JPH06203712A - Absolute pressure type semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To lessen the wiring resistance by forming an electrode wiring from a metal material. CONSTITUTION:A silicon board 5 is fitted with a diaphragm 5a consisting of a recess, a lower electrode 2 formed over the diaphragm, and a pad 8a as the external terminal of the lower electrode 2, and to this silicon board 5, a glass board 1 provided with an upper electrode 1a and a hole 9 mating with the pad is anode joined to form a sealed space, and the pressure is sensed by the diaphragm 5a. In this semiconductor pressure sensor of absolute pressure type, electrodes of the silicon board 5 and glass board 1 are formed from metal material, and a step smaller than the thickness of the metal electrode is formed in adjacency to the recess in the silicon board 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor and a pressure switch for measuring absolute pressure such as atmospheric pressure and water pressure with a capacitance or a contact switch.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 2 (a) and 2 (b), in an absolute pressure type semiconductor pressure sensor, particularly a capacitance type or switch type pressure sensor, an upper electrode 1 and a lower electrode 2 are provided with a cavity. In order to connect 3 to the external wiring while making it a closed space, it is normal to wire via the diffusion resistance 4. This is advantageous in that, if diffusion conditions are properly set, the surface of the silicon substrate is hardly changed even if diffusion resistance is formed, so that the sealed space can be easily formed by anodic bonding of the silicon substrate 5 and the glass substrate 6. This is because.

[0003]

However, in this conventional structure, since the wiring structure interposing the diffusion resistance is adopted, the wiring resistance depends on the concentration of the impurity diffusion into the silicon substrate, and is different from the case of the wiring of a simple metal. There was a problem that the resistance became larger than that.

Therefore, in order to solve the above-mentioned conventional problems, an object of the present invention is to have a resistance value similar to that of metal wiring and yet to have a sealed structure of a reference pressure chamber so as to function as an absolute pressure type pressure sensor. To obtain a structure that can maintain.

[0005]

In order to solve the above-mentioned problems, the present invention is an absolute pressure type semiconductor pressure sensor having a structure in which an upper electrode 1 and a lower electrode 2 are independently taken out, and a part adjacent to a cavity 3. An electrode receiving portion 7 having a recess shallower than the thickness of the wiring metal for relaying the upper electrode (glass-side electrode) is formed on the wiring, and the upper electrode and the lower electrode are individually wired, and the area of the pad for connecting the lead wire is The structure is larger than the hole 9 formed in the glass substrate.

[0006]

In the absolute pressure type semiconductor pressure sensor constructed as described above, both the upper electrode 1 and the lower electrode 2 can be wired without using the diffusion resistance 4, so that the wiring resistance can be as small as a metal. Moreover, since the metal of the pad wiring portion and the glass are hermetically bonded to each other by anodic bonding, the sealed space of the cavity 3 is maintained and the function of the absolute pressure sensor is not impaired. Therefore, it is possible to obtain a pressure sensor and a pressure switch that are of the absolute pressure type and have a wiring resistance as low as a metal wiring.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view and a plan explanatory view of a pressure sensor of the present invention. An upper electrode 1a formed on one plane of a glass substrate 1 is adjacent to a cavity 3 via an electrode receiving portion 7 provided on a silicon substrate 5. Contact the pad side metal wiring 8a. The pad 8 which is provided on the pad-side metal wiring 8a and serves as a lead wire connecting portion has a plane larger than the hole 9 formed in the glass substrate 1, and the periphery of the hole 9 is the pad-side metal wiring. The glass substrate 1 is anodically bonded to the silicon substrate 5 on 8a.

Next, an outline of a manufacturing process for realizing the structure of the pressure sensor according to the present invention is shown in FIG. First,
A silicon oxide film is formed on the n-type (100) silicon substrate 5 by thermal oxidation, and the pattern of the cavity 3 and the alignment mark are patterned by a photolithography method. Next, the cavity 3 portion is formed by anisotropic etching with KOH, and the electrode receiving portion 7 is similarly formed (FIG. 3A). Next, a silicon nitride film 10 for forming a silicon diaphragm is formed, and this is patterned to form a lower electrode 2 made of aluminum in the cavity portion (FIG. 3B). On the other hand, the glass substrate 1 is similarly patterned by photolithography and the portion to be the lead wire connection hole 9 is subjected to an etching process of about 50 μm by the hydrofluoric acid solution, and the upper electrode 1a made of aluminum is formed on this and patterned. FIG. 3C).

After that, the upper electrode 1a and the lower electrode 2 are made to face each other, and the glass substrate 1 and the silicon substrate 5 are placed.
Are anodically bonded, and then a diaphragm 5a is formed by a KOH solution, and then a portion corresponding to the pad of the glass substrate 1 is grooved with the diaphragm being thinned by about 40 μm (FIG. 3 (d)). Finally, the lead wire (not shown) is connected by timing with the outer shape of the desired pressure sensor. In addition,
Although aluminum is used as the wiring metal in this example, it goes without saying that a metal other than aluminum may be used as the wiring metal as long as anodic bonding is possible.

When the resistance of the pressure switch manufactured as described above when the switch was short-circuited was measured, it was about 30Ω. The resistance can be reduced to several Ω or less by changing the thickness and pattern of the wiring metal.

[0011]

As described above, according to the present invention, since the wiring is made of metal even though it is an absolute pressure type, the wiring resistance can be extremely reduced and a highly sensitive pressure sensor and pressure switch can be provided. There is an effect.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a structure of a pressure sensor of the present invention.

FIG. 2 is an explanatory diagram showing a structure of a conventional pressure sensor.

FIG. 3 is an explanatory view showing a method for manufacturing the pressure sensor of the present invention.

[Explanation of symbols]

 1 Upper electrode 2 Lower electrode 3 Cavity 4 Diffusion resistance 5 Silicon substrate 6 Glass substrate 7 Electrode receiving part 8 Pad part 9 Lead wire connection hole 10 Silicon nitride

Claims (2)

[Claims] 1. A diaphragm having a concave portion, a lower electrode formed on the diaphragm, and a silicon substrate having a pad as an external terminal of the lower electrode, and a hole facing the upper electrode and the pad are formed in the silicon substrate. In an absolute pressure type semiconductor pressure sensor in which a sealed space is formed by anodic bonding a glass substrate formed by the above, the electrodes of the silicon substrate and the glass substrate are formed of a metal material, and the silicon substrate is formed. An absolute pressure type pressure sensor, characterized in that a step having a thickness equal to or less than the thickness of the metal electrode is formed adjacent to the concave portion. 2. The absolute pressure type pressure sensor according to claim 1, wherein the hole formed in the glass substrate has an opening facing the pad of the silicon substrate and smaller than the size of the pad.