. A method for preparing metal using electroless plating— Preparation method of hydrogen sensor for metal electrode of half device 6 Modern industry and medical industry use hydrogen as a large amount of hydrogen as a flammable and explosive gas mixture. The concentration range reaches 4. 65 vol%. Therefore, based on industrial safety Considerations and environmental testers have been widely used in factories and laboratories for leaking hydrogen. 'However, at present, traditional and expensive,' most of them are passive components or conversion circuits for analysis or release. 5. Description of the invention (1) FIELD OF THE INVENTION The present invention is a method 'and is particularly a conductive hydrogen gas meter. BACKGROUND OF THE INVENTION When the air is on, it is important to have an explosion awareness; ^ In the hospital, in addition to the quasi-hydrogen sensor, other components must be large, unable to reach the intelligent intelligent active element S. In recent years, the layer-silicon semiconductor M0S In the environment of palladium metal for semiconductor hydrogen sensing, the hydrogen atoms that can be separated will face the 'Schottky barrier of these hydrogen atoms, and develop a new and effective important issue today. Progress' The palladium metal-oxidized semiconductor) structure is of interest to many people. The catalyst activity of its structure dissociates into hydrogen atoms in the molecules containing hydrogen, and is partially adsorbed on the boundary between the metal and the oxide layer to form the interface between the oxide layer and the silicon semiconductor, which changes the electrical properties of the device. Early

1 ^ · \\ Chenlin \ 19991103 \ P!]] 〇0 \ NSC11110.ptd Page 5 4470 04 V. Description of the invention (2) Phase I. Lundstrom proposed palladium gate / silicon dioxide / dream field effect electricity Crystals (Pd / Si02 / Si MOS field effect transistor) [Lundstrom, MS Shivaraman, and C. Svensson, J. Appl_ Phys ·, 46, 3876 (1 975)], after using a palladium gate to adsorb hydrogen, the threshold voltage ( Threshold voltage) and changes in capacitance at both ends are used as two basis for detecting hydrogen. However, the use of three-terminal components to achieve the functions of two-terminal components is not only not cost-effective, but also increases the difficulty of the process. In addition, the quality of the oxide layer is also related to the quality of the hydrogen sensing ability. In addition to the reliability problem, when the oxide layer grows When the quality is unstable due to ionic contamination or increased defects, the Fermi level of silicon semiconductors has a surface state pinning of Fermi-level. At this time, the Schottky barrier height is less affected. The influence of polarized hydrogen atoms, so the sensitivity to hydrogen is also poor. Many studies have improved on this issue, such as A, Dutta's oxidizer (ZnO) [A. Dutta, TK Chaudhuri, and S. Basu, Materials Science Engineering, B14, 31 (1992)] and L. Yadava et al. [L. Yadava, R. Dwivedi, and SK Srivastava, Solid-St. Electron., 33, 1 229 (1 990)] Replaced the silicon dioxide oxide layer with titanium dioxide (Ti02). On the other hand, if it is implemented with a Schottky barrier diode at both ends, it seems to be a more direct approach. It reduces the instability of the oxide layer and has obvious sensitivity to hydrogen. improve. Steele et al. Proposed a palladium / cadmium sulfide (Pd / CdS) structure [Μ · C. Steele and B. A 'Maciver, Appl. Phys. Lett., 28, 687 (1976)] and Ito et al. Proposed a palladium / oxide (Pd / ZnO) structure [K. Ito, Surface

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Mi Θ (94 V. Description of the invention (3)

Sc i. '86, 345 (1982)]' The semiconductor substrate was changed to a n-VI group compound 'but its sensitivity to hydrogen sensing was poor. In 1991, ^ 1111, et al. Used a III-V group compound as a substrate 'and deposited platinum metal on Shishenhua gallium substrate by vacuum evaporation technology to produce a hydrogen sensor based on Schottky ’s sensing principle [ L. M. Lechuga, A. Calle, D. Golmayo, P. Tejedor and F. Briones, J. Electrochem. Soc., 138, 159 (1991)]. They found that 'when the bell film is energized in a high energy manner, it will cause a surface state pinning of Fermi-level in the Fermi step of the semiconductor.' At this time, the Schottky barrier is less susceptible to polarization. Influence of hydrogen atom. The DIGS model theory proposed by Hasegawa et al. In 1986 can be used to explain this phenomenon [Η. Hasegawa and H. Ohno, J. Vac_Sci_ Technol., B5, 1130 (1986)]. In the past, because the wet method (also called the solution method) was often due to the variety of plating bath components and the complicated chemical reactions involved, it was rarely used in semiconductor processes to manufacture working elements. At present, electroplating technology has gradually revealed its superiority in the semiconductor processing industry, especially in the latter stage, because the electroplating technology can meet the flatness, coverage, via filling capacity, etc. required for multiple interconnect interconnection processes (mui ti-level interconnects). Demand 'while being taken seriously. In particular, the electroless plating method has a simple process, easy operation, low cost, and energy saving, and is suitable for continuous mass production in industry. The inventor of the present case found that if the plating bath formulation of the electroplating method is properly controlled, components with very good characteristics can be obtained, and the electroless plating method is very compatible with the semiconductor process. Preparation method of hydrogen sensor.

