Methods and systems for electric field-assisted lithography

Abstract

To provide methods and systems for electric field-assisted lithography.SOLUTION: There are provided lithographical systems and methods. Embodiments of methods disclosed herein comprise exposing a substrate to an electric field while exposing the substrate to electromagnetic radiation. Thus, dose reduction can be obtained.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] TECHNICAL FIELD This disclosure is in the field of lithography, such as EUV lithography, for patterning substrates, such as semiconductor substrates. [Background technology]

[0002] Extreme ultraviolet (EUV) lithography is an enabling technology for advanced semiconductor processing. It is still expensive, with a high cost per photon. It is therefore desirable to reduce the dose, the amount of photons required to fully expose the resist, called the "exposure dose." Summary of the Invention

[0003] Disclosed herein is a system for lithographic patterning of a semiconductor substrate comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber comprising a substrate support and an electrode assembly, where the EM radiation source is configured to generate electromagnetic radiation, the optical assembly is constructed and arranged to direct the EM radiation towards the substrate support, the substrate support is constructed and arranged to support the semiconductor substrate, and the electrode assembly is constructed and arranged to apply an electric field to an EM sensitive layer comprised within the semiconductor substrate.

[0004] In some embodiments, the electrode assembly is constructed and arranged to apply an electric field laterally to the EM susceptible layer.

[0005] In some embodiments, the electrode assembly comprises two electrodes disposed adjacent to the substrate support.

[0006] In some embodiments, the electrode assembly comprises two electrodes, each comprising a plurality of fingers that together form an interdigitating pattern.

[0007] In some embodiments, the fingers from the plurality of fingers are parallel to one another.

[0008] In some embodiments, the electrode assembly is constructed and arranged to apply an electric field laterally to the EM susceptible layer.

[0009] In some embodiments, the electrode assembly comprises a first electrode and a second electrode, the first electrode electrically connected to the substrate support and the second electrode disposed substantially parallel to the substrate and between the substrate and the EM radiation source.

[0010] In some embodiments, the electrode assembly comprises a first electrode and a second electrode, the first electrode electrically connected to the substrate and the second electrode disposed substantially parallel to the substrate and between the substrate and the EM radiation source.

[0011] In some embodiments, the EM radiation source comprises an extreme ultraviolet (EUV) source.

[0012] Further provided herein is a method including providing a system comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber comprising a substrate support and an electrode assembly; disposing a substrate on the substrate support, the substrate comprising an EM sensitive layer; exposing the substrate to EM radiation; and applying an electric field to the EM sensitive layer by an electrode pair comprising a first electrode and a second electrode while exposing the substrate to the EM radiation.

[0013] In some embodiments, the EM radiation comprises extreme ultraviolet (EUV).

[0014] In some embodiments, the electric field enhances secondary electron generation while exposing the substrate to EM radiation.

[0015] In some embodiments, the electric field comprises a DC electric field.

[0016] In some embodiments, the electric field comprises an AC electric field.

[0017] In some embodiments, the electric field is applied substantially parallel to the EM susceptible layer.

[0018] In some embodiments, the electric field is applied substantially perpendicular to the EM susceptible layer.

[0019] In some embodiments, the electric field comprises a component that is oblique to the EM susceptible layer.

[0020] In some embodiments, the EM sensitive layer includes an EUV resist and at least one of an underlayer, an adhesive layer, and an electron reflector layer.

