Patent Publication Number: US-10325999-B2

Title: Contact area to trench silicide resistance reduction by high-resistance interface removal

Description:
TECHNICAL FIELD 
     The field generally relates to semiconductor devices and methods of manufacturing same and, in particular, to semiconductor devices lacking a high-resistance interface between contact areas and trench silicide regions. 
     BACKGROUND 
     When scaling for next generation complementary metal-oxide semiconductor (CMOS) devices in connection with increased miniaturization, including, for example, very-large-scale integration (VLSI), middle-of-the-line (MOL) resistance can be a critical issue affecting device performance. 
     In conventional devices, increased MOL resistance can be caused by high-resistance interfaces between contact area (CA) metals and trench silicide (TS) regions. According to conventional processing, a liner that is needed for CA metallization, such as, for example, titanium nitride (TiN), has a high resistivity, and is positioned between a CA metal layer and a TS region. The liner, which is positioned as a high-resistance interface between the CA metal layer and a TS region, undesirably increases overall MOL resistance. 
     Accordingly, there is a need for a semiconductor device which does not include a high-resistance interface between the CA metal layer and a TS region and a method of manufacturing same. 
     SUMMARY 
     According to an exemplary embodiment of the present invention, a method for manufacturing a semiconductor device comprises forming a silicide region on a semiconductor substrate, forming a gate structure on the semiconductor substrate adjacent the silicide region, forming a dielectric layer on the gate structure and on the silicide region, forming a first liner layer on the dielectric layer, removing a portion of the first liner layer and a portion of the dielectric layer to form an opening exposing a top surface of the silicide region, forming a second liner layer on the first liner layer and on sides and a bottom of the opening, removing a portion of the second liner layer from a top surface of the first liner layer and from the bottom of the opening to re-expose a portion of the top surface of the silicide region, and forming a contact layer in the opening directly on the re-exposed portion of the top surface of the silicide region. 
     According to an exemplary embodiment of the present invention, a semiconductor device comprises a substrate, a gate structure on the substrate, a silicide region on the substrate adjacent the gate structure, a dielectric layer on the gate structure and on the silicide region, an opening in the dielectric layer formed over the silicide region, wherein the opening comprises a liner layer on sides of the opening, and a contact layer filling the opening and directly on the liner layer and a top surface of the silicide region. 
     According to an exemplary embodiment of the present invention, a method for manufacturing a semiconductor device comprises forming a fin on a semiconductor substrate, forming a plurality of silicide regions on the fin, forming a gate structure on the fin between the plurality of silicide regions, forming a dielectric layer on the gate structure and on the silicide regions, forming a first liner layer on the dielectric layer, removing a portion of the first liner layer and a portion of the dielectric layer to form a plurality of openings exposing a top surface of each silicide region, forming a second liner layer on the first liner layer and on sides and a bottom of each opening, removing a portion of the second liner layer from a top surface of the first liner layer and from the bottom of each opening to re-expose a portion of the top surface of each silicide region, and forming a contact layer in the openings directly on the re-exposed portion of the top surface of each silicide region. 
     These and other exemplary embodiments of the invention will be described in 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 
       Exemplary embodiments of the present invention will be described below in more detail, with reference to the accompanying drawings, of which: 
         FIG. 1  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing deposition of a dielectric layer and a first liner layer after completion of a replacement metal gate (RMG) process, according to an exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing patterning of the layers over trench silicide (TS) regions, according to an exemplary embodiment of the present invention. 
         FIG. 3  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing deposition of a second liner layer, according to an exemplary embodiment of the present invention. 
         FIG. 4  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing removal of a portion of the second liner layer, according to an exemplary embodiment of the present invention. 
         FIG. 5  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing deposition of a contact area (CA) metal, according to an exemplary embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of a semiconductor device taken perpendicular to a gate extension direction and showing removal and planarization of the first liner layer and portions of the CA metal and the second liner layer, according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the invention will now be discussed in further detail with regard to semiconductor devices and methods of manufacturing same and, in particular, to semiconductor devices lacking a high-resistance interface between contact areas and trench silicide regions. 
     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 complementary metal-oxide semiconductor (CMOS), fin field-effect transistor (FinFET), metal-oxide-semiconductor field-effect transistor (MOSFET) and/or other semiconductor 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 devices. In addition, certain elements may be left out of particular views for the sake of clarity and/or simplicity when explanations are not necessarily focused on the omitted elements. 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. 
     The semiconductor devices and methods for forming same in accordance with 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 semiconductor devices are contemplated embodiments of the invention. Given the teachings of 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. 
