Two-step implant for improving line edge roughness and line width roughness.

Abstract

A method for treating patterned photoresist to reduce line edge roughness and line width roughness on a semiconductor workpiece is disclosed. The method is performed after the photoresist is patterned and before the etching process begins. Two implants using different species are performed at a high tilt angle. In certain embodiments, the tilt angle can be 45° or greater. Furthermore, the implants are performed at a twist angle such that the ion trajectories are approximately parallel to the patterned photoresist lines. This causes ions from the two implants to strike the top and sidewalls of the photoresist lines. Using this technique, it is possible to reduce LER and LWR of the photoresist lines while minimizing the impact on CD.

Description

[Background technology]

[0001] This application claims priority to U.S. patent application Ser. No. 18 / 077,809, filed December 8, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] SUMMARY OF THE INVENTION Embodiments of the present disclosure relate to a method for improving line edge roughness and line width roughness of photoresist features using multiple implants.

[0003] As semiconductor manufacturing processes continue to evolve, line widths are becoming narrower. One of the effects of this is an increase in line width roughness (LWR) and line edge roughness (LER). Line width roughness is a measure of the variation in width of features on a semiconductor workpiece. Line edge roughness can be defined as the 3-sigma deviation of a line edge from a straight line.

[0004] These metrics need to be reduced as much as possible to ensure uniform device performance. Conventional lithography techniques can be used to achieve features with desirable critical dimensions (CDs). However, such features may have unacceptable line width roughness (LWR) and / or line edge roughness (LER) measurements. For example, pattern transfer artifacts (such as line roughness, line wiggling, and line width variations) can occur. This variation leads to performance variations and, in some cases, reduced yield.

[0005] Various processes have been proposed and attempted to reduce LER and LWR without affecting CD, but with limited success.

[0006] Therefore, it would be beneficial to have a method for treating patterned photoresist on a workpiece to reduce LER and LWR while minimizing the impact on critical dimensions. Summary of the Invention

[0007] A method for treating patterned photoresist to reduce line edge roughness and line width roughness on a semiconductor workpiece is disclosed. The method is performed after the photoresist is patterned and before the etching process begins. Two implants using different species are performed at a high tilt angle. In certain embodiments, the tilt angle can be 45° or greater. Furthermore, the implants are performed at a twist angle so that the ion trajectories are approximately parallel to the patterned photoresist lines. This allows ions from the two implants to strike the top and sidewalls of the photoresist lines. Using this technique, it is possible to reduce LER and LWR of the photoresist lines while minimizing the impact on CD.

[0008] According to one embodiment, a method for reducing line edge roughness (LER) and line width roughness (LWR) of patterned photoresist disposed on a workpiece is disclosed. The patterned photoresist has sidewalls and a thickness known as a critical dimension (CD). The workpiece is disposed on a platen that can be twisted about a rotation axis and tilted about a tilt axis. The method includes orienting the workpiece on the platen by selecting a twist angle of the platen and a high tilt angle to align an incident ion beam trajectory with a primary photoresist direction parallel to the sidewalls. After the orientation, directing a first ion beam having a first species toward the workpiece. After directing the first ion beam, directing a second ion beam having a second species different from the first species toward the workpiece while the workpiece remains oriented. In some embodiments, the implantation energy and dose of the first species and the implantation dose of the second species are selected to reduce LER and LWR by at least 10% and to affect the critical dimensions of the patterned photoresist by less than 1 nm. In certain embodiments, the first species comprises silicon. In some embodiments, the second species comprises an inert species. In certain embodiments, the inert species comprises argon. In certain embodiments, the second species comprises oxygen or nitrogen. In some embodiments, the patterned photoresist comprises a plurality of photoresist lines, and the high tilt angle is at least 45°. In certain embodiments, the high tilt angle is between 60° and 80°. In certain embodiments, orienting the workpiece comprises selecting a twist angle such that the angle between the primary photoresist direction and the trajectory of the incident ion beam is less than 5°.

