JPH11220137A - Semiconductor pressure sensor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a compact configuration of an overall body and to enable easy manufacture of sensors having different detecting sensitivities. SOLUTION: In an element forming thin film 4, which is provided on a supporting substrate 2 via an insulating separation film 3, a first trench 5 and a second trench 6 which are parallel with each other are formed. A part, which is held with these trenches 5 and 6, is provided as a diaphragm 7, which is elastically deformable in approximately parallel direction with the upper surface of a sensor chip 1. In this diaphragm 7, impurities are introduced in high concentration. In the element forming thin film 4, a fixed electrode part 9, wherein the impurities are introduced at high concentration is formed at a position facing opposite through the diaphragm 7 and the first trench 5. Thus, the capacitor, whose capacitance is changed in accordance with the deformation of the diaphragm, is formed between the diaphragm 7 and the fixed electrode part 9. The first trench 5 is sealed airtightly by a sealing film 10, and this sealing space part functions as a pressure reference chamber 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive semiconductor pressure sensor for detecting a pressure acting on a diaphragm based on a change in capacitance between the diaphragm and a fixed electrode.

[0002]

2. Description of the Related Art A semiconductor pressure sensor of this type is disclosed, for example, in JP-A-57-64978. This is a diaphragm which can be elastically deformed in a vertical direction (a direction perpendicular to the substrate) by etching a silicon substrate formed with a high impurity concentration layer as a buried layer from the front and back sides until the buried layer is exposed. And a metal layer is arranged in a state where a cavity to which a reference pressure is applied is present on the diaphragm, and the pressure acting on the diaphragm changes the capacitance between the diaphragm and the metal layer. To be taken out. In this case, a wiring pattern for signal extraction is formed on a sensor chip having the diaphragm and the metal layer.

[0003]

In the above-described semiconductor pressure sensor, since the displacement direction of the diaphragm is perpendicular to the sensor chip surface, the occupation rate of the diaphragm in the chip area must be large. For this reason, it has been difficult to reduce the chip size and thus the overall size. Further, since the pressure detection sensitivity is proportional to the size of the diaphragm, when manufacturing pressure sensors having different sensitivities, the effective area of the diaphragm is changed. However, in the conventional configuration, since the area occupation ratio of the diaphragm is large as described above, when changing the effective area of the diaphragm, the position of the wiring pattern on the sensor chip must be changed. There was a situation that was troublesome.
In particular, when integrated with a signal processing circuit,
The work for such a position change was further complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a semiconductor pressure sensor which can realize a small size as a whole and which can easily manufacture products having different pressure detection sensitivities. A second object is to provide a method of manufacturing a semiconductor pressure sensor having such an effect.

[0005]

To achieve the first object, the means described in claim 1 can be adopted. According to this means, since the diaphragm provided for pressure detection is deformed in a direction substantially parallel to the upper surface of the support substrate, the area occupied by the diaphragm on the upper surface of the support substrate can be reduced. This makes it possible to reduce the overall size. Also, since the effective area of the diaphragm is the area of the surface perpendicular to the substrate,
Even when the effective area is changed, the occupied area on the upper surface of the support substrate does not change. For this reason, even if the diaphragm area is enlarged, it is possible to prevent a situation that affects the arrangement of other components (for example, a signal extraction wiring pattern or a signal processing integrated circuit) provided on the support substrate. It is. Therefore, when manufacturing a diaphragm having a different pressure detection sensitivity by changing the effective area of the diaphragm, there is an advantage that it is not necessary to change the arrangement of other components, and the manufacture is facilitated.

In order to achieve the second object, a manufacturing method as set forth in claim 3 or a manufacturing method as set forth in claim 4 can be adopted. According to these manufacturing methods, an impurity is introduced into a semiconductor thin film formed on a support substrate in a state insulated from the support substrate, and first and second trenches are formed, and the first trench is formed. The semiconductor pressure sensor having the above-described effects can be manufactured only by performing the respective steps of hermetically sealing with a sealing member in a predetermined order.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the entire plane structure, FIG. 2 schematically shows a cross-sectional structure along the line AA in FIG.
FIG. 3 schematically shows a cross-sectional structure along the line BB in FIG.

In FIGS. 1 to 3, a rectangular sensor chip 1 (corresponding to a semiconductor pressure sensor according to the present invention) comprises:
For example, it is composed of an SOI wafer.
As shown in FIG. 3, an insulating isolation film 3 made of a silicon oxide film and a device forming thin film 4 made of a single crystal silicon thin film (corresponding to a semiconductor thin film in the present invention) on a support substrate 2 made of single crystal silicon. It is a configuration in which
On the element forming thin film 4, a protective film 4a made of a silicon thermal oxide film is formed.

