Abstract:
A method for manufacturing a fin field-effect transistor (FinFET) device comprises forming a plurality of fins on a substrate, epitaxially growing a sacrificial epitaxy region between the fins, stopping growth of the sacrificial epitaxy region at a beginning of merging of epitaxial shapes between neighboring fins, and forming a dielectric layer on the substrate including the fins and the sacrificial epitaxy region, wherein a portion of the dielectric layer is positioned between the sacrificial epitaxy region extending from fins of adjacent transistors.

Description:
TECHNICAL FIELD 
       [0001]    The field generally relates to methods of manufacturing fin field-effect transistor (FinFET) devices and, in particular, to a method for manufacturing a FinFET device using a sacrificial epitaxy region for improved fin merge. 
       BACKGROUND 
       [0002]    Epitaxy is often used to merge individual fins that belong to a single transistor in order to provide enough material in the source drain for silicidation as well as to relax the requirements on a contact. Conventional epitaxy processes are not self-limited. This means that there is a variation in epitaxy thickness based on the fin-to-fin spacing to ensure that all fins that need to be merged are merged. 
         [0003]    However, there is a need to avoid unwanted shorts between neighboring transistors as well as a source to drain shorts caused by the merging of fins of different transistors, and the variation in the epitaxy thickness makes it difficult to design growth rates to avoid the unwanted shorts. Known methods have employed extra spacing between neighboring transistors. 
         [0004]    In conventional faceted epitaxy growth, the point where the tips of the facets merge is a weak point from a silicide formation point of view as there is not enough material in these to be consumed during epitaxy. 
         [0005]    Accordingly, there is a need for an improved method for fin merge that prevents the unwanted shorts while providing for an adequate merge of fins in a transistor. 
       SUMMARY 
       [0006]    In general, exemplary embodiments of the invention include methods of manufacturing FinFET devices and, in particular, to a method for manufacturing a FinFET device using a sacrificial epitaxy region for improved fin merge. 
         [0007]    According to an exemplary embodiment of the present invention, a method for manufacturing a fin field-effect transistor (FinFET) device comprises forming a plurality of fins on a substrate, epitaxially growing a sacrificial epitaxy region between the fins, stopping growth of the sacrificial epitaxy region at a beginning of merging of epitaxial shapes between neighboring fins, and forming a dielectric layer on the substrate including the fins and the sacrificial epitaxy region, wherein a portion of the dielectric layer is positioned between the sacrificial epitaxy region extending from fins of adjacent transistors. 
         [0008]    According to an exemplary embodiment of the present invention, a fin field-effect transistor (FinFET) device comprises a substrate, a first plurality of fins on the substrate corresponding to a first transistor, a second plurality of fins on the substrate corresponding to a second transistor, a first epitaxy region extending between the first plurality of fins, a second epitaxy region extending between the second plurality of fins, and a dielectric layer on the substrate, wherein a portion of the dielectric layer is positioned between the first epitaxy region and the second epitaxy region preventing contact between the first epitaxy region and the second epitaxy region. 
         [0009]    According to an exemplary embodiment of the present invention, a method for manufacturing a fin field-effect transistor (FinFET) device comprises forming a first plurality of fins on a substrate corresponding to a first transistor, forming a second plurality of fins on the substrate corresponding to a second transistor, epitaxially growing a sacrificial epitaxy region between the first plurality of fins corresponding to the first transistor and between the second plurality of fins corresponding to the second transistor, stopping growth of the sacrificial epitaxy region to avoid contact of the sacrificial epitaxy region between the first plurality of fins and the second plurality of fins, and forming a dielectric layer on the substrate between the sacrificial epitaxy region extending from adjacent fins of the first and second transistors. 
         [0010]    These and other exemplary embodiments of the invention will be described or become apparent from the following detailed description of exemplary embodiments, which is to be read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Exemplary embodiments of the present invention will be described below in more detail, with reference to the accompanying drawings, of which: 
           [0012]      FIG. 1  is a cross-sectional view illustrating fin formation in a method of manufacturing a FinFET device, according to an exemplary embodiment of the present invention. 
