Patent Description:
The performance characteristics of optical modulators that include a polycrystalline silicon (also referred to as Poly-Si) region may be negatively affected by parasitic or access resistances in the polycrystalline region, which is a function of the doping level and mobility of free carriers therein. Higher levels of doping, however, may negatively affect optical signal losses, and the mobility of the free carrier may be bounded by grain boundaries within the Poly-Si region and interfaces between the Poly-Si region and other regions of the optical modulator.

<NPL>et al. , is directed to "A high-speed silicon optical modulator based on a metal-oxide-semiconductor capacitor".

<CIT> is directed to an optical modulator that may include a lower waveguide, an upper waveguide, and a dielectric layer disposed therebetween. The lower waveguide may include a u-shaped region within an optical mode of the light passing through the optical modulator. By conforming the dielectric layer to the surfaces of the u-shaped region, the amount of area of the dielectric layer within a charge modulation region is increased relative to forming the dielectric layer on a single plane. Folding the dielectric layer in this manner may improve modulation efficiency. The u-shaped region may be formed by using ridge structures that extend from an upper surface of the lower waveguide towards the upper waveguide. To aid in lateral confinement of the optical mode, the dielectric layer may be deposited on one side surface of the ridge structures while a different dielectric material is deposited on the opposite side surface.

<CIT> is directed to an electro-optic device wherein a stack structure including a first silicon layer of a first conductivity type and a second silicon layer of a second conductivity type has a rib waveguide shape so as to form an optical confinement area, and a slab portion of a rib waveguide includes an area to which a metal electrode is connected. The slab portion in the area to which the metal electrode is connected is thicker than a surrounding slab portion. The area to which the metal electrode is connected is set so that a range of a distance from the rib waveguide to the area to which the metal electrode is connected is such that when the distance is changed, an effective refractive index of the rib waveguide in a zeroth-order mode does not change.

The invention of the present European patent is set out in the appended claims.

One embodiment presented in this disclosure provides for an optical modulator, comprising: a first silicon region; a polycrystalline silicon region; a gate oxide region joining the first silicon region to a first side of the polycrystalline region; and a second silicon region grown on a second side of the polycrystalline silicon region opposite to the first side, thereby defining an active region of an optical modulator between the first silicon region, the polycrystalline region, the gate oxide region, and the second silicon region. The polycrystalline silicon region may be between <NUM> and <NUM> nanometers thick, and may be formed or patterned to the desired thickness. The second silicon region may be epitaxially grown from the polycrystalline silicon region and patterned into a desired cross sectional shape separately from or in combination with the polycrystalline silicon region.

One embodiment presented in this disclosure provides for a method of forming an optical modulator, the method comprising: forming a polycrystalline layer of silicon on a silicon oxide insulator layer of a base component, wherein the base component includes a first silicon layer and a gate oxide layer of an optical modulator; thinning the polycrystalline layer of silicon into a desired cross-sectional shape; and epitaxially forming a second silicon layer on the polycrystalline layer, wherein the first silicon layer, the gate oxide layer, the polycrystalline layer and the second silicon layer define an active region for the optical modulator.

One embodiment presented in this disclosure provides for optical modulator, comprising: a first silicon region, including a silicon hub that extends a first height from an insulator, a first silicon wing that extends in a first direction from the silicon hub and at a second height from the insulator, and a second silicon wing that extends in a second direction from the silicon hub and at the second height from the insulator; a polycrystalline silicon region extending in parallel to the first silicon region, separated from the first silicon region by a gate oxide layer, the polycrystalline silicon region including a polycrystalline silicon hub that extends a third height from the insulator, a first polycrystalline silicon wing that extends in the first direction from the polycrystalline silicon hub and at a fourth height from the insulator, and a second polycrystalline silicon wing that extends in the second direction from the polycrystalline silicon hub and at the fourth height from the insulator; and a regrown silicon region extending in parallel to the polycrystalline silicon region, in contact with the polycrystalline silicon region and separated from the gate oxide layer by the polycrystalline silicon region, the regrown silicon region including a regrown hub that extends a fifth height from the polycrystalline silicon region, a first regrown wing that extends in the first direction from the regrown hub and at a sixth height from the polycrystalline silicon region, and a second regrown wing that extends in the second direction from the regrown hub and at the sixth height from the polycrystalline silicon region.

