A method for improving the doping concentration in an oxide

Abstract

The application discloses a method for improving the doping concentration in an oxide, and belongs to the technical field of semiconductor devices. The method comprises the following steps: constructing an alpha-SiO2 crystal structure containing B or P atom doping, and performing Gibbs formation energy calculation on the B or P atom doping; and regulating the B or P atom doping by changing the axial direction deformation degree of the alpha-SiO2 crystal structure, so as to change the impurity content in the alpha-SiO2, and effectively improve the electrical performance of a field effect transistor.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a method for improving the doping concentration in oxides. Background Technology

[0002] During the fabrication of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), boron (B) and phosphorus (P) act as impurities to adjust the doping concentration of the polysilicon gate, substrate, source / drain, and channel. During this process, the impurities diffuse across the interface into α-SiO2 (silicon dioxide). In addition, ion implantation during the process can cause structural defects in the oxide. When annealing is used, B and P atoms will redistribute in α-SiO2, and the excess will precipitate as impurities.

[0003] Meanwhile, due to the mismatch between the oxide and its adjacent layers, significant stress is generated in α-SiO2, with local stresses reaching up to 30%. This stress significantly affects the formation ability of B and P atoms in α-SiO2, thus severely impacting MOSFET performance, such as gate leakage current. Therefore, controlling the formation energy of α-SiO2 doping under different deformations is of great significance for the fabrication of electronic devices and the regulation of their electrical performance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the doping concentration in oxides, so as to effectively improve the problem of B and P atom doping in α-SiO2 of MOSFETs.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for improving the doping concentration in an oxide, comprising:

[0006] Construct α-SiO2 crystal structures doped with B or P atoms, and calculate the Gibbs formation energy for B or P atom doping.

[0007] The axial deformation of the α-SiO2 crystal structure can be altered to regulate the doping of B or P atoms, thereby changing the impurity content in α-SiO2.

[0008] In one embodiment, the construction of the α-SiO2 crystal structure doped with B or P atoms includes: constructing an α-SiO2 physical model based on the experimental lattice parameters of α-SiO2, transforming the optimized α-SiO2 unit cell along a:

[110] , b: [-110] and c:

[001] to make it into a cuboid, and doping it with P and B atoms, and then obtaining the structure at TK using molecular dynamics, where T is the temperature.

[0009] In one embodiment, the calculation of the Gibbs formation energy of the B or P atom doping includes:

[0010]

[0011] Where ΔG f For Gibbs formation energy, Let be the formation enthalpy of the system containing element i at temperature TK. Let H be the entropy of the formation of a system containing element i at temperature TK, where T is temperature and H is temperature. i Let S be the enthalpy of element i at temperature TK. i Let be the entropy of element i at temperature TK; element i includes O, Si, P, and B.

[0012] In one implementation, the formation enthalpy of the system containing element i at temperature TK. The calculation formula is:

[0013]

[0014] in The enthalpy change of the system containing element i from 0K to TK. Let i be the enthalpy of the system containing element i at temperature 0 K. The enthalpy change of the system without element i from 0K to TK. The enthalpy of the system containing element i at temperature 0 K;

[0015] Formation entropy of a system containing element i at temperature TK The calculation formula is:

[0016]

[0017] in The entropy change of a system containing element i from 0K to TK. Let i be the entropy of the system containing element i at temperature 0 K. The entropy change of a system containing element i from 0K to TK. Let be the entropy of the system containing element i at temperature 0 K.

[0018] In one implementation, the enthalpy calculation formula for O, Si, P, and B atoms under O-Rich conditions is as follows:

[0019]

[0020]

[0021] H P (T)=ΔH P (T)+H P (OK)

[0022] H B (T)=ΔH B (T)+H B (OK)

[0023] H atoms of O, Si, P and B under O-Poor conditions O The calculation formula is:

[0024]

[0025] H Si (T)=ΔH Si (T) / 8+H Si (0K) / 8

[0026] H P (T)=ΔH P (T)+H P (OK)

[0027] H B (T)=ΔH B (T)+H B (OK)

