Technique and apparatus for unidirectional hole elongation using tilted ion beams.

Abstract

To provide a patterning method including providing a cavity in a layer arranged in a substrate.SOLUTION: The patterning method includes a step 402 of providing a cavity in a layer arranged on a substrate. The cavity has: a first length along a first direction; a first width along a second direction perpendicular to the first direction; and a first height along a third direction perpendicular to the first and second directions. The method also includes: a step 404 of depositing a sacrificial layer over the cavity in a first deposition procedure; and a step 406 of directing angled ions to the cavity to etch the cavity in a first exposure. After the first exposure, the cavity has a second length that is longer than the first length along the first direction, and the cavity has a second width that is less than or equal to the first width along the second direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001]

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 779,757, filed December 14, 2018, entitled "Techniques and Apparatus for Unidirectional Hole Extension Using an Inclined Ion Beam," the entire contents of which are incorporated herein by reference.

[0002]

[0002] The present embodiments relate to transistor processing technology, and more particularly to etching processes in patterning devices. [Background technology]

[0003] As semiconductor devices continue to shrink to smaller dimensions, the ability to pattern features becomes increasingly challenging.

[0004] One particular challenge is printing small features, such as cavities, separated by small distances on the scale of nanometers or tens of nanometers with current technology. As an example, as the overall pitch of device structures continues to shrink, it becomes increasingly difficult to print adjacent linear trenches or holes with adequate tip-to-tip distances. In particular, lithographic printing of small cavities at small pitches can be unreliable due to overlay issues. In other words, achieving small separations of small cavities can require multiple masks, and overlay errors between masks can result in overlapping cavities or excessively wide separations between cavities.

[0005]

[0005] One possible strategy for generating such a pattern in a given layer using a single mask layer is to lithographically pattern a series of cavities and then etch the cavities to enlarge them. In particular, a drawback of etching cavities in a given layer is that layer thickness is lost during etching.

[0006]

[0006] With regard to these and other considerations, the present improvements may be useful. Summary of the Invention

[0007] In one embodiment, a method for patterning a substrate is provided. The method may include providing a cavity in a layer disposed on the substrate, the cavity having a first length along a first direction and a first width along a second direction perpendicular to the first direction, and the layer having a first height along a third direction perpendicular to the first and second directions. The method may include depositing a sacrificial layer over the cavity in a first deposition procedure and directing tilted ions into the cavity in a first exposure, wherein the cavity is etched such that after the first exposure, the cavity has a second length along the first direction that is greater than the first length and a second width along the second direction that is less than or equal to the first width.

[0008] In another embodiment, a method for patterning a substrate may include providing a cavity in a first layer disposed on the substrate, the cavity having a first length along a first direction and a first width along a second direction perpendicular to the first direction, and the layer having a first height along a third direction perpendicular to the first and second directions. The method may include depositing a sacrificial layer over the cavity in a first deposition procedure, and directing tilted ions into the cavity in a first exposure. The tilted ions may include a first tilted ion beam having a first trajectory directed toward a first sidewall of the cavity and a second tilted ion beam having a second trajectory directed toward a second sidewall of the cavity opposite the first sidewall. Thus, the cavity is etched, and after the first exposure, the cavity has a second length along the first direction that is greater than the first length and a second width along the second direction that is less than or equal to the first width.

[0009] In a further embodiment, an apparatus is provided. The apparatus may include a load lock for receiving a substrate and a transfer chamber coupled to the load lock and configured to transfer the substrate under vacuum. The apparatus may include a tilted ion beam etching station coupled to the transfer chamber for directing a tilted reactive ion beam at the substrate at a non-zero angle of incidence relative to a normal to a plane of the substrate. The apparatus may include a polymer deposition chamber coupled to the transfer chamber and configured to deposit a polymer layer on the substrate, and a controller coupled to the polymer deposition chamber, the transfer chamber, and the tilted ion beam etching station. The controller may be configured to cycle the substrate through a plurality of etching cycles, a given etching cycle including depositing a polymer layer in the polymer deposition chamber, etching the substrate in the tilted ion beam etching station, and transporting the substrate between the polymer deposition chamber and the tilted ion beam etching station via the transfer chamber. [Brief explanation of the drawings]

[0010] [Figure 1A-E] 1A-1D are side views illustrating various stages of processing of a substrate according to an embodiment of the present disclosure. [Figure 1F-J] 1A to 1E are top views showing the steps corresponding to the respective FIGS. 1A to 1E. [Figure 2A] 1A-1C show experimental results of selective extension of cavities, according to some embodiments of the present disclosure. [Figure 2B] 10A-10C show further experimental results of selective extension of cavities, according to another embodiment of the present disclosure. [Figure 2C] 10A-10C show further experimental results of selective extension of cavities, according to another embodiment of the present disclosure. [Figure 3A-E] 10A-10C are side views illustrating various stages of processing of a substrate according to another embodiment of the present disclosure. [Figure 3F-J] 3A to 3E are top views showing the steps corresponding to the respective FIGS. 3A to 3E. [Figure 4A]FIG. 10 is a block diagram illustrating another processing device according to a further embodiment of the present disclosure. [Figure 4B] 3B is a top view illustrating an extraction geometry of the processing device of FIG. 3A according to a further embodiment of the present disclosure. [Figure 4C] FIG. 10 is a block diagram illustrating another processing device according to a further embodiment of the present disclosure. [Figure 5] FIG. 10 illustrates another processing apparatus according to an additional embodiment of the present disclosure. [Figure 6] FIG. 1 illustrates an exemplary process flow according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0022] The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, which show several embodiments. The subject matter of this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

