Lithographic process window enhancement for photoresist patterning

Abstract

A method for enhancing a depth of focus window during a photolithography process includes applying a photoresist layer including a photoacid generator on a material layer disposed on a substrate, exposing a first portion of the photoresist layer not protected by a photomask to a light radiation in a photolithography exposure process, providing thermal energy to the photoresist layer in a post-exposure bake process, applying an electric field or a magnetic field while the post-exposure bake process is being performed, and dynamically changing a frequency of the generated electric field while the thermal energy is being provided to the photoresist layer.

Description

Technical Field

[0001] This disclosure generally relates to methods and apparatus for processing substrates, and more specifically to methods and apparatus for enhancing photoresist contour control. Background Technology

[0002] Integrated circuits have evolved into complex devices that can contain millions of components (e.g., transistors, capacitors, and resistors) on a single chip. Photolithography is used to form these components on the chip. Typically, the photolithography process involves several basic stages. Initially, a photoresist layer is formed on the substrate. This layer can be formed, for example, by spin coating. The photoresist layer may include a resist resin and a photoacid generator. After exposure to electromagnetic radiation during the subsequent exposure stage, the photoacid generator alters the solubility of the photoresist in the development process. Excess solvent can be removed in a pre-exposure bake process.

[0003] During the exposure stage, a photomask or mask plate can be used to selectively expose certain areas of the photoresist layer disposed on the substrate to electromagnetic radiation. Other exposure methods may include maskless exposure. The electromagnetic radiation can have any suitable wavelength, such as wavelengths in the extreme ultraviolet region. The electromagnetic radiation can be formed from any suitable source, such as a 193 nm ArF laser, electron beam, ion beam, or other source. Exposure to electromagnetic radiation causes the photoacid generator to decompose, thereby generating acid and creating a latent acid image in the resist resin. After exposure, the substrate can be heated in a post-exposure baking process. In the post-exposure baking process, the acid generated by the photoacid generator reacts with the resist resin in the photoresist layer, thereby altering the solubility of the resist in the photoresist layer during subsequent development processes.

[0004] After exposure and baking, the substrate, especially the photoresist layer, can be developed and rinsed. Following development and rinsing, a patterned photoresist layer is then formed on the substrate, as shown in FIG1. ​​FIG1 depicts an exemplary orthogonal cross-sectional view of a substrate 100 having a patterned photoresist layer 104 disposed on a target material 102 to be etched. After development and rinsing, openings 106 are defined between the patterned photoresist layers 104, thereby exposing the underlying target material 102 for etching to transfer features onto the target material 102. However, imprecise control or low resolution in the photolithography exposure process may fail to maintain the critical dimensions of the photoresist layer 104, resulting in unacceptable linewidth roughness 108. Furthermore, during the exposure process, acid generated from the photoacid generator (as shown in Figure 1) may randomly diffuse into any area, including protected areas beneath the mask where it is not desired to diffuse, thereby forming unwanted wobble or rough profiles 150 at the edges or interfaces of the patterned photoresist layer 104 adjacent to the opening 106. The large linewidth roughness 108 of the photoresist layer 104 and the unwanted wobble profiles 150 can lead to inaccurate feature transfer to the target material 102, ultimately resulting in device malfunction and yield loss.

[0005] Therefore, there is a need for a method and apparatus to control linewidth roughness and improve resolution and dose sensitivity in order to obtain patterned photoresist layers with the desired critical dimensions. Summary of the Invention

[0006] Embodiments of this disclosure include methods for effectively controlling the distribution and diffusion of acid from photoacid generators in a photoresist layer during post-exposure baking processes to improve the lithography window, such as the depth of focus range. The methods can enhance and expand the depth of focus window during lithography processes.

[0007] In one embodiment, a method of processing a substrate includes: applying a photoresist layer comprising a photoacid generator to a material layer disposed on the substrate; exposing a first portion of the photoresist layer not protected by a photomask to light radiation during a photolithography exposure process; providing heat to the photoresist layer during a post-exposure baking process; applying an electric field or magnetic field while performing the post-exposure baking process; and dynamically changing the frequency of the generated electric field while providing heat to the photoresist layer.

[0008] In another embodiment, a method for processing a substrate includes: applying a photoresist layer on the substrate; exposing a first portion of the photoresist layer not protected by a photomask to light radiation during a photolithography exposure process; performing a post-exposure baking process on the photoresist layer; and vertically changing the drift direction of the photoacid generator in the photoresist layer while providing heat energy to the photoresist layer.

[0009] In yet another embodiment, a device structure includes: a material layer disposed on a substrate, and a plurality of openings formed in the material layer, wherein the openings formed across the substrate have corner angles between about 85 degrees and about 95 degrees. Attached Figure Description

[0010] To gain a more detailed understanding of the features described above in this disclosure, a more specific description of the disclosure, which has been briefly outlined above, can be obtained by referring to the embodiments, some of which are depicted in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of the disclosure and should therefore not be construed as limiting its scope, as the disclosure allows for other equivalent embodiments.

[0011] Figure 1 depicts an orthogonal cross-sectional view of an exemplary structure of a patterned photoresist layer conventionally disposed on a substrate in the art;

[0012] Figure 2 This is a schematic cross-sectional view of an apparatus for processing a substrate according to one embodiment;

[0013] Figure 3 It is set in Figure 2 A top cross-sectional view of an embodiment of an electrode assembly in a device;

[0014] Figure 4 The acid distribution control of the photoresist layer set on the film structure during the post-exposure baking process is described;

[0015] Figure 5 This is a flowchart of a method for controlling the acid distribution of a photoresist layer during exposure and post-exposure baking processes; and

[0016] Figure 6 A schematic cross-sectional view of the photoresist layer on the substrate after exposure and baking is depicted.

[0017] For ease of understanding, the same reference numerals have been used as much as possible to denote common, identical elements in the figures. Furthermore, elements of one embodiment may be advantageously adapted to other embodiments described herein. Detailed Implementation

[0018] A method for enhancing contour control of photoresist layers formed by photolithography is provided. The diffusion of acid generated by a photoacid generator, which affects line edge / width roughness during post-exposure baking, can be controlled by adjusting the electric field applied during the post-exposure baking process. The application of the electric field controls the diffusion and distribution of the acid generated by the photoacid generator in the photoresist layer, thereby expanding the processing window that can improve lithographic resolution. For example, by appropriately controlling and assisting the diffusion of the acid generated by the photoacid generator during the post-exposure baking process, the depth of focus range during photolithography can be effectively improved and enhanced. Suitable processing parameters controlled during the post-exposure baking process include: voltage level and frequency for controlling the electric field generated during the baking process; continuous or pulsed mode of the voltage power used to generate the electric field; substrate temperature control; and the duration of the electric field applied during the post-exposure baking process. In one example, dynamic frequency control during the post-exposure baking process can be utilized.