In the element forming thin film 4, a first trench 5 and a second trench 6 each having a narrow and narrow rectangular shape are provided.
They are formed in parallel with each other and with the opposite sides of the element forming thin film 4. These trenches 5 and 6 are configured to reach the insulating isolation film 3.

In this case, the first thin film 4 in the element forming thin film 4 is formed.
The portion sandwiched between the trench 5 and the second trench 6
The diaphragm 7 functions as a diaphragm 7 that can be elastically deformed in a direction substantially parallel to the upper surface of the support substrate 2 (the upper surface of the sensor chip 1).
A high impurity concentration region 8a (shown by a hatched band in FIG. 1) in which an N-type impurity such as phosphorus is introduced is formed in a region corresponding to.

Further, a high impurity concentration region 8b (indicated by a hatched area in FIG. 1) into which an N-type impurity is introduced is also formed in a region of the element forming thin film 4 which faces the first trench 5. The portion of the high-concentration region 8b facing the diaphragm 7 functions as the fixed electrode portion 9. In this case, the distance between the diaphragm 7 and the fixed electrode portion 9 (corresponding to the width of the first trench 5)
Is set, for example, to about 0.5 to 5 μm. The impurity concentration of each of the high impurity concentration regions 8a and 8b is set to, for example, about 10 ¹⁸ to 10 ²⁰ cm ⁻³ .

The space existing between the diaphragm 7 and the fixed electrode portion 9, that is, the first trench 5, is hermetically sealed by a sealing film 10 (corresponding to a sealing member in the present invention) made of, for example, a silicon nitride film. The sealed space is configured to function as the pressure reference chamber 11.

On the protective film 4a, a wiring pattern 12 having bonding pads 12a and 13a for taking out signals is provided.
And 13 are formed, and the base end sides of these wiring patterns 12 and 13 are respectively joined to the high impurity concentration regions 8a and 8b via contact portions (see FIG. 3) penetrating the protective film 4a. I have.

In the sensor chip 1 configured as described above, a capacitor having the bonding pads 12a and 13a as terminals is formed between the diaphragm 7 and the fixed electrode portion 9. In this case, the diaphragm 7
In contrast, when pressure is applied through the second trench 6, the diaphragm 7 bends (resiliently deforms) in a direction substantially parallel to the upper surface of the sensor chip 1, and the capacitance of the capacitor changes. By extracting such a change in capacitance through the bonding pads 12a and 13a, the applied pressure can be detected.

The range of pressure detection by the sensor chip 1 can be set to a range of, for example, 1 to 10000 KPa by changing the effective area of the diaphragm 7 and the like. Also, since the diaphragm 7 is in a state where its lower surface and both ends are fixed,
This corresponds to a bending deformation mode (the upper edge portion and the central portion are largely deformed), and the sealing film 10 is compressed or expanded during the bending deformation.

In the above-described sensor chip 1 according to the present embodiment, the diaphragm 7 supported on the supporting substrate 2 via the insulating separation film 3 is deformed in a direction substantially parallel to the upper surface of the sensor chip 1. Therefore, the area occupied by the diaphragm 7 on the upper surface of the sensor chip 1 can be reduced, and the entire sensor chip 1 can be reduced in size. Specifically, the area occupied by the diaphragm 7 on the upper surface of the sensor chip 1 is:
In practice, the length of the diaphragm 7 is about 0.1 to 2 mm, and the thickness is 0.00.
The width is set to about 1 to 0.1 mm, which is extremely small, and the width of the first and second trenches 5 and 6 can be extremely small. It can be realized.

Since the effective area of the diaphragm 7 is the area of the surface perpendicular to the sensor chip 1, when the effective area is changed (actually, the film thickness of the element forming thin film 4 is increased. However, the occupied area on the upper surface of the sensor chip 1 does not change. For this reason, even when the effective area of the diaphragm 7 is enlarged, the arrangement of the signal extraction wiring patterns 12 and 13 (in some cases, a signal processing integrated circuit or the like), which are other components provided on the sensor chip 1, is performed. Influence can be prevented beforehand. Therefore, there is an advantage in that, when manufacturing the one having a different pressure detection sensitivity by changing the effective area of the diaphragm 7, it is not necessary to change the arrangement of other components, and the manufacturing becomes easier.

FIG. 4 is a schematic cross-sectional view showing an example of a manufacturing process of the sensor chip 1 having the above-mentioned effects, which will be described below. First, FIG.
As shown in (1), an SOI wafer 14 is prepared, and a thermal oxide film 15 having a thickness of about 0.1 to 1 μm is formed on the surface thereof.
This thermal oxide film 15 finally becomes the protective film 4a of the sensor chip 1. The single-crystal silicon substrate 14a serving as the base of the SOI wafer 14 finally becomes the support substrate 2 for the sensor chip 1, and the silicon oxide film 14b and the single-crystal silicon thin film 14c finally become the sensor chip 1 respectively.
Of the insulating isolation film 3 and the thin film 4 for element formation. In this case, the conductivity type of the single-crystal silicon thin film 14c is, for example, N-type, while the conductivity type of the single-crystal silicon substrate 14a is N-type, P-type.
Any type may be used. Note that the thickness of the single-crystal silicon thin film 14c is set to about 5 to 50 μm.

