JP2023014372A - Method of suppressing bending of pressure sensor diaphragm, and pressure sensor diaphragm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that achieves a structure for reducing film stress by a realistic processing dimension, and suppresses bending of a pressure sensor diaphragm in which a zero-point shift caused by a deposit film of the sensor diaphragm is minimized as much as possible.

SOLUTION: When a film formation-purpose measured fluid is introduced to a pressure chamber of a pressure sensor having a part of a wall formed by a diaphragm, and a deposit film is formed in the diaphragm, a method suppresses bending of a pressure sensor diaphragm by film stress when the deposit film is contracted. A rugged structure is configured by use of many inclination planes 53 and 54 for one plane contacting with the measured fluid of the sensor diaphragm 41 (diaphragm). The deposit film 55 is formed in the inclination planes 53 and 54, and when the film stress occurs by the deposit film 55, a bending moment M in a nearly vertical direction with respect to the sensor diaphragm 41 acts on the inclination planes 53 and 54, and the bending moment M acting on the inclination plane 53 and the bending moment M acting on the adjacent inclination plane 54 are caused to cancel out each other.

SELECTED DRAWING: Figure 10

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a method and a pressure sensor diaphragm for suppressing deflection of a pressure sensor diaphragm that contacts a fluid to be measured.

Semiconductor manufacturing equipment is a typical device that uses a capacitive diaphragm vacuum gauge. The main reason diaphragm vacuum gauges are used in semiconductor manufacturing equipment is that they do not depend on gas types, unlike thermal vacuum gauges such as Pirani gauges and ionization vacuum gauges. This is because it has corrosion resistance, and by heating the sensor, adsorption of the raw material gas and deposition of by-products can be suppressed.

Diaphragm vacuum gauges are used not only in the film formation process but also in the process of etching wafers made of Si or the like among various processes performed in semiconductor manufacturing equipment. Examples of film formation methods performed in the film formation process include sputtering, CVD (chemical vapor deposition), and ALD (atomic layer deposition).
When the above substances are deposited on the sensor chip of the diaphragm vacuum gauge that measures and controls the gas pressure of the process in the film formation process, the shrinkage of the deposited film causes unnecessary deformation of the sensor diaphragm, resulting in a zero point shift and a pressure drop. It is known that it brings about a change in sensitivity and greatly affects the quality of film formation and etching.

In order to prevent deposition of by-products on the diaphragm vacuum gauge as described above, the sensor chip is kept at a high temperature, baffles are provided in the path of the process gas to the sensor diaphragm, and the path is formed in a complicated maze shape. However, methods (Patent Documents 1 to 3) have been devised and implemented to capture gas that tends to adhere as far as possible. In addition, in order to control the gas inflow route together with such a baffle, there is also a structure in which the position of the gas introduction port that guides the process gas to the sensor diaphragm is located slightly outside the diaphragm, avoiding the vicinity of the center of the diaphragm where the influence of deposition is large. It has been proposed (Patent Documents 1, 2, 4 and 5).

Furthermore, for a process such as ALD in which a uniform film is formed based on physical and chemical adsorption on the surface, the moment is adjusted as described in Patent Documents 6 and 7. A diaphragm structure has been proposed that suppresses the deflection itself of the sensor diaphragm.
On the other hand, as an attempt to suppress the influence of the deposited film in the structure of the diaphragm of the diaphragm vacuum gauge, structures as shown in Patent Documents 8 and 9 have been proposed. In these Patent Documents 8 and 9, the deposited film is divided by providing a table-shaped, reverse-tapered, or square wave-shaped structure or a beam structure so as to have a honeycomb shape on the diaphragm, and film stress is applied to the diaphragm. Techniques for limiting impacts are described.

JP 2011-149946 A Japanese Patent No. 6096380 JP 2015-34786 A JP 2014-126504 A JP 2014-109484 A JP 2010-236949 A JP 2009-265041 A Japanese Patent Publication No. 2009-524024 JP 2008-107214 A

The technique of dividing the deposited film on the sensor diaphragm to eliminate the influence thereof, as disclosed in Patent Documents 8 and 9, is highly effective but has the problem of being difficult to implement. The results of a numerical simulation performed as a specific verification example of this technology are shown below.
FIG. 18 shows one of the models for calculating the effect of membrane disruption. The sensor diaphragm is usually a disc with a fixed periphery, but in order to simplify the numerical simulation, a two-dimensional model of a flat plate 1 with both sides fixed was used to perform the calculations. Calculation results are shown in FIGS. 19 and 20. FIG.

