JP2005337956A - Physical quantity sensor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a physical quantity sensor satisfactory for detecting physical quantities, such as pressure and flow rate of fluid with high yield. <P>SOLUTION: On a silicon substrate 10, a silicon oxide film 12 is formed on one main surface and a silicon nitride film 16 is formed by way of the silicon oxide film 14 on the other main surface. On the film 12, a resistive member 18, consisting of semiconductor and the like exhibiting a piezoresistive effect for example, is formed. Instead of the resistive member 18, an insulation member, showing piezoelectric effect or a conductive member constituting capacitance and capable of displacing may be provided. Under the resistive member 18, a penetration hole 20 is formed so as to penetrate the films 14, 16, the substrate 10 and the film 12, and to make a part of the resistance member 18 lift in the air. For forming the penetration hole 20, after forming a stress-relaxing groove in the film 16 surrounding the planned position for forming the hole 20, an opening corresponding to the hole 20 is formed on the layers of films 14, 16 and an opening is formed in the substrate 10 through wet etching using the layers as a mask. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a physical quantity sensor suitable for detecting a physical quantity such as a pressure and a flow rate of a fluid, and a manufacturing method thereof.

  Conventionally, as a physical quantity sensor to which silicon micromachining technology is applied, a diaphragm type sensor as shown in FIG. 30 is known (for example, see Patent Document 1).

In FIG. 30, a silicon nitride film 2 is formed on one main surface of the silicon substrate 1, and a function made of a resistor such as platinum (showing a piezoresistance effect) is formed on the upper surface of the silicon nitride film 2. A thin film 3 is formed. The functional thin film 3 is formed to have, for example, a folded pattern, and electrode terminals 3a and 3b are provided at one end and the other end, respectively. The silicon substrate 1 is provided with an opening 1 </ b> A below the functional thin film 3. A compensation thin film 4 for canceling the residual stress of the functional thin film 3 is provided on the lower surface of the silicon nitride film 2.
JP-A-5-231970

  According to the above-described prior art, since the deformation or strain generated in the portion in the opening 1A in the silicon nitride film 2 is converted into an electric signal by the functional thin film 3, for example, when detecting the gas pressure, the functional thin film 3 There is a problem that it is impossible to detect a small pressure that does not cause deformation in the silicon nitride film portion to which is fixed.

  An object of the present invention is to provide a novel physical quantity sensor capable of detecting a physical quantity such as pressure and flow rate of a fluid with high sensitivity and a method for producing the same.

The physical quantity sensor according to the present invention is:
A semiconductor substrate;
An insulating film formed to cover one main surface of the semiconductor substrate;
A sensor member formed on the insulating film, and a through hole is provided in the laminated body of the semiconductor substrate and the insulating film so that a part of the sensor member is floated in the air. As the sensor member, a resistive member such as a metal or a semiconductor that exhibits a piezoresistance effect, an insulating member such as a crystal that exhibits a piezoelectric effect, or a displaceable conductive member that forms a capacitance with an opposing conductor is used. it can.

  According to the physical quantity sensor of the present invention, since a part of the sensor member is floated in the air at the position of the through hole, the contact area of the sensor member with respect to the fluid is increased by passing the fluid (gas or liquid) through the through hole. In addition, physical quantities such as fluid pressure and flow rate can be detected with high sensitivity.

  In the physical quantity sensor according to the present invention, the sensor member has an electrode portion connected to a connected portion of the semiconductor substrate through a connection hole provided in the insulating film, and the sensor member is insulated from the sensor member by the electrode portion. You may fix to the said insulating film and the said semiconductor substrate in the state spaced apart from the film | membrane. In this case, the sensor member is separated from the insulating film and supported by the electrode portion, and the contact area with the fluid is further increased, so that the detection function is improved.

The manufacturing method of the first physical quantity sensor according to the present invention is as follows:
Forming an insulating film covering one main surface of the semiconductor substrate;
Forming a sensor member on the insulating film;
Forming a protective film covering the sensor member on the insulating film;
In the state where the sensor member and the insulating film are covered with the protective film, an anisotropic selective etching process is performed on the other main surface of the semiconductor substrate to correspond to a part of the sensor member and to the insulating film. Forming a reaching opening in the semiconductor substrate;
An opening that penetrates the insulating film continuously to the opening of the semiconductor substrate by selectively etching the insulating film using the semiconductor substrate as a mask in a state where the sensor member and the insulating film are covered with the protective film. Forming a part;
And removing the protective film to float a part of the sensor member in the air through the opening of the insulating film.

  According to the first physical quantity sensor manufacturing method, after the sensor member is formed on the insulating film, the opening is formed in the semiconductor substrate in a state where the sensor member and the insulating film are covered with the protective film, or the insulating film is opened. Since the portion is formed, the sensor member can be prevented from being damaged. In addition, since the insulating film is used as an etching stopper film when forming the opening of the semiconductor substrate, variations in the shape and size of the opening can be suppressed.