[0012]

[0023] The present embodiments provide novel techniques and apparatus for patterning a substrate, particularly for etching cavities disposed in a substrate along a designed direction. The process can be considered elongation patterning, in which a feature, such as a via or trench, can be formed to have an initial shape and size and then elongated along a designed direction using a series of etching steps. The designed direction can correspond to a horizontal direction in the plane of the substrate. According to various embodiments, feature elongation can occur along the designed direction (first direction), while the cavities are not enlarged or are enlarged only along a direction perpendicular to the designed direction in the plane of the substrate (second direction). In this manner, the cavities can be selectively elongated along only one direction, providing various attendant advantages for patterning a substrate as disclosed herein.

[0013]

[0024] In certain embodiments, unidirectional extension of a cavity in a given layer is achieved using a novel deposition and etching process. Unidirectional extension of a cavity may refer to the selective extension of the dimension of a cavity (or hole) along a selected direction, such as along the Y-axis of a Cartesian coordinate system, with the extension not occurring along orthogonal directions, such as along the X-axis and along the Z-axis. In some embodiments, the cavity may be processed such that the original thickness (along the Z-direction) of the layer containing the cavity is maintained, but the cavity is etched in the plane of the layer only along one direction and not the other.

[0014]

[0025] In certain embodiments, a cavity is provided in a layer such that the cavity has a first length along a first direction. A first step involves depositing a sacrificial layer over the cavity in a first deposition procedure, and a second step involves directing tilted ions into the cavity in a first exposure, during which the cavity is etched. After the first exposure, the cavity can reach a second length along the first direction that is longer than the first length, and the cavity has a final width along the second direction that is equal to or less than the first width. In some cases, the final width is the same as the first width.

[0015]

[0026] Figures 1A-1E are side views illustrating various stages in the processing of a substrate according to an embodiment of the present disclosure, and Figures 1F-1J are top views illustrating stages corresponding to Figures 1A-1C, respectively.

[0016]

[0027] 1A-1E, which illustrate a series of examples of substrate pattern implementation on a substrate 100, according to some embodiments of the present disclosure. According to various embodiments, a combination of deposition and etching processes is performed sequentially. By way of background, the substrate 100 may include an array of features, with only one feature, shown as a cavity 110, being illustrated. For example, the lateral dimensions of the features may be on the scale of 30 nm, 20 nm, 10 nm, 5 nm, or 3 nm in some cases, while the designed separation between the features may have similar values. To precisely create these features, novel combinations of deposition and etching processes are provided to selectively vary the size of features, such as trenches or vias. In particular, trenches or vias may be selectively elongated along a target direction to create a designed shape and size of the trenches or vias, while the separation between the trenches may be adjusted to achieve the designed separation. At the same time, the thickness of the layer containing the features may be maintained while avoiding undesired expansion of the features in a direction perpendicular to the target direction.

[0017]

[0028] 1A and 1F illustrate an extraction system 120 for directing deposition species as well as etching species into the substrate 100. The extraction system 120 may be implemented in a plasma-based tool in some embodiments. In other embodiments, the extraction system 120 may be omitted. As shown in FIG. 1A, a plasma 122 is generated. The plasma 122 may, in some embodiments, generate deposition species for depositing polymer-type films. Gaseous species such as CHF or CH or other known polymer-forming species may be provided, react in the plasma 122, and exit the extraction system 120 through extraction apertures 128. These species may form reactive deposition species 132, which impinge on the substrate 100. In this example, a cavity 110 is formed in layer 116, which may be a hard mask layer, a soft mask layer, or a device layer to be preserved. Thus, the cavity 110 may be defined by dimensions along different directions, including L1 along the Y-axis, H1 along the Z-axis, and W1 along the X-axis of the illustrated Cartesian coordinate system. Reactive deposition species may deposit on layer 116, including sidewalls 114A, 114C, and 114B of cavity 110, as shown in FIGS. 1A and 1F. In some embodiments, substrate 100 may be negatively biased with respect to plasma 122, e.g., at −200 V, −100 V, −50 V, or −20 V. The embodiments are not limited in this context. Thus, a polymer layer tends to deposit on substrate 100, forming sacrificial layer 115, as shown in FIGS. 1B and 1G. The deposition process may advantageously deposit a thicker polymer on the upper horizontal surfaces or within the cavity 110 than on the vertical surfaces (sidewalls) due to the higher solid angle of the flux of radical and neutral species (represented by reactive deposition species 132) coming from the plasma 122.