FIG. 18(A) is a perspective view showing the entire flat plate, and FIG. 18(B) is an enlarged perspective view showing a part of the flat plate. A large number of slits 2 are formed on the flat plate 1 . A membrane 3 is provided on the surface of the plate 1 divided by these slits 2 . The numerical simulation was performed by contracting the film 3 to generate film stress. In this embodiment, the stress generated in the film due to the film deposited on the sensor diaphragm shrinking or expanding during film formation is referred to as "film stress".
Due to this film stress, the flat plate 1 receives a bending moment and, for example, in the case of contraction, bends downward convexly. corresponds to

FIG. 19 shows a schematic diagram of the calculation result. The deformation scale is unified, and the more the number of divisions of the flat plate 1 (the number of slits 2) is increased, the smaller the deformation becomes. 19A shows the case where the slit 2 is not provided, and FIG. 19B shows the case where the film 3 is divided into two by the slit 2. FIG. 19(C) shows the case where the film 3 is divided into 20 parts by the slit 2, and FIG. 19(D) shows the case where the film 3 is divided into 200 parts by the slit 2. FIG. FIG. 19 shows that the higher the dot density, the greater the displacement.

FIG. 20 plots the absolute value of the displacement at the central portion of the flat plate when the number of divisions of the film is plotted on the horizontal axis and the undivided uniform film is used as the reference (100%). From these results, it can be seen that the more finely divided the film, the smaller the displacement, and the greater the effect when the film is formed on the sensor diaphragm.
However, when trying to actually divide the film and apply the structures disclosed in the cited documents 8 and 9, as a practical problem, it faces difficulties in terms of sensor manufacturing. The span of the flat plate 1 in the calculation model shown in FIGS. 18 to 20 (interval between fixed portions at both ends) is 5000 μm. should be as small as 500-1000.

Therefore, the structure for membrane severing has a lateral dimension of several μm. However, with the contact mask aligner and dry etching techniques used in the manufacture of MEMS sensors, it is extremely difficult to reproducibly form the aforementioned structure with a dimension of several μm or less. It requires equipment and is not practical. Moreover, if the structure for film division is formed excessively finely, it is easily imagined that the formed structure itself will be buried in the deposited film, and the effect cannot be expected. Therefore, there is a demand for a structure in which effects can be obtained even with a realistic processing dimension of several tens of micrometers.

It is an object of the present invention to realize a structure for reducing film stress with realistic processing dimensions, and a method of suppressing deflection of a pressure sensor diaphragm by minimizing the zero point shift caused by the deposited film on the sensor diaphragm. and to provide a diaphragm for a pressure sensor.

In order to achieve this object, a method for suppressing deflection of a pressure sensor diaphragm according to the present invention is provided by introducing a fluid to be measured for film formation into a pressure chamber of a pressure sensor, a wall of which is partially formed by the diaphragm. A method for suppressing deflection of a diaphragm for a pressure sensor due to film stress when a deposited film is formed on the diaphragm and the deposited film shrinks, the method comprising: A deposited film is formed on the sloped surface, and when film stress is generated by the deposited film, the sloped surface is bent in a direction close to perpendicular to the diaphragm. In this method, a moment acts and the bending moment acting on the inclined surface cancels out the bending moment acting on the adjacent inclined surface.

In the method for suppressing deflection of the pressure sensor diaphragm according to the present invention, the inclined surface has a conical shape or a trapezoidal cross-sectional shape in which the bending moments generated on the inclined surfaces which are protruding from the one surface and which are opposed to each other cancel each other out. It may be a spherical surface of a hemispherical protrusion where said bending moments occurring on the side surfaces of the protrusion or on rounded inclined surfaces facing each other cancel each other.

A pressure sensor diaphragm according to the present invention is a pressure sensor diaphragm used in a method for suppressing deflection of the pressure sensor diaphragm, wherein the diaphragm has a pressure to which a fluid to be measured capable of forming a deposited film is introduced. One surface of the diaphragm that is in contact with the fluid to be measured is arranged so that a bending moment due to the deposited film acts in a direction that is nearly perpendicular to the diaphragm. The uneven structure may be formed using a plurality of inclined surfaces that are inclined with respect to the thickness direction of the diaphragm and directed toward the inside of the pressure chamber.

