JP2014170007A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor which can improve a breakdown withstand pressure of a diaphragm.SOLUTION: A semiconductor pressure sensor comprises: a first semiconductor substrate 3 having a recessed part 2 which is opened at one surface in the thickness direction; a second semiconductor substrate 4 which is arranged to be opposed to one surface of the first semiconductor substrate 3; and a first silicon oxide film 6 which is interposed between the first semiconductor substrate 3 and the second semiconductor substrate 4 and has a through-hole 5 which makes the recessed part 2 and the second semiconductor substrate 4 communicate with each other. When viewed from a facing side to the through-hole 5 and the opening of the recessed part 2, at least one part of an edge of the through-hole 5 is positioned inside of an opening edge of the recessed part 2.

Description

  The present invention relates to a semiconductor pressure sensor.

A conventional semiconductor substrate for a pressure sensor is manufactured by the following procedure.
First, an oxide film having a predetermined thickness is formed on one surface side of a first semiconductor substrate made of a single crystal silicon substrate, and a part of the oxide film is removed from a through hole that matches the hole direction in the thickness direction of the oxide film. Form. Next, a recess having an inner peripheral surface flush with the inner peripheral surface of the through hole is formed in the first semiconductor substrate. Next, a second semiconductor substrate made of a single crystal silicon substrate is bonded to the first semiconductor substrate via the oxide film so as to cover the through hole exposed on the surface of the oxide film. In addition, a conventional semiconductor substrate for a pressure sensor is manufactured by thinning the second semiconductor substrate to form a diaphragm at a portion of the second semiconductor substrate facing the recess, and further forming a strain detecting element on the surface of the diaphragm. (See, for example, Patent Document 1).

Japanese Patent No. 4214567

  In the conventional semiconductor substrate for pressure sensors, the position of the opening edge of the recess formed in the first semiconductor substrate coincides with the position of the edge of the through hole formed in the oxide film. Here, although the residual stress is generated in the oxide film, the magnitude of the stress caused by the residual stress acting on the oxide film is discontinuous at the edge of the through hole. Further, when pressure is applied to the diaphragm from the outside and the diaphragm is bent, a large stress is generated at the opening edge of the recess. When the position of the opening edge of the recess and the position of the edge of the through hole coincide with each other as in the conventional semiconductor substrate for pressure sensor, the stress generated in the diaphragm when the diaphragm bends is reduced. Stress that becomes discontinuous with the edge as a boundary is superimposed. For this reason, the breakdown pressure of the diaphragm when pressure is applied to the diaphragm from the outside is significantly reduced.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a semiconductor pressure sensor capable of improving the breakdown voltage of a diaphragm.

  The semiconductor pressure sensor according to the present invention includes a first semiconductor substrate having a recess formed in one surface in the thickness direction, a second semiconductor substrate disposed opposite to the one surface of the first semiconductor substrate, and the first semiconductor substrate. And a first insulating film interposed between the recess and the second semiconductor substrate, and having a through hole communicating between the recess and the second semiconductor substrate, the first semiconductor substrate, the second semiconductor substrate, An airtight reference pressure chamber is formed from the first insulating film, and at least a part of the edge of the through hole is located inside the opening edge of the recess as viewed from the side facing the opening of the through hole and the recess. Yes.

  According to the semiconductor pressure sensor of the present invention, at least a part of the edge of the through hole as viewed from the side opposite to the through hole formed in the first insulating film and the opening of the recess formed in the first semiconductor substrate. However, it is located inside the opening edge part of a recessed part. As a result, the opening edge of the recess and the edge of the through hole are spaced apart from each other, so that the edge of the through hole is bounded by the stress generated in the second semiconductor substrate when the second semiconductor substrate is bent. As a result, discontinuous stress is not superimposed, and the breakdown voltage of the second semiconductor substrate when pressure is externally applied to the portion of the second semiconductor substrate facing the recess can be improved.

It is sectional drawing of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a figure explaining the preparatory process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a figure explaining the insulating film and recessed part formation process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a figure explaining the board | substrate connection process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a figure explaining the diaphragm formation process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a figure explaining the distortion detection element formation and a post-processing process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a principal part expanded sectional view of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the breakdown pressure | voltage resistance of the semiconductor pressure sensor which concerns on Embodiment 1 of this invention, and (extension amount of a 1st silicon oxide film) / (thickness of a 1st silicon oxide film). It is sectional drawing of the semiconductor pressure sensor which concerns on Embodiment 2 of this invention. It is sectional drawing of the semiconductor pressure sensor which concerns on Embodiment 3 of this invention. It is a figure explaining the connection board | substrate oxidation treatment process of the semiconductor pressure sensor which concerns on Embodiment 3 of this invention. It is a figure explaining the diaphragm formation process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 3 of this invention. It is a figure explaining the distortion detection element formation and a post-processing process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 3 of this invention. It is sectional drawing of the semiconductor pressure sensor which concerns on Embodiment 4 of this invention. It is a figure explaining the insulating film and recessed part formation process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 4 of this invention. It is a figure explaining the oxide film selective removal process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 4 of this invention. It is a figure explaining the board | substrate connection process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 4 of this invention. It is a figure explaining the diaphragm formation process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 4 of this invention. It is a figure explaining the distortion detection element formation and a post-processing process of the manufacturing method of the semiconductor pressure sensor which concerns on Embodiment 4 of this invention. It is sectional drawing of the semiconductor pressure sensor which concerns on Embodiment 5 of this invention. It is sectional drawing of the semiconductor pressure sensor which concerns on Embodiment 6 of this invention. It is a block block diagram of the internal combustion engine apparatus with a semiconductor pressure sensor which concerns on Embodiment 7 of this invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
1 is a cross-sectional view of a semiconductor pressure sensor according to Embodiment 1 of the present invention.

