摘要
晶片专用X射线荧光分析装置在半导体工业中被用于多种工程的评价。在半导体分析中XRF法的显著特征是能分析各种薄膜(氧化膜、硅化物膜、金属膜等);能同时分析晶片上同一部位的膜厚及组成;XRF法是非破坏分析,因受化学键的影响不大,同一个试样可以反复使用。 厚度在400nm以上的掺硼磷硅玻璃(BPSG)膜的分析结果已做报道。近年,随着对半导体器件的高度集成化、高性能化(64 Mbit以上)要求的提高,希望能更准确地分析。作为有代表性的氧化膜——BPSG膜,为改善其在工程中的热处理特性,B_2O_3、P_2O_5的浓度控制是不可缺少的。为了满足这些要求,必须分析更薄的薄膜(300nm以下),在薄膜分析中的关键问题是B Kα背底的变动。 B分析的新光学系统改善了声噪比(S/N),使250nm以上的BPSG膜的分析成为可能。为了提高晶片分析器的性能,在装置上做了一些改良:真空度的稳定化;减轻污染的特制真空泵;分光室部分的恒温化。新的晶体分析器无论在短期或长期的测定,对10％B_2O_3的测定能做到1％的相对精度。 对在硅晶片上的钨硅化物的分析,不能使用W Lα及Si Kα两种谱线,而应使用W的两种谱线(浓度分析用W-N线,膜厚分析对用W-Lα线)。 膜厚测定的相对精度在0.2％以下,对于Si/W=2.5,摩尔比精度约0.015％(相对精度约为0.56％)。
The wafer analyzer has been used to fulfil many applications needs in the semiconductor industry. The prominent features of the XRF method for semiconductor analysis are as follows: (1) Many types of films such as oxides, silicides and metallic alloy films can be analyzed. (2) Simultaneous analysis of film thickness and compositions in the films can be performed at the same location on a wafer. (3) The same standard samples for standardizing operation can be used repeatedly in most cases since XRF is a non-destructive method and isn’ t influenced significantly by the chemical bonding effect.In the past paper, the analysis results of BPSG (Boron-doped Phospho-Silicate Glass) films, with thicknesses greater than 400 nm, were reported. With the recent increased demand for larger scale and higher quality semiconductor devices (larger than 64 Mbit), more accurate analysis with high precision has been required. For the BPSG films as a typical oxide film, it is essential to control the concentrations of B2O3 and P2O5 to improve the effects of thermal processing in the manufacturing of such films. It has also become necessary to analyze thinner films (less than 300 nm) to accommodate the needs of these wafer devices. In the analysis of very thin films, the analytical problem of potentially significant background fluctuations in measuring B Ka must be addressed. A newly designed optical system for boron analysis has improved the signal-to-noise ratio enabling the analysis of BPSG films with thicknesses greater than 250 nm.Other developments designed to improve the capabilities for wafer analysis have been studied as follows: (1) Stability control of the vacuum condition. (2) A special vacuum pump to reduce contamination. (3) A stability device to control the temperature in the analysis chamber.With the new wafer analyzer, 1% relative precision at 10% B2O3 was achieved both in short and long term measurements.The analysis of tungsten silicide on silicon wafer was developed using two kinds of tungsten spectra instead of W La and Si Ka combination (concentration analysis; W-N X-ray, thickness measurement; W La).The relative precision of thickness measurement is less than 0. 2% and the precision of molecular ratio is almost 0. 015 at 2. 5 of Si/W molecular ratio (relative precision is almost 0.56%).
