U.S. patent application number 09/833351 was filed with the patent office on 2001-09-13 for method for applying photoresist to a base body surface.
This patent application is currently assigned to Heidelberger Druckmaschinen AG. Invention is credited to Bottcher, Reinulf, Daaud, Simone, Luthje, Holger.
Application Number | 20010021419 09/833351 |
Document ID | / |
Family ID | 7803030 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021419 |
Kind Code |
A1 |
Luthje, Holger ; et
al. |
September 13, 2001 |
Method for applying photoresist to a base body surface
Abstract
An applicator device for applying photoresist to a surface of a
base body having a receiving device therefor, including a
photoresist feeder movable relative to the base body, the feeder
being a point source device, and a device for performing a defined
movement of the base body, comprising a conically shaped tip formed
on the point source device for applying photoresist in a defined
spot.
Inventors: |
Luthje, Holger;
(Halstenbeck, DE) ; Daaud, Simone; (Braunschweig,
DE) ; Bottcher, Reinulf; (Bielefeld, DE) |
Correspondence
Address: |
WERNER H. STEMER
P.O. Box 2480
Hollywood
FL
33022
US
|
Assignee: |
Heidelberger Druckmaschinen
AG
|
Family ID: |
7803030 |
Appl. No.: |
09/833351 |
Filed: |
April 12, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09833351 |
Apr 12, 2001 |
|
|
|
09242768 |
Feb 19, 1999 |
|
|
|
09242768 |
Feb 19, 1999 |
|
|
|
PCT/EP97/04510 |
Aug 19, 1997 |
|
|
|
Current U.S.
Class: |
430/271.1 ;
427/154; 427/425; 427/427.2; 427/96.9; 427/98.4; 438/780;
438/782 |
Current CPC
Class: |
B05C 5/0216 20130101;
G03F 7/18 20130101; B05C 11/1034 20130101; B05B 13/0442
20130101 |
Class at
Publication: |
427/421 |
International
Class: |
B05D 001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 19, 1996 |
DE |
196 33 407.1 |
Claims
We claim:
1. A method for applying photoresist to a surface of a base body,
which comprises displacing a photoresist feeder and the surface of
the base body to be provided with the photoresist relative to one
another in one of a predeterminable and a predetermined manner,
adjusting the layer thickness of the photoresist on the surface of
the base body by at least one of varying the displacement speed of
the photoresist feeder, varying the permeability of at least one
point source device of the photoresist feeder, and varying the
rotational speed of the base body, applying the photoresist in a
defined spot, and transporting photoresist from the point source
device to the surface of the base body by one of gravity flow and
regulating the feed pressure of the photoresist from a supply
chamber.
2. The method according to claim 1, which includes guiding the
photoresist through one of a conically tapering fiber bundle and a
capillary system provided with a conically tapering tip.
3. The method according to claim 1, which includes controlling at
least one of the application of photoresists of different
viscosities and compositions, and the application of one of the
groups of primers and other adhesion promoters, so that a cohesive
layer is formed in a defined region or over the entire surface of
the base body.
4. The method according to claim 1, which includes applying the
photoresist in a chamber wherein the base body and the photoresist
feeder are disposed, and which contains saturated solvent
vapor.
5. The method according to claim 1, which includes, on the surface
of the base body, at least one of applying different resist layer
thicknesses and applying the photoresist homogeneously in at least
one of a small, defined region and partial fields in locally or
linearly limited form.
6. The method according to claim 1, which includes applying the
photoresist in droplet form, with a layer thickness of up to 10
.mu.m, to the surface of the base body by at least one of feeding
the photoresist from a distance thereto and by having the
photoresist directly contact the surface of the base body.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a division of U.S. application Ser. No. 09/242,768,
filed Feb. 19, 1999, which was a continuation of copending
International Application PCT/EP97/04510, filed Aug. 19, 1997,
which designated the United States.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] The invention relates to a method for applying photoresist
to a base body surface.
[0004] From semiconductor coating, especially of wafers, methods
such as spinning, immersion or spraying are known for applying a
coating of photoresist. Because an exposure time has to be
selected, especially in the coating of wafers, a precise resist
thickness is very important.
