Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-01-10
2003-02-04
Echols, P. W. (Department: 3726)
Metal working
Method of mechanical manufacture
Electrical device making
C324S210000, C324S252000, C366S128000
Reexamination Certificate
active
06513227
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of manufacturing methods for magnetic transducers (heads) and more particularly to methods and structures for monitoring the results of a manufacturing process for producing fine structures used as pole tips in magnetic transducers.
BACKGROUND OF THE INVENTION
A typical prior art magnetic head and disk system is illustrated in FIG.
1
. In operation the head
10
is supported by a suspension
13
as it flies above the disk
16
. The magnetic transducer, usually called a “head,” is composed of elements that perform the task of writing magnetic transitions (the write head
23
) and reading the magnetic transitions (the read head
12
). The electrical signals to and from the read and write heads
12
,
23
travel along conductive paths (leads)
14
which are attached to or embedded in the suspension arm (not shown). Typically there are two electrical leads each for the read and write heads. Wires or leads are connected to these pads and routed in the suspension
13
to the arm electronics (not shown). The disk
16
is attached to spindle
18
that is driven by a spindle motor
24
to rotate the disk. The disk
16
comprises a substrate
26
on which a plurality of thin films
21
are deposited. The thin films include ferromagnetic material that is used to record the magnetic transitions in which information is encoded.
The write head
23
portion of the transducer typically includes two pole pieces (P
1
and P
2
formed from ferromagnetic material) (not shown) and a coil (not shown). To decrease the side writing and, therefore, to reduce the track width the pole pieces are shaped into narrow tips at the gap. In a typical prior art method P
1
is deposited first and initially has a broad, flat tip that is subsequently ion milled (sometimes called “notching”) using the P
2
tip as a mask to form the P
1
tip. This process insures that P
1
and P
2
have a closely matched tip size. U.S. Pat. No. 6,111,724 to Hugo Santini discusses a prior art process for making P
2
tips and describes an improvement using a zero-throat-height defining layer.
Regardless of the method used to form P
2
, the width of the track written by this type of inductive head is largely determined by the width of the bottom of P
2
(P
2
b
). P
2
tends to be wider at the top (away from the gap) which creates an additional complication in measuring the width of P
2
b
. It is important to be able to measure P
2
b
with some precision to monitor the manufacturing process. There are numerous variables in the process which affect the formation and shape of P
2
including those affecting the photolithography used to define the shapes, the plating process used for depositing the ferromagnetic material, the seed layer removal process and the ion milling used to shape P
1
using P
2
as a mask. These variables can change from time to time in the manufacturing process and may even vary across a single wafer.
Thus, there is a need for an efficient method of measuring the width of P
2
b
from wafer to wafer and also across each wafer.
SUMMARY OF THE INVENTION
Applicant discloses a method for forming metrology structures on a wafer, on which magnetic transducers are being fabricated, which have a measurable electrical resistance which is an accurate surrogate for a physical dimension of the nearby P
2
tip structures formed on the wafer for the magnetic transducers. The metrological structure of the invention is formed in parallel with and proximate to the production P
2
structure to subject the metrology structure to the same local process variables affecting the P
2
production structure, including those which result in the bottom being narrower than the top. The metrology structure is preferably a resistor with pads which are usable with a four point probe. The resistor is preferably formed by creating a sacrificial P
2
structure over a pad of millable resistive material. A selected area of the P
2
structure is used as a milling mask to replicate the width of the selected area in the resistive material. The selected area should include the narrowest area of P
2
. Preferably an ion milling process is used to remove the resistive material outside of the masked area of the resistor pad, thus replicating the width of P
2
in the resistive material. Since the resistor pad is under P
2
, it is milled down to the width of the bottom of P
2
, i.e., P
2
b
. Control structures with unmilled pads of resistive material (sheet resistors) are formed along with the metrology structures to provide the sheet resistance of the pads prior to milling. Knowledge of the sheet resistance allows the resistance of the milled structure to be converted into an accurate measure of the physical dimension.
The metrological structure of the invention provides a way to measure the width in a more convenient way than is available in the prior art. In addition, since ion milling of the P
1
tip using the P
2
tip as a mask is already a typical part of the prior art process of manufacturing transducers, the metrology structure can be milled at the same time and in the same way.
REFERENCES:
patent: 5996213 (1999-12-01), Shen et al.
patent: 6111724 (2000-08-01), Santini
patent: 6370763 (2002-04-01), Watanuki et al.
LandOfFree
Method for measuring fine structure dimensions during... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for measuring fine structure dimensions during..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for measuring fine structure dimensions during... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3179639