Preparation method for improving compactness of deposited metal film

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and particularly relates to a preparation method for improving compactness of a deposited metal film, which comprises the following steps: pre-sputtering a target material for 1-10 minutes by adopting the sputtering power P1; the substrate is conveyed into a magnetron sputtering vacuum cavity, the temperature of the carrying table is set to be 25-300 DEG C, the vacuum degree of the cavity is kept below 5.0 * 10 <-8 > Torr, first inert gas is introduced into the upper area of the magnetron sputtering vacuum cavity, second inert gas is introduced into the lower area of the magnetron sputtering vacuum cavity, and the reaction pressure of the cavity is 2.3-9.3 mTorr; two kinds of inert gases with different molar masses are introduced into the magnetron sputtering cavity, the radio frequency current with the frequency of F1 is input into the target material, the radio frequency current with the frequency of F2 is input into the carrying table, F1 is larger than or equal to F2, and two kinds of radio frequency power are input, so that the plasma concentration between the target material and the carrying table is greatly improved; the compactness of the metal film can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a preparation method for improving the density of a deposited metal film. Background Art

[0002] Film density is an evaluation index of film structure. Materials with good film density can maintain the integrity and stability of the material, prevent the material from being polluted and oxidized by the external environment, and thus ensure the performance and application life of the material. In material preparation, film density is of vital importance to the performance and application of the material. On the one hand, good film density can improve the mechanical properties and chemical stability of the material, making the material less prone to problems such as breakage and corrosion during use. On the other hand, film density can also affect the dielectric properties, optical properties, and magnetic properties of the material, thereby affecting the application field of the material.

[0003] In the semiconductor manufacturing process, PVD (Physical Vapor Deposition, referred to as PVD) thin film deposition technology is a key technology, and magnetron sputtering coating is one of them. The density of metal films is crucial to the construction of complex microelectronic device structures. By accurately and uniformly depositing thin films on substrates, the combination and accumulation of multiple layers of thin films can be achieved to form the required electron 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. Their density 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 the semiconductor interconnection process, Ti film can also be used as a diffusion barrier layer. Its density helps to prevent metal atoms from diffusing into the semiconductor material during heat treatment, protecting the structure and performance of semiconductor devices from damage.

[0004] Existing magnetron sputtering technology is difficult to produce high-density films. Most of them improve the density of the film by reducing the pressure of the sputtering gas and reducing the scattering of the target atoms, so that the target atoms move toward the substrate with higher kinetic energy. However, this method has a very limited effect on improving the density of the film. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for improving the density of deposited metal films. The present invention introduces two inert gases of different molar masses into the magnetron sputtering chamber, respectively, introducing the first inert gas into the upper region of the chamber closer to the target material, and introducing the second inert gas into the lower region of the chamber closer to the carrier, the molar mass of the first inert gas is greater than the molar mass of the second inert gas; the target material is input with a radio frequency of F1, and the carrier is input with a radio frequency of F2, the radio frequency F1 is greater than or equal to the radio frequency F2, and the input of the two radio frequency powers greatly improves the plasma concentration between the target material and the carrier, which can improve the density of the prepared metal film.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is: A preparation method for improving the density of a deposited metal film comprises the following steps: (1) Pre-sputtering: Use a sputtering power of P1 and pre-sputter the target for 1-10 min; (2) Preparation of metal film by magnetron sputtering: The substrate is transferred to the magnetron sputtering vacuum chamber, the stage temperature is set to 25-300°C, and the chamber vacuum is maintained at 5.0×10 -8 Torr or less, a first inert gas with a flow rate of 20-60 sccm is introduced into the upper area of ​​the magnetron sputtering vacuum chamber, and a second inert gas with a flow rate of 20-100 sccm is introduced into the lower area of ​​the magnetron sputtering vacuum chamber, and the chamber reaction pressure is 2.3-9.3 mTorr; 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 carrier is F2, the RF input power of the carrier is P2, and the sputtering time is 60-600s to obtain a titanium film.

[0007] Furthermore, when magnetron sputtering is performed, a metal titanium target with a target purity of 99.999% is selected, the target diameter is 300-302 mm, and the distance between the target and the substrate is 200-450 mm.

