CN112593185A

CN112593185A - Film preparation method

Info

Publication number: CN112593185A
Application number: CN202011284775.8A
Authority: CN
Inventors: 张同文; 王宽冒; 赵联波; 傅新宇
Original assignee: Beijing Naura Microelectronics Equipment Co Ltd
Current assignee: Beijing Naura Microelectronics Equipment Co Ltd
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2021-04-02

Abstract

The embodiment of the invention provides a film preparation method, which comprises the following steps: doping active particles into the substrate material from the substrate surface; and depositing to form a film on the surface of the doped substrate. During deposition of the thin film, the active particles serve as catalysts to promote the ions in the thin film material to react with atoms in the substrate material to form chemical bonds. The film preparation method provided by the embodiment of the invention can enable the film and the substrate to be connected through chemical bonds and intermolecular forces, thereby improving the adhesion strength between the film and the substrate.

Description

Film preparation method

Technical Field

The embodiment of the invention relates to the field of semiconductor manufacturing, in particular to a film preparation method.

Background

In the field of semiconductor manufacturing, physical vapor deposition is a process commonly used for thin film fabrication. The basic principle of the physical vapor deposition process is as follows: the surface of the material source is gasified into gaseous atoms, molecules or part of the gaseous atoms is ionized into ions by a physical method, and a film with a specific function is deposited on the surface of the substrate by a low-pressure gas (or plasma) process.

Magnetron sputtering is one of a variety of physical vapor deposition processes. The current commonly used magnetron sputtering process flow is as follows: argon is filled into the process chamber, the argon is ionized into ions and electrons by an electric field, and the argon ions are accelerated to bombard the target under the action of the electric field and the magnetic field, so that the target is sputtered out and deposited on the surface of a workpiece to be processed to form a film. However, the film formed by magnetron sputtering adheres to the surface of the workpiece through intermolecular forces (van der waals forces), so that the adhesion between the film and the workpiece is small, and the film is prone to falling off in the subsequent process of the workpiece, which seriously affects the yield.

Disclosure of Invention

The embodiment of the invention aims to solve at least one technical problem in the prior art, and provides a film preparation method which can improve the adhesive strength between a film and a substrate.

To achieve the object of the present invention, there is provided a method for preparing a thin film, comprising: doping active particles into the substrate material from the substrate surface;

depositing to form a film on the surface of the doped substrate;

during deposition of the thin film, the active particles serve as catalysts to promote the ions in the thin film material to react with atoms in the substrate material to form chemical bonds.

Optionally, doping the active particles into the substrate material from the surface of the substrate specifically includes:

placing the substrate into a first chamber;

introducing doping gas into the first chamber;

the dopant gas is energized to form a plasma containing the active species to dope the active species into the substrate material.

Optionally, the first chamber is a pre-cleaning chamber;

the doping of active particles from the surface of a substrate into a substrate material specifically comprises:

placing the substrate in the pre-clean chamber;

simultaneously introducing etching gas and the doping gas into the pre-cleaning chamber;

and starting an excitation power supply and a bias power supply, and exciting the etching gas and the doping gas to respectively form etching plasma and plasma containing the active particles so as to etch the surface of the substrate and dope the active particles into the substrate material.

Optionally, the doping gas includes hydrogen, or a mixed gas of hydrogen and an inert gas.

Optionally, in the mixed gas, the volume concentration of the hydrogen gas ranges from 1% to 4%.

Optionally, the flow rate of the mixed gas is more than 10 sccm.

Optionally, in the step of pre-starting the excitation power supply and the bias power supply, exciting the etching gas and the mixed gas to respectively form etching plasma and plasma containing the active particles, so as to etch the surface of the substrate and dope the active particles into the substrate material,

in a plasma glow starting stage, the bias power supply outputs first bias power;

and in the etching stage, the bias power supply outputs second bias power, and the second bias power is larger than the first bias power.

Optionally, the value ranges of the first bias power and the second bias power are both 100W to 1000W.

Optionally, depositing a film on the doped substrate surface to form a film specifically includes: the doped substrate is moved out of the first chamber and placed into a second chamber, and the second chamber is a physical vapor deposition chamber;

introducing sputtering gas into the second chamber;

and starting an excitation power supply and a bias power supply, exciting the sputtering gas to form plasma for sputtering, and enabling the plasma for sputtering to bombard the target so as to deposit and form a film on the surface of the doped substrate.

Optionally, the substrate material includes silicon, silicon oxide or silicon nitride; the thin film material comprises titanium or a titanium alloy.

The invention has the following beneficial effects:

according to the film preparation method provided by the embodiment of the invention, the active particles are doped in the substrate surface material, and the active particles can be used as a catalyst to promote ions in the film material to react with atoms in the substrate material to form chemical bonds in the process of depositing the film, so that the film is connected with the substrate through the chemical bonds and intermolecular forces, and the adhesion strength between the film and the substrate is further improved.

