JP5580844B2 - Etching method - Google Patents

Description

  According to the present invention, an object to be processed having an SiC portion or an SiN portion, for example, a semiconductor wafer having an SiC film or an SiN film as a barrier layer and an interlayer insulating film formed thereon is accommodated in a processing container. The present invention relates to an etching method for etching a SiC portion or a SiN portion of a processing body with an etching gas plasma.

  In the wiring process of the semiconductor device, an interlayer insulating film is formed between the wiring layers, and the interlayer insulating film is etched to make the wiring layer conductive. In this case, an SiC film or SiN film is formed as a barrier layer under the interlayer insulating layer. When the SiC film or SiN film is etched subsequent to the interlayer insulating film to form the wiring pattern, these are etched using the interlayer insulating film as a mask.

  On the other hand, in a semiconductor device, a low dielectric constant material is being used as an interlayer insulating film because of a demand for higher speed. As such a low dielectric constant material, an organic Si-based material is known.

By the way, as a technique for etching a SiC film, Patent Document 1 discloses a technique using CF ₄ and O ₂ , and Patent Document 2 discloses a technique using CF ₄ , CHF ₃ and O _2. Patent Document 3 discloses techniques using CHF ₃ and Ar, but these techniques are not necessarily sufficient because the etching rate is about 10 nm / min. In addition, when etching a SiC film using an organic Si-based low dielectric constant film as a mask with these techniques, in addition to a low etching rate, the selectivity to the upper organic Si-based low dielectric constant film is not sufficient. There's a problem.

  Also, a technique for etching with a high etching selectivity with respect to an organic Si-based low dielectric constant film while maintaining a sufficient etching rate for the SiN film has not yet been obtained.

JP 57-124438 A JP 62-216335 A JP-A-4-293234

  This invention is made | formed in view of this situation, Comprising: It aims at providing the etching method which can etch the SiC part of a to-be-processed object with sufficient etching rate. Also, an etching method capable of performing etching by increasing the etching rate and the etching selectivity with respect to the organic Si low dielectric constant film when etching the SiC portion of the object to be processed using the organic Si low dielectric constant film as a mask. The purpose is to provide.

The present inventors can etch a SiC portion at a high etching rate when an object to be processed including a SiC portion such as a SiC film is accommodated in a processing container and the SiC portion is etched by plasma of an etching gas. As a result of repeated studies on the etching gas, it was found that a gas containing CH ₂ F ₂ and a gas containing CH ₃ F are effective. Further, it has been found that a gas containing CH ₂ F ₂ and a gas containing CH ₃ F have an effect of increasing the etching selectivity of SiC with respect to the organic Si-based low dielectric constant film.

The present invention has been made based on such knowledge, and according to one aspect of the present invention, an object to be processed including an SiC portion is accommodated in a processing container, and the SiC portion of the object to be processed is removed from an etching gas. There is provided an etching method for etching by plasma, characterized in that a gas containing CH ₃ F and CF ₄ is used as an etching gas.

In one aspect of the present invention, a gas further containing O ₂ can be used as the gas. Further, it is possible to use those containing A r instead of O ₂ or in addition to O _2.

In the one aspect, by etching the SiC to SiC portion of the object to be processed and the organic Si-based low-dielectric-constant film as a mask, it is possible to increase the etching selection ratio with respect to organic Si-based low-dielectric constant film as described above it can.

According to the present invention, by etching the SiC in the gas containing a _CH 3 F and CF _4, it is possible to obtain a high etching rate. Further, if the etching of SiC as a mask an organic Si-based low-dielectric constant film with a gas containing a CH ₃ F and CF _4, can be etched by increasing the etch selectivity to the etch rate and an organic Si-based low-dielectric constant film Can do.

