TWI621179B - Dry etching method - Google Patents

Abstract

The present invention provides a dry etching method capable of etching tantalum oxide and polysilicon at an equal rate.

The present invention uses a dry etching method characterized in that it is a method of etching a dry etchant and applying a bias voltage to etch a laminate film of a tantalum oxide layer and a tantalum layer, and the dry etchant comprises a fluorine-containing unsaturated hydrocarbon and iodine hexafluoride represented by C ₃ H _x F _y (an integer of x=1 to 5, an integer of y=1 to 5, x+y=4 or 6), in the above dry etchant The volume of the iodine hexafluoride contained is in the range of 0.1 to 1.0 times the volume of the fluorine-containing unsaturated hydrocarbon contained in the dry etchant.

Description

Dry etching method

This invention relates to a dry etching process using a dry etchant comprising a fluorine-containing unsaturated hydrocarbon.

At present, in the semiconductor manufacturing industry, the miniaturization is approaching the physical limit, and in order to compensate for this, a method of integrating the structures in the height direction and integrating them has been developed. This trend is particularly evident in NAND flash memory, where the industry is actively conducting research and development of three-dimensional NAND flash memory.

For example, in the three-dimensional NAND flash memory manufacturing process described in Non-Patent Document 1, polycrystalline germanium (hereinafter referred to as poly-Si or p-) is prepared in advance for the purpose of producing a portion for holding electric charges. The Si) layer 1 and the tantalum oxide (hereinafter referred to as SiO _x ) layer 2 are alternately laminated on the substrate.

Next, in order to embed wiring in separate memory cells, through holes are formed in the laminated film. The method of forming the through-holes in the laminated film is performed, for example, by applying a resist having a specific opening portion to the uppermost portion of the film in which the p-Si layer 1 and the SiO _x layer 2 are alternately laminated on the substrate. 3 as a mask, and a fluorine atom containing gases in contact with the plasma, thereby removing the p-Si and SiO _x. At this time, since the etching is performed anisotropically in the direction perpendicular to the film of the laminated film, a DC voltage called a bias voltage is generated between the upper electrode and the lower electrode in the chamber to control the ions in the plasma. Collision direction. The bias voltage is a potential difference spontaneously generated between the upper electrode and the lower electrode due to the difference between the moving speed of ions and electrons in the plasma, but can be controlled by supply of external alternating current power.

However, since the preferable etching conditions of each of p-Si and SiO _x are different, a through-hole is formed for the laminated film of the p-Si layer 1 and the SiO _x layer 2, as disclosed in Non-Patent Document 2, it is disclosed that p- The Si etching step and the SiO _x etching step are alternately repeated as separate steps to form a through hole.

Further, as a gas containing a fluorine atom for etching, for example, as disclosed in Patent Document 1, a saturated fluorocarbon such as CF ₄ or C ₂ F ₆ or C ₃ F _{8 is} widely used, but the saturated fluorocarbon is used. In the case, in many cases, an etching in a non-target direction called a side etch as shown in FIG. 2 is performed. For example, in FIG. 2, when the etching target layer 5 having the mask 6 having the specific opening pattern on the substrate 4 is provided with a hole having the same width as the opening pattern, if not only the longitudinal direction is etched, but also the lateral direction is etched, It will be cut more widely than the opening pattern, resulting in side erosion 7.

Patent Document 2 discloses a plasma etching method using hexafluoropropylene (C ₃ F ₆ ), octafluoropropane (C ₃ F ₈ ), heptafluoropropane (C ₃ HF ₇ ), and hexafluoropropane (C ₃ H). ₂ F ₆ ), the cerium oxide is selectively etched compared to tantalum nitride.

Patent Document 3 discloses a plasma etching method for selectively etching a ruthenium oxide layer on a tantalum nitride layer using hexafluorobutadiene, hexafluorocyclobutene or hexafluorobenzene.

Patent Document 4 discloses a dry etching method for a ruthenium layer which is formed on a side surface of a hole or a groove formed in a laminate film having a ruthenium layer and a ruthenium oxide layer, and a gas containing a fluorinated halogen compound and fluorine. The gas is etched by gas.

On the other hand, according to Patent Document 5, Patent Document 6, and Patent Document 7, it is disclosed that when a fluorine-containing unsaturated hydrocarbon represented by C ₃ H ₂ F ₄ or C ₃ HF ₃ is used as an etchant, it can be suppressed. Lateral erosion.

