US20080149272A1

US20080149272A1 - Surface Microstructuring Device

Info

Publication number: US20080149272A1
Application number: US11/631,311
Authority: US
Inventors: Djamel Bouraya; Christophe Place
Original assignee: Centre National de la Recherche Scientifique CNRS; Ecole Normale Superieure de Lyon
Current assignee: Centre National de la Recherche Scientifique CNRS; Ecole Normale Superieure de Lyon
Priority date: 2004-07-05
Filing date: 2005-07-01
Publication date: 2008-06-26
Also published as: JP2008506145A; CA2572725A1; WO2006013257A1; FR2872502B1; FR2872502A1; EP1779200A1

Abstract

The invention concerns a device for microstructuring the surface of at least one substrate characterized in that it comprises a support frame (2) including at least means (6) for conveying the substrate (S) comprising preferably means (15) for supporting the substrate adapted to maintain the substrate in or relative to each of the modules so as to avoid any change of support when the substrate is shifted from one module to the other, a module for applying a photosensitive resin layer on the substrate, a module (20) for automatic exposure using a laser beam of the resin layer on the substrate based on a programmed scheme, a so-called developing module for removing the part of the resin layer which has been exposed of the part or the resin layer which has not been exposed, a module for chemically etching the substrate, a module for cleaning the substrate, and a control unit (7).

Description

This present invention concerns the technical area of microstructuring of the surface of various substrates such as glass, metal or silicon slices, for example,
Thus, the invention more particularly concerns the creation, at the surface of materials, of structures that have dimensions of less than one millimetre. In one more particularly preferred but not limiting application, the invention is aimed, more particularly, at the creation of structures that have dimensions of between 1 μm and 100 μm.
In order to create such structures or engraving at the surface of a material, several techniques are already known, such as laser ablation or photolithography.
The engraving technique by laser ablation has the advantage of offering a very high execution accuracy, but requires the use of high-power lasers resulting in high cost, rendering the use of this technique prohibitive for the execution of microstructured substrates that are intended to have a short period of use or to constitute disposable components, as is the case in particular for the creation of substrates in microstructured glass, used for analyses by optical microscopy.
The second technique mentioned, namely photolithography, consists of depositing a thickness of photosensitive resin on the surface of the substrate to be machine treated or to be microstructured. Next, the resin layer is partially exposed with a pattern corresponding to the projection in a plane of the microstructuring to be effected, and then, once this exposure operation has been completed, the substrate is developed in order to removed the exposed resin and to retain the part of the resin that has not been exposed. Once this operation is done, the substrate is chemically etched with hydrofluoric acid for example, which attacks the parts of the substrate that are not covered by the resin. Finally, after the etching process, the substrate is washed so as to remove every trace of resin from the latter, as well as all traces of the acid used.
Such a technique offers a very wide range of patterns and allows a satisfactory level of accuracy to be attained.
However, when it is desired to create relatively large numbers of substrates with a given microstructuring pattern and with satisfactory reproducibility, compatible with the reliability requirements of the tests for example, it becomes necessary to employ different machines, each of which are capable of performing successive stages of photolithography, with these machines having to be used in conditions of hygiene and of cleanliness which most often necessitate the creation of clean rooms.
Now this obligation can appear to be prohibitive in the context of research laboratories or small units which have neither the premises nor the financial resources to create an expensive microstructuring installation for the production of microstructured substrates by the unit or in small production runs.
Thus, the need arises for a microstructuring device which is capable of executing all the stages of a microstructuring of surface by photolithography, being of reasonable dimensions, and without requiring the installation of a clean room, and while also haven a low production cost. Such a device should also have a great deal of flexibility in use, and allow the execution, rapidly and simply, of different types of microstructuring from one substrate to the next, according to requirements.
In order to attain these objectives, the invention concerns a device for microstructuring the surface of at least one substrate, characterised in that it has a support chassis that includes at least the following:

- resources for holding the substrate,
- a module for the application of a layer of photosensitive resin onto the substrate,
- resources for curing and/or drying the resin layer
- a module for automatic exposure, using a laser beam, of the resin layer on the substrate in accordance with a programmed pattern,
- a so-called “development” module for removal of the part of the resin layer that was exposed or of the part of the resin layer that was not exposed,
- a module for chemical etching of the substrate,
- a module for cleaning the substrate,
- as well as a control unit which will ensure coordinated operation, in an automatic or semi-automatic manner, of the manipulating resources and of the different modules or resources of the device, in order to perform microstructuring of the surface of the substrate in accordance with a programmed pattern.

