JP2758128B2 - Semiconductor acceleration sensor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor comprising an acceleration detecting circuit using a semiconductor strain gauge and a method of manufacturing the same.

[0002]

2. Description of the Related Art Normally, a semiconductor acceleration sensor is composed of a beam (spring element K) and a weight (mass element M), and a natural frequency (√ (k / m)) where k is a spring constant and m is a mass.
have. Therefore, when an impact that vibrates in a wide frequency range is applied, an excessive displacement occurs at a natural frequency unique to the sensor, and the sensor is destroyed. Therefore, in order to secure the shock resistance of the silicon sensor which is weak to shock, by encapsulating silicon oil or the like in the packaging for mounting the detection body and adding the damping element C, it is possible to prevent excessive displacement due to resonance. Be composed.
However, the disadvantage of filling with silicone oil is that
The following points are mentioned.

[0003] (1) The reduction in sensitivity due to silicone oil is 3
The sensitivity burden on the detection object increases from 0 to 60%.

(2) Silicon oil has a large change in viscosity with respect to temperature, significantly lowering the temperature characteristics of the sensor and complicating the temperature assurance circuit.

As a method for coping with this, recently, a silicon detector has a three-layer structure made of glass or silicon having a depression, and minute gaps in which air exists above and below the weight plane of the detector are formed. Accordingly, an acceleration sensor using the squeeze film effect generated in the minute gap as a damping element C is being developed. When utilizing such a squeeze film effect, the dimension of the minute gap is important as a parameter of the damping coefficient.

FIG. 3 shows an example of a conventional semiconductor acceleration sensor. This acceleration sensor has a structure in which a silicon detector 200, an upper glass 201, and a lower glass 202 are joined in three layers. 3A is a cross-sectional view of the semiconductor acceleration sensor, FIG. 3B is a perspective view showing a lower surface of the upper glass 201 (a surface facing the upper surface of the silicon detector 200), and FIG. 3C is a top view of the silicon detector 200. , (D) is the lower glass 2
FIG. 2 is a perspective view showing an upper surface of the sensor 02 (a surface facing a lower surface of the detection body 200). The detection body 200 includes a support frame 220 and a beam 22.
1, having a weight 222 partitioned by a groove 223,
1 has a structure that connects the support frame 220 and the weight 222. A semiconductor strain gauge (not shown) is formed on the beam 221, and its terminal 224 is connected to the detector 20.
0 is formed on a part of the surface. The upper glass 201 is provided with a partially open depression 205A, while the lower glass 202 is provided with a depression 205B. These depressions 205A and 205B allow the detection object 200
The weight 222 can move up and down.

Next, a process for manufacturing such a semiconductor acceleration sensor will be described.

[0008] As shown in FIG.
An upper glass 201 in which a preliminary groove 204 deeper than the depression 205A is formed on a surface of the detection object facing the terminal 224;
The lower glass 202 on which the 05B is formed and the silicon detector 200 are bonded in a wafer state. The depth of the preliminary groove 204 of the upper glass 201 is usually set to 70% of the total thickness of the upper glass.
% Or less. A plurality of semiconductor chips (two in the figure)
Sensors).

Thereafter, as shown in FIG.
The upper glass 201 is cut by the first grindstone 210 from the upper side of 04 to release the terminal portion of the detection body 200. Further, each chip is divided by the second grindstone 211 to manufacture a semiconductor acceleration sensor.

[0010]

However, such a conventional acceleration sensor has the following problems.

First, as shown in FIG. 3, a gap for damping the upper glass is released, and the gap between the upper glass 201 and the detector 200 is large. Garbage 225 has weight 222
When the sensor enters a gap between the sensor and the upper glass 201 and receives vibration, there is a possibility that the displacement of the weight 222 is obstructed and the characteristics of the sensor deteriorate.

Second, during the manufacturing process, as shown in FIG. 4, dust 225 such as chipping or abrasive grains is inevitably invaded during cutting by the first and second grindstones, which hinders the characteristics of the sensor. Become.

The present invention solves such a conventional disadvantage,
It is an object of the present invention to increase the reliability and production yield of a semiconductor acceleration sensor.

[0014]

To solve this problem, the present invention uses the following two means.

