Semiconductor structure and method for forming the same

Abstract

A semiconductor structure and a method for forming the same, wherein the structure comprises: a substrate; a work function layer located on the substrate, the work function layer containing aluminum, the work function layer comprising a first surface and a second surface facing each other, the first surface being closer to the substrate surface than the second surface, and the molar concentration of aluminum atoms in the work function layer decreasing along the direction from the first surface to the second surface. Since the molar concentration of aluminum atoms in the bottom work function layer is higher, it is more conducive to lowering the threshold voltage of the formed device, thereby improving the ability to adjust the device threshold voltage without changing the thickness of the work function layer. At the same time, the molar concentration of aluminum atoms in the top work function layer is lower, which helps reduce the probability of aluminum atoms accumulating in the work function layer. The structure can improve the ability to adjust the device threshold voltage, thereby improving the performance of the formed semiconductor structure.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a semiconductor structure and a forming method thereof. Background Art

[0002] With the development of integrated circuit manufacturing technology, the integration density of integrated circuits has continued to increase, while the feature size of integrated circuits has continued to decrease. Furthermore, as semiconductor devices develop towards high density and small size, metal oxide semiconductor (MOS) devices have become the main driving force in integrated circuits. The performance of MOS transistors directly affects the overall performance of the integrated circuit. Among the various parameters of the MOS structure, the threshold voltage (Vt) is a key control parameter of the MOS transistor.

[0003] In the existing preparation process of multiple semiconductor devices with different threshold voltages, the threshold voltage of each semiconductor device is often adjusted by performing ion doping of different types, energies and doses on the gate oxide layer, channel region, well region, source and drain of each semiconductor device, or by forming work function layers of different thicknesses in the conductor device.

[0004] However, as the size of semiconductors becomes smaller, there is not enough space to fill the work function layer, and it is difficult to adjust the threshold voltage to a predetermined value by increasing the thickness of the work function layer, resulting in a decrease in device performance. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a semiconductor structure and a method for forming the same, so as to improve the ability to adjust the threshold voltage of the device and thus improve the performance of the formed semiconductor structure.

[0006] In order to solve the above technical problems, the technical solution of the present invention provides a semiconductor structure, including: a substrate; a work function layer located on the substrate, the work function layer containing aluminum elements and oxygen elements, the work function layer including a first surface and a second surface relative to each other, the distance between the first surface and the surface of the substrate is smaller than the distance between the second surface and the surface of the substrate, and along the direction from the first surface to the second surface, the molar percentage concentration of aluminum atoms in the work function layer decreases, and the molar percentage concentration of oxygen atoms in the work function layer decreases.

[0007] Optionally, the work function layer includes a first work function portion and a second work function portion located on the first work function portion, and the molar percentage concentration range of aluminum atoms in the first work function portion is 70% to 90%, and the molar percentage concentration range of aluminum atoms in the second work function portion is 50% to 70%.

[0008] Optionally, the work function layer further includes: a third work function portion located between the first work function portion and the second work function portion, and the molar percentage concentration of aluminum atoms in the third work function portion is in a range of 60% to 80%.

[0009] Optionally, the material of the work function layer includes titanium aluminum compound, titanium aluminum carbon compound or titanium aluminum oxide compound.

[0010] Optionally, the work function layer has a thickness ranging from 20 angstroms to 100 angstroms.

[0011] Optionally, the method further comprises: a barrier layer located on the surface of the work function layer; a protective layer located between the work function layer and the substrate; and a high-K dielectric layer located between the protective layer and the substrate.

[0012] Optionally, the molar percentage concentration of oxygen atoms at the interface between the work function layer and the protective layer is in a range of 5% to 50%; the molar percentage concentration of oxygen atoms at the interface between the work function layer and the barrier layer is in a range of 0% to 5%.

[0013] Optionally, the material of the barrier layer includes: tantalum-containing nitride; the material of the protective layer includes: titanium-containing nitride; the material of the high-K dielectric layer includes hafnium oxide, zirconium oxide, hafnium silicon oxide, lanthanum oxide, zirconium silicon oxide, titanium oxide, tantalum oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide or aluminum oxide.

[0014] Correspondingly, the technical solution of the present invention also provides a method for forming a semiconductor structure, comprising: providing a substrate; forming a work function layer on the substrate, the work function layer containing aluminum elements and oxygen elements, the work function layer comprising a first surface and a second surface relative to each other, the distance between the first surface and the surface of the substrate being smaller than the distance between the second surface and the surface of the substrate, and along the direction from the first surface to the second surface, the molar percentage concentration of aluminum atoms in the work function layer decreases, and the molar percentage concentration of oxygen atoms in the work function layer decreases.

[0015] Optionally, before forming the work function layer, a high-K dielectric layer is formed on the surface of the substrate; a protective layer is formed on the surface of the high-K dielectric layer; after forming the protective layer, the work function layer is formed on the surface of the protective layer; after forming the work function layer, a blocking layer is formed on the surface of the work function layer.

[0016] Optionally, the work function layer and the barrier layer are formed in the same reaction chamber.

[0017] Optionally, the material of the work function layer includes titanium aluminum compound, titanium aluminum carbon compound or titanium aluminum oxide compound.