The present disclosure provides optical modulators, and methods of fabrication thereof, with improved operational characteristics including a silicon region that is re-grown from a polycrystalline silicon region. For example, in a semiconductor-insulator-semiconductor capacitor (also referred to as a SISCAP) a silicon region is separated from a Poly-Si region by an insulator (such as SiO<NUM>). By removing some of the Poly-Si region and re-growing another silicon region on the remaining Poly-Si region, the resistances in the Poly-Si region are reduced (e.g., due to there being less material included in the active Poly-Si region) and the available bandwidth is increased (e.g., due to the potential grain size in the active Poly-Si region being reduced).

<FIG> illustrates a cross-section in a first plane of an optical modulator <NUM> having a Poly-Si region <NUM> from which a regrown Silicon region <NUM> is formed. The optical modulator <NUM> includes an insulator <NUM>, such as SiO<NUM>, which may be grown or deposited on a substrate <NUM>, such as a Silicon wafer, and in which the other components are encapsulated or captured. For purposes of discussion, terms such as "up" or "above" shall relate to features further from the substrate <NUM>, and terms such as "under" or "below" shall refer to features closer to the substrate <NUM>. For example, as illustrated in <FIG>, the first silicon region <NUM> shall be understood to be located above the substrate <NUM> and below the Poly-Si region <NUM> regardless of the relative orientation of the optical modulator <NUM>.

The first silicon region <NUM> (also referred to as the body region) is fabricated at a first distance above the substrate <NUM>, and is separated from the Poly-Si region <NUM> by a gate oxide region <NUM>. The first silicon region <NUM> includes a silicon hub <NUM> that extends upward from the substrate <NUM>, two silicon wings 122a,b (generally, silicon wings <NUM>) that extend outward from the silicon hub <NUM> in opposing directions, and two silicon interfaces 123a,b (generally, silicon interfaces <NUM>). In some embodiments, the silicon hub <NUM> extends a first height from the substrate <NUM> and the silicon wings <NUM> extend a second, different height from the substrate <NUM>; defining a ridge that projects upward from the first silicon region <NUM>. In some embodiments, the silicon hub <NUM> and the silicon wings <NUM> extend a uniform height from the substrate <NUM> relative to one another. In some embodiments, at an end of the silicon wings <NUM> distal to the silicon hub <NUM>, a corresponding silicon interface <NUM> of a third height is defined, that connects the first silicon region <NUM> with a via <NUM>. Although <FIG> distinguishes the silicon hub <NUM> from the silicon wings <NUM> and silicon interfaces <NUM> via dashed lines, the first silicon region <NUM> is contiguous, and the silicon hub <NUM>, the silicon wings <NUM>, and silicon interfaces <NUM> are defined by relative heights and/or concentrations of dopants applied thereto.

In one embodiment, the first silicon region <NUM> is fabricated from a Silicon semiconductor material that may be doped with various dopants to affect the optical and electrical properties of the first silicon region <NUM>, and the level of doping may vary in the silicon hub <NUM> from the silicon wings <NUM>. For example, the first silicon region <NUM> may include a partially or fully depleted CMOS (Complementary Metal-Oxide Semiconductor) element, strained silicon, Silicon Germanium, monocrystalline silicon, etc. In various embodiments, the silicon wings <NUM> are doped with a higher concentration of the dopant(s) used in the first silicon region <NUM> than the silicon hub <NUM> is doped with. As will be appreciated, a first region may be described as being doped at a higher concentration than a second region, or the second region may be described as being doped at a lower concentration than the first region, interchangeably.

The Poly-Si region <NUM> (also referred to as the polycrystalline region) is fabricated at a second distance above the substrate <NUM>, above the first silicon region <NUM>. The Poly-Si region <NUM> includes a Poly-Si hub <NUM> and two Poly-Si wings 142a,b (generally, Poly-Si wings <NUM>) that extend outward from the Poly-Si hub <NUM> in opposing directions. In some embodiments, the Poly-Si hub <NUM> has a greater height than the Poly-Si wings <NUM> and extends as a downward projecting ridge (i.e., towards the substrate <NUM>) relative to the Poly-Si wings <NUM>. In some embodiments, the Poly-Si hub <NUM> and the Poly-Si wings <NUM> extend a uniform height from the substrate <NUM> relative to one another. Although <FIG> distinguishes the Poly-Si hub <NUM> from the Poly-Si wings <NUM> via dashed lines, the Poly-Si region <NUM> is contiguous, and the Poly-Si hub <NUM> and the Poly-Si wings <NUM> are defined by relative heights and/or concentrations of dopants applied thereto.

