Enantio- and regiocontrol in palladium- and tungsten-catalyzed allylic substitutions

1998 ◽  
Vol 70 (5) ◽  
pp. 1035-1040 ◽  
Author(s):  
R. Prétôt ◽  
G. C. Lloyd-Jones ◽  
A. Pfaltz
Keyword(s):  
Allylic Substitutions ◽  
And Tungsten

Influence of carbon fibers and tungsten disulfide on the properties and structure of polytetrafluoroethylene

2018 ◽  
Vol 4 (3) ◽  
pp. 26-34
Author(s):  
A. A. Okhlopkova ◽  
A. P., Vasilev ◽  
T. S. Struchkova ◽  
A. G. Alekseev ◽  
P. N. Grakovich
Keyword(s):  
Carbon Fibers ◽  
Tungsten Disulfide ◽  
And Tungsten

A Latent Issue of Via Resistance: Mechanism and Solution

2018 ◽  
Author(s):  
Wentao Qin ◽  
Scott Donaldson ◽  
Dan Rogers ◽  
Lahcen Boukhanfra ◽  
Julien Thiefain ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Chemical Mechanical Planarization ◽  
Resistance Mechanism ◽  
Formation Enthalpy ◽  
Metal Line ◽  
Device Failure ◽  
Valence Electrons ◽  
Wafer Processing ◽  
Field Failure ◽  
And Tungsten

Abstract Many semiconductor products are manufactured with mature technologies involving the uses of aluminum (Al) lines and tungsten (W) vias. High resistances of the vias were sometimes observed only after electrical or thermal stress. A layer of Ti oxide was found on such a via. In the wafer processing, the post W chemical mechanical planarization (WCMP) cleaning left residual W oxide on the W plugs. Ti from the overlaying metal line spontaneously reduced the W oxide, through which Ti oxide formed. Compared with W oxide, the Ti oxide has a larger formation enthalpy, and the valence electrons of Ti are more tightly bound to the O ion cores. As a result, the Ti oxide is more resistive than the W oxide. Consequently, the die functioned well in the first test in the fab, but the via resistance increased significantly after a thermal stress, which led to device failure in the second test. The NH4OH concentration was therefore increased to more effectively remove residual W oxide, which solved the problem. The thermal stress had prevented the latent issue from becoming a more costly field failure.

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