According to the present invention, in the pressure sensor diaphragm, the inclined surface may be a side surface of a conical protruding portion protruding from the one surface.

In the pressure sensor diaphragm according to the present invention, the pyramidal protrusion may be formed of a large number of square pyramids, and may be formed such that adjacent square pyramids are in close contact with each other.

In the pressure sensor diaphragm according to the present invention, the inclined surface may be an inclined side surface of a protrusion having a trapezoidal cross section and protruding from the one surface.

In the pressure sensor diaphragm according to the present invention, the inclined surface may be a spherical surface of a hemispherical projecting portion projecting from the one surface.

In the pressure sensor diaphragm according to the present invention, the height of the protrusion is 25% or more and 75% or less of the thickness of the entire diaphragm, and includes the protrusion end of the protrusion and intersects the side surface. In the cross section, the angles formed by a side corresponding to one side surface and a plane parallel to the diaphragm and between a side corresponding to the other side surface and a surface parallel to the diaphragm are 45° or more and 80° or less, respectively, and the protrusion The interval between the portions may be at least 100 times the particle size of the substance that causes the deposition film.

By using the pressure sensor according to the present invention in an environment where by-products accumulate, a deposited film is formed on the inclined surface of the diaphragm. Stress (film stress) is generated in the diaphragm by contraction of the deposited film with respect to the diaphragm. As a result, a bending moment acts on the diaphragm, causing the plurality of inclined surfaces to bend individually. The direction of the bending moment acting on each inclined surface is along the inclined surface. That is, unlike the case where a deposited film is formed on a flat diaphragm, a bending moment acts in a direction inclined with respect to the planar direction of the diaphragm, in other words, in a direction nearly perpendicular to the diaphragm.

Moreover, since the bending moment acting on the inclined surface cancels out the bending moment acting on the adjacent inclined surface, the magnitude of the bending moment can be reduced.
As a result, the force for bending the diaphragm is reduced, making it difficult for the diaphragm to flex, so that the zero point shift can be kept small.
Unlike the case of forming a large number of grooves in the diaphragm, the inclined surface can be realized with realistic machining dimensions.
Therefore, according to the present invention, a structure for reducing film stress is realized with realistic processing dimensions, and the zero point shift caused by the deposited film on the sensor diaphragm is minimized. A method and diaphragm for a pressure sensor can be provided.

1 is a cross-sectional view of a diaphragm gauge equipped with a pressure sensor according to the invention; FIG. It is a sectional view of a sensor chip. It is a schematic diagram which shows the calculation model of the simulation of a mountain-shaped structure. It is a perspective view which shows the result of the simulation of a chevron structure. It is a graph which shows the result of the simulation of a chevron structure. It is a graph which shows the result of the simulation of a chevron structure. It is a schematic diagram for demonstrating the angle of an inclined surface. FIG. 4 is a cross-sectional view showing a structure in which slits are formed between peaks; It is sectional drawing which shows shapes other than a chevron. FIG. 4 is a cross-sectional view for explaining a bending moment due to a film; FIG. 4 is a perspective view showing a square pyramid-shaped projection; FIG. 4 is a perspective view showing a conical projection; FIG. 4 is a perspective view showing a truncated pyramid-shaped projection; FIG. 10 is a perspective view showing a truncated cone-shaped projection; FIG. 4 is a perspective view showing a hemispherical projection; FIG. 4 is a perspective view showing a computational model for simulating a three-dimensional structure; It is a schematic diagram which shows the simulation result of a three-dimensional structure. FIG. 4 is a perspective view showing a computational model for membrane division simulation; FIG. 10 is a perspective view showing the results of membrane division simulation; 4 is a graph showing results of a membrane splitting simulation;

An embodiment of a method for suppressing deflection of a pressure sensor diaphragm and a pressure sensor diaphragm according to the present invention will now be described in detail with reference to FIGS. 1 to 17. FIG.
A capacitive diaphragm gauge 11 shown in FIG. 1 includes a package 12 located on the outermost side in FIG. In this embodiment, the sensor chip 13 corresponds to the "pressure sensor" according to the invention.

