# Patent

## Title
Methods of forming nanowire devices with doped extension regions and the resulting devices

## Abstract

A method of forming a nanowire device includes patterning a plurality of semiconductor material layers such that each layer has first and second exposed end surfaces. The method further includes forming doped extension regions in the first and second exposed end surfaces of the semiconductor material layers. The method further includes, after forming the doped extension regions, forming epi semiconductor material in source and drain regions of the device.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Disclosure
The present disclosure generally relates to the formation of semiconductor devices, and, more specifically, to various methods of forming nanowire devices with doped extension regions and the resulting devices.
2. Description of the Related Art
The fabrication of advanced integrated circuits, such as CPUs (central processing units), storage devices, ASICs (application specific integrated circuits) and the like, requires the formation of a large number of circuit elements in a given chip area according to a specified circuit layout, wherein so-called metal oxide semiconductor field effect transistors (MOSFETs or FETs) represent one important element that substantially determines performance of the integrated circuits. A FET is a planar device that typically includes a source region, a drain region, a channel region that is positioned between the source region and the drain region, and a gate structure positioned above the channel region. These elements are sometimes referred to as the source, drain, channel, and gate, respectively. Current flow through the FET is controlled by controlling the voltage applied to the gate electrode. For example, for an NMOS device, if there is no voltage applied to the gate electrode, then there is no current flow through the NMOS device (ignoring undesirable leakage currents, which are relatively small). However, when an appropriate positive voltage is applied to the gate electrode, the channel region of the NMOS device becomes conductive, and electrical current is permitted to flow between the source region and the drain region through the conductive channel region.
To improve the operating speed of FETs, and to increase the density of FETs on an integrated circuit device, device designers have greatly reduced the physical size of FETs over the years. More specifically, the channel length of FETs has been significantly decreased, which has resulted in improving the switching speed of FETs. However, decreasing the channel length of a FET also decreases the distance between the source region and the drain region. In some cases, this decrease in the separation between the source and the drain makes it difficult to efficiently inhibit the electrical potential of the source region and prevent the channel from being adversely affected by the electrical potential of the drain. This is sometimes referred to as a short channel effect, wherein the characteristic of the FET as an active switch is degraded.
In contrast to a FET, which has a planar structure, there are so-called 3D devices, such as an illustrative FinFET device, which is a three-dimensional structure. More specifically, in a FinFET, a generally vertically positioned fin-shaped active area is formed, and a gate electrode encloses both sides and an upper surface of the fin-shaped active area to form a tri-gate structure so as to use a channel having a three-dimensional structure instead of a planar structure. In some cases, an insulating cap layer, e.g. silicon nitride, is positioned at the top of the fin and the FinFET device only has a dual-gate structure. Unlike a planar FET, in a FinFET device, a channel is formed perpendicular to a surface of the semiconducting substrate so as to reduce the physical size of the semiconductor device.
Another form of 3D semiconductor device employs so-called nanowire structures for the channel region of the device. There are several known techniques for forming such nanowire structures. As the name implies, at the completion of the fabrication process, the nanowire structures typically have a generally circular cross-sectional configuration. Nanowire devices are considered to be one option for solving the constant and continuous demand for semiconductor devices with smaller feature sizes. However, the manufacture of nanowire devices is a very complex process.
FIG. 1 is a simplified view of an illustrative nanowire device 100 at an early stage of manufacturing that is formed on a semiconducting substrate 10. FIG. 1 is provided so as to explain one example of how nanowire devices may be fabricated. At the point of fabrication depicted in FIG. 1, various layers of semiconducting material 11, 12, 13 and 14 were formed above the substrate 10. In general, in the depicted example, the layers 11 and 13 include a semiconductor material that may be selectively removed or etched relative to the materials used for the semiconducting material layers 12 and 14. As described more fully below, portions of the semiconductor material layers 11 and 13 will be removed while the semiconducting material layers 12 and 14 will be left in place. Thus, the portions of the semiconducting material layers 11 and 13 within the channel region of the device are sacrificial in nature. The semiconductor materials 11, 12, 13 and 14 may include a variety of different materials such as, for example, silicon, doped silicon, silicon-carbon, silicon-germanium, a III-V material, germanium, etc., and they may be formed to any desired thickness by performing any appropriate process, e.g., an epitaxial growth process, deposition plus ion implantation, etc. In one embodiment, the semiconducting material layers 11 and 13 may be made from silicon-germanium, while the semiconducting material layers 12 and 14 may be made from silicon.
