JP3324395B2 - Electric field type vacuum tube, pressure sensor and acceleration sensor using the same, and methods of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro sensor using silicon, such as a pressure sensor for measuring gas pressure or an acceleration sensor for measuring acceleration applied to a moving object typified by an accelerometer for an automobile. The present invention relates to a small semiconductor type sensor that makes full use of machining technology.

[0002]

2. Description of the Related Art FIG. 15 (a) uses a silicon semiconductor,
FIG. 3 is a cross-sectional view of a semiconductor pressure sensor that makes full use of micromachining technology. The silicon sensor chip 51 provided with the recess 52 is mounted on a base 53 such that the recess 52 is kept at a vacuum. A sensor portion 54 of a diffusion resistance layer formed by introducing impurities is formed on the back side of the recess 52 of the sensor chip 51 in the figure, and the sensor portion 54 is formed by a pressure difference between the gas pressure in the cap 58 and the vacuum of the recess 52. Is applied, the diffusion resistance layer is distorted, and the resistance changes. An electrode 55 provided on the surface of the sensor chip 51 and a lead 56 penetrating the table 53 are connected by a bonding wire 57.
8 can be sensed.

FIG. 15B is a sectional view of an acceleration sensor also using a silicon semiconductor. Upper and lower stoppers 60
Are attached to a ceramic case 63. The sensor chip 6
A diffusion resistance layer formed by introducing impurities into silicon is formed in one sensor section 64, and when the weight 69 thereabove receives acceleration to deform the sensor section 64, the resistance of the diffusion resistance layer changes. Although only one is shown in the figure, the acceleration change can be sensed by measuring the resistance change between two electrodes 65 provided with the sensor unit 64 interposed therebetween through the bonding wire 67 and the lead 66. Silicone oil may be filled in the ceramic case 63 for damping.

[0004]

Generally, semiconductor sensors have the following disadvantages. Sensors utilizing semiconductor characteristics are difficult to use at high temperatures. In particular, the most commonly used silicon cannot be used at 150 ° C. or higher. There is a characteristic change due to temperature, and temperature compensation is required.

A method of reading a sensor output by an absolute value is generally used, and a method of correcting a variation of a sensor by an external circuit is taken, which is troublesome. Furthermore, vacuum sealing is necessary especially for the pressure sensor, and a post-process such as a vacuum packaging process is troublesome.

There is also a drawback. In view of the above problems, an object of the present invention is to provide a sensor which can be used at a high temperature, does not require temperature compensation, has no variation in characteristics of individual elements, and is easy to manufacture, and a method for manufacturing the same.

[0007]

[Means for Solving the Problems]

(1) In general, a sensor using solid physical properties such as a semiconductor cannot ignore the temperature characteristic, and it is inevitable that the usable temperature is naturally limited. Therefore, in order to solve the above-mentioned problems, it is necessary to find a material with excellent temperature resistance and small temperature change,
Or it seems to have to take a method that does not utilize the physical properties of the solid.

In the present invention, in order to solve the above-mentioned problem (1),
Method was chosen. That is, the response inside the vacuum tube is used as a sensor. Within the vacuum tube, the fact that the sensor section is completely shut off from the outside can be expected to be excellent not only in temperature but also in environmental resistance. In particular, if the collector current is changed by the pressure or acceleration from the outside in a field-type electron-emitting device, an ideal environment that is completely unaffected by the environment because some of the electrons running in vacuum are the sensor response function. A sensor can be realized.

That is, the electric field type vacuum tube of the present invention comprises an emitter, a collector and first and second gates, and emits electrons from the emitter by a voltage applied between the emitter and the first gate. When an external force is applied to the second gate, the second gate is deformed, and the potential distribution formed by the emitter, the second gate, and the collector changes, causing a change in the collector current.

In particular, the vacuum tube is formed by finely processing silicon and a silicon oxide film and is formed minutely, and the emitter and the collector are mounted on the insulating film on the substrate so as to face in parallel at a predetermined interval. , Two gates above and below the space between the emitter and the collector. Specifically, the configuration is as shown in the conceptual cross-sectional views shown in FIGS. FIG. 12A shows a case where the present invention is applied to a pressure sensor, and FIG. 12B shows a case where the present invention is applied to an acceleration sensor.