\\ Chenlin \ l9991103 \ Pni00 \ SSC11110.ptd Page 7 4470 04 V. Description of the invention (4) The main purpose of the present invention is to provide a method for preparing a metal-semiconductor hydrogen sensor. Another object of the present invention is to provide a method for preparing a metal-semiconductor hydrogen sensor, which uses an electroless plating method to prepare a metal electrode of the metal-semiconductor hydrogen sensor. SUMMARY OF THE INVENTION The present invention provides a method for preparing a hydrogen sensor having the following structure. The hydrogen sensor includes: a semiconductor substrate; a phase electrode and a cathode formed on the semiconductor substrate and formed on the semiconductor thin film, wherein The anode forms a Schottky contact and forms an ohmic contact as a thin film, wherein the height of the energy barrier based on the exposure of the first metal when the hydrogen is contacted is reduced. N-type or p-type semiconductor thin film on the surface; and a first metal on the same surface but spaced from each other and a second metal of the semiconductor thin film cathode and the material and thickness of the semiconductor first metal can make the surface ' In the hydrogen sensor of the present invention, the Schottky contact is #hydrogen contacting the surface of the first metal = surface $, the hydrogen is dissociated into a hydrogen atom, and the hydrogen atom penetrates the genus. -The interface between the metal and the semiconductor thin film has a high absorption energy barrier, and the change in electrical properties of the light-emitting diode is obtained, so that the nitrogen content at a low concentration can be detected. The hydrogen sensor of the present invention

The preparation method comprises the following steps:

V. Description of the invention (5)-a) Forming an n-type or p-type semiconductor thin film on a semiconductor substrate. I) One: forming a patterned first metal electrode on a semiconductor film, the second metal electrode and the semiconductor The thin film forms an ohmic contact. A second metal electrode spaced from the first metal electrode is formed on the Λ conductive thin film to form a semiconductor thin film with the semiconductor thin film. The thickness can be such that when the hydrogen degree decreases: the first metal electrode, the Schottky energy barrier of the Schottky contact is preferably high. The method of the present invention further includes after the first metal electrode of step b) is formed. Thermally tempering the first metal electrode to improve the characteristics of the ohmic contact. More preferably, the temperature of the thermal tempering is between 300 t and 50 ° C, and the time is between 20 seconds and 5 minutes. Preferably, step b) of the method of the present invention comprises: I. coating a photoresist layer on the semiconductor film; II * exposing the photoresist layer by patterning a photomask; III. Exposing the photoconductor by patterning The photoresist layer of the photoresist layer is transferred to the photoresist layer, so a part of the patterned photoresist film is exposed; f IV. The patterned photoresist layer is used as a mask on the semiconductor. Depositing a first metal layer on the exposed portion of the film; and V. peeling the patterned photoresist layer, and forming the patterned first metal electrode on the semiconductor film. Preferably, step c) of the method of the present invention includes: I. coating on the entire surface of the semiconductor thin film containing the first metal electrode

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447 / Q V. Description of the invention (6) A photoresist layer; Π _ exposure of the photoresist layer by patterning a photomask; displaying the photoresist layer exposed by the pattern, and transferring to the photoresist layer , So a patterned photoresist is formed? A part of the bulk film is exposed; the second photoconductive film is used as a mask to deposit a second metal layer on the exposed adjacent knife of the semiconductor film; and V. the patterned photoresist layer is peeled off And forming the patterned second metal electrode on the semiconductor thin film. Preferably, the first metal layer deposition of the step of the method of the present invention is performed by physical vapor deposition, such as vacuum evaporation. The physical vapor deposition is. Preferably, the second metal layer of the method of the present invention is palladium'palladium alloy or platinum. More preferably, the second metal layer is palladium. Preferably, the second metal layer deposition in step c_jy) of the method of the present invention is performed by an electroless recording key film. Preferably, the electroless plating method includes contacting the exposed portion of the semiconductor thin film with an electroless plating solution for a period of time. The electroless plating solution is a metal ion (such as palladium ion) containing the second metal layer, An aqueous solution of a mixture, a reducing agent, a pH buffering agent and a stabilizer. The palladium ion is preferably provided by dissolving a palladium complex or a palladium salt in water. The complexing agent is preferably selected from the group consisting of ethylenediamine, tetramethylethylenediamine 'and ethylenediamine tetraacetic acid (EDTA).