The gate structure 25 may include a variety of different materials and a variety of configurations. As shown, the gate structure 25 includes a gate insulation layer 25A, a gate electrode 25B, and a gate cap layer 25C. A deposition or thermal growth process may be performed to form the gate insulation layer 25A, which may be made of silicon dioxide in one embodiment. Thereafter, the materials for the gate electrode 25B and the gate cap layer 25C may be deposited above the device 100, and the layers may be patterned by performing photolithographic and etching techniques. The gate electrode 25B may include a variety of materials, such as polysilicon or amorphous silicon.
When the device 100 is completed, there will be two illustrative nanowires in the nanowire channel structure that will be arranged in the form of a vertical stack, where one nanowire is positioned above the other nanowire. To reduce parasitic resistance, the regions between the spacers may be doped. Each of the nanowires may be equally doped to reduce device performance variability. However, each nanowire will not have the same characteristics when formed by performing known techniques. Specifically, performing known doping techniques results in the nanowires having different “dopant profiles.” A dopant profile of a nanowire is defined by the location, concentration and type of dopant within the nanowire. Thus, two nanowires with the same dopant profiles are doped with substantially the same types of dopants, in substantially the same concentration, and at substantially the same locations within the nanowires. Ideally, all of the nanowires in a device should have substantially the same dopant profile. Nanowires with different dopant profiles result in devices with uneven performance, reliability and unpredictable costs for testing.
To reduce production cost and increase circuit functionality, the semiconductor industry strives to increase the number of transistors and their speed or performance within an integrated circuit. The present disclosure is directed to various methods of forming nanowire devices with doped extension regions and the resulting devices to realize such gains. Additionally, the methods and devices disclosed herein reduce or eliminate one or more of the problems identified above.
SUMMARY
The following presents a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. This summary is not an exhaustive overview. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
Generally, the present disclosure is directed to devices and methods of forming nanowire devices with doped extension regions and the resulting devices. One illustrative method of forming a nanowire device disclosed herein includes patterning a plurality of semiconductor material layers such that each layer has first and second exposed end surfaces. The method further includes forming doped extension regions in the first and second exposed end surfaces of the semiconductor material layers. The method further includes, after forming the doped extension regions, forming epitaxial semiconductor material in source and drain regions of the device.
Another illustrative method of forming a nanowire device includes forming a plurality of semiconductor material layers above a semiconductor substrate. The method further includes forming a gate structure above the plurality of semiconductor material layers. The method further includes forming a first sidewall spacer adjacent to a gate structure and forming a second sidewall spacer adjacent to the first sidewall spacer. The method further includes patterning the plurality of semiconductor material layers such that each layer has first and second exposed end surfaces, wherein the gate structure, the first sidewall spacer and the second sidewall spacer are used in combination as an etch mask during the patterning process. The method further includes removing the first and second sidewall spacers, thereby exposing at least a portion of the patterned semiconductor material layers. The method further includes, after removing the first and second sidewall spacers, forming doped extension regions in the first and second exposed end surfaces of the patterned semiconductor material layers.
An illustrative device disclosed herein includes a gate structure and a nanowire channel structure positioned under the gate structure. The nanowire channel structure includes first and second end portions. The device further includes a continuous portion of spacer material adjacent to the gate structure and the first and second end portions.
Another illustrative method of forming a nanowire device includes forming a gate structure above a plurality of semiconductor material layers. The method further includes forming a first sidewall spacer adjacent to the gate structure and forming a second sidewall spacer adjacent to the first sidewall spacer. The method further includes patterning the plurality of semiconductor material layers such that each layer has first and second exposed end surfaces. The method further includes removing the second sidewall spacer, thereby exposing at least a portion of the patterned semiconductor material layers. The method further includes recessing at least a first of the semiconductor material layers relative to a second of the semiconductor material layers. The method further includes removing the first sidewall spacer, thereby exposing at least another portion of the patterned semiconductor material layers. The method further includes forming doped extension regions in at least the exposed portions of the patterned semiconductor material layers.



BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
FIG. 1 depicts a cross-sectional view of an illustrative prior art nanowire device;
FIGS. 2A-2G depict various novel methods disclosed herein of forming nanowire devices with doped extension regions and the resulting novel nanowire devices;
FIGS. 3A-3C depict various novel methods disclosed herein of forming nanowire devices with doped extension regions and the resulting novel nanowire devices; and
FIGS. 4A-4R depict various novel methods disclosed herein of forming nanowire devices with doped extension regions and the resulting novel nanowire devices.



While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.
NOTATION AND NOMENCLATURE
Certain terms are used throughout the disclosure to refer to particular components. However, different entities may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. The terms “including” and “comprising” are used herein an open-ended fashion, and thus mean “including, but not limited to.”
DETAILED DESCRIPTION
The present subject matter will now be described with reference to the attached figures. Various structures, systems, and devices are schematically depicted in the drawings for purposes of explanation only. The attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those in the industry. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those in the industry, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
The present disclosure is directed to various methods of forming nanowire devices with doped extension regions and the resulting devices. As will be readily apparent, the present method is applicable to a variety of devices, including, but not limited to, logic devices, memory devices, etc., and the methods disclosed herein may be employed to form N-type or P-type semiconductor devices. With reference to the attached figures, various illustrative embodiments of the methods and devices disclosed herein will now be described in more detail.
In the depicted examples, the device 200 will be disclosed in the context of performing FinFET formation techniques. However, the present disclosure should not be considered to be limited to the examples depicted herein. The substrate 101 may include a variety of configurations, such as a bulk silicon configuration or an SOI configuration. Thus, the terms “substrate” or “semiconducting substrate” should be understood to cover all substrate configurations. The substrate 101 may also be made of materials other than silicon.
FIG. 2A depicts a device 200 after several process operations were performed. First, various layers of semiconducting material 110, 120, 130 and 140 were formed above the silicon substrate 101. In general, in the depicted example, the layers 110 and 130 include a semiconductor material that may be selectively removed or etched relative to the materials used for the semiconducting material layers 120 and 140. As described more fully below, in the channel region of the device 200, portions of the semiconductor material layers 110 and 130 will be removed while the semiconducting material layers 120 and 140 will be left in place. Thus, the portions of the semiconducting material layers 110 and 130 within the channel region of the device 200 are sacrificial in nature. The semiconductor materials 110, 120, 130 and 140 may include a variety of different materials such as, for example, silicon, doped silicon, silicon-carbon, silicon-germanium, a III-V material, germanium, etc., and they may be formed to any desired thickness by performing any appropriate process, e.g., an epitaxial growth process, deposition plus ion implantation, etc. In one embodiment, the layer 110 and the layer 130 are made of silicon-germanium, while the semiconducting material layers 120 and 140 are made of silicon. The thickness of the layers 110, 120, 130 and 140 may vary depending upon the application, and they may be formed to the same or different thicknesses.
Next, an illustrative gate structure 250 was formed above the layer 140. The illustrative gate structure 250 is intended to be representative in nature of any type of gate structure that may be formed on a nanowire device. In the depicted example, the gate structure 250 includes a gate insulation layer 250A, a gate electrode 250B and a gate cap layer 250C. A deposition process or thermal growth process may be performed to form the gate insulation layer 250A, which includes silicon dioxide in one embodiment. Thereafter, the material for the gate electrode 250B and the material for the gate cap layer 250C may be deposited above the device 200, and the layers may be patterned by performing known photolithographic and etching techniques. The gate electrode 250B may include a variety of materials such as polysilicon or amorphous silicon. The gate cap layer 250C, the gate electrode 250B and the gate insulation layer 250A are sacrificial in nature as they will be removed at a later point during the formation of the device 200. Finally, the sidewall spacer 280 may be formed adjacent to the gate structure 250. The sidewall spacer 280 may be formed by depositing a layer of spacer material, such as silicon nitride, and thereafter performing an anisotropic etching process to define the spacer 280.
