Title: Method of making conductive stud for magnetic recording devices
Abstract: Methods of making a magnetic recording device with an "anchored" conductive stud which is securely attached within its surrounding insulator materials. The conductive stud is formed over a conductive layer which is coupled to or part of a read or a write head element of the magnetic recording device. The conductive stud has a top stud portion and a bottom undercut portion formed over the conductive layer. In one illustrated embodiment, the bottom undercut portion has a width that is greater than the width of the top stud portion. Since an insulator is formed around the conductive stud and over its bottom undercut portion, a secure coupling between the conductive stud and the conductive layer is provided. Preferably, the conductive layer is made of copper (Cu), the conductive stud is made of gold (Au), and the insulator is alumina (Al2O3). A seed layer may be formed between the conductive stud and the conductive layer.
Patent Number: 7,020,959 Issued on 04/04/2006 to Krause, et al.
| Inventors:
|
Krause; Rainer Klaus (Kostheim, DE);
Marien; Jan (Selzen, DE);
Paul; Johannes Thomas (Mainz, DE);
Sandmann; Gunther Wilhelm (Mainz, DE);
Scherb; Gerhard Anton (Mainz, DE);
Schuy; Hubert Erwin (Oppenheim, DE);
Seifried; Stefan (Nidderau, DE)
|
| Assignee:
|
Hitachi Global Storage Technologies Netherlands B.V. (Amsterdam, NL)
|
| Appl. No.:
|
314067 |
| Filed:
|
December 6, 2002 |
| Current U.S. Class: |
29/846; 29/603.07; 29/DIG.16; 427/96.2; 427/99.4; 216/42; 216/48 |
| Current Intern'l Class: |
H01K 3/10 (20060101); G11B 5/12.7 (20060101) |
| Field of Search: |
29/60307,603.13,846,847,854,DIG.16
427/962,994
216/22,42,48
360/122,125
|
References Cited [Referenced By]
U.S. Patent Documents
| 5226232 | Jul., 1993 | Boyd.
| |
| 5462637 | Oct., 1995 | Thiele.
| |
| 5863448 | Jan., 1999 | Otani et al.
| |
| Foreign Patent Documents |
| 61-68718 | Apr., 1986 | JP.
| |
| 4-10534 | Jan., 1992 | JP.
| |
Primary Examiner: Tugbang; A. Dexter
Attorney, Agent or Firm: Oskorep, Esq.; John J.
Claims
What is claimed is:
1. A method of making a conductive stud, comprising the acts of:
forming, over a conductive layer, a resist structure which has a recess with
a bottom undercut;
forming, within the recess structure, the conductive stud which has a top stud
portion and a bottom undercut portion formed over the conductive layer;
removing the resist structure;
forming an insulator around the conductive stud and over the bottom undercut
portion; and
providing an exposed top surface of the top stud portion for a lead connection
to the conductive stud.
2. The method of claim 1, further comprising the act of:
forming a seed layer between the conductive layer and the resist structure.
3. The method of claim 1, wherein the act of forming the resist structure comprises
performing a photolithography process.
4. The method of claim 1, wherein the act of forming the resist structure comprises
forming a dual layer resist structure.
5. The method of claim 1, wherein the act of forming the conductive stud comprises
forming the bottom undercut portion with a width that is greater than the width
of the top stud portion such that the insulator is formed over the bottom under
cut portion.
6. The method of claim 1, wherein the act of forming the conductive stud comprises
forming the bottom undercut portion to extend laterally relative to the top portion
such that the insulator is formed over the bottom under cut portion.
7. The method of claim 1, further comprising the act of:
performing a planarization process to form a substantially planar top surface
with tops of the insulator and the conductive stud.
8. The method of claim 1, further comprising the act of:
connecting a lead to the exposed top surface of the top stud portion.
9. A method of making a conductive stud for a magnetic recording device comprising
the acts of:
forming a conductive layer which is coupled to or part of a read or write head element;
forming a seed layer over the conductive layer;
forming a resist layer over the seed layer;
performing a photolithography process to form a resist structure from the resist
layer, the resist structure having a recess formed with a bottom undercut;
electroplating a conductive stud within the recess, the conductive stud having
a top stud portion and a bottom undercut portion formed over the conductive layer;
removing the resist structure;
etching away end portions of the seed layer to form a central seed layer between
the conductive layer and the conductive stud;
depositing an insulator around the conductive stud and over the bottom undercut
portion; and
performing a planarization process to form a substantially planar top surface
with tops of the insulator and the top stud portion to provide a lead connection
to the conductive stud.
