JPH0553308B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a wiring structure for a semiconductor pressure sensor, and more specifically, a diaphragm type semiconductor typified by a medical semiconductor pressure sensor attached to the tip of a catheter. This invention relates to the wiring structure of a pressure sensor.

<Prior Art> Semiconductor pressure sensors were developed based on the fact that when mechanical stress is applied to a semiconductor crystal such as silicon, a large change in resistance value occurs due to the piezoresistive effect. In a conventional semiconductor pressure sensor, four strain gauge resistors are formed by diffusion on the surface layer of a silicon single crystal substrate, and these four strain gauge resistors are wired through diffusion leads to form a Wheatstone bridge. The structure is such that an Al pad as an external wiring terminal is provided on the diffusion lead portion. A thin diaphragm that deforms under pressure is provided in the region of the silicon single crystal substrate where the strain gauge resistor is formed. This diaphragm is formed by forming an etching stop layer at a predetermined depth in a silicon single crystal substrate and etching the back surface of the silicon single crystal substrate.

The above-mentioned semiconductor pressure sensors are very small, and in order to receive multiple semiconductor pressure sensors at the tip of a catheter and insert them into the body, especially for medical use, peripheral circuits such as a temperature compensation circuit and a pressure sensitivity compensation circuit are incorporated. Even if it's something, one side of one chip is one.
It needs to be small, about mm or less. Moreover, since it is placed at the tip of the catheter, Al
It is necessary to shift the position of the pad to one side on the surface of the semiconducting pressure sensor. Diffused lead portions are formed on the surface of the substrate and wired between the Al pad and the strain gauge resistor, sensor, and the above-mentioned peripheral circuits.

<Problems to be Solved by the Invention> In the above-described conventional configuration, all wiring is performed by diffusion lead members on the substrate. Therefore,
In order to add elements such as sensors and transistors to the surface of a small board, it is necessary to add at least two diffusion leads for wiring in conjunction with the addition of elements, so there is no impact on other wiring. big.
For this reason, there is a problem in that the degree of freedom in designing circuit patterns on the board is significantly restricted. In particular, in semiconductor pressure sensors attached to the tip of a catheter, the chip size is very small and the Al pad is placed on one side of the substrate surface, so if the number of wires is increased,
Designing circuit patterns becomes extremely difficult.

<Objective of the Invention> The object of the present invention has been made in view of the above-mentioned problems, and is to provide a semiconductor pressure sensor which can facilitate the design of a circuit pattern by using an etching stop layer as a wiring. The purpose is to provide a wiring structure.

<Means for Solving the Problems> To achieve the above object, the wiring structure of the semiconductor pressure sensor of the present invention includes a base made of silicon single crystal and implantation or deposition of conductive ions on the surface of the base. a conductive type etching stop layer formed by a diffusion method; a single crystal silicon layer of a predetermined thickness formed by epitaxial growth on the etching stop layer; A diaphragm type semiconductor comprising a substrate including a recess formed by etching from the side opposite to the layer and an element formed on the surface of the silicon single crystal layer, and a terminal provided on the substrate. The wiring structure of a pressure sensor, characterized in that it includes connection means for connecting at least one of the terminal and the element to the etching stop layer via a path penetrating the single crystal silicon layer. It is something.

Note that a conductive wiring region is formed on the surface of the substrate in parallel with the etching stop layer by conductive ion implantation or a deposition diffusion method, and between at least one of the terminal and the element and the wiring region. The device may further include connecting means for connecting through a path penetrating the single crystal silicon layer.

Further, the connection means includes a conductivity type diffusion region formed on the surface of the single crystal silicon layer so as to be connected to at least one of the terminal and the element, and between the diffusion region and the etching stop layer. It may include a connection region that penetrates the single crystal silicon layer and connects the single crystal silicon layer.

Furthermore, a hole with a depth equal to or greater than the depth close to the etching stop layer is formed in the position where the connection region is to be formed in the single crystal silicon layer, and the connection region is formed on the circumferential surface of the hole with a conductive layer. The structure may be formed by forming a mold diffusion region.

