CN114908331A

CN114908331A - Deposition method of amorphous carbon film

Info

Publication number: CN114908331A
Application number: CN202210443389.1A
Authority: CN
Inventors: 周洁鹏; 宋维聪
Original assignee: Shanghai Betone Semiconductor Energy Technology Co ltd
Current assignee: Shanghai Betone Semiconductor Energy Technology Co ltd
Priority date: 2022-04-25
Filing date: 2022-04-25
Publication date: 2022-08-16
Anticipated expiration: 2042-04-25
Also published as: CN114908331B

Abstract

The invention provides a deposition method of an amorphous carbon film, which comprises the following steps: s1: providing a PECVD vacuum reaction chamber, and stabilizing the temperature in the reaction chamber at 400-550 ℃; s2: introducing oxygen and helium, and cleaning the reaction chamber for the first time; s3: introducing nitrogen fluoride gas and argon gas, cleaning the reaction chamber for the second time, and forming an aluminum fluoride protective layer on the surface of the upper electrode at the top of the reaction chamber; s4: introducing ethyl silicate gas, carrier gas and oxygen for a preset time, and continuously maintaining the pressure in the reaction chamber at a first pressure so as to form a silicon oxide film with the thickness of 1500-2000 angstroms on the inner surface of the reaction chamber, wherein the silicon oxide film is coated with an aluminum fluoride protective layer; s5: and placing the growth substrate on a base of a reaction chamber, introducing carbon-containing gas and helium, and depositing the amorphous carbon film on the surface of the growth substrate under the condition of keeping the pressure in the reaction chamber at the first pressure. The invention can greatly reduce particle pollution and improve the production yield.

Description

Deposition method of amorphous carbon film

Technical Field

The invention relates to the technical field of semiconductor manufacturing, in particular to a deposition method of an amorphous carbon film.

Background

Since underground carbon resources are almost endless and carbon is harmless, carbon is an excellent raw material from the viewpoint of resources and environment. Carbon is known to exist in many different crystal forms, such as diamond, diamond-like carbon, graphite, fullerene, carbon nanotubes, and the like, and the different crystal forms depend on the bonding manner of carbon atoms. Among them, amorphous carbon has an amorphous structure and is attracting great attention as a functional material. Amorphous carbon is excellent in wear resistance and solid lubricity, has properties such as insulation, visible/infrared light transmittance, low dielectric constant, and oxygen barrier properties, and is expected to be widely used in various industrial fields.

In the semiconductor field, amorphous carbon films are generally formed by Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD). For example, an amorphous carbon film can be formed by activating a raw material gas containing carbon to a plasma state by a plasma chemical vapor deposition method (one of chemical vapor deposition methods), and depositing a reaction product on a substrate surface.

Specifically, the conventional method for depositing an amorphous carbon film by using a chemical vapor deposition method comprises the following steps:

1. providing a chemical vapor deposition chamber, and controlling the temperature in the chamber to be a preset temperature;

2. introducing oxygen and helium to clean the interior of the chamber;

3. the method comprises the following steps of putting a growth substrate into a chamber, introducing carbon-containing gas and helium into the chamber, and depositing an amorphous carbon film on the surface of the growth substrate under a preset pressure.

The method has a problem in that the amorphous carbon film deposited on the surface of the upper electrode on the top of the aluminum reaction chamber is prone to fall off and form particles due to the different adsorption capacities between carbon and metal, which causes wafer and chamber contamination, especially when depositing a relatively thick film, for example, when the thickness of the deposited amorphous carbon film is more than 1 μm, the particle contamination is serious.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for depositing an amorphous carbon film, which is used to solve the problems that the amorphous carbon film deposited on the upper electrode surface of the top of the aluminum reaction chamber is prone to fall off and form particles due to different adsorption capacities between carbon and metal when the existing chemical vapor deposition method is used to deposit the amorphous carbon film, which causes contamination of the wafer and the chamber, especially when a relatively thick film layer is deposited, for example, when the thickness of the deposited amorphous carbon film is more than 1 μm, the particle contamination is especially serious, and the like.

