Power device and preparation method thereof

Abstract

The invention provides a power device and a preparation method thereof. The preparation method comprises the following steps: (1) preheating a substrate in a self-ionization plasma reaction chamber; (2) performing first deposition on the surface of the preheated substrate to prepare a Ti film; (3) carrying out second deposition on the surface of the Ti film to prepare a TiN film; (4) vacuumizing and cooling the reaction chamber; (5) placing the substrate in a chemical vapor deposition reaction chamber, and carrying out third deposition to prepare a W film; argon and nitrogen are introduced in the second deposition process, and the flow ratio of the argon to the nitrogen is 1: (1-2). By regulating and controlling the TiN thin film deposition process, the roughness of the TiN thin film is remarkably reduced, and the phenomenon that the W thin film falls off due to defects such as dislocation or cracks is reduced; and the flow ratio of argon to nitrogen is regulated and controlled, the pressure stress and thermal stress in the TiN film are reduced, extrusion of the TiN film on the W film is avoided, and the problem that the W film falls off is further solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to power devices, and more particularly to a power device and its fabrication method. Background Technology

[0002] In power devices (such as SiC / GaN MOSFETs, IGBTs, and RF power devices), the combined application of self-ionized titanium nitride (TTN) and CVD tungsten thin films can significantly improve the electrical performance, thermal stability, reliability, and power density of the devices. The synergistic effect of the two is mainly reflected in: TTN optimizes interface characteristics such as contact resistance, adhesion, and diffusion barrier properties; CVD tungsten provides a low-resistance, high-melting-point conductive / interconnect layer and enhances heat dissipation. The combined application of these two technologies results in lower contact resistance, stronger current carrying capacity, more stable high-temperature performance, and better thermal management.

[0003] However, TTN is prone to defects such as stress, dislocations, and microcracks during its fabrication. Stress in the TiN film causes compressive stress in the TTN to be transferred to the W film at the TiN-W interface through atomic bonds (e.g., Ti-NW covalent / metallic bonds). This leads to elastic strain in the W lattice due to TiN compression, and the stress component parallel to the interface attempts to "slide" the W film away. If the stress distribution in TiN is uneven (e.g., stress concentration at the edges), the stress on the W film will also be uneven, leading to localized delamination. Simultaneously, dislocations and microcracks in the TiN film propagate towards the interface under stress, forming interfacial cracks. These cracks extend along the TiN / W interface or TiN grain boundaries. If the TiN / W interface bonding is weak (e.g., the presence of impurities or unreacted Ti), the cracks directly cause the W film to delaminate. If the W film is thick, plastic deformation (dislocation movement) may occur first, but ultimately, the stress will exceed the adhesion force, causing detachment. Therefore, reducing stress and defects in the TiN film is crucial to preventing W film detachment.

[0004] CN107475661A discloses a TiN thin film on a pure titanium surface and its in-situ self-growth method, including processes such as mechanical polishing, degreasing, surface chemical activation, and aging heat treatment of the pure titanium surface. This invention uses industrial pure N2 as the atmosphere source and aging heat treatment as the driving force for TiN thin film growth, enabling in-situ self-growth of a functional TiN thin film on a pure Ti surface. This effectively mitigates the high growth stress at the TiN / Ti interface caused by compositional or structural differences, reducing the tendency for surface film cracking.

[0005] CN1603428A discloses an annealing process for MOCVD TiN films. By performing post-annealing on the MOCVD TiN film, the film undergoes recrystallization and thermal reflow, becoming more dense and improving its flatness. Furthermore, by relying on gases such as N2 / H2 to remove impurities such as C and O from the TiN film, the stress of the TiN film is eliminated, the film resistance is reduced, and the film quality becomes more stable.