WChenl in \ 19991103 \ Pin〇0 \ NSC] l 110. pid page 10 4470 〇4. Description of the invention (7) The β-reducing agent of the group is preferably selected from hydrazine, hypodiacetate ( hypophosphite), borohydride and Cformaldehyde). The pH buffer is preferably a substance such as boric acid or hydrogen emulsified ammonium (N （40Η). Preferably, the pH value of the electroless plating solution is maintained at 9 -1 2. Preferably, the electroless plating film includes contacting the exposed portion of the semiconductor film with the electroless plating solution for a period of time between 1 minute and 1 hour, and the electroless plating solution is maintained at a range of 2 〇 It is a temperature between 70 ° (:). Preferably, the electroless plating film further comprises an acidic stannous ion-containing film before the exposed portion of the semiconductor film contacts the electroless plating solution. The sensitizing solution is contacted for a period of time (for example, between 5 minutes and 10 minutes) to perform a sensitization treatment, and the exposed portion of the sensitized semiconductor film is contacted with an acidic palladium ion-containing activating solution for a period of time. (For example, between 5 minutes and 10 minutes) to perform an activation treatment. Preferably, the semiconductor substrate in step a) of the method of the present invention is made of semi-insulating indium phosphide (InP) or gallium arsenide (GaAs) material. form. ′ Preferably, the semiconductor film in step a) of the method of the present invention is an n-type π-ν group compound. Preferably, the doping degree of the nsHI_v group compound is between 5x1015 and 1x1018 cm-3. Preferably, the thickness of the C-type compound is between 0.050 microns and 10 microns. The nsIINv family may be n-type InP or GaAs, preferably ^ -type 111 ?. Preferably, step a) of the method of the present invention is to form the semiconductor thin film by an organic metal phase deposition method or a molecular beam epitaxial growth method. It is preferable that the first metal electrode of the hydrogen sensor of the present invention is a gold fault.

^ Λ1 〇 〇5. Description of the invention (8) Alloy (AuGe) or gold germanium nickel alloy (AuGeNi). Preferably, the first metal electrode is AUGe. Preferably, the thickness of the first metal electrode is between 0.30 micrometers and 5 micrometers. Preferably, the thickness of the second metal electrode of the hydrogen sensor of the present invention is between 0.30 micrometers and 5 micrometers. Preferably, the second metal electrode of the hydrogen sensor of the present invention has a C-shape or a C-like shape, and the first metal electrode has—corresponding to the shape of the second metal electrode such that the first metal electrode Surrounded by the second metal electrode. The first metal electrode of the hydrogen sensor of the present invention is selected to have a C-shape or a C-like shape, and the second metal electrode has a shape corresponding to the first metal electrode so that the second metal electrode Surrounded by the first gold electrode. '' In order to make the purpose, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below, and a detailed description of the preferred embodiment according to the present invention will be given in detail with reference to the accompanying drawings of the present invention. A high-level palladium / indium phosphide hydrogen sensor completed in a preferred embodiment is shown in the first figure and includes an insulative indium phosphide substrate 1 2; an n-type indium phosphide film 1 4, It is located on the edge of indium phosphide substrate 12; an ohmic contact of gold-germanium alloy and a Schottky contact metal layer 18 of palladium metal are adjacent to each other but 6 and on the indium phosphide film 14. '和 位

447004 V. Description of the invention (9) In the helium-sensitivity palladium / indium phosphide hydrogen sensor 10, type 0 indium phosphide thin film 14 is made of organic metal vapor deposition (MOCVD) or molecular beam lei. The crystal growth method (MBE) grows a layer of high-quality n-type indium phosphide film on the semi-insulating indium phosphide substrate 12, so it has a very low surface state potential density. The Schottky barrier height between metal and semiconductor is closely related to the number of polarized hydrogen atoms, that is, the surface state potential density. In addition, the indium phosphide material has a high hydrogen coverage, and the relatively low hydrogen content in the air can significantly change the height of the Schottky barrier. This characteristic is suitable for low concentration detection of less than one percent. In terms of temperature characteristics, the bandgap of the indium phosphide material is about 1.35eV ', which is larger than that of silicon, and also has good temperature resistance performance. In addition, the indium phosphide material growth and process technology has matured, both photoelectric and microwave integrated circuits have been used in the industry. The method for preparing the hydrogen lice sensor of the present invention can be integrated with the method for preparing photovoltaic elements. The preparation method of a multi-functional intelligent sensor that can simultaneously detect photoelectricity and hydrogen will have great potential in commercial applications. In another preferred embodiment of the present invention, a method for preparing a low-temperature and energy-saving method that combines an electroless plating film with a semiconductor process is provided, wherein the Schottky contact metal layer 18 of the metal is electrolessly plated in a ^ type. Indium phosphide film 14 on a substrate. The principle of non-electric key recording film is an autocatalytic redox reaction. In the preferred embodiment, the reaction used in the present invention is: 2Pd2 + (aq) + N3H4 (aq) + 40H- (aq)-> 2PdCs) + N2 (g) +4