[0018] Optionally, the method for forming the work function layer includes: performing several first treatments to form a first work function portion on the substrate; performing several second treatments to form a second work function portion on the first work function portion, and the molar percentage concentration of aluminum atoms in the first work function portion is greater than the molar percentage concentration of aluminum atoms in the second work function portion.

[0019] Optionally, the thickness of the first work function portion ranges from 5 angstroms to 50 angstroms; and the number of times the first treatment is performed ranges from 1 to 10 times.

[0020] Optionally, the thickness of the second work function portion ranges from 5 angstroms to 50 angstroms; and the number of times the second treatment is performed ranges from 1 to 10 times.

[0021] Optionally, the method for forming the work function layer also includes: after forming the first work function portion and before forming the second work function portion, performing several third treatments to form a third work function portion on the surface of the first work function portion, the molar percentage concentration of aluminum atoms in the third work function portion is less than the molar percentage concentration of aluminum atoms in the first work function portion, and greater than the molar percentage concentration of aluminum atoms in the second work function portion.

[0022] Optionally, the first treatment method includes: using a first ventilation process to introduce a first gas into the substrate surface to form a first precursor film; using a second ventilation process to introduce a second gas, and the second gas reacts with the first precursor film to form a first work function material film.

[0023] Optionally, the first ventilation process includes: a first ventilation stage, introducing the first gas; a first exhaust stage, removing the unadsorbed first gas; the second ventilation process includes: a second ventilation stage, introducing the second gas; and a second exhaust stage, removing the second gas that has not reacted with the first precursor film.

[0024] Optionally, the parameters of the first ventilation process include: the first gas includes titanium-containing gas, the inlet flow rate of the first gas is 0 standard ml / min to 1000 standard ml / min, and the time of the first ventilation stage is 0 to 60 seconds; the parameters of the second ventilation process include: the second gas includes aluminum-containing gas, the inlet flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the time of the second ventilation stage is 20 seconds to 60 seconds.

[0025] Optionally, the second treatment method includes: using a third ventilation process to introduce a first gas into the substrate surface to form a second precursor film; using a fourth ventilation process to introduce a second gas, and the second gas reacts with the second precursor film to form a second work function material film.

[0026] Optionally, the third ventilation process includes: a third ventilation stage, introducing the first gas; a third exhaust stage, removing the unadsorbed first gas; the fourth ventilation process includes: a fourth ventilation stage, introducing the second gas; and a fourth exhaust stage, removing the second gas that has not reacted with the second precursor film.

[0027] Optionally, the parameters of the third ventilation process include: the first gas includes titanium-containing gas, the inlet flow rate of the first gas is 0 standard ml / min to 1000 standard ml / min, and the time of the third ventilation stage is 0 to 60 seconds; the parameters of the fourth ventilation process include: the second gas includes aluminum-containing gas, the inlet flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the time of the fourth ventilation stage is 10 seconds to 50 seconds.

[0028] Optionally, the third treatment method includes: using a fifth ventilation process to introduce a first gas into the substrate surface to form a third precursor film; using a sixth ventilation process to introduce a second gas, and the second gas reacts with the third precursor film to form a third work function material film.

[0029] Optionally, the fifth ventilation process includes: a fifth ventilation stage, introducing the first gas; a fifth exhaust stage, removing the unadsorbed first gas; the sixth ventilation process includes: a sixth ventilation stage, introducing the second gas; and a sixth exhaust stage, removing the second gas that has not reacted with the third precursor film.

[0030] Optionally, the parameters of the fifth ventilation process include: the first gas includes titanium-containing gas, the inlet flow rate of the first gas is 0 standard ml / min to 1000 standard ml / min, and the time of the fifth ventilation stage is 0 to 60 seconds; the parameters of the sixth ventilation process include: the second gas includes aluminum-containing gas, the inlet flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the time of the sixth ventilation stage is 15 seconds to 55 seconds.

[0031] Optionally, the molar percentage concentration of oxygen atoms at the interface between the work function layer and the protective layer is in a range of 5% to 50%; the molar percentage concentration of oxygen atoms at the interface between the work function layer and the barrier layer is in a range of 0% to 5%.

[0032] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0033] In the semiconductor structure provided by the technical solution of the present invention, the semiconductor device is used to form an N-type device. The work function layer located on the substrate contains aluminum elements, and the molar percentage concentration of aluminum atoms in the work function layer gradually decreases along the direction away from the substrate surface. Since the molar percentage concentration of aluminum atoms in the bottom work function layer is higher, it is more conducive to lowering the threshold voltage of the formed device, thereby improving the ability to adjust the threshold voltage of the device without changing the thickness of the work function layer. At the same time, the molar percentage concentration of aluminum atoms in the top work function layer is lower, which is conducive to reducing the probability of aluminum atoms accumulating in the work function layer. In summary, the ability to adjust the threshold voltage of the device can be effectively improved, thereby improving the performance of the formed semiconductor structure.

[0034] Furthermore, the work function layer has a barrier layer on its surface, which can reduce the influence of the external environment on the work function layer material, so that the performance of the work function layer remains stable, thereby facilitating the improvement of the performance of the formed semiconductor structure.

