1. An automatic pressure canning appliance, comprising:
a main body in which a pot is received;
a heater disposed in the main body in close proximity to the pot when the pot is received in the main body;
a top lid movable between open and closed positions and sealing to the pot when in the closed position, the pot and lid when the lid is in the closed position and sealed to the pot defining a pressure chamber;
a pressure chamber vent having an inlet that opens to the pressure chamber and an outlet that opens to atmosphere;
a primary temperature sensor that senses a temperature in the pressure chamber;
a control module having a plurality of pre-programmed canning recipe programs, each of the pre-programmed canning recipes having a pre-programmed processing time, the primary temperature sensor coupled to the control module;
the appliance having a canning recipe program selection stage followed by a heating stage followed by a processing stage followed by a cooling stage;
the control module when the appliance is in the canning recipe program selection stage configured to be responsive to a user input via a control panel of the appliance to select one of the pre-programmed canning recipe programs;
the control module configured to transition the appliance to the heating stage in response to a user start input via the control panel of the appliance after selection of the pre-programmed canning recipe programs, the control module when the appliance is in the heating stage configured to energize the heater to heat the pressure chamber and to cycle the heater on and off to maintain the temperature in the pressure chamber sensed by the primary temperature sensor between an upper temperature set point and lower temperature set point that are both above a temperature at which water boils, wherein during the heating stage water received in the pot is boiled into steam and all air is vented from the pressure chamber via the vent creating a pure steam environment in the pressure chamber;
the control module configured to transition the appliance to the processing stage upon expiration of a predetermined heating time, wherein when the appliance is in the processing stage, the control module is configured to continue to cycle the heater on when the temperature sensed by the primary temperature sensor falls to the lower temperature set point and to cycle the heater off when the temperature sensed by the primary temperature sensor rises to the upper temperature set point wherein during the processing stage a pure steam environment is maintained inside the pressure chamber; and
the control module configured to transition the appliance to the cooling stage upon expiration of the pre-programmed processing time for the selected canning recipe program.
2. The appliance of claim 1 wherein when the appliance is in the cooling stage, the control module is configured to de-energize the heater and the pressure chamber depressurizes to atmospheric pressure.
3. The appliance of claim 1 further including a pre-heating stage that precedes the canning recipe program selection stage wherein in response to user input via the control panel, the control module is configured to energize the heater and in response to a pot temperature sensor sensing that a temperature of the pot is at or above a pre-heat temperature set point, the control module is configured to de-energize the heater for a short cooling period and then to reenergize the heater and configured to repeat de-energizing the heater for a short cooling period when the temperature of the pot is at or above the pre-heat temperature set point and then re-energize the heater after the short cooling period until a pre-heat period expires or the appliance has been transitioned to the canning recipe program selection stage in response to the user canning recipe program selection input.
4. The appliance of claim 1 wherein the lid includes a loading chamber therein, the vent is a vent pipe extending into the loading chamber and having an outlet above which a steam diffuser is disposed in spaced relation to the outlet of the vent pipe a distance to provide enough back pressure so that pressure in the pressure chamber can reach up to 8 psi at a higher elevation of 6000 feet above sea level.
5. The appliance of claim 4 wherein the steam diffuser is disposed 5 millimeters above the outlet of the vent pipe.
6. The appliance of claim 4 wherein the top lid includes a drip ring disposed around a lower periphery of the top lid.
7. The appliance of claim 6 wherein the pot is an inner pot and the main body includes an outer pot in which the inner pot is received, the main body including a shell that surrounds the outer pot in spaced relation to the outer pot.
8. The appliance of claim 4 wherein the upper temperature set point is in the range of 103\xb0 C. to 122\xb0 C. and the lower temperature set point is in the range of 95\xb0 C. to 101\xb0 C.
9. The appliance of claim 8 wherein the upper temperature set point is 103\xb0 C. and the lower temperature set point is 101\xb0 C.
10. The appliance of claim 1 further including a secondary temperature sensor that also senses the temperature in the pressure chamber, the control module configured to read the temperature sensed by secondary temperature sensor when it reads the temperature sensed by the primary temperature sensor and configured to determine that a fault exits if there is more than a predetermined temperature difference between the temperature sensed by the primary temperature sensor and the temperature sensed by the secondary temperature sensor, the controller configured to terminate selected canning recipe program and shut the heater off upon determining that a fault exists.
11. The appliance of claim 10 wherein the primary temperature sensor and the secondary temperature sensor are disposed at a bottom of the lid.
12. The appliance of claim 11 wherein the primary temperature sensor is an NTC temperature sensor and the secondary temperature sensor is an NTC temperature sensor.