The schematic sectional drawing which shows an example of the dry etching apparatus for enforcing the etching method of this invention. A structure in which an SiC film is formed on a wiring layer and an organic Si-based low dielectric constant film is further formed thereon, and the SiC film is etched following the organic Si-based low dielectric constant film in the structure. FIG. A structure in which an SiN film is formed on a wiring layer and an organic Si-based low dielectric constant film is further formed thereon, and the SiN film is etched following the organic Si-based low dielectric constant film in the structure. FIG. The graph which shows the relationship between the amount of Ar and gas pressure, the etching rate of a SiN film, and the etching selectivity of an SiN film to an organic Si system low dielectric constant film in etching of a SiN film.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic sectional view showing a dry etching apparatus for carrying out the present invention.

  This etching apparatus 1 is configured as a capacitively coupled parallel plate etching apparatus in which electrode plates face each other in parallel in the vertical direction and a plasma forming power source is connected to one of them.

  The etching processing apparatus 1 has a chamber 2 formed into a cylindrical shape made of aluminum whose surface is ceramic sprayed, for example, and the chamber 2 is grounded for safety. A semiconductor wafer (hereinafter simply referred to as “wafer”) W made of, for example, silicon and having a predetermined film formed thereon is horizontally placed in the chamber 2, and a susceptor 3 functioning as a lower electrode is provided as a support member. 4 is provided in a supported state. This support member 4 is supported by a support base 6 of a lifting device (not shown) via an insulating plate 5 such as ceramic, and the susceptor 3 can be lifted and lowered by this lifting mechanism. The atmospheric portion at the lower center of the support base 6 is covered with a bellows 7, and the inside of the chamber 2 and the atmospheric portion are separated.

  A refrigerant chamber 8 is provided inside the support member 4. In the refrigerant chamber 8, for example, a refrigerant such as Galden is introduced and circulated through the refrigerant introduction pipe 8 a, and the cold heat is supplied to the susceptor 3. Then, heat is transferred to the wafer W through this, whereby the processing surface of the wafer W is controlled to a desired temperature. Further, a gas passage 9 for supplying a heat transfer medium, for example, He gas, is provided on the back surface of the wafer W, which is an object to be processed. The transmitted wafer W is maintained at a predetermined temperature.

  The susceptor 3 is formed in a disk shape having a convex center at the top, and an electrostatic chuck 11 having an electrode 12 interposed between insulating materials is provided on the susceptor 3 and connected to the electrode 12. When a DC voltage is applied from the DC power source 13, the wafer W is electrostatically adsorbed by, for example, Coulomb force. An annular focus ring 15 for improving the uniformity of etching is disposed on the periphery of the upper end of the susceptor 3 so as to surround the wafer W placed on the electrostatic chuck 11.

  Above the susceptor 3, a shower head 21 that functions as an upper electrode is provided in parallel with the susceptor 3. The shower head 21 is supported on the upper portion of the chamber 2 via an insulating material 22, and has a large number of discharge holes 23 on the surface 24 facing the susceptor 3. The susceptor 3 and the shower head 21 are separated from each other by about 25 to 55 mm, for example, and this distance can be adjusted by the lifting mechanism.

  A gas inlet 26 is provided in the center of the shower head 21, and a gas supply pipe 27 is connected to the gas inlet 26. Further, a valve 28 is connected to the gas supply pipe 27 through a valve 28. An etching gas supply source 30 is connected. Then, a predetermined etching gas is supplied from the etching gas supply source 30.

The etching gas supply source 30, when etching the SiC film, CH ₃ F or _CH 2 _{F 2} gas source, CF ₄ gas source, _{O 2} gas source, and the Ar gas source, respectively CH ₃ F gas or It is configured to supply CH ₂ F ₂ gas, CF ₄ gas, O ₂ gas, and Ar gas. On the other hand, when the SiN film is etched, the CH ₂ F ₂ gas, the O ₂ gas source, and the Ar gas source are supplied with CH ₂ F ₂ gas, O ₂ gas, and Ar gas, respectively. Is done.

  An exhaust pipe 31 is connected near the bottom of the side wall of the chamber 2, and an exhaust device 35 is connected to the exhaust pipe 31. The exhaust device 35 includes a vacuum pump such as a turbo molecular pump, and is configured so that the inside of the chamber 2 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. Further, a gate valve 32 is provided on the side wall of the chamber 2, and the wafer W is transported between adjacent load lock chambers (not shown) with the gate valve 32 opened. ing.

