Patent Publication Number: US-11646232-B2

Title: Method of manufacturing semiconductor devices and semiconductor device

Description:
RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 63/028,900 filed on May 22, 2020, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     As the semiconductor industry has progressed into nanometer technology process nodes in pursuit of higher device density, higher performance, lower power consumption and lower costs, challenges from both fabrication and design issues have resulted in the development of three-dimensional designs, such as a fin field effect transistor (Fin FET). In a Fin FET device, it is possible to utilize additional sidewalls and to suppress a short channel effect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIGS.  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13 ,  14 ,  15 ,  16 ,  17  and  18    show cross sectional views of various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
         FIGS.  19 ,  20 ,  21 ,  22  and  23    show cross sectional views of various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
         FIGS.  24 A,  24 B,  24 C,  24 D and  24 E  show cross sectional view of the various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
         FIG.  25    shows a cross sectional view of one of the various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
         FIG.  26    shows a cross sectional view of one of the various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
         FIGS.  27 A and  27 B  show cross sectional views of one of the various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
         FIGS.  28 ,  29 , and  30    show cross sectional views of one of the various stages of a sequential manufacturing operation for a semiconductor device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific embodiments or examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, dimensions of elements are not limited to the disclosed range or values, but may depend upon process conditions and/or desired properties of the device. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Various features may be arbitrarily drawn in different scales for simplicity and clarity. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. In addition, the term “made of” may mean either “comprising” or “consisting of.” 
     Fin structures used in FinFETs are manufactured by various patterning methods. When a critical dimension (CD) of a fin structure decreases below 20 nm, for example, it is generally difficult to directly form a pattern having such a small dimension by a single optical lithography process, and some fine patterning processes have been developed. For example, the fin structures may be patterned using double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer, which is often referred to as a mandrel pattern, is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers may then be used to pattern the fin structures. This operation may be repeated to manufacture desired fin patterns. 
       FIGS.  1 - 18    show various stages of a sequential manufacturing process of a semiconductor FinFET device according to embodiments of the present disclosure. It is understood that additional operations may be provided before, during, and after processes shown by  FIGS.  1 - 18   , and some of the operations described below can be replaced or eliminated in additional embodiments of the method. The order of the operations can be changed in some embodiments. 
     As shown in  FIG.  1   , multiple layers for hard masks are formed over a substrate  10  to be patterned into fin structures. In some embodiments, the substrate  10  is a silicon substrate. Alternatively, the substrate  10  may comprise another elementary semiconductor, such as germanium; a compound semiconductor including Group IV-IV compound semiconductors such as SiC and SiGe, Group III-V compound semiconductors such as GaAs, GaP, GaN, InP, InAs, InSb, GaAsP, AlGaN, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. 
     In some embodiments, a first layer  11  is formed over the substrate  10 . In some embodiments, the first layer  11  is a pad silicon oxide layer formed by, for example, a thermal oxidation process or a chemical vapor deposition (CVD) process. In some embodiments, the thickness of the first layer  11  is in a range from about 1 nm to about 5 nm. Further, in some embodiments, a second layer  12  made of a different material than the first layer  11  is formed over the first layer  11 . In some embodiments, the second layer  12  is a second pad layer or a hard mask layer including, for example, silicon nitride formed by, for example, a CVD or atomic layer deposition (ALD) process. In some embodiments, the thickness of the second layer  12  is in a range from about 2 nm to about 20 nm. 
     Further, in some embodiments, a third layer  13  made of a different material than the second layer  12  is formed over the second layer  12 . In some embodiments, the third layer  13  is a hard mask layer formed by, for example, a CVD process. In some embodiments, the third layer  13  includes silicon oxide, SiON, SiOC, SiOCN, aluminum oxide or any other suitable material. In some embodiments, the thickness of the third layer  13  is in a range from about 5 nm to about 30 nm. In some embodiments, the third layer  13  is made of a same material as or a different material than the first layer  11 . 