By incorporating all the resources necessary for the photolithography of substrates into a single device, and controlling these by means of a single control unit, the invention provides the user, even if unpractised in the technique of microstructuring, with the ability to obtain a microstructured substrate that will meet the requirements with a minimum of handling operations.
It should be noted that, in a preferred manner, the control unit will include computer interface resources that allow the transfer of microstructure patterns to be executed, and will then be adapted to calculate and determine, automatically and transparently to the user, all of the procedural stages necessary to execute the microstructure according to the pattern programmed by the user and with the depth and relief characteristics specified by the latter as a function of the substrate used.
In addition, it should be noted that the operation of an automatic exposure module, by means of a laser beam, to expose a resin layer on the substrate in accordance with a programmed pattern, has the advantage of relying on a technique, called maskless photolithography, that will allow maximum simplification of the device, and the production costs of a microstructured substrate to be reduced still further.
Thus, according to one characteristic of the invention, the exposure module includes:

- a laser source emitting an exposure beam,
- optical resources for focussing the laser beam,
- and optical resources for the application and the automatic movement of the exposure beam on the substrate along a trajectory that is determined as a function of the programmed pattern.

In a preferred manner, in order to facilitate the adjustment of the device to ensure perfect exposure of the substrate, the exposure module according to another characteristic of the invention includes at least the following:

- resources for viewing the resources holding the substrate,
- resources for adjusting the optical centering and focussing of the laser beam,
- and resources for lighting the resources holding the substrate, with a visible pattern, intended to allow adjustment of the optical centering and focussing of the laser beam.

Still with the aim of facilitating adjustment, and to guarantee perfect exposure of the substrate, or more exactly of the coating of photosensitive resin applied onto the latter, the microstructuring device according to the invention, according to another characteristic of the invention, includes resources for adjusting the relative position of the resources holding the substrate and of the resources for application and movement of the laser beam.
According to one advantageous characteristic of the invention, the manipulating resources include support resources that are designed to hold the substrate within or in relation to each of the modules, so as to prevent any change of support during passage of the substrate from one module to the next. Thus, the substrate remains attached to the same support resources both during the treatment phases and during the waiting phases or while being transferred between the treatment phases.
According to the invention, the resources holding the substrate can be created in different ways and, for example, one could envisage having the substrate held by a mobile holder which would move from one module to the next, in order to allow sequential execution of the different stages of maskless photolithography as effected by the device according to the invention. According to a preferred, but not limiting, form of implementation of the invention, the microstructuring device includes the following, as resources for holding the substrate:

- an arm which is fitted onto the chassis so as to be mobile at least in translation in a vertical direction, and an actuator operated by the control unit and designed to move the arm in vertical translation between at least two positions, called raised and lowered,
- a pivoting head fitted onto the arm so as to be mobile in rotation about a horizontal axis, and an actuator operated by the control unit and designed to cause the head to pivot between two positions called raised and lowered,
- as support resources for the substrate, a holder plate for receiving and fixing of the substrate fitted onto the head so that, in the raised position of the head, it is positioned to face the optical resources for application of the exposure beam onto the substrate
- and the means for driving the holder plate in rotation on itself, which are operated by the control unit and designed to make the holder plate turn at sufficient speed to achieve centrifugal spreading of the resin on the substrate.

The use of such resources holding the substrate has the advantage of limiting, as far as possible, the manipulations to be effected on the substrate, while also minimising the movements of the latter, so that it is possible to guarantee a high reproducibility of the microstructuring patterns or patterns created.
According to one characteristic of the invention, still with the aim of high accuracy in the holding of the substrate, the holder plate includes the following:

- a recess for reception of the substrate,
- and as resources for curing and/or heating the photosensitive resin, electrical heating resources operated by the control unit.

According to the invention, it is then possible to envisage the use of different types of interchangeable recess, to allow the positioning of substrates of different shapes or variable dimensions. The gripping system immobilises the substrate by controlling the forces applied to the latter, independently of the shape conferred upon it.
In a preferred form of implementation, in order to be able to successively place the substrate in relation to the different modules corresponding to the different phases of photolithography, the device includes resources for movement of the modules. According to the invention, the resources for moving the modules can be created in any appropriate manner such as in the form of a guide track for example, supporting holders that are each equipped with a module, and driven by an endless belt.
In a preferred form of implementation, the resources for moving the modules include a mobile table to which at least the following are fitted:

- the module for the application of a layer of photosensitive resin onto the substrate,
- the development module,
- a first module for cleaning the substrate
- the module for chemical etching of the substrate,
- a second module for cleaning the substrate,
- and resources for moving the table which are operated by the control unit and designed to place each module, in a sequential manner, under the holder plate for receiving and maintaining the substrate. According to the invention, the modules can be created in any appropriate manner.

