Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/26—Bombardment with radiation
  • H01L21/263—Bombardment with radiation with high-energy radiation
  • H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
  • H01L21/26506—Bombardment with radiation with high-energy radiation producing ion implantation in group IV semiconductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/26—Bombardment with radiation
  • H01L21/263—Bombardment with radiation with high-energy radiation
  • H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
  • H01L21/26506—Bombardment with radiation with high-energy radiation producing ion implantation in group IV semiconductors
  • H01L21/26513—Bombardment with radiation with high-energy radiation producing ion implantation in group IV semiconductors of electrically active species
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/01—Manufacture or treatment
  • H10D30/021—Manufacture or treatment of FETs having insulated gates [IGFET]
  • H10D30/0223—Manufacture or treatment of FETs having insulated gates [IGFET] having source and drain regions or source and drain extensions self-aligned to sides of the gate
  • H10D30/0227—Manufacture or treatment of FETs having insulated gates [IGFET] having source and drain regions or source and drain extensions self-aligned to sides of the gate having both lightly-doped source and drain extensions and source and drain regions self-aligned to the sides of the gate, e.g. lightly-doped drain [LDD] MOSFET or double-diffused drain [DDD] MOSFET
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/60—Insulated-gate field-effect transistors [IGFET]
  • H10D30/601—Insulated-gate field-effect transistors [IGFET] having lightly-doped drain or source extensions, e.g. LDD IGFETs or DDD IGFETs 
  • H10D30/608—Insulated-gate field-effect transistors [IGFET] having lightly-doped drain or source extensions, e.g. LDD IGFETs or DDD IGFETs  having non-planar bodies, e.g. having recessed gate electrodes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/60—Insulated-gate field-effect transistors [IGFET]
  • H10D30/791—Arrangements for exerting mechanical stress on the crystal lattice of the channel regions
  • H10D30/797—Arrangements for exerting mechanical stress on the crystal lattice of the channel regions being in source or drain regions, e.g. SiGe source or drain
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
  • H10D62/01—Manufacture or treatment
  • H10D62/021—Forming source or drain recesses by etching e.g. recessing by etching and then refilling
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
  • H10D62/80—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials
  • H10D62/82—Heterojunctions
  • H10D62/822—Heterojunctions comprising only Group IV materials heterojunctions, e.g. Si/Ge heterojunctions

Definitions

• the present disclosure relates to the fabrication of integrated circuits, and, more particularly, to the formation of transistors having strained channel regions by using embedded silicon/germanium (Si/Ge) to enhance charge carrier mobility in the channel regions of the transistors.
• Si/Ge embedded silicon/germanium
• CMOS complementary transistors
• inverters and other logic gates
• a MOS transistor or generally a field effect transistor, irrespective of whether an N-channel transistor or a P-channel transistor is considered, comprises so-called PN junctions that are formed by an interface of highly doped drain and source regions with an inversely or weakly doped channel region disposed between the drain region and the source region.
• the conductivity of the channel region i.e., the drive current capability of the conductive channel, is controlled by a gate electrode formed in the vicinity of the channel region and separated therefrom by a thin insulating layer.
• the conductivity of the channel region upon formation of a conductive channel due to the application of an appropriate control voltage to the gate electrode, depends on the dopant concentration, the mobility of the charge carriers and, for a given extension of the channel region in the transistor width direction, on the distance between the source and drain regions, which is also referred to as channel length.
• the reduction of the channel length, and associated therewith the reduction of the channel resistivity is a dominant design criterion for accomplishing an increase in the operating speed of the integrated circuits.
• the continuing shrinkage of the transistor dimensions involves a plurality of issues associated therewith that have to be addressed so as to not unduly offset the advantages obtained by steadily decreasing the channel length of MOS transistors.
• highly sophisticated dopant profiles in the vertical direction as well as in the lateral direction, are required in the drain and source regions to provide low sheet and contact resistivity in combination with a desired channel controllability.
• the gate dielectric material may also be adapted to the reduced channel length in order to maintain the required channel controllability.
• some mechanisms for maintaining a high channel controllability may also have a negative influence on the charge carrier mobility in the channel region of the transistor, thereby partially offsetting the advantages gained by the reduction of the channel length.
• One efficient mechanism for increasing the charge carrier mobility is the modification of the lattice structure in the channel region, for instance by creating tensile or compressive stress in the vicinity of the channel region to produce a corresponding strain in the channel region, which results in a modified mobility for electrons and holes, respectively.
• creating tensile strain in the channel region for a standard crystallographic configuration of the active silicon material, i.e., a (100) surface orientation with the channel length aligned to the ⁇ 110> direction increases the mobility of electrons, which in turn may directly translate into a corresponding increase in the conductivity.
• compressive strain in the channel region may increase the mobility of holes, thereby providing the potential for enhancing the performance of P-type transistors.
• strained silicon may be considered as a "new" type of semiconductor material, which may enable the fabrication of fast powerful semiconductor devices without requiring expensive semiconductor materials, while many of the well-established manufacturing techniques may still be used.
• a silicon/germanium layer material next to the channel region to induce a compressive stress that may result in a corresponding strain.
• the transistor performance of P-channel transistors may be considerably enhanced by the introduction of stress-creating materials next to the channel region.
• a strained silicon/germanium material may be formed in the drain and source regions of the transistors, wherein the compressively strained drain and source regions create uniaxial strain in the adjacent silicon channel region.
