Methods and apparatus for forming patterned layers of material

Abstract

Methods and apparatus for forming patterned layers of material are disclosed. In one arrangement, a deposition process material is provided in gaseous form. A layer of the deposition process material is formed on a substrate by causing condensation or deposition of the gaseous deposition process material. Selected portions of the layer of deposition process material are irradiated to modify the deposition process material in the selected portions.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to European application 20160615.9, filed on 03 March 2020, and the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present invention relates to a method and apparatus for forming a patterned layer of material. BACKGROUND

[0004] As semiconductor manufacturing processes continue to advance, the size of circuit elements has continually decreased while the amount of functional elements, such as transistors, per device has steadily increased, following a trend often referred to as “Moore’s Law”. To keep up with Moore’s Law, the semiconductor industry is pursuing techniques that enable the creation of increasingly smaller features.

[0005] There are various deposition techniques for manufacturing two-dimensional materials. Such deposition techniques include, for example, chemical vapor deposition (CVD) and atomic layer deposition (ALD). It is of interest to use such deposition techniques to form device structures, such as circuit elements, as part of a semiconductor manufacturing process. It has proven difficult to achieve an acceptably high throughput. For example, it is difficult to configure a deposition process, such as CVD and ALD, such that deposition occurs rapidly in a desired pattern while maintaining a high quality of the deposited material. SUMMARY

[0006] It is an object of the present invention to provide an alternative or improved method of forming a patterned layer.

[0007] According to an aspect, there is provided a method of forming a patterned layer of material, comprising: providing a deposition process material in a gaseous form; forming a layer of the deposition process material on a substrate by causing condensation or deposition of the gaseous deposition process material; and irradiating selected portions of the layer of deposition process material to modify the deposition process material in the selected portions.

[0008] Thus, a method of forming a layer of a liquid or solid of a deposition process material (e.g., a precursor material for a deposition process) from a gas is provided. The gas can be provided, for example, at a pressure close to or at the saturation vapor pressure. The layer is then modified in selected portions by exposure to radiation as part of a deposition process. Irradiating a layer in a liquid or solid state significantly increases the deposition rate and / or reduces the required radiation dose compared to alternative radiation-induced deposition processes involving gaseous precursors. Forming the liquid or solid layer in situ from a gas allows the layer to be provided with a suitable thickness in a controlled manner. Forming the layer from a gas also facilitates removal of unmodified material from the layer after the irradiation. This can be achieved, for example, by reversing the thermodynamic conditions used to promote the formation of the liquid or solid layer (e.g., by reducing the partial pressure of the gas or by warming the substrate). No separate processing steps (e.g., etching, rinsing, cleaning) are required to remove the unmodified material. The method allows a pattern to be formed directly on a complex architecture without the need for a fill step or the use of sacrificial components. Additional processing steps (e.g., exposing a subsequent layer) can be performed without moving the substrate to a different substrate table or processing apparatus, thereby improving overlay errors.

[0009] In embodiments, the formation of the layer of the deposition process material is at least partially achieved by applying a cooling process to the substrate to maintain the substrate below ambient temperature. Cooling of the substrate means that the deposition process material will preferentially condense or deposit on the substrate W relative to other elements that gaseous deposition process material can come into contact with, thereby reducing or eliminating unwanted contamination of the other elements (e.g., optical elements) by condensing or depositing the deposition process material on the other elements (e.g., optical elements).

[0010] According to an aspect, a method of forming a patterned layer of a material is provided, comprising: providing a substrate in a chamber; supplying a gas of a deposition process material to the chamber at a temperature higher than the substrate, the temperature difference between the substrate and the gas causing a high-density gaseous layer of deposition process material to form in close proximity to the substrate, the high-density gaseous layer of deposition process material having a higher density than the gas of the deposition process material in other regions of the chamber; and irradiating selected portions of the layer of deposition process material to modify the deposition process material in the selected portions.

[0011] Thus, a method is provided of forming a high-density gaseous layer of deposition process material (e.g. a precursor material for a deposition process) from a lower-density gas. The layer is then modified in selected portions by exposure to radiation as part of a deposition process. Irradiating the layer in a high-density state significantly increases the deposition rate and / or reduces the required radiation dose compared to alternative radiation-induced deposition processes involving lower-density gaseous precursors, with a low or no risk of contamination due to unwanted condensation of deposition process material on sensitive device elements.

[0012] In embodiments, the irradiation of the selected portions is performed using radiation having a wavelength of less than 100 nm. Using such low-wavelength radiation allows high resolution to be achieved, as well as providing efficient driving of a range of deposition processes facilitated by secondary electrons. At such wavelengths, the photons are primarily absorbed by the substrate, so there is little or no requirement for the deposition process material itself to have high absorption. This broadens the choice of composition of deposition process material (e.g. precursors for deposition).

[0013] In embodiments, the irradiation of the selected portions is performed using an electron beam. Providing a high-density gas, liquid or solid layer of deposition process material helps to maximise throughput, which can otherwise be challenging in processes relying on electron beam-based irradiation.

[0014] According to an aspect, there is provided a method of forming a patterned layer of material, comprising: forming a layer of deposition process material on a substrate by condensation or deposition of deposition process material from a gas; and irradiating selected portions of the formed layer of deposition process material to modify the deposition process material in the selected portions.

[0015] According to an aspect, there is provided a method of forming a patterned layer of material, comprising: forming a layer of deposition process material on a substrate by condensation or deposition of deposition process material from a gas; and irradiating selected portions of the formed layer of deposition process material to modify the deposition process material in the selected portions. BRIEF DESCRIPTION OF DRAWINGS

[0016] Embodiments of the invention will now be described by way of example only, with reference to the accompanying illustrative drawings, in which:

[0017] Figure 1 A first example of a lithography system including lithography equipment and a radiation source is depicted;

[0018] Figure 2 A second example of a lithography system including lithography equipment and a radiation source is depicted;

[0019] Figure 3 A schematic depiction of the irradiation of a selected portion of the substrate during the first step of the atomic layer deposition process;

[0020] Figure 4 schematic depiction Figure 3 The steps in the atomic layer deposition process described in the image are the subsequent steps.

