JPS62154736A - Dry etching - Google Patents

Abstract

PURPOSE:To efficiently remove poisonous substances remaining in a reaction container after a dry etching is performed and to improve an etching accuracy by a method wherein, after the dry etching is performed on substrates, oxygen gas flows into the reaction container and ozone and a nascent oxygen which are generated by ultraviolet ray irradiation are used. CONSTITUTION:A dry etching device 1 has a high-purity quartz window 6 and a low- pressure mercury-arc lamp 5 for ultraviolet ray emission,an anode 7 is designed in a movable type and can be bilaterally shifted, and a susceptor 10 can be directly irradiated with ultraviolet light. After an etching is performed, O2 gas flows into a reaction container 2 until the gas pressure in the interior reaches a normal pressure. Thereafter, irradiation of ultraviolet light of about 10% of light of 2,537Angstrom wavelength from the low-pressure mercury-arc lamp 5 takes place in the reaction container 2 through the high-purity quartz window 6. As the result, ozone (O3) and nascent oxygen (O*) having strong oxidative effect are produced. Residues are subjected to oxidative destruction by the strong oxidative effect of the O* and O3, and CO2 and Cl2 are produced and exhausted through 9. Moreover, photo resists are also decomposed and removed by the O* and O3. Thus, the interior of the reaction container is cleaned by a 'UV-ozone treatment'.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a dry etching method. This invention relates to a dry etching method that is less toxic to humans.

[Background of the invention]

Dry etching is widely used for processing LSIs, thin film devices, and metal films. Carbon and sulfur are used as reaction gases for dry etching because the reaction products have high vapor pressure and are easily dispersed.

Nitrogen compounds such as nitrogen and boron are often used. However, after etching, reaction intermediate products may remain in the reaction vessel and adhere to them, which reduces the accuracy and reproducibility of the next etching and is harmful to the safety and health of workers. . Conventionally, as a countermeasure against this, after etching, oxygen gas is introduced into the reaction vessel and high frequency is applied.
"Oxygen plasma treatment method" is known. However, this method is insufficiently effective and cannot remove all harmful substances.

In addition, for example, solid state technology (5solid
5tate Technology) /Japanese version/Q
This method is described in Ctober, 1983.

[Purpose of the invention]

It is an object of the present invention to provide a method for efficiently removing harmful substances remaining in a reaction vessel after dry etching and improving etching accuracy, and a dry etching method that completely blinds the mechanism.

[Summary of the invention]

A feature of the present invention is that after dry etching, rUV-ozone treatment is performed as a means to remove harmful substances remaining in the reaction vessel. rUV-ozone treatment oxidizes harmful substances in reaction intermediate products using the strong oxidizing effect of ozone and nascent oxygen generated by flowing oxygen gas into a reaction vessel and irradiating it with ultraviolet light. This is a method of decomposition.

[Embodiments of the invention]

Examples implemented using the method of the present invention will be described below.

Example 1. An example of etching an At film for wiring in an LSI process will be explained. In FIG. 2(a), 21 is a silicon semiconductor substrate in which circuit elements such as diodes and transistors are built, 22 is a 5fOz film, and 23 is a Si
An At film is formed on the O* film 22 by sputtering, and 24 is a photoresist mask for processing the At film 23 into a predetermined pattern. As an anisotropic etching method for the At film 23, a parallel plate dry etching apparatus 1 shown in FIG. 1 was used. A sample 20 shown in FIG. 2(a) was placed in a water-cooled cathode/susceptor 10, the inside of the reaction vessel 2 was evacuated by the vacuum pump 3, and liquid nitrogen was introduced into the trap 4. CCl2. as a reaction gas. .

Flow rate L Qcc/min, He, flow rate 5cc/m
A mixed gas of fn was flowed into the reaction vessel 2. The pressure inside the reaction vessel 2 was kept constant at 5 Pa by the vacuum pump 3, and the frequency was 13.56 MHz by the high frequency power source 11.