[0035] In the method for forming a semiconductor structure provided by the technical solution of the present invention, the semiconductor device is used to form an N-type device. A work function layer is formed on a substrate, and the molar percentage concentration of aluminum atoms in the work function layer gradually decreases, that is, the molar percentage concentration of aluminum atoms in the bottom work function layer is high, and the molar percentage concentration of aluminum atoms in the top work function layer is low. Since the molar percentage concentration of aluminum atoms in the bottom work function layer is higher, it is more conducive to lowering the threshold voltage of the formed device, thereby improving the ability to adjust the threshold voltage of the device without changing the thickness of the work function layer. At the same time, the molar percentage concentration of aluminum atoms in the top work function layer is lower, which is conducive to reducing the probability of aluminum atoms accumulating in the work function layer. In summary, the method can improve the ability to adjust the threshold voltage of the device, thereby improving the performance of the formed semiconductor structure.

[0036] Furthermore, after the work function layer is formed, a barrier layer is formed on the surface of the work function layer. The barrier layer can reduce the influence of the external environment on the work function layer material, so that the performance of the work function layer remains stable, which is conducive to improving the performance of the formed semiconductor structure.

[0037] Furthermore, the work function layer and the barrier layer are formed in the same chamber, thereby avoiding the surface of the work function layer from being exposed to the external environment during the process of switching from one working chamber to another, further ensuring that the performance of the work function layer remains stable, which is beneficial to improving the performance of the formed semiconductor structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic structural diagram of an existing semiconductor structure;

[0039] Figures 2 to 141 is a schematic structural diagram of each step of a method for forming a semiconductor structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] It should be noted that the terms “surface” and “on” in this specification are used to describe relative positional relationships in space and are not limited to whether there is direct contact.

[0041] First, the reasons why the performance of the existing semiconductor structure is poor are described in detail with reference to the accompanying drawings. Figure 1 It is a structural schematic diagram of an existing semiconductor structure.

[0042] Please refer to Figure 1 , a semiconductor structure includes: a substrate 100; a high-K dielectric layer 110 located on the surface of the substrate 100; and a work function layer 120 located on the surface of the high-K dielectric layer 110.

[0043] In this embodiment, the semiconductor structure is used to form an N-type device. The work function layer 120 is made of a titanium-aluminum compound. The work function layer 120 can adjust the threshold voltage of the device. The higher the content of aluminum atoms in the work function layer 120, the lower the threshold voltage of the semiconductor structure.

[0044] To ensure a sufficiently low threshold voltage for the semiconductor structure, the aluminum content in the work function layer 120 can be increased by increasing the molar concentration of aluminum atoms in the work function layer 120, thereby effectively reducing the threshold voltage. However, if the molar concentration of aluminum atoms in the work function layer 120 is too high, the aluminum atoms in the material may aggregate to form particles, thereby affecting the performance of the work function layer 120.

[0045] To address the above issues, the molar percentage concentration of aluminum atoms in the work function layer 120 is reduced while the thickness of the work function layer 120 is increased, so that the aluminum content in the work function layer 120 remains high, thereby effectively reducing the threshold voltage. However, excessive thickness of the work function layer 120 reduces the process window, cannot meet the requirements of high device integration, and is detrimental to the performance of the semiconductor structure.

[0046] In order to solve the technical problem, an embodiment of the present invention provides a semiconductor structure and a method for forming the same, wherein the structure includes: a work function layer located on the substrate, the work function layer contains aluminum elements, the work function layer includes a first surface and a second surface relative to each other, the distance between the first surface and the substrate surface is less than the distance between the second surface and the substrate surface, and along the direction from the first surface to the second surface, the molar percentage concentration of aluminum atoms in the work function layer decreases. Since the molar percentage concentration of aluminum atoms in the bottom work function layer is higher, it is more conducive to reducing the threshold voltage of the formed device, thereby improving the ability to adjust the threshold voltage of the device without changing the thickness of the work function layer. At the same time, the molar percentage concentration of aluminum atoms in the top work function layer is lower, which is conducive to reducing the probability of aluminum atoms accumulating in the work function layer. In summary, the ability to adjust the threshold voltage of the device can be effectively improved, thereby improving the performance of the formed semiconductor structure.

[0047] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0048] Figures 2 to 14 1 is a schematic structural diagram of each step of a method for forming a semiconductor structure in an embodiment of the present invention.

[0049] Please refer to Figure 2 , providing a substrate 200.

[0050] The substrate 200 provides a process platform for subsequent formation of a semiconductor structure.

[0051] In this embodiment, the substrate 200 is made of single crystal silicon. In another embodiment, the substrate may be made of a semiconductor material such as single crystal germanium, silicon germanium, or gallium arsenide. In other embodiments, the substrate may be a semiconductor-on-insulator structure, which includes an insulator and a semiconductor material layer disposed on the insulator. The semiconductor material layer may be made of a semiconductor material such as silicon, germanium, silicon germanium, gallium arsenide, or indium gallium arsenide.

[0052] Please refer to Figure 3 , a high-K dielectric layer 210 is formed on the surface of the substrate 200 .

[0053] The high-K dielectric layer 210 is used to form a gate structure.

[0054] The material of the high-K dielectric layer 210 includes hafnium oxide, zirconium oxide, hafnium silicon oxide, lanthanum oxide, zirconium silicon oxide, titanium oxide, tantalum oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide or aluminum oxide.

[0055] In this embodiment, the material of the high-K dielectric layer 210 is hafnium oxide.

