阅读说明：本技术 cREO上方的外延层中的局部应变场 (Local strain field in epitaxial layer over cREO ) 是由 A·克拉克 R·佩尔策尔 R·哈蒙德 于 2021-04-14 设计创作，主要内容包括：公开了cREO上方的外延层中的局部应变场。一种用于声波的传输的层状结构(100),该层状结构(100)包括：基板层(102)；以及在基板层(102)上方的第二层(104),其中,第二层(104)包括彼此相邻的多个离散部分(105),多个离散部分(105)中的每个离散部分(105)包括第一子区域(104A)和第二子区域(104B)；以及外延层(108),生长在第二层(104)上方,用于外延层(108)的主平面中的声波的传输,其中,要通过外延层(108)传输的声波的波长的周期(λ)近似等于第一子区域(104A)的宽度(d-(A))与第二子区域(104B)的宽度(d-(B))之和。(Local strain fields in the epitaxial layer over the cREO are disclosed. A layered structure (100) for the transmission of acoustic waves, the layered structure (100) comprising: a substrate layer (102); and a second layer (104) over the substrate layer (102), wherein the second layer (104)) Comprises a plurality of discrete portions (105) adjacent to each other, each discrete portion (105) of the plurality of discrete portions (105) comprising a first sub-region (104A) and a second sub-region (104B); and an epitaxial layer (108) grown over the second layer (104) for transmission of the acoustic wave in a main plane of the epitaxial layer (108), wherein a period (λ) of a wavelength of the acoustic wave to be transmitted through the epitaxial layer (108) is approximately equal to a width (d) of the first sub-region (104A) A ) And the width (d) of the second sub-region (104B) B ) And (4) summing.)

1. A layered structure (100) for the transmission of acoustic waves, the layered structure (100) comprising:

a substrate layer (102);

a second layer (104) over the substrate layer (102), wherein the second layer (104) comprises a plurality of discrete portions (105) adjacent to each other, each discrete portion (105) of the plurality of discrete portions (105) comprising a first sub-region (104A) and a second sub-region (104B); and

an epitaxial layer (108) grown over the second layer (104) for transmission of acoustic waves in a main plane of the epitaxial layer (108),

wherein the period (λ) of the wavelength of the acoustic wave to be transmitted through the epitaxial layer (108) is approximately equal to the width (d) of the first sub-region (104A)_A) And the width (d) of the second sub-region (104B)_B) And (4) summing.

2. The layered structure (100) of claim 1, wherein the first sub-region (104A) is selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof; and

wherein the second subregion (104B) is selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof.

3. The layered structure (100) of claim 1 or 2, wherein the epitaxial layer (108) is one of a semiconductor layer (508), a RE-III-N layer (608), an epitaxial metal layer (708), a crystalline rare earth oxide (cREO) layer (808), and a silicon layer (908).

4. The layered structure (100) of any preceding claim, wherein the substrate (120) comprises one or more group IV elements selected from the group comprising silicon (Si), germanium (Ge), silicon-on-insulator (SOI), and SiGe.

5. The layered structure (100) according to any preceding claim, further comprising an electrode (112) disposed above the epitaxial layer (108), wherein the electrode (112) is distributed based on the period (λ) of the second layer (104).

6. A method of forming a layered structure (100) for transmission of acoustic waves, the method comprising:

providing a substrate layer (102);

etching a surface of the substrate layer (102) to form a second layer (104) over the substrate layer (102), the second layer (104) comprising a plurality of discrete portions (105) adjacent to each other, each discrete portion (105) of the plurality of discrete portions (105) comprising a first sub-region (104A) and a second sub-region (104B), wherein the first sub-region (104A) forms a void;

depositing a material into the voids of the first sub-region (104A) of the second layer (104) to form a local stress in the second layer (104); and

growing an epitaxial layer (108) over the second layer (104) for transmission of acoustic waves,

wherein, when an acoustic wave is to be transmitted through the epitaxial layer (108), the period (λ) of the wavelength of the acoustic wave and the width (d) of the first sub-region (104A) are such that_A) And the width (d) of the second sub-region (104B)_B) And the sum is matched.

7. The method of claim 6, further comprising:

a second sub-region (104B) of the second layer (104) is treated with an anodic etch to render the second sub-region porous.

8. The method of claim 6 or 7, wherein growing epitaxial material into the first sub-region (104A) of the second layer (104) comprises growing a material selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof.

9. The method of any of claims 6 to 8, wherein growing the epitaxial layer (108) over the second layer (104) comprises growing one of a semiconductor layer (508), a RE-III-N layer (608), an epitaxial metal layer (708), a crystalline rare earth oxide (cREO) layer (808), and a silicon layer (908).

10. A method of forming a layered structure (100) for transmission of acoustic waves, the method comprising:

providing a substrate layer (102);

depositing a second layer (104) over the substrate layer (102), the second layer (104) comprising a plurality of discrete second sub-regions (104B) adjacent to one another with gaps therebetween;

depositing a material into the void to form a first sub-region (104A) of the second layer (104) to provide a local stress in the second layer (104); and

growing an epitaxial layer (108) over the second layer (104) for transmission of acoustic waves,

wherein, when an acoustic wave is to be transmitted through the epitaxial layer (108), the period (λ) of the wavelength of the acoustic wave and the width (d) of the first sub-region (104A) are such that_A) And the width (d) of the second sub-region (104B)_B) And the sum is matched.

