JPH0770514B2 - Dry etching method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dry etching method using plasma.

Conventional technology Conventional silicon oxide film (SiO ₂ film) and phosphorus silica glass film (PSG film) have been etched by parallel plate type dry etching equipment using gases such as CF ₄ , C ₂ F ₆ , CHF ₃ and so on. It was

Problems to be Solved by the Invention However, there is a problem that a polymer is generated on the electrode surface and the inner wall of the reaction chamber during etching, and the etching rate is gradually decreased, and the generated polymer falls on the sample surface and causes contamination. There was a problem of becoming. Further, there is a problem that it takes a lot of time for cleaning to remove the generated polymer, productivity is lowered, and a large amount of dust is present for a while after cleaning.

The present invention has been made in view of the above problems, to prevent a decrease in etching rate by significantly reducing the generation of polymer,
A dry etching method that reduces the frequency of cleaning is provided.

Means for Solving the Problems In order to solve the above-mentioned problems, the dry etching method of the present invention places a sample on one of parallel plate electrodes, and a sample outer peripheral part on the electrode or an outer peripheral part and a reaction chamber inner wall are made of alumina. The sample is coated with a material, and plasma is generated between both electrodes while flowing an etching gas to dry-etch the sample.

Effect The present inventors have found that during the dry etching of a SiO ₂ film or a PSG film with a fluorocarbon gas or a gas containing hydrogen in the molecule, almost no polymer is formed on the alumina material. It was a hit. That is, according to the present invention, by coating the electrodes on the outer peripheral portion of the sample with the alumina material, it is possible to prevent the generation of polymer on the outer peripheral portion of the sample. Furthermore, by coating the inner wall of the reaction chamber with an alumina material, it is possible to prevent the generation of polymer on the inner wall of the reaction chamber.

Example An example of the present invention will be described below.

FIG. 1 shows a dry etching apparatus used in the first embodiment of the present invention. It comprises a reaction chamber 1, an upper electrode 2, a lower electrode 3, a gas inlet 4, a high-frequency power source 5 at 1356 MHz, and a vacuum outlet 6. On the lower electrode 3 On the Si substrate
A silicon substrate 7 having a PSG film formed thereon with a thickness of 7,000 Å was placed, and an alumina ring (thickness: 3 mm) was placed on the outer periphery thereof. Both upper and lower electrodes are made of hard alumite treated aluminum, and the upper electrode is provided with a large number of pores having a diameter of 0.3 mm for gas introduction. First, the reaction chamber was evacuated to 1 × 10 ^-3 Torr, and then C ₂ F ₆ gas was supplied from the gas inlet 4 to ₂₀ SCCM and CHF ₃
The gas was flowed at 30 SCCM and the pressure was maintained at 0.5 Torr. High-frequency power of 500 W was applied to generate plasma, and the PSG film was etched for 2 minutes. FIG. 2 shows the change in etching rate when 100 substrates in total were etched. Curve a
Is the result when the alumina ring of the present invention is provided,
Little decrease in etching rate. Almost no polymer was formed on the surface of the alumina ring on the lower electrode inside the reaction chamber. For comparison, the result of dry etching of the PSG film under the same conditions as in the above example without using an alumina ring is shown by the curve b in FIG. The etching rate was greatly reduced, and the polymer was formed in a thickness of 10 μm or more on the outer peripheral portion of the silicon substrate on the lower electrode. When the alumina ring was placed, the selection ratio to the base (Poly Si film) was 8/1, and the variation in the etching rate was within ± 5%, which was the same value as when the alumina ring was not used.

As described above, according to the present embodiment, by providing the alumina ring on the outer peripheral portion of the silicon substrate on the electrode, it is possible to suppress the generation of polymer on the electrode and prevent the etching rate from decreasing. The frequency of cleaning can be reduced.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic diagram of a dry etching apparatus showing a second embodiment of the present invention.

In the figure, the difference from FIG. 1 is that the alumina material 9 is provided on the inner wall of the reaction chamber 1. Using the above dry etching apparatus, the PSG film was dry-etched under the same conditions as in the example. Although the etching rate was slightly reduced (3,500Å / min) as compared with Example 1, the etching rate was hardly reduced even if the number of substrates to be etched was increased.
Compared to Example 1, less polymer was formed on the inner wall of the reaction chamber.

As described above, by coating the inner wall of the reaction chamber with the alumina material, it is possible to prevent the generation of the polymer on the inner wall of the reaction chamber, thereby reducing the frequency of cleaning.

In Examples 1 and 2, C ₂ F ₆ and CHF _{3 were used} as etching gases.
However, the same effect was confirmed when a mixed gas of C ₃ F ₈ and CHF ₃ , C ₂ F ₆ and C ₂ H ₄ F ₂ was used.

Further, when the SiO ₂ film was etched similarly to the PSG film, the same effect as in Examples 1 and 2 was obtained.

Furthermore, the same effect as in Examples 1 and 2 was obtained when the dry etching apparatus had an intermediate electrode between the upper and lower electrodes.

As described above, the present invention suppresses the generation of polymer by coating the outer peripheral portion of the sample on the electrode or the outer peripheral portion of the sample and the inner wall of the reaction chamber with the alumina material, whereby the etching rate with time is changed. It is possible to prevent deterioration and perform etching with good reproducibility. Further, since the amount of produced polymer is small, the frequency of cleaning can be reduced, productivity can be improved, and the amount of dust can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a dry etching apparatus in the first embodiment of the present invention, FIG. 2 is an etching characteristic diagram of the same embodiment, and FIG. 3 is a schematic of a dry etching apparatus in the second embodiment of the present invention. It is a figure. 4 ... Gas inlet, 6 ... Exhaust port, 9 ... Alumina material.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-59-178731 (JP, A) Actual opening 55-11818 (JP, U) Actual opening Sho-56-99848 (JP, U) Special table Sho-57- 500399 (JP, A)

Claims (1)

[Claims] 1. In a dry etching method using a parallel plate electrode, an alumina ring is installed on the outer peripheral portion of the sample on the electrode, the inner wall of the reaction chamber is covered with an alumina material, and plasma is generated between the electrodes to form the sample. Dry etching method for etching.