In FIG. 12A, there are an emitter 2 and a collector 3 placed on an insulating film 4a on a first gate 1, and a second gate 5 on the emitter 2 and the collector 3 via an insulating film 4b. Is provided. The space where the tips of the emitter 2 and the collector 3 are placed is a vacuum. A voltage _VG1 is applied between the emitter 2 and the first gate 1 to emit electrons from the emitter 2. The emitted electron current flows through the first gate 1, the collector 3, and the second gate 5 according to the electric field inside the space. When the second gate 5 to the external force (in this case, pressure) is applied, the second gate 5 is deformed, the current I _CE flowing through the collector 3 (X), or the second gate - current flowing through the preparative 5 I _G2 ( If X) changes, then _ICE (X)
Or the force applied to the second gate from the change in I _G2 (X)
(X) can be detected.

In FIG. 1B, it is not possible to use the change in the electron current due to the deformation of the second gate 5 'only when the external force is the force of the mass and acceleration of the weight 6 on the second gate 5'. Is the same. (2) As a means for solving the problem of variation among individual sensors, a difference or a ratio with respect to a reference value is measured instead of an absolute measurement.

The emission current from the emitter is basically determined by the material of the emitter, the geometry of the emitter, the surface condition, and the electric field strength between the emitter and the first gate. The geometric shape is set within a certain range by a photo process or the like, but individual differences may occur depending on the surface state of the emitter. Therefore, individual differences are eliminated by keeping the total current constant or by taking a ratio to the total current. That is, since I = I _CE (X) + I _G1 (X) + I _G2 (X) = constant, I _G2 (X) = I−I _CE (X) −I _G1 (X) where I _G1 (X) is , The current flowing through the first gate 1 when an external force (in this case, pressure) is applied to the second gate. When an external force (in this case, pressure) is applied to the second gate, only the second gate is deformed by the external force (X), so if the total current is constant, the current flowing to the first gate I _G1 (X) does not change.

Alternatively, by evaluating the values of _ICE (X) / I and _IG2 (X) / I, the magnitude of the externally applied force can be sensed irrespective of the variation of each sensor. For the above reason, the first gate current may be referred to. Specifically, as shown in FIG. 12A, a first gate 1 is provided below the emitter 2, and a second gate 5 is provided above the emitter 2. When an external force (in this case, pressure) is applied to the second gate 5, the current I flowing through the second gate
_{Although G2} (X) changes, this can be evaluated against the total current I or the current _IG1 flowing through the first gate to eliminate individual differences.

(3) As a means for simplifying the vacuum packaging step, a method of vacuum sealing in-process was devised. That is, one of the upper and lower gates is a substrate, and the other also serves as a cap for sealing the space between the emitter and the collector in a vacuum, and the space between the emitter and the collector is formed. A hole connected to the space is previously provided in the covering cap, and the space between the emitter and the collector is held in a vacuum by the metal embedded in the hole.

The sealing method will be described below. FIG. 13 is a view for explaining the sealing mechanism.
(A) and (b) are a perspective view and a sectional view before sealing, respectively, and FIGS. 13 (c) and (d) are sectional views after sealing. The base 8 having a recess and the cap 9 having holes (in this case, two holes) are attached to each other (FIG. 13B). As the means, for example, bonding can be performed by heat treatment like a bonded SOI (silicon-on-insulator) wafer.

In this state, if the sealing metal 7 such as Al is vacuum-deposited to such an extent that the hole of the cap 9 is completely filled, a vacuum chamber 10 having at least the degree of vacuum at the time of the deposition can be formed [FIG. )]. As the aspect ratio (depth of the hole / size of the hole) of the hole of the cap portion 9 is higher, the amount of the sealing metal 7 flowing into the vacuum chamber 10 is smaller, and good vacuum sealing is possible.