Next, as shown in FIG. 2B, one or more etching processes were performed to remove the exposed portions of the material layers 110-140 that were not covered by the gate structure 250 and the spacer 280. The etching processes may include dry etching and wet etching techniques to remove materials from the device 200. The etching process exposed vertical end surfaces of the material layers 110-140 and they are generally referred to as the first end surface 350 and the second end surface 351.
Next, as shown in FIG. 2C, one or more angled ion implantation processes were performed on the first end surface 350 and the second end surface 351 of the material layers 110, 120, 130 and 140 to form doped extension regions 300. Due to shadowing caused by the presence of adjacent gate structures (not shown), few if any ions are implanted into the substrate 101 during the angled ion implantation process. Consequently, by performing the methods disclosed herein, the doped extension regions 300 formed in the end surfaces 350 and 351 of the semiconducting layers 110, 120, 130 and 140 are substantially uniform in terms of dopant concentration and depth. As such, each of the layers 110, 120, 130 and 140 has the substantially the same extension implant dopant profile. Additionally, a substantially abrupt junction between the doped region in the material and the undoped regions in the material was formed. The doping process was performed prior to epitaxy regrowth in at least one embodiment, and specifically, prior to the formation of the source and drain regions for the device 200. The doping may be performed with N- or P-type dopant materials depending upon the device under construction. The implant angle, dopant dose and energy level of the ion implantation process may vary depending upon the particular application. If desired, carbon may be introduced into the regions 300 in an effort to limit dopant migration.
FIG. 2D depicts an embodiment wherein the extension regions 300 may be formed by performing a plasma doping process instead of an ion implantation process, as depicted in FIG. 2C. Performing a plasma doping process results in the formation of the doped extension regions 300 in the first and second end surfaces 350 and 351 of the material layers 110-140 as well as in the portions of the substrate 101 not positioned under the gate structure 250 and the sidewall spacer 280. That is, a plasma doping process may be used to avoid the shadowing effect experienced when performing an angled ion implantation process, which occurs when the height and close spacing of adjacent gate structures prevents homogenous doping of the lower layers. In one illustrative embodiment, the plasma doping process may be performed prior to epitaxy regrowth. If desired, carbon may be introduced into the regions 300 during or before the plasma doping process in an effort to limit dopant migration. During plasma doping, plasma is first generated over the wafer and a potential is applied to the wafer. Ionized dopants are accelerated towards the voltage-biased wafer, and the dopants are implanted into the wafers at energies determined by the applied voltage. During this plasma doping process, a thin film may form on the device. However, so as not to obscure the present invention, such a thin film is not depicted in the attached drawings.
FIG. 2E depicts the device 200 of FIG. 2D after several process operations were performed. First, raised epitaxial (epi) source/drain regions 131 were formed on the device 200 by performing known epi deposition processes. As depicted, the epi source/drain regions 131 will engage the doped extension regions 300 in the layers 120, 140. Next, a layer of insulating material 145 was deposited onto the device 200 by performing one or more deposition processes. Any excess insulating material 145 positioned above the gate structure was removed by performing one or more planarization or etching processes. Additionally, the materials of the sacrificial gate structure 250 were removed by performing one or more etching processes so as to define a gate cavity 132. The removal of the gate structure 250 exposes the layers 110 and 130 for further processing. Next, the layers 110 and 130 were selectively removed relative to the layers 120 and 140 by performing one or more etching processes through the gate cavity 132.
