JP3405222B2 - Semiconductor acceleration sensor element and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an automobile, an aircraft,
The present invention relates to a semiconductor acceleration sensor element used for home electric appliances and the like and a manufacturing method thereof, and more particularly to a triaxial acceleration sensor element having sensitivity in x-axis, y-axis and z-axis.

[0002]

2. Description of the Related Art Generally, a cantilever type and a double-supported beam type have been proposed as acceleration sensors. As a detection method, there are a method of detecting mechanical strain as a change in electric resistance and a detection method by a change in capacitance. For example, Japanese Unexamined Patent Publication No. 6-109755 discloses a double-ended beam type acceleration sensor that detects mechanical strain as a change in electrical resistance.
It is disclosed in Japanese Patent No. 289327.

FIG. 3 is a schematic sectional view showing a manufacturing process of a semiconductor acceleration sensor according to a conventional example, and FIG. 4 is a schematic plan view showing a state of the semiconductor acceleration sensor according to the above drawing as viewed from above. First, the silicon oxide film 10 is formed on one main surface of the n-type single crystal silicon substrate 7 by thermal oxidation or the like,
The opening 10a is formed by etching the silicon oxide film 10 using a resist mask (not shown) patterned into a predetermined shape, and the resist mask is removed by plasma ashing or the like. At this time, the opening 1
0a is formed at a location surrounding the substantially square central portion 7a of the single crystal silicon substrate 7.

Subsequently, a p + type buried sacrificial layer 8 is formed by ion-implanting a p-type impurity such as boron (B) and an annealing process using the silicon oxide film 10 having the opening 10a as a mask. (FIG. 3A), the silicon oxide film 10 is removed by etching.

Next, an n-type epitaxial layer 9 is formed on one main surface of the single crystal silicon substrate 7, and the n-type epitaxial layer 9 is substantially opposed to the epitaxial layer 9 with a beam portion 2b, which will be described later, interposed therebetween, and the central portion 2a. A p + type reaching the p + type buried sacrificial layer 8 by ion implantation and anneal of a p type impurity such as boron (B) using a resist mask (not shown) in a rectangular shape with a lacking vicinity. Forming an impurity layer (not shown),
The resist mask is removed (FIG. 3B). Here, since the epitaxial layer 9 becomes the bending portion 2 later, it is formed to have a thickness that bends when acceleration is applied.

Next, a p-type impurity such as boron (B) is diffused to form a piezoresistor 11 at a portion of the epitaxial layer 9 corresponding to the bending portion 2 (FIG. 3C), and the piezoresistor 1 is formed.
1 is diffused with p-type impurities such as boron (B) in the epitaxial layer 9 so as to be electrically connected to the diffusion layer 12 (FIG. 3D).

Next, CV is formed on the two main surfaces of the single crystal silicon substrate 7 and on the surface of the epitaxial layer 9 on which the piezoresistor 11 is formed.
A protective film 13 such as a silicon nitride film is formed by the D method or the like,
By etching the protective film 13 formed on the two main surfaces of the single crystal silicon substrate 7 using a resist mask (not shown) patterned in a predetermined shape, the outer peripheral edge of the weight portion 3 described later. The opening 13a is formed at a position corresponding to (3) and the resist mask is removed (FIG. 3E).

Next, the protective film 1 in which the opening 13a is formed
3 is used as a mask to perform anisotropic etching on the single crystal silicon substrate 7 using an alkaline etchant such as a potassium hydroxide (KOH) solution to form the cut portion 5 reaching the p + type buried sacrificial layer 8. Form (Fig. 3
(F)).

Next, the protective film 13 at a desired position on the diffusion wiring 12 is removed by etching, and a metal wiring 14 is formed by sputtering and etching so as to be electrically connected to the diffusion wiring 12 (see FIG. 3 (g)).