[0021] Figure 5 A lithography apparatus for providing radiation to an environmental control system according to an embodiment is schematically depicted;

[0022] Figure 6 It is a schematic depiction of the energy diagram of the potential barrier for secondary electrons escaping from a solid substrate to the gaseous environment above the substrate;

[0023] Figure 7 This is a schematic side cross-sectional view of a substrate having a deposition process material provided in gaseous form above the substrate;

[0024] Figure 8 It is a schematic depiction of the energy diagram of the potential barrier for secondary electrons escaping from a solid substrate to a high-density layer of material deposited above the substrate;

[0025] Figure 9 It is a schematic side cross-sectional view of a substrate having deposited process material in a high-density layer disposed above the substrate;

[0026] Figure 10 It is an optical microscope image of a rectangular area exposed to EUV radiation during the testing process;

[0027] Figure 11 An optical microscope image of a portion of the boundary of a rectangular region, the portion of which indicates optical contrast and step height across the entire boundary between the interior of the rectangular region where radiation-induced deposition has occurred and the exterior of the rectangular region where radiation-induced deposition has not yet occurred;

[0028] Figure 12 yes Figure 11 An atomic force microscope image of the boundary portion shown in the image;

[0029] Figure 13 is an optical microscope image of another portion of the boundary showing the optical contrast and step height similar to that observed in Figure 11

[0030] Figure 14 is an atomic force microscope image of the portion of the boundary shown in Figure 13

[0031] Figure 15 is a flow chart depicting an example method of patterning a layer of a material. DETAILED DESCRIPTION

[0032] A lithography apparatus is a machine constructed to apply a desired pattern to a substrate. The lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). For example, the lithography apparatus can project a pattern (which can be a latent image) from a patterning device (for example, a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate.

[0033] To project a pattern on a substrate, a lithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithography apparatus can be used to form smaller features on a substrate than those formed using an apparatus that uses radiation with a wavelength of, for example, 193 nm. Such an apparatus can be a lithography apparatus that uses extreme ultraviolet (EUV) radiation, for example, with a wavelength in a range of about 5-100 nm, for example, 6.7 nm or 13.5 nm.

[0034] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultra-violet radiation, for example having a wavelength in the range of about 5-100 nm), as well as electron beam radiation.

[0035] Figure 1 ​​A lithography apparatus LA is schematically depicted. The lithography apparatus LA includes: an irradiation system (also called an irradiator) IL configured to modulate a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning apparatus MA according to certain parameters; a substrate support (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW configured to accurately position the substrate support according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted by the patterning apparatus MA to the radiation beam B onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0036] In operation, the irradiation system IL receives a radiation beam from the radiation source SO, for example, via a beam delivery system BD. The irradiation system IL may include various types of optical components for guiding, shaping, and / or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components or any combination thereof. The irradiator IL can be used to adjust the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the pattern forming apparatus MA.

[0037] The term “projection system” PS as used herein should be interpreted broadly to encompass any type of projection system suitable for the exposure radiation used and / or for other factors such as immersion in liquids or vacuum, including refractive, reflective, reflective-refractive, distorting, magnetic, electromagnetic, and / or electrostatic optical systems or any combination thereof. Any use of the term “projection lens” herein may be considered synonymous with the more general term “projection system” PS.

[0038] Photolithography equipment (LA) can fall into the following categories: at least a portion of the substrate can be covered by a liquid (e.g., water) with a relatively high refractive index to fill the space between the projection system (PS) and the substrate (W), also known as immersion lithography. Further information on immersion techniques is given in US6952253, which is incorporated herein by reference.

[0039] Photolithography equipment (LA) can also be of the type with two or more substrate supports (WT) (also known as "dual platforms"). In such a "multi-platform" machine, substrate supports (WT) can be used in parallel, and / or subsequent exposure steps for preparing substrate W can be performed on substrate W located on one of the substrate supports (WT), while another substrate W on other substrate supports (WT) is used to expose patterns on other substrate W.

[0040] In addition to the substrate support WT, the lithography apparatus LA can include a measurement platform. The measurement platform is arranged to hold a sensor and / or a cleaning device. The sensor can be arranged to measure a property of the projection system PS and / or a property of the radiation beam B. The measurement platform can hold a plurality of sensors. The cleaning device can be arranged to clean a part of the lithography apparatus, for example a part of the projection system PS or a part of the system that provides the immersion liquid. The measurement platform can be moved under the projection system PS when the substrate support WT is away from the projection system PS.

[0041] In operation, the radiation beam B is incident on the patterning device (e.g., mask) MA held on the mask support MT and patterned by a pattern (design layout) present on the patterning device MA. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. By means of the second positioner PW and the position measurement system IF, the substrate support WT can be accurately moved, for example, so as to position a different target portion C in the path of the radiation beam B at a focus and alignment position. Similarly, the first positioner PM and possibly another position sensor (not explicitly depicted in FIG. 1) can be used to accurately position the patterning device MA in the path of the radiation beam B. The patterning device MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. While the substrate alignment marks P1, P2 as illustrated occupy dedicated target portions, the substrate alignment marks P1, P2 can be located in spaces between target portions. When the substrate alignment marks P1, P2 are located between target portions C, the substrate alignment marks P1, P2 are referred to as scribe-lane alignment marks. Figure 1

[0042] Figure 2 A lithographic system is shown comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0043] ​The illumination system IL is configured to condition the EUV radiation beam B before it is incident upon the patterning device MA. The illumination system IL can also include a facetted field mirror device 10 and a facetted pupil mirror device 11. The facetted field mirror device 10 together with the facetted pupil mirror device 11 form a pupil expansion device for expanding the angular range accepted from the beam generated by the source SO and / or for reducing the angular divergence of the beam in the field plane. Other forms of

[0044] After being so conditioned, the EUV radiation beam B is incident on the patterning device MA. As a result of the interaction between the EUV radiation beam B and the patterning device MA, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto a substrate W. For that purpose, the projection system PS can include a plurality of mirrors 13, 14, which are configured to project the patterned EUV radiation beam B' onto a substrate W held by a substrate table WT. The projection system PS can apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image having a dimension smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 can be applied. Although the projection system PS is illustrated as having only two mirrors 13, 14 in Figure 2 The projection system PS can include a different number of mirrors (e.g., six or eight mirrors).

