JP2005033016A - Method of dry-etching low-dielectric constant interlayer insulating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which the fall of a resist selection ratio can be prevented and, in addition, no damage is given to a low-dielectric constant interlayer insulating film covered with a resist mask and composed of an SiOCH- or SiOC-based material in dry-etching the interlayer insulating film. <P>SOLUTION: In the method, the low-dielectric constant interlayer insulating film is etched with an etching gas composed of a mixed gas prepared by adding a CxHx gas containing C atoms by a number of 1-4 or HFC gas containing C atoms by the number of 1-3 to a perfluorocarbon gas at a rate of 20-50% of the total flow rate of the etching gas by introducing the etching gas under a working pressure of ≤1 Pa. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for dry etching an interlayer insulating film, and more particularly to a method for dry etching a low dielectric constant interlayer insulating film containing carbon.

In general, when an interlayer insulating film made of SiO ₂ is dry-etched in a plasma atmosphere to finely process wiring holes and trenches, a mixed gas containing a CF-based gas is used (Patent Document 1). In this case, if etching is performed only with the CF-based gas, the gases generated by decomposition during the etching process are recombined to cause clustering in the gas phase, and CF-based film deposition occurs. For this reason, it is considered that argon is used as an etching gas, and a mixed gas obtained by adding a fluorocarbon gas to argon is used to prevent clustering (Non-patent Document 1).

  By the way, with the recent high integration and miniaturization of semiconductor devices, as an interlayer insulating film, for example, a SiOCH-based low dielectric constant interlayer insulating film (which is a porous material) having a relative dielectric constant (k) of 2.6 or less. May be developed). In this case, when the low dielectric constant interlayer insulating film covered with the resist mask is etched using the above-described mixed gas containing argon as the main gas without chemical reactivity, the constituent material of the SiOCH-based film contains carbon. Therefore, for example, H in the film disappears due to ion bombardment when the interlayer insulating film is etched, and a layer of —C—C— or Si—C— is formed at the bottom of the hole, causing an etching stop phenomenon. For this reason, a method of etching using a mixed gas to which a large amount of oxygen or fluorine is added or a method for promoting the generation of fluorine has been proposed.

JP-A-11-31678 (for example, description of claims). W. chen, M. Itoh, T. Hayashi and T. Uchid, J. Vac. Sci. Technol., A16 (1998) 1594

  However, the above-described method has a problem in that the resist mask is etched with oxygen or fluorine, so that the etching rate of the resist increases rapidly and the selectivity to resist decreases. In addition, the above-described method has a problem that, for example, CHx groups in the interlayer insulating film are extracted due to high reactivity of oxygen itself, and the interlayer insulating film (particularly, the sidewall of the hole) is damaged.

  Therefore, in view of the above points, the present invention can prevent a reduction in the selectivity to resist when dry etching a low dielectric constant interlayer insulating film covered with a resist mask, and damage the interlayer insulating film. It is an object of the present invention to provide a dry etching method of a low dielectric constant interlayer insulating film that does not give a low temperature.

  In order to solve the above-described problems, the low dielectric constant interlayer insulating film dry etching method of the present invention etches a low dielectric constant interlayer insulating film made of a SiOCH or SiOC-based material and finely processes wiring holes and trenches. In a dry etching method of a low dielectric constant interlayer insulating film, CxHy having 1 to 4 C atoms or HFC having 1 to 3 C atoms in a perfluorocarbon gas at a ratio of 20 to 50% with respect to the total flow rate Etching is performed by using a mixed gas to which a gas is added as an etching gas and introducing the etching gas under an operating pressure of 1 Pa or less.