           [0013]      FIG. 2  is a cross-sectional view illustrating formation of a sacrificial epitaxy region in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0014]      FIG. 3  is a cross-sectional view illustrating deposition of a dielectric in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0015]      FIG. 4  is a cross-sectional view showing opening of a trench in a dielectric layer in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0016]      FIG. 5  is a cross-sectional view showing removal of a sacrificial epitaxy region in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0017]      FIG. 6  is a cross-sectional view showing formation of an epitaxy region for a transistor in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0018]      FIG. 7  is a cross-sectional view illustrating further deposition of a dielectric in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0019]      FIG. 8  is a cross-sectional view showing opening of a trench in a dielectric layer in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0020]      FIG. 9  is a cross-sectional view showing removal of a sacrificial epitaxy region in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0021]      FIG. 10  is a cross-sectional view showing formation of an epitaxy region for a transistor in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
           [0022]      FIG. 11  is a cross-sectional view showing removal of a portion of a dielectric layer in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0023]    Exemplary embodiments of the invention will now be discussed in further detail with regard to methods of manufacturing FinFET devices and, in particular, to a method for manufacturing a FinFET device using a sacrificial epitaxy region for improved fin merge. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 
         [0024]    The embodiments of the present invention include a replacement epitaxy process, where a sacrificial faceted epitaxy region is first grown to merge the fins. Then, a dielectric is deposited to cover the sacrificial epitaxy region. Trenches are opened in the dielectric, the sacrificial epitaxy is removed and its space is filled with the desired epitaxy. 
         [0025]    It is to be understood that the various layers and/or regions shown in the accompanying drawings are not drawn to scale, and that one or more layers and/or regions of a type commonly used in FinFET devices may not be explicitly shown in a given drawing. This does not imply that the layers and/or regions not explicitly shown are omitted from the actual FinFET devices. Moreover, the same or similar reference numbers used throughout the drawings are used to denote the same or similar features, elements, or structures, and thus, a detailed explanation of the same or similar features, elements, or structures will not be repeated for each of the drawings. 
         [0026]    The FinFET devices and methods for forming same in accordance with the embodiments of the present invention can be employed in applications, hardware, and/or electronic systems. Suitable hardware and systems for implementing embodiments of the invention may include, but are not limited to, personal computers, communication networks, electronic commerce systems, portable communications devices (e.g., cell and smart phones), solid-state media storage devices, functional circuitry, etc. Systems and hardware incorporating the FinFET devices are contemplated embodiments of the invention. Given the teachings of the embodiments of the invention provided herein, one of ordinary skill in the art will be able to contemplate other implementations and applications of embodiments of the invention. 
         [0027]    Referring to  FIG. 1 , which is a cross-sectional view illustrating fin formation in a method of manufacturing a FinFET device, according to an exemplary embodiment of the present invention, fins  116  are formed by patterning a silicon-on-insulator (SOI) layer. Patterning is performed by, for example, image transfer and etching. In  FIG. 1 , the cross-section is taken through the fins  116  in the source drain region. The fins  116  are formed on a buried oxide (BOX) layer  112 , which is formed on a semiconductor substrate  110 . It is to be understood that the embodiments of the invention are not limited to use of an SOI layer, and that the embodiments can be applied independent of the underlying substrate. 
         [0028]    In accordance with an embodiment of the present invention, after formation of the fins  116 , a gate stack layer (not shown) can be deposited and patterned to form gate stacks around sides and on upper surfaces of designated portions of the fins  116  for the gate areas. A spacer layer is also deposited and patterned by, for example, reactive ion etching (RIE) to form spacer patterns (not shown) along sides of the gate stacks. 
         [0029]    Referring to  FIG. 2 , which is a cross-sectional view illustrating formation of a sacrificial epitaxy region  118  in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, the fins  116  are merged by epitaxially growing SiGe or other material having a relatively high etch selectivity with respect to silicon, such as, for example, germanium (Ge), so that the fins  116  contact each other via the epitaxy region  118  in an integrated structure. According to an embodiment, growth of the sacrificial epitaxy region  118  is stopped when or at some time after the sacrificial epitaxy region  118  between the fins  116  of a transistor  120   a  or  120   b  is merged as shown in  FIG. 2  by the diamond shapes touching each other in each transistor  120   a ,  120   b . The growth is stopped so that end fins of adjacent transistors are not merged via the sacrificial epitaxy region  118  (i.e., the sacrificial epitaxy regions  118  of separate transistors  120   a  and  120   b  are separated from each other and do not touch. According to an embodiment, to make sure that all fins that are desired to be merged are merged (e.g., fins of the same transistor), the growth thickness of the sacrificial epitaxy region  118  from each fin is larger than half of the fin-to-fin spacing. For example, the growth thickness may be greater than 15 nm for fins positioned at a 40 nm fin pitch in a transistor. 
         [0030]    In accordance with an embodiment of the present invention, a maximum lateral growth of the sacrificial epitaxy region  118  is determined by the fin height. For example, given a (111) facet (using Miller Indices), the lateral growth of the sacrificial epitaxy region  118  is about equal to 
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         [0031]    where h fin  is the height of the fin. 