FIG. 2F depicts the device 200 of FIG. 2E after one or more process operations were performed. Specifically, an insulator 301 was deposited, such that it overfilled the openings left by the removed layers 110 and 130, by performing one or more deposition processes. In various embodiments, the insulator 301 includes silicon dioxide or a low-k material (a material having a dielectric constant less than about 3.3). The insulator 301 is selected such that it can be selectively removed relative to the layer of insulating material 145, the sidewall spacer 280 and the surrounding structures.
FIG. 2G illustrates the device 200 of FIG. 2F after several process operations were performed. First, a portion of the insulator 301 was removed by performing one or more anisotropic etching processes leaving portions of the layer of the insulator 301 positioned under the doped regions 300. Second, a high-k gate insulation material 135 (a material having a dielectric constant greater than about 10) was deposited onto the nanowires 120 and 140 by performing one or more deposition processes. Next, a replacement gate structure including a replacement gate electrode 133 was formed in the gate cavity 132. The replacement gate electrode 133 may include of a variety of conductive materials, such as one or more metal layers, in various embodiments. Next, a CMP process was performed to remove excess materials positioned outside of the gate cavity 132 above the layer of insulating material 145. A recess etching process was then performed on the gate electrode 133 to make room for the gate cap 134. The gate cap 134 was formed by depositing a layer of gate cap material, e.g., silicon nitride, and thereafter performing a planarization process (CMP) to remove gate cap materials above the layer of insulating material 145 to arrive at the device 200 configuration shown.
In addition to doping techniques prior to epi regrowth, recessing layers of the device may also improve the similarity of the nanowire dopant profiles. FIGS. 3A-3B depict an embodiment wherein the layers of material 110 and 130 are recessed prior to performing the above-described plasma doping process. Accordingly, FIG. 3A depicts the device 475 after the layers 110, 120, 130 and 140 were patterned and after the layers 110 and 130 were selectively recessed by performing one or more etching processes to define layers 110A and 130A such that they have a shorter length (in the current transport direction), as viewed in cross-section, than the layers 120 and 140. In at least one embodiment, the layers 110A and 130A are recessed such that the ends of the recessed materials 110A and 130A are approximately aligned with the interface between the sidewall spacer 280 and the gate electrode 250B, as viewed in cross-section.
Next, as shown in FIG. 3B, the above-described plasma doping process was performed on the first end surface 350 and the second end surface 351 (now staggered rather than being substantially vertically aligned) of the layers 110A, 120, 130A and 140 so as to form the above-described extension implant regions 300 in those layers, as well as in the exposed portions of the substrate 101. As such, the layers 110A and 130A have substantially the same dopant profile, and the layers 120 and 140 have substantially the same dopant profile. Furthermore, a substantially abrupt junction between doped material and undoped material was formed.
FIG. 3C depicts the device 475 after several process operations were performed. First, raised epitaxial (epi) source/drain regions 131 were formed on the device 475 by performing known epi deposition processes. Next, a layer of insulating material 145 was deposited onto the device 475 by performing one or more deposition processes. Any excess insulating material 145 was removed by performing one or more planarization or etching processes. Next, the sacrificial gate structure 250 and the sacrificial layers 110A and 130A were removed by performing one or more etching processes. The above-described insulator 301 was then deposited, such that it overfilled the openings left by the removed layers 110 and 130.
Next, a portion of the insulator 301 was removed by performing one or more anisotropic etching processes, leaving portions of the insulator 301 positioned under the doped regions 300 of the nanowires 120 and 140. Next, a high-k gate insulation material 135 was deposited onto the nanowires 120 and 140. Finally, a replacement gate structure including the above-described replacement gate electrode 133 and replacement gate cap 134 was formed as described above.
FIGS. 4A-4R depict various cross-sectional views of one illustrative embodiment of a nanowire device 900 that may be formed by performing the methods disclosed herein. In the illustrative example depicted herein, the device 900 will be depicted as including four illustrative nanowires. Of course, after a complete reading of the present application, those skilled in the art will appreciate that the methods disclosed herein may be employed to form a nanowire device with any desired number of nanowires, e.g., one or more nanowires.
