JP2007205862A - Detecting section structure of gas rate sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy and sensibility by forming a circular wire section at the tip of each projection arm in a silicon frame type substrate, configuring its both edges as free edges and preventing any thermal stress from occurring therein. <P>SOLUTION: A detecting section structure of a gas rate sensor is provided, wherein circular wire sections (6, 7) are formed at the tip of each projection arm (2, 3, 4 and 5) made up in the inner surface of the silicon frame type substrate (1, 1B) so as to project, and the both edges (6a, 6b, 7a and 7b) of the wire sections (6, 7) are configured as the free edges, thereby preventing the thermal stress from occurring therein. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a detection unit structure of a gas rate sensor, and in particular, an arc-shaped wire part whose both ends are free ends is formed for each projecting arm of a silicon frame substrate formed of a silicon wafer or an SOI wafer. The present invention relates to a novel improvement for preventing the occurrence of thermal stress during thermal expansion and contraction and improving detection accuracy and sensitivity.

Examples of the detection unit structure of this type of gas rate sensor that has been conventionally used include structures disclosed in Patent Document 1, Non-Patent Document 1, and the like.
That is, the configuration shown in FIG. 4 is a conventional uniaxial detection unit structure, in which four pin-shaped electrodes 2 to 4 are independently implanted on the substrate 1, and a pair of electrodes 2, 2 are arranged. Between the electrodes 3 and the pair of electrodes 4 and 5, wires 6 and 7 called hot wires are stretched between those skilled in the art and are integrally connected by welding or the like.

In the above-described configuration, when a current is supplied to the wires 6 and 7 and a gas supplied from a gas supply hole (not shown) is supplied as the gas flow 8 and an angular velocity is applied from the outside, the Coriolis is supplied. When the gas flow 8 is deflected by the force, a temperature difference is generated between the wires 6 and 7.
This temperature difference state is detected by a bridge circuit (not shown) in which the wires 6 and 7 are incorporated on two sides, and an angular velocity is detected as a resistance difference.

FIG. 5 shows a conventional configuration in which the uniaxial type in FIG. 4 is changed to a biaxial type.
6, the wires 6 and 7 are stretched using the plate-like electrodes 2 to 5 instead of the pin-like electrodes 2 to 5 shown in FIGS. 4 and 5, and the detection parts having the same shape are different from each other. A conventional biaxial configuration is shown by combining in the direction of the detection axis.
FIG. 7 shows only the electrode portion configured in the upper and lower two-stage type of FIG.

In addition, “Design and Fabrication of Semiconductor Gas Gyro” of “Proceeding of Asia Pacific Conference of Transducers and Micronano Technology” held in Sapporo in 2004 Scope "voL. 3-1, pp. A detection part structure of a gas rate sensor formed by various etching processes (micro machining process) using an SOI wafer (silicon-on-insulator wafer) announced in 257-262 is shown below.
What is indicated by reference numeral 10 in FIG. 9 is a well-known SOI wafer (silicon-on-insulator wafer), and this SOI wafer has a number of sections, and the detection section shown in FIG. 10 for each section. 20 is formed.

  The detection unit 20 is formed by various etching processes (micromachining) as in the process of manufacturing the SOI wafer 10 for ICs, and is configured as shown in FIGS.

  That is, in the cross-sectional view of FIG. 11, the detection unit 20 is made of silicon and has a support substrate 1 having an opening 1A, an insulating layer 31 made of an insulating oxide film (BOX) on the support substrate 1, and this insulating layer. As shown in the plan view of FIG. 10, there are four conductive active layers 32 on the conductive layer 32 and conductive patterns 33 made of aluminum and formed on the active layer 32. Wires 6 and 7 are formed as hot wires.

  When viewed in plan, the insulating layer 31 and the support substrate 1 have an opening 1A formed by etching (corresponding to the white portion in FIG. 10) and four protrusions, as shown in FIG. The arms 2, 3, 4, 5 are formed so as to protrude inward, and each of the protruding arms 2, 3, 4, 5 is a multilayer of the support substrate 1, the insulating layer 31, the active layer 32 and the conductive pattern 33. It consists of a structure.

Accordingly, the wires 6 and 7 made of the active layer 32 are formed between the projecting arms 2, 3, 4 and 5, and the wires 6 and 7 are arranged in a quadrangular shape so that they are arranged in the biaxial direction. An angular velocity input can be detected.
The conductive pattern 33 formed in a state of being integrally connected to the wires 6 and 7 is formed in two layers together with the active layer 32.

