TW201419527A - Epitaxial layer and method of forming the same - Google Patents

Abstract

A method of forming an epitaxial layer includes the following steps. At first, a first epitaxial growth process is performed to form a first epitaxial layer on a substrate, and a gas source of silicon, a gas source of carbon, a gas source of phosphorous and a gas source of germanium are introduced during the first epitaxial growth process to form the first epitaxial layer including silicon, carbon, phosphorous and germanium. Subsequently, a second epitaxial growth process is performed to form a second epitaxial layer, and a number of elements in the second epitaxial layer is smaller than a number of elements in the first epitaxial layer.

Description

Epitaxial layer and manufacturing method thereof

The invention relates to an epitaxial layer and a manufacturing method thereof, in particular to an epitaxial layer having germanium, carbon, phosphorus and germanium and a manufacturing method thereof.

As semiconductors move toward miniaturized sizes, the size of the gate, source, and drain of the transistor continues to shrink as the feature size decreases. However, due to the limitation of the physical properties of the material, the reduction of the size of the gate, the source and the drain may cause a decrease in the amount of the current-determining carrier in the transistor element, thereby affecting the performance of the transistor. Therefore, increasing the carrier mobility to increase the speed of the MOS transistor has become a major issue in the field of semiconductor technology.

Among the currently known techniques, there is a method of comprehensively manufacturing mechanical stress by changing the composition of the substrate, thereby increasing the mobility of the carrier. For example, a germanium germanium (SiGe) layer is epitaxially formed on a germanium substrate, and a silicon epitaxial layer is formed on the germanium germanium layer. The lattice constant of germanium is 5.431 angstroms (angstrom, A). ), the lattice constant of ytterbium is 5.646 angstroms, and the bismuth epitaxial layer with a small lattice constant is deposited on the bismuth telluride layer, which will undergo lateral tension and cause strain. This layer can be called strain enthalpy ( Strained silicon) layer. The strained ruthenium layer facilitates the formation of a better quality gate oxide layer and provides stress to the channel region of the transistor to improve its carrier mobility. In addition, there is also a selective epitaxial growth method, after the gate is formed, the source/drain on both sides of the gate A germanium (SiGe) epitaxial layer is formed in the region to provide compressive stress to enhance the operating speed of the PMOS; or a germanium carbon (SiC) epitaxial layer is formed in the NMOS process to provide tensile stress to enhance the operating speed of the NMOS.

However, when the source/drain region of the NMOS has an N-type dopant and a strained germanium epitaxial layer that provides tensile stress, such as a phosphorus-doped germanium carbon epitaxial layer, due to the atomic radius of the phosphorus element (1.26 angstroms) The atomic radius (0.91 angstrom) with carbon is smaller than the atomic radius of the lanthanum element (1.46 angstrom). This difference in atomic radius will be detrimental to the twinning of the phosphorus-doped bismuth carbon epitaxial layer in the lattice direction (111). On the circular surface, the phosphorus-doped germanium carbon epitaxial layer cannot fill the grooves on both sides of the NMOS gate structure to form a complete source/drain region, thereby affecting the electrical performance of the NMOS. Therefore, how to improve the strain 矽 epitaxy process with elemental compositions with different atomic radii is a subject that the related art desires to improve.

One of the objects of the present invention is to provide an epitaxial layer having elements having different atomic radii and a method of fabricating the epitaxial layer to obtain an epitaxial layer having a desired shape to improve the electrical performance of the semiconductor device.

A preferred embodiment of the present invention provides a method of making an epitaxial layer comprising the following steps. First, a first epitaxial growth process is performed to form a first epitaxial layer on a substrate, wherein the first epitaxial growth process includes simultaneously introducing a gas such as a germanium source, a carbon source, a phosphorus source, and a germanium source. The first epitaxial layer is made of germanium, carbon, phosphorus, and antimony. Then, performing a second epitaxial growth process to form a second epitaxial layer, and the second epitaxial layer includes the element The number of species is less than the number of element species included in the first epitaxial layer.

Another preferred embodiment of the present invention provides an epitaxial layer comprising: a first epitaxial layer and a second epitaxial layer. The first epitaxial layer substantially comprises germanium, carbon, phosphorus, and antimony. The second epitaxial layer is disposed on the first epitaxial layer, wherein the second epitaxial layer includes a number of element types smaller than the number of element types included in the first epitaxial layer.

