DESC:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to the field of electron assisted lithography. In particular, the present disclosure relates to a lithographic system with high throughput, improved repeatability of pattern generation and increased operating life, and a method thereof.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Conventional fabrication of microelectronic or semiconductor devices involves lithography processes for engineering specific designs on a substrate. Existing technology in the field of pattern generation includes optical lithography, e-beam lithography, selective anodic dissolution, dip-pen lithography etc. Optical lithography and e-beam lithography systems include expensive and complex set of equipment and hence, special training is required to be given to users to handle the equipment. Optical lithography is used to fabricate features having micrometre dimensions, whereas e-beam technique can also be used for fabricating patterns with sub-micrometre feature generation. Some simpler methods based on localized chemical reaction by passing electric current have also been developed for pattern generation. These techniques are based on the selective anodic dissolution of a metal film. However, there are limitations associated with implementing these techniques such as tip damage, sample damage, debris formation, non- repeatability, rate of pattern generation etc.
[0004] In addition, although a few other techniques of micromachining by electrochemical process have been reported, all of these have been used for the fabrication of a certain design or structure by etching of bulk material. These techniques have not been utilized on thin metal film for the pattern drawing process. Also, the electrolyte used in these processes are often hazardous chemicals.
[0005] In the known art, similar electric field chemical reaction has been used for the pattern drawing on metal films. However, the process is carried out only in the air environments, where it is highly uncontrolled leading to issues in achieving resolution and repeatability of patterns. Other limitations include tip and sample damage due to contact mode operation.
[0006] Atomic force microscopy (AFM) has been used for the direct writing process on metal film where the AFM probe tip is used as cathode electrode. The technique has been used to draw patterns of dimension of 25 nm or less. However, the process is not repeatable mainly because of the sticking of the material formed during the chemical reaction to the tip. The new material stuck to the probe tip decreases the tip-conductivity, which reduces the probability of further reaction and also effects the resolution of the pattern because of its increased diameter. After a few trials, a pattern cannot at all be drawn by the same tip and requires replacement of the tip, which is expensive, and also prohibits a possibility of high throughput requirements.
[0007] There is, therefore, a requirement in the art for an approach for generating patterns on metal films that can achieve a high degree of repeatability of patterns, while being able to provide high throughput and having a high operating life.
[0008] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

OBJECTS OF THE PRESENT DISCLOSURE
[0009] A general object of the present disclosure is to provide a non-contact, mask less, voltage induced electrochemical lithography technique.
[0010] Another object of the present disclosure is to provide an electrochemical lithography system and method for generating patterns on metal films with a high degree of repeatability of patterns.
[0011] Another object of the present disclosure is to provide an electrochemical lithography system and method for providing high throughput and having a high operating life.
[0012] Another object of the present disclosure is to provide an electrochemical lithography system and method, which includes DI water that is non-hazardous, non-corrosive, and eco-friendly.
[0013] Another object of the present disclosure is to provide an efficient, eco-friendly, and eco-friendly voltage induced electrochemical lithography technique.

SUMMARY
[0014] Aspects of the present disclosure relates, in general, to the field of electron assisted lithography. In particular, the present disclosure relates to a lithographic system with high throughput, improved repeatability of pattern generation and increased operating life, and a method thereof.
[0015] An aspect of the present disclosure pertains to an efficient, cost-effective, and eco-friendly water based electrochemical lithography system. The lithography system comprises a container that is adapted to accommodate a sample, where the sample may include a metal film deposited on a substrate. Further, the container may be filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water.
[0016] In an aspect, the system comprises a metal probe configured with an electrical power source, the electrical power source may be activated such that a pre-defined potential difference is created between a surface of the sample and a tip of the metal probe. The creation of pre-defined potential difference between the surface of the sample and the tip of the metal probe further induces a chemical reaction in the metal film to facilitate etching of the metal film.
[0017] In an aspect, the system comprises a movement control unit operatively coupled to any or a combination of the metal probe and the sample, where the movement control unit may be configured to facilitate controlled movement of the metal probe along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.
[0018] In an aspect, the metal film is constituted such that the residuals produced, during the chemical reaction induced, may get dissolved in the DI water, therefore enabling creation of a clean and residual free pattern over the sample. Moreover, due to non-corrosive nature of the DI water, an accurate pattern can be created on the sample. Further, the DI water provides a low resistive path for movement of the metal probe, and also functions as a reactant for the induced chemical reaction occurring between the tip of the metal probe and the metal film. As the DI water serves as a medium between the metal probe and the metal film, therefore a non-contact etching can be carried out, which reduces wear and tear of the metal probe and the sample, thereby making the technique more viable and economic.