The aforementioned detection unit 20 is mounted inside a known gas rate sensor 25 shown in FIG. 8, and is configured so that the gas flow 8 from the gas ejection holes 26 is supplied to the wires 6 and 7.
In addition, it can also be set as a uniaxial detection type by using only the two wires 6 or 7 with respect to the biaxial detection type | mold of FIG.

Japanese Patent Publication No. 1-56275 2, 2, 4 (1) gas rate sensor on page 56 of gyro technology (Tamagawa Seiki Co., Ltd., published by Industrial Research Council 2002)

Since the detection part structure of the conventional gas rate sensor is configured as described above, the following problems exist.
That is, in the case of the conventional configuration shown in FIGS. 4 to 7, when the wire is stretched between the electrodes, the wire is fixed by electric resistance welding. However, since the wire is extremely fine at the time of fixing, the wire is easily damaged. This is due to the force (stress) and heat generated during welding and fixing.
When the degree of damage to the wire increases, disconnection or the like occurs, resulting in a decrease in yield and reliability.
Further, in the case of the conventional configuration shown in FIGS. 8 to 11, it is not necessary to stretch the wires as in the case of the conventional configuration shown in FIGS. 4 to 7, but both ends of each wire are fixed to the protruding arms. Therefore, when pressure is applied to the silicon wafer or SOI wafer from the gas rate sensor case, etc. due to temperature changes, etc., tensile stress and compression are generated in the wire via each protruding arm, which may cause detection errors, etc. It was.
Further, when the temperature of the wire changes, the wire expands and contracts, and a thermal stress is generated, thereby changing the resistance value of the wire due to the piezoresistance effect.
The change in resistance value due to the piezoresistance effect changes in the opposite direction to the change in resistance value due to the thermal resistance effect, and the sensitivity as a gas rate sensor has been reduced.
For example, when the temperature of the wire is increased, the resistance value increases due to the thermal resistance effect. However, compressive stress is generated by thermal expansion, and the resistance value is lowered by the piezoresistance effect. Therefore, as a whole, the change in resistance value becomes small, and the sensitivity is lowered. This phenomenon is the same when the temperature of the wire decreases.

  The detection structure of the gas rate sensor according to the present invention includes a silicon frame substrate obtained by processing a silicon wafer or a silicon-on-insulator (SOI) wafer, and an inner surface of the silicon frame substrate. A plurality of projecting arms projecting inward, an insulating layer formed on an upper surface of the silicon frame substrate, an arc-shaped wire portion formed on the insulating layer on each projecting arm, and A pair of land portions formed on the insulating layer corresponding to each protruding arm, and a conductive pattern formed on each land portion and connected to the first and second end portions of the wire portion. And each end of each wire portion is a free end and spaced apart from each other, and the wire portion and the land portion are semiconductors in the case of the silicon wafer. Or A configuration consisting of silicon layer, the wire portion and the land portion, in the case of the SOI wafer has a configuration composed of the active layer of the SOI wafer.

Since the detection part structure of the gas rate sensor according to the present invention is configured as described above, the following effects can be obtained.
That is, a wire portion is formed using a silicon wafer or an SOI wafer, and both ends of the wire portion provided at the tip of each protruding arm are free ends, and both ends of each wire portion adjacent to each other are mutually connected. Since they are separated from each other, when the temperature of each wire portion changes, thermal expansion and thermal contraction occur, but almost no thermal stress is generated.
Moreover, since the shape of each wire part is an arc shape, compared with a straight wire part, the ratio of the wire part located in the alternating current speed area of the gas flow which passes a wire part is large, and a sensitivity is raised by that much. Can be made.
In addition, since the wire portion is formed of a semiconductor material, the thermal resistance effect or detection sensitivity is higher than that of a conventional metal material wire portion.

  The present invention forms an arc-shaped wire portion having free ends at each projecting arm of a silicon frame substrate formed of a silicon wafer or SOI wafer, and thermal stress during thermal expansion and contraction. It is an object of the present invention to provide a detection structure for a gas rate sensor that prevents the occurrence of gas and improves detection accuracy and sensitivity.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a gas rate sensor detection unit structure according to the present invention will be described with reference to the drawings.
In addition, the same code | symbol is attached | subjected and demonstrated to a part the same as that of a prior art example, or an equivalent part.
In FIG. 1, a reference numeral 1 denotes a silicon frame-shaped substrate made of a silicon wafer and having a frame shape having an opening 1 </ b> A. The silicon frame-shaped substrate 1 has four projecting arms 2, 3, 4 on the inner surface. , 5 are formed to protrude inward.

