Method for patterning integrated circuits

Abstract

An embodiment of the present invention discloses a method for patterning an integrated circuit, comprising: forming a resist pattern having grooves oriented longitudinally along a first direction and separated by resist walls along both the first direction and a second direction perpendicular to the first direction. The method also includes: loading the resist pattern into an ion implanter so that the top surface of the resist pattern faces the ion propagation direction; and tilting the resist pattern so that the ion propagation direction forms an inclination angle relative to an axis perpendicular to the top surface of the resist pattern. The method also includes: rotating the resist pattern around the axis to a first position; injecting ions into the resist wall when the resist pattern is in the first position; rotating the resist pattern around the axis 180 degrees to a second position; and injecting ions into the resist wall when the resist pattern is in the second position.

Description

Technical Field

[0001] Embodiments of the present invention relate to methods of patterning integrated circuits. Background Art

[0002] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, each smaller and more complex than the previous one. In the evolution of integrated circuits, functional density (i.e., the number of interconnected devices per chip area) has generally increased, while their geometry (i.e., the smallest component or line that can be manufactured using a manufacturing process) has decreased. This scaling down process generally brings the benefits of increased production efficiency and reduced associated costs. This scaling down has also increased the complexity of processing and manufacturing ICs, and similar developments in IC processing and manufacturing are needed to realize these advantages.

[0003] For example, photolithography is a technique often used in IC manufacturing to transfer IC designs to semiconductor substrates. A typical photolithography process includes: coating a resist (or photoresist or photoresist) over a substrate; exposing the resist to radiation (such as deep ultraviolet (DUV) rays or extreme ultraviolet (EUV) rays); and developing and partially stripping the resist to leave a patterned resist (or resist pattern) over the substrate. The patterned resist is then used in a subsequent etching process to form the IC. With the continued miniaturization of ICs, even the resolution of EUV lithography (e.g., pitch ≤ 35nm) may not be sufficient to meet design requirements in some cases, especially when considering both one-dimensional dimensions (e.g., line width) and two-dimensional dimensions (e.g., line end to line end space). This is because the process of reducing one-dimensional dimensions sometimes increases two-dimensional dimensions at the same time. Therefore, in order to meet the needs of continued miniaturization of semiconductors, advances in photolithography processes are generally expected. Summary of the invention

[0004] According to one aspect of the present invention, a method for patterning an integrated circuit is provided, comprising: forming a resist layer above a structure; patterning the resist layer to produce a resist pattern, the resist pattern having elongated grooves oriented substantially along a first direction in length, and adjacent grooves being separated by resist walls along the first direction and a second direction perpendicular to the first direction; loading the structure and the resist pattern into an ion implanter so that the top surface of the resist pattern faces the ion propagation direction of the ion implanter; tilting the structure and the resist pattern so that the ion propagation direction forms an inclination angle relative to an axis perpendicular to the top surface of the resist pattern; performing a first rotation of the structure and the resist pattern around the axis to a first position so that the ion propagation direction is located in a plane containing the first direction and the axis; first injecting ions into the resist wall when the structure and the resist pattern are in the first position; after the first injection, performing a second rotation of the structure and the resist pattern around the axis by 180 degrees to a second position; and second injecting ions into the resist wall when the structure and the resist pattern are in the second position.

[0005] According to another aspect of the present invention, a method for patterning an integrated circuit is provided, comprising: forming a resist pattern above a structure, wherein the resist pattern comprises a first resist wall oriented longitudinally substantially along a first direction and a second resist wall oriented longitudinally substantially along a second direction perpendicular to the first direction, and the first resist wall and the second resist wall intersect; loading the structure and the resist pattern into an ion implanter so that a top surface of the resist pattern faces an ion propagation direction of the ion implanter; tilting the structure and the resist pattern so that the ion propagation direction forms an inclination angle of at least 40 degrees relative to an axis perpendicular to the top surface of the resist pattern; and placing the structure and the resist pattern around an ion implanter. The axis is initially rotated to an initial position so that the ion propagation direction is in an initial plane containing a first direction and the axis; the structure and the resist pattern are first rotated around the axis from the initial position to a first position by a first angle, the first angle being less than 90 degrees; ions are first injected into the first resist wall and the second resist wall when the structure and the resist pattern are in the first position; after the first injection, the structure and the resist pattern are second rotated around the axis from the first position to a second position by a second angle, the second angle being less than the sum of 90 degrees and the complementary angle of the first angle; and ions are second injected into the first resist wall and the second resist wall when the structure and the resist pattern are in the second position.

[0006] According to another aspect of the present invention, a method for patterning an integrated circuit is provided, comprising: forming a resist pattern above a structure; loading the structure and the resist pattern into an ion implanter so that the top surface of the resist pattern faces the ion propagation direction of the ion implanter; using the ion implanter to first implant ions into the resist pattern using a first recipe, the first recipe comprising applying a first ion dose to the resist pattern, wherein the resist pattern is maintained at a first tilt angle and each of a plurality of first twist angles; and using the ion implanter to second implant ions into the resist pattern using a second recipe, the second recipe comprising applying a second ion dose to the resist pattern, wherein the resist pattern is maintained at a second tilt angle and each of a plurality of second twist angles, wherein the first ion dose is different from the second ion dose, the first tilt angle is different from the second tilt angle, or the plurality of first twist angles are different from the plurality of second twist angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Aspects of the present invention will be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, the dimensions of the various components may be arbitrarily increased or decreased for clarity of discussion.

[0008] Figure 1A , Figure 1B , Figure 1C and Figure 1D Various flow charts of methods of forming a target pattern on a substrate for implementing one or more embodiments of the present invention are shown.

[0009] Figure 2 , Figure 3 and Figure 4 A three-dimensional view of forming a target pattern according to the method of FIG. 1 is shown according to some embodiments.

[0010] Figure 5 Ion beam tilt angle and twist angle during ion implantation in operation of the method of FIG. 1 are shown.

[0011] Fig. 6A and Figure 6B A side view and a top view of processing a target pattern for implementing an embodiment of the present invention are shown.

[0012] Figure 6C and Fig.6D A side view and a top view of processing a target pattern for implementing an embodiment of the present invention are shown.

[0013] Fig. 7A and Figure 7B A side view and a top view of processing a target pattern for implementing an embodiment of the present invention are shown.

[0014] Fig. 8A , Figure 8B and Figure 8C The structure is shown rotating during one or more embodiments of the present invention.

[0015] Fig.9A and Fig. 9B A top view of processing a target pattern for implementing another embodiment of the present invention is shown.

[0016] Fig.10 A top view of processing a target pattern for implementing yet another embodiment of the present invention is shown.

[0017] Fig.11A and Fig. 11B Tilting a structure in an ion implanter during one or more embodiments of the present invention is shown.

[0018] Fig. 12A and Fig. 12B Cross-sectional views of a resist pattern before and after processing are shown according to an embodiment of the present invention.

