JPH032523A - Production of silicon microsensor element - Google Patents

Abstract

PURPOSE:To easily reproduce the microsensor element having a desired sensitivity characteristic with good reproducibility by providing a stage for forming a marker part and a stage for etching a silicon substrate until the index part in the marker part peels from the substrate. CONSTITUTION:A thermally oxidized silicon film 30 is formed over the entire surface of a surface 12 opposite to an etching surface 11 of the silicon substrate 10. The marker part 20 has a frame-shaped etching mask 21 formed to a square frame shape on the etching surface 11 of the substrate 10 and the square index part 22 in the central part of the surface 11. The part to be formed with the sensor element is etched together with the marker part 20. A remaining project ing part 15 has a quadrangular prism shape and the index part 22 peels from the projecting part 15 at the point of the time when the etching progresses to the depth of 1/2 the length on one side of the index part 22. An etching part 13 of the quadrangular prismoid shape smaller in the area in the aperture than the area in an inner deep part is, therefore, formed in the part enclosed with the mask 21.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention utilizes thermal changes to detect infrared rays, flow rate, gas, etc., or physical displacement.
The present invention relates to a method for manufacturing silicon microsensor elements used in sensors that detect pressure, vibration, acceleration, etc.

(Prior Art) With the development of various control devices, various sensors that detect information from the outside world and output electrical signals are also required to have higher precision. For example, infrared sensors, flow sensors, gas sensors, etc., use a sensor element that outputs a predetermined electrical signal based on the temperature change of the sensor part that receives changes in the outside world. Alternatively, if the heat capacity of the heat generating part is reduced, higher sensitivity, higher speed response, and furthermore, lower power consumption becomes possible, so sensor parts and heat generating parts are miniaturized or thinned. In addition, in pressure sensors, vibration sensors, acceleration sensors, etc., the sensor element is supported by a predetermined support part so that the sensor part that receives changes in the outside world is physically displaced, and the displacement of the sensor part causes a predetermined electric current to be generated. Output a signal. In such a sensor, by making the sensor part and the support part thinner, it is possible to achieve miniaturization, and since the sensor part can be moved by minute pressure or the like, it is also possible to increase the sensitivity. moreover,
Whether it is a sensor that uses thermal changes or a sensor that uses physical displacement, multiple sensors can be combined and integrated by supporting the sensor part on a support part made of a thin film. It becomes possible.

For these reasons, in recent years, there has been active development of silicon microsensor elements in which a support part is formed of a thin film of silicon oxide formed on a silicon substrate, and a sensor part is formed on the support part.

A silicon microsensor element uses silicon crystal anisotropy and photolithography technology to etch a silicon substrate into a fine shape.A part of the silicon substrate is etched and the etched portion is covered. A supporting portion made of a silicon oxide film is formed and manufactured as shown in FIG.

In a silicon microsensor element, a support portion formed of a silicon oxide film has a shape as shown in FIGS. 5 to 7, for example. In the silicon microsensor element shown in FIGS. 5(a) and 5(b), the upper part of the silicon substrate 10 is etched into a truncated quadrangular pyramid shape with a large area on the opening side, and the etched surface of the silicon substrate 10 is etched. A silicon oxide film 40 is formed so as to cover the center of the opening in the etched portion 13.
A supporting portion 41 made of a silicon oxide film and having each end integrally connected to each other is installed in the shape of a bridge. A membrane-like sensor section is laminated on the support section 41 . The entire surface of the silicon substrate 10 opposite to the etched surface is covered with a silicon oxide film 30. In the solicon microsensor element shown in FIGS. 6(a) and 6(b), the silicon substrate 10 has an etched portion 13 similar to the silicon substrate shown in FIG. A support portion 41 made of a silicon oxide film that covers the center of the opening is supported on one side by the silicon oxide film 40 in the form of a cantilever. In the silicon microsensor element shown in FIGS. 7(a) and 7(b), an etched portion 13 penetrating the silicon substrate 10 in the shape of a truncated quadrangular pyramid is formed, and a small-area opening of the penetrating portion in the silicon substrate 10 is formed. The entire side surface of the part is covered with a silicon oxide film 40, and the diaphragm-shaped silicon oxide film covering the opening serves as a support part 41. The surface of the silicon substrate 10 on the side of the large opening of the etched portion 13 is covered with a silicon oxide film 30 except for the opening.

A silicon microsensor element having such a shape is manufactured by the following method. Silicon single crystal is EP
W (mixture of ethylenediamine, pyrocatechol and water)
When etched with an alkaline solution such as , NaOH, KOH, etc., it has crystal axis anisotropy, where the etching rate differs depending on the direction of the crystal axis, and the etching rate in the <1.11> direction is lower than that in the other <100> directions. , the etching speed is extremely slow compared to the etching speed in the <110> direction. For example, using a silicon oxide film as an etching mask, the etching surface is (10
0) When a silicon substrate with a crystal plane is etched, it is etched into a concave truncated pyramid shape with a large cross-sectional area on the opening side, and the etched part is at an angle of 54.7 degrees from the etched plane.
It is surrounded by four inclined planes having an angle of .