10. The method of claim 9, wherein the conductive stud comprises gold (Au), the
conductive layer comprises copper (Cu), and the planarization process comprises
chemical mechanical polishing (CMP).
11. The method of claim 9, wherein the act of forming a resist layer over the
seed layer comprises forming a dual resist layer.
12. The method of claim 9, wherein the act of electroplating the conductive stud
comprises forming a top stud portion and a bottom undercut portion which extends
laterally relative to the top stud portion such that the insulator is deposited
over the bottom undercut portion.
13. The method of claim 9, wherein the act of electroplating the conductive stud
comprises forming a top stud portion and a bottom undercut portion which has a
width that is greater than the width of the top stud portion such that the insulator
is deposited over the bottom undercut portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to conductive studs formed across several functional
layers of magnetic recording devices, and more particularly to conductive studs
formed with bottom undercut portions which are anchored within surrounding insulative materials.
2. Description of the Related Art
Thin film magnetic heads are primarily used in magnetic storage systems to write/read
information in the form of magnetic pulses to/from a relatively moving magnetic
medium. A magnetic transducer, such as an inductive or magnetoresistive head (MR
or GMR type), is typically formed on a slider which is then mounted to a suspension
arm of an actuator. The suspension arm suspends the head in close proximity to
a disk surface.
Head supporting sliders are generally fabricated from a thin wafer of substrate
including a matrix of thin film magnetic heads formed on one of the wafer surfaces.
A number of known fabrication techniques may be used to form the heads, e.g., sputtering,
vapor deposition, photolithography, and plating. The particular processes used
will depend on the type of head being constructed, but generally each process includes
a stage wherein terminal pads or studs are formed at the slider's trailing edge
for providing an electrical contact to the functional head element. For example,
the formation of an inductive head can be separated into four stages: the construction
of the first magnetic pole; formation of the conductor coil; construction of the
second magnetic pole; and formation of the electrical conductors (studs). Four
terminal pads or studs are usually required for each head. Upon completion of the
studs, wafers are sliced and diced by known methods to form individual sliders.
The sliders are then bonded to suspension arms, and leads from the suspension are
soldered to the studs. Relatively large conductors are used in thin film heads
to provide desired characteristics of mechanical stability, chemical stability
and low contact resistivity.
Depending on the shape of the stud, it may have an undesirable tendency
to break away from its surrounding materials. To illustrate, FIG. 1 is a cross-sectional
view of a conventional interconnection structure
200 of a magnetic recording
device. A conductive stud
220 includes a top stud portion
202 made
of gold (Au) and a bottom stud portion
206 made of copper (Cu). In the cross-sectional
view, top stud portion
202 has a generally rectangular shape and bottom
stud portion
206 has a generally trapezoidal shape with its shorter base
side formed over conductive layer
204 (on top of seed layer
208).
Bottom stud portion
206 is formed over and coupled to a full conductive
layer
204 made of copper (Cu), typically through a thin conductive seed
layer
208. Conductive layer
204 is also coupled to either the read
head element or the write head element of the magnetic head. An insulator
210
is formed around bottom stud portion
206 over conductive layer
204,
such that a top planarized surface is formed with the top of bottom stud portion
206. Top stud portion
202 is formed to make contact with and cover
the top of bottom stud portion
206 and has edges which extend over top portions
of insulator
210. A lead (not shown) is typically connected to top stud
portion
202.
A more simplified cross-sectional view of this interconnection structure is shown
in FIG. 2. FIG. 2 shows a conventional trapezoidal stud
304 formed within
surrounding materials
302 (e.g. an insulator) with its top generally exposed.
A conventional process of making trapezoidal stud
304 involves etching a
hole into surrounding materials
302 and forming the stud
304 within
the hole. Unfortunately, the etch process is relatively unstable in forming a suitable
shape and size for stud
304. As illustrated in FIG. 3, such a trapezoidal
stud
304 has a tendency to physically break away from these surrounding
materials
302 due to the segregation effect along the borderline. This is
highly undesirable, as conductive studs should be securely attached to provide
for a reliable electrical coupling within the magnetic recording device.
Accordingly, what are needed are improved interconnection structures
and conductive studs for magnetic recording devices and methods of making the same.
