JP2008078678A - Method for processing plasma - Google Patents

Abstract

There is provided a dry cleaning method capable of removing a source of dust generated on an inner wall of a semiconductor etching apparatus.
A process gas comprising a combination of different gases including a fluorine-containing gas is supplied into a processing chamber in a multi-stage step, and an etching process is performed on the material to be etched, which is a laminated film containing Al, in a multi-stage step. A first cleaning process for removing a deposit containing a material to be etched that adheres to the processing chamber using a gas and an ion sputter of an internal component material in the processing chamber that adheres to the processing chamber are removed using a gas containing B. A second cleaning process is performed.
[Selection] Figure 1

Description

The present invention relates to a dry cleaning method in a semiconductor manufacturing apparatus used for performing fine processing or film formation on a substrate in a manufacturing process of a semiconductor device.

If dust (foreign matter) adheres to the substrate in the manufacturing process of the semiconductor device, it will cause a pattern defect of the target device and reduce the yield in the manufacturing process.

On the other hand, in recent manufacturing processes, processes such as dry etching and CVD using plasma have become important. That is, various gases are introduced into the apparatus, and microfabrication such as film formation and etching is performed using the plasma reaction of the introduced gas. In these processes, the deposited film adheres not only to the substrate to be finely processed, that is, to the inner wall of the manufacturing apparatus. For example, in dry etching, an etching gas is decomposed or combined in plasma, and a deposited film adheres to the inner wall of the apparatus due to etching by-products generated by etching. Such a deposited film partially peels off and becomes dust when the number of processed films increases and the film thickness increases, causing a pattern defect of the device. Therefore, it is necessary to periodically remove these deposits.

Conventionally, as a method for removing such deposits, so-called wet cleaning in which the apparatus is opened to the atmosphere and wiped with a solvent such as alcohol or pure water, for example, a chlorine-based gas disclosed in Patent Document 1 is used. There are known dry cleaning using a combination of oxygen gas and fluorine gas or plasma of a mixed gas of oxygen gas and chlorine gas disclosed in Patent Document 2.
JP-A-3-62520 Japanese Patent Laid-Open No. 7-508313

  However, the conventional cleaning method has the following problems.

First, with regard to wet cleaning, it is necessary to periodically open the apparatus to the atmosphere and disassemble it, and further evacuation after wet cleaning is required. Accordingly, the apparatus is stopped for a long time every cleaning, which causes a significant decrease in apparatus operation rate and throughput.

Next, in the disclosure example of Patent Document 1, the material to be etched is an alloy containing Al and W, and in order to remove the Al etching product and the W etching product, that is, cleaning a plurality of etching objects. It is characterized by the combination. Further, the conventional dry cleaning represented by the disclosure example of Patent Document 2 is based on a material to be etched and an etching gas, or a photoresist (carbon) that is a mask material at the time of etching and an etching gas or a polymer of etching gas. It is characterized by removing so-called reaction products.

In these conventional disclosure examples, cleaning related to the product of the etching gas and the material on the wafer substrate, such as the material to be etched and the mask material, is considered, but the ion sputter of the material in the apparatus or the material in the apparatus No consideration is given to the cleaning of compounds of materials and etching gases.

In the etching apparatus, the plasma by the etching gas etches the surface of the substrate to be etched, and also hits the internal material of the apparatus. As a result, not only the etching reaction product but also the ion spatter of the internal material of the apparatus, or A compound of material inside the device and etching gas is attached and deposited on the inner wall of the device.

That is, in the conventional dry cleaning method, there has been a big problem that the ion sputtered material in the apparatus member material or the compound of the apparatus member material and the etching gas accumulates without being removed and generates foreign matters.

An object of the present invention is to solve these problems, and to provide a dry cleaning method capable of effectively removing a deposited film adhering to an inner wall of a manufacturing apparatus, that is, capable of removing a dust generation source. is there.

The above object has a step of removing an etching reaction product and a step of removing an ion sputter of a material inside the processing apparatus or a compound of an internal member material and an etching gas in the dry cleaning process. Is achieved.