[0005] In the spinning method, for example, the wafer is rotated
after the photoresist has been applied as centrally as possible
thereon. The centrifugal forces that are then operative thus
distribute the photoresist substantially uniformly over the surface
of the flat wafer.
[0006] Immersion and spray methods can be employed, for example,
for three-dimensional substrates. In the immersion method, however,
it often happens that the layer thickness cannot be made
homogeneous in all the regions of the surface, but rather, a bead
of resist remains at the end of the surface region and does not
permit uniform exposure or illumination. A problem also arises in
the spraying method. Although relatively large surfaces may be
wetted quite well therewith, nevertheless, the resist contracts
during drying. As a result, similarly to the immersion method,
deviations occur in the peripheral region of the structure which
impair the uniformity of the resist layer. The thickness of the
resist beads at the edge can amount to five times the desired layer
thickness.
[0007] The application of photoresist to smooth base bodies is
employed for photolithographic techniques. These techniques are
used to produce layer structures, with the aid of masks or locally
acting beam-type recording devices using high-energy radiation, a
radiation-sensitive material being applied to a surface to be
structured and irradiated, and then developed. In this way,
photoresist patterns that serve as a mask for various thin-film
technologies can be created. Irradiating the radiation-sensitive
material can be performed, for example, by electromagnetic waves or
corpuscular radiation.
[0008] In photolithography, ultraviolet light having a wavelength
of approximately 430 nm to 200 nm is typically employed.
Photolithographic methods are widely applicable in the field of
producing semiconductor circuits, sensors, or microcircuitry
systems.
[0009] In the heretofore known applications, even and, in
particular, macroscopically flat substrates, or substrates with
only very slightly curved surfaces, are coated as base bodies.
[0010] In the conventional spinning method, the desired photoresist
thickness is adjusted by way of the rotational speed of the spinner
and the viscosity of the photoresist. Depending upon the particular
application, layer thicknesses of a few hundred nanometers to a few
tens of micrometers are needed, and must be applied with great
homogeneity in the region of the surface of the base body to be
structured. As already noted hereinbefore, however, the spinning
method can be used only for macroscopically even or flat surfaces
of a base body.
[0011] The beads of resist that form as a resist-thickness
inhomogeneity in the peripheral region, particularly in the
immersion method, lead to an impermissible spacing between the mask
and the substrate known as the "proximity effect", upon the
exposure to light in the contact method. This affects the quality
and resolution of the photoresist structures, which proves to be
disadvantageous. A further disadvantage is considered to be that
this peripheral region, because of the greater layer thickness,
receives too slight a radiation dosage, and the patterns provided
thereat are therefore only inadequately formed, and/or residues of
resist remain between the patterns.
[0012] With resist coating by the spray method, the same structural
problems discussed above arise. Furthermore, with this method, the
layer thicknesses of a few micrometers that are typically employed
for photolithography can be attained only with highly diluted
photoresists, which has a disadvantageous effect upon the quality
of the photoresist layer. The layer has inhomogeneities in resist
thickness at the corners and edges. In addition, with the spraying
method, only large-area coatings can be provided, which, from a
technological and economic standpoint, with a view to low
photoresist consumption, is actually undesirable. In view of these
considerations, it would be more appropriate to coat defined
portions of a surface. Another disadvantage of both the spraying
method and the immersion method is the comparatively high
consumption of photoresist.
[0013] A method of spraying layers of flat or even surfaces has
become known heretofore from the published European Patent Document
EP 0 609 478 A1. In this regard, discrete drops are applied to the
surface and are then evened or spread out evenly in further method
steps. The method is also suitable only for flat substrates, such
as printed circuit boards.
[0014] The published German Patent Document DE 43 29 338 A1
discloses only a flat substrate in which a pattern is produced by a
type of ink jet printing head.
[0015] In the prior art, to apply relatively thick layers of
photoresist, photoresist films are applied to base bodies, as a
result of which better homogeneities in thickness can be achieved.
