Thickness Controlled Thick And Thin Lines in One Damascene Level

Thickness Controlled Thick And Thin Lines in One Damascene Level

       Excellent thickness control is achieved for both thick
and thin conductive lines defined by a Damascene, single mask
process.  Via hole definition and filling is accomplished as an
integral part of this process.  Control of trade-offs between line
resistance, capacitance and electromigration resistance of thin lines
is achieved with the process.

      Referring to Fig. 1, diffusion 10 in silicon substrate 12 is to
be contacted through a via hole in insulating layer 14 first defined
by masking and creating an opening through non-erodable mask layer
16.  Then, photoresist 18 is patterned for wide, thick line and
narrow, thin line definition.  A wide line is to be connected through
the via hole to diffusion 10.  Layer 14 is then anisotropically
etched part way through at via holes to complete the cross-section
shown in Fig. 1.

      Layer 16 is etched through openings in photoresist 18 and then
oxide 14 is anisotropically etched to form a trough of depth
appropriate for definition of thickness of narrow, thin lines.  This
etch of insulator 14 also completes via hole openings and exposes
diffusion 10.  Removal of photoresist 18, conformal deposition of
tungsten (W) 20 having total thickness t, and isotropic etch removal
of a thickness t of W results in the cross-section shown in Fig. 2.

      Using masking comprised of layer 16 and remaining W 20, oxide
14 is etched again to a dep...