The Poly-Si region <NUM> is fabricated from a polycrystalline Silicon material that may be doped with various dopants to affect the optical and electrical properties of the Poly-Si region <NUM>, and the level of doping may vary in the Poly-Si hub <NUM> from the Poly-Si wings <NUM>. In embodiments in which the Poly-Si region <NUM> is P doped, the first silicon region <NUM> is N doped, and in embodiments in which the Poly-Si region <NUM> is N doped, the first silicon region <NUM> is P doped. In various embodiments, the Poly-Si wings <NUM> are doped with a higher concentration of the dopant(s) used in the Poly-Si region <NUM> than the Poly-Si hub <NUM> is doped with.

The regrown Silicon region <NUM> (also referred to as the regrown region or the second silicon region) is fabricated on the upper surface of the Poly-Si region <NUM> (relative to the substrate <NUM>). The regrown silicon region <NUM> includes a regrown hubs <NUM> two regrown wings 152a,b (generally, regrown wings <NUM>) that extend outward from the regrown hub <NUM> in opposing directions, and two regrown interfaces 153a,b (generally, regrown interfaces <NUM>). In some embodiments, the regrown hub <NUM> has a greater height than the regrown wings <NUM>, and extends upwards (i.e., away from the substrate <NUM>) relative to the regrown wings <NUM>; defining a ridge that projects upward from the regrown silicon region <NUM>. In some embodiments, the regrown hub <NUM> and the regrown wings <NUM> extend a uniform height from the Poly-Si region <NUM> relative to one another. Each regrown wing <NUM> is connected to the regrown hub <NUM> on one end, and to a regrown interface <NUM> at the other end. The regrown interfaces <NUM> extend upward relative to the regrown wings <NUM>, and may extend upward further than, the same as, or less than the regrown hub <NUM> in various embodiments.

Although <FIG> distinguishes the various regions (e.g., regrown hub <NUM>, the regrown wings <NUM>, regrown interfaces <NUM>) via dashed lines, the regrown region <NUM> is contiguous, and the regrown hub <NUM>, the regrown wings <NUM>, and regrown interfaces <NUM> are defined by relative heights and/or concentrations of dopants applied thereto.

The regrown silicon region <NUM> is fabricated from a Silicon semiconductor material that may be doped with various dopants to affect the optical and electrical properties of the regrown silicon region <NUM>, and the level of doping may vary in the regrown hub <NUM> from the regrown wings <NUM> and regrown interfaces <NUM>. In some embodiments, the regrown silicon region <NUM> may include a partially or fully depleted CMOS (Complementary Metal-Oxide Semiconductor) element, strained silicon, Silicon Germanium, monocrystalline silicon, etc. In various embodiments, the regrown region <NUM> is epitaxially grown from the Poly-Si region <NUM> and shares the PIN doping characteristics with the Poly-Si region <NUM> or may remain individually doped. In various embodiments, the regrown wings <NUM> and regrown interfaces <NUM> are doped with a higher concentration of the dopant(s) used in the regrown silicon region <NUM> than the regrown hub <NUM> is doped with. The regrown interfaces <NUM> provide contact points for the regrown Silicon region <NUM> with the vias <NUM>, and in various embodiments may be doped with the same or a different concentration of dopants than the regrown wings <NUM>. Together with the Poly-Si region <NUM>, the regrown silicon region <NUM> forms a gate region for the optical modulator <NUM>.