  A high frequency power supply 40 is connected to the shower head 21 that functions as an upper electrode, and a matching unit 41 is interposed in the power supply line. The high frequency power supply 40 supplies a high frequency of, for example, 60 MHz. The shower head 21 is connected to a low pass filter (LPF) 42.

  A high frequency power supply 50 is connected to the susceptor 3 functioning as the lower electrode, and a matching unit 51 is interposed in the power supply line. The high frequency power supply 50 supplies a high frequency of 2 MHz, for example. The susceptor 3 is connected to a high pass filter (HPF) 16.

  Next, a method for etching a SiC film using the etching apparatus will be described. Here, as shown in FIG. 2A, an SiC film 61 as a barrier layer is formed on a wiring layer 60 made of Cu, for example, and an interlayer insulating film 62 made of an organic Si-based low dielectric constant film is formed thereon. 2 is etched using the resist layer 63 as a mask to form the structure shown in FIG. 2B, and then the SiC film is etched using the interlayer insulating film 62 as a mask.

ただし、化学式中、Ｒは、メチル基、エチル基、プロピル基等のアルキル基、もしくはそれらの誘導体、またはフェニル基等のアリル基、もしくはその誘導体である。 Here, as a typical example of the material constituting the organic Si-based low dielectric constant film, polyorganosiloxane having the following chemical formula can be given.

In the chemical formula, R represents an alkyl group such as a methyl group, an ethyl group, or a propyl group, or a derivative thereof, an allyl group such as a phenyl group, or a derivative thereof.

  In this etching, the gap between the susceptor 3 and the shower head 21 of the etching apparatus 1 is set to 80 mm, for example, the gate valve 32 is opened, and a predetermined pattern is formed on the SiC film 61 shown in FIG. A wafer W having an interlayer insulating film 62 made of an etched organic Si-based low dielectric constant film (low-k film) is carried into the chamber 2 and placed on the susceptor 3. Then, a DC voltage is applied from the DC power source 13 to the wafer W, and the wafer W is electrostatically attracted by the electrostatic chuck 11. Next, the gate valve 32 is closed, and the inside of the chamber 2 is evacuated to a predetermined vacuum level by the exhaust device 35.

In this state, a predetermined etching gas is supplied from the etching gas supply source 30 into the chamber 2. Here, in order to etch the SiC film 61, the etching gas supply source 30 includes a CH ₃ F or CH ₂ F ₂ gas source, a CF ₄ gas source, an O ₂ gas source, and an Ar gas source. Then, CH ₃ F gas or CH ₂ F ₂ gas, CF ₄ gas, O ₂ gas, and Ar gas are supplied into the chamber 2. Then, by applying a high-frequency power source 40 to the shower head 21 a high frequency power of a predetermined frequency, thereby causing high frequency electric field between the susceptor 3 as a shower head 21 and the lower electrode as an upper electrode, the CH ₃ F gas or CH ₂ F ₂ gas, CF ₄ gas, O ₂ gas, and Ar gas are turned into plasma, and as shown in FIG. 2C, these are allowed to act on the SiC film 61 to etch the SiC film 61. Make it progress. At this time, high-frequency power of a predetermined frequency is applied from the high-frequency power supply 50 to the susceptor 3 that is the lower electrode so that ions in the plasma are drawn to the susceptor 3 side.

At this time, when CH ₃ F is used, a high etching rate is obtained by the synergistic effect of CH ₃ F, CF ₄ , O ₂ , and Ar, and the SiC film is mainly obtained by the action of CH ₃ F and Ar. The etching selectivity ratio of 61 to the low-k film 62 can be made high. Specifically, the etching rate of the SiC film can be 20 nm / min or more, and the etching selectivity with respect to the low-k film can be 10 or more. In the case of using CH ₂ F ₂ instead of CH 3 _F, the etching selection ratio than with CH 3 _F is somewhat inferior, it is possible to obtain the same high etching rate. Of these gases, CH ₃ F has the effect of selectively etching the SiC film to increase the etching selectivity. CH ₂ F ₂ exert the same action as CH ₃ F, but the effect of increasing the etching selection ratio than CH ₃ F is somewhat inferior. Ar also has the effect of increasing the etching selectivity of the shoulder portion.

