Method and system for electric field assisted lithography

Abstract

The invention relates to a lithographic system and method. Embodiments of the methods disclosed herein include exposing a substrate to an electric field while exposing the substrate to electromagnetic radiation. Thus, a dose reduction can be obtained.

Description

Technical Field

[0001] The present disclosure is in the field of lithography, such as EUV lithography, for patterning of substrates such as semiconductor substrates. Background Art

[0002] Extreme ultraviolet (EUV) lithography is an enabling technology for advanced semiconductor processing. But it is still expensive, with a high cost per photon. Therefore, there is a need for dose reduction, where “dose” refers to the number of photons required to fully expose the resist. Summary of the invention

[0003] A system for photolithographically patterning a semiconductor substrate is described herein, comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber, the exposure chamber comprising a substrate support and an electrode assembly; the EM radiation source is configured to generate electromagnetic radiation; the optical assembly is constructed and arranged to direct the EM radiation to the substrate support; the substrate support is constructed and arranged to support a semiconductor substrate; and the electrode assembly is constructed and arranged to apply an electric field to an EM-sensitive layer contained in the semiconductor substrate.

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

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

[0006] In some embodiments, the electrode assembly includes two electrodes, each electrode including a plurality of fingers that together form an interdigitated pattern.

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

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

[0009] In some embodiments, the electrode assembly includes a first electrode and a second electrode, wherein the first electrode is electrically connected to a substrate support, and wherein the second electrode is positioned substantially parallel to the substrate, between the substrate and a source of EM radiation.

[0010] In some embodiments, the electrode assembly includes a first electrode and a second electrode, wherein the first electrode is electrically connected to the substrate, and wherein the second electrode is positioned substantially parallel to the substrate, between the substrate and a source of EM radiation.

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

[0012] Also described herein is a method comprising: providing a system comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber, the exposure chamber comprising a substrate support and an electrode assembly; positioning a substrate on the substrate support, the substrate comprising an EM-sensitive layer; exposing the substrate to the EM radiation; and while exposing the substrate to the EM radiation, applying an electric field to the EM-sensitive layer through an electrode pair comprising a first electrode and a second electrode.

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

[0014] In some embodiments, when the substrate is exposed to EM radiation, the electric field enhances secondary electron generation.

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

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

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

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

[0019] In some embodiments, the electric field includes a component that is tilted relative to the EM sensitive layer.

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

[0021] This summary is provided to introduce some concepts in a simplified form. These concepts are further described in detail in the detailed description of the example embodiments disclosed below. This summary is not intended to identify the 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 An embodiment of a system 100 for forming a pattern on a substrate is shown.

[0023] Figures 2 to 6 Embodiments of electrode assemblies 200 - 600 described herein are shown.

[0024] Figures 7 to 9 An embodiment of the structure described herein is shown.

[0025] Fig.10 An embodiment of the method described herein is shown.

[0026] It should be understood that the elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, the size of some elements in the drawings may be exaggerated relative to other elements to help improve the understanding of the illustrated embodiments of the present disclosure. DETAILED DESCRIPTION

[0027] Although certain embodiments and examples are disclosed below, those skilled in the art will appreciate that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention and their obvious modifications and equivalents. Therefore, it is intended that the scope of the disclosed invention should not be limited by the specifically disclosed embodiments described below.

[0028] As used herein, the term "substrate" may refer to any one or more underlying materials, including any one or more underlying materials 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. A plate-like substrate may include wafers of various shapes and sizes. A substrate may be made of semiconductor materials, including, for example, silicon, silicon germanium, silicon oxide, gallium arsenide, gallium nitride, and silicon carbide.

[0029] The continuous substrate may extend beyond the boundaries of the processing chamber in which the deposition process occurs. In some processes, the continuous substrate may be moved through the processing chamber so that the process continues until the end of the substrate is reached. The continuous substrate may be provided from a continuous substrate feed system to allow the continuous substrate to be manufactured and output in any suitable form.

[0030] The illustrations presented herein are not meant to be actual views of any particular material, structure, or device but are merely idealized representations used to describe embodiments of the present disclosure.

[0031] The specific embodiments shown and described are illustrations of the present invention and its best mode and are not intended to limit the scope of these aspects and embodiments in any way. In fact, for the sake of brevity, the traditional manufacturing, connection, preparation and other functional aspects of the system may not be described in detail. In addition, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and / or physical connections between various elements. Many alternative or additional functional relationships or physical connections may exist in actual systems, and / or may not exist in some embodiments.

[0032] It should be understood that the configuration and / or method described herein are exemplary in nature, and these specific embodiments or examples should not be considered restrictive, because many variations are possible. The specific routine or method described herein can represent one or more of any number of processing strategies. Therefore, the various actions shown can be performed in the order shown, in other orders, or omitted in some cases.