Next, an impurity introduction step shown in FIG. In this step, the openings 15a, 1b are formed in the respective regions of the thermal oxide film 15 corresponding to the high impurity concentration regions 8a and 8b using, for example, a hydrofluoric acid-based etchant.
5b is formed, and an N-type impurity such as phosphorus is diffused into the single-crystal silicon thin film 14c through the openings 15a and 15b. Thereafter, a heat treatment at about 800 to 1200 ° C. is performed to diffuse the impurities, thereby forming a high impurity concentration region 8.
a and 8b are formed. The heat treatment conditions at this time are set so that the high impurity concentration regions 8a and 8b reach the silicon oxide film 14b. The impurity concentration is 10 ¹⁸
It is set to about ^10-20 cm- ³ .

Next, a first trench processing step shown in FIG. 4C is performed. In this step, after the thermal oxide film 15 is re-deposited on the single-crystal silicon thin film 14c, the impurity introduction region in the single-crystal silicon thin film 14c is made to correspond to the impurity-doped regions 8a and 8b. First trench 5 divided into two
To form Thereby, the portion of the high impurity concentration region 8b facing the first trench 5 functions as the fixed electrode portion 9. The first trench 5 has reached the silicon oxide film 14b (the single-crystal silicon thin film 1).
4c is completely removed), and its width dimension is set to, for example, about 0.5 to 5 μm.

Next, a sealing step shown in FIG. In this step, a silicon nitride film is deposited on the thermal oxide film 15 under reduced pressure by using, for example, a plasma CVD apparatus, so that the first trench 5 is hermetically sealed to form the pressure reference chamber 11. At the same time, the sealing film 10 is formed by patterning the silicon nitride film. Since the width of the first trench 5 is extremely small, the silicon nitride film deposited in the sealing step is formed in a bridge state in which the opening of the first trench 5 is closed. .

Thereafter, a second trench processing step shown in FIG. In this step, for example, by performing dry etching, the single crystal silicon 14c
Then, a second trench 6 in parallel with the first trench 5 is formed. Thus, the portion corresponding to the impurity introduction region 8a functions as the diaphragm 7 sandwiched between the first trench 5 and the second trench 6.

Thereafter, although not specifically shown, a step of forming the wiring patterns 12 and 13 (including a step of forming contact portions with the high impurity concentration regions 8a and 8b) and dicing of the SOI wafer 14 are performed. By sequentially performing the steps and the like, the sensor chip 1 having the configuration shown in FIGS. 1 to 3 is completed.

According to such a manufacturing method, an impurity introduction step, a first trench processing step, a sealing step, a second trench processing step, and the like are sequentially performed on the single crystal silicon thin film 14c of the SOI wafer 14. Only by this, the sensor chip 1 having the above-described effects can be easily and reliably manufactured. In this case, in order to change the effective area of the diaphragm 7, only the thickness of the single crystal silicon thin film 14c of the SOI wafer 14 needs to be changed, and in order to change the thickness of the diaphragm 7, the second It is only necessary to change the formation position of the trench 6, and the sensor chips 1 having different detection sensitivities can be easily manufactured.

(Second Embodiment) FIG. 5 is a schematic sectional view showing a method of manufacturing a sensor chip 1 according to a second embodiment of the present invention.
Only parts different from the embodiment will be described. First, as shown in FIG. 5A, an SOI wafer 14 is prepared, a thermal oxide film 15 having a thickness of about 0.1 to 1 μm is formed on the surface thereof, and then, as shown in FIG. A first trench processing step is performed. In this step, the first trench 5 is formed in the single-crystal silicon thin film 14c, for example, by performing dry etching.

Next, an impurity introduction step shown in FIG. In this step, the single-crystal silicon thin film 14c
At both sides of the first trench 5
By introducing a type impurity, the first trench 5
The impurity-doped regions 8a and 8b, which are the impurity-introduced regions separated by the above, are formed, and one of the impurity-doped regions 8b is formed as the fixed electrode portion 9 facing the first trench 5.

Next, a sealing step shown in FIG. In this step, a silicon nitride film is deposited on the thermal oxide film 15 under reduced pressure by using, for example, a plasma CVD apparatus, so that the first trench 5 is hermetically sealed to form the pressure reference chamber 11. At the same time, the sealing film 10 is formed by patterning the silicon nitride film.