The present invention relates an element having an atomic radius close to that of germanium, for example, germanium doped in a germanium carbon phosphorus (SiCP) epitaxial layer to form an epitaxial layer containing germanium, carbon, phosphorus, germanium, etc., which can slow down the germanium and carbon. Or the influence of the lattice mismatch caused by the difference in the atomic radius of bismuth and phosphorus, so that the epitaxial layer can be formed on the surface of the germanium wafer in the lattice direction (111) to obtain the desired epitaxial layer. shape. In addition, the epitaxial layer process of the present invention can be further combined with the source/drain region process to improve the electrical performance of the MOS transistor.

The present invention will be further understood by those of ordinary skill in the art to which the present invention pertains. .

Please refer to Figures 1 to 2. 1 to 2 are schematic views showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention. As shown in FIG. 1, a substrate 10 including at least one recess 12 is provided. The substrate 10 may comprise, for example, a semiconductor composed of a gallium arsenide, a silicon-on-insulator (SOI) layer, an epitaxial layer, a germanium layer or other semiconductor substrate material. Substrate. The substrate 10 can further include at least one gate structure 14 and at least one shallow trench isolation 16 and the recess 12 is located in the active region between the gate structure 14 and the shallow trench isolation 16. The gate structure 14 includes a gate dielectric layer 18, a gate conductive layer 20 disposed on the gate dielectric layer 18, and a cap layer 22 selectively disposed on the gate conductive layer 20. The gate dielectric layer 18 may be formed of an insulating material such as tantalum oxide, oxynitride or a high-k dielectric layer having a dielectric constant greater than 4 formed by a process such as thermal oxidation or deposition. The gate conductive layer 20 may be composed of a conductive material such as polysilicon, metal halide or a metal material having a specific work function. The selectively formed cap layer 22 may be composed of a dielectric material such as tantalum nitride, hafnium oxide or hafnium oxynitride. The shallow trench isolation 16 may comprise an insulating material such as tantalum oxide. The method of forming the gate structure 14 and the shallow trench isolation 16 is well known to those skilled in the art and will not be further described herein.

The method of forming the recess 12 may include the following steps: first, selectively forming a first sidewall 24 on the sidewall of each gate structure 14; thereafter, using the formed gate structure 14 and the first sidewall spacer 24 as a mask The mask is subjected to an etching process, such as an anisotropic dry etching process, in which grooves 12 are formed in the substrate 10 on either side of the gate structure 14. In addition, a dry and wet etching process may be mixed to form various shapes such as a barrel shape (a straight shape), a hexagonal shape, and a polygonal groove 12, which are formed in the groove 12 of such a shape in a subsequent process. The epitaxial layer in the layer will provide greater stress to channel region C. Wherein, the first sidewalls 24 may comprise a single film layer or a composite film layer structure composed of yttrium oxide, tantalum nitride or a combination thereof or other suitable materials, and the first sidewalls 24 may serve as a temporary sidewall (disposable) Spacer), therefore, after the selective epitaxial growth process is completed, the first sidewalls 24 can be selectively partially or completely removed, but not limited thereto. In addition, other single or multiple layers of sidewalls (not shown) may be selectively included between the first sidewall 24 and the gate structure 14.

In order to form a better quality epitaxial layer in the recess 12, a pre-clean step may be performed before the subsequent epitaxial layer process, for example, by diluting a hydrofluoric acid aqueous solution or containing sulfuric acid. A cleaning solution such as hydrogen peroxide or a SPM mixed solution of deionized water to remove an impurity such as a native oxide layer on the surface of the groove 12. In addition, a pre-bake may be performed, such as heating the substrate 10 in a chamber in which hydrogen is introduced to remove the native oxide layer or residual cleaning liquid on the surface of the recess 12.