However, these techniques are suitable only for relatively great
layer thicknesses. Furthermore, when used for base bodies in the
form of bodies of rotation, a seam is formed. From the published
German Patent Document DE 30 12 988 A1, a device and a method for
producing a printing plate blank have become known, wherein a plate
with a substrate is provided with a photopolymer strip of precisely
dimensioned shape and thickness. To that end, the device is
provided with a reservoir for the photopolymer, a bar or beam
movable across the plate and being formed with a channel at an
underside thereof, supply lines connecting the channel to the
reservoir, and a stripper blade formed in the bar. During the
production of the printing plate blank, the photopolymer layer is
applied to the substrate. Next, the photopolymer layer is
irradiated through a mask by a chemically active radiation, and the
nonirradiated region covered by the mask is then removed. The
photopolymer is delivered under the influence of gravity and, to
that end, the photopolymer is kept at a pressure of a predetermined
liquid level of 2.5 to 25 cm in the reservoir. The viscosity of the
photopolymer is described in this reference as being 500 to 20,000
cP, preferably 2000 cP. The photopolymer layer is applied with a
layer thickness of 25 to 510 .mu.m. The supply lines for the liquid
photopolymer are provided as capillary channels formed in the bar.
The individual supply lines have a diameter of 0.76 to 12.7 mm, in
particular 2.28 to 6.35 mm. The individual outlet openings and
supply lines, respectively, have a mean spacing of 3.18 to 25.4 mm,
and in particular 6.35 to 12.7 mm. As a result, a polymer strip
approximately 40 cm wide and approximately 60 cm long is formed in
one operating step or pass on the substrate of the smooth plate of
the printing plate blank.
SUMMARY OF THE INVENTION
[0016] It is accordingly an object of the invention to provide a
method for applying photoresist to a base body surface, more
particularly, also to a surface that is not even or flat, and may
be on a body of rotation, and wherein a defined, homogeneous,
uniformly thin and reliable resist layer may be applied in an
advantageous manner to the surface of the body.
[0017] With the foregoing and other objects in view, there is
provided, in accordance with one aspect of the invention, an
applicator device for applying photoresist to a surface of a base
body having a receiving device therefor, including a photoresist
feeder movable relative to the base body, the feeder being a point
source device, and a device for performing a defined movement of
the base body, comprising a conically shaped tip formed on the
point source device for applying photoresist in a defined spot.
[0018] In accordance with another feature of the invention, the
conically shaped tip is formed as one of a conically tapering fiber
bundle and a capillary system provided with a conically tapering
tip.
[0019] In accordance with a further feature of the invention, the
point source device has a pulse printer.
[0020] In accordance with an added feature of the invention, the
conically shaped tip has a radius of curvature of from 1 .mu.m to
100 .mu.m.
[0021] In accordance with an additional feature of the invention,
the point source device has a tubule with a reservoir for
photoresist and, in conjunction therewith, a fiber bundle with the
conically shaped tip, and a shrink-fitting sleeve connecting the
fiber bundle and the tubule.
[0022] In accordance with yet another feature of the invention, the
pulse printer has at least one nozzle-like element, an actuator
system, at least one of a supply chamber and a reservoir for
photoresist, and connecting elements for connecting the at least
one nozzle-like element and the at least one supply chamber and
reservoir.
[0023] In accordance with yet a further feature of the invention,
the point source device is at least one of an indexable array of
nozzles and an indexable array of styli.
[0024] In accordance with yet an added feature of the invention,
the at least one indexable array of nozzles and indexable array of
styli is formed of a plurality of separately triggerable nozzles
and styli, respectively, as a microsystem.
[0025] In accordance with another aspect of the invention, there is
provided a method for applying photoresist to a surface of a base
body, which comprises displacing a photoresist feeder and the
surface of the base body to be provided with the photoresist
relative to one another in one of a predeterminable and a
predetermined manner, adjusting the layer thickness of the
photoresist on the surface of the base body by at least one of
varying the displacement speed of the photoresist feeder, varying
the permeability of at least one point source device of the
photoresist feeder, and varying the rotational speed of the base
body, applying the photoresist in a defined spot, and transporting
photoresist from the point source device to the surface of the base
body by one of gravity flow and regulating the feed pressure of the
photoresist from a supply chamber.