[0006] CN103540893A discloses a PVD method for preparing TiN, comprising: forming rare gas ions by glow discharge of rare gas under vacuum conditions filled with nitrogen and rare gas; nitriding the wafer surface and the Ti target surface using nitrogen; bombarding the Ti target surface with rare gas ions under an electric field acceleration to sputter TiN and Ti ions; depositing TiN on the wafer surface under a magnetic field to form a TiN layer, while Ti ions incident on the wafer surface cause stress in the TiN layer; increasing the kinetic energy of Ti ions incident on the wafer surface to increase the amorphization rate of the TiN layer, thereby increasing the stress of the TiN layer. According to the PVD method for preparing TiNx of the present invention, by controlling process parameters to increase the kinetic energy of Ti ions incident on the wafer, the amorphization rate of TiNx is increased, thereby increasing the stress of the TiNx film.

[0007] Therefore, it is of great significance to provide a method for fabricating power devices that can eliminate internal stress in TiN thin films and reduce defects in TiN thin films. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a power device and its fabrication method. This invention significantly reduces the roughness of the TiN thin film by controlling the TiN thin film deposition process, thereby reducing the phenomenon of W film detachment caused by defects such as dislocations or cracks. Simultaneously, by controlling the flow ratio of argon to nitrogen, the compressive stress generated in the TiN thin film due to sputtering, or the thermal stress generated by the exothermic reaction of Ti and N to form TiN, is reduced, thus avoiding the compression of the W film by the TiN film and further improving the problem of W film detachment.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for fabricating a power device, the method comprising:

[0011] (1) Place the substrate in a pre-evacuated self-ionizing plasma reaction chamber and preheat it; (2) Perform a first deposition on the substrate surface after preheating in step (1) to prepare a Ti thin film; (3) Perform a second deposition on the surface of the Ti thin film obtained in step (2) to prepare a TiN thin film; (4) Evacuate the self-ionizing plasma reaction chamber and cool it down; (5) Place the substrate with deposited Ti and TiN thin films in a chemical vapor deposition reaction chamber and perform a third deposition on the surface of the TiN thin film to prepare a W thin film; In step (3), argon and nitrogen are introduced during the second deposition process, and the flow rate ratio of argon to nitrogen is 1:(1~2).

[0012] This invention regulates the argon to nitrogen flow ratio to 1:(1~2) during TiN thin film deposition. On one hand, by controlling the N2 plasma density through the argon to nitrogen flow ratio, the compressive stress introduced by atoms squeezing into interstitial spaces or substitution sites caused by N2 plasma bombardment of the film surface is controlled. This controls the local non-equilibrium close-packed structure formed by the migration of atoms from the TiN film surface into the film interior, as well as the stress accumulation caused by ion bombardment of the film. On the other hand, controlling the argon to nitrogen flow ratio can prevent the formation of a nitrogen-rich phase and prevent excess N atoms from occupying the TiN surface. The interstitial sites in the center-cubic lattice prevent macroscopic compressive stress caused by an increase in the lattice constant. In addition, the flow ratio of argon to nitrogen affects the sputtering yield and the kinetic energy distribution of deposited atoms. A low flow ratio of argon to nitrogen will lead to a decrease in the average kinetic energy of deposited atoms, a decrease in surface mobility, the formation of porous or columnar structures, an increase in internal stress, and will also lead to enhanced gas phase scattering, causing atoms to be non-perpendicularly incident, exacerbating surface roughness and local stress concentration. Furthermore, the reaction of Ti and N to form TiN is an exothermic process, and an excessively high N2 flow rate may also lead to a local increase in substrate temperature, generating thermal stress.

[0013] The compressive stress of the TiN film will squeeze the W lattice, causing the W film to "slide" away. Therefore, the stress distribution in the TiN film is uneven, resulting in uneven stress on the W film, which leads to local peeling. The higher the surface roughness of the TiN film, the easier it is to form dislocation pile-up or microcracks, which will propagate towards the interface under stress. The TiN film with high surface roughness is prone to forming stress concentration points, which will aggravate the local strain of the W film and cause crack propagation. The formation of interface cracks at the TiN / W interface directly leads to the peeling of the W film or dislocation movement.

[0014] Preferably, argon gas is introduced during the first deposition process, and the flow rate of the argon gas is 8 sccm to 16 sccm.