[0019] Another aspect of the present disclosure pertains to an efficient, cost-effective, and eco-friendly water based electrochemical lithography method that includes placing a sample, comprising a metal film deposited on a substrate, in a container filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water. The method also includes creating, through an electric power source, a pre-defined potential difference between a surface of the sample and a tip of a metal probe, and correspondingly inducing a chemical reaction in the metal film to facilitate etching of the metal film. Further, the method includes moving, through a movement control unit, of the metal probe in a controlled manner along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.

BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.
[0021] FIGs. 1A and 1B illustrates an exemplary schematic representation and an image of a water based electrochemical lithography (W-ELG) system, to elaborate upon its working in accordance with an embodiment of the present disclosure.
[0022] FIGs. 2A and 2B illustrate patterns generated using the proposed system and conventional lithographic approaches respectively.
[0023] FIGs. 3A – 3C illustrate exemplary etches of different widths achieved using the proposed system, in accordance with an embodiment of the present disclosure.
[0024] FIGs. 4A and 4B illustrate probe tips, after being used to generate a few patterns, of the proposed W-ELG system and conventional lithographic system respectively.
[0025] FIG. 5 illustrates a method for carrying out water based electrochemical lithography, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0026] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0027] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0028] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0029] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. The invention disclosed may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof.
[0030] Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.
[0031] The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non – claimed element essential to the practice of the invention.
[0032] Embodiments of the present disclosure relates, in general, to the field of electron assisted lithography. In particular, the present disclosure relates to a lithographic system with high throughput, improved repeatability of pattern generation and increased operating life, and a method thereof.
[0033] According to an embodiment, the present disclosure pertains to an efficient water based electrochemical lithography system. The system comprises: a container adapted to accommodate a sample comprising a metal film deposited on a substrate, wherein the container is filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water; a metal probe, wherein a pre-defined potential difference is created between a surface of the sample, and a tip of the metal probe, which correspondingly induces a chemical reaction in the metal film to facilitate etching of the metal film; and a movement control unit operatively coupled to any or a combination of the metal probe and the sample, the movement control unit configured to facilitate controlled movement of the metal probe along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.
[0034] In an embodiment, the metal probe can function as a cathode, and the sample can function as an anode, and wherein the metal probe and the sample can be electrically configured with an electrical power source, to create the pre-defined potential difference between the surface of the sample, and the tip of the metal probe.
[0035] In an embodiment, the DI water can be adapted to dissolve any residual produced during etching of the sample.
[0036] In an embodiment, the DI water can provide a low resistive path for movement of the metal probe, and can also function as a reactant for the induced chemical reaction occurring between the metal probe and the metal film.
[0037] In an embodiment, the sample can be electrically grounded, which allows uniform current distribution between the tip of the metal probe and the sample.
[0038] In an embodiment, any or a combination of the applied potential difference between the metal probe and the sample and a gap between the metal probe and the sample can be adjusted to control a rate of etching of the sample.
[0039] In an embodiment, the sample can be placed on a movable stage which is operatively coupled to the movement control unit, and is placed horizontally with respect to the metal probe.
[0040] In an embodiment, the sample can be configured using the metal film made up of any or a combination of Chromium and Molybdenum deposited on a Silicon based substrate.
[0041] According to another embodiment, the present disclosure pertains to an efficient water based electrochemical lithography method. The method comprises: placing a sample, comprising a metal film deposited on a substrate, in a container filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water; creating, through an electric power source, a pre-defined potential difference between a surface of the sample and a tip of a metal probe, and correspondingly inducing a chemical reaction in the metal film to facilitate etching of the metal film; and moving, through a movement control unit, of the metal probe in a controlled manner along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.
[0042] In an embodiment, the method comprises placing the sample horizontally with respect to the metal probe on a movable stage, and wherein any or a combination of the applied potential difference between the metal probe and the sample and a gap between the metal probe and the sample can be adjusted for controlling a rate of etching of the sample.
[0043] FIGs. 1A and 1B illustrates an exemplary schematic representation and an image of a water based electrochemical lithography (W-ELG) system, in accordance with an embodiment of the present disclosure. The water based electrochemical lithography (W-ELG) system 100 (interchangeably referred to as system 100, herein) includes a metal probe tip 102 (hereinafter, also referred to as “probe” or “tip”) that functions to etch a surface of a sample 104. The sample can be a metal film that is to be etched that has been deposited on a substrate. The probe 102 can function as a cathode and the sample 104 can function as a node electrode. The sample can be placed on a movable Z-stage 106.
[0044] In an embodiment, the sample 104 is placed within a container 108, and the DI water is filled in the container 108 such that the sample 104 can be completely submerged.
