A preparation method for improving the compactness of a deposited metal thin film

Abstract

The application belongs to the technical field of semiconductor manufacturing, and particularly relates to a preparation method for improving the compactness of a deposited metal film, comprising the following steps: pre-sputtering a target material for 1-10 min by using a sputtering power of P1; transmitting a substrate into a magnetron sputtering vacuum cavity, setting the temperature of a carrier at 25-300 DEG C, keeping the vacuum degree of the cavity at 5.0*10 ‑8 Torr or below, inputting a first inert gas into the upper region of the magnetron sputtering vacuum cavity and inputting a second inert gas into the lower region, and the cavity reaction pressure is 2.3-9.3 mTorr; in the magnetron sputtering cavity, two inert gases with different molar masses are inputted respectively, a radio frequency current with a frequency of F1 is inputted to the target material, a radio frequency current with a frequency of F2 is inputted to the carrier, F1 is greater than or equal to F2, and the input of the two radio frequency powers greatly improves the plasma concentration between the target material and the carrier, and the compactness of the metal film can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor manufacturing, and particularly relates to a preparation method for improving the denseness of a deposited metal film. BACKGROUND

[0002] Thin film denseness is an evaluation index for thin film structure. Materials with good thin film denseness can maintain the integrity and stability of the materials, prevent the materials from being polluted and oxidized by external environment, and thus ensure the performance and application life of the materials. In material preparation, thin film denseness is of great significance to the performance and application of the materials. On the one hand, good film denseness can improve the mechanical properties and chemical stability of the materials, so that the materials are not prone to problems such as fracture and corrosion during use. On the other hand, film denseness can also affect the dielectric properties, optical properties and magnetic properties of the materials, thereby affecting the application field of the materials.

[0003] In the semiconductor manufacturing process, PVD (Physical Vapor Deposition) thin film deposition technology is a key technology, and magnetron sputtering film deposition is one of them. The denseness of the metal film is crucial for building complex microelectronic device structures. By precisely and uniformly depositing thin films onto substrates, the combination and accumulation of multiple thin films can be achieved, forming the required electronic accumulation and transmission channels. In semiconductor devices such as MOSFET (Metal Oxide Semiconductor Field Effect Transistor), metal silicide films are often used as gate materials, and their denseness helps to ensure good contact between the gate and the channel, reduce contact resistance and leakage current, and improve the switching speed and stability of the device. In semiconductor interconnection processes, Ti films can also be used as diffusion barriers, and their denseness helps to prevent metal atoms from diffusing into semiconductor materials during heat treatment, protecting the structure and performance of semiconductor devices from damage.

[0004] Existing magnetron sputtering technology is difficult to prepare thin films with high denseness. Most of them reduce the pressure of the sputtering gas, reduce the scattering of target atoms, and make the target atoms move to the substrate with higher kinetic energy to improve the denseness of the film. However, this method has very limited effect on improving the denseness of the film. SUMMARY

[0005] The application aims at overcoming the deficiencies in the prior art and providing a preparation method for improving the compactness of deposited metal thin film.

[0006] To achieve the above technical purposes, the technical solution adopted by the embodiments of the application is:

[0007] A preparation method for improving the compactness of deposited metal thin film, comprising the following steps:

[0008] (1) Pre-sputtering: using a sputtering power P1 to pre-sputter the target for 1-10 min;

[0009] (2) Magnetron sputtering preparation of metal thin film: transferring the substrate into a magnetron sputtering vacuum chamber, setting the temperature of the carrier at 25-300℃, keeping the vacuum degree of the chamber below 5.0x10 -8 Torr, introducing a first inert gas with a flow rate of 20-60 sccm into the upper region of the magnetron sputtering vacuum chamber, introducing a second inert gas with a flow rate of 20-100 sccm into the lower region of the magnetron sputtering vacuum chamber, and keeping the chamber reaction pressure at 2.3-9.3 mTorr;

[0010] The frequency of the radio frequency power source and matching network connected with the target is F1, the radio frequency input power of the target is P1, the frequency of the radio frequency power source and matching network connected with the carrier is F2, the radio frequency input power of the carrier is P2, the sputtering time is 60-600 s, and a titanium thin film is obtained.

[0011] Further, when magnetron sputtering is performed, a metal titanium target with a purity of 99.999% is selected, the diameter of the target is 300-302 mm, and the distance between the target and the substrate is 200-450 mm.