Next, an etchant made of an acidic solution containing hydrofluoric acid or the like is introduced into the cut portion 5, and the p + type buried sacrificial layer 8 and the p + type impurity layer are removed by isotropic etching to form the cut groove 4. As shown in FIG. 4, the slits 15 are formed by RIE (Reactive Ion Etching) or the like so that the bending is concentrated on the bending portion 2 at a desired portion of the epitaxial layer 9, and the weight portion 3 and The frame 1 including the epitaxial layer 9, the support member 6 that supports the lower surface side of the frame 1, the central portion 2a and the beam portion 2b,
The neck portion 3a of the weight portion 3 is connected to the central portion 2a, the beam portion 2b extends in all directions from the outer peripheral edge of the central portion 2a, and the cross-shaped flexible portion 2 connected to the inner peripheral edge of the frame 1 is formed. Formed (FIG. 3 (h)).

An upper stopper (not shown) having a recess at a position corresponding to the weight 3 is joined to the frame 1, and a lower stopper (not shown) having a recess at a position corresponding to the weight 3 is supported. It is joined to the member 6.

In this semiconductor acceleration sensor, when an acceleration is applied to the weight portion 3, the weight portion 3 is displaced in the direction opposite to the direction in which the acceleration is applied and the bending portion 2 bends, and is formed on one surface of the bending portion 2. The piezoresistor 11 bends and the piezoresistor 11
The resistance value of changes. The acceleration is detected by converting the change in the resistance value into an electric signal.

[0013]

In the semiconductor acceleration sensor having the structure having the cross-shaped bending portion 2 as described above, the residual stress existing in the sensor chip is concentrated in the portion easily deformed structurally, that is, the bending portion 2. To do.

The cause of this residual stress is considered to be thermal stress from the upper stopper and the lower stopper.
As the material of the upper stopper and the lower stopper, glass is often used because it is easily bonded to the sensor material (silicon). In this case, since the thermal expansion coefficient of silicon is different from that of glass, residual stress due to thermal stress remains in the sensor chip after bonding, and warpage occurs in the chip, especially in the flexible portion 2 that is most susceptible to stress. Due to this warpage, the characteristics of the sensor are adversely affected such that the offset voltage is largely deviated, and this also causes variations in characteristics.

Further, since the amount of warp also changes depending on the temperature, there is a problem that the temperature characteristics are deteriorated such that the sensitivity and the offset voltage largely change depending on the temperature. A similar problem also occurs due to stress from the outside of the sensor chip such as a package.

When the residual stress is generated as a tensile stress in the longitudinal direction of the bending portion 2, the bending portion 2 becomes difficult to bend,
This causes sensitivity deterioration. When compressive stress is generated in the longitudinal direction,
Since the bending portion 2 is formed in a cross shape, the beam portion 2b on the same straight line has no escape area for the stress, and a large compressive force causes a buckling phenomenon, so that the bending portion 2 does not bend and the sensitivity is also deteriorated. Invite.

The present invention has been made in view of the above points, and an object of the present invention is to reduce the thermal stress from the outside to the sensor chip, have excellent temperature characteristics, and achieve high-performance semiconductor acceleration. A sensor element and a manufacturing method thereof are provided.

[0018]

The invention according to claim 1 is
A flexible portion having a central portion and a beam portion extending from the central portion, a frame supporting the flexible portion, a weight portion connected to the central portion via a neck portion, the beam portion and the weight. A notch groove provided at a predetermined position between the parts, and a supporting member that surrounds the weight part through the notch part and supports one surface side of the frame, and the notch part communicates with the notch groove. In the semiconductor acceleration sensor element, the beam portion is arranged so as not to be located on the center line of the bending portion forming surface, and the bending portion is rotationally symmetrical with respect to the bending portion forming surface. It is characterized by having done.

Furthermore, epitaxial invention of claim 1, wherein said neck portion, the weight portion and the support member so as to form with the semiconductor substrate, that will be formed with the frame and the flexible portions on the semiconductor substrate Epitaxial layer formed using layers to form the frame and flexure
The beam part and the front part so that part of the layer is used as a weight part.
It is characterized in that a cut groove is provided between the weight portions .

