阅读说明：本技术 一种用于铝基片的等离子体刻蚀方法 (Plasma etching method for aluminum substrate ) 是由 陈国动 朱海云 于 2018-06-25 设计创作，主要内容包括：本发明提供了一种用于铝基片的等离子体刻蚀方法,所述刻蚀方法包括：采用氯基气体对表面设置有掩膜层的铝基片进行刻蚀；去除所述铝基片上的所述掩膜层；采用氮气对所述铝基片进行预定时间的防腐蚀处理。所述等离子体刻蚀方法可以有效地除去铝基片表面的残留氯离子,并在铝基片的表面形成稳定的钝化层,提升铝基片在空气中的防腐蚀能力。(The invention provides a plasma etching method for an aluminum substrate, which comprises the following steps: etching the aluminum substrate with the mask layer on the surface by adopting chlorine-based gas; removing the mask layer on the aluminum substrate; and carrying out corrosion prevention treatment on the aluminum substrate for a preset time by adopting nitrogen. The plasma etching method can effectively remove residual chloride ions on the surface of the aluminum substrate, and form a stable passivation layer on the surface of the aluminum substrate, thereby improving the corrosion resistance of the aluminum substrate in air.)

1. A plasma etching method for an aluminum substrate, the etching method comprising:

etching the aluminum substrate with the mask layer on the surface by adopting chlorine-based gas;

removing the mask layer on the aluminum substrate;

and carrying out corrosion prevention treatment on the aluminum substrate for a preset time by adopting nitrogen.

2. The plasma etching method according to claim 1, wherein the step of performing etching of the aluminum substrate having the mask layer provided on the surface thereof with a chlorine-based gas comprises:

and introducing chlorine-based gas into the first process chamber, and ionizing the chlorine-based gas to perform the step of etching the aluminum substrate.

3. The plasma etching method of claim 1, wherein the step of removing the mask layer on the aluminum substrate comprises:

transferring the aluminum substrate subjected to the etching step from the first process chamber to the second process chamber;

and introducing oxygen into the second process chamber, and ionizing the oxygen to form plasma so as to etch the mask layer on the surface of the aluminum substrate.

4. The plasma etching method according to claim 3, wherein the step of performing corrosion prevention treatment of the aluminum substrate with nitrogen gas for a predetermined time comprises:

and introducing nitrogen and auxiliary process gas into the second process chamber, and ionizing the nitrogen and the auxiliary process gas to form plasma so as to perform anti-corrosion treatment on the aluminum substrate after the mask layer is removed.

5. The plasma etching method of claim 4, wherein the auxiliary process gas comprises at least one of oxygen, argon, and helium.

6. The plasma etching method according to claim 1, wherein the step of performing corrosion prevention treatment of the aluminum substrate with nitrogen gas for a predetermined time comprises:

and ionizing the nitrogen to form plasma so as to carry out anti-corrosion treatment on the aluminum substrate after the mask layer is removed.

7. The plasma etching method according to claim 4,

the flow rate of the nitrogen introduced into the second process chamber is 50 sccm-1000 sccm;

the flow rate of the auxiliary process gas introduced into the second process chamber is 0sccm to 1000 sccm.

8. The method of claim 4, wherein the second process chamber has a pressure ranging from 10mT to 2000mT after the steps of flowing the nitrogen gas and the auxiliary process gas into the second process chamber are performed.

9. The plasma etching method according to claim 4 or 6, wherein, when the aluminum substrate from which the mask layer has been removed is subjected to an anti-corrosion treatment,

the radio frequency power range of the upper electrode is 500W-2500W;

the radio frequency power range of the lower electrode is 30W-1000W.

10. The plasma etching method according to claim 6 or 8, wherein the predetermined time is in a range of 20s to 300 s.

11. The plasma etching method according to claim 6 or 8, wherein the temperature of the aluminum substrate after removing the mask layer is in the range of 30 to 300 ℃ when the aluminum substrate is subjected to the corrosion prevention treatment.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a plasma etching method for an aluminum substrate.

