Combination differential and absolute pressure transducer for load lock control

Combination differential and absolute pressure transducer apparatus for controlling a load lock that facilitates transfer of parts between a room at ambient atmospheric pressure and a vacuum processing chamber maintained at a pressure less than one (1) torr and that has an evacuatable load lock chamber, an exterior door positioned between the load lock chamber and the room, a interior door positioned between the load lock chamber and the processing chamber, a exterior door actuator that is responsive to an exterior door control signal to open or close the exterior door, an interior door actuator that is responsive to an interior door control signal to open or close the interior door, and a vacuum pump connected to the load lock chamber for evacuating the load lock chamber, wherein combination differential and absolute pressure transducer comprises:

• a differential pressure sensor that is capable of sensing a pressure difference between a first side of the differential pressure sensor and a second side of the differential pressure sensor, said differential pressure sensor being connected in fluid flow relation to the load lock chamber and mounted such that said first side is exposed to the ambient atmospheric pressure in the room and such that the second side is exposed to pressure in the load lock chamber;
• a differential pressure transducer circuit connected to the differential pressure sensor and which is capable of generating an exterior door control signal at a preset differential pressure value;
• an absolute pressure sensor that is capable of sensing absolute pressure, said absolute pressure sensor being connected in fluid flow relation to the load lock chamber in such a manner that the absolute pressure sensor is exposed to pressure in the load lock chamber;
• an absolute pressure transducer circuit connected to the absolute pressure sensor and which is capable of generating an interior door control signal at a preset absolute pressure value.

A method of automatically controlling a load lock that facilitates transfer of parts between a room at ambient atmospheric pressure and a vacuum processing chamber maintained at a pressure less than one (1) torr and that has an evacuatable load lock chamber, an exterior door positioned between the load lock chamber and the room, a interior door positioned between the load lock chamber and the processing chamber, a exterior door actuator that is responsive to an exterior door control signal to open or close the exterior door, an interior door actuator that is responsive to an interior door control signal to open or close the interior door, and a vacuum pump connected to the load lock chamber for evacuating the load lock chamber, comprising:

• sensing differential pressure between the load lock chamber and the ambient pressure in the room;
• transducing the sensed differential pressure to a voltage that corresponds in value to the sensed differential pressure;
• producing a differential pressure reference voltage that corresponds in value to the voltage that is transduced from the differential pressure when the differential pressure is at a desired differential pressure value for opening the exterior door;
• comparing the differential pressure reference voltage to the transduced voltage that corresponds in value to the differential pressure, and, when the transduced voltage equals the differential pressure reference voltage, producing the exterior door control signal and delivering the exterior door control signal to the exterior door actuator
• sensing absolute pressure in the load lock chamber;
• transducing the sensed absolute pressure to a voltage that corresponds in value to the absolute pressure;
• producing an absolute pressure reference voltage that corresponds in value to the voltage that is transduced from the absolute pressure when the absolute pressure is at a desired absolute pressure for opening the interior door;
• comparing the absolute pressure reference voltage to the transduced voltage that corresponds in value to the voltage that is transduced from the absolute pressure when the absolute pressure is at a desired absolute pressure value for opening the interior door;
• and
• comparing the absolute pressure reference voltage to the transduced voltage that corresponds in value to the absolute pressure, and, when the transduced voltage equals the absolute pressure reference voltage, producing the exterior door control signal and delivering the interior door control signal to the interior door actuator.

A method of automatically controlling a load lock that facilitates transfer of parts between a room at ambient atmospheric pressure and a vacuum processing chamber maintained at a pressure less than one (1) torr and that has an evacuatable load lock chamber, an exterior door positioned between the load lock chamber and the room, a interior door positioned between the load lock chamber and the processing chamber, a exterior door actuator that is responsive to an exterior door control signal to open or close the exterior door, an interior door actuator that is responsive to an interior door control signal to open or close the interior door, and a vacuum pump connected to the load lock chamber for evacuating the load lock chamber, comprising:

• predetermining a desired differential pressure value at which to open the external door, and predetermining a desired absolute pressure value at which to open the internal door;
• sensing actual differential pressure between the load lock chamber and the ambient pressure in the room;
• comparing the actual differential pressure to the predetermined differential pressure value, and, when the actual differential pressure equals the predetermined differential pressure value, producing the exterior door control signal and delivering the exterior door control signal to the exterior door actuator;
• sensing actual absolute pressure in the load lock chamber;
• and
• comparing the actual absolute pressure to the predetermined absolute pressure value, and, when the actual absolute pressure equals the predetermined absolute pressure value, producing the interior door control signal and delivering the interior door control signal to the interior door actuator.