[0018]

[0029] 1B and 1G, a directional reactive ion etching process is performed after the completion of deposition of the sacrificial layer 115 to extend the cavity along the Y-axis. At the stage of FIG. 1B, the sacrificial layer 115 coats the top surface of the layer 116, as well as the first and second sidewalls 114A and 114C. The reactive ion etching chemistry can be a known etching chemistry selected according to the properties of the layer 116, as well as the polymer layer and the sacrificial layer 115. For example, if the layer 116 is a SiON layer, the etching chemistry can be selected to selectively etch SiON relative to other materials, such as the substrate base layer 118. The etching process includes forming a plasma 142 and directing an oblique reactive ion beam 150 at a non-zero angle of incidence (θ) with respect to a normal 134 to the plane of the substrate 130, which may represent the upper major surface of the wafer. Suitable reactive species 152 may be present in the reactive environment and may involve the oblique reactive ion beam 150, as in known reactive ion beam etching recipes. 1A, where a tilted reactive ion beam 150 is extracted from plasma 142 through an extraction aperture 128 between extraction section 126 and extraction section 124. As shown in FIG. 1E, in different non-limiting embodiments, extraction aperture 128 can be elongated along the X direction such that its size along the X direction is 3, 5, 10, 20, or 50 times its size along the Y direction.

[0019]

[0030] In some non-limiting embodiments, this angle of incidence can range from 15 degrees to 75 degrees. Therefore, both horizontal and vertical surfaces can be exposed to ions and etched. Now, because of the protective polymer (sacrificial layer 115) disposed on the top surface 125 of layer 116, this etching results in a reduction in thickness loss of layer 116 (or a reduction in vertical etching of layer 116) as the pattern is stretched. Given that there is some polymer deposition on the sidewalls, the lateral etching rate may also be reduced.

[0020]

[0031] 1C and 1H, which illustrate the structure of substrate 100 at a further stage in the etching process of Fig. 1B, where material has been removed from the top surface of sacrificial layer 115 along horizontal planes by angled reactive ion beam 150, and sacrificial layer 115 has been completely removed from first sidewall 114A.

[0021]

[0032] 1D and 1I, which illustrate the structure of substrate 100 at a further stage in the etching process of FIG. 1C (with angled reactive ion beam 150 removed for clarity). At this stage, more material has been removed from the top surface of sacrificial layer 115 by angled reactive ion beam 150, and sacrificial layer 115 has been completely removed from first sidewall 114A. As shown, corners of sacrificial layer 115 may be rounded due to the angled ion etching, while layer 116 remains protected at the top surface. Cavity 110 is elongated along the Y-axis by etching a portion of first sidewall 114A to a length L2, with the width of cavity 110 remaining at a value of W1 and the thickness of layer 116 remaining at H1.

[0022]

[0033] 1E and 1J, which illustrate the structure of substrate 100 after completion of the etching step of FIG. 1D. Although cavity 110 has been extended along the Y-axis to a length L3, the width of cavity 110 remains at a value W1, and the thickness of layer 116 remains at H1. More specifically, at the stage of FIG. 1E, cavity 110 has been further extended by etching first sidewall 114A with angled reactive ion beam 150. Subsequently, upon completion of etching using angled reactive ion beam 150, a portion of sacrificial layer 115 may remain, which may be removed, for example, by a suitable wet or dry etch designed to preferentially etch polymer material relative to the material of layer 116. Thus, after removal of the polymer layer, the corners of cavity 110 may exhibit less rounding than would occur without the use of sacrificial layer 115.

[0023]

[0034] As shown in the above example, this approach facilitates etching of structures such as cavity 110 in a manner that expands the cavity along only one direction while maintaining the thickness of the layer containing the cavity. The degree of unidirectional etching can be adjusted depending on the exact amount of polymer deposited in the step of FIG. 1A and the duration of the etching step of FIG. 1B. See FIG. 2A, which shows the relative change in cavity dimensions as a function of etching time in a CF4 / O2 plasma-based 1 kV ion beam. The ion beam forms a tilted ion beam according to this embodiment, as described above. The dimensions are relative to cavities within an array of cavities formed in an insulating layer of a substrate, with the cavities having initial lateral dimensions on the order of 25 nm formed in a layer with an initial thickness on the order of 50 nm. In this example, a polymer layer is deposited prior to the etching process. The polymer layer is deposited into the cavity from a plasma generated by CH3F, with zero bias applied between the substrate and the plasma chamber. The polymer layer had a thickness of just over 10 nm on the horizontal plane (in the Z direction) of the cavity array, but the width of the polymer deposited on the sidewalls was approximately half the thickness of the polymer layer on the horizontal plane. Thus, the initial cavity width and length were reduced prior to etching. Curve 170 represents the thickness H of the original layer containing the cavities, curve 172 represents the length along the Y axis, and curve 174 represents the width along the Z axis. In this example, the cavity length L increases by approximately 25% after 1.8 minutes of etching time, but the width W does not increase at all. The total thickness loss in H is less than 10 nm. The polymer layer was consumed at the end of etching, along with several nm of the original layer containing the cavities.