[0021] This Summary is provided to introduce selected concepts in a simplified form. These concepts are described in more detail in the Detailed Description of Example Embodiments of the Disclosure below. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 illustrates an embodiment of a system 100 for forming a pattern on a substrate. [Diagram 2] FIG. 2 illustrates an embodiment of an electrode assembly 200 as described herein. [Diagram 3] FIG. 3 illustrates an embodiment of an electrode assembly 300 as described herein. [Figure 4] FIG. 4 illustrates an embodiment of an electrode assembly 400 as described herein. [Diagram 5] FIG. 5 illustrates an embodiment of an electrode assembly 500 as described herein. [Figure 6] FIG. 6 illustrates an embodiment of an electrode assembly 600 as described herein. [Figure 7] FIG. 7 illustrates an embodiment of a structure described herein. [Figure 8] FIG. 8 illustrates an embodiment of a structure described herein. [Figure 9] FIG. 9 illustrates an embodiment of a structure described herein. [Figure 10] FIG. 10 illustrates an embodiment of a method described herein. It will be appreciated that the elements in the figure are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help improve understanding of the illustrated embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Although certain specific embodiments and examples are disclosed below, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention, and obvious modifications and equivalents thereof, and therefore it is not intended that the scope of the disclosed invention should be limited by the specific disclosed embodiments described below.

[0024] As used herein, the term "substrate" may refer to any underlying material or materials, including any underlying material or materials, on which a device, circuit, or film may be formed, that may be modified or on which a device, circuit, or film may be formed. A "substrate" may be continuous or non-continuous, rigid or flexible, solid or porous, and combinations thereof. A substrate may be in any form, such as a powder, a plate, or a workpiece. Substrates in the form of plates may include wafers of various shapes and sizes. Substrates may be made of semiconductor materials, including, for example, silicon, silicon germanium, silicon oxide, gallium arsenide, gallium nitride, and silicon carbide.

[0025] The continuous substrate may extend beyond the boundaries of the process chamber in which the deposition process occurs. In some processes, the continuous substrate may move through the process chamber so that the process continues until the edge of the substrate is reached. The continuous substrate may be supplied from a continuous substrate supply system to enable the production and output of the continuous substrate in any suitable form.

[0026] The illustrations presented herein are not meant to be actual representations of any particular materials, structures, or devices, but merely idealized representations used to describe embodiments of the present disclosure.

[0027] The particular implementations shown and described are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of aspects and implementations in any way. Indeed, for the sake of brevity, conventional manufacturing, association, preparation, and other functional aspects of the system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent example functional relationships and / or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in an actual system and / or may not be present in some embodiments.

[0028] It should be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be construed in a limiting sense, as numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. Thus, various illustrated operations may be performed in the order illustrated, in other orders, or omitted in some cases.

[0029] The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, and other features, functions, operations and / or properties disclosed herein, as well as all equivalents thereof.

[0030] Described herein is a system for lithographic patterning a semiconductor substrate. The system may include an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber. The exposure chamber may include a substrate support and an electrode assembly. The EM radiation source may be configured to generate electromagnetic radiation. The optical assembly may be constructed and arranged to direct EM radiation toward the substrate support. The substrate support may be constructed and arranged to support a semiconductor substrate. The electrode assembly may be constructed and arranged to apply an electric field to an EM-sensitive layer contained within the semiconductor substrate. In some embodiments, the EM radiation source includes an extreme ultraviolet (EUV) source.

[0031] In some embodiments, the electrode assembly is constructed and arranged to apply an electric field laterally to the EM susceptible layer, examples of such embodiments are illustrated by Figures 2, 5, and 6.

[0032] In some embodiments, the electrode assembly comprises two electrodes disposed adjacent to the substrate support, an example of such an embodiment is illustrated by FIG.

[0033] In some embodiments, the electrode assembly comprises two electrodes, each with a plurality of fingers that together form an interdigitated pattern, examples of such embodiments are illustrated by Figures 5 and 6.

[0034] In some embodiments, the electrode assembly is constructed and arranged to apply an electric field laterally to the EM susceptible layer. Examples of such embodiments are illustrated by Figures 3 and 4.

[0035] In some embodiments, the electrode assembly includes a first electrode and a second electrode. The first electrode can be electrically connected to the substrate support. The second electrode can be disposed between the substrate and the EM radiation source and substantially parallel to the substrate. An example of such an embodiment is illustrated by FIG.

