JP4848504B2 - Method for cleaning ceramic substrate or inorganic heat resistant substrate, device manufacturing method using the same, and device - Google Patents

Description

  The present invention relates to a method for cleaning a substrate having a surface on which structures such as electrodes and heaters are formed, a method for manufacturing an element using this cleaning method, and an element. The present invention also relates to a functional element and a sensing device, and relates to a method for producing an element that can be used for detection and quantification of various compounds.

  Conventionally, the measurement of a reducing gas is generally analyzed by a solid adsorption / solvent extraction method, a solid adsorption / thermal desorption method, or a combination of a container sampling method and a gas chromatograph / mass spectrometry method. In measuring the reducing gas, the sample collection method is important for ensuring reliability, and it is necessary to absorb the sample for a certain period of time with a dedicated adsorbent. For this reason, the measurement of the concentration level of the reducing gas in the room is costly and time consuming, and is currently measured only at the site where the problem has become apparent.

  On the other hand, a semiconductor gas sensor using a semiconductor electrical resistance, transistor action or rectification action is known as a small and functional sensor for detecting a small amount of gas components contained in a gas. Among these, the electrical resistance type utilizes the fact that the electrical resistance element of a porous metal oxide semiconductor changes depending on the gas atmosphere for gas detection.

In the following Patent Document 1, a heater and a pair of electrodes are provided on a substrate as a gas sensor having low sensitivity to an organic solvent vapor such as ethanol and ether and increasing the relative sensitivity of isobutane, methane, and CO. A gas sensor has been proposed in which a metal oxide semiconductor film for gas detection is provided thereon. This metal oxide semiconductor is, for example, a SiO ₂ film formed by vacuum deposition, sputtering, CVD, or the like, and has a thickness of 5 μm to 100 μm, even a thin film having a thickness of 0.1 μm to 1 μm. .

Patent Document 2 below proposes a moisture sensitive element using a SnO ₂ fine particle film whose electric conductivity changes with respect to a change in the amount of moisture present in the atmosphere. The SnO ₂ fine particle film is formed by a vapor deposition method, and is porous with an average particle diameter of 10 to 200 nm and an average pore radius of 5 to 250 nm. Moreover, the film thickness in an Example is 300 nm.

The following Patent Document 3 is intended to provide a multilayer ceramic free from cracks due to internal electrode peeling. SiO contained in the SiC abrasive is reacted with an alkaline aqueous solution to be changed to SiO ₂ . The occurrence of cracks due to peeling of the internal electrodes is suppressed by polishing the sintered body using the SiC abrasive thus treated.

Patent Document 4 listed below is useful for an ammonia-free cleaning composition for cleaning a microelectronic substrate, particularly a microelectronic substrate characterized by a highly sensitive porous dielectric, a low-κ or high-κ dielectric, and a copper metal coating. For cleaning compositions with improved compatibility with them, stripping photoresist, cleaning residues from plasma-generated organic, organometallic and inorganic compounds, and cleaning residues from planarization processes This relates to a cleaning composition. The cleaning composition contains one or more non-ammonium producing strong bases containing a non-nucleophilic, positively charged counterion and one or more corrosion-inhibiting solvent compounds, the corrosion-inhibiting solvent compounds comprising: It has at least two sites capable of complexing with the metal.
JP-A-5-149907 JP-A-7-197237 Japanese Patent Laid-Open No. 7-297081 JP-T-2004-536910

  The sensors of Patent Document 1 and Patent Document 2 do not solve the influence of polishing residues existing on the substrate surface, and cannot guarantee the performance of the electronic element.

  Patent Document 3 is intended to provide a multilayer ceramic free from cracks due to internal electrode peeling, and is intended to polish a sintered body using a SiC abrasive, so that SiC impurities are not removed. It cannot be expected that the temperature of the substrate is kept at 400 ° C. to 700 ° C. to eliminate the peeling of the electrode and the heater, and the high-sensitivity and stable performance of the electronic element is guaranteed.