     Then, a fourth layer  14  made of a different material than the third layer  13  is formed over the third layer  13  in some embodiments. In some embodiments, the fourth layer  14  is a sacrificial layer for a mandrel pattern formed by, for example, a CVD process. In some embodiments, the fourth layer  14  includes amorphous or polycrystalline Si, SiGe or Ge, silicon oxide, SiOC, SiON, SiOCN or any other suitable material. In certain embodiments, non-doped poly silicon is used as the fourth layer  14 . In some embodiments, the thickness of the fourth layer  14  is in a range from about 5 nm to about 30 nm. Further, in some embodiments, a fifth layer  15  made of a different material than the fourth layer  14  is formed over the fourth layer  14 . In some embodiments, the fifth layer  15  is a hard mask layer formed by, for example, a CVD process. In some embodiments, the fifth layer  15  includes silicon oxide, silicon nitride, SiON, SiOC, SiOCN or any other suitable material. In certain embodiments, silicon nitride is used as the fifth layer  15 . In some embodiments, the thickness of the fifth layer  15  is in a range from about 4 nm to about 20 nm. 
     Then, an organic bottom antireflective coating (BARC) layer  16  is formed over the fifth layer  15 , and a photo resist layer is formed over the BARC layer  16  in some embodiments. Then, the photo resist layer is patterned by using a lithography operation, thereby forming a photo resist pattern  17 , as shown in  FIG.  1   . In some embodiments, a width W 1  of the photo resist pattern  17  is in a range from about 20 nm to about 100 nm and a space S 1  is in a range from about 30 nm to about 200 nm, depending on design requirements. In some embodiments, the space S 1  is greater than the width W 1 . 
     Then, the BARC layer  16  is patterned by using the photo resist pattern  17  as an etching mask, and the fifth layer  15  is further patterned using the patterned BARC layer  16  (and the photo resist pattern  17 ) as an etching mask, thereby forming a first hard mask pattern  15 A. Then, the fourth layer (sacrificial layer)  14  is patterned using one or more plasma dry etching operations by using the first hard mask pattern  15 A, thereby forming a mandrel pattern  14 A, as shown in  FIG.  2   . Then, the first hard mask pattern  15 A is removed as shown in  FIG.  3    by wet and/or dry etching. 
     In some embodiments, the etching of the fourth layer  14  is a taper etching operation forming a trapezoidal cross sectional shape having a top smaller than the bottom as shown in  FIGS.  2  and  3   . The effects of the trapezoidal shape will be explained later. 
     Then, as shown in  FIG.  4   , a sixth layer  18  for sidewall spacers is conformally formed on the mandrel pattern  14 A and the exposed third layer  13 . In some embodiments, the sixth layer  18  is made of a different material than the mandrel patterns  14 A and the third layer  13 , and includes silicon nitride, SiON, SiCN or any other suitable material. In certain embodiments, silicon nitride layer is used as the sixth layer  18 . In some embodiments, the thickness of the sixth layer  18  is in a range from about 5 nm to about 15 nm, and is in a range from about 7 nm to about 12 nm in other embodiments, depending on design requirements and/or process requirements. In some embodiments, the sixth layer  18  is formed by an ALD process. 
     Next, as shown in  FIG.  5   , anisotropic etching is performed on the sixth layer  18  to remove the horizontal portions of the sixth layer  18  deposited on the top of the mandrel patterns  14 A and the third layer  13  between the adjacent mandrel patterns  14 A. As the result of the anisotropic etching, the sixth layer  18  remains as sidewall spacers  18 A disposed on opposing side faces of the mandrel patterns  14 A as shown in  FIG.  5   . 
     Then, as shown in  FIG.  6   , the mandrel patterns  14 A are removed by one or more dry and/or wet etching operations, thereby leaving the sidewall spacers  18 A as second hard mask patterns. As shown in  FIG.  6   , the second hard mask patterns  18 A extend substantially vertically, due to the trapezoidal shape of the mandrel patterns  14 A. The effects of the trapezoidal shape will be explained later. As shown in  FIG.  6   , a mandrel-space MS is a space from which a mandrel pattern  14 A is remove and which is formed by a left sidewall  18 A-L and a right sidewall  18 A-R, and a spacer-space SS is a space where no a mandrel pattern  14 A existed and which is formed by a right sidewall  18 A-R and a left sidewall  18 A-L. In some embodiments, the width and/or space of the mandrel patterns  14 A and/or the thickness of the sixth layer  18  are adjusted or set such that the second hard mask patterns  18 A have a substantially constant pitch. In some embodiments, a variation of the pitches is more than zero and less than about 0.5 nm. In some embodiments, the space between the second hard mask patterns  18 A at the mandrel-space MS is greater than the space between the second hard mask patterns  18 A at the spacer-space SS, and in other embodiments, the space between the second hard mask patterns  18 A at the mandrel-space MS is smaller than the space between the second hard mask patterns  18 A at the spacer-space SS. 