The package 12 is formed in a bottomed cylindrical shape by welding a plurality of members together. A plurality of members constituting the package 12 are a lower package 15 having a small diameter portion 14 located at the bottom in FIG. and a disk-shaped cover 19 that closes the open end of the upper package 18 .

The support diaphragm 17 is made of a corrosion-resistant metal material and has an annular plate shape. The opening of the support diaphragm 17 is formed in a circular shape when viewed from the thickness direction of the support diaphragm 17, and the sensor chip 13 is connected to the support diaphragm 17 with the first base plate 21 interposed therebetween. is blocked. Therefore, the support diaphragm 17 cooperates with the sensor chip 13 to divide the inside of the package 12 into the introduction portion 22 and the reference vacuum chamber 23 . A baffle 24 is provided in the introduction portion 22 .

The reference vacuum chamber 23 is kept at a predetermined degree of vacuum.
The first pedestal plate 21 cooperatively sandwiches the support diaphragm 17 with the second pedestal plate 25 . The first and second pedestal plates 21 and 25 are each made of sapphire in the form of discs and are bonded to the supporting diaphragm 17 respectively. Communication holes 26 to 28 are formed in the first and second base plates 21 and 25 for passing the fluid to be measured.

A plurality of electrode lead portions 32 are embedded in the cover 19 with hermetic seals 31 interposed therebetween. The electrode lead portion 32 includes an electrode lead pin 33 and a metal shield 34 . Electrode lead pins 33 are supported within shield 34 via hermetic seals 35 . One end of the electrode lead pin 33 is exposed to the outside of the package 12 and connected to an external signal processing section via wiring (not shown). The other end of the electrode lead pin 33 is connected to a contact pad 37 of the sensor chip 13 to be described later via a contact spring 36 having conductivity.

The sensor chip 13 detects the pressure of the lead-in portion 22 inside the package 12 based on the capacitance, and is supported inside the package 12 by the support diaphragm 17 and the first and second base plates 21 and 25. there is The sensor chip 13, as shown in FIG. 2, comprises a sensor diaphragm 41 located on the lower side in FIG. The sensor diaphragm 41 is made of sapphire and is disc-shaped, and is attached to the first base plate 21 via a spacer 43 as shown in FIG. A pressure chamber 44 into which the fluid to be measured is introduced is formed between the sensor diaphragm 41 and the first base plate 21 . Therefore, the sensor diaphragm 41 forms part of the wall of the pressure chamber 44 . In this embodiment, this sensor diaphragm 41 corresponds to the "diaphragm" referred to in the present invention.

The sensor pedestal 42 is made of sapphire and has a rectangular shape with a cylindrical recess. The opening of the recess of the sensor pedestal 42 is closed by the sensor diaphragm 41 . As shown in FIG. 2, the sensor pedestal 42 is provided with a communication hole 46 for communicating between the capacity chamber 45 inside the sensor pedestal 42 and the reference vacuum chamber 23 outside the sensor pedestal 42 . The capacity chamber 45 and the reference vacuum chamber 23 maintain the same degree of vacuum.
Two types of electrodes 47 to 50 are provided on the inner bottom surface 42a of the sensor pedestal 42 and one surface 41a of the sensor diaphragm 41 facing the inner bottom surface 42a of the sensor pedestal 42, respectively. A pair of pressure-sensitive electrodes 47 and 48 are provided at the central portion of the sensor diaphragm 41 and the central portion of the inner bottom surface 42 a of the sensor pedestal 42 . A pair of reference electrodes 49 and 50 are provided on the outer peripheral portion of the sensor diaphragm 41 and the outer peripheral portion of the inner bottom surface 42 a of the sensor pedestal 42 . The sensor chip 13 detects the pressure applied to the sensor diaphragm 41 based on the capacitance of the pressure-sensitive capacitor including the pressure-sensitive electrodes 47 and 48 and the capacitance of the reference capacitor including the reference electrodes 49 and 50. To detect.

The other surface 41b (the lower surface in FIG. 1) of the sensor diaphragm 41, which is located on the opposite side of the sensor pedestal 42 and is in contact with the fluid to be measured, is provided with a pressure chamber 44 for the fluid to be measured for film formation. to form a film (not shown). Although details will be described later, the sensor diaphragm 41 according to this embodiment is constructed so that the bending moment due to film stress generated by film deposition is negligibly small.

