阅读说明：本技术 半导体元件及使用该半导体元件的流量测定装置 (Semiconductor element and flow rate measuring device using the same ) 是由 石塚典男 小野濑保夫 于 2018-08-06 设计创作，主要内容包括：本发明提供一种半导体装置及热式流体流量传感器,其抑制在铝膜上产生的应变,抑制由铝膜的反复金属疲劳引起的断线。本发明的半导体装置及热式流体流量传感器使硅膜和铝膜的高度在流量传感器部(隔膜端部正上方)部D和电路部(LSI部)D1中为D>D1。(The invention provides a semiconductor device and a thermal fluid flow sensor, which can restrain strain generated on an aluminum film and restrain disconnection caused by repeated metal fatigue of the aluminum film. The semiconductor device and thermal fluid flow sensor of the present invention have the height of the silicon film and the aluminum film in D > D1 in the flow sensor section (directly above the diaphragm end) D and the circuit section (LSI section) D1.)

1. A semiconductor device includes:

a semiconductor substrate having a cavity; and

a laminated portion laminated on the semiconductor substrate,

the laminated portion forms a diaphragm covering the cavity portion,

the laminated part has a silicon film constituting a thermocouple, an aluminum film, and a connecting part connecting the silicon film and the aluminum film,

the connecting portion is provided on the diaphragm,

the semiconductor element is characterized in that it is,

the silicon film is provided on the side of the substrate with respect to the neutral axis of the diaphragm,

the aluminum film is provided at a position opposite to the substrate side of the neutral axis in a portion crossing an end of the diaphragm.

2. A semiconductor device includes:

a semiconductor substrate having a cavity; and

a laminated portion laminated on the semiconductor substrate,

the laminated portion forms a diaphragm covering the cavity portion,

the laminated part has a silicon film constituting a thermocouple, an aluminum film, and a connecting part connecting the silicon film and the aluminum film,

the connecting portion is provided on the diaphragm,

the semiconductor element is characterized in that it is,

the disclosed electric power tool is provided with a circuit unit which is provided with: a transistor disposed outside the diaphragm; a first aluminum layer formed outside the separator in the laminated portion; and a second aluminum layer formed on the upper layer side of the first aluminum layer,

a portion of an aluminum film constituting the thermocouple, which portion crosses an end of the diaphragm, is formed on an upper layer of the first aluminum layer.

3. A semiconductor device includes:

a semiconductor substrate having a cavity; and

a laminated portion laminated on the semiconductor substrate,

the laminated portion forms a diaphragm covering the cavity portion,

the laminated part has a silicon film constituting a thermocouple, an aluminum film, and a connecting part connecting the silicon film and the aluminum film,

the connecting portion is provided on the diaphragm,

the semiconductor element is characterized in that it is,

having a circuit portion including a transistor disposed outside the diaphragm portion,

a distance D in a thickness direction of the silicon film and the aluminum film in the end portion of the diaphragm is larger than a distance D1 in the thickness direction of the transistor and an aluminum film formed directly above the transistor.

4. The semiconductor device according to any one of claims 1 to 3,

the diaphragm portion is formed with an intermediate layer,

the silicon film and the aluminum film are electrically connected via the intermediate layer.

5. The semiconductor element according to claim 2 or 3,

an intermediate layer is formed on the diaphragm on a lower layer side of the aluminum film and on an upper layer side of the silicon film,

the connecting part has a first connecting part and a second connecting part,

the aluminum film and the intermediate layer are connected via a first connection portion,

the intermediate layer and the silicon film are connected via a second connection portion.

6. The semiconductor element according to claim 5,

the intermediate layer is an aluminum film,

the first and second connection portions are through holes,

the height of the through hole connecting the silicon film and the middle layer is the same as the height of the through hole connecting the transistor and the aluminum film right above the transistor.

7. The semiconductor device according to any one of claims 1 to 3,

the aluminum film at the end of the diaphragm portion is provided at a portion where strain is generated to 0.015 or less.

8. The semiconductor device according to any one of claims 1 to 3,

an aluminum film constituting the thermocouple formed directly above the end of the diaphragm is disposed in a second layer from the uppermost layer of the laminated portion.

9. A flow rate measuring device is characterized in that,

a semiconductor device comprising the semiconductor device according to any one of claims 1 to 7.

Technical Field

The present invention relates to a semiconductor element and a flow rate measuring device using the same.

Background

An air flow meter that is installed in an electronically controlled fuel injection device of an internal combustion engine of an automobile or the like and measures intake air is currently used. As a fluid flow sensor used in such an air flow meter, a thermal fluid flow sensor using a heating resistor is mainly used because it can directly detect mass air. Among them, a thermal air flow sensor manufactured by MEMS technology using a semiconductor is attracting attention because it can be driven with low power while reducing manufacturing cost.