[0028] in This represents the enthalpy change of the O atom from 0 K to T K. The enthalpy of the O atom at 0 K; The enthalpy change of α-SiO unit cell from 0K to TK. ΔH is the enthalpy of an α-SiO2 unit cell at 0 K. O (T) represents the enthalpy change of the O atom from 0K to TK, H O (0K) represents the enthalpy of the O atom at a temperature of 0K;

[0029] ΔH Si (T) / 8 represents the enthalpy change of Si atoms from 0K to TK, H Si (0K) / 8 is the enthalpy of Si atoms at 0K; ΔH P (T) represents the enthalpy change of the P atom from 0K to TK, H P (0K) is the enthalpy of the P atom at 0K; ΔH B (T) represents the enthalpy change of the B atom from 0K to TK, H B (0K) is the enthalpy of the B atom at 0K;

[0030] The formulas for calculating the entropy of O, Si, P, and B atoms are as follows:

[0031]

[0032] S Si (T)=ΔS Si (T) / 8+SSi (0K) / 8

[0033] S P (T)=ΔS P (T)+S P (OK)

[0034] S B (T)=ΔS B (T)+S B (OK)

[0035] in The entropy change of the O atom from 0K to TK. ΔS represents the entropy of an O atom at 0 K. Si (T) / 8 represents the entropy change of Si atoms from 0K to TK, S Si (0K) / 8 is the entropy of Si atoms at 0K; ΔS P (T) represents the entropy change of the P atom from 0K to TK, S P (0K) is the entropy of the P atom at 0K; ΔS B (T) represents the enthalpy change of the B atom from 0 K to T K, and S B (0K) is the entropy of the B atom at 0K.

[0036] In one embodiment, the B or P atom doping control is calculated based on the deformation of the α-SiO2 crystal structure along different crystal axes.

[0037] In one embodiment, the B or P atom substitution doping at the O atom position gradually decreases the Gibbs formation energy of the B or P atom doping as the stretching deformation of the α-SiO2 crystal structure increases, and gradually increases the Gibbs formation energy of the B or P atom doping as the compressive deformation of the α-SiO2 crystal structure increases.

[0038] In one embodiment, the Si atom sites are replaced with B or P atoms for doping. As the tensile deformation of the α-SiO2 crystal structure increases, the Gibbs formation energy of P atom doping gradually decreases, while as the compressive deformation of α-SiO2 increases, its Gibbs formation energy gradually increases. The Gibbs formation energy of B atom doping shows the opposite trend: as the tensile deformation of α-SiO2 increases, the Gibbs formation energy of B atom doping gradually increases, while as the compressive deformation of α-SiO2 increases, its Gibbs formation energy gradually decreases.

[0039] In a method for improving the doping concentration in an oxide provided by the present invention, the method includes constructing an α-SiO2 crystal structure doped with B or P atoms and calculating the Gibbs formation energy of the B or P atom doping; and controlling the B or P atom doping by changing the axial deformation of the α-SiO2 crystal structure to change the impurity content in α-SiO2, thereby effectively improving the electrical performance of the field-effect transistor. Attached Figure Description

[0040] Figure 1 This is the α-SiO2 band structure proposed in this invention;

[0041] Figure 2 This is the α-SiO2 structure transformation diagram proposed in this invention;

[0042] Figure 3 This is a schematic diagram of the Gibbs formation energy of B and P atoms doped in α-SiO2 under deformation proposed in this invention. Detailed Implementation

[0043] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for improving the doping concentration in oxides according to the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0044] like Figure 1 As shown, based on the optimized α-SiO2 unit cell physical model, band structure calculations were performed and compared with experimental values. Its lattice constant ( (α=β=90°; γ=120°) agrees with the experimental values, and its band gap is smaller than the experimental values;

[0045] like Figure 2 As shown, the optimized α-SiO2 unit cell is structurally transformed along a:

[110] , b: [-110] and c:

[001] , and expanded by 2 times, 1 times and 2 times along the a, b and c axes respectively (i.e., the cell is increased by 1 times along the a axis, remains unchanged along the b axis, and increases by 1 times along the c axis); the Si atoms in the α-SiO2 supercell model formed after the cell expansion are replaced with B or P atoms, or the O atoms are replaced with B or P atoms.

