U.S. patent application number 11/218932 was filed with the patent office on 2006-02-09 for cleaning sheet and method for a probe.
Invention is credited to Akihiro Sakamoto, Satoru Sato.
Application Number | 20060030247 11/218932 |
Document ID | / |
Family ID | 18982630 |
Filed Date | 2006-02-09 |
United States Patent
Application |
20060030247 |
Kind Code |
A1 |
Sato; Satoru ; et
al. |
February 9, 2006 |
Cleaning sheet and method for a probe
Abstract
A cleaning sheet has a base sheet, a foamed layer of a porous
material on the base sheet and a polishing layer formed on the
foamed layer. The foamed layer includes non-fibrous abrading
particles and air bubbles. Such a cleaning sheet may be produced by
preparing a paint having air bubbles dispersed inside by
mechanically foaming a foaming material containing a foaming resin
material and abrading particles, forming on the base sheet a foamed
layer having abrading particles dispersed inside by coating a
surface of the base sheet with this paint and drying it, and
forming a polishing layer on the foamed layer. A probe having a tip
may be cleaned with such a cleaning sheet by causing a surface of
its polishing layer to be pressed against the tip of the probe and
causing the tip of the probe to penetrate the polishing layer and
further to be inserted into the foamed layer having abrading
particles dispersed inside.
Inventors: |
Sato; Satoru; (Tokyo,
JP) ; Sakamoto; Akihiro; (Tokyo, JP) |
Correspondence
Address: |
BEYER WEAVER & THOMAS LLP
P.O. BOX 70250
OAKLAND
CA
94612-0250
US
|
Family ID: |
18982630 |
Appl. No.: |
11/218932 |
Filed: |
September 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10298310 |
Nov 14, 2002 |
|
|
|
11218932 |
Sep 2, 2005 |
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Current U.S.
Class: |
451/49 |
Current CPC
Class: |
B24D 3/32 20130101; B24B
19/16 20130101; B08B 1/00 20130101; B24D 18/00 20130101; G01R 3/00
20130101; B24B 29/08 20130101; B24D 15/04 20130101; G01R 1/06711
20130101 |
Class at
Publication: |
451/049 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2001 |
JP |
2001-135090 |
Apr 3, 2002 |
WO |
PCT/JP02/03335 |
Claims
1. A cleaning sheet comprising: a base sheet; a foamed layer formed
on said base sheet, said foamed layer having non-fibrous abrading
particles dispersed therein; and a polishing layer formed on said
foamed layer.
2. A method of producing a cleaning sheet, said method comprising
the steps of: producing a paint having air bubbles dispersed
therein by mechanically foaming a foaming material comprising a
foaming resin material and non-fibrous abrading particles; forming
on a base sheet a foamed layer having abrading particles dispersed
therein by coating a surface of said base sheet with said paint and
drying said paint; and forming a polishing layer on a surface of
said foamed layer.
3. The method of claim 2 wherein the step of producing said paint
comprises the step of sending air into said foaming material while
stirring said foaming material and thereby dispersing said air
bubbles and said abrading particles inside said paint.
4. The method of claim 2 wherein the step of forming said polishing
layer comprises the steps of: applying a paint including a resin
binder and said abrading particles on a surface of said foamed
layer; and drying said applied paint whereby said polishing layer
is formed on the surface of said formed layer having said abrading
particles dispersed therein.
5. A method of cleaning a probe, said probe having a tip, said
method comprising the steps of: preparing a cleaning sheet
comprising a base sheet, a foamed layer formed on said base sheet,
said foamed layer having non-fibrous abrading particles dispersed
therein, and a polishing layer formed on said foamed layer; causing
a surface of said polishing layer to be pressed against said tip of
said probe; causing said tip to penetrate said polishing layer and
to be thereby inserted into said foamed layer having said abrading
particles dispersed therein.
6. The method of claim 5 wherein the step of preparing said
cleaning sheet comprises the steps of: producing a paint having air
bubbles dispersed therein by mechanically foaming a foaming
material comprising a foaming resin material and abrading
particles; forming on a base sheet a foamed layer having abrading
particles dispersed therein by coating a surface of said base sheet
with said paint and drying said paint; and forming a polishing
layer on a surface of said foamed layer.
7. The method of claim 6 wherein the step of producing said paint
comprises the step of sending air into said foaming material while
stirring said foaming material and thereby dispersing said air
bubbles and said abrading particles inside said paint.
8. The method of claim 6 wherein the step of forming said polishing
layer comprises the steps of: applying a paint including a resin
binder and said abrading particles on a surface of said foamed
layer; and drying said applied paint whereby said polishing layer
is formed on the surface of said formed layer having said abrading
particles dispersed therein.
Description
[0001] This is a continuation-in-part of application Ser. No.