[0036] With reference to FIG. 1, a particular embodiment of a system 100 for forming a pattern on a substrate is described herein. The system 100 includes an electromagnetic (EM) radiation source 110. The EM radiation source 110 may be constructed and arranged to generate one or more of visible light, ultraviolet (UV), and extreme ultraviolet (EUV). The EM radiation may pass through an optical assembly 120 to reach an exposure chamber 130. The optical assembly 120 may include one or more lenses. Additionally or alternatively, the optical assembly 120 may include one or more mirrors, e.g., Bragg reflectors. The exposure chamber may include a substrate support 131 and an electrode assembly 132. The substrate support 131 may be constructed and arranged to support a substrate, such as a semiconductor wafer, during exposure to the EM radiation. The substrate is composed of an EM-sensitive layer, such as a resist, such as one or more of a UV resist, an EUV resist, a chemically amplified resist, and an organometallic resist. The exposure chamber 130 further includes an electrode assembly 132. The electrode assembly can be constructed and arranged to apply an electric field over the EM sensitive layer, and thus the amount of EM radiation, e.g., EUV exposure, required to develop the EM sensitive layer after exposure can be advantageously reduced.

[0037] Figure 2 shows an embodiment of an electrode assembly 200 as described herein. The embodiment of Figure 2 comprises two electrodes 211, 212 that can be positioned adjacent to, i.e. laterally of, a substrate 240, which can be supported by a substrate support (not shown). Thus, an electric field can be applied laterally, i.e. in the plane of a patternable layer 241 contained within the substrate 240. The electrodes 211, 212 can be connected to a voltage source 220 by a conductive wire 230. Figure 2 shows the electrode assembly 200 comprising a DC voltage source 220. Additionally or alternatively, the electrode assembly 200 can comprise an AC voltage source.

[0038] FIG. 3 illustrates another embodiment of an electrode assembly 300 as described herein. The embodiment of FIG. 3 includes two electrodes 311, 312. The first electrode 311 is disposed parallel to a substrate 340 that is comprised of an EM radiation sensitive layer 341, on the side of the substrate 340 that is comprised of an EM radiation patternable layer 341. The first electrode 311 can be transparent, partially transparent, or substantially transparent to EUV radiation. For example, the first electrode can have a thickness that is sufficiently thin to allow a substantial portion of the EUV radiation to pass through. For example, the first electrode can have a thickness of at least 1.0 nm to a maximum of 10 μm, or at least 1.0 nm to a maximum of 10 nm, or at least 10 nm to a maximum of 100 nm, or at least 100 nm to at least 1 μm, or at least 1 μm to a maximum of 10 μm. For example, the first electrode may transmit 10-99%, or 20-99%, or 50-99%, or 70-99%, or greater than 99%, or substantially all of the incident EUV radiation. While all materials absorb EUV radiation to at least some degree,

[0039] The second electrode is configured in a substrate support 350 that supports the substrate 340 on the far side of the substrate 340. The first electrode 311 and the second electrode 312 may be parallel or substantially parallel. Thus, an electric field may be applied transversely to the patternable layer 341, i.e., perpendicular to the plane of the patternable layer 341. The electrodes 311, 312 may be connected to a voltage source 320 by a conductive wire 330. FIG. 3 shows the electrode assembly 300 comprising a DC voltage source 320. Additionally or alternatively, the electrode assembly 300 may comprise an AC voltage source.

