U.S. patent application number 11/203895 was filed with the patent office on 2006-02-23 for method and apparatus for removing material from a substrate surface.
This patent application is currently assigned to Nanofilm Technologies International PTE LTD. Invention is credited to Li Kang Cheah, Xu Shi.
Application Number | 20060037700 11/203895 |
Document ID | / |
Family ID | 33042295 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060037700 |
Kind Code |
A1 |
Shi; Xu ; et al. |
February 23, 2006 |
Method and apparatus for removing material from a substrate
surface
Abstract
Methods and apparatus for removing material from a substrate,
such as an IC component, are disclosed. The methods include
creating a plasma in an evacuatable chamber, by providing a power
source to an electrode in the chamber, and contacting the substrate
surface with at least one of ions, atoms and free radicals of the
plasma. The power source, preferably DC, is supplied to the
electrode as a variable, and preferably a pulsed voltage to prevent
arcing.
Inventors: |
Shi; Xu; (Singapore, SG)
; Cheah; Li Kang; (Singapore, SG) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
UNITED PLAZA, SUITE 1600
30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
Nanofilm Technologies International
PTE LTD
Singapore
SG
|
Family ID: |
33042295 |
Appl. No.: |
11/203895 |
Filed: |
August 15, 2005 |
Current U.S.
Class: |
156/345.43 ;
156/345.28; 156/345.45; 216/67; 257/E21.256 |
Current CPC
Class: |
H01J 2237/335 20130101;
H01L 2224/85009 20130101; H01L 2224/85013 20130101; H01J 2237/0206
20130101; H05K 3/26 20130101; H01J 37/32027 20130101; H01L 21/02068
20130101; H01L 21/31138 20130101; B29C 33/72 20130101 |
Class at
Publication: |
156/345.43 ;
216/067; 156/345.28; 156/345.45 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2004 |
GB |
0418494.1 |
Claims
1. A method of removing material from a substrate surface
comprising the steps of: providing a plasma using a power source;
and contacting the substrate surface with one or more of ions,
atoms or free radicals of the plasma, wherein the power source is
supplied as a variable voltage.
2. A method of removing material from a substrate surface
comprising the steps of: placing the substrate in an evacuatable
chamber having an electrode therein; providing a variable voltage
to the electrode to provide a plasma in the chamber between the
electrode and the substrate; and contacting the substrate surface
with one or more of ions, atoms or free radicals of the plasma to
remove at least a portion of the material on the surface.
3. The method of claim 1 wherein the variable voltage is a pulsed
voltage.
4. The method of claim 1 wherein the voltage is pulsed once per
consecutive 3-30 kHz periods.
5. The method of claim 1 wherein the variable voltage is pulsed
from 0V to a voltage between -300V and -1000V.
6. The method of claim 1 wherein the variable voltage is pulsed
from 0V to a voltage between -380V and -600V.
7. The method of claim 1 wherein the voltage is applied in a 3 to
20 .mu.s pulse.
8. The method of claim 1 comprising two opposed electrodes, wherein
the power source is supplied to one of the electrodes and the other
electrode is floating, and wherein the substrate is on the floating
electrode.
9. The method of claim 1 comprising two opposed electrodes, wherein
the power source is supplied to one of the electrodes and the other
electrode is grounded, and wherein the substrate is on the grounded
electrode.
10. The method of claim 1 comprising two opposed electrodes,
wherein the power source is supplied to one of the electrodes, and
the other electrode is floating, wherein the substrate is on said
one of the electrodes.
11. The method of claim 1 comprising two opposed electrodes,
wherein the power source is supplied to one of the electrodes, and
the other electrode is grounded, wherein the substrate is on said
one of the electrodes.
12. The method of claim 1 comprising two opposed electrodes,
wherein the power source is supplied to both of the electrodes, and
the other electrode is floating, wherein the substrate is on the
one of the electrodes.
13. The method of claim 1 wherein the plasma is provided in an
O.sub.2 environment.
14. The method of claim 1 wherein the plasma is provided in an
O.sub.2/CF.sub.4 environment.
15. The method of claim 1 wherein the plasma is provided in a
chamber evacuated to about 80 to 1500 mTorr.
16. The method of claim 8 comprising two said substrates located on
respective electrodes.
17. The method of claim 8 comprising a plurality of spaced
electrodes, at least some of which respectively support a
respective one of a plurality of said substrates.
18. The method of claim 8 wherein at least one of the electrodes
supports at least two said substrates on one or both of its
opposing sides.