[0026] In accordance with a further mode, the method of the
invention includes guiding the photoresist through one of a
conically tapering fiber bundle and a capillary system provided
with a conically tapering tip.
[0027] In accordance with an added mode, the method of the
invention includes controlling at least one of the application of
photoresists of different viscosities and compositions, and the
application of one of the groups of primers and other adhesion
promoters, so that a cohesive layer is formed in a defined region
or over the entire surface of the base body.
[0028] In accordance with an additional mode, the method of the
invention includes applying the photoresist in a chamber wherein
the base body and the photoresist feeder are disposed, and which
contains saturated solvent vapor.
[0029] In accordance with yet another mode, the method of the
invention includes, on the surface of the base body, at least one
of applying different resist layer thicknesses and applying the
photoresist homogeneously in at least one of a small, defined
region and partial fields in locally or linearly limited form.
[0030] In accordance with a concomitant mode, the method of the
invention includes applying the photoresist in droplet form, with a
layer thickness of up to 10 .mu.m, to the surface of the base body
by at least one of feeding the photoresist from a distance thereto
and by having the photoresist directly contact the surface of the
base body.
[0031] The object of the invention is thus attained by a device for
applying photoresist to surfaces of a base body, the device
including a receptacle for the base body, a photoresist feeder
movable relative thereto, and a device for moving the base body in
a defined manner, the photoresist feeder having at least one point
or dot source device, and the latter having a conically formed tip
for applying photoresist in a defined dot form.
[0032] Provision is also made for the conically shaped tip to be
formed as a conically tapering fiber bundle or a capillary system
provided with a conically tapering tip.
[0033] The object of the invention is also attained by a method for
applying photoresist to a surface of a base body, in that the
surface of the base body to be provided with the resist, and a
feeder for the photoresist are moved relative to one another in a
predeterminable or predetermined manner, the layer thickness of the
photoresist on the surface of the base body being adjusted by
varying the displacement speed of the photoresist feeder and/or the
permeability of one or more point source devices of the photoresist
feeder and/or the rotational speed of the base body.
[0034] Thus, a device and a method for applying photoresist are
created by which arbitrarily shaped base bodies can be uniformly
provided with an especially thin layer of resist. The
disadvantageous beads of resist at the respective edge or end of
the three-dimensional body, which otherwise typically occur in the
prior art, are no longer created. The most varying
three-dimensional structures can be coated, in particular including
machine components, tools, and components of the most varied type,
as well as spectral photometers and other optical devices,
respectively, in order to produce lens geometries and the like.
Different resist thicknesses can also be applied to the respective
base body, due to which graduated masks can also very
advantageously be created. One application of this is particularly
in optical devices in which gradients in the resist thickness are
needed. In microoptics, otherwise, the problem often arises of
different etching rates for the photoresist and for the material to
which the photoresist is to be applied. This problem is
advantageously solved, however, by the method of the invention and
with the aid of the device of the invention. According to the
invention, it is in fact possible to address even very markedly
structured surfaces that are otherwise inaccessible to the method
of the prior art. Even microscopic pores can be provided with a
suitable photoresist layer. It proves to be especially advantageous
that even a single resist trace can be formed and, in particular,
photoresist can be applied in small regions and locally,
respectively. As a result, not only can arbitrary shapes be formed
from the photoresist, but also economies in cost are also achieved,
because the photoresist is applied solely to those locations at
which it is actually needed. Otherwise, particularly in large-area
coverage applicable by the methods of the prior art, the costs for
photoresist are very high.
[0035] According to the invention, in relation to the resist
thicknesses mentioned in the published German Patent Document DE 30
12 988 A1, very thin resist layer thicknesses of up to about 10
.mu.m are possible. The very thin resist layer thicknesses required
in semiconductor coating, of one to two micrometers, for example,
can therefore be achieved very easily with the method and device
according to the invention.
[0036] This thin resist layer thickness is especially important
particularly in high-precision manufacture, that is, uniform
application over the entire surface of the body of rotation,
because a light exposure time of only a few seconds is employed.
