JPH02304923A - Dry cleaning method - Google Patents

Abstract

PURPOSE:To remove a bromine constituent remaining in a reaction chamber in a short time by introducing a gas for cleaning into the reaction chamber after dry etching is conducted, forming plasma and dissociating or etching- removing the residual bromine constituent adhering and depositing in the reaction chamber. CONSTITUTION:A gas for cleaning is introduced from a gas supply port 22, the inside of a reaction chamber 11 is decompressed, a high-frequency power supply 14 is connected to one of a pair of counter electrodes 17, 24 mounted into the reaction chamber 11, the other is connected to a ground 23, and glow discharge is generated between these electrodes 17, 24. The gas introduced into the reaction chamber 11 is changed into plasma, and a bromine constituent remaining in the reaction chamber 11 is removed by the plasma. Accordingly, the bromine constituent remaining in the etching reaction chamber 11 can be taken off safely in a short time.

Description

[Detailed Description of the Invention] [Summary] Regarding a dry cleaning method, particularly a dry cleaning method for an etching reaction chamber in which dry etching using a bromine gas is carried out, it is possible to remove bromine components remaining in the etching reaction chamber in a short time. The purpose of this method is to provide a dry etching method that can generate plasma by introducing a cleaning gas into the reaction chamber after performing dry etching using a bromine-based gas such as bromine (Brz) or hydrogen bromide (HBr). The present invention also includes a dry cleaning method characterized by dissociating or etching away residual bromine components attached or deposited in the reaction chamber.

(Industrial Application Field) The present invention relates to a dry cleaning method, and particularly to a dry cleaning method for removing bromine gas from an etching reaction chamber in which dry etching using bromine gas is performed.

[Prior art] In recent years, with the miniaturization of semiconductor devices, insulating oxide films (S
In etching the polycrystalline silicon deposited on this 5iOz film, an etching technique that can obtain a high selectivity to 5i02 is required. For this reason, a dry etching method using a bromine-based gas such as bromine (Brz) or water bromide (HBr) as an etching gas is effective, but bromine remains in the etching reaction chamber after the etching process, and the etching equipment becomes unstable. This residual bromine must be removed because it will corrode.

(Problem to be Solved by the Invention) Regarding the conventional removal of residual bromine, the etching apparatus is opened from vacuum to the atmosphere, the reaction chamber is removed, and hydrofluoric acid ()I is removed.
Chemical cleaning using chemicals such as F) was carried out regularly.

However, during the removal of residual bromine, the etching equipment must be shut down to clear the reaction chamber. That is, in order to perform cleaning, it takes time to perform operations such as releasing the vacuum to the atmosphere, cleaning with chemicals, drying, assembling the reaction chamber, and re-evacuating, which requires the etching apparatus to be stopped for a long time. Although this time depends on the frequency of regular cleaning of the device, it takes several minutes to remove the device, 30 to 60 minutes to clean the device, 10 to 30 minutes to dry, and 2 to 3 hours to vacuum.

Therefore, in the conventional cleaning method, the etching apparatus is stopped for a long time, resulting in a reduction in throughput and a problem in that mass production of products is not possible. If a replacement device is prepared, the above-mentioned time can be shortened, but the problem is what kind of gas remains in the device to be removed, and if there is a reaction with residue inside. Removing the chamber and cleaning it with chemicals poses risks to worker safety.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry cleaning method that can safely remove bromine remaining in an etching reaction chamber in a short time.

[Means for solving the problem] The above problem is solved by using bromine (Brz) or hydrogen bromide (01Br)
A cleaning gas is introduced into the reaction chamber after dry etching using a bromine-based gas such as bromine gas, and plasma is generated to dissociate or remove residual bromine that has adhered or accumulated in the reaction chamber. Achieved by a characteristic dry cleaning method.

