JPH06169095A - Method for joining silicon structure with glass structure and dynamics quantum sensor based thereon - Google Patents

Abstract

PURPOSE:To provide a method for joining a silicon structure with glass structures and a highly accurate dynamics quantum sensor based thereon for providing well-controlled gaps between electrodes. CONSTITUTION:A silicon structure 13, 14 and 15 with part of its substrate 13 etched, and glass structures 11a and 12a, and 11b and 12b with grooves 11c and 11d formed therein, are joined by anodic junction to form a sensor which detects dynamics quanta. The glass structure is obtained by forming glass thin films 12a and 12b on glass substrates 11a and 11b containing metal ions, and etching the resultant glass thin films to form the grooves 11c and 11d. This obtains smooth grooves 11c and 11d excellent in depth controllability, and an well-controlled gap (d) between electrodes 16a and 16b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for joining a silicon structure and a glass structure, and a mechanical quantity sensor using the same for detecting a mechanical quantity such as displacement and acceleration. The present invention relates to a mechanical quantity sensor that can be created.

[0002]

2. Description of the Related Art Conventionally, there is a mechanical quantity sensor as a sensor for indirectly detecting an external force by detecting a deformation, a displacement caused by an external force, a resistance change, a capacitance change or the like of the deformed or displaced object. Currently, mechanical quantity sensors that are mainly used include a piezoelectric type using a piezoelectric effect, a metal resistor, or a strain gauge type using a semiconductor, and detect acceleration, pressure, and the like. Attempts have also been made to manufacture a small acceleration sensor by manufacturing a cantilever using semiconductor IC process technology. For example, Japanese Patent Application Laid-Open No. 1-240865 proposes a servo type acceleration sensor that detects a strain of a beam portion by a piezoelectric element and feeds back the strain to correct a displacement of a weight by an electrostatic force.

FIG. 7 shows this acceleration sensor formed by using a semiconductor IC process. The vibrating body has a cantilever structure including a support beam 74 and a weight 75 in which single crystal silicon is integrally formed by microfabrication.
When acceleration is applied in the vertical direction of FIG. 7, the beam 74 undergoes bending deformation, and the deformation is detected by the piezoresistive element 76 formed on the surface of the beam. This signal is sent to the servo circuit 77 to detect the deformation of the beam 74. This signal is the servo circuit 7
7 and the electrostatic force that suppresses the deformation of the beam 74 is applied to the weight 75.
It is generated in the electrodes 73a and 73b formed above and below.
As the output of the sensor, the voltage applied to the two electrodes 73a and 73b can be obtained through the arithmetic processing circuit 78. Electrodes 73a and 73b are structural bodies 72 in which grooves are formed, respectively.
Structures 72a, 72b formed in the groove portions of a, 72b
Are bonded by sandwiching the silicon substrate body 71.

When the minute displacement of the weight 75 is suppressed by an electrostatic force or detected by an electrostatic capacity, in order to measure it with high accuracy, the gap between the electrodes 73a and 73b is well controlled, and is smooth and has a low resistance. It is necessary to make electrodes. Therefore, in order to form an accurate sensor, the upper and lower structures 72a,
It is essential that the groove of 72b be manufactured with good controllability and be smooth, and that the groove be bonded to the silicon substrate 71 while maintaining dimensional accuracy. Currently, both the upper and lower structures are made of silicon, and anisotropic etching is used to form grooves with good controllability.
Fabrication has been attempted by directly aligning this to obtain dimensional accuracy, or by etching the glass structure to perform anodic bonding that enables the glass structure to be bonded at relatively low temperature with good dimensional accuracy.

[0005]

However, the above-mentioned prior art has the following problems. If a silicon structure is used, a groove can be formed with good controllability, but direct bonding is a high-temperature process, which makes it difficult to manufacture a metal electrode in terms of process steps.

On the other hand, the glass structure can be joined with dimensional accuracy at a relatively low temperature, but the glass etching tends to proceed isotropically, and the etching rate greatly changes due to a delicate composition ratio. It is difficult to form a smooth groove with good controllability.

Therefore, an object of the present invention is to solve the above-mentioned problems, to bond a silicon structure and a glass structure, and to manufacture an air gap between electrodes with good controllability by using this method. It is to provide a mechanical quantity sensor.

[0008]

In the bonding method according to the present invention for achieving the above object, in the method for bonding silicon and a glass structure, the glass structure forms a glass thin film on a glass substrate containing metal ions. It is formed as a film and is characterized in that silicon and a glass structure are joined by anodic bonding.

More specifically, for example, a thermal oxide film or a sputtered oxide film is formed on silicon and bonded.