• Figure Ia schematically illustrates a cross-sectional view of a conventional semiconductor device 100 comprising an advanced P-channel transistor 150, the performance of which may be increased on the basis of a strained silicon/germanium alloy, as explained above.
• the semiconductor device 100 comprises a substrate 101 , such as a silicon substrate, which may have formed thereon a buried insulating layer 102. Furthermore, a crystalline silicon layer 103 is formed on the buried insulating layer 102, thereby representing a silicon- on-insulator (SOI) configuration.
• SOI silicon- on-insulator
• An SOI configuration may be advantageous in view of overall transistor performance since, for instance, the parasitic junction capacitance of the transistor 150 may be reduced compared to a bulk configuration, i.e., a configuration in which a thickness of the silicon layer 103 may be significantly greater than a vertical extension of the transistor 150 into the layer 103.
• the transistor 150 may be formed in and above an "active" region, generally indicated as 103 A, which represents a portion of the semiconductor layer 103, which may be bordered by respective isolation structures (not shown), such as shallow trench isolations and the like.
• the transistor 150 comprises a gate electrode structure 151 which may be understood as a structure including a conductive electrode material 151 A, representing the actual gate electrode, which may be formed on a gate insula- tion layer 15 IB of the structure 151, thereby electrically isolating the gate electrode material
• the gate electrode structure 151 may comprise a sidewall spacer structure 151 C which may include one or more spacer elements, possibly in combination with etch stop liners, depending on the overall device requirements.
• the transistor 150 may comprise drain and source regions 153, which may be defined by an appropriate dopant species, such as boron, which may, in combination with the channel region 152 and any further portion of the active region 103 A positioned between the drain and source regions 153, define PN junctions 153P, which may significantly affect the overall behavior of the transistor 150.
• the degree of overlap of the drain and source regions 153 with the gate electrode 151 A may determine the effective channel length and may thus also determine the capacitive coupling between the gate electrode 151 A and each of the drain and source regions 153.
• the effective length of the PN junctions 153P may finally determine the parasitic junction capacitance of the transistor 150, which may also affect the finally achieved performance of the transistor 150.
• regions of increased counter doping levels 154 may be provided adjacent to the drain and source regions 153 at specified positions within the active region 103 A, which may also be referred to as halo regions.
• the adjustment of punch through behavior, threshold voltage and the like may be accomplished on the basis of complex dopant profiles in the active region 103 A, by appropriately creating the counter doped region 154 in combi- nation with providing a desired concentration profile in the drain and source regions 153.
• the transistor 150 may comprise a silicon/germanium alloy 155 in the drain and source regions 153, wherein the silicon/germanium alloy may have a natural lattice constant that is greater than the lattice constant of the surrounding silicon material in the active region 103 A. Consequently, upon forming the silicon/germanium alloy on the basis of a template material having a reduced lattice constant compared to the natural lattice constant of the material 155, a strained state may be generated and a corresponding strain may also be induced in the channel region 152. As previously explained, for a standard crystallographic orientation of the material of the semiconductor layer 103, a uniaxial compressive strain component, i.e., a strain component along the horizontal direction in
• Figure Ia may be generated and may result in increased hole mobility, thereby also enhancing overall performance of the transistor 150.
• the semiconductor device 100 as shown in Figure 1 a may be formed on the basis of the following conventional process strategies.
• the active region 103 A may be defined on the basis of isolation structures which may be formed by using well-established photolithography, etch, deposition and planarization techniques. Thereafter, the basic doping level in the corresponding active regions 103 A may be established, for instance, by implantation processes.
• the gate electrode structure 151, without the spacer structure 151C may be formed by using complex lithography and patterning regimes to obtain the gate electrode
• the patterning process for the gate electrode structure 151 may also include a patterning of an appropriate cap layer (not shown), which may be used as a mask during the further processing for forming the silicon/germanium material 155.
• appropriate sidewall spacers may be formed on sidewalls of the gate electrode structure 151 so as to encapsulate, in combination with the cap layer, the gate electrode 15 IA and the gate insulation layer 15 IB during the further processing.
• an appropriate mask layer may be formed above other transistor areas in which the strained silicon/germanium material 155 may not be required.
• an etch process may be performed in order to obtain a cavity within the active region 103 A adjacent to the gate electrode 151 A.
• the size and shape of the corresponding cavity may be adjusted on the basis of process parameters of the corresponding etch process, that is, a substantially isotropic etch behavior may result in a corresponding under-etching of a sidewall spacer structure, while a substantially anisotropic etch process may result in more precisely defined boundaries of the cavity, while nevertheless a certain degree of rounding of corresponding corners may be observed.
• corresponding well-established isotropic or anisotropic etch processes may be understood as spatially isotropic or anisotropic processes while, however, an etch rate with respect to different crystallographic orientations within the material of the semiconductor layer 103 may be substantially identical.
• using etch techniques having substantially the same etch rate for any crystallographic orientation may provide a high degree of flexibility in adjusting the size and shape of the corresponding cavities, irrespective of whether "spatially" isotropic or anisotropic etch recipes are used.
• the corre- sponding cavities may be obtained on the basis of a substantially spatially anisotropic etch process with a certain degree of corner rounding.
• a selective epitaxial growth process is typically used to deposit the silicon/germanium material, wherein the fraction of germanium may be selected such that a desired degree of lattice mismatch and thus of strain may be obtained.