[0045] The substrate W can include a previously formed pattern. In that case, the lithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0046] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen gas) at a pressure well below atmospheric pressure, can be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS.

[0047] The radiation source SO can be a laser-produced plasma (LPP) source, a discharge-produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0048] As mentioned in the introductory part of the description, while there is interest in using deposition techniques such as CVD or ALD to fabricate two-dimensional materials as part of a semiconductor manufacturing process, it has proven difficult to achieve high throughput. The embodiments described below address such problems and / or other problems to thereby provide an alternative and / or improved way of forming patterned layers of material.

[0049] Embodiments of the present disclosure provide a method of forming a patterned layer 22 of material based on illuminating 24 a selected portion 20 of a substrate W, as schematically depicted in Figure 3 and Figure 4 The size and shape of the selected portion 20 define the pattern of the patterned layer 22 of material (e.g., by defining where the desired material is or is not present in the patterned layer of material). For ease of illustration, a simple rectangle is depicted, but it is understood that any complex pattern can be formed subject to the resolution limits of the illumination system used.

[0050] The illumination can define the pattern to be formed by driving the deposition process in the selected portion 20 but not elsewhere. In embodiments, the deposition process is configured to form a single layer (or multiple single layers if the deposition process is repeated). In embodiments, the deposition process comprises an atomic layer deposition process. In other embodiments, a different deposition process or combination of deposition processes is used, including, for example, one or more of the following used independently or in combination: atomic layer deposition; chemical vapor deposition; plasma-enhanced chemical vapor deposition; epitaxy; sputtering; and electron beam-induced deposition. The formation of the patterned layer 22 of material can constitute a step in a method of forming at least one layer of a device to be fabricated, such as a semiconductor device.

[0051] In embodiments, the irradiating is performed with radiation capable of locally driving the deposition process. In embodiments, the radiation comprises, consists essentially of, or consists of any type of EUV radiation (having a wavelength of less than 100 nm) capable of locally driving the deposition process. The use of EUV radiation provides a high spatial resolution. In embodiments, the radiation comprises, consists essentially of, or consists of an electron beam (e.g., encompassing one or more focused beams and / or patterned beams provided by a single beam or multi-beam system). In some embodiments, the irradiating (e.g., using EUV radiation and / or electron beam radiation) is performed in combination with other forms of radiation including one or more of: an electron beam; radiation having a wavelength in the range of 100 nm to 400 nm (including DUV radiation); and laser radiation. Driving the deposition process with EUV radiation generally occurs primarily through EUV radiation interacting with a solid material (e.g., the substrate W or a layer formed on the substrate W) to release electrons from the solid material. The released electrons drive chemical reactions related to the deposition process. Using an electron beam in conjunction with EUV radiation provides a high concentration of electrons and / or further facilitates breaking bonds to create reactive species, thereby facilitating faster deposition of material.

[0052] The irradiating locally drives the deposition process in the selected portions 20 and thereby causes the layer 22 of deposited material to be formed in the pattern defined by the selected portions 20 (see FIG. 2B). Figure 4 Thus, the pattern is formed without any need for resist. There is therefore no need for processing to remove resist, which reduces the risk of damaging the patterned layer 22 of material or damaging any delicate underlying material. This approach is particularly desirable in cases where resist residue can significantly affect the properties of the delicate underlying material and / or peeling of the resist can significantly damage the delicate underlying material. Examples of delicate underlying material include very thin film coatings, 2D materials such as graphene or transition metal dichalcogenides (TMDs), and free-standing membranes or films. In contrast to traditional lithography-based semiconductor manufacturing processes, the radiation is not used to modify a resist material, but rather to drive one or more chemical reactions involved in the deposition process.

[0053] Atomic layer deposition is a known thin film deposition technique in which each of at least two chemicals, which can be referred to as precursor materials, is reacted with a surface of a material in a sequential, self-limiting manner. In contrast to chemical vapor deposition, the two precursor materials are not typically present simultaneously over the substrate W.

[0054] In at least some embodiments in which atomic layer deposition is used as the deposition process, the atomic layer deposition comprises at least a first step and a second step. In the first step, an example of which is depicted in Figure 3 , a first precursor material 31 is reacted with a surface of a substrate W. In the second step, an example of which is depicted in Figure 4 , a second precursor material 32 is reacted with the substrate W in regions of the substrate W in which the first precursor material 31 reacted in the first step (in this example, the selected portion 20). Figure 3 and Figure 4 In examples of and

[0055] Embodiments of the present disclosure relate to the use of radiation to drive a deposition process. The deposition process typically involves the deposition of a solid material derived from a deposition process material that is initially provided in gaseous form. In examples of Figure 3 and Figure 4 The first precursor material 31 is an example of such a deposition process material in examples of

[0056] Figure 5 An apparatus 40 for performing the method is schematically depicted. The apparatus 40 thus forms a patterned layer 22 of material. The apparatus 40 comprises an illumination system. In the example shown, the illumination system comprises a lithographic apparatus LA. The lithographic apparatus LA projects a patterned beam of radiation onto the substrate W from a patterning device MA. The lithographic apparatus LA can be configured in the manner described above with reference to Figure 1 (e.g. when the illumination comprises DUV radiation and / or immersion lithography is required) or in the manner described above with reference to Figure 2 (e.g. when the illumination comprises EUV radiation).