In FIG. 1, a semiconductor pressure sensor 1 </ b> A is arranged with a first semiconductor substrate 3 formed with a recess 2 opening on one surface in the thickness direction, one surface facing away from the recess 2, and the other surface facing the recess 2. A first insulation having a through hole 5 formed between the second semiconductor substrate 4 and the first semiconductor substrate 3 and the second semiconductor substrate 4 to be communicated with each other. A first silicon oxide film 6 as a film and a strain detection element 7 provided on one surface side of the second semiconductor substrate 4 are provided.
In addition, although not shown, the semiconductor pressure sensor 1A is configured to supply power to the strain detection element 7, take out an electrical signal output from the strain detection element 7, and wiring and electrodes to protect the outside, and protection for protecting them. It has a membrane.

  Each of the first semiconductor substrate 3 and the second semiconductor substrate 4 is a single crystal silicon substrate, and such a structure having a silicon oxide film between the single crystal silicon substrates is generally called SOI (Silicon On Insulator). .

  The recess 2 is formed so that the depth direction coincides with the thickness direction of the first semiconductor substrate 3, and the outer shape of the cross section orthogonal to the depth direction is formed in a square shape. Further, the thickness direction of the first silicon oxide film 6 coincides with the thickness direction of the first semiconductor substrate 3 and the second semiconductor substrate 4, and the hole direction of the through hole 5 is in the thickness direction of the first silicon oxide film 6. Match.

  And the edge part of the through-hole 5 is located inside the opening edge part of the recessed part 2 in the whole region seeing from the side facing the opening of the through-hole 5 and the recessed part 2, and the opening edge part of the through-hole 5 and the recessed part 2 The distance between is a predetermined value. That is, the first silicon oxide film 6 extends from the opening edge of the recess 2 by a predetermined length.

  In addition, the reference pressure chamber 8 is formed by a space surrounded by the wall surface that forms the recess 2 and the through hole 5 and the wall surface of the second semiconductor substrate 4 that covers the opening of the through hole 5. Further, the region of the second semiconductor substrate 4 facing the recess 2 constitutes the diaphragm 9. That is, the boundary between the diaphragm 9 in the second semiconductor substrate 4 and other regions is defined by the frame of the second semiconductor substrate 4 facing the opening edge of the recess 2. A part of the outer peripheral edge of the diaphragm 9 is opposed to the recess 2 with the first silicon oxide film 6 interposed therebetween.

Also, a plurality of strain detecting elements 7 are formed on one surface of the diaphragm 9 facing away from the concave portion 2 so as to be separated from each other.
When pressure is applied to the diaphragm 9 from the outside, the diaphragm 9 bends, and mainly the boundary side portion of the diaphragm 9 is distorted.
The strain detection element 7 includes a resistance element whose resistance changes in accordance with the amount of strain of the diaphragm 9 and is configured to output an electrical signal corresponding to the change in resistance.
That is, since the diaphragm 9 bends in accordance with the differential pressure between the reference pressure chamber 8 and the external pressure, the semiconductor pressure sensor 1A has a pressure applied to one surface of the diaphragm 9 (surface opposite to the recess 2). A pressure corresponding to the differential pressure with respect to the reference pressure chamber 8 is detected. When the pressure in the reference pressure chamber 8 is a vacuum, the pressure added to the diaphragm 9 can be measured as an absolute pressure.

  According to the semiconductor pressure sensor 1A configured as described above, the entire area of the edge of the through hole 5 is located inside the opening edge of the recess 2 when viewed from the side facing the opening of the through hole 5 and the recess 2. positioned. Here, residual stress is generated in the first silicon oxide film 6, and the magnitude of the stress caused by the residual stress of the first silicon oxide film 6 changes discontinuously at the edge of the through hole 5. In the semiconductor pressure sensor 1 </ b> A, the opening edge of the recess 2 and the edge of the through hole 5 are spaced apart from each other. Thus, the stress generated in the diaphragm 9 when the diaphragm 9 is bent is not superposed on the stress of the first silicon oxide film 6 generated so as to be discontinuous with the edge of the through hole 5 as a boundary. Thereby, local stress concentration on the diaphragm 9 is suppressed, and the breakdown pressure of the diaphragm 9 is increased, so that the diaphragm 9 can be prevented from being broken.

Next, a manufacturing method of the semiconductor pressure sensor 1A will be described.
FIG. 2 is a diagram for explaining a preparation step of the method for manufacturing a semiconductor pressure sensor according to the first embodiment of the present invention. FIG. FIG. 4 is a diagram for explaining the steps, FIG. 4 is a diagram for explaining a substrate connecting step of the manufacturing method of the semiconductor pressure sensor according to the first embodiment of the present invention, and FIG. FIG. 6 is a diagram for explaining a strain detecting element forming / post-processing step of the method for manufacturing a semiconductor pressure sensor according to the first embodiment of the present invention.

In the preparation step, as shown in FIG. 2, a first semiconductor substrate 10 and a second semiconductor substrate 11 are prepared.
The first semiconductor substrate 10 and the second semiconductor substrate 11 are single crystal silicon substrates having a plane orientation of 100. The conductivity type and resistivity of the first semiconductor substrate 10 are not particularly limited. For example, the first semiconductor substrate 10 has a P-type conductivity and 1 to 10 Ω · cm. Those having a degree of resistivity are preferred. The second semiconductor base substrate 11 is preferably an N-type conductivity type and having a resistivity of about 1 to 10 Ω · cm.

  In the insulating film / concave forming step, as shown in FIG. 3, the surface of the first semiconductor substrate 10 is oxidized by a thermal oxidation method. As a result, the first semiconductor base substrate 10 becomes the semiconductor / insulating film substrate 12 including the first semiconductor substrate 3 and the first silicon oxide film 6 formed over the entire surface of the first semiconductor substrate 3. The thickness of the first silicon oxide film 6 is preferably 0.1 μm or more, more preferably 0.2 to 3.0 μm. By setting the thickness of the first silicon oxide film 6 to 0.2 to 3.0 μm, moisture is easily absorbed by the surface of the first silicon oxide film 6.

  Next, a predetermined portion of the first silicon oxide film 6 on one surface side in the thickness direction of the first semiconductor substrate 3 is removed by using a photoengraving technique and a plasma etching technique to form a through hole 5 having a square inner shape. To do.