[0015] Preferably, the source power of the first deposition is 10kW to 20kW.

[0016] Preferably, the bias power of the first deposition is 100W~300W.

[0017] Preferably, the source power of the second deposition is 10kW to 20kW.

[0018] Preferably, the bias power of the second deposition is 100W~300W.

[0019] Preferably, in step (3), during the second deposition process, the flow rate of argon gas is 5 sccm to 15 sccm.

[0020] Preferably, in step (3), during the second deposition process, the flow rate of nitrogen gas introduced is 10ccm~15sccm.

[0021] Preferably, the third deposition includes first introducing SiH4 to form an amorphous silicon layer on the TiN surface; then simultaneously introducing SiH4 and WF6 to form a W seed layer; and finally stopping the introduction of SiH4 while simultaneously introducing H2 and WF6 to deposit a W thin film.

[0022] Preferably, the Ti target is pre-sputtered before the first deposition and / or the second deposition.

[0023] Preferably, the thickness of the Ti thin film is 400 Å to 600 Å.

[0024] Preferably, the thickness of the TiN thin film is 800 Å to 1200 Å.

[0025] Preferably, the thickness of the W film is 0.5 μm to 2 μm.

[0026] Preferably, the preparation method further includes depositing SiO2 on the substrate surface before preheating the substrate.

[0027] Preferably, the thickness of the SiO2 is 800 Å to 1200 Å.

[0028] In this invention, the method of depositing SiO2 is not specifically limited; for example, it can be high-temperature oxidation or chemical vapor deposition.

[0029] Preferably, after the vacuuming in step (4), the pressure inside the reaction chamber is less than 10. -6 torr.

[0030] In a second aspect, the present invention provides a power device, which is prepared by the preparation method described in the first aspect.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention significantly reduces the roughness of TiN films by controlling the TiN film deposition process, thereby reducing the phenomenon of W film detachment caused by defects such as dislocations or cracks. At the same time, by controlling the flow ratio of argon and nitrogen, the compressive stress generated in the TiN film due to sputtering or the thermal stress generated by the exothermic process of Ti reacting with N to form TiN is reduced, thus avoiding the compression of the W film by the TiN film and further improving the problem of W film detachment.

[0033] In this invention, the terms "first aspect," "second aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity. Attached Figure Description

[0034] Figure 1 The image shows the surface morphology of the TiN thin film prepared in Example 1.

[0035] Figure 2 The image shows the surface morphology of the TiN thin film prepared in Example 4.

[0036] Figure 3 The image shows the surface morphology of the TiN thin film prepared in Comparative Example 1. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. In this invention, "a combination of at least two" means, unless otherwise specified, a quantity greater than or equal to two. For example, "any combination of one or at least two" means one or more of two. It is understood that when referring to "a combination of at least two," it means any suitable combination of multiple items, i.e., a combination of "at least two" items carried out in a manner that does not conflict with and allows for the implementation of the invention.

[0039] In the description of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0040] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0042] In one specific embodiment, the present invention provides a method for fabricating a power device, the method comprising:

[0043] (1) Place the substrate in a pre-evacuated self-ionizing plasma reaction chamber and preheat it; (2) Perform a first deposition on the surface of the substrate after preheating in step (1) to prepare a Ti thin film; (3) Perform a second deposition on the surface of the Ti thin film obtained in step (2) to prepare a TiN thin film; (4) Evacuate the self-ionizing plasma reaction chamber and cool it down; (5) Place the substrate with deposited Ti and TiN thin films in a chemical vapor deposition reaction chamber and perform a third deposition on the surface of the TiN thin film to prepare a W thin film; In step (3), argon and nitrogen are introduced during the second deposition process, and the flow ratio of argon to nitrogen is 1:(1~2), for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.