If a groove connected to the sealing hole is provided in the cap portion, the positioning of the cap portion is facilitated because the vacuum chamber 10 and the groove may be connected. In particular, it is preferable that at least a part of the metal buried in the hole to keep the space between the emitter and the collector in a vacuum gets residual gas. If the getter metal 7a that gets such residual gas is used, the residual gas and the released gas are gettered, so that the degree of vacuum in the vacuum chamber 10 is not deteriorated, a high vacuum is maintained, and the reliability of the vacuum tube is improved. And the life is extended [FIG.

As getter metals for gettering residual gas, for example, zirconium-aluminum alloys and zirconium-iron alloys containing 7 to 30% by weight of aluminum are known. A vacuum tube having the above structure becomes a pressure sensor if the external force applied to the cap portion serving as the second gate is a pressure, and an acceleration sensor if the external force is caused by an acceleration applied to a weight on the cap.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a measure for taking the above measures, a first gate and a first gate are provided below a line connecting an emitter and a collector.
A second gate is provided above, and the second gate is deformed by an external force applied to the second gate, and the emitter and the second gate are deformed.
And the potential distribution created by the collector changes, causing a change in the collector current.

In particular, a silicon and silicon oxide film are finely processed to be formed minutely, the first gate is a silicon substrate, and the emitter and collector are silicon thin films formed on the silicon substrate via an oxide film. The two gates are made of another silicon thin film. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022]

FIG. 1 is a perspective sectional view of a chip of a pressure sensor according to a first embodiment of the present invention. On a silicon substrate 11, an emitter 12 made of a silicon thin film and having a comb-like tip with a partly lacking oxide film 14 interposed therebetween, and a collector 13 also made of a silicon thin film opposed thereto are provided. A second gate 15 made of a silicon thin film is provided on the emitter 12 and the collector 13 with an oxide film 16 interposed therebetween, and an oxide film 18 covers the second gate 15. The uppermost oxide film 18 is opened, and an upper gate electrode 25 made of an Al alloy is in contact with the second gate 15 through the opening. Oxide film 1
8, the second gate 15 and the oxide film 16 are also provided with connection holes through which the emitter electrode 2 made of Al alloy is formed.
2 is an emitter 12, and a collector electrode 23 is a collector 13.
Is in contact with each. The side wall of the connection hole is covered with an oxide film, and is insulated from the second gate 15. On the uppermost oxide film 18, a vacuum sealing pad 26 made of an Al alloy that seals a space between the emitter 12 and the collector 13, that is, a hole communicating with the vacuum chamber 27 is also seen. Emitter 1
2. Oxide film 16 between collector 13 and second gate 15
Is partially removed, and the second gate 15 faces the vacuum chamber 27. The silicon substrate 11 is also a first gate,
A three-layer film of Ti / Ni / Au is formed on the back surface, and forms a lower gate electrode 21. The vacuum chamber 27 between the emitter 12 and the collector 13 is maintained at a vacuum of 4 × 10 ⁻⁴ Pa.

FIGS. 2 to 11 are sectional views in the order of steps for explaining the method of manufacturing the pressure sensor according to the embodiment of the present invention shown in FIG. [FIG. 2 (a) to FIG. 3 (e), FIG. 3 (a) to FIG. 3 (f), FIG.
(C)], a process of forming a groove in the cap portion [FIG.
(E)] and the vacuum sealing process (FIGS. 6 to 11) will be described below.

FIGS. 2A to 2D are cross-sectional views showing a main manufacturing process of a groove forming process for a scribe line in a base portion. Silicon substrate 11 (ρ = 10Ω-c
m, n-type, 4 inchφ wafer) / oxide film 14 (thickness t = 1μ)
m) / SOI wafer composed of silicon thin film 17 (ρ = 10Ω-cm, t = 2 μm) [FIG. 2 (a)]. In the present invention, a so-called bonded SOI wafer in which a silicon wafer and a thermally oxidized silicon wafer are overlapped and bonded by heat treatment, and one surface is wrapped to a desired thickness, is used. A so-called SIMOX wafer having an SOI layer formed by heat treatment may be used.