     Next, as shown in  FIG.  7   , a mask pattern, such as a photo resist pattern  19 , is formed over the second hard mask patterns  18 A, and portions of the second hard mask patterns are removed and the second hard mask patterns are cut into pieces by one or more etching operations. As described later, the cut of second hard mask patterns  18 A correspond to fin structures used in FinFETs. After the etching operation, the mask pattern  19  is removed as shown in  FIG.  8   . In some embodiments, the remaining hard mask patterns  18 A constitute mandrel-spaces MS, as shown in  FIG.  8   . Further, in some embodiments, an isolated second hard mask pattern  18 A (the rightmost pattern in  FIG.  8   ), which is separated from adjacent hard mask pattern by a space greater than the space of the mandrel-space MS and/or spacer-space SS, is included. 
     Then, as shown in  FIG.  9   , an optional additional hard mask layer  18 B is conformally formed over the second hard mask layer  18 A to adjust thickness (width) of the second hard mask layer  18 A. In some embodiments, the additional hard mask layer  18 B is made of the same or similar material to the second hard mask layer  18 A, and includes silicon nitride, SiON, SiCN or any other suitable material, formed by an ALD process. In certain embodiments, silicon nitride is used as the additional hard mask layer  18 B. In some embodiments, the thickness of the additional hard mask layer  18 B is in a range from about 1 nm to about 2 nm. After the additional hard mask layer  18 B is formed, anisotropic etching is performed to remove horizontal part of the deposited additional hard mask layer  18 B in some embodiments. 
     In  FIG.  10   , the combination of the second hard mask pattern  18 A and the additional hard mask layer  18 B are shown as hard mask pattern  18 C. Then, as shown in  FIG.  11   , the third layer  13  is patterned by one or more plasma dry etching by using the hard mask pattern  18 C as an etching mask, thereby forming a third hard mask pattern  13 A. Then, the hard mask pattern  18 C is removed by one or more dry and/or wet etching operations. 
     Further, the second layer  12  is patterned by one or more plasma dry etching using the third hard mask pattern  13 A as an etching mask, thereby forming a fourth hard mask pattern  12 A. In some embodiments, after the patterning operation, an additional hard mask layer  13 B is conformally formed over the third hard mask pattern  13 A and fourth hard mask pattern  12 A to adjust thickness (width) of the hard mask pattern. In some embodiments, the additional hard mask layer  13 B is made of the same or similar material to the third hard mask layer  13 A, and includes silicon oxide, SiON, SiOC or any other suitable material, formed by an ALD process. In certain embodiments, silicon oxide is used as the additional hard mask layer  13 B. In some embodiments, the thickness of the additional hard mask layer  13 B is in a range from about 0.5 nm to about 2 nm. After the additional hard mask layer  13 B is formed, anisotropic etching is performed to remove horizontal part of the deposited additional hard mask layer  13 B in some embodiments. 
     Then, the first layer  12  and the substrate  10  are patterned by one or more plasma dry etching using the hard mask pattern  13 A and/or  12 A as an etching mask, thereby forming fin structures  20  as shown in  FIG.  13   . In some embodiments, after the patterning etching, the hard mask pattern  12 A and a patterned first layer  11 A remain on the top of each of the fin structures  20 . In some embodiments, the hard mask pattern  13 A is removed during and/or after the patterning of the substrate  10 . 
     Then, an insulating layer  30 L for an isolation insulating layer is formed to fully cover the fin structures as shown in  FIG.  14   . The insulating layer  30 L includes one or more layers of insulating materials such as silicon oxide, silicon oxynitride or silicon nitride, formed by LPCVD (low pressure chemical vapor deposition), plasma-CVD or flowable CVD. In the flowable CVD, flowable dielectric materials instead of silicon oxide are deposited. Flowable dielectric materials, as their name suggests, can “flow” during deposition to fill gaps or spaces with a high aspect ratio. Usually, various chemistries are added to silicon-containing precursors to allow the deposited film to flow. In some embodiments, nitrogen hydride bonds are added. Examples of flowable dielectric precursors, particularly flowable silicon oxide precursors, include a silicate, a siloxane, a methyl silsesquioxane (MSQ), a hydrogen silsesquioxane (HSQ), a mixture of MSQ and HSQ, a perhydrosilazane (TCPS), a perhydro-polysilazane (PSZ), a tetraethyl orthosilicate (TEOS), or a silyl-amine, such as trisilylamine (TSA). These flowable silicon oxide materials are formed in a multiple-operation process. After the flowable film is deposited, it is cured and then annealed to remove un-desired element(s) to form silicon oxide. The flowable film may be doped with boron and/or phosphorous. The insulating layer  30 L may be formed by one or more layers of spin-on-glass (SOG), SiO, SiON, SiOCN and/or fluoride-doped silicate glass (FSG) in some embodiments. 