To achieve the above and other related objects, the present invention provides a method for depositing an amorphous carbon film, comprising the steps of:

s1: providing a PECVD vacuum reaction chamber, wherein a base is arranged in the reaction chamber, so that the temperature in the reaction chamber is stabilized at 400-550 ℃;

s2: introducing oxygen and helium to keep the pressure in the reaction chamber at a first pressure, wherein the radio frequency power is 800W-1200W, so as to clean the reaction chamber for the first time;

s3: introducing nitrogen fluoride gas and argon gas, dissociating the nitrogen fluoride gas and the argon gas outside the reaction chamber into fluorine ions, supplying the fluorine ions into the reaction chamber, maintaining the pressure in the reaction chamber at the first pressure so as to perform secondary cleaning on the reaction chamber, and forming an aluminum fluoride protective layer on the surface of the upper electrode at the top of the reaction chamber;

s4: after introducing inert gas into the reaction chamber for purging, introducing ethyl silicate gas, carrier gas and oxygen in a ratio of 1:1:1 for a preset time, continuously maintaining the pressure in the reaction chamber at a first pressure, wherein the radio frequency power of the reaction chamber is 500W-1000W, so that a silicon oxide film with the thickness of 1500-2000 angstroms is formed on the inner surface of the reaction chamber, and the silicon oxide film is coated with an aluminum fluoride protective layer;

s5: placing a growth substrate on a base of a reaction chamber, introducing carbon-containing gas and helium gas into the reaction chamber for a preset time, and depositing an amorphous carbon film on the surface of the growth substrate under the condition of keeping the pressure in the reaction chamber at a first pressure.

Optionally, the base includes any one of an aluminum nitride base and an aluminum fluoride base.

Alternatively, in step S2, the flow rates of oxygen and helium are 1: 1.

More optionally, in step S2, the flow rates of the oxygen gas and the helium gas are both 4000sccm, and the time for introducing is 30S-60S.

Alternatively, in step S3, the flow ratio of the nitrogen fluoride gas and the argon gas is introduced to be 1: 2.

More optionally, in step S3, the flow rate of the introduced nitrogen fluoride gas is 4000sccm, the flow rate of the argon gas is 8000sccm, and the gas introduction time is 30S to 60S.

Optionally, in step S4, the flow rates of the introduced ethyl silicate gas, the carrier gas and the oxygen gas are all 4000sccm to 5500sccm, and the introduction time is 30S to 50S.

Optionally, in step S5, the carbon-containing gas includes propylene, the flow ratio of the carbon-containing gas to the helium gas is 5:1-1:1, and the flowing time is 5S-10S.

More optionally, in step S5, the rf power during the amorphous carbon film deposition is 1500W-1600W, the deposition time is 1min-3min, and the deposited amorphous carbon film has a thickness of 2 μm or less.

Optionally, the first pressure is 1torr to 10 torr.

As described above, the deposition method of an amorphous carbon film according to the present invention has the following advantageous effects: through the improved process design, under the condition of keeping the pressure intensity in the reaction chamber unchanged, firstly, oxygen and helium are adopted to clean the reaction chamber for the first time, then, nitrogen fluoride gas and argon are introduced to clean the reaction chamber for the second time so as to effectively remove impurities in the reaction chamber, an aluminum fluoride protective layer is formed on the inner surface of the reaction chamber, including the surface of the upper electrode, then, ethyl silicate, helium and oxygen are introduced to continue to form a silicon oxide layer on the inner surface of the reaction chamber, the silicon oxide is easier to adsorb on the upper surface of the aluminum fluoride protective layer formed on the surface, the adhesion force can be greatly increased, the adsorption force of the silicon oxide layer on the amorphous carbon film is stronger than that of the metal surface of the upper electrode and the aluminum fluoride layer, so that the film deposited on the inner wall of the reaction chamber, particularly the film formed on the upper electrode, is not easy to fall off, and simultaneously, the pressure and other conditions in the reaction chamber are kept stable, so that the formed films can be attached more tightly, and the damage of the films caused by the stress change of the films due to the pressure change is avoided. Through such an integrated technical scheme, particle pollution can be greatly reduced, and the production yield is improved.

Drawings

FIG. 1 is a flow chart illustrating a method for depositing an amorphous carbon film according to the present invention.

FIG. 2 is a graph showing a comparison of particles deposited with the present invention and with a prior art amorphous carbon film.

