Temperature control for insertable target holder for solid dopant materials
An ion source with a target holder for holding a solid dopant material is disclosed. The ion source comprises a thermocouple disposed proximate the target holder to monitor the temperature of the solid dopant material. In certain embodiments, a controller uses this temperature information to vary one or more parameters of the ion source, such as arc voltage, cathode bias voltage, extracted beam current, or the position of the target holder within the arc chamber. Various embodiments showing the connections between the controller and the thermocouple are shown. Further, embodiments showing various placement of the thermocouple on the target holder are also presented.
1. An indirectly heated cathode ion source, comprising:
an arc chamber, comprising a plurality of walls connecting a first end and a second end;
an indirectly heated cathode disposed on the first end of the arc chamber;
a target holder, having a pocket to hold a dopant material;
a thermocouple in contact with the target holder;
a controller in communication with the thermocouple, wherein the controller varies a one or more parameters of the ion source based on a temperature measured by the thermocouple; and
an actuator assembly, the actuator assembly comprising:
wires to electrically connect the thermocouple to the controller;
a housing, comprising a rear housing, a front housing and an outer housing connecting the rear housing and the front housing;
a shaft affixed to the target holder, and having a retaining plate disposed within the housing;
a bellows disposed within the housing and affixed to the retaining plate on one end and to the rear housing on an opposite end;
an actuator to translate the shaft so as to move the target holder between a first position and a second position, wherein a first parameter of the one of more parameters comprises a position of the target holder.
2. The indirectly heated cathode ion source of claim 1 , wherein a second parameter of the one or more parameters is selected from the group consisting of arc voltage, filament current, cathode bias voltage, flow rate of feed gas, and beam extraction current.
3. The indirectly heated cathode ion source of claim 1 , further comprising a heating element in communication with the target holder, and wherein a second parameter of the one or more parameters comprises current supplied to the heating element.
4. The indirectly heated cathode of claim 1 , comprising a connector mounted in the front housing, wherein the wires pass from the controller through a space between the outer housing and the bellows, and terminate at the connector; and comprising a second connector, mated to the connector wherein thermocouple wires are disposed between the second connector and the thermocouple.
5. The indirectly heated cathode of claim 4 , wherein the thermocouple wires are coiled to allow target holder position adjustment with respect to the arc chamber.
6. The indirectly heated cathode of claim 1 , wherein the wires pass through a hollow interior of the shaft.
7. The indirectly heated cathode ion source of claim 1 , wherein a cavity is disposed on an interior surface of the target holder, and the thermocouple is disposed in the cavity.
8. The indirectly heated cathode ion source of claim 1 , further comprising a heating element in communication with the target holder, wherein the heating element comprises resistive wires.
9. The indirectly heated cathode ion source of claim 1 , wherein the target holder comprises:
a target base;
a crucible shaped as a hollow cylinder;
a crucible plug to cover one open end of the crucible and disposed proximate the target base; and
a porous plug to cover an opposite end of the crucible, wherein gaseous dopant material may pass through the porous plug.
10. The indirectly heated cathode ion source of claim 9 , wherein the thermocouple is affixed to an outer surface of the crucible.
11. The indirectly heated cathode ion source of claim 9 , wherein the thermocouple is disposed in a channel in a wall of the crucible.
12. The indirectly heated cathode ion source of claim 9 , wherein a cavity is disposed in the target base proximate the crucible plug and the thermocouple is disposed in the cavity proximate the crucible plug.
13. The indirectly heated cathode ion source of claim 9 , wherein a channel is disposed in the target base, the channel in communication with the cavity to allow wires to be routed to the thermocouple.
14. The indirectly heated cathode ion source of claim 9 , further comprising a shaft affixed to the target base, wherein an interior of the shaft is hollow to allow wires to be routed through the hollow interior of the shaft to the thermocouple.