If the sensor diaphragm 41 has a flat surface, no matter how finely it is divided, a bending moment due to film stress acts on each of them, and it is practically difficult to completely eliminate the influence of the diaphragm as a whole. is.
Instead of dividing the surface of the sensor diaphragm 41 on which the film is deposited, the inventor inclines this surface so that the direction in which the bending moment acts approaches the direction perpendicular to the sensor diaphragm, so that the sensor diaphragm 41 is I thought it would be harder to bend.
That is, an uneven structure is formed using inclined surfaces so that flat portions perpendicular to the thickness direction of the sensor diaphragm 41 on the surface of the sensor diaphragm 41 are minimized, thereby suppressing deflection due to film stress.

Here, first, simulations performed by the inventor to come up with the pressure sensor of the present invention will be described with reference to FIGS. 3 to 6. FIG.
FIG. 3A is a cross-sectional view showing a calculation model for simulating the mountain-shaped structure, FIG. 3B is a cross-sectional view showing an enlarged part of the mountain-shaped structure, and FIG. It is a perspective view which expands and shows a part.
On one surface of a flat plate 51 shown in FIG. 3, a large number of projecting portions 52 having a mountain-shaped cross section are formed side by side. The projecting portion 52 shown in FIG. 3 is a ridge extending in a direction perpendicular to the thickness direction of the flat plate 51 . Therefore, one surface of the flat plate 51 has a plurality of inclined surfaces 53 that are inclined with respect to the side surface of the projecting portion 52, in other words, the thickness direction of the flat plate 51 (the direction perpendicular to the other flat surface 51a of the flat plate 51). , 54 . In this embodiment, the other flat surface 51a of the flat plate 51 corresponds to the "surface parallel to the diaphragm" in the eighth aspect of the invention.
These inclined surfaces 53 and 54 are oriented upward, that is, to the outside of the flat plate 51 in FIG. If this flat plate 51 is used as the sensor diaphragm 41 , the inclined surfaces 53 and 54 are oriented inward of the pressure chamber 44 . Such protruding portions 52 can be formed by dry etching, for example. A deposited film 55 is formed on the inclined surfaces 53 and 54 .

In carrying out this simulation, similarly to the calculation of membrane division, a mountain-shaped structure was arranged on a flat plate 51 with a span of 5000 μm, and the height H of the mountain (protruding portion 52) was such that the total thickness T was 200 μm. and the width W were set and the calculation was performed. The thickness of the deposited film 55 was set to 10 μm.
When a simulation was performed, results as shown in FIGS. 4 and 5 were obtained. FIG. 4(A) shows the result of the diaphragm model adopting the chevron structure, and FIG. 4(B) shows the result of the flat diaphragm model. FIGS. 4(A) and 4(B) are displayed together with the deformation scale. In FIG. 4, the degree of displacement is represented by dot density. It can be seen that the peaks (protruding portions 52) of the mountain-shaped structure are 100 μm wide and 100 μm high, and the number of divisions is 50, but they are hardly bent.

FIG. 5 is a graph showing the displacement of the central portion of the sensor diaphragm calculated by changing the width W and height H of the mountain structure. In FIG. 3, the horizontal axis represents the number of divisions, and the vertical axis represents the displacement value when the shift of a flat flat plate of 200 μm is assumed to be 100%. When the structure is changed, not only when the membrane is changed, but also when the membrane is subjected to pressure, the deflection changes. It can be seen that the higher the height H of the crest, the higher the effect, and a sufficient effect can be obtained when the number of divisions is 50. The number of divisions of 50 corresponds to 100 μm, which is extremely practical in terms of processing.

The height of the crest is 25% (50 μm in FIG. 5) or less of the thickness of the diaphragm. In order to secure the slope angle, the pattern must be made small, which makes processing difficult, and deposition during the process results in a chevron structure. may be filled. If the peak height exceeds 75% (150 μm in FIG. 5), there is a possibility that strength problems will occur when subjected to excessive pressure such as atmospheric pressure. Therefore, it is desirable that the height of the projecting portion 52 is 25% to 75% of the thickness of the entire diaphragm.

FIG. 6 is obtained by plotting the slope angle on the horizontal axis in relation to the graph of FIG. The % on each line represents the peak height relative to the diaphragm. According to FIG. 5, the shift value is approximately 20% or less with respect to the flat structure when the slope angle is 45° or more, and is 50% or less when the slope angle is 20° or more. A steeper angle is advantageous, but if the angle exceeds 80°, the width of the peak becomes too small, making it difficult to process by photolithographic patterning and dry etching using a contact exposure apparatus. Therefore, the effect can be obtained if the slope angle of the protruding portion is 20° to 90°. A desirable bevel angle is 45° to 80°.