FIG. 3 is a comparison graph of particles of an amorphous carbon film deposited on the surface of a wafer using the present invention and the same number of wafers using the prior art, in which a curve (i) shows the particles of an amorphous carbon film deposited using the prior art, and a curve (ii) shows the particles of an amorphous carbon film deposited using the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated. In order to keep the drawings as compact as possible, not all structures are labeled in the figures.

Please refer to fig. 1to 3.

As shown in FIG. 1, the present invention provides a method for depositing an amorphous carbon film, comprising the steps of:

s1: providing a PECVD vacuum reaction chamber, wherein a base is arranged in the reaction chamber, so that the temperature in the reaction chamber is stabilized at 400-550 ℃ (including endpoints in the specification, and when the numerical value range is referred to, the endpoints are included in the specification if no special description exists), and the temperature is preferably kept unchanged in each subsequent step; the reaction chamber is preferably an aluminum chamber, i.e., the chamber is made of mainly aluminum, and the susceptor is an aluminum-containing susceptor, such as an aluminum nitride susceptor or an aluminum fluoride susceptor, or a susceptor with an aluminum nitride layer or an aluminum fluoride layer coated on the surface of the aluminum susceptor, which has the advantage of high temperature resistance to ensure no deformation at high temperatures of 400 ℃ to 550 ℃; in the example, a base made of pure aluminum nitride is preferred, and the base has the advantages of good wear resistance and the like, and is beneficial to further reducing particle pollution;

s2: introducing oxygen and helium to keep the pressure in the reaction chamber at a first pressure, wherein the radio frequency power is 800W-1200W, so as to clean the reaction chamber for the first time, and thus impurities in the reaction chamber are removed; the flow rates of oxygen and helium may be set as required, for example, according to parameters such as a condition in the chamber (for example, a contamination condition in the chamber is preliminarily determined according to a condition of a previous process to set a gas flow rate), a cleaning time (for example, the shorter the set cleaning time is, the larger the flow rate of the gas is), a size of the chamber (for example, the larger the chamber is, the larger the gas flow rate is), and the like, but the inventors have found through a lot of experiments that, when the ratio of helium to oxygen is 1:1, the effect of dissociating oxygen atoms is best, so the cleaning effect is better; in a preferred example, the flow rates of the oxygen and the helium are 4000sccm, the gas introduction time is kept between 30s and 60s, so that the first pressure in the reaction chamber is kept between 1torr and 10torr, more preferably between 3torr and 6torr, and better and faster chamber cleaning can be realized;

s3: introducing nitrogen fluoride gas and argon gas, dissociating the nitrogen fluoride gas and the argon gas outside the reaction chamber into fluorine ions, and supplying the fluorine ions into the reaction chamber, so that the pressure in the reaction chamber is maintained at the first pressure to perform second cleaning on the reaction chamber, thereby further removing impurity particles in the reaction chamber, and simultaneously forming an aluminum fluoride protective layer on the surface of an upper electrode at the top of the reaction chamber; namely, the pressure in the reaction chamber is kept unchanged, and the temperature is preferably kept unchanged, so that the condition in the reaction chamber is kept constant as much as possible; the method mainly comprises the following steps that fluorination treatment is carried out on all parts in a reaction chamber, particularly an upper electrode, and an aluminum fluoride layer is formed on the surface of the upper electrode to serve as a protective layer; certainly, in this process, an aluminum fluoride protective layer is also formed on the surface of the base and the inner surface of the reaction chamber (it should be specifically explained here that the aluminum fluoride plating on the base outside the chamber is obviously different from the aluminum fluoride plating on the base in the chamber, and the aluminum fluoride plating in the chamber is much better); the inventor finds out through a large amount of experiments that when the ratio of the nitrogen fluoride gas to the argon gas is 1:2, the concentration of the effective fluoride ions is optimal; the gas flow can be adjusted according to the size of the chamber, but the flow of the nitrogen fluoride is preferably 2000sccm-6000 sccm, and the argon flow is proportionally changed according to the proportion; combining the cost and other factors, in one specific example, the flow rate of the nitrogen fluoride gas is 4000sccm, the flow rate of the argon gas is 8000sccm, and the feeding time can be adjusted according to the thickness of the aluminum fluoride protective layer to be grown, preferably 30s-60s, so that the thickness of the formed aluminum fluoride protective layer is not more than 1 μm;