[0019] Fig. 12C , Fig.12D and Fig.12E A cross-sectional view showing forming a target pattern and forming a circuit pattern according to an embodiment of the present invention is shown.

[0020] Fig.13A and 13B Components of an ion implanter useful in implementing one or more embodiments of the present invention are shown. DETAILED DESCRIPTION

[0021] The following disclosure provides many different embodiments or examples of different components for implementing the provided subject matter. Specific examples of components and arrangements are described below to simplify the present invention. Of course, these are merely examples and are not intended to limit the present invention. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are directly contacted, and may also include an embodiment in which an additional component may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. In addition, the present invention may repeat reference numerals and / or characters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0022] Moreover, for ease of description, spatially relative terms such as "under," "below," "lower," "above," "upper," and the like may be used herein to describe the relationship of one element or component to another (or other) elements or components as shown in the figures. Spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein may be interpreted accordingly. In addition, when "about," "approximately," and the like are used to describe a number or a range of numbers, unless otherwise stated, the term encompasses numbers within certain variations (such as plus or minus 10% or other variations) of the number, based on the knowledge of those skilled in the art in view of the specific technology disclosed herein. For example, the term "about 5 nm" may encompass a size range from 4.5 nm to 5.5 nm, 4.0 nm to 5.0 nm, and the like.

[0023] The present invention generally relates to forming patterns or devices for integrated circuits (ICs) using photolithography processes, and more specifically to methods for treating a patterned resist layer (or resist pattern) using ion implantation from one or more pairs of directions so as to reduce a dimension of the resist pattern (corresponding to a line end to line end space in a metal layer) without (or not significantly) enlarging another dimension of the resist pattern (corresponding to a line width in the metal layer). The treated resist pattern is used in a subsequent etching process, which ultimately results in forming metal lines in the metal layer or forming other circuit components (such as silicon fins). The disclosed method can be used in conjunction with EUV lithography to achieve direct patterning of advanced process nodes with only one lithography patterning process and one etching process (so-called 1P1E), or can be used with EUV or other lithography processes to expand the process window during a double patterning process (e.g., two lithography patterning and two etching processes or so-called 2P2E processes).

[0024] Figures 1A to 1D A flow chart of a method 100 for forming a target pattern or device according to various aspects of the present invention is shown. Additional operations may be provided before, during, and after the method 100, and some operation descriptions may be replaced, eliminated, or moved. The method 100 is an example and is not intended to limit the present invention beyond what is explicitly described in the claims. Figures 2 to 10 Method 100 is described.

[0025] In operation 102, method 100 ( Figure 1A ) A resist layer 210 is formed over the structure 209, such as Figure 2 Reference Figure 2In various embodiments, the structure 209 includes a substrate 202 and various layers thereon. The substrate 202 includes one or more material layers and is an intermediate step in a manufacturing process for forming the device 200.

[0026] Device 200 may be an IC or a portion thereof, which may include static random access memory (SRAM) and / or other logic circuits, passive components (such as resistors, capacitors, and inductors), and active components such as p-type field effect transistors (PFETs), n-type FETs (NFETs), metal oxide semiconductor field effect transistors (MOSFETs), complementary metal oxide semiconductor (CMOS) transistors, bipolar transistors, high voltage transistors, high frequency transistors, other memory cells, and combinations thereof. Device 200 may include three-dimensional devices and multi-gate devices such as dual-gate FETs, FinFETs, tri-gate FETs, ΩFETs, gate-all-around (GAA) devices, and vertical GAA devices.

[0027] In one embodiment, substrate 202 is a semiconductor substrate (e.g., a silicon wafer). In one embodiment, substrate 202 includes silicon in a crystalline structure. In an optional embodiment, substrate 202 includes other elemental semiconductors such as germanium, or compound semiconductors such as silicon carbide, gallium arsenide, indium arsenide, and indium phosphide. Substrate 202 may include a silicon-on-insulator (SOI) substrate, may be strained / stressed to improve performance, may include epitaxial regions, may include isolation regions, may include doped regions, may include one or more semiconductor devices or portions thereof (such as fins, nanowires, nanosheets), may include conductive layers (such as source, drain, gate, contact, etc.) and / or non-conductive layers, and / or may include other suitable components and layers.

[0028] In this embodiment, the various layers between the substrate 202 and the resist layer 210 include a dielectric layer 203, a hard mask layer 204, a bottom material layer 206, and an anti-reflective coating (ARC) 208. In various embodiments, some of the material layers 203, 204, 206, and 208 may be omitted and / or replaced, or alternatively, other material layers may be added between the resist layer 210 and the substrate 202. In one embodiment, the resist layer 210 is formed by a spin coating process followed by a soft bake process.

[0029] In one embodiment, dielectric layer 203 comprises a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, tetraethyl orthosilicate (TEOS), phosphosilicate glass (PSG), low-k dielectric material, other suitable dielectric materials or combinations thereof. In one embodiment, dielectric layer 203 is an interlayer dielectric (ILD) layer in which metal lines are to be formed. To facilitate this embodiment, resist layer 210 is patterned with grooves, which are then transferred to dielectric layer 203. The grooves in dielectric layer 203 are filled with one or more metals to form metal lines. In some embodiments, dielectric layer 203 is formed by a flowable CVD (FCVD) process, which includes, for example, depositing a flowable material (e.g., a liquid compound) over substrate 202 and converting the flowable material into a solid material by a suitable technique such as thermal annealing and / or ultraviolet radiation treatment. Dielectric layer 203 may include a multilayer structure having a variety of dielectric materials. For example, dielectric layer 203 may include a 30 nm thick TEOS layer over another low-k oxide layer that is approximately 170 nm to 200 nm thick.

[0030] In various embodiments, the hard mask layer 204 may use amorphous silicon (a-Si), silicon oxide, silicon nitride, titanium nitride, silicon oxide, silicon carbide nitride or other suitable materials or components; the bottom material layer 206 may contain silicon, oxygen and / or carbon such as spin-on glass (SOG); the ARC layer 208 may be a polymer material layer (e.g., containing carbon, hydrogen and oxygen for enhancing the adhesion of the resist 210) or a silicon-containing material layer such as amorphous silicon, silicon oxide, silicon carbide and plasma enhanced chemical vapor deposition silicon oxide. The various material layers 204, 206 and 208 may be formed by various processes. For example, these material layers may be formed by chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD) or other suitable deposition methods.

[0031] The resist layer 210 may be a positive resist or a negative resist. Positive resists are generally insoluble in resist developers, but may become soluble by exposure to radiation, such as deep ultraviolet (DUV) rays, extreme ultraviolet (EUV) rays, electron beams (e-beams), x-rays, or other suitable radiation. An exemplary positive resist material is a chemically amplified resist (CAR) containing a main chain polymer protected by an acid-sensitive group (ALG). Negative resists have the opposite behavior, i.e., they are generally soluble in resist developers, but become insoluble by exposure to radiation, such as DUV rays, EUV rays, electron beams, x-rays, or other suitable radiation. An exemplary negative resist is a polymer that forms intramolecular and / or intermolecular crosslinks when irradiated, such as polymerization of ethyl (α-hydroxy)acrylate (EHMA) and methacrylic acid (MAA).