Further, the first semiconductor substrate 3 is etched through the through holes 5 to form the recesses 2 opened on one surface of the first semiconductor substrate 3.
The formation of the recess 2 is a so-called Bosch process in which perfluorocyclobutane gas and sulfur hexafluoride gas are alternately introduced into a region to be etched, whereby etching in the thickness direction of the first semiconductor substrate 3 can be performed. Is adopted. By adjusting the etching conditions of the first semiconductor substrate 3, one side of the inner shape of the recess 2 is made approximately 1 to 5 μm larger than one side of the through hole 5 of the first silicon oxide film 6. The formation of the recess 2 is not limited to the one using the Bosch process, and wet etching using an alkaline solution such as potassium hydroxide or tetramethylammonium hydroxide may be adopted.

  In the substrate connecting step, as shown in FIG. 4, the second semiconductor base substrate 11 will be described below so as to cover the through hole 5 and face the first semiconductor substrate 3 with the first silicon oxide film 6 interposed therebetween. The semiconductor / insulating film substrate 12 and the second semiconductor substrate 11 are connected by the direct bonding method.

  In the connecting operation of the semiconductor / insulating film substrate 12 and the second semiconductor substrate 11, first, 98% sulfuric acid and 30% hydrogen peroxide are mixed at a volume ratio of 4: 1. A mixed solution heated to 130 ° C. is prepared, and the semiconductor / insulating film substrate 12 is washed with this mixed solution for about 10 minutes, and then washed with pure water. Thereby, the surface of the semiconductor / insulating film substrate 12 is hydrophilized.

  Next, the semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11 are temporarily fixed in close contact with each other so that the second semiconductor base substrate 11 covers the through hole 5 at room temperature.

  Temporary fixation between the semiconductor / insulating film substrate 12 and the second semiconductor substrate 11 may be performed in a pressure environment of atmospheric pressure to vacuum. However, when the reference pressure chamber 8 formed in a subsequent process is evacuated. It is preferable to perform temporary fixing in a vacuum.

  Then, the temporarily fixed semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11 are annealed to join the semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11 together. Thereby, the reference pressure chamber 8 is formed by a space surrounded by the recess 2, the wall surface of the through hole 5, and the wall surface of the second semiconductor substrate 11 covering the opening of the through hole 5.

  In order to firmly bond the semiconductor / insulating film substrate 12 and the second semiconductor substrate 11, it is preferable that the annealing process is performed in a temperature range of 1000 to 1200 ° C., and the processing time is 2 More than 6 hours or more is preferable. Further, in order to oxidize the surfaces of the semiconductor / insulating film substrate 12 and the second semiconductor substrate 11, it is preferable to perform an annealing process in an environment in which oxygen or water vapor is introduced. The illustration of the oxide film formed by the annealing process is omitted.

  In the diaphragm forming step, as shown in FIG. 5, the second semiconductor base substrate 11 is thinned to a predetermined thickness using a technique such as grinding or chemical mechanical polishing. The second semiconductor substrate 4 is constituted by a thinned second semiconductor substrate 11. A diaphragm 9 is formed by the region of the second semiconductor substrate 4 that faces the opening of the recess 2.

  Since the second semiconductor base substrate 11 is ground and polished in an atmospheric pressure environment, when the reference pressure chamber 8 is vacuum, the second semiconductor base substrate 11 becomes thinner as the second semiconductor base substrate 11 becomes thinner. 2 A portion of the semiconductor base substrate 11 (hereinafter referred to as a diaphragm forming region) may bend and the thickness of the formed diaphragm 9 may vary.

  The limit of the thinning of the diaphragm 9 is determined by the variation in the thickness of the diaphragm 9 and the amount of deflection of the diaphragm 9. The variation in the thickness of the diaphragm 9 and the amount of deflection of the diaphragm 9 are desirably 1 μm or less. Depending on the pressure range measured by the semiconductor pressure sensor 1A, for example, when the semiconductor pressure sensor 1A is used to measure a pressure range of 0 to 1 atm, the outer shape is a square having a side of 500 μm and a thickness of 20 μm. In the case of the diaphragm 9, the variation in thickness and the amount of deflection of the diaphragm 9 can be reduced to 1 μm or less.

In the post-process step for forming the strain detection element, first, as shown in FIG. 6, the strain detection element 7 is formed at a predetermined position of the diaphragm 9 as described below.
For example, the strain detection element 7 is preferably formed in the second semiconductor substrate 4 by injecting and diffusing P-type impurities such as boron into the N-type second semiconductor substrate 4.

In addition, since the recessed part 2 is not visible with visible light, it is difficult to determine the boundary of the diaphragm 9. Therefore, by irradiating the first semiconductor substrate 3, the first silicon oxide film 6, and the second semiconductor substrate 4 with white light having a wavelength of 1000 nm or more, and imaging the transmitted light or reflected light with an infrared camera, The boundary of the diaphragm 9 can be confirmed.
Thereby, when the pressure applied to the diaphragm 9 from the center of the diaphragm 9 or from the outside acts on the strain detecting element 7 in the direction in which the diaphragm 9 is deflected, the outer peripheral edge of the diaphragm 9 having the largest distortion amount. It can be formed at an accurate position in the region on the part side.

  And although not shown in figure, after forming the power supply to the strain detection element 7, the wiring and the electrode for taking out the electric signal output from the strain detection element 7, the protective film for protecting these, etc. Then, the integrated first semiconductor substrate 3, first silicon oxide film 6, and second semiconductor substrate 4 are diced into a predetermined shape. Furthermore, the first silicon oxide film 6 on the other surface side of the first semiconductor substrate 3 is deleted as necessary, thereby completing the manufacture of the semiconductor pressure sensor 1A.

Since the effect of having constituted semiconductor pressure sensor 1A as mentioned above was confirmed by the test, the contents are explained concretely below.
7 is an enlarged cross-sectional view of the main part of the semiconductor pressure sensor according to the first embodiment of the present invention, and FIG. 8 is a breakdown voltage of the semiconductor pressure sensor according to the first embodiment of the present invention and the extension of the first silicon oxide film. It is a figure which shows the relationship with (quantity) / (thickness of a 1st silicon oxide film).