[0012] Further, F1 and F2 simultaneously satisfy the following conditions: F1≥2MHz, 400kHz≤F2≤27MHz, and F1≥F2.

[0013] Further, P1 and P2 satisfy the following conditions: 1000W≤P1≤10000W, 100W≤P2≤1000W.

[0014] Further, the molar mass of the first inert gas is greater than the molar mass of the second inert gas.

[0015] Further, the first inert gas is introduced into the upper region of the magnetron sputtering vacuum chamber close to the target, and the second inert gas is introduced into the lower region of the magnetron sputtering vacuum chamber close to the substrate carrier.

[0016] Further, the substrate is made of one of Si, GaAs, SiC, quartz glass, alumina, InP, GaN, Ga2O3 and AlN.

[0017] The technical scheme provided by the embodiment of the present application has the following beneficial effects:

[0018] The present application uses the ionization of two different molar mass inert gases, and applies two different frequency and power radio frequency power sources to the target and the carrier respectively to control the partition bombardment effect of the positive ions after the ionization of the two sputtered gases, so that the compact film with stronger anti-deterioration performance can be obtained after the same deterioration experiment.

[0019] The present application creatively proposes a method for improving the resistance of deposited metal film in a magnetron sputtering device, two different inert gases are introduced respectively, the main ionization regions of the two gases are in the upper and lower regions of the chamber, the ionization of the first inert gas is in the upper gas inlet region close to the cathode target, and the ionization of the second inert gas is in the lower gas inlet region close to the carrier. The ions in the two different glow discharge regions will bombard in different directions due to the existence of electric field, wherein the positive ions of the first inert gas bombard the target, so that the target atoms are deposited on the substrate, at the same time, the positive ions of the second inert gas bombard the film layer on the substrate surface with relatively small energy due to the relatively small mass, and two different frequency and power radio frequency power sources are applied to the target and the carrier respectively to control the bombardment effect of the positive ions after the ionization of the two sputtered gases.

[0020] The input of two radio frequency powers greatly improves the plasma concentration between the target and the carrier. Among them, the positive ions of the first inert gas bombard the target, so that the metal atoms are separated from the surface of the target, the metal atoms collide with the capacitively coupled plasma to generate a large number of metal ions, the metal ions will accelerate due to the negative bias voltage in addition to the original kinetic energy, and the kinetic energy will further increase to accelerate the migration to the substrate surface, when the metal ions form a film, the kinetic energy energy is converted into heat energy, which produces a heat annealing effect on the film, and the film is more compact. The positive ions of the second inert gas bombard the substrate surface, so that the loose atoms of the film on the substrate surface are bombarded, leaving more compact film-forming atoms, and the molar mass of the positive ions of the second inert gas is smaller than that of the positive ions of the first inert gas, so the bombardment energy is relatively small, and the closely combined film-forming atoms are not easily bombarded by the positive ions of the second inert gas. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the internal structure of the magnetron sputtering vacuum cavity in an embodiment of the present invention.

[0022] Figure 2 This is a cross-sectional SEM image of the titanium metal thin film prepared in Example 1 of the present invention.

[0023] Figure 3 This is a cross-sectional SEM image of the titanium metal thin film prepared in Example 2 of the present invention.

[0024] Figure 4 This is a cross-sectional SEM image of the titanium metal thin film prepared in Comparative Example 3 of this invention. Detailed Implementation

[0025] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "inner" and "outer", "upper" and "lower", "left" and "right" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1

[0028] A method for improving the density of deposited metal thin films, using an SJI-SEMI Depommerits P188Pro PVD system, employing a titanium target with a purity of 99.999% and a diameter of 300 mm, with a distance of 250 mm between the target and the silicon substrate; including the following steps:

[0029] (1) Pre-sputtering: Use 3000W sputtering power and pre-sputter the target for 5 minutes;

[0030] (2) For example Figure 1 As shown, the substrate silicon wafer is transferred to the magnetron sputtering vacuum chamber, the stage temperature is set to 200℃, and the chamber vacuum level is maintained at 5.0×10⁻⁶. -8 Below Torr, Ar with a flow rate of 30 sccm is introduced into the upper region of the cavity closer to the target, and He with a flow rate of 30 sccm is introduced into the lower region of the cavity closer to the substrate stage. The cavity reaction pressure is 3.5 mTorr.