  According to the present invention, for example, when etching a porous low dielectric constant interlayer insulating film containing carbon in the film, the number of C at a predetermined flow rate is 1 to 4 CxHy or the number of C is 1 to 3 Since the HFC gas is added, it is possible to prevent the resist etching rate from being greatly reduced and the selectivity to the resist from being lowered. In addition, for example, during fine processing of wiring holes by etching, the H—C—F film is deposited and protected on the sidewalls of the holes, thereby preventing the entry of reactive particles into the interlayer insulating film by etching. Thus, the interlayer insulating film is not damaged. In this case, if CxHy or HFC gas is added at a ratio of less than 20%, the resist high selectivity cannot be obtained, and if CxHy or HFC gas is added at a ratio exceeding 50%, etching stops. Further, when the number of C exceeds 4 in CxHy, the etching is stopped, and when the number of C exceeds 3 in HFC gas, the etching is stopped.

Note that at least one of CH ₃ CHF ₂ and CH ₂ F ₂ may be selected as the HFC gas.

As the CxHy gas, CH _{4 gas,} may be selected at least one of C 2 _{H 6} gas.

  Further, a rare gas may be added to the mixed gas.

The perfluorinated gas may be selected from C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , and C ₅ F ₈ .

  As a result, the method for etching a low dielectric constant interlayer insulating film of the present invention can prevent a reduction in the resist selectivity when etching a low dielectric constant interlayer insulating film covered with a resist mask, for example. The etching stop phenomenon does not occur and the interlayer insulating film is not damaged.

  Referring to FIG. 1, reference numeral 1 denotes an etching apparatus for performing fine etching of wiring holes and trenches by dry etching the low dielectric constant interlayer insulating film of the present invention. This etching apparatus 1 is capable of etching by low-temperature and high-density plasma, and has a vacuum chamber 11 provided with a vacuum exhaust means 11a such as a turbo molecular pump. A plasma generator 12 formed of a dielectric cylindrical wall is provided at the upper part, and a substrate electrode part 13 is provided at the lower part. Three magnetic field coils 15, 16, and 17 are provided outside the wall (dielectric side wall) 14 that partitions the plasma generation unit 12, and the magnetic field coils 15, 16, and 17 provide an annular magnetism in the plasma generation unit 12. A neutral line (not shown) is formed. A high frequency antenna coil 18 for plasma generation is disposed between the intermediate magnetic field coil 16 and the outside of the dielectric sidewall 14, and this high frequency antenna coil 18 is connected to a high frequency power source 19, and three magnetic field coils 15, 16, An alternating electric field is applied along the magnetic neutral line formed by 17 to generate a discharge plasma in the magnetic neutral line.

  A substrate electrode 20 on which the processing substrate S is placed is provided via an insulator 20a in the substrate electrode portion 13 so as to face the surface formed by the magnetic neutral line. The substrate electrode 20 is connected to a high-frequency power source 22 via a capacitor 21 and becomes a floating electrode in terms of potential and has a negative bias potential. The top plate 23 of the plasma generator 12 is hermetically fixed to the upper flange of the dielectric side wall 14 and is in a floating state in potential to form a counter electrode. A gas introduction nozzle 24 for introducing an etching gas into the vacuum chamber 11 is provided on the inner surface of the top plate 23, and this gas introduction nozzle 24 is connected to a gas source via a gas flow rate control means (not shown). Has been.

  As the low dielectric constant interlayer insulating film formed on the processing substrate S using the etching apparatus and finely processed for wiring holes and trenches, a SiOCH-based material formed by spin coating such as HSQ or MSQ is used. Alternatively, it is a low-k material having a relative dielectric constant of 2.0 to 3.0, which is a SiOC material formed by CVD, and includes a porous material. Examples of the SiOCH material include trade name LKD5109r5 / manufactured by JSR, trade name HSG-7000 / manufactured by Hitachi Chemical, trade name HOSP / Honeywell Electric Materials, trade name Nanoglass / Honeywell Electric Materials, trade name OCD T-12 / manufactured by Tokyo Ohkasha, trade name OCD T-32 / manufactured by Tokyo Ohkasha, trade name IPS2.4 / manufactured by Catalytic Kasei Kogyo, trade name IPS2.2 / manufactured by Catalytic Kasei Kogyo, trade name ALCAP-S5100 / Asahi Kasei Co., Ltd.