[0008] Furthermore, F1 and F2 simultaneously satisfy the following conditions: F1≥2MHz, 400kHz≤F2≤27MHz, and F1≥F2.

[0009] Furthermore, P1 and P2 satisfy the following conditions: 1000W≤P1≤10000W, 100W≤P2≤1000W.

[0010] Further, the molar mass of the first inert gas is greater than the molar mass of the second inert gas.

[0011] Furthermore, the first inert gas is introduced into an upper region of the magnetron sputtering vacuum chamber that is closer to the target material, and the second inert gas is introduced into a lower region of the magnetron sputtering vacuum chamber that is closer to the substrate carrier.

[0012] Furthermore, the substrate is made of one of Si, GaAs, SiC, quartz glass, alumina, InP, GaN, Ga2O3 and AlN.

[0013] The technical solution provided by the embodiment of the present invention has the following beneficial effects: The present invention utilizes the ionization of two inert gases with different molar masses, and applies two radio frequency power supplies of different frequencies and powers to the target material and the carrier respectively to control the partition bombardment effect of positive ions after the two gases are ionized by sputtering. The prepared film is subjected to the same deterioration experimental treatment to obtain a dense film with stronger anti-deterioration experimental performance.

[0014] The present invention creatively proposes a method for improving the resistance of deposited metal film in magnetron sputtering equipment, by respectively introducing two different inert gases, the main ionization areas of the two gases are respectively in the upper and lower areas of the cavity, the first inert gas is ionized in the upper gas inlet area close to the cathode target, and the second inert gas is ionized in the lower gas inlet area close to the carrier. The ions in the two different glow discharge areas will bombard in different directions due to the existence of the electric field, wherein the positive ions of the first inert gas bombard the target material, so that the target atoms are deposited on the substrate, and at the same time, the positive ions of the second inert gas bombard the film layer on the surface of the substrate with less energy due to their relatively small mass, and two power supplies with different frequencies and radio frequency powers are applied to the target material and the carrier respectively to control the bombardment effect of the positive ions after the ionization of the two gases during sputtering.

[0015] The input of two kinds of RF power greatly increases the plasma concentration between the target material and the carrier. Among them, the first inert gas positive ions bombard the target material, causing the metal atoms to detach from the target surface. The metal atoms collide with the capacitively coupled plasma to produce a large number of metal ions. In addition to the original kinetic energy, the metal ions will be accelerated by the negative bias voltage, and the kinetic energy will be further increased, accelerating the migration to the substrate surface. When the metal ions form a film, the kinetic energy is converted into thermal energy, which has a thermal annealing effect on the film, making the film denser. The second inert gas positive ions bombard the substrate surface, so that the loose film atoms on the substrate surface are bombarded, leaving behind film-forming atoms with a denser structure. The molar mass of the second inert gas positive ions is smaller than that of the first inert gas positive ions, and its bombardment energy is relatively small. The tightly bound film-forming atoms are not easily bombarded by the second inert gas positive ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1Schematic diagram of the internal structure of the magnetron sputtering vacuum chamber in an embodiment of the present invention.

[0017] Figure 2 This is a cross-sectional SEM image of the titanium metal film prepared in Example 1 of the present invention.

[0018] Figure 3 This is a cross-sectional SEM image of the titanium metal film prepared in Example 2 of the present invention.

[0019] Figure 4 It is a cross-sectional SEM image of the titanium metal film prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0020] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "inside, outside", "up, down", "left, right", etc. are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention.

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] Example 1 A preparation method for improving the density of a deposited metal film, using Depomerits P188Pro PVD equipment from SJI-SEMI, selecting a metal titanium target with a target purity of 99.999%, a target diameter of 300 mm, and a distance between the target and a substrate silicon wafer of 250 mm; comprising the following steps: (1) Pre-sputtering: Use a sputtering power of 3000 W and pre-sputter the target for 5 min; (2) If Figure 1 As shown, the substrate silicon wafer is transferred to the magnetron sputtering vacuum chamber, the stage temperature is set to 200°C, and the chamber vacuum is maintained at 5.0×10 -8 Torr, 30 sccm of Ar was introduced into the upper area of ​​the chamber closer to the target, and 30 sccm of He was introduced into the lower area of ​​the chamber closer to the substrate stage. The reaction pressure of the chamber was 3.5 mTorr. The frequency of the RF power supply and matching network connected to the target material is 13.56 MHz, the RF input power of the target material is 3000 W, the frequency of the RF power supply and matching network connected to the carrier is 2 MHz, the RF input power of the carrier is 500 W, the sputtering time is 300 s, a titanium thin film is obtained, and the film square resistance Rs1 is measured.

