Plasma etching method

Abstract

A plasma etching method is provided that enables the etching of silicon at high etching rates using iodine fluoride in the presence of carbon or silicon oxide materials. The plasma etching method comprises an etching step that uses plasma obtained by ionizing an etching gas to perform plasma etching of silicon in the presence of carbon or silicon oxide materials. The etching gas contains iodine fluoride and a hydrogen-containing compound, which is a compound having hydrogen atoms within its molecule and no oxygen atoms within its molecule.

Description

Technical Field

[0001] This disclosure relates to a plasma etching method. Background Technology

[0002] In recent years, the development of semiconductor chip stacking has been exemplified by 3D ICs. In stacking chips, through-silicon vias (TSVs) are formed in the silicon substrate to electrically connect the stacked chips. Forming these vias requires high-speed etching of silicon, and Bosch's process has become the mainstream method for this process.

[0003] In Bosch's processes, sulfur hexafluoride (SF6) is used as an etching gas. If carbon materials such as photoresist or amorphous carbon are used as masks, sulfur hexafluoride can be used to etch silicon at high rates. However, due to its high global warming potential (GWP), the amount of sulfur hexafluoride used must be reduced.

[0004] Iodine fluorides such as iodine pentafluoride and iodine heptafluoride are known as etching gases with low global warming potential. For example, Patent Document 1 discloses a technique for plasma etching of silicon using iodine fluorides such as iodine pentafluoride and iodine heptafluoride.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Publication No. 177209, 2008 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, through the research of the inventors, it has been shown that if carbon or silicon oxide materials are used as masks and silicon is etched with iodine fluoride, the etching rate of silicon sometimes becomes insufficient.

[0010] The present disclosure aims to provide a plasma etching method that can use iodine fluoride to etch silicon at a high etching rate in the presence of carbon materials or silicon oxide materials.

[0011] Methods for solving problems

[0012] To address the aforementioned issues, one solution disclosed herein is as follows [1] to

[10] .

[0013] [1] A plasma etching method comprising an etching step of performing plasma etching of silicon in the presence of a carbon material or a silicon oxide material using plasma obtained by plasmaizing an etching gas.

[0014] The aforementioned etching gas contains iodine fluoride and hydrogen-containing compounds.

[0015] The aforementioned hydrogen-containing compounds are compounds that have hydrogen atoms within the molecule but no oxygen atoms within the molecule.

[0016] [2] According to the plasma etching method described in [1], the hydrogen-containing compound is at least one of hydrogen, hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrocarbon and halogenated hydrocarbon.

[0017] [3] According to the plasma etching method described in [2], the above-mentioned halogenated hydrocarbon is at least one of monofluoromethane, difluoromethane, trifluoromethane, difluoroethylene, bromofluoroethylene, chlorofluoroethylene, pentafluoropropylene, hexafluorobutene and heptafluorobutene.

[0018] [4] In any one of the plasma etching methods described in [1] to [3], the iodine fluoride is at least one of iodine pentafluoride and iodine heptafluoride.

[0019] [5] The plasma etching method according to any one of [1] to [4] is performed at a pressure of 0.2 Pa or more and 133.3 Pa or less.

[0020] [6] In any one of the plasma etching methods described in [1] to [5], the source power applied when plasmaifying the etching gas is 3000W or less.

[0021] [7] According to any one of [1] to [6], the etched component having the above-described silicon is placed on a lower electrode supporting the etched component, and the above-described plasma etching is performed while applying a bias power of 0W or more and 1500W or less to the lower electrode.

[0022] [8] The plasma etching method according to any one of [1] to [7] is performed at a temperature of -100°C or higher and 250°C or lower.

[0023] [9] In any one of the plasma etching methods [1] to [8], the etching gas further contains a fluorocarbon compound.

[0024]

[10] According to the plasma etching method described in [9], the fluorocarbon compound is at least one of tetrafluoromethane, hexafluoroethane, octafluorobutane, hexafluorobutadiene and octafluorocyclobutane.