• a dopant species may be introduced in order to form a shallow portion of the drain and source regions 153. Frequently, respective shallow implantation regions in the drain and source regions may be referred to as extensions.
• the dopant species required for forming deep areas of the drain and source regions 153 may be introduced during the selective epitaxial growth process, thereby growing the material 155 as a heavily doped semiconductor alloy.
• the drain and source regions 153 may be completed on the basis of implantation sequences, in which the spacer structure 151C may act as an implantation mask for adjusting the lateral profile of the drain and source regions 153.
• the spacer structure 151C may act as an implantation mask for adjusting the lateral profile of the drain and source regions 153.
• one or more anneal cycles may have to be performed in order to adjust the finally desired dopant profile for the drain and source regions 153 and/or to activate dopants which may have been incorporated by ion implantation, and also repair implantation-induced damage.
• a significant degree of dopant diffusion may occur, which may depend on the characteristics of the basic semiconductor material and the size of the dopant atoms. For instance, boron is a very small atom and may thus exhibit a pronounced diffusion activity at elevated temperatures.
• the corresponding diffusion may advance in a highly non-uniform manner due to the presence of the silicon/germanium alloy and the preceding manufacturing steps. That is, upon epitaxially growing the material 155 within the cavity, different crystallographic orientations may be present in the exposed surface portions of the cavity, in particular at the rounded corner portions, thereby creating a plurality of stacking defects of the re-grown material 155.
• the increased lattice constant of the material 155 may also contribute to an increased diffusion activity of boron material.
• the boron species may "penetrate" into the region between the drain and source regions 153 in a spatially highly non-uniform manner.
• Figure Ib schematically illustrates an enlarged view of a corner portion 155A of the material 155 in the vicinity of the PN junction 153P.
• the diffusion activity of the boron species may result in "boron pipes" which may therefore contribute to the significantly increased overall length of the PN junction 153P in combination with nonuniform dopant gradients.
• a corresponding variability in transistor performance may also be observed which may possibly not be compatible with the overall device margins during the entire manufacturing process.
• the per se highly efficient strain-inducing mechanism provided by the material 155 may have to be used in a less pronounced manner in order to obtain increased process margins, while in other conventional solutions the cavity etch process may be performed on the basis of an etch tech- nique, which provides a highly anisotropic etch behavior with respect to a different crystallographic axis of the base material 103.
• etch tech- nique which provides a highly anisotropic etch behavior with respect to a different crystallographic axis of the base material 103.
• crystallographically anisotropic etch techniques are well known in which, for instance, the removal rate in a ⁇ 1 11> direction is significantly less compared to other directions, such as ⁇ 110> or ⁇ 100> orientations.
• applying a respective crystallographically anisotropic etch technique may result in a sigma-like cavity, which may be bordered by the corresponding ⁇ 11 1> surfaces.
• the former approach may not fully exploit the potential of the strain-inducing mechanism provided by the material 155
• the latter approach may require specifically designed etch processes thereby reducing the flexibility in adjusting the size and shape of the corresponding cavities and thus of the strain-inducing material 155.
• the present disclosure is directed to various methods and devices that may avoid, or at least reduce, the effects of one or more of the problems identified above.
• the present disclosure relates to methods and semiconductor devices in which transistor performance may be improved by reducing non-uniformities of a PN junc- tion of drain and source regions, which may comprise a strain-inducing semiconductor alloy, such as silicon/germanium and the like.
• a dopant species such as boron
• the diffusion characteristics of a dopant species may be controlled on the basis of a reduced degree of discontinuities in the vicinity of the PN junction, which may have been created during the preceding manufacturing processes including spatially isotropic or anisotropic etch processes in combi- nation with epitaxial growth techniques for providing the strain-inducing semiconductor alloy.
• the degree of non-uniform diffusion of dopant species may be reduced by incorporating an appropriate diffusion hindering species, such a nitrogen, carbon and the like, which may be positioned along a certain distance of the PN junction, in particular at critical locations such as corners and the like of cavities includ- ing the strained semiconductor alloy, thereby significantly reducing the locally highly nonuniform diffusion behavior, as may be encountered in conventional devices, which may be formed on the basis of spatially isotropic or anisotropic etch techniques. Consequently, respective boron piping effects may be reduced, thereby contributing to enhanced uniform transistor behavior, for instance with respect to the resulting parasitic capacitance of the PN junctions.
• an appropriate diffusion hindering species such as a nitrogen, carbon and the like
• the semiconductor base material may be provided with an appropriate crystallographic configuration that results in a reduced amount of lattice discontinuities, such as stacking faults and the like, upon re-growing the strain-inducing semiconductor alloy.
• the "vertical" and “horizontal” growth directions may represent crystallographic orientations corresponding to equivalent crystal axes, thereby reducing the amount of lattice mismatch and stacking faults in critical locations, such as corners of a corresponding cavity.
• One illustrative method disclosed herein comprises forming drain and source regions of a field effect transistor in an active semiconductor region, wherein the drain and source regions comprise a strain-inducing semiconductor alloy.
• the method additionally comprises positioning a diffusion hindering species within the active semiconductor region at a spatially restricted area corresponding to at least a section of a PN junction formed by the drain and source regions.
• the method comprises annealing the drain and source regions to activate dopants in the drain and source regions.
• a further illustrative method disclosed herein comprises forming a cavity in a crystalline semiconductor region adjacent to a gate electrode structure that is formed above a portion of the crystalline semiconductor region.