[0057] The apparatus 40 also includes an environment control system 42. The environment control system 42 allows the composition of the environment 44 above the substrate W to be controlled in a manner that allows the deposition process (e.g. an atomic layer deposition process) to continue. In embodiments, the environment control system 42 includes a chamber 46 to seal the environment 44 from ambient conditions outside the chamber 46. In some embodiments, the entirety of the substrate W will be located within the chamber 46 during the deposition process. In embodiments, a material exchange system 48 (e.g. a port into the chamber 46, and associated valves and / or conduits) is provided that allows material to be added to and removed from the sealed environment 44 to allow different composition environments to be established within the sealed environment 44. Material can be provided to and from the material exchange system 48 by a flow manager 50. The flow manager 50 can include any suitable combination of reservoirs, tubing, valves, tanks, pumps, control systems, temperature control systems (e.g. heaters and / or coolers) and / or other components necessary to provide the required material flow into and out of the chamber 46. The different composition environments achieved in this way can correspond to different respective stages of an atomic layer deposition process. In some embodiments, the material added to and removed from the sealed environment 44 as defined in the chamber 46 is gaseous, thereby providing composition environments composed of different combinations of gases. In embodiments where one or more steps of the deposition process are performed by irradiating the substrate W through an immersion liquid, the environment control system 42 can be configured to allow switching between a state in which a controlled liquid environment is maintained above the substrate W (e.g. during exposure in an immersion lithography mode) and a state in which a controlled gaseous environment is maintained above the substrate W (e.g. during adsorption of a precursor from a gaseous precursor material).

[0058] In some embodiments, the composition environment is controlled to provide different gas mixtures at different times. Different gas mixtures can be provided to deposit different materials, or to switch between a mode of depositing material and a mode of etching away material. Different gas mixtures can also be used to controllably vary the deposition rate as a function of time (i.e. over time), which can be used, for example, to produce features with well-defined edges and / or shapes.

[0059] In some embodiments, the driving of the deposition process includes driving a chemical reaction involving a precursor material. The precursor material is to be provided as part of the composition environment that is established over the substrate W during the irradiation. The driving of the chemical reaction can cause the chemical reaction to proceed at a faster rate than would occur in the absence of the irradiation. Alternatively, the chemical reaction can be one that would not occur at all in the absence of the irradiation. In embodiments, the chemical reaction is endothermic and the irradiation provides the energy necessary to allow the chemical reaction to proceed. In some embodiments, the chemical reaction is driven at least in part by heat generated in the substrate W by the irradiation. Thus, the chemical reaction driven by the irradiation can include a chemical reaction that requires high temperatures to proceed or proceeds more rapidly at high temperatures. In some embodiments, the chemical reaction includes a photochemical reaction driven by the irradiation. Thus, at least one of the species involved in the chemical reaction absorbs photons directly from the irradiation, and the absorption of the photons allows the chemical reaction to proceed. In some embodiments, the photochemical reaction includes a multi-photon photochemical reaction involving the absorption of two or more photons by each of the at least one species involved in the photochemical reaction. The requirement to absorb two or more photons makes the chemical reaction much more sensitive to changes in the intensity of the irradiation (i.e., the rate of the chemical reaction changes much more strongly with changes in intensity) than in the case of a single photon photochemical reaction. The increased sensitivity to intensity provides improved lateral contrast. In embodiments, a photochemical reaction is combined with radiation-induced heating to provide a well-defined process window in which the chemical reaction is driven locally to produce a pattern. In embodiments, the chemical reaction is driven by a plasma generated by an interaction between the radiation and the substrate W, a layer formed on the substrate W, and / or a gas present above the substrate. In embodiments, the generated plasma is generated in a localized region defined by the irradiation. In embodiments, the chemical reaction is driven by electrons provided by the irradiation. The electrons can include photoelectrons or secondary electrons (electrons generated by photoelectron or inelastic scattering events of electrons from an electron beam). In embodiments, the photons absorbed by the substrate W can provide high energy electrons near the surface of the substrate W that participate in the deposition process. In embodiments using a combination of electromagnetic radiation and an electron beam, a portion of the deposition process can be driven by the electrons from the electron beam.

[0060] A challenge with methods such as the method described above is that the radiation dose necessary to form the desired material thickness can be very high. The reasons for this and solutions to the challenge are described below.

[0061] Nominal thickness deposition requires a nominal radiation dose At a given radiation-induced deposition rate and radiation intensity :

[0062]

[0063] wherein is the nominal deposition time, and is derived from the nominal deposition time

[0064]

[0065] The nominal required dose may thus be reduced by increasing the radiation-induced deposition rate . For a first order approximation, the radiation-induced deposition rate can be described by

[0066]

[0067] wherein:

[0068] denotes the yield of secondary electrons (SE) near the substrate part surface inside and outside the bulk of the substrate W. Depends on the EUV absorption of the substrate W and the properties of the substrate material. The higher the EUV absorption, the higher the yield .

[0069] denotes the part of the secondary electrons generated in the substrate W that come into contact with the deposition process material above the substrate W. Depends on the phase of the deposition process material: is lower when the deposition process material is in a gaseous state and higher when the deposition process material is in a solid or liquid state.

[0070] denotes the reaction cross section for the reaction between secondary electrons and deposition process material. Depends on the secondary electron kinetic energy and the dissociation energy of the molecules of the deposition process material.

[0071] denotes the local surface density of the deposition process material at the substrate W.

[0072] denotes the molecular weight of the deposition process material, or of the part of the deposition process material that remains intact after interaction with secondary electrons and is deposited on the substrate W.