Even a minimal layer thickness of 25 .mu.m is markedly above the
photoresist thickness required for thin-film applications. One such
method, described in the aforementioned published German Patent
Document DE 30 12 988 A1, is entirely unsuitable for producing
homogeneous layers with thicknesses ranging from 0.1 to 3 .mu.m,
used especially for layer structuring, especially also because
tolerable variations in photoresist thickness are only in the range
of up to 10%. For a uniform irradiation dosage, thick resist layers
are otherwise not developed all the way through, or if there is an
overdose of UV (ultraviolet) radiation, the structural dimensions
are subject to locally sharp fluctuations. It is especially
advantageously possible with the method and the device of the
invention to provide a locally defined resist coating in the range
in particular of a few hundred square micrometers. One especially
preferred technological application here is in the field of sensor
systems. An especially precise coating is very relevant in this
field. By the methods of the prior art, coating of only a minimum
area of several hundred square centimeters is possible, and local
variation of the photoresist layer thickness to form the
geometrical structure thereof is impossible.
[0037] An especially preferred application is also in the field of
microoptics or microsystem technology. Its use in machine
components proves to be especially advantageous as well,
particularly on a shaft with integrated and directly applied
thin-film sensors. The photoresist mask required for the
structuring is then applied locally by the method of the
invention.
[0038] Besides the cost savings for the photoresist, the reduced
environmental pollution proves especially advantageous, because the
photoresist losses, which otherwise occur in great quantities in
the spraying or spinning methods, are absent or virtually absent
here.
[0039] It proves to be especially advantageous that in varnishing
especially previously-coated machine components, in which the
coating has a low surface energy, that the photoresist layer
applied according to the invention, with a thickness of 2.2 .mu.m,
for example, exhibits markedly better adhesion to the surface of
the machine component, or of the corresponding substrate on the
surface thereof, than is possible with varnishing by the immersion
method of the prior art. The machine components here may for
example be cylinders, shafts, bearing shells, round bars, or tools
of arbitrary shapes.
[0040] The point source devices of the photoresist feeder are
understood to mean feeders or sources for the photoresist that make
it possible to apply the photoresist to the surface of the base
body in dots using especially small dosages. Preferably, either
glass-fiber bodies or fiber bodies or styli with a suitably shaped
tip geometry or capillary tubules with a suitably shaped tip
geometry or nozzle-like devices, in particular in conjunction with
a pulse or impulse printer, are used. In a particularly preferred
embodiment, the point source devices may be provided in the form of
a so-called array, that is, a plurality of individual devices in
front of and next to one another. Depending upon the particular
embodiment of the point source devices, the photoresist application
can be performed by the dot source device coming in contact with
the surface of the base body, or by photoresist droplets applied to
the surface of the base body, in which case the dot source devices
or dot source device is disposed at a defined spaced distance from
the surface of the base body. If a so-called array of point source
devices is provided, then the individual devices are liftable, that
is, indexable, in a predetermined order from the surface, so that
photoresist is then applied in a defined manner only to certain
points.
[0041] A spacing sensor is advantageously provided for guiding the
photoresist feeder having the point source device or point source
devices at a constant, predetermined distance from the surface of
the base body. As a result, advantageously, even arbitrarily shaped
surfaces of a body of rotation or of a rotatable base body can be
provided precisely with a defined resist layer thickness.
[0042] Especially advantageously, stepping motors are used for the
advancement of the photoresist feeder having the point source
device or devices. In an application-specific manner, the stepping
motors can also execute the tiniest possible advancement
increments, and in particular also a motion in different
directions. By suitable construction of the feed of the photoresist
feeder and the rotational speed of the base body in the device,
major degrees of freedom are advantageously provided for applying
the photoresist to the base body surface.
[0043] Also especially advantageously, an impulse or pulse printer
with a nozzle-like point source device cooperates with an actuator
system, in particular a piezoelectric actuator system. The
nozzle-like point or dot source device or devices preferably
communicate with the supply chamber for the photoresist via
suitably dimensioned connecting elements. The supply chamber may be
disposed at an arbitrary location, because the pulse printer
intrinsically transports the photoresist to the nozzle-like point
source devices. If conversely the nozzle-like dot or point source
devices are acted upon by the photoresist via gravity flow, it is
then preferred that the supply chamber for the photoresist be
disposed above the nozzle-like dot or point source devices.