The manufacturing method of the second physical quantity sensor according to the present invention is as follows:
Forming an insulating film covering one main surface of the semiconductor substrate;
Performing an anisotropic selective etching process on the other main surface of the semiconductor substrate to form an opening reaching the insulating film in the semiconductor substrate;
Forming a sensor member on the insulating film so as to overlap the opening of the semiconductor substrate through the insulating film;
Forming a protective film covering the sensor member on the insulating film;
An opening that penetrates the insulating film continuously to the opening of the semiconductor substrate by selectively etching the insulating film using the semiconductor substrate as a mask in a state where the sensor member and the insulating film are covered with the protective film. Forming a part;
And removing the protective film to float a part of the sensor member in the air through the opening of the insulating film.

  According to the second physical quantity sensor manufacturing method, after the opening is formed in the semiconductor substrate, the sensor member is formed on the insulating film, and the opening is formed in the insulating film in a state where the sensor member and the insulating film are covered with the protective film. Therefore, the sensor member can be prevented from being damaged. In addition, since the insulating film is used as an etching stopper film when forming the opening of the semiconductor substrate, variations in the shape and size of the opening can be suppressed.

  In the first or second physical quantity sensor manufacturing method, in the step of forming the insulating film, a stack in which the first and second insulating films made of different materials are stacked in this order is formed as the insulating film. In the step of forming the sensor member, a connection hole corresponding to the connected portion of the semiconductor substrate is formed in the stacked layer, and then the electrode portion is connected to the connected portion through the connecting hole. After the step of forming the sensor member on the second insulating film and removing the protective film, the second insulating film is removed and a part of the sensor member is removed from the first insulating film. You may make it space apart. In this way, it is possible to obtain a physical quantity sensor having a configuration in which the sensor member is separated from the first insulating film and supported by the electrode portion.

The manufacturing method of the third physical quantity sensor according to the present invention is as follows:
Preparing a semiconductor substrate having one main surface covered with an insulating film and the other main surface covered with an etching stopper film;
Forming a sensor member on the insulating film;
An opening corresponding to a part of the sensor member and exposing a part of the semiconductor substrate is formed in the insulating film by an isotropic selective etching process, and a part of the sensor member is formed in the opening of the insulating film. The process of floating in the air at
An anisotropic selective etching process using the insulating film as a mask is performed on one main surface of the semiconductor substrate so that an opening continuous to the opening of the insulating film and reaching the etching stopper film is formed in the semiconductor substrate. Forming, and
Removing the etching stopper film at least in a part corresponding to the opening of the semiconductor substrate to expose the opening of the semiconductor substrate on the other main surface side of the semiconductor substrate.

  According to the third physical quantity sensor manufacturing method, since the other main surface of the semiconductor substrate is covered with the etching stopper film before the sensor member is formed, the process of covering with the etching stopper film is performed after the sensor member is formed. In comparison, damage to the sensor member can be suppressed. Further, by using the etching stopper film when forming the opening in the semiconductor substrate, variation in the shape and size of the opening can be suppressed.

  In the third physical quantity sensor manufacturing method, in the step of preparing the semiconductor substrate, the insulating film is formed by stacking first and second insulating films made of different materials from each other in this order, In the step of forming the sensor member, after forming a connection hole corresponding to the connected portion of the semiconductor substrate in the stacked layer, the sensor has an electrode portion connected to the connected portion through the connection hole. After the step of forming a member on the second insulating film and removing a part of the etching stopper film, the second insulating film is removed and a part of the sensor member is replaced with the first insulating film. You may make it leave | separate from. In this way, it is possible to obtain a physical quantity sensor having a configuration in which the sensor member is separated from the first insulating film and supported by the electrode portion.

  According to the present invention, it is possible to realize a physical quantity sensor that can detect a physical quantity such as a pressure and a flow rate of a fluid with high sensitivity, and to obtain an effect of manufacturing such a physical quantity sensor with a high yield.

  FIG. 1 shows a physical quantity sensor according to an embodiment of the present invention. For example, a silicon oxide film (insulating film) 12 is formed on one main surface of a silicon substrate (semiconductor substrate) 10 made of single crystal silicon, and a silicon oxide film 14 is formed on the other main surface of the substrate 10. A silicon nitride film 16 is formed therethrough. A resistance member (sensor member) 18 is formed on the silicon oxide film 12 in accordance with a predetermined folding pattern, and electrode portions 18a and 18b are provided on one end and the other end of the resistance member 18, respectively. The resistance member 18 is fixed to the silicon oxide film 12 at a portion having a predetermined length from the electrode portion 18a, a portion having a predetermined length from the electrode portion 18b, and each folded portion.

  A through-hole 20 is provided in the stacked body of the substrate 10, the silicon oxide films 12 and 14, and the silicon nitride film 16 so as to be positioned below the resistance member 18. The through hole 20 is rectangular as an example, but may be square, circular, elliptical, or the like. The resistance member 18 is in a state in which a straight line portion extending from the electrode portion 18a to the folded portion, a straight line portion for each successive folded portion, and a straight portion extending from the electrode portion 18b to the folded portion are floated in the air through the through hole 20. It has become.

