JP3473462B2 - Semiconductor acceleration sensor 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 used for home electric appliances and the like and a manufacturing method thereof.

[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. 12 is a schematic top view showing a semiconductor acceleration sensor according to a conventional example, FIG. 13 is a schematic cross-sectional view according to the above figure, and (a) is a schematic cross-sectional view taken along the line CC ′. FIG. 14B is a schematic cross-sectional view taken along line DD ′ of FIG.
Is C- in FIG. 12 of the semiconductor acceleration sensor according to the conventional example.
It is a schematic sectional drawing which shows the manufacturing process in C ', and FIG.
It is a schematic sectional drawing which shows the manufacturing process in DD 'of FIG. 12 of the semiconductor acceleration sensor which concerns on a prior art example.

First, a p-type impurity such as boron (B) is ion-implanted or the like on one main surface of an n-type single crystal silicon substrate 1 which is a semiconductor substrate by using a resist mask 2 patterned in a predetermined shape. Then, the p + type buried sacrificial layer 3 is formed (FIGS. 14A and 15A). At this time, the opening for patterning is formed in a portion surrounding the substantially square central portion 1a of the single crystal silicon substrate 1.

Then, after removing the resist mask 2,
Silicon having the same conductivity type as the single crystal silicon substrate 1 and the same impurity concentration is epitaxially grown on one main surface of the single crystal silicon substrate 1 to form the epitaxial layer 4 (FIGS. 14B and 15 ( b)). Here, since the epitaxial layer 4 becomes the bending portion 10 later, it is formed to have a thickness that bends when acceleration is applied. Further, the p-type impurity introduced previously is also diffused into the epitaxial layer 4.

Next, a p-type impurity is introduced and diffused into a portion of the epitaxial layer 4 corresponding to a beam portion 4b, which will be described later, by using a resist mask 2 patterned in a predetermined shape to diffuse the piezoresistor 5 and the diffusion wiring ( (Not shown) is formed (FIGS. 14C and 15C).

Next, after removing the resist mask 2, a silicon nitride film 6 is formed on the epitaxial layer 4 and on the two main surfaces of the single crystal silicon substrate 1 by a CVD method or the like (FIG. 14 (d), FIG. 15 (d)), the silicon nitride film 6 is etched using a resist mask (not shown) patterned into a predetermined shape as a mask (FIGS. 14 (e) and 1).
5 (e)). At this time, in the silicon nitride film 6 formed on the two main surfaces of the single crystal silicon substrate 1, an opening 6a is formed at a position corresponding to the outer peripheral edge of the weight portion 13 described later,
Silicon nitride film 6 formed on the epitaxial layer 4
Has an opening 6a formed at a position adjacent to the beam 10b.

Next, using the silicon nitride film 6 having the opening 6a as a mask, the epitaxial layer 4 and the single crystal silicon substrate 1 are anisotropically formed by using an alkaline etchant such as potassium hydroxide (KOH) solution. Of the etchant is formed in the epitaxial layer 4 to reach the p + -type buried sacrificial layer 3 by performing the reactive etching, and the cut portion is formed in the single crystal silicon substrate 1 at a position corresponding to the outer peripheral edge of the weight portion 13. 7 is formed (FIG. 14 (f),
FIG. 15 (f)). At this time, the etching for forming the cut portion 7 is stopped before reaching the p + type buried sacrificial layer 3. Therefore, the p + type buried sacrificial layer 3
The single crystal silicon substrate 1 exists between and the reaching point of the cut portion 7.

Next, an etchant (50% hydrofluoric acid aqueous solution: 69% nitric acid aqueous solution: acetic acid = 1: 1 to 3: 8 by volume) which is an acidic solution containing hydrofluoric acid is introduced into the etchant introducing port 8. Then, the p + type buried sacrificial layer 3 is removed by isotropic etching to form a groove 9, and the central portion 1 is formed.
0a and a beam portion 10b extending from the outer peripheral edge of the central portion 10a in all directions to form a flexible portion 10 (FIG. 14).
(G), FIG. 15 (g)).

Next, the silicon nitride film 6 at a desired position on the diffusion wiring is removed by etching to form a contact hole, and sputtering, vapor deposition, or the like is performed so as to be electrically connected to the diffusion wiring through the contact hole. Metal wiring 11 and electrode pads (not shown) are formed (FIG. 14).
(H), FIG. 15 (h)). Therefore, the electrode pad is electrically connected to the piezoresistor 5 via the metal wiring 11 and the diffusion wiring.

Finally, the single crystal silicon substrate 1 existing between the cut groove 9 and the cut portion 7 is removed by etching the entire surface, and the single crystal silicon substrate 1 is exposed to the outside of the weight portion 13 from the epitaxial layer 4 forming surface side. Among the portions corresponding to the peripheral edge, the portion excluding the portion where the flexible portion 10 is formed is the cut portion 7
Until the flexure 1
A frame 12 for supporting 0, a weight portion 13 suspended and supported by a central portion 10a via a neck portion 13a, and a weight portion 1
While enclosing the outer peripheral edge of 3 via the notch 7,
The support member 14 that supports the lower surface side of the frame 12 is formed (FIGS. 14 (i) and 15 (i)).