The gate oxide region <NUM> separates the first silicon region <NUM> from the Poly-Si region <NUM> between the respective silicon hub <NUM> and the Poly-Si hub <NUM>. The gate oxide region <NUM> may be a thin layer of the insulator <NUM> or a different material that forms the dielectric of the optical modulator <NUM>. In various embodiments, the gate oxide region <NUM> is formed from several layers of materials including: Silicon Dioxide, Silicon Oxy-Nitride, various high-k dielectrics (including Hafnium and Zirconium based films), Aluminum Oxide, among others. Although <FIG> distinguishes the gate oxide region <NUM> from the insulator <NUM> via dashed lines, the gate oxide region <NUM> may be contiguous with the insulator <NUM>, and is defined by the dopants/materials applied thereto or the relative positions of the silicon hub <NUM>, Poly-Si hub <NUM>, and regrown hub <NUM>. The silicon hub <NUM>, gate oxide region <NUM>, Poly-Si hub <NUM>, and regrown hub <NUM> collectively form an active region <NUM> for an active waveguide (directing light into or out of the page relative to the view illustrated in <FIG>). The gate oxide region <NUM> provides for the efficient transport of carriers into and out of the first silicon region <NUM> and the Poly-Si region <NUM> when an electric field is applied across the contact pads 160a-d (generally, contact pads <NUM>) of the optical modulator <NUM> to bias the optical modulator <NUM> and affect/modulate optical signals applied thereto.

The contact pads <NUM> are metallizations on a surface of the optical modulator <NUM> that allow for external devices to be electrically connected to various layers of the optical modulator <NUM> through vertical electrical connectors, such as the illustrated vias 170a-d (generally, vias <NUM>). Although illustrated in <FIG> on an upper surface of the optical modulator <NUM>, in other embodiments, one or more contact pads <NUM> may be located on different surfaces of the optical modulator <NUM>, such as an underside of the substrate <NUM>. Additionally, although illustrated as direct traces from the contact pads <NUM> to the various wings of the regions, in various embodiments, a via <NUM> may be a Through Silicon Via (TSV) that runs from a contact pad <NUM> on one surface to a corresponding contact pad <NUM> on an opposite surface of the optical modulator <NUM>, to allow multiple contact points for external electrical devices to connect to the region that the via <NUM> runs through.

<FIG> illustrate different stepwise fabrication options for an optical modulator <NUM> according to embodiments of the present disclosure. The relative sizes and shapes of the various layers used in <FIG> are provided for illustrative purposes, and are not limiting as to the actual thickness and sizes of the layers relative to one another. In various embodiments, the Poly-Si region <NUM> is patterned to have a thickness in a range between <NUM>-<NUM> nanometers (nm) (± <NUM>%), although a Poly-Si wing <NUM> may be patterned to have a thickness less than a corresponding Poly-Si hub <NUM>. For example, a Poly-Si region <NUM> may have Poly-Si wings <NUM> patterned to have thicknesses between a range of <NUM>-<NUM>, and the Poly-Si hub <NUM> with a thickness between a range of <NUM>-<NUM>.

<FIG> illustrates the layered formation of components 200a-d of an optical modulator <NUM> with a winged modulator region with a broad gate to form an active region <NUM>. In <FIG>, a first component 200a includes a silicon substrate <NUM>, a Buried Oxide (BOX) layer <NUM>, and a first silicon layer <NUM>, which may correspond to the substrate <NUM>, (a portion of) the insulator <NUM>, and the first silicon region <NUM> of <FIG>, respectively. A fabricator may fabricate or otherwise use a wafer corresponding to the first component 200a as a base component for fabricating optical modulators <NUM> on a wafer-level scale.

The fabricator forms a second oxide layer <NUM> above the first silicon layer <NUM>, and forms a Poly-Si layer <NUM> of a first thickness above the second oxide layer <NUM> to create the second component 200b from the first component 200a. To form the third component 200c, the fabricator trims the Poly-Si layer <NUM> of the second component 200b to a new, desired height. In various embodiments, the second oxide layer may correspond to the gate oxide region <NUM> and/or the insulator <NUM> of <FIG>, and the Poly-Si layer <NUM> corresponds to the Poly-Si region <NUM> of <FIG>. In various embodiments, the fabricator may use various chemical or physical polishing and etching processes to trim the Poly-Si layer <NUM> from the first height to the second height.

Once the Poly-Si layer <NUM> is trimmed to the desired height, the fabricator epitaxially grows a second silicon layer <NUM> on the Poly-Si layer <NUM>. In various embodiments, the second silicon layer <NUM> corresponds to the regrown silicon region <NUM> of <FIG>. The fabricator may pattern, etch, and planarize the second silicon layer <NUM> into a desired shape to thereby form the fifth component 200e from the fourth component 200d. As illustrated in <FIG>, the fabricator has imparted a winged shaped to the second silicon layer <NUM>, in which a regrown hub <NUM> extends a greater height above the Poly-Si layer <NUM> than the corresponding regrown wings <NUM>.