• the crystalline semiconductor region comprises a cubic lattice structure and the cavity defines a length direction corresponding to a first crystallographic direction that is substantially equivalent to a second crystallographic direction defined by a surface orientation of the crystalline semiconductor region.
• the method further comprises forming a strain-inducing semiconductor alloy in the cavity and forming drain and source regions in the semiconductor region adjacent to the gate electrode structure.
• One illustrative semiconductor device disclosed herein comprises a transistor formed above a substrate.
• the transistor comprises drain and source regions that are formed in an active region on the basis of boron as a dopant species, wherein the drain and source regions form PN junctions with a channel region of the transistor, wherein the drain and source regions include a strain-inducing semiconductor alloy.
• the transistor comprises a non-doping diffusion hindering species positioned at least along a portion of the PN junctions.
• Figure 1 a schematically illustrates a cross-sectional view of a semiconductor device including an advanced transistor element with a silicon/germanium alloy formed in the drain and source areas, wherein a significant non-uniform boron diffusion may occur, according to conventional strategies;
• Figure Ib schematically illustrates an enlarged view of a critical area with respect to non-uniform boron diffusion of the conventional transistor device of Figure Ia;
• FIGS. 2a-2e schematically illustrate cross-sectional views of a semiconductor device during various manufacturing stages for forming PN junctions of enhanced uniformity on the basis of flexible etch processes and a strain-inducing semiconductor alloy, in accordance with illustrative embodiments;
• Figure 2f schematically illustrates an enlarged view of a critical portion of a PN junction of the device of Figure 2e;
• Figures 3a-3b schematically illustrate a top view and a cross-sectional view, respectively, of a transistor including a semiconductor base material in which crystallographic planes in the horizontal and vertical directions may be equivalent in order to reduce lattice defects upon re-growing a strain-inducing semiconductor alloy, according to illustrative embodiments;
• Figures 3c-3d schematically illustrate a top view and a cross-sectional view, respectively, wherein different types of crystallographic planes may be used, according to still further illustrative embodiments;
• Figures 3e-3f schematically illustrate cross-sectional views at various manufacturing stages in forming a strain-inducing semiconductor alloy on the basis of the principles discussed with reference to Figures 3a-3d so as to reduce diffusion non-uniformities of a dopant species, such as boron, according to still further illustrative embodiments; and
• Figure 4 schematically illustrates a transistor having a strain-inducing semiconductor alloy and PN junctions with enhanced uniformity, according to still further illustrative embodiments.
• the present disclosure provides techniques and semiconductor devices in which enhanced uniformity of PN junctions in transistors comprising a strain-inducing semiconductor alloy in the drain and source regions may be accomplished by reducing the degree of out-diffusion of the dopant species, such as boron, while not unduly reducing the flexibility in forming an appropriate cavity prior to the selective epitaxial growth process for forming the strain-inducing semiconductor alloy.
• the dopant species such as boron
• at least critical portions of the PN junctions may be "embedded" into a diffusion hindering "environment" which may result in a reduced diffusivity of the dopant species.
• an appropriate diffusion hindering species such as nitrogen, carbon, fluorine and the like, may be appropriately positioned in the vicinity of at least critical portions of the PN junctions in order to reduce any "piping" effects, which may conventionally be observed in sophisticated P-channel transistors using a boron dopant species. Consequently, a reduced variability of the transistor characteristics may be accomplished, while generally a tendency to enhance performance may be obtained, since, typically, at least the parasitic junction capacitance may be reduced due to the "straightening" effect of the diffusion hindering species during any heat treatments, which may typically result in dopant diffusion.
• the diffusion hindering species may be provided in the form of a "non-doping" species, a significant influence on the electronic characteristics at the PN junction, except for the enhanced uniformity of the shape and thus of the dopant gradient, may be avoided, thereby also contributing to enhanced overall uniformity of the transistor characteristics.
• the generation of lattice defects may be reduced while nevertheless maintaining a high degree of flexibility in forming the cavity for receiving the strain-inducing semiconductor alloy in that the conditions during the selective epitaxial growth process may be improved by providing more precisely defined template planes in the cavity, which may, for instance, be formed on the basis of a spatially anisotropic etch process.
• substantially vertical and substantially horizontal surfaces of the cavity may represent equivalent crystallographic planes so that the corresponding vertical and horizontal growth of the strain-inducing semiconductor alloy may occur with a reduced degree of lattice mismatch even at critical device areas, such as corners of the cavity, in which typically a plurality of different crystallographic axes may be present.
• critical device areas such as corners of the cavity, in which typically a plurality of different crystallographic axes may be present.
• transistor performance variability may be reduced or enhanced flexibility with respect to using well-established etch techniques may be main- tained, when compared to conventional crystallographically anisotropic etch techniques which may frequently be used in order to reduce the number of lattice defects upon selectively growing a strain-inducing semiconductor alloy.
• Figure 2a schematically illustrates a cross-sectional view of a semiconductor device 200 comprising a substrate 201, above which may be formed a semiconductor layer 203.
• the substrate 201 may represent any appropriate carrier material for forming thereabove the semiconductor layer 203.
• a buried insulating layer 202 such as an oxide layer, a silicon nitride layer and the like may be positioned between the substrate 201 and the semiconductor layer 203, thereby defining an SOI configuration.
• SOI transistors in which generally the advantage of a reduced PN junction capacitance may be obtained due to the fact that the PN junction may extend down to the buried insulating layer 202.
