Technical Field
[001] The present disclosure relates to a system for fabrication of microstructures
having portable and miniaturized cleanroom architecture. The present disclosure also
relates to a method using the system of the present invention for the fabrication of
microstructures.
Background of the invention
[002] Miniaturization is the driving force for the current technological development.
Micro and Nano fabrication is the backbone of this era of the development, where all
the information related tools; gadgets have been entirely based on the concept of
miniaturization. Microfabrication system and methods were originally developed for
the need of electronics industry, which needs batch fabrication and bulk processing of
miniature micro-electronic components. However, in the last few years,
microfabrication techniques are also used to fabricate micro and nano mechanical
devices, micro and nano photonic devices etc., apart from micro and nano electronic
devices.
[003] One of the preferred substrates that is currently used for producing micro
devices is a Silicon (Si) wafer. Processing of such substrates having a diameter in the
range of 300-450 mm to fabricate micro and nano devices normally entails a large
amount of physical space and bulky machinery. Above all, such a huge physical space,
containing bulky machines with active human assistance needs to be maintained in
clean ambient conditions and which are also comfortable for human beings. These
specially designed work environments are generally referred as cleanrooms.
[004] In order to fabricate such micro and nano devices, especially on a large scale
and under batch processing, the micro fabrication facilities incorporate various
machinery and technologies. Such facilities normally include incorporation of
cleanrooms, specialized equipment and skilled human resources. These facilities do
consume an enormous amount of energy and natural resources such as water and
electricity during the course of fabrication. This in many ways adds to the problem of
excess carbon dioxide emission.
[005] In a conventional system for the fabrication of microstructures, the system as shown in FIGs.1-3 generally includes at least an outer cleanroom building 10, acting as
an enclosure to an inner cleanroom structure 11. The inner clean room structure 11 is a
large entity, to accommodate plurality of large machine systems to perform fabrication
of microstructures viz., material cleaning platforms, and pattern writing e.g.
photolithography, spin coating, physical vapour deposition, material growth, substrate
manipulation and the like. The inner clean room 11 also provides space for the entry
and presence of users to physically operate these machines and perform various tasks of
microfabrication, physically and within the confines of the inner cleanroom 11. The
outer cleanroom building 10 isolates the inner cleanroom 11 from outside environment.
An utility building 12, in which all the auxiliary equipment rendering functions such as
filtration, storage and a control of main supply are located, is connected to the clean
rooms 10 and 11, by means of a closed conduit, which carries all the connections from
utility building 12 to the cleanrooms 10 and 11. The cleanroom 11 is separated
vertically into three main zones viz., a bottom zone 13 for utilities, a main cleanroom
14 for wafer processing and a top zone 15 for air handling unit and filters. The area 19,
the return air chase, is used to recirculate the air, which is filtered and passed again into
the main cleanroom 14. The main cleanroom 14 is normally built on a raised perforated
platform, 20 to facilitate laminar air flow from top to bottom in the clean room 14. Air
handling units 18 along with the Filters such as High-Efficiency Particulate Absorption
(HEPA) filters 17 are arranged on the roof 16 and are used to filter the incoming air
into the clean room 14. The clean room, as shown in FIG.3, is normally provided with
a user entry portion 21 which is connected to the cleanroom 14, and provided with an
air shower arrangement, to blow off the dust and contaminants from the bodies of users
entering into the cleanroom 14. A gowning portion 22 connected to the entry portion 21
where a special cleanroom suit has to be worn by the users. Bay areas or workings
sections are connected to the gowning portion 22, which are divided generally based on
major classification of microfabrication processes. The separate working areas that are
allocated for the microfabrication functions include machinery to perform material
deposition 23, material cleaning 24, photolithography 25, material removal 26, material
growth 27.