\\ Chenlin \ 1999] 103, 'Plll〇〇WSC] 1110.ptd Page 13 :, 4470 04 V. Description of the invention (ίο) Plating bath composition' except for palladium metal precursor salt-vaporized palladium (PdCl2) In addition to hydrazine (N2H4) reducing agent, according to actual needs, some other ingredients are appropriately added, which are described as follows: a. Complexing agent: The purpose is to control the concentration of palladium ions available in the plating solution for reaction to avoid chain bath production. Decomposition (decompos iti on), so that the reaction can only occur on the surface of the substrate with catalytic properties. In the electroless plating process, the is-mismatched ions will release an appropriate amount of saturated ions due to the need for mismatch balance. The addition amount of the complexing agent has a significant effect on the coating rate and microstructure of the metal plating layer, which in turn affects its Schottky electrical properties and sensing characteristics. Therefore, it is necessary to select the appropriate type and concentration of the complexing agent. b. Accelerator: The addition of the complexing agent tends to reduce the rate of non-electric bond reaction. Therefore, for practical needs in industrial production, a small amount of organic additives can be added to the bell solution to increase the rate of the electroless plating reaction and increase the ductility of the metal film. c. Stabilizer: The purpose is to reduce the spontaneous decomposition of the plating bath and make the recording bath more stable. Generally speaking, the 'stabilizer does not have catalytic activity, and even inhibits the reaction of the reducing agent', so its addition amount is usually reported in a trace amount. d. Buffer: During the electroless plating reaction, the pH of the plating solution changes due to the consumption of nitrogen ions by the reaction. In order to maintain the stability of 疋 ,,,, ^ ^ ^ and avoid the change of electroless plating rate, it is necessary to use a damping agent such as + „and a balance agent to control the plating solution.

4470 04 V. Description of the invention (11) Example 1 (Vacuum evaporation) A high-sensitivity palladium / indium phosphide hydrogen sensor 10 as shown in the first figure was prepared. The edge preparation method includes first preparing a half-insulating indium phosphide substrate 12. Secondly, using a technique of organometallic chemical vapor deposition method or molecular beam epitaxial growth method to grow a good quality n-type scaled thin film 貘 14 on the semi-insulating indium phosphide substrate 丨 2, its concentration and thickness are respectively For lxl0l? Cm_3 and 3 0 0 0 angstroms. Then, using traditional photolithography and vacuum evaporation techniques, the ohmic contact metal layer 16 of gold-germanium alloy and the Schottky contact metal layer 18 of Kie metal were vapor-deposited on the surface of the η-type scaled indium thin film, respectively. As the cathode and anode of the sensor. After the ohmic contact metal layer i 6 of the gold-germanium alloy is formed, thermal annealing is performed at a temperature of 400 ° C for about 1 minute. The charge density distribution and the energy band diagram of the sensor of this embodiment when (a) no hydrogen is sensed and (b) hydrogen is sensed are shown in the second figure. Before the introduction of hydrogen, the charge distribution at the interface of the sensor's palladium metal 18 and 11 tantalum indium phosphide film 14 is in equilibrium, and a metal-semiconductor Schottky barrier is formed, as shown in the second figure (a) As shown. After the introduction of hydrogen, palladium metal 18 has a catalytic effect on hydrogen. When hydrogen molecules are adsorbed on the surface of palladium metal, they will be dissociated into hydrogen atoms, and most of the hydrogen atoms will diffuse through palladium metal 18 'and pass through A dipole moment layer is formed between the interface between the metal 18 and the n-type indium phosphide film 14. This moment moment will change the equilibrium state of the original charge distribution and reach a new equilibrium state. This new equilibrium state is reduced. The width of the empty region of the n-type indium phosphide semiconductor further reduces the height of the Schottky barrier, as shown in the second figure (b).

