Observation and control of the interfacial reaction of multilayr thin films for lead bonding wire using optical reflectivity technique.

利用x射线衍射和光学反射率技术研究了在100 ~ 250℃范围内退火的Al/Au和Al/Cu薄膜中金属间相的形成。首先在SiO_2板上沉积厚度为100nm的Au或Cu金属，然后在真空中在Au或Cu薄膜上制备厚度为100nm的Al薄膜。退火后的x射线分析证实了几种金属间化合物的形成。通过光学反射率随波长的变化可以观察到Al_2Cu、AlCu和Al_2Au的形成和生长。退火过程中，金属在Al/Au薄膜中的相互扩散速度比Al/Cu薄膜中的扩散速度快。例如，在200℃下退火的薄膜中，Al_2Au和Al_2Cu层的生长速率常数(k)分别为3.4 × 10^<-6>和2.4 × 10^<-7> cm/sec^<1/2>。这些金属间层在薄膜中的生长速度比在大块金属扩散偶中的生长速度快。采用压痕法研究了Al与Cu界面反应产物的强度。随着反应区厚度的增加和反应时间的延长，强度迅速增大，然后减小。适当的界面反应区厚度有助于提高铝铜铅结合线的强度。

Formation of intermetallic phases in Al/Au and Al/Cu thinfilm couples annealed at temperatures between 100ﾟC and 250ﾟC has been investigated using X-ray diffraction and optical reflectivity technique. The Au or Cu metals with the thickness of 100nm were first deposited on SiO_2 plate and then Al thin film with the thickness of 100nm was produced on the Au or Cu film in vacuum. Formation of several intermetallic compounds was confirmed by X-ray analysis after annealing. The formation and growth of Al_2Cu, AlCu and Al_2Au could be observed by the variation of optical reflectivity with wavelength. The inter-diffusion of metals in Al/Au thin film occurred faster than that in Al/Cu during annealing. For example, the growth rate constants (k) of Al_2Au and Al_2Cu layrs in thin film couples annealed at 200ﾟC were 3.4x10^<-6> and 2.4x10^<-7> cm/sec^<1/2>, respectively. The growth rate of these intermetallic layrs was faster in thin films than in diffusion couples of bulk metals.The strength of interfacial reaction products between Al and Cu was investigated using indentation test. The strength increased rapidly with increasign time and thickness of reaction zone, and then decreased. An appropriate thickness of the reaction zone at the interface contributed to the improvement of the strength of Al-Cu lead bonding wires.