After thermally oxidizing the wafer to form an oxide film 16 having a thickness of 1 μm (FIG. 4B), the photoresist is patterned using a photomask shown in FIG. The oxide film 16 in the groove forming portion for the line and vacuum sealing and the silicon thin film 17 thereunder are etched out by immersion in a buffered hydrofluoric acid solution (hereinafter referred to as BHF) and reactive ion etching. A groove reaching the film 14 is formed [FIG.

After that, the silicon thin film 17 exposed on the side surface of the groove is thermally oxidized to oxidize the silicon thin film 17 having a thickness of about 1 μm.
6 'was formed [FIG. (D)]. Thus, the step of forming the grooves 37 for vacuum sealing and scribe lines in the base portion is completed. FIG. 2E is a perspective view showing a state where this step is completed. The base portion having undergone the step of forming the grooves for the vacuum sealing and the scribe line is shifted to the process of forming the next emitter-collector portion.

FIGS. 3A to 3D are cross-sectional views showing the main manufacturing steps in the step of forming the emitter-collector section following FIG. 2D. The base portion having completed the groove forming process up to FIG. 2D is subjected to resist patterning using a mask shown in FIG. 4B and immersed in BHF to expose the vacuum chamber forming portion, and at the same time, to expose the oxide film 16. Next, an emitter electrode connection hole 28 and a collector electrode connection hole 29 are opened (FIG. 3A).

Subsequently, a photoresist 19a is applied,
Resist patterning is performed using the mask shown in FIG. 4C, and the silicon thin film 17 is formed by reactive ion etching.
Is processed into an emitter 12 and a collector 13 each having a comb-shaped tip [FIG. 3 (b)]. Next, the oxide film 14 under the emitter 12 and the collector 13 is immersed in a BHF solution.
Is etched to obtain 1 from the emitter 12 and the collector 13.
After being retracted by about μm [FIG. 3C], the photoresist is removed to complete the process of forming the emitter-collector portion [FIG. During this time, the tip of the comb-shaped emitter 12 may be sharpened by immersion in a potassium hydroxide solution.

FIG. 3E is an enlarged perspective view of the emitter-collector portion after the emitter-collector portion has been formed. It can be clearly seen that the emitter 12 and the collector 13 face each other. The square holes in the oxide film 16 are an emitter electrode connection hole 28 'and a collector electrode connection hole 29'. FIG.
(A) to (d) are cross-sectional views showing steps for forming a grooved SOI wafer to be a cap portion.

Another Si substrate 31 (ρ = 10Ω-cm, n-type, 3.
SOI consisting of 5 inchφ wafer) / SiO ₂ 18 (t = 1 μm) / silicon thin film 32 (ρ = 10Ω-cm, t = 30 μm)
The silicon thin film 32 of the wafer is oxidized to form an oxide film 34 having a thickness of 1 μm (FIG. 5A). Next, the oxide film 34 in the groove forming portion is selectively removed by a normal photo process, and the silicon thin film 32 is etched by plasma etching using the oxide film 34 as a mask to form a desired groove [FIG. )].

Thereafter, the entire surface of the wafer is oxidized to form an oxide film 34 'having a thickness of 1 μm on the side surface of the groove [FIG. Finally, in order to remove the oxide film 34 other than the groove portion of the silicon thin film 32 and to make the silicon thin film 32 thinner, polishing is performed mechanically and chemically, and the silicon thin film 32 is finished to be flat enough to be bonded and bonded [ FIG.

FIG. 5E is a perspective view after the formation process of the grooved SOI wafer serving as the cap portion is completed. A groove whose side is covered with an oxide film is formed. The square holes are an emitter electrode connection hole 28 and a collector electrode connection hole 29. However, these connection holes are stopped by the oxide film 18 at this stage. Next, the grooved SOI wafer of the cap portion of FIG. 5D is applied to the base portion where the formation process of the emitter-collector portion of FIG.
The surface having the groove is bonded as a bonding surface.

Specifically, as shown in FIG. 6, the orientation flats provided on the wafer from the beginning (however, the length of the orientation flat is the same for all wafers) are aligned and superposed. And heat-treat. The reason why the diameter of the grooved SOI wafer in the cap portion is slightly reduced is that the S
This is because the alignment marker provided near the outer periphery of the OI wafer can be aligned when viewed from above.

