CONTROLLING THE THICKNESS AND WIDTH OF A CRYSTALLINE SHEET FORMED ON THE SURFACE OF A MELT USING COMBINED SURFACE COOLING AND MELT HEATING
An apparatus for controlling a thickness of a crystalline ribbon grown on a surface of a melt includes a crucible configured to hold a melt; a cold initializer facing an exposed surface of the melt; a segmented cooled thinning controller disposed above the crucible on a side of the crucible with the cold initializer; and a uniform melt-back heater disposed below of the crucible opposite the cooled thinning controller. Heat is applied to the ribbon through the melt using a uniform melt-back heater disposed below the melt. Cooling is applied to the ribbon using a segmented cooled thinning controller facing the crystalline ribbon above the melt.
1 . An apparatus for controlling a thickness of a crystalline ribbon grown on a surface of a melt comprising:
a crucible configured to hold a melt;
a cold initializer facing an exposed surface of the melt;
a segmented cooled thinning controller disposed above the crucible on a side of the crucible with the cold initializer, wherein the segmented cooled thinning controller is configured to cool a surface of the melt; and
a uniform melt-back heater disposed below of the crucible opposite the cooled thinning controller, wherein the uniform melt-back heater is configured to uniform heat to the melt.
2 . The apparatus of claim 1 , further comprising two insulating diffusion barriers disposed on the crucible between the cool thinning controller and the uniform melt-back heater, wherein the insulating diffusion barriers are disposed in the melt on opposite sides of a ribbon formed on the melt.
3 . The apparatus of claim 1 , wherein the cooled thinning controller includes a plurality of gas jets.
4 . The apparatus of claim 1 , wherein the cooled thinning controller includes a cold block and a plurality of heaters.
5 . The apparatus of claim 4 , wherein the cooled thinning controller includes one or more heat shields between the heaters.
6 . The apparatus of claim 1 , wherein the crucible has a depth of 0.5 cm or more.
7 . The apparatus of claim 1 , further comprising a puller configured to pull a ribbon formed on a surface of the melt in the crucible.
8 . The apparatus of claim 1 , further comprising an insulating diffusion barrier disposed on the crucible between the cold initializer and the cooled thinning controller.
9 . A method comprising:
providing a melt in a crucible;
forming a ribbon floating on the melt using a cold initializer facing an exposed surface of the melt, wherein the ribbon is single crystal;
applying heat to the ribbon through the melt using a uniform melt-back heater disposed below the melt;
applying cooling to the ribbon using a segmented cooled thinning controller facing the crystalline ribbon above the melt;
pulling the ribbon, wherein the ribbon is formed at a same rate as the pulling; and
separating the ribbon from the melt at a wall of the crucible where a stable meniscus forms.
10 . The method of claim 9 , further comprising minimizing diffusion of heat into an edge of the ribbon using two insulating diffusion barriers disposed in the melt.
11 . The method of claim 9 , wherein the segmented cooled thinning controller includes a plurality of gas jets.
12 . The method of claim 9 , wherein the segmented cooled thinning controller includes a cold block and a plurality of heaters.
13 . The method of claim 9 , further comprising adjusting the segmented cooled thinning controller and/or the uniform melt-back heater to provide a targeted thickness profile to the ribbon.
14 . The method of claim 13 , further comprising measuring a thickness of the ribbon and providing dynamic feedback control of channels in the segmented cooled thinning controller to maintain the thickness profile over an extended length of the ribbon.
15 . The method of claim 9 , wherein the melt includes silicon.