[006] Various functions for the microfabrication of micro devices are performed
inside the cleanroom 14, by users, in the presence of user-operated machines, in the
respective bay areas. For instance, in the process of cleaning of Si wafers, wet benches are used by the users, with chemicals and in batches. The-aforementioned cleaning
process of the wafers is associated with problems, viz., and contamination of the wafers
during the course of their handling and exposure of users to hazardous use of
chemicals. However, alternately, automatic cleaning of Si wafers is adopted for batch
cleaning, which however, reduces flexibility of the operations and increases the
operational cost. Similarly, cleaned wafers are subject to pattern creation using
processes such as photolithography, which is a laborious and time consuming
operation, resulting in avoidable human errors and excessive use of energy even for
fabricating small samples. The energy consumption assumes greater proportions,
especially during the process of baking of the wafers. In the continuing
microfabrication process, the patterned wafers are subjected to material removing
process in the allotted bays having the necessary process tools, particularly vacuumbased etching tools. In this arrangement a main operational chamber is connected to an
electric power unit, a gas chamber, pump for evacuation of material and a cooling
system. The machinery that is associated with the material removing process occupies a
large working space volume, even though the size of the materials (wafers) that are
used for microfabrication is substantially small as compared with the size of
components as used in the system, resulting in avoidable occupation of the precious
space of expensive clean room. In yet another step in the process of microfabrication,
the wafers are subjected to the process of material growth, in a furnace operating at
very higher temperature and in gaseous conditions. The large equipment size,
associated with their huge thermal mass, ramp down rates and high power
consumption.
[007] Similarly, various other material deposition methods that are associated with
fabrication of micro devices include sputtering, evaporation, pulsed laser deposition,
atomic layer deposition etc., also occupy the precious space of the clean room and in
most of the cases the size of the deposition tools do not commensurate with the size of
the wafers. In other words, these deposition tools impose a huge burden on by virtue of
sheer size, especially while producing micro devices for the prototyping purpose.
[008] The Centre Suisse d’Electronique et de Microtechnique (CSEM) has disclosed
microfactory concept for the precise assembly of tiny watch components. CSEM
discloses a small assembly machine for assembling the smaller components by using
delta robots and pneumatic actuators.

[009] Microfabrication systems for the preparation of Si wafers of the size in the
range of 350-450 mm are known. For instance, the microfabrication system for the
preparation of Si wafer of the size of 450 mm is housed in a facility spread over the
area of 1.3 million sq. ft
[0010] It is therefore, advantageous to have a compact microfabrication system that can
be implemented on a small platform or a desk, to prepare micro and nanoelectronic
devices, particularly, without a direct human intervention that is required in the
conventional clean room. It is also preferred to have method where the manual
intervention is either substantially eliminated or contained to a maximum extent. Such
systems and methods will eventually reduce the exposure of users to hazardous
manufacturing processes, limits the usage of chemicals and substantially reduces the
energy consumption. It is also preferable to have a system and method for the
microfabrication of devices, which can save the depletion of precious natural resources
and reduce the carbon print. Above all, there is a greater value to the concept of
miniaturization of microfabrication, and portable facility.
Brief description of the drawings
[0011] FIG.1 is a general layout view of a conventional cleanroom and auxiliary utility
infrastructure for the fabrication of micro devices.
[0012] FIG.2 is a schematic layout of a conventional cleanroom facility that is used for
the fabrication of micro devices
[0013] FIG.3 is a schematic layout of various functional components of a conventional
clean room facility.
[0014] FIG.4 is a perspective view of the system of the present disclosure for
fabrication of microstructures on substrates, having portable and miniaturized
cleanroom architecture.
[0015] FIG.5 is a perspective view of the system of the present disclosure arranged in a
portable container.
[0016] FIG.6 is a schematic depiction of the broad system architecture of the present
disclosure.
[0017] FIG.7 is a perspective view of material cleaning module of the system of the
present disclosure.
[0018] FIG.8 is a perspective view of compact substrate manipulation module of the
system of the present disclosure.
[0019] FIG.9 is a perspective view of compact furnace module of the system of the
present disclosure.
[0020] FIG.10 is a perspective view of compact photolithography module of the
system of the present disclosure.
[0021] FIG.11 is a perspective view of the compact spin coater module of the system
of the present disclosure.
