End Point Detection of Chemical/ Mechanical Polishing of Thin Film Structures
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Carr, JW: AUTHOR [+2]
Described is a technique for detecting the end-points of chemical- mechanical (chem-mech) polishing of thin film structures as used in the fabrication of semiconductor devices.
End Point Detection of Chemical/ Mechanical Polishing of
a technique for detecting the end-points of
chemical- mechanical (chem-mech) polishing of thin film structures as
used in the fabrication of semiconductor devices.
In prior art,
the determination of the end-point of a polishing
cycle was set by either varying the polishing time or by modifing the
removal rate. Since the polishing time can vary widly from run to
run, this technique has a large window of error. It is also possible
to use an etch stop layer below the material to be removed. The etch
rate of this material is essentially zero. When the polishing slurry
encounters this material, removal stops and an end-point is reached.
One disadvantage of this method is a limitation in the number of
materials suitable for use as an etch-stop layer.
Fig. 1 shows
the chem-mech polish process, known as the
Damascene process. Step 1 shows the patterned trench material "B"
consisting of polyimide, quartz, etc. Step 2 shows liner material
"C" added consisting of Cr, Ti, etc. Step 3 shows the structure after
the deposition of trench-filling material "A" consisting of Cu, Al,
etc. Blanket material "A" is deposited over and into a patterned film
of material "B". The polish process consists of removing the blanket
film, leaving only patterned structures of material "A" embedded in
material "B", as shown in step 4. Specific combinations of "A/B"
include Cu/ polyimide, Al-Cu/Quartz and poly-Si/SiO2. For many
combinations of materials, an intermediate thin layer of material
"C", located between "A" and "B", is normally used to enhance "A/B"
adhesion, thereby improving the film quality of "A".
described herein proposes to use specific
analytical techniques to detect the presence of material "C" during
the blanket process of removing material "A". This specific
analytical technique provides a means of detecting when all of
material "A" has been removed, enabling the process to be stopped.