JP4316322B2 - Interlayer dielectric film dry etching method - Google Patents

Description

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

  In general, for example, in order to anisotropically etch SiO2 constituting an interlayer insulating film, ion implantation energy is required. For this reason, power for main discharge is supplied via the first high-frequency power source, and power for substrate bias for supplying the ion species generated by the main discharge to the substrate is supplied via the second high-frequency power source. The device is used (Patent Document 1). In this case, when the ion incident energy to the interlayer insulating film is high, a micro trench is generated on the bottom surface of the trench by etching. Although this micro-trench generation can be eliminated by over-etching, in the case of a dual damascene structure that does not have an intermediate layer between the trench and the via, it is necessary to stop etching in the middle of the interlayer insulating film when etching the trench. is there. For this reason, etching involving micro-trenching can have a significant effect on varimeta film formation and electrical characteristics. On the other hand, once the micro-trench is generated, it is difficult to eliminate it even if etching is performed in the depth direction.

  In order to solve such problems, a method of reducing the effective ion incident energy by increasing the operating pressure during the execution of the etching process to increase the plasma density, or a substrate bias supplied via the second high frequency power source. A method of suppressing the generation of micro-trench by reducing the power supplied to the substrate is conceivable.

JP2003-109947A (for example, refer to FIG. 1).

  However, as described above, when the operating pressure at the time of executing the etching process is increased, it is considered that the etching characteristics such as electrical characteristics change due to the change in the process atmosphere. In addition, when etching a low dielectric constant interlayer insulating film (Low-K), the side walls may be damaged because the collision of reactive atoms and molecules to the side walls of the trench becomes higher. On the other hand, if the bias power is reduced, the etching rate is greatly reduced and the etching process time is increased, and in some cases, the trench cannot be completely etched.

  Therefore, in view of the above points, the present invention provides an interlayer insulating film in which when an interlayer insulating film is dry-etched, a high etching rate is obtained without changing etching characteristics and the interlayer insulating film is not damaged. It is an object of the present invention to provide a dry etching method for a film.

In order to solve the above-described problem, the method for dry etching an interlayer insulating film according to the present invention supplies power for main discharge through a first high frequency power supply and ions generated by main discharge through the second high frequency power supply. A method for dry-etching an interlayer insulating film that supplies substrate bias power for making seeds incident on the substrate, introduces an etching gas to dry-etch the interlayer insulating film, and finely processes wiring holes and trenches. The dry etching is performed by setting the frequency of the second high-frequency power source to a predetermined value within a range of 3 MHz to 6 MHz, and the frequency of the second high-frequency power source is set to a predetermined frequency and the interlayer insulating film Once etching is performed, the optimum etching conditions for the ion incident energy distribution on the interlayer insulating film are found to suppress the generation of micro-trench. In this etching condition, and changing the frequency of the second high frequency power source to the predetermined value.

  According to the present invention, by setting the frequency of the second high-frequency power source to a predetermined value within the range of 3 MHz to 6 MHz, the ratio that contributes to plasma generation on the substrate is increased and more etchants are generated. Thus, the etching rate can be increased without changing the etching characteristics. When the frequency of the second high frequency power source is lower than 3 MHz or higher than 6 MHz, a high etching rate and high shape controllability cannot be obtained as compared with the conventional one.

  If the dry etching is performed under an operating pressure of 1.5 Pa or less, radical reaction can be suppressed and damage to the interlayer insulating film can be prevented.

  The interlayer insulating film includes a low dielectric constant interlayer insulating film having a low relative dielectric constant.

  As a result, according to the method for etching an interlayer insulating film of the present invention, when the interlayer insulating film is dry-etched, a high etching rate is obtained without changing the etching characteristics, and the interlayer insulating film is not damaged. There is an effect.

  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 19 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 first high frequency power source 19, and includes three magnetic field coils 15, 15, An alternating electric field is applied along the magnetic neutral line formed by 16 and 17 to generate 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 the second high-frequency power source 22 via the 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 and finely processed in the trench using the etching apparatus, a SiOCH material such as HSQ or MSQ formed by spin coating, or CVD is used. It is a low-k material having a relative dielectric constant of 2.0 to 3.0, and may be a porous material. Examples of the coating system and SiOCH-based material include, for example, trade name NCS / catalyst chemical industry, trade name LKD5109r5 / JSR, trade name HSG-7000 / Hitachi Chemical, trade name HOSP / Honeywell Electric Materials Product name: Nanoglass / Honeywell Electric Materials, trade name: OCD T-12 / Tokyo Ohkasha, trade name: OCD T-32 / Tokyo Ohkasha, trade name: IPS 2.4 / Catalyst Chemical Industries, trade name There are IPS2.2 / catalyst chemical industry, trade name ALCAP-S5100 / Asahi Kasei, trade name ISM / ULVAC.