[0073] In principle, the radiation-induced deposition rate The parameter , , , , , can be increased by increasing any one of them. cannot be increased indefinitely, since the radiation will eventually cause unacceptable damage to the substrate W, or to a layer previously deposited on the substrate W. In the embodiments of the present disclosure described below, methods are provided to increase the deposition rate caused by the radiation: by changing the phase of the deposition process material from gas to liquid or solid during the irradiation, or by providing a high-density gaseous layer of the deposition process material in close proximity to the substrate W, all of which result in a substantial increase of and .

[0074] Increasing the density of the deposition process material increases the number of molecules that interact with secondary electrons is intuitive.

[0075] As described below, the effect of the change of phase on can be understood phenomenologically with reference to Figures 6 to 9 . Figure 6 and Figure 7 schematically depict the case where the deposition process material is in gaseous form. Figure 8 and Figure 9 schematically depict the case where the deposition process material is in liquid or solid form. Figure 6 and Figure 8 are energy diagrams with the vertical axis representing energy E. Figure 7 and Figure 9 are schematic side cross-sectional views of the substrate W with a deposition process material / arranged in gaseous or solid / liquid form above the substrate W. Figure 6 and Figure 8 the horizontal axis in Figure 7 and Figure 9 schematically represent the variation of position across the interface 52 between the solid substrate W and the deposition process material / . The small circles in each figure represent secondary electrons. Figure 7 and Figure 9 the larger circles schematically represent molecules 54 of the deposition process material. Molecules 56 of the deposition process material that have been modified by the irradiation are schematically shown as Figure 7 and Figure 9The combination of the large circle and the small circle in

[0076] Factor Depending on the number of secondary electrons generated in the substrate W that can come into contact with the deposition process material, which depends on the difference between their Fermi energies.

[0077] As Figure 6 And Figure 7 depicted in When the deposition process material is in the gaseous state, the relevant energy difference between the Fermi energy in the solid substrate W and the vacuum level is relatively large. A large energy difference means that relatively few secondary electrons can be available to drive the deposition process by interacting with the deposition process material Only secondary electrons that can overcome the potential barrier between the substrate Fermi energy and the vacuum level can escape the substrate W and interact with the deposition process material Thus, is small when the deposition process material is provided in the gaseous state.

[0078] As Figure 8 And Figure 9 depicted in When the deposition process material is in the solid or liquid state, the secondary electrons transfer from the Fermi energy in the solid substrate W to the Fermi energy in the deposition process material . The energy difference between and Figure 8 can also be adjusted to be small (as shown in ) or even negative (not shown) by appropriate selection of the substrate material and the deposition process material In the negative case, the transfer of electrons from the substrate W to the deposition process material is energetically favorable. In both cases, the provision of the deposition process material in the solid or liquid state means that a much larger fraction of the secondary electrons can come into contact with the molecules of the deposition process material and thereby contribute to the deposition process involving the deposition process material (for example, by modifying them to produce modified molecules 56). From Figure 7 And Figure 9It can be seen that the density of the deposition process material is greater in the case of Figure 7 deposition process material provided in solid or liquid form is expected to significantly increase the radiation-induced deposition rate Figure 9 compared to the case where the deposition process material is provided only in gaseous form .

[0079] The magnitude of the above effects has been demonstrated by an unannounced contamination incident during exposure of a gold layer in a test sequence. The test sequence comprised exposure of gold by EUV radiation at a dose of 250 mJ / cm 2 . The exposure was performed while the substrate was cryogenically cooled to 125 K. A contaminant gas comprising carbon compounds was accidentally present in the test chamber during the exposure and condensed onto the test substrate due to the lower temperature of the substrate. Figure 10 An image obtained from optical microscopy of a rectangular area exposed by EUV radiation is depicted. The area 62 surrounding the rectangular area was not exposed by EUV radiation. Figure 11 An enlarged optical image showing the optical contrast across the border of the portion of the border of the rectangular area. Figure 12 An atomic force microscope (AFM) image of the same portion of the border is shown and indicates a step of 21 nm in height. Figure 13 and Figure 14 Corresponding images of a different portion of the border are shown and indicate a similar step height of 22 nm. Thus, the EUV radiation caused growth of a uniform thick layer of material having a thickness of about 20 nm from the condensed carbon-containing contaminant gas. A thickness of 20 nm was deposited at a dose of 250 mJ / cm 2 . According to the literature, in a similar experiment performed at room temperature with a low pressure gaseous precursor material, about 10 nm of carbon contaminant required a dose of about 100 J / cm 2 or even more (see, for example, Proc. of SPIE Vol. 7969 79690M 2011). Thus, changing the phase of the precursor material from gas to liquid was found to reduce the required EUV dose by a factor of about 1000, i.e. to 1 / 1000.

[0080] In the above discussion with reference to Figures 6 to 14 In other embodiments, instead, a layer of the deposition process material in high density gaseous form is irradiated. The high density state increases the density of the deposition process material in the layer ​This increases the number of molecules interacting with the secondary electrons. High-density states can also be achieved by referring to the above... Figures 6 to 9 The mechanism described below lowers the energy barrier of secondary electrons generated in the substrate W in contact with the material during the deposition process to increase the factor. .

[0081] Figure 15 This is a flowchart depicting an example method for forming patterned layers of materials based on the above insights. The method improves the radiation-induced deposition rate. You can use the above reference. Figure 5 The method is performed using the apparatus 40 described for forming patterned layers of material. A control system 66 may be configured to control the apparatus 40 to perform the method steps described below.

[0082] In the first step S1, a deposition process material is provided in gaseous form. The deposition process material may include precursors for a deposition process locally driven by irradiation. The deposition process material is not necessarily limited to this. The deposition process material may be any material that contributes to the radiation-induced deposition process under consideration, including, for example, materials considered as co-reactants and / or catalysts. The deposition process material may be provided to a chamber 46 containing the substrate W.