  Examples of the SiOC material include trade name Aurola 2.7 / manufactured by ASM Japan, trade name Aurola 2.4 / manufactured by Japan ASM, trade name Orion 2.7 / TRIKON, trade name Coral / Novellaf, trade name There are NCS / Catalyst Chemical Industries, trade name Black Diamond / AMAT. Also, trade name SiLK / Dow Chemical, trade name Porous-SiLK / Dow Chemical, trade name FLARE / Honeywell Electric Materials, trade name Porous FLARE / Honeywell Electric Materials, trade name Porous-FLARE / Honeywell An organic low dielectric constant interlayer insulating film such as that manufactured by Electric Materials and trade name GX-3P / Honeywell Electric Materials may also be used. A predetermined pattern is formed on the low dielectric constant interlayer insulating film by photolithography after applying a resist. A known resist is used as the resist.

As an etching gas used in the dry etching process, CxHy having 1 to 4 C or 1 to 3 C in a ratio of 20 to 50% with respect to the total flow rate in a fluorocarbon gas (CnFm). A mixed gas to which HFC gas is added is used. The perfluorinated gas is selected from C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , and C ₅ F ₈ . The CxHy having 1 to ₄ C is selected from CH ₄ and C ₂ H ₆ . In addition, as the HFC gas having 1 to 3 carbon atoms, CH ₃ CHF ₂ (HFC-152a), CH ₂ F ₂ (HFC-32), C ₂ HF ₅ (HFC-125), CH ₂ FCF ₃ ( HFC-134a) or CHF ₃ (HFC-23).

  If this mixed gas is introduced and etched under an operating pressure of 1 Pa or less, for example, when etching a porous low dielectric constant interlayer insulating film containing carbon in the film, the etching rate of the resist is greatly reduced. , It can be prevented that the selectivity to resist is lowered. In this case, FIG. 2 schematically shows a difference between the case where etching is performed using the mixed gas of the present invention and the case where etching is performed using a mixed gas to which a large amount of oxygen or fluorine is added. That is, in the mixed gas containing a large amount of oxygen or fluorine, as shown in (a), since the selectivity ratio to the resist is low, the recessing of the resist mask M causes the faceting that leads to a short circuit in the interlayer insulating film I. Although generated, in the mixed gas of the present invention, as shown in (b), faceting does not occur in the interlayer insulating film I because of a high resist selectivity ratio. Note that S shown in FIG. 2 is a substrate.

In addition, since the H—C—F film is deposited and protected on the sidewalls of the holes and trenches during the microfabrication of the wiring holes and trenches by etching, the reactive particles by etching are applied to the interlayer insulating film. Intrusion is prevented and the interlayer insulating film is not damaged. Note that either CH ₃ CHF ₂ or CH ₂ F ₂ is desirable as the HFC gas, and any of CH ₄ gas or C ₂ H ₆ gas is desirable as the CxHy gas. Further, a rare gas such as Ar, Kr, or Xe may be added to this mixed gas. In this case, the main component of the mixed gas may be (rare gas + CnFm + O ₂ + HFC) or (rare gas + CnFm + O ₂ + CxHy).

  In this example, an MSQ SiOCH material having a relative dielectric constant (k) of 2.5 was used, and a low dielectric constant interlayer insulating film having a thickness of 500 nm was formed on a substrate using a spin coater. Then, a resist was applied on the low dielectric constant interlayer insulating film by a spin coater, and a predetermined pattern was formed by photolithography. In this case, UV-II was used as the resist, and the thickness of the resist layer was 500 nm.

Next, using the etching apparatus 1 shown in FIG. 1, a mixed gas containing C ₃ F ₈ as a main gas and CH ₄ is added to the inside of the vacuum chamber 11 by changing the mixing ratio of CH ₄ with respect to the total flow rate. Then, the low dielectric constant interlayer insulating film was etched. The mixing ratio is a value when (C ₃ F ₈ + CH ₄ ) is 100%. In this case, the output of the high frequency power source 19 connected to the plasma generating high frequency antenna coil 18 is set to 2 KW, the output of the high frequency power source 22 connected to the substrate electrode 21 is set to 400 W, the substrate set temperature is 10 ° C., and the pressure of the vacuum chamber 11 is set to 1 Pa. did.