  Examples of the SiOC material include trade name Aurola 2.7 / manufactured by ASM Japan, trade name Aurola 2.4 / made by ASM Japan, trade name Orion 2.7 / TRIKON, trade name Coral / Novellf, trade name Available from 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 GX-3P / Honeywell An organic low dielectric constant interlayer insulating film such as that manufactured by 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, a mixed gas obtained by using a fluorocarbon gas as an etching gas and adding a rare gas to the fluorocarbon gas is used. In this case, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , C ₅ F ₈ , CF ₃ I, C ₃ F ₇ I, or the like is used as the fluorocarbon gas, and Ar is used as the rare gas. , Kr, Xe, etc. are used. Moreover, the operating pressure in the case of etching is set to 1.5 Pa or less in order to suppress radical reaction.

Then, power for main discharge is supplied via the first high-frequency power source 19, and power for substrate bias that causes the ion species generated by the main discharge to enter the processing substrate S is supplied via the second high-frequency power source 22. At the same time, an etching gas is introduced to dry-etch the interlayer insulating film. The frequency of the second high-frequency power source 22 is set to a predetermined value within the range of 3 MHz to 6 MHz, preferably 4 MHz. In this case, the frequency of the second high-frequency power source 22 is set to the frequency used in the conventional etching process (for example, 2 MHz), and the interlayer insulating film is once etched to suppress the generation of the microtrench. For example, the anisotropic etching conditions of the SiO ₂ or Low-K material are found by changing the input power of the second high-frequency power supply 22 so as to obtain an optimum ion incident energy distribution on the interlayer insulating film. Next, the frequency of the second high-frequency power source 22 is changed within the above range so that a large proportion of the etchant is generated by increasing the ratio that contributes to plasma generation on the processing substrate S, and interlayer insulation is performed under the same etching conditions. Etch the film. As a result, generation of micro-trench and change in etching characteristics are prevented, and a high etching rate is obtained.

  In this example, MSQ having a relative dielectric constant (k) of 2.5 was used as the SiOCH material, and a low dielectric constant interlayer insulating film having a thickness of 500 nm was formed on the processing substrate S 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, for example, 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 low dielectric constant interlayer insulating film was etched by introducing a mixed gas in which CF ₄ was used as an etching gas and argon was added to CF ₄ into the vacuum chamber 11. In this case, the gas flow rate of the mixed gas of CF ₄ and argon was set to 400 sccm. Further, the output of the high frequency power source 19 connected to the plasma generating high frequency antenna coil 18 is 1.2 kW (frequency 13.56 MHz), the output of the high frequency power source 22 for substrate bias connected to the substrate electrode 21 is 80 W, and the substrate temperature is 0 ° C. The pressure in the vacuum chamber 11 was set to 0.7 Pa. Etching was performed by setting the frequency of the second high frequency power supply 22 for substrate bias to 2 MHz, 4 MHz, 13.56 MHz, and 27 MHz, respectively.

  FIG. 2 shows the etching depth for each trench pattern size under the above conditions, and FIG. 3 shows the etching rate when etching is performed at each frequency at that time. FIG. 4 is an SEM photograph when the low dielectric constant interlayer insulating film and the resist mask are etched under the above conditions. According to this, it can be seen that at 2 MHz and 4 MHz, the distribution of incident ion energy is appropriate and the generation of micro-trench is suppressed (see FIG. 4). Further, when the frequency of the second high-frequency power source 22 is set to 4 MHz, the etching rate is improved by about 30% compared to when the frequency is set to 2 MHz. This is because more etchant is generated by optimizing the ratio that contributes to plasma generation on the processing substrate S. If the frequency of the second high-frequency power source 22 was set to 13.56 MHz and 27 MHz, the etching rate decreased compared to the case where it was set to 2 MHz, which was not practical and microloading occurred.

The figure which shows schematically the etching apparatus which enforces the etching method of the low dielectric constant interlayer insulation film of this invention. The graph which shows the etching depth with respect to each trench pattern size at the time of etching an interlayer insulation film by changing the frequency of the high frequency power supply for bias. The graph which shows the etching rate at the time of etching an interlayer insulation film by changing the frequency of the high frequency power supply for bias. (A) And (b) is the SEM photograph at the time of changing the frequency of the high frequency power supply for bias, and etching the interlayer insulation film.

Explanation of symbols

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

Claims (3)

The main discharge power is supplied via the first high-frequency power supply, and the substrate bias power for causing the ion species generated by the main discharge to enter the substrate is supplied via the second high-frequency power supply, and the etching gas is introduced. In this method, the interlayer insulating film is dry etched, and the wiring holes and trenches are finely processed. The method of dry etching the interlayer insulating film sets the frequency of the second high frequency power source to a predetermined value within a range of 3 MHz to 6 MHz. Then, in what is to perform the dry etching,
The frequency of the second high frequency power supply is set to a predetermined frequency, the interlayer insulating film is once etched, and an etching condition that provides an ion incident energy distribution to the interlayer insulating film optimal for suppressing the generation of the microtrench is found. A dry etching method for an interlayer insulating film, wherein the frequency of the second high-frequency power source is changed to the predetermined value under etching conditions . 2. The method of dry etching an interlayer insulating film according to claim 1, wherein the dry etching is performed under an operating pressure of 1.5 Pa or less. 3. The method of dry etching an interlayer insulating film according to claim 1, wherein the interlayer insulating film includes SiO ₂ or an interlayer insulating film having a low relative dielectric constant.

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