11. The method of claim 10, further comprising:

the first sub-region (104A) of the second layer (104) is treated with an anodic etch to make the first sub-region porous.

12. The method of claim 10 or 11, further comprising:

a second sub-region (104B) of the second layer (104) is treated with an anodic etch to render the second sub-region porous.

13. The method of claim 11 or 12, wherein growing epitaxial material into the voids of the second layer (104) comprises growing a material selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof.

14. The method of any of claims 11 to 13, wherein growing the epitaxial layer (108) over the second layer (104) comprises growing one of a semiconductor layer (508), a RE-III-N layer (608), an epitaxial metal layer (708), a crystalline rare earth oxide (cREO) layer (808), and a silicon layer (908).

Technical Field

The present application relates to semiconductor designs and, more particularly, to a layered structure for transmitting acoustic waves through a locally stressed epitaxial layer, in which a second layer sandwiched between a substrate and the epitaxial layer comprises discrete regions that locally stress the epitaxial layer and improve the transmission of acoustic waves through the epitaxial layer.

Background

Epitaxy, epitaxial growth, and epitaxial deposition refer to growing or depositing a crystalline layer on a crystalline substrate. The crystalline layer is referred to as an epitaxial layer. The crystalline substrate serves as a template and determines the orientation and lattice spacing of any epitaxial layers. In some examples, the epitaxial layers may be lattice matched or lattice coincident. The lattice-matched crystal layer may have the same or very similar lattice spacing as the top surface of the crystalline substrate. The lattice coincident crystal layer may have a lattice spacing that is an integer multiple of the lattice spacing of the crystal substrate. The quality of epitaxy is based in part on the crystallinity of the crystalline layer. In practice, a high quality epitaxial layer will be a single crystal with minimal defects and little or no grain boundaries. Traditionally, a metal contact layer is applied to the epitaxial structure at some point in downstream processing. Where complex epitaxial structures often contain more than one device function, this may require significant etching and deposition of metal on wafers with a large number of features.

The interaction between the substrate layer and the epitaxial layer is often important for device operation. One example of such interaction between the substrate and the epitaxial layer (e.g., semiconductor layer) occurs in thin film resonators such as RF filters, where the overall acoustic performance is defined by the product of the acoustic impedance of the electrodes and the acoustic impedance of the piezoelectric material. In fact, in order to obtain a high resonance frequency, it is important to make both the electrodes and the piezoelectric material thin.

Disclosure of Invention

In some cases, an Acoustic Bragg Reflector (ABR) is used to surround the resonant cavity to form a resonator. Such resonators may improve efficiency but are much more complex to manufacture. In the present invention, the epitaxial layer may be locally stressed by a second layer sandwiched between the substrate layer and the epitaxial layer. By providing a layer that can locally stress subsequently grown layers, improved epitaxially grown devices can be fabricated. The second layer may include a plurality of discrete regions formed over the substrate layer. Each of the discrete regions is adjacent to another discrete region. Each discrete region comprises at least two different materials, for example, each discrete region may comprise two of the following materials: cERO, non-porous silicon, and fully depleted porous silicon. These discrete regions create local stresses that can be used to manipulate the in-plane properties of an epitaxial layer formed over a second layer having discrete regions.

For example, the discrete region may include a first sub-region and a second sub-region. The discrete regions may include crystalline rare earth oxide (crystalline rare earth oxide) and a second material (e.g., non-porous silicon, silicon oxide (SiO)₂) Etc.). Such discrete regions in the second layer may improve epitaxial growth of additional material over the patterned template wafer.

The epitaxial growth of layers in a layered structure over a semiconductor layer is disclosed in USPN 10,573,686, the contents of USPN 10,573,686 being incorporated herein by reference in its entirety.

By utilizing the cREO in the first sub-region of the discrete regions, the second layer can control the stress applied to the subsequently grown layer. The thickness of the cREO controls the stress applied to the epitaxial layer grown over the second layer of the region containing the cREO. These discrete regions not only promote further epitaxial growth of additional material, but also act as acoustic bragg reflectors (ABS) by reflecting acoustic waves transmitted through the epitaxial layers, similar to, for example, Surface Acoustic Wave (SAW) filters. SAW filters include coupled electromechanical resonators that convert electrical signals into acoustic waves at a desired resonant frequency. The resonant frequency is selected to give the desired bandpass frequency. The combined width of the first and second sub-zones in one discrete region may be defined as the period (λ) of the second layer and is selected in a predetermined relationship to the wavelength of the acoustic wave to be transmitted. In addition, the individual acoustic impedances of the materials in the sub-regions of the discrete regions are considered in determining the period of the second layer and the relative widths of the sub-regions within the period. The discrete regions act as acoustic bragg reflectors by having a pitch defined by the period of the wavelength, the discrete regions imposing an improved efficiency of acoustic wave transmission on the epitaxial layers. That is, the discrete regions reflect wavelengths and prevent them from exiting the epitaxial layers as the acoustic waves propagate through the epitaxial layers.

The layer structure may be included in a Radio Frequency (RF) filter. The epitaxial layer (e.g., semiconductor layer) grown over the second layer may be a piezoelectric material that serves as a coupled electromechanical resonator. The epitaxial layer may be a first electrode for the RF filter. Epitaxial layers are particularly useful for electrodes in RF filters because they provide the high conductivity of metals with a single crystal structure that serves as a template for subsequent growth of single crystal layers (e.g., semiconductor layers) over metal layers. Single crystal semiconductor layers are useful as semiconductor materials in RF filters because they provide higher piezoelectric coefficients, narrower bandwidths, and lower losses.