As shown in FIG. 2, a first epitaxial growth process is performed to form a first epitaxial layer 26 on the substrate 10. Performing the first epitaxial growth process includes performing an in-situ epitaxial process, in detail, in a reaction chamber having a specific operating pressure system of substantially between about 10 and 50 torr Medium, a source gas such as a helium source, a carbon source, a phosphorus source, and a helium source, and a carrier gas such as a nitrogen gas and a hydrogen gas are introduced at the same time, that is, when a bismuth carbon phosphate epitaxial layer is formed, At the same time, it is doped in the bismuth carbon phosphorus epitaxial layer to directly form the first epitaxial layer 26 containing four elements such as bismuth (Si), carbon (C), phosphorus (P), and germanium (Ge). The helium source gas may comprise Dichlorosilane (DCS) or a decane compound, and the chemical formula may include Si _x H _2x+2 ; x>1, for example: silane (SiH ₄ ) or disilane (Si _{2 )} H ₆ ); the carbon source gas may comprise monomethyl silane (MMS, (CH ₃ )SiH ₃ ) or polymethyl decane, the chemical formula of which may include Si(CH ₃ ) _x H _4-x ; x>1; phosphorus The source gas may comprise phosphine (PH ₃ ); the helium source gas may comprise germane (GeH ₄ ); to form a first epitaxial layer 26 within the recess 12. It is worth noting that the material composition of the first epitaxial layer 26 can be represented by carbon phosphide (SiC _x P _y Ge _z ), and the atomic radius of the lanthanum element (1.52 angstrom) is close to the atomic radius of the lanthanum element (1.46 angstrom). Compared with an epitaxial layer having only germanium, carbon, and phosphorus elements, the presence of germanium can lower the difference in atomic radius between different elements in the first epitaxial layer 26, such as germanium and carbon, or between germanium and phosphorus. The resulting lattice mismatch affects the formation of the first epitaxial layer 26 on the surface of the germanium wafer in the lattice direction (111). In addition, in order to provide tensile stress, the doping concentration of carbon is substantially greater than the doping concentration of cerium, that is, the material of the first epitaxial layer 26, that is, bismuth carbon phosphide (SiC _x P _y Ge _z ). Preferably, the value of x is substantially greater than the value of z. In this embodiment, the doping concentration of carbon is greater than 0, the doping concentration of phosphorus is substantially greater than or equal to 5E19 cm ^-3 , and the doping concentration of germanium is substantially greater than 1E18 cm. ^-3 and the doping concentration of carbon is substantially greater than the doping concentration of germanium such that the first epitaxial layer 26 can provide tensile stress to the channel region C.

In one embodiment, the first epitaxial growth process may be a co-flow deposition process in which the element source gas, the carrier gas, and the etching gas are simultaneously introduced to contain hydrogen chloride gas during the deposition process. In the reaction chamber, during the process of forming the epitaxial layer, an etching process is simultaneously performed to remove a portion of the epitaxial layer. In another embodiment, the first epitaxial growth process may be a cyclic deposition process in which the element source gas and the etching gas are alternately introduced during the deposition process, and may be matched with the carrier gas to be repeatedly performed multiple times. The cycle of deposition and etching. Alternatively, after the co-current deposition process, or in the cyclic deposition process, a purification process can be performed, such as flushing the process chamber with a carrier gas or other gas, and/or evacuating the process chamber with a vacuum pump. Excess element source gases, reaction by-products and other contaminants are removed. In addition, it can also be in the epitaxial layer of bismuth carbon After the formation, an ion implantation process is further performed, and the conductive type dopant includes an N-type conductivity type dopant such as phosphorus ions doped in the bismuth carbon phosphide epitaxial layer, so that part of the first epitaxial layer 26 can serve as a source. /汲polar doped area.

Then, a second epitaxial growth process is performed to form a second epitaxial layer 28 on the first epitaxial layer 26, and the second epitaxial layer 28 includes a smaller number of element types than the first epitaxial layer 26 includes. The number of element types, that is, the type of element source gas source that is introduced during the second epitaxial growth process is less than the type of gas source that is introduced when the first epitaxial growth process is performed. In detail, performing the second epitaxial growth process includes performing an in-situ epitaxial process in a reaction chamber having a specific operating pressure system substantially between about 10 and 50 torr. A gas such as a helium source and a phosphorus source is introduced so that the second epitaxial layer 28 includes an element such as germanium or phosphorus. The gas such as a helium source and a phosphorus source is as described above, and will not be repeated here. The arrangement of the second epitaxial layer 28 prevents the germanium element in the first epitaxial layer 26 from diffusing upward to the surface of the substrate 10 during subsequent processes such as formation of a nickel/germanium metal telluride, affecting subsequently formed semiconductor devices such as: The electrical quality of the NMOS. In addition, in other embodiments, when the electrical performance of the semiconductor device is not significantly correlated with the diffusion of germanium, the second epitaxial growth process may also include performing a simultaneous access to the germanium source, the phosphor source, the germanium source, and the like. The in-situ epitaxial process of the gas causes the second epitaxial layer to contain three elements such as germanium, phosphorus, and antimony. In addition, a bismuth phosphorite epitaxial layer may be formed first, and then an ion implantation process is performed to dope the conductive type dopant including an N-type conductivity type dopant such as phosphorus ions in the bismuth phosphorite epitaxial layer as a source/ Bungee doped area.