[0022] FIG.12 is a perspective view of the physical vapour deposition module of the
system of the present disclosure.
[0023] FIG.13 is a flow drawing of the method of the present invention.
Description of the invention
[0024] Accordingly, the present disclosure provides a system for fabrication of
microstructures on substrates, having portable and miniaturized cleanroom architecture.
[0025] In an aspect of the present disclosure, a system for fabrication of
microstructures on substrates, having portable and miniaturized cleanroom architecture,
particularly for the fabrication of micro devices, is disclosed.
[0026] In another aspect of the present disclosure, provides a system for fabrication of
microstructures on substrates, which is modular and automated.
[0027] In yet another aspect of the present disclosure the system for fabrication of
microstructures on substrates, having portable and miniaturized cleanroom architecture
comprises a compact table-top clean enclosure as against conventional large clean room
facility that incorporates all primary components that are required for the
microfabrication of micro devices. This clean enclosure could be supported by small
load lock chamber for sample loading and unloading, so that the conditions in the clean
enclosure are not disturbed.
[0028] In further aspect of the present disclosure, the system for fabrication of
microstructures on substrates, having portable and miniaturized cleanroom architecture,
the enclosure of the system is operable either under vacuum or an inert atmosphere.

[0029] In yet another aspect of the present disclosure, the system for fabrication of
microstructures on substrates, with a portable and miniaturized cleanroom architecture,
in which the functional aspects of the primary components of the system are controlled
by a digital processor, thereby preventing the manual interventions and exposure,
which hitherto are some of the main sources for contamination, during microfabrication
process.
[0030] In further aspect of the present disclosure, the system wherein vertical and
lateral dimensions of the primary components are engineered resulting in the reduction
of vertical and lateral dimensions of the primary components in the range of minimum
of about 5-10 times.
[0031] In yet another aspect of the present disclosure, the system wherein the vertical
and lateral dimensions of auxiliary components, such as vacuum pumps are also
reduced considerably.
[0032] In still another aspect of the present disclosure, compact apparatuses, which are
integrally and modularly inter-connected for substrate manipulation inside the
enclosure includes apparatuses to perform functions such as lithography, physical
vapour deposition, etching, baking, spin coating etc.
[0033] In yet another aspect of the present invention, a system wherein micro
fabrication is performed on a desk.
[0034] The embodiments of the present system of the disclosure are now described, in
an exemplary manner, by referring initially to FIG.4. FIG.4 depicts a system for the
fabrication of microstructures, on substrates, having portable and miniaturized
cleanroom architecture 100. The system 100 comprises an enclosure 101, built with
surrounding walls 102, having compact dimensions and equipped to be mounted on a
small platform, a stand or a table 103, with a user positioned outside the enclosure 101.
The enclosure 101 is exemplarily shown as a box-like structure with an inner space 104
to accommodate an arrangement of the various components or modules of the system
100, in a modular manner, as hereinafter described. The enclosure 101 is shown as a
rectangular box in FIG.4. However, the enclosure 101 can be made in other suitable
shapes as long as it permits an inner space for the arrangement of the microfabrication
components. The components or modules of the system 100 are operable remotely by
user, without physically intervening with the manipulation of the various components of the system 100 during the course of the microfabrication process. The enclosure 101
is provided with suitable portable and mobile means and can be accommodated on
smaller platforms, such as desks, without warranting any need for clean rooms and
large infrastructure.
[0035] Guide rails 105 are connected to the walls 102 of the enclosure 101, as shown
in FIG.4. The enclosure 101 is provided with a passage or an opening, through which a
movable rack 106 is arranged in the enclosure 101 and provided with corresponding
guide channels to slide through the guide rails 105. The movable rack 106 acts as base
member on which various modules of the system are mounted.