However, in a preferred but non-limiting form of implementation, which is designed to greatly simplify the design of the table and therefore to achieve particularly advantageous production costs, the resin application module includes:

- a window created in the table,
- a resin reservoir placed under the table and open at the top opposite to the window,
- and at least one motor-driven shutter for closing the window and which is opened and closed by the control unit.

Likewise, the development module includes:

- a window created in the table,
- a reservoir for a development solution, placed under the table and open at the top opposite to the window,
- and at least one motor-driven shutter for closing the window, which is opened and closed by the control unit.

Likewise, the chemical etching module includes:

- a window created in the table,
- a reservoir for a chemical etching solution placed under the table and open at the top opposite to the window,
- and at least one motor-driven shutter for closing the window, which is opened and closed by the control unit.

Such a design can, also, be used to advantage for the cleaning modules, which each then includes:

- a window created in the table,
- a reservoir for a cleaning solution placed under the table and open at the top opposite to the window,
- and at least one motor-driven shutter for closing the window and which is opened and closed by the control unit.

It should be noted that, in a more particularly preferred form of implementation, the reservoir of each module will be designed to be detachable from the table, allowing it to be changed rapidly according to the chemistry employed, or for replacement when the reservoir is empty or contaminated.
In a preferred form of implementation, each reservoir will include a removable drawer moving on slides mounted on the table. This removable drawer can be supplied to the user already sealed by means of a film or a removable opercule which will be removed after installation of the drawer on the table. Such a form of implementation will then be particularly advantageous when the chemical product used is of a toxic or volatile character.
It should be noted that the shutters** of each of the modules will preferably be made so as to provide a seal, at least partial, for the content of the reservoirs, given that the device according to the invention can also include a general casing in which a vacuum can be created in order to eliminate any risk of toxic emanations outside of the device.
According to a preferred implementation characteristic of the invention, in order to allow simple and rapid execution of each of the photolithography stages, the resources holding the substrate are created so that the distance between the receiving holder plate and the pivoting head allows movement of the holder plate into each of the reservoirs, so that in the wait position, the substrate and the holder plate are placed at a distance from the level of the content or of the bath of the reservoir and, in an annealing or curing position, allows an at least partial immersion of the holder plate and of the substrate in the content of the reservoir, while also being designed to hold the closure shutter firmly in either of its two positions.
According to another characteristic of the invention, in order to allow simple and rapid operation, without any particular knowledge of the technique of microstructuring by photolithography, the control unit is designed so that, after the installation of a substrate onto the holder plate, it can perform the following operations in a sequential automatic or semi-automatic manner:

- deposition of a layer of photosensitive resin on the substrate,
- drying and/or annealing of the layer of photosensitive resin,
- exposure of the layer of photosensitive resin according to a programmed pattern,
- development of the layer of photosensitive resin,
- cleaning of the substrate and of the remaining part of the resin layer,
- chemical etching of the substrate,
- and removal of the remaining part of the layer of photosensitive resin and cleaning of the substrate.

In a more particularly preferred form of implementation of the photolithography process according to the invention, the control unit is designed to automatically execute the deposition of photosensitive resin by controlling the following operations at least:

- placement of the reception holder plate of the substrate, with recess oriented downwards,
- partial immersion of the holder plate and of the substrate in the photosensitive resin,
- removal of the holder plate and of the substrate from the photosensitive resin,
- rotation of the holder plate, with recess oriented downwards, at a given speed of rotation and for a given time in order to obtain a uniform layer of a given thickness at the surface.

In fact, the inventors were able to demonstrate that the direction or the orientation, whether right-way up or upside down, of the holder plate made no difference to the creation of a uniform layer of resin on the substrate during the centrifugal spreading of the latter.
Thus, this demonstration led to a method of operation of the device according to the invention which firstly allowed the immersion of the substrate in the resin and then raising the holder plate so as to place the substrate above the level of the resin for the centrifugal spreading stage, while also keeping closed the shutters** for closing off the module for application of the resin, so that there is no splashing of resin to the exterior, and so that there is no pollution of the device and of the other modules.
Naturally, the different characteristics of the invention mentioned above can be implemented together in different combinations whenever they are not exclusive of each other.

Furthermore, diverse other characteristics of the invention will emerge from the description that follows, given with reference to the appended patterns which illustrate, in a simplified manner, one preferred but non limiting form of implementation of a microstructuring device according to the invention.

FIG. 1 is a schematic section of a surface microstructuring device according to the invention.

FIG. 2 is a plan view of the microstructuring device of FIG. 1.

