Ivo Teerlinck

Deposition of HfO2 on germanium and the impact of surface pretreatments

The deposition behavior of HfO2 by metalorganic chemical vapor deposition on germanium has been investigated. HfO2 films can be deposited on Ge with equally good quality as compared to high-k growth on silicon. Surface preparation is very important: compared to an HF-last, NH3 pretreatments result in smoother films with strongly reduced diffusion of germanium in the HfO2 film, resulting in a much better electrical performance. We clearly show that much thinner interfacial layers can be obtained, approximately half the thickness of what is typically found for depositions on silicon, suggesting the possibility of more aggressive equivalent oxide thickness∕leakage scaling.

Cost-effective cleaning and high-quality thin gate oxides

Some recent findings in the area of wafer cleaning and thin oxide properties are presented in this paper. Results are shown for a practical implementation of a simplified cleaning concept that combines excellent performance in terms of metal and particle removal with low chemical and DI-water consumption. The effect of organic contamination on ultrathin gate-oxide integrity is illustrated, and the feasibility of using ozonated DI water as an organic removal step is discussed. Metal outplating from HF and HF/HCI solutions is investigated. Also, the final rinsing step is critically evaluated. It is demonstrated that Si surface roughness without the presence of metal contaminants does not degrade gate-oxide integrity. Finally, some critical remarks on the reliability measurements for ultrathin gate oxides are given; it is shown that erroneous conclusions can be drawn from constant-current charge-to-breakdown measurements.

Implementation of the IMEC-Clean in advanced CMOS manufacturing

We present data measured using the wet bench in the prototyping line of IMEC. This wet bench has been running for 3 years an IMEC Clean for prediffusion cleans including the most critical one: the pre-gate oxidation clean. The clean was introduced at IMEC for the 0.35 /spl mu/m CMOS process and its use has been succesfully extended to the 180 nm and 130 nm CMOS modules presently developed at IMEC.

Optimized HF solutions for ultra-clean Si surfaces

HF based solutions are widely used in IC manufacturing industry, e.g. for etching, patterning and cleaning. However, trace amounts of nobel metal ions, such as Cu, Ag or Au ions, present in the HF solution can deposit on the Si surface. This metallic contamination destroys the chemical stability of the Si surface and results in a reduced production yield. A more fundamental understanding of the outplating behaviour of impurities from HF solutions is therefore necessary. In this study the Cu outplating on Si surfaces is investigated in detail. Since mobile charge carriers are involved in the Cu deposition process, Si semiconductor properties play an important role. This is demonstrated by evaluating the effect of illumination of the Si surface on the Cu outplating behaviour. Also the effect of HCl addition to HF solutions is investigated. A model is presented to explain the observed phenomena and various strategies to reduce the metal outplating from HF solutions are illustrated.

Cost-effective cleaning for advanced Si-processing

The effect of various metal contaminants on the thin gate oxide integrity is investigated and a classification is made according to their final position in the structure. A simplified cleaning strategy is presented which is highly performant and at the same time cost-effective and has less environmental impact than the traditional cleaning sequences. Finally, a novel environmentally friendly ozone/DI-water process for the removal of photoresist and organic post-etch residues is proposed.

Outplating of metallic contaminants on silicon wafers from diluted acid solutions

The outplating behaviour of Fe and Cu was investigated for diluted solutions of HCl and HNO 3 . The deposition of the metallic contaminants was found to be strongly dependent on the type of surface that is exposed to the contaminated solution. Cu deposits heavily on bare silicon surfaces, whereas only low levels of Fe deposition are observed. On the other hand, on thermal oxide surfaces, the levels of deposited Fe are consistently higher than the Cu ones. The acid used appears to have no major impact on the deposition process. The pH of the solutions has a major effect on the Cu deposition and a minor effect on the Fe case.

Critical issues in post Cu CMP cleaning

Application of dilute HF with respect to post Cu CMP cleaning showed evidence of some critical issues that may seriously impact process performance. First of all it was seen that due to the heterogeneity of the surface after CMP drying problems can occur due to differences in wettability or due to topography. The cleaning of alumina slurry by under-etching with HF showed possible redeposition of these particles on the surface in case of a non-optimised rinsing and drying step. Furthermore a pattern dependent form of corrosion of the Cu was observed. Since single lines were more seriously impacted than dense meander/fork structures extrapolation of the latter to give process yield data may result in erroneous results. Finally it was shown that megasonic energy was very efficient in order to remove deposited slurry residues from the wafer surfaces.