[0020] According to a second aspect of the invention, meet a method of manufacturing a semiconductor acceleration sensor device according to claim 1, the high concentration impurity layer in which the notches are formed on one main surface of the semiconductor substrate is removed by etching It is characterized by being formed by the above.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a semiconductor acceleration sensor element according to an embodiment of the present invention, (a) is a schematic plan view, and (b) is A of (a).
It is a schematic sectional drawing in -A ', (c) is B- of (a).
It is a schematic sectional drawing in B '. The semiconductor acceleration sensor element according to the present embodiment has a frame-shaped frame 1 and a central portion 2a.
The flexible portion 2 including the beam portion 2b, the weight portion 3, and the support member 6 are included. The bending portion 2 extends in all directions from the outer peripheral edge of the central portion 2a, excluding the center lines CC ′ and DD ′ of the bending portion 2 forming surface of the semiconductor acceleration sensor element. The beam portion 2b is provided so as to be rotationally symmetrical with respect to the surface on which the flexible portion 2 is formed.

A weight portion 3 is connected to the central portion 2a via a neck portion 3a. Thereby, the cut groove 4 is formed between the weight portion 3 and the beam portion 2b. Also,
A support member 6 is provided so as to surround the weight portion 3 via the cut portion 5 and to support the lower surface side of the frame 1.

The cut portion 5 is constructed so as to communicate with the cut groove 4. Further, in the present embodiment, a single crystal silicon substrate which is a semiconductor substrate is used as the weight portion 3 and the supporting member 6, and an epitaxial layer formed on the semiconductor substrate is used as the frame 1 and the bending portion 2.

Further, the shape of the weight portion 3 is not limited to the shape of the weight portion 3 shown in FIG. 1 and may be at least rotationally symmetrical with respect to the surface on which the flexible portion 2 is formed. good. However, if the volume of the weight portion 3 is made as large as possible, the mass of the weight portion 3 is increased accordingly, and the sensitivity can be improved. Here, in the present embodiment, the volume of the weight portion 3 is increased by using a part of the epitaxial layer forming the frame 1 and the bending portion 2 as the weight portion 3.

Further, a piezoresistor (not shown) and a diffusion wiring (not shown) are provided at a predetermined position on one surface side of the bending portion 2, and a metal wiring (not shown) is electrically connected to the diffusion wiring. No) is provided.

Therefore, in the present embodiment, the beam portion 2a of the bending portion 2 is not positioned on the center lines CC 'and DD', and is rotationally symmetrical with respect to the bending portion forming surface. Since the bending portion 2 is configured so that the bending of the bending portion 2 due to the residual stress from the external force is eliminated, fluctuations in sensitivity, offset voltage, etc. due to temperature can be suppressed, and good and stable characteristics can be obtained. be able to.

In order to detect the acceleration using the semiconductor acceleration sensor element shown in FIG. 1, it is necessary to provide an acceleration detecting means. As the acceleration detecting means, for example,
Using a piezoresistor whose resistance value changes due to the bending of the bending portion 2, a method of converting the change in the resistance value of the piezoresistor into an electric signal to detect acceleration, or using electrodes arranged opposite to each other,
There is a method of detecting acceleration by using the change in the electrostatic capacitance between the electrodes due to the bending of the bending portion 2.

The manufacturing process of the semiconductor acceleration sensor according to this embodiment will be described below. FIG. 2 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to the present embodiment. Note that FIG. 2 shows the manufacturing process in the AA ′ cross section in FIG.

The semiconductor acceleration sensor according to the present embodiment has a silicon oxide film (not shown) formed on one main surface of a single crystal silicon substrate 7 which is an n-type semiconductor substrate having a thickness of 400 to 600 μm by thermal oxidation or the like. Are formed, an opening is formed by etching the silicon oxide film using a resist mask (not shown) patterned in a predetermined shape, and the resist mask is removed by plasma ashing or the like.
At this time, the opening is the neck portion 3 of the single crystal silicon substrate 7.
Predetermined position on the outer peripheral edge of the portion that becomes a (beam portion 2a forming portion)
Is formed so as to extend from.

Subsequently, by using the silicon oxide film having the opening formed as a mask, deposition and thermal diffusion of p-type impurities such as boron (B) or ion implantation and annealing treatment are performed to form a p + high concentration impurity layer. The mold embedding sacrificial layer 8 is formed, and the silicon oxide film is removed by etching (FIG. 2A). At this time, the impurity concentration of the p + type buried sacrificial layer 8 is preferably 10 ¹⁹ cm ⁻³ or more.

In the present embodiment, the p + type buried sacrificial layer 8 is formed by using the silicon oxide film having the openings as a mask, but the silicon nitride film may be used as a mask.