That is, by utilizing a second layer having discrete regions defined by the period (λ) of the second layer and selected in a predetermined relationship to the wavelength of the acoustic wave to be transmitted, the layered structure may support improved epitaxial growth of additional material over the patterned template wafer, resulting in higher quality of the subsequent film.

A layered structure for transmission of acoustic waves, the layered structure comprising: a substrate layer; a second layer over the substrate layer, wherein the second layer comprises a plurality of discrete portions adjacent to one another, each discrete portion of the plurality of discrete portions comprising a first sub-region and a second sub-region; and an epitaxial layer grown over the second layer for transmission of the acoustic wave in a main plane of the epitaxial layer, wherein a period (λ) of a wavelength of the acoustic wave to be transmitted through the epitaxial layer is approximately equal to a sum of a width of the first sub-region and a width of the second sub-region.

Advantageously, the discrete portions apply local stress to the epitaxial layer, which improves acoustic transmission.

The first subregion may be selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof; and wherein the second subregion may be selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof.

The epitaxial layer may be one of a semiconductor layer, a RE-III-N layer, an epitaxial metal layer, a crystalline rare earth oxide (cREO) layer, and a silicon layer.

The substrate may include one or more group IV elements selected from the group consisting of silicon (Si), germanium (Ge), silicon-on-insulator (SOI), and SiGe.

The layered structure may further comprise an electrode (112) arranged above the epitaxial layer (108), wherein the electrode (112) is distributed based on the period (λ) of the second layer (104).

A method of forming a layered structure for transmission of acoustic waves, the method comprising: providing a substrate layer; etching a surface of the substrate layer to form a second layer over the substrate layer, the second layer comprising a plurality of discrete portions adjacent to one another, each discrete portion of the plurality of discrete portions comprising a first sub-region and a second sub-region, wherein the first sub-region forms a void (void); depositing a material into the voids of the first sub-regions of the second layer to create a local stress in the second layer; and growing an epitaxial layer over the second layer for transmission of the acoustic wave, wherein, when the acoustic wave is to be transmitted through the epitaxial layer, a period (λ) of a wavelength of the acoustic wave matches a sum of a width of the first sub-region and a width of the second sub-region.

Advantageously, the discrete portions apply local stress to the epitaxial layer, which improves acoustic transmission.

The method may further comprise: the second sub-region of the second layer is treated with anodic etching to make the second sub-region porous.

Growing the epitaxial material into the first sub-region of the second layer may include growing a material selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof.

Growing the epitaxial layer over the second layer may include growing one of a semiconductor layer, a RE-III-N layer, an epitaxial metal layer, a crystalline rare earth oxide (cREO) layer, and a silicon layer.

A method of forming a layered structure for transmission of acoustic waves, the method comprising: providing a substrate layer; depositing a second layer over the substrate layer, the second layer comprising a plurality of discrete second sub-regions adjacent to one another with voids therebetween; depositing a material into the void to form a first sub-region of the second layer to provide a local stress in the second layer; and growing an epitaxial layer over the second layer for transmission of the acoustic wave, wherein, when the acoustic wave is to be transmitted through the epitaxial layer, a period (λ) of a wavelength of the acoustic wave matches a sum of a width of the first sub-region and a width of the second sub-region.

Advantageously, the discrete portions apply local stress to the epitaxial layer, which improves acoustic transmission.

The method may further comprise: the first sub-region of the second layer is treated with anodic etching to make the first sub-region porous.

The method may further comprise: the second sub-region of the second layer is treated with anodic etching to make the second sub-region porous.

Growing the epitaxial material into the voids of the second layer may include growing a material selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof.

Growing the epitaxial layer over the second layer may include growing one of a semiconductor layer, a RE-III-N layer, an epitaxial metal layer, a crystalline rare earth oxide (cREO) layer, and a silicon layer.

Drawings

Other features of the present disclosure, its nature and various advantages will be apparent from the following detailed description considered in conjunction with the accompanying drawings in which:

FIG. 1 shows a cross-sectional view of an illustrative layered structure having a second layer between a substrate and a semiconductor layer defined by a period (λ) and selected in a predetermined relationship to an acoustic wavelength, in accordance with an illustrative implementation;

fig. 2-4 illustrate examples of layered structures having various second layers according to illustrative implementations;

fig. 5-9 illustrate examples of layered structures having various epitaxial layers over a second layer in accordance with an illustrative implementation;

fig. 10 is a graph illustrating film stress versus oxide thickness for epitaxial cREO on silicon in accordance with an illustrative implementation;

fig. 11 depicts an exemplary method of forming a layered structure according to an exemplary implementation;

fig. 12 depicts an exemplary method of forming a layered structure according to an exemplary implementation;

fig. 13 shows an example of a layered structure with various epitaxial layers over a second layer in accordance with an illustrative implementation; and

fig. 14 is a flow diagram depicting a method for growing the layered structure shown in fig. 1 according to an illustrative implementation.