Patent Document 8 discloses a method of anisotropic plasma etching of a tantalum substrate using an etching gas containing fluorinated iodine.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2007-537602

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2001-517868

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2002-530863

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2013-70012

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2011-176291

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2012-114402

[Patent Document 7] Japanese Patent Laid-Open Publication No. 2013-30531

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2008-177209

[Non-patent literature]

[Non-Patent Document 1] Qingming Yingming, 2 others, Toshiba Review, September 2011, 66 volumes, 9th, p16~19

[Non-Patent Document 2] Ichikawa Toshi, 2 others, Toshiba Review, May 2011, 66, 5, p29~33

As described above, Non-Patent Document 2 discloses a method in which p-Si etching and SiO _x etching are alternately repeated as separate steps to form through-holes in the laminated film. However, in this method, since the p-Si etching step and the SiO _x etching step are independent steps, it is necessary to switch the etching conditions. This process is time consuming, and as the number of layers of memory cells increases, the production takes a lot of time and becomes a problem. In consideration of the productivity directly related to the manufacturing cost, the time required for the etching steps is preferably short, and it is expected that the etching is performed by a single etching step to shorten the time taken to form the through holes.

Further, in Non-Patent Document 2, when the respective etching steps are alternately repeated as separate steps in the p-Si etching step and the SiO _x etching step, the etching rate of p-Si and SiO _x is different. On the other hand, irregularities are formed on the wall of the hole, and the case where the diameter of the hole is thinner toward the lower portion is exhibited. The unevenness of the hole walls or the unevenness of the hole diameter is one of the causes of deterioration of the performance of the memory cells formed in the respective layers. Therefore, it is desirable to reduce the unevenness of the pore walls and also to make the pores uniform in the upper and lower portions.

The unevenness of the irregularities or apertures is caused by the p-Si etching step being independent of the SiO _x etching step. For example, in the SiO _x etching step, it is preferable to completely suppress the etching of p-Si, but actually the etching is slightly performed. Further, since the p-Si etching step is different from the etching conditions in the SiO _x etching step, for example, the protective film formed in the p-Si etching step for suppressing the progress of the side etching is removed in the SiO _x etching step. Thus, as the etching step proceeds, the closer to the surface portion, the larger the pore diameter, and the unevenness of the pore wall (inner surface) also becomes apparent.

Therefore, by forming the through-holes in the laminated film of SiO _x and p-Si by the etching rate of p-Si and the etching rate of SiO _x , separate p-Si etching steps and SiO _x etching can be performed. The step is a step, and in the etching step, a uniform protective film can be formed on p-Si and SiO _x , and side etching can be reduced to reduce the unevenness of the pore walls.

However, Patent Documents 2 and 3 disclose a method of selectively etching yttrium oxide with respect to tantalum nitride, but a method of etching both p-Si and SiO _{x is} not disclosed. Further, Patent Document 4 discloses a step of etching a tantalum layer after forming a through-hole of a laminated film, and a method of forming a through-hole is not disclosed. Further, Patent Document 5, Patent Document 6, and Patent Document 7 disclose a method of selectively etching SiN or SiO _x , but a method of making the etching rate of p-Si and SiO _x equivalent is not disclosed.

Further, as a method of improving the etching selectivity of germanium, a method of adding O ₂ is disclosed. However, in this method, the amount of etching of the resist applied as a mask on the surface of the laminated film is greatly increased, and it is practically impossible to obtain The full effect of the mask.

On the other hand, Patent Document 8 cites IF ₇ as an example of fluorinated iodine, but in the examples, IF ₅ was used, and IF _{7 was} not used. Further, a method of making the etching rate of p-Si and SiO _x equivalent is not disclosed.

The present invention has been made in view of the above problems, and an object thereof is to provide a dry etching method capable of etching SiO _x and p-Si at an equal rate.

The inventors of the present invention conducted various studies in order to achieve the above object, and as a result, found that plasma etching is performed by using a dry etchant containing a fluorine-containing unsaturated hydrocarbon having a carbon number of 3 and iodine hexafluoride, p-Si The etching rate and the etching rate to SiO _{x are} substantially equal, thereby completing the present invention.

That is, a dry etching method is provided, which is characterized in that it is a method of etching a dry etchant and applying a bias voltage to etch a laminate film of a tantalum oxide layer and a tantalum layer, and the dry etchant includes C ₃ H _x F _y (an integer of x=1 to 5, an integer of y=1 to 5, x+y=4 or 6), a fluorine-containing unsaturated hydrocarbon and iodine hexafluoride, in the above dry etchant The volume of the iodine hexafluoride contained is in the range of 0.1 to 1.0 times the volume of the fluorine-containing unsaturated hydrocarbon contained in the dry etchant.

