JP2004335523A - Method for etching and rie system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for etching that is improved in selectivity and productivity, and to provide an RIE system. <P>SOLUTION: The method for etching includes a step of placing a substrate 2 to be treated in a chamber 1, a step of introducing a gas containing a fluorocarbon gas into the chamber 1, and a sep of generating plasma 9 in the chamber 1 by simultaneously or alternately impressing a first high frequency and a second high frequency higher than the first high frequency. The method also includes a step of etching the substrate 2 with the plasma 9. The C/F ratio of the fluorocarbon gas is adjusted to ≥0.65. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an etching method and an apparatus used in a semiconductor manufacturing process and the like.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a semiconductor etching process, an RIE (Reactive Ion Etching) apparatus that performs processing using plasma has been widely used. FIG. 3 shows a capacitively coupled RIE apparatus. This is done by placing a wafer 12 in a vacuum chamber 11, introducing an etching gas, and applying a high frequency (generally, 13.56 MHz RF) input from an RF power supply 15 from a lower electrode 14 to generate a plasma 19. Is generated and the wafer is etched.
[0003]
In such an RIE apparatus, the SiO ₂ film formed on the wafer is generally etched using a fluorocarbon-based gas such as CF ₄ . Usually, the selectivity with respect to the resist as a mask material (SiO ₂ film etching rate / resist etching rate) is 3 to 4. When the SiO ₂ film to be etched becomes thicker, the resist is also formed to a certain thickness. Need to be kept.
[0004]
[Problems to be solved by the invention]
With the miniaturization of semiconductor elements, it has become difficult to form a resist thicker in accordance with the SiO ₂ film thickness due to the problem of resolution in the exposure step, and an improvement in the selectivity with respect to the resist has been strongly demanded. Then, when the etching gas was optimized, it was found that the selection ratio depends on the C / F ratio of the etching gas, and when the ratio is 0.65 or more, the selection ratio with the resist is improved to 7 to 10. However, on the other hand, there was a problem that the etching rate was lowered, and the productivity was greatly reduced.
[0005]
Accordingly, an object of the present invention is to eliminate the drawbacks of the conventional etching method and apparatus, and to provide an etching method and an RIE apparatus having high selectivity and productivity.
[0006]
[Means for Solving the Problems]
The etching method of the present invention includes a step of placing a substrate to be processed in a chamber, a step of introducing a gas containing a fluorocarbon gas into the chamber, and a step of: The method comprises the steps of simultaneously or alternately applying a high frequency of a second high frequency to generate plasma, and etching the substrate to be processed with the plasma, wherein the C / F ratio of the fluorocarbon gas is 0. The number is 65 or more.
[0007]
Further, the etching method of the present invention is further characterized in that a magnetic field of 30 to 60 Gauss is applied in the chamber.
[0008]
Further, the etching method of the present invention is characterized in that a magnetic field is further applied to the inside of the chamber, and the high frequency of the second frequency is applied while being changed to a lower frequency.
[0009]
Further, the RIE apparatus of the present invention includes a chamber, a unit for introducing a gas containing carbon and fluorine into the chamber, and a high frequency of a first frequency and a high frequency of a second frequency in a chamber. It is characterized by comprising a lower electrode to be applied simultaneously or alternately, and a stage mounted on the lower electrode for mounting a substrate.
[0010]
Further, the RIE apparatus of the present invention is characterized in that it is a capacitively coupled RIE apparatus.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 shows a capacitively coupled magnetron RIE apparatus used in the present embodiment. In a vacuum chamber 1 for generating plasma, a stage 3 made of an insulator and on which a wafer (substrate to be processed) 2 is mounted, and a lower electrode 4 is provided below the stage 3. The RF power supply (L) 5 and the RF power supply (H) 6 for applying high frequencies (hereinafter referred to as RF) of several MHz and several tens MHz, respectively, and matching for matching the impedance on the RF power side and the chamber side. Box 7 is connected to lower electrode 4. Further, a magnetron 8 for applying a magnetic field is provided above the chamber 1.
[0013]
Such an RIE apparatus is used as follows. First, a wafer 2 having a resist mask formed on an SiO ₂ film is placed on a stage 3 in a chamber 1, and after decompression, a mixed gas containing a C ₄ F ₆ gas (C / F ratio of 0.65 or more) is supplied. Introduce. On the other hand, the RF (L) input from both the RF power source (L) 5 and the RF power source (H) 6 and the RF (H) having a higher frequency than the RF (L) are impedance-matched by the matching box 7 and the lower electrode 4 To generate a plasma 9. At this time, a predetermined magnetic field is applied by the magnetron 8 as needed. Then, the wafer 2 placed on the stage 3 reacts with ions and radicals in the plasma to progress the etching.
[0014]
It is considered that the etching of the SiO ₂ film proceeds when the generated ions collide with C _x F _y radicals in the plasma attached to the surface. On the other hand, it is considered that the etching of the resist proceeds by ions and F radicals in the plasma, and further, sputtering occurs simultaneously by ion collision. Therefore, when a large amount of ions and F radicals are generated, the selectivity of the SiO ₂ film to the resist becomes low.
