JP4693437B2 - Sensor for measuring minute mass and manufacturing method thereof - Google Patents

Description

          The present invention relates to a highly reliable sensor for measuring a minute mass and a method for manufacturing the same.

          Conventionally, a sensor element for measuring a minute mass (QCM Quartz Crystal Microbalance sensor element) using an AT-cut quartz crystal resonator uses a thickness-shear vibration mode of quartz, and is used as a metal film material formed on the surface of the quartz substrate. Chromium (Cr), Nickel chromium (NiCr), Titanium (Ti), etc. are used in consideration of adhesion to the quartz substrate, but such a sensor element for measuring a small mass is immersed in a solution. In this case, the previous vibration mode is suppressed by the resistance of the solution, and it cannot be used as a sensor element for measuring a minute mass. Therefore, the vibration mode can be detected even when immersed in the solution by setting the metal film of the quartz substrate on the side where the reaction of the solution is not detected to a gas phase state.

In order to keep the metal film on one side of the quartz substrate in a gas phase state, the entire periphery of the sensor element for measuring the minute mass must be fixed with an adhesive or the like to prevent the solution from entering. In general, in order to make the influence on the vibration mode of the sensor element for measuring the minute mass as small as possible,
Silicon-based insulating adhesives with low bonding stress are often used. However, even when using silicon-based adhesives, the amount of adhesive applied varies depending on the skill level of the operator. However, it is difficult to accurately fix the sensor element for measuring the minute mass horizontally, and in either case, the sensitivity of the sensor element for measuring the minute mass is individually determined. There was a risk that it would be different.

          In addition, when the adhesive is cured, by-products such as organic substances are generated from the adhesive, and the by-products are attached to the surface of the sensor element for measuring the minute mass for detecting extremely minute reactions. There is also a risk of letting it go. In particular, when a silicon-based adhesive is used, low molecular siloxane may be generated as a by-product and may adhere to the metal film surface. Once this low molecular weight siloxane adheres to the surface of the metal film, there is a risk that the detection sensitivity of the sensor element for measuring a minute mass will be significantly reduced.

JP 2001-153777 A Japanese Patent Laid-Open No. 11-14525

          In addition, the applicant did not find any prior art documents related to the present invention by the time of filing of the present application other than the prior art documents specified by the above prior art document information.

          By using an adhesive to fix the sensor element for measuring the micromass, the detection sensitivity of the sensor element for measuring the micromass is not individually reduced due to adhesion of the by-product of the adhesive to the surface of the sensor element for measuring the micromass. There has been a problem that it may be uniform and its detection sensitivity may be significantly reduced.

          The present invention has been made based on the technical background as described above. Accordingly, an object of the present invention is to provide a highly reliable sensor for measuring a minute mass and a method for manufacturing the same. .

A sensor element for measuring a minute mass using a quartz crystal formed by forming a metal film on the surface of a quartz substrate, and a signal output end provided integrally with glass or quartz and extending to the upper edge. a cylindrical container having a horizontal step therein, and having a bonding surface that is bonded by anodic bonding in terms of the cylindrical container within the stepped opening side.

          Further, the cylindrical container in which the sensor element for measuring the minute mass is accommodated is made of glass or quartz.

A peripheral portion of one surface of a sensor element for measuring a minute mass using a crystal resonator formed by forming a metal film on the surface of a quartz substrate is provided on the side of the step opening portion inside the cylindrical container body provided integrally . The element is bonded to the surface by anodic bonding, and a sensor for measuring a minute mass is placed thereon.

          According to the sensor for measuring a minute mass of the present invention, since no adhesive is used for fixing the sensor element for measuring a minute mass, an adhesive by-product adheres to the sensor element (sensor element for measuring a minute mass). There is no possibility of reducing the detection sensitivity, and a very reliable sensor for measuring a minute mass can be obtained.

          Moreover, according to the method for manufacturing a sensor for measuring a minute mass of the present invention, a large number of sensors for measuring a minute mass having a remarkably uniform detection sensitivity can be efficiently manufactured.

          Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol in each figure shall show the same object.