[0024]

[0035] FIG. 2B presents data for etching an array of cavities having dimensions similar to the example of FIG. 2A. In this example, curve 180 represents the thickness H of the original layer containing the cavities, curve 182 represents the length along the Y axis, and curve 184 represents the width along the Z axis. Prior to etching, a polymer layer slightly greater than 15 nm is deposited on the array of cavities. The extra polymer deposition ensures that virtually no original layer thickness is lost after 1.8 minutes of etching. Similarly, no change in width W is observed, while length L increases by approximately 20%.

[0025]

[0036] The results in Figures 2A and 2B show that the combination of deposition and angled reactive ion beam etching can be tailored to optimize directional etching. In particular, we observed that when a polymer layer is not deposited in the cavity and selective extension etching is performed along a given direction, as in Figure 1B, the directional etching stops after an initial period. That is, etching initially proceeds along the Y axis, but after an induction period of several minutes, etching also proceeds along the X axis, resulting in undesired expansion of the cavity in a direction perpendicular to the designed expansion direction. The length of the initial period may depend on the film stack being etched and the etching chemistry used.

[0026]

[0037] To illustrate this phenomenon, the steps of FIGS. 1A and 1B can be repeated periodically in a manner that replenishes the polymer coating on the cavity before orthogonal etching of the cavity begins. FIG. 2C presents data showing the relative change in cavity dimensions as a function of etching time in a CF4 / O2 plasma-based ion beam using tilted ion beams, according to a further embodiment. In this case, the initial cavity conditions are the same as in the example of FIG. 2A, and a first polymer layer slightly greater than 10 nm thick (in the Z direction) is deposited in the cavity prior to etching. In particular, after an etching duration of approximately 1.8 minutes, a second polymer layer is deposited to a similar thickness, followed by a second etching or etching duration of approximately 1.8 minutes. A third polymer deposition is then performed to form a polymer layer of similar thickness to the other depositions, and the third etching is performed for another 1.8 minutes. As shown, curve 190 represents the thickness H of the original layer comprising the cavity, curve 192 represents the length along the Y axis, and curve 194 represents the width along the Z axis. In this example, the cavity length L increases by approximately 70% after 1.8 minutes of etching time, but the width W does not increase at all. The total thickness loss in H is less than 10%. Because the process was performed in three cycles, etching was stopped in each cycle before orthogonal etching (along the X-axis) began. Therefore, after a total of 5.4 minutes of etching, orthogonal etching was not observed. This means that the cavity did not expand along the X-axis. In various experiments, cavity elongation of up to 16 nm was observed. However, the results of Figure 2C can be extended to produce larger elongation simply by performing more cycles. Similarly, as reflected in Figure 2B, by adjusting the polymer deposition process and selecting an appropriate etching time, it is possible, in principle, to achieve unidirectional etching in which the Y-axis is elongated without losing thickness of the layer containing the cavity; the cavity is not elongated along the X-axis. By comparison, when directional etching is performed without prior deposition of a thin polymer layer using an ion beam as generally shown in Figure 1B, orthogonal etching begins after the initial etching period.Curve 196 shows the change in cavity width along the X-axis as a function of etching time for an etch performed on a cavity generally positioned as in the other data in FIG. 2C, but without a polymer layer deposited prior to etching. As shown in curve 196, the width along the X-axis remains unchanged for the first 2 minutes, but after 2.5 minutes, the width increases with increasing etching time. Thus, in the absence of a thin polymer layer, unidirectional etching does not persist beyond the initial period of etching.

[0027]

[0038] 3A-3E are side views illustrating various stages of substrate processing according to an embodiment of the present disclosure. FIGS. 3F-3J are top views illustrating the stages corresponding to FIGS. 3A-3E, respectively. The process of FIGS. 3A-3J is generally similar to that illustrated in FIGS. 1A-1J, with one difference being the provision of a tilted reactive ion beam 150A along a first trajectory and a tilted reactive ion beam 150B along a second trajectory opposite the first trajectory. This configuration can be achieved by providing a beam blocker 129 to define a first extraction aperture 128A and a second extraction aperture 128B to define two tilted ribbon ion beams. These ribbon beams can impinge on opposing surfaces of the cavity, shown as a first sidewall 114A and a second sidewall 114C, resulting in equal removal of polymer from both sidewalls and symmetrical elongation of the cavity, as illustrated in FIGS. 3E and 3J.

[0028]

[0039] 3A and 3F illustrate an extraction system 120A for directing deposition and etching species toward the substrate 100. The extraction system 120A may be implemented in a plasma-based tool in some embodiments. In other embodiments, the extraction system 120A may be omitted. As shown in FIG. 3A, a plasma 122 is generated. The plasma 122 may generate deposition species for depositing polymer-type films in some embodiments. Gaseous species such as CHF or CH or other known polymer-forming species may be provided, react in the plasma 122, and exit the extraction system 120A through extraction apertures 128A and 128B. These species may form reactive deposition species 132, which impinge on the substrate 100. In this example, a cavity 110 is formed in layer 116, which may be a hard mask layer, a soft mask layer, or a device layer to be preserved. Thus, the cavity 110 may be defined by dimensions along different directions, including L1 along the Y-axis, H1 along the Z-axis, and W1 along the X-axis of the illustrated Cartesian coordinate system. Reactive deposition species may be deposited on a layer 116, including the first and second sidewalls 114A, 114C of the cavity 110, as shown in FIGS. 3B and 3G. In some embodiments, the substrate 100 may be negatively biased with respect to the plasma 122, e.g., −200 V, −100 V, −50 V, or −20 V. The embodiments are not limited in this context. Thus, a polymer layer tends to deposit on the substrate 100, forming the sacrificial layer 115 shown in FIGS. 3B and 3G. The deposition process may advantageously deposit a thicker polymer on the upper horizontal surfaces or within the cavity 110 than on the vertical surfaces (sidewalls) due to the higher solid angle of the flux of radical and neutral species (represented by reactive deposition species 132) coming from the plasma 122.