         [0032]    In accordance with an embodiment, the growth of the sacrificial epitaxy region  118  does not exceed a pre-determined time period so that growth can be stopped once or at some time after the sacrificial epitaxy region  118  between the fins  116  of a transistor  120   a  or  120   b  is merged, and prior to contact of the sacrificial epitaxy region between fins of adjacent transistors. In accordance with an embodiment, the sacrificial epitaxy region on the fin forms a diamond shape, and with enough time the diamond shape grows bigger and merges with a neighboring diamond shape. According to an embodiment, growth can be stopped at a beginning of merging, such as immediately or shortly after merging of neighboring epitaxial shapes occurs. 
         [0033]    Referring to  FIG. 3 , which is a cross-sectional view illustrating deposition of a dielectric in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, a dielectric layer  128 , for example, an oxide, is formed on the substrate  110  including the BOX layer  112 , fins  116  and sacrificial epitaxy region  118 . In accordance with an embodiment of the present invention, lower gaps  122  between the fins  116  that are not filled by the sacrificial epitaxy region  118  are filled by the dielectric layer  128 . Alternatively, the lower gaps  122  are not filled by the sacrificial epitaxy region  118 , and are left open. According to an embodiment, the dielectric layer  128  is planarized down to a top of the gate structure, using, for example, chemical mechanical polishing (CMP). 
         [0034]    Referring to  FIG. 4 , which is a cross-sectional view showing opening of a trench in a dielectric layer in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, a portion of the dielectric layer  128  corresponding to a first transistor  120   a  is removed by, for example, etching, such as, for example, reactive ion etching (RIE) to form a trench  131 . According to an embodiment, the transistor  120   a  is an NFET transistor. The trench  131  is an opening formed to expose the sacrificial epitaxy region  118  for transistor  120   a.    
         [0035]    Referring to  FIG. 5 , which is a cross-sectional view showing removal of a sacrificial epitaxy region in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, the sacrificial epitaxy region  118  corresponding to the transistor  120   a  is removed by etching. Etching can include, wet and/or dry etch processes. For example, a wet etch with hot ammonia can be used, or an HCl gas etch can be used. In one embodiment, the HCl gas etch can be done immediately prior to the deposition of the second (or final epitaxy) in the same epitaxial reactor where the final epitaxial deposition is performed. According to an embodiment of the present invention, after trench opening and cleans, the wafer is introduced into the epitaxial reactor, HCl gas etch is employed to remove the sacrificial epitaxy SiGe around the fins, and the final epitaxy is grown after that. The process ensures increased or maximum cleanliness and improved or best epitaxial quality, since the fins are not exposed to ambient air after sacrificial SiGe removal. Both mentioned wet and dry etches are selective to the dielectric. 
         [0036]    Referring to  FIG. 6 , which is a cross-sectional view showing formation of an epitaxy region for a transistor in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, epitaxy region  138  is grown for transistor  120   a  in the space previously occupied by the sacrificial epitaxy region  118 . As can be seen, the epitaxy region  138  further can be overgrown (e.g., grown higher above a top surface of the fins  116 ) to result in a smooth top surface of the epitaxy region  138 . According to an embodiment, the height above a top surface of the fins  116  can be in the range of about 10 nm to about 20 nm. A height higher than about 20 nm can result in a gate capacitance penalty. Due to the presence of the dielectric layer  128 , the epitaxy region  138  is prevented from excessive lateral growth from end fins. As a result, an epitaxy region  138  is blocked by the dielectric layer  128  and does not extend to connect fins from adjacent transistors (e.g.,  120   a  and  120   b ). Thereby, shorts between neighboring transistors as well as source to drain shorts can be prevented. 
         [0037]    According to an embodiment, the epitaxy region  138  is for an NFET. Embodiments of the present invention form epitaxy regions for transistors with the same doping at the same time, while shielding transistors with different doping. For example, epitaxy regions for transistors with the same doping as transistor  120   a  (in this case n-type) can be formed at the same time, while transistors with the same doping as transistor  120   b  (in this case p-type) remain covered. It is to be understood that doping of the transistors  120   a  and  120   b  can be reversed. 