[0040] FIG. 4 shows another embodiment of an electrode assembly 400 as described herein. The embodiment of FIG. 4 comprises two electrodes 411, 412. The first electrode 411 is disposed on the side of the substrate comprised of the EM radiation sensitive layer 441, parallel or substantially parallel to the substrate 440 comprised of the EM radiation patternable layer 441. The first electrode may be transparent to EM radiation. The second electrode 412 is in electrical contact with the substrate 440. It is understood, of course, that in at least this embodiment, the substrate comprises a conductor such as a metal or a doped or undoped semiconductor. The first electrode 411 and the substrate 440 may be parallel or substantially parallel. Thus, an electric field may be applied transversely to the patternable layer 441, i.e. perpendicular to the plane of the patternable layer 441. The electrodes 411, 412 may be connected to a voltage source 440 by a conductive wire 430. FIG. 4 shows an electrode assembly 400 comprising a DC voltage source 420. Additionally or alternatively, the electrode assembly 400 may include an AC voltage source.

[0041] FIG. 5 shows another embodiment of an electrode assembly 500 as described herein. The embodiment of FIG. 5 comprises two interdigitated electrodes 511, 512. The first electrode 511 and the second electrode 512 are each an alternating arrangement of a plurality of conductive wires 513, 514 or sheets, etc., in particular arranged parallel or substantially parallel to each other and to the substrate. The wires 513 from the first electrode 511 are alternating with the wires 514 from the second electrode 512 to form an interdigitated pattern. The first electrode 511 and the second electrode 512 are arranged on the side of the substrate constituting the EM radiation sensitive layer 541. The first electrode may be transparent to EM radiation. Thus, an electric field may be applied substantially parallel to the patternable layer 541, i.e., substantially in the plane of it. The electrodes 511, 512 may be connected to a voltage source 540 by conductive wires 530. FIG. 5 shows the electrode assembly 500 comprising a DC voltage source 520. Additionally or alternatively, the electrode assembly 500 may include an AC voltage source.

[0042] An embodiment of electrodes 611, 612 that may be used in the electrode assembly 500 of Figure 5 is shown in Figure 6. The first electrode 611 and the second electrode 612 each include a plurality of first electrode fingers 613 and second electrode fingers 614. The first electrode fingers 613 and second electrode fingers 614 are arranged in an interlocking or interdigitating pattern.

[0043] In some embodiments, the EM sensitive layer is comprised of a layer that is sensitive to EUV radiation, i.e., EUV resist. Exemplary structures comprised of EUV resist are shown in Figures 7-9.

[0044] 7 shows a structure comprising a substrate 700, an underlayer 720 overlying the substrate 700, and a resist 740 overlying the underlayer 720. Suitable underlayers are described in any one of U.S. patent applications Ser. Nos. 17 / 899,928, 17 / 900,578, and 17 / 900,065, which are incorporated herein by reference in their entireties.

[0045] 8 shows a structure comprising a substrate 800, an underlayer 820 overlying the substrate 800, an adhesive layer 830 overlying the underlayer 820, and a resist 840 overlying the adhesive layer 830. Advantageously, the adhesive layer 830 may provide adhesion between the underlayer 820 and the resist 840. Exemplary adhesive layers and methods for their manufacture are described in U.S. Pat. No. 1,173,5422, which is incorporated herein by reference in its entirety.

[0046] 9 shows a structure comprising a substrate 900, an electron reflective layer 910 overlying the substrate, an underlayer 920 overlying the electron reflective layer 910, an adhesive layer 930 overlying the underlayer 920, and a resist 940 overlying the adhesive layer 930. Advantageously, the electron reflective layer 910 can reflect electrons generated in the underlayer 920, which can result in additional exposure dose reduction. Suitable electron reflective layers 910 and methods for their manufacture are described in U.S. Provisional Patent Application No. 63 / 484,346, which is incorporated herein by reference in its entirety.

