Patent Application
20130175632
The present invention generally relates to the field of semiconductors, and more particularly relates to forming silicide regions for a semiconductor device.
Silicide formation is of specific importance to integrated circuits, including those having complementary metal-oxide-semiconductor (CMOS) devices, because of the need to reduce the electrical resistance of the contacts (particularly at the source/drain and gate regions) in order to increase chip performance. Silicides are metal compounds that are thermally stable and provide for low electrical resistivity at the silicon/metal interface. Reducing contact resistance improves device speed, therefore increasing device performance.
In one embodiment, a method for forming silicide regions on a metal-oxide-semiconductor device is disclosed. The method comprises forming a buried insulator layer on a substrate. A semiconductor layer is formed on the buried insulator layer. A first set of source/drain regions s formed in the semiconductor layer for an n-type metal-oxide-semiconductor (nMOS) device. A second set of source/drain regions is formed in the semiconductor layer for a p-type metal-oxide-semiconductor (pMOS) device. A first set of silicide regions is formed on at least the first set of source/drain regions. A second set of silicide regions is formed on at least the second set of source/drain regions. The first and second sets of silicide regions each comprise a first metallic material and a second metallic material. A percentage of the first metallic material in the first and second set of silicide regions is substantially the same. A percentage of the second metallic material in the second set of silicide regions is greater than the percentage of the second metallic material in the first set of silicide regions.
In another embodiment, another method for forming silicide regions on a metal-oxide-semiconductor device is disclosed. The method comprises forming a buried insulator layer on a substrate. A semiconductor layer is formed on the buried insulator layer. A first set of source/drain regions is formed in the semiconductor layer for an n-type metal-oxide-semiconductor (nMOS) device. A second set of source/drain regions is formed in the semiconductor layer for a p-type metal-oxide-semiconductor (pMOS) device. The first set of source/drain regions comprises a junction depth that is greater than a junction depth of the second set of source/drain regions. A first set of silicide regions is formed on at least the first set of source/drain regions. A second set of silicide regions is formed on at least the second set of source/drain regions. The first and second sets of silicide regions each comprise nickel and platinum. A percentage of the platinum ranges from 10.01% to 20%.
In yet another embodiment, a semiconductor device is disclosed. The semiconductor device comprises an n-type metal-oxide-semiconductor (nMOS) device and a p-type metal-oxide-semiconductor (nMOS) device. The nMOS device comprises a buried insulator layer formed on a substrate. A semiconductor layer is formed on the buried insulator layer. A first set of source/drain regions is formed in the semiconductor layer. A first set of silicide regions is formed on at least the first set of source/drain regions. The pMOS device comprises the buried insulator layer formed on the substrate. The pMOS device also comprises the semiconductor layer formed on the buried insulator layer. The pMOS device further comprises a second set of source/drain regions formed in the semiconductor layer, and a second set of silicide regions formed on at least the second set of source/drain regions. The first and second sets of silicide regions each comprise a first metallic material and a second metallic material. A percentage of the first metallic material in the first and second set of silicide regions is substantially the same. A percentage of the second metallic material in the second set of silicide regions is greater than the percentage of the second metallic material in the first set of silicide regions.
The accompanying figures where like reference numerals refer to identical or functionally similar elements throughout the separate views, and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention, in which:
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention.
The terms “a” or “an”, as used herein, are defined as one as or more than one. The term plurality, as used herein, is defined as two as or more than two. Plural and singular terms are the same unless expressly stated otherwise. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. The terms program, software application, and the like as used herein, are defined as a sequence of instructions designed for execution on a computer system. A program, computer program, or software application may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library/dynamic load library and/or other sequence of instructions designed for execution on a computer system.
