JPH04239130A - Plasma processor and processing method - Google Patents

Abstract

PURPOSE:To provide the title processor and processing method capable of avoiding the production of the pollutants such as fine projections on a semiconductor substrate surface during the plasma processing step. CONSTITUTION:A reactive gas containing O2 is fed to a reactive container 1 with a discharge electrode from a gas leading-in port 1a and then discharged from an exhaust port 1b. A semiconductor substrate 4 to be plasma-processed is arranged on an RF electrode 2 in the reactive vessel 1 and the space between the RF electrode 2 and an opposite electrode 3 is impressed with high-frequency voltage 5 while a reactive gas is fed to the reactive vessel 1 so as to be discharged for producing plasma. On the other hand, the reactive vessel 1 is composed of Al, while an Al2O3 film 6 is formed on the inner wall surface by anode electrode oxidation step besides, forming the other Al2O3 films 7, 8 on the opposite surface of the discharge electrodes 2, 3. Accordingly, extremely flat etching surface can be formed. Furthermore, when the plasma is produced using fluorocarbon as the reactive gas, the vessel inner wall and the electrode surfaces are coated with polymer film to be a barrier layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a plasma processing method for subjecting a sample such as a semiconductor substrate to plasma processing such as plasma etching or plasma CVD.

0002

2. Description of the Related Art As semiconductor devices become more highly integrated, there is a strong demand for the development of a technique for forming multilayer wiring on a semiconductor substrate on which various elements are formed to improve the efficiency of occupying the elements. The most important thing when forming multilayer wiring with high reliability is to planarize the interlayer insulating film and prevent the cross-sectional area of the wiring formed thereon from decreasing with respect to the underlying stepped portion.

[0003] SO is a method for planarizing an interlayer insulating film.
Examples include a spin-on-glass (G) method, a method using a bias sputtering CVD device, and a resist etch-back method. Among these, the resist etch-back method is an inexpensive processing method because it can utilize a resist coater commonly used in a lithography process, has good controllability, and has an extremely good degree of planarization. This resist etch-back method is a method in which a resist film is spin-coated on an interlayer insulating film mainly composed of SiO2, baked, and then subjected to reactive plasma etching to planarize the substrate surface. In this plasma etching, oxygen is added to the fluorocarbon-based reactive gas, and the etching rate of SiO2 and the etching rate of the resist are set to be the same, so that the surface of the substrate is etched flat.

Furthermore, plasma processing methods are used not only for plasma etching but also for various equipment processes of semiconductor devices, such as plasma CVD methods, and there is a strong demand for its utilization in the manufacture of semiconductor devices. has been done.

[0005]

[Problems to be Solved by the Invention] As mentioned above, plasma etching equipment can be used in the manufacturing process of various semiconductor devices;
．． Minute columnar protrusions of about 2 μm may be formed. Once such microprotrusions are formed,
The surface of the semiconductor substrate cannot be flattened, and on the contrary, the productivity of semiconductor devices is significantly reduced. For this reason, the reality is that the resist etch-back method is not widely used in mass production factories, even though it is an inexpensive process. There are methods to solve this problem, such as lowering the amount of oxygen added or changing the amount of oxygen added in stages, but these methods not only take a long time to process, but also do not provide sufficient flattening. The reality is that there is not. Note that this protrusion occurs not only in resist etchback but also in polycrystalline silicon etching processing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a plasma processing apparatus and a plasma processing method that can prevent minute protrusions from being generated on the surface of a semiconductor substrate during plasma processing and can perform appropriate plasma processing. It is in.

[0007]

[Means for Solving the Problems] A plasma processing apparatus according to the present invention includes a reaction vessel and a discharge electrode disposed in the reaction vessel, supplies a reaction gas to the reaction vessel to generate plasma, and generates plasma. A plasma processing apparatus that performs plasma processing by irradiating a sample to be processed with plasma, characterized in that at least a portion of the inner wall surface of the reaction vessel and the surface of the discharge electrode is subjected to plasma inactivation treatment. be. Furthermore, the plasma processing method according to the present invention includes a reaction vessel and a discharge electrode disposed in the reaction vessel, supplies a reaction gas to the reaction vessel to generate plasma, and directs the generated plasma to the sample to be treated. When performing plasma treatment by irradiating a sample, before irradiating the sample with plasma, a reaction gas is supplied to a reaction vessel, and this reaction gas is plasma-polymerized to form a polymer. This method is characterized in that a polymer film is formed on a portion of the sample, and then the sample is subjected to plasma treatment using the reaction gas.