[0032] In operation 104, method 100 ( Figure 1A ) patterning the resist layer 210, thereby forming a resist pattern. For convenience, the resist pattern is referred to as the resist pattern 210. In one embodiment, the patterning process transfers the pattern from the mask (or photomask or intermediate mask) to the resist layer 210. Alternatively, the patterning process can use a maskless patterning technology, such as electron beam direct writing (EBDW). In one embodiment, patterning the resist layer 210 includes: exposing the resist layer 210 to radiation; post-exposure baking; developing the resist layer 210 in a resist developer; and hard baking, thereby removing the exposed portion of the resist layer 210 (or in the case of a negative resist, removing the unexposed portion) and leaving its unexposed portion (or in the case of a negative resist, leaving its exposed portion) on the ARC layer 208 as the resist pattern 210. The radiation can be DUV rays, EUV rays, electron beams, x-rays, ion beams, or other suitable radiation. In an embodiment where a mask is used to pattern the resist layer 210, the mask can be of different types, such as a transmissive mask or a reflective mask, and can be formed with various techniques, such as a binary mask or a phase shift mask (PSM). In one example, the binary mask includes a transparent substrate (e.g., fused quartz) and an opaque material (e.g., chrome) coated in the opaque areas of the mask. In another example, the PSM includes various features configured to have an appropriate phase difference to enhance resolution and imaging quality. In this embodiment, the patterning process uses EUV lithography (i.e., it uses EUV radiation for exposure) to transfer the pattern from the reflective mask to the resist layer 210.

[0033] In this example, if Figure 3 As shown, the resist pattern 210 includes line patterns 210a and 210b. Specifically, the line pattern 210a ( Figure 3Three are shown in FIG. 210 and 211 ) are longitudinally oriented along the X direction, and the line pattern 210b ( Figure 3 210a and 210b are longitudinally oriented along the Y direction perpendicular to the X direction. Line patterns 210a and 210b intersect to form resist grooves 210c. Since line patterns 210a and 210b are used as walls of grooves 210c, they are also referred to as resist walls 210a and 210b, respectively. In this example, line patterns 210a and 210b are used for simplicity and ease of understanding, and embodiments are not necessarily limited to any number of line patterns, any arrangement of line patterns, and / or other types of patterns such as groove patterns, hole patterns, patterns with bends, etc.

[0034] As discussed earlier, the trench 210c will be transferred to the layer 203 in the structure 209. The dimensions of the trench 210c substantially correspond to the dimensions of the metal lines formed in the layer 203. For example, the width of the trench 210c (dimension D1) corresponds to the width of the metal lines, and the distance along the X direction (dimension D2) between the ends of the two trenches 210c corresponds to the end-to-end spacing of the two metal lines. As the miniaturization of the device 200 continues, it is desirable to reduce both dimensions D1 and D2. However, the size of dimensions D1 and D2 is limited by the resolution of the photolithography process used to expose the resist layer 210. For example, using existing EUV lithography, dimension D2 is limited to approximately 30 nm or greater, and dimension D1 is limited to approximately 18 nm or greater (approximately half the spacing of the line pattern 210a). For designs requiring smaller dimensions (particularly smaller D2), further processing is required. The present invention introduces such a process, which includes Figure 1A Operations 106 to 112 of the present invention are described. The process greatly reduces dimension D2 and slightly expands dimension D1 by directly trimming line pattern 210b (and sometimes also trimming line pattern 210a) using ion implantation. This will be discussed further below.

[0035] In operation 106, method 100 ( Figure 1A ) The device 200 (having the resist pattern 210 and the structure 209) is loaded into the ion implanter 300. For example, the device 200 can be attached to a platen 304, which is mounted on a rotating plate assembly 306, such as Fig.11A As shown. The pressure plate 304 and the rotating plate assembly 306 are part of the device 301 installed in the ion implanter 300. The rotating plate assembly 306 is operable to rotate and tilt the pressure plate 304 with the device 200. The device 301 also includes a cover 302, which is used to protect the pressure plate 304 and the rotating plate assembly 306 (which may contain metal elements) from ion bombardment. The cover 302 will be further discussed in the subsequent parts of the present invention.

[0036] The ion implanter 300 is provided with one or more ion beams 212. In the present embodiment, the ion beam 212 is a focused ion beam and can be substantially directed to the device 200 along a certain direction (ion propagation direction). When the device 200 is initially loaded into the ion implanter 300, the ion beam 212 is not applied to the device 200 (i.e., the device is closed). In one embodiment, the device 200 is installed in an initial position in which the ion propagation direction directly faces the ion beam 212. In other words, the ion propagation direction is aligned with the normal of the top surface of the device 200 and forms a 0 degree tilt angle. In an optional embodiment, the device 200 is installed in an initial position in which the ion propagation direction does not directly face the ion beam 212. On the contrary, the ion propagation direction forms a tilt angle greater than 0 degree (such as 10 degrees) with the normal of the top surface of the device 200.

[0037] Figure 4 and Figure 5 The concept of the tilt angle and twist angle of the ion beam 212 relative to the device 200 is further illustrated. Figure 4 An ion beam 212 is shown directed toward the resist pattern 210 from both sides. Figure 5 The ion beam 212 is shown to form a tilt angle with respect to a normal line (Z-axis) with respect to the top surface of the device 200 in a plane containing both the normal line and the ion beam 212 . Figure 5 It is also shown that the plane containing both the normal and the ion beam 212 forms a twist angle with the XZ plane.

[0038] In operation 108, method 100 ( Figure 1A ) The device 200 is tilted so that the ion propagation direction and the normal to the top surface of the device 200 form a tilt angle. In one embodiment, the tilt angle is at least 40 degrees, such as at least 60 degrees, or in the range of 60 degrees to 80 degrees. In another embodiment, the tilt angle may be less than 40 degrees. Figure 4As shown in the following figures, ion beam 212 is used to shear the sidewalls of resist wall 210b (sometimes also shear the sidewalls of resist wall 210a). Larger tilt angles allow ions to more directly impact the sidewalls of resist wall 210b, rather than impacting its top surface. This prevents or reduces the height loss of resist pattern 210. Higher resist pattern 210 is more desirable because when etching lower layers (such as layers 208, 206, 204 and / or 203), the higher resist pattern is used as an etching mask. Therefore, compared with smaller tilt angles, larger tilt angles are usually more desirable. However, since there are many resist lines 210 in the resist pattern, there is a shadow effect, wherein if the tilt angle is too large (e.g., close to 90 degrees), one resist line will (wholly or partially) block ions from reaching another resist line behind it. Therefore, in an embodiment of the present invention, a tilt angle in the range of 40 to 80 degrees is generally sufficient to shear the resist line 210 while reducing its height loss. In addition, in the present embodiment, the resist groove 210c is designed to be a long groove along the X direction, which allows the tilt angle to be large, such as in the range of 40 to 80 degrees or in the range of 60 to 80 degrees. If the resist grooves 210c are short, they will introduce a large shadow effect and will not allow large tilt angles to be effectively achieved. Fig. 11B An embodiment is shown in which the device 200 is tilted so that the ion beam tilt angle is about 80 degrees. Note that tilt is a relative term. In various embodiments, operation 108 may tilt the ion beam 212 instead of tilting the device 200 to achieve the ion beam tilt angle discussed above.