[0083] In the subsequent step S2, a layer of the deposition process material, serving as the rectangular region, is formed on the substrate W, such as... Figure 9 The layer 60 of the deposition process material is schematically depicted. The layer 60 can be formed by condensing (changing from gaseous to liquid) or depositing (changing from gaseous to solid) the gaseous deposition process material onto the substrate W. Alternatively, the layer 60 can be formed by supplying a gaseous deposition process material to the chamber 46 at a temperature higher than that of the substrate W, and by creating a temperature difference between the substrate W and the gas to form a high-density gaseous layer of deposition process material immediately adjacent to the substrate W. In this type of embodiment, the gaseous deposition process material layer 60 has a higher density than the gaseous deposition process material in other areas of the chamber 46.

[0084] In an embodiment, the initially provided gaseous deposition process material can be maintained at a partial pressure suitable for inducing condensation or deposition during the formation of layer 60 of the deposition process material. This partial pressure can, for example, be approximately equal to the saturated vapor pressure of the deposition process material. In an embodiment, condensation is promoted by cooling the substrate W to below ambient temperature. In another embodiment, condensation at room temperature on the substrate W is achieved by providing the gaseous deposition process material at a temperature above ambient temperature (see below).

[0085] In the subsequent step S3, a selected portion of layer 60 of the material being deposited is irradiated, such as... Figure 9 The image is schematically depicted. The irradiation 24 modifies the material in the selected portion of the deposition process (e.g., to form...). Figure 9 Modified molecules 56 in the process. A range of different modifications can be applied. In some embodiments, irradiation of selected portions increases the activity of particles derived from the material of the deposition process (e.g., Figure 9 The adsorption strength of the modified molecules 56 in the substrate W is determined by the adsorption of these molecules. In some embodiments, irradiation of a selected portion induces the adsorption of particles (e.g., from the material deposited during the deposition process) onto the substrate W. Figure 9 Crosslinking between modified molecules 56 in the irradiation. Thus, the irradiation provides a material more resistant to removal compared to unmodified material outside the selected portion. Therefore, the irradiation locally drives the deposition process involving the material (e.g., as a precursor material) in the deposition process.

[0086] In a subsequent optional step S4, the unmodified deposited process material in a portion of the deposited process material layer 60 outside the selected portion is evaporated (changing the deposited process material from a liquid to a gaseous state) or sublimated (changing the deposited process material from a solid to a gaseous state). During the evaporation or sublimation of the unmodified deposited process material, the gaseous deposited process material can be maintained at a pressure substantially below the saturated vapor pressure of the deposited process material. Evaporation or sublimation leaves a layer of solid material in the pattern defined by the selected portion. Therefore, no additional steps are required to remove the material outside the selected portion.

[0087] thus, Figure 5 The environmental control system 42 in the example can be configured to control the partial pressure of the deposition process material to control (e.g., by increasing the partial pressure) whether the deposition process material is driven to condense or deposit on the substrate W (e.g., during step S2), or whether the deposition process material is driven to evaporate or sublimate and thus leave the substrate W (e.g., during step S4).

[0088] A solid material layer is provided in a pattern during the radiation-induced deposition process involving the material in the deposition process. This method allows for the formation of solid material layers in a wide range of compositions. However, as referenced above… Figures 10 to 14 As discussed, the method has been found to be particularly effective when the material in the deposition process contains a carbon source and the solid material layer left in the pattern includes carbon.

[0089] In an embodiment, the formation of the layer 60 of the deposition process material is achieved at least in part by applying a cooling process to the substrate W to maintain the substrate W below ambient temperature (e.g., room temperature or 298 K) (step S2). The substrate W can be maintained below ambient temperature by at least 5 degrees, optionally at least 10 degrees, optionally at least 20 degrees, optionally at least 40 degrees, optionally at least 60 degrees, or optionally at least 100 degrees. The choice of temperature can depend on the vapor pressure versus temperature profile of the deposition process material. For a given partial pressure, this profile determines the condensation initiation temperature. The temperature of the substrate W is then selected to be below this initiation temperature. Cooling the substrate W drives the condensation or deposition of the gaseous deposition process material onto the substrate W (or the formation of a high-density gaseous layer). Gas molecules are cooled and transformed into a liquid or solid state (or into a high-density gaseous state) through contact with the substrate W. Cooling the substrate W makes it possible to provide the gaseous deposition process material at a partial pressure lower than the saturated vapor pressure of the deposition process material at ambient temperature. Cooling the substrate W means that the deposition process material will preferentially condense or deposit on the substrate W relative to other components accessible to the gas deposition process material, thereby reducing or eliminating unwanted contamination of other components (e.g., optical components) through the condensation or deposition of the deposition process material on those other components. In embodiments, such as Figure 5 As schematically depicted, in the apparatus 40 for performing the method, cooling can be performed by a substrate cooling system 64. The substrate cooling system 64 can be formed within a substrate stage WT configured to support the substrate W within the environmental control system 42. The substrate cooling system 64 can provide cooling in various ways, including, for example, using a Peltier element, or by driving a cooling liquid through channels in the substrate stage WT. In an embodiment, the substrate stage WT also includes a substrate heating system, or the substrate cooling system can be configured to also heat the substrate (e.g., by driving a current through a resistive element via a Peltier element to induce Joule heating, or by driving a heating liquid through channels in the substrate stage WT). The substrate heating system can be used to heat the substrate W during the evaporation or sublimation of unmodified deposition process material (in step S4). In another embodiment, during the formation of layer 60 of deposition process material by condensation or deposition (in step S2), one or more elements other than the substrate (e.g., optical elements) are heated at a temperature above ambient temperature, thereby reducing or eliminating unwanted condensation of deposition process material on the elements.

[0090] In an embodiment, the formation of layer 60 of the deposition process material is achieved at least in part by providing the deposition process material at a temperature above ambient temperature. Figure 5In an example apparatus 40 in which the environmental control system 42 supplies the deposition process material in gaseous form above the environment 44 at a temperature higher than the ambient temperature. The gaseous deposition process material at an elevated temperature can be provided by the material exchange system 48 under control of the control system 66. The temperature difference between the gaseous deposition process material and the substrate W again drives condensation or deposition of the deposition process material to form the layer 60, but in this case there is no need to cool the substrate W. This approach avoids the need to complicate the structure of the substrate table WT by providing a substrate cooling system 64 while still allowing the layer 60 to be efficiently formed.