[0009] According to another embodiment, a method is disclosed for reducing line edge roughness (LER) and line width roughness (LWR) of patterned photoresist disposed on a workpiece, the patterned photoresist having sidewalls and a thickness known as a critical dimension (CD), and the workpiece is disposed on a platen that can twist about a rotation axis and tilt about a tilt axis. The method includes orienting a workpiece on the platen by selecting a platen twist angle and a high tilt angle to align a primary photoresist direction parallel to the sidewall with the trajectory of an incident ion beam; directing a first ion beam including silicon ions toward the workpiece after the orientation; rotating the workpiece by 180° after directing the first ion beam; directing the first ion beam toward the workpiece again after the rotation; directing a second ion beam having a second species different from silicon ions toward the workpiece; rotating the workpiece by 180° after directing the second ion beam; and rotating the workpiece a second time after the second rotation; In some embodiments, the implantation energy and dose of the silicon ions and the implantation energy and dose of the second species are selected to reduce LER and LWR by at least 10% and to have an impact on the critical dimension of the patterned photoresist of less than 1 nm. In some embodiments, the second species includes an inert species. In certain embodiments, the inert species comprises argon. In certain embodiments, the second species comprises oxygen or nitrogen. In some embodiments, the patterned photoresist comprises a plurality of photoresist lines, and the high tilt angle is at least 45°. In certain embodiments, the high tilt angle is between 60° and 80°. In certain embodiments, orienting the workpiece comprises selecting a twist angle such that the angle between the primary photoresist direction and the trajectory of the incident ion beam is less than 5°.

[0010] According to another embodiment, a method for reducing line edge roughness (LER) and line width roughness (LWR) of patterned photoresist disposed on a workpiece is disclosed. The patterned photoresist has sidewalls and a thickness known as a critical dimension (CD), and the workpiece is disposed on a platen that can be twisted about a rotation axis and tilted about a tilt axis. The method includes orienting the workpiece on the platen by selecting a twist angle of the platen to align an incident ion beam trajectory with a primary photoresist direction parallel to the sidewalls and selecting a high tilt angle, and directing an ion beam having an inert species toward the workpiece while the workpiece remains oriented. In certain embodiments, orienting the workpiece includes selecting a twist angle such that the angle between the primary photoresist direction and the trajectory of the incident ion beam is less than 5° and selecting a high tilt angle of at least 45°. In some embodiments, the implant energy and dose of the inert species are selected to reduce LER and LWR by at least 10% and have less than 1 nm impact on the critical dimensions of the patterned photoresist.

[0011] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference. [Brief explanation of the drawings]

[0012] [Figure 1A] 1 shows a pattern of photoresist on a workpiece. [Figure 1B] 1 shows a pattern of photoresist on a workpiece. [Figures 2A-2C] 1 shows the rotation and tilt of the workpiece on the platen. [Figure 3] 1 is an ion implantation system that may be used to carry out the processes described herein, according to one embodiment. [Figure 4] 1 illustrates a sequence for reducing LER and LWR of photoresist features. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1A illustrates a workpiece 10 having patterned photoresist according to one embodiment. In this embodiment, the patterned photoresist is deposited in photoresist lines 100 such that trenches 110 are formed between adjacent photoresist lines 100. The thickness of the photoresist lines 100, defined as the distance between two parallel sidewalls 102 of the line, is referred to as the "critical dimension" (CD) 120. The distance between two photoresist lines 100 disposed in the same column is referred to as the "tip-to-tip distance" 130. The photoresist lines 100 have a longitudinal dimension corresponding to the sidewalls 102 and a width (i.e., CD). In this disclosure, the direction parallel to the sidewalls 102 of the photoresist lines 100 may be referred to as the primary photoresist direction 101.

[0014] FIG. 1B illustrates a workpiece 10 having patterned photoresist according to another embodiment. In this embodiment, the patterned photoresist is disposed to create a photoresist recess 150, with the photoresist covering the rest of the workpiece 10. Thus, FIG. 1A illustrates an area where photoresist is present, while FIG. 1B illustrates an area where photoresist is absent. A critical dimension 151 of the photoresist recess 150 is defined as the width of the photoresist recess 150. In this disclosure, the direction parallel to the longitudinal direction corresponding to the sidewall 152 of the photoresist recess 150 may be referred to as the primary photoresist direction 101.

[0015] As discussed above, minimizing LER and LWR in patterned photoresist without adversely affecting CD is the desired outcome. In some embodiments, it is advantageous to reduce LER and LWR by at least 10%. In other embodiments, it is advantageous to reduce LER and LWR by at least 15%. However, reducing LER and LWR typically also results in a change in CD120. This disclosure describes techniques for reducing LER and LWR with minimal impact on CD120 (<1 nm).

[0016] The photoresist can be a CAR (chemically amplified resist) photoresist or another suitable material.