The fabricator may then form various contact pads <NUM>, vias <NUM>, and encapsulate and passivate the active layers in additional insulator material in the fifth component 200e to form an optical modulator <NUM>.

<FIG> illustrates the layered formation of components 300a-d of an optical modulator <NUM> with a winged modulator region with a narrow gate to form an active region <NUM>. In <FIG>, a first component 300a includes a silicon substrate <NUM>, a first BOX layer first <NUM>, a first silicon layer <NUM>, and a second BOX layer <NUM> which may correspond to the substrate <NUM>, (a portion of) the insulator <NUM>, the first silicon region <NUM>, and (a portion of) the insulator <NUM> and the gate oxide region <NUM> of <FIG>, respectively. A fabricator may fabricate or otherwise use a wafer corresponding to the first component 300a as a base component for fabricating optical modulators <NUM> on a wafer-level scale. Unlike the broad gated winged modulator in <FIG>, which includes a first silicon layer <NUM> with a silicon hub <NUM> of a shared height to the silicon wings <NUM>, the narrow gated winged modulator of <FIG> includes a first silicon layer <NUM> with a silicon hub <NUM> of a greater height than the corresponding silicon wings <NUM>.

The fabricator forms a Poly-Si layer <NUM> of a first thickness above the second BOX layer <NUM> of the first component 300a to form the second component 300b. To form the third component 300c, the fabricator trims the Poly-Si layer <NUM> of the second component 300b to a new, desired height, and epitaxially grows a second silicon layer <NUM> on the Poly-Si layer <NUM>. In various embodiments, the Poly-Si layer <NUM> and the second silicon layer <NUM> correspond to the Poly-Si region <NUM> and regrown silicon region <NUM> of <FIG>, respectively. In various embodiments, the fabricator may use various chemical or physical polishing and etching processes to trim the Poly-Si layer <NUM> from the first height to a desired second height.

Once the Poly-Si layer <NUM> is trimmed to the desired height, the fabricator may pattern, etch, and planarize the second silicon layer <NUM> into a desired shape to thereby form the fourth component 300d from the third component 300c. For example, the second silicon layer <NUM> may be trimmed to a new, desired height to be planar, or as illustrated in <FIG>, may be selectively trimmed to provide a regrown hub <NUM> and regrown wings <NUM>. The fabricator may then form various contact pads <NUM>, vias <NUM>, and encapsulate and passivate the active layers in additional insulator material.

<FIG> illustrates the layered formation of components 400a-d of an optical modulator <NUM> with an inverted winged modulator region with a broad gate to form an active region <NUM>. In <FIG>, a first component 400a includes a silicon substrate <NUM>, a first BOX layer first <NUM>, a first silicon layer <NUM>, and a second BOX layer <NUM> which may correspond to the substrate <NUM>, (a portion of) the insulator <NUM>, the first silicon region <NUM>, and (a portion of) the insulator <NUM> and the gate oxide region <NUM> of <FIG>, respectively. A fabricator may fabricate or otherwise use a wafer corresponding to the first component 400a as a base component for fabricating optical modulators <NUM> on a wafer-level scale. Unlike the broad gated winged modulator region illustrated in <FIG>, which includes a planar Poly-Si layer <NUM>, the inverted winged modulator region illustrated in <FIG> defines a Poly-Si layer <NUM> with a Poly-Si hub <NUM> that projects downward (i.e., towards the silicon substrate <NUM>) relative to the corresponding Poly-Si wings <NUM>.

The fabricator forms the second component 400b from the first component 400a by etching a slot <NUM> into the second BOX layer <NUM> using use various chemical or physical etching processes. When the fabricator forms a Poly-Si layer <NUM> above the second BOX layer <NUM> to form the third component 400c from the second component 400b, the slot <NUM> is filled with the Poly-Si material and defines the downward projecting Poly-Si hub <NUM>.