In this semiconductor acceleration sensor, when acceleration is applied to the weight portion 13, the weight portion 13 is displaced in the direction opposite to the direction in which the acceleration is applied, and the bending portion 10 bends.
The piezoresistor 5 formed at a predetermined position on the one side of 0 bends, and the resistance value of the piezoresistor 5 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 above-described configuration, when the applied acceleration becomes large, the upper end of the weight portion 13 is the lower surface of the bending portion 10 as shown by the wavy line in FIG. However, even if a higher acceleration is applied, good operation cannot be obtained.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor acceleration sensor capable of increasing a detectable acceleration range and a manufacturing method thereof. is there.

[0015]

The invention according to claim 1 is
A flexure portion having a frame having an upper surface side and a lower surface side and a plurality of beam portions and a central portion, the beam portion extending between at least a part of an inner edge portion of the frame and the central portion. The beam portion and the central portion are integrally connected to each other, the weight portion suspended and supported by the central portion, the lower surface side of the frame is supported, and the inner side surface is a side surface of the weight portion. And a support member facing each other across a notch portion, a notch groove formed between the weight portion and the beam portion, and an acceleration detecting portion that detects the acceleration by converting the strain generated in the bending portion into an electric signal. And a semiconductor acceleration sensor in which the cutout portion and the cutout groove communicate with each other, wherein the width defined by the weight portion and the beam portion of the cutout groove is the central portion. Make the frame neighborhood wider than the neighborhood And it is characterized in and.

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, the acceleration detecting section includes:
A piezoresistor whose resistance value changes due to bending is used, and acceleration is detected by converting a change in the resistance value of the piezoresistor into an electric signal.

According to a third aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, the acceleration detecting section includes:
It is characterized in that the electrodes arranged substantially opposite to each other are used to detect the bending of the bending portion and / or the weight portion at the time of applying an acceleration as a change in the capacitance by the electrode, thereby detecting the acceleration. is there.

According to a fourth aspect of the invention, in the semiconductor acceleration sensor according to any one of the first to third aspects,
The width of the cut groove, which is defined between the weight portion and the beam portion, is removed by etching on the cut groove forming surface side of the beam portion and the weight portion, so that the frame is formed more than the vicinity of the central portion. It is characterized by widening the neighborhood.

The invention according to claim 5 is the semiconductor acceleration sensor according to any one of claims 1 to 3,
The width of the cut groove defined between the weight portion and the beam portion is removed by etching on the cut groove forming surface side of the weight portion so that the frame vicinity is wider than the central portion vicinity. It is characterized by having done.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor acceleration sensor according to the fourth aspect, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the flexible portion and the frame are formed. The first high-concentration impurity region is formed by processing an epitaxial layer formed on one main surface of the semiconductor substrate and introducing an impurity having a small diffusion coefficient into a predetermined portion of the one main surface of the semiconductor substrate. And forming a second high-concentration impurity region by introducing an impurity having a large diffusion coefficient into a predetermined portion of the one main surface of the semiconductor substrate adjacent to the first high-concentration impurity region, By etching away the second high-concentration impurity region, a notch groove is formed in which the width defined between the weight portion and the beam portion is wider in the frame vicinity than in the central portion. It is characterized in.

The invention according to claim 7 is the method for manufacturing a semiconductor acceleration sensor according to claim 4, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are The semiconductor layer is formed by processing an epitaxial layer formed on one main surface of the semiconductor substrate, and impurities are introduced into a predetermined portion of the one main surface of the semiconductor substrate to form a first high-concentration impurity region. Impurities are introduced into a first high-concentration impurity region forming portion and a predetermined portion of one main surface of the semiconductor substrate adjacent to the first high-concentration impurity region to make the first high-concentration impurity region have a higher concentration. While forming a second high concentration impurity region,
By removing the first and second high-concentration impurity regions by etching, a notch groove having a width defined between the weight portion and the beam portion which is wider in the frame vicinity than in the central portion is formed. It is characterized by being formed.

The invention according to claim 8 is the method for manufacturing a semiconductor acceleration sensor according to claim 5, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are formed. Formed by processing the epitaxial layer formed on the one main surface of the semiconductor substrate, after introducing impurities into a predetermined portion of the one main surface of the semiconductor substrate to form a first high-concentration impurity region, One main surface of the semiconductor substrate adjacent to the first high-concentration impurity region formation location and the first high-concentration impurity region by thermal diffusion to diffuse the first high-concentration impurity region to a deeper region And forming a second high-concentration impurity region by introducing an impurity into a predetermined portion of the second high-concentration impurity region, the surface concentration of the second high-concentration impurity region is substantially the same as the surface concentration of the first high-concentration impurity region. Then By making the diffusion distances of impurities from the first and second high-concentration impurity regions into the epitaxial layer substantially the same, and removing the first and second high-concentration impurity regions by etching, It is characterized in that a notch groove is formed in which a width defined between the beam portion and the vicinity of the frame is wider than that of the vicinity of the central portion.

