RU1778576C - Capacitive pressure converter - Google Patents

Abstract

Usage: the invention can be used to measure pressure with increased accuracy. Essence: an increase in accuracy and manufacturability is achieved by the fact that a movable electrode is formed on a dielectric layer on a semiconductor membrane, and it is connected by a metallized conductor through holes made in the dielectric layer with a semiconductor region in a silicon substrate having a different type of conductivity. This circumvents the metallized juice. 2 ill.

Description

The invention relates to measuring technique, namely to micromechanical sensor devices for measuring non-electrical quantities by electrical methods.

A known construction and method for manufacturing a capacitive pressure transducer consisting of an upper glass plate, a silicon plate and a lower glass plate are joined together by electrostatic bonding of anode welding.

The main disadvantage of this design and method of connection is the impossibility of providing an electrostatic connection of a sealed connection between the silicon wafer in which the membrane and the first electrode of the sensing element (SE) are formed. and a glass plate having on the surface of the molten metallization, serving as the response (second) electrode of the SE. In addition, product reliability is reduced due to

possible corrosion of metallization not protected from environmental influences,

The transducer design and its manufacturing method are also known, according to which the transducer includes two main parts — an elastic element formed in a silicon orientation plate (100) and containing a first capacitor plate and a glass substrate (Corning Glass 7070 and Schoft 8284), on which a second pressure sensitive capacitor plate. In order to provide electrical contact between the conductive region of the glass substrate and the silicon wafer, a recess is formed in the glass substrate, passing through the glass layer to the silicon substrate. A portion of the conductive metal film is located above the region of this recess,

The disadvantages of the prototype include:

- the complexity of manufacturing technology:

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a) when a glass substrate is connected to a conductive region with a silicon elastic element, due to the thickness of the conductive region, anodic welding is skewed, which can be eliminated only by performing additional technological operations, for example, etching in silicon under the conductive region of the recess with a depth of less than or equal to the thickness of the metal film, which increases the complexity of manufacturing;

b) the need to form a through hole in the glass, which complicates the design and, as a consequence, the complexity of manufacturing;

c) the complexity of forming and ensuring the reliability of the contact, which is associated with the size of the through hole and the conductivity of silicon. Ensuring contact reliability requires increasing the size of the through hole, which increases the size of the structure;

-for the manufacture of the sensor, only low-resistance semiconductor material is used, since otherwise the resistance between the conductive layers of the glass substrate and the silicon wafer sharply increases.

The aim of the invention is to improve the accuracy and manufacturability of the capacitive pressure transmitter,

The goal is achieved in that the design of the capacitive pressure transducer, in addition to the movable and fixed electrodes and the contact pads for them, contains a silicon substrate of any type of conductivity and various resistivity with a formed membrane with a dielectric coating, local doped portions of the type of conductivity opposite to the silicon substrate and located outside membrane zones, two holes in the dielectric coating to local doped areas At least one to the cre mnoezoy substrate, closed metallized juice, covering the membrane and passing over the local doped portions and between the holes to them and over the holes to the silicon substrate providing electrical contact with the latter, the first contact pad of the fixed electrode between the metallized strip and the membrane, providing electrical contact with a second contact pad of a fixed electrode located on a glass substrate.

The proposed capacitive pressure transducer differs from the prototype

1) the presence of local doped regions with the type of conductivity opposite to the type of conductivity of the silicon substrate, and located outside the membrane;

52) the presence of a closed metallized along the ska, covering the membrane; 3) the presence of holes or holes in the dielectric coating to the silicon substrate to provide electrical

0 contact between the metallized strip and the substrate, which ensures a decrease in the working voltage during the electrostatic connection of silicon and glass substrates;

5 4) the exclusion of mechanical operations, such as drilling, etc .;

5) the ability to create a multi-electrode capacitive converter. Such signs in known sources

0 not found, which indicates their novelty. The construction of the capacitive pressure transducer of the invention is shown in Fig. 1, which shows the cross section of the transducer; figure 2 is a top view of a silicon substrate.

The proposed capacitive pressure transducer comprises a silicon substrate 1 with a dielectric coating 2, in which a recess and a membrane are formed

0 3, on which there is a movable electrode 4 with a metallized conductor 4, outside the membrane there are local doped sections 5, holes b to the doped sections, hole 7 to the silicon

5 to the substrate and metallized juice 8 extending over the hole 7 and between the holes 6 to the doped portion 5, the first contact pad 9 is between the metallized along the membrane and the membrane, and outside the surface limited by the metallized along the lip, there are lead contact pads 10 movable and fixed electrodes for external connection of a capacitive pressure transducer 5; the silicon substrate 1 is electrostatically connected to a glass substrate 11 on which there is a fixed electrode 12 with a metallized conductor 12a and a second

0 contact pad 13, which when connected should coincide with the first contact pad 9 of the silicon substrate 1. When packaging the capacitive pressure transmitter

5 is attached from the deep indentation side of the membrane directly to the housing or to a glass substrate having an opening for connection to an external medium, the pressure of which is measured, and then to the housing.

A capacitive pressure transducer was manufactured as follows.