[0044] This invention regulates the argon to nitrogen flow ratio to 1:(1~2) during TiN thin film deposition. On one hand, by controlling the N2 plasma density through the argon to nitrogen flow ratio, the compressive stress introduced by atoms squeezing into interstitial spaces or substitution sites caused by N2 plasma bombardment of the film surface is controlled. This controls the local non-equilibrium close-packed structure formed by the migration of atoms from the TiN film surface into the film interior, as well as the stress accumulation caused by ion bombardment of the film. On the other hand, controlling the argon to nitrogen flow ratio can prevent the formation of a nitrogen-rich phase and prevent excess N atoms from occupying the TiN surface. The interstitial sites in the center-cubic lattice prevent macroscopic compressive stress caused by an increase in the lattice constant. In addition, the flow ratio of argon to nitrogen affects the sputtering yield and the kinetic energy distribution of deposited atoms. A low flow ratio of argon to nitrogen will lead to a decrease in the average kinetic energy of deposited atoms, a decrease in surface mobility, the formation of porous or columnar structures, an increase in internal stress, and will also lead to enhanced gas phase scattering, causing atoms to be non-perpendicularly incident, exacerbating surface roughness and local stress concentration. Furthermore, the reaction of Ti and N to form TiN is an exothermic process, and an excessively high N2 flow rate may also lead to a local increase in substrate temperature, generating thermal stress.

[0045] The compressive stress in the TiN film will compress the W lattice, causing the W film to "slide" away. Therefore, the uneven stress distribution in the TiN film leads to uneven stress on the W film, resulting in localized delamination. Higher surface roughness of the TiN film makes it easier for dislocation pile-ups or microcracks to form, which propagate towards the interface under stress. The formation of interfacial cracks at the TiN / W interface directly leads to W film delamination or dislocation movement. High surface roughness in the TiN film easily creates stress concentration points, which exacerbates local strain in the W film and triggers crack propagation.

[0046] This invention achieves simultaneous control of internal stress, defects, and roughness by regulating the TiN thin film deposition process, effectively improving the problem of W thin film detachment caused by stress or defects.

[0047] In some embodiments, argon gas is introduced during the first deposition process, and the flow rate of the argon gas is 8 sccm to 16 sccm, for example, it can be 8 sccm, 9 sccm, 10 sccm, 11 sccm, 12 sccm, 13 sccm, 14 sccm, 15 sccm or 16 sccm.

[0048] In some implementations, the source power of the first deposition is 10kW to 20kW, for example, it can be 10kW, 11kW, 12kW, 13kW, 14kW, 15kW, 16kW, 17kW, 18kW, 19kW or 20kW.

[0049] In some embodiments, the bias power of the first deposition is 100W to 300W, for example, it can be 100W, 125W, 150W, 175W, 200W, 225W, 250W, 275W or 300W.

[0050] In some embodiments, the source power of the second deposition is 10kW to 20kW, for example, it can be 10kW, 11kW, 12kW, 13kW, 14kW, 15kW, 16kW, 17kW, 18kW, 19kW or 20kW.

[0051] In some embodiments, the bias power of the second deposition is 100W to 300W, for example, it can be 100W, 125W, 150W, 175W, 200W, 225W, 250W, 275W or 300W.

[0052] In this invention, the nitrogen flow rate during the TiN thin film deposition process affects the N2 concentration in the plasma. + and N + The concentration of nitrogen gas. This invention improves the stress of TiN films by controlling the nitrogen flow rate, sputtering power, and bias power to influence the energy and density of the plasma bombarding the thin film.

[0053] If the nitrogen flow rate is too high, high-energy ions will bombard the surface of the thin film, forcing atoms to squeeze into the interstitial spaces or substitute sites, introducing compressive stress. The bombardment will also cause surface atoms to migrate into the interior of the thin film, forming a local non-equilibrium close-packed structure. At the same time, under the action of bias voltage, the ion bombardment will be further intensified, leading to stress accumulation.

[0054] In some embodiments, during the second deposition process in step (3), the flow rate of argon gas is 5 sccm to 15 sccm, for example, it can be 5 sccm, 6 sccm, 7 sccm, 8 sccm, 9 sccm, 10 sccm, 11 sccm, 12 sccm, 13 sccm, 14 sccm or 15 sccm.