[0036] A lid 107 is connected to the movable rack 106, preferably on its front portion,
to act as a sealing member of the enclosure 101 when the movable rack 106 is moved
into the enclosure 101. A window 108 is arranged on the lid 107, which is covered with
a transparent material, to provide an inner view of the various components of the
system 100. In this embodiment, the opening of the enclosure is shown in the front
portion of the enclosure 101, it is understood here that the opening with the lid 107 can
be provided to the enclosure 101 on any side of the enclosure, including plurality of
openings and lids. The enclosure 101 can be hermitically sealed and an inert
atmosphere is maintained inside the enclosure 101 through the supply of inert gases
through conduits.
[0037] Rolling means 109 and 110 with suitable locking arrangement are connected to
the bottom portion of the desk 103 to facilitate the movement and locking of the desk
103 and move and lock the movement of the enclosure at a pre-determined place. A
desirable sensor-activated lock-an-open arrangement can be incorporated to the
enclosure 101 to open the lid 107 only under ambient and desirable conditions and after
the completion of all the processes.
[0038] The enclosure 101 is evacuated using external vacuum pump or provided with
an inert atmosphere. All the connections inside the enclosure 101 are made using
vacuum sealed connectors. The loading and unloading of consumables will be an
occasional exercise. The Si pre-cut pieces (samples) are kept inside in a magazine to
provide for various trials of making and optimizing device fabrication, without
interrupting the inert or vacuum atmosphere.
[0039] In another aspect of the present disclosure, the modular integration of
apparatuses or devices that are required for the fabrication of microstructures on
substrates is shown in FIG.4.
[0040] The inner area of the enclosure 101 is provided with a base 108 on which
various miniaturized modules that are required to perform functions viz., substrate
cleaning module 109, material growth on substrates 110, oxidation of substrates 111,
physical vapor deposition of substrates 111, photolithography 112 and substrate
manipulation 113 are mounted on the base 108 and are integrally connected, as shown
in FIG.5. The various integrated modules of the system of the present disclosure as
shown in FIG.5 are controlled, monitored and executed by a control panel and a digital
processor.
[0041] The broad system architecture of the present disclosure is as shown in FIG.6,
with all the modules are integrated to function as single automated unit. The various
functional modules of the system are implemented by an automated material handling
system whereby human intervention is avoided. The complete processing cycle of the
substrate is performed inside the enclosure 101 as shown in FIG.6.
[0042] As shown in FIG.6a, various auxiliary components such as vacuum pumps,
power systems, control panel etc., are positioned outside the enclosure 101 and
functionally connected to the various modules of the system.
[0043] The functional aspects of various modules as shown in FIG.6 and FIG.6a are
handled by a material handler, which is a digital processor, programmed to execute
automated functions of the modules of the system.
[0044] In another aspect of the present disclosure, the substrate cleaning module 109,
as shown in FIG.7 includes a portable chemical deck 114 to hold a plurality of
chemical dispensers 115, is mounted along the longitudinal periphery of the base 108,
and is elevated from the ground level of the base 108. A pair of vertical structures 116
and 116a are mounted on the base 108 and erected along the other longitudinal
periphery of the base 108 as shown in FIG.4. A slider 117 is arranged to extend along
the Y-axis of the base 108. A slider 118 is connected to the slider 117 and positioned
substantially perpendicular to the axis of the slider 117 and disposed to extend along Xaxis of the base 108. A container 119 is connected to the slider 118. The sliders 117 and
118 are equipped to move along their respective X and Y axes, thereby carrying along
the container 119, which holds a substrate, towards and along the chemical desk, to
receive the dispensed chemicals from the dispensers 116. Each of the chemical
dispensers 115 is provided with a valve 120, preferably a solenoid valve to regulate the
flow of chemical from the dispenser 115. A reservoir 121 is arranged in conjunction
with the dispensers 115 to regulate the pressure drop during the filling of the containers
with chemicals. A heater and sonicator 122 is also provided and connected to the
container 119. A drain member 123 is mounted on the base 108 and aligned with
chemical dispensers 115 to collect and drain out the excess or spilled chemicals. The
various functions of the substrate cleaning module 109 are performed by a digital
processor.