Standard metal salicidation typically experiences a variety of defects that can reach the p-n junction (if shallow enough). One type of defect is a pipe defect (or encroachment), which is localized overgrowth on existing defects in the silicon. Another type of defect is a divot defect, which comprises silicon/STI topography and edge effect. These defects can act as a leakage path if reaching the p-n junction. Therefore, one or more embodiments of the present invention utilizes a metal layer for forming silicide regions, where the metal layer comprises a first metal, such as nickel (Ni), and second metal, such as platinum (Pt), for simultaneously reducing contact resistance and junction leakage in both nMOS and pMOS devices. In one embodiment, the metal layer formed on the pMOS device comprises a higher percentage of the second metal than the metal layer formed on the nMOS device. In another embodiment, the percentage of the second metal in the metal layer formed on the pMOS and nMOS devices is substantially the same. However, the nMOS device comprises a greater junction depth than that of the pMOS device to prevent any defects resulting from the higher percentage of Pt in the nMOS device from going through the junction.
The thickness of the buried insulator layer 104 can be, for example, form 50 nm to 500 nm, although lesser and greater thicknesses can also be employed. The thickness of the top semiconductor layer 106 can be, for example, from 3 nm to 60 nm, and typically from 5 nm to 10 nm, although lesser and greater thicknesses can also be employed. The top semiconductor layer 106 can comprise any semiconducting material, including but not limited to Si (silicon), strained Si, SiC (silicon carbide), Ge (geranium), SiGe (silicon germanium), SiGeC (silicon-germanium-carbon), Si alloys, Ge alloys, GaAs (gallium arsenide), InAs (indium arsenide), InP (indium phosphide), any combination thereof, as well as other III/V or II/VI compound semiconductors and alloys thereof. Also, each of the nMOS and pMOS devices can include top semiconductor layer 106 with different materials.
The various single crystalline semiconductor portions (108, 110, 112, 114, 116) in the top semiconductor layer 106 can be formed by introducing electrical dopants such as B, Ga, In, P, As, and/or Sb by ion implantation, plasma doping, and/or gas phase doping employing various masking structures as known in the art. Before implanting electrical dopants into various portions of the top semiconductor layer 106, a gate stack structure 120 and gate spacer 122 are formed. The gate stack 120 is formed on the semiconductor layer 106 over the body region 108. In one embodiment, the gate stack 120 comprises a gate dielectric 124 and a gate conductor 126. In the illustrated embodiment, a gate polysilicon cap 128 is deposited on the gate conductor layer 126, such as through LPCVD or silicon sputtering. It should be noted that instead of first forming the gate stack 120, a conventional reverse metal gate process (RMG) can be utilized for forming the gate structure 120.
The gate stack 120 can be formed by depositing a stack of a gate dielectric material and a gate conductor material on the top semiconductor layer 106. This stack is then patterned and etched to form the gate dielectric 124 and the overlying gate conductor 126 on a portion of the top semiconductor layer 106. The gate dielectric 124 of this embodiment is a conventional dielectric material (such as silicon oxide, silicon nitride, silicon oxynitride, or a stack thereof) that is formed by thermal conversion of a top portion of the active region and/or by chemical vapor deposition (CVD). In an alternative embodiment, the gate dielectric 124 is a high-k dielectric material (such as hafnium oxide, zirconium oxide, lanthanum oxide, aluminum oxide, titanium dioxide, strontium titanate, lanthanum aluminate, yttrium oxide, an alloy thereof, or a silicate thereof) that is formed by CVD, atomic layer deposition (ALD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), liquid source misted chemical deposition (LSMCD), or physical vapor deposition (PVD). Alternatively, the gate dielectric may comprise any suitable combination of those dielectric materials.
The gate conductor 126 is a semiconductor (e.g., polysilicon) gate layer and/or a metal gate layer. For example, the gate dielectric 124 can be a conventional dielectric material and the gate conductor 126 can be a semiconductor gate layer. Alternatively, the gate dielectric 124 can be a high-k dielectric material and the gate conductor 126 can be a metal gate layer of a conductive refractory metal nitride (such as tantalum nitride, titanium nitride, tungsten nitride, titanium aluminum nitride, triazacyclononane, or an alloy thereof). In a further embodiment, the gate conductor 126 comprises a stack of a metal gate layer and a semiconductor gate layer. The gate stack 120 can also include a work function metallic layer as well. In yet a further embodiment, the gate stack 120 can be formed atop an optional chemical oxide layer (not shown) (also referred to herein as an “interfacial layer”), which is formed on an exposed semiconductor surface of the body portion 108 of the top semiconductor layer 106.
