Method and structure for semiconductor interconnect

A semiconductor structure, comprising:

• a substrate;
• a source/drain feature over the substrate;
• a first conductive structure adjacent to the source/drain feature and over the substrate;
• a first dielectric layer over the first conductive structure and the source/drain feature;
• a second conductive structure disposed over the source/drain feature and at least partially surrounded by the first dielectric layer, wherein the second conductive structure is electrically connected to the source/drain feature, the second conductive structure includes a first metal-containing layer and a second metal-containing layer surrounded by the first metal-containing layer, wherein the first and the second metal-containing layers include different materials, wherein a lower portion of the first metal-containing layer includes a transition metal or a transition metal nitride and an upper portion of the first metal-containing layer includes a transition metal fluoride or a transition metal chloride;
• a second dielectric layer over the first dielectric layer;
• and
• a third conductive structure disposed over the second conductive structure and at least partially surrounded by the second dielectric layer, wherein the third conductive structure is electrically connected to the second conductive structure, the third conductive structure includes a third metal-containing layer and a fourth metal-containing layer surrounded by the third metal-containing layer, wherein the third and the fourth metal-containing layers include different materials, wherein a lower portion of the third metal-containing layer includes a transition metal or a transition metal nitride and an upper portion of the third metal-containing layer includes a transition metal fluoride or a transition metal chloride.

A semiconductor structure, comprising:

• a substrate;
• a source/drain feature over the substrate, wherein the source/drain feature is part of a transistor;
• and
• a source/drain contact disposed over the source/drain feature and electrically connected to the source/drain feature, wherein the source/drain contact includes a first metal-containing layer and a second metal-containing layer surrounded by the first metal-containing layer, wherein the first and the second metal-containing layers include different materials, wherein a lower portion of the first metal-containing layer includes titanium or a titanium nitride and an upper portion of the first metal-containing layer includes a titanium fluoride or a titanium chloride.