FIGS. 7A to 7D and FIGS.
(D) shows a vacuum sealing process after bonding the grooved cap portion SOI wafer and the base portion SOI wafer on which the emitter and collector are formed, along the line D─D ′ in FIG. 9 (a) to 9 (d) and FIGS. 10 (a) to 10 (d) are partial sectional views taken along the line EE ′ shown in FIG.

The base SOI wafer on which the emitter-collector section is formed and the cap SOI wafer are replaced by the oxide film 16 of the base SOI wafer and the cap SOI wafer.
The silicon thin film 32 of the I-wafer is attached and bonded (FIG. 7A). In this cross-sectional view, the SO
Portions of the I-wafer without the silicon thin film 32 are the emitter electrode connection holes 28 and the collector electrode connection holes 29. The emitter electrode connection holes 28 'and the collector electrode connection holes 29' of the oxide film 16 of the SOI wafer at the base are Each has been combined.

The Si substrate 31 of the SOI wafer in the cap portion
Is removed by etching to expose the oxide film 18 [FIG. Next, a photoresist 19b is applied on the exposed oxide film 18 and patterning is performed [FIG.
The oxide film 18 on the emitter electrode connection hole 28, the collector electrode connection hole 29, the upper portion of the upper gate electrode connection hole, and the portion where the vacuum sealing hole 30 is formed is removed by dry etching [FIG. The emitter electrode connection hole 28, the collector electrode connection hole 29, and the upper gate electrode connection hole penetrate.

FIGS. 9A to 9D show FIGS.
It is sectional drawing in another cross section in the stage respectively corresponding to (d). S of the base portion where the emitter-collector portion is formed
The OI wafer and the SOI wafer of the cap portion are bonded together (FIG. 9A). In this cross-sectional view, there is no oxide film 16 and silicon thin film 17 of the SOI wafer of the base portion, and it is not bonded to the silicon thin film 32 of the SOI wafer of the cap portion. Portions of the SOI wafer where the silicon thin film 32 does not exist are caps formed. The emitter 12 outside the cross section is indicated by a dotted line.

The Si substrate 31 of the SOI wafer in the cap portion
Is removed by etching to expose the oxide film 18 [FIG. Next, a photoresist 19b is applied on the exposed oxide film 18 and patterning is performed [FIG.
The oxide film 18 in the vacuum sealing hole forming portion is removed by dry etching [FIG. The sealing hole 30 communicates with the vacuum chamber 27 where the emitter 12 is located.

After the photoresist 19b was ashed and removed, the photoresist 19b was set in a vacuum evaporation chamber of an electron beam evaporation apparatus and evacuated by heating the substrate at 300 ° C. for 4 hours. The ultimate vacuum was 7 × 10 ⁻⁶ Pa. Thereafter, the substrate temperature is set to 200 ° C., and a Zr-15% Al alloy is deposited by argon sputter deposition. Spatter condition is 0.27Pa, DC3kW
It is. A Zr-15% Al alloy getter film 20 is deposited on the bottom of the sealing hole 30 reaching the vacuum sealing groove [FIG.
0 (a)]. At this time, the getter film 20 is deposited also on the bottoms of the emitter electrode connection hole 28, the collector electrode connection hole 29 and the upper gate electrode connection hole, and also on the SOI wafer [FIG. 8 (a)].

Subsequently, Al is vapor-deposited by 5 μm. Since the sealing hole 30 reaching the groove for vacuum sealing is filled with Al, the vacuum chamber (that is, the space in which the emitter-collector is provided) 27 is vacuum sealed [FIG.
(B)]. At the same time, the emitter electrode connection hole 28, the collector electrode connection hole 29, and the upper gate electrode connection hole are filled with Al (FIG. 8B). Getter film 20 on SOI wafer
An Al film 24 is also deposited on the top.