The gate spacer 122 comprises a dielectric material (such as silicon oxide, silicon nitride, silicon oxynitride or any combination of these). The gate spacer 122 is formed on gate stack 120 and on a portion of the top semiconductor layer 106. In one embodiment, a reactive-ion etch process is used to remove the dielectric material on horizontal surfaces such as the top of the gate stack 120, the STI regions 118, and portions of the top semiconductor layer 106 to form a gate spacer only on the sidewall of the gate structure 120. However, the gate spacer material can be etched such that the gate spacer 122 also resides on top of the gate structure 120 as well.
An anneal process, such as a rapid thermal anneal (RTA), is performed to form silicide, such as (but not limited to) NiSi with Pt, on both devices.
A tensile stress liner 432 and a hard mask 434 are then formed over the nMOS device. For example,
Various methods now known or later developed can be used for depositing the tensile-stressed liner material and hard mask material. Examples of some of these methods are chemical vapor deposition (CVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PECVD), semi-atmosphere CVD (SACVD) and high density plasma CVD (HDPCVD), rapid thermal CVD (RTCVD), ultra-high vacuum CVD (UHVCVD), limited reaction processing CVD (LRPCVD), metalorganic CVD (MOCVD), sputtering deposition, ion beam deposition, electron beam deposition, laser assisted deposition, thermal oxidation, thermal nitridation, spin-on methods, physical vapor deposition (PVD), atomic layer deposition (ALD), chemical oxidation, molecular beam epitaxy (MBE), plating, evaporation.
Any tensile stress liner material and hard mask material that has been formed over the pMOS device is removed. A second metal layer 436 is formed over the wafer as shown in
A compressive stress liner 538 is then formed over the pMOS device. For example,
From this point, conventional fabrication processes are used to form the remainder of the integrated circuit that includes this transistor. The resulting structure comprises a pMOS device with a higher percentage of Pt in the silicide regions than the percentage of Pt in the silicide regions of the nMOS device. The addition of Pt in the silicide regions reduces the contact resistance and junction leakage in both the nMOS and pMOS devices. By increasing the percentage of Pt for the pMOS device, as compared to the nMOS device, the contact resistance of the pMOS device can be reduced by, in one embodiment, approximately 20-30%.
In another embodiment, an RMG process can be utilized to form the gate structure 120, as discussed above. In this embodiment a dielectric layer 640 is formed during the RMG process. The dielectric layer 640 covers the entire wafer and extends above the gate spacer 120, 320 of both devices, as shown in
Portions of the metal layer are then selectively removed (e.g., through an aqua regia wet etch) from non-active regions while leaving the silicide regions 631, 633, 635 untouched. For example,
Portions of the dielectric layer 640 over the source/drain regions 314, 316 of the pMOS device are removed (e.g., through a dry etch such as RIE and/or a wet etch using HF) so as to create trenches/openings 742, 744, 746. These trenches/openings 742, 744, 746 expose at least a portion of the source/drain regions 314, 316 of the pMOS device, as shown in
An anneal process, such as a rapid thermal anneal (RTA), is performed to form silicide regions 737, 739, 741 on the pMOS device with a higher percentage of Pt than the silicide on the nMOS device. For example, the percentage of Pt in the silicide regions 737, 739, 741 of the pMOS device is 10.01% to 20% and the percentage of Pt in the silicide regions 631, 633, 635 of the nMOS device is 1% to 10%. It should be noted that in another embodiment, the trenches/openings for both the nMOS device and pMOS device can be filled with another material such as, but not limited to, Aluminum, to set the work function. In this embodiment, silicide is not formed. Portions of the second metal layer are then selectively removed (e.g., through an aqua regia wet etch) from non-active regions while leaving the silicide regions 737, 739, 741 untouched. For example,
In another embodiment, the silicide regions of the nMOS device can comprise substantially the same high percentage (e.g., 10.01% to 20%) of Pt as the silicide regions of the pMOS device. In this embodiment, the implantation process that is performed to form the source/drain regions 114, 116 of the nMOS device is a deep implantation process. This results in implant regions of the nMOS device having a depth that is greater than the implant regions of the pMOS device. In one embodiment, the implant regions of the nMOS device can be above, below, or stop on the boundary between the buried insulator layer 104 and the semiconductor layer 106. Therefore, any NiSi silicide related defects experienced by the nMOS device as a result of the high percentage of Pt are prevented from going through the junction.
