Pressure gauge for organic materials

1. A vacuum gauge of the Pirani type for measuring the pressure of vaporized organic or inorganic material used in forming a layer of a device, comprising:

a) an extended filament having a thickness of 5 microns or less and having a temperature coefficient of resistance greater than 0.0035/° C., the filament being subject to the vaporized organic or inorganic material;

b) means for applying a current to the filament so that the temperature of the filament is less than 650° C. so as not to degrade the molecular structure of the organic material; and

c) means responsive to a change in resistance or a change in current to determine heat loss from the filament, which is a function of the pressure of the vaporized organic or inorganic material.

2. The vacuum gauge of claim 1 wherein the filament is helically wound.

3. The vacuum gauge of claim 2 wherein the helically wound filament is further formed into a second helix.

4. The vacuum gauge of claim 3 wherein the helically wound filament has an apparent length of greater than 1 cm.

5. The vacuum gauge of claim 1 wherein the current applying means is a constant current source.

6. The vacuum gauge of claim 1 wherein the current applying means further includes a circuit for maintaining a constant filament temperature.

7. The vacuum gauge of claim 1 wherein the filament is made from tungsten, molybdenum, nickel, platinum, copper, iron, or alloys thereof which have the required temperature coefficient of resistance.

8. The vacuum gauge of claim 1 wherein the filament has a thickness of 4 microns or less.