Note that the holes can be formed by, for example, anisotropic etching.

Further, the connection region may be formed by, for example, conductive ion implantation.

Furthermore, the element may be a diffused resistor.

Further, in addition to the diffused resistor, another element formed on the surface of the single crystal silicon layer may be further included.

<Function> If the wiring structure of the semiconductor pressure sensor is as described above,
Any terminal or element on the substrate and the etching stop layer are connected by a connecting means through a path penetrating the single crystal silicon layer. Therefore, the etching stop layer can be used as backside wiring.

As a result, part of the wiring can be replaced by the etching stop layer, so the number of wiring on the surface of the substrate can be reduced. As a result, circuit pattern design becomes easier.

Furthermore, even if the number of wires increases with the addition of elements, the increase in the number of wires on the surface of the substrate can be suppressed, so there is no difficulty in designing a circuit pattern even when adding more elements.

<Examples> Hereinafter, examples will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the wiring structure of a semiconductor pressure sensor according to the present invention, and FIG. 2 is a cross-sectional view thereof. Also, Figure 3 shows B-B in Figure 1.
FIG. 3 is a cross-sectional view along a line showing a wiring pattern layer. Note that FIG. 1 is a sectional view taken along line A-A in FIG. 2.

This semiconductor pressure sensor has an overall thickness of approximately
It has a very small substrate 6 of 400 μm. The substrate 6 is formed by patterning an etching stop layer 2 with a thickness of about 2 μm and wiring portions 3 and 4 near the surface of a base 1 made of n ^- type silicon single crystal (see wiring pattern layer in FIG. 3), The thickness is approximately 10~
It is formed by stacking epitaxial growth layers 5 of 20 μm. The etching stop layer 2 is formed by implanting or depositing boron ions at a high concentration near the surface of the substrate 1. At this time, the boron ionicity is set to be 7.0×10 ¹⁹ ions/cm ³ or more. Further, the wiring portions 3 and 4 are formed in parallel to the etching stop layer 2, as shown in FIG.

The middle region of the substrate 6 has a thickness of about 10 to
A diaphragm 7 of 20 μm is formed. This diaphragm 7 is formed by hollowing out the back surface of the substrate 6 by etching. Since the etching at this time is reliably stopped by the etching stop layer 2, the thickness of the diaphragm 7 can be controlled accurately.

On the surface of the diaphragm 7, p ^- type strain gauge resistors 81, 82, 83, and 84 whose resistance value changes due to the piezoresistance effect are diffused and formed.
An Al pad 9 is provided on one side of the board 6 and serves as a terminal for external wiring.
On the other side are strain gauge resistors 81, 82, 83, 8.
A temperature sensor 10 is provided for compensating for the influence of ambient temperature changes on 4. Further, an insulating layer 11 made of SiO ₂ is formed on the surface of the substrate 6.

The etching stop layer 2 determines the thickness of the diaphragm 7 and is used as wiring, and the wiring portions 3 and 4 formed on both sides of the etching stop layer 2 are used only for wiring.

The surface of the board 6 has P ⁺ for wiring connection.
A diffusion lead portion 12 of the mold is patterned. Strain gauge resistor 81, 82, 83, 84
are connected in series via a diffusion lead section 12. These strain gauge resistors 81, 82, 83,
Each diffusion lead part 12 connected to 84 is further connected to an Al pad 9 provided on one side of the substrate 6.
... are connected to each other. In this way,
A predetermined pair of Al pads 9 connected to strain gauge resistors 81, 82, 83, 84
An external voltage is applied to the pads 9, 9, and a voltage appearing between another predetermined pair of Al pads 9, 9 is taken out as a pressure detection signal. In this way, the four strain gauge resistors 81, 8
2, 83, and 84 constitute a Wheatstone bridge circuit.