[0033] The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems and configurations, and other features, functions, acts and / or properties disclosed herein, and any and all equivalents thereof.

[0034] A system for lithographically patterning a semiconductor substrate is described herein. 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 the electromagnetic 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 in the semiconductor substrate. In some embodiments, the EM radiation source includes an extreme ultraviolet (EUV) source.

[0035] In some embodiments, the electrode assembly is constructed and arranged to apply an electric field laterally to the EM sensitive layer. Examples of such embodiments are shown in FIG. Figure 2 , 5 and 6 are shown.

[0036] In some embodiments, the electrode assembly includes two electrodes positioned adjacent to the substrate support. Examples of such embodiments are shown in FIG. Figure 2 Shown.

[0037] In some embodiments, the electrode assembly includes two electrodes, each electrode including a plurality of fingers that together form a cross-hatched pattern. Examples of such embodiments are shown in FIG. Figure 5 and 6 Shown.

[0038] In some embodiments, the electrode assembly is constructed and arranged to apply an electric field laterally to the EM sensitive layer. Examples of such embodiments are shown in FIG. Figure 3 and 4 Shown.

[0039] 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 positioned substantially parallel to the substrate, between the substrate and the EM radiation source. Examples of such embodiments are shown in FIG. Figure 3 Shown.

[0040] refer to Figure 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) radiation, and extreme ultraviolet (EUV) radiation. The EM radiation may pass through an optical assembly 120 to 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, such as a Bragg reflector. 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 includes 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 a metal organic resist. The exposure chamber 130 also includes an electrode assembly 132. The electrode assembly may be constructed and arranged to apply an electric field to the EM-sensitive layer. Thus, the EM radiation dose, such as an EUV dose, required to develop the EM-sensitive layer after exposure may be advantageously reduced.

[0041] Figure 2 An embodiment of an electrode assembly 200 as described herein is shown. Figure 2 The embodiment comprises two electrodes 211, 212 which can be positioned adjacent to, i.e. to the side 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 included in the substrate 240. The electrodes 211, 212 can be connected to a voltage source 220 via a wire 230. Figure 2 The electrode assembly 200 is shown with a DC voltage source 220. Additionally or alternatively, the electrode assembly 200 may include an AC voltage source.

[0042] Figure 3 Another embodiment of an electrode assembly 300 described herein is shown. Figure 3Embodiments of include two electrodes 311, 312. The first electrode 311 is positioned parallel to the substrate 340 including the EM radiation patternable layer 341, on the side of the substrate including the EM radiation sensitive 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 thin enough to allow most of the EUV radiation to pass through. For example, the first electrode can have a thickness of at least 1.0 nm to at most 10 μm, or at least 1.0 nm to at most 10 nm, or at least 10 nm to at most 100 nm, or at least 100 nm to at least 1 μm, or at least 1 μm to at most 10 μm. For example, the first electrode can allow 10 to 99%, or 20 to 99%, or 50 to 99%, or 70 to 99%, or greater than 99%, or substantially all of the incident EUV radiation to pass through. Note that although all materials absorb EUV radiation at least to some extent.

[0043] The second electrode is included in the substrate support 350, which supports the substrate 340 at the far side of the substrate 340. The first electrode 311 and the second electrode 312 can be parallel, or can be substantially parallel. Therefore, the electric field can be applied transversely to the patternable layer 341, that is, perpendicular to the plane of the patternable layer 341. The electrodes 311, 312 can be connected to the voltage source 320 through the wire 330. Figure 3 The electrode assembly 300 is shown with a DC voltage source 320. Additionally or alternatively, the electrode assembly 300 may include an AC voltage source.

[0044] Figure 4 Another embodiment of an electrode assembly 400 described herein is shown. Figure 4 The embodiment includes two electrodes 411, 412. The first electrode 411 is positioned parallel or substantially parallel to a substrate 440 including an EM radiation patternable layer 441, on a side of the substrate including an EM radiation sensitive layer 441. The first electrode may be transparent to EM radiation. The second electrode 412 electrically contacts the substrate 440. It should be understood that, at least in this embodiment, the substrate includes an electrical conductor, such as a metal or a doped or undoped semiconductor. The first electrode 411 and the substrate 440 may be parallel, or may be 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 via a wire 430. Figure 4 The electrode assembly 400 is shown with a DC voltage source 420. Additionally or alternatively, the electrode assembly 400 may include an AC voltage source.