[0046] like Figure 3 As shown, according to the formula for calculating Gibbs formation energy,

[0047]

[0048] Where ΔG f For Gibbs formation energy, Let be the formation enthalpy of the system containing element i at temperature TK. Let H be the entropy of the formation of a system containing element i at temperature TK, where T is temperature and H is temperature. i Let S be the enthalpy of element i at temperature TK. i Let be the entropy of element i at temperature TK, where element i includes O, Si, P, and B.

[0049] The calculation formula is as follows:

[0050]

[0051] in The enthalpy change of the system containing element i from 0K to TK. Let i be the enthalpy of the system containing element i at temperature 0 K. The enthalpy change of the system without element i from 0K to TK. Let be the enthalpy of the system without element i at a temperature of 0 K.

[0052] The calculation formula is as follows:

[0053]

[0054] in The entropy change of a system containing element i from 0K to TK. Let i be the entropy of the system containing element i at temperature 0 K. The entropy change of a system containing element i from 0K to TK. Let be the entropy of the system containing element i at temperature 0 K.

[0055] The formulas for calculating the enthalpy of O, Si, P, and B atoms under O-Rich conditions are as follows:

[0056]

[0057]

[0058] H P (T)=ΔH P (T)+H P (OK)

[0059] H B (T)=ΔH B (T)+H B (OK)

[0060] H atoms of O, Si, P and B under O-Poor conditions O The calculation formula is as follows:

[0061]

[0062] HSi (T)=ΔH Si (T) / 8+H Si (0K) / 8

[0063] H P (T)=ΔH P (T)+H P (OK)

[0064] H B (T)=ΔH B (T)+H B (OK)

[0065] in This represents the enthalpy change of the O atom from 0 K to T K. The enthalpy of the O atom at 0 K; The enthalpy change of α-SiO unit cell from 0K to TK. ΔH is the enthalpy of an α-SiO2 unit cell at 0 K. O (T) represents the enthalpy change of the O atom from 0K to TK, H O (0K) represents the enthalpy of the O atom at a temperature of 0K;

[0066] ΔH Si (T) / 8 represents the enthalpy change of Si atoms from 0K to TK, H Si (0K) / 8 is the enthalpy of Si atoms at 0K; ΔH P (T) represents the enthalpy change of the P atom from 0K to TK, H P (0K) is the enthalpy of the P atom at 0K; ΔH B (T) represents the enthalpy change of the B atom from 0K to TK, H B (0K) is the enthalpy of the B atom at 0K.

[0067] The formulas for calculating the entropy of O, Si, P, and B atoms are as follows:

[0068]

[0069] S Si (T)=ΔS Si (T) / 8+S Si (0K) / 8

[0070] S P (T)=ΔS P (T)+S P (OK)

[0071] S B (T)=ΔS B (T)+S B (OK)

[0072] in The entropy change of the O atom from 0K to TK. ΔS represents the entropy of an O atom at 0 K. Si (T) / 8 represents the entropy change of Si atoms from 0K to TK, S Si (0K) / 8 is the entropy of Si atoms at 0K; ΔS P (T) represents the entropy change of the P atom from 0K to TK, S P (0K) is the entropy of the P atom at 0K; ΔS B (T) represents the enthalpy change of the B atom from 0 K to T K, and S B (0K) is the entropy of the B atom at 0K.

[0073] By calculating the Gibbs formation energies of B and P atoms under different deformations, it can be seen that as the tensile deformation of α-SiO2 increases, the Gibbs formation energy of B or P atoms doped at the O site gradually decreases. Conversely, as the compressive deformation of α-SiO2 increases, the Gibbs formation energy of B or P atoms doped at the O site gradually increases.

[0074] For B or P atom doping at Si sites, it can be seen that as the tensile deformation of α-SiO2 increases, the Gibbs formation energy of P atom doping gradually decreases, while as the compressive deformation of α-SiO2 increases, its Gibbs formation energy gradually increases. The Gibbs formation energy of B atom doping shows the opposite trend: as the tensile deformation of α-SiO2 increases, the Gibbs formation energy of B atom doping gradually increases, while as the compressive deformation of α-SiO2 increases, its Gibbs formation energy gradually decreases.