In a silicon substrate 1 with a thickness of 380 μm, an orientation (100) of the KEF brand, a resistivity of 0.30 m-cm, a membrane 3 is formed, while for measuring pressure up to 1 atm, the notch on the front side of the substrate was 5-10 μm, and a recess of a depth of about 270 microns, which was located under the recess of the front side, was etched from the reverse side: the thickness of the membrane 3 formed by both recesses was 100 microns.

To form the membrane 3, a dielectric coating 2 was applied to both surfaces of the silicon substrate, either 1.2 μm oxide obtained by gas-phase deposition or a composition consisting of 0.05 μm thick thermal oxide films, 0.1 μm silicon nitride, and deposited oxide 0.3 microns. By means of double-sided photolithography or successive photolithographs, corresponding openings (windows) were formed in the coating to form the membrane.

Etching in an anisotropic etchant KOH formed recesses lying one above the other and forming a membrane 3 of 4.54.5 mm in size. Then the dielectric coating was removed, the dielectric coating was formed again - thermal oxide by thermal oxidation at T 1150 ° C to obtain an oxide thickness of 0.6-1.0 microns in an atmosphere of moist oxygen. Through this photolithographic process, holes (windows) were opened in which oxide was doped with boron at T 950 ° C, followed by acceleration at T 1050 ° C in moist oxygen to create local doped zones 5. of the type of conductivity; opposite to the type of conductivity of the substrate.

After removal of borosilicate glass, in the case of diffusion doping with boron from a liquid or solid source, heat treatment was again carried out in an oxidizing atmosphere to form oxide over the doped regions. Then, using the photolithographic process, holes (windows) were formed, two holes (windows) and one or several holes (windows) 7 to each local doped area; In order to provide a better electrical contact, a layer of aluminum with a thickness of 1.3 ± 0.15 μm was deposited by vacuum spraying onto the front surface of silicon substrate 1 by a vacuum. This conductive layer was subjected to a photolithographic process, as a result of which a movable electrode 4 located on the membrane was formed , with a metallized conductor 4a, metallized along the juice 8, passing over the hole 7 and between the holes 6 to the local doped sections 5. The first contact pad 9 between the metallized 8 and the membrane 3 is bounded by a metallized strip outside the conductivity, contact pads 10 are withdrawn. It should be noted that the metallized juice passes between the holes 6 to the local doped portions 5 without shorting the holes 6 with each other. The size of the conductive (metallized) movable electrode was 2.7 x 2.7 mm, the size of the conductor was 1.5 x 1.0 mm, and the size of the contact pads was 0.5 x 1.0 mm.

All of these sizes may be different when using appropriate templates for photolithography.

To ensure adhesion and better contact with the substrate and doped regions, the Al layer was heat treated at T 450 ° C for 30 minutes.

The silicon substrate of the 88 mm capacitive pressure transducer with a formed membrane, local doped zones, a metallic electrode along the strips, metallized conductors and contact pads was obtained after dividing the silicon wafer / 7Q mm into separate chips. The glass substrate 11 on which the stationary electrodes 12 were formed, the metallized conductor 12a and the second contact pad 13 were made as follows.

As glass substrates, LK-105 or pyrere glass was used. 1 mm thick, a conductive layer of aluminum or chromium was applied to the glass substrate by vacuum spraying. Then, using a photolithographic process, a fixed electrode with a size of 2.8 x 2.8 mm, a metallized conductor with a size of 1.5 x 1.0 mm, connecting the electrode and a second contact pad with a size of 0.4 x 0.9 mm were formed.

The glass substrate with metallization was fired at a temperature of 450 ° C for 1B min in an argon atmosphere.

The silicon and glass substrates were interconnected electrostatically at T 400 ° C, Unp 400-1500 V and I 5 mA.

Claims (1)

SUMMARY OF THE INVENTION A capacitive pressure transducer containing a silicon substrate in which the membrane is integral with it, and a movable electrode of the measuring capacitor is formed on the membrane, a glass substrate is bonded to the silicon substrate, on which a terminal block is formed with a metallized conductor connected to its second end with a movable electrode, a fixed electrode of the measuring capacitor located with an interelectrode gap from the movable electrode, metal a juice, covering the membrane, and a silicon substrate, and the output terminal of the fixed electrode is located outside the surface limited by metallized skim, characterized in that, in order to improve accuracy and manufacturability, it is on the silicon substrate and the membrane under the movable electrode a dielectric layer is formed on the metallized conductor and the contact pads on which between the metallized cone and the membrane the first contact pad is made, and outside the surface bounded by a metallized strip, there is a lead-out contact pad of a movable electrode, a second contact pad, connected by a metallized conductor to a fixed electrode, is placed on the glass substrate in a dielectric layer under the second holes are made with the end of the metallized conductor, the first contact pad, lead-out contact pads, and metallized along the strips, and sections with a conductivity of a different type than in it are made in the silicon substrate, and through these sections and through the holes of the first, the fixed electrode pad and the second end of the metallized conductor connected respectively the lead-out pad of the fixed electrode and the lead-out pad of the movable electrode, the glass substrate is bonded at its periphery to a metallized slope, and the first and second contact pads of the fixed electrode are fastened together. & , / /, /, 7- / - -, / / / / Л / / # / /, V //// S7r779r // Y /// / 2 / g 3/3 / g and Zz tfr / S / TjL Srig. 1 N