SUMMARY OF THE INVENTION
According to the present invention, a magnetic recording device utilizes
an "anchored" conductive stud which is securely attached within its surrounding
materials. The conductive stud is formed over a conductive layer which is coupled
to or part of a read or a write head element of the magnetic recording device.
The conductive stud has a top stud portion and a bottom undercut portion which
is formed over the conductive layer. Preferably, the bottom undercut portion has
a width that is greater than the width of the top stud portion. Since an insulator
is formed around the conductive stud and over its bottom undercut portion, a secure
coupling between the conductive stud and the conductive layer is provided. Preferably,
the conductive layer is made of copper (Cu), the conductive stud is made of gold
(Au), and the insulator is alumina (Al
2O
3). A seed layer
may be formed between the conductive stud and the conductive layer.
A method of making such a conductive stud utilizes a photolithography process.
More particularly, the method includes forming a conductive layer which is coupled
to or part of a read or a write head element of the magnetic recording device.
A seed layer is deposited over the conductive layer, followed by the formation
of a resist layer. Next, a photolithography process is used to form a resist structure
that includes a recess formed with a bottom undercut. A conductive stud material
is plated within this recess and the resist structure is removed to thereby expose
the conductive stud. Next, exposed end portions of the seed layer are etched away
to form a central seed layer between the conductive layer and the conductive stud.
An insulator is then deposited over the conductive layer and around the conductive
stud. A planarization process, such as a chemical mechanical polishing (CMP), is
performed to form a substantially planar top surface with tops of the insulator
and the conductive stud. Advantageously, the conductive stud is formed with a top
stud portion and a bottom undercut portion which has a width that is greater than
the width of the top stud portion, such that surrounding insulator materials over
the bottom undercut portion provide for a secure attachment.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and advantages of the present invention,
as well as the preferred mode of use, reference should be made to the following
detailed description read in conjunction with the accompanying drawings:
FIG. 1 is a cross-sectional view which shows a conductive stud of the prior art;
FIG. 2 is a cross-sectional view which shows the conductive stud of the prior
art in simplified form;
FIG. 3 is a cross-sectional view which shows one particular problem of the conductive
stud of the prior art;
FIG. 4 is a planar view of a conventional magnetic disk drive;
FIG. 5 is an end view of a slider with a magnetic head of the disk drive as
seen in plane V—V of FIG. 4;
FIG. 6 is an elevation view of the magnetic disk drive wherein multiple disks
and magnetic heads are employed;
FIG. 7 is an isometric illustration of an exemplary suspension system for supporting
the slider and magnetic head;
FIG. 8 is a top view of the second pole piece, a coil layer with all insulation
material removed, and an electrically conductive stud of the present invention;
FIG. 9 is the first in a series of ten cross-sectional illustrations in FIGS.
9-18 which describe a method of forming an interconnection structure which includes
an electrically conductive stud for a magnetic recording device, showing more particularly
a seed layer formed over a conductive layer;
FIG. 10 is the second in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 9 except that a dual resist layer is formed over the conductive layer;
FIG. 11 is the third in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 10 being subjected to a photolithography process;
FIG. 12 is the fourth in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 10 except that a recess with undercuts is formed within the
resist layer;
FIG. 13 is the fifth in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 12 except that a conductive stud material is formed within
the recess;
FIG. 14 is the sixth in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 13 except that the resist structure is removed;
FIG. 15 is the seventh in a series of ten illustrations of FIGS. 9-18 which
describe a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 14 except that end portions of the seed layer are removed
by etching;
FIG. 16 is the eighth in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 15 except that an insulator material is deposited over it;
FIG. 17 is the ninth in a series of ten illustrations of FIGS. 9-18 which describe
a method of forming the electrically conductive stud, showing more particularly
the structure of FIG. 16 except that its top surface has been planarized by chemical
mechanical polishing (CMP), to thereby form the interconnection structure of the
present invention; and
FIG. 18 is the tenth and final illustration in FIGS. 9-18 which describe a method
of forming the electrically conductive stud, showing more particularly perspective
view of the stud formed by the method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description is the best embodiment presently contemplated for carrying
out the present invention. This description is made for the purpose of illustrating
the general principles of the present invention and is not meant to limit the inventive
concepts claimed herein.
Referring now to the drawings, wherein like reference numerals designate
like or similar parts throughout the several views, there is illustrated in FIGS.