As shown in FIG. 7, the distance from the opening edge of the recess 2 of the semiconductor pressure sensor 1 </ b> A to the edge of the through hole 5 of the first silicon oxide film 6, in other words, the first from the opening edge of the recess 2. The extension amount of the silicon oxide film 6 is X, and the thickness of the first silicon oxide film 6 is T.
Although not shown, a comparative semiconductor pressure sensor described below was prepared. As a comparative semiconductor pressure sensor, the edge of the through hole 5 coincides with the opening edge of the recess 2 when viewed from the side facing the opening of the through hole 5 and the recess 2, and the edge of the through hole 5 is The thing located outside the opening edge part of the recessed part 2 was prepared.
For convenience of explanation, hereinafter, the distance from the opening edge of the recess 2 of the comparative semiconductor pressure sensor to the edge of the through hole 5 is assumed to be −X.

Then, the breakdown pressure of the diaphragm 9 of the semiconductor pressure sensor 1A and the comparative semiconductor pressure sensor was measured using X / T as a parameter.
Semiconductor pressure sensors for comparison are prepared with X / T of 0 and about −20 and −40, and semiconductor pressure sensor 1A has X / T of about 20, 40, 60, 80, and 100. Prepared.

The breakdown voltage varies depending on the size and thickness of the diaphragm 9 and the thickness of the first silicon oxide film 6. The size of the diaphragm 9 refers to the size of the outer shape of the cross section perpendicular to the thickness direction of the diaphragm 9.
For each of the semiconductor pressure sensors, for each value of X / T, a plurality of different conditions of the size and thickness of the diaphragm 9 and the thickness of the first silicon oxide film 6 are prepared. At this time, in each semiconductor pressure sensor, one side of the outer shape of the diaphragm 9 is in the range of 200 to 2000 μm, the thickness of the diaphragm 9 is in the range of 5 to 50 μm, and the thickness T of the first silicon oxide film 6 is 0. The thing in the range of 1-5.0 micrometers is used.

The measurement result of the breakdown voltage is shown in FIG.
In FIG. 8, the value of the breakdown voltage measured by each semiconductor pressure sensor is shown as a relative value normalized by the breakdown voltage value of the comparative semiconductor pressure sensor where X / T is 0. The average value of the breakdown voltage values measured by a plurality of semiconductor pressure sensors having the same value of X / T is indicated by ◆.

  The breakdown breakdown voltage of the comparative semiconductor pressure sensor with X / T of 0 is minimized, and the breakdown breakdown voltage increases continuously as the absolute value of X / T increases for both the semiconductor pressure sensor 1A and the comparative semiconductor pressure sensor. It was. The breakdown pressure of the comparative semiconductor pressure sensor with X / T of 0 is approximately half the maximum value of the breakdown pressure of the diaphragm 9 of the semiconductor pressure sensor 1A.

  Compared to the breakdown pressure of the comparative semiconductor pressure sensor of X / T = 0, the breakdown pressure of the semiconductor pressure sensor 1A is 1.5 times as long as the X / T value is about 15, and X / T = 50. And doubled. Moreover, when X / T exceeded 50, the increase in the breakdown voltage of the semiconductor pressure sensor 1A accompanying the increase in X / T turned to saturation.

  Regardless of the value of X / T, the breakdown pressure of the semiconductor pressure sensor 1A is greater than the breakdown pressure of the comparative semiconductor pressure sensor where X / T is 0 because the pressure is applied to the diaphragm 9 from the outside. This is considered to be because the stress generated in the diaphragm 9 at the time of bending of the first silicon oxide film 6 generated so as to be discontinuous with the edge of the through hole 5 as a boundary is not superimposed. . When X / T was 50 or more, a substantially constant breakdown voltage was measured regardless of the value of X / T. This is because the local stress concentration on the diaphragm 9 is greatly suppressed. It is considered that the breakdown voltage value of the diaphragm 9 that is originally exhibited under the condition that avoids local stress concentration on the surface appears in the measurement result.

  Also, the breakdown pressure decreases as X / T of the semiconductor pressure sensor 1A approaches 0 when the edge of the through hole 5 coincides with the outer edge of the diaphragm 9 facing the opening edge of the recess 2. In addition, it is considered that the stress generated when pressure is applied to the diaphragm 9 from the outside is most likely to be concentrated on the boundary side of the diaphragm 9.

On the other hand, even in the comparative semiconductor pressure sensor with X / T <0, the breakdown voltage of the diaphragm 9 was larger than that with the comparative semiconductor pressure sensor with X / T = 0.
However, assuming that the outer shapes of the first semiconductor substrate 3 and the second semiconductor substrate 4 are constant, the first oxidation of the first semiconductor substrate 3 and the second semiconductor substrate 4 increases as the absolute value of X / T becomes larger than zero. The junction area through the silicon film 6 is reduced. For this reason, setting X / T <0 means ensuring the bonding strength between the first semiconductor substrate 3 and the second semiconductor substrate 4 via the first silicon oxide film 6 and the airtightness of the reference pressure chamber 8. It is not preferable from the viewpoint of securing the property.
In addition, when a certain junction area between the first semiconductor substrate 3 and the second semiconductor substrate 4 is ensured, the outer sizes of the first semiconductor substrate 3 and the second semiconductor substrate 4 become large, which is not preferable.

  In summary, by setting X / T> 0, there is an effect that the breakdown voltage of the diaphragm 9 can be improved without reducing the junction area between the first semiconductor substrate 3 and the second semiconductor substrate 4. can get. In the region where X / T> 50, the increase in the breakdown voltage of the diaphragm 9 accompanying the increase in X / T is saturated. Further, when X / T> 50, the etching time in the insulating film / recess formation process takes a long time, and it becomes difficult to form the first silicon oxide film 6 with a desired dimension. For this reason, it is more preferable that X / T of the semiconductor pressure sensor 1A is set in a range of 0 <X / T ≦ 50.