Further, the fluorine-containing unsaturated hydrocarbon is preferably at least one selected from the group consisting of C ₃ HF ₅ , C ₃ H ₂ F ₄ , and C ₃ HF ₃ , and the bias voltage is preferably 500 V or more.

According to the present invention, a dry etching method capable of etching SiO _x and p-Si at an equal rate can be provided. When the present invention is applied to a step of forming a vertical through hole in a portion where p-Si and SiO _x are alternately laminated on a substrate, the etching rate for p-Si can be made equal to the etching rate for SiO _x . Therefore, it is possible to reduce the unevenness of the through-hole wall formed in the laminated film, and it is also possible to suppress the unevenness of the aperture between the upper portion and the lower portion.

1‧‧‧p-Si layer

2‧‧‧SiO _x layer

3‧‧‧ mask

4‧‧‧Substrate

5‧‧‧ etching target layer

6‧‧‧ mask

7‧‧‧Side eclipse

10‧‧‧Reaction device

11‧‧‧ chamber

12‧‧‧ Pressure gauge

13‧‧‧High frequency power supply

14‧‧‧ lower electrode

15‧‧‧Upper electrode

16‧‧‧ gas inlet

17‧‧‧ gas discharge line

18‧‧‧sample

Fig. 1 is a schematic view showing a laminated structure of an element before a through hole is formed.

Fig. 2 is a schematic view showing the side etching generated when etching is performed.

Fig. 3 is a schematic view showing a reaction apparatus used in Examples and Comparative Examples.

Fig. 4 is a graph showing the experimental results of Examples 1 to 10 and Comparative Examples 1 and 2.

Hereinafter, an embodiment of the present invention will be described. In addition, the scope of the present invention is not limited by the scope of the invention, and may be appropriately modified without departing from the spirit and scope of the invention.

In the dry etching method of the present invention, the fluorine is not expressed by C ₃ H _x F _y (an integer of x=1 to 5, an integer of y=1 to 5, x+y=4 or 6). A dry etching agent containing iodine octafluoride is added to the saturated hydrocarbon, and a bias voltage is applied to perform plasma etching, and the laminated film of the tantalum oxide layer (SiO _x layer) and the polycrystalline germanium layer (p-Si layer) is etched.

The fluorine-containing unsaturated hydrocarbon having 3 carbon atoms represented by C ₃ H _x F _y (an integer of x=1 to 5, an integer of y=1 to 5, x+y=4 or 6) may be selected from C ₃ HF ₅ , C ₃ H ₂ F ₄ , C ₃ H ₃ F ₃ , C ₃ H ₄ F ₂ , C ₃ H ₅ F, C ₃ HF ₃ , C ₃ H ₂ F ₂ , C ₃ H ₃ F a compound of the group and a mixture thereof. Since the etching rate becomes faster when the amount of F atoms is large, it is preferably used as C ₃ H _x F _y (an integer of x=1 to 5, an integer of y=1 to 5, x+y=4 or 6) , x ≦ y), C ₃ HF ₅ , C ₃ H ₂ F ₄ , C ₃ H ₃ F ₃ , C ₃ HF ₃ , C ₃ H ₂ F ₂ of the fluorine-containing unsaturated hydrocarbon. Further, it is particularly preferable that the CF ₃ group is bonded to the unsaturated bond by a single bond and C ₃ HF ₅ , C ₃ H ₂ F ₄ , and C ₃ HF ₃ of CF ₃ ⁺ ions having high etching efficiency at a high frequency.

Further, in the fluorine-containing unsaturated hydrocarbon having 3 carbon atoms, a stereoisomer, that is, a trans form (E form) and a cis form (Z form) may be present. In the present invention, it may be used in the form of any one of the isomers or a mixture of the two.

Further, as C ₃ HF ₅ , trans-1,2,3,3,3-pentafluoropropene (HFO-1225ye(E)), cis-1,2,3,3,3-five can be used. Any of fluoropropene (HFO-1225ye (Z)) and 1,1,3,3,3-pentafluoropropene (HFO-1225zc), as C ₃ H ₂ F ₄ , ₂ , _{3, 3, 3} can be used. -tetrafluoropropene (HFO-1234yf), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), cis-1,3,3,3-tetrafluoropropene (HFO- Any of 1234ze(Z)).