     The embodiments of the present invention can be used in connection with semiconductor devices that may require CMOSs, MOSFETs and/or FinFETs. By way of non-limiting example, the semiconductor devices can include, but are not limited to CMOS, MOSFET and FinFET devices, and/or semiconductor devices that use CMOS, MOSFET and/or FinFET technology. 
     As used herein, “parallel to a gate extension direction” refers to an extension direction of a gate structure perpendicular to a channel length (e.g., perpendicular to a fin extension direction). 
     As used herein, “perpendicular to a gate extension direction” or “across a channel of a gate structure” refers to a channel length direction of a gate structure (e.g., parallel to a fin extension direction) and to the left and right in the cross-sectional views herein, wherein source/drain regions are located to left and right sides of the gate structure in the cross-sectional views. In other words, left and right in these cross-sections represents a length of a fin and a channel length, and the width direction of the fin and a gate extension direction are going into the page. 
     As used herein, “height” refers to a vertical size of an element (e.g., a layer, trench, hole, etc.) in the cross-sectional figures measured from a bottom surface to a top surface of the element, and/or measured with respect to a surface on which the element is directly on. Conversely, a “depth” refers to a vertical size of an element (e.g., a layer, trench, hole, etc.) in the cross-sectional figures measured from a top surface to a bottom surface of the element. 
     As used herein, “lateral,” “lateral side,” “lateral surface” refers to a side surface of an element (e.g., a layer, opening, etc.), such as a left or right side surface in the cross-sectional figures. 
     As used herein, “width” refers to a horizontal size of an element (e.g., a layer, trench, hole, etc.) in the figures measured from a left or right side surface to an opposite surface of the element. 
     Embodiments of the present invention provide a method for removing an interface metal between a CA and a TS, without removing a liner layer needed for CA metallization (e.g., TiN on sidewalls and on the outside of CA trench). The preservation of the liner layer on sidewalls and on the outside of CA trench prevents metal delamination. In accordance with one or more embodiments of the present invention, referring, for example, to  FIG. 6  described herein below, the resulting device does not include a high-resistance interface between one or more CAs and TSs, so that overall MOL resistance is maintained at desirable levels. 
       FIG. 1  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing deposition of a dielectric layer and a first liner layer after completion of a replacement metal gate (RMG) process, according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , a semiconductor substrate  102  can be, for example, a bulk substrate or a silicon-on-insulator (SOI) substrate including a buried insulating layer, such as, for example, a buried oxide or nitride layer located on an upper surface of the semiconductor substrate. The substrate  102  may comprise semiconductor material including, but not limited to, Si, SiGe, SiC, SiGeC or other like semiconductor. In addition, multiple layers of the semiconductor materials can be used as the semiconductor material of the substrate. 
     In accordance with an embodiment of the present invention, as can be seen in  FIG. 1 , a fin  105  is formed on the substrate  102 , using, for example, known methods of epitaxial growth and patterning. 
     As is known in the art, a fin of a FinFET can comprise, for example, silicon, and is a conducting channel that protrudes vertically from a substrate and extends in a direction from a source to a drain. As can be understood by one of ordinary skill in the art, a plurality of fins can be formed on the substrate  102  and spaced apart from each other at regular intervals along a gate extension direction. A plurality of gates can intersect the fins and extend perpendicular to the extension direction of the fins. Multiple gates can be spaced apart from each other along the extension direction of the fins. 
     Terms such as “epitaxial growth” and “epitaxially formed and/or grown” refer to the growth of a semiconductor material on a deposition surface of a semiconductor material, in which the semiconductor material being grown has the same crystalline characteristics as the semiconductor material of the deposition surface. In an epitaxial deposition process, the chemical reactants provided by the source gases are controlled and the system parameters are set so that the depositing atoms arrive at the deposition surface of the semiconductor substrate with sufficient energy to move around on the surface and orient themselves to the crystal arrangement of the atoms of the deposition surface. Therefore, an epitaxial semiconductor material has the same crystalline characteristics as the deposition surface on which it is formed. For example, an epitaxial semiconductor material deposited on a {100} crystal surface will take on a {100} orientation. 
     Examples of various epitaxial growth processes include, for example, rapid thermal chemical vapor deposition (RTCVD), low-energy plasma deposition (LEPD), ultra-high vacuum chemical vapor deposition (UHVCVD), atmospheric pressure chemical vapor deposition (APCVD), liquid-phase epitaxy (LPE), molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). The temperature for an epitaxial growth process can range from, for example, 550° C. to 900° C., but is not necessarily limited thereto, and may be conducted at higher or lower temperatures as needed. 
