Bake System Research Articles

Thermal design of hot plate for 300-mm wafer heating in post-exposure bake

Temperature uniformity of a wafer during post-exposure bake (PEB) in lithography is an important factor in controlling critical dimension (CD) uniformity. In this study, a new hot plate system for the PEB of a 300-mm wafer was analyzed and designed. First, temperature deviation on the wafer caused by warpage was investigated, and the heater pattern of the multi-zone hot plate in the bake system was numerically analyzed. Then, a new heater pattern to enhance the temperature uniformity was proposed and tested experimentally. As a result, temperature uniformity within 0.087 °C on a 300-mm wafer was achieved.

An air-flow based wafer bake system for improved temperature uniformity

This paper presents an innovative apparatus for wafer baking/chilling using a stream of temperature controlled air-flow. This apparatus takes the form of a baking chamber on which the wafer is placed. A stream of hot air is passed through the chamber below the wafer. Heat is transferred from the hot air to the wafer from the bottom surface of the wafer. If the chamber has a uniform cross-section, heat will be lost along the direction of flow and eventually the far-end of the wafer will be cooler. As a result, temperature uniformity across the wafer will be very poor. In our innovation, we have designed a tapered chamber through which the hot air-flows. The idea is to control the speed of the air-flow through the channel which in turn improves the coefficient of heat transfer between the hot air and the wafer. This helps tremendously in achieving temperature uniformity of the wafer. Numerical analysis and simulation results are used to support our design. We show how the gradient of the tapered channel affects temperature uniformity and we are able to deduce the optimal gradient under simulation conditions.

Comparación técnica de la mezcla de arena para el proceso CO2 y el sistema de arenas autofraguantes

En este artículo se presentan los resultados de la comparación técnica entre dos sistemas de arena de moldeo usados para la elaboración de machos y moldes en empresas de fundición. El primero es el proceso CO2 que es un sistema tradicional de endurecimiento por gasificación, y el segundo es el sistema de Arenas Autofraguantes, una tecnología de moldeo moderna, la cual emplea una mezcla de resinas y catalizador. Los resultados muestran que el sistema de arenas autofraguantes incrementa la productividad del proceso y ofrece un mejor acabado superficial de las piezas.

Global critical dimension uniformity improvement for mask fabrication with negative-tone chemically amplified resists by zone-controlled postexposure bake

The multizone hotplate approach of the APB5500 bake system achieves temperature uniformity significantly superior to conventional bake tools, resulting in unmatched global critical dimension (CD) uniformity from the postexposure bake (PEB) process. Progress toward 65-nm next-generation lithography, however, requires the application of negative-tone chemically amplified resists (nCARs) like NEB22. This nCAR is characterized to show a strong sensitivity to postexposure delay (PED) in vacuum during electron-beam writing of 0.5 nm/h, and also a strong PEB sensitivity of 7.8 nm/°C, both resulting in systematic CD errors. These CD errors are compensated with the APB5500 bake system during PEB by automatically applying an appropriate nonuniform temperature profile. This temperature profile is calculated by an algorithm considering the resist and mask heat transfer properties. A CD uniformity improvement from 8.9 to 6.7 nm total range (25%) on a state of the art production mask is achieved.

Prediction of mechanical dough development, water absorption and baking performance from farinograph parameters

AbstractTwo systems for measuring flour water absorption (WA), the farinograph (FAR) and the Wheat Research Institute, 125 g mechanical dough development (MDD) standard bake test system, were compared using a representative sample of 20 commercial flours. A highly significant correlation (r = 0.93) was found which yielded the predictive equation: WAMDD = 0.66 × WAFAR + 181 The 95% prediction limits for 125 g MDD water absorptions from this equation were ± 15 g kg−1. This degree of accuracy was largely due to excellent farinograph reproducibility.Other farinograph parameters (development time, stability and breakdown) were highly correlated with the work input required for 125 g mechanical dough development, but only development time was significantly correlated with the volume of loaves baked on the 125 g standard bake system. This lack of prediction of baking quality for the farinograph could partly be because it simulates bulk fermentation mixing, rather than the more intensive mixing of the mechanical dough development process used for the loaves in this experiment. However, the loaf volume range was diminished since sample preparation involved bulking flours by water absorption.