[0031] The frequency of the radio frequency power source and matching network connected to the target material is 13.56 MHz, the radio frequency input power of the target material is 3000 W, the frequency of the radio frequency power source and matching network connected to the carrier is 2 MHz, the radio frequency input power of the carrier is 500 W, the sputtering time is 300 s, the titanium thin film is obtained, and the sheet resistance Rsl of the thin film is measured.

[0032] Comparative Example 1

[0033] A preparation method of a deposited metal thin film, using a Depomerits P188 Pro PVD device of SJI-SEMI, selecting a metal titanium target with a purity of 99.999%, a target diameter of 300 mm, and a distance between the target and the substrate silicon wafer of 250 mm; comprising the following steps:

[0034] (1) Pre-sputtering: using a sputtering power of 3000 W, pre-sputtering the target for 5 min;

[0035] (2) As shown in Figure 1 , the substrate silicon wafer is transported into the magnetron sputtering vacuum cavity, the temperature of the carrier is set to 200°C, the cavity vacuum degree is maintained below 5.0x10 -8 Torr, Ar with a flow rate of 60 sccm is introduced into the upper region of the cavity close to the target, no gas is introduced into the lower region of the cavity close to the carrier, and the cavity reaction pressure is 3.5 mTorr;

[0036] The frequency of the radio frequency power source and matching network connected to the target material is 13.56 MHz, the radio frequency input power of the target material is 3000 W, the frequency of the radio frequency power source and matching network connected to the carrier is 2 MHz, the radio frequency input power of the carrier is 500 W, the sputtering time is 300 s, the titanium thin film is obtained, and the sheet resistance Rsl of the thin film is measured.

[0037] The titanium thin films prepared in Example 1 and Comparative Example 1 are respectively placed in an annealing furnace at 300°C for thin film deterioration experiments. The specific conditions of the thin film deterioration experiment are: oxygen and water vapor are introduced into the annealing furnace, oxygen is introduced at a pressure of 190 Torr, water vapor is continuously introduced until the pressure rises to 380 Torr, and the sheet resistance Rsl of the thin film is measured again after the annealing furnace pressure is 380 Torr and the treatment time is 30 min. The sheet resistance changes of the dense thin films prepared in Example 1 and Comparative Example 1 before and after the deterioration experiment treatment are shown in Table 1 below.

[0038] Table 1 Comparison of sheet resistance of titanium thin films prepared in Example 1 and Comparative Example 1 before and after deterioration experiment treatment

[0039]

[0040] As can be seen from Table 1, He is added in Example 1 as the gas source of the plasma in the lower region of the magnetron sputtering vacuum chamber, and forms He + The bombardment of the surface of the silicon wafer makes the thin film denser, the sheet resistance growth value smaller, and the ability to resist deterioration experiments improved. The sheet resistance growth value indicates the degree of oxidation of the titanium thin film. The smaller the sheet resistance growth value, the stronger the denseness of the titanium thin film. Because the dense titanium thin film can protect the inner layer from being oxidized by the external environment, the loose titanium thin film is more easily affected by the deterioration experiment, resulting in a significant increase in the sheet resistance growth value.

[0041] Example 2

[0042] A preparation method for improving the denseness of a deposited metal thin film, using a Depomerits P188 Pro PVD device of SJI-SEMI, selecting a metal titanium target with a purity of 99.999% as the target material, the target material having a diameter of 300 mm, and the distance between the target material and the substrate silicon wafer being 250 mm; comprising the following steps:

[0043] (1) Pre-sputtering: using a sputtering power of 3000 W, pre-sputtering the target material for 5 min;

[0044] (2) Transporting the substrate silicon wafer into the magnetron sputtering vacuum chamber, setting the temperature of the carrier to 200°C, and keeping the vacuum degree of the chamber below 5.0x10 -8 Torr, introducing Ar with a flow rate of 30 sccm into the upper region of the chamber closer to the target, and introducing He with a flow rate of 30 sccm into the lower region of the chamber closer to the carrier, and the reaction pressure of the chamber being 3.5 mTorr;

[0045] The frequency of the radio frequency power source and matching network connected to the target material is 2 MHz, the radio frequency input power of the target material is 3000 W, the frequency of the radio frequency power source and matching network connected to the carrier is 400 KHz, the radio frequency input power of the carrier is 500 W, the sputtering time is 300 s, the titanium thin film is obtained, and the sheet resistance Rsl of the thin film is measured.