[0056] Please refer to Figure 4 , forming a protection layer 220 on the surface of the high-K dielectric layer 210 .

[0057] The protection layer 220 is used to isolate the high-K dielectric layer 210 from a subsequently formed work function layer.

[0058] The material of the protection layer 220 includes titanium nitride.

[0059] In this embodiment, the material of the protection layer 220 is titanium nitride.

[0060] Next, a work function layer is formed on the substrate 200, wherein the work function layer contains aluminum elements and oxygen elements. The work function layer includes a first surface and a second surface relative to each other, wherein the distance between the first surface and the surface of the substrate is smaller than the distance between the second surface and the surface of the substrate, and along the direction from the first surface to the second surface, the molar percentage concentration of aluminum atoms in the work function layer decreases, and the molar percentage concentration of oxygen atoms in the work function layer decreases.

[0061] In this embodiment, after the protective layer 220 is formed, the work function layer is formed on the surface of the protective layer 220 .

[0062] The method for forming the work function layer includes: performing several first treatments to form a first work function portion on the substrate 200; performing several second treatments to form a second work function portion on the first work function portion, and the molar percentage concentration of aluminum atoms in the first work function portion is greater than the molar percentage concentration of aluminum atoms in the second work function portion.

[0063] In this embodiment, the method for forming the work function layer further includes: after forming the first work function portion and before forming the second work function portion, performing a third treatment several times to form a third work function portion on the surface of the first work function portion, wherein the molar percentage concentration of aluminum atoms in the third work function portion is less than the molar percentage concentration of aluminum atoms in the first work function portion and greater than the molar percentage concentration of aluminum atoms in the second work function portion. For the specific process of forming the first work function portion, the second work function portion and the third work function portion, please refer to Figures 5 to 13 .

[0064] Please refer to Figure 5 , a first ventilation process is adopted to introduce the first gas 1 into the surface of the substrate 200 to form a first precursor film 231.

[0065] Specifically, in this embodiment, the first gas 1 is passed toward the surface of the protective layer 220 on the substrate 200 .

[0066] The first ventilation process includes: the first ventilation stage, introducing the first gas 1; and the first exhaust stage, removing the unadsorbed first gas 1.

[0067] The parameters of the first ventilation process include: the first gas 1 includes titanium-containing gas, the flow rate of the first gas 1 is 0 standard ml / min to 1000 standard ml / min, and the time of the first ventilation stage is 0 to 60 seconds.

[0068] Through the first ventilation stage, the introduced first gas 1 is saturatedly adsorbed on the surface of the protective layer 220 to form a monomolecular layer.

[0069] Through the first gas extraction stage, the unadsorbed first gas 1 is removed, so that the second gas 2 introduced subsequently can fully react with the first precursor film 231 .

[0070] In this embodiment, the first gas 1 is TiCl 4 .

[0071] Please refer to Figure 6 A second gas 2 is introduced using a second ventilation process, and the second gas 2 reacts with the first precursor film 231 to form a first work function material film 232 .

[0072] The second ventilation process includes: a second ventilation stage, introducing the second gas 2; and a second exhaust stage, removing the second gas 2 that has not reacted with the first precursor film 231.

[0073] During the second ventilation stage, the second gas 2 reacts with the first precursor film 231. In this embodiment, the aluminum element contained in the second gas 2 forms a chemical bond with the titanium element in the first precursor film 231, so that the material of the first work function material film 232 is a titanium aluminum compound.

[0074] The flow rate and time of the second gas 2 can affect the chemical reaction rate between the second gas 2 and the first precursor film 231, thereby affecting the content of the titanium aluminum compound in the formed first work function material film 232, and further affecting the molar percentage concentration of aluminum atoms.

[0075] The second pumping stage removes the unadsorbed second gas 2, thereby not affecting the subsequent ventilation process.

[0076] The parameters of the second ventilation process include: the second gas 2 includes aluminum-containing gas, the flow rate of the second gas 2 is 0 standard ml / min to 6000 standard ml / min, and the time of the second ventilation stage is 20 seconds to 60 seconds.

[0077] In this embodiment, the second gas 2 is Al(C2H5)3.

[0078] It should be noted that the first treatment includes the first ventilation process and the second ventilation process, and the first treatment is performed once to form the first work function material film 232 .

[0079] Please refer to Figure 7 , performing the first treatment multiple times to form a first work function portion 240 on the substrate 200 .

[0080] Specifically, the first work function material film 232 is formed multiple times by performing the first treatment multiple times, thereby forming the first work function portion 240 on the surface of the protection layer 220 .

[0081] In this embodiment, the thickness of the first work function portion 240 ranges from 5 angstroms to 50 angstroms; and the number of times the first treatment is performed ranges from 1 to 10 times.

[0082] In this embodiment, after forming the protective layer 220 and before forming the first work function part 240, the semiconductor structure is transferred from a vacuum chamber to a non-vacuum environment, and the surface of the protective layer 220 is exposed to the external environment, so that the molar percentage concentration of oxygen atoms in the first work function part 240 formed on the surface of the protective layer 220 is relatively large.

[0083] In this embodiment, the molar concentration of oxygen atoms in the first work function portion 240 ranges from 5% to 50%.