19. The method of claim 1 wherein the substrate is one of an IC, IC
component, IC mould, die, wafer, ball grid array, IC package,
leadframe, PCB, microvia, disk holder, reader arm, or hard
disk.
20. The method of claim 1 wherein the material is one of an organic
substance, organic contaminant, solvent residue or epoxy resin.
21. Apparatus for removing material from a substrate surface
comprising: a vacuum chamber; an electrode in the vacuum chamber;
and a power source for providing a variable voltage to the
electrode, such that a plasma is formable within the chamber and
one or more of ions, atoms or free radicals of the plasma contact
the substrate surface, wherein the power source is supplied as a
variable voltage.
22. The apparatus of claim 21 wherein the variable voltage is
configured to be provided as a pulsed voltage.
23. The apparatus of claim 21 comprising two opposed electrodes,
wherein the power source is supplied to one of the electrodes and
the other electrode is floating, and wherein the substrate is on
the floating electrode.
24. The apparatus of claim 21 comprising two opposed electrodes,
wherein the power source is supplied to one of the electrodes and
the other electrode is grounded, and wherein the substrate is on
the grounded electrode.
25. The apparatus of claim 21 comprising two opposed electrodes,
wherein the power source is supplied to one of the electrodes, and
the other electrode is floating, wherein the substrate is on said
one of the electrodes.
26. The apparatus of claim 21 comprising two opposed electrodes,
wherein the power source is supplied to one of the electrodes, and
the other electrode is grounded, wherein the substrate is on said
one of the electrodes.
27. The apparatus of claim 21 comprising two opposed electrodes,
wherein the power source is supplied to both of the electrodes, and
the other electrode is floating, wherein the substrate is on the
one of the electrodes.
28. The apparatus of claim 21 comprising a plurality of spaced
electrodes, at least some of which respectively support a
respective one of a plurality of said substrates.
29. The apparatus of claim 21 wherein the chamber comprises an
opening adapted for hermetic abutment with a surface of a conveyor,
the substrate being positioned on the conveyor.
30. The apparatus of claim 21 wherein the substrate is one of an
IC, IC component, IC mould, die, wafer, ball grid array, IC
package, leadframe, PCB, microvia, disk holder, reader arm, or hard
disk.
31. The apparatus of claim 21 wherein the material is one of an
organic substance, organic contaminant, solvent residue or epoxy
resin.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to methods and apparatus for
removing material from a substrate surface and in particular to
methods and apparatus for the cleaning or etching of surfaces of
electronics components and components related to the manufacture
thereof. However, as will be understood by the skilled addressee,
the invention is not limited to such uses.
BACKGROUND
[0002] Failure of electronics circuits due to problems experienced
during manufacture is common. While there may be several sources of
problems, a typical problem is commonly attributed to the existence
of material such as residual surface organic contaminants (e.g.,
dirt, finger prints, etc), or residual material from different
manufacturing stages, such as solvent residue and epoxy
bleed-outs.
[0003] Integrated circuits (ICs) are manufactured in a
multi-layered process of moulding and bonding of component parts.
Bonding typically includes wire bonding, where two adjacent 1C
components are bonded by fusing wires between mounting pads of the
adjacent components. Problems can occur in the bonding process if
the mounting pads are not clean, resulting in a non-integral or
weak bond, and thus a defective 1C.
[0004] One proposed solution for improving the wire bonding is
cleaning the mounting pads prior to the bonding process. Two
cleaning methods are known: capacitive cleaning using a radio
frequency (RF) power source; and ion cleaning using an ion beam in
an Ar/O.sub.2 environment at 1500 eV. RF cleaning is achieved by
applying RF to an electrode in a vacuum chamber which also contains
a component requiring surface cleaning. A source of Ar is
introduced into the chamber and a plasma is formed. The plasma ions
chemically react with the material on the surface of the component.
There are several problems associated with RF cleaning. Firstly, it
is only possible to control the power input to an RF cleaning
system. Secondly, there are significant health and safety
requirements associated with operating high powered RF equipment,
as well as ensuring any RF leakage doesn't affect nearby people and
equipment. Thirdly, RF generators require complex matching networks
to allow greater flexibility in cleaning regimes. Different
matching networks are required for different applications or
different operating pressures. Both RF and ion cleaning may also
damage the components being cleaned by voltage discharge or arc
formation.