On the surface of the board 6, locations where wiring is difficult;
That is, the Al pad 9a formed on the diffusion lead portion 12a in FIG. 2 and the strain gauge resistor 82
Wiring between the diffusion lead portion 12b and the connected diffusion lead portion 12b is achieved via the P ⁺⁺ type connection regions 13, 13 formed to penetrate the epitaxial growth layer 5 and the etching stop layer 2. . That is, the diffusion lead part 1 connected to the Al pad 9a
Connection regions 13, 13 formed by implanting boron ions are formed in the diffusion lead portion 2a and the diffusion lead portion 12b, respectively. This connection area 13, 13
are the diffusion lead part 12a and the diffusion lead part 12b.
and the etching stop layer 2 disposed below are electrically connected. In this way, the etching stop layer 2 is used as a so-called back wiring, and thereby wiring can be easily made between the Al pad 9a and the diffusion lead portion 12b.

Furthermore, wiring between the temperature sensor 10 added on the semiconductor pressure sensor and the Al pads 9b and 9c is achieved in the same manner. That is, as shown by imaginary lines in FIG. 2, conductive connection regions 13b and 13c penetrating the epitaxial growth layer 5 are formed at both ends of the temperature sensor 10, respectively. As a result, the temperature sensor 10 and
Connecting area 13b,
13c and wiring portions 3 and 4. Note that the connection regions 13b and 13c can be formed by implanting boron ions.

To summarize the above, the etching stop layer 2, the wiring parts 3, 4, and the diffusion lead parts 12...
3, 13, 13b, and 13c, wiring can be performed using the etching stop layer 2 and the wiring portions 3 and 4 formed inside or on the back surface of the substrate 6. Therefore, the number of wires on the surface of the substrate 6 can be reduced, making it easier to design a circuit pattern.

Furthermore, even if the number of wires increases due to the addition of temperature sensors 10, etc., the number of wires can be easily increased by using the etching stop layer 2 and the wiring portions 3 and 4 as backside wiring or internal wiring. . Therefore, designing the circuit pattern does not become difficult. Furthermore, there is no need to expand the area of the substrate 6.

FIG. 4 is a longitudinal sectional view showing the wiring structure of a semiconductor pressure sensor according to another embodiment of the present invention. In FIG. 4, parts corresponding to those shown in FIGS. 1 to 3 described above are designated by the same reference numerals. In this embodiment, a hole 14 having a depth equal to or greater than the depth close to the etching stop layer 2 is provided at a predetermined position of the substrate 6. A p ⁺ -type diffusion region 15 is formed on the circumferential surface of the hole 14 and between the hole 14 and a terminal such as the Al pad 9. Thereby, the etching stop layer 2 and the terminal such as the Al pad 9 are connected via the p ⁺ type diffusion region 15. The holes 14 can be formed, for example, by anisotropic etching. Note that wiring between the wiring portions 3 and 4 and the Al pad 9 can be performed in the same manner.

This configuration has the advantage that when forming the p ⁺ type diffusion region 15, the diffusion depth of the p type impurity can be made shallow. That is, the first
In the embodiments shown in FIGS.
3, it is necessary to diffuse impurities (boron ions) to a depth approximately equal to the thickness of the epitaxial growth layer 5. In comparison, in the configuration shown in FIG. 4, since the holes 14 are formed, the diffusion depth of impurities can be made shallow. As a result, the thermal load on the substrate 6 during the manufacturing process can be significantly reduced.

As a result, strain gauge resistors 81, 82, 8
It is possible to effectively suppress impurities such as 3 and 84 and the diffusion lead portion 12 from being diffused in the lateral direction and distortion of the diaphragm 7 . This further indicates that the strain gauge resistors 81, 8
2, 83, 84 and the diffusion lead portion 12, etc., it is possible to make the patterns thinner.
As a result, circuit pattern design can be further facilitated.

Note that the present invention is not limited to the above-mentioned embodiments; for example, when adding an element for pressure sensitivity in addition to the temperature sensor, the wiring sections 3 and 4 may be further divided. The number of wires may be increased.

Further, if there is enough space on the surface of the board 6, the wiring parts 3 and 4 are not necessarily provided, and the board 6
Wiring between the temperature sensor 10 and the Al pad 9 may be performed by a diffusion lead portion provided on the surface of the substrate.