[0029]

[0040] 3B and 3G, a directional reactive ion etching process is performed after the deposition of the sacrificial layer 115 is completed to elongate the cavity along the Y-axis. At the stage of FIG. 3B, the sacrificial layer 115 coats the top surface of the layer 116, as well as the first and second sidewalls 114A and 114C. The reactive ion etching chemistry can be any known etching chemistry selected according to the properties of the layer 116, the polymer layer, and the sacrificial layer 115. For example, if the layer 116 is a SiON layer, the etching chemistry can be selected to selectively etch SiON relative to other materials, such as the substrate base layer 118. The etching process includes directing a pair of tilted reactive ion beams at a non-zero angle of incidence (θ) with respect to a normal to the plane of the substrate 130, which may represent the upper major surface of the wafer. These tilted reactive ion beams are shown as tilted reactive ion beam 150A directed along a first trajectory and tilted reactive ion beam 150B directed along a second trajectory. As previously mentioned, this configuration can be achieved by providing a beam blocker that defines first and second apertures, shown as extraction aperture 128A and extraction aperture 128B, to define two tilted ribbon ion beams.

[0030]

[0041] Suitable reactive species 152 may involve a tilted reactive ion beam, as in known reactive ion beam etching recipes. In some embodiments, the etching step may be performed in the same apparatus and chamber as the deposition step of FIG. 3A, with tilted reactive ion beams 150A and 150B extracted through extraction apertures 128A and 128B located between extraction portions 126A and 124A. As shown in FIG. 3G, extraction apertures 128A and 128B may be elongated along the X direction such that their size along the X direction is 3, 5, 10, 20, or 50 times their size along the Y direction in different non-limiting embodiments.

[0031]

[0042] In some non-limiting embodiments, the angle of incidence of the tilted ions 152A and the tilted ions 152B can range from 15 degrees to 75 degrees. Therefore, both horizontal and vertical surfaces can be exposed to the ions and etched. At this point, a protective polymer (sacrificial layer 115) is disposed on the top surface 125 of the layer 116, reducing the thickness loss of the layer 116 (or reducing the vertical etching of the layer 116) due to this etching when the pattern is extended. Given that there is some polymer deposition on the sidewalls, the lateral etching rate may also be reduced.

[0032]

[0043] 3C and 3H, which show the structure of substrate 100 at a further stage in the etching process of FIG. 3B. At this stage, material has been removed from the top surface of sacrificial layer 115, sacrificial layer 115 has been completely removed from first sidewall 114A by angled reactive ion beam 150A, and sacrificial layer 115 has been completely removed from second sidewall 114C by angled reactive ion beam 150B. Sacrificial layer 115 still remains along the top of layer 116.

[0033]

[0044] 3D and 3I, which illustrate the structure of the substrate 100 at a further stage of the etching process of FIG. 3C (with the angled reactive ion beams 150A and 150B removed for clarity). At this stage, more material has been removed from the top surface of the sacrificial layer 115, and the first and second sidewalls 114A and 114C have been elongated to produce a length L4 of the cavity 110 that is longer than L1. As shown, the corners of the sacrificial layer 115 may be rounded due to the angled ion etching, and the layer 116 remains protected at the top surface. The width of the cavity 110 remains at the value W1, and the thickness of the layer 116 remains at H1, but the cavity 110 has been elongated. In particular, the structure of FIG. 3D may represent the cavity 110 after etching is completed using the angled reactive ion beams 150A and 150B.

[0034]

[0045] 3E and 3J, which show the structure of substrate 100 after removal of sacrificial layer 115 by a suitable wet or dry etch designed to preferentially etch the polymer material relative to the material of layer 116. Thus, after removal of the polymer layer, the corners of cavity 110 may exhibit less rounding than would occur if sacrificial layer 115 were not used.

[0035]

[0046] Reference is now made to FIG. 4A , which shows a processing apparatus 200 in schematic form. The processing apparatus 200 represents a processing apparatus for selectively etching portions of a substrate, such as selectively forming cavities. The processing apparatus 200 may be a plasma-based processing system having a plasma chamber 202 for generating a plasma 204 by any convenient method known in the art. The power source 230 may be, for example, an RF power source for generating the plasma 204. As shown, an extraction plate 206 having extraction apertures 208 may be provided, through which selective etching may be performed to selectively remove sidewall layers. A substrate, such as the substrate 100 shown in FIG. 1B and having the aforementioned structure, is placed in the process chamber 222. The substrate plane of the substrate 100 is represented by the XY plane of the illustrated Cartesian coordinate system, with the normal to the plane of the substrate 100 being along the Z-axis (Z direction).