[0055] In some embodiments, during the second deposition process in step (3), the flow rate of nitrogen gas is 10ccm to 15sccm, for example, it can be 10sccm, 10.5sccm, 11sccm, 11.5sccm, 12sccm, 12.5sccm, 13sccm, 13.5sccm, 14sccm, 14.5sccm or 15sccm.

[0056] In some embodiments, the third deposition includes first introducing SiH4 to form an amorphous silicon layer on the TiN surface; then simultaneously introducing SiH4 and WF6 to form a W seed layer; and finally stopping the introduction of SiH4 while simultaneously introducing H2 and WF6 to deposit a W thin film.

[0057] In some embodiments, during the formation of the amorphous silicon layer, the flow rate of SiH4 introduced is 20 sccm to 40 sccm, for example, it can be 20 sccm, 25 sccm, 30 sccm, 35 sccm or 40 sccm.

[0058] In some embodiments, during the formation of the W seed layer, the flow rate of SiH4 is 20 sccm to 30 sccm, for example, it can be 20 sccm, 22 sccm, 24 sccm, 26 sccm, 28 sccm or 30 sccm, and the flow rate of WF6 is 40 sccm to 60 sccm, for example, it can be 40 sccm, 45 sccm, 50 sccm, 55 sccm or 60 sccm.

[0059] In some embodiments, during the deposition of the W thin film, the flow rate of H2 is 500 sccm to 600 sccm, for example, 500 sccm, 520 sccm, 540 sccm, 560 sccm, 580 sccm or 600 sccm, and the flow rate of WF6 is 90 sccm to 100 sccm, for example, 90 sccm, 92 sccm, 94 sccm, 96 sccm, 98 sccm or 100 sccm.

[0060] In some embodiments, prior to the first and / or second deposition, the Ti target is pre-sputtered to clean its surface, remove oxides or contaminants, and activate the plasma. This creates a clean sputtering zone on the target surface, improving the purity of subsequent depositions.

[0061] In some embodiments, the thickness of the Ti film is 400 Å to 600 Å, for example, it can be 400 Å, 450 Å, 500 Å, 550 Å or 600 Å.

[0062] In some embodiments, the thickness of the TiN film is 800 Å to 1200 Å, for example, it can be 800 Å, 850 Å, 900 Å, 950 Å, 1000 Å, 1050 Å, 1100 Å, 1150 Å or 1200 Å.

[0063] In some embodiments, the thickness of the W film is 0.5 μm to 2 μm, for example, it can be 0.5 μm, 0.75 μm, 1 μm, 1.25 μm, 1.5 μm, 1.75 μm or 2 μm.

[0064] In some embodiments, the preparation method further includes depositing SiO2 on the substrate surface before preheating the substrate.

[0065] In some embodiments, the thickness of the SiO2 is 800 Å to 1200 Å, for example, it can be 800 Å, 850 Å, 900 Å, 950 Å, 1000 Å, 1050 Å, 1100 Å, 1150 Å or 1200 Å.

[0066] In this invention, the method of depositing SiO2 is not specifically limited; for example, it can be high-temperature oxidation or chemical vapor deposition.

[0067] In some embodiments, after the vacuuming in step (4), the pressure inside the reaction chamber is less than 10. -6 torr, for example, could be 0.1 × 10 -6 torr, 0.2×10 -6 torr, 0.3×10 -6 torr, 0.4×10 -6 torr, 0.5×10 -6 torr, 0.6×10 -6 torr, 0.7×10 -6 torr, 0.8×10 -6 torr or 0.9×10 -6 torr.

[0068] In another specific embodiment, the present invention provides a power device, which is prepared by the preparation method described in one of the preceding specific embodiments.