[0044] The defined tip geometry of the dot or point source devices
is especially advantageously shaped conically, and in particular it
has a radius of curvature in the range of from 1 .mu.m to 100
.mu.m.
[0045] If an impulse or pulse printer for the dot or point source
device is provided, then for supplying photoresist in a defined
manner, pressure regulation may be provided in the region of the
supply chamber for the photoresist.
[0046] When photoresists of different viscosities and compositions
are applied, or if primers or other adhesion promoters are applied,
then especially advantageous control of the method is provided, so
that a cohesive layer of photoresist is created in a defined
portion of the base body. Furthermore, the application of
photoresist is especially advantageously performed in a chamber
containing a saturated solvent vapor, the base body and the
photoresist feeder, that is, elements of the device of the
invention, being disposed in that chamber.
[0047] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0048] Although the invention is illustrated and described herein
as a method for applying photoresist to a base body surface, it is
nevertheless not intended to be limited to the details shown,
because various modifications and structural changes may be made
therein without departing from the spirit of the invention and
within the scope and range of equivalence of the claims.
[0049] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 is a diagrammatic side elevational view of a basic
layout of a device for applying photoresist to a base body
surface;
[0051] FIG. 2 is an enlarged fragmentary side elevational view,
partly in section, of FIG. 1, showing a first embodiment of a point
source device according to the invention;
[0052] FIG. 3 is an enlarged fragmentary view of FIG. 1 showing the
cylinder thereof having a surface that is partly varnished;
[0053] FIG. 4 is a sectional view of a substrate with photoresist
varnish profiles formed thereon;
[0054] FIG. 5 is a sectional view like that of FIG. 4 of a
substrate with a different photoresist varnish profile;
[0055] FIG. 6 is a fragmentary side elevational view of a gear
wheel shaft with a gear wheel mounted thereon, and with thin-film
sensors applied to the shaft surface in accordance with the
invention;
[0056] FIG. 7 is a diagrammatic side elevational view of an
alternative embodiment of the point source device;
[0057] FIG. 8 is a diagrammatic sectional view of a plurality of
point source devices disposed side by side in a row; and
[0058] FIG. 9 is a view from below on an array of point source
devices.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] Referring now to the drawings and, first, particularly to
FIG. 1 thereof, there is shown therein in a diagrammatic side
elevational view, the layout of a device 1 according to the
invention for applying photoresist. The device 1 has a frame 10. On
the frame 10, supported on suitable retaining elements,
displacement devices or rotation devices for creating relative
motion between a base body 40 and a photoresist feeder 20 are
shown. The photoresist feeder 20 has a displaceable housing 21. The
housing 21 is displaceable in an X-Z or horizontal direction along
an X-Z or horizontal displacement device 11 as shown in FIG. 1. The
displacement device 11 may be a spindle, for example. It is
supported on retaining elements 18 by respective bearings 13. The
displacement device 11 is driven by a motor-driven drive 12. This
may preferably be a stepping motor. Consequently, even tiny
advancement increments can be achieved. By making a suitable change
within the retaining elements 18 or the bearings 13 of the
displacement device 11, a change in the y or vertical direction can
also be made, so that the photoresist feeder 20 is thereby movable
in all three directions in space.
[0060] The base body 40 is disposed in a receptacle 14 and, as
shown in FIG. 1, is formed as a cylinder held at both ends thereof
by suitable clamping devices 17. The clamping devices 17 are
rotatably supported in respective bearings 15 of the receptacle 14.