[0045] In another embodiment, a constant potential difference can be created across the surface of the sample 104 and the tip 102. Water molecules, at the tip 102, may split due to high current density and induces a chemical reaction on the surface of the film to be etched. The chemical reaction can produce a chemical, which dissolves in the DI water, thereby etching away the film on the sample 104.
[0046] The DI water medium between the tip 102 and the sample 104 can provide a low resistive path for tip movement and also functions as a reactant for the chemical reaction occurring between the tip 102 and the film on the sample 104. Further, the sample 104 is grounded from all sides allowing for current distribution between the tip 102 and the sample 104 to be uniform.
[0047] In an embodiment, the applied potential difference (also referred to as voltage, herein) and the gap between the tip 102 and the sample 104 can determine the rate of etching of the film of the sample 104. The gap can be changed as required by movement of the Z-stage 106.
[0048] In another embodiment, the tip 102 can be adapted to move on a pre-determined path. The movement can be controlled through a movement control unit (not shown in the figure) that can be coupled with the tip 102. As the tip 102 moves over the surface of the film of the sample 104, the film can get selectively etched underneath the tip 102. The chemical formed due to the chemical reaction on the film may get dissolved in the DI water and may leave no residual on the etched portion of the film 104 as well as the tip 102. As the film gets etched, the substrate of the sample 104 can get exposed under the etched sections of the film. The trench pattern formed on the film can be transferred to the desired substrate by conventional lift-off methods.
[0049] The gap between the tip 102 and the sample 104 plays an important role in the etching process. For patterning of a sample to occur, it is vital that the gap be maintained at across the surface of the sample 104, i.e. it is vital for the sample 104 to be completely horizontal. This is ensured by touching the tip 102 on multiple points on the surface of the sample 104 while applying a small voltage. If the current measured at the points are the same, then the sample 104 can be considered to be horizontal. The sample 104 can be moved using a spring screw system attached to each corner of the sample 104.
[0050] The proposed W-ELG system 100 uses DI water as a medium in which etching occurs. Due to lack of electrolytes, it can be ensured that reaction between the tip 102 and the sample 104 can occur without any interference from any electrolytes present in the DI water, thereby improving the accuracy of the pattern being tracked by the tip 102.
[0051] The proposed W-ELG system 100 is low cost and environment friendly, as it uses DI water, an easily available and environmentally friendly reagent. Further, a faster rate of chemical reaction and the dissolution of the formed chemical product in DI water mean that the etching process can occur at higher speeds or rates compared to conventional electron mediated lithographic approaches, thereby allowing for higher throughput from the proposed system 100 compared with conventional lithographic approaches. The proposed W-ELG system 100, can be implemented, for instance, in fabrication processes for micro-electronics and semiconductor devices such as sensors, actuators, transistors, and the likes.
[0052] In an exemplary instance, the metal film to be etched can be chromium (Cr), Molybdenum (Mo) etc. and the substrate can be Silicon (Si) based.
[0053] Embodiments described hereunder shall demonstrate the proposed W-ELG system 100 using Chromium film on an Si/SiO2 substrate as an illustrative sample.
[0054] FIGs. 2A and 2B illustrate patterns generated using the proposed system 100 and conventional lithographic approaches respectively. Due to limitations of ability to pass electric currents in reagents used in conventional electron induced lithographic approaches, there is a constraint to etching rate and, consequently, patterning rate of a sample using the conventional approach. Typically, using approaches such as STM and AFM based lithographic techniques, patterning rates of around 10 µm/s can be achieved. Using the proposed W-ELG system 100, patterning rates as high as 1.5 mm/s can be achieved.
[0055] FIGs. 3A – 3C illustrate exemplary etches of different widths achieved using the proposed system, in accordance with an embodiment of the present disclosure. Typically, width achieved using conventional approaches ranges from 9 – 200 nm. Using the proposed W-ELG system, widths from a few micrometres up to a few millimetres can be achieved.
[0056] FIGs. 4A and 4B illustrate probe tips, after being used to generate a few patterns, of the proposed W-ELG system 100 and conventional lithographic system respectively. As the proposed W-ELG system 100 etches the sample in a water medium, and there is little limitation to the quantity of water that can be used, the chemical product formed can be dissolved easily. This not only removes debris produced due to the chemical reaction, from the patterns, but also keeps the tip clean, as shown in FIG. 4A. The patterns produced using the proposed W-ELG system are therefore relatively free of debris, consequently improving the operating life of the tip.
