Manufacturing method of semiconductor device

Abstract

In MOSFET having SBD as a protection element, a TiW (alloy having tungsten as a main component) film is used as an aluminum-diffusion barrier metal film below an aluminum source electrode in order to secure properties of SBD. The present inventors have found that a tungsten-based barrier metal film is in the form of columnar grains having a lower barrier property than that of a titanium-based barrier metal film such as TiN so that aluminum spikes are generated relatively easily in a silicon substrate. In the present invention, when a tungsten-based barrier metal film is formed by sputtering as a barrier metal layer between an aluminum-based metal layer and a silicon-based semiconductor layer therebelow, the lower layer is formed by ionization sputtering while applying a bias to the wafer side and the upper layer is formed by sputtering without applying a bias to the wafer side.

1 . A manufacturing method of a semiconductor device comprising the steps of:
 (a) forming a recess downwards from the upper surface of a first insulating film over a first main surface of a semiconductor wafer;   (b) forming a tungsten-based barrier metal film on the inner surface of the recess and the upper surface of the first insulating film by ionization sputtering film formation while applying a bias voltage to the semiconductor wafer; and   (c) after the step (b), forming an aluminum-based metal layer to cover therewith the tungsten-based barrier metal film over the inner surface of the recess and the upper surface of the first insulating film.   
     
     
         2 . The manufacturing method of a semiconductor device according to  claim 1 , wherein in the step (b), the tungsten-based barrier metal film contains tungsten as a main component thereof and titanium as a secondary component. 
     
     
         3 . The manufacturing method of a semiconductor device according to  claim 1 , wherein the tungsten-based barrier metal film has a layer having mainly an amorphous structure. 
     
     
         4 . The manufacturing method of a semiconductor device according to  claim 1 , wherein the semiconductor wafer has, over the first main surface thereof, a number of semiconductor chip regions and a Schottky barrier diode is formed in each of the chip regions. 
     
     
         5 . The manufacturing method of a semiconductor device according to  claim 4 , wherein a power MOSFET is formed in each of the chip regions. 
     
     
         6 . The manufacturing method of a semiconductor device according to  claim 1 , wherein the recess has a two-stage structure.