The invention according to claim 9 is the method for manufacturing a semiconductor acceleration sensor according to claim 5, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are The first high-concentration impurity region is formed by processing an epitaxial layer formed on one main surface of the semiconductor substrate and introducing an impurity having a small diffusion coefficient into a predetermined portion of the one main surface of the semiconductor substrate. And forming a second high-concentration impurity region by introducing an impurity having a large diffusion coefficient into a predetermined portion of the one main surface of the semiconductor substrate adjacent to the first high-concentration impurity region by a high-energy ion implantation method. Then, the diffusion distances of the impurities from the first and second high-concentration impurity regions into the epitaxial layer are made substantially the same, and the first and second high-concentration impurity regions are removed by etching. By the width defined between the weight portion and the beam portion, and is characterized in that than the central portion near the formation of the wide was cut groove the frame near.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 and FIG. 2 are schematic cross-sectional views showing a manufacturing process of a semiconductor acceleration sensor according to one embodiment of the present invention, and FIG.
It is a schematic plan view which shows the semiconductor acceleration sensor which concerns on this Embodiment, FIG. 4 is a schematic sectional drawing which shows the state where the acceleration of the semiconductor acceleration sensor which concerns on this embodiment was applied, (a) is an upper part. FIG. 9 is a schematic cross-sectional view taken along the line AA ′ of FIG.
(B) is a schematic sectional view taken along the line BB 'in the above figure. In addition,
1 shows a schematic sectional view taken along the line AA 'in FIG. 3, and FIG. 2 shows a schematic sectional view taken along the line BB' in FIG.

The semiconductor acceleration sensor according to the present embodiment is a semiconductor acceleration sensor shown in FIGS. 14 (i) and 15 (i) as a conventional example, and has a notch defined between the beam portion 10b and the weight portion 13. The interval (width) of the groove 9 is wider in the vicinity of the frame 12 than in the vicinity of the neck portion 13a (FIGS. 1 (i) and 2 (i)). Here, in the present embodiment, the weight portion 13 forming surface side of the beam portion 10b near the frame 12 is removed by etching, and the bending portion 10 forming surface side of the weight portion 13 near the frame 12 is removed by etching. The intervals between the cut grooves 9 are widened.

In the present embodiment, the shape of the cut groove 9 is configured in two steps, but the shape is not limited to this, and the cut groove 9 is formed in the direction from the neck portion 13a to the frame 12, for example. The interval may be gradually widened, or may be configured in three or more steps.

Therefore, in the present embodiment, as shown in FIG. 4, the distance between the outer peripheral edge of the upper end of the weight portion 13 and the side of the flexible portion 10 on which the weight portion 13 is formed becomes wider, and the displacement of the weight becomes larger. Can be increased, and the range of acceleration that can be sensed can be increased.

The manufacturing process of the semiconductor acceleration sensor according to this embodiment will be described below with reference to FIGS. First, using a resist mask 2 patterned into a predetermined shape, a p-type impurity having a small diffusion coefficient such as BF _{2 is} introduced into one main surface of an n-type single crystal silicon substrate 1 which is a semiconductor substrate by ion implantation or the like. Then, the p + type buried sacrificial layer 3a which is the first high concentration impurity region is formed (FIGS. 1A and 2A). At this time, the opening for patterning is formed in a portion surrounding the substantially square central portion 1a of the single crystal silicon substrate 1.

The shape of the central portion 1a is not particularly limited, and may be, for example, a circle, an ellipse, or a rectangle (rectangle, square).

The p + type buried sacrificial layer 3a has a central portion 1
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. When extending from the whole, the p + -type buried sacrificial layer 3a may have an annular shape, for example, the central portion 1a is circular, and the p + -type buried sacrificial layer 3a is formed by a concentric circle and a central portion. 1a is an annular portion, or the central portion 1a is an inner square, and the p + type buried sacrificial layer 3a is formed by an outer square that is concentric with and has the same direction as that of the inner square. It may be a part. Further, the p + -type buried sacrificial layer 3a may be a portion formed by a portion between the circular central portion 1a and the outer square or the opposite combination, and further, instead of the square, a rectangular shape may be used. Alternatively, an elliptical shape may be used.

Further, the p + type buried sacrificial layer 3a is formed in the central portion 1
p + type buried sacrificial layer 3 when extending from a part of the outer edge of a
a is an equal angle (eg 90 °) around the central portion 1a
, The p + buried sacrificial layer 3a may have four beam configurations facing each other in the central portion 1a (ie, in the central portion 1a). It will be a cross shape). In other words, the p + type buried sacrificial layer 3a may extend radially from the central portion 1a, and the number thereof is not limited.

Then, after removing the resist mask 2,
Boron (B) is formed on one main surface of the single crystal silicon substrate 1 by using a resist mask 2 patterned in a predetermined shape.
A p-type impurity having a large diffusion coefficient such as is introduced by ion implantation or the like to form a p + type buried sacrificial layer 3b which is a second high-concentration impurity region (FIGS. 1B and 2B). . At this time, the p + type buried sacrificial layer 3b is the p + type buried sacrificial layer 3a.
Is formed adjacent to the frame 12 and at a position corresponding to the frame 12 forming side.