[0069] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0070] Example 1

[0071] This embodiment provides a method for fabricating a power device, the method comprising:

[0072] (1) Place a substrate pre-deposited with SiO2 of a thickness of 1000 Å in a pre-evacuated self-ionizing plasma reaction chamber and preheat it;

[0073] (2) Pre-sputter the Ti target to form a clean sputtering zone and activate the plasma;

[0074] (3) Set the argon flow rate to 12 sccm and the source power to 15 kW, and perform the first deposition on the substrate surface after preheating in step (1) to prepare a Ti thin film with a thickness of 500 Å;

[0075] (4) Set the source power to 15kW, the bias power to 100kW, the argon flow rate to 5sccm, the nitrogen flow rate to 10sccm, and the argon to nitrogen flow rate ratio to 1:2. Perform a second deposition on the surface of the Ti film obtained in step (3) to prepare a TiN film with a thickness of 1000Å.

[0076] (5) Evacuate the self-ionizing plasma reaction chamber to a pressure of 0.5 × 10⁻⁶. -6 torr, to cool down;

[0077] (6) Place the substrate with deposited Ti thin film and TiN thin film in the chemical vapor deposition reaction chamber, first introduce SiH4 to form an amorphous silicon layer on the TiN surface; then introduce SiH4 and WF6 at the same time to form a W seed layer; finally stop introducing SiH4 and introduce H2 and WF6 at the same time to deposit a W thin film with a thickness of 1μm.

[0078] Example 2

[0079] This embodiment provides a method for fabricating a power device, the method comprising:

[0080] (1) Place the substrate pre-deposited with SiO2 with a thickness of 800 Å in a pre-evacuated self-ionizing plasma reaction chamber and preheat it;

[0081] (2) Pre-sputter the Ti target to form a clean sputtering zone and activate the plasma;

[0082] (3) Set the argon flow rate to 8 sccm and the source power to 10 kW, and perform the first deposition on the substrate surface after preheating in step (1) to prepare a Ti thin film with a thickness of 400 Å;

[0083] (4) Set the source power to 10kW, the bias power to 80kW~120kW, the argon flow rate to 10sccm, the nitrogen flow rate to 10ccm, and the argon to nitrogen flow rate ratio to 1:1. Perform a second deposition on the surface of the Ti film obtained in step (3) to prepare a TiN film with a thickness of 800Å.

[0084] (5) Evacuate the self-ionizing plasma reaction chamber to a pressure of 0.8 × 10⁻⁶. -6 torr, to cool down;

[0085] (6) Place the substrate with deposited Ti thin film and TiN thin film in the chemical vapor deposition reaction chamber, first introduce SiH4 to form an amorphous silicon layer on the TiN surface; then introduce SiH4 and WF6 at the same time to form a W seed layer; finally stop introducing SiH4 and introduce H2 and WF6 at the same time to deposit a W thin film with a thickness of 0.5 μm.

[0086] Example 3

[0087] This embodiment provides a method for fabricating a power device, the method comprising:

[0088] (1) Place the substrate pre-deposited with SiO2 with a thickness of 1200 Å in a pre-evacuated self-ionizing plasma reaction chamber and preheat it;

[0089] (2) Pre-sputter the Ti target to form a clean sputtering zone and activate the plasma;

[0090] (3) Set the argon flow rate to 16 sccm and the source power to 20 kW. Perform the first deposition on the substrate surface after preheating in step (1) to prepare a Ti thin film with a thickness of 600 Å.

[0091] (4) Set the source power to 20kW, the bias power to 120kW, the argon flow rate to 15sccm, the nitrogen flow rate to 15sccm, and the argon to nitrogen flow rate ratio to 1:1. Perform a second deposition on the surface of the Ti film obtained in step (3) to prepare a TiN film with a thickness of 1200Å.

[0092] (5) Evacuate the self-ionizing plasma reaction chamber to a pressure of 0.9 × 10⁻⁶. -6 torr, to cool down;

[0093] (6) Place the substrate with deposited Ti thin film and TiN thin film in the chemical vapor deposition reaction chamber, first introduce SiH4 to form an amorphous silicon layer on the TiN surface; then introduce SiH4 and WF6 at the same time to form a W seed layer; finally stop introducing SiH4 and introduce H2 and WF6 at the same time to deposit a W thin film with a thickness of 2μm.