In this embodiment, the first epitaxial layer 26 is filled in the recess 12, and the first epitaxial layer The top surface S1 of 26 and the top surface S2 of the second epitaxial layer 28 are both higher than the surface S3 of the substrate 10 to increase the first epitaxial layer 26 and the second epitaxial layer 28 for the channel region C under the gate structure 14. Provides the effectiveness of stress, but not limited to it.

The invention adjusts the material composition of the strain 矽 epitaxial layer for different component characteristics, and includes performing a third epitaxial growth process in addition to the first epitaxial growth process and the second epitaxial growth process. For example, at least the following implementations are included:

The first embodiment:

Please refer to Figure 3. FIG. 3 is a schematic view showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention. As shown in FIG. 3, first, the third epitaxial growth process includes performing an in-situ epitaxial process, and the element source gas species introduced during the third epitaxial growth process is less than the first epitaxial process. The source gas source that is introduced during the growth process, for example, can simultaneously pass a gas such as a helium source, a carbon source, and a phosphorus source to a reaction chamber having a specific operating pressure system of substantially 10 to 50 torr. In the chamber, a third epitaxial layer 30 is formed in the recess 12, wherein the third epitaxial layer 30 includes three elements such as germanium, carbon, and phosphorus, and the third epitaxial layer 30 includes a smaller number of element types than the first The number of element types included in an epitaxial layer 26, and the gases such as a germanium source, a carbon source, and a phosphorus source are as described above, and are not repeated herein. Then, the first epitaxial growth process and the second epitaxial growth process are sequentially performed to form the first epitaxial layer 26 and the second epitaxial layer 28 .

Second implementation aspect:

Referring to FIG. 3 again, as shown in FIG. 3, the second embodiment is identical to the first embodiment in the epitaxial growth process, and the third epitaxial layer 30 includes a smaller number of element types. The number of element types included in the first epitaxial layer 26 is different in the type of element source gas. In the second embodiment, the third epitaxial growth process includes simultaneously introducing a source of germanium, a source of carbon, and a source of germanium. a gas, but not including a phosphorus source gas, to form a third epitaxial layer 30 in the recess 12, wherein the third epitaxial layer 30 will include three elements such as germanium, carbon, and germanium, and the germanium source, the carbon source, and the germanium source The gas is as described above and will not be repeated here.

The third embodiment:

Please refer to FIG. 3 again. As shown in FIG. 3, the third embodiment and the second embodiment have the same implementation sequence in the epitaxial growth process, and the element source gases used in each epitaxial growth process are the same. The first epitaxial growth process includes introducing a carbon source gas having a flow rate change with time, so that the first epitaxial layer 26 has a carbon doping concentration as a gradient change, and more specifically, when the third epitaxy The crystal layer 30 is disposed under the first epitaxial layer 26 , and the carbon doping concentration of the first epitaxial layer 26 is along the interface of the first epitaxial layer 26 and the third epitaxial layer 30 to the first epitaxial layer 26 . The direction of the interface with one of the second epitaxial layers 28 is increased, for example, the third epitaxial layer 30 has a fixed carbon doping concentration of substantially 0.1%, and the first epitaxial layer 26 has a carbon doping concentration profile substantially Between 0.1% and 2.5%.

Fourth implementation aspect:

Please refer to FIG. 3 again. As shown in FIG. 3, the fourth embodiment and the second embodiment have the same implementation sequence in the epitaxial growth process, and the element source gases used in each epitaxial growth process are the same. The third epitaxial growth process includes introducing a carbon source gas having a flow rate change with time, so that the third epitaxial layer 30 also has a carbon doping concentration gradient, and in more detail, the third Lei The carbon doping concentration of the crystal layer 30 is increased along the bottom surface B of the third epitaxial layer 30 to the interface between the first epitaxial layer 26 and the third epitaxial layer 30. For example, the third epitaxial layer 30 has carbon doping. The impurity concentration profile is substantially between 0.1% and 2.5%, while the first epitaxial layer 26 has a fixed carbon doping concentration of substantially 2.5%.