     In some embodiments, before the insulating layer  30 L is formed, one or more fin liner layers (not shown) are conformally formed on the fin structures  20 . In some embodiments, the fin liner layer includes a first layer and a second layer made of a different material than the first layer. In some embodiments, the fin liner layers are formed of silicon nitride or a silicon nitride-based material (e.g., silicon oxynitride, silicon carbon nitride, or silicon carbon oxynitride) and a silicon oxide based material (e.g., silicon oxide, or silicon carbon oxide). In some embodiments, the thickness of each of the first and second fin liner layers is in a range from about 1 nm to about 5 nm. 
     Then, one or more planarization operations, such as an etch back operation or a chemical mechanical polishing (CMP) operation, are performed to expose the hard mask pattern  12 A as shown in  FIG.  15   . Subsequently, the hard mask pattern  12 A is removed as shown in  FIG.  16    by one or more wet and/or dry etching operations. 
     Further, the insulating layer  30 L is recessed, thereby forming an isolation insulating layer  30  as shallow trench isolation (STI), as shown in  FIG.  17   . As shown in  FIG.  17   , an upper portion of the fin structure  20 U protrudes from the isolation insulating layer  30  and a lower portion of the fin structure  20 B is embedded in the isolation insulating layer  30 . In some embodiments, during or after the recess etching, the patterned first layer  11 A is removed. When the fin liner layer is formed, the fin liner layer is also recessed during and/or after the insulating layer  30 L is recessed. 
     After the fin structures  20  are formed, a sacrificial gate structure is formed over the channel region of the fin structures, a source/drain epitaxial layer is formed at the source/drain region of the fin structure, and one or more dielectric layers  60  are formed over the sacrificial gate structure and the source/drain epitaxial layer. Further, the sacrificial gate structure is replaced with a metal gate structure, as shown in  FIG.  18   . In some embodiments, the metal gate structure  80  includes a gate dielectric layer  82  and one or more conductive layers  84 . In some embodiments, the gate dielectric layer  82  includes one or more layers of a dielectric material, such as silicon oxide, silicon nitride, or a high-k dielectric material, other suitable dielectric material, and/or combinations thereof. Examples of high-k dielectric materials include HfO 2 , HfSiO, HfSiON, HfTaO, HfTiO, HfZrO, zirconium oxide, aluminum oxide, titanium oxide, hafnium dioxide-alumina (HfO 2 —Al 2 O 3 ) alloy, La 2 O 3 , HfO 2 —La 2 O 3 , Y 2 O 3 , Dy 2 O 3 , Sc 2 O 3 , MgO or other suitable high-k dielectric materials, and/or combinations thereof. 
     In some embodiments, the conductive layers  84  include a barrier layer, one or more work function adjustment layers, a glue layer and a body metal layer. In some embodiments, the barrier layer includes a metal nitride, such as WN, TaN, TiN and TiSiN. In some embodiments, the work function adjustment layers include WN, WCN, Ru, TiAlN, AlN TaN, TiN, TiSiN, W, TaAlC, TiC, TaAl, TaC, Co, Al, TiAl, or TiAlC, or a multilayer of two or more of these materials. In some embodiments, the glue layer is made of one or more of TiN, Ti, and Co. In some embodiments, the body metal layer includes one or more layers of conductive material, such as polysilicon, aluminum, copper, titanium, tantalum, tungsten, cobalt, molybdenum, tantalum nitride, nickel silicide, cobalt silicide, TiN, WN, WCN, Ru, TiAl, TiAlN, TaCN, TaC, TaSiN, metal alloys, other suitable materials, and/or combinations thereof. 
       FIGS.  19 - 23    show various stages of a sequential manufacturing process of a semiconductor FinFET device according to embodiments of the present disclosure. It is understood that additional operations may be provided before, during, and after processes shown by  FIGS.  19 - 23   , and some of the operations described below can be replaced or eliminated in additional embodiments of the method. The order of the operations can be changed. Materials, configuration, processes and/or dimensions explained with respect to above embodiments may be applied to the following embodiments, and the detailed description thereof may be omitted. 