^ Chenhn \ 19991] 〇3 \ Ρΐη〇〇 \ ^] 1π〇ιρΐ £ 3 p. 15 447004

The second figure is the current-voltage characteristic curve of the sensor of this embodiment in the air and air containing different hydrogen contents (200ppm, 500ppin, 1000ppm, 5000ppm, ° 1000ppm) in environmental measurement. Illustration. The forward bias in this figure is defined as the positive voltage applied to the Schottky contact relative to the ohmic contact. Conversely, the reverse bias is applied to a negative voltage. Since the larger the amount of hydrogen ^, the smaller the Schottky barrier height is, the larger the current is. It can be seen from the figure that 'whether it is a forward biased current or a reverse biased current, both of them increase with the increase of the hydrogen content in the air'. It is more obvious that the increasing trend of the reverse current " IL is The linear increase is proportional to the hydrogen content. The fourth graph shows the relationship between the Schottky barrier height of the sensor of this embodiment and the hydrogen content in the air. The height of the energy barrier in the air is about 500 meV. With the increase of the hydrogen content, the height of the energy barrier gradually decreases. When the hydrogen content is greater than 0.5%, the height of the energy barrier reaches almost the lowest value. Conduction to current has been very similar to ohmic characteristics. The fifth graph is a transient response graph measured by the sensor of this embodiment when the temperature is 12 5 t. When hydrogen gas is introduced, air representing a hydrogen content of 200 ppm flows into the test chamber at a rate of 5000 m 1 / mi η. The test conditions are that the palladium contact metal layer 18 and the ohmic contact metal layer 16 A constant reverse current of 8 mA is maintained between the two electrodes, because the dissociated hydrogen atoms form a dipole moment layer, the reverse current through the Schottky contact increases, so the voltage between the two electrodes is relatively reduced by about 1.2V, another On the one hand, when the hydrogen gas is turned off, the sensor is directly exposed to the air, and the hydrogen atoms combine to form hydrogen molecules or oxygen to form water molecules to desorb the surface of the palladium metal, thereby causing the voltage recovery between the two electrodes. If the reaction time and recovery time are defined to reach individual stable values

4470 04 V. Description of the invention (13) The time required for 90% is shown in the figure. The response time of the sensor is about 5 seconds and the recovery time is about 12 seconds. In addition, repeating the measurement method of the first cycle yielded the second cycle, which was found to exhibit fairly high reproducibility. The sixth figure is a graph of the relationship between the saturation sensitivity and the hydrogen content in the air of the sensor of the present invention. The saturation sensitivity S is defined as the ratio of the change in current flowing between the two electrodes to the reference current under a fixed reverse voltage, nH2-Iair) / Iair. It is obvious from the figure that the sensitivity increases with the increase of the hydrogen content. With 0.5 V reverse bias, saturation sensitivity measured in air with 1% hydrogen content can reach 130, and saturation sensitivity measured in air with relatively low 200ppm hydrogen content can reach 2. Example 2 (Electroless plating) A high cryogenic sensitivity 1 bar / indium phosphide hydrogen sensor 10 ′ as shown in the first figure was prepared by a procedure similar to that of Example 1. The base contact metal layer 18 is formed by electroless plating. After the ohmic contact metal layer 16 is vacuum-evaporated and thermally tempered, an η-type indium phosphide film 14 (concentration: 5 × 10i7cnr3) (containing the ohmic contact metal layer 16) is coated with The resist layer 'imagewise exposing the photoresist layer through a photomask, developing the patterned exposed photoresist layer, and transferring the pattern of the photomask to the photoresist layer', thus forming a pattern The photoresist layer was exposed so that a part of the n-type indium phosphide film 14 was exposed. The patterned photoresist layer was used as a mask to immerse the semiconductor substrate in a 30-ton electroless plating bath for 10 seconds. A palladium metal layer 18 is deposited on the exposed portion of the n-type indium phosphide film 14. The electroless plating bath is a water having the following composition

4 47 0 〇4 V. Description of the invention (14) Solution: PdCl2 2.7 g / L NH40H (28%) 195 ml / L Na2EDTA 3 5 g / L N2H4 (lM) 100 ml / L thiourea (T hiourea) 0. 0006 g / L Take out the semiconductor substrate from the electroless plating bath, lift-off the patterned photoresist layer 1 after washing, and form the pattern on the n-type indium phosphide film 14 Schottky contact metal layer of palladium metal 18 □ The seventh picture shows the sensor of this embodiment in an environment with different hydrogen content in the air and air (200ppm 50 0 ppm 100ppm 'SOOOppm, 10,000ppm) A graph of the measured current-voltage characteristics. As the content of hydrogen is larger, the Schottky barrier is smaller, so the current is relatively larger. It can be seen from the figure that both the forward biased current and the reverse biased current increase with the increase of the hydrogen content in the air, and it is more obvious that the increase trend of the reverse current is with the hydrogen content. Proportionally increases linearly. The eighth figure shows the relationship between the Schottky barrier height of the sensor of this embodiment and the hydrogen content in the air. The south degree of the monthly envelope barrier in the air is about 686 meV. As the hydrogen content increases, the south degree of the barrier gradually decreases. Small, when the hydrogen content is greater than 0.5%, the south degree of the energy barrier almost reaches the lowest value. At this time, the forward current conduction is very close to the ohmic characteristic 0. The ninth figure is the sensor of this embodiment at a temperature of 1 Measured at 2 5 t