[0047] As further described herein and with reference to FIG. 10, an embodiment of a lithography method is described. The method may include step 1100 of providing a system comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber. The exposure chamber may then comprise a substrate support and an electrode assembly. The method may further include step 1200 of disposing a substrate on the substrate support. The substrate may comprise an EM sensitive layer. The method may further include step 1300 of exposing the substrate to EM radiation, such as UV radiation or EUV radiation. During exposing the substrate to EM radiation, the method may include applying an electric field to the EM sensitive layer by an electrode pair consisting of a first electrode and a second electrode. For example, the electric field may have a magnitude of at least 0.1 kV / cm to up to 100 kV / cm, e.g., at least 0.1 kV / cm to up to 1.0 kV / cm, or at least 1.0 kV / cm to up to 10 kV / cm, or at least 10 kV / cm to up to 100 kV / cm.

[0048] Advantageously, the electric field may enhance secondary electron generation while exposing the substrate to EM radiation. A suitable electric field may consist of a constant or quasi-constant electric field, i.e., a DC field. A suitable electric field may consist of a time-varying electric field, i.e., an AC field. For example, the AC field may have a frequency of at least 1 Hz up to 1 MHz, such as 10 Hz, 100 Hz, 1 kHz, 10 kHz, or 100 kHz.

[0049] In some embodiments, the electric field may be applied substantially parallel to the EM susceptible layer, for example the configurations of Figures 2 and / or 5 may be used for this purpose.

[0050] In some embodiments, the electric field is applied substantially perpendicular to the EM susceptible layer, for example, the configurations of Figures 3 and / or 4 may be used for this purpose.

[0051] In some embodiments, the electric field comprises a component that is oblique to the EM susceptible layer.

[0052] In some embodiments, the EM sensitive layer includes an EUV resist and at least one of an underlayer, an adhesive layer, and an electron reflector layer. An embodiment of such an EM sensitive layer is illustrated by Figs. 7, 8, and 9. In fact, EUV exposure reduction may depend on generating more secondary electron yield in the photoresist. By applying an external magnetic field to the stack of layers, it is possible to simply improve the generation, and more importantly, improve the escape of the secondary electrons generated in the stack of layers and guide them to the photoresist. Although the present invention does not wish to be bound by any particular theory or mode of operation, EUV exposure reduction may be achieved by simultaneously subjecting the substrate to EUV radiation and an electric field by one or more of the following mechanisms: avalanche multiplication of secondary electrons, Pockel effect, i.e., electric field induced refractive index change for EUV radiation, and Kerr effect, i.e., electric field induced EUV polarization / propagation direction change.

[0053] For example, without the present disclosure being bound to any particular theory or mode of operation, the Pockels effect is characterized by the change in the refractive index of a material in the presence of an external electric field. The amount of change in the refractive index depends on the magnitude and direction of the applied electric field, as well as the properties of the material. The change in the refractive index can be described by the Pockels equation, which relates the change in the refractive index to the electric field strength of the material and the so-called Pockels coefficient: Δn=rE, where Δn is the change in the refractive index, r is the Pockels coefficient, and E is the electric field strength. The Pockels coefficient is a material-specific constant that depends on the crystal structure and symmetry of the material. The Pockels effect can be used to control the polarization and propagation direction of electromagnetic waves, including EUV radiation, by placing a material with the appropriate Pockels coefficient in the path of the electromagnetic wave and applying an external electric field.

[0054] For example, without the present disclosure being bound to any particular theory or mode of operation, the Kerr effect is characterized by the change in refractive index in the presence of an external electric field. The amount of change in refractive index depends on the magnitude and direction of the applied electric field, as well as the properties of the vacuum, such as its density and temperature. The change in refractive index can be described by the Kerr equation, which relates the change in refractive index to the electric field strength and the so-called Kerr constant of the vacuum: Δn=n^3*(2π / λ)^2*K*E^2, where Δn is the change in refractive index, n is the refractive index of the vacuum, λ is the wavelength of the radiation, K is the Kerr constant of the vacuum, and E is the electric field strength. The Kerr effect is relatively weak compared to other effects, such as the Pockels effect, and is usually only observable at very high electric field strengths. However, it may still play a role in certain applications. In fact, the refractive index of a material affects EUV radiation in several ways. The refractive index is a measure of how much the speed of light is reduced when it propagates through a material compared to when it propagates through a vacuum. This reduction in speed results from interactions between the electromagnetic wave and electrically charged particles within the material, which causes the electromagnetic wave to slow down and change direction. The refractive index of a material determines how much the path of the EUV wave is bent as it passes through the material, and is determined by Snell's law of refraction. When an EUV wave passes from one material to another with a different refractive index, its direction of propagation changes, which is called refraction. The amount of refraction depends on the difference in refractive index between the two materials, as well as the angle of incidence of the wave. For EUV radiation, which has a very short wavelength, the refractive index can vary significantly with wavelength and material properties. [Explanation of symbols]