FIG. 3 is a view in detail, in partial section, of a module for immersion of the device according in FIG. 1, where this view also illustrates a particular method of operation of the device according to the invention.

FIG. 4 is a schematic view in perspective of one possible form of an exposure module constituting the microstructuring device illustrated in FIG. 1.

A microstructuring device according to the invention, as illustrated in FIGS. 1 and 2, and referred to as a whole by the reference 1, includes a support chassis 2 to which are fitted the different functional assemblies that are designed to implement the different stages of substrate microstructuring by maskless photolithography. According to the example illustrated, the chassis 2 includes, in its bottom part, a chemistry compartment 3 which includes the different chemistry modules, and which is designed to effect the chemical part of the microstructuring, as will appear more clearly in what follows.
The chassis 2 also includes an optical compartment 4, placed above the chemistry compartment 3 and connected to the latter by a column 5 forming part of the chassis 2. The device 1 also includes resources 6 for holding at least one substrate attached to the chassis 2.
The device 1 also includes a control unit 7 supported, according to the example illustrated, by a pillar 8 attached to the column 5. Of course the control unit could be independent and connected to the component elements of the device according to the invention by appropriate connecting resources.
According to the invention, the manipulating resources 6 of a substrate can be created in different ways.
According to the example illustrated, the manipulating resources 6 includes an arm 10 which is fitted to a column 11 that is fixed to the chassis 2. The arm 10 is oriented more-or-less horizontally, and is fitted to the chassis 2 so as to be mobile, at least in vertical translation on axis D1. According to the example illustrated, this movement is performed by a movement in translation of the column 11, parallel to axis D1, under the effect of an actuator 12 such as, for example but not exclusively, an electric actuator operated by the control unit 7. The resources to accept at least one substrate also include a pivoting head 13, fitted at the end of the arm 10 opposite to the column 11.
The pivoting head 13 is connected to the arm 10, so as to be mobile in rotation about a horizontal axis D2. The head 13 is then driven in rotation by an actuator, such as, for example but not exclusively, a geared electric motor 14, placed within the arm 10 as shown in FIG. 3. The geared motor is operated by the control unit, causing the head 13 to pivot between a raised position C, illustrated by solid lines in FIG. 1, and a lowered position D, as illustrated with mixed lines in FIG. 1.
In order to perform the manipulation proper of a substrate S, such as a slice of material of rectangular shape for example, as shown schematically with mixed lines in FIG. 3, the resources 6 include, as support resources for the substrate, a holder plate 15 designed to receive and retain the substrate S.
In order to allow perfect immobilisation of the substrate S during all of the microstructuring operation, the holder plate 15 includes a recess 16 in which the substrate is accommodated. The recess 16, which preferably has a shape that is complementary to that of the substrate S, can be created in different ways in order to achieve immobilisation of the substrate S in the recess 16. According to a preferred form of implementation. The recess 16 is created from an elastically deformable material such as a synthetic elastomer like silicon for example, whose elasticity can be used to advantage in order to immobilise the substrate S in the recess 16. It should be noted that the device according to the invention is also able to allow the microstructuring of substrates that come indifferent sizes, and to this end, the recess 16 can be modular or the holder plate detachable in order to allow it to be changed according to the size of the substrate to be microstructured.
The holder plate 15 is also fitted onto the head 13 so as to be mobile in rotation about a vertical axis D3. The head 13 will then include the driving resources in rotation of the holder plate 15 on itself on axis D3. The driving resources 17 can be composed, for example, of an electric motor, operated by the control unit 7 and designed to make the holder plate turn 15 at sufficient speed to achieve centrifugal spreading of a resin deposited on the substrate S, as will appear more clearly in what follows. The holder plate 15 is also equipped with a heating system 18, such as a resistance element whose power supply is controlled by the unit 7 and which forms resources for curing and/or drying a resin layer applied onto the substrate S.
It should be noted that the resources 6 for holding the substrate S and, more particularly, the head 13 and the holder plate 15, are situated between the chemistry compartment 3 and the optical compartment 4, so that through the rotary movements of the head 13, the holder plate 15 can be either placed in the raised position C opposite to the optical compartment 4 or in lowered position D opposite to the chemistry compartment 3.
According to the invention, the optical compartment 4 is equipped with a module 20 for the automatic exposure of a resin layer applied onto the substrate. As will emerge more particularly from FIG. 4, the exposure module 20 includes a laser source 21, emitting a laser beam 22 that is designed act as an exposure beam onto the substrate S, as will appear more clearly in what follows. The module 20 also includes optical resources 23 for focussing the laser beam. According to the example illustrated, the optical focussing resources 23 include in particular a lens 24 that is mobile in translation, so as to allow the adjustment of focus. The exposure module 20 also includes optical resources 25 for application and automatic movement of the exposure beam on the substrate S (by scanning) along a trajectory that is determined as a function of a programmed pattern.
The optical resources 25 for application and automatic movement of the laser beam 22 are naturally coupled to the control unit 7, which will control its operation.
In order to allow optimal adjustment of the position of the laser beam 22 on the substrate and, in particular, initialisation of this position before exposure, the exposure module 20 also includes resources for viewing the resources holding the substrate S and, as in the example, of the recess 16 in the holder plate 15. According to the example illustrated, the viewing resources 26 take the form of a video camera, coupled to the control unit 7 and designed to display, on a screen 27 of the latter, the image of the recess 16 and, more particularly, of the substrate S placed in the latter.