s4: introducing inert gas, such as nitrogen or argon, into the reaction chamber for purging, introducing ethyl silicate gas, carrier gas and oxygen at a ratio of 1:1:1 for a preset time, wherein the carrier gas is helium, continuously maintaining the pressure in the reaction chamber at a first pressure, namely, the pressure in the reaction chamber is continuously kept unchanged, and the radio frequency power of the reaction chamber is set to be 500W-1000W, so as to ensure better film growth speed, thereby forming a silicon oxide film with a thickness of 1500-2000 angstroms on the inner surface of the reaction chamber, the silicon oxide film will wrap the whole inner surface of the reaction chamber, and this will also wrap the upper electrode, the formed silicon oxide film covers the aluminum fluoride protective layer of the upper electrode, and the adhesion force between the silicon oxide film and the upper electrode is superior to that between the amorphous carbon film and the metal (such as aluminum) of the upper electrode, so that the silicon oxide film is not easy to fall off in the subsequent process; in the step, the flow rates of the ethyl silicate gas, the carrier gas and the oxygen are preferably 4000sccm-5500sccm, and the radio frequency power and the argon are matched, so that the silicon oxide film can grow rapidly, and the production efficiency and the equipment yield are improved; in the case of using the flow rate gas, the gas introduction time is preferably 30s to 50s, so that the thickness of the grown silicon oxide film is in the range of 1500 a to 2000 a, because the inventors have confirmed through a large number of experiments that if the silicon oxide film is too thick, the subsequent coating film is affected, causing particles to fall off, and if the silicon oxide film is too thin, it is difficult to ensure that a uniform coating film is formed on the surface of the upper electrode, and also particle contamination is caused;

s5: placing a growth substrate, for example, an 8-inch or 12-inch wafer on a base of a reaction chamber, introducing carbon-containing gas and helium gas into the reaction chamber for a preset time, and depositing an amorphous carbon film on the surface of the growth substrate under the condition of maintaining the pressure in the reaction chamber at a first pressure, namely, the pressure in the reaction chamber is kept unchanged all the time in the whole process, so that the damage of the deposited film caused by pressure fluctuation is avoided, and meanwhile, the adjustment of process parameters is simplified; in this step, the carbon-containing gas is, for example, propylene and helium are used as carrier gas, and parameters such as gas flow rate, gas introduction time and radio frequency power can be determined according to the thickness of the amorphous carbon film to be grown, for example, for the convenience of the growth of the amorphous carbon film, the flow rate of the carbon-containing gas and helium is preferably 5:1-1:1, the introduction time is 5s-10s, the film deposition time is 1min-3min, and the thickness of the formed amorphous film is less than or equal to 2 μm.

Through the improved process design, under the condition of keeping the pressure intensity in the reaction chamber unchanged, firstly, oxygen and helium are adopted to carry out the first cleaning on the reaction chamber, then, nitrogen fluoride gas and argon are introduced to carry out the second cleaning on the reaction chamber so as to effectively remove impurities in the reaction chamber, an aluminum fluoride protective layer is formed on the inner surface of the reaction chamber, including the surface of the upper electrode, then ethyl silicate, helium and oxygen are introduced to continue to form a silicon oxide layer on the inner surface of the reaction chamber, the silicon oxide is easier to adsorb on the upper surface with the aluminum fluoride protective layer formed on the surface, the adhesive force can be greatly increased, the adsorption force of the silicon oxide layer to the amorphous carbon film is stronger than that of the metal surface of the upper electrode and the aluminum fluoride layer, so that the film deposited on the inner wall of the reaction chamber, especially the film formed on the upper electrode is not easy to fall off; meanwhile, the conditions such as pressure intensity in the reaction chamber are kept stable, so that the process can be simplified, formed films can be attached more tightly, and the damage of the films caused by the stress change of the films due to the pressure intensity change is avoided. Through such an integrated technical scheme, particle pollution can be greatly reduced, the quality of the amorphous carbon film is improved, and the production yield is improved. The amorphous carbon film deposition method provided by the invention can be used for depositing the amorphous carbon film serving as a dielectric layer and can also be used for depositing an anti-reflection layer in a photomask, and has great application prospects.

