JPH10125935A - Manufacture of movable capacitor structure and movable capacitor structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to manufacture easily a movable capacitor structure. SOLUTION: Recessed parts 21 are formed in the side of one surface of a first substrate 2 and an N<+> layer is formed on a substrate region equivalent to the bottoms 21a of the recessed parts 21 from the side of the one surface. Then, a second substrate 3 is joined to the side of one surface of the substrate 2 and after the recessed parts 21 are blocked and space layers 4 are formed, the substrate region is polished to a prescribed thickness. Subsequently, an N<+> layer is formed on the above substrate region from the side of the other surface of the one surface to form this substrate region into an N-type semiconductor layer extending over the whole in the thickness direction and the above substrate region is etched in a prescribed pattern in such a way as to thrust through the substrate region from the side of the other surface to the side of the one surface to form a movable part 5. In such a way, the space layers 4, which constitute a capacitor, are formed between the side periphery part and lower part of the region of one part of the substrate 2 and the other region of the substrate 2, the region of the one part is constituted as the movable part 5 and a movable capacitor structure, which leads out a change in the capacitance to respond to the motion of the above part 5, for example, to the outside as an electrical signal, is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor or an actuator such as an acceleration sensor by forming a movable portion having a fine structure on a semiconductor substrate, for example, a silicon substrate, and changing the capacity of a space layer according to the movement of the movable portion. The present invention relates to a method of manufacturing a movable capacitance structure that can be used as a capacitor and a movable capacitance structure.

[0002]

2. Description of the Related Art A technique for forming a fine movable structure by combining a silicon substrate bonding technique and silicon deep etching is known, for example, in "Silicon Fusion Bonding".
and Deep Reactive Ion Etching; A New Technology
for Microstructure “, Erno H. Klaasen, et al p556, Tr
Reported in ansducer 95. In this technique, for example, as shown in FIG. 6, after a concave portion 12 is first formed in a first substrate 11 by etching (FIG. 6A), a first substrate 11 is formed.
The second substrate 13 is bonded from above the first substrate 11 so as to form the space layer 14 between the first substrate 11 and the second substrate 13 (FIG. 6B). Next, after the second substrate 13 is polished to a predetermined thickness (FIG. 6C), the second substrate 13 is polished.
A predetermined mask pattern is formed on the surface of the substrate 13 (FIG. 6D). Finally, etching is performed, and FIG.
As shown in (e), a movable structure having a movable portion 15 that moves vertically and horizontally is formed.
In the above document, a current is passed through the movable part to heat it,
There is an example of application to a thermal actuator utilizing the fact that a movable portion is deformed in response to an electric current.

The present inventors have focused on applying such a movable structure to, for example, an acceleration sensor, an angular velocity sensor, a pressure sensor, and the like. By the way, in order to apply the movable structure to such a sensor, it is necessary to partially form an electric circuit, that is, it is required to form a conductive region in the movable portion and electrically insulate it from other regions. You.

FIG. 7A is a schematic plan view showing an example in which the movable capacitance structure is applied to an acceleration sensor. When a force in the left-right direction (the direction of the arrow) acts on this sensor, the sensor responds to this force. The size of the space layers 14a and 14b between the movable part 15 and the left and right fixed pieces 16 changes, and
The magnitudes of the capacities a and b change. Therefore, when the both ends of the DC power supply 17 are connected to the left and right fixed pieces 16 and 16, respectively, and the output is taken out from the movable portion 15, as shown in an equivalent circuit in FIG. Is applied and the potential of the output terminal drawn from between the capacitors C1 and C2 is measured, and the angular velocity when a moving body equipped with a sensor, such as a gyro, is caught can be detected. . In addition, the present invention can also be applied as an acceleration sensor that detects acceleration in the direction of an arrow, for example.

[0005]

Here, in order to make the movable portion 15 of the above-mentioned movable capacitance structure a conductive region, for example, an n-type impurity (or a p-type impurity) is implanted to reduce the electric resistance of the silicon substrate. Must be lowered. The movable portion 15 needs to have a thickness of about 10 to 50 μm in order to secure mechanical strength.
When the ion implantation is performed from the surface side of the second substrate 13 after bonding the second substrate 13 and the
5, the ion implantation from one side takes a long time.

Therefore, before bonding the first substrate 11 and the second substrate 13, for example, ion implantation is performed from both sides of the second substrate 13 as shown in FIG. As shown in b), the first substrate 11 and the second substrate 13
It is conceivable to paste them together. However, in this method, it is difficult to recognize the doping region 13a of the second substrate 13 when the substrates 11 and 13 are bonded to each other, so that the doping region 13a and the recess 12 of the first substrate 11 In order to perform the alignment, an alignment key 17 is formed in the vicinity of the doping region 13a of the second substrate 13, and the alignment key 17 is formed by infrared rays from the surface opposite to the bonding surface of the first substrate 11. It is necessary to detect the key 17 and perform the alignment by using this key. However, in this case, there is a problem that the number of alignment steps is increased and the operation becomes complicated.