The module 20 also includes resources for adjusting the optical centering and focus of the laser beam which, according to the example illustrated, are integrated into the optical resources for application and movement of the laser beam 22, and in particular include the focussing lens 24.
Finally, the exposure module 20 includes resources 28 for lighting the resources holding the substrate and, more particularly, the recess 16 in the holder; plate 15, with a pattern than can be seen via the viewing resources 26 and intended to allow adjustment of optical centering and focussing of the laser beam 22.
In order to perform the so-called chemical part of the microstructuring process effected by the device according to the invention, the chemistry compartment 3 includes a module 30, as shown in FIG. 2, for the application of a layer of photosensitive resin onto the substrate S, a development module 31, a first cleaning module 32 of the substrate S, a module 33 for chemical etching of the substrate S and a second module 34 for cleaning the substrate.
The different chemistry modules 30 to 34 can be arranged in different ways in the chemistry compartment 3. According to the example illustrated, these chemistry modules 30 to 34 are all attached to a table 35 that is mobile in rotation about a vertical axis D4. The table 35 thus comprises resources for moving the modules. The chemistry modules 30 to 34 are then placed on the table so as to be oriented at 60° from each other. It will be noted that according to the example illustrated, the table 35 includes a sixth chemistry module 36 that is available to receive an additional bath as a function of the type of chemical etching adopted.
The table 35 is driven in rotation by driving resources 37 such as a geared electric motor, operated by the control unit 7, so as to allow sequential positioning of each chemistry module 30 to 34 and 36 under the holder plate for receiving and retaining 15 the substrate S, as will appear more clearly in what follows.
According to the form of implementation illustrated, each chemistry module 30 to 34 and 36 are more-or-less identical in their make-up. Thus each chemistry module 30, 31, 32, 33, 34 and 36, includes a window 40, associated with the reservoir 41 of a chemistry bath 42. The reservoir 41 is open at the top opposite to the window 40. According to the example illustrated, each reservoir 41 is created in the form of, a removable drawer supported by slides 43 fixed onto the bottom face 35 i of the table 35. According to the nature of the bath 42, one could envisage fitting a peripheral sealing gasket 44 on the upper part of the drawer 41, designed to create a seal between the drawer 41 and the bottom face 35 i of the table 35.
It should be noted that the window 40 and the reservoir 41 are of sufficient dimensions to allow at least partial immersion of the holder plate 15 in the chemistry bath 42.
Each chemistry module 30 to 34 and 36 also has at least one and, as in the example illustrated, two motor-driven shutters 45, 46 for closing the window 40. The motorised shutters 45, 46 are then opened and closed by the control unit 7. The shutters 45, 46 are fitted to the top face 35 s of the table 35 so as to perform the corresponding closure of the window 40. In the closed position, this system creates a seal against dust, light and vapours from the bath 42.
In addition, in order to allow at least partial immersion of the holder plate 15 in the bath 42 of each chemistry module 30 to 34 and 36, the holder plate 15 is fitted onto the head 13 by means of a shaft 47 so as to be placed at a distance from the pivoting head 13, as shown in FIG. 3. Each shutter 45, 46 is then preferably designed so that when the holder plate is placed within the reservoir 41, it is possible to perform the closure of the window 40 while also allowing the passage of the shaft 47 and maintaining the seal. To this end, each shutter 45, 46 is equipped with a sealing gasket 48, which is designed to hug the shape of a sleeve 50 surrounding the shaft 47. Of course, according to the invention, other resources can be employed in order to achieve a certain seal to the air and to splashes when the holder plate 15 is located within a module.
The microstructuring device 1, as described previously, can be implemented in the following manner.
Firstly, the user of the device 1 loads or selects a pattern of the microstructuring to be effected, at the level of the control unit 7. This loading or selection can be effected in different ways. Thus, loading can be the result of sending a computer file to the control unit 7 from a personal computer (not shown) via an interface device (not shown either) incorporated into the control unit 7. Once the pattern has been programmed, meaning the representation in two dimensions of the wanted microstructuring, the user can then select another microstructuring parameter, such as the depth of the action on the substrate for example. From this choice of engraving depth or chemical attack, the control unit 7 determines a suitable processing time, in an automatic or semi-automatic manner, as a function of the chemistry baths used and of the nature of the substrate.
Once the microstructuring parameters have been recorded in the unit 7, the user places the substrate S to be microstructured at the level of the receiving resources and, more particularly, of the recess 16 in the holder plate 15. As described earlier, the substrate S is suitable for accommodating different shapes, and the recess 16 will therefore be designed so as to present a shape that is complementary to that of the substrate S so that it is held in a totally secure manner.
One can then proceed to the application of a layer of photosensitive resin onto the surface of the substrate S. To this end, the control unit 7 performs control over the driving resources of the table 35, so as to ensure that the module for application of the photosensitive resin 30 is placed opposite to the pivoting head 13.
At this stage, the unit 16 then executes a rotation of the head 13 so as to place it in the lowered position D, with the substrate oriented downwards. Next, the control unit 7 executes the opening of the shutters 45 and 46 and lowering of the head 13 and of the holder plate 15 by controlling the actuator 12. The lowering of the holder plate 15 continues until the substrates S is immersed in the bath of resin 42 in partial immersion position F in FIG. 3. The unit 7 then effects the closure of the motorised shutters 45 and 46, so that the gaskets 48 close onto the sleeve 50 of the shaft 47.
Next, the control unit 7 effects the raising of the head to the intermediate position E in which the substrate S is located above the bath of resin 42 while also being in the receptacle 41. The unit 7 then triggers the operation of the motor 17 in order to drive the holder plate 15 in rotation on itself and perform a spreading and a centrifugal distribution of the resin on the surface of the substrate S.