[0036]

[0047] During the directional etching process, a tilted ion beam 210 is extracted through an extraction aperture 208, as shown. In one embodiment, the tilted ion beam 210 may represent the tilted reactive ion beam 150 described above. As in known systems, the tilted ion beam 210 may be extracted when a voltage difference is applied between the plasma chamber 202 and the substrate 100 using a bias power supply 220. The bias power supply 220 may be coupled to the process chamber 222, for example, where the process chamber 222 and the substrate 100 are held at the same potential. In various embodiments, the tilted ion beam 210 may be extracted as a continuous beam or a pulsed ion beam, as in known systems. For example, the bias power supply 220 may be configured to supply a voltage difference between the plasma chamber 202 and the process chamber 122 as a pulsed DC voltage, where the voltage, pulse frequency, and duty cycle of the pulsed voltage may be adjusted independently of one another.

[0037]

[0048] The substrate stage, including the substrate 100, moves along a scan direction 216 relative to the extraction aperture 208 and thus relative to the tilted ion beam 210. 214By scanning the tilted ion beam 210, the tilted ion beam 210 can etch structures such as the cavity 110 when the target surface of the structure is oriented, for example, perpendicular to the scanning direction 216, as further shown in FIG. 4B. In various embodiments, for example, the tilted ion beam 210 can be provided as a ribbon ion beam having a long axis extending along the X direction of the Cartesian coordinate system shown in FIG. 4B. The substrate 100 can be positioned, for example, so that one set of sidewalls (see first sidewall 114A) of the cavity 110 is exposed to the tilted ion beam 210. In this way, as shown in FIG. 4A, the tilted ion beam 210, which forms a non-zero angle of incidence with respect to the Z axis (normal to the substrate plane), can impinge on the sidewall oriented along the XZ plane, as noted. This geometry facilitates reactive ion etching of the XZ sidewalls without etching the YZ sidewalls, thus selectively elongating the cavity 110 and generating an elongated structure of the cavity 110, as shown in FIG. 1C or 1F. In various embodiments, the value of the non-zero angle of incidence may vary from 10 degrees to 75 degrees, while in some embodiments, the value may range between 20 degrees and 60 degrees. The embodiments are not limited in this context. The angled ion beam 210 may be comprised of any convenient gas mixture, including inert gases, reactive gases, and, in some embodiments, may be provided in combination with other gas species. The gases may be provided from a gas source 224, which may be a gas manifold coupled to provide multiple different gases to the plasma chamber 202. In certain embodiments, the angled ion beam 210 and other reactive species may be provided to the substrate 100 as an etch recipe to perform directional reactive ion etching of targeted sidewalls of a patterned layer of the substrate 100. As described above, the etch recipe may be selective to the material of the substrate base layer 118, such that the substrate base layer 118 is not etched or is etched to a lesser extent to remove material from the polymer layer (sacrificial layer 115) and layer 116.

[0038]

[0049] 4B, the tilted ion beam 210 is provided as a ribbon ion beam extending to a beam width along the X direction that is sufficient to expose the entire width of the substrate 100 at its widest point along the X direction. Exemplary beam widths can range from 10 cm, 20 cm, 30 cm, or more, while exemplary beam lengths along the Y direction can range from 3 mm, 5 mm, 10 mm, or 20 mm. Embodiments are not limited in this context.

[0039]

[0050] As also shown in FIG. 4B , the substrate 100 may be scanned in a scan direction 216, which lies in the XY plane, such as along the Y direction. In particular, the scan direction 216 may represent scanning of the substrate 100 in two opposing (180-degree) directions along the Y direction, or simply scanning to the left or right. As shown in FIG. 3B , the long axis of the tilted ion beam 210 extends along the X direction, perpendicular to the scan direction 216. Thus, when the substrate 100 is scanned along the scan direction 216 for an appropriate length from the left side to the right side of the substrate 100, as shown in FIG. 4B , the entire substrate 100 may be exposed to the tilted ion beam 210.

[0040]

[0051] Reference is now made to FIG. 4C , which illustrates another processing apparatus 240, depicted in schematic form. The processing apparatus 240 represents a processing apparatus for performing tilted ion processing of substrates and may be substantially similar to the processing apparatus 200, except for the differences described below. In particular, the processing apparatus 240 includes a beam blocker 232 disposed adjacent to the extraction aperture 208. The beam blocker 232 is sized and positioned to define a first aperture 208A and a second aperture 208B, where the first aperture 208A forms a first tilted ion beam 210A and the second aperture 208B forms a second tilted ion beam 210B. The two tilted ion beams may define equal but opposite angles of incidence with respect to the normal 226. In one embodiment, the first tilted ion beam 210A may represent the tilted reactive ion beam 150A, and the second tilted ion beam 210B represents the tilted reactive ion beam 150. A beam blocker offset along the Z-axis relative to the extraction plate 206 can help define the angle of the tilted ion beam. Thus, the first tilted ion beam 210A and the second tilted ion beam 210B can simultaneously process opposing sidewalls of the semiconductor fin in a similar manner, as roughly shown in FIG. 4C . When configured in a ribbon beam configuration, as in FIG. 4B , these tilted ion beams can expose the entire substrate 100 to reactive ion etching of cavities 110 distributed throughout the device by scanning the substrate platen 214 as shown. In this configuration, opposing sidewalls of the cavities 110 can be etched simultaneously, elongating the cavities 110 in two opposing directions along the Y-axis in a single scanning step.