10/298,310 filed Nov. 14, 2002, now pending.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a cleaning sheet for and a method
of removing foreign substances attached to the tip and side
surfaces of a probe used for inspecting a planar target object such
as a semiconductor device having integrated circuits installed
thereon.
[0003] Chips are produced by installing semiconductor elements and
integrated circuits on a semiconductor wafer through various
wafer-producing processes. The chips thus produced on a
semiconductor wafer are cut off from the wafer after a
current-passing test and are packaged. Tests with a current are
carried out also before and after the packaging to separate faulty
products stringently from qualified products.
[0004] Such current-passing tests are carried out by means of a
test apparatus of a known kind such as a wafer prober. A
position-matching process by moving a prober needle ("probe")
serving as an electrode of a tester and the electrodes on the chip
(pads or lead lines) and a contacting process between the probe and
the chip electrodes are repeated for carrying out electrical
measurements of different kinds.
[0005] While such position-matching and contacting processes are
repeated by moving the probe and the electrodes on the chips, the
tip of the probe slides over the electrodes on the chips, scraping
off portions of the electrodes. Such portions of the electrodes
that have been scraped off become attached to the tip and the side
surfaces of the probe as foreign substances.
[0006] The foreign substances, that thus become attached to the
probe, are metals such as aluminum. If such a metal is oxidized,
the electrical contact resistance between the probe and the
electrodes on the chip becomes larger, making it impossible to
carry out accurate electrical measurements. Thus, it is necessary
to clean the tip portion of the probe regularly after each time a
specified number of contact processes have been carried out in
order to remove such foreign substances from the probe.
[0007] Removal of such foreign substances from the tip portion of a
probe is carried out by using the same apparatus used for the
current-passing tests such as the aforementioned wafer prober,
except the target object to be tested such as a semiconductor wafer
attached to the apparatus is replaced with a cleaning device having
a similar shape. Examples of a prior art cleaning device of this
kind include hard polishing plates of a grinding stone, glass and a
ceramic material (as disclosed, for example, in Japanese Patent
Publications Tokkai 7-199141, 5-209896, 5-166893, 4-96342 and
3-105940) and sheets with a polishing layer formed on an uneven
surface of an elastic member having protrusions and indentations
(as disclosed, for example, in Japanese Patent Publication Tokkai
2000-332069). The probe is pressed against the surface of such a
cleaning device, as done in the aforementioned current-passing
test.
[0008] If a polishing plate of a hard material is used as the
cleaning device and the probe is pressed too hard against it, its
tip portion will become deformed and hence it is necessary to
reduce the pressure with which the probe can be pressed against the
cleaning device. As a result, only the portions very close to the
tip can be cleaned. If a cleaning device of the type with a
polishing layer formed on an elastic member is used, on the other
hand, the tip of the probe penetrates the polishing layer and
cannot be cleaned sufficiently. Thus, the common practice has been
to provide separately a device for cleaning the tip and another
device for cleaning the side surfaces, attaching them to a
current-passing test apparatus consecutively one at a time. It was
therefore both cumbersome and time-consuming to clean a probe.
SUMMARY OF THE INVENTION
[0009] It is therefore an object of this invention in view of the
above to provide a cleaning sheet capable of cleaning both the tip
and the side surfaces of a probe, a method of producing such a
sheet and also a method of cleaning a probe.
[0010] A cleaning sheet embodying this invention, with which the
above and other objects can be accomplished, may be characterized
as comprising a base sheet, a foamed layer of a porous material
which is formed on the base sheet and includes non-fibrous abrading
particles and air bubbles, and a polishing layer formed on the
foamed layer.
[0011] Such a cleaning sheet may be produced by preparing a paint
having air bubbles dispersed therein by mechanically foaming a
foaming material comprising a foaming resin material and abrading
particles, forming on a base sheet a foamed layer having abrading
particles dispersed inside by coating a surface of the base sheet
with this paint and drying it, and forming a polishing layer on a
surface of the foamed layer.
[0012] Such paint may be produced by sending air into the foaming
material while stirring the foaming material and thereby dispersing
the air bubbles and the abrading particles inside the paint.
Because it is by a mechanical means that the foaming material is
caused to be foamed, the abrading particles and the air bubbles can
be dispersed uniformed throughout the interior of the foamed layer
without strictly maintaining the conditions for the foaming
reaction such as the reaction time and temperature.
[0013] A probe having a tip may be cleaned with a cleaning sheet
embodying this invention, structured and produced as described
above, by causing a surface of its polishing layer to be pressed
against the tip of the probe and thereby causing the tip of the
probe to penetrate the polishing layer and further to be inserted
into the foamed layer having abrading particles dispersed inside.