In addition, the purpose of the above is that when the dry cleaning process is performed, the value of the interatomic bond energy with respect to the elements constituting the gas used in the etching and cleaning processes is different from that of the elements constituting the material to be etched. This is achieved by using a gas containing a substance having a larger value than the value of the interatomic bond energy of the elements constituting the gas used in the applying step.

In addition, the above-described object is that, in the process of performing dry cleaning, the value of the interatomic bond energy with respect to the elements constituting the gas used in the processes of etching and cleaning is determined by the etching and cleaning with the elements constituting the material in the apparatus. This is achieved by using a gas containing a substance having a value larger than the value of the interatomic bond energy of the elements constituting the gas used in the step of applying.

Since this invention is provided with the above structure, the deposited film adhering to the inner wall of a manufacturing apparatus can be removed efficiently. As a result, it becomes possible to prevent the peeling of the deposited film and the generation of dust due to the increase in the deposited film thickness (increase in the number of processed sheets), thereby improving the yield in the manufacturing process and improving the operating rate of the manufacturing apparatus. be able to.

Embodiments of the dry cleaning method of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration diagram of a microwave etching apparatus used in the dry cleaning method according to the present invention. In the figure, reference numeral 1 denotes a silicon wafer (substrate) to be finely processed, and reference numerals 3 and 4 denote a quartz bell jar and a main chamber, respectively, which create a vacuum atmosphere. 10 is an exhaust port for evacuation, and 15 is a gas introduction part for etching or dry cleaning. Reference numeral 9 is a substrate stage for fixing and holding the wafer, and 8 is a clamper for clamping the wafer. In general, the clamper is often made of ceramics such as alumina ceramics. As a method for fixing and holding the wafer on the substrate stage 9, a method using electrostatic attraction may be used. 7 is a ground plate, and 11 is an RF between the ground 7 and the wafer stage 9.
This is a high-frequency power source for applying a bias.

The microwave etching apparatus first introduces a gas for generating plasma after high vacuum evacuation. Then, the microwave 14 is oscillated from a magnetron (not shown) and introduced into the quartz bell jar 3 (processing chamber) through the waveguide 5 to resonate with the magnetic field formed by the solenoid coil 6 disposed around the processing chamber ( Using ECR, the gas in the processing chamber is turned into plasma and etching is performed using the plasma. An RF bias is applied between the ground 7 and the wafer stage 9 by a high-frequency power source 11 for the purpose of performing anisotropic etching by drawing ions.

At this time, a reaction product formed as a by-product of the etching process is a quartz bell jar 3.
The deposited film 13 is formed on the main chamber 4, the outlet 15 of the gas introduction section, and the components of the processing chamber such as the clamper 8. Such a deposited film partially peels off and becomes dust when the number of processed films increases and the film thickness increases, causing a pattern defect of the device.

Here, as an example, a silicon oxide film (S
The case where the (iO2 film) 17 is etched using a fluorocarbon-based gas, for example, a plasma of CF4 gas and plasma of additive gases Ar and O2 gas will be described. As shown in this figure, for example, a SiO2 film 17 is formed on a substrate 16, and a mask pattern 18 made of a photoresist is formed thereon, and this is subjected to an etching process with an etching apparatus as shown in FIG. At this time, the etching gas is dissociated in the plasma, and etching proceeds by hitting the wafer. At this time, unnecessary deposits adhering to the inner wall of the apparatus due to the object to be etched become oxides containing silicon and compounds containing organics.

By the way, the gas at the time of dry cleaning is carried out with the aim of reacting with the deposit to be removed to become a compound having a high vapor pressure.
Remove by evacuation. For example, if the deposit is a carbon compound, it is removed by applying plasma of O2 gas to CO or CO2 as gases. JP-A-7
In the example disclosed in -508313, a cleaning gas in which an oxygen-based gas is mixed with a chlorine-based gas is used. By mixing oxygen, carbon is cut off from compounds containing metal, chlorine and organic matter, and at the same time, by cleaning the metal with chlorine,
The aim is to improve the overall effect.

