1. Field of the Invention
The present invention relates to a technique of etching gold, platinum, iridium or a conductive metal oxide with plasma, and more particularly, it relates to a technique of cleaning a plasma etching apparatus introducing a microwave for generating plasma.
2. Description of the Prior Art
In a high-frequency device or a ferroelectric memory applied to a mobile communicator such as a portable telephone, for example, a metal such as gold, platinum or iridium is employed as the material for a wire or an electrode in an LSI. In an element employing a substrate of gallium arsenide as a high-frequency device, for example, gold is employed as the material for a gate electrode or the like due to requirement for the characteristics of the element. In a ferroelectric memory employing a metal oxide for a dielectric, oxidation resistance is required for an electrode material and gold, platinum or iridium having small reactivity is employed for the electrode material not to reduce the dielectric.
While an RIE (reactive ion etching) apparatus or the like is employed for patterning the metal, an etching apparatus such as an ECR (electron cyclotron resonance) plasma apparatus or a surface wave plasma etching apparatus employing high-density plasma is now being employed following refinement of devices.
Dissimilarly to silicon or aluminum, however, the aforementioned metal has small reactivity with plasma. When subjected to plasma processing, therefore, the metal is scattered from the processed material mainly by sputtering, to adhere to the inner part of a chamber of the plasma apparatus.
The material adhering to the inner part of the chamber in the aforementioned manner is conductive. In a plasma etching apparatus generating plasma with an electrode, generation of the plasma is not remarkably influenced by such a conductive material adhering to the electrode. In a plasma etching apparatus generating plasma by introducing a microwave, however, a conductive material adhering to a window for introducing the microwave reflects the microwave, to cause difficulty in generation of the plasma.
While the aforementioned metal partially reacts with chlorine or fluorine, a chloride or a fluoride of the aforementioned metal has low vapor pressure. Under ordinary pressure, for example, AuF3 is sublimed at about 300xc2x0 C., PtF6 is vaporized at 69xc2x0 C., IrF3 is decomposed at 250xc2x0 C., and InF3 is vaporized at a temperature of at least 1200xc2x0 C. Despite plasma processing, therefore, the reactant is hardly discharged as vapor but adheres to the inner part of the chamber, and this conductive reactant disadvantageously causes the aforementioned difficulty in generation of the plasma. When chlorine is employed as etching gas, further, this etching gas may corrode and damage a metal film or an insulator film of an aluminum alloy such as Al or AlSiCu or a high dielectric constant metal oxide such as SBT (strontium bismuth tantalate) or BST (barium strontium titanate), for example, separately formed on a substrate formed with the metal to be etched. Therefore, employment of chlorine is unpreferable.
While the electrode material to be etched may be prepared from a conductive oxide such as tin oxide, ruthenium oxide or iridium oxide or an oxide such as indium oxide or tantalum oxide attaining conductivity due to addition of an impurity in place of the aforementioned metal, this material also adheres to the inner part of the chamber, particularly the microwave introduction window, as a result of sputtering to cause the aforementioned problem.
An object of the present invention is to reduce inhibition of generation of plasma caused by a deposit in a technique of introducing a microwave through a microwave introduction window for generating plasma and performing etching on the basis of this plasma.
In order to attain the aforementioned object, a plasma processing method according to an aspect of the present invention introduces a microwave and gas into a chamber capable of storing a sample having a conductive layer through a microwave introduction mechanism and from a gas inlet port respectively for processing the conductive layer with plasma, while at least a part of the microwave introduction mechanism exposed to the plasma consists of quartz, the gas contains at least fluorine, and the part of quartz is etched at the same time during the processing.
In an example of this plasma processing method, the gas contains no halogen element but fluorine.
A plasma processing method according to another aspect of the present invention introduces a microwave and gas into a chamber capable of storing a sample having a conductive layer through a microwave introduction mechanism and from a gas inlet port respectively for processing the conductive layer with first plasma, while the sample is discharged and a part of the microwave introduction mechanism exposed to the first plasma is cleaned with second plasma when prescribed information changed by processing the conductive layer with the first plasma satisfies a prescribed condition.
According to this plasma processing method, the part of the microwave introduction mechanism exposed to the first plasma, to which a conductive material adheres as a result of processing the conductive layer with the first plasma, is cleaned with the second plasma after the sample is discharged, whereby the cleaning can be performed without damaging the material of the sample by the second plasma.
When the number of processed samples, for example, is employed as the prescribed information, the part of the microwave introduction mechanism exposed to the plasma can be prevented from adhesion of a large quantity of conductive material caused by processing an excessive number of samples.