Fifth embodiment:

Please refer to FIG. 3 again. As shown in FIG. 3, the fifth embodiment and the second embodiment have the same implementation sequence in the epitaxial growth process, and the element source gases used in each epitaxial growth process are the same. The first epitaxial growth process and the third epitaxial growth process both include a carbon source gas having a flow rate change with time, so that the first epitaxial layer 26 and the third epitaxial layer 30 each have a carbon. The doping concentration changes in a gradient such that the carbon doping concentration increases along the bottom surface B of the third epitaxial layer 30 toward one of the first epitaxial layer 26 and the second epitaxial layer 28. For example, the epitaxial layer from the bottom surface B of the third epitaxial layer 30 to the top surface T of the first epitaxial layer 26 has a carbon doping concentration distribution substantially between 0.1% and 2.5%.

Sixth implementation aspect:

Referring to FIG. 3 again, as shown in FIG. 3, the sixth embodiment can be combined with the third embodiment, the fourth epitaxial growth process and the third epitaxial process of the fourth embodiment or the fifth embodiment. The conditions for the growth process are similar. The difference is that the second epitaxial growth process simultaneously introduces an in-situ epitaxial process of a gas such as a helium source, a phosphorus source, and a helium source, that is, a carbon source that closes the first epitaxial growth process. The gas causes the second epitaxial layer 28 to contain three elements such as germanium, phosphorus, and antimony.

The seventh embodiment:

Please refer to Figure 4. FIG. 4 is a schematic view showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention. As shown in FIG. 4, first, the first epitaxial growth process is performed to form the first epitaxial layer 26, and then, the third epitaxial growth process includes performing an in-situ epitaxial process and simultaneously introducing the source. a gas such as a carbon source and a phosphorus source, that is, a source gas that closes the first epitaxial growth process, to form a third epitaxial layer 32 in the recess 12, wherein the third epitaxial layer 32 includes germanium, carbon, Three elements such as phosphorus. Then, the second epitaxial growth process described above is performed, that is, the carbon source gas of the third epitaxial growth process is turned off to form the second epitaxial layer 28.

It should be noted that, in the above embodiment, the number of element types included in the second epitaxial layer 28 and the number of element types included in the third epitaxial layer 30/32 are smaller than the element types included in the first epitaxial layer 26. The number. In other words, the type of elemental source gas that is introduced during the second epitaxial growth process or the third epitaxial growth process is less than that of the first The source gas source that is introduced during an epitaxial growth process.

In addition, in order to protect the formed epitaxial layer, a fourth epitaxial growth process may be selectively performed, and only the germanium source gas is introduced to form a fourth epitaxial layer 34 on the second epitaxial layer 28. The fourth epitaxial layer 34 includes only germanium, which is used for the consumption of the germanium substrate during the nickel/germanium metal telluride process, and helps maintain the structural integrity of the epitaxial layer formed under the fourth epitaxial layer 34. The semiconductor device 36/38/40 has thus been completed. Since the present invention is completed by adding a germanium source gas to an epitaxial layer providing tensile stress, such as a germanium carbon epitaxial layer or a germanium carbon epitaxial layer containing a phosphorus dopant, the epitaxial layer can be completed. Formed on the germanium wafer, and the formed epitaxial layer will contain germanium, carbon, phosphorus and germanium at the same time. Therefore, the present invention is preferably integrated into the semiconductor process of the NMOS to provide an epitaxial layer of tensile stress in the NMOS. It has a predetermined shape, that is, the formed semiconductor device 36/38/40 is preferably an NMOS.

Further, the first epitaxial layer 26 and the second epitaxial layer 28 are not limited to being formed in the recess 12, please refer to FIG. 5 and FIG. 5 and 6 are schematic views showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention. As shown in FIG. 5 and FIG. 6, the first epitaxial layer 26 and the second epitaxial layer 28 may be directly formed on the substrate 10 in combination with the foregoing embodiments to provide stress to the channel region C.