Detailed Description

The structures and methods described herein provide a layered structure comprising a substrate layer, a second layer over the substrate, and an epitaxial layer over the second layer. The second layer is integrated between the substrate layer and the epitaxial layer and contains discrete regions to exert localized stress within the epitaxial layer that transmits acoustic waves.

Fig. 1 shows a cross-sectional view of an exemplary layered structure having a second layer between a substrate and a semiconductor layer matched to a period of an acoustic wavelength, in accordance with an exemplary embodiment. The layered structure 100 may be used as an RF filter. The layered structure 100 includes a substrate 102, a second layer 104 over the substrate layer 102, an epitaxial layer 108 grown over the second layer, and an electrode 112 disposed over a top of the epitaxial layer. The second layer 104 includes discrete regions 105. Each discrete region 105 includes a first sub-region 104A and a second sub-region 104B.

The substrate layer 102 may be monocrystalline and may be doped or undoped and have any crystal orientation including on-axis or off-axis <111>, <110>, or <100 >. For example, the substrate 102 may include one or more group IV elements selected from the group consisting of silicon (Si), germanium (Ge), silicon-on-insulator (SOI), and SiGe. Substrate layer 102 may be monolithic.

The second layer 104 includes discrete regions 105. Each discrete region 105 includes a first sub-region 104A and a second sub-region 104B. The discrete regions repeat throughout the second layer, each discrete region being adjacent to another discrete region. The plurality of discrete regions may have different densities and may be horizontally distributed. In one embodiment, the second sub-region 104B of the discrete region 105 may include a periodic variation in porosity through the depth of the second sub-region. In this case, the porosity of the second subregion may be gradually varied and gradually increased. The first and second sub-regions of each discrete region of the second layer may be grown or deposited over the substrate 102 and the epitaxial layer may be grown or deposited over the first and second sub-regions of each discrete region of the second layer. The material for the first layer may be selected from the group consisting of non-porous silicon, crystalline rare earth oxide (cREO), and combinations thereof. A transition layer (not shown) (e.g., in the form of successive sublayers of the substrate 102) may be located between the substrate 102 and any other layers grown or deposited over the substrate 102 to transition the material of the substrate 102 to the material of the second layer (in this example, the second layer 104 comprising two materials). The transition layer may have a thickness of 5-10 nm.

Alternatively, there may be no transition layer between the substrate 102 and the second layer 104. Each discrete region of the second layer may comprise a region of cREO and non-porous silicon, cREO and porous silicon, or porous silicon and non-porous silicon. In such an example, the first and second sub-regions of each discrete region of the second layer 104 are grown or deposited directly over the substrate 102.

The discrete region 105 may have a non-continuous pattern, for example, having a first sub-region 104A and a second sub-region 104B that do not overlap with each other. The first and second sub-regions 104A, 104B of the discrete region 105 of the second layer may take a form similar to a grid, rows, columns, dots, rings, or other irregular shape. The discrete regions 105 provide local stress to an epitaxial layer subsequently grown or deposited over the second layer 104.

In some embodiments, the width of the discrete region, i.e., the width d of the first sub-region 104A_AAnd the width d of the second sub-region 104B_BThe sum may be defined as a period λ that is related to the wavelength of the acoustic wave to be transmitted through the epitaxial layers. For example, the widths of the first and second sub-regions may be varied to produce a period λ that results in the most efficient transmission of acoustic waves through the epitaxial layers.

The epitaxial layer 108 may be in direct contact with the second layer 104. Epitaxial layer 108 may be any III-N material that exhibits a piezoelectric response, where the III-N material includes an alloy of Al, In, and Ga, or any combination of these elements. In some embodiments, the epitaxial layer may be a semiconductor layer, a RE-III-N layer, an epitaxial metal layer, a crystalline rare earth oxide (cREO) layer, or a silicon layer. In some embodiments, the epitaxial layer comprises a doped III-N alloy or RE-III-N alloy (III)_XRE_1-XN), wherein the Rare Earth (RE) element includes lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

The thickness of epitaxial layer 108 may be selected based on equation 1 below, where equation 1 defines the relationship between frequency, speed of sound through the epitaxial layer, and thickness.

f_A＝v_S/(2*t_f) [1]

Wherein f is_AIs the frequency, v_SIs the speed of sound through the piezoelectric layer, and t_fIs the piezoelectric layer thickness.

The electrode 112 disposed above the epitaxial layer 108 is based on the periodic distribution of the layer 104. For example, where the period is one period of the acoustic wave, the electrodes may be spaced apart such that both electrodes fall within one period of the layer 104 (e.g., period λ 2 ═ 2 × λ 1). The period λ of the layer may vary based on the wavelength of the acoustic wave set by the period λ 2 of the electrodes. The period λ of the second layer 104 may be a multiple of the period λ 2 of the electrodes. The multiple of the period λ of the second layer may be in a range from 0.5 to 2 of the period λ 2 of the electrode. For example, the period λ of the second layer may be approximately equal to the period λ of the electrode (period λ ═ period λ 2). In another example, the period λ of the second layer 104 may be 2 times the period λ 2 of the electrode (period λ ═ 2 × period λ 2).

Fig. 2-4 illustrate examples of layered structures having various second layers according to exemplary embodiments. It should be noted that the layered structure 200, 300 or 400 or any feature of the layered structure 200, 300 or 400 may be provided in any of the devices shown in fig. 1 and 5-9. For example, the second layer 204 may be implemented in the layered structure 100 (fig. 1).