When information reflecting the state of the first plasma, position information of a microwave matcher interposed between a microwave generation source and the chamber or a reflected power value of the microwave, for example, is employed as the prescribed information, the part of the microwave introduction mechanism exposed to the plasma is cleaned by detecting the state of the plasma changed by adhesion of the conductive material, whereby the part of the microwave introduction mechanism exposed to the plasma can be prevented from adhesion of a large quantity of conductive material.
In an example of this plasma processing method, at least the part of the microwave introduction mechanism exposed to the first plasma consists of quartz, and the second plasma is generated from gas containing fluorine.
The conductive layer contains gold, silver, copper, a platinum metal, indium, gallium, germanium, arsenic or phosphorus, an alloy of any of these metals, or a metal oxide.
A plasma processing apparatus according to still another aspect of the present invention comprises a chamber capable of storing a sample having a conductive layer to be etched with plasma, a gas inlet port for introducing gas containing fluorine into the chamber, and a microwave introduction mechanism, consisting of quartz at least in a part exposed to the plasma, for introducing a microwave for generating the plasma from the gas into the chamber.
The microwave introduction mechanism preferably has a microwave introduction window of quartz. The microwave introduction window of quartz is provided to fill up a through hole of a conductor member having the through hole, for example.
In an example of this plasma processing apparatus, the microwave introduction mechanism has a microwave introduction window and a separator, consisting of quartz at least in a part exposed to the plasma, for separating the microwave introduction window from the plasma. The microwave introduction window is formed by a conductor member having a through hole, for example.
According to the plasma processing apparatus having the aforementioned structure, the microwave introduced from the microwave introduction mechanism generates plasma from the gas containing fluorine. When the conductive layer or a compound thereof adheres to the part of the microwave introduction mechanism exposed to the plasma due to plasma processing, fluorine contained in the plasma etches this part of the microwave introduction mechanism, thereby preventing deterioration of introduction of the microwave.
A plasma processing apparatus according to a further aspect of the present invention comprises a sample holder, receiving a sample having a conductive layer to be etched with plasma, capable of applying high-frequency power to the sample, a sample holder cover, consisting of quartz at least in a part exposed to the plasma, for covering the periphery of the sample holder without coming into contact with the sample, a chamber capable of storing the sample holder and the sample holder cover, a gas inlet port for introducing gas containing fluorine into the chamber, and a microwave introduction mechanism for introducing a microwave for generating the plasma from the gas into the chamber.
According to the aforementioned structure, the conductive layer or a compound thereof will not adhere to the sample holder as a result of plasma processing. When the conductive layer or a compound thereof adheres to the sample holder cover, fluorine contained in the plasma etches the sample holder cover thereby preventing disturbance of application of the high-frequency power.
The upper end of the sample holder cover is preferably located downward beyond a position of the sample holder for receiving the sample. Thus, the upper end of the sample holder cover will not inhibit the sample from coming into contact with the sample holder, whereby the high-frequency power can be sufficiently applied to the sample.
A plasma processing apparatus according to a further aspect of the present invention comprises a chamber capable of storing a sample having a conductive layer to be etched with plasma, a gas inlet port for introducing gas into the chamber, and a microwave introduction mechanism for introducing a microwave for generating the plasma from the gas into the chamber, while the microwave introduction mechanism includes a waveguide for propagating the microwave, a microwave introduction window having microwave transmissibility interposed between the waveguide and the chamber, and reflection quantity detection means detecting the quantity of reflected microwave, and plasma for cleaning a part of the microwave introduction window exposed to the plasma is generated in the chamber when the quantity of the reflected microwave exceeds a prescribed level.
According to this structure, the quantity of the reflected microwave increased by a conductive material adhering to the microwave introduction window as a result of etching the conductive layer is so detected as to clean the microwave introduction window when the quantity of the reflected microwave is increased, whereby stable plasma processing can be carried out.
A plasma processing apparatus according to a further aspect of the present invention comprises a chamber capable of storing a sample having a conductive layer to be processed with plasma, a gas inlet port for introducing gas into the chamber and a microwave introduction mechanism for introducing a microwave for generating the plasma from the gas into the chamber, while the microwave introduction mechanism includes a waveguide for propagating the microwave, a microwave introduction window having microwave transmissibility interposed between the waveguide and the chamber, and a microwave matcher for matching the microwave with the plasma by controlling the position or the quantity of a member inserted into a part propagating the microwave, and plasma for cleaning a part of the microwave introduction window exposed to the plasma is generated in the chamber when the position or the quantity of the member of the microwave matcher inserted into the part propagating the microwave is out of a prescribed range.
According to this structure, the position or the quantity of insertion of the member of the microwave matcher changed by a conductive material adhering to the part of the microwave introduction window exposed to the plasma as a result of etching the conductive layer is so detected as to clean the microwave introduction window when the position or the quantity is out of the prescribed range, whereby stable plasma processing can be carried out.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.