  In addition, although the example in which the size of the through hole 20 is small inside the respective folded portions of the resistance member 18 is shown, the size of the through hole 20 may be larger than the respective folded portions of the resistance member 18. If it does in this way, the resistance member 18 will be fixed to the silicon oxide film 12 only in two places, the electrode part 18a and its vicinity part, and the electrode part 18b and its vicinity part.

  As the material of the resistance member 18, a metal, a semiconductor, or the like that exhibits a piezoresistance effect can be used. For example, polysilicon or polycide (a laminate in which a silicide of a refractory metal such as W, Mo, Ti is stacked on polysilicon) Can be used. Further, as the sensor member, an insulating member such as a crystal showing a piezoelectric effect may be used instead of the resistance member 18.

  The physical quantity sensor shown in FIG. 1 can be used as a piezoelectric microphone as an example. That is, when a sound wave (air vibration) is supplied to the through-hole 20 in the direction of arrow A, the resistance member 18 is distorted and changes in resistance according to the amplitude (pressure) and frequency (pitch) of the sound wave. A corresponding electrical signal (audio signal) can be obtained. As another example, the pressure, flow rate, and the like of the fluid (for example, breathing air) supplied to the through hole 20 can be detected.

  FIG. 2 shows a modification of the sensor member with respect to the physical quantity sensor of FIG. 1, and the same parts as those in FIG. In FIG. 2, the laminated structure including the substrate 10 and the films 14 and 16 under the film 12 is the same as that in FIG.

  A feature of the example of FIG. 2 is that conductive members 22 and 24 that extend in parallel with each other and constitute a capacitance are provided on the silicon oxide film 12 instead of the resistance member 18. The conductive members 22 and 24 are both made of a conductive material such as metal or semiconductor. The silicon oxide film 12 is provided with an opening 12A constituting the through hole 20 (FIG. 1).

  An electrode portion 22 a is provided at one end of the conductive member 22. A portion of the conductive member 22 having a predetermined length from the electrode portion 22a is fixed to the silicon oxide film 12, a portion ahead of the fixed portion extends above the opening 12A, and the extended end is a free end. . For this reason, the portion of the conductive member 22 extending on the opening 12A can be displaced according to the pressure of the fluid passing through the opening 12A.

  An electrode portion 24 a is provided at one end of the conductive member 24. A portion of the conductive member 24 having a predetermined length from the electrode portion 24 a is fixed to the silicon oxide film 12, a portion ahead of the fixing portion extends above the opening 12 </ b> A, and an extended end is fixed to the silicon oxide film 12. Has been. For this reason, the portion of the conductive member 24 extending on the opening 12A can be made substantially undisplaceable according to the pressure of the fluid passing through the opening 12A. Accordingly, the capacitance between the conductive members 22 and 24 changes according to the pressure of the fluid passing through the opening 12A, and the pressure and the like can be detected by detecting the change in the capacitance.

  The conductive member 24 may be formed so as to be fixed to the silicon oxide film 12 as a whole from one end to the other end along the one side 12a of the opening 12A, for example. In this way, the displacement of the conductive member 24 can be more reliably suppressed.

  3 to 10 show a first manufacturing method of the physical quantity sensor of FIG. In the process of FIG. 3, the silicon oxide film 12 is formed so as to cover one main surface, and the silicon oxide film 14 and the silicon nitride film 16 are formed in this order from the single crystal silicon so as to cover the other main surface. A silicon substrate 10 is prepared. The silicon oxide film 12 serves as a base film for the resistance member 18 shown in FIG. 4, and the stack of the silicon oxide film 14 and the silicon nitride film 16 is etched when an opening is formed in the substrate 10 by a selective etching process. It is used as a mask.

When the silicon oxide film 14 and the silicon nitride film 16 are formed, for example, after the silicon oxide film 14 is formed by a thermal oxidation method, a low pressure CVD (chemical vapor deposition) method is formed on the silicon oxide film 14. Thus, the silicon nitride film 16 is formed. In the thermal oxidation process for forming the silicon oxide film 14, the processing conditions are as an example.
Gas flow rate: N ₂ / O ₂ = 18/10 [l / min]
Substrate temperature: 1025 [° C.]
It can be. In the low-pressure CVD process for forming the silicon nitride film 16, the processing conditions are as an example.
Gas flow _{rate: SiH 2 Cl 2 / NH 3} ( or _{NH 3 + N 2) = 0.05~6} /
0.5-6 [l / min]
Reaction chamber pressure: 60 [Pa]
Substrate temperature: 700 to 800 [° C.]
It can be.

  The silicon oxide film 12 can be formed by a thermal oxidation method or a CVD method after forming a stack of the silicon oxide film 14 and the silicon nitride film 16. As an example, the thicknesses of the silicon oxide film 12, the silicon oxide film 14, and the silicon nitride film 16 can be about 100 nm, 300 nm, and 200 nm, respectively.

  In the process of FIG. 4, the resistance member 18 is formed on the silicon oxide film 12. For this purpose, a resistance material constituting the member 18 is deposited on the surface of the silicon oxide film 12 by sputtering or the like, and then the deposited layer is folded back by photolithography and dry etching as shown in FIG. Then, patterning may be performed.