[0075] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for improving the doping concentration in an oxide, characterized in that, include: Construct α-SiO2 crystal structures doped with B or P atoms, and calculate the Gibbs formation energy for B or P atom doping. The axial deformation of the α-SiO2 crystal structure can be altered to regulate the doping of B or P atoms, thereby changing the impurity content in α-SiO2. The construction of the α-SiO2 crystal structure doped with B or P atoms includes: constructing an α-SiO2 physical model based on the experimental lattice parameters of α-SiO2, transforming the optimized α-SiO2 unit cell along a: [110], b: [-110] and c: [001], and expanding the cell by 2 times, 1 times and 2 times along the a, b and c axes respectively to make it into a cuboid, and doping it with P and B atoms, and then obtaining the structure at TK using molecular dynamics, where T is the temperature; The calculation of the Gibbs formation energy of the B or P atom doping includes: in For Gibbs formation energy, Let be the formation enthalpy of the system containing element i at temperature TK. Let T be the formation entropy of the system containing element i at temperature TK, where T is the temperature. Let be the enthalpy of element i at temperature TK. Let be the entropy of element i at temperature TK; element i includes O, Si, P, and B. Enthalpy of formation of a system containing element i at temperature TK The calculation formula is: in The enthalpy change of the system containing element i from 0 K to TK. Let i be the enthalpy of the system containing element i at temperature 0 K. The enthalpy change of the system without element i from 0 K to TK. The enthalpy of the system containing element i at 0 K; Formation entropy of a system containing element i at temperature TK The calculation formula is: in The entropy change of a system containing element i from 0 K to TK. Let i be the entropy of the system containing element i at temperature 0 K. The entropy change of a system containing element i from 0 K to TK. Let i be the entropy of the system containing element i at temperature 0 K. The formulas for calculating the enthalpy of O, Si, P, and B atoms under O-Rich conditions are as follows: O-Poor concentration of O, Si, P, and B atoms The calculation formula is: in This represents the enthalpy change of the O atom from 0 K to TK. The enthalpy of the O atom at 0 K; The enthalpy change of α-SiO unit cell from 0 K to TK. The enthalpy of an α-SiO2 unit cell at 0 K; This represents the enthalpy change of the O atom from 0 K to TK. The enthalpy of the O atom at 0 K; / 8 represents the enthalpy change of Si atoms from 0 K to TK. / 8 represents the enthalpy of Si atoms at 0 K; This represents the enthalpy change of the P atom from 0 K to TK. The enthalpy of the P atom at 0 K; This represents the enthalpy change of the B atom from 0 K to TK. The enthalpy of the B atom at 0 K; The formulas for calculating the entropy of O, Si, P, and B atoms are as follows: in The entropy change of O atoms from 0 K to TK. The entropy of the O atom at temperature 0 K; / 8 represents the entropy change of Si atoms from 0 K to TK. / 8 represents the entropy of Si atoms at 0 K; This represents the entropy change of the P atom from 0 K to TK. The entropy of the P atom at 0 K; This represents the enthalpy change of the B atom from 0 K to TK. Let be the entropy of the B atom at 0 K.

2. The method for improving doping concentration in oxides as described in claim 1, characterized in that, The B or P atom doping control is based on The crystal structure is obtained by calculation of deformation along different crystal axes.

3. The method for improving the doping concentration in an oxide as described in claim 2, characterized in that, The B or P atom substitution doping at the O atom position, as... As the stretching deformation of the crystal structure increases, the Gibbs formation energy of B or P atom doping gradually decreases; with... As the compressive deformation of the crystal structure increases, the Gibbs formation energy of B or P atom doping gradually increases.

4. The method for improving the doping concentration in an oxide as described in claim 2, characterized in that, The B or P atom substitution doping at the Si atomic position, as... As the stretching deformation of the crystal structure increases, the Gibbs formation energy of P-doped crystals gradually decreases, while as... As compressive deformation increases, the Gibbs formation energy gradually increases; however, the Gibbs formation energy of boron-doped materials exhibits the opposite trend, increasing with... As tensile deformation increases, the Gibbs formation energy of boron-doped atoms gradually increases, and as... As compressive deformation increases, its Gibbs formation energy gradually decreases.

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