Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Grebe, KR: AUTHOR [+2]
AbstractPassivation coatings of (poly)para-xylylene can be precisely patterned by masking with oxidation-resistant materials and subsequently subtractively etching in an oxidizing environment.
Passivation coatings of (poly)para-xylylene can be precisely patterned by masking with oxidation-resistant materials and subsequently subtractively etching in an oxidizing environment.
The ductile and plastic behavior of para-xylylene materials (e.g., parylene passivating material) makes them suitable for cryogenic applications. It is also possible to use these films as insulation layers for microelectronic circuits because of their low dielectric constant (approx. 3) and low loss properties. The low dielectric constant is most attractive for high speed microstrips or strip lines.
One of the disadvantages of using para-xylylene materials is
that they are difficult to pattern, especially in micron or submicron
dimensions. There are, however, a number of masking materials to
pattern para-xylylene materials using oxygen plasma or other
oxidizers such as CF(4)-O(2). Removal using oxygen plasma can be
achieved in both the reactive ion etching mode as well as in the
plasma etching mode. By the same principle, the para-xylylene
materials can be removed in the reactive ion-beam etching mode using
oxygen ion beams. In the RIE (reactive ion etching) mode the etch
rate can be from less than 100 Angstroms/minute to more than 1000
Angstroms/minute depending on the bias voltage and power density.
Masking for the etching can be achieved by photo-patterning metal,
insulator thin films, or photo-sensitive organic materials.
a. Deposit, on top of the para-xylyene layer 1, a metal
thin film 2.
b. The metal thin film can be defined by lift-off (Fig. 1A), or
by wet or dry subtractive etching (not illustrated).
The metal film thickness is not crucial
(e.g.,<1000 Angstorms), and can be Al, Au, Cr,
Cu, Nb, Ag, etc. (Fig. 1B).
c. After photoresist removal, para-xylylene layer 1 is etched in
oxygen plasma. Metal thin film 2 is not etched or is
etched very little (Fig. 1C).
d. The metal thin films (surface oxidized) can be subsequently
removed (by etching) or left in place depending on
compatibility of applications (Fig. 1D). #:AB 2. INSULATOR
a. Deposit an insulator thin film 2 onto para-xylyene layer 1.
b. Thin film 2 is an insulator film defined by lift-off or
subtractive etching (Fig. 1A). The insulator film
thickness is not crucial, e.g., <2000 Angstroms. Materials
can be SiO, SiO(2), etc. (Fig. 1B).
c. After lift-off or photoresist removal, the para-xylylene
layer 1 is etched in the oxygen plasma. Insulator
film 2 is only slightly etched (mostly by sputter
removal) by oxygen plasma (Fig. 1C).
d. The insulator...