Subsequently, by patterning a photoresist and etching the Al film 24 and the getter film 20, an emitter electrode 22, a collector electrode 23, an upper gate electrode 25, and a vacuum sealing pad 26 are formed [FIG. 8 (c) and 10 (c)]. Finally, add Ti /
Ni / Au is deposited and used as the lower gate electrode 21 to complete the process [FIGS. 8 (d) and 10 (d)]. A
Since the degree of vacuum at the time of vapor deposition was 4 × 10 ⁻⁴ Pa, the degree of vacuum in the vacuum chamber 27 was estimated to be substantially the same as that initially, but the degree of vacuum was improved by cooling and gettering by the getter film 20, and the long The period is kept.

FIG. 11 shows the SOI wafer of the base portion 35 having the emitter-collector portion of FIG.
(D) is a perspective plan view of a state where the SOI wafer of the cap portion 36 is bonded to the groove forming surface, and a solid line in the drawing is a processing pattern of the SOI wafer of the base portion 35, and a dotted line is a processing pattern of the SOI wafer of the cap portion 36. Is shown. Vacuum chamber 27
Inside, a comb-shaped emitter 12 and collector 13 can be seen. 28 is a connection hole for an emitter electrode, and 29 is a connection hole for a collector electrode. The vacuum sealing hole 30 can be seen on the groove of the cap portion 36 beside the vacuum chamber 27.

FIG. 14A shows a state of pressure measurement using the sensor chip of FIG. The chip is placed in a container 40 having a vent, and the emitter electrode 22, the collector electrode 23, the lower gate electrode 21 and the upper gate electrode 25 are connected to the E, C, G ₁ and G ₂ terminals, respectively. A voltage V _CE is applied between EC, a voltage V _G1 is applied between EG ₁ , and a voltage V _G2 is applied between EG ₂ , and respective currents _ICE , IG ₁ and IG ₂ are measured.

[0044] shows the measured results of the I _CE in FIG 14 (b). The horizontal axis in the figure is the voltage between the emitter and the collector (V _CE ), and the vertical axis is the current (I _CE ) flowing between the emitter and the collector. V
_ICE is increasing with _CE . Also, 1 × 10
According Yuku by subtracting the external pressure from ⁵ Pa (atmospheric pressure) to 1 Pa, that slide into increased at a constant rate which is I _CE was observed.

The lower gate - gate electrode and the upper gate - each gate electrode by applying a voltage of 20V, the respective gate - measuring the current flowing through the gate electrode as I _G1, I _G2. Assuming that the current flowing through the entire sensor is I,

[0046]

[Equation 1] I [V _CE = 70V, P = P (X)] = I _CE [V _CE = 70V, P = P
(X)] + I _G1 [V _CE = 70V, P = P (X)] + I _G2 [V _CE = 70V, P = P
(X)] Here, since the current I _G1 flowing into the first gate electrode is not subject to pressure changes,

[0047]

## EQU2 ## I _G1 [V _CE = 70 V, P = P (X)] = I _G1 [V _CE = 70 V, P = P ₀ ]
= I _G1 [V _CE = 70V] If the change in I _CE , ΔI _CE / I, is taken as the evaluation function

[0048]

(Equation 3) Thus, changes in pressure and _ICE can be normalized, and individual differences between sensors can be canceled. Table 1 shows the results of the evaluation in which the above-described arithmetic circuit was incorporated.

[0049]

[Table 1] Here, V _CE = 70 V, V _G1 = V _G2 = 20 V, P ₀ = 1 × 10 ^-3
Pa. That is, a pressure sensor having no element variation can be obtained by using the entire current or the current of the first gate electrode as a reference. In addition, since this pressure sensor does not use semiconductor characteristics, it does not require temperature compensation and can be used in a high temperature environment of 150 ° C. or higher.

If the method using two SOI wafers as described above is adopted as the manufacturing method, the manufacturing is easy. And if you take a vacuum sealing method that fills the small diameter sealing hole with deposited metal, it can be done during the vacuum process,
No special vacuum sealing process is required. In particular, by using a metal film having a getter function as the sealing metal, realization and maintenance of a high degree of vacuum were facilitated and reliability was improved.

[Embodiment 2] When used as an acceleration sensor, after the step of FIG. 8 (c), a photoresist pattern is formed, a metal such as Pd is deposited, and then the second gate should be weighted by lift-off. It is obvious that this can be easily realized by selectively forming a metal.