  In the process of FIG. 5, a protective film 30 such as a polyimide resin is formed on the silicon oxide film 12 so as to cover the resistance member 18. The protective film 30 protects the resistance member from various subsequent processes and serves as an etching stopper when the silicon oxide film 12 is etched.

  In the process of FIG. 6, the silicon substrate 10 of FIG. 5 is turned over. Then, a stress relaxation groove 16A is formed in a part of the silicon nitride film 16 by selective dry etching using the resist layer 32 as a mask.

  The stress relaxation groove 16A has a mask shape change due to concentration of film stress at the corner of the mask opening when the stacked layer of the silicon oxide film 14 and the silicon nitride film 16 is used as an etching mask, or the silicon nitride film 16 It is provided in order to prevent cracks from occurring. FIG. 11 shows an example of a planar pattern of the stress relaxation grooves 16A. In this example, the stress relaxation grooves 16A are formed according to a frame-like pattern surrounding the mask opening 36A shown in FIG. 6 corresponds to a cross section taken along line A-A ′ of FIG. 11.

  12 to 14 show first to third modifications of the stress relaxation groove. In these drawings, the same parts as those in FIGS. 6 and 11 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The example of FIG. 12 shows a rectangular stress relaxation groove that surrounds the mask opening 36A in the rectangular silicon region surrounded by the scribe region 26 and that the four sides of the mask opening 36A are non-parallel. 16A is formed on the silicon nitride film 16. The width W of the groove 16A can be 10 [μm] or more, and the distance D between one corner of the mask opening 36A and one side of the groove 16A can be 100 [μm] or more.

  In the example of FIG. 13, an annular stress relaxation groove 16A is formed so as to surround the mask opening 36A. In the example of FIG. 14, four stress relaxation grooves 16 </ b> A to 16 </ b> D are formed so as to surround the mask opening 36 </ b> A and correspond to the four corners of the mask opening 36 </ b> A, respectively.

  In the example of FIGS. 12 to 14, since one or a plurality of stress relaxation grooves are provided around the mask opening 36 </ b> A, there are stress relaxation grooves in the vicinity of the four corners of the mask opening 36 </ b> A. . Therefore, the concentration of the film stress on the corner can be suppressed, and the mask shape abnormality and crack abnormality can be prevented.

In the dry etching process for forming the stress relaxation grooves such as 16A, when the parallel plate type plasma etching method is used, the processing conditions are, for example,
Gas used: SF ₆ / He
The pressure in the reaction chamber can be around 0.50 [Torr]. In addition, when the downflow method is used, the processing conditions are as an example,
Gas used: SF ₆ / He
The pressure in the reaction chamber may be around 0.20 [Torr]. After the dry etching process, the resist layer 32 is removed by a known method.

  In the step of FIG. 7, a resist 34 having a hole corresponding to a desired mask opening 36A is formed on the silicon nitride film 16 by photolithography so as to cover the stress relaxation groove 16A. Then, a mask opening 36A is formed in a part of the laminated layer of the silicon oxide film 14 and the silicon nitride film 16 with a rectangular planar pattern as shown in FIG. 11 by selective dry etching using the resist layer 34 as a mask. The remaining portion of the stack of films 14 and 16 is left as an etching mask 36.

In the dry etching process for forming the mask opening 36A, when the parallel plate type plasma etching method is used, the processing conditions are, for example,
Gas used: CF ₄ / O ₂
The pressure in the reaction chamber can be around 1.0 [Torr]. In addition, when the magnetron type RIE (reactive ion etching) method is used, the processing conditions are, for example,
Gas used: CF ₄ / CHF ₃ / N ₂
The pressure in the reaction chamber may be around 0.25 [Torr]. Furthermore, when the narrow electrode RIE method is used, the processing conditions are, for example,
Gas used: CF ₄ / CHF ₃ / He
The pressure in the reaction chamber may be around 0.15 [Torr]. After the dry etching process, the resist layer 34 is removed by a known method. Note that the selective dry etching process of FIG. 7 may be performed before the selective dry etching process of FIG.

  In the process of FIG. 8, the silicon substrate 10 is selectively and anisotropically etched using the etching mask 36 and an alkaline etchant to form the substrate opening 10A. The substrate opening 10 </ b> A is formed so as to reach the silicon oxide film 12.

  As the alkaline etching solution, TMAH or KOH (potassium hydroxide) can be used, and the concentration can be about 25 [%] and the temperature of the solution can be about 90 [° C.]. Since the roughness of the etched surface of silicon increases as the concentration increases, it is preferable that the concentration be slightly lower. However, if the concentration is too low, the etching rate is lowered and the processing time is lengthened.

  In the wet etching process of FIG. 8, since the stress relaxation grooves 16A are provided in the etching mask 36 in the process of FIG. 7, no abnormal mask shape or abnormal cracks occur, and the rectangular substrate corresponding to the mask opening 36A. An opening 10A is obtained. Further, in the wet etching process at this time, since the resistance member 18 and the silicon oxide film 12 are covered with the protective film 30, damage can be avoided.