[0019] Figure 2 This is a schematic cross-sectional view of an apparatus for processing a substrate according to one embodiment. Figure 2 As shown in the embodiments, the device can be in the form of a vacuum processing chamber 200. In other embodiments, the processing chamber 200 may not be coupled to a vacuum source.

[0020] Processing chamber 200 may be a separate, independent processing chamber. Alternatively, processing chamber 200 may be part of a processing system, such as an in-line processing system, a cluster processing system, or a track processing system. Processing chamber 200 is described in detail below and may be used for pre-exposure baking, post-exposure baking, and / or other processing steps.

[0021] Processing chamber 200 includes chamber wall 202, electrode assembly 216, and substrate support assembly 238. Chamber wall 202 includes sidewall 206, cover assembly 210, and bottom 208. Chamber wall 202 partially surrounds processing space 212. Substrate transfer port (not shown) configured to facilitate the movement of substrate 240 into and out of processing chamber 200 enters processing space 212. In embodiments where processing chamber 200 is part of a processing system, substrate transfer port may allow substrate 240 to be transferred to and from adjacent transfer chambers.

[0022] Pump port 214 may be selectively disposed through one of the cover assembly 210, sidewall 206, or bottom 208 of processing chamber 200 to couple processing space 212 to an exhaust port. The exhaust port couples pump port 214 to various vacuum pumping components, such as a vacuum pump. The pumping components reduce the pressure in processing space 212 and expel any gases and / or processing byproducts from processing chamber 200. Processing chamber 200 may be coupled to one or more supply sources 204 for delivering one or more source compounds into processing space 212.

[0023] A substrate support assembly 238 is located centrally within the processing chamber 200. The substrate support assembly 238 supports the substrate 240 during processing. The substrate support assembly 238 may include a body 224 encapsulating at least one embedded heater 232. In some embodiments, the substrate support assembly 238 may be an electrostatic chuck. The heater 232, such as a resistive element, is disposed within the substrate support assembly 238. The heater 232 controllably heats the substrate support assembly 238 and the substrate 240 located thereon to a predetermined temperature. The heater 232 is configured to rapidly raise the temperature of the substrate 240 and precisely control the temperature of the substrate 240. In some embodiments, the heater 232 is connected to and controlled by a power supply 274. The power supply 274 may alternatively or additionally apply power to the substrate support assembly 238. The power supply 274 may be configured similarly to the power supply 270, as discussed below. In addition, it should be noted that the heater 232 may be provided in other locations in the processing chamber 200 as needed, such as in the chamber wall, chamber liner, edge ring surrounding the substrate, chamber top plate, etc., to provide thermal energy to the substrate 240 disposed on the substrate support assembly 238.

[0024] In some embodiments, the substrate support assembly 238 can be configured to rotate. In some embodiments, the substrate support assembly 238 is configured to rotate about the z-axis. The substrate support assembly 238 can be configured to rotate continuously or constantly, or the substrate support assembly 238 can be configured to rotate step-wise or indexingly. For example, the substrate support assembly 238 can rotate a predetermined amount, such as 90°, 180°, or 270°, and then the rotation can be stopped for a predetermined amount of time.

[0025] Typically, the substrate support assembly 238 has a first surface 234 and a second surface 226. The first surface 234 is opposite to the second surface 226. The first surface 234 is configured to support the substrate 240. The second surface 226 has a rod 242 coupled thereto. The substrate 240 can be any type of substrate, such as a dielectric substrate, a glass substrate, a semiconductor substrate, or a conductive substrate. The substrate 240 may have a material layer 245 disposed thereon. The material layer 245 can be any desired layer. In some embodiments, the substrate 240 may have more than one material layer 245. The substrate 240 also has a photoresist layer 250 disposed on the material layer 245. During the exposure stage of the photolithography process, the substrate 240 has been previously exposed to electromagnetic radiation. The photoresist layer 250 has latent image lines 255 formed therein during the exposure stage. The latent image lines 255 may be substantially parallel. In other embodiments, the latent image lines 255 may not be substantially parallel. As also shown in the figure, the first surface 234 of the substrate support assembly 238 is separated from the electrode assembly 216 by a distance d in the z-direction. A rod 242 is coupled to a lifting system (not shown) for moving the substrate support assembly 238 between an elevated processing position (as shown) and a lowered substrate transport position. The lifting system can precisely and accurately control the position of the substrate 240 in the z-direction. In some embodiments, the lifting system can also be configured to move the substrate 240 in the x-direction, y-direction, or both. The rod 242 further provides conduits for electrical and thermocouple leads between the substrate support assembly 238 and other components of the processing chamber 200. A bellows 246 is coupled to the substrate support assembly 238 to provide a vacuum seal between the processing space 212 and the atmosphere outside the processing chamber 200, and to facilitate movement of the substrate support assembly 238 in the z-direction.

[0026] Cover assembly 210 may optionally include inlet 280 through which gas supplied by supply source 204 enters processing chamber 200. Supply source 204 may optionally pressurize processing space 212 in a controllable manner using a gas such as nitrogen, argon, helium, other gases, or combinations thereof. Gas from supply source 204 may establish a controlled environment within processing chamber 200. Actuator 290 may optionally be coupled between cover assembly 210 and electrode assembly 216. Actuator 290 is configured to move electrode assembly 216 in one or more of the x, y, and z directions. The x and y directions are referred to herein as lateral directions or dimensions. Actuator 290 enables electrode assembly 216 to scan the surface of substrate 240. Actuator 290 also enables distance d to be adjusted. In some embodiments, electrode assembly 216 is coupled to cover assembly 210 via a retaining rod (not shown). In other embodiments, the electrode assembly 216 may be coupled to the inside of the bottom 208 of the processing chamber 200, coupled to the second surface 226 of the substrate support assembly 238, or coupled to the rod 242. In other embodiments, the electrode assembly 216 may be embedded between the first surface 234 and the second surface 226 of the substrate support assembly 238.