Applying an output of 100 Wffi, the At film 23 was etched using the entire resist 24 as a mask by reactive ion etching (CRIE method). As a result, Figure 2)
The cross-sectional shape shown in is obtained. However, CCl2 in the reaction gas
In the etching process using ClC14, C*Ct
An organic substance represented by CxC1y such as a is produced as a reaction intermediate product and remains in the reaction vessel 2. These remaining reaction intermediate products impair etching accuracy and reproducibility, and in order to prevent these, it is necessary to frequently clean the apparatus. In addition, the remaining organic substances emit a foul odor and may be toxic or carcinogenic to the human body, so special care must be taken when cleaning. Next, as a method for removing these remaining reaction products, r
UV-ozone treatment" was carried out.

The dry etching apparatus 1 has a high-purity quartz window 6 and a low-pressure mercury lamp 5 for emitting ultraviolet light, and the anode 7 is movable and can be moved left and right, so that ultraviolet light can be directly irradiated onto the susceptor 10. After etching, there is 0 in the reaction vessel 2! After the gas has flowed in from 8 to normal pressure, the low pressure mercury lamp 5 has a wavelength of 2.
Ultraviolet light of about 10 parts of 537^ light is irradiated into the reaction vessel 2 through the entire high purity quartz window 6. As a result, according to the following formula, 0, 1849AO+0 11111−÷0+0! →Os O, shukomi O scream 0゜Ozone (0,) with strong oxidizing power and nascent oxygen (0'') are generated.Oxidized residues are oxidized and decomposed by the strong oxidizing action of O'' and O8. Cot and CL are generated and exhausted from 9. Furthermore, the photoresist 24 is also decomposed and removed by O" and 03.Thus, the inside of the reaction vessel is cleaned by the rUV-ozone treatment, which not only improves etching precision and reproducibility, but also simplifies the process of completely removing the photoresist 24. During cleaning, the human body is no longer exposed to harmful substances, improving safety.

EXAMPLE An example of plasma etching of 5iotv used as an insulating film and a passivation film in the ZLSI process will be described. In Figure 3(a), 31 is 3i
The substrate 32 is formed by thermal oxidation on the Si substrate 31.
:Ot film; 33 indicates a photoresist mask for processing the SiO□ film into a predetermined pattern.

The entire dry etching apparatus 1 shown in FIG. 1 was used for isotropic etching of the 5-hot film. 7. in the reaction vessel 2;
The polarity of both electrodes 10 was changed, and 7 was used as a cathode and 10 was used as an anode. A sample 30 shown in FIG. 3(a)K was placed in a water-cooled anode/susceptor 10, and the inside of the υ reaction vessel 2 was evacuated by the vacuum pump 3, and liquid nitrogen *' was introduced into the trap 4. CHF5 as reaction gas.

Flow jt20 cc/min XHe + (kg L
A mixed gas of Occ/min is introduced into the reaction vessel 2, and the pressure inside the reaction vessel 2 is reduced to Th200 by the vacuum pump 3.
With the Pa constant, the frequency of the high frequency power source 11 is 13.6.
Applying a 6MH2° output of 100 W', 5 lots were etched using the resist 33 as a mask by plasma etching.
The membrane 32 was etched. As a result, the cross-sectional shape shown in FIG. 3(b) is obtained. After this, in order to remove the reaction products remaining in the reaction vessel 2, the rU
As a result of carrying out "V-ozone treatment", the inside of the reaction vessel 2 is cleaned, and the etching accuracy and reproducibility are excellent, and the photoresist 33 is not exposed to substances harmful to the human body, resulting in safety. improved.

