Patent Document

FIELD OF THE INVENTION 
   This invention generally relates to microelectronic integrated circuit (IC) semiconductor device fabrication and more particularly to a multiple gate Field Effect Transistors (FET&#39;s) including a multiple fin shaped FET structure having improved device speed and performance for forming advanced integrated circuit devices. 
   BACKGROUND OF THE INVENTION 
   With increasing demands for advanced device structures, the use of dopants to control the conducting channel in traditional CMOS devices is reaching its limits. As CMOS devices are scaled to the nanometer regime, SOI structures including fully depleted (FD) and partially depleted (PD) structures have provided an evolutionary pathway for MOSFETS operating at low power. CMOS designs below about 0.1 microns are plagued by shortcomings such as short channel effects (SCE) and gate oxide tunneling. In addition, sever restraints are placed on the uniformity of the active silicon channel region which is correspondingly reduced in dimension. One approach to overcome such shortcomings is to change the device structure such that the gate length may be scaled down while using thicker gate oxides and increased active silicon channel dimensions. 
   For example FET designs have included forming non-planar active silicon regions by forming fin-like silicon channel structures also referred to as finFETs and triple gated structures referred to a tri-gate FETs. 
   While these structures have been shown to have acceptable short channel behavior and may be formed with conventional gate oxide thicknesses to overcome gate oxide tunneling, majority carrier mobility is frequently compromised by prior art formation processes. 
   There is therefore a continuing need in the integrated circuit (IC) semiconductor device processing art to develop advanced CMOS FET devices including multiple gate regions. 
   It is therefore an object of the invention to provide an advanced CMOS FET device structure including multiple gate regions. 
   SUMMARY OF THE INVENTION 
   To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a multiple gate region field effect transistor (FET) device for forming up to 6 FET devices and method for forming the same. 
   In a first embodiment, the multiple gate region FET device includes a multiple fin shaped structure comprising a semiconductor material disposed on a substrate; said multiple fin shaped structure comprising substantially parallel spaced apart sidewall portions, each of said sidewall portions comprising major inner and outer surfaces and an upper surface; wherein, each of said surfaces comprises a surface for forming an overlying field effect transistor (FET). 
   In another embodiment, a method for forming the trough shaped structure comprising the multiple gate region FET device includes providing a semiconductor substrate; forming a second semiconductor material on the semiconductor substrate; forming an opening in the second semiconductor material to expose the semiconductor substrate at the opening bottom; lining the opening with a layer of the first semiconducting material; and, removing the second semiconductor material to leave the trough shaped structure. 
   These and other embodiments, aspects and features of the invention will be better understood from a detailed description of the preferred embodiments of the invention, which are further described below in conjunction with the accompanying Figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A-1I  are cross sectional views of an exemplary multiple gate region device at stages in manufacture according to embodiments of the present invention. 
       FIGS. 2A-2E  are cross sectional views of a multiple gate region at stages in manufacture according to embodiments of the present invention. 
       FIG. 3  is a 3-dimensional representation of an exemplary multiple gate region FET device according to an embodiment of the present invention. 
       FIG. 4  is a process flow diagram including several embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The non-planar concave or multiple fin shaped gate region FET structure of the present invention may be used in a variety of circuits including high performance logic, low power logic, high density memory, and high density DRAMs. Moreover, the multiple gate region FET device of the present invention may readily be combined with other elements of analog, digital, as well as mixed signal circuits. 
   For example referring to  FIG. 1A  is shown a cross sectional view of an exemplary portion of a semiconductor substrate  12 , for example a silicon semiconductor wafer. In one embodiment, an epitaxially grown semiconductor layer  14 , preferably strained SiGe, is grown on the silicon substrate  12  by conventional epitaxial growth methods to a thickness of from about 300 Angstroms to about 1500 Angstroms. In another embodiment, shown below in  FIGS. 2A-2E , the substrate may include an insulator layer (e.g., buried oxide) between semiconductor layers, e.g., silicon on insulator (SOI). An antireflective coating (ARC) layer  16 A, preferably an inorganic material such as SiN, SiON, SiC, SiOC, or combinations thereof, also functioning as a hard mask, is preferably formed on the SiGe layer  14 , followed by formation of a patterned photoresist layer (etching mask) having an opening  18 A for etching a trench in the SiGe layer  14 . 
