JPH02106975A - Micro-bridge flow sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To inhibit the undercut of a semiconductor base minimally, to make a fixed gas flow through a detecting section and to obtain a micro-bridge flow sensor having high quality by integrally forming a protruding section not etched in the face <110> direction to the edge section of the semiconductor base. CONSTITUTION:A heater element 7 and temperature-sensing resistance elements 8, 9 are shaped at the specified positions of the surface of a wafer 20, and opening 2, 3 and trenches 24 with V-shaped cross sections to a longitudinal street section 21a and a lateral street section 21b are formed. The V-shaped etching trench 24 is shaped continuously to the lateral street section 21b, and the discontinuous V-shaped etching trench 24 having a section 25 not etched in the face <110> direction is formed in a section crossed with the lateral street section 21b in the longitudinal street section 21a. The silicon wafer 20 is cut in the directions shown by the arrows, thus acquiring a micro-bridge flow sensor chip 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microbridge flow cell for detecting extremely small gas flow rates and a method for manufacturing the same.

[Conventional technology]

Conventionally, this type of microbridge flow sensor has a third
As shown in the figure, a thin film with extremely low heat capacity is formed using thin film technology and anisotropic etching technology. ! This is a flow sensor depth with a bridge structure. This sensor has many excellent features, such as extremely fast response, high sensitivity, low power consumption, and ease of mass production.

FIG. 3 shows the configuration of the microbridge flow sensor. FIG. 5(a) is a perspective view, and FIG. 1(b) is a cross-sectional view taken along the line BB'. In the same figure, a semiconductor base 1
The left and right openings 2.3 are created by anisotropic etching in the center of the
A through hole 4 is formed in the upper part of the through hole 4 to communicate with the semiconductor, which is spatially separated from the base 1 in a bridge shape, and is thermally insulated from the semiconductor base 1. A bridging portion 5 is formed. On the surface of this 1n28 section 5, a thin film heater element 7 sandwiched between the purulent retention membrane 6 and a thin film lateral temperature resistance element 8.9 sandwiching the heater element 7 are arranged and arranged. Furthermore, a thin film surrounding temperature sensing resistance element 10 is formed at a corner of the semiconductor base 1.

In such an L411 configuration, if the heater element 7 is controlled at a certain high temperature than the ambient temperature, the temperature distribution near the thin film bridge will be symmetrical with the heater element 7 at the center, for example, as shown in Figure 2(a). When the gas moves in the direction of the arrow 11 shown, the temperature-measuring resistance element 8 on the upstream side is cooled, and the temperature-measuring resistance element 9 on the downstream side uses the flow of gas as a medium to promote heat conduction from the heater element 7, thereby increasing the temperature. A temperature difference occurs because of the rise in temperature. Therefore, by incorporating the temperature measuring resistance elements 8 and 9 formed on both sides of the heater element 7 into the wheat strike 2 bridge circuit, the temperature difference can be converted into voltage, and a voltage output corresponding to the flow velocity can be obtained, as shown in the figure (c). The gas flow velocity can be detected as shown in .

[Problem to be solved by the invention]

However, the conventional microbridge flow sensor described above has a silicon wafer 2 as shown in Figure 4 (a).
(Fig. 4, etc.)
A microbridge flow sensor chip 22 as shown in
However, according to such a method, as shown in FIG. 6), a chip 23 occurs at the edge portion of the microbridge flow sensor chip 22, and the microbridge flow sensor chip 22 is destroyed. was done,
Further, if the chipping 230 occurs on the upstream side of the gas flow, the gas flow is disturbed and there is a problem that a constant gas flow cannot be obtained at the flow rate detection section.

Figure 4(a) shows a solution to this problem.
A method is adopted in which the street portions 21m and 21b are etched in advance and then cut and divided as shown in FIG. However, according to such a method, the street portion 21a
, 21b causes a problem that the undercut of the edge portion of the microbridge flow sensor chip 22 in the direction of the chip increases.

[Means to solve the problem]

In the micro bridge flow sensor of the present invention, a dangerous protrusion is integrally provided on the edge portion of the semiconductor base by etching in the plane <110> direction.

The method for manufacturing a microbridge flow cell of the present invention includes:
(T) - Anisotropic etching is performed to leave a part of the <110> direction on the top portion.

[Effect]

In the microbridge flow sensor of the present invention, undercuts at the edges are minimized.