[0017] FIG. 2A shows a top view of a rotatable platen 160, referred to as a roplat. FIG. 2B shows a side view of the platen 160. The platen 160 can twist about a rotation axis 161, which includes the center of the platen 160 and is perpendicular to the front surface of the platen 160. Rotation about this rotation axis 161 is referred to as a twist angle 162. The platen 160 can also rotate about a tilt axis 163, which includes the center of the platen 160 and is parallel to the front surface of the platen. FIG. 2C shows the platen 160 tilted by a tilt angle 164 relative to vertical. Note that a tilt angle 164 of 0° indicates that the incident ion beam 230 is perpendicular to the front surface of the platen 160, and a tilt angle of 90° indicates that the incident ion beam 230 is parallel to the front surface of the platen 160.

[0018] FIG. 3 illustrates a beamline ion implantation system 200 utilizing a ribbon ion beam. As illustrated in this figure, the beamline ion implantation system 200 may include an ion source and a complex series of beamline components through which an ion beam 220 passes. The ion source may include an ion source chamber 202 in which ions are generated. The ion source may also include a power supply 201 and an extraction electrode 204 disposed near the ion source chamber 202. The extraction electrode 204 may include a suppression electrode 204a and a ground electrode 204b. The ion source chamber 202, the suppression electrode 204a, and the ground electrode 204b may each include an aperture. The ion source chamber 202 may include an extraction aperture (not shown), the suppression electrode 204a may include a suppression electrode aperture (not shown), and the ground electrode 204b may include a ground electrode aperture (not shown). The apertures may be in communication with each other, allowing ions generated in the ion source chamber 202 to pass toward the beamline components.

[0019] The beamline components may include, for example, a mass analyzer 206, a mass resolving aperture 207, a first acceleration or deceleration (A1 or D1) stage 208, a collimator 210, and a second acceleration or deceleration (A2 or D2) stage 212. The beamline components may filter, focus, and manipulate ions or an ion beam 220, much like a series of optical lenses manipulating a light beam. The ion beam 220 passing through the beamline components may be directed toward a workpiece 10 mounted on a platen 160. The incident ion beam 230 may be much wider in a first direction than in a second direction and may be wider than the diameter of the workpiece 10 in the first direction. The direction of travel of the incident ion beam 230 perpendicular to the first and second directions may be referred to as the trajectory of the incident ion beam. The workpiece 10 may be moved in one or more dimensions by the platen 160. For example, the platen 160 may move from its first position to its second position and then move in a second direction (corresponding to the height of the incident ion beam 230) so that the entire workpiece 10 is exposed to the incident ion beam 230. The platen 160 may be configured to rotate the workpiece 10 about a rotation axis 161 and a tilt axis 163 (see FIGS. 2A-2C).

[0020] A controller 280 is also used to control the implantation. The controller 280 includes a processing unit 281 and an associated memory device 282. The memory device 282 stores instructions 283 that, when executed by the processing unit 281, enable the system to perform the functions described herein. The controller 280 can control the twist angle 162 and tilt angle 164 of the platen 160. The memory device 282 can be any non-transitory storage medium, including non-volatile memory such as FLASH ROM, electrically erasable ROM, or other suitable devices. In other embodiments, the memory device 282 can be volatile memory such as RAM or DRAM. In certain embodiments, the controller 280 can be a general-purpose computer, an embedded processor, or a specially designed microcontroller. The actual implementation of the controller 280 is not limited by this disclosure.

[0021] FIG. 4 illustrates a process sequence that can be performed to reduce LER and LWR in photoresist lines or photoresist recesses while minimizing the impact on CD. This sequence can be advantageous, for example, when CAR is used as the photoresist material. First, as shown in box 400, the platen 160 is oriented for a first implant. The platen 160 is set at a tilt angle 164, which may be a high tilt angle. For photoresist lines 100 such as those shown in FIG. 1A, a high tilt angle is defined as an angle of at least 45°. In some embodiments, the tilt angle may be 60° or greater. The tilt angle may be on the order of 80°. For photoresist recesses 150 such as those shown in FIG. 1B, a high tilt angle may be defined as an angle between 20° and 30°. Furthermore, a twist angle 162 is set to align the trajectory of the incident ion beam 230 with the primary photoresist direction 101. In some embodiments, the twist angle is selected so that the trajectory of the incident ion beam 230 and the main photoresist direction 101 are parallel. In some embodiments, the difference between the trajectory of the incident ion beam 230 and the main photoresist direction 101 can be 5° or less. In certain embodiments, the difference can be 3° or less. In some embodiments, the difference can be 1° or less.