In the case of etching the SiO2 film as mentioned in this embodiment, cleaning by mixing or combination of fluorine-based gas and oxygen-based gas is generally used. However, as described above, the plasma by the etching gas etches the substrate surfaces 17 and 18 to be etched, as well as internal materials such as the clamper 8,
As a result, the deposited film 13 is not only a reaction product with respect to the material to be etched but also an ion sputtered material of the internal member material or a compound of the internal member material and the etching gas as a by-product of the etching process. It becomes a constituent element.

In general, alumina parts are often used in plasma application semiconductor manufacturing apparatuses such as etching apparatuses. In this embodiment (example in FIG. 2), unnecessary deposits adhering to the inner wall of the apparatus are first caused by the object to be etched. The clamper 8 is struck by plasma, ion-sputtered, and adhered and deposited on the inner wall of the apparatus in the form of alumina. A part of this adheres and accumulates in the form of aluminum fluoride by fluorine during etching.

Conventional dry cleaning only cleans SiO2 and organic compounds of resist materials. That is, it is not taken into account that the ion sputtered material of the internal member material of the apparatus or the compound of the internal member material of the apparatus and the etching gas is deposited, and therefore cleaning of these is not considered. Therefore, these finally remain as the cause of the generation of foreign matter.

According to the present invention, in the dry cleaning step, in addition to the step of removing the etching reaction product, the step of removing the ion sputter of the member material in the apparatus and the compound of the member material in the device and the etching gas. Therefore, it is possible to remove deposits made of the compound of the material in the apparatus, which has been overlooked in the conventional dry cleaning, and it is possible to improve the cleaning effect and the effect of suppressing the generation of foreign matter.

In this embodiment, specifically cleaning with a mixed gas of Bcl3 and Cl2 is added as cleaning of the material inside the apparatus. For aluminum deposits, Cl2
It is effective to generate and remove AlCl3 with high vapor pressure by gas plasma.

However, when aluminum is an oxide or fluoride, Al-C
Since the interatomic bond energy of Al-O and Al-F is larger than the interatomic bond energy of l, AlCl3 cannot be generated by Cl2 alone plasma and cannot be removed by cleaning. Therefore, by mixing Bcl3, a gas containing B, whose interatomic bond energy for fluorine and oxygen is larger than the interatomic bond energies of Al-O and Al-F, Al-O and Al-F Pull out O and F from, and enable cleaning with Cl2. As a result, in addition to the etching reaction product, the ion sputtered material of the member in the apparatus can be removed.

Here, the cleaning effect in the apparatus and the foreign matter suppression effect can be remarkably improved by sequentially cleaning O2 and sulfur hexafluoride (SF6) and cleaning with a mixed gas of BCl3 and Cl2.

In this way, in addition to dry cleaning for removing reaction products on the material to be etched, by performing dry cleaning for removing ion spatter of the member material in the apparatus or a compound of the member material in the apparatus and the etching gas. The cleaning effect in the apparatus can be remarkably improved. Here, the dry cleaning for the etching reaction product and the cleaning for the material inside the apparatus are performed in order, but the cleaning gases of both may be mixed.

Next, an example applied to tungsten wiring will be described with reference to FIG. FIG.
Thus, for example, a tungsten wiring 19 is formed on the substrate 16, and a mask pattern 18 made of a photoresist is formed thereon, and this is subjected to an etching process by an etching apparatus as shown in FIG. Etching is performed on tungsten with SF6 gas plasma.

