Method of forming silicon carbide

A method of providing a silicon carbide emitter structure for a silicon heterojuntion bipolar transistor comprising the steps of:

• providing a substrate for an integrated circuit comprising a surface dielectric layer having defined therein an emitter opening, the emitter opening defining an active device region of the substrate including a heavily doped base region;
• exposing the substrate within a reaction chamber;
• purging the chamber with an inert carrier gas to remove residual oxygen;
• and then exposing the substrate to a mixture of reactant gases comprising di-tert-butyl silane at a flow rate of 250 to 350 sccm and tert-butyl phosphine at a flow rate of 130 to 350 sccm in an oxygen free inert carrier gas, at a flow rate from 200 to 1000 sccm, while maintaining the pressure in the range from 0.25 to 1 Torr and the temperature in the range from 550.degree. to 800.degree. C., whereby a layer of n.sup.+ doped amorphous silicon carbide is deposited on the substrate, said layer of silicon carbide comprising less than 0.1 atomic percent oxygen,
• and subsequently annealing the silicon carbide layer in an inert atmosphere at a temperature greater than the deposition temperature and less than 1100.degree. C. and for a time sufficient to form a polycrystalline phase of n.sup.+ doped silicon carbide.

A method of forming polycrystalline silicon carbide for an integrated circuit structure comprising:

• exposing a substrate in a chemical vapour deposition chamber and purging the chamber with an inert gas to remove residual oxygen;
• exposing the substrate to a gaseous reactant mixture comprising di-tert-butyl silane and an oxygen free inert gas, at a controlled flow rate and pressure and at a deposition temperature in the range 550.degree. C. to 800.degree. C., thereby depositing a layer of amorphous silicon carbide on the substrate;
• and
• annealing the deposited amorphous silicon carbide layer in an inert atmosphere at a temperature above the deposition temperature and below 1100.degree. C. for a time sufficient to form polycrystalline silicon carbide.

A method of forming silicon carbide for an integrated circuit structure comprising:

• exposing a surface of a substrate of an integrated circuit in a chemical vapour deposition chamber, and after purging the chamber with inert gas, sequentially performing the steps of:
• a) precleaning and passivating the substrate surface by exposure to a reactive fluorine species;
• b) purging the chamber with an inert gas;
• c) depositing silicon carbide by pyrolysis a reactant gas mixture comprising a source of silicon and carbon, and an inert gas;
• d) purging the chamber with an inert gas;
• e) exposing the deposited silicon carbide to the reactive fluorine species thereby passivating exposed surfaces of silicon carbide with fluorine;
• and,
• repeating steps b) to e) until a layer of a desired thickness of silicon carbide has been deposited;
• and,
• subsequently annealing the layer of silicon carbide, thereby incorporating fluorine therein.

A method of forming silicon carbide for an integrated circuit, comprising:

• exposing a surface of a substrate of an integrated circuit in a chemical vapour deposition chamber, and after purging the chamber with inert gas, sequentially performing the steps of:
• a) pre-cleaning and preparing the substrate surface by exposure to a reactive fluorine containing gas;
• b) purging the chamber with an inert gas;
• c) providing a layer of doped silicon carbide on the substrate surface by a method of chemical vapour deposition from a mixture of reactant gases comprising a source of silicon and carbon derived from a volatile liquid phase precursor and a source of a dopant species, and an inert gas;
• d) purging the chamber with the inert gas to remove the reactant gases;
• e) exposing the deposited silicon carbide to said reactive fluorine containing gas thereby passivating exposed surfaces of silicon carbide with fluorine;
• and
• then sequentially repeating the steps b) to e) until a desired thickness of silicon carbide has been deposited, thereby incorporating fluorine into the silicon carbide.