With continuing reference to FIG. 4A, various layers of semiconducting material 909, 908, 907, 906, 905, 904, 903 and 902 are formed above the substrate 102. In general, in the depicted example, the layers 909, 907, 905 and 903 include a semiconductor material that may be selectively removed or etched relative to the materials used for the semiconducting material layers 908, 906, 904 and 902. As described more fully below, in the channel region of the device 900, portions of the semiconductor material layers 909, 907, 905 and 903 will be removed while portions of the semiconducting material layers 908, 906, 904 and 902 will be left in place as nanowires. Thus, the portions of the semiconducting material layers 909, 907, 905 and 903 within the channel region of the device are sacrificial in nature. The semiconductor materials 909, 908, 907, 906, 905, 904, 903 and 902 may include a variety of different materials such as, for example, silicon, a doped silicon, silicon-carbon, silicon-germanium, a III-V material, germanium, etc., and they may be formed to any desired thickness by performing any appropriate process, e.g., an epitaxial growth process, deposition plus ion implantation, etc. In one embodiment, the semiconducting material layers 909, 907, 905 and 903 include silicon-germanium with a thickness of about 6-25 nm, while the semiconducting material layers 908, 906, 904 and 902 include silicon also with a thickness of about 6-25 nm. In various embodiments, the layers 909, 907, 905 and 903 are not made of the same semiconducting material and they are not the same thickness. Similarly, in some embodiments, the layers 908, 906, 904 and 902 are not made of the same semiconducting material and they are not the same thickness in various embodiments.
Also depicted in FIG. 4A is an illustrative gate structure 251. The gate structure 251 may include a variety of different materials and a variety of configurations. As shown, the gate structure 251 includes a gate insulation layer 251A, a gate electrode 251B and a dual layer cap comprised of a first cap layer 251C and a second cap layer 251D. A deposition process may be performed to form the gate insulation layer 251A, which includes silicon dioxide in one embodiment. Thereafter, the materials for the gate electrode 251B and the gate cap layers 251C and 251D may be deposited above the device 900, and the layers may be patterned by performing known photolithographic and etching techniques. The gate electrode 251B may include a variety of materials such as polysilicon or amorphous silicon. The gate structure 251 and its various components are sacrificial in various embodiments because they will be removed during further formation of the device 900. In at least one embodiment, the first gate cap layer 251C may be silicon nitride, and the second gate cap layer 251D may be silicon dioxide.
FIG. 4B illustrates the device 900 after a layer of spacer material 301A, such as silicon nitride in at least one embodiment, was conformably deposited over the gate structure 251 and the layer 902 by performing one or more deposition processes. In various embodiments, the spacer material 301A includes an oxide, a nitride or other sacrificial material. The thickness of the layer 301A may vary depending upon the application.
FIG. 4C illustrates the device 900 after one or more etching processes, such as an anisotropic etch in at least one embodiment, were performed on the layer 301A to define the first sidewall spacer 301.
FIG. 4D illustrates the device 900 after another layer of spacer material 302A, such as oxynitride in at least one embodiment, was conformably deposited over the gate structure 251 and the layer 902 by performing a conformal deposition process. In various embodiments, the spacer material 302A may be made of an oxide, a nitride or other sacrificial material. In at least one embodiment, the spacer material 302A is different from the spacer material 301A such that the resulting spacers may be selectively removed relative to one another.
FIG. 4E illustrates the device 900 after an anisotropic etching process was performed on the layer 302A to define the second sidewall spacer 302.
FIG. 4F illustrates the device 900 after one or more etching processes were performed to remove the exposed portions of the layers 909, 908, 907, 906, 905, 904, 903 and 902 using the gate structure 251 and the spacers 301 and 302 as an etch mask. The patterning of the layers 909, 908, 907, 906, 905, 904, 903 and 902 results in those layers having exposed end portions 350, 351. For simplicity, the semiconductor materials are depicted as having a rectangular shape with sharp corners.
FIG. 4G illustrates the device 900 after one or more epitaxial deposition processes were performed to form an epitaxial semiconductor layer 303, on either side of the gate structure 251, that functions as source and drain regions for the device 900. The epi material 303 may be doped in situ or it may be doped after it is formed by performing an ion implantation process.