[0005] Other problems may arise due to lack of cleanliness of parts
related to the manufacture of an 1C. For example, moulds used
during the moulding process may have residual epoxy films which
eventually need to be cleaned from the mould. Current cleaning
processes for moulds include the use of wire brushes or chemical
baths. However wire bath cleaning damages the mould and shortens
its lifecycle, and chemical baths are relatively slow. One proposed
method for extending the mould life is to coat the mould surface
with 3-10 .mu.m of CrN, or "hard chrome", to increase resistance,
to damage from wire brush cleaning. While extending the life of the
mould by increasing resistance to wear, such coatings have the
disadvantage of reducing the accuracy of the intended mould
dimensions.
[0006] It is an object of at least one of the embodiments of the
present invention to ameliorate or overcome at least one of the
above problems associated with the prior art, or at least to
provide a suitable alternative thereto.
SUMMARY
[0007] According to a first aspect of the present invention there
is provided a method of removing material from a substrate surface
comprising the steps of
[0008] providing a plasma using a power source; and
[0009] contacting the substrate surface with one or more of ions,
atoms or free radicals of the plasma,
[0010] wherein the power source is supplied as a variable
voltage.
[0011] According to a second aspect of the present invention there
is provided a method of removing material from a substrate surface
comprising the steps of:
[0012] placing the substrate in an evacuatable chamber having an
electrode therein;
[0013] providing a variable voltage to the electrode to provide a
plasma in the chamber between the electrode and the substrate;
and
[0014] contacting the substrate surface with one or more of ions,
atoms or free radicals of the plasma to remove at least a portion
of the material on the surface.
[0015] Advantageously, by supplying the power source as a variable
voltage, the problems of arcing are prevented, and therefore the
substrate is not unnecessarily damaged.
[0016] Preferably, the variable voltage is a pulsed voltage, and
more preferably the voltage is pulsed in consecutive 3-30 kHz
periods. By providing the voltage in a pulse, a plasma can be
formed without providing an arc and without unnecessarily heating
the environment in which the material removing method is
provided.
[0017] Preferably the variable voltage is pulsed from 0V to a
voltage between -300V and -1000V, and more preferably from 0V to a
voltage between -380V and -600V. Also preferably, the voltage is
applied in a 3 to 20 .mu.s pulse. Preferably, the pulse is provided
once per 3-30 kHz period. Alternatively, the pulse may be provided
more than once per period. For example, a pair of 3 .mu.s pulses, 5
.mu.s apart, may be provided per 3-30 kHz period.
[0018] Preferably there are two opposed electrodes, wherein the
power source is supplied to one of the electrodes and the other
electrode is floating, and wherein the substrate is on the floating
electrode. Alternatively, the other electrode is grounded, or the
other electrode is either grounded, floating or of generally equal
potential to the one electrode, and the substrate is on the one
electrode.
[0019] Preferably, the plasma is provided in an O.sub.2
environment, and more preferably the plasma is provided in an
O.sub.2/CF.sub.4 environment.
[0020] Preferably the plasma is provided in a chamber evacuated to
about 80 to 1500 mTorr.
[0021] Alternatively two substrates are provided on respective
electrodes. In another alternative arrangement there are a
plurality of spaced electrodes, at least some of which respectively
support a respective one of a plurality of said substrates. In
another alternative arrangement, at least one of the electrodes
supports at least two said substrates on one or both of its
opposing sides.
[0022] Preferably the substrate is one of an 1C, 1C component, 1C
mould, die, wafer, ball grid array, 1C package, leadframe, PCB,
microvia, disk holder, reader arm, or hard disk. Also preferably,
the material is one of an organic substance, organic contaminant,
solvent residue or epoxy resin.
[0023] According to a third aspect of the present invention there
is provided an apparatus for removing material from a substrate
surface comprising:
[0024] a vacuum chamber;
[0025] an electrode in the vacuum chamber; and
[0026] a power source for providing a variable voltage to the
electrode, such that a plasma is formable within the chamber and
one or more of ions, atoms or free radicals of the plasma contact
the substrate surface,
[0027] wherein the power source is supplied as a variable
voltage.
[0028] Preferably the variable voltage is provided as a pulsed
voltage.
[0029] Preferably there are two opposed electrodes, wherein the
power source is supplied to one of the electrodes and the other
electrode is floating, and wherein the substrate is on the floating
electrode. Alternatively, the other electrode is grounded, or, the
other electrode is either grounded, floating or of generally equal
potential to the one electrode, and the substrate is on the one
electrode.
[0030] Preferably the chamber comprises an opening for hermetic
abutment with a surface of a conveyor, the substrate being
positioned on the conveyor.