[0084] In other embodiments, after forming the first work function portion and before subsequently forming the rest of the work function layer, the semiconductor structure is transferred from one chamber to another chamber, and the first work function portion is exposed to the external environment, so that the molar percentage concentration of oxygen atoms in the first work function portion is larger.

[0085] The interface between the first work function portion 240 and the protective layer 220 contains oxygen elements, which is beneficial for driving aluminum elements to aggregate, thereby facilitating an increase in the molar percentage concentration of aluminum atoms in the first work function portion 240 .

[0086] The molar concentration of aluminum atoms in the first work function portion 240 is in a range of 70% to 90%.

[0087] Please refer to Figure 8 , a fifth ventilation process is used to introduce the first gas 1 into the surface of the substrate 200 to form a third precursor film 251 .

[0088] Specifically, the first gas 1 passes through the surface of the first work function portion 240 on the substrate 200 .

[0089] The fifth ventilation process includes: a fifth ventilation stage, introducing the first gas; and a fifth exhaust stage, removing the unadsorbed first gas.

[0090] Parameters of the fifth ventilation process include: the first gas 1 includes titanium-containing gas, the flow rate of the first gas 1 is 0 standard ml / min to 1000 standard ml / min, and the time of the fifth ventilation stage is 0 to 60 seconds.

[0091] In this embodiment, the first gas 1 is TiCl 4 .

[0092] Please refer to Figure 9 The second gas 2 is introduced by adopting the sixth ventilation process, and the second gas 2 reacts with the third precursor film 251 to form a third work function material film 252.

[0093] The sixth ventilation process includes: a sixth ventilation stage, introducing the second gas 2; and a sixth exhaust stage, removing the second gas 2 that has not reacted with the third work function material film 252.

[0094] The parameters of the sixth ventilation process include: the second gas 2 includes aluminum-containing gas, the flow rate of the second gas 2 is 0 standard ml / min to 6000 standard ml / min, and the time of the sixth ventilation stage is 15 seconds to 55 seconds.

[0095] In this embodiment, the second gas 2 is Al(C2H5)3.

[0096] It should be noted that, in this embodiment, the sixth ventilation stage time is shorter than the second ventilation stage time, and longer than the fourth ventilation stage time in the subsequent second treatment, so that the molar percentage concentration of aluminum atoms in the formed third work function material film 252 is smaller than the molar percentage concentration of aluminum atoms in the first work function material film 232, and is greater than the molar percentage concentration of aluminum atoms in the subsequently formed second work function material film.

[0097] It should be noted that the third process includes the fifth ventilation process and the sixth ventilation process, and the third process is performed once to form the third work function material film 252 .

[0098] Please refer to Figure 10 , performing the third treatment multiple times to form a third work function portion 260 on the substrate 200 .

[0099] Specifically, the third process is performed multiple times to form the third work function material film 252 multiple times, thereby forming the third work function portion 260 on the surface of the first work function portion 240 .

[0100] The number of times of the third treatment ranges from 1 to 10 times.

[0101] In this embodiment, the thickness of the third work function portion 260 is in a range of 5 angstroms to 50 angstroms.

[0102] In this embodiment, the molar concentration of aluminum atoms in the third work function portion 260 ranges from 60% to 80%.

[0103] In other embodiments, the third work function portion may not be formed.

[0104] Please refer to Figure 11 , a third ventilation process is used to introduce the first gas 1 into the surface of the substrate 200 to form a second precursor film 271.

[0105] Specifically, the first gas 1 passes through the surface of the third work function portion 260 on the substrate 200 .

[0106] The third ventilation process includes: a third ventilation stage, introducing the first gas 1; and a third exhaust stage, removing the unadsorbed first gas 1.

[0107] The parameters of the third ventilation process include: the first gas 1 includes titanium-containing gas, the inlet flow rate of the first gas 1 is 0 standard ml / min to 1000 standard ml / min, and the time of the third ventilation stage is 0 to 60 seconds.

[0108] In this embodiment, the first gas 1 is TiCl 4 .

[0109] Please refer to Figure 12 The second gas 2 is introduced by adopting the fourth ventilation process, and the second gas 2 reacts with the second precursor film 271 to form a second work function material film 272.

[0110] The fourth ventilation process includes: a fourth ventilation stage, introducing the second gas 2; and a fourth exhaust stage, removing the second gas 2 that has not reacted with the second precursor film 271.

[0111] The parameters of the fourth ventilation process include: the second gas 2 includes aluminum-containing gas, the inlet flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the duration of the fourth ventilation stage is 10 seconds to 50 seconds.

[0112] In this embodiment, the second gas 2 is Al(C2H5)3.

[0113] It should be noted that, in this embodiment, the fourth ventilation stage time is shorter than the second ventilation time, so that the molar percentage concentration of aluminum atoms in the formed second work function material film 272 is lower than the molar percentage concentration of aluminum atoms in the second precursor film 271 .

[0114] It should be noted that the second treatment includes the third ventilation process and the fourth ventilation process, and the second treatment is performed once to form the second work function material film 272 .

[0115] Please refer to Figure 13 , performing the second treatment multiple times to form a second work function portion 280 on the substrate 200 .

[0116] Specifically, the second work function material film 272 is formed multiple times by performing the second treatment multiple times, thereby forming the second work function portion 280 on the surface of the third work function portion 260 .