In the example shown in fig. 2, the second layer 204 includes discrete regions 205. The discrete region 205 may include a first sub-region 204A and a second sub-region 204B. The first subregion 204A can be non-porous silicon. The second subregion 204B may be porous silicon. In some embodiments, the sum of the width of the first sub-region 204A of non-porous silicon and the width of the second sub-region 204B of porous silicon may be defined as a period related to the wavelength of the acoustic wave expected to propagate through the epitaxial layer. According to such a combination of the first and second sub-regions, the second layer may promote local strain on the grown or deposited additional layer. Such local strain may improve epitaxial growth of additional layers.

In the example shown in fig. 3, the second layer 304 includes discrete regions 305. The discrete region 305 may include a first sub-region 304A and a second sub-region 304B. The first subregion 304A can be a crystalline rare earth oxide. The second subregion 304B can be non-porous silicon. In some embodiments, the sum of the width of the first subregion 304A of cREO and the width of the second subregion 304B of non-porous silicon may be defined as a period related to the wavelength of the acoustic wave expected to propagate through the epitaxial layers. According to such a combination of the first and second sub-regions, the second layer may promote local strain on the grown or deposited additional layer. Such local strain may improve epitaxial growth of additional layers.

In the example of fig. 3, the figure depicts the cREO first sub-region. In some embodiments, the cREO first sub-region may be an island (island) grown over the substrate 102. The left diagram of the schematic diagram 300 depicts mask material portions 304A and 304B on the surface of the substrate layer 102 to define the desired gaps for growth of discrete areas of the cREO first sub-region 304A. For the purposes of this disclosure, discrete regions of cREO may also be referred to as cREO islands. In some embodiments, the discrete regions may be arranged in a particular manner as desired to grow or deposit cREO regions/islands as required by the device. In some embodiments, the conductive layer comprises In₂O₃Or a rare earth nitride or rare earth silicide. This is at 20PCT application No. PCT/US2017/022821 filed on day 16, 3/17 and U.S. provisional patent application No.62,398,416 filed on day 22, 9/2016, each of which is hereby incorporated by reference in its entirety.

In the example shown in fig. 4, the second layer includes discrete regions 405. The discrete region 405 may include a first sub-region 404A and a second sub-region 404B. The first subregion 404A can be a crystalline rare earth oxide. The second subregion 404B can be porous silicon. The porous silicon may be a fully depleted porous region depleted of all free carriers. This is described in U.S. patent application No.16/257,707 filed on 25.1.2019, U.S. patent application No.16/178,495 filed on 1.11.2018, U.S. patent No.10,128,350 filed on 13.11.2018, and U.S. provisional patent application No.62/398,416 filed on 22.9.2016, the respective entireties of each of these applications being incorporated herein by reference.

In some embodiments, the sum of the width of the first subregion 404A of cREO and the width of the second subregion 404B of porous silicon may be defined as a period related to the wavelength of the acoustic wave expected to propagate through the epitaxial layers. According to such a combination of the first and second sub-regions, the second layer may promote local strain on the grown or deposited additional layer. Such local strain may improve epitaxial growth of additional layers.

Fig. 5-9 illustrate examples of layered structures having various epitaxial layers over a second layer in accordance with an illustrative embodiment. It should be noted that the layered structure 500, 600, 700, 800, or 900 or any feature of the layered structure 500, 600, 700, 800, or 900 may be provided in any of the devices shown in fig. 1-4. For example, the epitaxial layer 508 may be implemented in the layered structure 100 (fig. 1).

In the example shown in fig. 5, the layered structure 500 includes a semiconductor layer over the second layer 104. Semiconductor refers to any solid material having a conductivity between that of an insulator and that of most metals. An example semiconductor layer is composed of silicon. The semiconductor layer may include a single intrinsic layer or a plurality of sub-layers. Specifically, the silicon semiconductor layer may include a plurality of porous regionsA domain. The plurality of porous regions may have different densities and may be horizontally distributed. The porous regions 104B of the discrete regions 105 may also include a periodic variation in porosity through the depth of the second sub-region 104B. In this case, the porosity of the second subregion may be gradually varied and gradually increased. The semiconductor layer 108 may include one or more of a group III nitride material, a group III-V material, and a group IV material. Group III-V materials include one or more species from group III of the periodic table (such As B, Al, Ga, In, and Tl) and one or more species from group V of the periodic table (such As N, P, As, Sb, and Bi). Group III nitrides are group III-V materials and include species from group III and nitrogen. Examples of group III nitride materials include GaN, In_XAl_YGA_1-X-YN (x is more than or equal to 0 and y is less than or equal to 1) and/or AlN. Examples of other III-V materials include one or more of GaAs, InP, InAs, InSb, InGaAs, GaAsP, InGaAsP, and the like.

If the semiconductor material is used in a filter and is epitaxial, it facilitates the integration of additional semiconductor elements (not necessarily directly electrically connected to the filter) that may be grown over the filter. For example, transistors (examples of which include field effect transistors, high electron mobility transistors, and heterojunction bipolar transistors) may be grown over the filter, thus reducing the chip area required for a given system.

In the example shown in fig. 6, the layered structure 600 includes a RE-III-N layer 608 over the second layer 104. In the RE-III-N layer, RE represents a rare earth element. III represents group III of the periodic Table (such as B, Al, Ga, In and Tl). N represents nitrogen.