Please refer to Table 1 and Table 2, and please refer to Figure 3 and Figure 4 together. Table 1 and Table 2 show a reference material composition table of an epitaxial layer according to a preferred embodiment of the present invention. As shown in Table 1 and Table 2, the present invention provides an epitaxial layer comprising a first epitaxial layer 26, a second epitaxial layer 28, a third epitaxial layer 30/32, and a fourth epitaxial layer 34. It is disposed on a substrate 10 or in a recess 12. Each of the epitaxial layers can be formed by an in-situ epitaxial process through which different element source gases are passed. The first epitaxial layer 26 substantially comprises four elements such as germanium, carbon, phosphorus and germanium, and the material composition thereof can be represented by carbon phosphide (SiC _x P _y Ge _z ), wherein the value of x is preferably substantially greater than the value of z. To provide tensile stress to the channel region of a semiconductor device such as an NMOS. In addition, the atomic radii ratio of lanthanum and cerium is substantially smaller than the atomic radii ratio of carbon to lanthanum or the atomic radii ratio of phosphorus to lanthanum, which contributes to the formation of the first epitaxial layer 26 on the surface of the germanium wafer in the lattice direction (111). The first epitaxial layer 26 is made to have a desired structural shape. The second epitaxial layer 28 is disposed on the first epitaxial layer 26, wherein the second epitaxial layer 28 includes a number of element types smaller than the number of element types included in the first epitaxial layer 26, and the second epitaxial layer 28 is substantially It may contain two elements such as ruthenium and phosphorus or three elements such as ruthenium, phosphorus and ruthenium. The third epitaxial layer 30/32 is disposed under the first epitaxial layer 26 or between the first epitaxial layer 26 and the second epitaxial layer 28, wherein the third epitaxial layer 30/32 includes an element type The number is substantially smaller than the number of element types included in the first epitaxial layer 26, and the third epitaxial layer 30/32 may substantially contain three elements such as germanium, carbon, and phosphorus or germanium, carbon, and germanium. The fourth epitaxial layer 34 is disposed above the first epitaxial layer 26, the second epitaxial layer 28, and the third epitaxial layer 30/32, and the fourth epitaxial layer 34 includes only germanium as a protective layer. In addition, the first epitaxial layer 26 or/and the third epitaxial layer 30/32 may have a gradient of carbon doping concentration, for example, when the third epitaxial layer 30 is disposed under the first epitaxial layer 26. The carbon doping concentration of the first epitaxial layer 26 is along the interface of the first epitaxial layer 26 and the third epitaxial layer 30 to the interface of the first epitaxial layer 26 and the second epitaxial layer 28. The direction of the addition, or/and the carbon doping concentration of the third epitaxial layer 30 increases along the bottom surface B of the third epitaxial layer 30 toward one of the first epitaxial layer 26 and the third epitaxial layer 30.

In summary, the present invention has an element having an atomic radius close to that of germanium, for example, germanium doped in a germanium carbon phosphorus (SiCP) epitaxial layer to form an epitaxial layer containing germanium, carbon, phosphorus, germanium, and the like. Slowing down the lattice mismatch caused by the difference in atomic radius between bismuth and carbon or bismuth and phosphorus, so that the epitaxial layer can be formed on the surface of the germanium wafer in the lattice direction (111), which is expected The shape of the epitaxial layer. In addition, the epitaxial layer process of the present invention can be further combined with the source/drain region process to improve the electrical performance of the MOS transistor.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

10‧‧‧Base

12‧‧‧ Groove

14‧‧‧ gate structure

16‧‧‧Shallow trench isolation

18‧‧‧ gate dielectric layer

20‧‧‧ gate conductive layer

22‧‧‧ cover

24‧‧‧First side wall

26‧‧‧First epitaxial layer

28‧‧‧Second epilayer

30,32‧‧‧ third epitaxial layer

34‧‧‧ fourth epitaxial layer

36,38,40‧‧‧ semiconductor devices

B‧‧‧ bottom

C‧‧‧Channel area

T, S1, S2, S3‧‧‧ top

1 to 2 are schematic views showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention.

FIG. 3 is a schematic view showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention.

FIG. 4 is a schematic view showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention.

FIG. 5 is a schematic view showing a method of fabricating an epitaxial layer according to a preferred embodiment of the present invention.

Figure 6 is a schematic view showing a method of fabricating an epitaxial layer in accordance with a preferred embodiment of the present invention.

