Advanced ULSI multilevel metallization using non-steady state by Flow Modulation technique

器件集成需要窄布线技术，导致高电阻率。这将导致采用多层金属化方案，其中导电金属线的宽度保持在同一水平。因此，金属线层的数量现在超过了8层，在不久的将来将增加到12层。所谓的制造多层金属层的后端工艺成为ULSI工艺的主导工艺。这些结构需要CVD工艺来形成金属线，因为它在高纵横比的沟槽/孔中具有优越的台阶覆盖剖面。由于ULSI器件的尺寸小，厚度小于10nm的超薄薄膜也很重要。然而，由于成核问题，新材料的集成将抑制连续薄层的形成。普通CVD采用稳定的工艺条件，如气体流速、温度和压力。如果引入这些参数的顺序变化，则会增强前驱体的吸附和解吸。这可能有助于控制薄膜生长的初始阶段。当我们开始这个研究项目时，没有那么多相关的研究，但最近提出了ALD（原子层沉积）工艺来改进ULSI器件的制造。这些方法使用源前体的顺序流。例如，在我们的研究中，研究了TiCl_4/NH_3化学沉积TiN。在沉积过程中一直向反应器提供NH_3。TiCl_4供应的开关可以用NH_3沉积TiN或仅用NH_3还原TiN。当TiCl_4/NH_3浓度增大时，TiCl_4/NH_3对TiN膜的阶梯覆盖效果较好。这种行为的原因可以通过以下机制来解释。当TiCl_4浓度较高时，由于表面吸附饱和，生长速率与TiCl_4浓度无关。这是均匀台阶覆盖的理想情况，但高浓度的表面吸附剂会导致高余氯浓度。因此提出了FMCVD序列。在较高的TiCl_4浓度范围内进行沉积，以实现良好的台阶覆盖。下一步，只向反应器提供NH_3进行氯还原。实验证明，FMCVD序列可以同时实现良好的阶跃覆盖和低电阻率。我们还研究了如何使用TDS， TEM和EDX去除TiN膜上的余氯。结果清楚地表明，残氯主要存在于TiN多晶的晶界中。循环次数多的FMCVD也有助于去除掺杂在TiN颗粒中的氯。这些研究有助于设计FMCVD和ALD的最佳工艺条件。少

The device integration requires narrow wiring technique which results in high resistivity. This will lead to employ multilevel metallization scheme, in which the width of conductive metal line keeps the same level. Thus, the number of metal line layers now exceeds 8 and it will go up to 12, in the near future. The so-called back end process to fabricate multilevel metal layers became the dominant process for ULSI process. These structures require CVD process to form metal lines, because it has superior step coverage profile in high aspect ratio trenches/holes. The ultra thin films with a thickness of less than 10nm are also important, because of the small dimension of the ULSI devices. However, the integration of novel material will suppress the formation of continuous thin layers due to the nucleation issues.The normal CVD employed steady process conditions, such as gas flow rate, temperature, and pressure. If we introduce sequential change of these parameters, it will enhance the ads … More orption and desorption of the precursor. That may contribute to control the initial step of thin film growth. When we started this research project, there were not so much related research, but recently ALD (Atomic Layer Deposition) process was proposed to improve ULSI device fabrication. Those methods are using sequential flow of source precursors. For example, in our study, TiN deposition from TiCl_4/NH_3 chemistry was investigated. NH_3 was supplied to the reactor all the time of deposition. TiCl_4 supply was switched on/off to make TiN deposition with NH_3 or just to make reduction by NH_3. The step coverage of TiN films from TiCl_4/NH_3 becomes excellent when the concentration of TiCl_4 becomes high. The reason for this behavior can be explained by following mechanisms. When the TiCl_4 concentration is high, the growth rate becomes independent of TiCl_4 concentration due to saturated surface adsorbates. This is an ideal situation for uniform step coverage, however, the high concentration of surface adsorbates turns into high residual chlorine concentration. Thus the FMCVD sequence is proposed. The deposition will be made with high TiCl_4 concentration range to realize excellent step coverage. In the next step, only NH_3 will be supplied to reactor to make chlorine reduction. We have proved that FMCVD sequence can realize the excellent step coverage and low resistivity at the same time. We also worked on how the residual chlorine is removed from TiN film using TDS, TEM amd EDX. The results clearly showed that residual chlorine mainly exists in the grain boundaries of TiN poly crystals. The FMCVD with many cycle times also contributed to remove chlorine which was incorporated in TiN grain. These investigations contributed to design the optimum process conditions for FMCVD and ALD. Less