JPH10242534A - Micro device having hollow beam and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micro device having a hollow beam wherein warp and bend of the beam are extremely little and sensitivity is excellent, and a manufacturing method of it. SOLUTION: A three-layered laminated member which has a part 21 on a peripheral part of a recessed part 12 and a linear beam part 22 bridging the recessed part 12 is arranged on a silicon substrate 11 on which surface of the recessed part 12 is formed. The three-layered laminated member is constituted of an SiO2 film 13, an Si3 N4 film 14 and an SiO2 film 15. On the central part of the beam part 22, an element forming part composed of a single crystal silicon layer 16 is arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro device such as a temperature sensor, an infrared sensor, a vibration sensor, an acceleration sensor and a micro gyro, and a method of manufacturing the same, and more particularly, it can minimize the influence of heat from a silicon substrate. The present invention relates to a micro device having a hollow beam and a method for manufacturing the same.

[0002]

2. Description of the Related Art Microdevices such as temperature sensors are formed on a silicon substrate. In order to minimize the influence of heat from the silicon substrate, the devices are formed on a silicon substrate supported by beams. Techniques are known.

FIG. 6 is a sectional view showing a conventional micro device having a hollow beam. A concave portion 2 is formed on the surface of a silicon substrate 1.
An O ₂ film 3 and a Si ₃ N ₄ film 4 are formed. And
The SiO ₂ film 3 and the Si ₃ N ₄ film 4 is etched into the recess 2 on a thin beam-like (linear), polycrystalline silicon layer 5 is provided in the center of the beam portion. A functional element such as a temperature sensor is formed on the polycrystalline silicon layer 5. In this conventional micro device, a polycrystalline silicon layer 5 on which a sensor is formed is supported on a beam composed of a laminate of an SiO ₂ film 3 and a Si ₃ N ₄ film 4, and a contact with these laminates as a substrate is made. Since the area is extremely small, there is an advantage that the sensor is hardly affected by heat from the supporting substrate.

[0004]

However, this conventional micro device having a hollow beam has a SiO ₂ film 3
And the Si ₃ N ₄ film 4, there is a drawback that warpage and bending tend to occur due to differences in internal stress and thermal expansion. In addition, since the substrate on which the functional element such as a temperature sensor is formed is the polycrystalline silicon layer 5, the sensitivity is lower than when the functional element is formed on a single crystal substrate.

[0005] The present invention has been made in view of such problems, and the warp and deflection of the beam are extremely small.
It is an object of the present invention to provide a micro device having a hollow beam having excellent sensitivity and a method for manufacturing the same.

[0006]

According to the present invention, there is provided a micro device having a hollow beam according to the present invention, comprising: a silicon substrate having a concave portion formed on the surface thereof; A three-layer body including a silicon oxide film, a silicon nitride film, and a silicon oxide film, and an element forming portion including a silicon layer provided on a central portion of the beam portion. It is characterized by.

In the micro device having the hollow beams, the silicon layer is preferably a single crystal silicon layer.

According to the method of manufacturing a micro device having a hollow beam according to the present invention, a step of forming a first silicon oxide film on a first silicon substrate and a step of forming a second silicon oxide film on a second silicon substrate and Forming a silicon nitride film, laminating the first silicon oxide film and the silicon nitride film and joining the first and second silicon substrates to each other, and grinding the second silicon substrate to a predetermined thickness. A step of forming a thickness, a step of forming an element forming portion by etching the second silicon substrate, and a step of forming a linear beam by etching the first silicon oxide film, the silicon nitride film and the second silicon oxide film. And a step of etching a surface layer portion of the first silicon substrate below the beam portion to form a concave portion below the beam portion.

In the method of manufacturing a micro device having a hollow beam, the second silicon substrate is preferably a single crystal silicon substrate.

In the present invention, the beam portion is composed of a three-layered laminate of a silicon oxide film, a silicon nitride film and a silicon oxide film. Changes do not cause the beam sections to warp or flex. In the method of the present invention, the first silicon substrate and the second silicon substrate are bonded to each other, and then the second silicon substrate is ground to a predetermined thickness to form a silicon layer for element formation. Therefore, the silicon layer serving as the substrate of this element can be a single crystal silicon substrate. Therefore, if a functional element such as a temperature-sensitive element is formed on the single crystal silicon layer, a microdevice with high sensitivity can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be specifically described with reference to the accompanying drawings. FIG. 1 is a sectional view showing a micro device according to an embodiment of the present invention (a).
And a plan view (b). A concave portion 12 is formed on the surface (bonding surface) of the silicon substrate 11. The SiO ₂ film 13 and the Si ₃ N ₄ film 1 are formed on the silicon substrate 11.
4 and three-layer laminate consisting of SiO ₂ film 15 is formed. This laminated body includes a portion 21 on the peripheral edge of the concave portion 12 of the silicon substrate 11 and a beam portion 22 on the concave portion 12, and the beam portion 22 extends from the four corners of the upper peripheral portion 21 toward the center thereof. It extends linearly. The beam portion 22 has a rectangular portion at the center where the linear portions gather. A rectangular single crystal silicon layer 16 is provided on a rectangular portion at the center of the stacked body. On the single-crystal silicon layer 16, a functional element such as an oxygen sensor is formed.