• the semiconductor device 200 may be based on a bulk configuration or may comprise in other device areas a bulk configuration, if deemed appropriate for the overall performance of the semiconductor device 200.
• a portion of the semiconductor layer 203 may represent an active region, which may also be referred to as active region 203A. It should be appreciated that the active region 203A may receive a plurality of transistor elements of the same conductivity type or may include a single transistor, depending on the overall device configuration.
• a plurality of transistor elements of the same conductivity type may be provided within a single active region, wherein at least some of these transistor elements may receive a strain-inducing semiconductor alloy.
• the active region 203 A may be configured to form therein and thereabove a P-channel transistor.
• N-channel transistors may be considered when a corresponding diffusion activity of an N-type dopant species may be considered inappropriate.
• a transistor 250 may be provided in an early manufacturing stage, wherein a gate electrode 25 IA may be formed above a channel region 252 with an intermediate gate insulation layer 25 IB.
• the gate electrode 25 IA may be comprised of any appropriate material in this manufacturing stage, such as polycrystalline silicon and the like, wherein a portion or the entire gate electrode 25 IA may be replaced by a material of enhanced conductivity, depending on the overall process and device requirements.
• the gate insulation layer 25 IB may be comprised of various materials, such as silicon dioxide-based materials, silicon nitride and the like, wherein, in combination with such "conventional" dielectrics or instead of these materials, high-k dielectric materials may also be used, such as hafnium oxide, zirconium oxide and the like.
• a high-k dielectric material is to be understood as a material having a dielectric constant of 10.0 or greater.
• the gate electrode 25 IA may be encapsulated by a cap layer 204 and sidewall spacers 205, which may be comprised of silicon nitride or any other appropriate material that may act as a mask during an etch process 207 in order to provide recesses or cavities 206 adjacent to the gate electrode 251 A, i.e., the sidewall spacers 205.
• the semiconductor device 200 as shown in Figure 2a may be formed on the basis of the following processes. After forming the active region 203A, for instance by providing appropriate isolation structures (not shown), which may involve well-established manufacturing techniques, the gate electrode 25 IA and the gate insulation layer 25 IB may be formed, for instance on the basis of process techniques as previously described with reference to the device 100. During this manufacturing sequence, the cap layer 204 may also be patterned, for instance by forming a respective silicon nitride layer on a corresponding gate electrode material.
• the sidewall spacers 205 may be formed by depositing an appropriate material, such as a silicon nitride material, and anisotropically etching the material above the active region 203A, while covering the silicon nitride material in other device areas in which the formation of spacer elements may not be desired.
• the etch process 207 may be performed on the basis of appropriately selected etch parameters in order to adjust the desired size and shape of the cavities 206.
• the process 207 may represent an etch process in which the removal rate may be substantially independent from any crystallographic orientations of the material of the layer 203.
• the process parameters of the etch process 207 may be selected with respect to a spatial degree of isotropy or anisotropy while the crystallographic orientations of the semiconductor material 203 may not significantly affect the removal rate. That is, well-established plasma-based etch techniques may be used in which the spatial degree of anisotropy or isotropy may by adjusted by selecting parameters, such as bias power, pressure, temperature and the like, in combination with specific organic polymer species, which may more or less protect respective sidewall portions during the etch process, thereby allowing a substantially vertical progression of the etch front.
• any positional statements such as horizontal, vertical and the like, are to be considered with respect to a reference plane, such as an interface 202 S between the buried insulating layer 202 and the semiconductor layer 203.
• a horizontal direction is to be considered as a direction substantially parallel to the interface 202S
• a vertical direction is to be understood as a direction substantially perpendicular to the interface 202S.
• the etch process 207 may represent a substantially anisotropic etch process since a significant under-etching of the spacer structure 205 may be considered inappropriate for the device 200.
• a more isotropic behavior may be adjusted by using appropriate parameters in the process 207, at least during a certain phase of the etch process, when a more rounded shape of the cavity 206 is desired.
• one or more implantation processes may be performed in order to introduce a dopant species and/or a diffusion hindering species, depending on the manufacturing strategy.
• the dopant species for forming drain and source extension regions 253 E may be introduced, for instance in the form of boron or boron fluoride ions, in accordance with the requirements of the characteristics of the transistor 250.
• a diffusion hindering species 256A may additionally be introduced in a separate ion implantation step when an "embedding" of the drain and source extension regions 253E may be considered advantageous for enhancing the overall uniformity of the PN junctions of the transistor 250.
• a restriction of the diffusion activity of, for instance, boron may nevertheless be advantageous in view of more precisely controlling the finally obtained channel length, and thus the resulting overlap capacitance, during subsequent heat treatments of the device 200.
• the incorporation of the diffusion hindering species 256A may thus contribute to enhanced uniformity of the finally obtained transistor characteristics.
• a specifically designed implantation step may be performed so as to position the species 256A around the PN junction 253P such that, during a subsequent diffusion activity of the dopant species, the additional diffusion hindering species 256A may provide an environment in which the average diffusion path length may be less compared to an area defined or delineated by the diffusion hindering species 256 A.
• an area defined by the diffusion hindering species 256 A may be considered as an area in which the concentration of the diffusion hindering species drops to two orders of magnitude compared to a maximum concentration. That is, any area outside of a "diffusion hindering area" may be defined as including the diffusion hindering species with a concentration that is less than two orders of magnitude of the maximum concentration.