  The aforementioned Patent Document 4 provides an ammonia-free cleaning composition for cleaning a microelectronic substrate, but it is not sufficient for removing polishing residues on the substrate, and the structure formed on the substrate is peeled off. It is impossible to expect that electronic devices will exhibit stable performance.

  Here, in order for a functional element such as a sensor to operate stably, it is inevitable to significantly improve the bonding strength between the structure and the substrate. The reason why the adhesive strength between the substrate and the structure is fragile is that the substrate surface is polished with an inorganic abrasive to improve the flatness of the substrate surface, but a small amount of polishing residue is left on the substrate surface. This is because the adhesive strength between the substrate and the structure is greatly impaired by peeling with the structure.

Specifically, an alumina substrate is generally used as a representative example of a ceramic substrate and an inorganic heat resistant substrate, and a silicon carbide (SiC) abrasive is generally used as a representative example of an inorganic abrasive. While the silicon carbide abrasive is mixed with cooling water and supplied to the buffing disk, the surface of the alumina substrate is polished at a high speed to produce large frictional heat locally at the contact surface between the alumina substrate and the buff, and silicon carbide (SiC) polishing. The material is locally exposed to high temperatures and part of it is transformed into silicon oxide (SiO ₂ ). This silicon oxide (SiO ₂ ) becomes a paste-like binder, and the silicon carbide (SiC) abrasive and silicon oxide (SiO ₂ ) adhere to the surface of the alumina substrate with a strong adhesive force. It will be in a state without.

  The present invention has been made in view of the above problems, and provides a substrate cleaning method for removing a polishing residue on a substrate surface to obtain a clean substrate surface, a device manufacturing method using the same, and a device.

  The present invention is characterized in that a residue of an inorganic abrasive present on the surface of the substrate is removed by impregnating an alkali carbonate molten salt with a ceramic substrate or an inorganic heat resistant substrate polished with an inorganic abrasive. It is a cleaning method. According to this, it is possible to remove the polishing residue present on the substrate surface. Therefore, when a metal or ceramic structure having various shapes and functions is formed on the substrate surface, the substrate surface and the structure can be firmly bonded.

  In the substrate cleaning method of the present invention, the alkali carbonate molten salt may be a molten salt obtained by mixing or mixing sodium carbonate and / or lithium carbonate heated to 500 to 800 ° C. When a mixed molten salt of sodium carbonate and lithium carbonate is used, the use of a mixture of sodium carbonate and lithium carbonate in a molar ratio of 7: 3 removes polishing residues mainly composed of silicon carbide or silicon nitride. This is the most preferable method.

  In the substrate cleaning method of the present invention, the inorganic abrasive may be a silicon carbide abrasive.

  In the substrate cleaning method of the present invention, the substrate may be an alumina substrate.

  The present invention is a device manufacturing method including a step of forming a metal or ceramic structure on the surface of a ceramic substrate or an inorganic heat resistant substrate cleaned by any of the above-described substrate cleaning methods. According to this, a metal or ceramic structure having various shapes and functions can be firmly bonded to the substrate surface. Therefore, it is possible to provide a method for manufacturing an element having stable performance by exposing a clean surface of a substrate and forming a structure thereon. The device manufacturing method of the present invention is used, for example, in a method for manufacturing a reducing gas sensor chip.

  In the device manufacturing method of the present invention, the structure may be formed by a liquid phase deposition method, patterning and dry etching using a photoresist, a screen printing method, or a coating method.

  In the element manufacturing method of the present invention, the structure may be a heater or an electrode.

  In the element manufacturing method of the present invention, an electrode is disposed on one surface of the substrate, and a ceramic thin film is deposited on the other surface by liquid phase deposition, and a heater is disposed on the other surface of the substrate. And a step of performing.

In the element manufacturing method of the present invention, the ceramic thin film may be any one of SnO ₂ , WO ₃ , In ₂ O ₃ , and ZnO.

    The element of the present invention is manufactured by any one of the manufacturing methods described above.

