Raised silicided source/drain electrode formation with reduced substrate silicon consumption

A method of forming silicided electrodes on an active area of a semiconductor substrate where devices are formed, the active area including a layer of single-crystal silicon adjacent the surface of the substrate, a gate structure on the single-crystal silicon, and electrode areas on the single-crystal silicon on opposite sides of the gate structure, the gate structure including a gate electrode, gate insulation, and insulating sidewalls, the steps in the method comprising:

• a) implanting doping impurities into the active area to form junction regions in the electrode regions of the active area, the electrode regions being regions of surface silicon where device electrodes are formed;
• b) depositing a layer of silicidation material on the active area;
• c) rapid-thermal-annealing at a temperature of less than 700.degree. C. to react silicidation material deposited in step b) with silicon in the electrode regions of the active area to form silicon-deficient silicide on the electrode regions, silicon-deficient silicide being a phase of silicide having proportionately less silicon and more silicidation material than disilicide phase silicide, whereby the electrode regions of the active area are covered with silicon-deficient silicide and the nonelectrode regions of the active area, outside the electrode regions, are covered with unreacted silicidation material;
• d) selectively etching the silicidation material to remove unreacted silicidation material from the nonelectrode regions of the active area and from the silicon-deficient silicide on the electrode regions of the active area;
• e) cleaning the silicon-deficient silicide on the electrode regions to remove surface oxide therefrom;
• f) depositing a layer of silicon;
• g) annealing at a higher temperature than step c) to react the silicon-deficient silicide on the electrode regions predominately with silicon in the layer of silicon deposited in step f) to transform the silicon-deficient silicide to the disilicide phase, whereby disilicide phase silicide is formed on the electrode regions;
• and
• h) removing unreacted deposited silicon remaining after annealing step g), whereby raised silicided electrodes are formed in the electrode regions.

A method of forming a MOS transistor with silicided source and drain electrodes in a selected area of a semiconductor substrate which includes a surface layer of single-crystal silicon and includes a gate structure centrally disposed on the selected area of the substrate, the gate structure including a gate electrode, gate insulation, and insulating sidewalls, the method comprising the following steps:

• a) implanting doping impurities into the selected area and forming source and drain junction regions extending less than 1000 .ANG. in depth from the surface of the single-crystal silicon, whereby source and drain junction regions are created on opposite sides of the gate structure;
• b) depositing silicidation material selected from the group consisting of refractory metals and noble metals on the selected area;
• c) rapid-thermal-annealing for between 10 seconds and 60 seconds at a temperature of less than 700.degree. C. to combine the silicidation material which is deposited on the silicon in the selected area with a surface portion of the silicon in the selected area, said surface portion being less than the full thickness of the source and drain junction regions formed in step a), and leaving at least 100 .ANG. of thickness of the junction regions in the selected area uncombined with silicidation material to produce a layer of silicon-deficient silicide overlying the source and drain junction regions, such silicon-deficient silicide being a phase of silicide having proportionately less silicon and more silicidation material than disilicide phase silicide;
• d) etching with a silicidation material etchant to remove from the selected area silicidation material which remains uncombined with silicon from the source and drain junction regions in preceding step c), whereby silicidation material is removed from all non-silicon surfaces and residual silicidation material is removed from the layer of silicon-deficient silicide created in step d);
• e) ion beam cleaning to remove surface oxide formed in the preceding steps;
• f) depositing a layer of silicon on the selected area;
• g) annealing at a higher temperature than step c) to react the silicon-deficient silicide predominately with the layer of silicon deposited in step f), whereby the silicon-deficient silicide is transformed into metal disilicide which is predominately disilicide phase silicide;
• h) etching with a silicon etchant to remove unreacted silicon from the areas of metal disilicide, whereby the metal disilicide areas form silicided electrodes.