• the diffusion hindering species 256A may be positioned with an appropriate concen- tration by selecting appropriate process parameters, such as implantation energy and dose, which may readily be determined on the basis of well-established simulation programs, experience, test runs and the like. For instance, carbon or nitrogen may be incorporated with a concentration of approximately 10 16 - 10 19 atoms per cm 3 or even higher, depending on the concentration of the boron species in the extension regions 253E. This may be accomplished by an implantation dose of approximately 10 14 - 10 16 ions per cm 2 while using implantation energies from several keV to several tens of keV.
• the diffusion hindering species 256 A may be incorporated in this manufacturing stage without forming the extension regions 253E, which may be formed in a later manufacturing stage, depending on the overall process strategy.
• FIG. 2b schematically illustrates the semiconductor device 200 according to further illustrative embodiments in which a diffusion hindering species 256 may be introduced by an ion implantation process 208 prior to filling the cavities 206 by a strain-inducing semicon- ductor alloy.
• the diffusion hindering species 256A may have also been incorporated while the extension regions 253E may be formed or not, depending on the overall strategy, as explained above.
• an appropriate implantation species such as nitrogen, carbon, fluorine and the like, may be introduced on the basis of specifically selected implantation parameters wherein also, as illustrated, a certain tilt angle may be used to provide the desired shape of the area defined by the species 256.
• the diffusion hindering species in this manufacturing stage may be advantageous with respect to process strategies in which the dopant species of deep drain and source areas may be incorporated on the basis of the selective epitaxial growth process to be performed in a later stage so as to fill the cavities 206.
• the region 256 may be formed in an efficient manner during the implantation process 208, while avoiding undue lattice damage in the strain-inducing semiconductor material to be formed in the cavities 206, while, also, due to a moderately low implantation dose, significant damage of exposed surface portions of the cavity 206 may be avoided.
• an appropriate anneal process may be performed in order to reduce lattice damage created by the implantation process 208, if the corresponding damage is considered inappropriate for the subsequent selective epitaxial growth process.
• an appropriate anneal process may be performed in order to reduce lattice damage created by the implantation process 208, if the corresponding damage is considered inappropriate for the subsequent selective epitaxial growth process.
• FIG. 2c schematically illustrates the semiconductor device 200 in a further advanced manufacturing stage according to other illustrative embodiments.
• a strain-inducing semiconductor alloy 255 may be formed in the cavities 206, which may be accomplished by using well-established selective epitaxial growth techniques in which the deposition parameters are adjusted in such a manner that a significant growth of a desired semiconductor alloy, such as silicon/germanium, silicon/carbon and the like, may be obtained at exposed crystalline surface portions, while substantially avoiding any deposition of the semiconductor alloy on other surface areas, such as the dielectric materials of the spacers 205 and the cap layer 204 ( Figure 2a).
• a desired semiconductor alloy such as silicon/germanium, silicon/carbon and the like
• the extension regions 253E may be formed during an implantation process 209 if the regions 253E may not have been formed in an earlier manufacturing stage. That is, after the removal of the spacer elements 205 and the cap layer 204 ( Figure 2a) and forming a corresponding offset spacer (not shown), if required, a dopant species, such as boron, boron difluoride and the like, may be incorporated during the implantation process 209, wherein, in some illustrative embodi- ments, an additional implantation step may be applied in order to incorporate a diffusion hindering species to form the region 256A, if required.
• a dopant species such as boron, boron difluoride and the like
• a tilted implantation process 209A may be performed to introduce an N-type dopant species, if the transistor 250 is to represent a P-channel transistor.
• FIG. 2d schematically illustrates the semiconductor device 200 in a further advanced manufacturing stage.
• a gate electrode structure 251 including the gate electrode 251A, the gate insulation layer 251 B and a spacer structure 251C may be provided in accordance with the overall device requirements. That is, the spacer structure 251C may have an appropriate width as required for the further processing of the device 200.
• the spacer structure 251C may, in combination with the gate electrode 25 IA, be used as an implantation mask for forming deep drain and source areas 253D which, in combination with the extension regions 253E, may define drain and source regions 253 of the transistor 250.
• the spacer structure 251C may include several individual spacer elements if a more complex lateral dopant profile for the drain and source regions 253 is required.
• the spacer structure 251C may represent a mask for a silicidation process to be performed in a later manufacturing stage when the drain and source regions 253 are to be formed on the basis of a dopant species incorporated during the epitaxial growth process for forming the strain-inducing semiconductor alloy 255.
• the dopant species for defining the deep drain and source areas 253D may at least partially be embedded in the diffusion hindering species 256, thereby providing more uniform diffusion behavior of the dopant species during a subsequent anneal process.
• a further implantation process 210 may be performed so as to position the diffusion hindering species 256 at least at critical portions of the active region 203A with respect to lattice defects, as previously explained. That is, the diffusion hindering species 256A may or may not have been incorporated during the preceding manufacturing sequence, depending on the overall process strategy, while, however, the species 256 may be introduced during the process 210 when a respective implantation in an earlier manufacturing stage, for instance as shown in Figure 2b, may not have been performed.
• appropriate process parameters with respect to dose, energy and tilt angle may be selected, for instance on the basis of well-established simulation programs, in order to appropriately position the diffusion hindering species 256.