       FIGS.  19  and  20    are the same as  FIGS.  5  and  6   . In some embodiments, in the fin cut operation explained with respect to  FIG.  7   , the remaining second hard mask pattern  18 A constitutes one or more mandrel-space patterns MS and one or more spacer-space patterns SS, as shown in  FIG.  21   . Subsequently, the operations as explained with respect to  FIGS.  9 - 13    are performed, thereby forming fin structures  20  as shown in  FIG.  22   . Further, the operations as explained with respect to  FIGS.  14 - 18    are performed, thereby forming an isolation insulating layer  30  and a metal gate structure as shown in  FIG.  23   . 
       FIGS.  24 A- 24 E  show various stages of a sequential manufacturing process of a semiconductor FinFET device according to another embodiment of the present disclosure. It is understood that additional operations may be provided before, during, and after processes shown by  FIGS.  24 A- 24 E , and some of the operations described below can be replaced or eliminated in additional embodiments of the method. The order of the operations can be changed. Materials, configuration, processes and/or dimensions explained with respect to above embodiments may be applied to the following embodiments, and the detailed description thereof may be omitted. 
     In another embodiments, as shown in  FIG.  24 A , the mandrel pattern  14 A′ has a substantially rectangular cross section having substantially vertical side faces. Then, similar to  FIG.  4   , the sixth layer  18  is conformally formed on the mandrel pattern  14 A′ and the exposed third layer  13 . Next, similar to  FIG.  5   , anisotropic etching is performed on the sixth layer  18  to remove the horizontal portions of the sixth layer  18  deposited on the top of the mandrel patterns  14 A′ and the third layer  13  between the adjacent mandrel patterns. Then, similar to  FIG.  6   , the mandrel patterns  14 A′ are removed by one or more dry and/or wet etching operations, thereby leaving the sidewall spacers  18 A as second hard mask patterns, as shown in  FIG.  24 C .  FIG.  24 D  shows a cross sectional view after the fin cut process as explained with respect to  FIGS.  7  and  8   . 
     Here, due to intrinsic stress of the material of the sixth layer  18  (sidewall spacers  18 A) and/or stress differences between the sixth layer  18  and the mandrel patterns  14 A′, after the mandrel pattern  14 A′ is removed, the sidewall spacers  18 A incline in different (opposite) directions as shown in  FIG.  24 C . For example, when viewed from left to right, even number sidewall spacers incline toward the right and odd number sidewall spacers incline toward the left, thereby forming a narrow top space in the spacer-space SS and a wider top space in the mandrel-space MS. When the top space is wider, the additional hard mask layer  18 B is deposited more in the mandrel-space MS, which causes a thicker sidewall spacer. 
     When the sidewall spacers  18 A (second hard mask pattern) are inclined, when patterning the third layer  13  into the hard mask layer, the etching rates between the mandrel-space MS and the spacer-space SS may be different from each other, causing different dimensions (widths) of the patterned hard mask layer in some embodiments. In other embodiments, deposition amounts of the additional hard mask layer  18 A (see,  FIG.  9   ) may be different on the second hard mask patterns  18 A at the mandrel-space MS and the spacer-space SS from each other, causing different dimensions (widths) of the patterned hard mask layer in some embodiments. For example, the deposition amount on the second hard mask patterns  18 A on the sides facing the mandrel-space MS having the wider top space is greater than the deposition amount on the second hard mask patterns  18 A on the sides facing the spacer-space MS having the narrower top space. This causes a wider pattern width for the second hard mask patterns  18 A constituting the mandrel-space MS than the spacer-space SS. Accordingly, the fin structure  20  formed by the operations explained with respect to  FIGS.  9 - 13    have different widths W 11  and W 12 , where W 11 &gt;W 12 , as shown in  FIG.  24 E . 
     In some embodiments, the fin structures formed from the sidewall spacers  18 A constituting the mandrel-space MS have a greater width than the fin structures formed from the sidewall spacers  18 A constituting the spacer-space SS. In some embodiments, the width variation between the fin structures formed from the mandrel-space MS and the fin structures formed from the spacer-space SS is about 0.3-0.5 nm. Moreover, the width variations within the fin structures formed from the mandrel-space MS or the fin structures formed from the spacer-space SS is about 7-10% of the average width, respectively. 