The fluorine-containing unsaturated hydrocarbon having 3 carbon atoms has a lower boiling point than the fluorine-containing unsaturated hydrocarbon having 4 or more carbon atoms, and has a high vapor pressure at normal temperature. Therefore, when a fluorine-containing unsaturated hydrocarbon having a carbon number of 4 or more is used, when the temperature of the liquefied gas in the gas cylinder is lowered by the latent heat of vaporization, there is a possibility that the process pressure is rapidly lowered, but if a carbon number of 3 is used, This is less of an issue with unsaturated hydrocarbons. Further, since the molecule has an unsaturated bond, it is polymerized in the plasma to be polymerized, and is deposited on the side wall of the through hole to form a protective film. Therefore, side etching can be prevented. Further, in the present invention, since the p-Si layer and the SiO _x layer are etched in one step, the formed protective film remains in the process, so that both the p-Si layer and the SiO _x layer can be suppressed. The side erosion is carried out.

Further, since the fluorine-containing unsaturated hydrocarbon having a carbon number of 3 contains an unsaturated bond and hydrogen in the molecule, it is decomposed into a fragment containing a large amount of C ₂ or more unsaturated hydrocarbon ions during plasma etching, and is easily adsorbed on the p-Si layer. Forming a film that protects the p-Si layer can suppress etching of the excess p-Si layer caused by IF ₇ . Further, since a portion having a high etching property to SiO _x such as CF _n ⁺ ions (n=1, 2 or 3) is also formed, it is also possible to etch the SiO _x layer which is hardly etchable by only IF _{7 .} . On the other hand, if perfluorocarbon containing no hydrogen in the molecule is used, it is difficult to form a protective film. Therefore, the etching rate of the p-Si layer is too fast without adding IF ₇ , and it is difficult to make the p-Si layer. The etching rate is the same as that of the SiO _x layer.

The concentration of the fluorine-containing unsaturated hydrocarbon having 3 carbon atoms in the dry etchant is preferably 1% by volume or more and 90% by volume or less in terms of obtaining a sufficient etching rate. On the other hand, when the concentration of the fluorine-containing unsaturated hydrocarbon in the etchant is more than 90% by volume, the concentration of iodine hexafluoride becomes insufficient, and although a large amount of expensive fluorine-containing unsaturated hydrocarbon is contained, the etching rate is not Correspondingly, it is not good in terms of cost-effectiveness. Further, as a practical range in terms of cost effectiveness, the concentration of the fluorine-containing unsaturated hydrocarbon is 10% by volume or more and 50% by volume or less.

Further, the volume of the iodine iodine contained in the dry etchant is 0.1 to 1.0 times the volume of the fluorine-containing unsaturated hydrocarbon having 3 carbon atoms contained in the dry etchant. That is, the mixing ratio of the fluorine-containing unsaturated hydrocarbon having a carbon number of 3 to the iodine hexafluoride is 1:0.1 to 1 in terms of volume ratio. The mixing ratio is preferably from 1:0.2 to 0.6, and particularly preferably from 1:0.3 to 0.5. Thereby, SiO _x and p-Si can be etched at the same rate. In the present invention, the difference between the etching rates of SiO _x and p-Si can be made within 5%, that is, the ratio of the etching rate of SiO _{x to} the etching rate of p-Si can be made 67% to 150%. More preferably, the ratio of the etching rate of SiO _{x to} the etching rate of p-Si is in the range of 80% to 120%.

Iodine hexafluoride is etched by p-Si and used as an oxidizing agent for fluorine-containing unsaturated hydrocarbons. Therefore, if too much, the etching rate of p-Si becomes too high compared with the etching rate of SiO _x . The oxidative decomposition of unsaturated hydrocarbons is stagnant, and neither p-Si nor SiO _x can obtain sufficient etching speed.

Iodine hexafluoride contains iodine in the molecule, and this iodine acts as an adsorbent for the excess F component during etching, and can reduce damage to the photoresist. Further, since the protective film deposited on the mask contains iodine, the strength of the protective film is increased, and the etching resistance is improved. Therefore, by including iodine hexafluoride, the selection ratio of the mask to the target of etching can be improved. Further, since the boiling point of iodine hexafluoride used in the present invention is about 5 ° C, it is easy to supply by gas.

Further, as a halogen compound of fluorine and iodine, iodine pentafluoride is also known, but the boiling point of iodine pentafluoride is about 98 ° C, which is troublesome for gas supply. Further, in terms of the fact that the iodine hexafluoride and the iodine pentafluoride are relatively high in choice between the mask and the target to be etched, and the oxidative decomposition of the fluorine-containing unsaturated hydrocarbon can be sufficiently performed, it is also preferable. Use iodine hexafluoride.