[0027] Electrode assembly 216 includes at least a first electrode 258 and a second electrode 260. As shown, the first electrode 258 is coupled to a power supply 270, and the second electrode 260 is coupled to a selective power supply 275. In other embodiments, one of the first electrode 258 and the second electrode 260 may be coupled to a power supply, while the other electrode may be coupled to ground. In some embodiments, the first electrode 258 and the second electrode 260 are coupled to ground, and the power supply 274 that transmits power to the substrate support is a bipolar power supply that switches between positive and negative bias. In some embodiments, power supply 270 or power supply 275 may be coupled to both the first electrode 258 and the second electrode 260. In other embodiments, power supply 270 or power supply 275 may be coupled to the first electrode 258, the second electrode 260, and the substrate support assembly 238. In such embodiments, the pulse delay for each of the first electrode 258, the second electrode 260, and the substrate support assembly 238 may be different. Electrode assembly 216 may be configured to generate an electric field parallel to the xy plane defined by a first surface of the substrate support assembly 238. For example, electrode assembly 216 can be configured to generate an electric field in one of the y-direction, x-direction, or other directions in the xy-plane.

[0028] Power supplies 270 and 275 are configured, for example, to supply between about 500 V and about 100 kV to electrode assembly 216 to generate an electric field with an intensity between about 0.1 MV / m and about 100 MV / m. In some embodiments, power supply 274 may also be configured to supply power to electrode assembly 216. In some embodiments, any one or all of power supplies 270, 274, or 275 are pulsed direct current (DC) power supplies. The pulsed DC wave may originate from a half-wave rectifier or a full-wave rectifier. The DC power may have a frequency between about 10 Hz and 1 MHz. The duty cycle of the pulsed DC power may be between about 5% and about 95%, for example, between about 20% and about 60%. In some embodiments, the duty cycle of the pulsed DC power may be between about 20% and about 40%. In other embodiments, the duty cycle of the pulsed DC power may be about 60%. The rise and fall times of the pulsed DC power can be between about 1 ns and about 1000 ns, for example, between about 10 ns and about 500 ns. In other embodiments, the rise and fall times of the pulsed DC power can be between about 10 ns and about 100 ns. In some embodiments, the rise and fall times of the pulsed DC power can be about 500 ns. In some embodiments, any one or all of power supplies 270, 274, and 275 are AC power supplies. In other embodiments, any one or all of power supplies 270, 274, and 275 are DC power supplies.

[0029] In some embodiments, any one or all of power supplies 270, 274, and 275 may use DC bias. DC bias may be, for example, between about 0% and about 75% of the applied voltage, such as between about 5% and about 60% of the applied voltage. In some embodiments, the first electrode 258 and the second electrode 260 are negatively pulsed, and the substrate support assembly 238 is also negatively pulsed. In these embodiments, the first electrode 258, the second electrode 260, and the substrate support assembly 238 are synchronized but time-discrepted. For example, when the substrate support assembly is in a "zero" state, the first electrode 258 may be in a "one" state, and then when the first electrode 258 is in a "zero" state, the substrate support assembly 238 may be in a "one" state.

[0030] Electrode assembly 216 spans approximately the width of substrate support assembly 238. In other embodiments, the width of electrode assembly 216 may be less than the width of substrate support assembly 238. For example, electrode assembly 216 may span between about 10% and about 80% of the width of substrate support assembly 238, such as between about 20% and about 40%. In embodiments where the width of electrode assembly 216 is less than that of substrate support assembly 238, actuator 290 may cause electrode assembly 216 to scan the surface of substrate 240 located on the first surface 234 of substrate support assembly 238. For example, actuator 290 may scan such that electrode assembly 216 scans the entire surface of substrate 240. In other embodiments, actuator 290 may scan only certain portions of substrate 240. Alternatively, substrate support assembly 238 may scan below electrode assembly 216.

[0031] In some embodiments, one or more magnets 296 may be positioned within the processing chamber 200. Figure 2 In the illustrated embodiment, magnet 296 is coupled to the inner surface of sidewall 206. In other embodiments, magnet 296 may be located within or outside the processing chamber 200. Magnet 296 may be, for example, a permanent magnet or an electromagnet. Representative permanent magnets include ceramic magnets and rare-earth magnets. In embodiments where magnet 296 includes an electromagnet, magnet 296 may be coupled to a power source (not shown). Magnet 296 is configured to generate a magnetic field in a direction perpendicular or parallel to the direction of the electric field lines generated by electrode assembly 216 at the first surface 234 of substrate support assembly 238. For example, when the electric field generated by electrode assembly 216 is in the y-direction, magnet 296 may be configured to generate a magnetic field in the x-direction. The magnetic field drives the charged material 355 (shown in the figure) generated by photoacid generator in photoresist layer 250 along a direction perpendicular to the magnetic field, for example, parallel to the latent image line 255. Figure 3 The charged material 355 and the polarizing material (not shown) are used. The line profile of the exposed photoresist layer can be controlled by driving the charged material 355 and the polarizing material in a direction parallel to the latent image line 255. The uniform directionality and / or controlled movement of the charged material 355 and the polarizing material are controlled by… Figure 3 The double-headed arrow 370 is shown in the diagram. Conversely, as shown by arrow 370', the charged material 355 and the polarized material can move randomly when no magnetic field is applied.

[0032] Continue to refer to Figure 3The electrode assembly 216 includes at least a first electrode 258 and a second electrode 260. The first electrode 258 includes a first terminal 310, a first support structure 330, and one or more antennas 320. The second electrode 260 includes a second terminal 311, a second support structure 331, and one or more antennas 321. The first terminal 310, the first support structure 330, and the one or more antennas 320 of the first electrode 258 may be integrally formed. Alternatively, the first electrode 258 may include separate portions that can be coupled together. For example, the one or more antennas 320 may be detachable from the first support structure 330. The second electrode 260 may similarly be integral or composed of separate, detachable components. The first electrode 258 and the second electrode 260 can be manufactured using any suitable technique. For example, the first electrode 258 and the second electrode 260 can be manufactured by machining, casting, or additive manufacturing.