The present invention has been made under such circumstances, and an object of the present invention is to make it easy to manufacture a movable capacitance structure by eliminating the need for alignment in a step of bonding substrates. It is to provide the technology that can be done.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a part of a semiconductor substrate is formed by forming a space layer which forms an electric capacitance between a peripheral part and a lower part of the part and another region. A method for manufacturing a movable capacitance structure in which a region is configured as a movable portion and a change in capacitance according to the movement of the movable portion is extracted to the outside as an electric signal or an electric signal is applied to a spatial layer to move the movable portion. Forming a concave portion on one surface side of the first semiconductor substrate, forming an impurity layer from one surface side in a substrate region corresponding to the bottom of the concave portion, and forming a second layer on one surface side of the first semiconductor substrate. Laminating the substrate and closing the concave portion in which the impurity layer is formed,
Polishing the substrate region to a predetermined thickness, forming an impurity layer in the substrate region from the other side, and forming the substrate region into a p-type or n-type semiconductor layer over the entire thickness direction. Forming a movable portion by etching the substrate region with a predetermined pattern so as to penetrate from the other surface side to the one surface side.

The above steps are not necessarily performed in the order described, but include a step of forming a concave portion and a step of forming an impurity layer in the substrate region from one surface side.
The step of bonding the substrates must be performed in this order. The step of polishing the substrate may be performed before the step of bonding the substrates. Further, the step of forming an electric circuit including a semiconductor element electrically connected to the movable portion on the first semiconductor substrate may be performed in addition to the above steps.

Further, according to the present invention, a second semiconductor substrate is bonded to a first semiconductor substrate having a concave portion formed on one surface side so as to cover the concave portion, and corresponds to a bottom portion of the concave portion of the first semiconductor substrate. The substrate region is etched with a predetermined pattern from one surface side to the other surface side, and the remaining portion of the substrate region is configured as a movable portion, and is n-type throughout the thickness direction of the movable portion. Alternatively, the present invention also covers a movable capacitance structure formed as a p-type semiconductor layer.

[0011]

Embodiments of the present invention will be described below. The feature of this embodiment is that FIG.
As shown in FIG. 1, a recess 2 is formed on one surface side of a first semiconductor
1 is formed (FIG. 1A), and then ion implantation is first performed on a substrate region corresponding to the bottom 21a of the concave portion 21 of the first substrate 2 from one surface side where the concave portion 21 is formed (FIG. 1A). (FIG. 1 (b)) Then, ion implantation is performed from the other surface side opposite to the concave portion 21 (FIG. 1 (c)).
After ion implantation from both sides of the first substrate 2, the first
By bonding the substrate 2 and the second substrate 3 to each other,
This eliminates the need for an alignment step between the substrates 2 and 3. Note that the second substrate 3 is not necessarily a semiconductor substrate, but a silicon substrate is used in this example for reasons such as easy bonding.

Next, an example of the movable capacitance structure manufactured by the method of the present invention will be described. As shown in the perspective view of FIG. 2, the plan view of FIG. 3 (a), and the side view of FIG. 3 (b), the second substrate 3 is attached to the lower surface side of the first substrate 2. A space layer 4 is formed between the substrates 2 and 3, and a partial region of the first substrate 2 is configured as a movable portion 5.

That is, a part of the first substrate 2 on the bonding surface side is separated from the second substrate 3 to form a space layer 4 between the first substrate 2 and the second substrate 3. Part of the substrate region located above the substrate 4 is etched with a predetermined pattern so as to pass from the space layer 4 to the space layer 4 from the surface side of the first substrate 2 (the side opposite to the bonding surface). . In this way, the space layer 4 is formed on a part of the lower side and the side of the substrate region, and the substrate region surrounded by the space layer 4 is configured as a movable portion 5 that can swing up and down, left and right.

The movable part 5 will be described in more detail.
The movable portion 5 has a plurality of, for example, four comb teeth 51 (51a, 5
1b) is formed in a protruding comb shape, and the projection area of the fixing portion 54 (54a, 54b), that is, the concave portion 21 through a predetermined space in the front-rear direction by thin connecting portions 53 (53a, 53b) in the front and rear. Is connected to the substrate main body 55 which is out of the way.

