Polysilicon contact

The method of removing unwanted native silicon oxide from the surface of a buried, multilayer polysilicon contact comprising:

• providing on a semiconductor substrate a layer of silicon oxide through which an opening has been formed to said semiconductor substrate at the location of said buried contact;
• removing native silicon oxide formed within said opening wherein some new native silicon oxide having a thickness of less than about 30 Angstroms will be formed before the next step can be performed;
• depositing a first polysilicon layer over said layer of silicon oxide and within said opening to said silicon substrate;
• forming at least one layer of native silicon oxide on top of said polysilicon layer having a thickness of less than about 30 Angstroms;
• wherein said one layer of native silicon oxide is formed by adding oxidizer to the chemical vapor deposition chamber used in depositing said polysilicon;
• forming a second polysilicon layer over said native silicon oxide;
• and
• annealing said semiconductor substrate causing silicon oxide gas from said native silicon oxide layers to be exhausted thereby removing all said unwanted native silicon oxide.

The method of forming a multilayer, polysilicon contact emitter in a bipolar integrated circuit comprising:

• providing on a semiconductor substrate a layer of silicon oxide through which an opening has been formed to said semiconductor substrate at the location of said emitter;
• removing native silicon oxide formed within said opening by using hydrofluoric acid, a de-ionized water rinse, and spin dry and immediately transferring said semiconductor substrate into a silicon deposition chamber;
• depositing at least one layer of undoped polysilicon over said layer of silicon oxide and within said opening to directly contact said silicon substrate;
• forming at least one layer of native silicon oxide on top of said undoped polysilicon layer having a thickness of less than about 30 Angstroms;
• forming a second polysilicon layer on said one layer of native silicon oxide;
• annealing said semiconductor substrate causing silicon oxide gas from said native silicon oxide layers to be exhausted through the grain boundaries of said first and second polysilicon layers;
• doping by ion implantation said undoped polysilicon layer to form a said doped multilayer, polysilicon contact emitter layer;
• ion implanting active device regions to be contacted by said emitter in said silicon substrate;
• and
• heating the structure to form said emitter region in said silicon substrate and to contact said active device regions.

The method of forming a multilayer, polysilicon buried contact in a static random access memory (SRAM) comprising:

• providing on a semiconductor substrate a layer of silicon oxide through which an opening has been formed to said semiconductor substrate at the location of said buried contact;
• removing native silicon oxide formed within said opening;
• depositing at least one layer of undoped polysilicon over said layer of silicon oxide and within said opening to directly contact with silicon substrate;
• forming at least one layer of native silicon oxide on top of said undoped polysilicon layer having a thickness of less than about 30 Angstroms;
• forming a second polysilicon layer on said one layer of native silicon oxide;
• annealing said semiconductor substrate causing silicon oxide gas from said native silicon oxide layers to be exhausted;
• doping by ion implantation said undoped polysilicon layer to form a said doped multilayer, polysilicon buried contact layer,
• ion implantation active device regions to be contacted by said buried contact in said silicon substrate;
• and
• heating the structure to form said buried contact region in said silicon substrate and to contact said active device regions.