After removing the resist mask 2, silicon having the same conductivity type as the single crystal silicon substrate 1 and the same impurity concentration is epitaxially grown on one main surface of the single crystal silicon substrate 1 to form an epitaxial layer. 4 is formed. At this time, the p-type impurities composing the p + -type buried sacrificial layer 3b have a larger nucleic acid coefficient than the p-type impurities composing the p + -type buried sacrificial layer 3a. The p + type buried sacrificial layer 3 is formed which diffuses deeply and has a deeper diffusion depth from the central portion 1a toward the periphery of the substrate (FIGS. 1C and 2C).

After the next step, as shown in FIG. 14 and FIG.
Since it is the same as the step (c) and subsequent steps shown in FIG. 5, description thereof will be omitted here.

Further, different manufacturing steps of the semiconductor acceleration sensor according to the present embodiment will be described with reference to FIGS. First, on one main surface of the single crystal silicon substrate 1,
A p-type impurity such as boron (B) is introduced by ion implantation or the like using the resist mask 2 patterned into a predetermined shape to form a p + type buried sacrificial layer 3c which is a first high-concentration impurity region. (FIG. 5 (a), FIG. 6 (a)). At this time, the opening for patterning is formed by the single crystal silicon substrate 1.
Is formed at a location surrounding the substantially square central portion 1a.

Then, after removing the resist mask 2,
Boron (B) is formed on one main surface of the single crystal silicon substrate 1 by using a resist mask 2 patterned in a predetermined shape.
A p-type buried sacrifice layer 3d which is a second high-concentration impurity region is formed by introducing a p-type impurity such as ion implantation. At this time, the openings for patterning are formed in the p + -type buried sacrificial layer 3c forming place and the place adjacent to the p + -type buried sacrificial layer 3c, and in the place corresponding to the central portion 1a forming side. Therefore, p-type impurities are further introduced into the p + -type buried sacrificial layer 3c by ion implantation or the like to form a p + -type buried sacrificial layer 3e having a higher impurity concentration than the p + -type buried sacrificial layer 3d (FIG. 5 (b), FIG. 6 (b)).

Next, after removing the resist mask 2, silicon having the same conductivity type as the single crystal silicon substrate 1 and the same impurity concentration is epitaxially grown on one main surface of the single crystal silicon substrate 1 to form an epitaxial layer. 4 is formed. At this time, since the impurity concentration of the p-type impurities composing the p + -type buried sacrificial layer 3e is higher than the impurity concentration of the p-type impurities composing the p + -type buried sacrificial layer 3d, the epitaxial layer 4 and the single crystal silicon substrate are formed. 1 is deeply diffused, and a p + type buried sacrificial layer 3 having a deeper diffusion depth is formed from the central portion 1a toward the periphery of the substrate (FIG. 5 (c),
FIG. 6C).

After the next step, as shown in FIG. 14 and FIG.
Since it is the same as the step (c) and subsequent steps shown in FIG. 5, description thereof will be omitted here.

Second Embodiment FIG. 7 is a schematic cross-sectional view showing a state in which acceleration is applied to a semiconductor acceleration sensor according to another embodiment of the present invention, (a) of FIG. It is a schematic cross-sectional view at A ',
(B) is a schematic sectional view taken along the line BB ′ of FIG. 3. In addition,
A schematic plan view of the semiconductor acceleration sensor according to the present embodiment is similar to the schematic plan view shown in FIG. 3 as the first embodiment. The semiconductor acceleration sensor according to the present embodiment has a configuration in which the interval between the cut grooves 9 defined between the beam portion 10b and the weight portion 13 is wider in the vicinity of the frame 12 than in the vicinity of the neck portion 13a. Here, in the present embodiment, the cut groove 9 is formed by etching away only the side of the weight portion 13 near the frame 12 where the flexible portion 10 is formed.
Is widened so that the beam portion 10b has a uniform thickness.

Therefore, in the present embodiment, as shown in FIG. 7, the distance between the outer peripheral edge of the upper end of the weight portion 13 and the side of the flexible portion 10 on which the weight portion 13 is formed becomes wider, and the weight is displaced. Can be increased, and the range of acceleration that can be sensed can be increased.

Further, since the beam portion 10b is formed to have a uniform thickness, the bending portion 10 when acceleration is applied.
It is possible to realize acceleration detection which is stable in bending and has excellent sensitivity linearity and stability.

The manufacturing process of the semiconductor acceleration sensor according to this embodiment will be described below with reference to FIGS. 8 and 9. 8 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to the present embodiment at AA ′ in FIG. 3, and FIG. 9 is a view of the semiconductor acceleration sensor according to the present embodiment shown in FIG. It is a schematic sectional drawing which shows the manufacturing process in BB '. First, p-type impurities such as boron (B) are introduced by ion implantation or the like on one main surface of the single crystal silicon substrate 1 using a resist mask 2 patterned into a predetermined shape, and thermal diffusion is performed. A p + type buried sacrificial layer 3f which is one high-concentration impurity region is formed (FIGS. 8A and 9A). At this time, the opening for patterning is formed in a portion surrounding the substantially square central portion 1a of the single crystal silicon substrate 1. Here, by introducing a p-type impurity by ion implantation or the like and performing thermal diffusion, the p + -type embedded sacrificial layer 3f is formed deeper than in the case where thermal diffusion is not performed, and the single crystal silicon substrate 1 is formed. The impurity concentration on one main surface is low.