The “slant angle” referred to here is the angle indicated by symbol α in FIG. 7 . FIG. 7 is a schematic diagram showing the cross-sectional shape of the mountain-shaped protruding portion 52. As shown in FIG. The cross section shown in FIG. 7 is a cross section that includes the protruding end 52a of the protruding portion 52 and intersects the inclined surfaces 53 and 54 of the protruding portion 52. As shown in FIG. In this cross section, the angle α between the side corresponding to one inclined surface 53 and the side corresponding to the other inclined surface 54 and the plane (surface 51a) parallel to the sensor diaphragm 41 is at least 20° to 90°, 45° to 80° is desirable. In FIG. 7, an imaginary plane 51a is drawn by a two-dot chain line at a position intersecting the inclined planes 53 and 54 so that the angle α can be easily understood.

What was found in this calculation process is that there is no effect at all when the film is integrated or when slits are provided at the peaks of the peaks, but the effect appears when the slits are provided at the valleys. A structure in which a groove is provided at the top of a mountain to divide the film is a portion where the supplied raw material gas is most likely to collide, so the groove is likely to be filled with the film, making it difficult to obtain an effect. On the other hand, since it is originally difficult for the material gas to reach the valleys compared to the peaks, and the film thickness tends to be thin, a great effect can be obtained.
Furthermore, when adopting a mountain-shaped structure, as shown in FIG. 8, a slit (groove) 56 having a rectangular cross section can be formed in a valley between two adjacent mountains (projections 52). . The width W of the slit 56 is equal to or less than the mean free path of the raw material gas involved in film formation. By forming the slits 56 in this manner, it is expected that the number of raw material gas molecules that can reach the valley portion is drastically reduced, and a great effect can be obtained.
When the slits 56 are provided, the groove width W of the slits 56 is desirably set to 10 to 50 μm so that the space between the adjacent protrusions 52 is not filled with the deposited film, and the slit depth D is the groove width. Larger is desirable.

The projecting portion 52 can be configured as shown in FIGS. 9(A) to 9(C). The protruding portion 52 shown in FIG. 9A is formed so that the top portion 52b has a convex curved surface. Even in the case where the apex of the mountain is rounded to form a convex curved surface in this way, since the side surfaces of the protruding portion 52 are the inclined surfaces 53 and 54, it is equivalent to the case where the apex of the mountain is sharp. effect is obtained.
A projecting portion 52 shown in FIG. 9B is formed to have a hemispherical cross-sectional shape. Thus, even if the projection 52 has a hemispherical cross section, since the side surface of the projection 52 is a rounded inclined surface (the convex curved surface 57 having an arcuate cross section), the projection 52 may have a mountain shape. A similar effect can be obtained.
A protruding portion 52 shown in FIG. 9C is formed to have a trapezoidal cross-sectional shape. The trapezoid is a shape in which the top edge 58 is included in the tip surface of the projecting portion 52 . Even if the protrusion 52 has a trapezoidal cross-section, the side surfaces of the protrusion 52 are the inclined surfaces 53 and 54, so that an effect equivalent to that of the protrusion 52 having a mountain shape can be obtained.

Next, the principle of suppressing the bending of the sensor diaphragm by forming a plurality of inclined surfaces on the sensor diaphragm will be described with reference to FIG.
10(A) shows a cross-sectional view of a conventional structure, and FIG. 10(B) shows a cross-sectional view of the structure of the present invention.
A sensor diaphragm 61 shown in FIG. 10A has a plurality of protrusions 62 having a rectangular cross section. The deposited film 55 is formed on the flat protruding end faces 63 of the protruding portions 62 and the flat diaphragm surface 61a of the sensor diaphragm 61 exposed between the protruding portions 62 .
When the sensor diaphragm 61 is formed with the portions (the projecting end surface 63 and the diaphragm surface 61a) parallel to the sensor diaphragm 61 in this way, the membrane stress moment M acting on the sensor diaphragm 61 is divided into individual portions. However, when synthesized as a whole, it becomes a reasonable value.