[0039] In operation 110, method 100 ( Figure 1A ) Positioning an alignment mark on the device 200 and aligning the alignment mark with the ion propagation direction. In other words, operation 110 rotates the device 200 so that the alignment mark is in a plane containing the ion propagation direction and a normal to the top surface of the device 200. In one embodiment, the alignment mark is a notch on the wafer 202, such as Figure 6B In one embodiment, substrate 202 is a silicon wafer, such as a silicon (100) wafer, and notch 222 indicates silicon <110> direction. Note that the silicon in the silicon (100) wafer is perpendicular to <110> direction or plane is another silicon <110> In an alternative embodiment, the alignment mark is a flat on the wafer (rather than a notch). For example, in some embodiments, the flat is used to indicate the silicon (100) wafer. <110> In one embodiment, the longitudinal direction of the resist line 210a and the resist groove 210c (which is Figure 3In the example shown, the direction X) is aligned with (or parallel to) the direction indicated by the alignment mark. For example, the longitudinal direction of the resist line 210a and the resist groove 210c is aligned with the silicon (100) wafer. <110> In another embodiment, the longitudinal direction of the resist line 210a and the resist groove 210c is perpendicular to the direction indicated by the alignment mark. As described above, this direction is also the direction of the silicon in the silicon (100) wafer. <110> direction. The resist trench in the silicon <110> Directional orientation facilitates exposure and patterning processes and facilitates fabrication of high-performance circuits in the device 200. In some embodiments, the resist trench 210c may be formed to have an angle between 0 and 90 degrees relative to the direction indicated by the alignment mark (e.g., with respect to the silicon in the silicon (100) wafer). <110> After locating the alignment mark and knowing the resist trench orientation (e.g., parallel, perpendicular, or offset from the direction indicated by the alignment mark), the method 100 learns the orientation of the resist trench 210c relative to the ion beam 212.

[0040] In some embodiments, method 100 may perform operation 108 before operation 110 , or vice versa.

[0041] In operation 112, method 100 ( Figure 1A ) The device 200 having the resist pattern 210 is rotated, and ions are implanted into the resist wall 210b (and sometimes also into the resist wall 210a) from one or more pairs of directions to shear the thickness of the resist wall 210b. Each pair of directions is selected to be opposite to each other. For example, one direction in the pair is along the X direction, and the other direction is along the -X direction. One goal is to reduce the dimension D2 while not enlarging (or not significantly enlarging) the dimension D1. Reference Figure 1B , Figure 1C and Figure 1D Various example embodiments of operation 112 are further described.

[0042] refer to Figure 1B In operation 120, the method 100 rotates the device 200 so that the ion propagation direction of the ion beam 212 is aligned with the longitudinal direction of the resist trench 210c (ie, Figure 3 and Figure 6B At the same time, the resist wall 210b is tilted at a tilt angle α relative to the ion propagation direction of the ion beam 212. Fig. 6A A side view of the resist wall 210 b is shown forming an inclined angle α with respect to the propagation direction of the ion beam 212 . Figure 6BA top view of the resist trench 210c aligned with the propagation direction of the ion beam 212 is shown. In this embodiment, the longitudinal direction of the resist trench 210c is also aligned with the direction indicated by the alignment mark 222. Therefore, the device 200 is rotated 0 degrees (i.e., not rotated) from the position achieved by operation 110. As discussed above, the tilt angle α is in the range of 40 degrees to 80 degrees, such as in the range of 60 degrees to 80 degrees.

[0043] In operation 121, method 100 ( Figure 1B ) implants ions (or ion species) into the resist wall 210b. The method may also incidentally implant ions into the resist wall 210a. In various embodiments, the ion species may be one or more of: arsenic, boron, carbon, indium, difluoroborate (BF2), germanium, gallium, fluorine, nitrogen (both N_14 and N_28), oxygen, phosphorus, silicon, xenon, argon, and SiF3. For singly charged ion species, the implantation energy may be in the range of 0.1 KeV to 60 KeV, for doubly charged ion species, the implantation energy may be in the range of 0.1 KeV to 120 KeV, for triply charged ion species, the implantation energy may be in the range of 0.1 KeV to 180 KeV, and so on. Depending on the ion species, the total ion dose may be about 2×e 12 ions / cm 2 to about 9×e 16 ions / cm 2 The total ion dose can be divided based on the number of ion implantation applications. Figure 1B In the flowchart shown, if operation 112 has only two ion implantation applications (i.e., only operations 121 and 123 and no repetition), the total ion dose can be divided into two parts, wherein half of the ion dose is applied during operation 121, and the other half is applied during operation 123. For example, if operation 112 has four ion implantation applications (i.e., each of operations 121 and 123 is performed twice), the total ion dose can be divided into four parts, wherein a quarter dose is applied during each of operations 121 and 123. The implanted ion species cause the resist wall 210b to recede by physical force, chemical reaction, or both. They also reduce the line edge roughness and line width roughness of the resist wall.

[0044] In operation 122, method 100 ( Figure 1B ) rotates the device 200 so that the ion propagation direction of the ion beam 212 is opposite to the operating direction 120 (ie, Figure 3 and Fig.6D It is worth noting that this is also the longitudinal direction of the resist groove 210c. At the same time, the resist wall 210b is tilted at an inclination angle α relative to the ion propagation direction of the ion beam 212. Figure 6C A side view of the resist wall 210 b is shown forming an inclined angle α with respect to the propagation direction of the ion beam 212 . Fig.6D FIG. 2 shows a top view of the resist trench 210 c aligned with the propagation direction of the ion beam 212. Figure 6B and Fig.6D As shown, the device 200 is Figure 6B The position in (as a result of operation 120) is rotated 180 degrees to its Fig.6D 122).