[0025] The effects of the invention

[0026] According to this disclosure, silicon can be etched at a high etching rate using iodine fluoride in the presence of carbon materials or silicon oxide materials. Attached Figure Description

[0027] Figure 1 A schematic diagram illustrating an example of a plasma etching apparatus for one embodiment of the plasma etching method disclosed herein. Detailed Implementation

[0028] The following describes one embodiment of this disclosure. It should be noted that this embodiment shows one example of this disclosure, and this disclosure is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modifications or improvements can also be included in this disclosure.

[0029] The plasma etching method described in this embodiment is a plasma etching method that includes an etching process of performing plasma etching of silicon (Si) in the presence of a carbon material (C) or a silicon oxide material (SiO) using plasma obtained by plasmaizing an etching gas. The etching gas contains iodine fluoride and a hydrogen-containing compound, which is a compound having hydrogen atoms (H) in its molecule and no oxygen atoms (O) in its molecule.

[0030] By using an etching gas containing iodine fluoride and hydrogen-containing compounds, silicon can be etched at a high etching rate. The inventors reason as follows: If plasma etching is performed using an etching gas containing hydrogen-containing compounds, the iodine molecules (I₂) generated from iodine fluoride react with the hydrogen-containing compounds, thus suppressing the reaction of iodine molecules with carbon or oxygen. As a result, it is less likely that silicon etching will be hindered by reaction products (iodides of carbon or oxides of iodine) formed by iodine molecules reacting with carbon or oxygen. Therefore, according to the plasma etching method of this embodiment, silicon can be etched at a high etching rate using iodine fluoride in the presence of carbon or silicon oxide materials.

[0031] Therefore, if the plasma etching method described in this embodiment is applied to the semiconductor manufacturing process, semiconductors can be manufactured with high productivity.

[0032] Furthermore, the plasma etching method described in this embodiment can contribute to reducing global warming gases because it uses iodine fluoride, which has a low global warming potential, as the etching gas.

[0033] The plasma etching method described in this embodiment will be further explained in detail.

[0034] The plasma etching using the plasma etching method described in this embodiment can be performed using a plasma etching apparatus. The plasma source in the plasma etching apparatus is not particularly limited, and examples include, for instance, high-frequency discharge plasmas such as inductively coupled plasma (ICP) and capacitively coupled plasma (CCP), and microwave discharge plasmas such as electron cyclotron resonance plasma (ECRP). Details will follow later. Figure 1 The plasma etching apparatus is a plasma etching apparatus that uses ICP as the plasma source.

[0035] [Etching Gas]

[0036] The etching gas contains iodine fluoride and hydrogen-containing compounds. The mixing ratio of iodine fluoride to hydrogen-containing compounds is not particularly limited, but the ratio of hydrogen-containing compounds to iodine fluoride is preferably greater than 0% by volume and less than 200% by volume.

[0037] If the ratio of hydrogen-containing compounds to iodine fluoride exceeds 0% by volume, the reaction of iodine molecules with carbon or oxygen is suppressed by the hydrogen-containing compounds, thus enabling silicon to be etched at a high etching rate in the presence of carbon or silicon oxide materials. Furthermore, if the ratio of hydrogen-containing compounds to iodine fluoride is less than 200% by volume, etching of silicon with iodine fluoride proceeds sufficiently, thus enabling silicon to be etched at a high etching rate in the presence of carbon or silicon oxide materials.

[0038] The lower limit of the ratio of hydrogen-containing compound content to iodine fluoride content can be 30% by volume or more, or 50% by volume or more. Furthermore, the upper limit of the ratio of hydrogen-containing compound content to iodine fluoride content can be 100% by volume or less, or 150% by volume or less. Moreover, the ratio of hydrogen-containing compound content to iodine fluoride content can be 30% by volume or more and 150% by volume, or 50% by volume or more and 100% by volume or less.