[Effect]

In the present invention, in order to remove bromine components attached and deposited on the inner wall of the etching reaction chamber 11 of the tE apparatus shown in FIG.
A cleaning gas is introduced from the gas supply port 22 to reduce the pressure inside the reaction chamber 11, and the high frequency power source 14 is connected to one of a pair of opposing electrodes 17.24 provided in the reaction chamber 11, and the other is connected to the ground 23. By connecting these electrodes 17 and 24 to , a glow discharge is generated between the electrodes 17 and 24, the gas introduced into the reaction chamber 11 is turned into plasma, and the bromine component remaining in the reaction chamber 11 is removed by the plasma. That is,
Bromine is removed by causing a dissociation or substitution reaction and exhausting it outside the device, replacing corrosive Br2 with non-corrosive and harmless HBr ((Br2+l).
I□)→2! (Br) Either scatter HBr out of the device, or replace (replace) Br, which has become 5iBrx and adhered to the inner wall of the device as a result of silicon etching, with F, or replace 8r bonded with C or F. Cover all bonded C, F, etc. with a polymer film of F [
Both the above-mentioned substitution and covering with F are collectively called passivation. ] to remove Br.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to an illustrated embodiment.

Figure 1 shows the parallel plate electric rod type RIE used in the embodiment of the present invention.
FIG. 2 is a schematic diagram of the device.

In the figure, 11 is an etching reaction chamber, 12 is a cooling water circulation mechanism, 13 is a DC power supply, 14 is a high frequency power supply, 15 is a gas exhaust port for gas conduction cooling, 16 is a gas supply port for gas conduction cooling, and 17 is a target electrode. , 18 is an insulator, 19 is a dummy wafer, 20 is an electrostatic chuck, 21 is a gas exhaust port, 22 is a gas supply port, 23 is a ground, 24 is a counter electrode,
25 is a quartz plate. In order to see the cleaning effect of the present invention, first, a dummy wafer was etched for 30 minutes using Brz as an etching gas, then the gas was switched to a cleaning gas and dry cleaning was performed for 10 minutes, and then etching was performed. The quartz plate 25 in the reaction chamber 1I was removed, and residual bromine remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis.

Here, the conditions for etching are as in the case of etching polycrystalline silicon, the gas flow rate of Br2 is 101
005e, and the pressure inside the etching reaction chamber 11 is Q, 1.
Torr, and apply power with a frequency of 13.56Ml1z to the substrate light for 300 seconds, and reduce the temperature of the cooling water to 35".
I went as C. Note that the electrostatic chuck 20 holds a dummy wafer 19.

Further, the conditions for cleaning were as follows: among the etching conditions described above, only the gas was switched to a cleaning gas and introduced at a constant flow rate, and the other conditions were left unchanged.

The measurement method of ion chromatography analysis used this time is
After etching and cleaning, the surface of the quartz plate 25 taken out is dipped in 25 cc of pure water, and this pure water is maintained on the quartz plate by surface tension for 1.30 minutes, and then immersed in this water.
After mixing r, collect the water, add pure water to make the total volume 50cc for easy analysis, and measure the number of Br contained in the solution using an ion chromato analyzer. did.

The results of implementing the present invention are shown below.

[Example 1] This example was conducted for the purpose of establishing standards for the experiments to be carried out below. After etching with Brz was performed under the etching conditions described above, the quartz plate 25 in the etching reaction chamber 11 was removed without cleaning, and the bromine content remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 16 μg, and this amount of BrO was used as a reference for the following experiment.

(Example 2) After performing etching with Brz under the etching conditions described above, sulfur hexafluoride (SF6) was added to the cleaning gas.
', the gas flow rate was set to loosccm, and dry cleaning was performed for 10 minutes under the cleaning conditions described above. Then, the quartz plate 2 in the etching reaction chamber 11
5 was removed, and the bromine content remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 5 μg. After this cleaning, the sample shown in FIG. 2 was etched with Br. Note that in the same figure, the sample is a silicon substrate 3.
A 1,000-layer SiO
A polycrystalline silicon layer 33 having a thickness of 4,000 wafers is formed by method D), and a mask pattern 34 is further formed thereon. As a result, the selectivity of the polycrystalline silicon layer 33 to the underlying 5i02 film 32 decreased from less than 100 to about 80. The reason for this decrease in selectivity is that it is a known fact that the selectivity in question increases in the order of fluorine (F), chlorine (CI), and bromine (Br). It is thought that the residual F causes a decrease in the selectivity. However, between cleaning with SF6 and etching with Brz, [lr,
The selectivity returned to its original value by removing F by performing cleaning for 10 minutes. In other words, cleaning
ng). ] There was no significant effect on subsequent etching.