Drawings

FIG. 1 is a flow chart of a method for preparing a thin film provided in example 1;

FIG. 2 is a flow chart of the active particle doping step provided in example 1;

FIG. 3 is a flow chart of the precleaning process provided in example 1;

FIG. 4 is a flowchart of the deposition process of forming a thin film provided in example 1.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the following describes the preparation method of the thin film provided by the embodiment of the present invention in detail with reference to the accompanying drawings.

Existing physical vapor deposition techniques typically utilize magnetron sputtering to deposit thin film materials directly on the substrate surface. However, only intermolecular forces exist between the film prepared by this method and the substrate. Since the intermolecular interaction is small, a film peeling phenomenon is likely to occur in a subsequent process of the substrate, which may seriously affect the yield of the product.

In order to solve the problem that the film is easy to fall off, the embodiment of the invention improves the existing film preparation method.

Example 1

The present embodiment provides a method for preparing a thin film, as shown in fig. 1, which specifically includes the following steps:

step S01: doping active particles into the substrate material from the substrate surface;

step S02: and depositing to form a film on the surface of the doped substrate.

Wherein, in the process of depositing the film, the active particles are used as a catalyst, which can promote ions in the film material to react with atoms in the substrate material to form chemical bonds, and the strength of the chemical bonds is higher than the intermolecular force, so that the adhesion strength between the film and the substrate is improved.

In some embodiments, as shown in fig. 2, the step S01 specifically includes the following steps:

step S11: placing a substrate into a first chamber;

step S12: introducing doping gas into the first chamber;

step S13: the dopant gas is energized to form a plasma containing the active species to dope the active species into the substrate material.

Of course, in practical applications, any other doping method of the active particles may be adopted.

In some embodiments, the above steps S11-S13 may be performed separately, or may be performed simultaneously with the pre-cleaning process in the pre-cleaning chamber. Specifically, the first chamber is a pre-cleaning chamber. As shown in fig. 3, the pre-cleaning process specifically includes the following steps:

step S111: placing a substrate in a pre-clean chamber;

step S121: simultaneously introducing etching gas and doping gas into the pre-cleaning chamber;

step S131: and starting the excitation power supply and the bias power supply, and exciting the etching gas and the doping gas to respectively form etching plasma and plasma containing active particles so as to etch the surface of the substrate and dope the active particles into the substrate material.

The above-described precleaning process is used to remove impurities deposited on the substrate surface by etching the substrate surface.

By doping the active particles into the substrate material while etching the substrate surface, the process flow can be saved and the process efficiency can be improved.

In some embodiments, the dopant gas comprises hydrogen, or a mixture of hydrogen and an inert gas. During the process of exciting the doping gas to form plasma, the hydrogen in the doping gas will react as follows:

H₂→H+H⁺+e^-

as can be seen from the above, the doping gas containing hydrogen gas is excited to form active hydrogen atoms, hydrogen ions and electrons, wherein the active hydrogen atoms can act as active particles to promote the ions in the thin film material to react with the atoms in the substrate material to form chemical bonds. In addition, optionally, in order to avoid explosion of hydrogen gas in case of leakage and improve process safety, the hydrogen gas needs to be mixed with an inert gas, and the inert gas can play a role in diluting the hydrogen gas concentration. For example, the volume concentration of hydrogen in the mixed gas ranges from 1% to 4%. Within the range, the hydrogen can be prevented from exploding when leaking, the process safety is ensured, and the volume concentration of the hydrogen can meet the process requirement.

In some embodiments, the substrate material comprises silicon, silicon oxide, or silicon nitride; the thin film material comprises titanium or a titanium alloy.

In some embodiments, in the step S131, in the plasma ignition stage, the bias power supply outputs the first bias power; in the etching stage, the bias power supply outputs a second bias power, which is greater than the first bias power. In the plasma glow starting stage, the plasma glow is promoted by adopting lower bias power, such as 100W; in the etching stage, the etching efficiency can be improved by increasing the bias power, for example, to 400W, thereby improving the productivity. Optionally, the value ranges of the first bias power and the second bias power are both 100W to 1000W.

In some embodiments, as shown in fig. 4, the step S02 specifically includes the following steps:

step S21: the doped substrate is moved out of the first chamber and placed into a second chamber, wherein the second chamber is a physical vapor deposition chamber;

step S22: introducing sputtering gas into the second chamber;

step S23: and starting an excitation power supply and a bias power supply, exciting the sputtering gas to form plasma for sputtering, and bombarding the target material by the plasma for sputtering so as to deposit and form a film on the surface of the doped substrate.

In the process of performing the above step S23, ions in the thin film material form chemical bonds with atoms in the substrate material under the catalytic action of the active particles, thereby improving the adhesive strength between the thin film and the substrate.