In the example shown in fig. 7, the layered structure 700 includes an epitaxial layer 708 over the second layer 104. The second layer 104, including the crystalline REO region 104A, is a template for an epitaxial metal layer 108, which may include one or more constituent epitaxial metal layers.

The epitaxial metal used may be a rare earth metal or a metal such as ruthenium or molybdenum or other representative metals. The properties to be considered for selecting the metal element for the epitaxial metal layer 708 include resistivity, as well as density, young's modulus, and refractive index, which determine the optical and acoustic properties of the layer.

The buried metal contact layer may be grown using epitaxial deposition of metal over the second layer. The epitaxial metal layer may be grown directly on the second layer and/or directly on the substrate layer. In some examples, an optional transition layer may be between the epitaxial metal layer and the underlying second layer, and/or between the epitaxial metal layer and the underlying substrate. In addition to the electrical advantage that a buried contact layer would bring, there is often an interaction between the metal and the overlying semiconductor that may be utilized. These interactions, such as in RF filters, are more useful when the interface between the metal and the semiconductor (and any intermediate interfaces) is of high quality and few defects. In addition, the epitaxial metal can be made thinner than the sputtered metal while retaining high film quality. This is partly because the quality of the epitaxial interface is higher and as the layer becomes thinner, the proportion of the interface in the bulk material becomes larger. Thus, while thick films are less affected by poor quality interfaces and their properties are determined by bulk material properties, the properties of thin films are more determined by the interface properties. Therefore, a high quality interface is important when depositing thin films.

In addition, an epitaxial metal layer may be used to modify the reflectivity of the epitaxial stack of layers. For devices where light is to be emitted from the top surface, the light emitted towards the substrate is generally considered to be a loss for the total output power. For example, in Vertical Cavity Surface Emitting Lasers (VCSELs), the back mirror needs to have a reflectivity of more than 99.8%. This is difficult to achieve with semiconductor materials alone. The spacing of the discrete regions in the second layer in relation to the wavelength of the acoustic wave improves the epitaxial growth of additional material over the patterned template wafer, which results in higher quality of the subsequent film and increases the reflectivity of the acoustic wave through the epitaxial layers.

In the example shown in fig. 8, the layered structure 800 includes a crystalline rare earth oxide layer 808 over the second layer 104. In some embodiments, the oxygen-to-metal ratio of the REO layer 808 is in the range of 1 to 2.

Crystalline Rare Earth Oxide (REO) epitaxial layers can be used as a semiconductor base such as siliconA template of epitaxial metal on the plate. Crystalline REO is a superior material compared to YSZ for metal epitaxy purposes. First, the interface between the crystalline REO and the second layer is set as part of the epitaxial process. By appropriate selection of the rare earth oxide, 100% (or nearly 100%) cubic, second-phase-free, crystalline REO templates can be epitaxially grown. Other parameters and handling characteristics of crystalline REO that are advantageous for epitaxial stacking of the whole body are the absence of any parasitic charges, a higher density (8.6 to 6.1 g/cm) than YSZ³) And an oxide-silicon interface with a thermal conductivity 5 times better than YSZ. In addition to serving as a template for epitaxial metal growth, the crystalline REO layer may also prevent interdiffusion between the epitaxial metal layer and any underlying substrate. This prevents the formation of e.g. unwanted metal silicides, where the substrate is silicon.

In one example, the crystalline REO layer may be epitaxially grown over the second layer, and the additional processing may include epitaxially growing a metal layer over the crystalline REO layer. A semiconductor layer may be grown over the epitaxial metal layer. The REO layer is a layer containing one or more Rare Earth (RE) species and oxygen. Rare earth species include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

REO is known to exhibit a fluorite type structure. These structures exhibit morphological differences that vary as the atomic weight of the rare earth cations present in the oxide varies (as well as any other factors).

On the other hand, from heavier rare earths (e.g. RE)₂O₃Etc.) formed oxides exhibit distorted CaF₂Form crystal structure of the CaF₂The crystal structure of type includes due to RE<3+>The ionized state of (a) to form an anion vacancy. The crystal structure associated with the heavier rare earth oxides is also known as "Bixbyite".

Having the formula RE₂O₃An illustrative example of a rare earth oxide of (a) is Er₂O₃。Er₂O₃The crystal structure of the unit cell of (a) is a fluorite derivative derived from oxygen vacancies (i.e., bixbyite junctions)Structure). The REO dielectric layer may include a collection of these unit cells.

The number and location of the anion vacancies determine the RE₂O₃Crystal shape of unit cell. The crystal shape of the cell can be designed to provide a suitable match to the lattice constant of the underlying semiconductor substrate. Oxygen vacancies along the body diagonal and/or face diagonal lead to a C-type cubic structure. For example, Er is contributed by two anion vacancies per fluorite unit cell₂O₃Increases to almost twice the unit cell size of Si. This in turn enables direct epitaxial growth of low strain single phase Er on silicon substrates₂O₃。

Furthermore, the number and location of the anion vacancies may be designed to induce a desired strain (tensile or compressive) in the dielectric layer and/or the overgrowth layer. For example, in some embodiments, strain in the semiconductor layer is desired in order to affect carrier mobility.

Each fluorite cell has two oxygen vacancies along the body diagonal. The presence of these two oxygen vacancies allows Er₂O₃The unit cell doubles in size, thereby doubling its lattice constant, which provides an AND<100>A suitable match of the lattice constant of silicon.