  In the first embodiment, the entire area of the edge of the through hole 5 is located on the inner side of the opening edge of the recess 2 when viewed from the side opposite to the opening of the through hole 5 and the recess 2. However, at least a part of the edge of the through hole 5 is located inside the opening edge of the recess 2. If positioned, the effect of improving the breakdown voltage of the diaphragm 9 can be obtained.

  In addition, the first semiconductor substrate 3 and the second semiconductor substrate 4 have been described as single crystal silicon substrates, but the first semiconductor substrate 3 and the second semiconductor substrate 4 are not limited to single crystal silicon substrates, and silicon A carbide substrate or the like may be used. Although the first insulating film is described as being the first silicon oxide film 6, the first insulating film is not limited to the first silicon oxide film 6, and a silicon carbide insulating film or the like may be used.

  Moreover, although the cross-sectional shape of the diaphragm 9 and the inner shape of the through hole 5 have been described as being square, the same effect as described above can be obtained even with other shapes such as a circle.

Embodiment 2. FIG.
FIG. 9 is a sectional view of a semiconductor pressure sensor according to Embodiment 2 of the present invention.
In FIG. 9, the same reference numerals are given to the same or corresponding parts as those in the first embodiment, and the description thereof is omitted.
In FIG. 9, the semiconductor pressure sensor 1 </ b> B has a second silicon oxide film 15 as a second insulating film covering the through hole 5 formed in the second semiconductor substrate 4 and the first silicon oxide film 6. Is provided on the surface of the concave portion. That is, the second silicon oxide film 15 is provided on the surface of the second semiconductor substrate 4 on the first silicon oxide film 6 side so as to be disposed between the diaphragm 9 and the recess 2.
Other configurations of the semiconductor pressure sensor 1B are the same as those of the semiconductor pressure sensor 1A.

A method for manufacturing the semiconductor pressure sensor 1B will be described below.
The manufacturing method of the semiconductor pressure sensor 1B is the same as the manufacturing method of the semiconductor pressure sensor 1A except that the second semiconductor base substrate oxidation step is performed prior to the substrate connecting step.
In the second semiconductor base substrate oxidation step, the second semiconductor base substrate 11 is oxidized so that the second silicon oxide film 15 is formed over the entire surface of the second semiconductor base substrate 11.

Hereinafter, for convenience of explanation, the oxidized second semiconductor substrate 11 will be described as the second semiconductor substrate 11.
In the substrate connecting step, one surface side of the second semiconductor substrate 11 is directed to the opposite side to the first silicon oxide film 6 and the other surface of the second semiconductor substrate 11 is disposed on the first silicon oxide film 6 side. As described above, the second semiconductor substrate 11 on which the second silicon oxide film 15 is formed is disposed. Thus, the second silicon oxide film 15 is provided so as to cover the through hole 5 of the first silicon oxide film 6.
Hereinafter, the semiconductor pressure sensor 1B can be manufactured by the same procedure as the manufacturing method of the semiconductor pressure sensor 1A.

  According to the second embodiment, the second silicon oxide film 15 is provided on the surface of the second semiconductor substrate 4 on the first semiconductor substrate 3 side so as to be disposed between the diaphragm 9 and the recess 2. Yes. Similar to the first silicon oxide film 6, residual stress is also generated in the second silicon oxide film 15, and the first silicon oxide film 6 and the second silicon oxide film 15 are disposed so as to be in contact with each other. The discontinuity at the edge of the through hole 5 due to the residual stress of the first silicon oxide film 6 is greatly reduced. Since the discontinuity of stress at the edge of the through hole 5 is greatly reduced, when the diaphragm 9 bends due to the difference between the pressure applied to the diaphragm 9 from the outside and the pressure in the reference pressure chamber 8, the diaphragm The stress generated in 9 can be suppressed only to those caused by the deflection of the diaphragm 9. Thereby, the breakdown voltage of the diaphragm 9 can be further improved.

  In the second embodiment, the second insulating film is described as being the second silicon oxide film 15, but is not limited to the second silicon oxide film 15, and a silicon carbide insulating film or the like may be used.

Embodiment 3 FIG.
10 is a sectional view of a semiconductor pressure sensor according to Embodiment 3 of the present invention.
In FIG. 10, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 10, the semiconductor pressure sensor 1 </ b> C includes a third silicon oxide film 16 as a third insulating film on the surface of the reference pressure chamber 8, in other words, the wall surface that forms the recess 2 and the through hole 5, and the through hole 5. It is formed over the entire wall surface of the second semiconductor substrate 4 covering the opening.
Other configurations of the semiconductor pressure sensor 1C are the same as those of the semiconductor pressure sensor 1A.

  According to the semiconductor pressure sensor 1 </ b> C configured as described above, the third silicon oxide film 16 is formed over the entire wall surface of the second semiconductor substrate 4 covering the wall surface forming the recess 2 and the through hole 5 and the opening of the through hole 5. Is formed. By forming the third silicon oxide film 16 on the surface layer of the recess 2, a region where stress is concentrated when pressure is applied to the diaphragm 9 is the first semiconductor substrate through the first silicon oxide film 6. 3 and the second semiconductor substrate 4 are displaced with respect to the bonding interface.

  Here, the bonding interface between the first semiconductor substrate 3 and the second semiconductor substrate 4 via the first silicon oxide film 6 is inconsistent with the crystal lattice constant of silicon of the first semiconductor substrate 3 and the second semiconductor substrate 4. As a result, residual stress is generated. When a large stress is concentrated on the bonding interface between the first semiconductor substrate 3 and the second semiconductor substrate 4 by applying pressure to the diaphragm 9, cracks generated in the second semiconductor substrate 4 develop to the diaphragm 9, It may lead to the destruction of the diaphragm 9.

  In the semiconductor pressure sensor 1 </ b> C, when pressure is applied to the diaphragm 9, the stress concentration region is shifted from the bonding interface between the first semiconductor substrate 3 and the second semiconductor substrate 4 via the first silicon oxide film 6. It is possible to prevent the diaphragm 9 from being broken due to the progress of cracks generated in the second semiconductor substrate. That is, the breakdown voltage of the diaphragm 9 can be improved.