[0031] For the purposes of the specification, the terms "cleaning"
and "etching" when used in the specification are to be considered
the same as "material removal" or "removal of material", also as
used in the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Preferred embodiments of the invention will now be
described, by way of example only, with reference to the
accompanying drawings in which:
[0033] FIG. 1 is a simplified schematic view of an apparatus
according to the present invention;
[0034] FIG. 2 is a graph representing an example of a pulsed
voltage used in the present invention;
[0035] FIGS. 3 and 4 are simplified schematic views of alternative
embodiments of apparatus according to the present invention;
and
[0036] FIGS. 5a and 5b are simplified schematic views of another
alternative embodiment of apparatus according to the present
invention, with the chamber in respective retracted and in use
positions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] Referring to FIG. 1, a preferred embodiment of the invention
is a method and apparatus for removing material from a substrate
surface. While not intended to be an exhaustive list, examples of
the substrate include electrical components, such as an IC, IC
package, bail grid array, or a component of an IC or IC package.
Such components may include wafers, chips, dies or moulded parts.
Another example of the type of substrate whose surface may be
cleaned by the invention includes the surfaces of moulds described
above in relation to the prior art, and as used in IC package
manufacture, or media holders for holding hard disks, etc, during
manufacturing coating processes.
[0038] A preferred embodiment of the apparatus comprises a vacuum
chamber 10 and an electrode 12a therein connected to a power source
in the form of a DC power supply 14. A second electrode 12b is
provided in a floating configuration. An inlet port 16 is provided
on the chamber 10 for the introduction of gas into the chamber. An
outlet port 18 is also provided on the chamber 10 for connection to
an external vacuum pump. A controller (not shown) is provided in
communication with the power supply 14 to control the power
supply's output, to provide a variable voltage, in the form of a
pulsed negative voltage supply as illustrated in FIG. 2, which is
described below in more detail. In alternative arrangements, any
power configuration can be used to provide the variable voltage.
For example, a rectified AC power supply or a monostable
multivibrator circuit may be used as or as part of the
controller.
[0039] In use, a substrate 22 is positioned in the chamber 10 on
the second electrode 12b with a surface 24 to be cleaned facing
toward the electrode 12. Material 26 to be cleaned from the surface
24, illustrated schematically in the relevant Figures, may include
general organic substances, surface organic contaminants, having
C--H and C--C bonds, solvent residue or epoxy resin.
[0040] In this embodiment, the distance between the electrodes 12a
and 12b is about 5 mm, but in other embodiments may range from 3 to
100 mm, depending on the substrate to be cleaned, and the cleaning
regime.
[0041] The chamber 10 is then evacuated via outlet port 18 to a
pressure of about 10-50 mTorr, and gas introduced into the chamber
10 via inlet port 16 to increase the pressure to about 150 mTorr,
though in alternative embodiments the increased pressure may be in
the range of 80 to 1500 mTorr. The introduced gas is typically a
mix of O.sub.2:CF.sub.4 at a ratio of 4:1, where the CF.sub.4 acts
as a catalyst to improve the formation of a plasma. In alternative
embodiments, the ratio may be different, or CF.sub.4 may not be
present. In yet another embodiment, the gas may be Ar.
[0042] In this embodiment, the gas is continually passed through
the chamber 10 during the cleaning process at a flow rate of 200
sccm, though in alternative embodiments the flow rate may range
from 50 to 1000 sccm. Aside from keeping a relatively consistent
quality of gas and therefore plasma in the chamber 10, the flow of
gas also acts to sweep or flush out any material 26 residue removed
during the cleaning process from the substrate surface 24.
[0043] The controller then activates the power supply 14 to provide
a pulsed voltage to the electrode 12. FIG. 2 illustrates an example
of a pulsed voltage waveform for use with this embodiment, where
-800V is pulsed once for 5 .mu.s during 10 kHz periods. The pulsed
voltage builds up a capacitance-type charge between the electrodes
12a and 12b and the substrate surface 24, and a plasma is formed.
Atoms and radical species of the plasma contact the substrate
surface and chemically react with the material 26 thereon. The
chemical reaction breaks down the material 26. For example, plasma
atom and radical species formed from the O.sub.2 gas present in the
chamber during plasma formation can contact and break, for example,
C--C and C--H bonds of the unwanted material 26. Also, ions of the
plasma bombard the substrate surface 24 further resulting in
removal of unwanted material 26 from the substrate surface 24.