  Next, the results of actually etching the SiC film using the low-k film mainly composed of polymethylsiloxane as a mask will be described. First, using the apparatus shown in FIG. 1, the pressure in the chamber is 6.65 Pa, high frequency power of 60 MHz for plasma formation is supplied to the shower head, and high frequency power of 2 MHz for ion attraction is supplied to the susceptor. Etching was performed with various changes in the etching gas composition and flow rate, and the high-frequency power as shown in Table 1. The gap between the susceptor and the shower head was 35 mm.

As a result, as shown in Table 1, it was confirmed that using an etching gas containing CH ₂ F ₂ or CH ₃ F resulted in an etching rate of 20 nm / min or more. In addition, as for these, the etching selectivity with respect to the low-k film was 10 or more at the shoulder portion of the low-k film.

Next, as an etching apparatus, unlike FIG. 1, an apparatus for performing magnetron plasma etching, which includes a dipole ring magnet that supplies high-frequency power only to the susceptor and forms a horizontal magnetic field in the space between the susceptor and the shower head. The pressure in the chamber was set to 9.98 Pa, high frequency power of 13.56 MHz was supplied to the susceptor, and the etching gas was changed to No. 1 in Table 1. Etching was performed by changing the flow rate and high-frequency power of these gases as shown in Table 2 using only CH ₃ F and O ₂ gas as in the case of No. 5. The gap between the susceptor and the shower head was 27 mm.

  As a result, as shown in Table 2, the etching rate was 130 nm / min or more and the etching selectivity was 10.7 or more.

  Next, a method for etching the SiN film using the etching apparatus will be described. Here, as shown in FIG. 3A, a SiN film 64 as a barrier layer is formed on a wiring layer 60 made of Cu, for example, as shown in FIG. In the structure in which the interlayer insulating film 62 made of an organic Si-based low dielectric constant film is formed, the interlayer insulating film 62 is etched using the resist layer 63 as a mask to form the structure shown in FIG. The SiN film is etched using the insulating film 62 as a mask.

  In this etching, the gap between the susceptor 3 and the shower head 21 of the etching apparatus 1 is set to 80 mm, for example, the gate valve 32 is opened, and a predetermined pattern is formed on the SiN film 64 shown in FIG. A wafer W having an interlayer insulating film 62 made of an organic Si-based low dielectric constant film (low-k film) is loaded into the chamber 2, placed on the susceptor 3, and electrostatically charged by the electrostatic chuck 11. After the adsorption, the gate valve 32 is closed and the inside of the chamber 2 is evacuated to a predetermined degree of vacuum by the exhaust device 35.

In this state, a predetermined etching gas is supplied from the etching gas supply source 30 into the chamber 2. Here, in order to etch the SiN film 64, the etching gas supply source 30 includes a CH ₂ F ₂ gas source, an O ₂ gas source, and an Ar gas source, from which CH ₂ F ₂ gas, O ₂ gas and Ar gas are supplied into the chamber 2. Then, a high frequency power of a predetermined frequency is applied from the high frequency power source 40 to the shower head 21, thereby generating a high frequency electric field between the shower head 21 as the upper electrode and the susceptor 3 as the lower electrode, and the CH ₂ F ₂ gas, O ₂ gas, and Ar gas are turned into plasma, and as shown in FIG. 3C, these are allowed to act on the SiN film 64 to advance the etching of the SiN film 64. At this time, high-frequency power of a predetermined frequency is applied from the high-frequency power supply 50 to the susceptor 3 that is the lower electrode so that ions in the plasma are drawn to the susceptor 3 side. At this time, etching is performed by adjusting the gas pressure in the chamber 2 in accordance with the amount of Ar.