Each inclined plane becomes a (111) crystal plane. Furthermore, when etching a silicon substrate whose etching plane is a (110) crystal plane, the etching plane is surrounded by a (111) crystal plane perpendicular to the etching plane and a (111) crystal plane tilted at an angle of 35.3° from the etching plane. A concave etched portion is formed.

The silicon microsensor element shown in FIGS. 5 to 7 is
Silicon substrate I whose etched plane is a (100) crystal plane
O is thermally oxidized silicon film by thermal oxidation method or CV
A silicon oxide film is formed by method D, and the silicon oxide film 40 is patterned so that the silicon substrate has a predetermined etched shape. Then, by etching the patterned silicon oxide film 40 as an etching mask, the silicon substrate=5=10 is etched into the shapes shown in FIGS. 5 to 7. In the case of the elements shown in FIGS. 5 and 6, the support portion 41 is a silicon oxide film having a predetermined shape that covers the etching portion 13 used as an etching mask.

(Problem to be Solved by the Invention) However, when etching a silicon single crystal with an alkaline solution, the temperature, concentration, component ratio, stirring conditions of the alkaline solution, degree of deterioration of the alkaline solution, or the silicon substrate to be etched must be changed. Even if the etching conditions, such as the etching area, are slightly different, it will not be possible to achieve a predetermined etching depth. For this reason, there is a possibility that a sensor element with desired performance cannot be obtained. Silicon microsensor elements manufactured on the same manufacturing line have different etched shapes and etched depths due to different etching conditions, resulting in variations in quality. As a result, when using thermal changes in the silicon microsensor element, there will be variations in the heat capacity of the heat generating part and the sensor part, and when using the physical displacement of the sensor part, there will be variations in the amount of displacement. will occur,
Sensors using such silicon microsensor elements cause variations in sensitivity characteristics.

The present invention solves the above-mentioned conventional problems, and its purpose is to provide a method by which a silicon microsensor element having desired sensitivity characteristics can be easily manufactured with good reproducibility.

(Means for Solving the Problems) The method for manufacturing a silicon microsensor element of the present invention includes a silicon substrate having a partially etched portion, and a mask arranged to cover the etched portion of the silicon substrate to be used as a mask during etching of the silicon substrate. 1. A method for manufacturing a silicon microsensor element having a film-like support part provided thereon and a film-like sensor part arranged on the support part, the method comprising: a region of the silicon substrate other than the sensor element formation part; a step of forming a part of the mano y by arranging an etching mask made of the same material as the support film as an index part so as to correspond to the crystal axis of the silicon substrate so that the lower part thereof is etched to a predetermined depth; The method includes a step of etching the entire silicon substrate until the index portion at the marker=8= portion is peeled off from the silicon substrate, thereby achieving the above object.

(Example) The present invention will be described below with reference to Examples.

The method for manufacturing a solicon microsensor element according to the present invention is to apply a silicon microsensor element to an area other than each silicon microsensor element formation area of a silicon substrate on which a large number of silicon microsensor elements are manufactured, as shown in FIGS. 1(a) to (c). A marker section 20 is provided. The silicon substrate 10 has an etching surface 1■
The direction shown by arrow A in FIGS. 1(b) and 1(C) is the <100> crystal axis direction so that the (100) crystal plane is the (100) crystal plane.

A thermally oxidized silicon film 3 is provided on the entire surface of the silicon substrate 10 (100), which is the opposite side to the etched surface 11 (100).
0 is formed.

The marker section 20 includes a frame-shaped etching mask 21 made of thermal oxidation foam formed in a square frame shape on the etching surface 11 of the silicon substrate 10, and an etching mask 21 on the silicon substrate 1o surrounded by the frame-shaped etching mask 21. On the center portion of the surface 11, there is provided an index portion 22 as an etching mask made of a thermally oxidized silicon film and having a square shape inclined at an angle of 45 degrees with respect to the square shape of the frame-shaped mask 21.

The square-shaped index portion 22 is separated from the inner peripheral edge of the frame-shaped etching mask 21, and the length of each side thereof is set to be twice the depth of the silicon substrate 10 to be etched.

In the portion of the silicon substrate 10 on which the sensor element is to be formed, on which the marker portion 20 is formed, on the etched surface 11 which is the (100) crystal plane,
A thermally oxidized silicon film (see FIGS. 5 and 6) having a predetermined shape is formed to serve as a support portion.