[0055] 110 Electromagnetic (EM) radiation sources 120 Optical Assembly 130 Exposure chamber 131 Substrate support 132 Electrode Assembly 341 EM radiation sensitive layer

Claims

1. 1. A system for lithographic patterning of a semiconductor substrate comprising: an electromagnetic (EM) radiation source; an optical assembly; and an exposure chamber comprising a substrate support and an electrode assembly, the system comprising: the EM radiation source is configured to generate electromagnetic radiation; the optical assembly is constructed and arranged to direct the EM radiation towards the substrate support; the substrate support is constructed and arranged to support a semiconductor substrate; A system for lithographic patterning of a semiconductor substrate, wherein the electrode assembly is constructed and arranged to apply an electric field to an EM susceptible layer comprised within the semiconductor substrate.

2. The system of claim 1 , wherein the electrode assembly is constructed and arranged to apply the electric field laterally to the EM susceptible layer.

3. The system of claim 2 , wherein the electrode assembly comprises two electrodes positioned adjacent to the substrate support.

4. The system of claim 2 , wherein the electrode assembly comprises two electrodes, each comprising a plurality of fingers that together form an interdigitated pattern.

5. The system of claim 4 , wherein fingers from the plurality of fingers are parallel to one another.

6. The system of claim 1 , wherein the electrode assembly is constructed and arranged to apply the electric field laterally to the EM susceptible layer.

7. 7. The system of claim 6, wherein the electrode assembly comprises a first electrode and a second electrode, the first electrode electrically connected to the substrate support and the second electrode disposed substantially parallel to the substrate and between the substrate and the EM radiation source.

8. 7. The system of claim 6, wherein the electrode assembly comprises a first electrode and a second electrode, the first electrode electrically connected to the substrate and the second electrode disposed substantially parallel to the substrate and between the substrate and the EM radiation source.

9. The system of any one of claims 1 to 8, wherein the EM radiation source comprises an extreme ultraviolet (EUV) source.

10. - providing a system comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber comprising a substrate support and an electrode assembly; - placing a substrate on said substrate support, said substrate being provided with an EM-susceptible layer; - exposing the substrate to EM radiation; - applying an electric field to the EM sensitive layer by an electrode pair comprising a first electrode and a second electrode while exposing the substrate to EM radiation.

11. The method of claim 10 , wherein the EM radiation consists of extreme ultraviolet (EUV) radiation.

12. The method of claim 10 , wherein the electric field enhances secondary electron generation while exposing the substrate to EM radiation.

13. The method of claim 10 or 11, wherein the electric field comprises a DC electric field.

14. The method of claim 10 or 11, wherein the electric field comprises an AC electric field.

15. The method of claim 10 or 11, wherein the electric field is applied substantially parallel to the EM susceptible layer.

16. 12. The method of claim 10 or 11, wherein the electric field is applied substantially perpendicular to the EM susceptible layer.

17. 12. The method of claim 10 or 11, wherein the electric field comprises a component that is oblique to the EM susceptible layer.

18. 12. The method of claim 10 or 11, wherein the EM sensitive layer comprises an EUV resist and at least one of an underlayer, an adhesive layer, and an electron reflector layer.

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