In the method for manufacturing a microbridge flow sensor of the present invention, even if the street portions are etched, undercuts in the chip direction are minimized.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of essential parts of an embodiment of a microbridge flow sensor according to the present invention), in which the same parts as in the previous figures are given the same reference numerals. In the same figure, the edge portion of the semiconductor base 1 includes a protrusion portion 1a formed from a portion that is not etched in the street portion in the <110> direction but remains when the silicon wafer is cut and divided.
1b, 1c, and 1d are provided integrally. Also,
In the micro bridge flow senna formed in this way, the street portion is cut at the anisotropically etched valley portion, so that each side of the semiconductor base 1 is formed with a slope that slopes toward the outer region.

FIGS. 2(a) and 2(b) are plan views illustrating an embodiment of the method for manufacturing a microbridge flow sensor according to the present invention, and the same parts as in the previous figures are given the same reference numerals. In the figure, a heater element T and a temperature measuring resistance element 8 are placed at predetermined positions on the surface of a silicon wafer 20.
9, a mask having corresponding openings (not shown) is placed on the silicon wafer 20, and anisotropic etching is performed to form the openings 2.3, the vertical street portions 21a, and the horizontal street portions 21a, respectively. A groove 24 having a figure 7 cross section is formed in the street portion 21b. in this case,
The horizontal street portion 21b K continuously forms a V-shaped etching groove 24, and the vertical street portion 21a
A discontinuous V-shaped etched groove 24 having a portion 25 that is not etched in the plane <110> direction is formed at a portion intersecting with the horizontal street portion 21b. These non-etched portions 25 can be easily formed by blocking corresponding predetermined portions of the mask. Next, this silicon wafer 20 is cut by using a dicing saw to cut the vertical street portion 21 and the horizontal street portion 21b in the direction shown by the arrow, and are divided into individual pieces as shown in FIG. A microbridge flow sensor chip 26 is obtained. That is, as shown in FIG. 1, protrusions 1a are formed on the edge portions of the semiconductor base 1 by etching in the <110> direction.

A microbridge flow sensor having 1b, Ic, and 1d is obtained.

According to such a method, a microbridge flow sensor with fewer undercuts at the edge portion can be easily obtained without changing the manufacturing process.

〔Effect of the invention〕

As explained above, according to the microbridge flow sensor according to the present invention, the edge portion of the semiconductor base has a surface <110
By providing an integral protrusion that will not be etched in the ＞ direction, undercutting of the semiconductor base is minimized and a constant gas flow is provided to the detection area, making it possible to create a high-quality microbridge flow sensor. can get. Further, according to the method for manufacturing a microbridge flow sensor according to the present invention, by performing anisotropic etching that leaves a part of the surface in the <110> direction on the street portion, the edge portion can be etched without changing the manufacturing process. This method has extremely excellent effects such as the ability to obtain a microbridge flow sensor with less undercuts with good productivity.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of a microbridge flow sensor according to the present invention, and FIG. , Figure 3(a). i) A diagram illustrating the configuration of a micro-bridge flow sensor (FIG. 4(a) and (b) is a plan view illustrating a method of manufacturing a conventional micro-bridge flow sensor. 1 ...Semiconductor base, 2,3116--opening, 4...
・・Communication hole, 5・・Bridging part, 6・・・Eel protective membrane, T
...Heater element, 83g...Temperature measuring resistance element, 20...N IJ concubine, 21a,
21b No. A fist/Street part, No. 24/War/V-shaped etching/groove, 25 Ho...--parts that are not etched,
26・Auto・Micro bridge flow sensor. Figure 1 Figure 2 (Q) Figure 3

Claims (2)

[Claims] (1) A through hole is provided on the surface of the semiconductor base and has a bridge part that is spatially separated from the semiconductor base and integrally formed, and communicates the left and right openings, and the surface of the bridge part In the micro bridge flow sensor, a detection section consisting of a thermally insulated heating element and a resistance temperature sensor is formed, and the flow velocity is detected from a change in the resistance value of the resistance temperature sensor. A microbridge flow sensor characterized in that a protrusion that is not etched in the <110> direction is integrally provided. (2) A method for manufacturing a micro-bridge flow sensor in which a large number of micro-bridge flow sensors are arranged on a semiconductor wafer, and the street portions of each micro-bridge flow sensor are anisotropically etched to be individually cut and divided. , the corner part of the street part has a surface <
A method for manufacturing a microbridge flow sensor, comprising a step of performing anisotropic etching in the 110> direction.