Then, after removing the resist mask 2,
Boron (B) is formed on one main surface of the single crystal silicon substrate 1 by using a resist mask 2 patterned in a predetermined shape.
A p-type buried sacrificial layer 3g which is a second high-concentration impurity region is formed by introducing a p-type impurity such as ion implantation. At this time, the openings for patterning are formed at the location where the p + type embedded sacrificial layer 3f is formed and the location adjacent to the p + type embedded sacrificial layer 3f, and at the location corresponding to the side where the central portion 1a is formed. Then, p is further added to the p + type buried sacrificial layer 3f.
Type impurities are introduced by ion implantation or the like to form a p + type buried sacrificial layer 3h having a surface impurity concentration similar to that of the p + type buried sacrificial layer 3g (FIG. 8).
(B), FIG. 9 (b)).

Next, after removing the resist mask 2, silicon having the same conductivity type as the single crystal silicon substrate 1 and the same impurity concentration is epitaxially grown on one main surface of the single crystal silicon substrate 1 to form an epitaxial layer. 4 is formed. At this time, since the surface impurity concentrations of the p + type buried sacrificial layers 3g and 3h are about the same, the diffusion depth into the epitaxial layer 4 is about the same and the single crystal silicon substrate 1 is also used.
A p + type buried sacrificial layer 3 having a longer diffusion distance is formed from the central portion 1a on one main surface toward the periphery of the substrate (FIGS. 8C and 9C).

After the next step, as shown in FIG. 14 and FIG.
Since it is the same as the step (c) and subsequent steps shown in FIG. 5, description thereof will be omitted here.

Further, different manufacturing steps of the semiconductor acceleration sensor according to the present embodiment will be described with reference to FIGS. First, using a resist mask 2 patterned in a predetermined shape, a p-type impurity having a small diffusion coefficient such as BF _{2 is} introduced into one main surface of the single crystal silicon substrate 1 by ion implantation or the like to obtain a first high concentration. P which is an impurity region
A + type embedded sacrificial layer 3i is formed (FIGS. 10A and 11).
(A)). At this time, the opening for patterning is formed in a portion surrounding the substantially square central portion 1a of the single crystal silicon substrate 1.

Then, after removing the resist mask 2,
Boron (B) is formed on one main surface of the single crystal silicon substrate 1 by using a resist mask 2 patterned in a predetermined shape.
By introducing a p-type impurity having a large diffusion coefficient, such as, by a high-energy ion implantation method into a second high-concentration impurity region
A + type embedded sacrificial layer 3j is formed. At this time, the openings for patterning are formed on the p + type buried sacrificial layer 3i and the p + type.
At a position adjacent to the mold-buried sacrificial layer 3i and at the frame 1
2 Formed at the location corresponding to the formation side. Since the p-type impurities are introduced by using the high-energy ion implantation method, the p + -type buried sacrificial layer 3j is formed only in the deep region of the single crystal silicon substrate 1 and is the main component of the single crystal silicon substrate 1. It is not formed on the surface (FIGS. 10B and 11B).

Next, after removing the resist mask 2, silicon having the same conductivity type as the single crystal silicon substrate 1 and the same impurity concentration is epitaxially grown on one main surface of the single crystal silicon substrate 1 to form an epitaxial layer. 4 is formed. At this time, the p-type impurities also diffuse into the epitaxial layer 4, and the p + -type buried sacrificial layers 3i and 3j become the p + -type buried sacrificial layer 3. The p + type buried sacrificial layer 3j is formed so that the diffusion distances of the p + type buried sacrificial layers 3i and 3j into the epitaxial layer 4 are substantially the same. Therefore,
A p + type buried sacrificial layer 3 having a longer diffusion distance is formed from the central portion 1a on one main surface of the single crystal silicon substrate 1 toward the periphery of the substrate (FIGS. 10C and 11).
(C)).

The subsequent steps are shown in FIGS. 14 and 1 as a conventional example.
Since it is the same as the step (c) and subsequent steps shown in FIG. 5, description thereof will be omitted here.

In all of the above-mentioned embodiments, the portions of the epitaxial layer 4 except the flexible portion 10 and the frame 12 are removed by etching, but the present invention is not limited to this. For example, a portion of the epitaxial layer 4 adjacent to the beam portion 10b and a portion of the inner side surface of the frame 12 excluding the portion where the beam portion 10b is formed are removed by etching, and a part of the epitaxial layer 4 is removed. If it is used as the weight portion 13, the volume of the weight portion 13 can be increased and the sensitivity can be improved.

Further, the ion implantation process is not limited to all of the above-mentioned embodiments, and the diffusion length becomes longer from the central portion 1a on one main surface of the single crystal silicon substrate 1 toward the periphery of the substrate. The p + type buried sacrificial layer 3 may be formed.

Further, in all the above-mentioned embodiments, the p + type embedded sacrificial layer 3 is formed as the sacrificial layer, but the n + type embedded sacrificial layer and other sacrificial layers are formed. Is also good.

Further, in all the above-mentioned embodiments, the case of the semiconductor acceleration sensor using the piezoresistor has been described, but the capacitance for detecting the acceleration by detecting the change in the electrostatic capacitance between the opposing electrodes. Type semiconductor acceleration sensor.