[0094] Example 4

[0095] This embodiment provides a method for preparing a power device. Except for adjusting the flow rate of nitrogen in step (4) to 20 sccm, the preparation method is the same as in embodiment 3.

[0096] Example 5

[0097] This embodiment provides a method for preparing a power device. Except for adjusting the flow rate of nitrogen in step (4) to 30 sccm, the preparation method is the same as in embodiment 3.

[0098] Example 6

[0099] This embodiment provides a method for fabricating a power device. The method is the same as that in Embodiment 1 except that step (2) is omitted.

[0100] Example 7

[0101] This embodiment provides a method for fabricating a power device. Except for the thickness of the TiN film deposited in step (4) being 700 Å, the method is the same as in Example 1.

[0102] Example 8

[0103] This embodiment provides a method for fabricating a power device. Except for the thickness of the TiN film deposited in step (4) being 1300 Å, the method is the same as in Example 1.

[0104] Comparative Example 1

[0105] This comparative example provides a method for preparing a power device. The preparation method is the same as in Example 1, except that the flow rate of argon gas in step (4) is adjusted to 15 sccm and the flow rate ratio of argon gas to nitrogen gas is 1:0.67.

[0106] Comparative Example 2

[0107] This comparative example provides a method for preparing a power device. The preparation method is the same as in Example 1 except that the flow rate of nitrogen in step (4) is adjusted to 15 sccm and the flow rate ratio of argon to nitrogen is 1:3.

[0108] Comparative Example 3

[0109] This comparative example provides a method for fabricating a power device. The method is the same as in Example 1 except that in step (5), no vacuum is drawn and the gas is stopped before cooling.

[0110] Performance testing:

[0111] The detachment of the W thin film from the surface of the power device prepared in all the above embodiments and comparative examples was observed, and the radius of curvature of the deposited TiN thin film was tested using the laser beam scanning method, based on the Stoney formula:

[0112]

[0113] Where: σ is the residual stress of the thin film, E s Base elastic modulus; ν s The base Poisson's ratio; t s R is the substrate thickness; R is the substrate radius of curvature; Δt is the film thickness. The stress of the TiN film is measured. In this invention, Es = 160 GPa, ν s =0.22, t s =625μm.

[0114] The surface roughness of the TiN films prepared in all examples and comparative examples was measured using atomic force microscopy (AFM). The arithmetic mean roughness Ra of the TiN film surface was calculated. The surface morphology images of the TiN films prepared in Examples 1, 4, and Comparative Example 1 are shown below. Figures 1 to 3 As shown.

[0115] The stress and roughness test results of TiN thin films are shown in Table 1.

[0116] Table 1

[0117]

[0118] According to the test results in Table 1, this invention significantly reduces the roughness of the TiN film by controlling the TiN film deposition process, thereby reducing the phenomenon of W film detachment caused by defects such as dislocations or cracks. At the same time, by controlling the flow ratio of argon to nitrogen, the compressive stress generated in the TiN film due to sputtering or the thermal stress generated by the exothermic process of Ti reacting with N to form TiN is reduced, thus avoiding the compression of the W film by the TiN film and further improving the problem of W film detachment.

[0119] According to the test results of Example 1, Comparative Example 1, and Comparative Example 2 in Table 1, if the flow ratio of argon to nitrogen does not meet the 1:(1~2) specified in this application during the deposition of TiN thin film, the compressive stress generated by N2 plasma bombardment, the stress concentration caused by the formation of nitrogen-rich phase, the unsatisfactory sputtering yield and kinetic energy distribution of deposited atoms, the internal stress caused by the large deviation of the stoichiometric ratio of Ti and N, and the thermal stress generated by the reaction will lead to excessive internal stress in the TiN thin film, which will squeeze the W thin film and cause the W thin film to "slide" and detach, resulting in local peeling. At the same time, the above-mentioned stress will increase the surface roughness of the TiN thin film, and the dislocation pile-up and microcracks formed will further exacerbate the detachment of the W thin film.