[0117] In this embodiment, the thickness of the second work function portion 280 ranges from 5 angstroms to 50 angstroms.

[0118] The number of times of the second treatment ranges from 1 to 10 times.

[0119] The molar concentration range of aluminum atoms in the second work function portion 280 is lower than the molar concentration range of aluminum atoms in the third work function portion 260 .

[0120] In this embodiment, the molar concentration of aluminum atoms in the second work function portion 280 ranges from 50% to 70%.

[0121] In this embodiment, the first work function portion 240 , the third work function portion 260 located on the surface of the first work function portion 240 , and the second work function portion 280 located on the surface of the third work function portion 260 constitute a work function layer 290 .

[0122] In this embodiment, the work function layer 290 includes a first surface 291 and a second surface 292 opposite to each other, and the distance between the first surface 291 and the surface of the substrate 200 is smaller than the distance between the second surface 292 and the surface of the substrate 200 .

[0123] Since the molar percentage concentration of aluminum atoms in the first work function portion 240 is greater than the molar percentage concentration of aluminum atoms in the third work function portion 260, the molar percentage concentration of aluminum atoms in the third work function portion 260 is greater than the molar percentage concentration of aluminum atoms in the second work function portion 280, and the second work function portion 280 is located on the surface of the third work function portion 260, and the third work function portion 260 is located on the surface of the first work function portion 240, therefore, along the direction from the first surface 291 to the second surface 292, the molar percentage concentration of aluminum atoms in the work function layer 290 gradually decreases.

[0124] The semiconductor device is used to form an N-type device. A work function layer 290 is formed on a substrate 200, and the molar percentage concentration of aluminum atoms in the work function layer 290 gradually decreases along the direction from the first surface 291 to the second surface 292, that is, the molar percentage concentration of aluminum atoms in the bottom work function layer 290 is high, and the molar percentage concentration of aluminum atoms in the top work function layer 290 is low. Since the molar percentage concentration of aluminum atoms in the bottom work function layer 290 is higher, it is more conducive to lowering the threshold voltage of the formed device, thereby improving the ability to adjust the threshold voltage of the device without changing the thickness of the work function layer 290. At the same time, the molar percentage concentration of aluminum atoms in the top work function layer 290 is lower, which is conducive to reducing the probability of aluminum atoms accumulating in the work function layer 290. In summary, the method can improve the ability to adjust the threshold voltage of the device, thereby improving the performance of the formed semiconductor structure.

[0125] Please refer to Figure 14 , forming a barrier layer 295 on the surface of the work function layer 290 .

[0126] Specifically, after the second work function portion 280 is formed, the barrier layer 295 is formed on the surface of the second work function portion 280 .

[0127] By forming a barrier layer 295 on the surface of the work function layer 290 , the barrier layer 295 can reduce the influence of the external environment on the work function layer 290 material, so that the performance of the work function layer 290 remains stable, thereby facilitating improving the performance of the formed semiconductor structure.

[0128] In this embodiment, the work function layer 290 and the barrier layer 295 are formed in the same reaction chamber.

[0129] The material of the barrier layer 295 includes: tantalum-containing nitride. In this embodiment, the material of the barrier layer 295 is tantalum nitride.

[0130] The molar concentration of oxygen atoms at the interface between the second work function portion 280 and the barrier layer 295 is in a range of 0% to 5%.

[0131] In this embodiment, the molar percentage concentration of oxygen atoms at the contact interface between the second work function portion 280 and the barrier layer 295 is 0, so that the aluminum elements in the work function layer 290 are not easily aggregated to the second work function portion 280, which is further beneficial to reducing the molar percentage concentration of aluminum atoms in the second work function portion 280.

[0132] Along the direction from the first surface 291 to the second surface 292, the molar percentage concentration of oxygen atoms in the work function layer 290 decreases. Since the oxygen element easily drives the aluminum element to gather in places with a higher molar percentage concentration of oxygen atoms, it is further beneficial to reduce the molar percentage concentration of aluminum atoms in the work function layer 290.

[0133] The work function layer 290 and the barrier layer 295 are formed in the same chamber, thereby preventing the surface of the work function layer 290 from being exposed to the external environment during the process of switching from one working chamber to another, further ensuring that the performance of the work function layer 290 remains stable, which is beneficial to improving the performance of the formed semiconductor structure.

[0134] Accordingly, the embodiment of the present invention further provides a semiconductor structure formed by the above method, please continue to refer to Figure 14 , including: a substrate 200; a work function layer 290 located on the substrate 200, the work function layer 290 containing aluminum elements, the work function layer 290 including a first surface 291 and a second surface 292 relative to each other, the distance between the first surface 291 and the surface of the substrate 200 is smaller than the distance between the second surface 292 and the surface of the substrate 200, and along the direction from the first surface 291 to the second surface 292, the molar percentage concentration of aluminum atoms in the work function layer 290 decreases.

[0135] The semiconductor device is used to form an N-type device. The work function layer 290 located on the substrate 200 contains aluminum elements, and the molar percentage concentration of aluminum atoms in the work function layer 290 gradually decreases as it moves away from the surface of the substrate 200. Since the molar percentage concentration of aluminum atoms in the bottom work function layer 290 is higher, it is more conducive to lowering the threshold voltage of the formed device, thereby improving the ability to adjust the threshold voltage of the device without changing the thickness of the work function layer 290. At the same time, the molar percentage concentration of aluminum atoms in the top work function layer 290 is lower, which is conducive to reducing the probability of aluminum atoms accumulating in the work function layer 290. In summary, the ability to adjust the threshold voltage of the device can be effectively improved, thereby improving the performance of the formed semiconductor structure.