WChenl in \ 19991103 \ P11100 \ NSC11110.p; d page 18, 4470 04 V. Description of the invention (15) Transient response diagram. When hydrogen gas is introduced, air representing 200 ppm hydrogen content flows into the test chamber at a rate of 50 Om 1 / miη, and the test conditions are maintained between the two electrodes of Schottky contact metal layer 18 and ohmic contact metal layer 16 of palladium metal. A fixed reverse current of 7 m A, because the dissociated hydrogen atoms form a dipole moment layer, the reverse current through the Schottky contact increases, thus causing the relative voltage between the two electrodes to decrease by about 0.15V, in addition,-- When the hydrogen gas is turned off, the sensor is directly exposed to the air. * The hydrogen atoms combine to form hydrogen molecules or combine with oxygen to form water molecules to desorb the surface of the palladium metal, thus causing the voltage recovery between the two electrodes. It can be seen from the figure that the response time of the sensor is about 5 seconds, and the recovery time is about 20 seconds. The tenth figure is a relationship diagram of the saturation sensitivity of the sensor of the present invention with respect to the hydrogen gas content in the air. It is clear from the figure that the sensitivity increases with increasing hydrogen content. Under a 0.5V reverse bias, the saturation sensitivity measured in air with 1% hydrogen content can reach 1 835%, even at a relatively low value of 2 0. 3%。 Saturation sensitivity of 0 ppm hydrogen content measured in the air can also reach 4.3%. The eleventh figure is a comparison chart of the electrical characteristics of the high sensitivity palladium / indium phosphide hydrogen sensor manufactured by the electroless plating technology of this embodiment and the Schottky of the same structure manufactured by the vacuum evaporation technology. Figure t shows that the components of the electroless plating process have better Schottky electrical performance than the components obtained by the vacuum evaporation process. This result confirms the theoretical model of DIGS proposed by Hasegawa et al. [H. Hasegawa and Η Ohno, J Vac. Sci. Technol., B5, 1130 (1986)] ο due to the metal vapor condensation released during the vacuum evaporation process Latent heat easily damages the surface of semiconductor substrates, causing pinning effects on the semiconductor Fermi level and making Schottky barriers highly independent of metal species.

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Compared with °, the process temperature of the non-money money is relatively low, so a Schottky contact layer with good characteristics can be obtained. The Schottky contact metal layer 18 of the palladium metal deposited by the electroless plating technique in this embodiment is observed by a cross-section electron microscope and the thickness of the palladium metal film layer is about 6000 angstroms and the structure of the palladium metal film layer is dense. It can be known from the above that the method of the present invention is simple, energy-saving, and can be integrated with a computer and a system, and has the potential for commercialization. The hydrogen sensor prepared by the method of the present invention shows, through experimental results, that it has characteristics such as high linearity, high response speed, high reproducibility, and high sensitivity, which are better than the conventional traditional nitrogen sensing V0, but it is not used. Without departing from the spirit of the present invention, the protection of the present invention shall prevail. Although the present invention has been limited to the preferred embodiment of the present invention, ‘anyone skilled in the art, and within the scope’ shall be subject to various changes and modifications. The scope shall be determined by the scope of the attached patent application.

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4470 04 Brief description of the diagram ----- The first diagram is a schematic diagram of a Syria / Indium Phosphide Hydrogen Sensor completed according to a first preferred embodiment of the present invention. The second figure is the charge density distribution of the palladium / indium phosphide hydrogen sensor completed according to the first preferred embodiment of the present invention when (a) no hydrogen is sensed and (b) hydrogen is sensed, and Sectional energy band diagram. The third figure shows that the palladium / indium phosphide hydrogen sensor completed according to the first preferred embodiment of the present invention contains different hydrogen contents in the air and air (200ppm, 5000ppm, 1000ppm, A current-voltage characteristic curve measured in an environment of 50,000 ppm, 1 (0.0000 ρρπι). The fourth figure is a graph showing the relationship between the Schottky barrier height and the hydrogen concentration of the palladium / indium phosphide hydrogen sensor completed according to the first preferred embodiment of the present invention. The fifth diagram is a transient response diagram of the palladium / lindene hydrogen sensor completed according to the first preferred embodiment of the present invention when the temperature is 125 ° C. The sixth figure is a graph of the relationship between the saturation sensitivity and the hydrogen content of the palladium / indium phosphide hydrogen sensor completed according to the first preferred embodiment of the present invention. The seventh diagram is a palladium / indium phosphide hydrogen sensor completed according to a second preferred embodiment of the present invention, which contains different hydrogen contents in the air and air (200ppm, 500ppm, 1000ppni, 5000ppm, 1000ppm) environment measured current-voltage characteristic curve. The eighth diagram is a graph showing the relationship between the height of the barrier energy and the hydrogen concentration of the palladium / indium phosphide hydrogen sensor according to the second preferred embodiment of the present invention. The ninth figure is the palladium completed according to the second preferred embodiment of the present invention