Background

In the fabrication process of integrated circuits, aluminum (Al) and its alloy materials are widely used for interconnect lines to connect different devices and areas. Currently, a plasma dry etching process is widely used for etching the interconnection of the Al substrate, and a chlorine-based gas is generally used as an etching process gas in the plasma dry etching process, and the chlorine-based gas includes Cl₂、BCl₃、CCl₄、SiCl₄And HCl, and the like. If the chlorine-based gas is used as the etching process gas to execute the plasma dry etching process, a large amount of Cl ions are deposited after the process is finishedDeposited on the surface of the Al substrate, these residual Cl ions cause corrosion of the Al substrate when the Al substrate is contacted with air or water vapor, and the corrosion rate is gradually increased with the lapse of time. The occurrence of these corrosions negatively impacts the product yield, placing higher demands on the time interval between the etching and cleaning processes of the Al substrate, which in turn further increases the substrate production time and operating costs.

Disclosure of Invention

The invention aims to provide a plasma etching method for an aluminum substrate. The plasma etching method can effectively remove residual chloride ions on the surface of the aluminum substrate, and form a stable passivation layer on the surface of the aluminum substrate, thereby improving the corrosion resistance of the aluminum substrate in air.

To solve the above problems, as an aspect of the present invention, there is provided a plasma etching method for an aluminum substrate, wherein the etching method comprises:

etching the aluminum substrate with the mask layer on the surface by adopting chlorine-based gas;

removing the mask layer on the aluminum substrate;

and carrying out corrosion prevention treatment on the aluminum substrate for a preset time by adopting nitrogen.

Optionally, the step of performing etching on the aluminum substrate with the mask layer disposed on the surface by using chlorine-based gas includes:

and introducing chlorine-based gas into the first process chamber, and ionizing the chlorine-based gas to perform the step of etching the aluminum substrate.

Optionally, the step of removing the mask layer on the aluminum substrate comprises:

transferring the aluminum substrate subjected to the etching step from the first process chamber to the second process chamber;

and introducing oxygen into the second process chamber, and ionizing the oxygen to form plasma so as to etch the mask layer on the surface of the aluminum substrate.

Optionally, the step of performing a corrosion prevention treatment of the aluminum substrate with nitrogen gas for a predetermined time comprises:

and introducing nitrogen or mixed gas into the second process chamber, ionizing the nitrogen and the auxiliary process gas to form plasma so as to perform anti-corrosion treatment on the aluminum substrate after the mask layer is removed, wherein the mixed gas comprises the nitrogen and the auxiliary process gas.

Optionally, the auxiliary process gas comprises at least one of oxygen, argon and helium.

Optionally, the step of performing a corrosion prevention treatment of the aluminum substrate with nitrogen gas for a predetermined time comprises:

and ionizing the nitrogen to form plasma so as to carry out anti-corrosion treatment on the aluminum substrate after the mask layer is removed.

Optionally, the flow rate of the nitrogen introduced into the second process chamber is 50sccm to 1000 sccm; the flow rate of the auxiliary process gas introduced into the second process chamber is 0sccm to 1000 sccm.

Optionally, after the step of introducing the nitrogen gas and the auxiliary process gas into the second process chamber is performed, the pressure of the second process chamber is in a range of 10mT to 2000 mT.

Optionally, when the aluminum substrate after the mask layer is removed is subjected to corrosion prevention treatment,

the radio frequency power range of the upper electrode is 500W-2500W;

the radio frequency power range of the lower electrode is 30W-1000W.

Optionally, the predetermined time is in a range of 20s to 300 s.

Optionally, when the aluminum substrate after the mask layer is removed is subjected to corrosion prevention treatment, the temperature of the aluminum substrate ranges from 30 ℃ to 300 ℃.