[0057] Further, the conventional approaches have issues related to control of reaction product formed at the tip. However, due to uniform nature of the DI water medium, the proposed W-ELG system 100 may allow for better control of formation of reaction products (Chromium Oxide, in the case of Chromium film over Si/SiO2 substrate) irrespective of etching parameters such as speed of movement of the tip, voltage applied etc. Additionally, due to use of DI water as a medium, the costs of the proposed W-ELG system 100 is significantly lower than other conventional STM or AFM based approaches. As a result, the operational cost of the proposed W-ELG system 100 is also lowered.
[0058] FIG. 5 illustrates a method 500 for carrying out water based electrochemical lithography, in accordance with an embodiment of the present disclosure.
[0059] In an embodiment, the method 500 can include placing, at block 502, a sample, comprising a metal film deposited on a substrate, in a container filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water.
[0060] In an embodiment, the method 500 can include creating, at block 504, through an electric power source, a pre-defined potential difference between a surface of the sample, placed in the container at the block 502, and a tip of a metal probe, and correspondingly inducing a chemical reaction in the metal film to facilitate etching of the metal film.
[0061] In an embodiment, the method 500 can include moving, at block 506, through a movement control unit, of the metal probe in a controlled manner along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.
[0062] In an embodiment, the method 500 can also include placing the sample horizontally with respect to the metal probe on a movable stage, and wherein any or a combination of the applied potential difference between the metal probe and the sample and a gap between the metal probe and the sample can be adjusted for controlling a rate of etching of the sample.
[0063] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive patent matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “includes” and “including” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0064] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practised with modification within the spirit and scope of the appended claims.
[0065] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0066] The present disclosure provides a a non-contact, mask less, voltage induced electrochemical lithography technique.
[0067] The present disclosure provides an electrochemical lithography system and method for generating patterns on metal films with a high degree of repeatability of patterns.
[0068] The present disclosure provides an electrochemical lithography system and method for providing high throughput and having a high operating life.
[0069] The present disclosure provides an electrochemical lithography system and method, which includes DI water that is non-hazardous, non-corrosive, and eco-friendly.
[0070] The present disclosure provides an efficient, eco-friendly, and eco-friendly voltage induced electrochemical lithography technique.
,CLAIMS:1. A water based electrochemical lithography system comprising:
a container adapted to accommodate a sample comprising a metal film deposited on a substrate, wherein the container is filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water;
a metal probe, wherein a pre-defined potential difference is created between a surface of the sample, and a tip of the metal probe, which correspondingly induces a chemical reaction in the metal film to facilitate etching of the metal film; and
a movement control unit operatively coupled to any or a combination of the metal probe and the sample, the movement control unit configured to facilitate controlled movement of the metal probe along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.
2. The system as claimed in claim 1, wherein the metal probe functions as a cathode, and the sample functions as an anode, and wherein the metal probe and the sample are electrically configured with an electrical power source, to create the pre-defined potential difference between the surface of the sample, and the tip of the metal probe.
3. The system as claimed in claim 1, wherein the DI water is adapted to dissolve any residual produced during etching of the sample.
4. The system as claimed in claim 1, wherein the DI water provides a low resistive path for movement of the metal probe, and also functions as a reactant for the induced chemical reaction occurring between the metal probe and the metal film.
5. The system as claimed in claim 1, wherein the sample is electrically grounded, which allows uniform current distribution between the tip of the metal probe and the sample.
6. The system as claimed in claim 1, wherein any or a combination of the applied potential difference between the metal probe and the sample and a gap between the metal probe and the sample are adjusted to control a rate of etching of the sample.
7. The system as claimed in claim 6, wherein the sample is placed on a movable stage which is operatively coupled to the movement control unit, and is placed horizontally with respect to the metal probe.
8. The system as claimed in claim 1, wherein the sample is configured using the metal film made up of any or a combination of Chromium and Molybdenum deposited on a Silicon based substrate.
9. A method for carrying out water based electrochemical lithography, the method comprising:
placing a sample, comprising a metal film deposited on a substrate, in a container filled with deionized (DI) water up to a predefined level such that a top surface of the sample is submerged in the DI water;
creating, through an electric power source, a pre-defined potential difference between a surface of the sample and a tip of a metal probe, and correspondingly inducing a chemical reaction in the metal film to facilitate etching of the metal film; and
moving, through a movement control unit, of the metal probe in a controlled manner along a pre-determined path over the sample, thereby enabling controlled electrochemical lithography.
10. The method as claimed in claim 9, wherein the method comprises placing the sample horizontally with respect to the metal probe on a movable stage, and
wherein any or a combination of the applied potential difference between the metal probe and the sample and a gap between the metal probe and the sample are being adjusted for controlling a rate of etching of the sample.