\\ Chenlin \ 1999n03 \ P11100 \ NSCllil0.ptd Page 21 4470 04 Brief description of the diagram ’The transient response diagram of the scaled steel hydrogen sensor when the temperature is 1 2 5 ° c. The tenth figure is a relationship diagram between the saturation sensitivity and the hydrogen content of the palladium / indium phosphide hydrogen sensor completed according to the second preferred embodiment of the present invention. The eleventh figure is a high-sensitivity palladium / indium phosphide-hydrogen bath manufactured by the I electroplating technology according to the second preferred embodiment of the present invention. Electrical characteristics; 2 = Symbols in the illustration: 1 0: Hydrogen sensor 1 2: Semi-insulating indium phosphide substrate 1 4: η-type indium phosphide film 16: Ohmic contact metal layer 18 of gold-germanium alloy 18 : Schottky contact metal layer of Yuki Metal

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Claims (1)

ΔΑΙΟΟ ^ τ 1 ′, a method for preparing a rolling sensor, including the following steps: a) forming an n-type or p-type semiconductor thin film on a semiconductor substrate; b) forming a patterned first metal electrode on a black semiconductor film, The first metal electrode forms an ohmic contact with the semiconductor thin film; and c) forming a first metal electrode spaced from the first metal electrode on the semiconductor thin film, the second metal electrode and the semiconductor thin film form a Schottky contact, and the material and thickness of the second metal electrode may be such that when hydrogen contacts the second metal electrode, the 特 tky contact is made of the ftkis energy. 2. The method according to item 丨 of the patent application, further comprising After the first metal electrode of step b) is formed, the first metal electrode is fired to improve the characteristics of the ohmic contact. 3. The method according to item 1 of the patent application scope, wherein the ten steps b) include: I. coating a photoresist layer on the semiconductor film; II. Exposing the photoresist layer by patterning a photomask; II I Develop the patterned photoresist layer, and transfer the pattern of the photomask to the photoresist layer, thereby forming a patterned photoresist layer, so that a part of the semiconductor thin film is exposed; IV. Patterning with edges The photoresist layer serves as a mask to deposit a first metal layer on the exposed portion of the semiconductor film; and, V. peel the patterned photoresist layer 'to form the patterned first metal electrode on the semiconductor film. ' 〇4 Scope of patent application • The method according to the scope of application for patent M, wherein Bu Dong. The semiconducting μ containing the first metal electrode contains, gold decoration ~ photoresist layer; m on the entire surface of the film ii, patterned by a photomask Expose the photoresist layer; see 111. Develop the patterned exposed photoresist layer, and half-release the 18) swatches of the photomask to the photoresist layer, and then form a patterned photoresist layer so that A part of the thin film is exposed; Ιν · depositing a second metal layer on the exposed portion of the semiconductor film using the patterned photoresist layer as a mask; and The patterned second metal electrode is formed on the semiconductor thin film. 5. The method of claim 3, wherein the deposition in step IV is performed by physical vapor deposition. 6. The method according to item 5 of the patent application, wherein the physical vapor deposition is vacuum evaporation. 7. The method according to item 4 of the patent application, wherein the deposition in step IV is performed by physical vapor deposition. 8-The method according to item 7 of the patent application, wherein the physical vapor deposition is vacuum evaporation. 4470 04 6. Scope of Patent Application 9. The large-scale application of item 4 in the scope of patent application is carried out by electroless plating of rhenium. , Wherein step IV is deposited 10. For example, the f, and t layer in item 7 of the scope of the patent application is palladium, a palladium alloy, or platinum. "Method" wherein the second metal layer is a method of Ji 1 1 ‘as in the method of the patent application No. 10, wherein the second metal 12. The method of the patent application No. 9 layer is palladium, a palladium alloy or platinum. The method of item 2, wherein the second metal 1 3 ′ is the method of item 12 of the patent scope, wherein the second metal layer is. 14. The method according to the scope of patent application No. 12, wherein the electroless plating film includes contacting the exposed portion of the semiconductor thin film with an electroless mineral liquid for a period of time. The electroless plating solution includes the second metal. A layer of an aqueous solution of metal ions, complexing agents, reducing agents, a p Η buffer and stabilizers. 15. The method of claim 3, wherein the electroless plating method includes contacting the exposed portion of the semiconductor film with an electroless plating solution for a period of time. The electroless plating solution contains palladium ions, Mixture, reduction \\ Chenlin \ 19991103 \ P11100 \ NSG1110.ptd Page 25 4470 04 6. Scope of patent application, an aqueous solution of p buffer and a stabilizer. 