[0091] Embodiments can be further described using the following aspects:

[0092] 1. A method of forming a patterned layer of material, comprising:

[0093] providing a deposition process material in gaseous form;

[0094] forming a layer of the deposition process material on a substrate by causing condensation or deposition of the gaseous deposition process material; and

[0095] irradiating selected portions of the layer of deposition process material to modify the deposition process material in the selected portions.

[0096] 2. The method of aspect 1, wherein the forming of the layer of deposition process material is at least partially achieved by applying a cooling process to the substrate to maintain the substrate below ambient temperature.

[0097] 3. The method of any preceding aspect, wherein the forming of the layer of deposition process material is at least partially achieved by providing the deposition process material at a temperature higher than ambient temperature.

[0098] 4. The method of any preceding aspect, further comprising evaporating or sublimating unmodified deposition process material in portions of the layer of deposition process material outside the selected portions to leave a layer of solid material in a pattern defined by the selected portions.

[0099] 5. The method of aspect 4, wherein:

[0100] during the forming of the layer of deposition process material, the deposition process material in gaseous form is maintained at a partial pressure substantially equal to the saturation vapour pressure of the deposition process material; and

[0101] During the evaporation or sublimation of the unmodified deposition process material, the deposition process material in gaseous form is maintained at a partial pressure substantially below the saturation vapor pressure of the deposition process material.

[0102] 6. A method of forming a patterned layer of material, comprising:

[0103] providing a substrate in a chamber;

[0104] supplying a gas of deposition process material to the chamber at a temperature higher than the substrate, the temperature difference between the substrate and the gas causing a high-density gaseous layer of deposition process material to form immediately adjacent to the substrate, the high-density gaseous layer of deposition process material having a higher density than the gas of deposition process material in other regions of the chamber; and

[0105] irradiating selected portions of the layer of deposition process material to modify the deposition process material in the selected portions.

[0106] 7. The method of any preceding aspect, wherein the irradiation of the selected portions is performed using radiation having a wavelength less than 100 nm.

[0107] 8. The method of any preceding aspect, wherein the irradiation of the selected portions is performed using an electron beam.

[0108] 9. The method of aspect 7 or 8, wherein the irradiation of the selected portions further uses one or more of: radiation having a wavelength in the range 100 nm to 400 nm; and laser radiation.

[0109] 10. The method of any preceding aspect, wherein the deposition process material comprises a precursor material for a deposition process.

[0110] 11. The method of aspect 10, wherein the deposition process is locally driven by the irradiation in the selected portions.

[0111] 12. The method of any preceding aspect, wherein the irradiation of the selected portions increases the adsorption strength of particles originating from the deposition process material to the substrate.

[0112] 13. The method of any preceding aspect, wherein the irradiation of the selected portions causes cross-linking between particles originating from the deposition process material.

[0113] 14. A method of forming a semiconductor device, comprising forming at least one layer in the device using the method of any preceding aspect.

[0114] 15. An apparatus for forming a patterned layer of a material, comprising:

[0115] an environmental control system configured to control a composition of an environment above a substrate;

[0116] an illumination system; and

[0117] a control system configured to control the environmental control system and the illumination system to:

[0118] form a layer of a deposition process material on the substrate by condensing or depositing the deposition process material from a gas; and

[0119] illuminate a selected portion of the formed layer of deposition process material to modify the deposition process material in the selected portion.

[0120] 16. The apparatus of aspect 15, wherein the control system is further configured to provide the deposition process material at a temperature higher than the temperature of the environment.

[0121] 17. The apparatus of aspect 15 or 16, wherein the control system is further configured to control the environmental control system to evaporate or sublimate unmodified deposition process material in portions of the layer of deposition process material outside of the selected portion to leave a layer of solid material in a pattern defined by the selected portion.

[0122] 18. The apparatus of aspect 17, wherein the control system is further configured to:

[0123] maintain the deposition process material in gaseous form at a partial pressure substantially equal to a saturation vapor pressure of the deposition process material during the formation of the layer of deposition process material; and

[0124] maintain the deposition process material in gaseous form at a partial pressure substantially below the saturation vapor pressure of the deposition process material during the evaporation or sublimation of the unmodified deposition process material.

[0125] 19. An apparatus for forming a patterned layer of a material, comprising:

[0126] an environmental control system configured to control a composition of an environment above a substrate in a chamber;

[0127] an illumination system; and

[0128] a control system configured to control the environmental control system and the illumination system to:

[0129] supplying a gas of deposition process material to the chamber at a temperature higher than the substrate, the temperature difference between the substrate and the gas causing a high-density gaseous layer of deposition process material to form directly adjacent to the substrate, the high-density gaseous layer of deposition process material having a higher density than the gas of deposition process material in other regions of the chamber; and

[0130] irradiating a selected portion of the formed layer of deposition process material to modify the deposition process material in the selected portion.

[0131] 20. The apparatus according to any one of aspects 15 to 19, wherein the irradiation system is configured for irradiating the selected portion using radiation having a wavelength of less than 100 nm.

[0132] 21. The apparatus according to any one of aspects 15 to 19, wherein the irradiation system is configured for irradiating the selected portion using an electron beam.

[0133] 22. The apparatus according to any one of aspects 20 to 21, wherein the irradiation system is configured for irradiating the selected portion using one or more of: radiation having a wavelength in the range of 100 nm to 400 nm; and laser radiation.

[0134] 23. The apparatus according to any one of aspects 15 to 22, wherein the environment control system is configured for supplying a precursor material for a deposition process.

[0135] 24. The apparatus according to aspect 23, wherein the precursor material is selected to locally drive the deposition process by the irradiation of the selected portion.