A method for manufacturing the semiconductor pressure sensor 1C will be described below.
FIG. 11 is a diagram for explaining a connecting substrate oxidation treatment process for a semiconductor pressure sensor according to Embodiment 3 of the present invention, and FIG. 12 is for explaining a diaphragm forming process of the method for manufacturing a semiconductor pressure sensor according to Embodiment 3 of the present invention. FIG. 13 is a diagram for explaining a strain detection element forming / post-processing step of the method of manufacturing a semiconductor pressure sensor according to the third embodiment of the present invention.
11 to 13, the same reference numerals are given to the same or corresponding parts as in the first embodiment, and the description thereof is omitted.
The manufacturing method of the semiconductor pressure sensor 1C includes a preparation process, an insulating film / recess formation process, a substrate connection process, a connection substrate oxidation process, a diaphragm formation process, and a strain detection element formation / post-process process.

  The preparation process and the insulating film / recess formation process are the same as the preparation process and the insulation film / recess formation process of the manufacturing method of the semiconductor pressure sensor 1A. In the substrate connecting step, before temporarily fixing the semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11, the semiconductor / insulating film substrate 12 is previously placed in an environment containing water vapor, and the inner wall surface of the recess 2. Moisturize with water.

  In the subsequent connected substrate oxidation treatment step, as shown in FIG. 11, the annealing process is performed on the semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11 at a high temperature. Thereby, the moisture contained in the inner wall surface of the recess 2 oxidizes the wall surface of the recess 2, the through hole 5, and the wall surface of the second semiconductor substrate 4 covering the opening of the through hole 5, thereby forming the third silicon oxide film 16. A space formed inside the third silicon oxide film 16 becomes the reference pressure chamber 8.

  Hereinafter, as shown in FIGS. 12 and 13, the semiconductor pressure sensor 1 </ b> C can be obtained by performing the diaphragm forming process and the strain detecting element forming / post-processing process in the same manner as the manufacturing method of the semiconductor pressure sensor 1 </ b> A. it can.

  Here, it may be considered that an oxide film corresponding to the third silicon oxide film 16 is formed in advance on the inner wall surface of the recess 2 and the through hole 5 of the semiconductor / insulating film substrate 12 before the substrate connecting step. However, if an oxide film is formed on the surface of the recess 2 in advance, the first semiconductor substrate 3 is distorted by the stress generated in the oxide film, or the first semiconductor substrate 3 near the opening edge of the recess 2 is formed. Due to the non-uniform stress, a bonding failure between the first semiconductor substrate 3 and the second semiconductor substrate 4 may occur.

Further, when the second semiconductor base substrate 11 and the semiconductor / insulating film substrate 12 in which the oxide film is formed in the recess 2 are bonded by annealing, a portion near the end of the semiconductor / insulating film substrate 12 on the recess 2 side The growth rate of the oxide film differs between the part of the second semiconductor substrate 11 that is opposite to the part. As a result, a portion of the semiconductor / insulating film substrate 12 in the vicinity of the end on the concave portion 2 side is raised, and the second semiconductor base substrate 11 is in contact with only this portion, and other parts of the semiconductor / insulating film substrate 12 are contacted. There is a possibility that the semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11 may cause a bonding failure without contacting the surface.
According to the manufacturing method of the semiconductor pressure sensor 1C, since the third silicon oxide film 16 is formed after the semiconductor / insulating film substrate 12 and the second semiconductor base substrate 11 are temporarily fixed in advance, this problem can be avoided.

Embodiment 4 FIG.
14 is a sectional view of a semiconductor pressure sensor according to Embodiment 4 of the present invention.
In FIG. 14, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 14, the semiconductor pressure sensor 1 </ b> D is configured in the same manner as the semiconductor pressure sensor 1 </ b> A except that the semiconductor pressure sensor 1 </ b> D is formed integrally with the first semiconductor substrate 3 and has a stopper 17 provided in the reference pressure chamber 8.

The stopper 17 protrudes from the bottom of the recess 2 that faces the center of the diaphragm 9.
Here, let the range of the pressure which semiconductor pressure sensor 1D measures be P1-P2.
When the atmospheric pressure around the semiconductor pressure sensor 1D is P1, a predetermined gap is formed between the protruding end of the stopper 17 and the diaphragm 9, and the atmospheric pressure around the semiconductor pressure sensor 1D becomes P2. When the diaphragm 9 is bent, the protruding end of the stopper 17 is not in contact with the diaphragm 9 and is as close as possible to the diaphragm 9.

  According to the semiconductor pressure sensor 1D configured as described above, when the diaphragm 9 is bent by a predetermined amount with a predetermined pressure (external force) larger than the maximum value P2 of the pressure range to be measured, the stopper 17 is moved to the diaphragm 17. 9 is contacted. As a result, even when an unexpected excessive pressure is applied to the diaphragm 9 from the outside, the stopper 9 restricts the diaphragm 9 from being bent more than a predetermined amount, so that the diaphragm 9 is destroyed as much as possible. Can be prevented.

Next, a manufacturing method of the semiconductor pressure sensor 1D will be described.
FIG. 15 is a diagram for explaining an insulating film / recess formation step of the semiconductor pressure sensor manufacturing method according to the fourth embodiment of the present invention. FIG. 16 is an oxidation diagram of the semiconductor pressure sensor manufacturing method according to the fourth embodiment of the present invention. FIG. 17 is a diagram for explaining a film selective removing step, FIG. 17 is a diagram for explaining a substrate connecting step of a manufacturing method of a semiconductor pressure sensor according to a fourth embodiment of the present invention, and FIG. 18 is a semiconductor pressure according to a fourth embodiment of the present invention. FIG. 19 is a diagram for explaining a diaphragm forming process of the sensor manufacturing method, and FIG. 19 is a diagram for explaining a strain detecting element forming / post-processing process of the semiconductor pressure sensor manufacturing method according to Embodiment 4 of the present invention.
15 to 19, the same reference numerals are given to the same or corresponding parts as those in the first embodiment, and the description thereof is omitted.