16. The method according to item 15 of the patent application range, wherein the palladium ion is provided by dissolving a ilium compound or a palladium salt in water, and the complexing agent is selected from ethylenediamine, tetramethyl Ethylene diamine (tetramethylethylenediamine), and ethylenediamine tetraacetic acid (EDTA) and other groups' and tritium reducing agents are selected from hydrazine, hypophosphite, hydride (Borohydride) and formic acid (formaldehyde). 17. The method according to item 15 of the patent application range, wherein the pH value of the non-money money liquid is maintained in the range of 9 to 12. 18. 18. The method according to item 15 of the scope of patent application, wherein the pH retarder is a substance such as boric acid or ammonium hydroxide (NΗ40Η). 19. The method according to item 15 of the scope of patent application, wherein the exposed portion of the semiconductor film is contacted with an acidic stannous ion-containing sensitization solution for a period of time before contacting the exposed portion of the semiconductor film with the electroless plating solution. Treatment, and contacting the exposed portion of the sensitized semiconductor film with an acidic red ion-containing activating solution for a period of time to perform an activation treatment. 2 0. The method of claim 15 in the scope of patent application, wherein the electroless plating method 4470 〇4. The scope of the patent application coating includes contacting the exposed portion of the semiconductor film with an electroless plating solution for a period of time between 1 minute and 1 hour, and the electroless plating solution is maintained at a range of 20 A temperature between ° C and 70 ° C. 21. The method of claim 19, wherein before the exposed portion of the semiconductor film is in contact with the electroless plating solution, it is contacted with an acidic solution containing stannous ions for between 5 minutes and 10 A period of time between minutes to perform a sensitization treatment, and contacting the exposed portion of the sensitized semiconductor film with an acidic palladium ion-containing activating solution for a period of time between 5 minutes and 100 minutes To perform an activation process. 22. The method of claim 2 in which the thermal tempering temperature is between 300 ° C. 〇 to 50 (TC, and the time is between 20 seconds to 5 minutes. 2 3. The method according to item 1 of the patent application range, wherein the semiconductor substrate is made of semi-insulating indium phosphide (丨 nP) or Formed with gallium arsenide (GaAs) material. 24. The method according to item 1 of the patent application, wherein the semiconductor thin film is an n-type III-V compound. 25. The method according to item 24 of the patent application, wherein the n-type The doping concentration of the Iπ_ν group compound is between 5 × 10 and 5 × l × 10S cm-3. \\ aienlin \ 19991103 \ PniOO \ NSCllii〇.ptd Page 27 447 0 〇4. Patent application scope 26. For example, the method of patent application scope item 24, wherein the thickness of the n-type III-V group compound is between 〇 .50 micron to 10 micron. 27. The method as claimed in claim 24, wherein the n-type III-V group compound is n-type Ιηρ or 杬. 28. The method according to item 27 of the patent application, wherein the η-type III-V group compound is η-type I ηρ ^ 2 9. The method according to item 1 of the patent application, wherein the semiconductor thin film is made of an organic metal Formed by chemical vapor deposition or molecular beam epitaxial growth. 30. The method of claim 1, wherein the first metal electrode is a gold germanium alloy (AuGe) or a gold staggered alloy (AuGeNi). 31. The method of claim 30, wherein the first metal electrode is gold-germanium alloy (AuGe). 32. The method according to item 1 of the application, wherein the thickness of the first gold chip electrode is between 0.30 micrometers and 5 micrometers. 3 3. The method according to item 32 of the scope of patent application, wherein the thickness of the first metal electrode is between 0.30 micrometers and 5 micrometers. \ \ Chen 1 in \] 9991103 \ P11] 00 \ N'SC111] 〇. Ptd page 28 4470 04 VI. Scope of patent application 34. For the method of the first scope of patent application, wherein the thickness of the second metal electrode It is between 0. 30 microns and 5 microns. 35. The method of claim 34, wherein the second metal electrode is made of a handle. 3 6. The method according to item 1 of the patent application, wherein the second metal electrode has a C-shape or a C-like shape, and the first metal electrode has a shape corresponding to the second metal electrode such that the first A metal electrode is surrounded by the second metal electrode. 37. The method of claim 1, wherein the first metal electrode has a C-shape or a C-like shape, and the second metal electrode has a shape corresponding to the first metal electrode such that the second The metal electrode is surrounded by the first metal electrode. UChenlin \ 1999U03 \ Pl] 100 \ NSC] l]] 〇.pid Page 29