For rotating the base body 40, a drive 16 is coupled to one of the
clamping devices 17 outside the respective bearing 15 of the
receptacle 14. Preferably, both of the drives 12 and 16 are
motor-driven and controllable. Consequently, an optimal adjustment
or adaptation can be made to the particular base body and the
particular coating surface to be made, and to the type and
thickness of the photoresist varnish coating, respectively. The
housing 21 of the photoresist feeder 20 moves, in the form of a
carriage, on the displacement device 11. During the motion of the
housing 21, photoresist from a point source device 30 of the
photoresist feeder 20 is applied in the form of a trace or track 51
to the base body 40 at desired locations. The point source device
30 shown in FIG. 1 is in contact with the surface 41 of the base
body 40. In an alternative embodiment, however, it is also possible
to provide a distance, preferably a defined spacing, between the
surface 41 of the base body 40 and the outlet opening at the tip 34
of the point source device 30. To maintain this defined spacing or
distance, it is especially advantageous to provide a sensor 60 for
monitoring the applicable spacing. In the embodiment of FIG. 1, one
such spacing sensor 60 is shown disposed, by way of example, on the
point source device 30. However, it may also be disposed at some
arbitrary location on the photoresist feeder 20 or the housing 21
thereof.
[0061] The point source device 30 has a reservoir 31, wherein the
photoresist is kept in reserve.
[0062] A first embodiment of a point source device 30 according to
the invention can be seen in greater detail in FIG. 2. The
embodiment of the point source device 30 shown therein has the
reservoir 31 for the photoresist 50 located in an upper region
thereof. The reservoir 31 is sheathed by a tubule 32. It is
especially preferred that the wall of the tubule 32 be
simultaneously the outer wall of the reservoir 31.
[0063] A fiber bundle 33 is disposed in the tubule 32 below the
reservoir 31. By way of example, it is a glass-fiber bundle. It has
a conically shaped tip 34. The tip 34 protrudes past the lower
boundary of the tubule 32. For a slip-free joinder of the tubule 32
and the fiber bundle 33, a shrink-fit sleeve 35 is shrunk thereon
in the transitional region between the end of the tubule 32 and the
protruding fiber bundle 33. Consequently, there is also no risk
that, upon contact with the surface 41 of the base body 40, the
fiber bundle 33 will be pushed by even slight contact inwardly into
the tubule 32. Such an effect is otherwise familiar in conventional
fiber-tipped markers. The tubule 32 is preferably made of
glass.
[0064] The photoresist varnish 50 reaches the tip 34 of the fiber
bundle 33 by force of gravity, whereupon the fiber bundle 33
absorbs the resist varnish 50 until full absorption has occurred.
It is therefore unnecessary to provide an additional pumping or
pressurizing device for feeding the photoresist out of the point
source device 30 and onto the base body 40. However, in an
alternative embodiment, such a provision may nevertheless be made,
especially in order to speed up the emergence of the resist from
the point source device 30.
[0065] The operation of applying the photoresist 50 is effected by
displacing the photoresist feeder 20 with the motor-driven drive 12
in a defined manner in the x-z direction. This is performed
continuously, in particular. During this adjustment or positioning,
the photoresist emerges from the tip 34 of the point source device
30. This, too, is preferably also continuous, in particular, due to
contact with the surface 41 of the base body 40. When the point
source device 30 is lifted, under the control of the
x-y-positioning device 19 in the retaining element 18, the feeding
of photoresist can then be stopped automatically. This interrupts
the formation of the trace or track 51 on the surface 41 of the
base body 40. The thickness of the photoresist layer, at a given
viscosity, is adjusted by the relative motion and relative speed
between the X-Z displacement motion of the delivery device 20 and
the rotary speed of the base body 40, which is controlled and
regulated by the drive 16. Preferably, at least the motor-driven
drive 12 is computer-controlled in this regard. Consequently, the
base body and also a substrate provided thereon, respectively,
together with the base body can advantageously be moved together in
rotation and in an oscillating motion relative to the point source
device 30. In this manner, full-surface varnishing of the surface
41 of the base body 40 can be achieved. However, it is also thus
possible, especially by an alternating reciprocating motion, to
perform the varnishing in partial fields or in a small, defined
region. The varnishing is thereby locally or linearly defined and
is applied homogeneously. The appropriate triggering is preferably
again performed with the aid of a computer.
[0066] By the device shown in FIG. 1, graduated courses of motion,
for example, can also be performed, by which a targeted local
variation in the layer thickness of the photoresist can be
produced. Accordingly, graduated patterns can be formed in the
photoresist mask and can be utilized, by employing suitable
lighting and etching processes to produce three-dimensional
microcircuitry components.