As the tip penetrates the polishing layer and becomes inserted into
the foamed layer having abrading particles dispersed inside, both
the tip and the side surfaces of the probe become cleaned not only
by the abrading particles inside the polishing layer but also those
in the foamed layer.
[0014] In summary, with a cleaning sheet thus structured and/or
produced, the tip and the side surfaces of a probe can be
effectively and simultaneously cleaned.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a sectional view of a cleaning sheet embodying
this invention when a tip portion of a probe is being cleaned
therewith.
[0016] FIG. 2 is a schematic side view of a wafer prober.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 2 shows a wafer prober 20 of a known kind. When a
cleaning process according to this invention is effected, a
cleaning sheet 10 embodying this invention to be described below
and shown in FIG. 1 is attached to such a wafer prober 20 instead
of a target object to be inspected such as a semiconductor wafer
which is normally attached thereto. As shown in FIG. 1, the
cleaning sheet 10 is comprised of a base sheet 11, a foamed layer
12 formed on a surface of the base sheet 11 and a polishing layer
13 formed on the surface of the foamed layer 12. The foamed layer
12 is a layer of a porous foamed material containing non-fibrous
abrading particles 14 and many air bubbles inside. Such a cleaning
sheet may be produced by first preparing a paint material by
mechanically foaming a material including a foaming resin and
abrading particle. A surface of the base sheet 11 is then coated
with this paint material and it is dried so as to form the foamed
layer 12 with the abrading particles dispersed therein. The
polishing layer 13 is thereafter formed on the surface of this
foamed layer 12.
[0018] The foaming material to be used in the production method
described above may be obtained by mixing a foaming agent such as a
salt of fatty acid, an acrylic thickener, a fluorine or silicon
type stabilizer, and also powder of aluminum hydroxide with average
diameter of 0.01-70 .mu.m for improving the stabilization effect,
and further by mixing in an epoxy cross linking agent. As the
abrading particles 14, particles of aluminum oxide, silicon
carbide, chromium oxide, iron oxide, diamond, boron carbide, cerium
oxide or silicon oxide with average diameter of 0.01-70 .mu.m are
also mixed into the foaming material in an amount of 5-80 weight %.
Throughout herein, the expression "particles" is intended to be
interpreted in a narrow sense of the word, excluding any small
objects that may be referred to as being fibrous or a fiber
particle.
[0019] The mechanical foaming of the foaming material thus prepared
is effected with stirring while sending in air at a specified rate
into the foaming material containing the abrading particles 14. As
a result of this process, the abrading particles 14 and the air
bubbles 15 become uniformly dispersed inside the foaming material
and a paint with a high degree of viscosity containing air bubbles
is obtained. The foaming multiplicity of the paint is in the range
of 2-5 times. Such a mechanical foaming process may be carried out
by using a continuous high-pressure foaming apparatus (such as
TW-70 produced by Aikosha Seisakusho of Japan) used for the
continuous mixing process of raw cream.
[0020] The paint material with air bubbles may be applied on a
surface of the base sheet 11 by a known method and with a known
means such as the knife coater method and the so-called direct
coating method. A sheet with a flat surface of a plastic material
such as polyester and polyethylene terephthalate (PET) may be used
as the base sheet 11. The drying process for the paint applied on
the base sheet 11 may be effected in an environment with
temperature in the range of 90.degree. C. -160.degree. C. In order
to completely solidify the paint, a far infrared ray may be applied
additionally. For forming a stable foamed layer 12 with abrading
particles dispersed on the surface of the base sheet 11,
furthermore, a ventilating means such as a fan may be used to cool
it after the foaming paint coated on the surface of the base sheet
11 is completely dried. After such a drying process, a foamed layer
12 with air bubbles 15 and abrading particles 14 uniformly
dispersed throughout is formed on the surface of the base sheet 11.
The thickness of the foamed layer 12 thus produced is within the
range of 50 .mu.m-200 .mu.m.
[0021] Since the foamed layer 12 according to this invention is
formed by a mechanical foaming process rather than by a chemical
method, the abrading particles and air bubbles can be uniformly
dispersed without the necessity of strictly controlling and
maintaining the conditions for the foaming reaction such as the
reaction time and the temperature.
[0022] The polishing layer 13 may be formed by preparing a polisher
paint having abrading particles dispersed within a resin solution
obtained by dissolving a resin binder selected from polyesters and
urethanes in a solvent such as methylethyl ketone, applying it on
the surface of the foamed layer 12 by a known method such as the
reverse coating method and then drying it. The thickness of the
polishing layer 13 is in the range of 5 .mu.m-30 .mu.m. Particles
of silicon carbide, silica, aluminum oxide and diamond with average
diameter of 0.001 .mu.m-10 .mu.m may be used as the abrading
particles.