  By impregnating the alkali carbonate molten salt with a ceramic substrate or inorganic heat-resistant substrate that has been surface-polished using an inorganic abrasive, the polishing residue on the substrate surface is removed, and a clean substrate surface is exposed. Adheres firmly to the structure. Thereby, the high performance and quality of the element constructed by the substrate and the structure can be guaranteed.

  Hereinafter, an embodiment of a reducing gas sensor including an element according to the present invention will be described with reference to the drawings. In FIG. 1, a reducing gas sensor 1 includes an element 2 (sensor element) according to the present invention. In FIG. 2, the element 2 included in the reducing gas sensor 1 includes a substrate 11, a pair of electrodes 12 and 13 provided on one surface 11 a of the substrate 11, and a surface 11 a of the substrate 11 and electrodes 12 and 13. A ceramic coating film 14 formed on the both sides by a liquid phase deposition method and a heater 15 provided on the other surface 11b of the substrate 11 are provided. For the substrate 11, for example, a high-density sintered alumina substrate that is excellent in electrical insulation, thermal conductivity, and heat resistance is used, and the electrodes 12, 13 and the heater 15 are excellent in heat resistance and corrosion resistance. For example, platinum or a platinum alloy is used.

  In FIG. 3, each of the thin-film electrodes 12 and 13 provided on one surface 11a of the substrate 11 has long pieces 12b and 13b protruding in a comb shape from the bases 12a and 13a, and is connected to one end of the bases 12a and 13a. The parts 12c and 13c are formed. The comb-shaped long pieces 12b and 13b are alternately arranged in parallel, and a facing portion 16 is formed between the long pieces 12b and 13b with the ceramic coating 14 interposed therebetween. The degree of energization of the elongated opposing portion 16 is measured via the electrodes 12 and 13. By setting the comb-like long pieces 12b and 13b to five, nine sections for forming the facing portion 16 are provided, and the energization area detected by the electrodes is increased. The ceramic coating 14 covers the electrodes 12 and 13 excluding the terminal connection portions 12c and 13c and the substrate 11 around the electrodes 12 and 13 so as to cover them. The terminal connecting portions 12c and 13c are connected to the input / output pins 4a and 4b in FIG. 1 through lead wires.

  In FIG. 4, the heater 15 provided on the other surface 11b of the substrate 11 has one zigzag energization path 15c arranged in parallel between the terminal connection portions 15a and 15b at both ends. The terminal connection portions 15a and 15b are connected to the input / output pins 4c and 4d in FIG. 1 through lead wires. The heater 15 is provided to heat the entire substrate to 450 to 500 ° C. so that the reducing gas can be detected by the ceramic coating 14.

  Next, a method for manufacturing the element 2 included in the reducing gas sensor 1 described above will be described.

The manufacturing method of the element 2 includes the following steps. Note that the order of the third step and the fourth step may be reversed.
(1) Substrate polishing step (first step)
(2) Substrate cleaning process (second process)
(3) Electrode attaching process for one surface of substrate (third process)
(4) Heater attachment process for the other surface of the substrate (fourth process)
(5) Coating process of ceramic thin film on electrode and substrate by LPD method (fifth process)

  First, the first step will be described. The surface of the alumina substrate 11 shown in FIG. 2 is polished in advance in order to make the growth direction and speed constant during thin film deposition. As the abrasive, a silicon carbide (SiC) abrasive that is a typical example of an inorganic abrasive is used.

In the second step, the alumina substrate 11 polished in the first step is impregnated into the alkali carbonate molten salt. As the alkali carbonate molten salt, a molten salt obtained by mixing sodium carbonate and lithium carbonate heated to 500 to 800 ° C is used. Here, a molten salt in which sodium carbonate and lithium carbonate are mixed at a molar ratio of 7 to 3 is used. FIG. 5 shows a system diagram of mixed Li ₂ CO ₃ -Na ₂ CO ₃ , and when the mixing ratio of Li ₂ CO ₃ and Na ₂ CO ₃ is 48:52, the lowest melting temperature is 500 ° C. and Li ₂ CO ₃ Alone, the melting temperature is 730 ° C., and Na ₂ CO ₃ alone has a melting temperature of 858 ° C.