Thereafter, the second trench processing step shown in FIG. 5E is performed in the same manner as in the first embodiment, so that the portion corresponding to the impurity-doped region 8a is removed from the first trench 5 and the first trench 5. It functions as a diaphragm 7 sandwiched between the second trenches 6, and further has a wiring pattern 1.
The process of forming the semiconductor chips 2 and 13 and the process of dicing the SOI wafer 14 and the like (both not shown) are sequentially performed to finally complete the sensor chip 1 (see FIGS. 1 to 3).

(Other Embodiments) The present invention is not limited to the above-described embodiment, but can be modified or expanded as follows. In the first embodiment, in the impurity introducing step, the impurity is diffused into the respective regions corresponding to the high impurity concentration regions 8a and 8b in a state where they are respectively separated in advance, but the high impurity concentration regions 8a and 8b
In addition, the impurity is diffused including the portion sandwiched between them (the portion forming the first trench 5), and the first trench 5 is diffused.
, The high impurity concentration regions 8a and 8b separated from each other may be formed.

The material of the support substrate 2 is not limited to the single crystal silicon substrate 14a which is the base of the SOI wafer 14, but may be another semiconductor substrate, a ceramic substrate having insulating properties, a glass substrate, or the like. in this case,
If the material of the supporting substrate itself has insulating properties, it is not necessary to use the SOI wafer 14.

[Brief description of the drawings]

FIG. 1 is a plan view of a sensor chip showing a first embodiment of the present invention.

FIG. 2 is a schematic sectional view taken along line AA in FIG.

FIG. 3 is a schematic sectional view taken along line BB in FIG.

FIG. 4 is a schematic sectional view showing a manufacturing process.

FIG. 5 is a schematic sectional view showing a manufacturing process according to a second embodiment of the present invention.

[Explanation of symbols]

1 is a sensor chip (semiconductor pressure sensor), 2 is a support substrate, 4 is an element forming thin film (semiconductor thin film), 5 is a first trench, 6 is a second trench, 7 is a diaphragm, 8
Reference numerals a and 8b denote high impurity concentration regions, 9 a fixed electrode portion, 10 a sealing film (sealing member), 11 a pressure reference chamber, 12 and 13 wiring patterns, 14 an SOI wafer, and 14a a single crystal silicon substrate. (Supporting substrate), 14c denotes a single crystal silicon thin film (semiconductor thin film).

Claims (4)

[Claims] A diaphragm made of a semiconductor material supported on a supporting substrate and configured to elastically deform in a direction substantially parallel to an upper surface of the supporting substrate; and a predetermined distance from the diaphragm on the supporting substrate. And a fixed electrode portion made of a semiconductor material configured so that the capacitance between the diaphragm and the fixed electrode portion changes according to the deformation of the diaphragm, between the diaphragm and the fixed electrode portion. A reference pressure chamber formed by hermetically sealing an existing space portion. 2. A first and a second, which are provided on the support substrate in an insulated state from the support substrate and are parallel to each other.
A semiconductor thin film having a trench formed therein, wherein the diaphragm is provided in the first portion of the semiconductor thin film.
And the fixed electrode portion is formed by introducing an impurity into a portion of the semiconductor thin film facing the first trench, and the fixed electrode portion is formed by introducing an impurity into a portion sandwiched between the second trenches. The semiconductor pressure sensor according to claim 1, wherein the pressure chamber is formed by hermetically sealing the first trench with a sealing member. 3. An impurity introducing step of introducing an impurity into a predetermined region of a semiconductor thin film formed on a supporting substrate while being insulated from the supporting substrate; and a state in which the impurity introducing region in the semiconductor thin film is divided into two. A first trench processing step of forming one of the divided impurity-introduced regions as a fixed electrode portion facing the first trench by forming the first trench of the first trench. A sealing step of hermetically sealing with a sealing member to form a pressure reference chamber; and forming a second trench in the semiconductor thin film in a state parallel to the first trench, thereby forming the divided impurities. The other of the introduction regions is to function as a diaphragm sandwiched between the first and second trenches.
And a trench processing step. 4. A first trench processing step of forming a first trench in a semiconductor thin film formed on a support substrate in a state insulated from the support substrate, and forming a first trench in the semiconductor thin film. By introducing an impurity into each of the two side regions, an impurity introduction region divided by the first trench is formed, and one of the impurity introduction regions is formed as a fixed electrode portion facing the first trench. An impurity introducing step of forming; a sealing step of forming a pressure reference chamber by hermetically sealing the first trench with a sealing member; and a second step of forming a pressure reference chamber in parallel with the first trench in the semiconductor thin film. The other of the divided impurity-introduced regions is made to function as a diaphragm sandwiched between the first and second trenches. Second
And a trench processing step.