  In the process of FIG. 9, for example, an opening 12A corresponding to the substrate opening 10A is formed by isotropic wet etching using dilute hydrofluoric acid + buffered hydrofluoric acid as an etchant and using the substrate 10 and the silicon nitride film 16 as a mask. A silicon oxide film 12 is formed. At this time, the protective film 30 serves as an etching stopper. Further, the exposed portion of the silicon oxide film 14 (such as a portion corresponding to the stress relaxation groove 16A) is slightly etched. As the etching process, a dry etching process or an anisotropic etching process may be used.

  In the process of FIG. 10, the silicon substrate 10 of FIG. 9 is inverted so that the resistance member 18 is on top. Then, the protective film 30 is removed by chemical treatment or the like. As a result, a part of the resistance member 18 is floated in the air at the opening 12A (FIG. 9) provided in the silicon oxide film 12. The through hole 20 shown in FIG. 1 includes a mask opening 36A (FIG. 7) provided in the etching mask 36, a substrate opening 10A (FIG. 8) provided in the substrate 10, and an opening provided in the silicon oxide film 12. 12A (FIG. 9). If the stacked layers of the silicon oxide film 14 and the silicon nitride film 16 are left, it is useful for preventing the substrate 10 from warping and increasing the strength.

  According to the first manufacturing method described above, since the resistance member 18 is protected by the protective film 30, damage to the resistance member 18 can be prevented during processing such as etching. In addition, since the stress relaxation groove 16A is provided in the etching mask 36, abnormal shapes and abnormal cracks of the mask 36 can be prevented. Furthermore, since the silicon oxide film 12 is used as an etching stopper film, variations in the shape and size of the substrate opening 10A can be suppressed. Therefore, the physical quantity sensor of FIG. 1 can be manufactured with a high yield.

  FIGS. 15 to 17 show a second manufacturing method of the physical quantity sensor of FIG. 1, and the same parts as those in FIGS. The second manufacturing method is different from the first manufacturing method described above in that the substrate opening 10 </ b> A is formed prior to the formation of the resistance member 18.

  In the step of FIG. 15, after preparing the silicon substrate 10 similar to that described above with reference to FIG. 3, the stress relaxation groove is formed by stacking the silicon oxide film 14 and the silicon nitride film 16 in the same manner as described above with reference to FIGS. A substrate opening 10A is formed in the silicon substrate 10 by anisotropic selective wet etching using an etching mask 36 having 16A and a mask opening 36A. The substrate opening 10 </ b> A is formed so as to reach the silicon oxide film 12.

  In the step of FIG. 16, the resistance member 18 is formed on the silicon oxide film 12 in the same manner as described above with reference to FIG. In the step of FIG. 17, the protective film 38 is formed on the silicon oxide film 12 so as to cover the resistance member 18 in the same manner as described above with reference to FIG. Then, after the opening 12A is formed in the silicon oxide film 12 in the same manner as described above with reference to FIGS. 9 and 10, the protective film 38 is removed.

  According to the second manufacturing method described above, the physical quantity sensor of FIG. 1 can be manufactured with a high yield in the same manner as described above with respect to the first manufacturing method. In the first or second manufacturing method described above, another sensor member may be formed instead of the resistance member 18. In addition, when forming the conductive members 22 and 24 of FIG. 2 as the sensor member, a material or pattern suitable for the conductive members 22 and 24 may be selected.

  FIG. 18 shows a physical quantity sensor according to another embodiment of the present invention. The same parts as those in FIG. The physical quantity sensor in FIG. 18 is different from the physical quantity sensor in FIG. 1 in that the resistance member 18 is formed on the silicon nitride film 16. The fixed state of the resistance member 18 with respect to the silicon nitride film 16 is the same as that described above with reference to the silicon oxide film 12 in FIG.

  The physical quantity sensor shown in FIG. 18 can detect voice-electrical conversion, fluid pressure, flow rate, and the like in the same manner as the physical quantity sensor shown in FIG. Instead of the resistance member 18, another sensor member can be used.

  FIG. 19 shows a modification of the sensor member with respect to the physical quantity sensor of FIG. 18, and the same parts as those in FIG. In FIG. 19, the laminated structure including the film 14 under the film 16, the substrate 10 and the film 12 is the same as that in FIG.

  The feature of the example of FIG. 19 is that the conductive members 22 and 24 constituting the capacitance are formed on the silicon nitride film 16 in the same manner as described above with reference to FIG. The fixed state of the conductive members 22 and 24 with respect to the silicon nitride film 16 is the same as that described above with reference to the silicon oxide film 12 in FIG. Since the conductive member 22 is disposed so as to be displaceable according to the pressure and the like, and the conductive member 24 is disposed so as not to be substantially displaceable according to the pressure and the like, the capacitance between the conductive members 22 and 24 is changed. By detecting it, it is possible to detect the pressure and the like.

  20 to 24 show a method of manufacturing the physical quantity sensor of FIG. In the process of FIG. 20, after preparing the silicon substrate 10 similar to that described above with reference to FIG. 3, the resistance member 18 is formed on the silicon nitride film 16 in the same manner as described above with reference to FIG. The silicon oxide film 12 serves as an etching stopper film when forming the substrate opening 10A in the step of FIG.