In some examples, the oxygen vacancies are at the ends of the facing lines. In some other examples, the oxygen vacancies are distributed between the ends of the body diagonal and the face diagonal.

In the example shown in fig. 9, the layered structure 900 includes a silicon layer 908 over the second layer 104. The silicon layer may be present in a substrate layer below the second layer and an epitaxial layer above the second layer. The porosity of the layer may vary from the substrate layer to the epitaxial layer over the second layer. The porous portions in the substrate 102 may be non-continuous, e.g., with non-continuous and non-overlapping porous portions 102 and 908. For example, the discontinuity of porous portions may extend to all three dimensions, e.g., different porous portions may be two-dimensionally distributed vertically or horizontally in the substrate 102. For another example, different portions or regions (e.g., 102) of the porous portion may have different porosities.

Fig. 10 is a graph showing film stress versus oxide thickness for epitaxial cREO on silicon. As the thickness of the oxide layer (e.g., cREO) increases, the layer exhibits increased stress. Here, the oxide thickness is adjusted to locally stress the subsequently grown or deposited epitaxial layers.

Fig. 11 depicts an exemplary method of forming a layered structure according to an exemplary embodiment. Process 1100 begins at a, where a silicon substrate is obtained. The silicon substrate is patterned and etched to form a recess in a surface of the silicon substrate and to form a second layer from the silicon substrate. As shown in the top view at a, the surface of the second layer may take a form similar to a grid, rows, columns, dots, rings, or other irregular shapes. The second layer is prepared by etching the surface of the substrate layer. At B, a first material is epitaxially grown or deposited over the second layer. The material epitaxially grown or deposited into the recess of the second layer may be a crystalline rare earth oxide. At C, the layered structure is processed by any suitable technique (e.g., Chemical Mechanical Polishing (CMP)) to prepare a surface of the second layer for growing an epitaxial layer over the second layer. At D, the second sub-region of the second layer may be further processed by processing the second sub-region of the second layer into porous silicon.

Fig. 12 depicts an exemplary method of forming a layered structure according to an exemplary embodiment. Process 1200 begins at a, where a silicon substrate comprises a continuous layer of silicon labeled "material B" over the silicon substrate via silicon epitaxy. At B, the continuous silicon layer over the silicon substrate is patterned and etched to form a recess in a surface of the continuous silicon layer. As shown in the top view at B, the surface of the continuous silicon layer may take a form similar to a grid, rows, columns, dots, rings, or other irregular shapes. At C, the layer is epitaxially grown into the recess of the continuous silicon layer via anodic etching of the silicon wafer. The layer epitaxially grown into the recess of the successive layers is porous silicon labeled "material a". This method may form porous regions in the continuous silicon layer, which may improve epitaxial growth of additional material over the patterned template wafer.

Fig. 13 shows an example of a layered structure with various epitaxial layers over a second layer in accordance with an illustrative embodiment. In particular, the examples in fig. 13 include various examples of the second layer discussed above in fig. 2-4 and various examples of the epitaxial layer over the second layer discussed above in fig. 5-9.

Fig. 14 is a flow chart depicting a method for growing the layered structure shown in fig. 1 in accordance with an illustrative embodiment. The process begins at 1402 with obtaining a substrate 102. At 1404, a second layer is prepared by etching a surface of the substrate layer. At 1406, a first material is epitaxially grown or deposited over the substrate layer, the first sub-region 104A. At 1408, an epitaxial layer 108 is epitaxially grown over the second layer 104.

At step 1402, a substrate is provided. In some embodiments, a substrate layer (optionally a monolithic substrate layer) may be grown or otherwise formed in a particular orientation. In some embodiments, the substrate comprises a group IV element selected from the group of silicon (Si), germanium (Ge), silicon-on-insulator (SOI), and silicon carbide (SiC), wherein, in one example, the substrate has an on-axis or up to 10 degree miscut crystal orientation.

Step 1404 includes etching a surface of the substrate layer to form a second layer over the substrate layer. In some embodiments, the second layer is formed with discrete regions, including a first sub-region and a second sub-region. For example, the top sub-layer of the substrate is etched and may form a first sub-region (e.g., a void) and a second sub-region of the original sub-layer.

Step 1406 comprises growing a material into the first sub-region of the second layer. For example, the cREO material is epitaxially deposited or grown into the first sub-region. The first subregion comprising cREO material can locally strain the layered structure.

At 1408, an epitaxial layer is epitaxially grown over the second layer (e.g., see epitaxial layer 108 in fig. 1). By exploiting the local stress of the second layer, the epitaxial layer grown over the second layer is improved.

The growth and/or deposition described herein may be performed using one or more of Chemical Vapor Deposition (CVD), Metal Organic Chemical Vapor Deposition (MOCVD), metal organic vapor phase epitaxy (OMVPE), Atomic Layer Deposition (ALD), Molecular Beam Epitaxy (MBE), Halide Vapor Phase Epitaxy (HVPE), Pulsed Laser Deposition (PLD), and/or Physical Vapor Deposition (PVD).

As described herein, a layer refers to a substantially uniform thickness of material that covers a surface. The layer may be continuous or discontinuous (i.e., have gaps between regions of material). For example, the layer may cover the surface completely or partially, or be divided into discrete regions that collectively define the layer (i.e., regions epitaxially formed using selective regions).