In the present invention, since the etching rate of p-Si and SiO _{x is} the same, the laminated film of the p-Si layer and the SiO _x layer can be etched in one step. Further, since the etching rate is the same, the irregularities formed on the pore walls (inner surface) of the laminated film are small, and the laminated film can be formed in the pores in which the upper and lower pores are uniform.

Further, the dry etchant may contain only fluorine-containing unsaturated hydrocarbons and octafluoroiodide. However, in order to reduce cost and increase handling safety, it is preferred to include an inert gas in the dry etchant. As an inert gas, rare gases such as argon, helium, neon, xenon, and xenon can be used. Body or nitrogen. As an inert gas, especially in the case of using Ar, a higher etching rate is obtained by a synergistic effect of a fluorine-containing unsaturated hydrocarbon and iodine hexafluoride. The total ratio of the fluorine-containing unsaturated hydrocarbons and iodine hexafluoride in the dry etchant is preferably from 2 to 95% by volume, more preferably from 10 to 80% by volume, still more preferably from 20 to 60% by volume. Further, it is preferable that the dry etchant substantially contains a fluorine-containing unsaturated hydrocarbon, iodine hexafluoride, and an inert gas.

Further, in order to increase the etching rate of p-Si and SiO _x , a dry etchant may be selected from the group consisting of O ₂ , O ₃ , CO, CO ₂ , COCl ₂ , COF ₂ , F ₂ , NF ₃ , Cl ₂ , Br. An oxidizing gas in the group consisting of ₂ and I ₂ . Further, in order to reduce the amount of F radicals and suppress isotropic etching, a dry etchant may be selected from the group consisting of CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₂ H ₆ , C ₃ H ₄ , C. _a reducing gas in a group consisting of ₃ H ₆ , C ₃ H ₈ , HF, HI, HBr, HCl, NO, NH ₃ and H ₂ .

By laminating the dry etchant of the present invention and applying a bias voltage, the laminated film of SiO _x and p-Si is etched, and etching can be performed in a direction perpendicular to the laminated film, thereby forming a high aspect ratio. Through hole. That is, it is possible to perform etching while maintaining anisotropy. Regarding the generated bias voltage, when IF _{7 having} a high isotropic etching property is used as the oxidizing agent, it is particularly important in reducing side etching, and is preferably 500 V or more, and more preferably 1000 V or more. The higher the bias voltage, the more the side etching can be reduced. On the other hand, if the bias voltage exceeds 10000 V, the damage to the wafer becomes large, which is not preferable.

The gas components contained in the etching gas may be independently introduced into the chamber, or may be previously adjusted to be mixed gas and introduced into the chamber. The total flow rate of the dry etchant introduced into the chamber can be appropriately selected depending on the volume of the reaction chamber and the exhaust capacity of the exhaust portion, taking into consideration the concentration conditions and pressure conditions in the chamber.

In order to obtain a stable plasma and to suppress side etching in order to improve the linearity of ions, the pressure at the time of etching is preferably 5 Pa or less, and particularly preferably 1 Pa or less. On the other hand, if the pressure in the chamber is too low, the free ions become small and a sufficient plasma density cannot be obtained, so it is preferably 0.05 Pa or more.

Further, the substrate temperature at the time of etching is preferably 50 ° C or lower, and particularly preferably 20 ° C or less for anisotropic etching. When the temperature is higher than 50 ° C, the amount of the protective film having a fluorocarbon radical as a main component on the side wall is reduced, and the tendency to perform isotropically is enhanced, and the desired processing accuracy cannot be obtained. Further, there is a case where the mask material such as a resist is significantly etched.

If the efficiency of the component manufacturing process is considered, the etching time is preferably within 30 minutes. Here, the etching time refers to a time during which a plasma is generated in a chamber to cause a dry etchant to react with a sample.

As long as the configuration of the laminated sheet laminated with a p-Si layer and the SiO _x layer, is not particularly limited, but is preferably a p-Si layer and the SiO _x layers are alternately laminated a plurality of layers. The number of layers in the build-up film or the depth of the through-holes formed is not particularly limited, but in terms of the integration effect by the build-up layer, it is preferable that the total number of layers of the p-Si layer and the SiO _x layer is 6 layers. As described above, the depth of the through hole is 0.2 μm or more.