[0008]

[Operation] As a result of various experiments and analyzes carried out by the present inventor in order to elucidate the cause of columnar protrusions occurring on semiconductor substrates, it was found that the metal of the discharge electrode or the wall of the reaction vessel used in the plasma processing equipment The material was found to act as a contaminant. That is, when reactive plasma etching was performed using oxygen and fluorocarbon gas as reactive gases, and the composition of columnar protrusions formed on the surface of a semiconductor substrate was analyzed, it was found that the main component of these columnar protrusions was polymerized fluorocarbon. Furthermore, as a result of elemental analysis using Auger analysis, a large amount of aluminum element was detected in addition to C and F elements. Since this aluminum is a constituent material of the discharge electrode, it is possible that the discharge electrode material acts as a contaminant. It has also been found that, in conditioning oxygen plasma etching, if a fluorocarbon polymer film is previously formed on the electrode surface and the inner wall surface of the reaction vessel, no columnar protrusions are generated. On the other hand, if the metal material of the discharge electrode or the wall of the reaction vessel is exposed, a large number of secondary electrons are emitted from this exposed part, locally increasing the plasma density, and a large amount of metal in that part is sputtered. It is thought that the metal atoms adhered to the semiconductor substrate to be processed, and the adhered metal atoms acted as a catalyst, causing local polymerization to proceed. In particular, since aluminum and nickel are used as polymerization accelerators for plasma polymerization, local polymerization is promoted in areas where aluminum atoms are attached, and many columnar protrusions are formed due to plasma polymerization. Conceivable.

From the above-mentioned analysis results, in the present invention, a high-density, highly dense coating that acts as a barrier layer against plasma is formed on at least a portion of the surface of the discharge electrode and the inner wall surface of the reaction vessel, thereby improving the surface of the metal material. Then, perform plasma inactivation treatment. Although such a film may be slightly sputtered by plasma, the amount sputtered is so small that it hardly causes any problem. As this inactivation film, an inert polymer film such as a fluorocarbon polymer film or a fluororesin polymer film, or a metal oxide film such as Al2O3 can be used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagrammatic sectional view showing the structure of an example of a plasma processing apparatus according to the present invention. In this example, a parallel plate plasma etching apparatus that performs reactive ion etching (RIE) will be explained. The reaction vessel 1 has a gas inlet a and a gas outlet 1b, and a reaction gas containing oxygen is supplied into the reaction vessel 1 from the gas inlet. An RF electrode 2 and a counter electrode 3 are arranged in the reaction vessel 1, and a semiconductor substrate 4 to be subjected to plasma processing is arranged on the RF electrode 2. The RF electrode 2 and the counter electrode 3 are connected to a high frequency high voltage power source 5. Then, a high frequency and high voltage is applied between the electrodes 2 and 3, and a reactive gas is supplied to generate discharge and generate plasma. In this example, the reaction vessel 1 is made of aluminum, and an aluminum oxide film 6 is formed on the inner wall surface of the reaction vessel 1 by anodizing. Further, the discharge electrodes 2 and 3 are also made of aluminum, and aluminum oxide films 7 and 8 are formed on the mutually opposing surfaces of these electrodes, respectively. Therefore, most of the reaction vessel and discharge electrode exposed to plasma are coated with an aluminum oxide film that is inert to plasma.

FIG. 2 shows a modification of the plasma processing apparatus according to the present invention. In this example, the flow rate adjustment system 10 adjusts the supply amounts of oxygen gas, reaction gas, and He dilution gas, and supplies the reaction gas containing oxygen into the reaction vessel 11. Then, a large number of holes are formed in the counter electrode 12, and a semiconductor substrate 14 to be subjected to plasma treatment is placed on the RF electrode 13. In this example as well, aluminum oxide films 15 and 16 are formed on the inner wall surface of the reaction vessel and the opposing surfaces of the electrodes, respectively. Further, a vacuum pump 17 is connected to the discharge hole of the reaction vessel to appropriately adjust the pressure inside the reaction vessel.