  In the third step, thin film electrodes 12 and 13 made of platinum or a platinum alloy are formed on one surface 11a of the alumina substrate 11 shown in FIG. 2 by patterning with a photoresist and dry etching, screen printing, or coating. Since the final size of the substrate 11 is as small as 1 mm × 1.5 mm, for example, the thin film electrodes 12 and 13 on the alumina substrate 11 are selected from the above-described methods suitable for fine processing. In addition, it is preferable that the electrode patterning shape is opposed to each other in an interdigitated arrangement of five or more comb-shaped electrodes, so that the inter-electrode facing area is substantially 9 times or more and the size can be reduced.

  In the fourth step, a platinum or platinum alloy heater 15 is formed on the other surface 11b of the alumina substrate 11 of FIG. 2 by patterning with a photoresist and dry etching, screen printing, or coating. Since the final size of the substrate 11 is small as described above, a method suitable for fine processing is selected from the above methods.

  In the fifth step, as shown in FIG. 2, a ceramic thin film 14 is formed by a liquid phase deposition method (LPD (Liquid Phase Deposition) method) so as to straddle both the alumina substrate 11 and the thin film electrodes 12 and 13. The ceramic coating is not limited to the one formed on the one surface of the substrate 11 by masking or the like, and the ceramic coating including the heater 15 may be applied. In addition, the substrate 11 is cut into a predetermined size of 1 mm × 1.5 mm, for example, after the fifth step. The ceramic thin film by the liquid phase deposition method has an ultra-thin crystal ultra-thin film structure, and has a dense density with a relative density of 90% or more with respect to the theoretical density. The ceramic thin film formed by this liquid phase deposition method performs a catalytic function of reacting selectively with a reducing gas, particularly when heated.

In the LPD method, an oxide dissolved in an acidic ammonium fluoride aqueous solution or an aqueous solution in which various metal hydroxides are dissolved is used as a ceramic precipitation reaction solution, and fluoride ions that are ligands in the hydrolysis equilibrium reaction are used. By adding it as a fluoride ion eater such as boric acid that forms a more stable complex, the equilibrium in the reaction solution is shifted to the oxide precipitation side, and the substrate is immersed in this reaction solution, so that This is a method for precipitating oxide or hydroxide. The oxide formed by the LPD method becomes a ceramic by firing. As this ceramic, any of SnO ₂ , WO ₃ , In ₂ O ₃ , and ZnO is used.

Here, when a SnO ₂ thin film is formed as the ceramic thin film 14, “(NH ₄ ) ₂ SnF ₆ + H ₃ BO ₃ ” or “(NH ₄ ) ₂ SnF ₆ + H ₃ BO ₃ + HSbF is used as the ceramic reaction solution. ₆ "is used. In this ceramic reaction solution, ceramics are deposited and laminated in a temperature range of 10 ° C. to 80 ° C., preferably in a temperature range of 20 ° C. to 40 ° C. Even within this temperature range, the deposited ceramic becomes an anatase crystal having a relative density of 90% or more with respect to the theoretical density. The substrate 11 on which the SnO ₂ thin film is formed is baked by high-temperature heat treatment at around 800 ° C. (750 to 850 ° C.). In order to fill the cracks generated by the high-temperature heat treatment, the above-described precipitation / stacking and high-temperature heat treatment are repeated twice. Furthermore, by performing an additional heat treatment at around 1,000 ° C. (950 to 1050 ° C.), an ultra-thin crystalline SnO ₂ deposited laminated film of 8 nm or less and an ultra-thin film structure of 80 to 300 nm is added to the aromatic hydrocarbon gas. Those that are selectively detectable are preferred.