Further, the etching method using the dry etchant of the present invention is not limited to capacitive coupling type plasma (CCP) etching, reactive ion etching (RIE), inductively coupled plasma (ICP) etching, and electron cyclotron resonance (ECR). ) Various etching methods such as plasma etching and microwave etching are performed.

[Examples]

The examples and comparative examples of the present invention are listed below, but the present invention is not limited to the following examples.

[Example 1]

(etching step)

Fig. 3 is a schematic view showing a reaction apparatus 10 used in the examples and comparative examples. In the chamber 11, a lower electrode 14, an upper electrode 15, and a pressure gauge 12 that function as a holding wafer and also function as a mounting table are provided. Further, a gas introduction port 16 is connected to the upper portion of the chamber 11. The chamber 11 can adjust the pressure and can be powered by a high frequency power supply (13.56 MHz) 13 The dry etchant is excited. Thereby, the excited dry etchant can be brought into contact with the sample 18 provided on the lower electrode 14, and the sample 18 can be etched. When the high-frequency power is applied from the high-frequency power source 13 in a state where the dry etchant is introduced, the upper electrode 15 and the lower electrode 14 can be formed by the difference in the moving speed of ions and electrons in the plasma. A DC voltage called a bias voltage is generated. The gas in the chamber 11 is discharged through the gas discharge line 17.

As the sample 18, a tantalum wafer A having a p-Si layer having a thickness of about 1 μm, a tantalum wafer B having a SiO ₂ layer having a thickness of about 1 μm, and an opening having a circular shape having a diameter of 1 μm were coated as an aperture. The tantalum wafer C having a p-Si layer having a thickness of about 1 μm as a mask as a resist for the pattern was placed on a stage cooled to 15 °C. The p-Si layer or the SiO ₂ layer is produced by a CVD (Chemical Vapor Deposition) method.

The dry etchant in which C ₃ HF ₅ (HFO-1225zc) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas were mixed at 10% by volume, 1% by volume, and 89% by volume, respectively, was passed. At 100 sccm, the pressure in the chamber 11 was set to 1 Pa, and high-frequency electric power was applied at 400 W to pulverize the etchant, thereby performing etching. Further, the applied high frequency power had a density of 1.0 W/cm ² and a bias voltage of 500V. Furthermore, since the volume of each of the gases is substantially equal to each other, the volume ratio can also be changed to the mass ratio.

(Evaluation 1: Etching speed ratio)

The etching rate ratio obtained by the following method was used to evaluate whether or not SiO _x and p-Si could be etched at the same rate.

First, the etching rate was determined from the change in thickness before and after etching of the p-Si layer of the germanium wafer A and the SiO ₂ layer of the germanium wafer B. Further, a value obtained by dividing the p-Si etching rate by the SiO ₂ etching rate was determined as the etching rate ratio. When the etching rate ratio of SiO _x to p-Si is in the range of 67% to 150%, it is possible to prevent the occurrence of irregularities formed on the side faces of the through holes of the laminated film, which is preferable.

(Evaluation 2: Aperture ratio)

The cross section of the etched silicon wafer C was observed by a scanning electron microscope, and the shape of the hole formed in the p-Si layer was observed. In order to evaluate the non-uniformity of the pore diameter caused by the occurrence of the side etching, the aperture ratio was calculated according to the following formula (1). Preferably, the aperture ratio is also less than 30%. If the etching is isotropic, the aperture ratio becomes large, and if the etching is anisotropic, the aperture ratio becomes small.

As a result, in Example 1, the etching rate ratio of p-Si to SiO ₂ was 81%, and the aperture ratio was also less than 30%.

[Embodiment 2]

Except that a dry etchant in which C ₃ HF ₅ (HFO-1225zc) as a fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas are mixed at 10% by volume, 2% by volume, and 88% by volume, respectively, Etching was performed under the same conditions as in Example 1.

[Example 3]

In addition to dry mixing of C ₃ H ₂ F ₄ (HFO-1234ze(E)) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas at 10% by volume, 2% by volume, and 88% by volume, respectively Etching was performed under the same conditions as in Example 1 except for the etchant.

[Example 4]

In addition to dry mixing of C ₃ H ₂ F ₄ (HFO-1234ze(E)) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas at 10% by volume, 3% by volume, and 87% by volume, respectively Etching was performed under the same conditions as in Example 1 except for the etchant.

[Example 5]

In addition to using C ₃ H ₂ F ₄ (HFO-1234ze(E)) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas, dry at 10% by volume, 4% by volume, and 86% by volume, respectively. Etching was performed under the same conditions as in Example 1 except for the etchant.