Such an operation, also known by the name of “spin coating” allows not only removal of the excess resin, but also a uniform distribution of the latter to be effected on the surface of the substrate. It should be noted that the inventors were able to demonstrate the fact that the orientation, upwards or downwards, of the substrate made very little difference to the quality of the resin distribution on its surface, in particular when the said surface has a horizontal orientation. Thus in the context of this present invention, this demonstration enables one to envisage application of the resin by immersion, and then centrifugal, spreading of the latter while also remaining within the receptacle 41, so that the risk of splashing the resin removed from the substrate is virtually eliminated, and these splashes are recovered automatically in the receptacle 41 within which the centrifugal spreading takes place.
After this operation, the control unit 7 executes the opening of the motorised shutters 45 and 46 and extraction of the holder plate out of the receptacle 41 by controlling the actuator 12 so as to raise the pivoting head 13 to position D. The control unit next places the head 13 in the raised position C, with the substrate S oriented upwards opposite to the exposure module 20.
At this stage, and according to the nature of the resin, the control unit 7 can then control the power feed to the resistance element 18, so as to heat the holder plate 15 and the substrate S that it is carrying and thus effects the drying and possible curing of the resin.
It is then possible to proceed to the exposure of the resin. To do this, the holder plate 15 is brought to its end-stop by the actuator 12 operated by the unit 7, against a support element 51 attached to the exposure module 20 and forming resources for adjusting the relative position of the resources holding the substrate in relation to the resources for application and moving of the laser beam.
At this stage, the control unit 7 or the user of the device 1 performs the adjustment of the optical part. This optical adjustment is effected by the lighting of the substrate with a test pattern in order to adjust the focus of the laser beam.
It should be noted that in order to prevent any unwanted exposure of the resin, projection of the test pattern is effected by means of a safe light. In addition, the device 1 includes a removable opaque casing 52 illustrated with mixed lines in FIG. 1, designed to protect the assembly from light and from external dust. Once these adjustments have been completed, the unit 7 controls the automatic exposure of the substrate S, or more particularly of the layer of photosensitive resin applied to the surface of the latter, by automatic movement and control of the spot of the laser beam 22 as a function of the programmed pattern of the microstructure to be effected at the surface of the substrate. Once exposure is complete, development of the resin can then take place.
In this regard it should be noted that, according to the invention, two types of photosensitive resin can be used, namely either a positive resin or a negative resin. These photosensitive resins differ from each other in that, for the so-called positive photosensitive resins, it is the exposed part of the resin that is removed, while for the photosensitive resins described as negative, it is the unexposed part of the resin that is removed.
To effect the development, the control unit 7 places the pivoting head 13 in its lowered position and brings the development module 31 to the level of the head. There then follows a sequence that is more-or-less the same as that described for the application of the resin. In fact, the substrate is inserted into the module 31 and, after closure of the shutters 45, 46, immersed in the bath of development solution of the module 31. After immersion, the holder plate and the substrate are extracted from the bath and placed in the intermediate position I and the unit 7 rotates the holder plate 15 so as to achieve centrifugal elimination of the drops of solution present on the surface of the substrate S. The control unit 7 next executes the extraction of the holder plate 15 and of the substrate S out of the development module 31.
The unit 7 then executes cleaning of the substrate by immersion of the latter in a bath of washing solution of the first cleaning module 32 washing will be effected, as for development, by immersion and then centrifugal removal of the solution present at the surface of the substrate. After the washing stage, next comes the etching or engraving of the substrate, which consists of attacking the part of the surface of the substrate that is not covered with resin, using a corrosive solution. To this end, the control unit 7 positions the chemical etching module 33 opposite to the head 13 and then, as in the development stage, the control unit 7 executes the opening of the shutters 45, 46 and the introduction of the holder plate 15, and of the substrate that it is carrying, into the module 33. The substrate S is then immersed for a given time depending on the engraving depth required, in a bath of acid solution, such as a solution of dilute hydrofluoric acid for example. After immersion, the substrate S will be caused to rotate in order to effect centrifugal removal of the drops of acid solution remaining on its surface. After extraction of the holder plate 15 and of the substrate S out of the engraving module, the substrate is cleaned in the second cleaning module 34, which will have been placed beforehand opposite to the head 13 by the unit 7. This second cleaning will be effected in a sequence similar to that of the first cleaning.
Once the second cleaning has ended, the control unit 7 returns the pivoting head to the raised position C and the user is then able to retrieve the cleaned and microstructured substrate S from the recess 16 in the holder plate 15. It should be noted that, according to the invention, the sixth chemistry module 36 could be arranged to effect a final rinsing of the substrate after its cleaning in the second cleaning module. Of course this is only one example of one method of implementation of the microstructuring device 1 according to the invention, and various other sequences of treatment can be envisaged without moving outside of the context of this present invention.
Furthermore, it will be noted that the substrate will have been held on the same holder plate 15, forming the support resources of the substrate, throughout the whole of the treatment. This advantageous characteristic of the invention guarantees a high reproducibility of the results, while also allowing simplification of the surface microstructuring device according to the invention.