Further, when a WO ₃ thin film is formed as the ceramic coating 14, an aqueous solution containing NH ₃ F · HF or HF is dissolved in WO ₃ or WO ₃ · xH ₂ O, and H _{3 is} added to the obtained fluoride complex aqueous solution. BO ₃ is added to make a reaction solution. When an In ₂ O ₃ thin film is formed as the ceramic coating 14, In ₂ O ₃ is added to the NH ₄ F / HF aqueous solution to dissolve and saturate it, and the indium oxide remaining undissolved is filtered, and the filtrate is used as the mother liquor. To do. An aqueous H ₃ BO ₃ solution is added to this mother liquor to make a reaction solution. In addition, since the deposited thin film is InOF which is a ceramic precursor, it is made into In ₂ O ₃ by firing. When a ZnO thin film is formed as the ceramic coating 14, NH ₄ F · HF is dissolved in an aqueous solution, and an aqueous H ₃ BO ₃ solution and an aqueous NH ₃ solution are added to obtain a reaction solution.

  In addition, it is also possible to add additives for improving the doping or deposition state, deposition rate, etc., for example, surfactants, etc., to these reaction solutions as necessary. Usually, in these reaction solutions, ceramics or ceramic precursors are deposited and laminated in a temperature range of 10 ° C. to 80 ° C., preferably in a temperature range of 20 ° C. to 40 ° C. Even within this temperature range, the precipitated ceramic or ceramic precursor forms anatase crystals having a relative density of 90% or more with respect to the theoretical density. Furthermore, the crystallinity can be increased by heat treatment at a high temperature. Ceramics or ceramic precursors by the LPD method can be made to have a relative density of 90% or more at the stage of deposition and lamination, and therefore hardly shrink even when subjected to a heat treatment at a high temperature.

Further, by repeating the precipitation / high-temperature firing heat treatment twice or more, a dense structure filled with cracks after firing can be obtained. Furthermore, by performing an additional heat treatment at a higher temperature than the high-temperature baking heat treatment, it is possible to finish the film with less influence of cracks and particularly with an increased sensitivity to a low concentration VOC gas. For example, in the case of a SnO ₂ film, the precipitation and the high-temperature baking heat treatment at around 800 ° C. (750 to 850 ° C.) are repeated at least twice, and further by additional heat treatment at around 1,000 ° C. (950 to 1050 ° C.) It is possible to obtain an ultra-thin film structure of 80 to 300 nm with a deposited laminated film of ultrafine crystalline SnO _{2 having} a thickness of 8 nm or less, which is selective with respect to aromatic hydrocarbons.

Next, the difference in the surface roughness of the alumina substrate surface between the substrate cleaning method of the present invention and the substrate cleaning method of the comparative example will be described.
FIG. 6 relates to a substrate cleaning method of the present invention, and an alumina substrate after polishing is impregnated for 10 seconds with an alkali carbonate molten salt obtained by mixing a molten sodium carbonate salt and a lithium carbonate molten salt at a molar ratio of 7: 3 at 680 ° C. for 10 seconds. The surface enlarged-microscope photograph (5000 times) before and behind cleaning of the alumina substrate surface at the time of cleaning the substrate surface is shown.
FIG. 7 relates to a substrate cleaning method of a comparative example, and the surface of the alumina substrate surface before and after cleaning when the alumina substrate after polishing was impregnated with a 380 ° C. potassium hydroxide melt for 5 seconds to clean the surface of the alumina substrate. An enlarged photomicrograph (5000 times) is shown.
According to the method for cleaning the surface of an alumina substrate of the present invention, as can be seen from FIG. 6, the surface of the alumina substrate does not become rough at all even if silicon carbide or nitrogen carbide impurities in the abrasive are cleaned. According to FIG. 7, as can be seen from FIG. 7, the surface of the substrate after cleaning is severely roughened, making it impossible to form electrodes and heaters.

In the above-described embodiment, the case where the polished alumina substrate is impregnated with the potassium hydroxide melt is described as the substrate cleaning method of the comparative example. However, the polished alumina substrate is HF, FeCl ₃ , NaOH. In the case of impregnating any one of the above melts, it was confirmed that the surface of the substrate after cleaning was severely roughened as in FIG. 7, and it was impossible to form electrodes and heaters.