The manufacturing method of the semiconductor pressure sensor 1D includes a preparation process, an insulating film / recess formation process, a substrate connection process, a diaphragm formation process, and a strain detection element formation / post-processing process.
The preparation process is the same as the preparation process of the manufacturing method of the semiconductor pressure sensor 1A.
In the insulating film / recess formation process, the through hole 5 is formed in the first silicon oxide film 6 by the same method as the semiconductor pressure sensor 1A. As shown in FIG. 15, the through hole 5 is formed at the center of the formation region. A predetermined portion of the first silicon oxide film 6 located is left in an island shape. Next, the recess 2 is formed by etching the first semiconductor substrate 3 through the through hole 5. As a result, a stopper 17 is formed in the recess 2 that protrudes from the bottom of the recess 2 and has a part of the third silicon oxide film 16 at the protruding end.

In the oxide film selective removal step, as shown in FIG. 16, only the portion of the third silicon oxide film 16 formed at the protruding end of the stopper 17 is selectively removed by dry etching or the like. Note that the portion of the third silicon oxide film 16 formed on the protruding end of the stopper may be selectively removed using a method such as ion milling.
At this time, not only the third silicon oxide film 16 but also a predetermined region is removed from the protruding end of the stopper 17 toward the base end. The protruding end surface of the stopper 17 is a rough surface.

  In the subsequent substrate connecting step, as shown in FIG. 17, as in the substrate connecting step of the method for manufacturing the semiconductor pressure sensor 1 </ b> A, the second semiconductor base substrate 11 covers the through hole 5, and the first silicon oxide film 6 is formed. The semiconductor / insulating film substrate 12 and the second semiconductor substrate 11 are temporarily fixed so as to face the first semiconductor substrate 3. At this time, a predetermined gap is formed between the protruding end of the stopper 17 and the second semiconductor substrate 11.

  Hereinafter, as shown in FIGS. 18 and 19, the semiconductor pressure sensor 1 </ b> D is manufactured by performing the diaphragm forming process and the strain detection element forming / post-processing process in the same manner as the manufacturing method of the semiconductor pressure sensor 1 </ b> A. Complete.

  According to the manufacturing method of the semiconductor pressure sensor 1D described above, in the diaphragm forming process, the second semiconductor base substrate 11 is ground and thinned by chemical mechanical polishing to form the diaphragm 9 as described above.

  For example, when the reference pressure chamber 8 is vacuum, the diaphragm forming region of the second semiconductor base substrate 11 bends as the second semiconductor base substrate 11 is thinned. When the formed diaphragm 9 is used for detecting a minute pressure, the thickness of the diaphragm 9 needs to be particularly thin. For this reason, when the stopper 17 is not provided, when the thickness of the second semiconductor base substrate 11 approaches the desired thickness of the diaphragm 9, the diaphragm formation of the second semiconductor base substrate 11 depends on the load during grinding. The area is greatly bent. As a result, the thickness of the formed diaphragm 9 may vary greatly. Moreover, when an unexpected excessive pressure is applied to the diaphragm 9, the displacement of the diaphragm 9 is not regulated, and the diaphragm 9 may be greatly bent and broken.

  On the other hand, by providing the stopper 17 before the diaphragm forming step as in the manufacturing method of the semiconductor pressure sensor 1D, the diaphragm forming region of the second semiconductor base substrate 11 is large when the second semiconductor base substrate 11 is ground. Even if it tries to bend, it is prevented from being greatly bent by coming into contact with the stopper 17. Thereby, the dispersion | variation in the thickness of the diaphragm 9 formed can be suppressed. Furthermore, even when an excessive pressure is applied to the diaphragm 9, the diaphragm 9 is restrained from being bent, so that the diaphragm 9 is prevented from being destroyed.

  Further, by making the protruding end surface of the stopper 17 rough, it is possible to prevent the stopper 17 and the diaphragm 9 from coming into close contact with each other when the diaphragm 9 abuts against the stopper 17 after the completion of the semiconductor pressure sensor 1D. it can.

  According to the fourth embodiment, the number of stoppers 17 to be formed has been described as one. However, the number of stoppers 17 to be formed is not limited to one, and the size of the diaphragm 9 and the like By appropriately setting the number of stoppers 17 formed and the arrangement position of the stoppers 17 in the reference pressure chamber 8 according to the thickness and the like, variations in the thickness of the diaphragm 9 in the diaphragm forming process can be suppressed and the breakdown voltage can be improved. In some cases, you can

Embodiment 5 FIG.
20 is a sectional view of a semiconductor pressure sensor according to Embodiment 5 of the present invention.
In FIG. 20, the same or corresponding parts as those in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In FIG. 20, the semiconductor pressure sensor 1 </ b> E includes a fourth silicon oxide film 18 as a third insulating film over the entire surface of the reference pressure chamber 8 including the surface of the stopper 17. Other configurations are the same as those of the semiconductor pressure sensor 1C.

  The manufacturing method of the semiconductor pressure sensor 1E is the same as the manufacturing process of the semiconductor pressure sensor 1D, and the same process as the connecting substrate oxidation process of the manufacturing method of the semiconductor pressure sensor 1C is added between the substrate connecting process and the diaphragm forming process. Configured.

  According to the semiconductor pressure sensor 1E configured as described above, the gap between the tip of the stopper 17 covered with the fourth silicon oxide film 18 and the diaphragm 9 is made smaller than the thickness of the first silicon oxide film 6. It is possible.

  Here, when the semiconductor pressure sensor 1E is placed in an environment where the maximum value P2 of the pressure range to be measured is added and the diaphragm 9 is bent, the diaphragm 9 protrudes from the through hole 5 toward the bottom of the recess 2. There are many things that are not done.

  Even when the semiconductor pressure sensor 1E is placed in an environment where the maximum value P2 of the pressure range is applied and the diaphragm 9 is bent, the protruding end of the stopper 17 is placed in the through hole 5 so that it does not come into contact with the diaphragm 9. By inserting, the following effects can be obtained.

  That is, in the diaphragm forming step, it is possible to further suppress the bending of the diaphragm forming region when the second semiconductor substrate 11 is ground, so that the variation in the thickness of the diaphragm 9 can be further reduced. In addition, when the diaphragm 9 is pressed from the outside and bent by an excessive pressure, the diaphragm 9 is further prevented from being greatly bent, so that the breakdown voltage can be further improved.