Claims

1. A device for microstructuring the surface of at least one substrate (S), characterised in that it includes a support chassis (2) that in turn includes at least the following:

resources (6) for holding the substrate,

a module (30) for the application of a layer of photosensitive resin onto the substrate,

resources (18) for curing and/or drying the resin layer,

a module (20) for automatic exposure, by means of a laser beam, of the resin layer on the substrate, in accordance with a programmed pattern,

a module (31), described as “development”, for removal of the part of the resin layer that was exposed or of the part of the resin layer that was not exposed,

a module (33) for chemical etching of the substrate,

a module (34) for cleaning the substrate,

as well as a control unit (7) which will ensure coordinated operation in an automatic or semi-automatic manner, of the manipulating resources (6) and of the different modules (30, 31, 33, 34), or resources (18) of the device in order to perform microstructuring of the surface of the substrate (S) in accordance with a programmed pattern.

2. A microstructuring device according to claim (1), characterised in that the manipulating resources (6) of the substrate (S) include resources (15) to support the substrate, designed to hold the substrate in or in relation to each of the modules so as to prevent any change of support during the passage of the substrate from one module to the next.

3. A microstructuring device according to claim 1, characterised in that it includes the following as the resources (6) for holding the substrate (S):

an arm (10) which is fitted to the chassis (2) so as to be mobile at least in translation in a vertical direction (D1) and an actuator (12) operated by the control unit (7) and designed to move the arm (10) in vertical translation,

a pivoting head (13) fitted onto the arm (10) so as to be mobile in rotation about a horizontal axis (D2), and an actuator (14) operated by the control unit (7) and designed to cause the head to pivot (13) between two positions described as raised (C) and lowered (D),

as the means for supporting the substrate, a holder plate (15) to accommodate and fix the substrate (S), fitted onto the head (13) so that, in the raised position of the head, it is positioned to face the optical resources (25) for application of the exposure beam onto the substrate (S),

and resources (17) to drive the holder plate (15) in rotation on itself, which are operated by the control unit (7) and designed to make the holder plate turn (15) at sufficient speed to achieve centrifugal spreading of the resin on the substrate.