[Example 3] After performing Brz etching under the etching conditions described above, nitrogen trifluoride (NF) was added to the cleaning gas.
Using a gas flow rate of 101005e, dry cleaning was performed for 10 minutes under the cleaning conditions described above. Then, the quartz plate 25 in the etching reaction chamber 11
was removed, and the amount of bromine remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 5 μg. B after cleaning
In RZ etching, SiO□ film 32 film pair 2
Regarding the selection ratio of the polycrystalline silicon layer 33, Example 2
The results were similar to those of .

[Example 4] After performing etching with Brz under the etching conditions described above, carbon tetrafluoride (CF4) was added to the cleaning gas.
Using a gas flow rate of 101005e, dry cleaning was performed for 10 minutes under the cleaning conditions described above. Then, the quartz plate 25 in the etching reaction chamber 11
was removed, and the amount of bromine remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 5 μg. After this cleaning, the sample shown in FIG. 2 was etched using Brz, and as a result, the selection ratio between the underlying SiO□ film 32 and the polycrystalline silicon layer 33 decreased from 100 to 20. C.F.
Although cleaning with Brz was performed for 10 minutes between the cleaning with No. 4 and the etching with Brz, the selectivity did not recover much and remained lower. The cause of this is thought to be the influence of carbon (C). The influence of this C is 0
Although it can be removed by treatment using □, using 02 is not preferable as shown in Example 6, indicating that cleaning using CF4 is extremely impractical.

[Example 5] After etching with Br2 under the etching conditions described above, using hydrogen (L) as a cleaning gas,
The gas flow rate was set to 50 seconds, and dry cleaning was performed for 10 minutes under the cleaning conditions described above. Then, remove the quartz plate 25 inside the etching reaction chamber 11,
The amount of bromine remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 3 μg or less (below the detection limit from an equipment standpoint). In this case, there was no change in the selectivity of the polycrystalline silicon layer 33 to the Sing film 32 before and after cleaning, which shows that this example is extremely good.

[Example 6] After etching with Brz was performed under the above etching conditions, dry cleaning was performed for 10 minutes using oxygen (02) as the cleaning gas and setting the gas flow rate to 101005e under the above cleaning conditions. .

Then, the quartz plate 25 in the etching reaction chamber 11 was removed, and the amount of bromine remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 3 μg. However, as a result of etching the sample shown in FIG. 2 using Br2 after this cleaning, there was a delay in the start of etching the polycrystalline silicon 33. This delay time varies and takes up to 5 minutes, resulting in a reduction in throughput. This is 0
This is because □ eats up the Br used in the next etching, and the remaining 02 oxidizes the surface of the polycrystalline silicon to be etched next.

[Example 7] After etching with Brz was performed under the above etching conditions, a mixed gas of SF6 and H2 was used as the cleaning gas, the total flow rate of the mixed gas was 101005c, and drying was performed for 10 minutes under the above cleaning conditions. I did some cleaning. Then, the quartz plate 25 in the etching reaction chamber 11 was removed, and the amount of bromine remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 3 μg. In etching with Br2 after this cleaning, SiO□
The selectivity ratio of 32 films to 2 polycrystalline silicon layers 33 was similar to the result of Example 2.

[Example 8] After etching with Br2 was performed under the above etching conditions, a mixed gas of Nh and H2 was used as the cleaning gas, the total flow rate of the mixed gas was 100 sec, and etching was performed for 10 minutes under the above cleaning conditions. I did some dry cleaning. Then, the quartz plate 25 in the etching reaction chamber 11 was removed, and the bromine content remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 3 μg. In the etching with Br2 after this cleaning, 5in2
The selection ratio of polycrystalline silicon layer 330 to film 32 was similar to the results of Example 2.

[Example 9] After performing etching with Br2 under the etching conditions described above, a mixed gas of 82 and N2 was used as the cleaning gas, and the total flow rate of the mixed gas was set to 101005e.
Dry cleaning was performed for 10 minutes under the cleaning conditions described above. Then, the quartz plate 25 in the etching reaction chamber 11 was removed, and the bromine content remaining on the surface of the quartz plate 25 was detected by ion chromatography analysis. The amount of residual bromine detected at this time was 3 μg or less (below the detection limit). At this time, before and after cleaning,
There was no change in the selectivity of the polycrystalline silicon layer 33 to the in2 film 32. From this result, by adding N2, N
Although it cannot be concluded that better results were obtained than with 2 alone, it was found that the addition of N2) did not produce worse results than with 1□ alone. Therefore,
As shown in this example, N2 can be diluted with N2, which has the effect of avoiding the danger of using explosive N2 alone.

