JP3585337B2 - Micro device having hollow beam and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL 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 for manufacturing the same, and in particular, a micro device having a hollow beam capable of minimizing the influence of heat from a silicon substrate, and It relates to the manufacturing method.
[0002]
[Prior art]
A micro device such as a temperature sensor is formed on a silicon substrate. In order to minimize a thermal effect from the silicon substrate, a technique for forming a device on a silicon substrate supported by beams is known. .
[0003]
FIG. 6 is a sectional view showing a micro device having a conventional hollow beam. A concave portion 2 is formed on the surface of a silicon substrate 1, and an SiO ₂ film 3 and a Si ₃ N ₄ film 4 are formed on the silicon substrate 1. The SiO ₂ film 3 and the Si ₃ N ₄ film 4 are formed by etching in the form of a thin beam (linear shape) on the concave portion 2, and the polycrystalline silicon layer 5 is provided at 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, the polycrystalline silicon layer 5 on which the sensor is formed is supported on a beam composed of a laminated body of the SiO ₂ film 3 and the Si ₃ N ₄ film 4, and a contact with these laminated bodies 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]
[Problems to be solved by the invention]
However, since this conventional micro device having a hollow beam is composed of a laminate of the SiO ₂ film 3 and the Si ₃ N ₄ film 4, warpage and bending are likely to occur due to differences in internal stress and thermal expansion. There is a disadvantage that. Further, 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 that in the case where the functional element is formed on a single crystal substrate.
[0005]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a microdevice having a hollow beam with extremely low warpage and deflection and excellent sensitivity, and a method for manufacturing the same.
[0006]
[Means for Solving the Problems]
A micro device having a hollow beam according to the present invention includes a silicon substrate having a concave portion formed on the surface thereof, a portion on the peripheral portion of the concave portion, and a linear beam portion bridged over the concave portion. It has a three-layer body composed of three layers of a film, a silicon nitride film and a silicon oxide film, and an element formation part composed of a silicon layer provided on a central portion of the beam portion.
[0007]
In the micro device having the hollow beams, the silicon layer is preferably a single crystal silicon layer.
[0008]
According to the method of manufacturing a micro device having a hollow beam according to the present invention, a first silicon oxide film is formed on a first silicon substrate, a second silicon oxide film is formed on a second silicon substrate, and a silicon nitride film is formed thereon. Forming the first silicon oxide film and the silicon nitride film, and bonding the first and second silicon substrates to each other; and grinding the second silicon substrate to a predetermined thickness. Forming a device forming portion by etching the second silicon substrate, and forming a linear beam portion 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.
[0009]
In the method for manufacturing a micro device having a hollow beam, the second silicon substrate is preferably a single crystal silicon substrate.
[0010]
In the present invention, the beam portion is composed of a three-layer laminate of a silicon oxide film, a silicon nitride film, and a silicon oxide film. However, this does not cause warping or bending of the beam portion. Further, in the method of the present invention, a first silicon substrate and a 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 specifically described with reference to the accompanying drawings. FIG. 1 is a sectional view (a) and a plan view (b) showing a micro device according to an embodiment of the present invention. A concave portion 12 is formed on the surface (attached surface) of the silicon substrate 11, and a three-layer stack including an SiO ₂ film 13, a Si ₃ N ₄ film 14, and an SiO ₂ film 15 is formed on the silicon substrate 11. The body is formed. This laminate 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. The beam portion 22 extends from the four corners of the peripheral upper 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.
[0012]