FIG. 4H illustrates the device 900 after a contact etch stop layer 302B, such as oxynitride or silicon nitride in at least one embodiment, and a layer of insulating material 304 (e.g., silicon dioxide) was deposited over the gate structure 251 and the epitaxial layer 303.
FIG. 4I illustrates the device 900 after a planarization process (CMP) was performed to remove excess materials using the gate cap layer 251D as a stop.
FIG. 4J illustrates the device 900 after one or more etching processes were performed to remove the second spacer 302 and the exposed portion of the etch stop layer 302B not covered by the layer of insulating material 304 selectively relative to the surrounding materials. Consequently, the material layers 902-909 of the device 900 are exposed for further processing.
FIG. 4K illustrates the device 900 after a selective etching process was performed to remove portions of the layers 909, 907, 905 and 903 and thereby define recessed layers 909B, 907B, 905B and 903B. The layers were selectively recessed by performing one or more etching processes such that they have a shorter length (in the channel length (current transport) direction of the device 900), than do the layers 908, 906, 904 and 902. In at least one embodiment, the layers 909B, 907B, 905B and 903B are recessed enough such that the ends of the recessed materials 909B, 907B, 905B and 903B are approximately aligned with the interface between the sidewall spacer 301 and the gate electrode 251B, as viewed in cross-section.
FIG. 4L illustrates the device 900 after one or more etching processes were performed to remove the first spacer 301 selectively relative to the surrounding materials.
FIG. 4M illustrates the device 900 after the above-described plasma doping process was performed on the device 900. Consequently, doped extension regions 401 were formed in the end portions of the layers 902, 904, 906, 908, 903B, 905B, 907B and 909B. As such, the layers 908, 906, 904 and 902 have substantially the same dopant profile. Furthermore, a substantially abrupt junction between doped material and undoped material was formed.
FIG. 4N illustrates the device 900 after deposition of a low-k spacer material 402 (a material having a dielectric constant less than about 3.3).
FIG. 4O illustrates the device 900 after a planarization process (CMP) was performed to remove excess spacer material 402 using the gate cap layer 251D as a stop.
FIG. 4P illustrates the device 900 after one or more etching processes were performed to remove the gate cap layers 251D and 251C, the gate electrode 251B and the gate insulation layer 251A. These etching processes result in the formation of a gate cavity 480 and expose the material layers of the device 900 for further processing.
FIG. 4Q illustrates the device 900 after the layers 909B, 907B, 905B and 903B were removed via selective etching processes leaving the nanowires 908B, 906B, 904B and 902B that include the doped extension implant regions 401 intact.
FIG. 4R illustrates the device 900 after several processes were performed. First, a high-k gate insulation material 701 (material having a higher dielectric constant than about 10) was deposited onto the nanowires 908B, 906B, 904B and 902B by performing one or more deposition processes. Next, a replacement gate electrode 702 was formed in the gate cavity 480. The replacement gate electrode 702 may include a variety of conductive materials, such as polysilicon as well as one or more metal layers, in various embodiments. Next, a CMP process was performed to remove excess materials positioned outside of the gate cavity above the layer of insulating material 304. Thereafter, a recess etching process was performed to remove some of the gate electrode material from within the gate cavity to make room for a gate cap layer. Then a nitride material was deposited to form a replacement gate cap 703. Next, a planarization process (CMP) was performed to remove excess nitride materials using the layer 304 as a stop to arrive at the device 900 configuration shown.
In the examples described herein, the channel structures of the devices are depicted as including two or four illustrative nanowires. However, the channel structure may include any desired number of nanowires and in some cases may include only a single nanowire. Thus, the disclosure should not be considered as being limited to any particular number of nanowires. The creation of nanowires with similar characteristics as described herein allows for improved performance, reliability and predictability.
The particular embodiments disclosed above are illustrative only, as the disclosure may be modified and practiced in different but equivalent manners apparent to those having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosure. Accordingly, the protection sought herein is as set forth in the claims below.