Furthermore, instead of connecting a predetermined position on the substrate 6 and the Al pad 9, the epitaxial growth layer 5 is connected between a predetermined position on the substrate 6 that requires wiring connection to the outside and the etching stop layer 2. The wiring may be connected through a penetrating path and drawn out from the back surface of the etching stop layer 2 by bonding.

In addition, various design changes are possible within the scope of not changing the gist of the present invention.

<Effects of the Invention> As described above, according to the wiring structure of the semiconductor pressure sensor of the present invention, the etching stop layer can be used as the back wiring, and a part of the wiring can be replaced by the etching stop layer. . This makes it possible to reduce the number of wires on the surface of the substrate, making it easier to design the circuit pattern.

Furthermore, even if the number of wires increases with the addition of elements, it is possible to suppress the increase in the number of wires on the surface of the substrate. Therefore, there is a large degree of freedom in designing wiring patterns, and circuit patterns can be designed easily.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view taken along the line A-A in FIG. 2 showing an embodiment of the wiring structure of a semiconductor pressure sensor of the present invention;
FIG. 2 is a cross-sectional view of a semiconductor pressure sensor, FIG. 3 is a cross-sectional view taken along line B-B in FIG. 1 showing a wiring pattern layer, and FIG. 4 is a vertical cross-sectional view showing another embodiment. . 1...Substrate, 2...Etching stop layer, 3, 4
...Wiring section, 5...Epitaxial growth layer, 6...
...Substrate, 7...Diaphragm, 9...Al pad,
10... Temperature sensor, 12... Diffusion lead part, 1
3, 13b, 13c... connection area, 14... hole,
15... p ⁺ type diffusion region, 81, 82, 83, 8
4...Strain gauge resistor.

Claims (1)

[Scope of Claims] 1. A base made of silicon single crystal, a conductive type etching stop layer formed on the surface of the base by conductive type ion implantation or deposition diffusion method, and an epitaxial etching layer formed on the etching stop layer. A single crystal silicon layer of a predetermined thickness formed by growth, a recess formed in a predetermined region of the base by etching from the side opposite to the single crystal silicon layer, and a recess of the silicon single crystal layer. A wiring structure for a diaphragm semiconductor pressure sensor, comprising a substrate including an element formed on a surface thereof, and a terminal provided on the substrate, the wiring structure comprising at least one of the terminal and the element, and the etching stop layer. A wiring structure for a semiconductor pressure sensor, characterized in that the wiring structure includes a connecting means for connecting between the two through a path penetrating the single crystal silicon layer. 2. A conductive wiring region formed on the surface of the substrate in parallel with the etching stop layer by implantation of conductive ions or a deposition diffusion method, and a connection between at least one of the terminal and the element and the wiring region. 2. The wiring structure of a semiconductor pressure sensor according to claim 1, further comprising connecting means for connecting between the two through a path penetrating the single crystal silicon layer. 3. The connecting means includes a conductive type diffusion region formed on the surface of the single crystal silicon layer so as to be connected to at least one of the terminal and the element;
and a connecting region connecting the diffusion region and the etching stop layer through the single crystal silicon layer.
Wiring structure of the semiconductor pressure sensor according to item 1 or 2. 4. A hole with a depth equal to or greater than the depth close to the etching stop layer is formed in the position of the single crystal silicon layer where the connection region is to be formed, and the connection region has a conductive type on the circumferential surface of the hole. The wiring structure of the semiconductor pressure sensor according to claim 3, which is configured by forming a diffusion region. 5. The wiring structure of a semiconductor pressure sensor according to claim 4, wherein the hole is formed by anisotropic etching. 6. Claim 3, wherein the connection region is formed by conductive ion implantation.
6. Wiring structure of the semiconductor pressure sensor according to any one of items 5 to 6. 7. The wiring structure of a semiconductor pressure sensor according to any one of claims 1 to 6, wherein the element is a diffused resistor. 8. The wiring structure of a semiconductor pressure sensor according to claim 7, further comprising another element formed on the surface of the single crystal silicon layer in addition to the diffused resistor.