As such a technique, for example, there is a technique described in patent document 1. Patent document 1 discloses a thermal fluid flow sensor including: a detection unit including a heating resistor provided on a semiconductor substrate; and a circuit unit (LSI unit) provided on the semiconductor substrate and including a control circuit for controlling the heating resistor.

Disclosure of Invention

Problems to be solved by the invention

A thermocouple-type fluid flow sensor using MEMS technology has a diaphragm structure. The diaphragm of the sensor that measures the flow rate of the air fluid is deformed due to the pressure generated by the flow of the air. As a result of the studies by the present inventors, it was found that when the diaphragm is deformed, stress is repeatedly applied to the aluminum wiring at the end of the diaphragm, metal fatigue is caused, and as a result, breakage is likely to occur. Patent document 1 does not mention the above problem, and has room for study.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a thermocouple fluid flow sensor that suppresses strain generated in an aluminum film and suppresses disconnection caused by repeated metal fatigue of the aluminum film.

Means for solving the problems

In order to achieve the above object, a thermocouple fluid flow sensor according to the present invention includes: a semiconductor substrate having a cavity; a laminated portion laminated on the semiconductor substrate; and a thermocouple formed so as to cross an end portion of the diaphragm portion which is a region of the laminated portion covering the hollow portion, wherein the thermocouple includes a silicon film and an aluminum film provided in the laminated portion, and is characterized in that the silicon film is provided on a substrate side with respect to a neutral axis of the diaphragm portion, and the aluminum film is provided on a substrate side with respect to the neutral axis in a portion crossing the diaphragm end portion.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, since the aluminum film as the metal film can be suppressed from being strained, the aluminum film can be suppressed from being broken.

Drawings

Fig. 1 is a plan view in the first embodiment.

Fig. 2 is a sectional view taken along line a-a in the first embodiment.

Fig. 3 is a sectional view taken along line a-a in the second embodiment.

Fig. 4 is a sectional view taken along line a-a in the third embodiment.

Fig. 5 is a diagram showing the operation and effect of the present invention.

Fig. 6 is a graph showing the fatigue strength of the aluminum film in the fourth example.

Fig. 7 is a sectional view taken along line a-a in the first embodiment.

Fig. 8 is a cross-sectional view of the fifth embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[ first embodiment ]

Embodiment 1 of the present invention will be described with reference to fig. 1, 2, 5, and 6.

The flow rate detecting unit 21 of the thermocouple fluid flow rate sensor measures the flow rate using the electromotive force generated at the connecting portion 5 between the silicon film 4 and the aluminum film 3 formed on the diaphragm 7.

The thermocouple fluid flow sensor includes a silicon substrate 1 and a diaphragm 7 formed to cover a cavity portion provided in the silicon substrate 1, and a heating resistor 25 and a thermocouple connection portion 5 arranged upstream and downstream of the heating resistor 25 are formed in the diaphragm 7. In the present embodiment, one thermocouple is disposed upstream and downstream of the heating resistor, and the temperature of the upstream and downstream of the heating resistor is measured.

The diaphragm 7 is formed by laminating an insulating film such as a silicon oxide film, an aluminum film or a silicon film for forming a thermocouple on the silicon substrate 1, and then removing a part of the back surface side of the silicon substrate 1 by dry etching or the like.

The aluminum film or silicon film is formed so as to cross the diaphragm end 2.

The fluid flow sensor of the present embodiment is provided with a circuit portion 8 that processes a signal from the flow rate detection portion 21.

Next, a cross-sectional structure will be described with reference to fig. 2. The fluid flow sensor includes a transistor 22 serving as the circuit unit 8 disposed outside the diaphragm 7.

The fluid flow sensor includes a silicon substrate 1 having a cavity portion formed therein and a laminated portion 18 formed on the silicon substrate. The laminated portion 18 includes the silicon film 4 and the aluminum film 3 forming the flow rate detection portion, and the silicon film 28 and the aluminum film 14 forming the circuit portion. The silicon film 4 is connected to the aluminum film 3 via a connection portion 5 formed on the diaphragm 7. The silicon film 28 constituting the transistor is connected to the second aluminum film 14 via the connection portion 27 formed on the circuit portion 8. Examples of the connection portions 5 and 27 include through holes.

Since the circuit section 8 has a plurality of wiring layers for integration and miniaturization, an aluminum film is formed in the plurality of layers 3, 14, and 15. In order to insulate the wiring layers from each other, insulating films 12, 13, and 16 are formed between the layers. The insulating films 12 and 13 are exemplified by a single layer, but a plurality of kinds of insulating films may be stacked, and a silicon oxide film, a silicon nitride film, or the like may be used.