A mechanical quantity sensor according to the present invention for achieving the above object is a mechanical quantity sensor for detecting a mechanical quantity produced by joining a silicon structure obtained by etching a part of a silicon substrate and a glass structure having a groove. The glass structure is characterized in that a glass thin film is formed on a glass substrate containing metal ions and the groove is formed by etching the glass thin film.

More specifically, the glass substrate is silicate glass or borosilicate glass, the glass thin film is silicate glass containing no ions, and the glass thin film is phosphate glass or borate glass. The glass thin film may be one of arsenic oxide glass or a silicate glass containing at least one of phosphorus, boric acid and arsenic as an element or an oxide.

In the mechanical quantity sensor having the above-mentioned structure, a glass thin film having a composition different from that of the substrate is formed on the glass substrate, and the etching rate is different because the composition is different, so that the glass has good controllability. , To form a desired groove.

Further, in one mode of the mechanical quantity sensor according to the present invention for achieving the above-mentioned object, a groove is formed in a facing portion of the weight and the Si structure having the weight supported by the beam by etching. In a mechanical quantity sensor manufactured by joining the formed glass structures, on a glass base substrate, a glass thin film having a different composition from the substrate glass is formed to a desired groove depth,
This thin film portion is etched to produce a glass structure.

[0014]

In the mechanical quantity sensor having the above-mentioned structure, a glass thin film having a composition different from that of the substrate is formed on the glass substrate, and since the composition is different, the etching rate is different so that the glass has good controllability. , To form a desired groove.

If the etching rate ratio of the glass thin film is sufficiently large, the etching in the depth direction can be completed when the surface of the substrate glass is exposed. For this reason, a groove which is smooth and has good depth controllability can be obtained, and the inter-electrode gap can be obtained with good controllability.

Further, the silicon structure and the glass structure can be bonded together by using the anodic bonding method, which can be carried out at a relatively low temperature, and the metal electrode can be easily manufactured.

[0017]

Embodiment 1 An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of the main part of the acceleration sensor of the first embodiment. The silicon substrate 13 including the support beam 14 and the weight 15 integrally formed by anisotropically etching silicon to form a rectangular groove 13a around the glass substrate 11a, 11b is formed through the glass thin films 12a, 12b.
It is sandwiched by b from above and below.

The upper surface of the weight 15 and the glass structures 11b, 1
In the groove portion 11c of 2b, the electrode 16a and the fixed electrode 16b are formed so as to face each other by forming a metal film using a vacuum deposition method, a plating method, a sputtering method or the like, and then patterning it by photolithography.
The positions of the electrodes are the lower surface of the weight 15 and the glass structure 11a,
You may arrange | position facing the recessed part 11d of 12a. In addition,
The distance d between the electrodes 16a and 16b is about several μm.

FIG. 2 shows the upper and lower glass structures 11a, 12a;
It is a block diagram of 11b, 12b. For example, the glass substrate 21 contains borosilicate glass containing 4% of metal ions having a small thermal expansion coefficient difference with silicon (12.7% boric acid).
(Product name: # 7740, manufactured by Corning Incorporated) is used.
On the glass substrate 21, a silicate glass thin film 22 containing no metal ions is deposited by a sputtering method to a desired groove depth. However, the film may be formed by any method as long as the film thickness can be controlled and deposited. After that, a resist mask is formed by photolithography, and the groove 23 is formed by etching. In the case of the above materials, for example, when a buffer etching solution having a weight ratio of HF and NH ₄ F of 1: 6 is used, the etching rate of the metal ion-containing borosilicate glass 21 is about 500 Å / min, whereas the silicate glass is The etching rate of the thin film 22 is 2500 Å / m
It is not less than in and has an etching rate ratio sufficient for selective etching. Thus, the groove 23 having a relatively smooth surface of the borosilicate glass 21 of the substrate and having a desired depth can be formed on the bottom surface.

The glass structures 11a and 12a and the silicon substrate 13 are joined by anodic bonding. FIG. 3 shows the film thickness dependence of VI characteristics when a glass structure having a thermal oxide film or a sputtered oxide film and a silicon substrate are bonded. The voltage V was measured after visually confirming the entire surface bonding (as seen by the interference fringes of the bonding surface of the glass structure and the silicon substrate), and the current was 3 minutes after the voltage was applied. I'm measuring. In FIG. 3, 33 is a thermal oxide film on the silicon substrate, 0.15 μm, 34 is 0.3 μm, and 35 is 0.5 μm.
m and 36 are formed in a thickness of 1 μm, 37 is a case where silicate glass is formed in a thickness of 2 μm on a silicon substrate by a sputtering method, 3
1 is 2 μm of silicate glass on the glass by the sputtering method, 3
Reference numeral 2 indicates a bonding condition between the silicon substrate and the glass structure when the film is formed to 1 μm. The sample temperature at the time of joining is 400 ° C. When the sputtered oxide film was formed to a thickness of 2 μm on the silicon substrate, no bonding was performed, but in all other cases, bonding was possible. Further, the specific resistance hardly depended on the film thickness.