FIG. 2 shows lines a and b when the low dielectric constant interlayer insulating film and the resist mask are etched under the above conditions. According to this, when the addition rate of CH ₄ is in the range of 0 to about 50%, the etching rate of the low dielectric constant interlayer insulating film is hardly reduced, and only the etching rate of the resist is greatly reduced. Therefore, a high resist-to-resist selection ratio is obtained as shown by line c. From this, due to the weak film deposition effect that is characteristic of a low-pressure process of 1 Pa or less, even in the case of a low dielectric constant interlayer insulating film having a porous structure, etching stop reduction does not occur, and resist resist Only the selectivity is considered improved.

Using the etching apparatus 1 shown in FIG. 1, C ₃ F ₈ (25 sccm) + Ar (220 sccm) + O ₂ (20 sccm) + CH ₄ (30 sccm) is used as a mixed gas, and this mixed gas is introduced into the vacuum chamber 11. The substrate S was etched. In this case, the output of the high frequency power source 19 connected to the plasma generating high frequency antenna coil 18 is set to 2 KW, the output of the high frequency power source 22 connected to the substrate electrode 21 is set to 400 W, the substrate set temperature is 10 ° C., and the pressure of the vacuum chamber 11 is set to 1 Pa. did.

FIG. 4B is an SEM photograph when etching is performed under the above conditions. According to this, etching could be performed without causing an etching stop phenomenon and damaging the sidewall of the hole. FIG. 4A is an SEM photograph in the case of etching with CH ₄ added at a ratio of 80%. According to this, the etching stop phenomenon has occurred. FIG. 4C is an SEM photograph in the case of etching without adding CH ₄ . According to this, it can be confirmed that many resist layers remain.

  Using the etching apparatus 1 shown in FIG. 1, the X-ray exposed 50 nm hole pattern was etched under the same conditions as described above. FIG. 5 is an SEM photograph at that time. According to this, a 50 nm hole could be etched to a depth of 800 nm without causing an etching stop phenomenon.

The figure which shows roughly the etching apparatus which enforces the etching method of the low dielectric constant interlayer insulation film of this invention. (A) And (b) is a figure which shows typically the difference with the method of this invention, and the conventional method. The graph which shows the etching rate of a low dielectric constant interlayer insulation film and a resist mask. The SEM photograph at the time of etching by implementing the method of the present invention. The SEM photograph at the time of etching by implementing the method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Etching apparatus 11 Vacuum chamber 12 Plasma generation part 13 Substrate electrode part S Substrate

Claims (5)

In a dry etching method of a low dielectric constant interlayer insulating film in which a low dielectric constant interlayer insulating film made of a SiOCH or SiOC-based material is etched to finely process wiring holes and trenches,
Etching gas is a mixed gas obtained by adding CxHy having 1 to 4 C atoms or HFC gas having 1 to 3 carbon atoms to a perfluorocarbon gas at a ratio of 20 to 50% with respect to the total flow rate. A dry etching method for a low dielectric constant interlayer insulating film, which comprises etching by introducing this etching gas under the following operating pressure. _2. The method for dry etching a low dielectric constant interlayer insulating film according to claim 1, wherein at least one of CH ₃ CHF ₂ and CH ₂ F ₂ is selected as the HFC gas. Examples CxHy gas, CH ₄ gas, C ₂ H ₆ claim 1 or claim 2 low dielectric constant dry etching method of the interlayer insulating film, wherein the selecting at least one of the gas. The dry etching method for a low dielectric constant interlayer insulating film according to any one of claims 1 to 3, wherein a rare gas is added to the mixed gas. Said perfluorinated _{gas, C 2 F 6, C 3} F 8, C 4 F 8, and _C 5 claims 1 to 4, characterized in that selected from _{F 8} according to any one A dry etching method for a low dielectric constant interlayer insulating film.

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