[0023] A wafer prober such as shown at 20 in FIG. 2, commonly used
for current-passing tests, may be used for cleaning a probe for
inspecting a planar object such as a semiconductor device with
integrated circuits installed thereon. As shown in FIG. 2, the
wafer prober 20 has a table 23 on which a target object for
inspection such as a semiconductor device is intended to be
attached. After such a target object for inspection is attached,
the table 23 is moved horizontally and vertically for positioning
and the target object is pressed against a probe 22 of a probe card
21 in order to carry out electrical measurements of different kinds
on the target object. When the probe 22 is to be cleaned, the
cleaning sheet 10 as described above is attached to the table 23,
instead of the target object for inspection and the table 23 is
similarly moved similarly to press the probe 22 against the surface
of the cleaning sheet 10 attached to the table 23.
[0024] The cleaning sheet 10 may be cut into a circular,
quadrangular or any other shape and pasted on the table 23 by means
of a double-side adhesive sheet. Alternatively the cleaning sheet
10 may be pasted on a flat plate of an appropriate shape and this
plate may then be attached to the table 23. In summary, the manner
of attaching the cleaning sheet 10 onto the table 23 does not limit
the scope of the invention.
[0025] When the tip of the probe 22 is pressed against the surface
of the cleaning sheet 10, it penetrates the polishing layer 13 as
shown in FIG. 1 and is inserted inside the foamed layer 12 with
abrading particles. Both the tip and side surfaces of the probe 22
are cleaned by the abrading particles in the polishing layer 13 as
the probe 22 penetrates the polishing layer 13 and thereafter by
the abrading particles 14 dispersed in the foamed layer 12. In
summary, since both the tip and side surfaces of the probe 22 are
also cleaned by the foamed layer 12, those of the foreign materials
not removed as the probe penetrates the polishing layer 13 may be
expected to be dependably removed inside the foamed layer 12 from
the tip and the side surfaces of the probe 22.
[0026] As a test, a cleaning sheet embodying this invention was
produced by adding 2.9 kg of particles of aluminum hydroxide (HM-43
by tradename produced by Dai-Nippon Inki Kagaku Kogyo Corporation)
for improving the stabilization effect and 2.9 kg of particles of
aluminum oxide (WA8000 by tradename produced by Fujimi
Incorporated) to 28 kg of foaming urethane resin (DICFORM F-505EL
by tradename produced by Dai-Nippon Inki Kagaku Kogyo Corporation),
mixing them together in a pot mill for 96 hours and thereafter
producing a foaming material by further adding thereto 8.7 kg of a
foaming agent (F-1 by tradename produced by Dai-Nippon Inki Kagaku
Kogyo Corporation), 0.29 kg of a stabilizer (NBA-1 by tradename
produced by Dai-Nippon Inki Kagaku Kogyo Corporation) and 0.58 kg
of a cross linking agent (CATALYST/PA-20 by tradename produced by
Dai-Nippon Inki Kagaku Kogyo Corporation), further mixing in 0.87
kg of a hardening agent (DR-5L by tradename produced by Dai-Nippon
Inki Kagaku Kogyo Corporation) and 1.45 kg of a thickener (VONCOAT
3750 by tradename produced by Dai-Nippon Inki Kagaku Kogyo
Corporation), and producing a paint with air bubbles by foaming
this material by using a continuous high-pressure foaming machine
(TW-70 by tradename produced by Aikosha Seisakusho). This paint was
applied on a polyethylene terephthalate (PET) sheet with thickness
of 75 .mu.m running at a rate of 2.0 m/minute by means of a knife
coater to a thickness of 400 .mu.m. After it was dried in an
environment of 100.degree. C., it was further dried by far infrared
irradiation (120.degree. C. and 140.degree. C.) and cooled by means
of an ordinary fan for family use to form a foamed layer with
dispersed abrading particles on the surface of the PET sheet.
[0027] Next, green carbon particles with average diameter of 1
.mu.m were dispersed in a resin solution obtained by dissolving a
urethane resin binder by means of a solvent such as methylethyl
ketone to obtain a polishing paint. This polishing paint was
applied on the surface of the aforementioned foamed layer by the
reverse coating method and then dried to form a polishing layer on
the surface of the foamed layer and to thereby produce a cleaning
sheet of the test example.
[0028] This cleaning sheet of the test example was used to clean
the tip portion of a probe by using a wafer prober as shown in FIG.
2 by removing the semiconductor device which had been inspected
therewith and attaching instead the aforementioned cleaning sheet
of the test example. The tip portion of the probe was
microscopically observed both before and after the cleaning process
and it was ascertained that the metallic foreign substances found
to be attached both at the tip and the side surfaces of the probe
had been completely removed.
* * * * *