To form the fourth component 400d from the third component 400c, the fabricator trims the Poly-Si layer <NUM> to a desired height, and epitaxially grows a second silicon layer <NUM> on the Poly-Si layer <NUM>. In various embodiments, the Poly-Si layer <NUM> and the second silicon layer <NUM> correspond to the Poly-Si region <NUM> and regrown silicon region <NUM> of <FIG>, respectively. In various embodiments, the fabricator may use various chemical or physical polishing and etching processes to trim the Poly-Si layer <NUM> from the first height to a second height.

Once the Poly-Si layer <NUM> is trimmed to the desired height, the fabricator may pattern, etch, and planarize the second silicon layer <NUM> into a desired shape. The fabricator may then form various contact pads <NUM>, vias <NUM>, and encapsulate and passivate the active layers in additional insulator material.

<FIG> illustrates the layered formation of components 500a-d of an optical modulator <NUM> with an inverted winged modulator region with a narrow gate to form an active region <NUM>. In <FIG>, a first component 500a includes a silicon substrate <NUM>, a first BOX layer <NUM>, a first silicon layer <NUM>, and a second BOX layer <NUM> which may correspond to the substrate <NUM>, (a portion of) the insulator <NUM>, the first silicon region <NUM>, and (a portion of) the insulator <NUM> and the gate oxide region <NUM> of <FIG>, respectively. A fabricator may fabricate or otherwise use a wafer corresponding to the first component 500a as a base component for fabricating optical modulators <NUM> on a wafer-level scale. Unlike the broad gated inverted winged modulator region illustrated in <FIG>, which includes a planar first silicon layer <NUM>, the inverted winged modulator region illustrated in <FIG> defines a first silicon layer <NUM> that includes a silicon hub <NUM> that projects upwards (i.e., away from the silicon substrate <NUM>) relative to the corresponding silicon wings <NUM>.

The fabricator forms the second component 500b by etching a slot <NUM> into the second BOX layer <NUM> of the first component 500a using use various chemical or physical etching processes. When the fabricator forms a Poly-Si layer <NUM> above the second BOX layer <NUM> to form the third component 500c from the second component 500b, the slot <NUM> is filled with the Poly-Si material and defines the downward projecting portion of the Poly-Si hub <NUM> in the slot <NUM>.

To form the fourth component 500d, the fabricator trims the Poly-Si layer <NUM> of the third component 500c to a desired height, thus defining the heights for the Poly-Si hub <NUM> and the Poly-Si wings <NUM> on which the fabricator grows a second silicon layer <NUM>. In various embodiments, the Poly-Si layer <NUM> and the second silicon layer <NUM> correspond to the Poly-Si region <NUM> and regrown silicon region <NUM> of <FIG>, respectively. In various embodiments, the fabricator may use various chemical or physical etching processes to trim the Poly-Si layer <NUM> from the first height to a second height.

<FIG> illustrates the layered formation of components 600a-d of an optical modulator <NUM> with a two-plate modulator region to form an active region <NUM>. In some embodiments, the cross sectional views of the components 600a-d in <FIG> represent a cross sectional plane of view perpendicular to the cross sectional planes of view illustrated in <FIG> (e.g., a ZX plane compared to a ZY plane). In some embodiments, the cross sectional views of the components 600a-d in <FIG> represent a cross sectional plane of view parallel or coplanar to the cross sectional planes of view illustrated in <FIG>.

In <FIG>, a first component 600a includes a silicon substrate <NUM>, a BOX layer <NUM>, and a first silicon plate <NUM>, which may correspond to the substrate <NUM>, the insulator <NUM> and gate oxide region <NUM>, and the first silicon region <NUM> of <FIG>, respectively. The BOX layer <NUM> includes an insulator portion <NUM> that is coplanar with the first silicon plate <NUM>; unlike the modulators illustrated in <FIG>, the first silicon plate <NUM> does not extend across the cross-sectioned plane of the components 600a-d. The BOX layer <NUM> extends for a first length, and encapsulates the first silicon plate <NUM> at a first height from the silicon substrate <NUM>, which extends for a second length (that is less than the first length) from a first side of the BOX layer <NUM> to a center of the components 600a-d. A fabricator may fabricate or otherwise use a wafer corresponding to the first component 600a as a base component for fabricating optical modulators <NUM> on a wafer-level scale.