Example 3. In the sample 30 shown in FIG.
An example of reactive ion beam etching of the 5ift film 32 using No. 3 as a mask will be described. A dry etching apparatus 40 shown in FIG. 4 was used for the reactive ion beam etching method. Dry etching equipment [i40 is equipped with an electron cyclotron resonance (ECR) ion source on the reaction vessel 2 that can generate plasma without electrodes and at low gas pressure, and on the top of the reaction vessel 2, there is a high-purity quartz window 6 and a window for ultraviolet light emission. It has a low pressure mercury lamp 5. All of the samples 30 were placed on a grounded water-cooled susceptor 10, the inside of the reaction vessel 2 was evacuated by the vacuum pump 3, and liquid nitrogen was introduced into the trap 4. C6F6. as a reaction gas. A flow of 50 cc/min 8 was introduced into the ionization chamber 12, and the pressure inside the ionization chamber 12 was kept constant at 1X10-''pa by the vacuum pump 3. At this time, the pressure inside the reaction vessel 2 was 5X10 -8 Pa.Next, the frequency 2..450H2 supplied from the magnetron 13
After generating an electron cyclotron resonance plasma in the ionization chamber 12 under the coexistence of the microwave and the magnetic field from the magnet coil 14, a voltage of 500 V is applied to the extraction electrode 15 to extract the ion beam and apply it to the surface of the sample 30. Reactive ion beam etching method (RIBE method)
Good luck, SjO using resist 33 as a mask! A total of 32 membranes were coated. As a result, the cross-sectional shape shown in FIG. 3(C) was obtained.After this, in order to remove the reaction products remaining in the reaction vessel 2, the rUV-ozone treatment described in Example 1 was carried out. As a result, the inside of the reaction vessel 2 was cleaned, and the etching accuracy and reproducibility were excellent, and the photoresist 33 was removed, so that the human body was not exposed to substances harmful to the body, and safety was improved.

Example t An example of optically excited etching of Si using the dry etching apparatus 1 shown in FIG. 1 will be described.

In FIG. 5, reference numeral 51 indicates a 3i substrate, and reference numeral 52 indicates an SiO□ film mask for processing the Si substrate 51 into a predetermined pattern. S
As a photoetching method for the i-substrate 51, FIG. 4(a) K
The sample 50 shown was placed on a susceptor 10 that was grounded and heated to 150° C., the inside of the reaction vessel 2 was evacuated by the vacuum pump 3, and liquid nitrogen was introduced into the trap 4. Anode 7
was moved so that ultraviolet light could be directly irradiated onto the susceptor 10. As a reaction gas, CIC2Fs, flow rate 5 Q c
c/rntn, O! *Flow 11i50 cc/
A mixed gas of 10 min and Hg vapor that acts as a sensitizer flow into the reaction vessel 2, and after the vacuum pump 3 maintains the pressure inside the reaction vessel 2 at a constant pressure of 370 pa, a low-pressure mercury lamp 5 Ultraviolet light having the wavelength and output described in Example 1 is irradiated into the reaction vessel 2 through the high-purity quartz window 6. As a result, etchants Ct'' and F'' are generated according to the following equation.

v Ct CtF s + Ot-→2COz+C6”+3
F"Bi and Ct" F% react to form volatile s 1c
tx.

5ipx and 9 yosu exhaust. As a result, Figure 4(b)
The cross-sectional shape shown in is obtained. After that, in order to remove the reaction products remaining in the reaction vessel 2, the rUV-ozone treatment described in Example 1 was performed for 5 seconds, and as a result, the inside of the reaction vessel 2 was cleaned, and the etching accuracy and p+ In addition to being highly effective, it also eliminates exposure to substances harmful to the human body, improving safety. .

As detailed above, the RUV Os Cleaning post-processing function is effective as a method for cleaning the inside of the reaction vessel after etching for any of reactive ion etching, plasma etching, reactive ion beam etching, and photoexcitation etching. It turned out to be.

〔Effect of the invention〕

According to the present invention, the inside of the reaction vessel after dry etching can be cleaned by "Uv-ozone treatment".

For this reason, 1) the lot-to-lot reproducibility of etching was improved from ±18 inch in the conventional example to well over ±4 inch; Furthermore, 2) toxic substances are decomposed and removed, odor is eliminated, and reaction products are below the detection limit, improving human safety. 3) By using "rUV-ozone treatment", the photoresist can be removed at the same time, which has the effect of simplifying the process.

[Brief explanation of drawings]

1 and 4 are schematic diagrams of a dry etching apparatus showing an embodiment using the dry etching method of the present invention, and FIG.
3 and 5 are schematic cross-sectional views of samples to be subjected to dry etching. 2... Reaction container, 5... Low pressure mercury lamp, 6...
High purity quartz window, 8... gas supply system, 9... gas exhaust system, 10... susceptor.

Claims (1)

[Claims] 1. Place the substrate in a reaction container, dry-etch the substrate by injecting and exciting a reaction gas, and then flow oxygen gas into the reaction container and irradiate it with ultraviolet rays to generate ozone and the generation period. A dry etching method characterized by strong oxidation cleaning using oxygen.