[0046] Comparative Example 2

[0047] A preparation method for a metal thin film, using a Depomerits P188 Pro PVD device of SJI-SEMI, selecting a metal titanium target with a purity of 99.999% as the target material, the target material having a diameter of 300 mm, and the distance between the target material and the substrate silicon wafer being 250 mm; comprising the following steps:

[0048] (1) Pre-sputtering: using a sputtering power of 3000 W, pre-sputtering the target material for 5 min;

[0049] (2) The substrate silicon wafer is transported into the magnetron sputtering vacuum cavity, the temperature of the carrier is set to 200°C, the vacuum degree of the cavity is kept below 5.0x10 -8 Torr, Ar with a flow rate of 60sccm is introduced into the upper region of the cavity close to the target, no gas is introduced into the lower region of the cavity close to the carrier, and the reaction pressure of the cavity is 3.5mTorr.

[0050] The frequency of the radio frequency power source and the matching network connected to the target is 2MHz, the input power of the target is 3000W, the frequency of the radio frequency power source and the matching network connected to the carrier is 400KHz, the input power of the carrier is 500W, the sputtering time is 300s, the titanium thin film is obtained, and the sheet resistance Rs1 of the titanium thin film is measured.

[0051] The titanium thin films prepared in Example 2 and Comparative Example 2 are respectively placed in an annealing furnace at 300°C for thin film deterioration experiments, and the specific conditions of the thin film deterioration experiments are as follows: oxygen and water vapor are introduced into the annealing furnace, oxygen is introduced, the pressure is 190 Torr, water vapor is continuously introduced until the pressure rises to 380 Torr, and the sheet resistance Rs2 of the titanium thin film is measured again after the pressure in the annealing furnace is 380 Torr and the treatment is performed for 30min.

[0052] The sheet resistance changes of the titanium thin films prepared in Example 2 and Comparative Example 2 before and after the deterioration experiment treatment are shown in Table 2.

[0053] Table 2 Comparison of sheet resistance of titanium thin films prepared in Example 2 and Comparative Example 2 before and after deterioration experiment treatment

[0054]

[0055] As shown in Table 2, Example 2 changes the frequency of the target and the carrier at the same time compared with Example 1, and Example 2 increases He gas as the gas source of the plasma in the lower region of the vacuum cavity compared with Comparative Example 2, and He + After ionization, it hammers the surface of the wafer, so that the thin film density is significantly improved, the sheet resistance growth value is reduced, and the ability to resist deterioration experiments is improved.

[0056] Comparative Example 3

[0057] A method for preparing a metal thin film, using a Depomerits P188 Pro PVD device of SJI-SEMI, selecting a metal titanium target with a purity of 99.999% as the target material, the diameter of the target material is 300mm, and the distance between the target material and the substrate silicon wafer is 250mm; comprising the following steps:

[0058] (1) Pre-sputtering: a sputtering power of 3000W is used to pre-sputter the target for 5min;

[0059] (2) The substrate silicon wafer is transported into the magnetron sputtering vacuum cavity, the temperature of the carrier is set to 200°C, the vacuum degree of the cavity is kept below 5.0x10 -8 Torr, Ar with a flow rate of 30 sccm is introduced into the upper region of the cavity close to the target, He with a flow rate of 30 sccm is introduced into the lower region of the cavity close to the carrier, the cavity reaction pressure is 3.5 mTorr, the input power of the direct current power supply to the target is set to 3000 W, the sputtering time is 300 s, a titanium thin film is obtained, and the sheet resistance Rsl of the titanium thin film is measured.

[0060] Comparative Example 4

[0061] A method for preparing a metal thin film, using a Depomerits P188 Pro PVD device of SJI-SEMI, selecting a metal titanium target with a purity of 99.999%, the diameter of the target is 300 mm, the distance between the target and the substrate silicon wafer is 250 mm; comprising the following steps:

[0062] (1) Pre-sputtering: using a sputtering power of 3000 W, pre-sputtering the target for 5 min;

[0063] (2) The substrate silicon wafer is transported into the magnetron sputtering vacuum cavity, the temperature of the carrier is set to 200°C, the vacuum degree of the cavity is kept below 5.0x10 -8 Torr. Then, Ar with a flow rate of 60 sccm is introduced into the upper region of the cavity close to the target, no He is introduced into the lower region of the cavity close to the carrier, the cavity reaction pressure is 3.5 mTorr, the input power of the direct current power supply to the target is set to 3000 W, the sputtering time is 300 s, a titanium thin film is obtained, and the sheet resistance Rsl of the titanium thin film is measured.

