Etching a substrate: processes – Forming or treating article containing magnetically...
Reexamination Certificate
2000-10-26
2003-04-15
Olsen, Allan (Department: 1746)
Etching a substrate: processes
Forming or treating article containing magnetically...
C204S192100, C427S251000
Reexamination Certificate
active
06547975
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to a method and apparatus for forming submicrometer structures on a substrate. In one embodiment, these structures can be magnetic poles of thin film heads for data storage devices.
Many electronic products require the construction of miniature metallic structures. An example of such a structure is the second pole tip of a thin film recording head. Conventional processes for the fabrication of magnetic recording heads often comprise a combination of lithographic, deposition, plating, and etching processes. Typical recording heads are formed on Al
2
O
3
/TiC ceramic wafers that are eventually formed into sliders that fly over magnetic disks to perform read and write functions.
In a thin film recording head, it is desirable that the width of the pole tip of a second pole piece is made as narrow as possible in order to increase track density, which represents the number of tracks per inch width of the recording medium on which the head writes. The higher the track density, a greater number of bits per a greater area can be stored on the magnetic medium. The effort to produce narrower trackwidths is a constant challenge to the field.
One conventional method of creating pole structures is to fabricate a mask or “resist frame for plating” in conjunction with an electroplating process. For example, a conventional image transfer process to create an anisotropic cavity or trench in a semiconductor device, with the cavity having a seedlayer as the floor, is discussed in U.S. Pat. No. 5,665,251 (the '
251
patent) and is shown in FIG.
1
.
In
FIG. 1
, a seedlayer
11
is formed over a substrate
10
. A thick photoresist layer
12
is formed over seedlayer
11
. A masking layer
13
is formed on top of the thick photoresist layer
12
, then a thin photoresist layer
14
is formed on masking layer
13
.
The magnetic pole structure then can be created on the seedlayer
11
in the cavity
16
, with the seedlayer providing an electrical path to the structure. A portion
15
of thin resist layer
14
is first removed in steps
101
(exposure to light) and
103
(wet development with an aqueous solution). In step
105
, mask layer
13
is etched by a reactive ion etching (“RIE”) process. To create the cavity, thick layer
12
, typically of polymeric photoresist, is etched (in step
107
) using a RIE process. RIE is used to etch the thick layer because RIE can produce highly anisotropic cavities. However, RIE can also damage the underlying seedlayer. To prevent this damage during photoresist etching, a deposition of a protective layer, such as alumina or silicon dioxide, (not shown), can be formed on top of the seedlayer
11
. After the creation of the cavity, the protective layer in the bottom of the cavity is removed in a subsequent step which does not damage the seedlayer nor undercut the thick layer. An electro-deposition process (step
109
) is used to form a pole structure
18
. The remaining thick photoresist layer
12
is then removed by further RIE etching.
It is desirable, however, to improve upon conventional processes, such as the process described above, in order to fabricate narrower pole structures for greater track densities on recording media. Such narrower pole structures preferably would have widths less than about 0.3 micrometers (&mgr;m).
SUMMARY OF THE INVENTION
In view of the foregoing, it would be desirable to provide a process for the fabrication of sub-micrometer structures on a substrate. According to one embodiment of the present invention, a method for forming a submicrometer structure is provided. A submicrometer structure is formed from a multi-layer mask structure that includes a substrate, a seedlayer deposited on the substrate, a first polymer layer deposited on the seedlayer, a mask layer deposited on the first polymer layer, and a second polymer layer deposited on the mask layer, where the first polymer layer is thicker than the second polymer layer. A first etch of the first polymer layer is performed to define a vertical sidewall portion of the first polymer layer. Next, atoms from the seedlayer are sputtered onto the vertical sidewall portion of the first polymer layer to form the submicrometer structure. From this method, structures, such as magnetic pole pieces, can be formed having widths of less than 0.3 micrometers, if desired.
According to another embodiment of the present invention, a method for forming a submicrometer structure is provided. A submicrometer structure is formed from a multi-layer mask structure that includes a substrate, a seedlayer deposited on the substrate, and a polymer layer deposited on the seedlayer. The polymer layer is lithographically patterned with an exposure to define a vertical sidewall portion of the polymer layer. Next, atoms from the seedlayer are sputtered onto the vertical sidewall portion of the polymer layer to form the submicrometer structure.
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Wolf-Dieter Domle, “Chemical amplification of resist lines: The CARL process”, Microlithography World, Spring 1999, pp. 2-5.
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Olsen Allan
Unaxis USA Inc.
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