Methods for producing a single crystal silicon ingot using boric acid as a dopant and ingot puller apparatus that use a solid-phase dopant
Methods for producing a single crystal silicon ingot are disclosed. The ingot is doped with boron using solid-phase boric acid as the source of boron. Boric acid may be used to counter-dope the ingot during ingot growth. Ingot puller apparatus that use a solid-phase dopant are also disclosed. The solid-phase dopant may be disposed in a receptacle that is moved closer to the surface of the melt or a vaporization unit may be used to produce a dopant gas from the solid-phase dopant.
1. An ingot puller apparatus for producing a doped single crystal silicon ingot, the ingot puller apparatus comprising:
an ingot puller outer housing;
an ingot puller inner chamber formed within the ingot puller outer housing;
a crucible disposed within the ingot puller inner chamber;
an outer feed tube that is at least partially disposed exterior to the ingot puller outer housing, the outer feed tube defining an outer feed tube chamber and having a distal end, proximal end and an outer feed tube axis that extends through the distal end and the proximal end;
an elongate member that is moveable within the outer feed tube chamber along the outer feed tube axis, the elongate member being a tube, rod or shaft; and
a dopant receptacle coupled to the elongate member such that movement of the elongate member along the outer feed tube axis causes the dopant receptacle to move along the outer feed tube axis, the dopant receptacle being moveable between a loading position in which the dopant receptacle is disposed exterior to the ingot puller outer housing and a feed position in which the dopant receptacle is disposed within the ingot puller inner chamber, wherein the dopant receptacle is a capsule that is separable from the elongate member to enable the capsule to be pulled through an access port that extends through the outer feed tube, the capsule being accessible externally from the ingot puller outer housing when the capsule is aligned with the access port along the outer feed tube axis.
2. The ingot puller apparatus as set forth in claim 1 wherein the capsule comprises:
an outer capsule housing; and
a weir disposed within the outer capsule housing, the weir forming a channel for dopant gas to pass through, the weir having an upper end and a lower end, the upper end and lower end being open, an annular chamber disposed between the weir and the ingot puller outer housing for holding solid-phase dopant.
3. The ingot puller apparatus as set forth in claim 2 wherein the elongate member includes a ledge, the capsule being seated on the ledge of the elongate member.
4. The ingot puller apparatus as set forth in claim 1 comprising a tube disposed below the dopant receptacle to direct dopant gas to a surface of a melt.
5. The ingot puller apparatus as set forth in claim 1 wherein the elongate member is a tube.
6. The ingot puller apparatus as set forth in claim 1 further comprising a valve for sealing the ingot puller inner chamber when the elongate member is withdrawn from the ingot puller inner chamber.
7. The ingot puller apparatus as set forth in claim 1 comprising a translation device for moving the dopant receptacle between the loading position and the feed position, the translation device being a magnetically coupled through-wall translation unit.
8. The ingot puller apparatus as set forth in claim 1 further comprising a heat shield for shrouding the single crystal silicon ingot during ingot growth, the heat shield including a channel formed therein, the elongate member being disposed in the channel when the dopant receptacle is in the feed position.