[0052]

As described above, according to the present invention, two gates are provided, and the electron current emitted from the emitter through the vacuum region between the two gates is changed to the second gate. The following effects can be obtained by using a vacuum tube that changes in response to a change in external force applied to the second gate, a pressure sensor in which the external force is pressure, or an acceleration sensor that is a force applied to the second gate.

Basically, it is hardly affected by the ambient temperature like a carrier flowing in a solid because of the vacuum tube structure.
There is an effect that a sensor excellent in environment resistance can be realized. In addition, a sensor with high sensitivity can be obtained, and sensing is performed by a standardized method. Therefore, the problem of individual difference, which has been a problem in the conventional sensor, can be avoided. Furthermore, in the manufacturing method, since the manufacturing is performed using a wafer having an SOI structure, the process can be greatly simplified, and the vacuum sealing in the in-process is realized, so that it is excellent in mass production such as a simplified packaging process. And so on.

[Brief description of the drawings]

FIG. 1 is a perspective sectional view of a pressure sensor according to a first embodiment of the present invention.

2 (a) to 2 (d) are cross-sectional views of respective main manufacturing steps of the pressure sensor of FIG. 1, and FIG. 2 (e) is a perspective cross-sectional view thereof.

3 (a) to 3 (e) are cross-sectional views showing main steps of an electron-emitting portion of the pressure sensor of FIG. 1 following FIG. 2 (d).

FIGS. 4A to 4C are views of a photomask used in the manufacturing steps of FIGS. 2 and 3;

5 (a) to 5 (d) are cross-sectional views of respective main manufacturing steps of a cap portion of the pressure sensor of FIG. 1, and FIG. 5 (e) is a perspective cross-sectional view thereof.

FIG. 6 is a view showing a state of a bonding step of the pressure sensor of FIG. 1;

7 (a) to 7 (d) are cross-sectional views of main steps of a bonding process of the pressure sensor of FIG.

8 (a) to 8 (d) are cross-sectional views for respective main manufacturing steps in the pressure sensor bonding step of FIG. 1 subsequent to FIG. 7 (d).

9 (a) to 9 (d) are cross-sectional views in different cross sections for respective main manufacturing steps of a bonding step of the pressure sensor of FIG.

10 (a) to 10 (d) are diagrams of FIG. 1 subsequent to FIG. 9 (d).
Sectional view of each main manufacturing process of the pressure sensor bonding process

FIG. 11 is a perspective view showing a state of bonding the pressure sensor of FIG. 1;

12A is an explanatory diagram of the operation principle of the pressure sensor of FIG. 1, and FIG. 12B is an explanatory diagram of the operation principle of the acceleration sensor.

13A is a perspective view of the pressure sensor of FIG. 1 before vacuum sealing, FIG. 13B is a cross-sectional view taken along line AA ′, and FIG.
Is a sectional view after vacuum sealing, and (d) is a sectional view after another vacuum sealing method.

14A is an explanatory diagram of the operation principle of the pressure sensor of FIG. 1, and FIG. 14B is a characteristic diagram of the pressure sensor.

FIG. 15A is a cross-sectional view of a conventional pressure sensor, and FIG.
Is a cross-sectional view of a conventional acceleration sensor

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 First gate 2 Emitter 3 Collector 4a, 4b Insulating film 5 Second gate 6 Weight 7 Sealing metal 7a Getter metal 8 Base part 9 Cap part 10 Vacuum region 11 Silicon substrate 12 Emitter 13 Collector 14 Oxide film 15 First gate 16 , 16 ′ oxide film 17 silicon thin film 18 oxide film 19a, 19b photoresist 20 getter metal 21 lower gate electrode 22 emitter electrode 23 collector electrode 24 Al film 25 upper gate electrode 26 vacuum sealing pad 27 vacuum chamber 28, 28 ′ emitter electrode Connection hole 29, 29 'Collector electrode connection hole 30 Vacuum sealing hole 31 Silicon substrate 32 Silicon thin film 34, 34' Oxide film 35 Base portion 36 Cap portion 37 Base portion groove 38 Cap portion groove 39 Scribe line 40 Container 51, 61 Sensor Chips 2 indentation 53 units 54 sensor unit 55, 65 electrode 56, 66 lead 57 and 67 bonding wire 58 cap 60 stopper 63 ceramic case 69 weight