4-6 a conventional magnetic disk drive
30. The drive
30 includes
a spindle
32 that supports and rotates a magnetic disk
34. The spindle
32 is rotated by a motor
36 that, in turn, is controlled by a motor
controller
38. A horizontal combined magnetic head
40 for reading
and recording is built into a slider
42. The slider
42 is supported
by a suspension
44 and actuator arm
46. A plurality of disks, sliders
and suspensions may be employed in a large capacity direct access storage device
(DASD), as shown in FIG. 6. The suspension
44 and actuator arm
46
position the slider
42 to locate the magnetic head
40 in a transducing
relationship with a surface of the magnetic disk
34. When the disk
34
is rotated by the motor
36, the slider is supported on a thin (typically,
0.015 μm) cushion of air (air bearing) between the disk and an air bearing
surface (ABS)
48.
The magnetic head
40 may be employed for writing information to multiple
circular tracks on the surface of the disk
34, as well as for reading information
therefrom. Processing circuitry
50 exchanges signals representing such information
with the head
40, provides motor drive signals, and also provides control
signals for moving the slider
42 to various tracks. In FIGS. 4 and 7 the
slider
42 is shown mounted to a head gimbal assembly (HGA)
52 that
is mounted to the suspension
44. All of the above components are supported
on a base
53. As shown in FIGS. 5 and 7, conductive pads
88,
90,
100, and
102 connect leads from a read sensor (not shown) and leads
104 and
106 from a write coil
68 (see FIG. 8) to leads
96,
98,
108, and
110 on the suspension
44. Write coils
68 are coupled to a conductive stud
112, which is part of an interconnection
structure used in disk drive
30.
FIGS. 9-17 are cross-sectional views of partially formed interconnection structures
which help describe a method of forming a conductive stud of the present invention.
The method of FIGS. 9-17 may be utilized while making the interconnection structure
in the disk drive described above in relation to FIGS. 4-8. The interconnection
structure will have the final stud structure shown and described in relation to
FIGS. 17-18.
As described previously, a conventional process of making a conductive stud involves
etching a hole into surrounding materials and forming the stud within the hole.
Unfortunately, the conventional etch process is relatively unstable in forming
a suitable shape and size for the conductive stud. According to the present invention,
a more suitable shape and size for the stud is formed using a photolithography process.
Beginning with FIG. 9, a full conductive layer
902 is formed over
a substrate by sputter deposition. Conductive layer
902 may be coupled to
or part of an element of the read head (e.g. a read sensor) or an element of the
write head (e.g. a write coil), for example. In the present embodiment, conductive
layer
902 is actually one of the layers of the write coil of the magnetic
recording device. Preferably, conductive layer
902 is made of copper (Cu),
but it could be made with any suitable conductive material such as nickel-iron
(Ni—Fe). Conductive layer
902 may vary in thickness between, for example,
about 1-3 micrometers (μm), and in the present embodiment has a thickness
of about 2 μm. Next, a seed layer
904 is sputter deposited on top
of this conductive layer
902. Seed layer
904 may vary in thickness
between, for example, about 50-100 nm, and in the present embodiment has a thickness
of about 80 nm. In the present embodiment, seed layer
904 is a dual layer
of nickel-iron (NiFe) and gold (Au) which have thicknesses of 20 nm and 60 nm, respectively.
In FIG. 10 it is shown that a resist
1002 is formed over seed layer
904.
Resist
1002 may vary in thickness between, for example, about 15-30 micrometers
(μm), and in the present embodiment has a thickness of about 20 micrometers
(μm). In this embodiment, resist
1002 is a dual layer resist which
includes a top resist layer
1004 and a bottom resist layer
1006.
Preferably, top resist layer
1004 is a photosensitive resist (e.g. well-known
HC-935) and bottom resist layer
1006 is a non-photosensitive resist (e.g.
well-known PMGI). This dual resist layer helps later facilitate the formation of
a bottom undercut structure with a recess within resist
1002. In the present
embodiment, top resist layer
1004 and bottom resist layer
1006 have
thicknesses of 15 μm and 5 μm, respectively.
In FIG. 11, it is shown that resist
1002 is exposed to light
1104
in a selected central area of resist
1002 with use of a mask
1102.
The central hole of mask
1102 may be any suitable width, and in the present
embodiment has a width of about 110 μm. In FIG. 12, it is shown that a recess
1204 is then formed within the resist using a wet etching process, which
leaves behind surrounding resist structures
1210,
1212,
1214,
and
1216. As illustrated, recess
1204 is formed with bottom undercuts
1206 and
1208. In this process, a suitable solvent or acid is applied
so that materials of the top resist layer are dissolved and the materials of the
bottom resist layer are etched over a suitable time period to achieve the desired
undercut width. Preferably, the width of the undercut is greater than 110% of the
top stud portion and, for a recess width of 110 μm, the undercut width may
be between about 120-130 μm.