13. An automatic pressure canning appliance, comprising:
a main body in which a pot is received;
a heater disposed in the main body in close proximity to the pot when the pot is received in the main body;
an top lid movable between open and closed positions and sealing to the pot when in the closed position, the pot and top lid when the top lid is in the closed position and sealed to the pot defining a pressure chamber;
a pressure chamber vent having an inlet that opens to the pressure chamber and an outlet that opens to atmosphere, the pressure chamber vent adapted to provide enough back pressure so that pressure in the pressure chamber can reach up to 8 psi at 6000 feet above sea level;
a primary temperature sensor that senses a temperature in the pressure chamber; and
a control module that when the appliance is in a processing stage, is configured to cycle the heater on and off to maintain a temperature sensed by the primary temperature sensor between an upper temperature set point and a lower temperature set point wherein the lower temperature set point is at least 100\xb0 C. and the upper temperature set point is above the lower temperature set point.
14. The appliance of claim 13 wherein the top lid includes a loading chamber therein, the vent is a vent pipe extending into the loading chamber and having an outlet above which a steam diffuser is disposed in spaced relation to the outlet of the vent pipe a distance to provide enough back pressure so that pressure in the pressure chamber can reach up to 8 psi at a higher elevation of 6000 feet above sea level.
15. The appliance of claim 14 wherein the steam diffuser is disposed 5 millimeters above the outlet of the vent pipe.
16. The appliance of claim 14 wherein the top lid includes a drip ring disposed around a lower periphery of the top lid.
17. The appliance of claim 16 wherein the pot is an inner pot and the main body includes an outer pot in which the inner pot is received, the main body including a shell that surrounds the outer pot in spaced relation to the outer pot.
18. The appliance of claim 13 wherein the upper temperature set point is in the range of 103\xb0 C. to 122\xb0 C. and the lower temperature set point is in the range of 95\xb0 C. to 101\xb0 C.
19. The appliance of claim 18 wherein the upper temperature set point is 103\xb0 C. and the lower temperature set point is 101\xb0 C.
20. The appliance of claim 19 wherein the primary temperature sensor is an NTC temperature sensor.
21. The appliance of claim 13 further including a heating stage that precedes the processing stage wherein when the appliance is in the heating stage, water received in the pot is boiled into steam and all air is vented from the pressure chamber via the vent creating a pure steam environment in the pressure chamber and the control module is
configured to cycle the heater on when the temperature sensed by the primary temperature sensor falls to the lower temperature set point and to cycle the heater off when the temperature sensed by the primary temperature sensor rises to the upper temperature set point and to transition the appliance to the processing stage upon expiration of a predetermined heating time, wherein the pure steam environment is
maintained in the pressure chamber during the processing stage.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A susceptor configured to receive a semiconductor wafer on the surface thereof during the deposition of a layer on a front surface of the semiconductor wafer by chemical vapor deposition (CVD), the susceptor comprising a gas-permeable structure with a porosity of at least 15%, a density of from 0.5 to 1.5 gcm3, a pore diameter of less than 0.1 mm and an internal surface area of the pores which is greater than 10,000 cm2cm3, wherein the structure consists essentially of at least one of graphite fibers coated with silicon carbide or graphite particles coated with silicon carbide, and wherein the silicon carbide coating thickness decreases from the surface of the susceptor toward the interior of the susceptor.
2. A process for producing a semiconductor wafer having a layer deposited on a front surface by chemical vapor deposition (CVD) and a polished or etched back surface, the semiconductor wafer, for deposition of the layer, being placed on a susceptor such that the back surface of the semiconductor wafer faces the susceptor, comprising passing gaseous substances through a susceptor of claim 1 by gas diffusion from a region below the back surface of the semiconductor wafer and above the surface of the susceptor.
3. The process of claim 2, wherein following chemical vapor deposition and removal of the semiconductor wafer from the chemical vapor deposition reactor, the back side of the wafer has a nanotopology expressed as PV (=peak to valley) height fluctuation of less than 5 nm, and a halo, expressed as haze, of less than 5 ppm.
4. The process of claim 2, wherein said layer is an epitaxial silicon layer.
5. The process of claim 2, further comprising removing from said susceptor, a semiconductor wafer having a back surface, and a front surface which has been coated by chemical vapor deposition (CVD), wherein the nanotopography of the back surface, expressed as the PV (=peak to valley) height fluctuation, is less than 5 nm, and at the same time the halo of the back surface, expressed as haze, is less than 5 ppm, measured following coating by chemical vapor deposition prior to further refining the surface by polishing or etching after removal from a CVD reactor.
6. A semiconductor wafer having a polished or etched back surface, a front surface which has been coated by chemical vapor deposition (CVD), wherein the nanotopography of the back surface produced by the process of claim 2, expressed as the PV (=peak to valley) height fluctuation, is less than 5 nm, and at the same time the halo of the back surface, expressed as haze, is less than 5 ppm, measured following deposition without any further refinement of the back surface.
7. A semiconductor wafer having a back surface, and a front surface which has been coated by chemical vapor deposition (CVD), wherein the nanotopography of the back surface, expressed as the PV (=peak to valley) height fluctuation, is less than 5 nm, and at the same time the halo of the back surface, expressed as haze, is less than 5 ppm, measured following coating by chemical vapor deposition prior to further refining the surface by polishing or etching after removal from a CVD reactor.