[0055]

According to the first aspect of the present invention, there is provided a frame having an upper surface side and a lower surface side, and a bending portion having a plurality of beam portions and a central portion, the beam portions being inner edge portions of the frame. A bending portion extending between at least a part of the center portion and the central portion, the beam portion and the central portion being integrally connected, a weight portion suspended and supported by the central portion, and a lower surface of the frame. A support member that supports the side, the inner side surface of which faces the side surface of the weight portion with a cut portion in between, a cut groove formed between the weight portion and the beam portion, and distortion generated in the bending portion. A semiconductor acceleration sensor, comprising: an acceleration detection unit that converts an electric signal to detect acceleration, and the cutout portion and the cutout groove communicate with each other, wherein the weight portion and the beam portion of the cutout groove are provided. The width defined between the Since the vicinity of the frame is made wider than the side, the distance between the outer peripheral edge of the upper surface of the weight portion and the bending portion is increased, the displacement of the weight portion can be increased, and the sensible acceleration range can be increased. An acceleration sensor could be provided.

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, the acceleration detecting section includes:
Since the piezoresistor whose resistance value changes due to bending is used and the acceleration is detected by converting the change in the resistance value of the piezoresistor into an electric signal, the same effect as that of the invention according to claim 1 is obtained. can get.

According to a third aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, the acceleration detecting section includes:
The electrodes arranged substantially opposite to each other are used to detect the bending of the bending portion and / or the weight portion at the time of applying an acceleration as the change of the electrostatic capacitance by the electrodes, and thus the acceleration is detected. In addition to the effect of the invention, the sensitivity temperature characteristic is improved, and the process can be simplified as compared with the case of forming a piezoresistor, and the sensitivity setting can be easily adjusted by the gap between the electrodes.

The invention according to claim 4 is the semiconductor acceleration sensor according to any one of claims 1 to 3,
The width of the cut groove, which is defined between the weight portion and the beam portion, is removed by etching on the cut groove forming surface side of the beam portion and the weight portion, so that the frame is formed more than the vicinity of the central portion. Since the vicinity is widened, the same effect as the effect of the invention according to any one of claims 1 to 3 can be obtained.

According to a fifth aspect of the present invention, in the semiconductor acceleration sensor according to any one of the first to third aspects,
The width of the cut groove defined between the weight portion and the beam portion is removed by etching on the cut groove forming surface side of the weight portion so that the frame vicinity is wider than the central portion vicinity. Therefore, claim 1 to claim 3
In addition to the effects of the invention described in any one of 1, the thickness of the flexure is uniform, the flexure of the flexure is stable when an acceleration is applied, and the acceleration has excellent linearity and stability. Detection can be realized.

The invention according to claim 6 is the method for manufacturing a semiconductor acceleration sensor according to claim 4, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are The first high-concentration impurity region is formed by processing an epitaxial layer formed on one main surface of the semiconductor substrate and introducing an impurity having a small diffusion coefficient into a predetermined portion of the one main surface of the semiconductor substrate. The second high-concentration impurity region is formed by forming an impurity having a large diffusion coefficient into a predetermined portion of one main surface of the semiconductor substrate adjacent to the first high-concentration impurity region. In addition to the effects of the invention described above, the diffusion end point of the first high-concentration impurity region is shallower (shorter) than the diffusion end point of the second high-concentration impurity region, and the first and second high-concentration regions are formed. Impurity region By removing by etching, it is possible to form a notch groove in which the width defined between the weight portion and the beam portion is made wider in the frame vicinity than in the central part vicinity, and a sensible acceleration range is obtained. It has been possible to provide a manufacturing method of a semiconductor acceleration sensor that can be increased in size.

The invention according to claim 7 is the method for manufacturing a semiconductor acceleration sensor according to claim 4, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are The semiconductor layer is formed by processing an epitaxial layer formed on one main surface of the semiconductor substrate, and impurities are introduced into a predetermined portion of the one main surface of the semiconductor substrate to form a first high-concentration impurity region. Impurities are introduced into a first high-concentration impurity region forming portion and a predetermined portion of one main surface of the semiconductor substrate adjacent to the first high-concentration impurity region to make the first high-concentration impurity region have a higher concentration. Moreover, since the second high-concentration impurity region is formed, the diffusion end point of the first high-concentration impurity region is not limited to that of the second high-concentration impurity region in addition to the effect of the invention of claim 4. End point of diffusion Remote deeper (longer) by the first and second removing high concentration impurity regions etched, the width defined between said beam portion and the weight portion,
It is possible to provide a method for manufacturing a semiconductor acceleration sensor that can form a notch groove that is wider in the vicinity of the frame than in the vicinity of the central portion, and can increase the detectable acceleration range.