[0044] It is important to reduce the risk of arc discharge between
the electrodes 12a and 12b and the substrate 22, as discharge may
damage the surface 24 of the substrate 22 on the second electrode
12b and render the substrate 22 unusable. On the other hand, if the
voltage is too low, either the plasma will not form, or will not
provide species of sufficient energy to remove the material 26 from
the substrate surface. The use of a pulsed voltage is therefore
advantageous in that a plasma with ions of sufficient energy for
cleaning may be formed, while the risk of discharge is reduced.
Furthermore, since the risk of discharge is reduced, the electrodes
can be positioned closer together, resulting in more efficient
cleaning, and more efficient use of space in the chamber 10.
Furthermore, unlike prior art RF cleaning where only power can be
modified to control the process, in the present invention the
parameters of voltage, frequency and pulse width can be
independently controlled to optimize the cleaning process.
[0045] In the embodiment described above, the second electrode 12b
is floating. By floating the electrode, risk of discharge between
the electrodes 12a and 12b damaging the substrate surface 24 is
relatively reduced. However, the cleaning effectiveness of the
plasma is also relatively reduced. For this reason, this embodiment
is suited to cleaning the surface of more sensitive components, as
described above. In an alternative embodiment, the substrate is
still placed on the second electrode, but the second electrode is
grounded. By grounding the second electrode, discharge risk is
increased, however voltage magnitude and pulsing parameters may be
adjusted for relatively more effective and more aggressive
cleaning. Hence, this embodiment is more suited to less sensitive
components than would be cleaned using the embodiment described
above in detail. In other alternative embodiments which provide a
more aggressive cleaning regime than those embodiments previously
described, the substrate is positioned on the first electrode 12a,
and the second electrode 12b is either floating or grounded. In yet
another alternative embodiment, the substrate is on the first
electrode 12a, and the second electrode 12b has a generally equal
negative potential to the first electrode.
[0046] This embodiment may be optimized for the cleaning of, for
example, 1C moulds, media holders or associated tools. In this
embodiment, the gap between component and opposed electrode can be
as small as 3 mm to 8 mm, which allows for more uniform plasma
distribution. For example, it is possible in this embodiment to
remove 20 .mu.m-100 .mu.m of epoxy moulding compound from a mould
surface in less than 10 minutes, compared with 1 hour for
chemically based prior art methods, or 3 nm of diamond-like carbon
(DLC) coating from a media holder in less than 10 seconds.
[0047] FIGS. 3 and 4 illustrate alternative embodiments of the
invention where like reference numerals denote like parts, and
where multiple substrates and/or electrodes are employed. In FIG.
3, two substrates 22a and 22b are placed in the chamber 10 on
respective grounded electrodes 12b. They are positioned such that
they face an electrode 12a therebetween, the electrode 12a being
negatively biased by having provided thereto a pulsed negative
voltage, as described in relation to previous embodiments. FIG. 4
illustrates an embodiment comprising two such negatively biased
electrodes 12a and three floating electrodes 12b with substrates
22a-d positioned thereon. The cleaning method of both these
embodiments is performed as described above in relation to the
embodiment illustrated in FIG. 1.
[0048] 1C packages are manufactured in several stages and may be
manufactured in batched arrays or conveyor lines. One or several
dies are attached to a package substrate, such as a wafer, printed
circuit board (PCB), leadframe or flex circuit board. The die is
then wire bonded to the package substrate by attaching wire strands
between respective corresponding mounting pads on the package
substrate and the die. An epoxy layer is then moulded over the die,
wire bonds and package substrate to form the 1C package. A
secondary layer may also be attached to the package and wire bonded
thereto via secondary wire bonding mounting pads.
[0049] Preferred embodiments of the invention may be used to
clean:
[0050] the package substrate prior to attaching the die;
[0051] the mounting pads prior to wire bonding (for example in a
chamber of pressure 100-200 mTorr with only O.sub.2 present as
introduced gas and with the substrate positioned on a floating
electrode);
[0052] the package after wire bonding and prior to moulding, to
improve mould adhesion (for example in a chamber of pressure of
about 100 mTorr with only O.sub.2 present as introduced gas and
with the substrate positioned on a floating electrode);
[0053] the moulded package prior to attaching the secondary layer
to clean epoxy bleed from the moulding process which may be
covering the secondary wire bonding pads (for example in a chamber
of pressure 700-800 mTorr with 9:1 of O.sub.2:CF.sub.4 present as
introduced gas and with the substrate positioned on a floating
electrode); and
[0054] the mould itself either after one moulding process or more
typically after 600-1000 uses (for example in a chamber of pressure
of about 200 mTorr with 9:1 of O.sub.2:CF.sub.4 present as
introduced gas and with the substrate positioned on one of two
opposed electrodes, where both electrodes are provided with a
pulsed negative voltage power supply).
