What is a poly/metal1 contact, and ndiff/poly contact?

[shemo]

What kind of material is the contact linking the poly and metal1?
Or linking ndiff and poly? Two different materials yet the contact able to link them together

 

[dick_freebird]

There is no single answer. Your metal to diffusion /
implant / poly could be simply the aluminum Met1
(though this is no longer real popular), could be a
barrier stack like TiN / TiW / Al, could be silicide
(CoSi, WSi, TiSi). The silicides are popular in CMOS
especially for driving down gate resistance (salicide).
Some sort of very inert barrier is preferable for
reliability especially at high temps / high currents
(your zener-zap trim diode used a plain aluminum-
silicon contact, aluminim spikes the junction and
shorts it out at relatively low input power).

Ndiff to poly is a rarity, I have never seen it as a
supported option in my time designing ICs (at the
trailing edge, but still). Maybe some technologies
that are in extremely layout-area-sensitive markets
(like DRAM?) might bother to engineer a poly-diff
direct contact (if so, probably N+ poly to NDiff,
a same-species silicon-silicon contact). SiGe HBTs
of course have poly emitters generally and a N+
poly to P (SiGe) base electrical contact (junction)
is made.