• the implantation parameters for instance the tilt angle during the process 210, may be selected so that the diffusion hindering species 256 may be provided at a corner portion 255A, at which an enhanced defect density may be created during the preceding manufacturing sequence, as previously explained.
• Figure 2e schematically illustrates the semiconductor device 200 during an anneal process 21 1 during which implantation-induced damage may be cured to a certain degree, while the finally desired profile of the drain and source regions 253 may also be adjusted due to the thermally induced diffusion of the corresponding dopant species, such as boron. Furthermore, if the drain and source regions 253, at least the deep drain and source areas 253D, may have been formed on the basis of an implantation process, the corresponding lattice damage may also be re-crystallized during the anneal process 21 1.
• a significant diffusion of light and small atoms may occur, such as boron, wherein the diffusivity may locally vary according to respective lattice defects and lattice mismatch obtained during the formation of the strain-inducing semiconductor alloy 255. Since the drain and source regions 253, after implantation or deposition, are embedded within the diffusion hindering species 256, a restriction of the diffusion activity may occur, thereby also reducing increased non-uniformities, in particular in critical device areas, such as the corner 255A.
• Figure 2f schematically illustrates an enlarged view of the critical area 255A as shown in Fig 2E.
• a moderate high degree of lattice defects 253F for instance in the form of stacking faults and the like, may be present in the corner portion 255A, which would conventionally result in a highly non-uniform diffusion behavior of the dopant species, such as boron, thereby creating "dopant pipes" that may contribute to a high degree of variability of the junction capacitance, as previously explained.
• the effect of the discontinuities 253F on the diffusion activity may be significantly reduced, thereby forming the PN junction 253P with less pronounced dopant pipes so that the PN junction 253P may be substantially confined within the area formed by the diffusion hindering species 256.
• the resulting junction capacitance may be less and may also exhibit a reduced tolerance, thereby contributing to an improvement of overall device characteristics while also reducing transistor variability in complex semiconductor devices. For example, in densely packed static RAM areas, operational stability of memory areas may be enhanced due to increasing uniformity of the diffusion behavior of the dopant species, such as boron.
• the diffusion hindering species 256A, 256 may be provided along the entire length of the PN junction 253P, as is for instance shown in Figure 2e, while, in other embodiments, the species 256 may be provided at critical areas, such as the corner portion 255A.
• Figure 3 a schematically illustrates a top view of a semiconductor device 300 comprising a transistor 350, which may be formed on a semiconductor layer 303, such as a silicon layer and the like, which may have a cubic lattice structure.
• the basic silicon layer may be provided with a (100) surface orientation, wherein the transistor length direction, i.e., in Figure 3a, the horizontal direction, is oriented along a ⁇ 110> direction.
• crystallographic orientations are typically expressed by so-called Miller indices which describe the position and orientation of a crystal plane by giving the coordinates of three non-collinear atoms lying in the plane. This may conveniently be expressed by the Miller indices which are determined as follows:
• Intercepts of three basis axes are to be determined in terms of the lattice constant of the semiconductor crystal under consideration.
• crystallographic directions may also be expressed on the basis of Miller indices representing the set of smallest integers having the same ratios as the components of a respective vector in the desired direction.
• Miller indices representing the set of smallest integers having the same ratios as the components of a respective vector in the desired direction.
• a crystallographic direction classified by a certain set of Miller indices is perpendicular to the plane represented by the same set of Miller indices.
• the respective surface is a (100) surface while the transistor length direction and the transistor width direction are aligned to ⁇ 110> directions. Consequently, for a crystalline material that has to be grown in a cavity including vertical and horizontal surface portions, the growth directions may represent different crystallographic orientations, i.e., a ⁇ 100> and a ⁇ 110> direction, which may result in increased stacking faults during the selective epitaxial growth process.
• the semiconductor layer 303 may have an appropriate configuration with respect to its crystallographic orientation such that the transistor 350, which may include, in the manufacturing stage shown, a gate electrode 35 IA, a gate insulation layer (not shown) and a sidewall spacer structure 305 is aligned to the crystallographic directions of the semiconductor layer 303 so as to present substantially the same, i.e., equivalent, crystalline growth directions when growing a semiconductor alloy in a recess 306.
• the semiconductor layer 303 may represent a silicon-based crystalline layer having a (100) surface orientation wherein the length direction is aligned along the ⁇ 100> direction. That is, with respect to conventional designs, the length direction is rotated by 45 degrees which may, for instance, be accomplished by correspondingly rotating a silicon wafer with respect to the conventional configuration, wherein typically a respective notch may indicate the ⁇ 110> direction.
• Figure 3b schematically illustrates a cross-sectional view of the device 300 as shown in Figure 3a, wherein schematically the cavity 306 is illustrated as a hatched area, which defines horizontal and vertical growth directions, which are specified by the same Miller indices, i.e., the respective template surfaces for the horizontal and vertical growth process are (100) surfaces, thereby reducing respective stacking faults which may be created in the conventional technique upon growing a strain-inducing semiconductor alloy, such as a silicon/germanium alloy.
• a strain-inducing semiconductor alloy such as a silicon/germanium alloy.
• Figure 3c schematically illustrates the semiconductor device 300 in accordance with further illustrative embodiments in which the semiconductor layer 303 may be provided so as to exhibit a (110) surface orientation so that, for a cubic lattice structure, such as silicon, a ⁇ 100> direction and a ⁇ 1 10> direction may be present with an angle offset of 90 degrees, as indicated by the corresponding arrows in Figure 3c.