[0033] The first support structure 330 may be made of a conductive material. For example, the first support structure 330 may be made of silicon, polycrystalline silicon, silicon carbide, molybdenum, aluminum, copper, graphite, silver, platinum, gold, palladium, zinc, other materials, or mixtures of the above materials. The first support structure 330 may have any desired dimensions. For example, the length L of the first support structure 330 may be between about 25 mm and about 450 mm, for example, between about 100 mm and about 300 mm. In some embodiments, the length L of the first support structure 330 is approximately equal to the diameter of a standard semiconductor substrate. In other embodiments, the length L of the first support structure 330 is greater than or less than the diameter of a standard semiconductor substrate. For example, in different representative embodiments, the length L of the first support structure 330 may be about 25 mm, about 51 mm, about 76 mm, about 100 mm, about 150 mm, about 200 mm, about 300 mm, or about 450 mm. The width W of the first support structure 330 may be between about 2 mm and about 25 mm. In other embodiments, the width W of the first support structure 330 is less than about 2 mm. In other embodiments, the width W of the first support structure 330 is greater than about 25 mm. The thickness of the first support structure 330 can be between about 1 mm and about 10 mm, for example, between about 2 mm and about 8 mm, for example, about 5 mm. In some embodiments, the first support structure 330 can be square, cylindrical, rectangular, elliptical, or other shapes. Embodiments with curved outer surfaces can prevent arcing.

[0034] The second support structure 331 may be made of the same material as the first support structure 330. The size range applicable to the first support structure 330 also applies to the second support structure 331. In some embodiments, the first support structure 330 and the second support structure 331 are made of the same material. In other embodiments, the first support structure 330 and the second support structure 331 are made of different materials. The length L, width W, and thickness of the first support structure 330 and the second support structure 331 may be the same or different.

[0035] One or more antennas 320 of the first electrode 258 may also be made of a conductive material. One or more antennas 320 may be made of the same material as the first support structure 330. One or more antennas 320 of the first electrode 258 may have any desired dimensions. For example, the length L1 of one or more antennas 320 may be between about 25 mm and about 450 mm, for example, between about 100 mm and about 300 mm. In some embodiments, the length L1 of one or more antennas 320 is approximately equal to the diameter of a standard substrate. In other embodiments, the length L1 of one or more antennas 320 may be between about 75% and 90% of the diameter of a standard substrate. The width W1 of one or more antennas 320 may be between about 2 mm and about 25 mm. In other embodiments, the width W1 of one or more antennas 320 is less than about 2 mm. In other embodiments, the width W1 of one or more antennas 320 is greater than about 25 mm. The thickness of one or more antennas 320 may be between about 1 mm and about 10 mm, for example, between about 2 mm and about 8 mm. One or more antennas 320 may have a square, rectangular, elliptical, circular, cylindrical, or other cross-sectional shape. Embodiments with a circular outer surface can prevent arcing.

[0036] Each antenna 320 may have the same dimensions. Alternatively, some of the one or more antennas 320 may have different dimensions than one or more of the other antennas 320. For example, some of the one or more antennas 320 may have a different length L1 than one or more of the other antennas 320. Each of the one or more antennas 320 may be made of the same material. In other embodiments, some antennas 320 may be made of a different material than the other antennas 320.

[0037] Antenna 321 may be made of the same range of materials as antenna 320. The size range applicable to antenna 320 also applies to antenna 321. In some embodiments, antenna 320 and antenna 321 are made of the same material. In other embodiments, antenna 320 and antenna 321 are made of different materials. The length L1, width W1, and thickness of antenna 320 and antenna 321 may be the same or different.

[0038] Antenna 320 may include 1 to about 40 antennas 320. For example, antenna 320 may include about 4 to about 40 antennas 320, such as about 10 to about 20 antennas 320. In other embodiments, antenna 320 may include more than 40 antennas 320. In some embodiments, each antenna 320 may be substantially perpendicular to the first support structure 330. For example, in an embodiment where the first support structure 330 is straight, each antenna 320 may be substantially parallel to the first support structure 330. Each antenna 320 may be substantially parallel to each other antenna 320. Each antenna 321 may be similarly positioned relative to the support structure 331 and each other antenna 321.

[0039] Each antenna 320 has a terminal 323. Each antenna 321 has a terminal 325. A distance C is defined between the first support structure 330 and the terminal 325. A distance C' is defined between the second support structure 331 and the terminal 323. Each of distances C and C' may be between about 1 mm and about 10 mm. In other embodiments, distances C and C' may be less than about 1 mm or greater than about 10 mm. In some embodiments, distances C and C' are equal. In other embodiments, distances C and C' are different.

[0040] A distance A is defined between the facing surfaces of one antenna in antenna 321 and its adjacent antenna in antenna 321. A distance A' is defined between the facing surfaces of one antenna 320 and its adjacent antenna in antenna 320. Distances A and A' can be greater than about 6 mm. For example, distances A and A' can be between about 6 mm and about 20 mm, such as between about 10 mm and about 15 mm. Distances A and A' between each adjacent antenna 321, 320 can be the same or different. For example, the distances A' between the first and second antennas, the second and third antennas, and the third and fourth antennas of one or more antennas 320 can be different. In other embodiments, distance A' can be the same.

[0041] A distance B is defined between the facing surfaces of one antenna in antenna 320 and the adjacent antenna in antenna 321. The distance B can be, for example, greater than about 1 mm. For example, the distance B can be between about 2 mm and about 10 mm, such as between about 4 mm and about 6 mm. The distances B defined therebetween can be the same, each distance B can be different, or some distances B can be the same while some distances B can be different. Adjusting the distance B allows for easy control of the electric field strength.

[0042] Antennas 320 and 321 can be oriented in an alternating arrangement over photoresist layer 250. For example, antenna 320 of first electrode 258 and antenna 321 of second electrode 260 can be positioned such that at least one antenna of antenna 320 is positioned between the two antennas of antenna 321. Alternatively, at least one antenna 321 may be located between the two antennas of antenna 320. In some embodiments, all antennas of antenna 320 except for one antenna are located between the two antennas of antenna 321. In those embodiments, all antennas of antenna 321 except for one antenna may be located between the two antennas of antenna 320. In some embodiments, antenna 320 and antenna 321 may each have only one antenna.

[0043] In some embodiments, the first electrode 258 has a first terminal 310, and the second electrode 260 has a second terminal 311. The first terminal 310 may be a contact between the first electrode 258 and a power supply 270, a power supply 275, or ground. The second terminal 311 may be a contact between the second electrode 260 and a power supply 270, a power supply 275, or ground. The first terminal 310 and the second terminal 311 are shown as one end of the first electrode 258 and the second electrode 260, respectively. In other embodiments, the first terminal 310 and the second terminal 311 may be located at other positions on the first electrode 258 and the second electrode, respectively. The first terminal 310 and the second terminal 311 may have shapes and sizes different from those of the first support structure 330 and the support structure 331, respectively. In other embodiments, the first terminal 310 and the second terminal 311 may have shapes and sizes substantially the same as those of the first support structure 330 and the support structure 331, respectively.