   Referring to  FIG. 1B , an opening  18 B, exposing a portion of the semiconductor substrate  12  at the bottom portion of the opening  18 B is then formed in the SiGe layer  14  by a conventional plasma (dry) etching process (e.g., reactive ion etch) to form the opening  18 B followed by removal of the photoresist etching mask and the ARC hardmask. Preferably, the width of the opening  18 B is formed having a width of from about 20 Angstroms to about 1500 Angstroms. 
   Referring to  FIG. 1C , in an important aspect of the invention a conventional epitaxial growth process is then carried out to grow a layer of silicon  20  to a predetermined thickness. Advantageously, by epitaxially growing the silicon layer  20 , the thickness of the silicon layer may be precisely controlled thereby improving the accuracy of the dimensions of the subsequently formed non-planar FET structure as shown below. The thickness of the epitaxially grown silicon layer  20  is preferably formed having a thickness of from about 10 Angstroms to about 200 Angstroms. Advantageously, the epitaxial layer lining the damascene opening as presented herein for forming the concave (trough shaped) FET structure of the present invention, may advantageously be formed with improved dimension tolerances across a wide range of dimensions compared to prior art processes. 
   Referring to  FIG. 1D , following formation of epi silicon layer  20 , an organic or inorganic filling material layer  22  is formed over the process surface to include backfilling opening  18 B and leaving a thickness portion overlying the SiGe layer  14 . For example, the inorganic filling material may be silicon oxide e.g., formed by a CVD process and the organic filling material may be an organic polymeric (resinous) material formed by a spin-on method or a polymer forming plasma assisted deposition method. If the filling material layer  22  is an organic polymeric material, a thermal baking and/or ultraviolet light treatment is preferably performed following deposition to harden the organic material (induce polymer cross-linking) sufficient for a subsequent planarization process. 
   Referring to  FIG. 1E , a planarization process, preferably a chemical mechanical polish (CMP) process, is then performed to remove surface portions of the filling material layer  22  as well as surface portions of the epi silicon layer  20  overlying the SiGe layer  14  to leave a concave or trough shaped epi silicon structure  20 B filled with remaining filling material portion  22 B. 
   Referring to  FIG. 1F , a wet or dry etching process, preferably a wet etching process, is then carried out to first selectively remove the remaining epi SiGe layer  14  portions to leave the concave (trough shaped) epi silicon structure  20 B filled with filling material portion  22 B. 
   Referring to  FIG. 1G , the filling material portion  22 B is then removed by a conventional wet or dry etching (stripping) process, preferably a wet stripping process, to leave a free standing concave (trough shaped) epi silicon structure  20 B having a width W 1 , of from about 20 Angstroms to about 1500 Angstroms, an epi silicon layer thickness T 1  (fin width) of about 10 Angstroms to about 300 Angstroms, and a height H 1  of about 300 Angstroms to about 1500 Angstroms. It will be appreciated that the epi silicon structure  20 B forms channel regions of a non-planar multiple gate region FET device (multiple FET&#39;s) according to an embodiment of the present invention as shown below in  FIG. 1I . It will also be appreciated that the epi silicon structure  20 B is advantageously formed having a tensile (e.g., when formed over SiGe) or compressive strain to improve channel region charge carrier mobility as a result of having portions grown on a strained semiconductor substrate, e.g. SiGe layer  14 . 
   Referring to  FIG. 1H , an electrical insulator layer  30  is then formed to partially fill “stuff” the epi silicon structure  20 B to provide electrical isolation, for example where 4 to 6 FET&#39;s are subsequently formed on the epi silicon structure  20 B. For example, a CVD deposited or spin on silicon oxide layer may be formed followed by an optional etchback process to expose fin (sidewall) portions of the epi silicon structure  20 B. 
   Referring to  FIG. 1I , an exemplary embodiment of forming a multiple gate structure on the epi silicon structure  20 B is shown in cross section including a contiguous gate electrode portion  34 . A gate dielectric portion  32  is formed by conventional methods on the epi silicon structure  20 B. For example, the gate dielectric material may be formed of silicon dioxide, silicon nitride, nitrogen doped silicon oxide, high-K dielectrics, or combinations thereof. The high-K dielectrics may include metal oxides, metal silicates, metal nitrides, transition metal-oxides, transition metal silicates, metal aluminates, and transition metal nitrides, or combinations thereof. 