In the micro device thus configured, since the functional element is formed on the single crystal silicon layer 16, the sensitivity of the temperature sensor and the like is excellent. Also,
As shown in FIG. 5A, the thermal expansion coefficient of the SiO ₂ film is larger than that of the Si layer. Therefore, when the temperature rises, the laminated body bends so that the SiO ₂ film is on the outside, and FIG. As shown in b), the Si ₃ N ₄ film has a lower coefficient of thermal expansion than the Si layer, so that when the temperature rises, the laminate bends so that the Si ₃ N ₄ film is on the inside. As described above, the oxide film and the nitride film have opposite stresses. Therefore, as in the present embodiment, the SiO ₂ film 13, the Si ₃ N ₄ film 14, and the SiO ₂ film 1
In a beam having a three-layer structure in which the layers 5 and 5 are stacked, a SiO ₃ film having a large coefficient of thermal expansion, centered on a Si ₃ N ₄ film having a small coefficient of thermal expansion, is used.
_{Since the two} films are arranged on both sides, stresses in opposite directions are applied at the two interfaces, and the SiO ₂ films 13 and 15 and the S
Since the thermal expansion of the i ₃ N ₄ film and the thermal expansion of the i ₃ N ₄ film cancel each other, no warpage or bending occurs.

Next, a method of manufacturing the micro device of this embodiment will be described with reference to FIGS. 2 to 4 and FIG. First, as shown in FIG. 2, an SiO ₂ film 13 is formed on the first silicon substrate 11 to a thickness of, for example, 5000 °. On the other hand, an SiO ₂ film 15 is formed on the surface of the bond silicon substrate 17 to a thickness of, for example, 5000 °.
On the O ₂ film 15, a Si ₃ N ₄ film 14 is formed to a thickness of, for example, 1500 °.

Then, as shown in FIG. 3, the Si ₃ N ₄ film 1
4 and the SiO ₂ film 13 are superimposed, and heated to, for example, 1100 ° C. while applying a clamping pressure, thereby directly joining the two.

Further, as shown in FIG.
Is polished on the side opposite to the bonding surface, and its thickness is set to, for example, 5 μm. Thus, a thin single-crystal silicon layer 18 is obtained.

Next, predetermined functional elements such as an oxygen sensor are formed on the single crystal silicon layer 18 by a semiconductor thin film forming technique. Thereafter, as shown in FIG. 1B, the single-crystal silicon layer 18 is patterned by etching, so that the fine element 16 remains at the center. Then, S
The laminated body composed of the iO ₂ film 15, the Si ₃ N ₄ film 14, and the SiO ₂ film 13 is etched to form a bridge portion 22 serving as a bridge.
Is patterned. Further, a rectangular recess 12 is formed on the surface of the silicon substrate 11 by etching the silicon substrate 11 below the beam portion into a predetermined shape.

In this embodiment, the silicon substrate 1
At the time of etching 1, Si ₃ N ₄
Since the film 14 is formed, the etchant does not enter the bonding interface between the silicon substrate 11 to which the tensile stress is applied and the silicon substrate 18 to which the compressive stress is applied. Therefore, the concave portion 12 of the silicon substrate 11 shown in FIG.
Does not enter the interface between the SiO ₂ film 13 and the Si ₃ N ₄ film 14 and peel off the wafer.

In this embodiment, a thin film silicon layer for forming a functional element is obtained by bonding a bond substrate and polishing the bond substrate to obtain a thin silicon layer for forming a functional element. It can be a single crystal silicon layer. Therefore, according to the present embodiment, a sensor element having excellent sensitivity can be easily obtained.

The present invention is not limited to the above embodiment,
For example, instead of the concave portion, a concave portion penetrating the silicon substrate may be used.

[0020]

As described above, according to the present invention,
Since a three-layer laminate of a silicon oxide film, a silicon nitride film, and a silicon oxide film is used for a beam portion supporting a silicon layer forming a functional element, warping and bending of the beam portion may occur. Can be prevented. Further, since the silicon nitride film and the silicon oxide film are directly bonded, a film having good adhesiveness at the interface can be formed, and therefore, penetration of chemicals during etching of the silicon substrate can be prevented. it can. Further, when a single crystal silicon layer is used as a silicon layer for forming an element, a highly sensitive element can be obtained.

[Brief description of the drawings]

1A and 1B are diagrams showing an embodiment of the present invention, wherein FIG. 1A is a cross-sectional view and FIG. 1B is a plan view.

FIG. 2 is a one-step diagram showing a method of an embodiment of the present invention.

FIG. 3 is a view showing a step subsequent to FIG. 2;

FIG. 4 is a view showing a step subsequent to FIG. 3;

FIG. 5 is a diagram illustrating warpage.

FIG. 6 is a cross-sectional view showing a conventional micro device.

[Description of Signs] 1,11: silicon substrate 2, 12: concave portion 3, 13, 15: SiO ₂ film 4, 14: Si ₃ N ₄ film 17: bond silicon substrate 16, 18: single crystal silicon layer

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 31/0248 H01L 31/08 K

Claims (4)

[Claims] 1. A silicon oxide film, a silicon nitride film, and a silicon substrate having a silicon substrate having a concave portion formed on its surface, a portion on the peripheral portion of the concave portion, and a linear beam portion extending over the concave portion. A micro device having a hollow beam, comprising: a three-layer body including three oxide films; and an element forming portion including a silicon layer provided on a central portion of the beam portion. 2. The micro device according to claim 1, wherein the silicon layer is a single crystal silicon layer. A step of forming a first silicon oxide film on the first silicon substrate; a step of forming a second silicon oxide film on the second silicon substrate and a silicon nitride film thereon; Stacking a silicon oxide film and a silicon nitride film and bonding the first and second silicon substrates to each other;
Grinding the second silicon substrate to a predetermined thickness, etching the second silicon substrate to form an element formation portion, and forming the first silicon oxide film, the silicon nitride film, and the second silicon Forming a linear beam portion by etching an oxide film; and forming the first beam portion below the beam portion.
Etching a surface layer portion of a silicon substrate to form a concave portion below the beam portion. A method of manufacturing a micro device having a hollow beam. 4. The micro device according to claim 3, wherein the second silicon substrate is a single crystal silicon substrate.