  In the process of FIG. 21, the stress relaxation grooves 16A are formed in the silicon nitride film 16 by selective dry etching using the resist layer 40 as a mask in the same manner as described above with reference to FIG. Thereafter, the resist layer 40 is removed.

  In the step of FIG. 22, a resist layer 42 having a hole corresponding to a desired mask opening 36A is formed on the silicon nitride film 16 by photolithography so as to cover the stress relaxation groove 16A and the resistance member 18. Then, a mask opening 36A is formed in a part of the stack of the silicon oxide film 14 and the silicon nitride film 16 by an isotropic selective wet (or dry) etching process using the resist layer 42 as a mask. The remaining part of the stack is left as an etching mask 36. At this time, a part of the resistance member 18 is floated in the air at the mask opening 36A. Thereafter, the resist layer 42 is removed. In addition, as the combination of the material of the resistance member 18 and the etchant (or etching gas), a material that does not etch the resistance member 18 is selected. The same applies to the etching process of FIGS.

  23, the substrate opening 10A is formed in the silicon substrate 10 by anisotropic selective wet etching using the etching mask 36 in the same manner as described above with reference to FIG. The substrate opening 10 </ b> A is formed so as to reach the silicon oxide film 12.

  In the step of FIG. 24, the protective film 44 is formed from a polyimide resin or the like so as to cover the silicon oxide film 12. Then, after the opening 12A is formed in the silicon oxide film 12 in the same manner as described above with reference to FIGS. 9 and 10, the protective film 44 is removed.

  20 to 24, since the silicon oxide film 12 for the etching stopper is formed before the resistor member 18 is formed, the silicon oxide film 12 is formed after the resistor member 18 is formed. In comparison, the resistance member 18 can be prevented from being damaged. In addition, since the stress relaxation groove 16A is provided in the etching mask 36, abnormal shapes and abnormal cracks of the mask 36 can be prevented. Furthermore, since the silicon oxide film 12 is used as an etching stopper film, variations in the shape and size of the substrate opening 10A can be suppressed. Therefore, the physical quantity sensor of FIG. 18 can be manufactured with a high yield.

  25 to 27 show a method of manufacturing a physical quantity sensor according to still another embodiment of the present invention, and the same parts as those in FIGS. 25 to 27, the deposition configuration of the film 12 under the substrate 10 is the same as that shown in FIGS.

In the process of FIG. 25, as an example, the connected portion 48 formed of an N ⁺ -type impurity doped region is formed on the main surface of the P-type semiconductor substrate 10. The connected portion 48 is connected to a sensor circuit (not shown) formed in another portion of the substrate 10. Next, the silicon oxide film 14 and the silicon nitride film 16 are sequentially formed on the main surface of the substrate 10 so as to cover the connected portion 48. Then, a connection hole 36a reaching the connected portion 48 is formed in the silicon oxide film 14 and the silicon nitride film 16 by photolithography and dry etching.

  Thereafter, a polysilicon layer, for example, is deposited on the silicon nitride film 16 so as to cover the connection hole 36a by the CVD method or the like. The polysilicon layer is doped with a conductivity-determining impurity during or after the deposition to reduce the resistance. By patterning the polysilicon layer according to a predetermined pattern by photolithography and dry etching, a resistance member 18 composed of the remaining portion of the polysilicon layer is formed. The resistance member 18 is formed so as to have an electrode portion 18a connected to the connected portion 48 through the connection hole 36a.

  In the step of FIG. 26, a mask opening 36A is formed by selective etching in a part of the stack of the silicon oxide film 14 and the silicon nitride film 16 in the same manner as described above with reference to FIGS. The remaining portion is left as an etching mask 36. As a result, a part of the resistance member 18 is floated in the air at the mask opening 36A. Thereafter, the substrate opening 10A is formed by anisotropic selective wet etching using the etching mask 36 in the same manner as described above with reference to FIG.

  In the step of FIG. 27, the opening 12A continuous to the substrate opening 10A is formed in the silicon oxide film 12 on the lower surface of the substrate 10 in the same manner as described above with reference to FIG. 24, and the through hole made of the openings 12A, 10A, 36A is formed. Get 20. Then, the silicon nitride film 16 (FIG. 26) is removed in the etching process, and a part of the resistance member 18 is separated from the silicon oxide film 14. The other electrode portion 18b (FIG. 18) of the resistance member 18 is also formed in the same manner as the electrode portion 18a described above.

  The physical quantity sensor shown in FIG. 27 has an advantage that the detection function is improved because the contact area with the fluid passing through the through hole 20 is increased.

  FIG. 28 shows a modification of the resistance member configuration with respect to the physical quantity sensor of FIG. 27, and the same parts as those of FIG.