[0064] The titanium thin films prepared in Comparative Example 3 and Comparative Example 4 are placed in an annealing furnace at 300°C for thin film deterioration experiments, the specific conditions of the thin film deterioration experiments are the same as those in Example 1, and the sheet resistance changes of the prepared dense thin films before and after the deterioration experiment treatment are shown in Table 3 below.

[0065] Table 3 Comparison of sheet resistance of titanium thin films prepared in Comparative Example 3 and Comparative Example 4 before and after deterioration experiment treatment

[0066]

[0067] As shown in Table 3, when the target input power is changed from radio frequency to direct current, the sheet resistance of the thin film is greatly increased, the sheet resistance growth value is significantly increased, the anti-worsening experiment capability is greatly reduced, and the thin film density is decreased. In addition, when the target input power in Comparative Example 4 is changed from radio frequency to direct current and the He gas is not introduced into the lower region, the density of the titanium thin film is slightly lower than that of the titanium thin film prepared by introducing the He gas into the upper and lower regions in Comparative Example 3. The reason is that the plasma concentration during direct current sputtering is far lower than that during radio frequency sputtering, and there are a large number of neutral inert gas atoms in the chamber. The sputtered metal atoms are easily collided with the neutral gas atoms and scattered, so that the metal atoms lose a large amount of kinetic energy, resulting in the decrease of the migration ability of the film-forming atoms, and the thin film density is slightly reduced.

[0068] The He gas is introduced as the gas source of the plasma in the lower region of the vacuum chamber, and forms He + atoms after ionization. The He atoms bombard the surface of the substrate, so that the sheet resistance growth value is reduced, the anti-worsening experiment capability is improved, and the thin film density is significantly improved.

[0069] From Figure 2 and 3 It can be seen that the titanium thin films prepared by the target and the carrier under different radio frequency frequencies are all dense columnar crystal structures. The titanium thin film in Example 1 has higher density and more compact grain arrangement. From Figure 4 It can be seen that when the direct current power source is used for sputtering and only argon gas is used as the sputtering gas, the thin film density is obviously poor, and the thin film presents a straight loose sheet structure.

[0070] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application is described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a thin film with improved density, characterized in that, Includes the following steps: (1) Pre-sputtering: Use sputtering power of P1 to pre-sputter the target for 1-10 min; (2) Magnetron sputtering for metal thin film preparation: The substrate is transferred to the magnetron sputtering vacuum chamber, the stage temperature is set to 25-300℃, and the chamber vacuum is maintained at 5.0×10⁻⁶. -8 Below Torr, a first inert gas with a flow rate of 20-60 sccm is introduced into the upper region of the magnetron sputtering vacuum cavity, and a second inert gas with a flow rate of 20-100 sccm is introduced into the lower region of the magnetron sputtering vacuum cavity, with a cavity reaction pressure of 2.3-9.3 mTorr; The upper region of the magnetron sputtering vacuum cavity is closer to the target material, and the lower region of the magnetron sputtering vacuum cavity is closer to the substrate stage; The frequency of the RF power supply and matching network connected to the target is F1, the RF input power of the target is P1, the frequency of the RF power supply and matching network connected to the stage is F2, the RF input power of the stage is P2, and the sputtering time is 60-600s to obtain a titanium thin film. F1 and F2 simultaneously satisfy the following conditions: F1≥2MHz, 400kHz≤F2≤27MHz, and F1≥F2; P1 and P2 satisfy the following conditions: 1000W≤P1≤10000W, 100W≤P2≤1000W; The first inert gas is Ar, and the second inert gas is He.

2. The method for preparing a denser deposited metal thin film according to claim 1, characterized in that, When performing magnetron sputtering, a titanium target with a purity of 99.999% is selected, with a target diameter of 300-302mm and a distance of 200-450mm between the target and the substrate.

3. The method for preparing a denser deposited metal thin film according to claim 1, characterized in that, The substrate is made of one of Si, GaAs, SiC, quartz glass, alumina, InP, GaN, Ga2O3 and AlN.

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