The fabricator forms the second component 600b from the first component 600a by forming a Poly-Si layer <NUM> above the BOX layer <NUM> at a second height above the silicon substrate <NUM>. To form the third component 600c from the second component 600b, the fabricator patterns the Poly-Si layer <NUM> to a desired height, and the fabricator may use various chemical or physical etching processes to trim the Poly-Si layer <NUM> from the first height to a second height. Once patterned, the fabricator epitaxially grows a regrown silicon layer <NUM> on the Poly-Si layer <NUM>. In various embodiments, the Poly-Si layer <NUM> and the regrown silicon layer <NUM> correspond to the Poly-Si region <NUM> and regrown silicon region <NUM> of <FIG>, respectively.

To form the fourth component 600d from the third component 600c, the fabricator patterns the Poly-Si layer <NUM> and the silicon layer <NUM> into a Poly-Si plate <NUM> and a regrown silicon plate <NUM> respectively. The Poly-Si plate <NUM> and the regrown silicon plate <NUM> do not extend across the cross-sectioned plane of the fourth components 600d, but extend partially across the length of the BOX layer <NUM> to vertically overlap with at least a portion of the first silicon plate <NUM>, to form the active region <NUM> therebetween. Stated differently, the Poly-Si plate <NUM> and the regrown silicon plate <NUM> extend from the center of the fourth component 600d (to which the first silicon plate <NUM> extends) in an opposite direction from which the silicon plate <NUM> extends. The fabricator also expands the BOX layer <NUM> to at least to the height of the second silicon plate <NUM>. The fabricator may then form various contact pads <NUM>, vias <NUM>, and encapsulate and passivate the active layers in additional insulator material.

<FIG> is a flowchart of a method <NUM> for producing an optical modulator <NUM> with a regrown region <NUM> that is epitaxially re-grown over a polycrystalline silicon region <NUM>. Method <NUM> begins at block <NUM>, where a fabricator patterns a first layer of Silicon on a base component for the optical modulator <NUM> and fills the patterned Silicon region <NUM> with a dielectric. In various embodiments, the fabricator forms the base component from a silicon substrate (such as a wafer) to include an insulator (such as SiO<NUM>) over which a silicon region <NUM> is formed, thus forming a Silicon On Insulator (SOI) region, from which further formation of the optical modulator <NUM> is based. In some embodiments, the silicon region <NUM> is of a uniform height (e.g., as per the first silicon layer <NUM> in component 200a in <FIG>), while in other embodiments, the silicon region <NUM> includes a silicon hub <NUM> and silicon wings <NUM> of differing heights (e.g., as per the first silicon layer <NUM> in <FIG>).

The silicon region <NUM> may be doped with various dopants with different concentrations at different portions of the silicon region <NUM> (e.g., N doped with a first dopant concentration in the silicon wings <NUM> and a second dopant concentration in the silicon hub <NUM>). In various embodiments, the silicon region <NUM> is doped with different concentrations of dopants at different locations by applying various masks to the semiconductor material during formation. In various embodiments, the base component extends to cover and encapsulate the silicon regions <NUM>, and may encapsulate the silicon region <NUM> with a planar surface (e.g., as per second oxide layer <NUM> in <FIG>) or with a surface defining a slot for the growth of a Poly-Si hub <NUM> (e.g., as per second BOX layer <NUM> with slot <NUM> in <FIG>).

At block <NUM>, the fabricator forms the dielectric of the gate oxide region <NUM> over the silicon hub <NUM>. The gate oxide region <NUM> may be formed from one or more thin layers of various dielectrics, such as, for example: Silicon Dioxide, Silicon Oxy-Nitride, various high-k dielectrics (including Hafnium and Zirconium high-k dielectric films), Aluminum Oxide high-k dielectric film, etc. The various layers may include one or more dopants.