[0067] As photoresist, for example, a suitable varnish made by
Hoechst and sold under the designation AZ 6615, can be used.
[0068] If a photoresist layer 2.3 .mu.m thick, for example, is to
be applied to a cylinder, this is then done by the contact method,
for example. As the base body 40, the cylinder is rotated
constantly by the drive 16, and the photoresist feeder 20 is also
displaced constantly, relative to the surface 41 to be varnished
and the jacket face of the cylinder, respectively, by the
motor-driven drive 12 in conjunction with the displacement device
11. A helical line 51 is formed thereby on the jacket surface 41.
This line 51 is made so narrow or fine that, due to the narrow or
fine thickness thereof, the adjacent lines of photoresist run
together. The viscosity of the photoresist is preferably equivalent
to the viscosity as shipped, and as specified by the manufacturer,
in particular as 21 cSt (and also provided in mm.sup.2/s at 25 C,
respectively). The thickness of the photoresist layer on the jacket
surface 41 of the cylinder is dependent not only upon the relative
motion of the photoresist feeder 20 and the cylinder 40, but also
on the supply pressure and on the permeability of the fiber bundle,
formed especially as a glass-fiber bundle, and particularly in the
region of tip 34 thereof. By purposefully changing these
parameters, the layer thickness of the photoresist can be varied in
a relatively simple manner.
[0069] The sought-after thicknesses of the photoresist layer may be
varied between 0.2 and 50 .mu.m, with an accuracy of less than 3%.
For example, a layer thickness of 2.2 .mu.m can be made with the
aforementioned photoresist at an advancement speed of the
photoresist feeder 20 of 1.2 mm/s and a rotational speed of the
base body 40 of 0.08 revolutions per second.
[0070] FIG. 3 shows a cylindrical base body 40, the surface 41 of
which is partly coated with photoresist. It is believed to be
readily apparent that, by the method of the invention, both
striplike and dotlike and, in particular, rectangular traces or
tracks can be applied to the surface 41 of the cylinder 40. The
coating method is therefore also suitable, among other purposes,
for making impression cylinder blanks for the printing industry,
and so forth.
[0071] In FIG. 4, a suitable substrate 42 is shown in a sectional
view. The substrate 42 is provided with traces or tracks 51 of
photoresist 50. The individual traces 51, respectively, have
different profiles. The corresponding thickness d of the
photoresist varies and can be adjusted by adjusting the relative
motion of the substrate 42 and the point source device 30, and by
controlling the supply pressure of the photoresist out of the
corresponding reservoir 31.
[0072] A correspondingly different embodiment of the photoresist
profile on the substrate surface is shown in FIG. 5. Here,
different graduations of resist thicknesses are provided, and a
graduated mask is joined to the surface of the substrate.
[0073] FIG. 6 is a plan view of a gear wheel shaft 43 for a gear
wheel 44, the shaft 43 being partly coated or varnished with
photoresist. This partial coating with the photoresist can be
utilized to form thin-film sensors on the surface of the gear wheel
shaft 43. Such thin-film sensors are used, for example, for
constantly monitoring whether the gear wheel shaft 43 is in a
proper condition thereof.
[0074] FIG. 7 is a side elevational view of the basic layout of a
pointd source device in the form of a pulse printing device. The
pulse printing device has a nozzle portion 36 in the form of a
front tip with an outlet opening 70. Behind the latter, a
piezoelectric actuator 37 is provided, that communicates with a
supply chamber 38 for photoresist. This chamber 38 is connected,
via a connecting element 39, to a centrally provided photoresist
reservoir and is supplied thereby with photoresist.
[0075] FIG. 8 is a sectional view of a plurality of point source
devices 30 disposed and retained side by side in rows. In
particular, the point source devices are pulse printing devices.
They form a row for varnishing or coating with a broad trace or
track an uneven surface of a base body.
[0076] FIG. 9 shows an embodiment of a plurality of point source
devices, arranged areally and offset from one another, in a view
from below. The point source devices accordingly form a so-called
array 80 for coating or varnishing with a broad trace or track. The
point source devices may be in nozzle or stylus form and may be
triggerable or controllable, in particular separately.
* * * * *