FIG. 1 is a schematic side sectional view of the sensor 8 for measuring a minute mass according to the present invention as viewed from the side. The sensor 8 for measuring a minute mass according to the present invention is a sensor 8 for measuring a minute mass using a crystal resonator 3 formed by forming a metal film 2 on the surface of a quartz substrate 1 having an arbitrary shape. A joint surface 11 is provided on the inner surface 6 of the cylindrical container 10 on the opening side surface 7 of the cylindrical container 10 of the previous step, that is, on the peripheral portion on the side of the quartz substrate 1 that can be used as a gas phase state. Of the structure. The sensor block 4 for measuring a minute mass placed inside the cylindrical container 10 has, for example, a shape as shown in FIG. 5, which is formed by depositing the material of the metal film 2 on the quartz substrate 1 by a vapor deposition method or a sputtering apparatus. The metal film 2 is made to volume on the quartz substrate 1 using As a method of joining the sensor element 4 for measuring the minute mass with the joining surface 11 in the step opening side surface 7 inside the cylindrical container 10 made of glass or quartz, an adhesive is used by using anodic bonding. The sensor element 4 can be fixed inside the cylindrical container 10 without using the. Here, FIG. 1 is a schematic side sectional view of the sensor 8 for measuring a minute mass when viewed from the side surface direction when the sensor element 4 is bonded by anodic bonding, and the metal film 2 as shown in FIG. With this structure, both surfaces of the sensor element 4 for measuring the minute mass can be completely separated by joining, and the sensor element 8 for measuring the minute mass of the present invention as shown in FIG. Can be used to obtain a very reliable sensor 8 for measuring a minute mass. As shown in FIG. 1, a metal bonding material such as aluminum used for anodic bonding is deposited on one side of the sensor element 4 by vapor deposition or the like, and a DC current is applied while being placed and pressed inside the cylindrical container 10. Join. In the structure shown in FIG. 1, the metal film 2 used for bonding, the metal film 2 used as an electrode formed on the quartz substrate 1, and the metal film 2 used as an electrode formed on the quartz substrate 1 are mutually connected. It has a structure that does not come into electrical contact.

          FIG. 2 is a schematic diagram of the minute mass measuring sensor 8 according to the present invention as viewed obliquely from above. The quartz substrate 1 has various shapes and sizes, and FIG. 2 is an example. Therefore, when the quartz substrate 1 is not a circular plate but a rectangular plate, the outer shape of the cylindrical container is a polygonal shape, and the inner diameter shape of the container in which the sensor element 4 for measuring the minute mass is accommodated is a rectangular parallelepiped. Of course, these cases are also included in the technical scope of the present invention. In addition, as shown in FIG. 2, the sensor 8 for measuring a minute mass according to the present invention is very suitable for using one side of the sensor element 4 in a liquid phase state and the other side in a gas phase state. Although it has a structure, it can also be used as a sensor 8 for measuring a minute mass using both sides as a gas phase.

          FIG. 3 is a schematic top view of the minute mass measuring sensor 8 of the present invention as seen from the top surface direction. In FIG. 3, the signal output end 9 of the sensor element 4 for measuring the minute mass placed in the container inside 6 is extended to the upper edge of the cylindrical container 10, and the sensor for measuring the minute mass is provided. This makes it very easy to carry out a micromass measurement using 8.

          FIG. 4 is a schematic cross-sectional view showing a conventional sensor element 4 for measuring minute mass. In the sensor element 4 for measuring a minute mass made by a conventional process, when titanium is used as the material of the base metal film 12 and gold is used as the material of the upper metal film 13, the surface of the gold film made of gold having low hardness is used. There is a problem that the hardness is low and the above-mentioned gold film surface is easily damaged when the sensor element 4 for measuring a small mass is used by immersing it alone in a solution, which may make it difficult to perform highly reliable measurement. However, according to the structure of the sensor 8 for measuring a minute mass of the present invention, the outer wall of the cylindrical container 10 protects the metal film 2 used as the electrode of the sensor element 4 for measuring the minute mass inside. Also play. FIG. 4 is a schematic cross-sectional view of a conventional sensor element 4 for measuring a minute mass. Many of the metal films 2 used as electrodes formed on the quartz substrate 1 described above are two layers of base metal films made of different materials. 12 and the upper metal film 13, and as the uppermost metal film material 13, chemically stable gold (Au) is often used.

          FIG. 5 is a schematic top perspective view of a conventional sensor element 4 for measuring a small mass, as viewed obliquely from above. The quartz substrate 1 has various shapes and sizes, and FIG. 5 is an example.

1 is a schematic side cross-sectional view of a sensor for measuring a minute mass of the present invention as viewed from the side. It is the schematic model which looked at the sensor for micro mass measurement of this invention from the diagonally upward direction. It is the schematic upper surface figure which looked at the sensor for micro mass measurement of the present invention from the upper surface direction. It is the general side sectional view which looked at the conventional sensor element for micro mass measurement from the side direction. It is the outline top perspective view which looked at the conventional sensor element for micro mass measurement from the slanting upper direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crystal substrate 2 Metal film 3 Crystal oscillator 4 Sensor element for micro mass measurement 5 Horizontal level | step difference 6 Inside of cylindrical container 7 Surface of step opening side 8 Sensor for micro mass measurement 9 Signal output end 10 Cylindrical container 11 Bonding film 12 Underlying metal film 13 Overlying metal film

Claims (1)

  A sensor element for measuring a minute mass using a quartz crystal formed by forming a metal film on the surface of a quartz substrate, and a signal output end provided integrally with glass or quartz and extending to the upper edge. A sensor for measuring a minute mass, characterized in that a cylindrical container having a horizontal step inside has a joint surface joined by anodic bonding at a surface on the step opening side inside the cylindrical container.

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