  In the physical quantity sensor of FIG. 28, the resistance member 18 is made of doped polysilicon or the like as described above with reference to FIG. 27, but the configuration of the electrode portion 18a is different from that of FIG. That is, in the process corresponding to FIG. 25, before depositing the polysilicon layer, the inside of the connection hole 36a is covered and a TiN film (adhesion film) is stacked on the Ti (titanium) film (resistance reduction film) by sputtering or the like. After forming the TiN / Ti stack, a W (tungsten) layer is deposited on the TiN / Ti stack by a blanket CVD method or the like so as to fill the connection hole 36a. Then, the Ti layer / Ti stack 18A and the W plug layer 18B are left in the connection hole 36a by etching back the W layer and the TiN / Ti stack until the silicon nitride film 16 is exposed.

  Next, a new TiN / Ti stack 18C is formed on the silicon nitride film 16 by a sputtering method or the like so as to cover the TiN / Ti stack 18A and the W plug layer 18B in the connection hole 36a, and then the TiN / Ti stack 18C. A doped polysilicon layer is formed on the same as described above. Then, the laminated body of the TiN / Ti laminated layer 18C and the doped polysilicon layer is subjected to the patterning process in the same manner as described above with reference to FIG. 25 to form the resistance member 18 having the TiN / Ti laminated layer 18C on the bottom surface. Thereafter, when the formation process of the openings 36A, 10A, 12A and the removal process of the silicon nitride film 16 are performed in the same manner as described above with reference to FIGS. 26 and 27, the sensor configuration shown in FIG. 28 is obtained.

  The etch back of the W layer and the TiN / Ti stack may be stopped when the TiN / Ti stack is exposed, and the formation of a new TiN / Ti stack 18C may be omitted. In this case, the TiN / Ti stack exposed by etch back can be used in place of the TiN / Ti stack 18C.

  FIG. 29 shows a modified example of the sensor member arrangement with respect to the physical quantity sensor of FIG. 27, and the same parts as those of FIG.

  In the physical quantity sensor of FIG. 29, the resistance member 18 is made of doped polysilicon as described above with reference to FIG. 27, but the resistance member 18 is provided on the main surface of the substrate 10 on the silicon oxide film 12 side. Is different. That is, in the process corresponding to FIG. 3, after the silicon oxide film 12 is formed, the connected portion 48 is formed on the main surface of the substrate 10 by a selective ion implantation method or the like (the formation of the connected portion 48 is performed by silicon oxide). It may be performed before the film 12 is formed). Then, after the silicon nitride film 17 is formed so as to cover the silicon oxide film 12, a connection hole 36a reaching the connected portion 48 is formed in the stack of the silicon oxide film 12 and the nitrogen silicon film 17 in the same manner as described above with reference to FIG. To do.

  Next, a doped polysilicon layer is formed in the same manner as described above with reference to FIG. 25, and the resistance member 18 having the electrode layer 18a connected to the connected portion 48 through the connection hole 36a is formed by patterning. . Thereafter, the protective film 30 forming process, the openings 36A, 10A, and 12A forming process and the protective film 30 removing process are performed in the same manner as described above with reference to FIGS. Then, when the silicon nitride film 17 is removed, the sensor configuration of FIG. 29 is obtained. Note that the sensor configuration of FIG. 29 can be manufactured by applying the manufacturing method of FIGS.

  In the sensor configuration described above with reference to FIGS. 25 to 29, another sensor member may be used instead of the resistance member 18. For example, a capacitive sensor member as shown in FIG. 2 or 19 is used. May be.

It is a partial cross section perspective view which shows the physical quantity sensor which concerns on one Embodiment of this invention. It is a partial cross section perspective view which shows the modification of a sensor member regarding the physical quantity sensor of FIG. It is sectional drawing which shows the board | substrate preparation process in the 1st manufacturing method of the physical quantity sensor of FIG. It is sectional drawing which shows the resistance member formation process following the process of FIG. It is sectional drawing which shows the protective film formation process following the process of FIG. It is sectional drawing which shows the stress relaxation groove | channel formation process following the process of FIG. FIG. 7 is a cross-sectional view showing a mask opening forming step following the step of FIG. 6. FIG. 8 is a cross-sectional view showing a substrate opening forming step following the step of FIG. 7. It is sectional drawing which shows the silicon oxide etching process following the process of FIG. It is sectional drawing which shows the protective film removal process following the process of FIG. It is a top view which shows an example of a stress relaxation groove | channel. It is a top view which shows the 1st modification of a stress relaxation groove | channel. It is a top view which shows the 2nd modification of a stress relaxation groove | channel. It is a top view which shows the 3rd modification of a stress relaxation groove | channel. It is sectional drawing which shows the board | substrate opening part formation process in the 2nd manufacturing method of the physical quantity sensor of FIG. It is sectional drawing which shows the resistance member formation process following the process of FIG. FIG. 17 is a cross-sectional view showing a silicon oxide etching step that follows the step of FIG. 16. It is a partial cross section perspective view which shows the physical quantity sensor which concerns on other embodiment of this invention. It is a partial cross section perspective view which shows the modification of a sensor member regarding the physical quantity sensor of FIG. It is sectional drawing which shows the resistance member formation process in the manufacturing method of the physical quantity sensor of FIG. FIG. 21 is a cross-sectional view showing a stress relaxation groove forming step following the step of FIG. 20. FIG. 22 is a cross-sectional view showing a mask opening forming step following the step of FIG. 21. FIG. 23 is a cross-sectional view showing a substrate opening forming step following the step of FIG. 22. FIG. 24 is a cross-sectional view showing a silicon oxide etching step following the step of FIG. 23. It is sectional drawing which shows the resistance member formation process in the manufacturing method of the physical quantity sensor which concerns on further another embodiment of this invention. FIG. 26 is a cross-sectional view showing a mask opening forming step and a substrate opening forming step following the step of FIG. 25. FIG. 27 is a cross-sectional view showing a silicon nitride film removing step that follows the step of FIG. 26. It is sectional drawing which shows the modification of a resistance member structure regarding the physical quantity sensor of FIG. It is sectional drawing which shows the modification of resistance member arrangement | positioning regarding the physical quantity sensor of FIG. It is sectional drawing which shows an example of the conventional physical quantity sensor.