FIG. 4 shows the film thickness dependence of the voltage required for bonding when the current obtained from the experimental value is constant. Figure 4
In the figure, 41 is the relationship when the glass thin film is formed on the silicon substrate, and 42 is the relationship when the glass thin film is formed on the glass substrate. When the glass thin film was formed on silicon by 2 μm, it was not joined (hatched circle), and when it was formed on glass by 2 μm, it was possible to join.
If it is possible to bond up to a voltage of 00 to 800 V,
When a glass thin film is formed on a glass substrate, the film thickness is 5-6.
It is possible to bond up to μm. .

From the above, the glass structure 11a, which has a large bonding strength at a low temperature and maintains dimensional accuracy, by using the anodic bonding method,
12a and the silicon substrate 13 can be joined.

A silicon substrate 13 and a glass structure 11b,
The joining of 12b is performed in the same manner.

In this way, the smooth flat groove 11c can be obtained by firmly joining the gap d between the electrodes 16a and 16b with high dimensional accuracy. Therefore, the acceleration sensor shown in FIG. However, the acceleration can be accurately detected.

[0026]

[Modification of Embodiment 1] As a modification of the first embodiment, glass substrates 11a, 1a having the same configuration as the first embodiment (FIG. 1) are used.
1b and glass thin films 12a and 12b are made of glass having another composition.

FIG. 5 is a table showing typical glass etching rates and etching solutions. For example, silicate glass containing metal ions is used for the glass substrate, silicate glass containing no metal ions is used for the glass thin film, and H is used for the etching solution.
If a buffer etching solution of F: NH ₄ F = 1: 6 is used, etching is performed at an etching ratio of 8: 1 (= 4000: 500), and the glass substrate is made of borosilicate glass containing metal ions and the glass thin film is made of phosphosilicate glass. If a buffer etching solution prepared by diluting HF: NH ₄ F = 1: 10 with pure water 100 times is used as the etching solution, only the thin film portion is etched.

As described above, depending on the composition of the mother substrate glass and the glass thin film, the temperature and the etching solution are taken into consideration, and if materials and conditions having a sufficient difference in etching rate are selected, a smooth groove can be formed with good controllability. be able to.

Further, as described above, since the glass structure and the silicon structure can be bonded at a low temperature by the anodic bonding method, the metal electrode can be easily manufactured.

Thus, by selecting a material having a sufficiently large etching ratio as the material of the glass substrate and the glass thin film, it becomes possible to obtain a strong joint with a groove on a smooth flat surface having a dimensional accuracy of an interelectrode gap and a high accuracy. It has become possible to detect changes in electrostatic capacity and accurately detect acceleration.

[0031]

Second Embodiment A second embodiment of the present invention will be described below with reference to FIG.

FIG. 6 is a sectional view of the main part of the pressure sensor of the second embodiment. In the second embodiment, the glass thin film 6 is formed by anisotropically etching silicon to form the silicon substrate 63 on which the pressure sensitive diaphragm portion 66 that receives the pressure to be measured is formed.
A reference pressure chamber 64 is formed by being joined to the glass substrate 61 through 2.

Electrodes 65a and 65b are formed on the groove portions 61a of the glass structures 61 and 62 and on the reference pressure chamber 64 side of the pressure sensitive diaphragm portion 66, respectively. An integrated circuit 67 formed by vapor deposition, diffusion, etc. is formed on the reference pressure chamber 64 side of the diaphragm portion 66. Distance d between the electrodes 65a and 65b
Is about several μm.

The glass structures 61 and 62 have the same structure as in the above embodiment. Further, as in the above embodiment, the glass substrate 6
1 and the glass thin film 62 are made of glass having a composition sufficiently different in etching rate to form the groove 61a with smoothness and good controllability. Further, since the glass structures 61 and 62 and the silicon structures 63 and 66 can be anodically bonded at a relatively low temperature as in the above-mentioned embodiment, the metal electrodes 65a and 65b can be easily manufactured.

By forming the glass structures 61 and 62 in this way, the grooves 61a on the smooth plane are formed in the interelectrode gap d.
It is now possible to obtain a strong joint with good dimensional accuracy, and it has become possible to detect changes in capacitance with high accuracy and measure minute pressure changes. In FIG. 6, 68 is a lead wire from the integrated circuit 67 which penetrates the hole formed in the silicon substrate 63.