[Embodiment 6]

In addition to dry mixing of C ₃ H ₂ F ₄ (HFO-1234ze(E)) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas at 10% by volume, 5% by volume, and 85% by volume, respectively. Etching was performed under the same conditions as in Example 1 except for the etchant.

[Embodiment 7]

In addition to using C ₃ HF ₃ (3,3,3-trifluoropropyne) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas are mixed at 10% by volume, 3% by volume, and 87% by volume, respectively. Etching was performed under the same conditions as in Example 1 except for the dry etchant.

[Embodiment 8]

In addition to the dry etchant in which C ₃ HF ₃ as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas are mixed at 10% by volume, 4% by volume, and 86% by volume, respectively, with Example 1 Etching is performed under the same conditions.

[Embodiment 9]

In addition to the dry etchant in which C ₃ HF ₃ as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas are mixed at 10% by volume, 5% by volume, and 85% by volume, respectively, with Example 1 Etching is performed under the same conditions.

[Embodiment 10]

In addition to the dry etchant in which C ₃ HF ₃ as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas are mixed at 10% by volume, 8% by volume, and 82% by volume, respectively, with Example 1 Etching is performed under the same conditions.

[Comparative Example 1]

In addition to dry mixing of C ₃ H ₂ F ₄ (HFO-1234ze(E)) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas at 10% by volume, 0.5% by volume, and 89.5% by volume, respectively. Etching was performed under the same conditions as in Example 1 except for the etchant.

[Comparative Example 2]

Dry type using 10% by volume, 11% by volume, and 79% by volume of C ₃ H ₂ F ₄ (HFO-1234ze(E)) as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas, respectively. Etching was performed under the same conditions as in Example 1 except for the etchant.

[Comparative Example 3]

Except that a dry etchant in which CF ₄ as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas were mixed at 10% by volume, 3% by volume, and 87% by volume, respectively, the pressure was set to 5 Pa, Etching was carried out under the same conditions as in Example 1. At this time, the bias voltage is 400V.

[Comparative Example 4]

In addition to the dry etchant in which C ₃ F ₈ as fluorocarbon, IF ₇ as an additive gas, and Ar as an inert gas are mixed at 10% by volume, 4% by volume, and 86% by volume, respectively, with Example 1 Etching is performed under the same conditions.

[Comparative Example 5]

Except that C ₃ H ₂ F ₄ (HFO-1234ze(E)) which is fluorocarbon, ClF ₃ (chlorine trifluoride) as an additive gas, and Ar as an inert gas are respectively 10% by volume and 3% by volume and Etching was performed under the same conditions as in Example 1 except that 87% by volume of the dry etchant was mixed.

[Comparative Example 6]

Except that C ₃ H ₂ F ₄ (HFO-1234ze(E)) which is fluorocarbon, IF ₅ (iodine pentoxide) as an additive gas, and Ar as an inert gas are respectively 10% by volume and 3% by volume and Etching was performed under the same conditions as in Example 1 except that 87% by volume of the dry etchant was mixed.

The results of the respective examples and comparative examples are shown in Table 1. The etching rate in Table 1 is the ratio of the etching rate of p-Si to SiO ₂ , and the aperture ratio of less than 30 means that the maximum aperture ratio is less than 30%.

As described above, in each of the embodiments using a dry etchant comprising a fluorine-containing unsaturated hydrocarbon having a carbon number of 3 and iodine hexafluoride, the etching rate ratio of p-Si to SiO ₂ is 67 to 150%. The aperture ratio is less than 30%. In particular, in the examples 1 to 9 in which the volume of the iodine hexafluoride is 0.1 to 0.5 times the volume of the fluorine-containing unsaturated hydrocarbon contained in the dry etchant, the etching rate ratio is 80 to 120%, especially The etching speed of SiO ₂ and p-Si is the same. Therefore, when the dry etchant of Examples 1 to 9 is applied to a laminated film in which a plurality of layers of SiO _x layer and p-Si layer are alternately laminated, a good through hole can be formed in one etching step.

On the other hand, in Comparative Example 1, since the mixing ratio of the fluorine-containing unsaturated hydrocarbon to the iodine hexafluoride was 1:0.05 by volume ratio, the p-Si etching rate and the SiO ₂ etching rate were insufficient. Further, in Comparative Example 2, since the mixing ratio of the fluorine-containing unsaturated hydrocarbon to the iodine hexafluoride was 1:1.1 by volume ratio, the p-Si etching rate became too fast, and the etching rate ratio became too high. As shown in FIG. 4, when the examples and comparative examples are plotted, the p-Si etching rate and the SiO ₂ etching rate are obtained when the ratio of iodine hexafluoride to fluorine-containing unsaturated hydrocarbon is between 0.1 and 1. The ratio is between 67 and 150%, so that SiO _x and p-Si can be etched at the same rate.

