Method and apparatus for forming nickel silicide with low defect density in FET devices
View Patent ↗A method and an apparatus are provided in which non-directional and directional metal (e.g. Ni) deposition steps are performed in the same process chamber. A first plasma is formed for removing material from a target; a secondary plasma for increasing ion density in the material is formed in the interior of an annular electrode (e.g. a Ni ring) connected to an RF generator. Material is deposited non-directionally on the substrate in the absence of the secondary plasma and electrical biasing of the substrate, and deposited directionally when the secondary plasma is present and the substrate is electrically biased. Nickel silicide formed from the deposited metal has a lower gate polysilicon sheet resistance and may have a lower density of pipe defects than NiSi formed from metal deposited in a solely directional process, and has a lower source/drain contact resistance than NiSi formed from metal deposited in a solely non-directional process.
1. An apparatus for depositing a metal on a substrate, comprising:
a holder for the substrate;
a target disposed opposite the substrate holder, whereby material removed from the target by bombardment from plasma in a first plasma region is deposited on the substrate;
an electrode disposed between the substrate holder and the target;
a first RF generator connected to said electrode and forming a plasma in a second plasma region in the interior of said electrode; and
a second RF generator connected to said substrate holder for electrically biasing the substrate,
wherein said electrode is a nickel wire screen made of a material containing nickel.
2. An apparatus according to claim 1 , wherein
said material is deposited non-directionally on the substrate in the absence of plasma formation in the second plasma region and in the absence of electrical biasing of the substrate, and
said material is deposited directionally on the substrate on condition of plasma being formed in the second plasma region and on condition of the substrate being electrically biased.
3. An apparatus according to claim 1 , wherein the plasma in the second plasma region increases an ion density of the material.
4. An apparatus according to claim 1 , wherein the biasing of the substrate causes ions from the second plasma region to travel in a direction normal to the substrate, thereby causing directional deposition of the material on the substrate.