A fixed piece 52 (52a, 52b) extends and enters from the substrate body 55 between the comb teeth 51 of the movable portion 5, and the comb tooth 51 is interposed between the comb tooth 51 and the fixed piece 52.
The space layer 4 is formed so that can swing. The movable portion 5 is supported by the substrate body 55 by the narrow connecting portions 53 at the front and rear while floating in the concave portion 21 so that when the force is applied in the left-right direction, the thin connecting portion is formed by the weight of the movable portion 5 by its own weight moment. 53 bends and moves in the left-right direction. On the other hand, the fixed piece 52 extends in the left-right direction and does not swing in the left-right direction because its own weight moment is small.

The movable portion 5, the fixed piece 52, and a part of the fixed portion 54 of the first substrate 2 are arranged as shown in FIG.
As shown in (b), for example, N-type impurity atoms are implanted from the upper side of the space layer 4 to the surface of the first substrate 2 to form an N-type impurity layer 22 (hereinafter, referred to as an N ⁺ layer 22). The N ⁺ layer 22 is formed continuously from the end of the movable portion 5 over a part of the substrate main body 55, and the surface of the N ⁺ layer 22 on the substrate main body 55 is made of, for example, an aluminum layer. The metal wiring layer 23 is formed, and a signal is taken out to the signal processing circuit 24 in another area on the substrate main body 55 apart from the metal wiring layer 23. On the surface of the other region of the N ⁺ layer 22, a SiO ₂ film 25 is formed.
On the surface of the SiO ₂ film 25, a protective film 26 made of, for example, phosphorus-doped silicon glass is formed.

Next, a method for manufacturing such a movable capacitance structure will be described with reference to FIGS. First,
After applying a resist 61 to the substrate 2 according to the shape of the concave portion 21 to be formed (FIG. 4A),
Etching is performed to form the recess 21 (FIG. 4B).
This concave portion 21 has, for example, 0.3 mm × 0.3 mm in length and width,
It is formed with a depth of 5 μm. Subsequently, for example, an N-type impurity atom 62 is implanted into the bottom 21a of the concave portion 21 from one surface where the concave portion 21 is formed by, for example, an ion implantation method (FIG. 4C), and then the resist 61 is removed. (FIG. 4D). Next, the first substrate 2 and the second substrate 3 are combined with each other on one surface side of the first substrate 2 where the concave portion 21 is formed and the second substrate 3, and a space layer is formed between the two substrates 2 and 3. 4
(FIG. 4E), the first substrate 2 and the second substrate 3 are bonded by annealing, and the impurity atoms 62 are diffused (FIG. 4E).
(F)).

Subsequently, the first substrate 2 is placed on the front side (the side opposite to the side on which the recess 21 is formed) by, for example, 20 μm.
After polishing to a thickness of m (FIG. 4 (g)), a resist 63 is applied to form the N ⁺ layer 22 in a predetermined pattern, and ion implantation is performed from the surface side (FIG. 4 (g)). h) The substrate region corresponding to the bottom 21a is formed as an N ⁺ layer 22 over the entire thickness direction (FIG. 4 (i)), and a SiO ₂ film as an insulating film is formed on the surface of the first substrate 2. 25, the N ⁺ layer 22 is formed on the other surface side of the substrate region in this example.
In the step of forming the N ⁺ layer, the N ⁺ layer 22 is also formed on the surface of the substrate
As shown in (a), a wiring layer 23 made of, for example, aluminum is formed on the surface of the N ⁺ layer 22.

On the other hand, on the surface of the first substrate 2, a signal processing circuit (corresponding to an electric circuit in the claims) including an amplifier made of a semiconductor device such as CMOS is formed in advance (FIG. 4). (J)), the N ⁺ layer 22 and the signal processing circuit 24 (see FIG. 3A) are electrically connected via the wiring layer 23. After a protective film 26 is formed on the surface of the first substrate 2 as shown in FIG. 5B, a resist film 64 is formed on the protective film 26 in a predetermined pattern (FIG. 5C). 5) According to this pattern, etching is performed so that the substrate region penetrates from the other surface side to the one surface side (FIG. 5D). Thereafter, the resist film 64 is removed,
Thus, a movable capacitance structure is formed on the first substrate 2 side.

The N ⁺ layer 22 is also formed on the surface of the substrate body 55 that is continuous with the base end of the fixing piece 52, and is similarly connected to a wiring layer (not shown). If the movable capacitance structure including the signal processing circuit 24 described above is mounted on a moving body, for example, as described in the section of the related art, a force is applied to the movable portion 5 in the left-right direction in accordance with the angular velocity, and the movable body 5 The portion 5 is shifted toward the fixing piece 52a or 52b side and the capacitance C of the space layer 4 is
1 and C2 change, and a signal corresponding to the angular velocity is extracted through the signal processing circuit 24 by applying, for example, a DC voltage between the fixed pieces 52a and 52b.