[0045] Figure 5 Another embodiment of an electrode assembly 500 described herein is shown. Figure 5The embodiment comprises two electrodes 511, 512 that cross each other. The first electrode 511 and the second electrode 512 each comprise a plurality of alternating wires 513, 514 or sheets or the like, which are particularly positioned parallel or substantially parallel to each other and parallel to the substrate. The wires 513 from the first electrode 511 are alternated with the wires 514 from the second electrode 512 to form a cross pattern. The first and second electrodes 511, 512 are positioned on the side of the substrate comprising the EM radiation sensitive layer 541. The first electrode may be transparent to EM radiation. Thus, the electric field may be applied substantially parallel to the patternable layer 541, i.e. substantially in the plane of the patternable layer 541. The electrodes 511, 512 may be connected to a voltage source 540 via wires 530. Figure 5 The electrode assembly 500 is shown with a DC voltage source 520. Additionally or alternatively, the electrode assembly 500 may include an AC voltage source.

[0046] Figure 6 Shows the available Figure 5 The first electrode 611 and the second electrode 612 respectively include a plurality of first electrode fingers 613 and second electrode fingers 614. The first electrode fingers 613 and the second electrode fingers 614 are arranged in a staggered or intersecting pattern.

[0047] In some embodiments, the EM sensitive layer comprises a layer sensitive to EUV radiation, ie, an EUV resist. Figures 7 to 9 An exemplary structure including EUV resist is shown.

[0048] Figure 7 A structure is shown including a substrate 700, an underlayer 720 overlying the substrate 700, and a resist 740 overlying the underlayer 720. Suitable underlayers are described in any of US Patent Application Nos. 17 / 899,928, 17 / 900,578, and 17 / 900,065, the entire contents of which are incorporated herein by reference.

[0049] Figure 8 A structure is shown including a substrate 800, an underlayer 820 covering the substrate 800, a glue layer 830 covering the underlayer 820, and a resist 840 covering the glue layer 830. Advantageously, the glue layer 830 can provide adhesion between the underlayer 820 and the resist 840. Exemplary glue layers and methods of making the same are described in U.S. Pat. No. 11735422, the entire contents of which are incorporated herein by reference.

[0050] Fig. 9A structure including a substrate 900, an electron reflective layer 910 covering the substrate, an underlayer 920 covering the electron reflective layer 910, a glue layer 930 covering the underlayer 920, and a resist 940 covering the glue layer 930 is shown. Advantageously, the electron reflective layer 910 can reflect electrons generated in the underlayer 920, which can result in additional dose reduction. Suitable electron reflective layers 910 and methods of making the same are described in U.S. Provisional Application No. 63 / 484,346, the entire contents of which are incorporated herein by reference.

[0051] Here is the reference Fig.10 An embodiment of a lithography method is further described. The method may include a step 1100 of providing a system including an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber. The exposure chamber may in turn include a substrate support and an electrode assembly. The method may also include a step 1200 of positioning a substrate on the substrate support. The substrate may include an EM sensitive layer. The method may also include a step 1300 of exposing the substrate to EM radiation, such as UV radiation or EUV radiation. When exposing the substrate to the EM radiation, the method may include applying an electric field to the EM sensitive layer through an electrode pair including a first electrode and a second electrode. For example, the electric field may have a magnitude of at least 0.1 kV / cm to at most 100 kV / cm, such as at least 0.1 kV / cm to at most 1.0 kV / cm, or at least 1.0 kV / cm to at most 10 kV / cm, or at least 10 kV / cm to at most 100 kV / cm.

[0052] Advantageously, the electric field can enhance secondary electron production when the substrate is exposed to EM radiation. Suitable electric fields can include constant or quasi-constant fields, i.e., DC fields. Suitable electric fields can include time-varying fields, i.e., AC fields. For example, the AC field can have a frequency of at least 1 Hz to at most 1 MHz, such as 10 Hz, 100 Hz, 1 kHz, 10 kHz, or 100 kHz.

[0053] In some embodiments, the electric field may be applied substantially parallel to the EM sensitive layer. Figure 2 and Figure 5 At least one of the configurations can be used for this purpose.

[0054] In some embodiments, the electric field is applied substantially perpendicular to the EM sensitive layer. Figure 3 and Figure 4 At least one of the configurations can be used for this purpose.

[0055] In some embodiments, the electric field includes a component that is tilted relative to the EM sensitive layer.

[0056] In some embodiments, the EM sensitive layer includes an EUV resist and at least one of an underlayer, a glue layer, and an electron reflector layer. Figure 7 , 8 and 9. In fact, EUV dose reduction can rely on generating more secondary electrons inside the photoresist. By applying an external field to the stack, the generation of secondary electrons generated inside the stack and more importantly the escape of secondary electrons can be simply improved and directed to the photoresist. Without wishing to be bound by any particular theory or mode of operation, it is believed that EUV dose reduction can be achieved by subjecting the substrate to EUV radiation and an electric field simultaneously by one or more of the following mechanisms: avalanche multiplication of secondary electrons, the Pockels effect, i.e., electric field induced refractive index change of EUV radiation, and the Kerr effect, i.e., electric field induced EUV polarization / propagation direction change.

