Semiconductor device and methods of manufacture thereof
The invention provides a method for use in forming a semiconductor device, the semiconductor device comprising a primary area and a periphery area, the method comprising: providing a substrate on which is situated: a stack in the primary area, the stack comprising a first oxide layer on the substrate, an oxynitride layer on the first oxide layer and a second oxide layer on the oxynitride layer; and a third oxide layer in the periphery area, the method further comprising: substantially removing the second oxide layer from the primary area and the third oxide layer from the periphery area; forming a fourth oxide layer in at least the primary area by an in situ steam generation (ISSG) process; and thereafter forming a polycrystalline semiconductor layer on the fourth oxide layer without any intervening oxidation process steps. Embodiments of the invention, when applied to, for example, the manufacture of SONOS devices, have the advantages that batch-to-batch variation of the thickness of the top blocking oxide of the ONO stack is reduced or eliminated, and ONO line width variation is reduced or eliminated.
1. A method for use in forming a semiconductor device, the semiconductor device comprising a primary area and a periphery area, the method comprising:
providing a substrate on which is situated:
a stack in the primary area, the stack comprising a first oxide layer on the substrate, an oxynitride layer on the first oxide layer and a second oxide layer on the oxynitride layer; and
a third oxide layer in the periphery area, the method further comprising:
substantially removing the second oxide layer from the primary area and the third oxide layer from the periphery area;
forming a fourth oxide layer in at least the primary area by an in situ steam generation (ISSG) process; and
thereafter forming a polycrystalline semiconductor layer on the fourth oxide layer without any intervening oxidation process steps.
2. The method according to claim 1 , wherein the polycrystalline semiconductor layer is formed on the fourth oxide layer without any intervening etching process steps.
3. The method according to claim 1 , wherein the second oxide layer in the primary area and the third oxide layer in the periphery area are removed in a single process step.
4. The method according to claim 1 , wherein the ISSG process is carried out in a rapid thermal processing chamber.
5. The method according to claim 1 , wherein the removal of the second and third oxide layers is performed using hydrofluoric acid.
6. The method according to claim 1 , further comprising setting the concentration of hydrogen in the ISSG process to obtain a desired thickness of the fourth oxide layer in the primary area.
7. The method according to claim 1 , further comprising performing RCA cleaning prior to forming the polycrystalline semiconductor layer.
8. The method according to claim 1 , wherein the semiconductor device is a SONOS device.