Effects of Process Variables on TiN Particle Formation during Metallorganic Chemical Vapor Deposition

Abstract

Titanium nitride particles formed in thermal and plasma-enhanced metallorganic chemical vapor deposition processes using tetrakis͑diethylamino͒titanium were investigated. Particle formation was studied by using a particle beam mass spectrometer calibrated by a certificate reference material ͑NaCl͒ as a function of process variables such as bubbler temperature, deposition temperature and pressure, sampling positions in the reactor, plasma conditions, and a flow rate of carrier gas. From these results, the effects of the sampling position and the thermal and plasma energies were studied. These measured results were in reasonable agreement with the transmission electron microscopy results.In recent years, the problems with particle contamination have been greatly emphasized in microelectronic processing because the particles have significant effects on device yield, performance, and reliability. 1 These particles have been the major causes of device failure because a 1% decrease in the product yield can cause more than a 2% loss in profits. 2 Generally, nanosized particles are typically produced by homogeneous nucleation and growth during fabrication processes. Therefore, to control particle contamination, it is essential to understand particle nucleation and growth in the chemically reacting environments. Chemical vapor deposition ͑CVD͒ is one of the most important processes. However, during the CVD process, the nanosized particles are generated, and these particles can have a fatal influence on the device quality. Particle measurement in the CVD process remains highly challenging because of the low pressure ambient and the particle size in nanometers. In terms of particle measurement methods, the levels of particle contamination have been conventionally monitored with either a wafer surface scanner or an in situ particle monitor ͑ISPM͒ sensor. However, the conventional wafer scanner, which utilizes an ex situ monitoring method, has difficulty detecting particles smaller than 50 nm. 3 In ISPM, the particles less than 0.1 m could not be detected because light scattering varies inversely with the sixth power of a particle diameter in this size range. 4 Hence, the particle beam mass spectrometer ͑PBMS͒ was developed in the mid-1990s to overcome these problems. Various semiconductor processes have been proven to be effective in measuring fine particles ͑0.005-0.5 m͒. With PBMS, the particle formation in CVD processes has drawn a lot of attention over the past decade. Experimental or theoretical studies were also carried out in the system of the thermal-5-9 or plasma-enhanced 10,11 chemical vapor deposition ͑PECVD͒ for the deposition of silicon films.A CVD titanium nitride ͑TiN͒ film deposited with a metallorganic precursor is widely used as a conformal barrier metal that protects shallow junctions during the formation of Al contacts on silicon as a glue layer because it is rigid and chemically stable. 12,13 For the CVD TiN process, tetrakis͑diethylamino͒titanium ͑TDMAT͒ was used by many researchers. However, because of...

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