[0120] According to the test results of Examples 3, 4 and 5, even if the flow ratio of argon to nitrogen meets the 1:(1~2) specified in this application, if the flow rate of nitrogen is too high, high-energy ions will bombard the surface of the thin film, forcing atoms to squeeze into the interstitial spaces or substitution sites, introducing compressive stress. The bombardment will also cause surface atoms to migrate into the interior of the thin film, forming a local non-equilibrium close-packed structure. At the same time, under the action of bias voltage, the ion bombardment will be further aggravated, leading to stress accumulation, which will cause the W thin film to fall off.

[0121] According to the test results of Examples 1 and 6, if the Ti target is not pre-sputtered, the contaminants or oxides on the surface of the titanium target will affect the purity of the deposition, resulting in poor adhesion between the W film and the TiN film, making it easy to fall off.

[0122] Based on the test results of Examples 1, 7, and 8, if the TiN film thickness is too large, it becomes more difficult to release the thermal stress inside the film, making it easier to generate microcracks or even large, penetrating cracks. Excessive stress can also cause device deformation, all of which exacerbate the detachment of the W film. If the TiN film thickness is too small, the continuity and integrity of the TiN film cannot be guaranteed, and it cannot provide a solid and stable "foundation" for the subsequent W film deposited on its surface. Tungsten atoms cannot form a tight bond on the TiN film surface, resulting in poor adhesion and also exacerbating the detachment of the W film.

[0123] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for fabricating a power device, characterized in that, The preparation method includes: (1) Place the substrate in a pre-evacuated self-ionizing plasma reaction chamber and preheat it; (2) A first deposition is performed on the substrate surface after preheating in step (1) to prepare a Ti thin film; (3) A second deposition is performed on the surface of the Ti film obtained in step (2) to prepare a TiN film; (4) Evacuate and cool the self-ionizing plasma reaction chamber; (5) Place the substrate with deposited Ti thin film and TiN thin film in a chemical vapor deposition reaction chamber, and perform a third deposition on the surface of TiN thin film to prepare W thin film; In step (3), argon and nitrogen are introduced during the second deposition process, and the flow rate ratio of argon to nitrogen is 1:(1~2).

2. The preparation method according to claim 1, characterized in that, Argon gas is introduced during the first deposition process, and the flow rate of the argon gas is 8 sccm to 16 sccm; And / or, the source power of the first deposition is 10kW~20kW; And / or, the bias power of the first deposition is 100W~300W.

3. The preparation method according to claim 1, characterized in that, The source power for the second deposition is 10kW~20kW; And / or, the bias power of the second deposition is 100W~300W.

4. The preparation method according to claim 1, characterized in that, In step (3), during the second deposition process, the flow rate of argon gas introduced is 5 sccm to 15 sccm; And / or, in step (3) the second deposition process, the flow rate of nitrogen gas introduced is 10ccm~15sccm.

5. The preparation method according to claim 1, characterized in that, The third deposition process includes first introducing SiH4 to form an amorphous silicon layer on the TiN surface; then simultaneously introducing SiH4 and WF6 to form a W seed layer; and finally stopping the introduction of SiH4 while simultaneously introducing H2 and WF6 to deposit a W thin film.

6. The preparation method according to claim 1, characterized in that, Prior to the first and / or second deposition, the Ti target is pre-sputtered.

7. The preparation method according to claim 1, characterized in that, The thickness of the Ti thin film is 400 Å to 600 Å; And / or, the thickness of the TiN film is 800 Å to 1200 Å; And / or, the thickness of the W film is 0.5μm~2μm.

8. The preparation method according to claim 1, characterized in that, The preparation method further includes depositing SiO2 on the substrate surface before preheating the substrate.

9. The preparation method according to claim 1, characterized in that, After the vacuuming process described in step (4), the pressure inside the reaction chamber is less than 10. -6 torr.

10. A power device, characterized in that, The power device is prepared by the preparation method according to any one of claims 1 to 9.

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