At this time, unnecessary deposits adhering to the inner wall of the apparatus are struck by plasma by a compound containing tungsten, fluorine and organic matter, and a clamper 8 which is an alumina part in the apparatus.
Ion sputtered and deposited on the inner wall of the device in the form of aluminum oxide. Part of this is in the form of aluminum fluoride due to the plasma of SF6 gas during etching. Here, cleaning with SF6 and cleaning with a mixed gas of BCl3 and Cl2 were performed in order. SF6 also has a cleaning effect on tungsten and organic compounds. Cleaning with a mixed gas of BCl3 and Cl2 exhibits a cleaning effect on aluminum oxide and aluminum fluoride as described in the first embodiment. This cleaning significantly improved the effect of suppressing foreign matter. As in the first embodiment, the dry cleaning for removing the reaction product for the etching material and the dry cleaning for the material in the apparatus are performed in this way.
The cleaning effect is remarkably improved.

Next, another embodiment using the present invention will be described. Here, the case where the present invention is applied to the case of etching an aluminum laminated wiring as shown in FIG. 4 will be described.

Recent metal wiring is not an aluminum single layer film but a barrier metal 2 as shown in FIG.
A laminated film with 1 is used, and a plurality of etching gases are used in the etching process. The purpose is to obtain electromigration resistance and diffusion barrier properties. Here, an example in which a laminated film of an aluminum wiring 20 and a titanium tungsten (TiW) barrier metal 21 is etched will be described. As already described, when etching is performed, a compound having a high vapor pressure is formed on the material to be etched to advance the etching. In this case, the first layer of aluminum 20 is AlCl3 having a high vapor pressure using Cl2 gas.
Then, the etching is advanced. At this time, the inner wall of the apparatus, for example, quartz bell jar 3,
Al for process chamber components such as main chamber 4, gas inlet 15 and clamper 8
Or, AlClx adheres and accumulates. Thereafter, TiW 21 of the second layer is formed by SF6 plasma. At this time, Ti or tungsten (W) adheres to and accumulates on the inner wall of the apparatus and the components of the processing chamber.

Normally, when cleaning Al or AlClx, when cleaning Ti, Cl2 plasma is used to remove AlCl3 and TiCl with high vapor pressure. In addition, when cleaning W, WF6 having a high vapor pressure is removed by using a fluorine-based gas such as SF6 plasma.

However, if the film that forms the wiring is not a single layer film but a laminated film, the configuration of the inner wall of the apparatus and the processing chamber is required in order to use multiple etching gas plasmas and multiple cleaning gases. The deposited film adhering to the parts is not a simple shape,
It will be in the form of compounds with these gases.

That is, the deposit is
1) Al or AlClx adheres and deposits during the etching of the first layer. The deposit becomes aluminum fluoride by SF6 plasma during the TiW etching of the second layer. Thereafter, TiW 20 of the second layer is formed by SF6 plasma. At this time, Ti or W is deposited and deposited on the inner wall of the apparatus and the components of the processing chamber.

2) Al and AlClx deposited during the etching of the first layer are further promoted by the cleaning process for removing W, which is a deposit during the TiW etching of the second layer, and SF6 plasma.

3) Plasma generated by etching gas or cleaning gas strikes and deposits on the inner wall of the apparatus in the form of aluminum oxide by ion sputtering by hitting alumina parts generally used for the parts inside the apparatus.

4) Aluminum oxide adhering to and depositing on the inner wall of the device due to the ion sputtering effect of the plasma is partially converted to aluminum fluoride by SF6 plasma during the TiW etching of the second layer.

5) Aluminum oxide adhering to and depositing on the inner wall of the device due to the ion sputtering action of the plasma is partially converted to aluminum fluoride by SF6 plasma during W cleaning.

Thus, when etching a multi-layer wiring, the plasma of the etching gas does not remove deposits adhering to the apparatus when another wiring layer is etched while one wiring layer is being etched. It is made into a compound. Further, while cleaning deposits of one element, cleaning gas plasma makes it difficult to remove deposits of other elements. These can interfere with the intended cleaning.

Further, the plasma generated by the etching gas and the cleaning gas also strikes the material inside the apparatus, and as a result, the ion sputtered material of the material inside the apparatus adheres to the apparatus. These also become compounds with etching gas and cleaning gas. These can interfere with the intended cleaning.