In a combination differential and absolute pressure transducer for controlling an exterior door and an interior door of a load lock chamber used to facilitate transfer of parts between a room at ambient atmospheric pressure and a vacuum processing chamber maintained at a pressure less than one (1) torr by matching load lock pressure to atmospheric pressure PA when the exterior door is to be opened and matching load lock pressure to the pressure in the vacuum processing chamber when the interior door is to be opened, wherein the combination differential and absolute pressure transducer has (i) a manifold connected in fluid flow relation to the load lock chamber so that pressure in the manifold is equal to pressure in the load lock chamber, (ii) a differential pressure sensor connected to the manifold and being configured for sensing and outputting a differential pressure signal that is indicative of pressure differential between atmospheric pressure and load lock pressure in the manifold and load lock chamber (iii) a differential pressure transducer circuit connected electrically to the differential pressure sensor and being capable of generating an exterior door control signal at a preset differential pressure value for opening or allowing opening of the exterior door, (iv) an absolute pressure sensor connected to the manifold for sensing and outputting an absolute pressure signal that is indicative of absolute pressure in the manifold and load lock chamber;

• and (v) an absolute pressure transducer circuit connected electrically to the absolute pressure sensor and being capable of generating an interior door control signal at a preset absolute pressure value for opening or allowing opening of the interior door, an improvement comprising:
• a miniaturized combination differential and absolute pressure transducer in which the differential pressure sensor and the absolute pressure sensor are mounted and electrically connected in an integral manner to a printed circuit board that contains the differential pressure transducer circuit and the absolute pressure transducer circuit, and wherein the printed circuit board is attached to a manifold in a manner that seals the differential pressure sensor and the absolute pressure sensor to the manifold in fluid flow communication with ducts in the manifold that are adapted to be in fluid flow communication with the load lock chamber when the manifold is connected to the load lock chamber.

A miniaturized combination differential and absoluted pressure transducer for producing control signals based on pressure in a chamber, comprising:

• a printed circuit board comprising a differential pressure transducer circuit and an absolute pressure transducer circuit, including a differential pressure sensor connected to the printed circuit board mechanically and electrically as an integral component of the differential pressure transducer circuit, an absolute pressure sensor connected to the printed circuit board mechanically and electrically as an integral component of the absolute pressure transducer circuit;
• and an electrical connector connected to the printed cirucit board mechanically and electrically as an integral component for output of the control signals from the differential pressure transducer circuit and from the absolute pressure circuit;
• and
• a manifold with a connector fitting adapted for connection of the manifold to the chamber and with ducts extending between the connector fitting and a surface, wherein said printed circuit board is mounted on said manifold with the differential pressure sensor and the absolute pressure sensor sealed against said surfae around respective ones of said ducts such that said differential pressure sensor and said absolute pressure sensor are exposed to the pressure in the chamber via said ducts upon connection of the manifold to the chamber.

A combination differential and absolute pressure transducer for producing load lock control signals based on pressure in a load lock chamber, comprising:

• a micropirani absolute pressure sensor, which includes:
• (i) a substrate with a first cavity extending into its midsection and positioned in fluid flow communication with the load lock chamber such that gas pressure in the first cavity is the same as gas pressure in the load lock chamber;
• (ii) a cover with a second cavity extending into its midsection, said cover being positioned on the substrate with said second cavity juxtaposed to said fist cavity and in fluid flow communication with the load lock chamber so that gas pressure in the second cavity is also the same as the gas pressure in the load lock chamber;
• (iii) a membrane extending between the first cavity and the second cavity;
• (iv) a first resistive element positioned in the membrane, said resistive element having a resistivity that changes as a function of temperature;
• and a second resistive element positioned on the substrate;
• a differential pressure sensor, which includes:
• (i) A substrate supporting a resiliently flexible membrane, said substrate being mounted and sealed in such a mannuer that one side of the membrane is exposed to ambient atmospheric pressure and the opposite side is exposed to a cavity that is in fluid flow communication with the load lock chamber such that gas pressure in said cavity on said opposite side of the membrane is the same as the gas pressure in the load lock chamber;
• and (ii) a third resistive element that changes resistivity as a function of flexture positioned on the membrane;
• and
• a load lock control circuit comrprising:
• (i) an absolute pressure transducer circuit including micropirani sensor bridge circuit in which the first and second resistive elements are connected as separate branches, a first bridge voltage controller for maintaining balance in the micropirani sensor brige circuit, a first voltage monitor for measuing voltages needed to keep the micorpirani sensor bridge circuit in balance as an indication of absolute pressure in the load lock chamber, and a first relay control circuit set to activate a first relay switch to produce a first control signal when the pressure of gas in the load lock chamber is pumped down to an absolute pressure set point;
• and (ii) a differential pressure transducer circuit including a differential pressure sensor bridge circuit in which said third resistive element is connected as a branch, a second bridge voltage controller for maintaining balance in the differential pressure sensor bridge circuit, a second voltage monitor for measuring voltages needed to keep the differential pressure sensor bridge circuit in balance as an indication of differential pressure between ambient atmospheric pressure and the gas pressure in the load lock chamber, and a second relay control circuit set to actuate a second relay switch to produce a second control signal when the differential pressure reaches a differential pressure set point.