At block <NUM>, the fabricator forms a layer of Poly-Si material over the gate oxide region <NUM> and the SOI region. In various embodiments, the Poly-Si material forms a Poly-Si region <NUM> that is of a uniform height (e.g., as per Poly-Si layer <NUM> in <FIG>) or that includes a Poly-Si hub <NUM> and Poly-Si wings <NUM> of differing heights (e.g., as per Poly-Si layer <NUM> in <FIG>). The Poly-Si region <NUM> may be doped with various dopants with different concentrations at different portions of the Poly-Si region <NUM> (e.g., P doped with a first dopant concentration in the Poly-Si wings <NUM> and a second dopant concentration in the Poly-Si hub <NUM>). In various embodiments, the Poly-Si region <NUM> is doped with different concentrations of dopants at different locations by applying various masks to the Poly-Si material during formation. In various embodiments, the fabricator forms the Poly-Si region <NUM> at a first height and trims or patterns the Poly-Si region <NUM> into a desired height. In various embodiments, the desired height of the Poly-Si region <NUM> is selected to be between <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, or <NUM>-<NUM> according to a desired manufacturing tolerance. The Poly-Si region <NUM> is doped to exhibit a different conductivity type than the silicon region <NUM>, for example, the Poly-Si region <NUM> is N-doped when the silicon region <NUM> is P-doped, and vice versa.

The exposed surface of the patterned/trimmed Poly-Si region <NUM> provides a material matrix on which the fabricator epitaxially grows a second silicon region (i.e., the regrown silicon region <NUM>) at block <NUM>. The regrown silicon region <NUM> may be doped with various dopants with different concentrations at different portions of the regrown silicon region <NUM> (e.g., P doped with a first dopant concentration in the regrown wings <NUM> and regrown interfaces <NUM>, and a second dopant concentration in the regrown hub <NUM>). In various embodiments, the regrown silicon region <NUM> is doped with different concentrations of dopants at different locations by applying various masks to the semiconductor material during formation. The regrown silicon region <NUM> is doped to exhibit the same conductivity type as the Poly-Si region <NUM>, for example, the regrown silicon region <NUM> is N-doped when the Poly-Si region <NUM> is N-doped, and the regrown silicon region <NUM> is P-doped when the Poly-Si region <NUM> is P-doped, although the regrown silicon region <NUM> and the Poly-Si region <NUM> may be doped with different dopants and at different concentrations.

At block <NUM>, the fabricator patterns the second silicon region <NUM> into a desired cross-sectional shape (e.g., defining a regrown hub <NUM> and/or regrown interfaces <NUM> of various heights relative to the regrown wings <NUM>). In some embodiments, the fabricator patterns the regrown silicon region <NUM> at block <NUM>, shaping the silicon region into a uniform desired height (e.g., as per the second silicon layer <NUM> in <FIG>) or into differing desired heights for the regrown hub <NUM> and regrown wings <NUM> (e.g., as per the second silicon layer <NUM> in <FIG>). In some embodiments, the fabricator patterns the regrown silicon region <NUM> and the underlying Poly-Si region <NUM> at block <NUM>, forming a second silicon plate <NUM> and a Poly-Si plate <NUM> respectively that run across a portion of the length of the optical modulator <NUM> to overlap vertically with a portion of the further underlying first silicon plater <NUM> or silicon region <NUM> to provide the active region for the optical modulator <NUM>.

At block <NUM>, the fabricator passivates and finalizes the optical modulator <NUM>. In various embodiments, passivation includes encapsulating the active components that are not already encapsulated in an insulator material (e.g., the Poly-Si region <NUM> and regrown silicon region <NUM>) in additional insulator material and patterning the insulator material to a desired height. Other finalization operations include, but at not limited to: the metallization of the optical modulator <NUM> (e.g., the formation of contact pads <NUM> and vias <NUM>), dicing individual dies of an optical modulator <NUM> from a wafer, and incorporating the optical modulator <NUM> into an optoelectronic circuit. Method <NUM> may then conclude.

In the current disclosure, reference is made to various embodiments. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the described features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Additionally, when elements of the embodiments are described in the form of "at least one of A and B," it will be understood that embodiments including element A exclusively, including element B exclusively, and including element A and B are each contemplated. Furthermore, although some embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the aspects, features, embodiments and advantages disclosed herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to "the invention" shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s).

Claim 1:
An optical modulator (<NUM>), comprising:
a first silicon region (<NUM>);
a polycrystalline silicon region (<NUM>);
a gate oxide region (<NUM>) joining the first silicon region to a first side of the polycrystalline silicon region; and further characterized in that it comprises
a second silicon region (<NUM>) grown on a second side of the polycrystalline silicon region opposite to the first side, thereby defining an active region of an optical modulator between the first silicon region, the polycrystalline region, the gate oxide region, and the second silicon region.