[0045] In another aspect of the present disclosure, the substrate manipulation module
of the system is now described by referring to FIG.8. The substrate manipulation
module comprises a first horizontal slider member 124 which is connected to the
vertical structures 116 and 116a that are mounted on the base 108. A second horizontal
slider member 125 is connected to the first horizontal slider member 124 and arranged
perpendicular to the planar axis of the first horizontal slider member 124. The first and
second horizontal slider members 124 and 125 are arranged to slide on y and x axes
along the plane of the base 108. A vertical slider member 126 is connected to the
second horizontal slider member 125 and disposed to move in vertical direction and
along Z-axis to the plane of the base 108. A substrate gripper 127 is fixed to the vertical
slider member 126 to hold and move the substrate through the different modules for
processing. Accordingly, in this arrangement, the movements of the substrate during its
manipulation are controlled automatically by the digital processor and without any
human intervention.
[0046] In another aspect of the present disclosure, a material growth module is
mounted on the base 108, as shown in FIG.9. The material growth module, which is
advantageously an oxidation furnace, comprises a furnace body holder 127, which is
connected to the base 108. The furnace body holder 127 is provide with a bottom plate
128 connected to the base 108. Side walls 129 and 130 are seamlessly connected to the
ends of the bottom plate 128, thereby providing an intervening space between the side
walls 129 and 130. A chamber with an inlet is anchored to the side walls 129 and 130
and suspended between the side wings side walls 129 and 130. The chamber is a
compact chamber where the oxidation of the substrate takes place is equipped to handle
the internal temperature of over 11000
C. The chamber is also adapted to perform

oxidation under either dry or wet conditions by using either dry oxygen or a water
steam sources respectively. The suspension of the chamber prevents the direct contact
of the chamber with the base 108. A cylinder member 131 with a piston (not shown in
the drawing) and a movable shaft 132 is connected to the side wing of the bracket 125.
The cylinder member 131 provides a bi-directional drive to the movable shaft 132. A
boat holder 133 with its one end connected to the movable shaft 132 and other end is
permitted to pass through the inlet and terminate inside the chamber. A boat 134 is
connected to the boat holder to carry the substrate into the chamber. A quartz tube 135
is arranged in the chamber. The oxidation of the substrate is performed in the quartz
tube 135. The loading, transmission and unloading of the substrate through the boat
holder 133 is performed automatically with remote controls.
[0047] In further aspect of the present disclosure, a photolithographic module is also
mounted on the base 108 and connected to the base 108 through photolithography base
136 as shown in FIG.10 on which a compact photolithography device 137 is mounted,
which is used to write patterns on the substrate having a layer of photosensitive
polymer. The lithography device 137 includes an illumination source, optics to write
desired patterns on the substrate. The photolithography machine is adapted to move x, y
and z planes while creating patterns.
[0048] In yet another aspect of the present invention, a spin coater module is arranged
on the base 108 and is integrated with other modules of the system, as shown in
FIG.11. The spin coater module comprises a spin coater machine comprising, a support
frame 138, to which a container 139 containing a photoresist material is connected. A
driving member 140, which is preferably a motor, is mounted on the base 108 on a
platform, along with spin coater 141 of the spin coating machine and connected to the
support frame 138. The container 139 is provided with a reservoir and a valve, to
control the flow of the photoresist material. The substrate is placed in the spin coater
141 and rotated at high speed to spread the photoresist material uniformly on the
substrate.
[0049] In further aspect of the present disclosure, a physical vapour deposition module
is integrated with other modules as shown in FIG.12. In an exemplary manner a
sputtering module 142 is incorporated in the enclosure 101 to convert gas into plasma
and the positively charged ions in that plasma are attracted towards the cathode, which
is a material to be deposited. These ions knock out the material in the form of atoms the
target, because of their high energy. These dug out dust of atoms settles on the Si
substrate. This is one of the materials adding process in the micro and nanofabrication
domain. This operation can be performed by various other methods like Atomic layer
deposition (ALD), Thermal evaporation, E-beam evaporation, Pulsed laser deposition
(PLD) Electrodeposition etc.