Example 2

In this example, a thin film preparation method is described in detail by taking titanium as a thin film material, hydrogen as a doping gas, and a silicon oxide substrate as a substrate material, on the basis of the above example 1. Specifically, the film preparation method comprises the following steps:

the first step is as follows: the substrate is subjected to a Degas process (Degas). And (3) placing the silicon oxide substrate into a degassing chamber, and keeping the temperature for a certain time to remove water and other volatile gases on the surface of the substrate. Wherein, the constant temperature time can be in the range of 60 s-300 s, and the constant temperature is higher than 100 ℃. It should be noted that the constant temperature time is dependent on the kind of the substrate material and should be set according to the actual production situation.

The second step is that: and carrying out a precleaning process on the substrate. The precleaning process is used to remove impurities from the surface of the substrate. The precleaning process specifically comprises the following steps:

step 1, starting an air suction pump to continuously suck air from the pre-cleaning chamber so as to maintain the vacuum state in the pre-cleaning chamber. And simultaneously introducing etching gas and doping gas into the pre-cleaning chamber.

In step 1, the gas is kept flowing for a certain period of time, for example, 5s, to stabilize the gas pressure in the pre-cleaning chamber. The etching gas is an inert gas such as argon, and the flow rate of the etching gas is, for example, 40 sccm; the doping gas is hydrogen or a mixed gas of hydrogen and an inert gas such as argon. The flow rate of the dopant gas should be greater than 10cccm to ensure sufficient generation of active particles, for example, 200 sccm. In addition, in the mixed gas, the volume concentration of the hydrogen is 1-4%, and in the range, the hydrogen can be prevented from exploding when leaking, the process safety is ensured, and the volume concentration of the hydrogen can meet the process requirement.

And 2, starting an excitation power supply and a bias power supply to excite the etching gas and the doping gas to respectively form etching plasma and plasma containing active particles.

In the above step 2, the excitation power supply is used for applying excitation power to the upper electrode (e.g. radio frequency coil), for example 400W; the bias power supply is used to apply bias power to the pedestal. In the plasma glow starting stage, the bias power supply outputs first bias power; in the etching stage, the bias power supply outputs a second bias power, which is greater than the first bias power. In the plasma ignition stage (time is 2s for example), the plasma ignition is facilitated by adopting lower bias power, for example 100W; by increasing the bias power, for example to 400W, during the etching phase (time for example 20s), the etching efficiency can be increased, thereby increasing the throughput. Optionally, the value ranges of the first bias power and the second bias power are both 100W to 1000W.

Specifically, during the process of exciting the doping gas to form plasma, the hydrogen in the doping gas will react as follows:

H₂→H+H⁺+e^-

During the doping process, a part of active hydrogen ions will be doped in the silicon oxide substrate material, and the rest of active hydrogen ions will have the following reduction reaction with the silicon oxide substrate material:

SiO₂+H→Si+H₂O

that is, the active hydrogen atoms undergo a reduction reaction with silicon oxide to form silicon and water. Based on this, in order to ensure the reducibility of the doping gas, the volume concentration of hydrogen in the doping gas may not be less than 1%.

And 4, step 4: and after the etching is finished, closing the excitation power supply and the bias power supply, and continuously introducing etching gas and doping gas into the pre-cleaning chamber at the same time.

The process time of the step 4 is, for example, 5s, and is used for removing the charges remaining on the surface of the silicon oxide substrate during the etching process.

And 5: and stopping introducing the etching gas and the doping gas into the pre-cleaning chamber, and enabling the pre-cleaning chamber to be restored to a vacuum state so as to finish the pre-cleaning process.

The process time of the step 5 is, for example, 3 seconds.

Specifically, the formulations of the degas process and precleaning process are shown in table 1 below:

TABLE 1 formulation of the degassing process and the precleaning process used in this example

The third step: and (4) depositing a titanium film. After the pre-cleaning process is finished, the silicon oxide substrate after the pre-cleaning is moved into a physical vapor deposition chamber from the pre-cleaning chamber, and a thin film deposition process is carried out in the physical vapor deposition chamber. In some embodiments, during the process of moving the silicon oxide substrate from the pre-cleaning chamber to the physical vapor deposition chamber, the silicon oxide substrate may be transported by a robot arm to ensure that the silicon oxide substrate is in a vacuum environment to maintain the active species on the substrate in a stable state.

The film deposition process specifically comprises the following steps:

step 1, firstly, starting an air suction pump to continuously suck air of a physical vapor deposition chamber so as to maintain the physical vapor deposition chamber in a vacuum state; then, sputtering gas is introduced into the physical vapor deposition chamber, so that the sputtering gas keeps the pressure in the physical vapor deposition chamber stable. The sputtering gas is an inert gas such as argon, and the flow rate of the sputtering gas is, for example, 100 sccm. The process time of step 1 is, for example, 5 s.