[0036]

As described above, in the mechanical quantity sensor manufactured by using the bonding method of the silicon structure and the glass structure according to the present invention, the interelectrode gap is well controlled, and the metal electrode can be obtained in the easy process. .

Therefore, it has become possible to manufacture a mechanical quantity sensor capable of detecting a change in capacitance with high accuracy and detecting a minute mechanical quantity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the main components of a first embodiment of the present invention.

FIG. 2 is a diagram showing a part of the main configuration of the first embodiment.

FIG. 3 is a graph of voltage-current characteristics when joining a glass structure and a silicon structure.

FIG. 4 is a graph showing the relationship between the film thickness of a thin film and the voltage required for bonding when bonding a glass structure and a silicon structure.

FIG. 5 is a table showing examples of typical glass etching rates and etching solutions.

FIG. 6 is a sectional view showing the main configuration of a second embodiment.

FIG. 7 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

11a, 11b, 21, 61 ... Glass substrate 11c, 11d, 23, 61a ... Groove portion of glass structure 12a, 12b, 22, 62 ... Glass thin film 13, 63, 71 ... Silicon structure substrate 13a, 23 …… Silicon substrate groove 14,74 …… Support beam 15,75 …… Weight 16a, 16b, 65a, 65b, 73a, 73b ……
Electrode 31 …… Voltage-current characteristics at the time of joining of a glass structure in which a silicate glass thin film is formed to a thickness of 2 μm on a silicon substrate and a borosilicate glass substrate 32 …… A silicate glass thin film is deposited on a silicon substrate and a borosilicate glass substrate. Voltage-current characteristics during bonding of glass structure with 1 μm film thickness 33 ... Borosilicate voltage-current characteristics during bonding of structure with thermal oxide film formed on glass substrate and silicon substrate 0.15 μm 34 ... Borosilicate acid Voltage-current characteristics at the time of joining structures with a thermal oxidation film of 0.3 μm deposited on a glass substrate and a silicon substrate 35 ... Bonding of structures with a thermal oxidation film of 0.5 μm deposited on a borosilicate glass substrate and a silicon substrate Voltage-current characteristics 36 …… Voltage-current characteristics at the time of bonding of a structure in which a thermal oxidation film was formed on a borosilicate glass substrate and a silicon substrate by 1 μm 37 …… A silicate glass thin film was formed on a borosilicate glass substrate and a silicon substrate. Voltage-current characteristics at the time of bonding of a structure having a film thickness of 2 μm 41 ... Relationship between voltage required for bonding a structure having a silicate glass thin film formed on a borosilicate glass substrate and a silicon film and glass thin film thickness 41 ...... Relationship between voltage and glass thin film thickness required when joining structures in which a silicate glass thin film is formed on a silicon substrate and a borosilicate glass substrate 64 …… Reference pressure chamber 66 …… Pressure sensitive diaphragm 67 ...... Signal processing circuit 68 ...... Lead wires 72a, 72b ...... Structure body in which grooves are formed 76 ...... Piezoresistive element 77 ...... Servo circuit 78 ...... Arithmetic processing circuit

Claims (10)

[Claims] 1. A method of bonding silicon and a glass structure, wherein the glass structure is formed by forming a glass thin film on a glass substrate containing metal ions, and the silicon and the glass structure are bonded by anodic bonding. A joining method characterized by: 2. A mechanical quantity sensor for detecting a mechanical quantity produced by bonding a silicon structure obtained by etching a part of a silicon substrate and a glass structure having a groove formed therein, wherein the glass structure contains a metal ion. A mechanical quantity sensor characterized in that a glass thin film is formed on the glass substrate and the groove is formed by etching the glass thin film. 3. The mechanical quantity sensor according to claim 2, wherein the glass substrate is silicate glass. 4. The mechanical quantity sensor according to claim 3, wherein the glass thin film is a silicate glass containing no ions. 5. The mechanical quantity sensor according to claim 3, wherein the glass thin film is one of phosphate glass, borate glass, and arsenic oxide glass. 6. The mechanical quantity sensor according to claim 3, wherein the glass thin film is a silicate glass containing at least one of phosphorus, boric acid, and arsenic as an element or an oxide. 7. The mechanical quantity sensor according to claim 2, wherein the glass substrate is borosilicate glass. 8. The mechanical quantity sensor according to claim 7, wherein the glass thin film is silicate glass or borosilicate glass containing no ions. 9. The mechanical quantity sensor according to claim 7, wherein the glass thin film is one of borate glass, phosphate glass, and arsenic oxide glass. 10. The mechanical quantity sensor according to claim 7, wherein the glass thin film is a silicate glass containing at least one of boron, phosphorus and arsenic as an element or an oxide.