[0044] In operation, voltage can be supplied from a power source such as power supply 270, power supply 274, or power supply 275 to the first terminal 310, the second terminal 311, and / or the substrate support assembly 238. The supplied voltage establishes an electric field between each of the one or more antennas 320 and each of the one or more antennas 321. The electric field will be strongest between the antennas of the one or more antennas 320 and the adjacent antennas of the one or more antennas 321. The staggered and aligned spatial relationship of the antennas 320 and 321 generates an electric field in a direction parallel to the plane defined by the first surface 234 of the substrate support assembly 238. The substrate 240 is positioned on the first surface 234 such that the latent image line 255 is parallel to the electric field lines generated by the electrode assembly 216. Since the charged material 355 is charged, it is affected by the electric field. The electric field drives the charged material 355 generated by the photoacid generator in the photoresist layer 250 along the direction of the electric field. By driving the charged material 355 in a direction parallel to the latent image line 255, line edge roughness can be reduced. The double-headed arrow 370 indicates uniform directional movement. Conversely, when no voltage is applied to the first terminal 310 or the second terminal 311, no electric field is generated to drive the charged material 355 in any particular direction. As a result, the charged material 355 can move randomly as indicated by arrow 370', which may lead to warnings or line roughness.

[0045] Figure 4 A film structure 404 is depicted on a substrate 400 after photolithography exposure. A photoresist layer 407 is disposed on the film structure 404. The film structure 404 includes a target layer 402 disposed on the substrate 400. The target layer 402 is then patterned to form desired device features within it. It should be noted that additional layers (e.g., hard masks), underlayers (e.g., organic materials, inorganic materials, or mixtures of organic and inorganic materials), or other suitable materials may be disposed on the target layer 402 and below the photoresist layer 407 as needed to enhance lithography resolution and photoresist profile control.

[0046] The photoresist layer 407 can be a positive photoresist and / or a negative photoresist capable of undergoing chemical amplification reactions. The photoresist layer 407 is a polymeric organic material.

[0047] In embodiments using a base layer or hard mask layer, the base layer may contain one or more additives, such as an acidagent (e.g., a photoacid generator (PAG) or acid catalyst), a base agent, a tackifier, or a photosensitizing component. One or more additives may be incorporated into an organic solvent or resin and / or an inorganic matrix material. Suitable examples of acidagents including photoacid generators (PAGs) and / or acid catalysts may be selected from the group consisting of sulfonic acids (e.g., p-toluenesulfonic acid, styrenesulfonic acid), sulfonates (e.g., pyridinium p-toluenesulfonate, pyridinium trilluoromethanesulfonate, pyridinium 3-nitrobenzensulfonate), and mixtures thereof. Suitable organic solvents may include homopolymers or higher polymers containing two or more repeating units and a polymer backbone. Suitable examples of organic solvents include, but are not limited to, propylene glycol methyl ether acetate (PGMEA), ethyl lactate (EL), propylene glycol methyl ether (PGME), propylene glycol n-propyl ether (PnP), cyclohexanone, acetone, gamma-lactone (GBL), and mixtures thereof.

[0048] In one example, the bottom layer provides an active acid, alkali, or ionic / nonionic substance during photolithography exposure, pre-exposure baking, or post-exposure baking to help control the direction of photoacid flow from the upper photoresist layer 407.

[0049] Hard mask layers can be antireflective coatings (ARCs) made of the following groups: silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, amorphous carbon, doped amorphous carbon, TEOS oxide, USG, SOG, organosilicon, oxide-containing materials, titanium nitride, titanium oxynitride, combinations thereof, and similar materials.

[0050] As described above, an electric field from the electrode 116 and a magnetic field from the magnet 296 can be applied during photolithography exposure, pre-exposure baking, or post-exposure baking, especially during post-exposure baking. Figure 4 In the example shown, an electric field and / or magnetic field are applied after photolithography exposure and during post-exposure baking. During post-exposure baking, thermal energy, along with the electric and / or magnetic fields, is applied to the substrate 400. Photoacid is generated in the first region 408 of the photoresist layer 407, such as... Figure 4 e -As shown, the photoacid generator (PAG) in this location has been exposed to light radiation 412 (e.g., UV light radiation) from the previous photolithography exposure process. However, the movement of the photoacid is typically random, and the distribution of the photoacid may be uneven in the first region 408, or the interface 430 formed in the plane defining the first region 408 and the second region 406 (adjacent to the second region 406) may not have a clear boundary, causing some of the photoacid to drift and diffuse into the second region 406, as indicated by arrow 422, where the second region 406 is not intended to have photoacid generation. Thus, as indicated by arrow 422, lateral photoacid movement (e.g., in a direction parallel to the plane of the substrate 400) drifting into the second region 406 can lead to line edge roughness, resolution loss, photoresist footing, contour distortion, and / or reduced depth of focus (DOF) windows during photolithography, resulting in the transfer of inaccurate features to the underlying target layer 402 and / or ultimately causing device failure.

[0051] Although the examples discussed herein are shown as the movement of electrons from photoacid, it should be noted that any suitable substance, including charges, charged particles, photons, ions, electrons, or any form of reactive substance, can have a similar effect when an electric field is applied to the photoresist layer 407.

[0052] By applying an electric and / or magnetic field to the photoresist layer 407 during post-exposure baking, the distribution of photoacid in the exposed first region 408 can be effectively redirected, controlled, and restricted. The electric field applied to the photoresist layer 407 can move the photoacid in the vertical direction (e.g., the y direction, substantially perpendicular to the plane of the substrate 400, indicated by arrows 416 and 420) with minimal lateral movement (e.g., the x-direction shown by arrow 422) without diffusing into the adjacent second region 406. Typically, the photoacid may have some polarity that can be influenced by the electric or magnetic field applied thereto, thereby orienting the photoacid in certain directions and producing a desired directional movement of the photoacid in the exposed first region 408 without crossing into the adjacent protected second region 406. Furthermore, when performing post-exposure baking, the roughness of the photoresist line edges, the processing window of the depth of focus (DOF) during photolithography, and the uniformity of line critical dimensions can also be well controlled, enhanced, and improved.