In the micro device configured as described above, since the functional element is formed in the single crystal silicon layer 16, the sensitivity of the temperature sensor and the like is excellent. Further, 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 laminate bends so that the SiO ₂ film is located outside. As shown in FIG. 5B, 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. . Thus, the oxide film and the nitride film have opposite stresses. Therefore, as in the present embodiment, in a beam having a three-layer structure in which the SiO ₂ film 13, the Si ₃ N ₄ film 14, and the SiO ₂ film 15 are stacked, the Si ₃ N ₄ film having a small coefficient of thermal expansion is used. Since the SiO ₂ films having a large thermal expansion coefficient at the center are arranged on both sides, stresses in opposite directions are applied at the two interfaces, and the thermal expansion between the SiO ₂ films 13 and 15 and the Si ₃ N ₄ film 14 is reduced. Since they cancel each other, no warping or bending occurs.
[0013]
Next, a method for manufacturing the microdevice 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 °, and a Si ₃ N ₄ film 14 is formed on the SiO ₂ film 15 to a thickness of, for example, 1500 °.
[0014]
Then, as shown in FIG. 3, the Si ₃ N ₄ film 14 and the SiO ₂ film 13 are overlapped and heated to, for example, 1100 ° C. while applying a clamping pressure, so that the two are directly joined.
[0015]
Further, as shown in FIG. 4, the surface of the bond substrate 17 opposite to the bonding surface is polished to a thickness of, for example, 5 μm. Thus, a thin single-crystal silicon layer 18 is obtained.
[0016]
Next, a predetermined functional element such as an oxygen sensor is 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 to leave the fine element 16 at the center. Next, the laminated body including the SiO ₂ film 15, the Si ₃ N ₄ film 14, and the SiO ₂ film 13 is etched to form a beam portion 22 serving as a bridge. Further, a rectangular concave portion 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.
[0017]
In the present embodiment, since the Si ₃ N ₄ film 14 is formed on the bond silicon substrate side when the silicon substrate 11 is etched, the silicon substrate 11 to which a tensile stress is applied and the silicon substrate 11 to which a compressive stress is applied The etching liquid does not enter the bonding interface with the substrate 18. For this reason, when forming the concave portion 12 of the silicon substrate 11 shown in FIG. 1, the etchant does not enter the interface between the SiO ₂ film 13 and the Si ₃ N ₄ film 14 and the wafer does not peel off.
[0018]
Further, in this embodiment, the bond substrate is bonded and the bond substrate is polished to obtain a thin-film silicon layer for forming the functional element. It can be a layer. Therefore, according to the present embodiment, a sensor element having excellent sensitivity can be easily obtained.
[0019]
Note that the present invention is not limited to the above-described embodiment. For example, instead of the concave portion, a concave portion penetrating the silicon substrate may be used.
[0020]
【The invention's effect】
As described above, according to the present invention, 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. Therefore, it is possible to prevent the beam portion from warping and bending. In addition, 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, it is possible to prevent chemical penetration during etching of the silicon substrate. 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]
FIG. 1 is a view showing an embodiment of the present invention, in which (a) is a sectional view and (b) is a plan view.
FIG. 2 is a one-step diagram showing a method according to 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.
[Explanation of symbols]
1, 11: silicon substrate 2, 12: concave portions 3, 13, 15: SiO ₂ film 4, 14: Si ₃ N ₄ film 17: bond silicon substrate 16, 18: single crystal silicon layer

Claims (4)

A silicon substrate having a concave portion formed on the surface thereof, a silicon oxide film, a silicon nitride film, and a silicon oxide film having a portion on the peripheral portion of the concave portion and a linear beam portion bridged over the concave portion; A micro device having a hollow beam, comprising: a three-layer body made of: and a device forming portion made of a silicon layer provided on a central portion of the beam portion. The micro device having a hollow beam according to claim 1, wherein the silicon layer is a single crystal silicon layer. Forming a first silicon oxide film on the first silicon substrate, forming a second silicon oxide film on the second silicon substrate and a silicon nitride film thereon; Superimposing a nitride film on the first and second silicon substrates to join each other, grinding the second silicon substrate to a predetermined thickness, and etching the second silicon substrate to form an element. Forming a portion, forming the linear beam portion by etching the first silicon oxide film, the silicon nitride film, and the second silicon oxide film; and forming the linear silicon beam portion below the beam portion. Forming a concave portion below the beam portion by etching a surface layer portion of the micro device. The micro device according to claim 3, wherein the second silicon substrate is a single crystal silicon substrate.

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