   The gate dielectric portion  32  may be formed by any process known in the art, e.g., thermal oxidation, nitridation, sputter deposition, or chemical vapor deposition. When using a high permittivity (high-K) gate dielectric, the dielectric constant is preferably greater than about 3.9. The high-K dielectric may be selected from a group including aluminum oxide (Al 2 O 3 ), hafnium oxide (HfO 2 ), hafnium oxynitride (HfON), hafnium silicate (HfSiO 4 ), zirconium oxide (ZrO 2 ), zirconium oxynitride (ZrON), zirconium silicate (ZrSiO 2 ), yttrium oxide (Y 2 O 3 ), lanthanum oxide (La 2 O 3 ), cerium oxide (CeO 2 ), titanium oxide (TiO 2 ), tantalum oxide (Ta 2 O 5 ), or combinations thereof. 
   A gate electrode portion  34  is then formed by conventional methods over the gate dielectric portion  32  to form a contiguous multiple gate structure. For example, a layer of the gate dielectric material  32  is first deposited followed by deposition of a gate electrode material  34 ; followed by conventional patterning and etching processes to form the multiple gate structure. The gate electrode  34  is preferably formed of a conductive material. The gate electrode  34  may include metal silicide portions electrically connected to other conductive electrical interconnect portions for applying an electrical potential to the multiple FET gate structure. 
   For example, the gate electrode  34  may be formed of conventional polysilicon, polysilicon-germanium, metals, metal silicides, metal nitrides, conductive metal oxides, or combinations thereof. In a preferred embodiment, the gate electrode  34  is formed of polysilicon. Metals or silicides thereof may be formed in an upper portion of the gate electrode  34  by a salicide formation process, for example including cobalt silicide or titanium silicided. Other exemplary metals and silicides thereof may include molybdenum, tungsten, tantalum, platinum, and hafnium. Metal nitrides may include, but are not limited to, molybdenum nitride, tungsten nitride, titanium nitride, and tantalum nitride. Conductive metal oxides may include, but are not limited to, ruthenium oxide and indium tin oxide. 
   It will be appreciated that each of six substantially planer surface portions of the sidewall portions of the epi silicon structure  20 B protruding above the insulator layer  30  may form a separate FET gate structure (e.g., 4 to 6). For example, source and drain regions are formed on the semiconductor substrate adjacent either side the gate dielectric  32  and gate electrode  34  portions as shown in  FIG. 3  below. 
   Referring to  FIG. 2A , in another embodiment, similar processes may be followed to produce a structure similar to that shown in  FIG. 1C  including opening  18 B an epi layer (silicon)  20 B according to the same preferred embodiments including s silicon semiconductor substrate  12  (e.g., Si wafer). In another embodiment, as shown, the substrate includes a lower silicon semiconductor portion  12 A (e.g., Si wafer), a buried oxide layer  12 B, and an epitaxially grown silicon layer  12 C. In this embodiment, the semiconductor layer  20 B is formed of epitaxially grown SiGe on the silicon layer  12 C. 
   Referring to  FIG. 2B , instead of filling the opening  18 B with filling material as shown in the first embodiment, an anisotropic etching process, preferably a dry etching process, is carried out to selectively remove a bottom portion of the epi semiconductor layer  20 B over the bottom portion of opening  18 B to expose the underlying substrate e.g.,  12 B. At the same time, the portion of epi semiconductor layer  20 B overlying the process surface is removed to leave sidewall epi semiconductor portions  20 C and  20 D. 
   Referring to  FIG. 2C , the remaining semiconductor layer portions e.g.,  12 C, adjacent the sidewall epi semiconductor structures  20 C and  20 D, are then removed, preferably according to a wet etching process, to leave free-standing sidewall epi semiconductor structures  20 C and  20 D. The semiconductor structures  20 C and  20 D have the same preferred dimensions as previously shown in  FIG. 1G  e.g., a thickness T 2  (fin width) of about 10 Angstroms to about 200 Angstroms; a fin height H 2  of about 300 Angstroms to about 1500 Angstroms; and, a width (fin spacing) W 2  of about 300 Angstroms to about 1500 Angstroms. 
   Referring to  FIG. 2D , is shown an exemplary embodiment of a multiple FET device gate structure including gate electrode portion  34  and gate dielectric portion  32 . The substrate on which the epi semiconductor (e.g., SiGe) sidewall (fin) portions  20 C and  20 D rest may be an insulator material e.g.,  12 B separating the sidewall portions e.g., forming the bottom portion. As such, an insulator dielectric “stuffing” between sidewall portions (fins) as shown above in  FIG. 1H  and below in  FIG. 2E , need not be formed to provide electrical isolation between the sidewall (fin) portions  20 C and  20 D. The gate dielectric  32  and gate electrode portions  34  may be formed as previously outlined to form from 4 to 6 FET&#39;s on the two sidewall (fin) portions  20 C and  20 D. 