(1) The height of a part of the peripheral portion surrounding the depression of the upper glass is made lower than that of the other part, thereby narrowing the gap between the upper glass and the detector, and preventing dust from entering from the gap. prevent.

(2) The upper glass is cut from the opposite side of the upper glass having the preliminary groove formed thereon by using a grindstone wider than the preliminary groove to release the terminal portion of the silicon detector.

That is, the semiconductor acceleration sensor according to the present invention is integrally processed from a silicon substrate, and has a weight, a support frame portion, and a beam connecting the weight and the support frame portion, and a semiconductor strain gauge is provided on an upper surface of the beam. A formed silicon detector, an upper glass provided above the silicon detector, and having a depression so that the weight can be displaced, and a lower glass provided below the silicon detector, the weight being displaceable And a lower frame having a recess as described above, wherein a portion of a peripheral portion surrounding the recess of the upper glass in a semiconductor acceleration sensor in which a support frame portion of the silicon detector is bonded to the upper glass and the lower glass, respectively. The height of the silicon detector is smaller than that of the other parts, and the gap between the lower edge and the silicon detector is 2 μm or less.

A method of manufacturing a semiconductor acceleration sensor according to the present invention is the method of manufacturing a semiconductor acceleration sensor according to claim 1, wherein the step of preparing the silicon detector and the lower glass is performed, wherein the depression is formed in the upper glass. Processing the height of a part of the peripheral portion surrounding the depression low, and further forming a preliminary groove deeper than the depression outside the low peripheral portion, the upper surface and the lower surface of the silicon detector, respectively; Bonding the upper glass and the lower glass to form a plurality of semiconductor acceleration sensors on a single wafer, and cutting the upper glass with a first grindstone wider than the preliminary groove, and then dividing and cutting each individual sensor. The method is characterized by having a performing step.

[0019]

According to the present invention, the possibility of dust entering the minute gap between the weight and the glass during the manufacturing process and during use can be minimized by the above-described structure, and the reliability of the semiconductor acceleration sensor can be ensured. be able to.

[0020]

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

FIG. 1 shows an embodiment of a semiconductor acceleration sensor according to the present invention.

The semiconductor acceleration sensor according to the present embodiment has a structure in which a silicon detector 100, an upper glass 101 and a lower glass 102 are joined in three layers. FIG. 1A is a cross-sectional view of the semiconductor acceleration sensor (A- in FIGS. 1B to 1D).
A ′ section), (b) is a perspective view showing the lower surface of the upper glass 101 (the surface facing the upper surface of the silicon detector 100),
(C) is a top view of the silicon detector 100, and (d) is a perspective view showing the upper surface of the lower glass 102 (the surface facing the lower surface of the detector 100). As in the conventional example shown in FIG. 3, the detection body 100 has a support frame 120, a beam 121, and a weight 122 divided by a groove 123.
20 and the weight 122 are connected. A semiconductor strain gauge (not shown) is formed on the beam 121, and its terminal 124 is formed on a part of the surface of the detection body 100. The upper glass 101 has a peripheral portion 103
A recess 105A is formed surrounded by
The height of the part 103A of the third part from the depression is lower than the height of the other part. This peripheral portion 103A is preferably provided at a position facing the terminal 124 formed on the detection body 100. On the other hand, the lower glass 102 has a peripheral portion 1.
A dent 105B surrounded by 06 is formed.
The upper surface of the support frame 120 of the silicon detector 100 and the peripheral portion 103 of the upper glass 101 excluding 103A, and the lower surface of the support frame portion 120 and the peripheral portion 106 of the lower glass 102 are joined to form a three-layer sensor. Is done. It is most preferable to use an electrostatic bonding method that does not use an adhesive for bonding.

Here, it has been confirmed by experiments that the depth of the depressions 105A and 105B is appropriately set to 12 to 20 μm in consideration of optimization of damping (air viscosity due to temperature, suppression of excessive displacement due to resonance). I have. On the other hand, the gap between the lower peripheral portion 103A and the silicon detector 100 is set to 2 μm or less. As a result, dust having a size of 2 μm or less may enter the assembled semiconductor acceleration sensor. However, even if dust enters, the size is 2 μm or less. Does not prevent this displacement.