[0041]

[0052] According to various embodiments of the present disclosure, the processing apparatus 200 or processing apparatus 240 may also be configured to deposit polymer films, as detailed above. Thus, before the etching process begins, a suitable species, such as ChF, may be provided to the plasma chamber to deposit a polymer layer on the substrate 100. After deposition, the gas chemistry may be switched and a tilted reactive ion beam etch may be performed, possibly using the tilted ion beam 210 or the tilted ion beams (210A, 210B).

[0042]

[0053] In other embodiments, the deposition and etching processes detailed above may be performed in separate stations of a cluster tool. FIG. 5 presents a top view (XY plane) of an exemplary system, designated as system 300, according to embodiments of the present disclosure. System 300 may be used to perform angled ion etching processes as well as normal incidence etching processes, according to embodiments disclosed herein. System 300 may be configured as a cluster tool including a load lock 302 and a transfer chamber 304 for transporting substrate 100 between various processing chambers. The transfer chamber 304 and processing chambers may be coupled to an exhaust system, such as a known pumping system (not shown), for maintaining transfer chamber 304 and the other processing chambers described below under vacuum or controlled ambient conditions. Thus, substrate 100 may be transported between various processing chambers and transfer chamber 304 without exposure to the ambient. The system 300 may include a tilted ion beam etching station 306 coupled to the transfer chamber 304, where the substrate 100 is exposed to ions oriented at a non-zero angle of incidence relative to a normal to the substrate plane and conforming to a shape generally shown in FIGS. 1A-1C or 3A-3C. The tilted ion beam etching station 306 may generally comprise the plasma chamber and extraction plate described above, or may comprise the plasma chamber, extraction plate, and process chamber described above. The system 300 may further include a polymer deposition chamber 308 coupled to the transfer chamber 304 and positioned to perform deposition of a thin polymer layer. Thus, to perform the sequence of steps shown in FIGS. 1A-1E, the substrate 100 may be transported sequentially between the tilted ion beam etching station 306 and the polymer deposition chamber 308 without breaking vacuum between steps. An advantage of the configuration of Figure 5 is that the same process can be repeated in a specific dedicated chamber, so that the process of Figures 1A-1E can be repeated in cycles and unidirectional etching can be maintained by periodically replenishing the thin polymer layer over cavity 110 without having to change the chemistry in a given chamber.The ability to rapidly replenish the sacrificial polymer layer over the cavity being etched in the directed ion beam chamber allows etching of the main layer being etched, such as layer 116, to proceed along only one direction, while the top of layer 116 is not etched due to the repeated replenishment of the polymer layer. This repeated replenishment may, for example, prevent or minimize corner rounding that occurs in layer 116.

[0043]

[0054] FIG. 6 illustrates an exemplary process flow 400. In block 402, a cavity is provided in at least one layer disposed on a substrate. In some embodiments, the cavity may be formed in a given layer. In some embodiments, the cavity may be characterized by a first length along a first direction and a first width along a second direction perpendicular to the first direction. The layer may be characterized by a first height. In block 404, a sacrificial layer is deposited. In some embodiments, the sacrificial layer may be a thin polymer layer. The sacrificial layer may be deposited to form a thicker layer on horizontal surfaces above the cavity and a relatively thinner layer on vertical surfaces of the cavity.

[0044]

[0055] In block 406, the cavity is exposed to angled ions, such as in a reactive ion etching process, such that the cavity is elongated to a second length along the first direction, but the cavity has a second width along the second direction that is less than or equal to the first width.

[0045]

[0056] At block 408, a second sacrificial layer is deposited. In some embodiments, the second sacrificial layer may be a thin polymer layer. The second sacrificial layer may be deposited to form a thicker layer on the horizontal surfaces above the cavity and a relatively thinner layer on the vertical surfaces of the cavity.

[0046]

[0057] In block 410, the cavity is exposed to angled ions, such as in a reactive ion etching process, such that the cavity is elongated along the first direction to a third length that is greater than the second length, but the cavity has a third width along the second direction that is less than or equal to the first width.

[0047]

[0058] This embodiment offers various advantages over conventional processes for defining features on a substrate. One advantage is the ability to selectively extend cavities along only one direction while maintaining the cavity dimensions along a second direction perpendicular to the first direction. Another advantage is the ability to shrink cavities below the spacing achieved by known lithography processes. An example of this ability is the reduction of chip-to-chip separation between adjacent trenches, such as contact trenches. Another advantage provided by this embodiment is the ability to selectively extend cavities along a target direction while preventing excessive hard mask thickness loss and reducing corner rounding of cavities formed in the hard mask layer. A further advantage is the ability to reduce the number of masks used to generate feature patterns; features can be separated by distances shorter than the threshold separation achievable with a single mask. This reduction in the number of masks has the additional beneficial effect of reducing overlay errors in printing feature patterns.