[0057] For example, the present disclosure is not bound by any particular theory or mode of operation, and the Pockels effect is characterized by a 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 refractive index can be described by the Pockels equation, which relates the change in refractive index to the strength of the electric field and the so-called Pockels coefficient of the material: Δn=rE, where Δn is the change in refractive index, r is the Pockels coefficient, and E is the strength of the electric field. 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 an appropriate Pockels coefficient in the path of the wave and applying an external electric field.

[0058] For example, the present disclosure is not bound by any particular theory or mode of operation, and the Kerr effect is characterized by a change in the refractive index 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 vacuum, such as its density and temperature. The change in the refractive index can be described by the Kerr equation, which relates the change in the refractive index to the strength of the electric field and the so-called Kerr constant of the vacuum: Δn=n^3*(2π / λ)^2*K*E^2, where Δn is the change in the 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 strength of the electric field. Compared to other effects such as the Pockels effect, the Kerr effect is relatively weak and is usually only observed at very high electric field strengths. However, it can still play a role in certain applications. In fact, the refractive index of a material affects EUV radiation in many ways. The refractive index is a measure of how much the speed of light is reduced when it propagates in a material compared to when it propagates in a vacuum. This reduction in speed is caused by the interaction between the electromagnetic wave and the charged particles in the material, which causes the wave to slow down and change direction. The refractive index of a material determines how much the path of an EUV wave bends as it passes through that material, as determined by Snell's law of refraction. When an EUV wave passes from one material into another material with a different refractive index, its direction of travel changes, a process known as refraction. The amount of refraction depends on the difference in refractive indices between the two materials, as well as the angle of incidence of the wave. For EUV radiation with very short wavelengths, the refractive index varies significantly with wavelength and material properties.

Claims

1. A system for photolithographically patterning a semiconductor substrate, comprising an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber, the exposure chamber comprising a substrate support and an electrode assembly; The EM radiation source is configured to generate electromagnetic radiation; an optical assembly constructed and arranged to direct EM radiation toward a substrate support; a substrate support constructed and arranged to support a semiconductor substrate; The electrode assembly is constructed and arranged to apply an electric field to an EM-sensitive layer contained in a semiconductor substrate.

2. The system according to claim 1, wherein: The electrode assembly is constructed and arranged to apply an electric field laterally to the EM sensitive layer.

3. The system according to claim 2, wherein: The electrode assembly includes two electrodes positioned adjacent to the substrate support.

4. The system according to claim 2, wherein: The electrode assembly includes two electrodes, each electrode including a plurality of fingers that together form an interdigitated pattern.

5. The system according to claim 4, wherein: Fingers from the plurality of fingers are parallel to each other.

6. The system according to claim 1, wherein: The electrode assembly is constructed and arranged to apply an electric field laterally to the EM sensitive layer.

7. The system according to claim 6, wherein: The electrode assembly includes a first electrode and a second electrode, wherein the first electrode is electrically connected to the substrate support, and wherein the second electrode is positioned substantially parallel to the substrate, between the substrate and the EM radiation source.

8. The system according to claim 6, wherein: The electrode assembly includes a first electrode and a second electrode, wherein the first electrode is electrically connected to a substrate, and wherein the second electrode is positioned substantially parallel to the substrate, between the substrate and the EM radiation source.

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

10. A method comprising: - providing a system including an electromagnetic (EM) radiation source, an optical assembly, and an exposure chamber, the exposure chamber including a substrate support and an electrode assembly; - positioning a substrate on a substrate support, the substrate comprising an EM-sensitive layer; - exposing the substrate to EM radiation; - When exposing the substrate to EM radiation, an electric field is applied to the EM sensitive layer by means of an electrode pair comprising a first electrode and a second electrode.

11. The method according to claim 10, wherein: The EM radiation includes extreme ultraviolet (EUV) radiation.

12. The method according to claim 10, wherein: When the substrate is exposed to EM radiation, the electric field enhances secondary electron generation.

13. The method according to any one of claims 10 to 12, wherein: The electric field comprises a DC field.

14. The method according to any one of claims 10 to 13, wherein: The electric field comprises an AC field.

15. The method according to any one of claims 10 to 14, wherein: The electric field is applied substantially parallel to the EM sensitive layer.

16. The method according to any one of claims 10 to 14, wherein: The electric field is applied substantially perpendicular to the EM sensitive layer.

17. The method according to any one of claims 10 to 14, wherein: The electric field comprises a component that is tilted relative to the EM sensitive layer.

18. The method according to any one of claims 10 to 17, wherein: The EM sensitive layer includes EUV resist and at least one of a primer layer, a glue layer and an electron reflector layer.

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