  Wire portions 6 and 7 having first and second end portions 6a and 6b and 7a and 7b formed at the free ends are formed at the tips of the protruding arms 5 at the ends of the silicon frame substrate. 1 and the above-mentioned micromachining process.

An insulating layer 31 made of a SiO ₂ layer is formed on the silicon frame substrate 1, and the conductive pattern shown in FIG. 3 is formed on the insulating layer 31 of each projecting arm 2, 3, 4, 5. 40 and land portions 50 are formed, and the conductive pattern 40 connected to each land portion 50 is connected to each end portion 6a, 6b and 7a, 7b of each wire portion 6, 7, and each wire portion 6 and 7 are connected via the land portions 50 as indicated by the one-dot line in FIG.
1 is formed by micromachining processing by etching using a silicon wafer.

Next, in the other embodiment shown in FIG. 2, the configuration of FIG. 1 described above uses a silicon wafer as the silicon frame substrate 1, but uses an SOI (silicon-on-insulator) wafer. Shows if there was.
That is, since the silicon frame substrate 1A of FIG. 2 is formed of an SOI wafer, the insulating layer 31, the active layer 32, and the conductive pattern 33 are formed on the silicon frame substrate 1A as shown in FIG. 1, the wire portion 6 is formed of a silicon layer or a semiconductor in the configuration of FIG. 1, but in the configuration of FIG. 2, the wire portions 6, 7 and the land portion 50 are formed by the active layer 32. Yes.

  The conductive pattern 40 made of aluminum or the like from the land portions 50 to the wire portions 6 and 7 in the configuration of FIGS. 1 and 2 is not disclosed in the perspective views of FIGS. 3 is formed on the insulating layer 31. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The present invention is applicable not only to a gas rate sensor but also to a rate sensor or the like.

It is a perspective block diagram which shows the 1st form of the detection part structure of the gas rate sensor by this invention. It is a perspective block diagram which shows the other form of FIG. FIG. 3 is an equivalent circuit diagram showing a bridge circuit formed by the wire portion and the like of FIGS. 1 and 2. It is a perspective block diagram which shows the detection part structure of the conventional gas rate sensor. FIG. 6 is a perspective configuration diagram showing another conventional configuration of FIG. 4. It is a disassembled perspective view which shows the other conventional structure of FIG. It is a top view which shows the state which accumulated each wire of FIG. It is a partially cutaway perspective view showing a conventional gas rate sensor. It is a perspective block diagram which shows the formation state of the detection part using the SOI wafer in the past and this invention. It is a top view of the detection part using the conventional SOI wafer. It is sectional drawing of FIG.

Explanation of symbols

1 Silicon frame substrate (silicon wafer)
1A Opening 1B Silicon frame substrate (SOI wafer)
2, 3, 4, 5 Projecting arms 6, 7 Wire portions 6a, 7a First end portions 6b, 7b Second end portion 10 SOI wafer 20 Detection portion 31 Insulating layer 32 Active layer 40 Conductive pattern 50 Land portion

Claims (3)

A silicon frame substrate (1,1B) formed by processing a silicon wafer or a silicon-on-insulator (SOI) wafer, and an inner surface of the silicon frame substrate (1,1B). A plurality of projecting arms (2, 3, 4, 5) projecting toward the top, an insulating layer (31) formed on the upper surface of the silicon frame substrate (1, 1B), and each projecting arm (2, The wire portions (6, 7) formed on the insulating layer (31) on the 3,4, 5) and having an arc shape, and the insulation corresponding to the projecting arms (2, 3, 4, 5). A pair of land portions (50) formed on the layer (31), and first and second ends (6a, 6b, 7a) of the wire portions (6, 7) formed on the land portions (50). 7b) and a conductive pattern (40) extending in connection with
The structure of the detection part of the gas rate sensor characterized in that the end parts (6a, 6b, 7a, 7b) of the wire parts (6, 7) are free ends and are spaced apart from each other. .   2. The gas rate sensor detection part structure according to claim 1, wherein the wire part (6, 7) and the land part (50) are made of a semiconductor or a silicon layer in the case of the silicon wafer.   The detection of a gas rate sensor according to claim 1, wherein the wire part (6, 7) and the land part (50) are made of an active layer (32) of the SOI wafer in the case of the SOI wafer. Part structure.

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