[0023] Comparative Example 1 A method for preparing a deposited metal film, using Depomerits P188 Pro PVD equipment from SJI-SEMI, selecting a metal titanium target with a target purity of 99.999%, a target diameter of 300 mm, and a distance between the target and a substrate silicon wafer of 250 mm; comprising the following steps: (1) Pre-sputtering: Use a sputtering power of 3000 W and pre-sputter the target for 5 min; (2) If Figure 1 As shown, the substrate silicon wafer is transferred to the magnetron sputtering vacuum chamber, the stage temperature is set to 200°C, and the chamber vacuum is maintained at 5.0×10 -8 Torr or less, Ar with a flow rate of 60 sccm is introduced into the upper area of ​​the chamber closer to the target, and no gas is introduced into the lower area of ​​the chamber closer to the stage, and the reaction pressure of the chamber is 3.5 mTorr; The frequency of the RF power supply and matching network connected to the target material is 13.56 MHz, the target material input power is 3000 W, the frequency of the RF power supply and matching network connected to the carrier is 2 MHz, the carrier input power is 500 W, the sputtering time is 300 s, a titanium thin film is obtained, and the film square resistance Rs1 is measured.

[0024] The titanium films prepared in Example 1 and Comparative Example 1 were placed in an annealing furnace at 300°C for film deterioration experiments. The specific conditions of the film deterioration experiments were as follows: oxygen and water vapor were introduced into the annealing furnace. The oxygen was introduced at a pressure of 190 Torr, and water vapor was introduced until the pressure rose to 380 Torr. The annealing furnace pressure was 380 Torr. After 30 minutes of treatment, the film square resistance Rs2 was measured again. The changes in square resistance before and after the deterioration experiment of the dense films prepared in Example 1 and Comparative Example 1 are shown in Table 1 below.

[0025] Table 1 Comparison of square resistance of titanium thin films prepared in Example 1 and Comparative Example 1 before and after deterioration experimental treatment As shown in Table 1, in Example 1, He is added as the gas source of the plasma in the lower area of ​​the magnetron sputtering vacuum chamber, and He is formed after ionization. +Bombarding the surface of the silicon wafer significantly improves the density of the film, reduces the square resistance growth value, and improves the ability to resist degradation experiments. The increase in square resistance indicates the degree of oxidation of the titanium film. The smaller the square resistance growth, the stronger the density of the titanium film. Because the dense titanium film can protect the inner layer from being easily oxidized by the external environment, and the loose titanium film is more easily affected by the degradation experiment, resulting in a significant increase in the square resistance growth value of the film.

[0026] Example 2 A preparation method for improving the density of a deposited metal film, using Depomerits P188Pro PVD equipment from SJI-SEMI, selecting a metal titanium target with a target purity of 99.999%, a target diameter of 300 mm, and a distance between the target and a substrate silicon wafer of 250 mm; comprising the following steps: (1) Pre-sputtering: Use a sputtering power of 3000 W and pre-sputter the target for 5 min; (2) The substrate silicon wafer was transferred to the magnetron sputtering vacuum chamber. The stage temperature was set to 200°C and the chamber vacuum was maintained at 5.0×10 -8 Torr, 30 sccm of Ar was introduced into the upper area of ​​the chamber closer to the target, and 30 sccm of He was introduced into the lower area of ​​the chamber closer to the stage. The reaction pressure of the chamber was 3.5 mTorr. The frequency of the RF power supply and matching network connected to the target material is 2MHz, the RF input power of the target material is 3000W, the frequency of the RF power supply and matching network connected to the carrier is 400KHz, the RF input power of the carrier is 500W, the sputtering time is 300s, a titanium thin film is obtained, and the film square resistance Rs1 is measured.