The silicon substrate 10 has a portion where a sensor element is to be formed, together with a marker portion 20, made of EP heated to near the boiling point.
Etched with W solution. At this time, the marker portion 20 on the silicon substrate 10 is
), since the silicon substrate 10 has crystal axis anisotropy in which the etching rate differs depending on the crystal axis, the portion surrounded by the frame-shaped etching mask 21 is as shown in (
100) 54.
Etching is performed sequentially along four (111) crystal planes inclined at an angle of 7 degrees, and a truncated quadrangular pyramid-shaped etched portion 13 surrounded by each crystal plane is formed. Furthermore, since the square-shaped index section 22 disposed in the center of the frame-shaped etching mask 21 is an etching mask made of a thermally oxidized silicon film, the silicon substrate 1 covered with the index section 22 is
The 0 part is etched so that a truncated quadrangular pyramid-shaped convex portion 15 surrounded by four (111) crystal planes inclined at an angle of 45 degrees with respect to the etched plane 11, which is a (100) crystal plane, remains. be done. The indicator portion 22 has a negative side twice as long as the depth to be etched, and the portion covered by the indicator portion 22 has a crystal plane inclined at an angle of 45 degrees with respect to the etching surface. Because the etching is performed sequentially along the etching depth, when the etching depth becomes 1/2 of the length of one side of the index portion 22, the remaining convex portion 15 becomes as shown in FIGS. 2(b) and 2(C). As shown in FIG. 2, it has a quadrangular pyramid shape, and the index portion 22 is supported at the top of the convex portion 15. As a result, the index portion 22 made of thermally oxidized silicon film is peeled off from the convex portion 15. Therefore, in the area surrounded by the frame-shaped etching mask 21,
A truncated square pyramid-shaped etched portion 13 in which the area of the opening on the etched surface 11 is smaller than the area of the inner depth is formed with the same etching depth.

At this time, the portion of the silicon substrate 10 where the sensor element is to be formed is also etched with the EPW solution using the thermally oxidized silicon film as an etching mask.
Each sensor element portion is also etched to the same depth as the marker portion 20. Then, at the time when the indicator part 22 in the marker part 20 is peeled off from the silicon substrate 10, E P
Etching of the entire silicon substrate 10 using the W solution is completed.

In the above embodiment, one square index section 22 is provided as the marker section 20, but for example, as shown in FIG. , the rectangular indicator portion 22 may be arranged at an angle of 45 degrees. In this case, the length of the short side of the index portion 22 is twice the desired etching depth.

Further, as shown in FIG. 4, a configuration may be adopted in which a plurality of index portions 22 of different sizes are arranged in parallel. In this way, by arranging the index parts 22 of different sizes in parallel, the silicon substrate 1
By visually observing that each indicator portion 22 peels off during the etching of 0.0, the etching depth at that point can be confirmed. In this case, it becomes possible to form sensor elements with different etching depths depending on the number of index portions using one mask pattern. When index portions 22 of different sizes are arranged, the etching depth indicated by each index portion 22 is displayed on each index portion 22 or on a frame-shaped mask Zl close to each index portion 22. It's okay. Such a display can be achieved by making the marker part 20 in the same number of steps as the manufacturing process of the sensor element if each sensor element part is made of the same material as the sensor part disposed on the silicon oxide film support part. Manufactured.

(Effects of the Invention) In this way, the method for manufacturing a silicon microsensor element of the present invention is such that the indicator portion of a portion of the macaque disposed on the silicon substrate is peeled off from the silicon substrate when a predetermined etching depth has been reached. The silicon substrate can be etched to a predetermined depth very easily. Therefore, a silicon microsensor element with a predetermined sensitivity can be easily manufactured with good reproducibility, and the accuracy and reliability of the silicon microsensor can be significantly improved.

Figure 1(a) is a plan view of a marker portion provided on a part of a silicon substrate used to carry out the method of the present invention.
b) and (C) are cross-sectional views taken along line B-B and line C-C in FIG. 1(a), respectively, FIG. C) is a sectional view taken along line B-B and line C-C in FIG. 2(a), FIGS. 3 and 4 are plan views of other embodiments of the marker section, and FIG. ) is a plan view for explaining the support part in the silicon microsensor element, and FIG.
b) is a sectional view thereof, FIG. 6(a) is a plan view for explaining another example of a support portion in a silicon microsensor element, FIG. 6(b) is a sectional view thereof, and FIG. 7(a) 7 is a plan view for explaining still another example of a support portion in a silicon microsensor element, and FIG. 7(b) is a sectional view thereof.

10... Silicon substrate, 20... Marker part, 21
...Frame-shaped etching mask, 2z...Indicator part, 30
. . . thermal oxidation silicon film, 41 . . . support portion.

that's all

Claims (1)

[Claims] 1. A partially etched silicon substrate, a film-like support part used as a mask during etching of the silicon substrate and disposed to cover the etched part, and the support part A method for manufacturing a silicon microsensor element having a film-like sensor section disposed on the silicon substrate, the lower part of which is etched to a predetermined depth in a region of the silicon substrate other than the sensor element formation section. forming a marker portion by arranging an etching mask made of the same material as the support film as an index portion in correspondence with the crystal axis of the silicon substrate; A method for manufacturing a silicon microsensor element, comprising: a step of etching until peeling;