S. Arnauts

A Wet chemical Method for the Determination of Thickness of SiO2 Layers below the Nanometer Level

A wet chemical procedure has been elaborated to measure the thickness of thin silicon dioxide layers. The procedure is based on the etching of the layer by HF and the determination of Si concentration in the microgram per liter range in the HF containing etch solutions. Two analytical techniques were optimized for this purpose: a spectrophotometric technique, the so‐called molybdenum blue method and inductively coupled plasma mass spectrometry (ICP‐MS). In the first method a detection limit of 3.3 μg/L Si could be achieved with a sensitivity of . Interference by HF up to 0.1% v/v (volume/volume %) HF could be eliminated by adding boric acid to the solution. In the second method Si was determined by ICP‐MS using the Si isotope. The detection limit in bidistilled water was 1.2 μg/L Si with a sensitivity of (5807 ± 98) cps/(μg/L Si). The presence of HF increased the background signal of Si due to the etching of the quartz plasma torch. In 0.005% v/v HF a detection limit of 5.9 μg/L Si could be achieved. For silicon dioxide layers below 1 nm, a reproducibility better than 5% was obtained.

A detailed study of semiconductor wafer drying

Publisher Summary In this chapter, the performance of several drying techniques commonly used in the semiconductor manufacturing industry is evaluated. This is done by measuring the residues on a wafer onto which a solution containing metal salts acting as tracer elements has been dispensed and dried. To correctly interpret the experimental data, the results are compared with predictions from a theoretical model. This model assumes two distinct mechanisms for deposition: adsorption and evaporative deposition. The first mechanism is a result of attractive interactions between the contaminant and the wafer surface, while the second mechanism is due to liquid evaporation during drying. For the latter case, the evaporated film thickness is introduced as a figure of merit for the drying process under study. In the tests, tests, spin drying was compared with two types of Marangoni based drying: on a vertically moving wafer and on a horizontally rotating wafer. The results show that for spin drying two consecutive phases occur: during the first seconds of spinning convective removal of liquid is the dominant mechanism, followed by a phase where evaporation takes over. This behavior is confirmed by models reported in the literature describing photo-resist coating. The amount of liquid evaporating during spin drying is inversely proportional to the square root of the rotation speed. This suggests that entrainment of liquid by the gas flow over the wafer surface is the dominant mechanism for evaporation. This finding is in agreement with fluid dynamics models describing the flow of gas entrained with a rotating substrate.

Chapter 19 – A Detailed Study of Semiconductor Wafer Drying

In this chapter, the performance of several drying techniques commonly used in the semiconductor manufacturing industry is evaluated. This is done by measuring the residues on a wafer onto which a solution containing metal salts acting as tracer elements has been dispensed and dried. To correctly interpret the experimental data, the results are compared with predictions from a theoretical model. This model assumes two distinct mechanisms for deposition: adsorption and evaporative deposition. The first mechanism is a result of attractive interactions between the contaminant and the wafer surface, while the second mechanism is due to liquid evaporation during drying. For the latter case, the evaporated film thickness is introduced as a figure of merit for the drying process under study. In the tests, spin drying was compared with two types of Marangoni based drying: on a vertically moving wafer and on a horizontally rotating wafer. The results show that for spin drying two consecutive phases occur: during the first seconds of spinning convective removal of liquid is the dominant mechanism, followed by a phase where evaporation takes over. This behavior is confirmed by models reported in the literature describing photo-resist coating. The amount of liquid evaporating during spin drying is inversely proportional to the square root of the rotation speed. This suggests that entrainment of liquid by the gas flow over the wafer surface is the dominant mechanism for evaporation. This finding is in agreement with fluid dynamics models describing the flow of gas entrained with a rotating substrate.

RCA and IMEC/SC2 Clean: Metallic Immunity and Gate Oxide Integrity

Dilute HF/RCA and IEMC/SC2 cleans have been evaluated on two process lines with different metallic contamination levels. VPD-DSE-TXRF and SPV techniques were used to monitor the metallic contamination. Gate oxide integrity(GOI) tests were performed on several structures. Both HF/RCA and IMEC/SC2 cleans have shown good Qbd and Ebd results for the clean process line. Lower Qbd and Ebd values were obtained for both cleans in the relatively contaminated process line. These results suggest that poor GOI is related to the metallic contamination in the oxide or at the SiO 2 /Si interface.