[0053] In one example, the photoacid can be further controlled to move directionally in the longitudinal direction (e.g., the z-direction, defined by arrow 428, in the plane adjoining the second region 406 of the photoresist layer 407 protected by photomask 410) along a transverse plane as indicated by arrow 414, to control the longitudinal distribution of the photoacid confined in the exposed first region 408 without crossing into the second region 406 of the photoresist layer 407 in the x-direction, as indicated by arrow 422. A magnetic field generated to the photoresist layer 407 can cause electrons to orbit along a magnetic field line, for example, in the longitudinal direction (e.g., the z-direction, as indicated by arrow 428), to further control the photoacid within a desired three-dimensional distribution. The interaction between the magnetic and electric fields can optimize the photoacid orbit along a desired path confined in the exposed first region 408. Furthermore, vertical photoacid movement is desired to eliminate standing waves naturally generated by the exposure tool, thereby improving exposure resolution.

[0054] In one embodiment, during post-exposure baking, an electric field with an intensity between about 100 Mv / m and about 2000 Mv / m may be applied to the photoresist layer 407 to confine photoacids generated in the photoresist layer 407 to a vertical direction, e.g., along the y-direction. In one embodiment, during post-exposure baking, a magnetic field between 5 Tesla (T) and 500 Tesla (T) may be applied to the photoresist layer 407 together with the electric field to confine photoacids generated in the photoresist layer 407 to a longitudinal and vertical direction (e.g., along the y and z directions) with minimal lateral direction (e.g., along the x-direction). When exposed to the combination of magnetic and electric fields, the generated photoacids may be further confined to a longitudinal distribution, e.g., along the direction indicated by arrow 428, and retained in a first region 408 of the photoresist layer 407, parallel to interface 430 within the exposed first region 408.

[0055] In one embodiment, an electric field and a magnetic field can be applied separately as needed. One or more characteristics of at least one electric field and magnetic field can be dynamically varied during application to control the shape of the field over time, for example, to give the field different densities, amplitudes, and / or shapes at multiple time periods within the post-exposure baking process. For example, the electric field applied during the post-exposure baking process can be controlled in a manner that restricts the movement of photoacid in certain directions and ways. In one example, the power supplied to generate the electric field during the post-exposure baking process can be controlled within a range of about 100 volts to about 5000 volts, for example, within a range of about 100 volts to about 1000 volts.

[0056] In one example, power can be applied in a modulated manner. Power can be modulated by at least one of modulating current and voltage. The frequency of power modulation is greater than 0.1 Hz, for example, between 0.5 and 10 Hz. Furthermore, the duty cycle of power application is between 25% and 75%, but can alternatively have a larger or smaller duty cycle. For example, power can be applied during multiple time periods separated by periods of no power application.

[0057] In one example, the voltage is modulated while keeping the current constant. The voltage can be modulated gradually, linearly, or using other voltage application curves. When modulated gradually, the voltage can be modulated between a first voltage and a lower second voltage. In the first example, both the first and second voltages are positive. In the second example, the first voltage is positive, and the second voltage is zero. In the third example, the first voltage is positive, and the second voltage is negative. In the second and third examples above, the amplitude of the first voltage is greater than or equal to the amplitude of the second voltage. In the above examples, the duration of applying the first voltage can be the same as, longer than, or shorter than the duration of applying the second voltage. In the above examples, the application of the first and second voltages can be cycled at least twice per second, for example, at least 30-120 times per second. Furthermore, the application of the first and second voltages can be cycled for a first time period at a first frequency, and the application of the first and second voltages can be cycled for a second time period at a second frequency. Optionally, a third voltage can be applied after the application of the first and second voltages and before a second application that cycles through the first and second voltages.

[0058] In another example, the current is modulated while keeping the voltage constant. The current can be modulated gradually, linearly, or using other current application curves. When modulated gradually, the current can be modulated between the current voltage and a lower second current. In the first example, both the first and second currents are positive. In the second example, the first current is positive, and the second current is zero. In the third example, the first current is positive, and the second current is negative. In the second and third examples above, the amplitude of the first current can be greater than or equal to the amplitude of the second current. In the above examples, the duration of applying the first current can be the same as, longer than, or shorter than the duration of applying the second current. In the above examples, the application of the first and second currents can cycle at least twice per second, for example, at least 30-120 times per second. Furthermore, the application of the first and second currents can cycle for a first time period at a first frequency, and the application of the first and second currents can cycle for a second time period at a second frequency. Optionally, a third current can be applied after the application of the first and second currents and before the second application that cycles through the first and second currents.

[0059] In yet another example, both current and voltage are modulated simultaneously.

[0060] In other examples, at least one or both of the magnetic and electric fields can be modulated. The magnetic and / or electric fields can be modulated with or without modulated power. The frequencies of the magnetic and / or electric fields are greater than 0.1 Hz, for example, between 0.5 and 10 Hz. Furthermore, the duty cycle of the applied magnetic and / or electric fields is between 25% and 75%, but can alternatively have larger or smaller duty cycles. For example, one or both of the magnetic and / or electric fields can be applied during multiple time periods separated by time periods with no field applied.

[0061] In one example, the electric field is modulated without modulating the magnetic field. The electric field can be modulated stepwise, linearly, or using other electric application curves. When modulated stepwise, the electric field can be modulated between a first electric field density and a lower second electric field density. In the first example, both the first and second electric fields are positive. In the second example, the first electric field is positive, and the second electric field is zero. In the third example, the first electric field is positive, and the second electric field is negative. In the second and third examples above, the amplitude of the first electric field is greater than or equal to the amplitude of the second electric field. In the above examples, the duration of applying the first electric field can be the same as, longer than, or shorter than the duration of applying the second electric field. In the above examples, the application of the first and second electric fields can be cycled at least twice per second, for example, at least 30-120 times per second. Furthermore, the application of the first and second electric fields can be cycled for a first time period at a first frequency, and the application of the first and second electric fields can be cycled for a second time period at a second frequency. Optionally, a third electric field can be applied after the application of the first and second electric fields and before a second application that cycles through the first and second electric fields.

[0062] In another example, the magnetic field is modulated without modulating the electric field. The magnetic field can be modulated gradually, linearly, or using other magnetic application curves. When modulated gradually, the magnetic field can be modulated between a first magnetic field density and a lower second magnetic field density. In the first example, both the first and second magnetic fields are positive. In the second example, the first magnetic field is positive, and the second magnetic field is zero. In the third example, the first magnetic field is positive, and the second magnetic field is negative. In the second and third examples above, the amplitude of the first magnetic field is greater than or equal to the amplitude of the second magnetic field. In the above examples, the duration of applying the first magnetic field can be the same as, longer than, or shorter than the duration of applying the second magnetic field. In the above examples, the application of the first and second magnetic fields can be cycled at least twice per second, for example, at least 30-120 times per second. Furthermore, the application of the first and second magnetic fields can be cycled for a first time period at a first frequency, and the application of the first and second magnetic fields can be cycled for a second time period at a second frequency. Optionally, a third magnetic field can be applied after the application of the first and second magnetic fields and before a second application that cycles through the first and second magnetic fields.