     A number of different sources may be used for the epitaxial growth. For example, the sources may include precursor gas or gas mixture including for example, a silicon containing precursor gas (such as silane) and/or a germanium containing precursor gas (such as a germane). Carrier gases like hydrogen, nitrogen, helium and argon can be used. 
     In an RMG process, a sacrificial material, which is replaced by a metal gate structure, is used to determine a geometry and location of the resulting metal gate structure. The sacrificial gate structure can comprise a material that can be selectively etched with respect to adjacent layers. For example, the sacrificial gate structure may comprise silicon, such as, polysilicon, and may be deposited and patterned. The sacrificial gate structure can be deposited using deposition techniques including, but not limited to, chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), radio-frequency CVD (RFCVD), physical vapor deposition (PVD), atomic layer deposition (ALD), molecular beam deposition (MBD), pulsed laser deposition (PLD), and/or liquid source misted chemical deposition (LSMCD), sputtering, and/or plating. 
     During the RMG process, spacers  154  are formed adjacent to the sacrificial gate structure, to be in direct contact with opposing sidewalls of the sacrificial gate structure. The spacers  154  can include a dielectric insulating material such as, for example, silicon oxide, silicon nitride, silicon oxynitride, boron nitride, silicon boron nitride, or multilayered stacks thereof. 
     A first dielectric layer  120 , comprising, for example, silicon dioxide (SiO 2 ), low-temperature oxide (LTO), high-temperature oxide (HTO), field oxide (FOX) or some other dielectric, is formed on the fin  105  adjacent sides of the spacers  154  and on the spacers  154  and the sacrificial gate structure using a deposition process, such as, for example, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD. The first dielectric layer  120 , and possibly top portions of the spacers  154  and the sacrificial gate structure are then planarized using a planarization process, such as, for example, chemical mechanical planarization (CMP), so that top surfaces of the first dielectric layer  120 , spacers  154  and sacrificial gate structure are level with each other, and an upper surface of the sacrificial gate structure is exposed. 
     TS regions  140  are formed adjacent the spacers  154  and on the fin  105 . The TS regions  140  can be formed by a lithography step first, then a reactive ion etching (RIE) is used to open trenches next to spacers  154 . After stripping of materials from the lithography step, a metal to form the silicide is deposited. The metal can include, but is not limited to, titanium, cobalt, tantalum, and nickel platinum. A CMP process can be used to remove the metal above dielectric layer  120 . The TS regions  140  may comprise a silicide, including, for example, nickel silicide (NiSi), nickel platinum silicide (NiPt y Si x ), cobalt silicide (CoSi x ), tantalum silicide (TaSi x ), titanium silicide (TiSi x ) and combinations thereof. 
     The sacrificial gate structure is removed to provide an opening exposing a portion of the fin  105  and in which the resulting gate structure is to be formed. The sacrificial gate structure can be removed using a selective etch process that selectively removes the sacrificial gate structure with respect to the first dielectric layer  120 , TS regions  140 , and spacers  154 . The etch can be, for example, an isotropic etch, such as a wet chemical etch, or an anisotropic etch, such as RIE, ion beam etching, plasma etching or laser ablation. 
     A metal gate structure is formed in the opening left after removal of the sacrificial gate structure. Referring to  FIG. 1 , the gate structure is formed on the fin  105 . The gate structure includes, for example, low resistance metal  150 , such as, for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum, ruthenium, copper, metal carbides, metal nitrides, transition metal aluminides, tantalum carbide, titanium carbide, tantalum magnesium carbide, or combinations thereof, and a dielectric  152  such as, for example, a high-K dielectric including but not limited to, HfO 2  (hafnium oxide), ZrO 2  (zirconium dioxide), hafnium zirconium oxide Al 2 O 3  (aluminum oxide), and Ta 2 O 5  (tantalum pentoxide). The gate structure may be formed using, for example, deposition techniques including, but not limited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. The spacers  154  are located on the metal gate structure, having a first edge located on a vertical sidewall the gate structure and a base that is located on the fin  105 . As can be understood by one of ordinary skill in the art, a plurality of gate structures can be formed on one or more fins, and spaced apart from each other along a length (e.g., extension) direction of the fins. 
     After formation of the replacement gate structure in the RMG process, a second dielectric layer  122  is deposited on top of the gate structure, TS regions  140  and first dielectric layer  120 . The second dielectric layer  122  can comprise the same material as or a different dielectric material from the first dielectric layer  120 , and may be formed using, for example, deposition techniques including, but not limited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. 