[0048]

[0059] The present disclosure should not be limited in scope by the specific embodiments described herein. Indeed, various other embodiments and modifications of the present disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. Accordingly, such other embodiments and modifications tend to fall within the scope of the present disclosure. Moreover, while the present disclosure has been described herein in the context of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that the utility is not limited thereto, and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in light of the full breadth and spirit of the present disclosure as described herein.

Claims

1. 1. An apparatus comprising: at least one plasma chamber; Controller and Equipped with The at least one plasma chamber comprises: directing an oblique reactive ion beam at a substrate at a non-zero angle of incidence relative to a normal to the substrate plane; and Directing deposition species to the substrate to deposit a polymer layer on the substrate. an extraction plate having extraction apertures arranged such that The controller a plasma processing device coupled to the at least one plasma chamber and configured to process the substrate through a plurality of etching cycles, a given etching cycle including deposition of the polymer layer from the deposition species on an upper surface of the substrate followed by etching of the substrate with the tilted reactive ion beam; The device comprises: a process chamber containing the substrate; a substrate stage disposed within the process chamber and arranged to scan the substrate relative to the tilted reactive ion beam along a first direction in a plane of the substrate; a bias power supply for applying a voltage between the at least one plasma chamber and the process chamber, wherein a first value of the voltage for generating the tilted reactive ion beam is greater than a second value of the voltage for depositing the polymer layer; The apparatus further comprises:

2. The device of claim 1 , wherein the extraction apertures are elongated along a second direction perpendicular to the first direction.

3. The apparatus of claim 1 , wherein the at least one plasma chamber is a single plasma chamber.

4. 10. The apparatus of claim 1, further comprising a beam blocker disposed over the extraction aperture, the beam blocker defining a first extraction aperture and a second extraction aperture, the tilted reactive ion beam being a first tilted reactive ion beam, and the second extraction aperture directing a second tilted reactive ion beam to the substrate at a second non-zero angle of incidence relative to the normal to the substrate plane.

5. The apparatus of claim 1 , wherein the second value is less than or equal to 200V.

6. An apparatus, at least one plasma chamber; Controller and Equipped with The at least one plasma chamber comprises: directing an oblique reactive ion beam at a substrate at a non-zero angle of incidence relative to a normal to the substrate plane; and Directing deposition species to the substrate to deposit a polymer layer on the substrate. an extraction plate having extraction apertures arranged such that The controller 1. A method of patterning a substrate using an apparatus coupled to the at least one plasma chamber and arranged to process the substrate through a plurality of etching cycles, a given etching cycle comprising deposition of the polymer layer from the deposition species on an upper surface of the substrate followed by etching of the substrate with the tilted reactive ion beam, comprising: providing a cavity disposed on the substrate, the cavity comprising a sacrificial layer and a first layer below the sacrificial layer, the sacrificial layer having a relatively greater thickness above a top surface of the first layer than on a sidewall of the cavity, the cavity having a first length along a first direction, and the first layer having a first height along a direction perpendicular to the first direction; directing tilted ions at a sidewall of the cavity in a first exposure, the sidewall of the cavity being etched, the cavity having a second length along the first direction that is longer than the first length after the first exposure, and the sacrificial layer being retained on the top surface of the first layer after the first exposure; A method comprising:

7. The method of claim 6 , wherein the first layer retains the first height after the first exposure.

8. depositing a second sacrificial layer over the cavity in a second deposition step; directing a second tilted ion beam into the cavity during a second exposure; 8. The method of claim 7, further comprising: wherein the cavity is etched such that after the second exposure, the cavity has a third length along the first direction that is longer than the second length; and wherein the sacrificial layer is retained after the second exposure.

9. 7. The method of claim 6, wherein the tilted ions are first tilted ions, the first tilted ions being directed along a first trajectory at a first non-zero angle of incidence relative to a normal to a plane of the substrate in the presence of a first reactive environment, the first trajectory being aligned with the first direction.

10. The tilted ions are directed in the presence of a first reactive environment, the tilted ions being: a first tilted ion beam having a first trajectory at a first non-zero angle of incidence relative to a normal to the plane of the substrate; a second tilted ion beam having a second trajectory at a second non-zero angle of incidence relative to a normal to the plane of the substrate; and 7. The method of claim 6, comprising:

11. The method of claim 10 , wherein the first and second tilted ion beams comprise first and second ribbon beams, respectively.

12. The sacrificial layer is generating a plasma containing a deposition species in a plasma chamber; providing extraction apertures along the sides of the plasma chamber; 7. The method of claim 6, wherein the deposition species diffuses through the extraction apertures to the substrate.

13. 13. The method of claim 12, wherein directing tilted ions into the cavity in the first exposure comprises directing the tilted ions through the extraction aperture.

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