In this way, CH ₂ F ₂ and O ₂ are introduced as the etching gas at the predetermined ratio, and the gas pressure in the chamber 2 is adjusted according to the amount of Ar, so that the low rate of the SiN film is maintained while maintaining a high etching rate. The etching selectivity with respect to the -k film can be increased.

Specifically, the relationship as shown in FIG. 4 is obtained. FIG. 4 shows that CH ₂ F ₂ is fixed at a flow rate of 0.01 L / min, O ₂ is fixed at a flow rate of 0.01 L / min, and the Ar flow rate is 0 in which Ar / (CH ₂ F ₂ + O ₂ ) corresponds to 0-15. It is a figure which shows the result of having changed the gas pressure in a chamber within the range of -0.3L / min and 1.3-12.0Pa which is a preferable range, and etching the SiN film | membrane. Here, high frequency power of 60 MHz and 1500 W was applied to the shower head, and high frequency power of 2 MHz and 100 W was applied to the susceptor. As shown in this figure, the etching selectivity of the SiN film is 100 nm / min or more and the etching selectivity to the low-k film is 10 or more in the hatched region of FIG. That is, it can be seen that there is an appropriate gas pressure in accordance with the Ar flow rate when the Ar flow rate is 0 to 0.3 L / min and the gas pressure in the chamber is 1.3 to 12.0 Pa.

  In addition, the peak-to-peak value Vpp of the high-frequency voltage in the shower head 21 that is the upper electrode is preferably 300 V or less. By defining Vpp in this way, it is possible to obtain a high value of an etching selection ratio of 30 or more with respect to the low-k film.

Next, the results of actually etching the SiN film using the low-k film as a mask within the range of preferable conditions will be described. Here, a low-k film containing polymethylsiloxane as a main component is used, and CH ₂ F ₂ is 0.01 L / min, O ₂ is 0.01 L / min, and Ar is 0.1 L / min as an etching gas. It is introduced into the chamber at a flow rate of min, the pressure in the chamber is set to 6.65 Pa, high frequency power of 60 MHz and 1500 W for plasma formation is supplied to the shower head, and high frequency power of 2 MHz and 100 W for ion attraction is supplied to the susceptor. Etching was performed. The gap between the susceptor and the shower head was 35 mm. As a result, the etching rate was 232.5 nm / min at the center and 250.0 nm / min at the edge, and the etching selectivity was 10 or more at the shoulder portion of the low-k film. At this time, the value of Vpp was 252V.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, the etching of the SiC film formed on the lower layer of the organic Si-based low dielectric constant film is shown, but the present invention is not limited to this. Further, although polyorganosiloxane is used as the organic Si-based low dielectric constant film, the present invention is not limited to this. Furthermore, in the above embodiment, as an etching apparatus, a shower head as an upper electrode and a susceptor as a lower electrode are provided in the chamber so as to face each other, and an etching gas is introduced while a wafer is supported by the susceptor, Although the high frequency power for plasma formation is applied to the shower head and the high frequency power for ion attraction is applied to the susceptor, the present invention is not limited to this. For example, either the upper electrode or the lower electrode A structure in which high-frequency power is applied to the substrate may be used, or magnetron plasma etching with a magnetic field superimposed may be performed.

DESCRIPTION OF SYMBOLS 1; Etching apparatus 2; Chamber 3; Susceptor 21; Shower head 30; Etching gas supply source 40, 50; High frequency power supply 61; SiC film 62; Interlayer insulation film (organic Si system low dielectric constant film)
64; SiN film W; Semiconductor wafer

Claims (4)

An etching method in which an object to be processed including an SiC portion is accommodated in a processing container, and the SiC portion of the object to be processed is etched by plasma of an etching gas , and a gas containing CH ₃ F and CF ₄ is used as an etching gas. An etching method characterized by the above. The etching method according to claim 1, wherein the gas further contains O ₂ . The etching method of claim 1 or claim 2, wherein the gas further containing Ar. The etching method according to any one of claims 1 to 3 , wherein the SiC portion of the object to be processed is etched using the organic Si-based low dielectric constant film as a mask.

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