[0045] In operation 123, method 100 ( Figure 1B ) to implant ions (or ion species) into the resist wall 210b. The method can also implant ions into the resist wall 210a. By operations 121 and 123, from both sides ( Fig. 6A and Figure 6C The resist wall 210b is sheared substantially symmetrically along the A side and the B side in the ion beam 212. Thus, the width of the resist wall along the X direction is reduced from D2 to D2'. In some embodiments, the dimension D1 may be slightly enlarged. However, the reduction in dimension D2 is substantially greater than the enlargement of dimension D1. For example, due to the directional application of the ion beam 212, the reduction in dimension D2 may be at least 4 or 5 times greater than the increase in dimension D1. In some embodiments, the dimension D2 is reduced by 5nm to 6nm, while the dimension D1 is enlarged by 1nm or less. Therefore, the method 100 effectively reduces the metal line ( Figure 2 ) while only slightly increasing the width of the same metal lines.

[0046] In operation 124, method 100 ( Figure 1B ) can repeat operations 120 to 123. For example, method 100 can: rotate device 200 (by operation 120) again 180 degrees from its position in operation 123; implant ions (by operation 121) into resist wall 210b; rotate device 200 (by operation 122) 180 degrees from its position in operation 120; and implant ions (by operation 123) into resist wall 210b. Method 100 can repeat operations 120, 121, 122, and 123 as many times as processing time allows. For example, in various embodiments, method 100 can repeat operations 120, 121, 122, and 123 two, three, four, six, eight, or other suitable number of repetitions. Each of operations 121 and 123 applies only an equal fraction of the total ion dose, as discussed above. Fig. 7A and Figure 7B A side view and a top view, respectively, are shown of an embodiment of operation 112 in which operations 120, 121, 122, and 123 are repeated four times.

[0047] Fig. 8A Four directions in which the longitudinal direction of the resist trench 210c can be set relative to the direction marked by the alignment mark 222 are shown. The examples of "azimuth 0°" and "azimuth 180°" correspond to FIG. 6A to FIG. 6D and FIG. 7A to FIG. 7B The example shown in Figure 8B 8C ). The examples of "90° orientation" and "270° orientation" correspond to the examples shown in FIG8C . Figure 8C , the longitudinal direction of the resist trench 210c is perpendicular to the direction marked by the alignment mark 222. For these examples, the rotation angle in operation 120 (relative to the position resulting from operation 110) is 90 degrees. In other words, operation 120 rotates the device 200 90 degrees so that the ion propagation direction of the ion beam 212 is aligned with the longitudinal direction of the resist trench 210c.

[0048] Figure 1C , Fig.9A and Fig. 9B Another embodiment of operation 112 is shown. Figure 1B and 6A to 8C One difference between the embodiment shown in is that in this embodiment, the ion beam 212 forms a non-zero twist angle with respect to the XZ plane (i.e., the plane containing the directions X and Z). Figure 1B and 6A to 8C In the embodiments shown, the ion beam 212 is in the XZ plane, so in those embodiments, the ion beam forms a zero twist angle relative to the XZ plane. However, the principle of the embodiments is the same, namely applying ion beams to the resist wall 210b from two opposite directions to reduce its thickness D2.

[0049] refer to Figure 1C In operation 130, the method 100 rotates the device 200 having the resist pattern 210 so that the propagation direction of the ion beam 212 is aligned with a direction deviating from the longitudinal direction of the resist groove 210c. Fig.9A As illustrated in FIG. 1 , this involves rotating the device 200 by an angle β between 0 and 90 degrees from the position achieved in operation 110. The angle β is the twist angle between the XZ plane and the plane containing the normal to the top surface of the device 200 and the ion beam 212 (e.g., Figure 5 ). Device 200 is still tilted at angle α, as previously discussed. In operation 131, method 100 ( Figure 1C ) ions are implanted into the resist walls 210b and 210a. The ion species, energy and dose are discussed above. Fig.9A and Fig. 9BIndicated as "Step 1" in FIG. 1 , ions are implanted from a twist angle β, which is in the lower left quadrant of the XY coordinate system.

[0050] In operation 132, method 100 ( Figure 1C ) rotates the device 200 from the position achieved in operation 130 by an angle θ. In this embodiment, the angle θ is less than the sum of 90 degrees and the complementary angle of the angle β (the complementary angle of the angle β is equal to (90°-β)), and is greater than the complementary angle of the angle β. In other words, the device 200 is rotated so that the ions are injected from the twist angle, which is at Fig.9A and Fig. 9B In one embodiment, angle θ is twice the complementary angle of angle β. In other words, the ion propagation directions in “step 1” and “step 2” are mirror reflections of each other relative to plane YZ. This helps to make the thickness of resist wall 210b decrease more uniformly along the Y direction. In operation 133, method 100 ( Figure 1C ) ions are implanted into the resist walls 210b and 210a, as Fig.9A The ion species, energy and dose are discussed above.

[0051] In operation 134, method 100 ( Figure 1C ) rotates the device 200 from the position achieved in operation 132 by a twist angle ω, where the angle ω is the complementary angle of the angle θ (i.e., ω+θ=180°), as shown in Fig.9A In fact, the ion propagation directions in "step 1" and "step 3" are opposite to each other. In operation 135, method 100 ( Figure 1C ) ions are implanted into the resist walls 210b and 210a, as Fig.9A and Fig. 9B As indicated by "Step 3" in FIG. 1 , the ion species, energy and dose are discussed above.

[0052] In operation 136, method 100 ( Figure 1C ) rotates the device 200 from the position achieved in operation 134 by a twist angle θ, such as Fig.9A In operation 137, method 100 ( Figure 1C ) ions are implanted into the resist walls 210b and 210a, as Fig.9A and Fig. 9B4, that is, from the lower right quadrant of the XY coordinate system. Ion species, energy, and dose are discussed above. Specifically, the ion doses of operations 131, 133, 135, and 137 are equal fractions of the total dose, as discussed above. In one embodiment, the angles β, θ, and ω are 75°, 30°, and 150°, respectively. Of course, other configurations consistent with the principles discussed above are also possible.

[0053] In operation 138, method 100 ( Figure 1C ) Operations 130, 131, 132, 133, 134, 135, 136, and 137 may be repeated. Specifically, the ion doses of operations 131, 133, 135, and 137 are equal fractions of the total dose, as discussed above. In some embodiments, method 100 may perform the above operations in any order. For example, the method may perform the operations in the order of "step 1", "step 2", "step 3", and "step 4" or "step 1", "step 3", "step 4", and "step 2", or in some other order. However, performing the operations in the order of "step 1", "step 2", "step 3", and "step 4" minimizes the total number of rotations (360 degree rotation) of device 200 and may save more time than other options. Of course, method 100 may perform the steps in a clockwise order or a counterclockwise order.