According to the present invention, the dry cleaning process includes a substance whose interatomic bond energy with the etching gas element is larger than the interatomic bond energy between the material to be etched and the element constituting the etching gas. Add gas cleaning. As a result, the deposit 1) can be removed. In other words, it is possible to remove the aluminum deposited during the etching of the first layer from the aluminum fluoride by SF6 plasma during the TiW etching of the second layer.

Further, according to the present invention, in addition to the step of removing the etching reaction product in the dry cleaning step, the step of removing the ion sputtered material of the member in the apparatus is added. Things can be removed. That is, it becomes possible to remove the ion spatter of the alumina parts used for the parts in the apparatus.

Further, during the dry cleaning process, the interatomic bond energy with the gas element in the cleaning process is higher than the interatomic bond energy between the material to be etched and the material constituting the apparatus and the element constituting the cleaning gas in another process. A cleaning with a gas containing a substance having a large value is added. As a result, 2),
The deposits 4) and 5) can be removed. In other words, it becomes possible to remove deposits that have become aluminum fluoride by SF6 plasma during W cleaning.

Specifically, the SF6 plasma used during etching and cleaning makes aluminum fluoride, so it cannot be removed by cleaning with Cl2 alone plasma. During the dry cleaning process, a substance B having an interatomic bond energy with fluorine larger than the interatomic bond energy between fluorine used for etching and cleaning and aluminum as the material to be etched is selected. By mixing the containing gas, Bcl3, with Cl2 gas to make a cleaning gas, F can be extracted from Al-F and Cl2 cleaning can be made effective.

In addition, B has higher interatomic bond energy of BO than aluminum oxide Al-O, which is an ion sputtered material in the equipment. Therefore, the gas containing B, Bcl3
By mixing with Cl2 gas, O is extracted from Al-O, and cleaning with Cl2 is enabled. That is, it is possible to remove the ion sputtered material of the internal member of the apparatus.

The cleaning process for the film deposited by reacting with the etching gas or cleaning gas in the next process because it is a laminated film is put after or before or both of the cleaning process of the etching reaction product alone. Good.

Although the embodiment of the present invention has been described with reference to an example applied to a microwave etching apparatus, the present invention is not limited to this, and may be a parallel plate etching apparatus, an inductively coupled etching apparatus, or a CVD apparatus. However, the effect can be obtained if the apparatus cleans the deposits on the inner wall of the apparatus with plasma.

The figure which shows the semiconductor manufacturing manufacturing apparatus to which this invention is applied. 1 is a cross-sectional view of a semiconductor wafer to which a first embodiment of the present invention is applied. The cross-sectional view of the semiconductor wafer to which the second embodiment of the present invention is applied. The cross-sectional view of the semiconductor wafer to which the third embodiment of the present invention is applied.

Explanation of symbols

1 ... wafer, 2 ... plasma, 3 ... quartz bell jar, 4 ... main chamber,
5 ... Waveguide, 6 ... Solenoid coil, 7, 12 ... Ground, 8 ... Wafer clamper,
DESCRIPTION OF SYMBOLS 9 ... Wafer stage, 10 ... Vacuum exhaust port, 11 ... High frequency power supply, 13 ... Deposit, 1
DESCRIPTION OF SYMBOLS 4 ... Microwave, 15 ... Gas inlet, 16 ... Semiconductor substrate, 18 ... Photoresist mask pattern, 19 ... Tungsten wiring, 20 ... Aluminum wiring film, 21 ... TiW barrier metal.

Claims (1)

A processing gas composed of a combination of different gases including a fluorine-containing gas is supplied into the processing chamber in a multi-stage step, and an etching process is performed in a multi-stage step on the material to be etched which is a laminated film containing Al.
A gas containing B is used as a first cleaning process for removing deposits containing an etching target material adhering to the processing chamber using a gas containing B, and an ion sputtered material of an internal constituent material in the processing chamber adhering to the processing chamber. And performing a second cleaning process to be removed.

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