[0136] In any of the above-described methods of forming a patterned layer of material, the patterned layer of material can comprise a final material to be present in a device (e.g. an IC device) being manufactured. For example, the final material can comprise a two-dimensional material such as one or more of: graphene, hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs). Alternatively or additionally, the patterned layer of material can comprise an auxiliary pattern which will functionally aid one or more subsequent manufacturing steps. In embodiments, the auxiliary material acts as a hard mask (e.g. when formed from amorphous C). In embodiments, the auxiliary material acts as a material which enhances photoelectron yield (e.g. when comprising one or more of Sn, In and / or compounds thereof). In embodiments, the auxiliary material acts as a precursor and / or co-reactant and / or catalyst (e.g. metals and compounds thereof) for one or more subsequent deposition steps. For example, in embodiments where the auxiliary material can be MoO2or Mo, the auxiliary material is deposited according to any of the embodiments described herein, followed by sulphidation in the same chamber or a different chamber, for example according to one of the following chemical reactions: MoO2+ 2H2S → MoS2+ 2H2O or Mo + 2H2S → MoS2+ 2H2.

[0137] Although specific reference can be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein can have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays such as liquid-crystal displays (LCDs), thin-film magnetic heads, etc.

[0138] While specific embodiments of the application have been described above, it will be appreciated that the application can be practiced otherwise than as described. The description is intended to be illustrative, not restrictive. It will be apparent to those skilled in the art that modifications can be made to the application as described without departing from the scope of the claims as set out below.

Claims

1. A method for forming a patterned layer of material on a substrate, comprising: Provide materials for the deposition process in gaseous form; A layer of the deposition process material is formed on the substrate by inducing the condensation or deposition of the gaseous deposition process material; A selected portion of the layer of the deposition process material is irradiated to modify the deposition process material in the selected portion, wherein the modification is based on creating crosslinks between the particles of the deposition process material to obtain a higher resistance to removal of the modified deposition process material compared to the unmodified deposition process material outside the selected portion; as well as The unmodified deposited process material in the portion of the layer located outside the selected portion, through evaporation or sublimation of the deposited process material, leaves a solid material layer within a pattern defined by the selected portion, instead of any treatment that removes resist throughout the method to form the patterned layer. The deposition process material includes a precursor material for the deposition process, and the deposition process is locally driven by the irradiation in the selected portion, and the driving of the deposition process includes driving a chemical reaction involving the precursor material, and thereby resulting in the formation of a layer of deposition material in the pattern defined by the selected portion.

2. The method according to claim 1, wherein, The formation of the layer of material in the deposition process is achieved at least partially by applying a cooling process to the substrate to keep the substrate below the ambient temperature.

3. The method according to claim 1, wherein, The formation of the layer of the deposition process material is at least partially achieved by providing the deposition process material at a temperature higher than the ambient temperature.

4. The method according to claim 1, wherein: During the formation of the layer of the deposition process material, the gaseous deposition process material is maintained at a partial pressure equal to the saturated vapor pressure of the deposition process material; and During the evaporation or sublimation of the unmodified deposition process material, the gaseous deposition process material is maintained at a partial pressure lower than the saturated vapor pressure of the deposition process material.

5. The method according to claim 1, wherein, The irradiation of the selected portion is performed using radiation with a wavelength of less than 100 nm.

6. The method according to claim 1, wherein, An electron beam is used to perform the irradiation of the selected portion.

7. The method according to claim 5 or 6, wherein, The irradiation of the selected portion also uses one or more of the following: radiation having a wavelength in the range of 100 nm to 400 nm.

8. The method according to claim 1, wherein, The chemical reaction is driven by electrons provided by irradiation, including EUV radiation.

9. The method according to claim 8, wherein, The electrons include photoelectrons or secondary electrons released through the interaction between the EUV radiation and the substrate or a layer formed on the substrate.

10. The method according to claim 8, wherein, The electrons include high-energy electrons that participate in the deposition process, provided near the surface of the substrate by photons absorbed by the substrate.

11. The method according to claim 1, wherein, The chemical reaction is driven by plasma generated in a localized region defined by the irradiation through the interaction between the irradiation and the substrate, the layer formed on the substrate, and / or the gas present above the substrate.

12. The method according to claim 1, wherein, The irradiation of the selected portion increases the adsorption strength of particles derived from the deposition process material onto the substrate.

13. The method according to claim 1, wherein, The irradiation of the selected portion causes cross-linking between particles originating from the material in the deposition process.

14. A method of forming a semiconductor device, comprising forming at least one layer of the semiconductor device using the method according to any of the preceding claims.

15. An apparatus for forming a patterned layer of a material, comprising: An environmental control system configured to control the composition of the environment above a substrate; Irradiation system; as well as The control system is configured to control the environmental control system and the irradiation system to: A layer of deposition process material is formed on the substrate by condensing or depositing the deposition process material from a gas; and Irradiating a selected portion of the layer formed by the deposition process material to modify the deposition process material in the selected portion. The control system is further configured to control the environmental control system to: evaporate or sublimate the unmodified deposited process material in the portion of the layer outside the selected portion to leave a solid material layer in the pattern defined by the selected portion, instead of any treatment that removes resist throughout the process to form the patterned layer; and The modification is based on creating cross-links between the particles of the deposition process material to obtain a modified deposition process material with higher resistance to removal compared to the unmodified deposition process material outside the selected portion. The deposition process material includes a precursor material for the deposition process, and the deposition process is locally driven by the irradiation in the selected portion, and the driving of the deposition process includes driving a chemical reaction involving the precursor material, and thereby resulting in the formation of a layer of deposition material in the pattern defined by the selected portion.

16. The apparatus of claim 15, further comprising: A substrate cooling system configured to maintain the substrate below ambient temperature.

17. The device according to claim 15, wherein, The irradiation system is configured to irradiate the selected portion using radiation with a wavelength of less than 100 nm.

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