[0054] Figure 1D and Fig.10 Another embodiment of operation 112 is shown. In this embodiment, operation 112 uses a mixture of two ion implantation recipes. For example, the two ion implantation recipes can be Figure 1B Two examples of the embodiments described in Figure 1C Two examples of the embodiments described in Figure 1B Examples of embodiments described in Figure 1C In addition, the two formulations are different in at least one aspect. For example, the two formulations may differ in their ion species, total ion dose, tilt angle and / or twist angle. Figure 1D , operation 112 may include: operation 140, which rotates the device 200 and implants ions into the resist wall 210b (sometimes the resist wall 210a) according to a first recipe; and operation 150, which rotates the device 200 and implants ions into the resist wall 210b (sometimes the resist wall 210a) according to a second recipe different from the first recipe. As indicated by operation 160, operation 112 may repeat operations 140 and 150. Fig.10 An example is shown where the two formulations are Figure 1CSpecifically, the first recipe uses the steps of "step 1", "step 2", "step 3", and "step 4" to implant ions into the resist walls 210b and 210a, while the second recipe uses the steps of "step 5", "step 6", "step 7", and "step 8" to implant ions into the resist walls 210b and 210a. The twist angles of the two recipes are different. Other aspects of the two recipes may be the same or different. In addition, operation 112 may be performed in a clockwise manner. Fig.10 , such as "step 1", "step 4", "step 8", "step 7", "step 3", "step 2", "step 6" and "step 5". Optionally, operation 112 may be performed in a counterclockwise manner. Fig.10 In one embodiment, the four steps of the same recipe are designed to be mirror reflections of each other in the XY coordinate system. For example, steps "Step 1", "Step 2", "Step 3", and "Step 4" are designed to be mirror reflections relative to the X-axis and the Y-axis, while steps "Step 5", "Step 6", "Step 7", and "Step 8" are designed to be mirror reflections relative to the X-axis and the Y-axis. Mirror symmetry helps to reduce the dimension D2 more uniformly over the entire length of the resist wall 210b.

[0055] Fig. 12A A cross-sectional view of the resist wall 210a (or 210b) before being treated with the ion beam 212 in operation 112 is shown, and Fig. 12B A cross-sectional view of the resist wall 210a (or 210b) after being treated with the ion beam 212 in operation 112 is shown to illustrate the effect of operation 112. For example, these cross-sectional views may be taken along Figure 3 The A-A line in FIG. 1 is used to illustrate the changes in the resist wall 210a, or it can be taken along the line perpendicular to Figure 31 is intercepted by the line A-A in to illustrate the changes in the resist wall 210b. Before being treated with the ion beam 212 in operation 112, the resist wall 210a (or 210b) has a height h1, and the groove 210c has a width w1 measured at half the resist height and a width w2 measured at the bottom of the groove 210c, where w1 is greater than w2. After being treated with the ion beam 212 in operation 112, the resist wall 210a (or 210b) has a height h2, and the groove 210c has a width w3 measured at half the resist height and a width w4 measured at the bottom of the groove 210c, where w3 is greater than w4. In one embodiment, due to the vertical treatment of the ion beam, the height h2 is about 10% to 15% smaller than the height h1, the width w3 is about 3% to about 5% larger than the width w1, and the width w4 is about 15% to about 20% larger than the width w2. The width variation (w3 to w4) of the bottom of the trench 210c is greater than the width variation (w1 to w3) of half the resist height in terms of both the rate of increase (relative increase) and the absolute value increase. Due to this treatment, the sidewalls of the trench 210c become more vertical.

[0056] refer to Figure 1A After the resist pattern 210 has been processed with the ion beam 212 in operation 112, the method 100 transfers the processed resist pattern 210 to the structure 209 ( Figure 2 , particularly layer 203). This may involve one or more dry (plasma) etching and other etching methods. For example, the dry etching process may implement an oxygen-containing gas, a fluorine-containing gas (e.g., CF4, SF6, CH2F2, CHF3 and / or C2F6), a chlorine-containing gas (e.g., Cl2, CHCl3, CCl4 and / or BCl3), a bromine-containing gas (e.g., HBr and / or CHBR3), an iodine-containing gas, other suitable gases and / or plasmas and / or combinations thereof. For example, the etching process may use the treated resist pattern 210 as an etching mask to etch layers 208, 206 and 204, and then remove the resist pattern 210 by a wet etching process using a photoresist stripper, an aqueous alkaline solution, an amine solvent mixture, or an organic solvent. As Fig. 12C As shown, this transfers the pattern into layers 204 and 206. Operation 114 may then etch layer 203 using one or more of the patterned layers 208, 206, and 204 as an etch mask, thereby transferring resist trenches 210c into trenches in layer 203, as shown. Fig.12D shown.

[0057] In operation 116, method 100 ( Figure 1A) to continue forming the final pattern or device. In one embodiment, the resist pattern 210 is part of the metal line definition. To facilitate this embodiment, the method 100: transfers the resist trench 210c to the dielectric layer 203 as a dielectric trench; fills the dielectric trench with one or more metal materials; and performs a chemical mechanical planarization (CMP) process on the metal material to form a metal line 402 in the layer 203, such as Fig.12E As shown, due to the shearing of the resist wall 210b, the end-to-end spacing (corresponding to dimension D2') of the metal line 402 is reduced.

[0058] Fig.13A and Fig. 13B FIG. 3 shows an embodiment of a device 301 for an ion implanter 300 according to the present embodiment. Specifically, Fig.13A and Fig. 13B The hood 302 is shown in more detail. Fig.11A and Fig. 11B ).like Fig. 11B As shown, when the tilt angle is large (e.g., close to 80 degrees), the ion beam 212 may hit the portion (or component) below the pressure plate 304, such as the rotating plate assembly 306 or the back of the pressure plate 304. This may damage the rotating plate assembly 306 and / or the pressure plate 304. In addition, the material (e.g., certain metals) of the rotating plate assembly 306 and the pressure plate 304 may be driven away by the ion beam 212 and may cause the device 200 to be contaminated. In this embodiment, a cover 302 is added to the device to protect the rotating plate assembly 306 and the pressure plate 304 from the impact of the ion beam 212. In one embodiment, the cover 302 is made of graphite or a similar material. As shown in FIG. Fig. 11B and Fig.13A As shown, the cover 302 may include sub-sections 302a and 302b. The cover 302a covers the main body of the rotating plate assembly 306, while the cover 302b covers the edge of the pressure plate 304. Fig.13A As shown, the cover 302b has an annular structure surrounding the edge of the pressure plate 304. Fig. 13B , Fig. 13B The left side of FIG. 1 shows a front view (facing the ion propagation direction of ion beam 212) of rotating plate assembly 306 with various sub-portions of cover 302a. In this embodiment, cover 302a includes a left cover, a right cover, a front cover, a rotating plate body cover, and a top plate cover. Fig. 13B The right side of FIG. 3 shows a rear view of the rotating plate assembly 306. Specifically, there is a motor cover 303 (which can be considered as part of the cover 302) for protecting the motor from ion bombardment and / or other environmental factors.

[0059] Although not intended to limit, the present invention provides many benefits.For example, various embodiments of the present invention apply ion beams to the resist wall from one or more pairs of opposite directions to reduce the line end to line end spacing in the metal layer and reduce surface roughness (line edge roughness and line width roughness).Embodiments of the present invention can be used in combination with double patterning methods or multiple patterning methods to further reduce pattern size.The present invention also discloses a protective cover for an ion implanter device.The disclosed embodiments can be easily integrated into existing photolithography and ion implantation tools to improve them.