Although the p + type buried sacrificial layer 8 is formed on the single crystal silicon substrate 7, the n type impurities such as phosphorus (P) are deposited and thermally diffused, or ion-implanted and annealed. Thus, the n + type buried sacrificial layer may be formed.

Further, the p + type buried sacrificial layer 8 is formed in the neck portion 3
It may extend from the entire outer edge of a to completely surround that portion, or it may extend from a portion of the outer edge.

Next, an n-type epitaxial layer 9 is formed on one main surface of the single crystal silicon substrate 7 with a thickness corresponding to the bending portion 2 that bends when acceleration is applied, and a resist mask patterned into a predetermined shape is formed. (Not shown) is used to perform deposition and thermal diffusion of p-type impurities such as boron (B) or ion implantation and annealing treatment on a portion of the epitaxial layer 9 corresponding to a bending portion 2 to be described later, and thereby the piezo resistance Diffusion wiring (not shown) is formed so as to be electrically connected to the piezoresistor by forming (not shown) and similarly performing p-type impurity deposition and thermal diffusion or ion implantation and annealing. After that, the photoresist is removed (FIG. 2B).

Next, a silicon oxide film (not shown) is formed on the two main surfaces of the single crystal silicon substrate 7 and the epitaxial layer 9, and a protective film such as a silicon nitride film (not shown) is formed on the silicon oxide film. ) Is formed. Then, the silicon oxide film / protective film formed on the two main surfaces of the single crystal silicon substrate 7 is etched by using a resist mask (not shown) patterned in a predetermined shape, so that the weight portion 3 is formed. An opening (not shown) is formed at a position corresponding to the outer peripheral edge of the resist mask and the resist mask is removed.

Next, anisotropic etching of the single crystal silicon substrate 7 is performed using an alkaline etchant such as potassium hydroxide (KOH) solution with the silicon oxide film / protective film having the openings formed as a mask. Thus, the cut portion 5 is formed to reach the p + type buried sacrificial layer 8 or to the vicinity (FIG. 2C). If the anisotropic etching is stopped in the vicinity of the p + type buried sacrificial layer 8, it is possible to prevent the bending portion 2 from being destroyed in a later step. In that case, the remaining portion must be removed by RIE or the like from the second main surface side of the single crystal silicon substrate 7.

Next, the silicon oxide film / protective film on the epitaxial layer 9 is selectively removed by etching to form an opening (not shown). At this time, the opening is formed on the p + type buried sacrificial layer 8 at a position adjacent to a position corresponding to the beam 2b formed in a later step. Then, using the silicon oxide film / protective film in which the opening is formed as a mask, the epitaxial layer 9 is removed by etching until it reaches the p + type buried sacrificial layer 8 to form an etchant introduction port (not shown).

Next, an etchant (50% hydrofluoric acid aqueous solution: 69% nitric acid aqueous solution: acetic acid = 1: 1 to 3: 8 by volume) is introduced from the etchant inlet through an acidic solution containing hydrofluoric acid and the like. The p + type buried sacrificial layer 8 is removed by etching to form the cut groove 4, and the weight portion 3 suspended and supported by the central portion 2a formed in the subsequent step through the neck portion 3a, and the weight portion 3 formed in the subsequent step. Supporting the lower surface side of the frame 1 and weight 3
And a support member 6 that surrounds the outer peripheral edge of the substrate through the cut portion 5.

Next, a part of the silicon oxide film / protective film on the diffusion wiring is removed by etching to form a contact hole (not shown) so that the diffusion wiring is electrically connected through the contact hole. A metal wiring (not shown) is formed on.

Finally, a predetermined portion of the epitaxial layer 9 and the silicon oxide film / protective film on the one main surface side of the single crystal silicon substrate 7 (in this manufacturing process, a white portion in the plan view of FIG. 1) is etched. It is removed to form a slit (not shown) and has a frame-shaped frame 1 and a central portion 2a and a beam portion 2b. The beam portion 2b includes at least a part of the inner peripheral side surface of the frame 1 and the central portion 2a. Extending between the beams 2b
And the central portion 2a are integrally connected to form a flexible portion 2 (FIG. 2D). At this time, the shape of the flexible portion 2 is configured as shown in FIG.