Explanation of symbols

  10: silicon substrate, 12, 14: silicon oxide film, 16, 17: silicon nitride film, 16A to 16D: stress relaxation groove, 18: resistance member, 18a, 18b, 22a, 24a: electrode portion, 20: through hole, 22, 24: conductive member, 30, 38, 44: protective film, 32, 34, 40, 42: resist layer, 36: etching mask, 48: connected portion.

Claims (7)

A semiconductor substrate;
An insulating film formed to cover one main surface of the semiconductor substrate;
A physical quantity sensor comprising a sensor member formed on the insulating film, wherein a through hole is provided in the laminated body of the semiconductor substrate and the insulating film so that a part of the sensor member floats in the air.   The sensor member has an electrode portion connected to a connected portion of the semiconductor substrate through a connection hole provided in the insulating film, and the sensor member is separated from the insulating film by the electrode portion. The physical quantity sensor according to claim 1, wherein the physical quantity sensor is fixed to an insulating film and the semiconductor substrate. Forming an insulating film covering one main surface of the semiconductor substrate;
Forming a sensor member on the insulating film;
Forming a protective film covering the sensor member on the insulating film;
In the state where the sensor member and the insulating film are covered with the protective film, an anisotropic selective etching process is performed on the other main surface of the semiconductor substrate to correspond to a part of the sensor member and to the insulating film. Forming a reaching opening in the semiconductor substrate;
An opening that penetrates the insulating film continuously to the opening of the semiconductor substrate by selectively etching the insulating film using the semiconductor substrate as a mask in a state where the sensor member and the insulating film are covered with the protective film. Forming a part;
And a step of floating a part of the sensor member in the air through the opening of the insulating film by removing the protective film. Forming an insulating film covering one main surface of the semiconductor substrate;
Performing an anisotropic selective etching process on the other main surface of the semiconductor substrate to form an opening reaching the insulating film in the semiconductor substrate;
Forming a sensor member on the insulating film so as to overlap the opening of the semiconductor substrate through the insulating film;
Forming a protective film covering the sensor member on the insulating film;
An opening that penetrates the insulating film continuously to the opening of the semiconductor substrate by selectively etching the insulating film using the semiconductor substrate as a mask in a state where the sensor member and the insulating film are covered with the protective film. Forming a part;
A method of manufacturing a physical sensor, comprising: removing the protective film to float a part of the sensor member in the air through the opening of the insulating film.   In the step of forming the insulating film, a layer in which first and second insulating films made of different materials are stacked in this order is formed as the insulating film, and in the step of forming the sensor member, the semiconductor is formed. After forming a connection hole corresponding to the connected part of the substrate in the laminated layer, the sensor member is placed on the second insulating film so as to have an electrode part connected to the connected part through the connection hole. 5. The physical quantity sensor according to claim 3, wherein after the step of removing the protective film, the second insulating film is removed and a part of the sensor member is separated from the first insulating film. Manufacturing method. Preparing a semiconductor substrate having one main surface covered with an insulating film and the other main surface covered with an etching stopper film;
Forming a sensor member on the insulating film;
An opening corresponding to a part of the sensor member and exposing a part of the semiconductor substrate is formed in the insulating film by an isotropic selective etching process, and a part of the sensor member is formed in the opening of the insulating film. The process of floating in the air at
An anisotropic selective etching process using the insulating film as a mask is performed on one main surface of the semiconductor substrate so that an opening continuous to the opening of the insulating film and reaching the etching stopper film is formed in the semiconductor substrate. Forming, and
Removing the etching stopper film at least at a part corresponding to the opening of the semiconductor substrate to expose the opening of the semiconductor substrate on the other main surface side of the semiconductor substrate.   In the step of preparing the semiconductor substrate, the insulating film is formed by stacking first and second insulating films made of different materials from each other in this order, and in the step of forming the sensor member, After the connection hole corresponding to the connected portion of the semiconductor substrate is formed in the stacked layer, the sensor member is formed on the second insulating film so as to have an electrode portion connected to the connected portion through the connecting hole. The physical quantity according to claim 6, wherein the second insulating film is removed and a part of the sensor member is separated from the first insulating film after the step of forming and removing a part of the etching stopper film. Sensor manufacturing method.

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