Further, by using a method as shown in FIG. 2 in the sensor manufacturing process, a more reliable semiconductor acceleration sensor can be realized. FIG. 2 shows two sensors. First, as shown in FIG. 2A, an upper glass 101 having a depression 105A, a peripheral portion 103 and a low peripheral portion 103A is formed on one wafer.
Then, the silicon detector 100 and the lower glass 102 having the recess 105B and the peripheral edge 106 are bonded in a wafer state at the above-described portion and by the above-described electrostatic bonding method. A spare groove 104 is provided in the middle portion of the upper glass between adjacent sensors, especially in the middle portion of the upper glass adjacent to the lower peripheral portion 103A. This spare groove 104 is deeper than the recess 105A, similarly to the spare groove 204 in the conventional example shown in FIG. 4, in other words, the thickness of the upper glass at that portion is smaller than the thickness of the upper glass at the portion of the recess 105A. The depth of the preliminary groove 104 is preferably 70% of the total thickness of the upper glass, and is 35 μm or less when the total thickness is, for example, 50 μm.

Next, as shown in FIG.
4, the first grinding wheel 1 wider than the preliminary groove 104
The upper glass 101 is divided by 10. Spare groove 10
By using the grindstone 110 having a width larger than 4, the lapping and abrasive grains flipped off from the end face of the grindstone prevent the lower edge portion 103A of the upper glass 101 from entering the gap between the silicon detector 100 and the lower edge portion 103A. Can be.

Furthermore, when chips are cut by the second grindstone 111 in the next process, the upper glass 101 has a gap of 2 μm or less provided by the peripheral portion 103A having a low height. Can be.

[0027]

As described above, the present invention has the following effects.

(1) It is possible to prevent dust from entering the minute gap during the manufacturing process.

(2) It is possible to prevent dust from entering the minute gap even during use of the sensor.

(3) As a result, a semiconductor acceleration sensor having high reliability and a high yield can be manufactured, and high reliability during use can be ensured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a semiconductor acceleration sensor according to the present invention.

FIG. 2 is a sectional view illustrating a method for manufacturing a semiconductor acceleration sensor according to the present invention.

FIG. 3 is a diagram illustrating a conventional semiconductor acceleration sensor.

FIG. 4 is a cross-sectional view illustrating a method for manufacturing a conventional semiconductor acceleration sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 silicon detector 101 upper glass 102 lower glass 103 peripheral portion 103A low peripheral portion 104 preliminary groove 105A, 105B recess 106 peripheral portion 110 first grindstone 111 second grindstone 120 support frame 121 beam 122 weight 123 groove 124 terminal Reference Signs List 200 silicon detector 201 upper glass 202 lower glass 204 preliminary groove 205A, 205B depression 210 first grindstone 211 second grindstone 220 support frame 221 beam 222 weight 223 groove 224 terminal 225 dust

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-194381 (JP, A) JP-A-5-119057 (JP, A) JP-A-4-286372 (JP, A) JP-A-2- 28973 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01P 15/12 H01L 29/84

Claims (2)

(57) [Claims] 1. A silicon detector which is integrally processed from a silicon substrate, has a weight, a support frame, and a beam connecting the weight and the support frame, and further has a semiconductor strain gauge formed on an upper surface of the beam. And an upper glass provided above the silicon detector and having a depression so that the weight can be displaced; and a lower glass provided below the silicon detector and having a depression so that the weight can be displaced. In a semiconductor acceleration sensor in which a support frame portion of the silicon detector is bonded to the upper glass and the lower glass, a height of a part of a peripheral portion surrounding a depression of the upper glass is other portion. The gap between the lower peripheral portion and the silicon detector is 2 μm.
A semiconductor acceleration sensor characterized by the following. 2. The method of manufacturing a semiconductor acceleration sensor according to claim 1, wherein the step of preparing the silicon detector and the lower glass includes forming the depression in the upper glass, and forming a peripheral portion surrounding the depression. Processing the height of the part lower,
Forming a preliminary groove deeper than the depression outside the lower peripheral portion; bonding the upper glass and the lower glass to upper and lower surfaces of the silicon detector, respectively, to form a plurality of semiconductors on a single wafer; A method of manufacturing a semiconductor acceleration sensor, comprising: forming an acceleration sensor; and cutting the upper glass with a first grindstone wider than the preliminary groove, and then dividing and cutting each individual sensor.