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Modeling SiH 4 /O 2 /Ar Inductively Coupled Plasmas Used for Filling of Microtrenches in Shallow Trench Isolation (STI)
Author(s) -
Tinck Stefan,
Bogaerts Annemie
Publication year - 2012
Publication title -
plasma processes and polymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 74
eISSN - 1612-8869
pISSN - 1612-8850
DOI - 10.1002/ppap.201100093
Subject(s) - sputtering , shallow trench isolation , trench , wafer , analytical chemistry (journal) , plasma enhanced chemical vapor deposition , plasma , deposition (geology) , silicon , materials science , chemistry , chemical vapor deposition , thin film , nanotechnology , optoelectronics , layer (electronics) , physics , paleontology , chromatography , quantum mechanics , sediment , biology
Abstract Modeling results are presented to gain a better insight in the properties of a SiH 4 /O 2 /Ar inductively coupled plasma (ICP) and how it interacts with a silicon substrate (wafer), as applied in the microelectronics industry for the fabrication of electronic devices. The SiH 4 /O 2 /Ar ICP is used for the filling of microtrenches with isolating material (SiO 2 ), as applied in shallow trench isolation (STI). In this article, a detailed reaction set that describes the plasma chemistry of SiH 4 /O 2 /Ar discharges as well as surface processes, such as sputtering, oxidation, and deposition, is presented. Results are presented on the plasma properties during the plasma enhanced chemical vapor deposition process (PECVD) for different gas ratios, as well as on the shape of the filled trenches and the surface compositions of the deposited layers. For the operating conditions under study it is found that the most important species accounting for deposition are SiH 2 , SiH 3 O, SiH 3 and SiH 2 O, while ${\rm SiH}_{{\rm 2}}^{{\rm + }} $ , ${\rm SiH}_{{\rm 3}}^{{\rm + }} $ , ${\rm O}_{2}^{ + } $ and Ar + are the dominant species for sputtering of the surface. By diluting the precursor gas (SiH 4 ) in the mixture, the deposition rate versus sputtering rate can be controlled for a desired trench filling process. From the calculation results it is clear that a high deposition rate will result in undesired void formation during the trench filling, while a small deposition rate will result in undesired trench bottom and mask damage by sputtering. By varying the SiH 4 /O 2 ratio, the chemical composition of the deposited layer will be influenced. However, even at the highest SiH 4 /O 2 ratio investigated (i.e., 3.2:1; low oxygen content), the bulk deposited layer consists mainly of SiO 2 , suggesting that low‐volatile silane species deposit first and subsequently become oxidized instead of being oxidized first in the plasma before deposition. Finally, it was found that the top surface of the deposited layer contained less oxygen due to preferential sputtering of O atoms, making the top layer more Si‐rich. However, this effect is negligible at a SiH 4 /O 2 ratio of 2:1 or lower.