[0022] Once the platen 160 is properly positioned, a first portion of a first implant may be performed, as shown in box 410. The first implant is an implant of a first species, which may include silicon ions.

[0023] After the first portion of the total dose is implanted, the platen 160 may be rotated 180°, as shown in box 420. This results in the angle between the primary photoresist direction 101 and the trajectory of the incident ion beam 230 being the same as in the implant performed in box 410. The tilt angle is not changed. In other words, after the rotation, the difference between the trajectory of the incident ion beam 230 and the primary photoresist direction 101 may be 5° or less. In certain embodiments, this difference may be 3° or less. In some embodiments, this difference may be 1° or less. Thus, although this disclosure refers to a twist angle of 180°, it is understood that the twist angle may vary slightly from that value, as long as the difference between the trajectory of the incident ion beam 230 and the primary photoresist direction 101 after the rotation is still within the desired range. Then, as shown in box 430, a second portion of the first implant is performed from the opposite direction. The total dose of the first species applied in the first and second parts is 1E14 ions / cm 2 to 1E17 ions / cm 2 In some embodiments, the total dose can be between 1E15 ions / cm 2 to 8E15 ions / cm 2 The energy of the first implant may be between 400 eV and 2 keV.

[0024] Note that in some embodiments, boxes 420-430 may be omitted, in which case the entire dose is provided in the first portion of the first injection.

[0025] After the first implant is complete, a second implant using a second species is performed. The tilt and twist angles are as described above. The second species may be argon, although other species may be used. In some embodiments, the second species may include other inert species (such as neon, radon, krypton, or xenon). In other embodiments, the second species may include oxygen or nitrogen. The second implant may be performed using the same energy as the first implant. The first portion of the second implant is then performed, as shown in box 440.

[0026] After the first portion of the second implant is complete, the platen 160 may then be rotated 180°, as shown in box 450. The second portion of the second implant may then be performed from the opposite direction, as shown in box 460. The total dose of the second species applied in the first and second portions of the second implant is 1E14 ions / cm. 2 to 1E17 ions / cm 2 In some embodiments, the total dose can be between 1E15 ions / cm 2 to 2E16 ions / cm 2 In some embodiments, the total dose is at least 4E15 ions / cm. 2 is.

[0027] Note that in some embodiments, boxes 450-460 may be omitted, in which case the entire dose is provided in the first portion of the second injection.

[0028] The sequence shown in Figure 4 can be modified. For example, the workpiece can be rotated before the first portion of the second implant (i.e., before box 440) so that the first portions of both implants are performed from the same direction.

[0029] The use of two implants provides advantages not possible with only one implant. Specifically, with certain photoresist materials (e.g., CAR), argon alone can reduce LER and LWR, but also significantly reduce CD. For example, 1E15 ions / cm 2 When these doses are used, the argon reduces the CD by more than 1 nm. Without being bound to any particular theory, it is believed that the first implant adds structural support to the photoresist, making it more resistant to the sputtering effects of the second implant.

[0030] It has also been found that for certain photoresist materials, the sequence shown in FIG. 4 can be simplified. For example, when a metal oxide (such as SnOx) is used as the photoresist material, many of the benefits described above can be realized by performing only the second implant. In other words, by orienting the trajectory of the incident ion beam 230 to align with the main photoresist direction 101, as described above, the implantation of the second species (which can be an inert species, oxygen, or nitrogen) can achieve a reduction in LER and LWR of at least 10% while minimizing the impact on CD (i.e., <1 nm). Thus, for metal oxide photoresists, the sequence shown in FIG. 4 can be modified by deleting boxes 410-430.

[0031] The embodiments described above in this application may have many advantages. To minimize the impact on CD and significantly reduce LER and LWR, the sequence shown in Figure 4 may be used. In some tests, using silicon as the first species and argon as the second species, a reduction in LER and LWR of more than 10% was achieved while the CD reduction was less than 1 nm. In some tests, the reduction in LER and LWR was more than 15% while the CD reduction was less than 1 nm. Such tests were performed using tilt angles between 60° and 80° and energies between 0.7 keV and 1.0 keV. The total dose of the first species was 1E15 ions / cm. 2 to 4E15 ions / cm 2 and the total dose of the second species is 2E15 ions / cm 2 to 2E16 ions / cm 2 It is between.

[0032] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, in addition to the embodiments of and modifications to the present disclosure described herein, various other embodiments and modifications will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Moreover, while the present disclosure is described herein in the context of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that the usefulness of the present disclosure is not limited to such contexts, and that the present disclosure may be beneficially implemented in several environments for several purposes. Accordingly, the claims set forth below should be construed in light of the full scope and nature of the present disclosure as described herein.

