Low resistant contact method and structure

A semiconductor device comprising:

• a Fin Field Effect Transistor (FinFET) having a first gate structure and a second gate structure, each of the first and second gate structures comprising a first gate spacer and a second gate spacer, each of the first gate spacers being separated from each of the second gate spacers by a gate electrode, each of the first gate spacers being a same height as each of the respective second gate spacers;
• a source/drain region between the first and second gate structures, the source/drain region comprising a semiconductor material, a metal silicide disposed at an upper area of the semiconductor material, and a first material embedded in the metal silicide, the first material comprising fluorine;
• and
• a contact comprising:
• sidewalls comprising a first metal material which coincide with the first gate spacer of the first gate structure and the second gate spacer of the second gate structure,
• a plug disposed between the sidewalls, the plug comprising a conductive material, and
• a cap layer disposed between the plug and the metal silicide of the source/drain region, the contact disposed on an uppermost surface of the source/drain region,
• wherein the first material embedded in the metal silicide has a highest concentration at an interface of the metal silicide and the contact, wherein a gradient of concentration decreases from the highest concentration to a positive second concentration at a first depth of the metal silicide, the first depth of the metal silicide disposed about midway between an upper extent of the metal silicide and a lower extent of the metal silicide, wherein the positive second concentration remains about the same from the first depth of the metal silicide to an interface between the metal silicide and the source/drain region, wherein the contact has a top surface that is level with a top surface of the first gate spacer and with a top surface of the second gate spacer, and further wherein the first material has a concentration equal to the positive second concentration in an upper portion of the source/drain region.

A device comprising:

• a gate stack comprising a first gate spacer and a second gate spacer formed on opposing sides of a gate electrode, wherein a sidewall of the first gate spacer has a first vertical slope and a sidewall of the second gate spacer has a second vertical slope, the first vertical slope being greater than the second vertical slope;
• a first semiconductor region comprising a metal-silicide region disposed in a semiconductor material, the metal-silicide region being in physical contact with the bottom surface of the first gate spacer, the first semiconductor region disposed under the first gate spacer and between the first gate spacer and an adjacent gate spacer of an adjacent gate stack, the metal-silicide region comprising a first material and a second material, the second material comprising fluorine, the metal-silicide region having a third width profile at a top surface of the metal-silicide region;
• a second semiconductor region comprising the semiconductor material and the second material, the second semiconductor region disposed under the second gate spacer;
• a contact over the metal-silicide region, the contact comprising a metal fill, wherein a top surface of the contact is aligned with the top surface of the first gate spacer and with the top surface of the second gate spacer, and wherein a bottom surface of the contact is aligned with the bottom surface of the first gate spacer and with the bottom surface of the second gate spacer, the contact having a fourth width profile at the bottom surface of the contact;
• and
• wherein the second material embedded in the metal-silicide region has a highest concentration at an interface of the metal-silicide region and the contact, a gradient of concentration decreasing from the highest concentration to a non-zero second concentration at a first depth of the metal-silicide region, the first depth of the metal-silicide region disposed about midway between an upper extent of the metal-silicide region and a lower extent of the metal-silicide region, the second concentration remains about the same from the first depth to the lower extent of the metal-silicide region.