Next, the cleaning effect of cleaning the silicon carbide and nitrogen carbide impurities of the abrasive by the method for cleaning the surface of the alumina substrate of the present invention will be described.
FIG. 8A shows an XPS spectrum of an alumina substrate surface impurity analysis before cleaning, and it can be confirmed that impurities of silicon carbide and silicon oxide as abrasives remain on the alumina substrate surface. The reason why these impurities remain on the surface of the alumina substrate is considered to be as follows. While the silicon carbide abrasive is mixed with cooling water and supplied to the buffing disk, the surface of the alumina substrate is polished at a high speed to produce large frictional heat locally at the contact surface between the alumina substrate and the buff, and silicon carbide (SiC) polishing. The material is locally exposed to high temperatures and part of it is transformed into silicon oxide (SiO ₂ ). This silicon oxide (SiO ₂ ) becomes a paste-like binder, and the silicon carbide (SiC) abrasive and the silicon oxide (SiO ₂ ) adhere to the surface of the alumina substrate with a strong adhesive force. It will be in a state without.
FIG. 8 (b) shows an XPS spectrum of an alumina substrate surface impurity analysis after impregnating an alumina substrate in a mixed carbonate of Na ₂ CO ₃ and Li ₂ CO ₃ heated to 650 ° C. for 10 seconds and cleaning the substrate surface. It can be confirmed that the residual impurities of the silicon carbide (SiC) abrasive and the silicon oxide (SiO ₂ ) binder on the surface of the alumina substrate were completely removed.

Next, regarding the element in which the platinum electrode is formed on the surface of the alumina substrate, the bonding state between the platinum electrode and the substrate after repeating the operation state at 400 to 700 ° C. will be described.
FIG. 9 shows magnified micrographs (5000 times and 1000 times) of the substrate surface when the platinum electrode is formed without cleaning the surface of the alumina substrate.
FIG. 10 shows a magnified micrograph (5,000 times) of the substrate surface when the platinum electrode is formed after the surface of the alumina substrate is washed with a carbonate melt.
Indicates.
When the platinum electrode is formed without cleaning the surface of the alumina substrate, the platinum electrode is peeled off from the surface of the alumina substrate, as can be seen from FIG. On the other hand, when the platinum electrode is formed after washing the alumina substrate surface with the carbonate melt, the platinum electrode is firmly bonded to the alumina substrate surface and does not peel off, as can be seen from FIG.

  As described above, in the element 2 of the present embodiment, the inorganic abrasive that exists on the surface of the alumina substrate by impregnating the alumina substrate 11 polished with a silicon carbide (SiC) abrasive into alkali carbonate molten salt. After the residue is removed, metal or ceramic structures having various shapes and functions are formed on the surface of the alumina substrate. Therefore, the surface of the alumina substrate and the structure can be firmly bonded, so that an element having stable performance can be provided.

Hereinafter, an example and a comparative example will be described in comparison.
[Example]
An alumina substrate in which a platinum electrode is provided on one side of the alumina substrate from which polishing residues existing on the surface of the alumina substrate polished with a silicon carbide abrasive are completely removed with an alkali carbonate molten salt and a platinum heater is provided on the other side Was subjected to precipitation treatment at 30 ° C. for 24 hours in a reaction solution of (NH ₄ ) ₂ SnF ₆ + H ₃ BO ₃ . The alumina substrate was fired at 800 ° C. After firing, the reaction solution was subjected to a short precipitation treatment and fired at 800 ° to infiltrate SnO ₂ into the cracks. Next, an additional heat treatment was performed at 1000 ° C. to reduce cracks. By these treatments, a SnO ₂ film having a crystal grain size of about 5 nm and a thickness of 100 nm and having a theoretical density of about 96% was formed.

[Comparative example]
In the same manner as in the examples, a crystal electrode was formed on one side of an alumina substrate having a platinum electrode on one side and a platinum heater on the other side by powder sintering of SnO _{2 so} that the crystal grains were about 100 nm and the thickness was 30 μm. Thus, a SnO ₂ film having a theoretical density of 90% was formed.