In FIG. 13, a conductive stud material
1204 is then electoplated within
recess
1204. Preferably, conductive stud material
1204 is made of
gold (Au), but it could be any other suitable conductive material such as copper
(Cu). Also preferably, conductive stud material
1204 is electroplated by
a conventional process known as non-cyanide gold plating. This process is typically
followed by a clean step which utilizes an ash process to remove any remaining
resist on the surface. Surrounding resist structures
1210,
1212,
1214, and
1216 of FIG. 13 are then removed by dissolving the resist
with a suitable solvent. This reveals the conductive stud
1302 shown in
FIG. 14.
As shown in FIG. 14, conductive stud
1302 is formed with a top stud portion
1402 and a bottom undercut portion
1404 which is formed over conductive
layer
902 (on seed layer
904). Formed in the same processing step,
top stud portion
1402 and bottom undercut portion
1404 are integrally
formed together as a single unit. In this embodiment, bottom undercut portion
1404
has an undercut
1406 which provides a width that is greater than the width
of top stud portion
1402. This extended width is formed all around the bottom
"perimeter" of conductive stud
1302. Thus, at least a portion of bottom
undercut portion
1404 is formed to extend laterally relative to top stud
portion
1402 so that subsequently deposited insulator materials may be formed
over it.
Next, a wet etch is used to remove exposed end portions of seed layer
904
to form a central seed layer
1502 as shown in FIG. 15. The wet etch may
use any suitable etch solution or acid. In FIG. 15, insulator materials
1602
are then deposited over and around conductive stud
1302 and conductive layer
902. These insulator materials
1602 are also formed over bottom undercut
portion
1404. Insulator materials
1602 may be any suitable electrically-insulating
material, such as alumina (Al
2O
3). In FIG. 16, it is shown
that a planarization process such as a chemical mechanical polishing (CMP) is performed
to form a substantially planarized top surface
1702 with the tops of insulator
materials
1602 and conductive stud
1302.
The conductive stud
1302 is thereby formed, and FIG. 18 shows a perspective
view of a top of a completed conductive stud
1302. The thickness of conductive
stud
1302 may vary between about 15-30 μm, and in the present embodiment
is about 20 nm. The general width of conductive stud
1302 may vary greatly,
but bottom undercut portion
1404 is formed to extend laterally relative
to top stud portion
1402 such that insulator materials
1602 are formed
over it for secure attachment In this embodiment, bottom undercut portion
1404
is formed all around conductive stud
1302 with a width that is greater than
top stud portion
1402. More specifically, top stud portion
1402 has
a width of about 110 μm and bottom undercut portion
1404 has a width
of between about 120-130 μm. A lead is subsequently wire-bonded to conductive
stud
1302, preferably using an ultrasonic wire bonding process.
As described herein, a magnetic recording device makes use of an "anchored" conductive
stud which is securely attached within its surrounding materials. The conductive
stud is formed over a conductive layer which is coupled to or part of a read or
a write head element of a magnetic head. In one illustrated example, the conductive
layer is one of the write coil layers of a magnetic write head. The conductive
stud has a top stud portion and a bottom undercut portion formed over the conductive
layer. Preferably, the bottom undercut portion has a width that is greater than
the width of the top stud portion. Since an insulator is formed around the conductive
stud (and over the bottom undercut portion), a secure coupling between the conductive
stud and the conductive layer is provided. Preferably, the conductive layer is
made of copper (Cu), the conductive stud is made of gold (Au), and the insulator
is alumina (Al
2O
3). A seed layer may be formed between the
conductive stud and the conductive layer. Such a conductive stud may be made with
use of a photolithography process as previously described.
It is to be understood that the above is merely a description of preferred embodiments
of the invention and that various changes, alterations, and variations may be made
without departing from the true spirit and scope of the invention as set for in
the appended claims. For example, the conductive studs described herein may be
utilized in any other suitable device, such as a semiconductor device. None of
the terms or phrases in the specification and claims has been given any special
particular meaning different from the plain language meaning to those skilled in
the art, and therefore the specification is not to be used to define terms in an
unduly narrow sense.
*