[0060] In one exemplary aspect, the present invention relates to a method. The method includes forming a resist layer above a structure and patterning the resist layer to produce a resist pattern having elongated grooves oriented longitudinally substantially along a first direction, and adjacent grooves are separated by a resist wall along both the first direction and a second direction perpendicular to the first direction. The method also includes: loading the structure and the resist pattern into an ion implanter so that the top surface of the resist pattern faces the ion propagation direction of the ion implanter; tilting the structure and the resist pattern so that the ion propagation direction forms an inclination angle relative to an axis perpendicular to the top surface of the resist pattern; rotating the structure and the resist pattern around the axis for the first time to a first position so that the ion propagation direction is in a plane containing the first direction and the axis; and implanting ions into the resist wall for the first time when the structure and the resist pattern are in the first position. After the first implantation, the method also includes: rotating the structure and the resist pattern around the axis for the second time by 180 degrees to a second position; and implanting ions into the resist wall for the second time when the structure and the resist pattern are in the second position.

[0061] In one embodiment where the structure includes a patterned layer, the method further comprises etching the patterned layer using the resist pattern as an etch mask after the second implantation.

[0062] In one embodiment of the method, the tilt angle is at least 60 degrees. In another embodiment, the tilt angle is in the range of 60 to 80 degrees.

[0063] In one embodiment of the method, the structure includes a silicon (100) substrate, and the first direction is along the silicon <110> Direction or Silicon <100> In one embodiment of the method, after the first rotation, a tilting of the structure and the resist pattern is performed.

[0064] wherein the structure includes a silicon <110> In one embodiment of a silicon (100) substrate having an alignment mark in a certain direction, the method further comprises positioning the alignment mark before the first rotation.

[0065] In one embodiment, the method further comprises repeating the first rotating, the first injecting, the second rotating, and the second injecting.

[0066] In one embodiment of the method, the ions during the first implantation and the second implantation include one or more ion species selected from arsenic, boron, carbon, indium, boron fluoride (BF2), germanium, gallium, fluorine, nitrogen, oxygen, phosphorus, silicon, xenon, argon and silicon fluoride (SF3).

[0067] In another exemplary aspect, the present invention relates to a method, the method comprising forming a resist pattern above a structure, wherein the resist pattern comprises a first resist wall oriented longitudinally substantially along a first direction and a second resist wall oriented longitudinally substantially along a second direction perpendicular to the first direction, and the first resist wall and the second resist wall intersect. The method also comprises: loading the structure and the resist pattern into an ion implanter so that the top surface of the resist pattern faces the ion propagation direction of the ion implanter; tilting the structure and the resist pattern so that the ion propagation direction forms an inclination angle of at least 40 degrees relative to an axis perpendicular to the top surface of the resist pattern; initially rotating the structure and the resist pattern around the axis to a first position so that the ion propagation direction is in an initial plane containing the first direction and the axis; first rotating the structure and the resist pattern around the axis from the initial position to a first position by a first angle, the first angle being less than 90 degrees; and first implanting ions into the first resist wall and the second resist wall with the structure and the resist pattern in the first position. After the first implantation, the method further includes: rotating the structure and the resist pattern around the axis for a second time from the first position to the second position by a second angle, the second angle being less than the sum of 90 degrees and the complementary angle of the first angle; and implanting ions into the first resist wall and the second resist wall for a second time when the structure and the resist pattern are in the second position.

[0068] In one embodiment, after the second ion implantation, the method further includes: rotating the structure and the resist pattern around the axis for a third time from the second position to the third position by a third angle, the third angle being a complementary angle of the second angle; and implanting ions into the first resist wall and the second resist wall for a third time when the structure and the resist pattern are in the third position. In another embodiment, after the third ion implantation, the method further includes: rotating the structure and the resist pattern around the axis for a fourth time from the third position to the fourth position by the second angle; and implanting ions into the first resist wall and the second resist wall for a fourth time when the structure and the resist pattern are in the fourth position. In another embodiment, the method further includes repeating the first rotation, the first ion implantation, the second rotation, the second ion implantation, the third rotation, the third ion implantation, the fourth rotation, and the fourth ion implantation.

[0069] In one embodiment of the method, the second angle is twice the complementary angle of the first angle. In one embodiment of the method, the tilt angle is in the range of 60 to 80 degrees.

[0070] In one embodiment, the method further comprises positioning an alignment mark on the structure prior to initially rotating the structure and the resist pattern.

[0071] In another exemplary aspect, the present invention relates to a method. The method includes: forming a resist pattern above a structure; loading the structure and the resist pattern into an ion implanter so that the top surface of the resist pattern faces the ion propagation direction of the ion implanter; using the ion implanter to implant ions into the resist pattern for a first time using a first recipe, the first recipe including applying a first ion dose to the resist pattern, wherein the resist pattern is maintained at a first tilt angle and each of a plurality of first twist angles; and using the ion implanter to implant ions into the resist pattern for a second time using a second recipe, the second recipe including applying a second ion dose to the resist pattern, wherein the resist pattern is maintained at a second tilt angle and each of a plurality of second twist angles, wherein the first ion dose is different from the second ion dose, the first tilt angle is different from the second tilt angle, or the plurality of first twist angles are different from the plurality of second twist angles.

[0072] In one embodiment of the method, the resist pattern includes a resist wall that is substantially longitudinally oriented along a first direction, and the first ion implantation includes: tilting the structure and the resist pattern so that the ion propagation direction forms a first tilt angle relative to an axis perpendicular to the top surface of the resist pattern; and for each of a plurality of first twist angles, performing the following operations: rotating the structure and the resist pattern for the first time by the corresponding twist angle; and implanting ions into the resist for the first time at a first ion dose.

[0073] In another embodiment of the method, the second ion implantation includes: tilting the structure and the resist pattern so that the ion propagation direction forms a second tilt angle relative to the axis perpendicular to the top surface of the resist pattern; and for each of the multiple second twist angles, performing the following operations: rotating the structure and the resist pattern by the corresponding twist angle for a second time; and implanting ions into the resist for a second time at a second ion dose.

[0074] In one embodiment of the method, the plurality of first twist angles includes at least four angles, and the plurality of second twist angles includes at least four angles.

[0075] The features of several embodiments are summarized above so that those skilled in the art can better understand aspects of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments introduced herein. Those skilled in the art should also appreciate that such equivalent constructions do not deviate from the spirit and scope of the present invention, and that they can make various changes, substitutions and modifications herein without departing from the spirit and scope of the present invention.