The invention according to claim 8 is the method for manufacturing a semiconductor acceleration sensor according to claim 5, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are formed. Formed by processing the epitaxial layer formed on the one main surface of the semiconductor substrate, after introducing impurities into a predetermined location of the one main surface of the semiconductor substrate to form a first high-concentration impurity region, One main surface of the semiconductor substrate adjacent to the first high-concentration impurity region formation location and the first high-concentration impurity region by thermal diffusion to diffuse the first high-concentration impurity region to a deeper region And forming a second high-concentration impurity region by introducing an impurity into a predetermined portion of the second high-concentration impurity region, the surface concentration of the second high-concentration impurity region is substantially the same as the surface concentration of the first high-concentration impurity region. Then The diffusion distances of impurities into the epitaxial layer from the first and second high-concentration impurity regions are made substantially the same, and in addition to the effect of the invention of claim 5, the first high-concentration impurity regions are added. Of the second high concentration impurity region is deeper (longer) than the diffusion end point of the second high concentration impurity region into the semiconductor substrate, and the first and second high concentration impurity regions are removed by etching. Thereby, it is possible to make the thickness of the bending portion uniform, and to form the notch groove in which the width defined between the weight portion and the beam portion is wider in the vicinity of the frame than in the vicinity of the central portion. Thus, it is possible to provide a method for manufacturing a semiconductor acceleration sensor that can increase the detectable acceleration range. The invention according to claim 9 is the method for manufacturing a semiconductor acceleration sensor according to claim 5, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are formed on the semiconductor substrate. Formed by processing the epitaxial layer formed on the one main surface, to form a first high-concentration impurity region by introducing an impurity having a small diffusion coefficient into a predetermined portion of the one main surface of the semiconductor substrate, An impurity having a large diffusion coefficient is introduced by a high energy ion implantation method into a predetermined portion of the one main surface of the semiconductor substrate adjacent to the first high concentration impurity region to form a second high concentration impurity region, The diffusion distances of the impurities from the first and second high-concentration impurity regions into the epitaxial layer are set to be substantially the same. Diffusion endpoint to the semiconductor substrate region, shallower than diffusion endpoint to the semiconductor substrate of the second high concentration impurity regions (short)
By etching away the first and second high-concentration impurity regions, the thickness of the flexible portion can be made uniform, and the width defined between the weight portion and the beam portion can be It is possible to provide a method for manufacturing a semiconductor acceleration sensor that can form a notch groove that is wider in the vicinity of the frame than in the vicinity of the central portion, and can increase the detectable acceleration range.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a manufacturing process of a semiconductor acceleration sensor according to an embodiment of the present invention.

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

FIG. 3 is a schematic plan view showing a semiconductor acceleration sensor according to the present embodiment.

FIG. 4 is a schematic cross-sectional view showing a state in which acceleration is applied to the semiconductor acceleration sensor according to the present embodiment, (a) is a schematic cross-sectional view taken along the line AA ′ in the above figure, and (b). [Fig. 4] is a schematic cross-sectional view taken along line BB 'in the above figure.

FIG. 5 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to another embodiment of the present invention, which is taken along the line AA ′ in FIG. 3;

FIG. 6 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to another embodiment of the present invention, taken along the line BB ′ in FIG. 3;

7 is a schematic cross-sectional view showing a state in which acceleration is applied to a semiconductor acceleration sensor according to another embodiment of the present invention, and FIG. 7A is a schematic cross-sectional view taken along the line AA ′ in FIG. ,
(B) is a schematic sectional view taken along the line BB ′ of FIG. 3.

FIG. 8 is a diagram of a semiconductor acceleration sensor according to the present embodiment.
FIG. 6 is a schematic cross-sectional view showing the manufacturing process at AA ′ in FIG.

FIG. 9 is a diagram of a semiconductor acceleration sensor according to the present embodiment.
FIG. 6 is a schematic cross-sectional view showing the manufacturing process at BB ′ in FIG.

FIG. 10 is a schematic cross-sectional view showing a manufacturing process of the semiconductor acceleration sensor according to another embodiment of the present invention at AA ′ in FIG. 3.

FIG. 11 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to another embodiment of the present invention, taken along the line BB ′ in FIG. 3;

FIG. 12 is a schematic top view showing a semiconductor acceleration sensor according to a conventional example.

FIG. 13 is a schematic cross-sectional view related to the above figure, in which (a) is C-
It is a schematic sectional drawing in C ', and (b) is a schematic sectional drawing in DD'.

FIG. 14 is a schematic cross-sectional view showing the manufacturing process at CC ′ of FIG. 12 of the semiconductor acceleration sensor according to the conventional example.

FIG. 15 is a schematic cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor according to the conventional example at DD ′ in FIG. 12.

[Explanation of symbols]

1 Single crystal silicon substrate 1a central part 2 resist mask 3, 3a to 3j p + type embedded sacrificial layer 4 Epitaxial layer 5 Piezoresistor 6 Silicon nitride film 6a opening 7 notch 8 Etchant inlet 9 notch 10 Deflection part 10a central part 10b Beam part 11 Metal wiring 12 frames 13 Weight 13a neck part 14 Support members

Continued front page    (72) Inventor Takuro Ishida               1048 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works               Within the corporation (72) Inventor Hitoshi Yoshida               1048 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works               Within the corporation                (56) References JP-A-9-289327 (JP, A)

Claims (9)