Embodiment 6 FIG.
FIG. 21 is a cross-sectional view of a semiconductor pressure sensor according to Embodiment 6 of the present invention.
In FIG. 21, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 21, the semiconductor pressure sensor 1 </ b> F has a communication hole 20 that communicates the bottom of the recess 2 and the other surface of the first semiconductor substrate 3. Other configurations are the same as those of the semiconductor pressure sensor 1A.

Next, a method for manufacturing the semiconductor pressure sensor 1F will be described.
The manufacturing method of the semiconductor pressure sensor 1F is the same as the manufacturing method of the first semiconductor pressure sensor 1A except that a communication hole forming step is added after the insulating film / recess forming step.

  In the communication hole forming step, the first silicon oxide film 6 on the other surface side of the semiconductor / insulating film substrate 12 is removed using a photoengraving technique and a plasma etching technique, and the bottom of the recess 2 and the other surface of the first semiconductor substrate 3 are removed. As in the method of forming the recesses in the insulating film / recess formation process, the communication holes 20 are formed using the Bosch process. By forming the communication hole 20 using the Bosch process, the first semiconductor substrate 3 can be etched by making the hole direction of the communication hole 20 coincide with the thickness direction of the first semiconductor substrate 3, so that the opening of the communication hole 20 is reduced. In addition, a region for securing the other surface of the first semiconductor substrate 3 to the casing or the like with a die bond material is secured.

  The semiconductor pressure sensor 1F configured as described above is a differential pressure sensor that measures the difference between the pressure on the first semiconductor substrate 3 side and the pressure on the second semiconductor substrate 4 side. That is, for example, the semiconductor pressure sensor 1F is arranged by arranging the diaphragm 9 so that the diaphragm 9 is exposed in one of the two divided spaces and exposing the opening of the communication hole 20 in the other space. Can be used as a differential pressure sensor that can measure a pressure difference in a partitioned space.

Embodiment 7 FIG.
FIG. 22 is a block diagram of an internal combustion engine device with a semiconductor pressure sensor according to Embodiment 7 of the present invention.

In FIG. 22, an internal combustion engine device 24 with a semiconductor pressure sensor includes an internal combustion engine 25 having an intake passage 26 and an exhaust passage 27, and a semiconductor pressure attached to the internal combustion engine 25 so that the pressure in the intake passage 26 of the internal combustion engine 25 can be measured. It has a sensor 1A.
That is, one surface of the diaphragm 9 of the semiconductor pressure sensor 1 </ b> A is disposed in the intake passage 26.

In the internal combustion engine 25, the measurement range of the pressure in the intake passage 26 is often about 5 at most, but when a backfire occurs, the pressure in the intake passage 26 becomes abnormally large.
For this reason, the diaphragm 9 is required to have a breakdown voltage of 5 to 10 times or more the measurement range of the pressure in the intake passage 26.
The semiconductor pressure sensor 1A has improved breakdown pressure resistance of the diaphragm 9, and can be used for measuring pressure in the intake passage 26 of the internal combustion engine 25 only by increasing the thickness of the diaphragm 9 to some extent.

  In the seventh embodiment, the semiconductor pressure sensor 1A is attached to the internal combustion engine 25 to configure the internal combustion engine device 24 with the semiconductor pressure sensor. However, instead of the semiconductor pressure sensor 1A, the semiconductor pressure sensors 1B to 1B are used. Any of 1F may be attached.

  1A to 1F Semiconductor pressure sensor, 2 recess, 3 first semiconductor substrate, 4 second semiconductor substrate, 5 through hole, 6 first silicon oxide film (first insulating film), 15 second silicon oxide film (second insulating film) ), 16 Third silicon oxide film (third insulating film), 18 Fourth silicon oxide film (third insulating film), 17 Stopper, 25 Internal combustion engine, 26 Intake passage.

Claims (7)

A first semiconductor substrate having a recess formed in one surface in the thickness direction;
A second semiconductor substrate disposed opposite one surface of the first semiconductor substrate;
A first insulating film interposed between the first semiconductor substrate and the second semiconductor substrate and having a through hole communicating between the recess and the second semiconductor substrate;
With
An airtight reference pressure chamber is formed from the first semiconductor substrate, the second semiconductor substrate, and the first insulating film,
A semiconductor pressure sensor, wherein at least a part of the edge of the through hole is located inside the opening edge of the recess as viewed from the side facing the opening of the through hole and the recess.   2. The semiconductor pressure sensor according to claim 1, wherein the entire region of the edge of the through hole is located inside the opening edge of the recess.   When the entire edge portion of the through hole is located at a predetermined distance X from the opening edge portion of the recess, and T is the thickness of the first insulating film, 0 <X / T ≦ 50 The semiconductor pressure sensor according to claim 2, wherein the semiconductor pressure sensor is satisfied.   The third insulating film is formed over the entire wall surface of the second semiconductor substrate that covers the wall surface that forms the recess and the through hole, and the opening of the through hole. The semiconductor pressure sensor according to any one of the above.   In the space surrounded by the wall surface of the second semiconductor substrate covering the opening of the through hole and the wall surface constituting the recess and the through hole, the portion of the second semiconductor substrate facing the recess is on the recess side. 5. The stopper according to claim 1, further comprising: a stopper that restricts the bending of the second semiconductor substrate when an external force that causes the bending is greater than a predetermined amount. Semiconductor pressure sensor.   6. The semiconductor according to claim 1, wherein a communication hole that communicates the recess and the other surface of the first semiconductor substrate is formed in the first semiconductor substrate. Pressure sensor.   The surface of the second semiconductor substrate is configured such that a pressure value corresponding to the pressure applied from the opposite side to the concave portion can be detected at a portion of the second semiconductor substrate facing the concave portion, and the pressure is applied to the surface of the second semiconductor substrate. The semiconductor pressure sensor according to any one of claims 1 to 6, wherein the semiconductor pressure sensor is disposed in an intake passage of an internal combustion engine.

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