[0063] Furthermore, the applied voltage power can be in continuous mode or pulsed mode as needed. In one example, the voltage power applied to generate an electric field is in pulsed mode. In one example, the voltage power supplied to generate the electric field can be pulsed between about 5% and about 75% of each duty cycle. Each duty cycle, for example, between each time unit, is between about 0.1 seconds and about 10 seconds, for example, about 5 seconds.

[0064] In one example, the frequency of the generated electric field can be adjusted or changed at any point during the post-exposure baking process. In another example, the electric field can be generated in a dynamic frequency control mode during the post-exposure baking process. For example, the frequency of the generated electric field can be changed from a first level to a second level during a set time period, such as from approximately 0.5 seconds to approximately 10 seconds as needed. The frequency of the generated electric field can be switched back and forth between the first and second levels as needed within a given time mode. At each switch, the selected level of the electric field frequency can be maintained for a defined time period, such as from approximately 0.5 seconds to approximately 5 seconds as needed. By dynamically changing the frequency of the generated electric field, the contour of the photoresist layer can also be changed as needed.

[0065] First refer to Figure 6 The exposed photoresist layer 407 is depicted in the image. This is related to the discussion above. Figure 4Similar to the photoresist layer 407 depicted, the photoresist layer 407 has sidewalls 604 and a top surface 602. The photoresist layer 407 is disposed on the top surface 606 of the target layer 402. The top surface 602 and the sidewalls 604 define a first angle α (e.g., a corner angle). When utilizing a dynamic frequency control mode of the electric field applied during the post-exposure baking process, the first angle α can be obtained and controlled between approximately 75 degrees and 105 degrees, for example, between approximately 85 degrees and approximately 95 degrees, such as an ideal right angle close to 90 degrees. Similarly, the sidewalls 604 of the photoresist layer 407 and the top surface 606 of the target layer 402 also define a second angle β (e.g., a corner angle) between approximately 75 degrees and 105 degrees, for example, between 85 degrees and approximately 95 degrees, such as an ideal right angle close to 90 degrees. Since conventional implementations often leave scum on the top surface 606 of the target layer 402, a relatively clean surface, such as a surface free of residues and / or scum, can be obtained by utilizing a dynamic frequency control mode of the electric field applied during the post-exposure baking process. Furthermore, due to the cleaner surface, the contour of the photoresist layer 407 can be better controlled after the development process. Defects such as photoresist footing, sidewall overhangs, or top portion taper can be eliminated to provide a photoresist layer 407 with a desired contour, such as having substantially vertical sidewalls and / or a first angle α and a second angle β controlled between approximately 85 degrees and approximately 95 degrees.

[0066] Therefore, by precisely controlling the contour of the photoresist layer 407, similar angle control can be achieved at the corners of features transferred to the target layer 402 (e.g., a material layer). Consequently, the features or openings transferred to the target layer 402 can also have a good contour, with desired corner angles controlled within a range of approximately 85 degrees to approximately 95 degrees. Thus, utilizing the well-controlled and desired contour of the photoresist layer 407, high resolution of the photolithography process can be achieved by enhancing and expanding the processing window, particularly the depth of focus (DOF) during the photolithography process. For example, the processing window for the depth of focus (DOF) can be increased by 20% to approximately 95%.

[0067] Furthermore, during the post-exposure baking process, the heat supplied to the substrate 400 and the photoresist layer 407 can be controlled in a manner that also helps to limit the movement of photoacid within the photoresist layer 407. This heat can be supplied by controlling an embedded heater 232 disposed in the substrate support assembly 238. In one example, the temperature of the substrate 400 can be controlled between approximately 10 degrees Celsius (such as room temperature) and approximately 130 degrees Celsius, for example, approximately 120 degrees Celsius. It is believed that the heat supplied during the post-exposure baking process can enhance the kinetic energy or momentum of electrons driven by electric and / or magnetic fields, thereby improving the efficiency of photoacid movement control.

[0068] In some embodiments, the thermal energy supplied to the substrate 400 may be before, concurrent with, or after the period of time in which the electric field and / or magnetic field are supplied. In one example, thermal energy (e.g., activating heater 232 in the substrate support assembly 238 on which the substrate 400 is placed) is supplied to the substrate 400 before the electric field and / or magnetic field is applied to the substrate 400. It is believed that the thermal energy provided before the electric field and / or magnetic field can help activate electrons to an active state, making it relatively easy to confine or accelerate electrons along a predetermined path of motion, thereby enhancing the electrical properties of the photoresist layer, such as photon absorption efficiency, dose sensitivity, or drift directionality control, during the post-exposure baking process. Since electrons are activated and / or driven not only by the electric field / magnetic field but also by thermal energy, the total processing time, such as the total time for performing the post-exposure baking process, can be reduced to between about 5% and 40% less than the processing time in which only thermal energy is applied during the post-exposure baking process, for example, about 20%.

[0069] After exposure and baking, anisotropic etching or other suitable patterning / etching processes can be performed as needed to transfer features into target layer 402.

[0070] Figure 5 A flowchart is depicted for a method 500 for assisting in controlling the distribution / diffusion / directionality of photoacids in a photoresist layer during post-exposure baking using electric and magnetic fields. Method 500 involves placing a substrate (such as substrate 400 described above) in a processing chamber in which electrode assemblies and magnetic components are disposed (e.g., Figures 2-3 The operation begins in the processing chamber 200 depicted in the figure.

[0071] In operation 504, after the substrate 400 is positioned, an electric field and / or a magnetic field can be applied individually or jointly to the processing chamber (during the photolithography exposure process and / or post-exposure baking process) to control the photoacid movement in the photoresist layer beneath which the underlying substrate is disposed. It should be noted that the electric field and / or magnetic field can be applied simultaneously, before, or after baking the substrate 400, as will be further discussed in operation 506. In other words, the individual or joint application of the electric field and / or magnetic field to the substrate in operation 504 can be performed as needed, before or after the baking process in operation 506.

[0072] After an electric field and / or magnetic field are applied, individually or together, to the photoresist layer and the underlying layer disposed on the substrate, the resulting photoacid can move primarily in the vertical, longitudinal, circumferential, or any desired direction. The movement of the photoacid in the photoresist layer can be effectively controlled thanks to the assistance provided by the electric and / or magnetic fields during the post-exposure baking process.