(57) [Claims] 1. A frame having an upper surface side and a lower surface side,
A bending portion having a plurality of beam portions and a central portion, the beam portion extending between at least a part of an inner edge portion of the frame and the central portion, and the beam portion and the central portion. A bending portion integrally connected with each other, a weight portion suspended and supported by the central portion, a lower surface side of the frame, and a support member whose inner side surface faces the side surface of the weight portion with a cut portion therebetween. A cutout groove formed between the weight portion and the beam portion, and an acceleration detection portion for converting a strain generated in the bending portion into an electric signal to detect acceleration, the cutout portion and the A semiconductor acceleration sensor communicating with a notch groove, wherein the width of the notch groove defined between the weight portion and the beam portion is made wider in the vicinity of the frame than in the vicinity of the central portion. A semiconductor acceleration sensor. 2. A piezoresistor whose resistance value changes due to bending is used as the acceleration detecting section, and acceleration is detected by converting a change in the resistance value of the piezoresistor into an electric signal. The semiconductor acceleration sensor according to claim 1. 3. The acceleration detecting section uses electrodes which are arranged to face each other, and detects the bending of the bending section and / or the weight section when acceleration is applied by the electrode as a change in electrostatic capacitance to detect acceleration. The semiconductor acceleration sensor according to claim 1, wherein: 4. The width of the cut groove defined between the weight portion and the beam portion is removed by etching on the cut groove forming surface side of the beam portion and the weight portion,
The semiconductor acceleration sensor according to claim 1, wherein the vicinity of the frame is wider than the vicinity of the central portion. 5. The width of the cut groove, which is defined between the weight portion and the beam portion, is removed by etching on the cut groove forming surface side of the weight portion so that the width of the cut groove is smaller than that near the central portion. The semiconductor acceleration sensor according to claim 1, wherein the vicinity of the frame is widened. 6. The method of manufacturing a semiconductor acceleration sensor according to claim 4, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are one main surface of the semiconductor substrate. The first high-concentration impurity region is formed by processing the epitaxial layer formed above and introducing an impurity having a small diffusion coefficient into a predetermined portion of one main surface of the semiconductor substrate to form a first high-concentration impurity region. An impurity having a large diffusion coefficient is introduced into a predetermined portion of one main surface of the semiconductor substrate adjacent to the high-concentration impurity region to form a second high-concentration impurity region, and the first and second high-concentration impurity regions are formed. A semi-conducting groove is formed by etching away the region so that the width defined between the weight portion and the beam portion is wider in the frame vicinity than in the central portion. Manufacturing method of body acceleration sensor. 7. The method of manufacturing a semiconductor acceleration sensor according to claim 4, wherein the weight portion and the support member are formed by processing a semiconductor substrate, and the bending portion and the frame are one main surface of the semiconductor substrate. The first high-concentration impurity region is formed by processing the epitaxial layer formed above, and introducing an impurity into a predetermined portion of one main surface of the semiconductor substrate to form a first high-concentration impurity region. An impurity is introduced into a predetermined portion of the one main surface of the semiconductor substrate adjacent to the region forming portion and the first high-concentration impurity region to increase the concentration of the first high-concentration impurity region, and A high-concentration impurity region is formed, and the first and second high-concentration impurity regions are removed by etching, so that the width defined between the weight portion and the beam portion is smaller than that near the central portion. The frame A method of manufacturing a semiconductor acceleration sensor, characterized in that a notched groove having a wide vicinity of a groove is formed. 8. The method of manufacturing a semiconductor acceleration sensor according to claim 5, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are one main surface of the semiconductor substrate. It is formed by processing the epitaxial layer formed above, and impurities are introduced into a predetermined portion of one main surface of the semiconductor substrate to form a first high-concentration impurity region, and then thermal diffusion is performed to perform the diffusion. The first high-concentration impurity region is diffused to a deeper region, and impurities are formed in the first high-concentration impurity region formation portion and a predetermined portion of the main surface of the semiconductor substrate adjacent to the first high-concentration impurity region. Is formed to form a second high-concentration impurity region, and the surface concentration of the second high-concentration impurity region and the surface concentration of the first high-concentration impurity region are made substantially the same, The first and second high-concentration impurity regions are made to have substantially the same diffusion distance from each other, and the first and second high-concentration impurity regions are removed by etching. A method of manufacturing a semiconductor acceleration sensor, characterized in that a notch groove is formed such that a width defined between and is closer to the frame than in the vicinity of the central portion. 9. The method of manufacturing a semiconductor acceleration sensor according to claim 5, wherein the weight portion and the supporting member are formed by processing a semiconductor substrate, and the bending portion and the frame are one main surface of the semiconductor substrate. The first high-concentration impurity region is formed by processing an epitaxial layer formed above and introducing an impurity having a small diffusion coefficient into a predetermined portion of one main surface of the semiconductor substrate to form a first high-concentration impurity region. An impurity having a large diffusion coefficient is introduced into a predetermined portion of one main surface of the semiconductor substrate adjacent to the high-concentration impurity region by a high-energy ion implantation method to form a second high-concentration impurity region. The diffusion distances of impurities from the first and second high-concentration impurity regions are substantially the same,
By removing the first and second high-concentration impurity regions by etching, a notch groove having a width defined between the weight portion and the beam portion which is wider in the frame vicinity than in the central portion is formed. A method of manufacturing a semiconductor acceleration sensor characterized by being formed.