[0136] The following is a detailed description with reference to the accompanying drawings.

[0137] The work function layer 290 includes a first work function portion 240 and a second work function portion 280 located on the first work function portion 240, and the molar percentage concentration range of aluminum atoms in the first work function portion 240 is 70% to 90%, and the molar percentage concentration range of aluminum atoms in the second work function portion 280 is 50% to 70%.

[0138] The work function layer 290 further includes a third work function portion 260 located between the first work function portion 240 and the second work function portion 280 . The molar percentage concentration of aluminum atoms in the third work function portion 260 ranges from 60% to 80%.

[0139] The material of the work function layer 290 includes titanium aluminum compound, titanium aluminum carbon compound or titanium aluminum oxide compound.

[0140] The work function layer 290 has a thickness ranging from 20 angstroms to 100 angstroms.

[0141] The semiconductor structure further includes: a barrier layer 295 located on the surface of the work function layer 290 ; a protection layer 220 located between the work function layer 290 and the substrate 200 ; and a high-K dielectric layer 210 located between the protection layer 220 and the substrate 200 .

[0142] The work function layer 290 has a barrier layer 295 on its surface. The barrier layer 295 can reduce the influence of the external environment on the work function layer 290 material, so that the performance of the work function layer 290 remains stable, thereby facilitating the improvement of the performance of the formed semiconductor structure.

[0143] The material of the barrier layer includes: tantalum-containing nitride; the material of the protective layer includes: titanium-containing nitride; the material of the high-K dielectric layer includes: the material of the high-K dielectric layer includes hafnium oxide, zirconium oxide, hafnium silicon oxide, lanthanum oxide, zirconium silicon oxide, titanium oxide, tantalum oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide or aluminum oxide.

[0144] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A semiconductor structure, characterized in that include: substrate; a work function layer located on the substrate, the work function layer containing aluminum and oxygen, the work function layer including a first surface and a second surface opposite to each other, the first surface being closer to the substrate surface than the second surface, and the molar percentage concentration of aluminum atoms in the work function layer decreasing and the molar percentage concentration of oxygen atoms in the work function layer decreasing along the direction from the first surface to the second surface; a barrier layer located on the surface of the work function layer; a protective layer located between the work function layer and the substrate; The molar percentage concentration of oxygen atoms in the work function layer at the interface between the work function layer and the protective layer is greater than the molar percentage concentration of oxygen atoms in the work function layer at the interface between the work function layer and the barrier layer.

2. The semiconductor structure according to claim 1, wherein The work function layer includes a first work function portion and a second work function portion located on the first work function portion, and the molar percentage concentration range of aluminum atoms in the first work function portion is 70% to 90%, and the molar percentage concentration range of aluminum atoms in the second work function portion is 50% to 70%.

3. The semiconductor structure according to claim 1, wherein: The work function layer further includes a third work function portion located between the first work function portion and the second work function portion, wherein the molar percentage concentration of aluminum atoms in the third work function portion ranges from 60% to 80%.

4. The semiconductor structure according to claim 1, wherein: The material of the work function layer includes titanium aluminum compound, titanium aluminum carbon compound or titanium aluminum oxide compound.

5. The semiconductor structure according to claim 1, wherein The work function layer has a thickness ranging from 20 angstroms to 100 angstroms.

6. The semiconductor structure according to claim 1, wherein Also includes: A high-K dielectric layer is located between the protective layer and the substrate.

7. The semiconductor structure according to claim 6, wherein: The molar percentage concentration of oxygen atoms at the interface between the work function layer and the protective layer is in a range of 5% to 50%; the molar percentage concentration of oxygen atoms at the interface between the work function layer and the barrier layer is in a range of 0% to 5%.

8. The semiconductor structure according to claim 6, wherein: The material of the barrier layer includes: tantalum-containing nitride; the material of the protective layer includes: titanium-containing nitride; the material of the high-K dielectric layer includes hafnium oxide, zirconium oxide, hafnium silicon oxide, lanthanum oxide, zirconium silicon oxide, titanium oxide, tantalum oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide or aluminum oxide.

9. A method for forming a semiconductor structure, characterized in that: include: providing a substrate; forming a work function layer on the substrate, the work function layer containing aluminum and oxygen, the work function layer including a first surface and a second surface opposite to each other, the first surface being closer to the substrate surface than the second surface, and the molar percentage concentration of aluminum atoms in the work function layer decreasing and the molar percentage concentration of oxygen atoms in the work function layer decreasing along the direction from the first surface to the second surface; Before forming the work function layer, forming a protective layer on the substrate; after forming the protective layer, forming the work function layer on the protective layer; after forming the work function layer, forming a barrier layer on the surface of the work function layer; The molar percentage concentration of oxygen atoms in the work function layer at the interface between the work function layer and the protective layer is greater than the molar percentage concentration of oxygen atoms in the work function layer at the interface between the work function layer and the barrier layer.

