# US 5,347,869 A · Structure of micro-pirani sensor

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- Number: US 5,347,869 A
- Document ID: US5347869A
- Status: Granted
- Kind: A
- Application number: 08/036,938
- Filed: 1993-03-25
- Granted: 1994-09-20
- Earliest claimed: 1993-03-25
- Assignees: Opto Tech Corporation
- Inventors: Jin-Shown Shie; Ping-Kuo Weng
- Web page: https://patentgrep.com/patent/US5347869A

## CPC

- G01L 21/12: measuring changes in electric resistance of measuring members, e.g. of filaments; Vacuum gauges of the Pirani type
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)

## Abstract

A new structure of a vacuum meter with good designs of temperature compensation and stabilization, The structure comprises a floating plate made by a micro-machining technique and a thermal sensitive element installed on the floating plate, The floating plate has a number of suspending arms extending outward to supporting the floating plate in a cavity of a semiconductor substrate for good heat isolation. The area of the floating plate and the length and width of the suspending arm has a specific ratio for an optimized sensitivity. A dummy resistor for temperature compensation is composed by a serial connection of a constant resistor with almost zero temperature coefficient and the thermal sensitive elements in a specific ratio. The vacuum meter further overlap on a temperature-controlled thermoelectric cooling device and is covered by a thermal shield so that the temperatures on and circumferential to the floating plate can be maintained stably.

## Claims

### Claim 1

A micro-Pirani vacuum meter, a structure thereof comprising:
(a) a floating plate suspended on a cavity of a silicon substrate made by a anisotropic etching technique;
(b) a plurality of suspending arms extending from said floating plate to connect to said substrate on the circumference of said cavity for supporting said floating plate suspended on said cavity; and
(c) a mixed resistor circuit for temperature compensations; said mixed resistor circuit being composed of a thermal sensitive constant resistor A with a zero temperature coefficient and a resistor B made of the same material as the thermal sensitive constant resistor A; both of said resistors being serially connected to each other on said floating plate.

### Claim 2 (depends on 1)

The vacuum meter of claim 1, wherein the ratio of the impedance of said thermal sensitive constant resistor A and the total impedance of said mixed resistor circuit is .beta. and .beta. is a value between 0.1 and 0.5.

### Claim 3 (depends on 1)

The vacuum meter of claim 1, further comprising a thermal shield which is convex and arched shaped and covers said floating plate with a gap therebetween; said thermal shield being adhered to the circumferential substrate of said cavity on the edges thereof with a number of openings on corresponding positions to said suspending arms of said floating plate.

### Claim 4 (depends on 3)

The vacuum meter of claim 3, further being stacked on a thermoelectric cooler having a constant temperature controlling means and then being packaged on a base for providing further temperature compensation and stabilization effects.

### Claim 5 (depends on 1)

The vacuum meter of claim 1, further being stacked on a thermoelectric cooler having a constant temperature controlling means and then being packaged on a base for providing further temperature compensation and stabilization effects.

### Claim 6 (depends on 1)

The vacuum meter of claim 1, wherein the material of said floating plate is SiO.sub.2 or Si.sub.3 N.sub.4 or SiON.

### Claim 7 (depends on 1)

The vacuum meter of claim 1, wherein the material of said thermal sensitive constant resistor A is a material with high thermal sensitivity.