In the present embodiment, the height D of the connection portion 5 formed on the diaphragm 7 and the height D1 of the connection portion 27 formed on the circuit portion 8 satisfy the relationship of D > D1. In other words, the aluminum film 3 is disposed on the surface side of the aluminum film 14. In other words, the distance D in the thickness direction between the aluminum film 3 and the silicon film 4 at the diaphragm end 2 is greater than the distance D1 in the thickness direction between the transistor 10 and the aluminum film 14 formed substantially directly above the transistor 10.

Next, the operation and effect of the present embodiment will be described. Fig. 5 is a diagram in which an aluminum film is disposed in a laminated film of a silicon oxide film and a silicon nitride film, and the stress (strain) of the aluminum film when the diaphragm is pressed is analyzed. As analysis conditions, the width of the diaphragm was 500 μm, the thickness of the diaphragm was 1 μm, the applied pressure was 10kPa, and the aluminum film was an elastic plastic material. In fig. 5, (a) shows a case where the aluminum film is closest to the diaphragm end 2, (b) shows a case where the aluminum film is disposed in the middle of the diaphragm thickness, and (c) shows a case where the aluminum film is disposed in the vicinity of the surface. As is apparent from fig. 5, the aluminum film is separated from the diaphragm end 2, whereby the strain generated in the aluminum film is reduced. This is considered to be a result of the aluminum film being away from the diaphragm end 2, since the influence of the diaphragm bending deformation on the diaphragm end is reduced. Therefore, in order to suppress the strain generated by the deformation of the diaphragm caused by the aluminum film, it is effective to separate the aluminum film from the diaphragm end 2.

In the present embodiment, the aluminum film 3 directly above the diaphragm end 2 of the flow rate detection unit 21 is disposed on the surface side of the circuit unit 8, whereby the influence of the stress generated in the diaphragm end 2 on the aluminum film 3 can be suppressed, and the occurrence of strain in the aluminum film 3 can be suppressed.

The silicon film 4 of the circuit portion 8 and the flow rate detecting portion 21 are manufactured by the same process. When the thermal fluid flow sensor having the circuit portion 8 is designed without knowing this knowledge, the aluminum films 3 and 14 are formed in the same layer and the height of the through- holes 5 and 27 is the same as in the conventional case. Therefore, the aluminum film 3 is closer to the diaphragm end 2 than in the present invention, and therefore, the strain in the aluminum film generated when pressure is applied becomes larger than in the present embodiment.

The silicon film 4 is formed on the surface side of the silicon substrate 1. When the aluminum film 3 is away from the diaphragm end 2, a strain reduction occurs. The silicon film 4 is preferably formed in the same step as the step of forming the transistor 10, and is thus provided on the silicon substrate 1 side. As shown in fig. 7, the silicon film 4 is more preferably disposed on the silicon substrate 1 side and the aluminum film 3 is more preferably disposed on the side (surface side) opposite to the silicon substrate side with respect to the neutral axis 26 of the diaphragm.

As a more preferable example, the aluminum film 3 in the diaphragm 7 is preferably positioned on the diaphragm surface from the viewpoint of suppressing strain, but the protective film 16 is formed because the aluminum film 3 needs to be protected from the external environment. Therefore, when the aluminum film 3 constituting the thermocouple is disposed from the second layer on the surface, it is preferable from the viewpoint of both protection of the aluminum film 3 and suppression of strain.

[ second embodiment ]

Next, a second embodiment will be described with reference to fig. 3. In addition, the same configurations as those of the first embodiment will not be described.

In the second embodiment, the silicon film 4 and the aluminum film 3 forming the thermocouple are connected via the intermediate aluminum film 29.

The intermediate aluminum film 29 is formed by the same process as the second aluminum film 14, and is formed in the same layer as the second aluminum film 14. The intermediate aluminum film 14 is provided so as not to cross the vicinity directly above the diaphragm end portion, and is formed so as to be less affected by the stress generated in the diaphragm end portion 2.

The aluminum film 3 and the intermediate aluminum film 29 are connected by the first connection portion 5a, and the intermediate aluminum film 29 and the silicon film 4 are connected by the second connection portion 5 a. Examples of the connection portions 5a and b include through holes.

The connecting portion 5b and the connecting portion 27 are formed in the same process, and the connecting portion 5a and the connecting portion 30 are formed in the same process, and the heights are made equal to each other, thereby making the aspect ratio the same.