[0041]

According to the first aspect of the present invention, the bending portion having the central portion and the beam portion extending from the central portion, the frame supporting the bending portion, and the neck portion in the central portion are provided. A weight portion to be connected, a notch groove provided at a predetermined position between the beam portion and the weight portion, and a support member that surrounds the weight portion via the notch portion and supports one surface side of the frame. In the semiconductor acceleration sensor element having the cutout portion communicating with the cutout groove, the beam portion is arranged so as not to be located on the center line of the bending portion forming surface, and the bending portion is provided with the bending portion. Since it is configured to be rotationally symmetric with respect to the part forming surface, warping of the bending part due to residual stress from external force is eliminated, and fluctuations in sensitivity, offset voltage, etc. due to temperature can be suppressed, and it is good and stable. Get the characteristics It can, to reduce thermal stress from the outside to the sensor chip, excellent temperature characteristics, it is possible to provide a high-performance semiconductor acceleration sensor element.

Further, in the invention according to claim 1 , the neck portion, the weight portion and the supporting member are formed by using a semiconductor substrate, and the frame and the bending portion are formed on the semiconductor substrate. Since it is formed by using, the thickness of the bending portion can be accurately formed in addition to the above effect. Moreover, the frame and the flexure are
Part of the formed epitaxial layer is used as a weight
Therefore, the volume of the weight part increases and the mass also increases, increasing the sensitivity
Can be improved.

[0043] According to a second aspect of the invention, meet a method of manufacturing a semiconductor acceleration sensor device according to claim 1, the high concentration impurity layer in which the notches are formed on one main surface of the semiconductor substrate is removed by etching Since it is formed in this way, in addition to the effect of the invention described in claim 1 , the thickness of the bending portion can be further accurately formed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a semiconductor acceleration sensor element according to an embodiment of the present invention, (a) is a schematic plan view, and (b) is a schematic view taken along the line AA ′ of (a). It is sectional drawing, (c) is a schematic sectional drawing in BB 'of (a).

FIG. 2 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to the present embodiment.

FIG. 3 is a schematic cross-sectional view showing a manufacturing process of a semiconductor acceleration sensor according to a conventional example.

FIG. 4 is a schematic plan view showing a state of the semiconductor acceleration sensor according to the above figure as viewed from above.

[Explanation of symbols]

1 frame 2 flexure 2a Central part 2b Beam part 3 Weight section 3a neck part 4 notch 5 notch 6 Support members 7 Single crystal silicon substrate 7a central part 8 p + type embedded sacrificial layer 9 Epitaxial layer 10 Silicon oxide film 11 Piezoresistor 12 Diffusion wiring 13 Protective film 13a opening 14 Metal wiring 15 slits

Front page continuation (72) Inventor Takuro Nakamura 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Takuro Ishida, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd. (56) References Kaihei 6-109755 (JP, A) JP 9-289327 (JP, A) JP 5-102495 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01P 15 / 12 G01P 15/18 H01L 29/84

Claims (2)

(57) [Claims] 1. A flexible portion having a central portion and a beam portion extending from the central portion, a frame supporting the flexible portion, a weight portion connected to the central portion via a neck portion, and A notch groove provided at a predetermined position between the beam portion and the weight portion, and a supporting member that surrounds the weight portion via the notch portion and supports one surface side of the frame, and the notch portion In a semiconductor acceleration sensor element communicating with the cut groove, the beam portion is arranged so as not to be located on the center line of the bending portion forming surface, and the bending portion is rotationally symmetrical with respect to the bending portion forming surface. And the neck portion, the weight portion, and the supporting member.
It is formed using a semiconductor substrate and the frame and
And an epitaxy in which the flexure is formed on the semiconductor substrate.
Formed using a Charl layer to configure the frame and flexure
Part of the epitaxial layer used as a weight part
Thus, the semiconductor acceleration sensor element is characterized in that a cut groove is provided between the beam portion and the weight portion . 2. A method of manufacturing a semiconductor acceleration sensor device according to claim 1, formed by the previous SL switching interrupt grooves are etched and removed at a high concentration impurity layer formed on one main surface of said semiconductor substrate method of manufacturing a semi-conductor acceleration sensor element you characterized in that it is.