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对微波晶体管质量上的重要要求是在高频时具有高增益及低噪声。为了满足这些要求,在超高频双极晶体管方面致力于高截止频率,小基区电阻及小的发射极-基极电容。这就要在小的基区面积上制造分割得很细的框条结构。目前这种技术的水平是条宽1微米,条距1.5微米。为了制做1微米以下的条距,对形成金属化结构的方法必然要提出更高的要求。较粗结构所用的一般方法是在整个硅衬底面积上金属化,通过感光胶掩模进行湿法化学腐蚀。此法现在已经不用了。因为在感光胶下面的横向腐蚀和纵向腐蚀是同一数量级的。由于一般使用化学腐蚀的金属系统的膜厚(诸如铝、钛-金或钼-金)至少为1微
An important requirement for the quality of microwave transistors is high gain and low noise at high frequencies. To meet these requirements, UHF bipolar transistors are dedicated to high cutoff frequencies, small base resistance and small emitter-base capacitance. This requires the fabrication of very finely divided box structures on a small base area. The current level of this technology is 1 micron wide and 1.5 microns wide. In order to make a pitch of less than 1 micron, a higher requirement must be placed on the method of forming a metallized structure. The general approach to coarser structures is to metallize over the entire silicon substrate area and wet chemical etch through a photomask mask. This law is now gone. Because the vertical and horizontal corrosion under the photoresist is the same order of magnitude of corrosion. Since the film thickness of a generally used chemically etched metal system, such as aluminum, titanium-gold or molybdenum-gold, is at least 1 micro