Claims

1. 1. A method for reducing line edge roughness (LER) and line width roughness (LWR) of patterned photoresist disposed on a workpiece, the patterned photoresist having sidewalls and a thickness known as a critical dimension (CD), the workpiece being disposed on a platen capable of twisting about a rotation axis and tilting about a tilt axis, the method comprising: orienting the workpiece on the platen by selecting a twist angle of the platen and a high tilt angle to align an incident ion beam trajectory with a primary photoresist direction parallel to the sidewall; directing a first ion beam having a first species toward the workpiece after the orientation; After directing the first ion beam, while the workpiece remains oriented, directing a second ion beam toward the workpiece, the second ion beam having a second species different from the first species; A method comprising:

2. 2. The method of claim 1, wherein the implant energy and dose of the first species and the implant energy and dose of the second species are selected to reduce the LER and LWR by at least 10% and have an impact on the critical dimension of the patterned photoresist of less than 1 nm.

3. The method of claim 1 , wherein the first species comprises silicon.

4. The method of claim 1 , wherein the second species comprises an inert species.

5. The method of claim 4 wherein the inert species comprises argon.

6. The method of claim 1 , wherein the second species comprises oxygen or nitrogen.

7. 2. The method of claim 1, wherein the patterned photoresist comprises a plurality of photoresist lines and the high tilt angle is at least 45 degrees.

8. The method of claim 7 , wherein the high tilt angle is between 60° and 80°.

9. 10. The method of claim 1, wherein orienting the workpiece comprises selecting a twist angle such that the angle between the primary photoresist direction and the trajectory of the incident ion beam is less than 5 degrees.

10. 1. A method for reducing line edge roughness (LER) and line width roughness (LWR) of patterned photoresist disposed on a workpiece, the patterned photoresist having sidewalls and a thickness known as a critical dimension (CD), the workpiece being disposed on a platen capable of twisting about a rotation axis and tilting about a tilt axis, the method comprising: orienting the workpiece on the platen by selecting a twist angle of the platen and a high tilt angle to align a primary photoresist direction parallel to the sidewall with the trajectory of an incident ion beam; directing a first ion beam including silicon ions toward the workpiece after the orientation; rotating the workpiece 180° after directing the first ion beam; directing the first ion beam toward the workpiece again after the rotation; directing a second ion beam having a second species different from the silicon ions toward the workpiece; rotating the workpiece 180° after directing the second ion beam; directing the second ion beam toward the workpiece after a second rotation; A method comprising:

11. 11. The method of claim 10, wherein the implantation energy and dose of the silicon ions and the implantation energy and dose of the second species are selected to reduce the LER and LWR by at least 10% and have an impact on the critical dimension of the patterned photoresist of less than 1 nm.

12. The method of claim 10 , wherein the second species comprises an inert species.

13. The method of claim 12 , wherein the inert species comprises argon.

14. The method of claim 10 , wherein the second species comprises oxygen or nitrogen.

15. 11. The method of claim 10, wherein the patterned photoresist comprises a plurality of photoresist lines and the high tilt angle is at least 45 degrees.

16. The method of claim 15, wherein the high tilt angle is between 60° and 80°.

17. 11. The method of claim 10, wherein orienting the workpiece comprises selecting a twist angle such that the angle between the primary photoresist direction and the trajectory of the incident ion beam is less than 5 degrees.

18. 1. A method for reducing line edge roughness (LER) and line width roughness (LWR) of patterned photoresist disposed on a workpiece, the patterned photoresist having sidewalls and a thickness known as a critical dimension (CD), the workpiece being disposed on a platen capable of twisting about a rotation axis and tilting about a tilt axis, the method comprising: orienting the workpiece on the platen by selecting a twist angle of the platen and a high tilt angle to align an incident ion beam trajectory with a primary photoresist direction parallel to the sidewall; directing an ion beam having an inert species toward the workpiece while the workpiece remains oriented; A method comprising:

19. 20. The method of claim 18, wherein orienting the workpiece comprises selecting a twist angle such that the angle between the primary photoresist direction and the trajectory of the incident ion beam is less than 5 degrees, and selecting a high tilt angle of at least 45 degrees.

20. 20. The method of claim 18, wherein the implant energy and dose of the inert species are selected such that the LER and LWR are reduced by at least 10% and the impact on the critical dimension of the patterned photoresist is less than 1 nm.

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