Monolithic integration refers to the formation on the surface of a substrate, typically by deposition of a layer disposed on the surface.

Disposed on means "present on" or "above" the underlying material or layer. The layer may include intermediate layers such as transition layers as needed to ensure a suitable surface. For example, if a material is described as being "disposed on" or "over" a substrate, this may mean (1) the material is in intimate contact with the substrate; or (2) the material is in contact with one or more transition layers located on the substrate.

Single crystal refers to a crystal structure comprising essentially only one type of unit cell. However, the single crystal layer may exhibit some crystal defects such as stacking faults, dislocations, or other commonly occurring crystal defects.

A monodomain refers to a crystal structure that includes substantially only one unit cell structure and substantially only one orientation of the unit cell. In other words, the monodomain crystal does not exhibit twin crystals or antiphase domains.

A single phase refers to a crystal structure that is both single crystal and single domain.

The substrate refers to a material on which a deposition layer is formed. Exemplary substrates include, without limitation: bulk germanium wafers, bulk silicon wafers, wherein the wafer comprises single crystal silicon or germanium of uniform thickness; a composite wafer, such as a silicon-on-insulator wafer comprising a silicon layer disposed on a silicon dioxide layer disposed on a bulk silicon handle wafer; or porous germanium, oxide and germanium over silicon, patterned germanium, germanium tin over germanium and/or the like; or any other material that serves as a base layer upon which or in which devices are formed. Examples of such other materials suitable for use as the substrate layer and bulk substrate, as a function of the application, include, without limitation, alumina, gallium arsenide, indium phosphide, silica gel, silica, borosilicate glass, pyrex (pyrex), and sapphire. The substrate may have a single bulk wafer or multiple sub-layers. In particular, the substrate (e.g., silicon, germanium, etc.) may include a plurality of porous portions. The multiple porous sections may have different densities and may be horizontally distributed or vertically layered.

A miscut substrate refers to a substrate that includes a surface crystal structure oriented at an angle associated with the crystal structure of the substrate. For example, a 6 ° miscut <100> silicon wafer includes a <100> silicon wafer cut at an angle of 6 ° from the <100> crystal orientation toward another primary crystal orientation such as <110 >. Typically, but not necessarily, the miscut will be up to about 20 °. Unless otherwise indicated, the phrase "miscut substrate" includes miscut wafers having any major crystal orientation. That is, <111> wafers miscut toward the <011> direction, <100> wafers miscut toward the <110> direction, and <011> wafers miscut toward the <001> direction.

Semiconductor refers to any solid material having a conductivity between that of an insulator and that of most metals. An example semiconductor layer is composed of silicon. The semiconductor layer may comprise a single bulk wafer or a plurality of sub-layers. Specifically, the silicon semiconductor layer may include a plurality of porous portions. The multiple porous sections may have different densities and may be horizontally distributed or vertically layered.

Semiconductor-on-insulator refers to a composition comprising a single crystal semiconductor layer, a single phase dielectric layer, and a substrate, wherein the dielectric layer is interposed between the semiconductor layer and the substrate. This structure contemplates a prior art silicon-on-insulator ("SOI") composite, which typically includes a single crystalline silicon substrate, a non-single phase dielectric layer (e.g., amorphous silicon dioxide, etc.), and a single crystalline silicon semiconductor layer. Several important differences between the prior art SOI wafer and the semiconductor-on-insulator composition of the present invention are:

the semiconductor-on-insulator composition includes a dielectric layer having a single phase morphology, whereas the SOI wafer does not. In fact, the insulator layer of a typical SOI wafer is not even monocrystalline.

Semiconductor-on-insulator compositions include silicon, germanium, or silicon-germanium "active" layers, whereas prior art SOI wafers use silicon active layers. In other words, exemplary semiconductor-on-insulator compositions include, without limitation: silicon-on-insulator, germanium-on-insulator, and silicon-germanium-on-insulator.

A first layer described and/or depicted herein as being "disposed on," "on," or "over" a second layer may be immediately adjacent to the second layer, or one or more intervening layers may be between the first and second layers. A first layer described and/or depicted herein as being "directly on" or "directly over" a second layer or substrate is immediately adjacent to the second layer or substrate without the presence of intervening layers, except for intervening alloy layers that may be formed as a result of mixing of the first layer with the second layer or substrate. In addition, a first layer described and/or depicted herein as "on," "over," "directly on," or "directly over" a second layer or substrate may cover the entire second layer or substrate, or a portion of the second layer or substrate.

During layer growth, the substrate is placed on the substrate holder so that the top or upper surface is the surface of the substrate or layer furthest from the substrate holder and the bottom or lower surface is the surface of the substrate or layer closest to the substrate holder. Any structure depicted and described herein may be part of a larger structure with additional layers above and/or below the depicted structure. For clarity, the figures herein may omit these additional layers, although these additional layers may be part of the disclosed structures. In addition, the depicted structures may repeat unit wise, even if such repetition is not depicted in the accompanying figures.

As used herein and in the claims that follow, the configuration of "one of a and B" shall mean "a or B".

From the above description, it is apparent that various techniques may be used to implement the concepts described herein without departing from the scope of the disclosure. The described embodiments are to be considered in all respects only as illustrative and not restrictive. It should also be understood that the techniques and structures described herein are not limited to the specific examples described herein, but may be implemented in other examples without departing from the scope of this disclosure. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.