Claims

1. A method for patterning an integrated circuit, comprising: forming a resist layer over the structure; patterning the resist layer to produce a resist pattern having elongated grooves oriented along a first direction in length, and adjacent elongated grooves are separated by first resist walls extending longitudinally along the first direction and second resist walls extending longitudinally along a second direction perpendicular to the first direction, wherein each of the elongated grooves has a longer length along the first direction than along the second direction; loading the structure and the resist pattern into an ion implanter so that a top surface of the resist pattern faces an ion propagation direction of the ion implanter; tilting the structure and the resist pattern so that the ion propagation direction forms an inclination angle with respect to an axis perpendicular to the top surface of the resist pattern; performing a first rotation of the structure and the resist pattern about the axis to a first position so that the ion propagation direction is located in a plane containing the first direction and the axis; first implanting ions into the second resist wall with the structure and the resist pattern in the first position; After the first implantation, performing a second rotation of the structure and the resist pattern by 180 degrees about the axis to a second position; and Ions are second implanted into the second resist wall with the structure and the resist pattern in the second position.

2. The method according to claim 1, wherein: The structure includes a patterned layer, and the method further includes: After the second implantation, the patterned layer is etched using the resist pattern as an etching mask.

3. The method according to claim 1, wherein: The inclination angle is at least 60 degrees. The method according to claim 3 , wherein the tilt angle is in the range of 60 to 80 degrees.

5. The method according to claim 1, wherein: The structure includes a silicon (100) substrate, and the first direction is along the silicon <110> Direction or Silicon <100> direction.

6. The method according to claim 1, wherein: After the first rotation, the tilting of the structure and the resist pattern is performed.

7. The method according to claim 1, wherein: The structure includes a silicon <110> A silicon (100) substrate having an alignment mark in a direction, the method further comprising: Prior to the first rotation, the alignment mark is positioned.

8. The method according to claim 1, further comprising: The first rotation, the first injection, the second rotation, and the second injection are repeated.

9. The method according to claim 1, wherein: The ions during the first implantation and the second implantation include one or more ion species selected from arsenic, boron, carbon, indium, boron fluoride (BF2), germanium, gallium, fluorine, nitrogen, oxygen, phosphorus, silicon, xenon, argon and silicon fluoride (SF3).

10. A method for patterning an integrated circuit, comprising: forming a resist pattern over the structure, wherein the resist pattern comprises elongated grooves surrounded by first resist walls oriented longitudinally along a first direction and second resist walls oriented longitudinally along a second direction perpendicular to the first direction, and the first resist walls and the second resist walls intersect, wherein each of the elongated grooves has a longer length along the first direction than along the second direction; loading the structure and the resist pattern into an ion implanter so that a top surface of the resist pattern faces an ion propagation direction of the ion implanter; tilting the structure and the resist pattern so that the ion propagation direction forms a tilt angle of at least 40 degrees with respect to an axis perpendicular to the top surface of the resist pattern; initially rotating the structure and the resist pattern about the axis to an initial position so that the ion propagation direction is in an initial plane containing the first direction and the axis; Rotating the structure and the resist pattern around the axis from the initial position to a first position by a first angle, wherein the first angle is less than 90 degrees; first implanting ions into the first resist wall and the second resist wall with the structure and the resist pattern in the first position; After the first implantation, second rotating the structure and the resist pattern around the axis from the first position to a second position by a second angle less than a sum of 90 degrees and a complementary angle of the first angle; and Ions are second implanted into the first resist wall and the second resist wall with the structure and the resist pattern in the second position.

11. The method according to claim 10, further comprising: After the second implantation, thirdly rotating the structure and the resist pattern around the axis from the second position to a third position by a third angle, the third angle being a complementary angle to the second angle; as well as Ions are thirdly implanted into the first resist wall and the second resist wall with the structure and the resist pattern in the third position.

12. The method according to claim 11, further comprising: After the third implantation, fourthly rotating the structure and the resist pattern around the axis from the third position to a fourth position by the second angle; as well as Ions are fourth implanted into the first resist wall and the second resist wall with the structure and the resist pattern in the fourth position.

13. The method according to claim 12, further comprising: The first rotation, the first injection, the second rotation, the second injection, the third rotation, the third injection, the fourth rotation, and the fourth injection are repeated.

14. The method according to claim 10, wherein: The second angle is twice the complementary angle of the first angle. The method according to claim 10 , wherein the tilt angle is in a range of 60 to 80 degrees.

16. The method according to claim 10, further comprising: Prior to the initial rotating of the structure and the resist pattern, alignment marks are positioned on the structure.

17. A method for patterning an integrated circuit, comprising: forming a resist pattern over the structure, wherein the resist pattern has an elongated groove surrounded by a first resist wall and a second resist wall, wherein the first resist wall extends longitudinally along a first direction, and the second resist wall extends longitudinally along a second direction perpendicular to the first direction, wherein the elongated groove has a longer length along the first direction than along the second direction; loading the structure and the resist pattern into an ion implanter so that a top surface of the resist pattern faces an ion propagation direction of the ion implanter; first implanting ions into the resist pattern using the ion implanter using a first recipe, the first recipe comprising applying a first ion dose to the first resist wall and the second resist wall of the resist pattern, wherein the resist pattern is maintained at each of a first tilt angle and a plurality of first twist angles; and implanting ions into the resist pattern using a second recipe using the ion implanter, the second recipe comprising applying a second ion dose to the first resist wall and the second resist wall of the resist pattern, wherein the resist pattern is maintained at each of a second tilt angle and a plurality of second twist angles, wherein the first ion dose is different from the second ion dose, the first tilt angle is different from the second tilt angle, or the plurality of first twist angles is different from the plurality of second twist angles, wherein each of the first tilt angle and the second tilt angle is an angle formed between the ion propagation direction and the axis perpendicular to the top surface of the resist pattern, and each of the multiple first torsion angles and the multiple second torsion angles is another angle formed between a plane containing the axis perpendicular to the top surface of the resist pattern and the first direction and another plane containing the axis perpendicular to the top surface of the resist pattern and the ion propagation direction.

18. The method according to claim 17, wherein: The resist pattern comprises resist walls oriented longitudinally along a first direction, wherein the first implant comprises: tilting the structure and the resist pattern so that the ion propagation direction forms the first tilt angle with respect to an axis perpendicular to the top surface of the resist pattern; and For each of the plurality of first twist angles, the following operations are performed: first rotating the structure and the resist pattern by the corresponding twist angle; and Ions are first implanted into the resist at the first ion dose.

19. The method according to claim 18, wherein: The second injection comprises: tilting the structure and the resist pattern so that the ion propagation direction forms the second tilt angle with respect to the axis perpendicular to the top surface of the resist pattern; and For each of the plurality of second twist angles, the following operations are performed: second rotating the structure and the resist pattern by the corresponding twist angle; and Ions are second implanted into the resist at the second ion dose.

20. The method according to claim 17, wherein: The plurality of first twist angles includes at least four angles, and the plurality of second twist angles includes at least four angles.

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