[Example 10] After performing Brz etching under the etching conditions described above, an inert gas such as helium (He) or argon (Ar) was added to the cleaning gas used in Examples 1 to 9. , 10 under the cleaning conditions described above.
Did a minute of dry cleaning. Then, the quartz plate 25 in the etching reaction chamber 11 is removed, and the quartz plate 25 is removed.
The bromine content remaining on the surface of No. 5 was detected by ion chromatography analysis. The amount of residual bromine detected at this time showed the same tendency as the results of Examples 1 to 9, depending on the type of cleaning gas used. The addition of this inert gas provides the physical effect of sputtering, ie, cleaning in a shorter time.

[Example 11] The etching gas used in Examples 1 to 10 was
Similar Example 1 to Example 10 by replacing z with HBr
As a result of etching and cleaning, similar results were obtained in terms of residual bromine content and selectivity.

As described above, it was confirmed that bromine remaining in the etching reaction chamber can be removed by dry cleaning according to the present invention and can be carried out in a short time.

Conventionally, a method of cleaning a reaction chamber by physical sputtering using the CVD method is known, but the method of the present invention described above differs from the conventional example in that it utilizes a chemical reaction.

Although sputtering cleaning using an inert gas is used in Example 10, this is different from the conventional example in that sputtering cleaning is additionally performed after a chemical reaction is performed.

In addition, conventionally, in order to remove C and α, CF4 +02
, NF3 +0
+H2 is used, which is also different from the conventional example.

Furthermore, as shown in Example 6, it is not preferable to use 0□ in the method of the present invention, so the present invention excludes examples using 0□.

〔Effect of the invention〕

As explained above, according to the present invention, by dry cleaning by introducing a cleaning gas into the reaction chamber after performing dry etching using bromine-based gas, the bromine content remaining in the etching reaction chamber can be removed. Since the reaction chamber can be removed without disassembling the reaction chamber and cleaning with chemicals, this has the effect of reducing the number of steps involved in removing the inside of the reaction chamber and eliminating the dangers associated with cleaning with chemicals.

[Brief explanation of the drawing]

Figure 1 shows a parallel plate electric scraping type RIE used in an example of the present invention.
A schematic diagram of the apparatus. FIG. 2 is a cross-sectional view of a sample used in an example of the present invention. In the figure, 11 is an etching reaction chamber, 12 is a cooling water circulation mechanism, 13 is a DC power supply, 14 is a high frequency power supply, 15 is a gas exhaust port for gas conduction cooling, 16 is a gas supply port for gas conduction cooling, 17 is a target electrode, 18 is an insulator, 19 is a dummy wafer, 20 is an electrostatic chuck, 21 is a gas exhaust port, 22 is a gas supply port, 23 is ground, 24 is a counter electrode, 25 is a quartz plate, 31 is a silicon base + anti-oxidant, 32 is a 33 is a polycrystalline silicon layer, and 34 is a mask pattern. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney: Akito Kukimoto
I used the 1st book of the tane-ryakusen of Etsuoki for the assembly and preparation of the moon disaster (1j); Figure 2 of the specimen.

Claims (3)

[Claims] (1) After performing dry etching using a bromine-based gas such as bromine (Br_2) or hydrogen bromide (HBr), a cleaning gas is introduced into the reaction chamber to generate plasma, and the plasma is deposited inside the reaction chamber. A dry cleaning method characterized by dissociating or etching away accumulated residual bromine components. (2) The cleaning gas is sulfur hexafluoride (SF_
6) Single gas, nitrogen trifluoride (NF_3) single gas, hydrogen (H_2) single gas, sulfur hexafluoride (SF_6) and hydrogen (
A mixed gas of nitrogen trifluoride (NF_3) and hydrogen (H_2), nitrogen trifluoride (NF_3) and hydrogen (
H_2) mixed gas, hydrogen (H_2) and nitrogen (N_2)
2. The dry cleaning method according to claim 1, wherein the dry cleaning method is a mixed gas of: (3) The dry cleaning method according to claim 1 or 2, characterized in that an inert gas is mixed in the cleaning gas.