4. A microstructuring device according to claim 3, characterised in that the holder plate (15) includes:

a recess (16) for reception of the substrate,

and, as resources for curing and/or drying the photosensitive resin, electric heating resources (18) operated by the control unit (7).

5. A microstructuring device according to claim 1, characterised in that it includes resources (35) for moving the modules.

6. A microstructuring device according to claim 5, characterised in that it includes, as resources for moving the modules, a mobile table (35) to which are fitted at least:

the module (30) for application of a layer of photosensitive resin onto the substrate,

the development module (31),

a first module (32) for cleaning the substrate,

the module (33) for chemical etching of the substrate,

a second module (34) for cleaning the substrate,

and resources (37) for moving the table (35), which are operated by the control unit (7) and designed to place each module in a sequential manner (30, 31, 32, 33, 34) under the holder plate (15) for reception and fixing of the substrate (S).

7. A microstructuring device according to claim 1, characterised in that the resin application module (30) includes:

a window (40) created in the table (35),

a reservoir (41) of resin placed under the table (35) and open at the top opposite to the window (40),

and at least one motor-driven shutter (45) for closing the window (40) and opened and closed by the control unit (7).

8. A microstructuring device according to claim 1, characterised in that the development module (31) includes:

a window (40) created in the table (35),

a reservoir (41) for a development solution, placed under the table (35) and open at the top opposite to the window (40),

9. A microstructuring device according to claim 1, characterised in that the chemical etching module (33) includes:

a window (40) created in the table (35),

a reservoir (41) for a chemical etching solution, placed under the table (35) and open at the top opposite to the window (40),

10. A microstructuring device according to claim 1, characterised in that each cleaning module (32, 34) includes:

a window (40) created in the table (35),

a reservoir (41) for a cleaning solution, placed under the table (35) and open at the top opposite to the window (40),

11. A microstructuring device according to claim 7, characterised in that the reservoir (41) of each module is fitted to the table in a detachable manner so as to allow easy changing of the reservoir.

12. A microstructuring device according to claim 7, characterised in that it includes the following as the resources (6) for holding the substrate (S):

and resources (17) to drive the holder plate (15) in rotation on itself, which are operated by the control unit (7) and designed to make the holder plate turn (15) at sufficient speed to achieve centrifugal spreading of the resin on the substrate,

and is further characterised in that:

the holder plate (15) for reception of the substrate (S) is supported by a shaft (47) so as to be placed at a distance from the pivoting head (13),

the window (40) of each module is designed to allow the passage of the holder plate (15) for reception of the substrate (s),

and the closure shutter (45) of each module (30, 31, 32, 33, 34) is designed to effect closure of the window while also allowing passage of the shaft when the holder plate (15) is placed inside the reservoir (41) while the pivoting head (13) is located outside the reservoir.

13. A microstructuring device according claim 1, characterised in that the control unit (7) is designed so that, after the insertion of a substrate (S) on the holder plate (15), perform, it is able to perform, in a sequential automatic or semi-automatic manner, at least the following operations:

deposition of a layer of photosensitive resin on the substrate,

drying and/or annealing of the layer of photosensitive resin,

exposure of the layer of photosensitive resin according to a programmed pattern,

development of the layer of photosensitive resin,

cleaning of the substrate and of the remaining part of the resin layer,

chemical etching of the substrate,

and removal of the part of the remaining layer of photosensitive resin and cleaning of the substrate.

14. A microstructuring device according to claim 13, characterised in that the control unit (7) is designed to automatically execute the deposition of photosensitive resin by controlling the following operations at least:

placement of the reception holder plate of the substrate with the recess oriented downwards,

partial immersion of the holder plate and of the substrate in the photosensitive resin,

extraction of the holder plate and of the substrate from the photosensitive resin,

rotation of the holder plate, with the recess oriented downwards, at a given speed of rotation and for a given time, in order to obtain a uniform layer of a given thickness at the surface of the substrate.

15. A microstructuring device according to one claim 1, characterised in that the exposure module (20) includes:

a laser source (21) emitting an exposure beam,

optical resources (23) for focusing the laser beam,

and optical resources (25) for application and automatic movement of the exposure beam on the substrate along a trajectory that is determined as a function of the programmed pattern.

16. A microstructuring device according to claim (15), characterised in that the device includes resources (51) for adjusting the relative position of the resources holding the substrate and of the resources (25) for application and for moving the laser beam.

17. A microstructuring device according to claim (16), characterised in that the exposure module (20) includes at least:

resources (26) for viewing the resources to accept the substrate,

of the resources for adjusting the optical centering and the focus of the laser beam,

and resources (28) for lighting the resources holding the substrate, with a visible pattern intended to allow adjustment of the laser beam focus.