   Still referring to  FIG. 2D , the sidewall (fin) portions  20 C and  20 D provide up to 6 surfaces for forming FET devices where the gate regions for each of the FET devices may be formed on sidewall portion upper surfaces, e.g., B 1 , and on sidewall major surfaces e.g., A 1 , A 2 . 
   It will be appreciated each of the sidewall portions  20 C and  20 D provides a semiconductor substrate including a channel region for forming up to 3 FET devices, for a total of up to 6 FET devices. 
   Referring to  FIG. 2E , where the substrate is a silicon substrate e.g.,  12 , for example, where the epi semiconductor sidewall (fin) portions  20 C and  20 D are formed of epi Si, an insulator dielectric layer  30  is preferably formed to electrically isolate the sidewall (fin) portions as previously shown in  FIG. 1H  prior to forming the gate dielectric  32  and gate electrode portions  34 . 
   Referring to  FIG. 3  is shown an exemplary 3-dimension representation of a portion of a multiple gate region FET device formed by sidewall (fin) epi semiconductor portions e.g.,  20 C and  20 D. For example the sidewall major surfaces of the sidewall epi semiconductor structures e.g., A 2  and A 2 ′, as well as opposite facing sides (not labeled for clarity), may be used to form source/drain regions adjacent either side of gate dielectric  32  and gate electrode  34  portions to form 4 FET devices. In addition, uppermost surface portions e.g., B 1  and B 1 ′ may be used to form source/drain regions for an additional FET device. It will be appreciated that corresponding source/drain, e.g. drain regions are formed on symmetrically adjacent surface portions of the sidewall (fin) portions, e.g., AA 2 , AA 2 ′, BB 1 , and BB 1 ′, to form each FET device. Thus, the number of gate regions (FET devices) that may be formed may be advantageously adjusted from 4 to 6. Also shown is a portion of an electrode electrical interconnect  36  for applying an electrical signal (voltage potential) to the gate electrode portion  34 . Thus, according to the present invention, multiple gate regions and associated source and drain regions forming multiple FET&#39;s, preferably from 4 to 6 FET devices, may be formed on the sidewall (fin) epi semiconductor structures  20 C and  20 D. 
   It will be appreciated by those skilled in the art that charge carrier mobility may be optimized for a particular polarity of conductivity, e.g., NMOS and PMOS devices, in an epitaxial silicon or SiGe portion forming a gate channel region where the substrate is formed with preferred crystal orientations and/or a selected tensile or compressive strain. For example, selection of an appropriate substrate e.g.,  12  orientation results in the formation of preferred channel (crystal) direction and surface orientation of the overlying epitaxial semiconductor structures e.g.,  20 B, or  20 C and  20 D. It will be appreciated that the epi semiconductor structures e.g.,  20 B, or  20 C and  20 D, may be formed with each having a selected strain, for example a tensile strain, preferably for NMOS devices or a compressive strain, preferably for PMOS devices to enhance electron charge carrier mobility and device performance. 
   Thus, a multiple gate region FET structure and method for forming the same has been presented. Advantageously, the number of gate regions may be varied between 4 and 6 gates to form multiple FET&#39;s on fin shaped semiconductor structures. Advantageously, both NMOS and PMOS devices may be formed on the fin shaped semiconductor structures. As a result, higher density and higher speed FET semiconductor devices may be formed having improved device performance. 
   Referring to  FIG. 4  is shown a process flow diagram including several embodiments of the present invention. In process  401  a substrate is provided. In process  403 , a first semiconductor layer is formed on the substrate. In process  405 , an opening is formed in the first semiconductor layer. In process  407 , a second semiconductor layer is formed to line the sidewalls of the opening. In process  409 , the second semiconductor layer is optionally removed from a bottom portion of the opening. In process  411 , a remaining portion of the first semiconductor layer is selectively removed to leave free standing second semiconductor layer portions including sidewall (fin) portions. In process  413 , an insulator layer is optionally formed to fill a space between the sidewall (fin) portions to provide electrical isolation. In process  415 , gate structures and source/drain regions are formed on the epi semiconductor fin portions to form 4 to 6 FET&#39;s. 
   The preferred embodiments, aspects, and features of the invention having been described, it will be apparent to those skilled in the art that numerous variations, modifications, and substitutions may be made without departing from the spirit of the invention as disclosed and further claimed below.

Technology Category: 5