[0015]
Therefore, by increasing the C / F ratio in the fluorocarbon gas to increase the C _x F _y radical density and depositing C _x F _y on the resist surface at a high rate, the resist selectivity with respect to the resist is improved. Can be. However, at the same time since in excess over the SiO ₂ film _C x _{F y} are attached, situation etching of SiO ₂ film is not proceed (etch stop) occurs.
[0016]
Therefore, to further advance the etching of the SiO ₂ film, and a higher energy (hereinafter ion energy) attracting ions to the wafer, it is necessary to collide with the SiO ₂ film C _x F _y radicals attached. For example, when etching high aspect ratio holes, C _x F _y adhered at the bottom than on the surface is low. Therefore, when high-energy ions are bombarded, the progress of etching is suppressed on the surface (resist) having a large amount of C _x F _y radical attached compared with the bottom portion (SiO ₂ film) having a small amount of attached C _x F _y radicals. In addition, the etching selectivity can be improved.
[0017]
As described above, in order to improve the etching selectivity and the etching rate, it is necessary to suppress the ion and F radical densities, increase the C _x F _y radical density, and increase the ion energy.
[0018]
The ion density and radical density of the plasma generated by the RF increase in proportion to the increase in the power of the applied RF. Also, the ion energy similarly increases. Therefore, as described above, in order to suppress the ion and F radical densities and increase the ion energy, it is necessary to control each of them independently. However, the ion density and the radical density can be reduced by RF (H). L) makes it possible to control the ion energy.
[0019]
As a result, the selectivity with respect to the resist becomes 8 or more, and the etching rate of the SiO ₂ film can be 450 nm / min or more.
[0020]
Note that, in addition to the capacitively coupled RIE device used in the present embodiment, an ECR (Electron Cyclotron resonance) plasma device, an ICP (Inductively Coupled Plasma) device, An SWP (Surface Wave Plasma) device or the like can be used, but the ion density and the radical density are higher than those of a capacitively coupled RIE device.
[0021]
In the present embodiment, RF (H) and RF (L) are applied from the lower electrode 4 of the stage 3, but one or more RFs may be applied from the upper electrode provided above the chamber. Although RF (H) is set to several tens of MHz and RF (L) is set to several MHz, the frequencies may be different, for example, H and L may be set at 13.56 MHz.
[0022]
Also, by suppressing the RF (H) power, the density of ions and F radicals can be suppressed, and the selectivity to resist can be improved. On the other hand, the density of C _x F _y radicals is also suppressed, so that the SiO ₂ film has a low density. The etching rate decreases. On the other hand, as shown in FIG. 2, by applying a magnetic field, the etching rate increases, and the selectivity to resist decreases. Therefore, by applying a magnetic field of 30 to 60 Gauss, the etching rate can be improved while maintaining a certain selectivity. At the same time, the selection ratio can be improved by shifting the RF (H) frequency to a lower frequency side while maintaining plasma discharge. In this case, since the etching rate decreases, it is effective to further increase the etching rate by setting the applied magnetic field to about 100 gauss or more.
[0023]
In this embodiment, the C ₄ F ₆ gas is used as the fluorine gas having a C / F ratio of 0.65 or more. However, the present invention is not particularly limited thereto. In addition, various fluorine gas such as C ₅ F ₈ may be used. Gas can be used.
[0024]
【The invention's effect】
According to the present invention, it is possible to provide an etching method and an RIE apparatus having high selectivity and high productivity.
[Brief description of the drawings]
FIG. 1 is a diagram showing an RIE apparatus of the present invention.
FIG. 2 is a diagram showing characteristics when a magnetic field is applied in the present invention.
FIG. 3 is a diagram showing a conventional RIE apparatus.
[Explanation of symbols]
1, 11 chamber 2, 12 wafer (substrate to be processed)
3, 13 Stage 4, 14 Lower electrode 5 RF power supply (L)
6 RF power supply (H)
7, 17 Matching box 8 Magnetron 9, 19 Plasma 15 RF power supply (13.56 MHz)

Claims (5)

Placing the substrate to be processed in the chamber;
A step of introducing a gas containing a fluorocarbon gas into the chamber;
A step of simultaneously or alternately applying a high frequency of a first frequency and a high frequency of a second frequency higher in the chamber to generate plasma,
A step of etching the substrate to be processed by the plasma,
An etching method, wherein the C / F ratio of the fluorocarbon gas is 0.65 or more. The etching method according to claim 1, wherein a magnetic field of 30 to 60 Gauss is applied to the chamber. 3. The etching method according to claim 1, wherein a magnetic field is applied to the inside of the chamber and the high frequency of the second frequency is changed to a low frequency. A chamber;
Means for introducing a gas containing carbon and fluorine into the chamber,
A lower electrode for simultaneously or alternately applying a high frequency of a first frequency and a higher frequency of a second frequency in the chamber;
An RIE apparatus comprising a stage placed on the lower electrode and on which a substrate is placed. 5. The RIE device according to claim 4, wherein the RIE device is a capacitively coupled RIE device.

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