     In the embodiments, explained with respect to  FIGS.  1 - 23   , the mandrel pattern  14 A has a trapezoidal cross section having inclined side faces, as shown in  FIGS.  2  and  3   . The trapezoidal shape compensates for inclination of the sidewall spacers  18 A caused by the intrinsic stress. Accordingly, as shown in  FIGS.  6  and  20   , the second hard mask pattern  18 A extends substantially perpendicular (vertical direction) to the third layer when the mandrel pattern is removed, thereby suppressing width variation of the fin structures  20 . In some embodiments, in the case of  FIGS.  18 - 23   , the width variation between the fin structures formed from the mandrel-space MS and the fin structures formed from the spacer-space SS is about 0.01-0.1 nm in some embodiments, and is about 0.04-0.07 nm in other embodiments. Moreover, the width variations within the fin structures formed from the mandrel-space MS or the fin structures formed from the spacer-space SS is about 0.5-3% of the average width, respectively. In some embodiments, the average width is in a range from about 8 nm to 10 nm. In some embodiments, the width of the fin structure is measured at a level of the upper surface of the isolation insulating layer  30 . 
       FIG.  25    is a line drawing of a TEM (transmission electron microscope) image of the mandrel pattern  14 A. In some embodiments, the sidewall of the mandrel pattern  14 A is defined between 10% of the total height H 1  of the mandrel pattern and the 90% of the height H 1 , and fitted by a linear line within this height range. The sidewall inclination angle θ 1  between the fitted line of the sidewall and the vertical line is in a range from about 5 degrees to about 15 degrees in some embodiments, and is in a range from about 6 degrees to about 10 degrees in other embodiments. When the sidewall inclination angle θ 1  is outside the ranges, the sidewall spacers  18 A may undesirably incline, which may cause fin width variations. 
     In some embodiments, the ratio of the widths at 10% of H 1  to 90% of H 1  is in a range from about 1.3 to about 1.5 and the ratio of the widths at 50% of H 1  to 90% of H 1  is in a range from about 1.1 to about 1.3. When the ratio of the widths is outside the ranges, the sidewall spacers  18 A may undesirably incline, which may cause fin width variations. 
       FIG.  26    is a line drawing of a TEM image of the second hard mask pattern  18 A. In some embodiments, the sidewall of the second hard mask pattern  18 A is defined between 10% of the total height H 2  of the second hard mask pattern (from the bottommost part) and the 90% of the height H 2 , and fitted by a linear line within this height range. The sidewall inclination angle θ 2  between the fitted line of the sidewall and the vertical line is in a range from about −10 degrees (inclined to left (to the mandrel-space MS)) to about 5 degrees (inclined to right (to the spacer-space SS)) in some embodiments, and is in a range from about −7 degrees to about −1 degrees in other embodiments. In other embodiments, the inclination angle θ 2  is in a range from about 1 degree to 7 degrees (e.g., 4-6 degrees) toward the spacer-space. In some embodiments, the inclination angle θ 2  is not zero. When the sidewall inclination angle θ 2  is outside the ranges, the sidewall spacers  18 A may undesirably incline, which may cause fin width variations. As shown in  FIG.  26   , in some embodiments, the third layer  13  is etched more in the spacer-space SS than in the mandrel-space MS. During removal etching of the mandrel pattern  14 A, the third layer  13  may be etched in some embodiments. In some embodiments, depending on the inclination angle θ 2 , the etching amount of the third layer  13  is smaller in the mandrel-space MS than in the space-space SS as shown in  FIG.  14   . In other embodiments, the etching amount of the third layer  13  is greater in the mandrel-space MS than in the space-space SS. 
       FIGS.  27 A and  27 B  are line drawings of TEM images of the fin structures  20  corresponding to  FIGS.  13  and  22   . 
     As set forth above, the width of the fin structures formed from the mandrel-space MS is substantially the same as the width of the fin structures formed from the spacer-space SS. The differences in the width is about 0.2% to about 1.2% because of the use of trapezoidal mandrel patterns  14 A. 
     In some embodiments, the depth of the space between adjacent fin structures may vary depending on whether the space is the mandrel-space MS or the spacer-space SS. In some embodiments, the depth D 1  of the mandrel-space MS is smaller than the depth D 2  of the spacer-space SS as shown in  FIG.  27 B . In some embodiments, D 2 /D 1  is in a range from about 1.03 to about 1.05. In other embodiments, the depth D 1  is greater than the depth D 2 . The depth differences may depend on the inclination angle θ 2  in some embodiments. 