The invention has the beneficial technical effects that:

according to the plasma etching method provided by the invention, the residual chloride ions on the surface of the aluminum substrate can be effectively removed through the anti-corrosion treatment of the nitrogen plasma on the aluminum substrate, and a stable passivation layer is formed on the surface of the aluminum substrate, so that the anti-corrosion capability of the aluminum substrate in the air is improved; in addition, the anti-corrosion treatment process and the process for removing the mask layer can be finished indoors in the same process, and other process manufacturing machines are not required to be added, so that the process cost is reduced; the invention adopts nitrogen as process gas to carry out anti-corrosion treatment, does not corrode the process chamber, is suitable for substrates made of various metal materials, and has wide applicability to process objects.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a flow chart of a standard aluminum etching process in the prior art;

FIG. 2 is a flow chart of a method for plasma etching a substrate according to the present invention;

FIG. 3 is a flow chart of the plasma etching method for etching an aluminum substrate according to the present invention;

FIG. 4a is a graph of surface corrosion 24 hours after a standard prior art aluminum etch process has been performed on an aluminum substrate;

FIG. 4b is a graph of surface corrosion 48 hours after a standard prior art aluminum etch process has been performed on an aluminum substrate;

FIG. 4c is a graph of surface corrosion 72 hours after a standard prior art aluminum etch process has been performed on an aluminum substrate;

FIG. 5a is a graph showing surface erosion 24 hours after performing the plasma etching method of the present invention on an aluminum substrate;

FIG. 5b is a graph showing surface erosion 48 hours after the plasma etching method of the present invention has been performed on an aluminum substrate;

FIG. 5c is a graph showing surface erosion 72 hours after performing the plasma etching method of the present invention on an aluminum substrate;

FIG. 5d is a graph showing surface erosion at 96 hours after the plasma etching method of the present invention has been performed on an aluminum substrate;

FIG. 5e shows the surface erosion 120 hours after the plasma etching method of the present invention is performed on the aluminum substrate.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In order to solve the problems existing in the background technology, two technical schemes are provided:

the first scheme is as follows: after the etching of the aluminum substrate is finished, adding fluoride into the reaction chamber, ionizing the fluoride to form plasma, bombarding the aluminum substrate by using the fluorine-containing plasma to form a passivation layer on the surface of the aluminum substrate, and weakening the corrosion effect of the aluminum substrate in the air by using the characteristic that the stability of a fluorine-containing aluminum compound is higher than that of aluminum; the reaction formula of the aluminum fluorination process is as follows:

Al+xF→AlFx

scheme II: a pretreatment step is added in the step of removing the photoresist in the etching of the aluminum substrate, and specifically, water vapor (H) is contained under certain pressure₂O), and a large amount of hydrogen radicals formed in the plasma take away Cl elements remained on the surface of the aluminum substrate after etching, so that the corrosion of the aluminum substrate caused by the Cl elements is reduced; the reaction expression of the anticorrosion mechanism in the water vapor-containing plasma treatment process is as follows:

H+Cl→HCl↑

the inventor researches and finds that the scheme has the following problems:

in the first scheme, since the fluorine element is one of the etching reactants of the aluminum, and the aluminum is continuously consumed in the passivation process, the etching reaction of the aluminum to a certain extent also occurs in the passivation process containing the fluorine, that is, the corrosion prevention effect is not complete. If the passivation condition of fluorine is not well controlled, such as the ratio of carbon to fluorine in the fluoride, the pressure and flow rate of the process chamber, etc., the corrosion effect of fluorine ions on the aluminum substrate is rather greater than the passivation effect, and the corrosion is more serious. Furthermore, this passivating effect on the aluminum fluorination is conditional, the corrosion protection is greatly reduced in the presence of oxygen in the reaction environment, and the corrosion is aggravated by elemental fluorine residues.

For scheme two, H in this technical scheme₂The addition of O forms part of the gaseous HCl during the removal of Cl ions, which would otherwise be associated with H if not pumped away in time₂The O reaction produces a portion of the hydrogen ions, which instead can cause some corrosion of the aluminum substrate. Simultaneously gaseous H₂The presence of O and gaseous HCl can cause corrosion of the chamber of the stripper, ultimately leading to particle problems on the surface of the aluminum substrate.

In order to solve the above problems, as a first aspect of the present invention, there is provided a plasma etching method for an aluminum substrate, wherein, as shown in fig. 2, the etching method comprises:

step S1, etching the aluminum substrate with the mask layer on the surface by adopting chlorine-based etching gas;

step S2, removing the mask layer on the aluminum substrate;

and step S3, performing corrosion prevention treatment on the aluminum substrate by adopting nitrogen for a preset time.