[0027] Comparative Example 2 A method for preparing a metal film, using Depomerits P188 Pro PVD equipment from SJI-SEMI, selecting a metal titanium target with a target purity of 99.999%, a target diameter of 300 mm, and a distance between the target and a substrate silicon wafer of 250 mm; comprising the following steps: (1) Pre-sputtering: Use a sputtering power of 3000 W and pre-sputter the target for 5 min; (2) The substrate silicon wafer was transferred to the magnetron sputtering vacuum chamber. The stage temperature was set to 200°C and the chamber vacuum was maintained at 5.0×10 -8 Torr, Ar with a flow rate of 60 sccm was introduced into the upper area of ​​the cavity closer to the target, and no gas was introduced into the lower area of ​​the cavity closer to the stage. The reaction pressure of the cavity was 3.5 mTorr.

[0028] The frequency of the RF power supply and matching network connected to the target material is 2MHz, the target material input power is 3000W, the frequency of the RF power supply and matching network connected to the carrier is 400KHz, the input power of the carrier is 500W, the sputtering time is 300s, and a titanium thin film is obtained, and the square resistance Rs1 of the titanium thin film is measured.

[0029] The titanium films prepared in Example 2 and Comparative Example 2 were respectively placed in an annealing furnace at 300°C for a film deterioration experiment. The specific conditions of the film deterioration experiment were as follows: oxygen and water vapor were introduced into the annealing furnace. Oxygen was introduced at a pressure of 190 Torr, and water vapor was continued to be introduced until the pressure rose to 380 Torr. When the pressure in the annealing furnace was 380 Torr, after treatment for 30 minutes, the square resistance Rs2 of the titanium film was measured again.

[0030] The changes in square resistance of the titanium films prepared in Example 2 and Comparative Example 2 before and after the deterioration experimental treatment are shown in Table 2 below.

[0031] Table 2 Comparison of square resistance of titanium thin films prepared in Example 2 and Comparative Example 2 before and after deterioration experimental treatment As shown in Table 2, compared with Example 1, Example 2 changes the target material and the carrier frequency at the same time. Compared with Comparative Example 2, Example 2 adds He gas as the gas source of the plasma in the lower area of ​​the vacuum chamber. After ionization, He + Bombarding the wafer surface significantly improves the density of the film, reduces the growth value of square resistance, and improves the ability to resist degradation experiments.

[0032] Comparative Example 3 A method for preparing a metal film, using Depomerits P188 Pro PVD equipment from SJI-SEMI, selecting a metal titanium target with a target purity of 99.999%, a target diameter of 300 mm, and a distance between the target and a substrate silicon wafer of 250 mm; comprising the following steps: (1) Pre-sputtering: Use a sputtering power of 3000 W and pre-sputter the target for 5 min; (2) The substrate silicon wafer is transferred to the magnetron sputtering vacuum chamber. The temperature of the stage is set to 200°C and the vacuum degree of the chamber is maintained at 5.0×10 -8 Torr, 30 sccm of Ar was introduced into the upper area of ​​the cavity closer to the target, and 30 sccm of He was introduced into the lower area of ​​the cavity closer to the stage. The reaction pressure of the cavity was 3.5 mTorr, the input power of the DC power supply to the target was set to 3000 W, the sputtering time was 300 s, a titanium thin film was obtained, and the square resistance Rs1 of the titanium thin film was measured.

[0033] Comparative Example 4 A method for preparing a metal film, using Depomerits P188 Pro PVD equipment from SJI-SEMI, selecting a metal titanium target with a target purity of 99.999%, a target diameter of 300 mm, and a distance between the target and a substrate silicon wafer of 250 mm; comprising the following steps: (1) Pre-sputtering: Use a sputtering power of 3000 W and pre-sputter the target for 5 min; (2) The substrate silicon wafer was transferred to the magnetron sputtering vacuum chamber. The stage temperature was set to 200°C and the chamber vacuum was maintained at 5.0×10 -8 Then, Ar with a flow rate of 60 sccm was introduced into the upper area of ​​the cavity closer to the target, and He was not introduced into the lower area of ​​the cavity closer to the stage. The cavity reaction pressure was 3.5 mTorr, the input power of the DC power supply to the target was set to 3000 W, the sputtering time was 300 s, and a titanium film was obtained, and the square resistance Rs1 of the titanium film was measured.