         [0038]    The fins  116  foaming the source drain region of transistor  120   a  (in this case an NFET) are merged by epitaxially growing Si:P (phosphorus doped silicon), Si:C(P) on the exposed silicon surfaces of the fins  116  so that the fins  116  contact each other through the epitaxy region  138  in an integrated structure. Si:C(P)=epitaxial silicon with carbon and phosphorous doping. In one embodiment, a crystalline semiconductor layer may include carbon doped silicon with an atomic carbon concentration of between about 0.2% to about 4.0% substitutional carbon. In another embodiment, a crystalline semiconductor layer may include a carbon doped silicon type material having a concentration of about 0.3% to about 2.5% substitutional carbon. It is to be understood that the total amount of carbon in a crystalline semiconductor layer may be higher than the substitutional amount. Another material could be phosphorus doped SiGe, with Ge % less than 10% to promote phosphorus incorporation. Si:C(P) allows for the application of a strain on the structure (fin). According to an embodiment, merging is performed with epitaxial in-situ phosphorus (as mentioned above) or arsenic doped silicon. In another alternative embodiment, merging is performed and subsequent ion implantation can follow the epitaxial merging process. The doping level can be about 1.0×10 20  cm −3  to about 2.0×10 21  cm −3 , for example, about 4.0×10 20  cm −3  to about 9.0×10 20  cm −3 . 
         [0039]    Referring to  FIG. 7 , which is a cross-sectional view illustrating further deposition of a dielectric in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, the dielectric layer  128  is deposited on the structure from  FIG. 6  to cover epitaxy region  138 , and chemical mechanical planarization (CMP) is performed to level the dielectric layer surface. Then, referring to  FIG. 8 , a portion of the dielectric layer  128  corresponding to a second transistor  120   b  is removed by, for example, etching, such as, for example, RIE to form a trench  133 . According to an embodiment, the transistor  120   b  is a PFET transistor. The trench  133  is an opening formed to expose the sacrificial epitaxy region  118  for transistor  120   b . As can be seen in  FIG. 8 , in accordance with an embodiment of the present invention, the trench does not necessarily overlap all of the fins for a transistor. According to an embodiment, while the trench can be large enough to overlap all of the fins, it is sufficient that the trench be large enough to remove the sacrificial epitaxy region  118  and fill the resulting gaps with the final epitaxy region. In connection with  FIG. 8 , the trench  133  overlaps some, but not all of the fins  116  for transistor  120   b , but still permits removal of the sacrificial epitaxy region and growth of the final epitaxy region. 
         [0040]    Referring to  FIG. 9 , which is a cross-sectional view showing removal of a sacrificial epitaxy region in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, the sacrificial epitaxy region  118  corresponding to the transistor  120   b  is removed by, for example, etching. Etching can include, wet and/or dry etch processes such as those described in connection with  FIG. 5 . 
         [0041]    Referring to  FIG. 10 , which is a cross-sectional view showing formation of an epitaxy region for a transistor in a method of manufacturing a FinFET device, according to an exemplary embodiment of the invention, epitaxy region  148  is grown for transistor  120   b  in the space previously occupied by the sacrificial epitaxy region  118 . As can be seen, the epitaxy region  148  can further be overgrown (e.g., grown relatively high above a top surface of the fins  116 ) to result in a smooth top surface of the epitaxy region  148 . Due to the presence of the dielectric layer  128 , like the epitaxy region  138 , the epitaxy region  148  is prevented from excessive lateral growth from end fins. As a result, the epitaxy region  148  is blocked by the dielectric layer  128  and does not extend to connect fins from adjacent transistors (e.g.,  120   a  and  120   b ). Thereby, shorts between neighboring transistors as well as source to drain shorts can be prevented. 
         [0042]    According to an embodiment, the epitaxy region  148  is for a PFET. Epitaxy regions for transistors with the same doping as transistor  120   b  (in this case p-type) can be formed at the same time, while transistors with the same doping as transistor  120   a  (in this case n-type) remain covered. 
         [0043]    The fins  116  forming the source drain region of transistor  120   b  (in this case an PFET) are merged by epitaxially growing in-situ boron doped SiGe (may include an introduced strain or Si) on the exposed silicon surfaces of the fins  116  so that the fins  116  contact each other through the epitaxy region  148  in an integrated structure. According to an embodiment, merging is performed with epitaxial in-situ boron doped silicon. The epitaxy region  148  can be in-situ doped with boron or other appropriate impurity. In another alternative embodiment, merging is performed and subsequent ion implantation can follow the epitaxial merging process. The doping level can be about 1.0×10 20  cm −3  to about 2.0×10 21  cm −3 , for example about 4.0×10 20  cm −3  to about 9.0×10 20  cm −3 . 
         [0044]    Referring to  FIG. 11 , after formation of the structure shown in  FIG. 10 , the portion of the dielectric layer  128  over the transistor  120   a  is removed, and remaining processes for forming the FinFET devices can be performed, including, but not limited to, silicide and contact formation, replacement metal gate (RMG), and back-end-of-line (BEOL) processes. 
         [0045]    Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be made by one skilled in the art without departing from the scope or spirit of the invention.