However, if the surface of the sensor diaphragm 41 is formed of a plurality of inclined surfaces 53 and 54 as in the mountain-shaped structure shown in FIG. no longer horizontal. That is, unlike the case where the deposited film is formed on the flat sensor diaphragm 41 , the bending moment M acts in a direction inclined with respect to the planar direction of the sensor diaphragm 41 , in other words, in a direction close to perpendicular to the sensor diaphragm 41 . works.
In addition, since each film stress moment M cancels out the film stress moment M generated on the slope on the opposite side of the peak (protruding portion 52), the film stress moment M of the sensor diaphragm 41 as a whole is reduced.
As a result, the force for bending the sensor diaphragm 41 is reduced, and it is assumed that the sensor diaphragm 41 is less likely to bend.

3-10, the individual projections 52 are formed by ridges. However, the present invention is not bound by such a limitation, and the individual projections 52 may be pyramidal, conical, truncated pyramidal, or pyramidal, as shown in FIGS. It can be formed in various shapes such as a truncated cone shape and a hemispherical shape. These pyramids, cones, truncated pyramids, truncated cones, etc. correspond to the "pyramidal protrusions" in the present invention. A pyramid is a three-dimensional polygon formed by connecting each point on a side of a polygon on a plane to a point outside the plane. For this reason, it includes many pyramidal shapes, such as triangular pyramids and square pyramids.
The projecting portions 52 can be arranged in a grid pattern on the sensor diaphragm 41, or can be arranged in a hexagonal shape when viewed from inside the pressure chamber 44, or can be changed as appropriate.

The projecting portion 52 shown in FIG. 11 is formed in the shape of a square pyramid. The four side surfaces 64 of this quadrangular pyramid correspond to the "inclined surfaces" of the present invention.
The projecting portion 52 shown in FIG. 12 is formed in a conical shape. The peripheral surface 65, which is the side surface of the cone, corresponds to the "inclined surface" in the present invention.
The projecting portion 52 shown in FIG. 13 is formed in the shape of a truncated pyramid having a square bottom surface. The four side surfaces 66 of this truncated pyramid correspond to the "inclined surfaces" of the present invention.
The projecting portion 52 shown in FIG. 14 is formed in a truncated cone shape. The peripheral surface 67 of this truncated cone corresponds to the "inclined surface" in the present invention.
The projecting portion 52 shown in FIG. 15 is formed in a hemispherical shape. This hemispherical spherical surface 68 corresponds to the "inclined surface" in the present invention.

Calculation results when a simulation is performed with square pyramids arranged in a lattice are shown below.
16A and 16B are diagrams showing a three-dimensional calculation model. FIG. 16A is a perspective view showing a part of a diaphragm model 71 provided with a protrusion 52 made of a square pyramid, and FIG. It is a perspective view which expands and shows a part of 16(A). FIG. 16(C) is a perspective view showing a portion of the flat diaphragm model 72, and FIG. 16(D) is a perspective view showing an enlarged portion of FIG. 16(C).
The thickness of the diaphragm model 71 is 100 μm as a whole. The quadrangular pyramid serving as the projecting portion 52 has a bottom width of 50 μm×50 μm and a height of 50 μm. The square pyramids are arranged in a lattice. Since the diameter of the diaphragm model 71 is 6.5 mm, the number of radial arrangement (that is, the number of divisions) is 130. A flat diaphragm model 72 for comparison had a thickness of 63.2 μm for equal pressure sensitivity.

The results of this simulation are shown in FIG. FIG. 17A is a perspective view showing the degree of displacement of a diaphragm model 71 having a quadrangular pyramid by dot density, and FIG. 17B is a perspective view showing the degree of displacement of a flat diaphragm model 72 by dot density. It is a perspective view showing. FIG. 17 shows that the higher the dot density, the greater the displacement. The displacement of the central portion of the diaphragm model 71 is about 1/12 of the displacement of the diaphragm model 72, and it has been verified that a sufficient effect can be obtained even in the case of three dimensions.

Unlike the case where the surface of the sensor diaphragm 41 is divided into about 500 to 1000 parts, such protrusions 52 can be realized with realistic processing dimensions.
Therefore, according to this embodiment, a structure for reducing film stress is realized with realistic processing dimensions, and a pressure sensor is provided in which the zero point shift caused by the deposited film 55 of the sensor diaphragm 41 is minimized. can do.