[0034] The titanium films prepared in Comparative Examples 3 and 4 were placed in an annealing furnace at 300°C for a film deterioration experiment. The specific conditions of the film deterioration experiment were the same as those in Example 1. The changes in square resistance of the prepared dense films before and after the deterioration experiment are shown in Table 3 below.

[0035] Table 3 Comparison of square resistance of titanium thin films prepared in comparative examples 3 and 4 before and after deterioration experimental treatment It can be seen from Table 3 that when the input power of the target material is changed from RF to DC, the square resistance of the film is greatly increased, the growth value of the square resistance of the film is significantly increased, the anti-deterioration experimental ability is greatly reduced, and the density of the film is reduced. In addition, when the input power of the target material in Comparative Example 4 is changed from RF to DC and the He gas is not introduced into the lower area, the density of the titanium film obtained is slightly lower than the density of the titanium film obtained by ventilating the upper and lower areas of Comparative Example 3 at the same time. The reason is that during DC sputtering, the plasma concentration is much lower than that of RF sputtering, and there are a large number of neutral inert gas atoms in the cavity. The sputtered metal atoms are easily collided with neutral gas atoms and scattered, causing the metal atoms to lose a lot of kinetic energy, resulting in a decrease in the migration ability of the film-forming atoms and a decrease in the density of the film.

[0036] He gas is added as the gas source of the plasma in the lower area of ​​the vacuum chamber, and He is formed after ionization. + Bombarding the substrate surface reduces the growth value of the film's square resistance and improves its ability to resist degradation experiments, that is, the film's density is significantly improved.

[0037] from Figure 2 and 3It can be seen that the titanium films prepared by the target and the carrier at different RF frequencies all grow into dense columnar crystal structures, among which the titanium film in Example 1 has higher density and more densely arranged grains; Figure 4 It can be seen that when DC power is used for sputtering and only argon is used as the sputtering gas, the density of the film is obviously poor, and the film presents an upright loose flaky structure.

[0038] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A preparation method for improving the density of a deposited metal film, characterized in that: The following steps are involved: (1) Pre-sputtering: Use a sputtering power of P1 and pre-sputter the target for 1-10 min; (2) Preparation of metal film by magnetron sputtering: The substrate is transferred to the magnetron sputtering vacuum chamber, the stage temperature is set to 25-300°C, and the chamber vacuum is maintained at 5.0×10 -8 Torr or less, a first inert gas with a flow rate of 20-60 sccm is introduced into the upper area of ​​the magnetron sputtering vacuum chamber, and a second inert gas with a flow rate of 20-100 sccm is introduced into the lower area of ​​the magnetron sputtering vacuum chamber, and the chamber reaction pressure is 2.3-9.3 mTorr; 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 carrier is F2, the RF input power of the carrier is P2, and the sputtering time is 60-600s to obtain a titanium film.

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

3. The method for improving the density of a deposited metal film according to claim 1, characterized in that: F1 and F2 simultaneously satisfy the following conditions: F1 ≥ 2 MHz, 400 kHz ≤ F2 ≤ 27 MHz, and F1 ≥ F2.

4. The method for improving the density of a deposited metal film according to claim 1, characterized in that: P1 and P2 meet the following conditions: 1000W≤P1≤10000W, 100W≤P2≤1000W.

5. The method for improving the density of a deposited metal film according to claim 1, characterized in that: The molar mass of the first inert gas is greater than the molar mass of the second inert gas.

6. The method for improving the density of a deposited metal film according to claim 1, characterized in that: The first inert gas is introduced into the upper region of the magnetron sputtering vacuum chamber which is closer to the target material, and the second inert gas is introduced into the lower region of the magnetron sputtering vacuum chamber which is closer to the substrate carrier.

7. The method for improving the density of a deposited metal 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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