Control of Ion Energy Distribution at Substrates during Plasma Processing

0078522 Wendt材料的等离子体处理广泛用于半导体工业。 在等离子体蚀刻中，通过经由光刻限定的模板或掩模将硅晶片暴露于电离气体来在硅晶片中限定图案。 等离子体蚀刻优于液体化学蚀刻的优点之一是定向蚀刻，其由从等离子体落下的正离子轰击表面而产生。 因为离子轰击垂直于衬底表面，所以可以避免掩模下的材料的底切或蚀刻。 在当今典型的制造等离子体工艺中，通过改变施加到衬底电极的RF正弦偏置电压的幅度来粗略地控制到达衬底表面的离子的能量，但是在衬底处产生的离子能量分布（IED）通常是宽的。 在离子冲击时提供给衬底表面的能量可以通过几种机制增强化学反应，对蚀刻特征轮廓和蚀刻选择性具有重要意义。 拟议的活动采用了一种新开发的技术，用于大幅减少基片处简易爆炸装置的宽度，并有可能大幅改善等离子体工艺的这些方面。 此外，由于过去在实际工艺条件下难以控制衬底处的离子能量，因此该方法开启了在对其它工艺参数的影响最小的情况下检查不同材料和工艺气体系统的蚀刻工艺中的离子轰击能量的作用的可能性。在衬底表面上，恒定的电势被周期性的电压尖峰打断。 因此，大多数离子在基底和等离子体之间的“鞘层”上看到恒定的电压降，因此以相同的能量到达基底。 潜在的测量已经证实了这种方法的可行性。 此外，毯膜的初步蚀刻速率测量表明，在碳氟化合物plasma.This方法中的SiO2/Si蚀刻的蚀刻选择性显着改善将被应用到几个蚀刻问题，以及在等离子体处理中的离子能量的作用的基本理解。 第一步将是直接测量衬底上的IED，以确认该方法产生窄离子能量分布的推测，并验证可以通过外部电压测量有效地监测平均离子能量。 此外，这两个蚀刻选择性和图案化的硅晶片上的蚀刻功能轮廓控制通过精确定制的IED使用这种方法将被检查。 感兴趣的特定工艺是二氧化硅的蚀刻，其继续对等离子体处理提出挑战。 最后，通过扫描离子能量，同时测量蚀刻速率，预计将提高对离子轰击在蚀刻过程中影响表面侵蚀的机制的理解。

0078522WendtPlasma processing of materials is used extensively in the semiconductor industry. In plasma etching, patterns are defined in silicon wafers by exposing them to an ionized gas through a lithographically defined stencil, or mask. One of the advantages of plasma etching over liquid chemical etching is the directional etching that results from bombardment of the surface by positive ions raining down from the plasma. Because the ion bombardment is normal to the substrate surface, undercutting, or etching of material under the mask, can be avoided. This enables the fabrication of ever-tinier transistors critical to the continuing advancement in integrated circuit performance.In typical manufacturing plasma processes today, the energy of ions reaching the substrate surface is coarsely controlled bv varying the amplitude of an RF sinusoidal bias voltage applied to the substrate electrode, but the resulting ion energy distribution (IED) at the substrate is generally broad. The energy provided to the substrate surface upon ion impact can enhance chemical reactions via several mechanisms, with significant implications for etched feature profiles and etch selectivity. The proposed activity employs a newly developed technique for significantly reducing the width of the IED at the substrate, with the potential for significantly improving these aspects of plasma processes. Furthermore, because of past difficulties in controlling ion energy at the substrate under realistic process conditions, this method opens up the possibility of examining the role of ion bombardment energy in etching processes for different materials and process gas systems with minimal impact on other process parameters.This technique for ion energy control replaces the conventional sinusoidal substrate bias voltage waveform with a waveform that produces, on the substrate surface, a constant potential punctuated by periodic voltage spikes. As a result, most ions see a constant voltage drop across the "sheath" that arises between the substrate and plasma, and therefore arrive at the substrate with the same energy. Potential measurements have confirmed the feasibility of this approach. In addition, preliminary etch rate measurements of blanket films show dramatic improvement in etch selectivity for SiO2/Si etching in a fluorocarbon plasma.This method will be applied to several etching problems, as well as to basic understanding of the role of ion energy in plasma processing. The first step will be to directly measure the IED at the substrate to both confirm the conjecture that this method produces a narrow ion energy distribution, and to verify that average ion energy can be effectively monitored through external voltage measurements. In addition, both etch selectivity and etch feature profile control on patterned silicon wafers by precise tailoring of the IED using this method will be examined. A particular process of interest is etching of silicon dioxide, which continues to pose challenges for plasma processing. Finally, by scanning the ion energy while measuring etch rates, improved understanding of the mechanisms by which ion bombardment affects surface erosion during etching processes is expected.***