     Further, in the present embodiments, the second hard mask patterns  18 A are designed to have a pitch P 0  at the mandrel-space MS and the spacer-space SS (i.e., on the layout design). In some embodiments, the depth D 0  between the second hard mask pattern having a pitch more than P 0  (e.g., 2P 0 , 3P 0 , . . . ) (the space other than the mandrel-space MS and the spacer-space) is greater than the depths D 1  and D 2 . In some embodiments, D 0 /D 1  or D 0 /D 2  is in a range from about 1.05 to about 1.15. 
       FIGS.  28 - 30    show various stages of a sequential manufacturing process of a semiconductor FinFET device according to embodiments of the present disclosure. It is understood that additional operations may be provided before, during, and after processes shown by  FIGS.  28 - 30   , and some of the operations described below can be replaced or eliminated in additional embodiments of the method. The order of the operations can be changed. Materials, configuration, processes and/or dimensions explained with respect to the above embodiments may be applied to the following embodiments, and the detailed description thereof may be omitted. 
     In some embodiments, depending on materials of the sixth layer  18  and/or the mandrel pattern  14 A, after the mandrel pattern is removed, the sidewall spacers  18 A incline in directions opposite to those shown in  FIG.  24 C  due to internal stress differences. For example, when viewed from left to right even number sidewall spacers incline toward the left and odd number sidewall spacers incline toward the right, thereby forming a narrow top space in the mandrel-space MS and a wider top space in the spacer-space SS. 
     Accordingly, in the embodiments of  FIGS.  28 - 30   , to compensate for the subsequently cause pattern inclination, the mandrel patterns  14 A″ have a reverse tapered shape having a wider top and a smaller bottom as shown in  FIG.  28   . Then, as shown in  FIG.  29   , the sixth layer  18  is conformally formed on the mandrel pattern  14 A″ similar to  FIG.  4   . By the operation explained with respect to  FIG.  5 - 6   , the second hard mask pattern  18 A which is substantially vertically extended can be obtained. 
     In some embodiments, the inclination angle θ 3  is in a range from about 5 degrees to about 15 degrees in some embodiments, and is in a range from about 6 degrees to about 10 degrees in other embodiments. Definition of the inclination angle θ 3  is the same as that of the inclination angle θ 1  except for the angle measurement direction. 
     In some embodiments, the taper angle is adjusted by a feedback operation based on measurement of the inclination angle of the second hard mask pattern  18 A after the mandrel pattern  14 A is removed. When the second hard mask pattern  18 A inclined more than a target inclination (criterion) such that the top space in the mandrel-space MS is wider than the top space in the spacer-space SS, the taper angle (inclination angle)  01  is increased, and when the second hard mask pattern  18 A inclined more than a target inclination such that the top space in the mandrel-space MS is smaller than the top space in the spacer-space, the taper angle (inclination angle)  01  is decreased. The taper angle of the mandrel pattern  14 A can be controlled by controlling one or more of etching gas kinds, flow rates of the etching gas, process pressure, process temperature and/or etching power (e.g., high-frequency power and/or DC bias power). 
     The various embodiments or examples described herein offer several advantages over the existing art. For example, in the present disclosure, the mandrel patterns have a tapered shape to compensate for the inclination of the sidewall spacers (the second hard mask pattern) after the mandrel patterns are removed, and thus it is possible to decrease variation in width of the fin structures patterned using a hard mask pattern formed from the sidewall spacers. 
     It will be understood that not all advantages have been necessarily discussed herein, no particular advantage is required for all embodiments or examples, and other embodiments or examples may offer different advantages. 
     In accordance with one aspect of the present disclosure, in a method of manufacturing a semiconductor device, sacrificial patterns are formed over a hard mask layer disposed over a substrate, sidewall patterns are formed on sidewalls of the sacrificial patterns, the sacrificial patterns are removed, thereby leaving the sidewall patterns as first hard mask patterns, the hard mask layer is patterned by using the first hard mask patters as an etching mask, thereby forming second hard mask patterns, and the substrate is patterned by using the second hard mask patterns as an etching mask, thereby forming fin structures. Each of the first sacrificial patterns has a tapered shape having a top smaller than a bottom. In one or more of the foregoing and following embodiments, the sacrificial patterns are made of poly silicon. In one or more of the foregoing and following embodiments, the first hard mask patterns are made of silicon nitride. In one or more of the foregoing and following embodiments, the first hard mask patterns are inclined. In one or more of the foregoing and following embodiments, an inclination angle of the first hard mask patterns is 1-7 degrees toward a space from which a corresponding one of the sacrificial patterns is removed. In one or more of the foregoing and following embodiments, an inclination angle of the first hard mask patterns is 1-7 degrees toward a space where no sacrificial pattern is formed. In one or more of the foregoing and following embodiments, a taper angle of sacrificial patterns is in a range from 5 degrees to 15 degrees. In one or more of the foregoing and following embodiments, the hard mask layer includes multiple layers of dielectric materials. In one or more of the foregoing and following embodiments, the sidewall patterns are formed by conformally forming a blanket layer by an atomic layer deposition, and performing anisotropic etching to remove horizontal part of the blanket layer. 