[0073] In operation 506, thermal energy is provided to bake (e.g., cure) the photoresist layer. Energy (e.g., electrical, thermal, or other suitable energy) may also be provided to the photoresist layer during post-exposure baking. In one example depicted here, the energy is the thermal energy provided to the substrate during post-exposure baking, along with the electric and / or magnetic fields applied at operation 504. By utilizing a dynamic frequency control mode while applying the electric and / or magnetic fields at operation 506, a desired edge profile with high resolution, dose sensitivity, line collapse resistance, an enhanced processing window for depth of focus (DOF), and minimal line edge roughness can be obtained. Photoacids, quenchers, ions, electrons, and other charged substances in the photoresist layer can be effectively guided to move in desired directions. Therefore, the benefits of applying electric and / or magnetic fields during post-exposure baking include an enhanced processing window for depth of focus (DOF), minimum required line edge roughness, linewidth roughness, local critical dimension uniformity, critical dimension feasibility, and reduction of nanodefects such as resist slagging, line merging, and line breaking. As a result, apparatus yield is improved.

[0074] In one example, the power provided to control the electric and / or magnetic fields can be in continuous mode, pulsed mode, or a combination of continuous or pulsed modes as needed.

[0075] The embodiments described above have numerous advantages, including the following. For example, the embodiments disclosed herein can reduce or eliminate line edge / width roughness with high resolution and sharp edge contours through dynamic frequency control modes during the application of electric and / or magnetic fields during post-exposure baking processes, and enhance the depth of focus (DOF) processing window during photolithography. The foregoing advantages are illustrative and not limiting. Not all embodiments necessarily possess all the advantages.

[0076] While the foregoing description is an embodiment of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, the scope of which is determined by the appended claims.

Claims

1. A method for processing a substrate, the method comprising: A photoresist layer including a photoacid generator is applied to a material layer disposed on a substrate; In the photolithography process, a first portion of the photoresist layer that is not protected by a photomask is exposed to light radiation; Thermal energy is provided to the photoresist layer during the post-exposure baking process; An electric field is applied while performing the post-exposure baking process; and While providing the heat energy to the photoresist layer, the characteristics of the electric field are dynamically changed. The characteristics of the electric field are dynamically changed to control the roughness of the photoresist line edges and the resist dross, and the power generating the electric field is modulated to provide a first electric field and a second electric field, wherein at least one of the amplitude, shape, or power density of the first electric field is greater than or equal to at least one of the amplitude, shape, or power density of the second electric field, and wherein the application of the first electric field and the second electric field is cyclically applied at a first frequency for a first time period, and the application of the first electric field and the second electric field is cyclically applied at a second frequency for a second time period.

2. The method of claim 1, further comprising applying a magnetic field while performing the post-exposure baking process, and dynamically changing the characteristics of the magnetic field, wherein applying the electric field or the magnetic field further comprises: The application of the electric field or the magnetic field is cyclical at least twice per second.

3. The method of claim 1, wherein dynamically changing the characteristics of the electric field further comprises: Power can be applied gradually, linearly, or using a power curve.

4. The method of claim 3, wherein the power generating the electric field is modulated between a first electric field density and a lower second electric field density.

5. The method of claim 3, wherein the power generating the electric field is modulated by modulating a voltage between a first voltage and a lower second voltage to provide the first electric field and the second electric field, wherein both the first voltage and the second voltage generating the first electric field and the second electric field are positive.

6. The method of claim 3, wherein the power generating the electric field is modulated by modulating a voltage between a first voltage and a lower second voltage to provide the first electric field and the second electric field, wherein one of the first voltage and the second voltage generating the first electric field and the second electric field is zero.

7. The method of claim 3, wherein the power generating the electric field is modulated by modulating a voltage between a first voltage and a lower second voltage to provide the first electric field and the second electric field, wherein the first voltage and the second voltage generating the first electric field and the second electric field have opposite polarities.

8. The method of claim 1, wherein during the post-exposure baking process, the electric field strength is controlled between 100 MV / m and 2000 MV / m.

9. The method of claim 2, wherein applying the magnetic field further comprises: The magnetic field is controlled within the range of 5 Tesla (T) and 500 Tesla (T).

10. The method of claim 1, further comprising: Remove the first portion of the photoresist layer to form an opening in the photoresist layer; and An etching process is performed to etch the material layer through the openings in the photoresist layer.

11. The method of claim 10, further comprising forming a feature in the material layer, wherein the feature has an angle between 85 degrees and 95 degrees.

12. A method for processing a substrate, the method comprising: A photoresist layer is applied to the substrate; In the photolithography process, a first portion of the photoresist layer that is not protected by a photomask is exposed to light radiation; The photoresist layer is subjected to exposure followed by baking. and When providing heat to the photoresist layer, the drift direction of the photoacid generator in the photoresist layer is vertically changed, wherein the change of the drift direction of the photoacid generator is implemented by dynamically changing the electric field during the post-exposure baking process to control the roughness of the photoresist line edges and resist dross, and wherein dynamically changing the electric field includes modulating the power that generates the electric field to provide a first electric field and a second electric field, wherein when providing heat to the photoresist layer, at least one of the amplitude, shape, or power density of the first electric field is greater than or equal to at least one of the amplitude, shape, or power density of the second electric field, and wherein the application of the first electric field and the second electric field is cyclically applied at a first frequency for a first time period, and the application of the first electric field and the second electric field is cyclically applied at a second frequency for a second time period.

13. The method of claim 12, wherein modulating the electric field further comprises: The electric field is applied at least twice per second.

14. The method of claim 12, wherein modulating the electric field further comprises: Power can be applied gradually, linearly, or using a power curve.

15. The method of claim 12, wherein changing the drift direction of the photoacid generator further comprises: Modulate the magnetic field.

16. The method of claim 15, wherein modulating the electric field further comprises: A first voltage and a second voltage are applied during different time periods of the post-exposure baking process, wherein at least one of the following is true: (a) the first voltage is zero or has a positive polarity, and (b) the second voltage is zero or has a negative polarity.

17. A semiconductor device structure, comprising: A material layer disposed on a substrate; and A plurality of openings are formed in the material layer, wherein the openings formed across the substrate have an angle between 85 degrees and 95 degrees, and wherein the openings have a linewidth roughness between 3 nm and 5 nm. The semiconductor device structure is formed by the method described in claim 1 or 12.

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