And 2, turning on a direct current power supply to load a certain direct current power on the target material so as to excite sputtering gas to form plasma for sputtering, bombarding the titanium target material by the plasma for sputtering, and depositing the film material sputtered from the target material on the silicon oxide substrate.

Wherein, in the glow starting stage, the sputtering power output by the direct current power supply is 1000W; during the deposition phase, the sputtering power output by the DC power supply is increased, for example, to 6000W, so as to improve the deposition rate of the film material.

The process time of step 2 is, for example, 20s to form a thin film of a prescribed thickness.

And 3, closing the direct current power supply, stopping introducing sputtering gas, and then restoring the physical vapor deposition chamber to a vacuum state to finish the physical film vapor deposition process.

For the preparation of titanium thin films, during the deposition of a thin film material of titanium on a silicon oxide substrate doped with active particles, the following chemical reactions occur:

that is, silicon atoms are chemically combined with titanium ions by the catalytic action of the active particles (H), and specifically, since titanium is excited to form ions of various valence states, carbon-silicon compounds such as TiSi and TiSi with various atomic weight ratios are generated accordingly₂And Ti₅Si₄And the like. Due to the covalent bond between the carbon silicon compound, a covalent bond exists between the thin film and the substrate, which can enhance the adhesion between the thin film and the substrate. Experiments show that the adhesion between the titanium film formed by the film preparation method provided by the embodiment of the invention and the substrate surface is 5.7N/cm, while the adhesion between the titanium film formed by the film preparation method in the prior art and the substrate surface is 0.3N/m, so that the adhesion of the titanium film formed by the film preparation method provided by the embodiment of the invention is effectively improved.

In some embodiments, after depositing the titanium film, there is a step of depositing a copper film. In this case, the substrate is taken out of the deposition chamber for the titanium thin film and put into the deposition chamber for the copper thin film, which is also a physical vapor deposition chamber, and the target is a copper target. The deposition process of the copper film specifically comprises the following steps:

step 1: firstly, the air pump is started to continuously pump the physical vapor deposition chamber so as to maintain the physical vapor deposition chamber in a vacuum state. Then, sputtering gas is introduced into the physical vapor deposition chamber, so that the sputtering gas keeps the pressure in the physical vapor deposition chamber stable. The sputtering gas is an inert gas such as argon, and the flow rate of the sputtering gas is, for example, 100 sccm. The process time of step 1 is, for example, 5 s.

Step 2: and starting a direct current power supply to load certain direct current power on the target material so as to excite sputtering gas to form plasma for sputtering, bombarding the copper target material by the plasma, and depositing the film material sputtered from the target material on the silicon oxide substrate.

Wherein, in the glow starting stage, the sputtering power output by the direct current power supply is 1000W; during the deposition phase, the sputtering power output by the DC power supply is increased, for example, to 8000W, so as to increase the deposition rate of the thin film material.

And 3, turning off the direct-current power supply, stopping introducing sputtering gas, and then restoring the physical vapor deposition chamber to a vacuum state to finish the physical vapor deposition copper film process.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. A method of making a thin film, comprising:

doping active particles into the substrate material from the substrate surface;

depositing to form a film on the surface of the doped substrate;

2. The method for preparing a thin film according to claim 1, wherein the doping of active particles from the surface of the substrate into the substrate material specifically comprises:

placing the substrate into a first chamber;

introducing doping gas into the first chamber;

3. The method of claim 2, wherein the first chamber is a pre-cleaning chamber;

placing the substrate in the pre-clean chamber;

4. The method for producing a thin film according to claim 3, wherein the dopant gas includes hydrogen gas or a mixed gas of hydrogen gas and an inert gas.

5. The method according to claim 4, wherein the volume concentration of the hydrogen gas in the mixed gas is in a range of 1 to 4%.

6. The method for producing a thin film according to claim 4, wherein a flow rate of the mixed gas is more than 10 sccm.

7. The method according to claim 3, wherein in the step of exciting the etching gas and the mixed gas to form plasma for etching and plasma containing the active particles, respectively, at the pre-start-up excitation power supply and the bias power supply, so as to etch the surface of the substrate while doping the active particles into the substrate material,

8. The method of claim 7, wherein the first bias power and the second bias power both have a value ranging from 100W to 1000W.

9. The method for preparing the thin film according to any one of claims 2 to 8, wherein depositing the thin film on the surface of the doped substrate comprises:

the doped substrate is moved out of the first chamber and placed into a second chamber, and the second chamber is a physical vapor deposition chamber;

introducing sputtering gas into the second chamber;

10. The method according to claim 1, wherein the substrate material comprises silicon, silicon oxide, or silicon nitride; the thin film material comprises titanium or a titanium alloy.