Kinetics of Thermal Growth of HCl-0[sub 2] Oxides on Silicon

Effects associated with the incorporation of chlorine during the thermal growth of SiO2 (500-1400A) on Si are investigated as a function of additive species (HC1, C12), additive concentration, and oxidation temperature (900~176 Chlorine profiles are measured mainly by nuclear backscattering spectroscopy, and oxide thicknesses and refractive, index changes by ellipsometry. The highest chlorine concentrations in unannealed oxides always occur at the Si-SiO2 interface. Under otherwise similar conditions, the use of C12 results in higher, more evenly distributed chlorine levels (up to 1.2 • 1021 at era-3). The incorporated chlorine is gradually removed by annealing at temperatures in excess of II00~ as well as under conditions where further oxide growth takes place without the presence, of HCI or Cl2. Additional oxide formation in steam effectively removes all the incorporated chlorine. MOS capacitors made from oxides grown in HCI or Cl2 show fixed charge levels lower than 10 n cm -2 and mobile charge levels less than 1O l~ cm -2. When biased at high fields (>6 MV/cm) signihcant shifts in the flatband potential of Si were observed. Chlorine-grown oxides exhibit positive and negative shifts attributed to a mobile species; the smaller negative shifts in HCI oxides are attributed to interface states. Other electrical data of intentionally Na-contaminated HCI oxides suggest that only a constant fraction of the Na is trapped.

Section: Resultssupporting

confidence: 79%

Properties of SiO2 Grown in the Presence of HCl or Cl2

Meulen

Osburn

Ziegler

1975

“…This would be consistent with a molecular composition such as Si203C1~ as suggested by several authors (19,20). Such compounds have been identified in the gas phase (21). Thus we are dealing with a phase-separation process similar to that found in many silicate glasses (22).…”

Section: Initial Oxide Thickness (Nm)supporting

confidence: 89%

Cl Incorporation at the Si / SiO2 Interface during the Oxidation of Si in HCl / O 2 Ambients

Tsai¹,

Butler²,

Williams³

et al. 1984

Transmission and analytical electron microscopy, nuclear backscattering, and secondary ion mass spectroscopy have been used to study the incorporation of C1 at the Si/SiO2 interface during the oxidation of Si. Oxidations were carried out in the range of 1100~176 for 10-120 min and with HC1 additions from 1-13%. It was found that a critical concentration of C1 (2 • 10~Scm -2) is required before a Cl-rich phase is observed. X-ray microanalysis indicates that the matrix in the interfacial region still contains at least about 2 • 1015 cm -2 as the Cl-rich phase forms. These two observations suggest that the Cl-rich phase formation takes place in order to reduce the reacted C1 supersaturation.in the SiO2 matrix. Agglomerates, whose growth occurs by thickening and/or coalescence phenomena, are the final morphology observed during the continuing C1 incorporation. Models relating Na-ion passivation to the Cl-rich phase are shown to require modification in terms of the microstructural development.The oxidation of silicon in chlorine-containing ambients is known to cause chlorine incorporation into the SiO2 near the Si/SiO2 interface il,. 2). For several oxidation conditions, phase separated regions have been observed (4-6). It has been asserted that both chlorine incorporation and sodium neutralization are related to the development of the Cl-rich phase formed at the Si/SiO2 interface (3-5).Recent CI concentration vs. distance profiles through the bulk oxide determined by secondary ion mass spectroscopy (SIMS) were interpreted to be the result of fieldaided diffusion (7). The profiles show the chlorine concentration to increase exponentially toward the Si/SiO2 interface where a peak occurs. Auger analysis-sputter profiles indicate the interface C1 peak is <~3 nm thick (7, 8). This peak is presumably the result of the Si/SiO2 interface acting as a "sink of the electrochemical potential" for C1 (7). Simple steady-state diffusion models have been proposed to describe the C1 incorporation as a function of oxide thickness (7-9).To improve the understanding of C1 incorporation, we have carried out detailed determinations of both the Si/SiO2 interface microstructure and the chlorine concentration and its lateral distribution along the interface. The interface morphology was determined by transmission electron microscopy (TEM). The total C1 content was obtained using nuclear backscattering (NBS) measurements (1, 2). The analytical electron microscope (AEM) [i.e. with the microscope operating in scanning transmission (STEM) mode] was .used to determine the local C1 concentration at the interface. The CI concentration profile was investigated in depth on several samples by SIMS. The effect of the initial oxide thickness on the chlorine incorporation process has also been studied. These results will be discussed with the objective of trying to understand the processes controlling chlorine incorporation. The relationship between the Cl-rich phase morphology and the Na-ion passivation models is briefly considered.

“…These and other studies have indicated that such chlorine additions provide certain benefits to the resulting device structures, such as alkali ion passivation, higher and more uniform oxide dielectric strength, and improved junction properties due to lower leakage (5)(6)(7)(8). Coincidentally increased oxidation rates have been observed with increasing chlorine concentration in the oxygen ambient (1)(2)(3)(4). The reported improvements in device properties are probably due in part to actual incorporation of a chlorine species in the silicon oxide and reaction of this species with impurities (8,9).…”

mentioning

confidence: 85%

“…Recent investigations concerning the oxidation kinetics of silicon in dry oxygen containing small additions of HC1 or C12 have been reported (1)(2)(3)(4). These and other studies have indicated that such chlorine additions provide certain benefits to the resulting device structures, such as alkali ion passivation, higher and more uniform oxide dielectric strength, and improved junction properties due to lower leakage (5)(6)(7)(8).…”

mentioning

confidence: 99%

Thermal Oxidation Kinetics of Silicon in Pyrogenic H 2 O and 5% HCl / H 2 O Mixtures

Deal

1978

The kinetics of the thermal oxidation of silicon in H20 and in 5 volume percent (v/o) HCI in H20 using a pyrogenic system have been investigated over the temperature range 900~Oxide thickness-oxidation time data, rate constants, and activation energies have been obtained for (111) and (100) oriented, 1 • 10 I~ cm -~, n-type silicon. Results obtained for oxidation in H20 are very similar to those reported previously for water bubbler systems. The addition of HCI to H20 does not increase the silicon oxidation rate as with dry O2, but the rate actually decreases apparently because of the reduced llzO vapor pressure. The HC1 also appears to reduce impurity contributions from the oxidation system.