As mentioned above, the etching method provided by the present invention can effectively remove the residual chloride ions on the surface of the aluminum substrate and form a stable passivation layer after performing the steps S1 to S3, thereby improving the corrosion resistance of the aluminum substrate in the air and further ensuring the device yield of the aluminum substrate.

As a preferred embodiment of the present invention, when step S1 is executed, the method specifically includes: and introducing chlorine-based gas into the first process chamber, and ionizing the chlorine-based gas to perform the step of etching the aluminum substrate.

As described above, it is easily understood that chlorine-based gas is introduced into the first process chamber as an etching process gas, and rf power is applied to the first process chamber through an upper electrode rf power source to ionize the chlorine-based etching gas to form a plasma, and the aluminum substrate is etched using the plasma.

Further, when step S2 is executed, the mask layer may be removed by using oxygen plasma dry etching, and specifically, the aluminum substrate after the etching step is executed is transferred from the first process chamber to a second process chamber; and introducing oxygen into the second process chamber, and ionizing the oxygen to form plasma so as to etch the mask layer on the surface of the aluminum substrate.

In step S3, the aluminum substrate is subjected to corrosion protection treatment with nitrogen for a predetermined time, specifically, nitrogen and an auxiliary process gas are introduced into the second process chamber, and the nitrogen and the auxiliary process gas are ionized to form a plasma, so as to perform corrosion protection treatment on the aluminum substrate after the mask layer is removed.

As described above, it should be noted that the plasma of nitrogen and the auxiliary process gas is used to perform the corrosion prevention treatment on the surface of the aluminum substrate for a predetermined time, so as to achieve two purposes, one is to remove the chloride ions remained on the surface of the aluminum substrate during the etching process, and the other is to form a stable passivation layer on the surface of the aluminum substrate to isolate the aluminum substrate from air or water vapor in the air, thereby preventing the corrosion reaction.

It should be noted that, as a preferred embodiment, the first process chamber may be an Al etching tool process chamber, and the second process chamber may be a photoresist stripper process chamber.

The step S2 is performed in the stripper process chamber, the step S3 may be performed in the stripper process chamber, or the step S3 may be performed in another process chamber, in short, the steps S2 and S3 are performed sequentially, which ensures that the original aluminum substrate etching process flow sequence is not changed, and reduces the process complexity.

As an alternative embodiment of the present invention, when step S3 is performed, only nitrogen gas may be introduced into the second process chamber, and then only the nitrogen gas is ionized to form a plasma, and the plasma may be used to perform an anti-corrosion treatment on the aluminum substrate after the mask layer is removed.

The plasma etching method provided by the present invention is described with reference to fig. 3, specifically, as shown in fig. 3, after the aluminum substrate is etched through steps P1 (providing an aluminum substrate to be etched) and P2 (performing aluminum etching), step P3 (including 1, removing the mask pattern on the surface of the aluminum substrate, and 2, performing corrosion protection treatment on the aluminum substrate) is performed, and the mask layer removing process is performed in the photoresist removing process chamber, and then the corrosion protection treatment on the aluminum substrate is performed, specifically, the steps S2 to S3 are performed; after the step P3 is completed, a process step P5 of cleaning the aluminum substrate and a subsequent process step P6 after the cleaning is completed are performed.

It should be noted that the etching process step of the aluminum substrate and the mask layer removing process step of the aluminum substrate are performed continuously, and the process difference between the mask layer removing process step of the aluminum substrate and the cleaning process step of the aluminum substrate is large, so there is an indeterminate time interval between the two, i.e., the interval P4 is performed between the step P3 and the step P4, and in the embodiment illustrated in fig. 3, the interval shown in the step P4 is 0 to 120 hours.