  Although the preferred embodiment of the present invention has been described above, the above is an example, and can be modified as follows, for example.

  In the above-described embodiment, an alumina substrate is used as the ceramic substrate or the inorganic heat resistant substrate, but the same effect can be obtained when a ceramic substrate or an inorganic heat resistant substrate other than the alumina substrate is used. Accordingly, by impregnating the sapphire substrate polished with a silicon carbide (SiC) abrasive into the alkali carbonate molten salt, the residue of the inorganic abrasive present on the surface of the sapphire substrate can be removed. In addition, although a silicon carbide abrasive is used as the inorganic abrasive, an inorganic abrasive other than the silicon carbide abrasive may be used. Moreover, although the molten salt which mixed sodium carbonate and lithium carbonate heated at 500-800 degreeC is used as alkali carbonate molten salt, another alkali carbonate molten salt may be sufficient.

1 is an overall external view of a reducing gas sensor including an element according to the present invention. FIG. 2 is an arrangement conceptual diagram of an alumina substrate, an electrode, a heater, and a ceramic coating of the element of FIG. 1. It is a conceptual diagram of the heater circuit formed on the alumina substrate of an element. It is a conceptual diagram of the electrode circuit formed on the alumina substrate of an element. Mixed carbonate melt _{(Li 2 CO 3 -Na 2 CO} 3) is a system phase diagram. It is the surface expansion microscope picture before and behind cleaning of the alumina substrate surface cleaned by the substrate cleaning method of the present invention. It is the surface expansion microscope picture before and behind washing | cleaning of the alumina substrate surface wash | cleaned with the board | substrate washing | cleaning method of the comparative example. FIG. 8A shows the result of analyzing the surface impurities on the alumina substrate before cleaning. FIG. 8B shows the result of analysis of impurities on the surface of the alumina substrate after cleaning. It is a substrate surface enlarged microscope picture at the time of forming a platinum electrode, without washing the alumina substrate surface. It is a substrate surface enlarged microscope picture at the time of forming a platinum electrode after washing the surface of an alumina substrate with a carbonate melt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reducible sensor 2 Element 11 Alumina substrate 11a Electrode side surface 11b of alumina substrate Heater side surface 12 of alumina substrate 12 Electrode 13 Electrode 14 Ceramic coating 15 Heater

Claims (10)

  A substrate cleaning method comprising removing a residue of an inorganic abrasive present on the substrate surface by impregnating an alkali carbonate molten salt with a ceramic substrate or an inorganic heat resistant substrate polished with an inorganic abrasive. The substrate cleaning method according to claim 1,
The method for cleaning a substrate, wherein the alkali carbonate molten salt is a molten salt obtained by mixing sodium carbonate and / or lithium carbonate heated to 500 to 800 ° C. alone or in combination. The substrate cleaning method according to claim 1 or 2,
The substrate cleaning method, wherein the inorganic abrasive is a silicon carbide abrasive. In any one of the board | substrate washing | cleaning methods of Claims 1-3,
The substrate cleaning method, wherein the substrate is an alumina substrate.   A device manufacturing method comprising a step of forming a metal or ceramic structure on a surface of a ceramic substrate or an inorganic heat resistant substrate cleaned by the substrate cleaning method according to any one of claims 1 to 4. In the manufacturing method of the element of Claim 5,
The structure is a method for manufacturing an element formed by a liquid phase deposition method, patterning and dry etching using a photoresist, a screen printing method, or a coating method. In the manufacturing method of the element of Claim 5 or 6,
The method for manufacturing an element, wherein the structure is a heater or an electrode. In the manufacturing method of the element of Claim 5,
A step of placing an electrode on one surface of the substrate and further depositing and coating a ceramic thin film thereon by liquid phase deposition;
And a step of disposing a heater on the other surface of the substrate. In the manufacturing method of the element of Claim 8,
The method for manufacturing an element, wherein the ceramic thin film is any one of SnO ₂ , WO ₃ , In ₂ O ₃ , and ZnO.   The element manufactured with the manufacturing method in any one of Claims 5-9.