According to the above-described embodiment, a conventional semiconductor manufacturing process can be used by manufacturing a movable capacitance structure using a silicon substrate. And a concave portion 21 serving as a space layer 4 for forming a movable capacitance structure
To the silicon substrate (first
Since the substrate 2) is formed, it is not necessary to align the concave portion 21 with the ion-implanted region (N ⁺ layer 22) when the substrates 2 and 3 are bonded to each other. Already, the mask forming process can be reduced,
Since no alignment is required, the process is simplified. In addition, since the conventional semiconductor manufacturing process can be used, the movable portion 5 and the semiconductor element as the signal processing circuit 24 can be formed on the same substrate, and the manufacture of the capacitive sensor becomes easy.

In the above, the method of forming the impurity layer is not limited to the ion implantation method. For example, a high-concentration impurity layer is formed on one surface (other surface) of the substrate by a chemical vapor reaction and then thermally diffused. May be adopted. The impurity atoms constituting the impurity layer are N
Not only the shape but also a P-type atom may be used. Also, the fixing piece 52
Is not limited to being formed as the space layer 4,
In this case, for example, the fixing pieces 52 may be formed by etching the first substrate 2 in advance with a predetermined pattern.

Further, the step of polishing the first substrate 2 comprises:
The method is not limited to being performed after the two substrates 2 and 3 are bonded. For example, the first substrate 2 is temporarily bonded to a dedicated support plate, and then the substrate 2 is polished and then the two substrates 2 and 3 are bonded. Such cases are also included in the scope of the present invention.

The movable capacitance structure according to the present invention can be used as a semiconductor sensor such as an angular velocity sensor or an acceleration sensor mounted on a gyro or the like, and a voltage is applied to a space layer forming an electric capacitance through a movable portion. Is applied to adjust the magnitude of the electrostatic attraction, whereby the actuator can be used as an actuator for moving a movable part.

[0025]

According to the present invention, since the movable portion is formed on the substrate on which the concave portion is formed, no alignment is required when the substrates are bonded, and the production of the movable capacitance structure is achieved. Becomes easier.

[Brief description of the drawings]

FIG. 1 is a process chart showing a manufacturing process of a movable capacitance structure according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a movable capacitance structure according to one embodiment of the present invention.

FIG. 3 is a plan view and a side view showing a movable capacitance structure according to an embodiment of the present invention.

FIG. 4 is a process chart showing a part of the manufacturing process of the movable capacitance structure according to the embodiment of the present invention.

FIG. 5 is a process chart showing a part of the manufacturing process of the movable capacitance structure according to the embodiment of the present invention.

FIG. 6 is a process diagram showing a manufacturing process of a conventional movable capacitance structure.

FIG. 7 is a plan view showing a part of a conventional movable capacitance structure.

FIG. 8 is a process diagram showing a manufacturing process of a conventional movable capacitance structure.

[Explanation of symbols]

2 first substrate 21 concave portion 22 N ⁺ layer 3 second substrate 4 space layer 5 movable capacitance structure 52 fixed piece

Claims (3)

[Claims] 1. A semiconductor device according to claim 1, wherein a part of the semiconductor substrate is formed as a movable part by forming a space layer forming an electric capacitance between a side peripheral part and a lower part of the semiconductor substrate and another region.
A method for manufacturing a movable capacitance structure that moves a movable portion by extracting a capacitance change according to the movement of the movable portion to the outside as an electric signal or applying an electric signal to a spatial layer, wherein one surface of a first semiconductor substrate is provided. Forming an impurity layer on one side in a substrate region corresponding to the bottom of the recess; and bonding a second substrate on one surface of the first semiconductor substrate to form an impurity layer. A step of closing the concave portion in which is formed; a step of polishing the substrate region to a predetermined thickness; a step of forming an impurity layer in the substrate region from the other surface side and covering the substrate region over the entire thickness direction. Forming a movable portion by etching a predetermined pattern so as to penetrate the substrate region from the other surface side to the one surface side. Content The method of manufacturing the mass structure. 2. The method according to claim 1, further comprising the step of forming an electric circuit comprising a semiconductor element electrically connected to the movable portion on the first semiconductor substrate. . 3. A part of the substrate is formed as a movable part by forming a spatial layer that forms an electric capacitance between a side peripheral part and a lower part of the part of the substrate and another part, A first semiconductor having a concave portion formed on one surface side in a movable capacitance structure for moving a movable portion by extracting a capacitance change according to the movement of the movable portion to the outside as an electric signal or applying an electric signal to a space layer. A second semiconductor substrate is bonded to the substrate so as to cover the concave portion, and is etched from one surface side to the other surface with a predetermined pattern in a substrate region corresponding to the bottom of the concave portion of the first semiconductor substrate. A movable capacitor structure, wherein the remaining portion of the substrate region is configured as a movable portion, and is formed as an n-type or p-type semiconductor layer over the entire thickness of the movable portion.