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01J 1/30 G01P 15/08 19/70 H01J 1/30 Z (72) Inventor Yoichi Ryokai Arata Tanabe, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Fuji Electric Co., Ltd. (72) Inventor Masato Nishizawa 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Fuji Electric Co., Ltd. (72) Akira Amano Akira Tanabe, Kawasaki-ku, Kawasaki, Kanagawa No. 1-1 Fuji Electric Co., Ltd. (56) References JP-A-6-288843 (JP, A) JP-A-6-235733 (JP, A) JP-A-6-66663 (JP, A) JP 4-2937 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 21/10 G01L 9/00 G01P 15/08 H01J 1/30-1/304 H01J 19/70 H01J 9/02

Claims (14)

(57) [Claims] 1. An electric field type vacuum tube comprising an emitter, a collector, and first and second gates and emitting electrons from the emitter by a voltage applied between the emitter and the first gate, wherein an external force is applied to the second gate. The electric field type vacuum tube is characterized in that the second gate is deformed by the addition of the electric current to change the potential distribution formed by the emitter, the second gate and the collector, thereby causing a change in the collector current. 2. The electric field type vacuum tube according to claim 1, wherein said electric field type vacuum tube is formed by finely processing silicon and a silicon oxide film. 3. The method according to claim 1, wherein the emitter and the collector are mounted on the insulating film on the substrate so as to face each other in parallel at a predetermined interval, and two gates are provided above and below a space between the emitter and the collector. The electric-field-type vacuum tube according to claim 1 or 2, wherein: 4. The semiconductor device according to claim 3, wherein the first gate is a silicon substrate, and the second gate also functions as a cap for sealing a space between the emitter and the collector to a vacuum.
4. The electric-field-type vacuum tube according to 1. 5. The electric field type vacuum tube according to claim 4, wherein the current flowing through the second gate is evaluated based on the current flowing through the first gate. 6. A cap portion covering the space between the emitter and the collector is provided with a sealing hole connected to the space in advance, and the space between the emitter and the collector is held in a vacuum by a metal embedded in the sealing hole. The electric field type vacuum tube according to claim 5, wherein 7. The electric field type vacuum tube according to claim 6, wherein a groove connected to the sealing hole is provided in the cap portion. 8. The electric field according to claim 7, wherein at least a part of the metal buried in the sealing hole for keeping a space between the emitter and the collector at a vacuum is to getter residual gas. Type vacuum tube. 9. The electric field type vacuum tube according to claim 8, wherein the metal for obtaining the residual gas is an aluminum-zirconium alloy containing 7 to 30% by weight of aluminum. 10. The electric field type device according to claim 5, wherein a distance between the upper and lower gate electrodes is changed by applying pressure to the cap portion. Pressure sensor using a vacuum tube. 11. A structure in which a weight is formed on the cap, and when acceleration is applied to the weight, a force is applied to the cap and the distance between the upper and lower gate electrodes fluctuates. An acceleration sensor using the electric-field-type vacuum tube according to any one of claims 5 to 9. 12. The electric field type vacuum tube according to claim 1, wherein two SOI (silicon on insulator) wafers are processed and bonded.
Manufacturing method of pressure sensor or acceleration sensor. 13. A cap that covers a space between the emitter and the collector is provided with a sealing hole that is connected to the space in advance. After the cap is joined on the emitter and the collector, the sealing hole is closed in a vacuum. 13. The method for manufacturing an electric field type vacuum tube, a pressure sensor or an acceleration sensor according to claim 12, wherein the space is maintained in a vacuum by embedding with a vapor-deposited metal. 14. The method for manufacturing an electric field type vacuum tube, pressure sensor or acceleration sensor according to claim 13, wherein a metal having a getter function is deposited, and then an aluminum alloy is deposited to fill the sealing hole.