In Comparative Example 3, since CF ₄ as a saturated perfluorocarbon was used as the fluorocarbon, and the bias voltage was also low, the etching rate ratio was too high, and the side etching was increased, and the aperture ratio was expanded to a maximum of 40%. In Comparative Example 4, since C ₃ F ₈ as saturated perfluorocarbon was used as the fluorocarbon, the p-Si etching rate became too fast, and the etching rate ratio became too high. In Comparative Example 5, since ClF _{3 was} used as the additive gas, the oxidative decomposition of the fluorine-containing unsaturated hydrocarbon was not sufficiently performed, and since the reactivity of ClF ₃ and p-Si was poor, etching of either SiO _{2 or} p-Si was performed. Almost none. In Comparative Example 6, since IF _{5 was} used as the additive gas, the oxidative decomposition of the fluorine-containing unsaturated hydrocarbon (C ₃ F ₄ H ₂ ) was not sufficiently performed as compared with Example 4 using IF ₇ , and SiO ₂ and p-Si were used. The etching of either of them was not carried out, but a deposited film of a polymer considered to be fluorocarbon was formed. When Example 4, Comparative Example 5, and Comparative Example 6 were compared, only the types of the added gases were IF ₇ , ClF _{3 ,} and IF ₅ , but as a result, only SiO ₂ and Example ₂ using IF ₇ were used. The etching of both p-Si is sufficiently performed.

[Industrial availability]

The present invention is effective in wiring formation in a three-dimensional integrated component in a semiconductor manufacturing process.

Claims (12)

A dry etching method is characterized in that a dry etchant is plasma-treated and a bias voltage is applied to etch a laminate film of a tantalum oxide layer and a tantalum layer formed with a mask having an opening portion, and the laminate is laminated thereon. a dry etching method for forming a vertical through hole in a film, and the dry etchant is represented by C ₃ H _x F _y (an integer of x=1 to 5, an integer of y=1 to 5, x+y=4 or 6) The fluorine-containing unsaturated hydrocarbon and the iodine hexafluoride, the volume of the iodine-iodide iodine contained in the dry etchant is in the range of 0.1 to 1.0 times the volume of the fluorine-containing unsaturated hydrocarbon contained in the dry etchant. The aperture ratio of the through-hole formed in the laminated film is not more than 30%, and the aperture ratio = (the width of the hole formed in the enamel layer / the width of the opening of the mask - 1) × 100% . The dry etching method of claim 1, wherein the fluorine-containing unsaturated hydrocarbon is at least one selected from the group consisting of C ₃ HF ₅ , C ₃ H ₂ F ₄ , and C ₃ HF ₃ . The dry etching method of claim 1, wherein the bias voltage is 500 V or more. The dry etching method of claim 2, wherein the bias voltage is 500 V or more. The dry etching method according to any one of claims 1 to 4, wherein the dry etchant further comprises an inert gas, and the total ratio of the fluorine-containing unsaturated hydrocarbon and the octafluoroiodide to the dry etchant is 2% by volume or more and 95% by volume or less. The dry etching method of claim 5, wherein the dry etchant substantially comprises only the fluorine-containing unsaturated hydrocarbon, the arsenic hexafluoride, and the inert gas. The dry etching method according to any one of claims 1 to 4, wherein a concentration of the fluorine-containing unsaturated hydrocarbon in the dry etchant is 1% by volume or more and 90% by volume or less. The dry etching method of claim 7, wherein the fluorine-containing fluorochemical agent The concentration of the unsaturated hydrocarbon is 10% by volume or more and 50% by volume or less. The dry etching method according to claim 5, wherein the concentration of the fluorine-containing unsaturated hydrocarbon in the dry etchant is 1% by volume or more and 90% by volume or less. The dry etching method according to claim 9, wherein the concentration of the fluorine-containing unsaturated hydrocarbon in the dry etchant is 10% by volume or more and 50% by volume or less. The dry etching method according to any one of claims 1 to 4, wherein the laminated film is a plurality of tantalum layers and a plurality of tantalum oxide layers are alternately laminated. The dry etching method according to any one of claims 1 to 4, wherein the ratio of the etching rate of the tantalum oxide to the etching rate of the tantalum is in the range of 67 to 150%.