     The first and second dielectric layers  120  and  122  can be referred to as inter-layer dielectric (ILD) layers. Silicon nitride layers  110 ,  112  and  114  are formed on the fin  105  between the fin  105  and the first dielectric layer  120 , on the spacers  154  between the spacers  154  and the TS regions  140 , and on the gate structure including the gate metal  150  and dielectric  152 , between the gate structure and second dielectric layer  122 . The SiN layers  110  and  112  are formed prior to deposition of the first dielectric layer  120 , and the SiN layer  114  is formed prior to deposition of the second dielectric layer using a deposition method, such as, for example, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. 
     As shown in  FIG. 1 , a first liner layer  130  comprising, for example, TiN, tantalum nitride (TaN) or ruthenium, is formed on the second dielectric layer  122  using, for example, a deposition technique including but not limited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. According to an embodiment, a height (i.e., thickness) of the first liner layer  130  can be, for example, about 5 nm-about 50 nm. 
       FIG. 2  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing patterning of the second dielectric layer  122  and first liner layer  130  over the TS regions  140 , according to an exemplary embodiment of the present invention. Referring to  FIG. 2 , patterning is performed by a method known in the art, for example, RIE to remove portions of the first liner layer  130  and the second dielectric layer  122  to form openings  160  (e.g., trenches) exposing the TS regions  140 . A depth of the openings  160  can be, for example, in the range of about 20 nm-about 50 nm. 
       FIG. 3  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing deposition of a second liner layer, according to an exemplary embodiment of the present invention. Referring to  FIG. 3 , a second liner layer  132  comprising, for example, TiN, tantalum nitride (TaN) or ruthenium, is formed on the first liner layer  130 , and in the openings  160  on sidewalls of the openings  160  and on the exposed TS regions  140 , using, for example, a deposition technique including but not limited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. The second liner layer  132  can comprise the same material as the first liner layer  130 . According to an embodiment, a height (i.e., thickness) of the second liner layer  132  can be, for example, about 1 nm to about 4 nm. 
       FIG. 4  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing removal of a portion of the second liner layer, according to an exemplary embodiment of the present invention. Referring to  FIG. 4 , portions of the second liner layer  132  on the first liner layer  130  outside of the openings  160 , and portions of the second liner  132  at the bottom of the openings  160  are removed to expose parts of the first liner layer  130  and the parts of the TS regions  140  that were under the removed portions of the second liner layer  132 . The removal of the portions of the second liner layer  132  can be performed using, for example, a gas cluster ion beam (GCM) process, a sputter etch process or other directional or anisotropic removal process capable of removing portions of the second liner layer  132  on the first liner layer  130  outside of the openings  160 , and portions of the second liner  132  at the bottom of the openings  160 , while portions of the second liner layer  132  remain on the sidewalls of the openings  160 . 
       FIG. 5  is a cross-sectional view illustrating fabrication of a semiconductor device taken perpendicular to a gate extension direction and showing deposition of a contact area (CA) metal, according to an exemplary embodiment of the present invention. Referring to  FIG. 5 , a CA metal  170 , such as, for example, tungsten, cobalt, ruthenium, copper, or combinations thereof, is deposited on exposed portions of the first and second liner layers  130  and  132 , and the TS regions  140 . The CA metal  170  may be formed using, for example, deposition techniques including, but not limited to, CVD, PECVD, RFCVD, PVD, ALD, MBD, PLD, and/or LSMCD, sputtering, and/or plating. 
       FIG. 6  is a cross-sectional view of a semiconductor device taken perpendicular to a gate extension direction and showing removal and planarization of the first liner layer and portions of the CA metal and the second liner layer, according to an exemplary embodiment of the present invention. Referring to  FIG. 6 , the first liner layer  130  and portions of the CA metal  170  and the second liner layer  132  are removed using a planarization process, such as, for example, CMP. As shown in  FIG. 6 , the planarization is performed down to the second dielectric layer  122  to expose top surface portions of the second dielectric layer  122  and the second liner layer  132 , and make a top surface of the CA metal  170  level with the top surface portions of the second dielectric layer  122  and the second liner layer  132 . As shown in  FIG. 6 , the circled regions A indicate interface free regions between the CA metal layers  170  and the corresponding TS regions  140 , such that the CA metal layers  170  are directly on the corresponding TS regions  140 , and there is no high-resistance liner between the CA metal layers  170  and the corresponding TS regions  140 . As a result, overall MOL resistance is maintained at desirable levels, while still providing the requisite liner layers  130 ,  132  (see  FIG. 4 ) to permit CA metallization (see  FIG. 5 ) without metal delamination. 
     While the embodiments of the present invention are illustrated as a FinFET device, including contact areas and trench silicide regions connecting to a fin, it is to be understood that the embodiments of the present invention are not necessarily limited to FinFET devices, and can be applied to other semiconductor devices where contact areas and silicide regions connect to source/drain regions of one or more gates. 
     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.