## Claims

1. A method of forming a nanowire device, comprising:
forming a gate structure above a plurality of semiconductor material layers;
patterning said plurality of semiconductor material layers using said gate structure as a mask to expose first and second exposed end surfaces of each layer not covered by said gate structure;
forming doped extension regions in said first and second exposed end surfaces of said semiconductor material layers; and
after forming said doped extension regions, forming epi semiconductor material in source and drain regions of said nanowire device.

2. The method of claim 1, further comprising recessing at least a first of said semiconductor material layers relative to a second of said semiconductor material layers before forming said doped extension regions.

3. The method of claim 1, wherein forming said doped extension regions comprises forming said doped extension regions such that said semiconductor material layers have substantially the same dopant profile.

4. The method of claim 1, wherein forming said epi semiconductor material comprises forming said epi semiconductor material such that it contacts said doped extension regions.

5. The method of claim 1, wherein forming said doped extension regions comprises doping said first and second exposed end surfaces by performing a plasma doping process.

6. The method of claim 1, wherein forming said doped extension regions comprises doping said first and second exposed end surfaces by performing an angled ion implantation process.

7. The method of claim 1, further comprising:
removing said gate structure so as to define a gate cavity that exposes at least a portion of said patterned plurality of semiconductor material layers,
performing at least one etching process through said gate cavity so as to remove at least a first of said patterned plurality of semiconductor material layers selectively relative to at least a second of said patterned plurality of semiconductor material layers; and
forming a replacement gate structure in said gate cavity.

8. A method of forming a nanowire device, comprising:
forming a second sidewall spacer adjacent to a first sidewall spacer;
patterning a plurality of semiconductor material layers such that each layer has first and second exposed end surfaces;
removing said second sidewall spacer, thereby exposing at least a portion of said patterned semiconductor material layers;
recessing at least a first of said semiconductor material layers relative to a second of said semiconductor material layers;
removing said first sidewall spacer, thereby exposing at least another portion of said patterned semiconductor material layers; and
forming doped extension regions in at least said exposed portions of said patterned semiconductor material layers.

9. The method of claim 8, wherein forming said doped extension regions comprises forming said doped extension regions such that said patterned semiconductor material layers have substantially the same dopant profile.

10. The method of claim 8, further comprising forming a gate structure above said plurality of semiconductor material layers.

11. The method of claim 10, further comprising forming said first sidewall spacer adjacent to said gate structure.

12. A method of forming a nanowire device, comprising:
removing a first sidewall spacer, thereby exposing at least a portion of each of a plurality of patterned semiconductor material layers; and
forming doped extension regions in at least said exposed portions of each of said patterned semiconductor material layers.

13. The method of claim 12, wherein forming said doped extension regions comprises forming said doped extension regions such that said patterned semiconductor material layers have substantially the same dopant profile.

14. The method of claim 12, further comprising forming a gate structure above said patterned semiconductor material layers.

15. The method of claim 12, further comprising forming said first sidewall spacer adjacent to a gate structure.

16. The method of claim 12, further comprising forming a second sidewall spacer adjacent to said first sidewall spacer.

17. The method of claim 12, further comprising patterning said semiconductor material layers such that each layer has first and second exposed end surfaces.

18. The method of claim 12, further comprising removing a second sidewall spacer, thereby exposing at least a portion of said patterned semiconductor material layers.

19. The method of claim 12, further comprising recessing at least a first of said semiconductor material layers relative to a second of said semiconductor material layers.