In the present embodiment, the intermediate aluminum film 29 is formed, so that the difference in shape between the connection portions 5a, b formed in the diaphragm 7 and the connection portions 30, 27 formed in the circuit portion 8 is smaller than that in embodiment 1. A plurality of metal layers are formed on the circuit portion 8. When the aluminum layer 3 is formed on the front surface side so as to be spaced apart from the diaphragm end 2 as in the present invention, the height of the connection portion 5 formed on the diaphragm 7 is different from the heights 27 and 30 of the connection portions formed on the circuit portion. In this case, in the case of forming through holes of different heights, a complicated process is required, but in the present embodiment, since only through holes of the same height are formed, it is possible to form through holes in a simple process.

In the present embodiment, the intermediate aluminum film 29 is formed on the M1 layer and the aluminum film 3 is formed on the M2 layer, taking the configuration in which the flow rate detection unit 21 is the metal 2 layer as an example, but the present invention is not limited thereto. For example, when the circuit portion 8 has a metal n-layer structure, the same effect can be obtained by forming the intermediate aluminum film 29 in each of the M1 to Mn-1 layers and forming the aluminum film 3 in the Mn layer.

[ third embodiment ]

A third embodiment will be described with reference to fig. 4. In addition, the same configurations as those of the first embodiment will not be described.

In the present embodiment, the silicon film 4 is disposed on the sixth insulating film 20 formed on the first insulating film 11. By providing the insulating film 20, the distance d from the surface of the silicon substrate 1 to the surface of the silicon film 4 is made larger than the distance d1 from the surface of the silicon substrate 1 to the surface of the silicon film 28.

When the height of the connection portion 5 between the silicon film 4 and the aluminum film 3 is equal to or greater than the height of the connection portion 27 between the silicon film 28 and the aluminum film 14, the aluminum film 3 is separated from the diaphragm end portion 2, and therefore, the strain of the aluminum film can be suppressed.

[ fourth embodiment ]

The fourth embodiment will be described with reference to fig. 6. In addition, the same configurations as those in the first to third embodiments 1 to 1 will not be described.

Fig. 6 is a graph of the fatigue strength (fracture frequency dependence of fracture strain) of the obtained submicron-thickness aluminum film. In order to obtain the fatigue strength of a general bulk material, both ends of the material are repeatedly stretched and determined from the number of passes and the stretching force, but in a sample having a submicron thickness, it is difficult to independently process the single-layer film, and it is necessary to repeatedly stretch both ends of the film, so that the fatigue test itself is very difficult. Therefore, we developed a fatigue strength test method for a submicron-thick film and measured the fatigue strength of an aluminum film. The results are shown in FIG. 6.

The frequency of pulsating pressure from the car is considered to be around 100Hz at maximum. If it is considered that the vehicle is continuously driven for 5 hours, 365 days and 11 years a day, the number of pulses is about 1E 10. From the fatigue strength curve shown in fig. 6, it can be said that it is effective to control the generated strain to 0.015 or less so as not to break the aluminum film. That is, by designing not to exceed this range, the aluminum film can be inhibited from breaking.

[ fifth embodiment ]

A fifth embodiment of the present invention will be described with reference to fig. 8. In addition, the same configurations as in embodiments 1 to 4 will not be described.

The fluid flow sensor of the present embodiment does not integrally form the arithmetic circuit 8, but has the function of another semiconductor element. In this embodiment, the silicon film 4 is also provided on the substrate 1 side of the neutral axis 26 of the diaphragm 7, and the aluminum film 3 is provided on the opposite side of the neutral axis 26 from the substrate 1 in the portion crossing the diaphragm end 2, whereby the aluminum film 3 is separated from the diaphragm end 2, and the same effect as in embodiment 1 is obtained.

In the above embodiments, the fluid flow sensor was described as an example of the semiconductor element including the thermocouple, but the present invention is not limited thereto, and the present invention can be applied to various sensors such as a temperature sensor and a humidity sensor.

The semiconductor element described in each of the embodiments can be applied to a physical quantity measuring device such as a flow rate detecting device for measuring a flow rate of an internal combustion engine or a humidity measuring device for measuring humidity.

Description of the symbols

1 … silicon substrate

2 … diaphragm end

3 … aluminum film

4 … silicon film

5 … connection part

5a … first connection

5b … second connecting part

7 … diaphragm

8 … Circuit section

9 … aluminum pad

10 … diffusion layer

11 … first insulating film

12 … second insulating film

13 … third insulating film

14 … second aluminum film

15 … third aluminium film

16 … fourth insulating film

17 … fifth insulating film

18 … laminate

20 … insulating film

21 … flow rate detecting part

22 … transistor

23 … distance from silicon substrate surface to silicon film surface at circuit part

24 … distance from silicon substrate surface to silicon film surface at flow sensor section

25 … heating resistor body

26 … neutral axis

27 … connection part

28 … silicon film

29 … intermediate aluminium film

30 … connection.