10. The method for forming a semiconductor structure according to claim 9, wherein: Before forming the work function layer, a high-K dielectric layer is formed on the surface of the substrate; and the protective layer is formed on the surface of the high-K dielectric layer.

11. The method for forming a semiconductor structure according to claim 10, wherein: The work function layer and the barrier layer are formed in the same reaction chamber.

12. The method for forming a semiconductor structure according to claim 9, wherein: The material of the work function layer includes titanium aluminum compound, titanium aluminum carbon compound or titanium aluminum oxide compound.

13. The method for forming a semiconductor structure according to claim 12, wherein: The method for forming the work function layer includes: performing several first treatments to form a first work function portion on the substrate; performing several second treatments to form a second work function portion on the first work function portion, and the molar percentage concentration of aluminum atoms in the first work function portion is greater than the molar percentage concentration of aluminum atoms in the second work function portion.

14. The method for forming a semiconductor structure according to claim 13, wherein: The thickness of the first work function portion ranges from 5 angstroms to 50 angstroms; the number of times of the first treatment ranges from 1 to 10 times.

15. The method for forming a semiconductor structure according to claim 13, wherein: The thickness of the second work function portion ranges from 5 angstroms to 50 angstroms; and the number of times of the second treatment ranges from 1 to 10.

16. The method for forming a semiconductor structure according to claim 13, wherein: The method for forming the work function layer also includes: after forming the first work function part and before forming the second work function part, performing several third treatments to form a third work function part on the surface of the first work function part, the molar percentage concentration of aluminum atoms in the third work function part is less than the molar percentage concentration of aluminum atoms in the first work function part, and is greater than the molar percentage concentration of aluminum atoms in the second work function part.

17. The method for forming a semiconductor structure according to claim 13, wherein: The first treatment method includes: using a first ventilation process to introduce a first gas into the surface of the substrate to form a first precursor film; using a second ventilation process to introduce a second gas, and the second gas reacts with the first precursor film to form a first work function material film.

18. The method for forming a semiconductor structure according to claim 17, wherein: The first ventilation process includes: a first ventilation stage, introducing the first gas; a first exhaust stage, removing the unadsorbed first gas; the second ventilation process includes: a second ventilation stage, introducing the second gas; a second exhaust stage, removing the second gas that has not reacted with the first precursor film.

19. The method for forming a semiconductor structure according to claim 18, wherein: The parameters of the first ventilation process include: the first gas includes titanium-containing gas, the inlet flow rate of the first gas is 0 standard ml / min to 1000 standard ml / min, and the time of the first ventilation stage is 0 to 60 seconds; the parameters of the second ventilation process include: the second gas includes aluminum-containing gas, the inlet flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the time of the second ventilation stage is 20 seconds to 60 seconds.

20. The method for forming a semiconductor structure according to claim 13, wherein: The second treatment method includes: using a third ventilation process to introduce a first gas to the surface of the substrate to form a second precursor film; using a fourth ventilation process to introduce a second gas, and the second gas reacts with the second precursor film to form a second work function material film.

21. The method for forming a semiconductor structure according to claim 20, wherein: The third ventilation process includes: a third ventilation stage, introducing the first gas; a third exhaust stage, removing the unadsorbed first gas; the fourth ventilation process includes: a fourth ventilation stage, introducing the second gas; a fourth exhaust stage, removing the second gas that has not reacted with the second precursor film.

22. The method for forming a semiconductor structure according to claim 21, wherein: The parameters of the third ventilation process include: the first gas includes titanium-containing gas, the flow rate of the first gas is 0 standard ml / min to 1000 standard ml / min, and the time of the third ventilation stage is 0 to 60 seconds; the parameters of the fourth ventilation process include: the second gas includes aluminum-containing gas, the flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the time of the fourth ventilation stage is 10 seconds to 50 seconds.

23. The method for forming a semiconductor structure according to claim 16, wherein: The third treatment method includes: using a fifth ventilation process to introduce a first gas into the substrate surface to form a third precursor film; using a sixth ventilation process to introduce a second gas, and the second gas reacts with the third precursor film to form a third work function material film.

24. The method for forming a semiconductor structure according to claim 23, wherein: The fifth ventilation process includes: a fifth ventilation stage, introducing the first gas; a fifth exhaust stage, removing the unadsorbed first gas; the sixth ventilation process includes: a sixth ventilation stage, introducing the second gas; a sixth exhaust stage, removing the second gas that has not reacted with the third precursor film.

25. The method for forming a semiconductor structure according to claim 24, wherein: The parameters of the fifth ventilation process include: the first gas includes titanium-containing gas, the flow rate of the first gas is 0 standard ml / min to 1000 standard ml / min, and the time of the fifth ventilation stage is 0 to 60 seconds; the parameters of the sixth ventilation process include: the second gas includes aluminum-containing gas, the flow rate of the second gas is 0 standard ml / min to 6000 standard ml / min, and the time of the sixth ventilation stage is 15 seconds to 55 seconds.

26. The method for forming a semiconductor structure according to claim 10, wherein: The molar percentage concentration of oxygen atoms at the interface between the work function layer and the protective layer is in a range of 5% to 50%; the molar percentage concentration of oxygen atoms at the interface between the work function layer and the barrier layer is in a range of 0% to 5%.

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