The principle of the corrosion-resistant treatment of the aluminum substrate with the nitrogen plasma is explained below:

firstly, the active group of nitrogen in the nitrogen plasma can effectively generate passivation reaction with the aluminum substrate, so that a stable aluminum nitride passivation layer is formed on the surface of the aluminum substrate, the corrosion resistance stability of the aluminum substrate in air at the later stage is realized, only the aluminum on the surface participates in the passivation reaction, and the aluminum substrate cannot be etched due to passivation. Secondly, nitrogen active groups in the nitrogen plasma can also gradually convert aluminum-chlorine compounds into aluminum nitride compounds, so that chlorine ions which participate in the reaction are removed and taken away, and the chlorine ions which are chemically adhered are removed. Finally, a large amount of nitrogen active ions in the nitrogen plasma have good cleaning effect on chloride ions or gaseous chlorine radicals adhered to the surface of the aluminum substrate in the process of bombarding the surface of the aluminum substrate, so as to remove the physically adhered chlorine. Compared with chlorine atoms or chlorine ions, nitrogen atoms or nitrogen ions have poor adhesiveness, the residual quantity of the nitrogen atoms or nitrogen ions is very small, and the residual nitrogen cannot cause other corrosion phenomena, but has good protection effect on the surface of the aluminum substrate.

According to the plasma etching method provided by the invention, the residual chloride ions on the surface of the aluminum substrate can be effectively removed through the anti-corrosion treatment of the nitrogen plasma on the aluminum substrate, and a stable passivation layer is formed on the surface of the aluminum substrate, so that the anti-corrosion capability of the aluminum substrate in the air is improved; in addition, the anti-corrosion treatment process and the process for removing the mask layer are finished indoors in the same process, and other process manufacturing machines are not required to be added, so that the process cost is reduced; the invention adopts nitrogen as process gas to carry out anti-corrosion treatment, does not corrode the process chamber, is suitable for substrates made of various metal materials, and has wide applicability to process objects.

Based on the above principle, as an alternative embodiment of the present invention, the auxiliary process gas introduced into the second process chamber includes at least one of oxygen, argon and helium.

The method comprises the following steps of introducing oxygen into an aluminum substrate anti-corrosion treatment process with nitrogen as a main process gas, ionizing the oxygen into plasma, and etching and removing a mask layer remained on the surface of the aluminum substrate by using the oxygen plasma; the introduction of argon gas further enhances the dissociation of the nitrogen plasma to form a high density plasma, while the introduction of helium gas adjusts the concentration of the nitrogen plasma to meet various process requirements, i.e., the passivation reaction rate of the nitrogen plasma with the aluminum substrate and the removal rate of chloride ions.

As an optional embodiment of the present invention, when the step of performing the corrosion prevention treatment on the aluminum substrate after removing the mask layer is performed, the rf power of the upper electrode ranges from 500W to 2500W; the radio frequency power range of the lower electrode is 30W-1000W.

It is noted that the purpose of setting the upper electrode power higher is to generate a high density nitrogen plasma, thereby increasing the number of nitrogen reactive groups in contact with the aluminum substrate surface, accelerating the passivation reaction rate and nitrogen exchange for chemically adhering chlorine, and scavenging physically adhering chlorine. The significance of the proper lower electrode power is that the bias effect is carried out on the nitrogen ions and the active groups, the speed and the density of the high-density nitrogen plasma bombarding the surface of the aluminum substrate are increased, and therefore the passivation reaction and the chlorine cleaning in the anticorrosion treatment are completed more quickly or fully.

As another optional embodiment of the present invention, when the step of performing the corrosion prevention treatment on the aluminum substrate for the predetermined time by using nitrogen gas is performed, the flow rate of the nitrogen gas introduced into the second process chamber is 50sccm to 1000 sccm; the flow rate of the auxiliary process gas introduced into the second process chamber is 0sccm to 1000 sccm; and the gas pressure of the second process chamber is ensured to be in the range of 10 mT-2000 mT after the steps are carried out.

In yet another alternative embodiment of the present invention, the predetermined time is in a range of 20s to 300 s.

As still another alternative embodiment of the present invention, the temperature of the substrate is in a range of 30 to 300 ℃ when the step of ionizing the nitrogen gas and the auxiliary process gas is performed.

It should be noted that the temperature of the substrate can be adjusted by adjusting the temperature of the electrostatic chuck, and the temperature of the substrate can be adjusted to obtain a better passivation reaction rate and a better removal rate of chloride ions, and specifically, the higher the temperature is in the above temperature range, the faster the passivation reaction rate and the removal rate of chloride ions are.

The following describes the effect of the plasma etching method provided by the present invention applied to etching an aluminum substrate with reference to fig. 1, 3, 4 and 5: