Influence of Gas Chemistry and Ion Energy on Contact Resistance

Abstract

Reactive ion etching (RIE) damage in contact hole etching is studied. The significant oxidation retardation layer (ORL) on Si surfaces is observed followed by high V pp (peak-to-peak voltage of 380 kHz RF) RIE. The depth of the ORL is linearly proportional to V pp, and it consists of a Si–C bond layer, according to X-ray photoelectron spectroscopy (XPS) analysis. The increase in contact resistance is found to be due to the existence of the ORL, using the sacrificial oxidation method and secondary ion mass spectroscopy (SIMS) analysis. The etch chemistries based on fluorocarbon-containing gas mixtures are characterized in terms of contact resistance and ORL. When hydride-containing gas mixtures are used in RIE, the contact resistance is low and the ORL depth is small. When CO-containing gas mixtures are used, the contact resistance is high and ORL depth is large. These different properties result from the different amounts of carbon implanted at the silicon surface.

Plasma process induced surface damage removal

“…The polymer thickness on the wafer is dependent on the process recipe, i.e., 33 Å for recipe M1 and 17 Å for recipe M2 with a process time of 60 s. It is interesting to note that the hydrogen containing process results in thinner fluorocarbon polymer on the wafer. Similar finding is recently reported by Hashimi et al 8 in their study of the effect of gas chemistry and ion energy on contact resistance. Hashimi et al showed that the use of hydrogen containing gases results in thinner oxidation retardation fluorocarbon layer, which also has lower contact resistance.…”

Developments of Plasma Etching Technology for Fabricating Semiconductor Devices

“…During O 2 plasma ashing, the bottom of the HARC is oxidized so as to grow a thin Si-O layer at the bottom. 39,92) Such a thin layer prevents the formation of an ideal contact resistance by using a CoSi layer for a 90 nm node and a NiSi layer for a 65 nm node. 93) The deposited film and the damaged layer at the bottom of the HARC should be removed by an additional dry cleaning/etching process.…”

“…The damage-induced thin modified layer formed at the bottom of the HARC is removed by applying additional CDE/cleaning using CF 4 , NF 3 , or SF 6 plasmas. 92,94,95,180,181) Recently, O 2 plasma cleaning methods such as O 2 CDE and O 2 RIE have been found to be effective in cleaning the thin damaged bottom layer; these methods minimize oxidation. 182) 9.2 Degradation and breakdown of the gate insulator by charge-up/antenna effect The following three modes are responsible for the degradation and breakdown of the gate insulator.…”

Reduction in Contact Resistance with In Situ O 2 Plasma Treatment

“…CDE is an isotropic etching process using fluorine-containing gases such as CF4, NF3, or SF6. 3,510,12 The damaged layer created by high energy ions during overetching can be removed by CDE. A downstream plasma etching apparatus is commonly used for CDE in order to prevent high-energy ions from bombarding and damaging silicon substrate surfaces.…”