Even when the protrusion 52 is formed in a pyramidal shape, a conical shape, a truncated pyramidal shape, a truncated cone shape, a hemispherical shape, or the like, the height is 25% to 75% of the total thickness of the sensor diaphragm 41. %.
Further, even when the projecting portion 52 is formed in the shape of a pyramid, a cone, a truncated pyramid, or a truncated cone, the angle between the inclined surfaces 53 and 54 and the plane parallel to the sensor diaphragm 41 is as shown in FIG. As indicated, they are at least 20° to 90°, preferably 45° to 80°, respectively.
Furthermore, even when the protrusions 52 are formed in a pyramidal or conical shape, a slit (groove) 56 having a rectangular cross section can be formed between two adjacent protrusions 52 . The slit 56 also has a groove width W of 10 to 50 μm as shown in FIG. 8, and it is desirable that the depth D is larger than the groove width.

DESCRIPTION OF SYMBOLS 1... Capacitance-type diaphragm vacuum gauge, 13... Sensor chip (pressure sensor), 41... Sensor diaphragm (diaphragm), 44... Pressure chamber, 52... Projection part, 53, 54... Inclined surface, 56... Slit (groove) , 64... Side surface, 65, 67... Peripheral surface, 68... Spherical surface.

Claims (8)

A fluid to be measured for film formation is introduced into a pressure chamber of a pressure sensor whose wall is partially formed by a diaphragm, a deposited film is formed on the diaphragm, and a film stress is generated when the deposited film contracts. A method for suppressing deflection of a diaphragm, comprising:
forming an uneven structure using a large number of inclined surfaces on one surface of the diaphragm that is in contact with the fluid to be measured;
A deposited film is formed on the inclined surface, and when film stress is generated by the deposited film, a bending moment acts on the inclined surface in a direction nearly perpendicular to the diaphragm, and acts on the inclined surface. A method for suppressing deflection of a pressure sensor diaphragm, comprising canceling out a bending moment and a bending moment acting on an adjacent inclined surface. In the method for suppressing deflection of the pressure sensor diaphragm according to claim 1,
The slanted surface is formed on the side surface of a conical or trapezoidal cross section protruding portion that cancels the bending moments generated on the slanted surfaces facing each other, or on the rounded slanted surfaces that face each other. A method for suppressing deflection of a diaphragm for a pressure sensor, characterized in that the bending moment cancels out the spherical surface of the hemispherical projection. A pressure sensor diaphragm used in the method for suppressing deflection of a pressure sensor diaphragm according to claim 1,
The diaphragm constitutes a part of the wall of the pressure chamber into which the fluid to be measured that can form the deposited film is introduced,
One surface of the diaphragm that is in contact with the fluid to be measured is inclined with respect to the thickness direction of the diaphragm and pressurized so that a bending moment due to the deposited film acts in a direction that is nearly perpendicular to the diaphragm. 1. A diaphragm for a pressure sensor, characterized in that a concave-convex structure is formed using a plurality of inclined surfaces directed inward of a chamber. In the pressure sensor diaphragm according to claim 3,
A diaphragm for a pressure sensor, wherein the inclined surface is a side surface of a conical protruding portion protruding from the one surface. In the pressure sensor diaphragm according to claim 4,
A diaphragm for a pressure sensor, wherein the pyramidal protrusion is formed of a large number of square pyramids, and the square pyramids adjacent to each other are formed in close contact with each other. In the pressure sensor diaphragm according to claim 3,
A diaphragm for a pressure sensor, wherein the inclined surface is an inclined side surface of a protrusion having a trapezoidal cross section and protruding from the one surface. In the pressure sensor diaphragm according to claim 5,
A diaphragm for a pressure sensor, wherein the inclined surface is a spherical surface of a hemispherical protruding portion protruding from the one surface. In the pressure sensor diaphragm according to any one of claims 4 to 7,
The height of the protrusion is 25% or more and 75% or less of the thickness of the entire diaphragm,
In a cross section that includes the projecting end of the projecting portion and intersects with the side surfaces, an angle formed between a side corresponding to one side surface and a plane parallel to the diaphragm and a side corresponding to the other side surface and a plane parallel to the diaphragm is Each is 45° or more and 80° or less,
A diaphragm for a pressure sensor, wherein the distance between the projections is at least 100 times the particle size of the substance that causes the deposited film.

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