[0050] The present disclosure also provides a method for compact microfabrication of
miniature structures on substrates as shown in the flow drawing FIG.13. The method is
performed initially by cutting the Si wafers into small pieces of desired dimensions.
The Si wafers (samples) are then loaded in a magazine for use in the process. The
materials that are required for the process such as reagents, solvents, water, photoresist
etc., are pre-filled in the respective containers of the system. The lid of the system is
closed and the system is evacuated. The system can also purged with inert gases to
maintain the inert atmosphere. A user selects a sample and directs the sample to reach
any of the system modules in order to subject the sample to a pre-determined process
steps, using fully automated material handling module. Normally, the sample is cleaned
initially in a material cleaning module in the presence of chemicals and reagents,
without any manual intervention. The cleaned sample is then transmitted automatically
to other modules of the system to perform functions such as material growth, material
deposition, material removal, and photolithography, to obtain the sample that is
fabricated with desired microstructures. The various steps of the process of the present
invention is controlled and executed outside the enclosure, through a digital processor.
Advantages:
[0051] The system of the present invention includes a clean room that is miniaturized
and fully portable. The system of the present invention can be installed on smaller
platforms such as desks, effortlessly. The system “Fab On Desk” of the present
invention, is devoid of any internal auxiliary equipment and such auxiliary equipment
are connected to the “Fab On Desk” externally, as required. The microfabrication
process using the system of the present invention is performed without a direct human
intervention, at all the stages of the process. The system can be adapted to use existing
and upcoming micro fabrication processes. The system provides flexibility in
incorporating various fabrication modules at minimal time, efforts and cost. The system
of the present invention saves considerable amount of energy and raw materials thereby
providing a first of its kind green micro fabrication system process. The system of the
present invention substantially eliminates the human intervention from the
microfabrication processes, which are very sensitive to the contamination issue, where
the intervention of humans is one of the major sources of contamination inside the
existing cleanrooms. The system of the present invention also ensures safe working
conditions for humans by avoiding the direct exposure to the hazardous chemicals, UV
light and not so work-conducive atmosphere for humans.

We Claim:
1. A portable and miniaturized cleanroom system for fabrication of
microstructures, comprising:
(a) a table-top and portable enclosure 101 with a lid 107, disposed on a
movable platform 103;
(b) a movable rack 106 with a base 108 connected to said platform 103;
(c) a substrate cleaning module 109 and substrate manipulating module 113,
material growth module 110, photolithographic module 112, a spin coater
module 141, physical vapour deposition module 142, disposed on said base
108 and are integrally connected; and
(d) a material handler.
2. The system as claimed in claim 1, wherein said substrate cleaning module
comprising;
(a) a portable chemical deck 114 to hold a plurality of chemical dispensers 115
disposed above a base 108, and
(b) a movable container 119 to hold a substrate 110, disposed on movable
sliders 117 and 118, to receive chemical dispensing from said chemical
dispensers 115.
3. The system as claimed in claim 2, wherein said movable container 119 disposed
to move in X and Y axes of said base 108.
4. The system as claimed in claim 1, wherein said substrate manipulating module
113, comprising:
(a) horizontal sliding members 124 and 125 connected to vertical structures 116
and 116a; and
(b) a vertical sliding member 126 with a substrate gripper 127 operably
connected to said horizontal sliding members 125 and 125 and disposed to
hold and move said substrate, through said modules.
5. The system as claimed in claim 1, wherein said material growth module 110 is
an oxidation furnace.
6. The system as claimed in claim 1, wherein said photolithographic module 112
comprises a photolithographic device.
7. The system as claimed in claim 1, wherein said spin coating module 141
comprises a spin coating device.
8. The system as claimed in claim 1, wherein said physical vapour deposition
module comprises one of sputterer, atomic layer depositor, thermal evaporator,
e-beam evaporator, pulsed laser depositor or an electro depositor.
9. The system as claimed in claim 1, wherein said material handler is a digital
processor, said material handler disposed to control said modules.