• the semiconductor layer 303 may be provided so as to exhibit a (110) surface orientation so that, for a cubic lattice structure, such as silicon, a ⁇ 100> direction and a ⁇ 1 10> direction may be present with an angle offset of 90 degrees, as indicated by the corresponding arrows in Figure 3c.
• Figure 3d schematically illustrates a cross-sectional view of the device of Figure 3c wherein a (100) plane is provided in the drawing plane of Figure 3d while the respective growth directions within the cavity 306 are based on respective ⁇ 110> direction.
• a strain-inducing semiconductor alloy such as silicon/germanium and the like
• a reduced number of stacking faults may be created, thereby providing advantages with respect to the diffusion behavior of a light dopant species, such as boron, as discussed above.
• Figure 3e schematically illustrates the semiconductor device 300 during a corresponding epitaxial growth process 312 in order to fill in a strain-inducing semiconductor alloy in the recesses 306.
• the gate electrode 35 IA and a gate insulation layer 351B may be encapsulated by a cap layer 304 and a sidewall spacer 305.
• substantially equivalent crystal planes as indicated by the Miller indices (hkl) may be encountered for substantially vertical surfaces 306V and substantially horizontal surfaces 306H. Consequently, a reduced degree of lattice discontinuities may be created during the growth process 312.
• Figure 3f schematically illustrates the semiconductor device 300 with a strain- inducing semiconductor alloy 355, which may represent a silicon/germanium material when the transistor 350 may represent a P-channel transistor.
• a diffusion hindering species 356, for instance in the form of nitrogen, carbon, fluorine and the like, may be provided to further reduce diffusion non-uniformities during subsequent anneal processes.
• the diffusion hindering material 356 may be spatially restricted to a critical portion 355 A, at which per se an increased amount of lattice defects may be generated during the preceding growth process 312.
• the diffusion hindering species 356 may be introduced, for instance, prior to the epitaxial growth process 312 on the basis of appropriate implantation parameters, for instance with respect to dose, energy and tilt angle, in order to provide the species 356 with a moderately low concentration and at a desired position.
• the diffusion hindering species 356 may be incorporated by ion implantation during an implantation sequence in which counter doped regions (not shown) also may be formed, as is also previ- ously explained with reference to the devices 100 and 200.
• the diffusion hindering species 356 may be incorporated so as to extend substantially along the entire length of a PN junction still to be formed, similarly as is shown in Figure 2e.
• the diffusion hindering species 356 may be provided, at least at critical device areas, however, at a reduced concentration, which may enhance overall transistor uniformity while even further reducing any effect of the diffusion hindering species in view of the overall device characteristics.
• Figure 4 schematically illustrates a cross-sectional view of a semiconductor device
• a transistor 450 may be formed in and above a portion of the semiconductor layer 403 and may comprise a gate electrode structure 451 , drain and source regions 453, in which a strain-inducing semiconductor material 455 may be provided.
• the transistor 450 may represent a P-channel transistor comprising a silicon/germanium alloy as the semiconductor alloy 455.
• drain and source regions may be formed in the semiconductor layer 403, thereby defining a PN junction 453P, which may have a portion 453N positioned within the strain-inducing material 455.
• a diffusion hindering species 456 may be provided at an interface between the material 455 and material of the semiconductor layer 403.
• the diffusion hindering material may be incorporated in the form of carbon, nitrogen and the like. Consequently, upon performing an anneal process, the diffusion hindering material 456 may appropriately reduce the overall diffusion activity of the dopant species of the drain and source regions 453 at a critical corner portion 455 A, thereby contributing to enhanced uniformity of the respective portion 453N of the PN junction 453P.
• the semiconductor device 400 as shown in Figure 4 may be formed on the basis of similar process techniques as previously described wherein, however, during a corresponding epitaxial growth process, the diffusion hindering species 456 may be incorporated, for instance in the form of nitrogen and the like, which may be accomplished by adding a respective precursor component to the deposition ambient. Thereafter, the supply of the diffusion hindering species into the deposition ambient may be discontinued and the growth process may be continued on the basis of well-established process parameters for obtaining the material 455. Thereafter, the further processing may be continued by forming the drain and source regions 453 and performing an anneal sequence in order to obtain the finally desired dopant profile, wherein the species 456 may provide enhanced overall uniformity, as is also previously discussed.
• the present disclosure relates to techniques and semiconductor devices in which transistor characteristics, such as behavior of P-channel transistors, may be enhanced by providing appropriate conditions during respective anneal processes to reduce diffusion related non-uniformities at the PN junction, in particular at critical portions, which may exhibit an increased defect density due to the preceding formation of a strain-inducing semiconductor alloy.
• a diffusion hindering species may appropriately be positioned at the PN junction so as to provide a neighborhood for the dopant species, such as boron, which may result in a less pronounced diffusion activity.
• the defect density at critical device portions may be reduced by appropriately selecting vertical and horizontal growth directions in a respective cavity, which may be assisted by the introduction of a diffusion hindering species which, however, may be provided with a reduced concentration, thereby also reducing any effects of the diffusion hindering species on the overall transistor characteristics.
• the process sequence for forming cavities adjacent to the gate electrode structure may be performed on the basis of crystallographically isotropic etch techniques, such as plasma-based etch processes with spatial anisotropy or isotropy, thereby providing enhanced flexibility in adjusting the size and shape of the strain-inducing semiconductor alloy.

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