In this embodiment, only a first metal layer needs to be deposited in the embodiments discussed above with respect to
A first metal layer 230, at step 912, comprising a first and second metallic material (e.g., Ni and Pt) is over at least the source/drain regions 114, 116, 314, 316 (and optionally the capping layers 128, 328) of the nMOS and pMOS devices. A first anneal, at step 914, is performed to form a first set of silicide regions 331, 333, 335 on the first set of source/drain regions 114, 116, a second set of silicide regions 337, 339, 341 on the second set of source/drain regions 314, 316, and optional the capping layers 128, 328 of the nMOS and pMOS devices. An optional tensile stress liner 432, at step 916, is formed over the nMOS device. A hard mask 434, at step 918, is formed over the tensile liner 432.
A second metal layer 436, at step 920, comprising the second metallic material (e.g., Pt) is formed over at least the source/drain regions 314, 316 (and optionally the capping layers 328) of the pMOS device. A second anneal, at step 922, is performed to increase the percentage of the second metallic material in the second set of silicide regions 337, 339, 341 of the pMOS device. An optional compressive stress liner 538, at step 924, is formed over the pMOS device. From this point, conventional fabrication processes are used to form the remainder of the integrated circuit that includes this transistor. The control flow then exits at step 926. It should be noted that in another embodiment only the first metal layer 230 is required to be deposited with a high percentage (e.g., 10.01% to 20%) of the second metal. In this embodiment, the implant regions for source/drain regions 114, 116 of the nMOS device have a greater depth than the implant regions for the source/drain regions 314, 316 of the pMOS device.
Trenches 742, 744, 746, at step 1012, are formed in the dielectric layer 640 over the source/drain regions 314, 316 and capping layer 328 of the pMOS device. A second metal layer comprising a first and second metallic material (e.g., Ni and Pt), at step 1014, is formed over at least the source/drain regions 314, 316 and capping layer 328 of the pMOS device. The second metal layer comprises a higher percentage of the second metallic material than the percentage of the second metallic material in the first metal layer. A second annealing process, at step 1016, is performed to form silicide regions 737, 730, 741 on the source/drain regions 314, 316 and capping layer 328 of the pMOS device. From this point, conventional fabrication processes are used to form the remainder of the integrated circuit that includes this transistor. The control flow then exits at step 1018.
It should be noted that some features of the present invention may be used in an embodiment thereof without use of other features of the present invention. As such, the foregoing description should be considered as merely illustrative of the principles, teachings, examples, and exemplary embodiments of the present invention, and not a limitation thereof.
It should be understood that these embodiments are only examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others.
The circuit as described above is part of the design for an integrated circuit chip. The chip design is created in a graphical computer programming language, and stored in a computer storage medium (such as a disk, tape, physical hard drive, or virtual hard drive such as in a storage access network). If the designer does not fabricate chips or the photolithographic masks used to fabricate chips, the designer transmits the resulting design by physical means (e.g., by providing a copy of the storage medium storing the design) or electronically (e.g., through the Internet) to such entities, directly or indirectly. The stored design is then converted into the appropriate format (e.g., GDSII) for the fabrication of photolithographic masks, which typically include multiple copies of the chip design in question that are to be formed on a wafer. The photolithographic masks are utilized to define areas of the wafer (and/or the layers thereon) to be etched or otherwise processed.
The methods as discussed above are used in the fabrication of integrated circuit chips.
The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare chip, or in a packaged form. In the latter case, the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case, the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product or electronic device that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard, or other input device, and a central processor.
Although specific embodiments of the invention have been disclosed, those having ordinary skill in the art will understand that changes can be made to the specific embodiments without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted, therefore, to the specific embodiments, and it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.