[0055] FIGS. 5a and 5b illustrate another alternative embodiment of
the invention where like reference numerals denote like parts. This
embodiment is configured for in-line substrate surface cleaning
during manufacture of IC packages, the process of which is
described immediately above. In this embodiment, the chamber 10a,
has an open side 28 which is sealed when the chamber 10a comes into
contact with a conveyor 30. A leading edge 32 of the chamber 10a
may be lined by a seal, such as a silicon or rubber seal, to aid in
producing an hermetic seal with the conveyor. In this embodiment,
the vacuum pump, gas and power supply (not shown) would typically
be positioned on the outside surface of a top sidewall 34 of the
chamber 10a.
[0056] The conveyor 30 carries substrates 22 to be cleaned. Once
the substrates are in position to be cleaned, as illustrated in
FIG. 5b, the chamber 10 is lowered, either mechanically,
hydraulically or pneumatically, over the substrates 22 to form an
evacuatable vacuum chamber with the conveyor 30. The cleaning
process then proceeds as described above, but without the use of a
second electrode, and thus with the substrate 22 electrically
floating upon the conveyor 30.
[0057] This apparatus can be used for cleaning after any or each
stage of the IC package manufacturing process described above. The
apparatus may either be built into new manufacturing equipment or,
due to its small size, retrofitted for use with existing equipment.
An example of dimensions of the chamber 10a are as follows: 80 mm
(depth).times.250 mm (width).times.20 mm (height). The same chamber
10a design can be used to clean in-line, for example, 1C package
moulds. For such an application, since the mould cavities would be
facing relatively downwardly, the chamber's 10a open face would
face relatively upwardly, and be configured to be moved upwardly to
form the vacuum chamber with the mould and about the mould surface
to be cleaned.
[0058] The embodiment of FIGS. 5a and 5b shows two substrates for
cleaning. As will be apparent, in alternative embodiments, the
chamber 10a can be adapted to accommodate fewer or more than two
substrates for simultaneous cleaning.
[0059] In another alternative embodiment, the power supply may be
connected to the substrate, and an electrode positioned in the
chamber opposed to the substrate surface, the electrode being
either grounded or floating.
[0060] As will be understood by the skilled addressee, the present
invention has several advantages over the prior art. For
example:
[0061] the risk of forming an arc is reduced;
[0062] operating temperature is kept to a minimum, thus reducing
the risk of heat damage to the component;
[0063] the system is less complicated compared with prior art RF
cleaning systems, since no matching network is required, and there
are no similar concerns with regard to health, safety and effect on
neighboring equipment;
[0064] there is greater and easier parameter control compared with
RF systems;
[0065] when used for cleaning moulds, the working life of the mould
is increased, due to less damage to the mould, and the quality of
moulded components is improved, since a thinner hard nickel
protective coating can be used on the mould surface;
[0066] cleaning times are relatively faster than those of the prior
art;
[0067] operating costs are lower compared to known cleaning
systems; and
[0068] due to low operating costs and simplicity of operation, the
invention can be used at more stages during the manufacture of IC
packages, thus increasing integral package production yield.
[0069] While the preferred embodiments have been described mainly
with reference to IC components and their manufacture, it will be
understood that the invention is not limited to the cleaning of
such products. For example, the invention may be used for cleaning
hard disk surfaces; magnetic reader arms of disk drives, prior to
coating by protective or other layers; microvias; sidewalls of PCB
drill holes, and so on. Furthermore, the invention may be used to
modify component surfaces, such as polyimide surfaces to improve
their adhesion properties.
[0070] While the invention has been described in reference to its
preferred embodiments, it is to be understood that the words which
have been used are words of description rather than limitation and
that changes may be made to the invention without departing from
its scope as defined by the appended claims.
[0071] Hence, methods and apparatus for removing material from a
substrate, such as an IC component, are disclosed. The methods
include creating a plasma in an evacuatable chamber, by providing a
power source to an electrode in the chamber, and contacting the
substrate surface with at least one of ions, atoms and free
radicals of the plasma. The power source, preferably DC, is
supplied to the electrode as a variable, and preferably a pulsed
voltage to prevent arcing.
* * * * *