Next, experimental results will be explained. In this experiment, the RIE apparatus shown in FIG. 2 was used. Gas inlet 1
A fluorocarbon gas containing oxygen is introduced from a. The total flow rate was 100 sccm, and the ratio of oxygen to fluorocarbon gas was 3:10. Further, the gas pressure was set to 1.75 Torr. The output power of the high voltage power supply 5 was 630W. When the semiconductor substrate was subjected to resist etching back treatment under these conditions, no columnar protrusions were generated on the surface of the semiconductor substrate, and an extremely flat etched surface could be formed. Furthermore, even when a polytetrafluoroethylene film with a thickness of 500 μm is formed on the opposing surfaces of electrodes 2 and 3, no columnar protrusions are formed at all, resulting in extremely good etching, as in the case of the anodic oxidation treatment described above. I was able to form a surface. on the other hand,
When the inner wall surface of the reaction vessel and the electrode surface were not inactivated, countless columnar protrusions of polymerized fluorocarbon were formed as described above.

Next, a plasma processing method according to the present invention will be explained. When a fluorocarbon is supplied as a reaction gas to a reaction vessel to generate plasma, the fluorocarbon undergoes plasma polymerization and becomes a polymer. This polymerized fluorocarbon is deposited as a polymer film on the electrode surface and the inner wall surface of the reaction vessel. On the other hand, as described above, when polymerized fluorocarbon is deposited on the electrode surface and the reaction vessel surface, the fluorocarbon film becomes a barrier layer and prevents the electrode and the reaction vessel wall from being sputtered by plasma. Although this fluorocarbon film acts as a barrier layer against plasma, it vaporizes at an extremely slow rate when plasma acts on it. However, even if it evaporates, it will not have any adverse effects on the sample during plasma processing because the material is the same as the reactive material (etching agent or deposited material) that acts on the sample being plasma processed. . Therefore, in the present invention, prior to the plasma treatment on the sample, a reaction gas having almost the same composition as the reaction gas acting on the sample is supplied to the reaction vessel,
This reaction gas is polymerized by plasma polymerization to form a polymer film on the inner wall surface of the reaction vessel or the electrode surface. After forming this polymer film, the sample is subjected to plasma treatment using the same reaction gas. If the polymer film is formed in this way, the polymer film becomes a barrier layer against plasma, and there is no need to previously provide a barrier film on the electrode surface or the reaction vessel surface.

The present invention is not limited to the above-described embodiments, but can be modified in various ways. For example, although the above-described embodiments have been described using plasma etching as an example, the present invention can also be applied to various other plasma treatments such as plasma CVD.

As explained above, according to the present invention, a barrier layer against plasma is formed on the discharge electrode and the inner wall surface of the reaction vessel, which are the sources of contaminants, so generation of contaminants can be prevented. , good plasma processing can be performed. In particular, since local plasma polymerization can be prevented, an extremely flat etched surface can be formed.

[Brief explanation of the drawing]

FIG. 1 is a diagrammatic cross-sectional view showing the configuration of an example of a plasma processing apparatus according to the present invention;

FIG. 2 is a diagrammatic cross-sectional view showing the configuration of a plasma etching apparatus according to the present invention.

[Explanation of symbols]

1 Reaction container 2 RF electrode 3 Counter electrode 4 Sample 5 High frequency high voltage power supply 6, 7, 8 Aluminum oxide film.

Claims (2)

[Claims] Claim 1: A method comprising a reaction vessel and a discharge electrode disposed within the reaction vessel, supplying a reaction gas to the reaction vessel to generate plasma, and irradiating a sample to be treated with the generated plasma to perform plasma treatment. In the plasma processing equipment that performs
A plasma processing apparatus characterized in that at least a portion of the inner wall surface of the reaction vessel and the surface of the discharge electrode are subjected to plasma inactivation treatment. 2. A method comprising a reaction vessel and a discharge electrode disposed within the reaction vessel, supplying a reaction gas to the reaction vessel to generate plasma, and irradiating the generated plasma onto a sample to be treated to perform plasma treatment. In this process, before irradiating the sample with plasma, a reaction gas is supplied to a reaction vessel, and the reaction gas is plasma-polymerized to form a polymer, thereby forming a polymer film on at least a portion of the inner wall surface of the reaction vessel and the surface of the discharge electrode. 1. A plasma processing method characterized in that the sample is plasma-treated using the reaction gas.