10‧‧‧Base

14‧‧‧ gate structure

16‧‧‧Shallow trench isolation

18‧‧‧ gate dielectric layer

20‧‧‧ gate conductive layer

22‧‧‧ cover

24‧‧‧First side wall

26‧‧‧First epitaxial layer

28‧‧‧Second epilayer

30‧‧‧ Third epitaxial layer

34‧‧‧ fourth epitaxial layer

38‧‧‧ semiconductor devices

B‧‧‧ bottom

C‧‧‧Channel area

T‧‧‧ top surface

Claims (20)

A method for fabricating an epitaxial layer includes: performing a first epitaxial growth process to form a first epitaxial layer on a substrate, wherein the first epitaxial growth process includes simultaneously introducing a germanium source, a carbon source, a phosphorus source and a gas such as a germanium source, such that the first epitaxial layer includes germanium, carbon, phosphorus, and antimony; and performing a second epitaxial growth process to form a second epitaxial layer, and the second epitaxial layer includes The number of element types is smaller than the number of element types included in the first epitaxial layer. The method for fabricating an epitaxial layer according to claim 1, wherein the second epitaxial growth process comprises simultaneously introducing a gas such as a germanium source and a phosphorus source such that the second epitaxial layer comprises germanium and phosphorus. The method for producing an epitaxial layer according to claim 1, wherein the second epitaxial growth process comprises simultaneously introducing a gas such as a germanium source, a phosphorus source, and a germanium source, so that the second epitaxial layer includes germanium, phosphorus, and germanium. The method of fabricating an epitaxial layer according to claim 1, wherein the second epitaxial layer is formed on the first epitaxial layer. The method for fabricating an epitaxial layer according to claim 1, further comprising performing a third epitaxial growth process to form a third epitaxial layer, and the number of element types included in the third epitaxial layer The mesh is smaller than the number of element types included in the first epitaxial layer. The method for producing an epitaxial layer according to claim 5, wherein the third epitaxial growth process is performed before the first epitaxial growth process, or the first epitaxial growth process and the second epitaxial growth process are performed. Between processes. The method for producing an epitaxial layer according to claim 5, wherein the third epitaxial growth process comprises simultaneously introducing a gas such as a germanium source, a carbon source, and a phosphorus source. The method for producing an epitaxial layer according to claim 5, wherein the third epitaxial growth process comprises simultaneously introducing a gas such as a germanium source, a carbon source, and a germanium source. The method of producing an epitaxial layer according to claim 8, wherein the third epitaxial layer has a carbon doping concentration in a gradient. The method of producing an epitaxial layer according to claim 1, wherein the first epitaxial growth process comprises introducing a carbon source gas having a flow rate change with time. The method for fabricating an epitaxial layer according to claim 1, further comprising performing a fourth epitaxial growth process to form a fourth epitaxial layer, wherein the fourth epitaxial layer comprises only germanium. An epitaxial layer includes: a first epitaxial layer, wherein the first epitaxial layer substantially comprises germanium, carbon, phosphorus, and antimony; And a second epitaxial layer is disposed on the first epitaxial layer, wherein the second epitaxial layer comprises a number of element types smaller than a number of element types included in the first epitaxial layer. The epitaxial layer of claim 12, wherein the second epitaxial layer comprises germanium and phosphorus. The epitaxial layer of claim 13, wherein the second epitaxial layer further comprises germanium. The epitaxial layer of claim 12, further comprising a third epitaxial layer, wherein the third epitaxial layer comprises a number of element types substantially smaller than the number of element types included in the first epitaxial layer. The epitaxial layer of claim 15, wherein the third epitaxial layer is disposed under the first epitaxial layer or between the first epitaxial layer and the second epitaxial layer. The epitaxial layer of claim 15, wherein the third epitaxial layer is disposed under the first epitaxial layer, and the carbon doping concentration of the third epitaxial layer is along the third epitaxial layer A bottom surface increases in interface with one of the first epitaxial layer and the third epitaxial layer. The epitaxial layer of claim 17, wherein the carbon doping concentration of the first epitaxial layer is along the interface between the first epitaxial layer and the third epitaxial layer to the first epitaxial layer The direction of the interface with one of the second epitaxial layers is increased. The epitaxial layer of claim 12, wherein the material composition of the first epitaxial layer is represented by bismuth carbon bismuth (SiC _x P _y Ge _z ), and the value of x is substantially greater than the value of z. The epitaxial layer according to claim 12, further comprising a fourth epitaxial layer disposed on the second epitaxial layer, wherein the fourth epitaxial layer comprises only germanium.