     In accordance with another aspect of the present disclosure, in a method of manufacturing a semiconductor device, a first hard mask layer is formed over a substrate, a sacrificial layer is formed over the first hard mask layer, a second hard mask layer is formed over the sacrificial layer, first hard mask patterns are formed by patterning the second hard mask layer, sacrificial patterns are formed by patterning the sacrificial layer using the first hard mask patterns as an etching mask, sidewall patterns are formed on sidewalls of the sacrificial patterns, the sacrificial patterns are removed, thereby leaving the sidewall patterns as second hard mask patterns, part of the second hard mask patterns is removed, after the part of the second hard mask patterns is removed, the hard mask layer is patterned by using the second hard mask patters as an etching mask, thereby forming third hard mask patterns, and the substrate is patterned by using the third hard mask patterns as an etching mask, thereby forming fin structures. Each of the first sacrificial patterns has a tapered shape. In one or more of the foregoing and following embodiments, an additional hard mask layer is further formed over the second hard mask layer. In one or more of the foregoing and following embodiments, an additional hard mask layer is further formed over the third hard mask layer. In one or more of the foregoing and following embodiments, the hard mask layer includes a first layer formed on the substrate, a second layer formed on the first layer and made of a different material than the first layer and a third layer formed on the second layer and made of a different material than the second layer. In one or more of the foregoing and following embodiments, the first layer and the third layer are made of a same material. In one or more of the foregoing and following embodiments, the second hard mask patterns includes a first pair of pattern structures from which a corresponding one of the sacrificial patterns is removed, and a second pair of pattern structures where no sacrificial pattern exist there between, and a width of the fin structures corresponding to the first pair of pattern structures is different from a width of the fin structures corresponding to the second pair of pattern structures. In one or more of the foregoing and following embodiments, a depth of a space between adjacent fin structures corresponding to the first pair of pattern structures is different from a depth of a space between adjacent fin structures corresponding to the second pair of pattern structures. 
     In accordance with another aspect of the present disclosure, in a method of manufacturing a semiconductor device, sacrificial patterns are formed over a hard mask layer disposed over a substrate, sidewall patterns are formed on sidewalls of the sacrificial patterns, the sacrificial patterns are removed, thereby leaving the sidewall patterns as first hard mask patterns, the hard mask layer is patterned by using the first hard mask patters as an etching mask, thereby forming second hard mask patterns, and the substrate is patterned by using the second hard mask patterns as an etching mask, thereby forming fin structures. Each of the first sacrificial patterns has a tapered shape, and a taper angle is adjusted such that an inclination angle of the first hard mask patterns is within a criterion. In one or more of the foregoing and following embodiments, each of the first sacrificial patterns has the tapered shape having a top smaller than a bottom. In one or more of the foregoing and following embodiments, the inclination angle of the first hard mask patterns is 1-7 degrees toward a space from which a corresponding one of the sacrificial patterns is removed. In one or more of the foregoing and following embodiments, the inclination angle of the first hard mask patterns is 1-7 degrees toward a space where no sacrificial pattern is formed. 
     In accordance with another aspect of the present disclosure, a semiconductor device includes a first fin field effect transistor including a first pair of fin structures and a first gate electrode disposed over the first pair of fin structures, and a second fin field effect transistor including a second pair of fin structures and a second gate electrode disposed over a second pair of fin structures. A width of the first pair of fin structures is different from a width of the second pair of fin structures by 0.01-0.1 nm. In one or more of the foregoing and following embodiments, a depth D 1  of a space between the first pair of fin structures from a top of the first pair of fin structures is different from a depth D 2  of a space between the second pair of fin structures from a top of the second pair of fin structures. In one or more of the foregoing and following embodiments, a ratio D 2 /D 1  is in a range from 1.03 to 1.05. In one or more of the foregoing and following embodiments, the first pair of fin structures and the second pair of fin structures are separated by a distance greater than a space between the first pair of fin structures. 
     The foregoing outlines features of several embodiments or examples so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments or examples introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.