In order to verify the effects of the present invention, the inventors conducted a number of experiments including comparison of the deposition of an amorphous carbon film only after cleaning the interior of a reaction chamber with oxygen and helium gases using the prior art method and the deposition of an amorphous carbon film of the same thickness using the method of the present invention under the same conditions of the reaction chamber structure, reaction gas, temperature, pressure, etc., and obtained results as shown in fig. 2 (the specification in fig. 2 indicates the number of particles acceptable in the process) and fig. 3. As can be seen from FIG. 2, the number of particles on the surface of the film is greatly reduced when the amorphous carbon film with the same thickness is deposited by using the method of the present invention compared with the prior art; as can be seen from fig. 3, the amorphous carbon films with the same thickness are deposited on the same number of wafer surfaces, and the number of impurity particles can be reduced by about 40% by using the method of the present invention compared with the prior art. This shows that the method provided by the invention can effectively reduce the number of impurity particles on the surface of the wafer.

In summary, the present invention provides a deposition method of amorphous carbon film, comprising the steps of: s1: providing a PECVD vacuum reaction chamber, wherein a base is arranged in the reaction chamber, so that the temperature in the reaction chamber is stabilized at 400-550 ℃; s2: introducing oxygen and helium to keep the pressure in the reaction chamber at a first pressure, wherein the radio frequency power is 800W-1200W, so as to clean the reaction chamber for the first time; s3: introducing nitrogen fluoride gas and argon gas, dissociating the nitrogen fluoride gas and the argon gas outside the reaction chamber into fluorine ions, supplying the fluorine ions into the reaction chamber, maintaining the pressure in the reaction chamber at the first pressure so as to perform secondary cleaning on the reaction chamber, and forming an aluminum fluoride protective layer on the surface of the upper electrode at the top of the reaction chamber; s4: after introducing inert gas into the reaction chamber for purging, introducing ethyl silicate gas, carrier gas and oxygen in a ratio of 1:1:1 for a preset time, continuously maintaining the pressure in the reaction chamber at a first pressure, wherein the radio frequency power of the reaction chamber is 500W-1000W, so that a silicon oxide film with the thickness of 1500-2000 angstroms is formed on the inner surface of the reaction chamber, and the silicon oxide film is coated with an aluminum fluoride protective layer; s5: placing a growth substrate on a base of a reaction chamber, introducing carbon-containing gas and helium gas into the reaction chamber for a preset time, and depositing an amorphous carbon film on the surface of the growth substrate under the condition of keeping the pressure in the reaction chamber at a first pressure. The invention can greatly reduce particle pollution, improve the quality of the amorphous carbon film and improve the production yield. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Those skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A method for depositing an amorphous carbon film, comprising the steps of:

2. The deposition method of claim 1, wherein the susceptor comprises any one of an aluminum nitride susceptor and an aluminum fluoride susceptor.

3. The deposition method according to claim 1, wherein the flow rates of the oxygen gas and the helium gas are 1:1 in step S2.

4. The deposition method according to claim 3, wherein the oxygen gas and the helium gas are introduced at a flow rate of 4000sccm for a time period of 30S to 60S in step S2.

5. The deposition method according to claim 1, wherein in step S3, the flow ratio of the nitrogen fluoride gas to the argon gas is 1: 2.

6. The deposition method according to claim 5, wherein in the step S3, the flow rate of the introduced nitrogen fluoride gas is 4000sccm, the flow rate of the argon gas is 8000sccm, and the gas introduction time is 30S to 60S.

7. The deposition method according to claim 1, wherein the ethyl silicate gas, the carrier gas and the oxygen gas are introduced at a flow rate of 4000sccm to 5500sccm for 30S to 50S in step S4.

8. The deposition method according to claim 1, wherein in step S5, the carbon-containing gas comprises propylene, the flow ratio of the carbon-containing gas to the helium gas is 5: 1to 1:1, and the feeding time is 5S to 10S.

9. The deposition method of claim 8, wherein in step S5, the rf power during the deposition of the amorphous carbon film is 1500W-1600W, the deposition time is 1min-3min, and the deposited amorphous carbon film has a thickness of 2 μm or less.

10. The deposition method of any one of claims 1to 9, wherein the first pressure is in a range of 1torr to 10 torr.