[0039] The etching gas can be formed solely from iodine fluoride and hydrogen-containing compounds, but may further contain components other than iodine fluoride and hydrogen-containing compounds. Examples of components other than iodine fluoride and hydrogen-containing compounds include, for example, at least one of fluorocarbons and inert gases.

[0040] That is, the etching gas can further contain fluorocarbons. If the etching gas contains fluorocarbons, the sidewall protection of the etched holes becomes good (the sidewalls of the holes formed by etching are easily formed approximately vertically).

[0041] The type of fluorocarbon compound used in the plasma etching method described in this embodiment is not particularly limited. The fluorocarbon compound can be at least one of tetrafluoromethane (CF4), hexafluoroethane (C2F6), octafluorobutane (C3F8), hexafluorobutadiene (C4F6), and octafluorocyclobutane (C4F8).

[0042] Furthermore, as described above, the etching gas may further contain inert gases. There are no particular limitations on the types of inert gases; examples include helium (He), argon (Ar), neon (Ne), krypton (Kr), xenon (Xe), and nitrogen (N2). These inert gases may be used individually or in combination of two or more.

[0043] There is no particular limitation on the amount of inactive gas used, but the ratio of the inactive gas content to the iodine fluoride content in the etching gas is preferably greater than 0% by volume and less than 100% by volume. If the ratio of the inactive gas content to the iodine fluoride content is greater than 0% by volume, the plasma can be more stabilized. Furthermore, if the ratio of the inactive gas content to the iodine fluoride content is less than 100% by volume, the etching of silicon with iodine fluoride is sufficiently performed, thus enabling the etching of silicon at a high etching rate in the presence of carbon or silicon oxide materials. The ratio of the inactive gas content to the iodine fluoride content can be greater than 0% by volume and less than 50% by volume, or greater than 0% by volume and less than 20% by volume.

[0044] The amount of etching gas used in the plasma etching method described in this embodiment is not particularly limited. For example, the total flow rate of the etching gas into the chamber in which plasma etching is performed in the plasma etching apparatus can be adjusted according to the volume of the chamber, the exhaust capacity, and the pressure inside the chamber.

[0045] Iodine fluoride

[0046] The type of iodine fluoride used in the plasma etching method described in this embodiment is not particularly limited, and the iodine fluoride may be at least one of iodine pentafluoride (IF5) and iodine heptafluoride (IF7).

[0047] [Hydrogen-containing compounds]

[0048] The type of hydrogen-containing compound used in the plasma etching method described in this embodiment is not particularly limited, as long as it is a compound having hydrogen atoms within its molecule and no oxygen atoms within its molecule. The hydrogen-containing compound can be at least one of hydrogen (H2), hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrocarbons, and halogenated hydrocarbons.

[0049] The hydrocarbon can be at least one of methane (CH4), ethane (C2H6), and propane (C3H8).

[0050] The haloalkane can be at least one of monofluoromethane (CH3F), difluoromethane (CH2F2), trifluoromethane (CHF3), difluoroethylene (C2H2F2), bromofluoroethylene (C2H2BrF), chlorofluoroethylene (C2H2ClF), pentafluoropropylene (C3HF5), hexafluorobutene (C4H2F6), and heptafluorobutene (C4HF7). Isomers are sometimes present in the above haloalkane, and any isomer can be used. For example, bromofluoroethylene can be 1-bromo-1-fluoroethylene or 1-bromo-2-fluoroethylene. Similarly, chlorofluoroethylene can be 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene.

[0051] [Carbon materials, silicon dioxide materials]

[0052] The plasma etching method described in this embodiment is a method for plasma etching silicon using iodine fluoride in the presence of a carbon material or a silicon oxide material. Examples of carbon materials include photoresists used as masks when etching a silicon-containing etched component (e.g., a silicon substrate), amorphous carbon, etc. Examples of silicon oxide materials include SiO2, SiON, SiOC, SiOCH, etc.

[0053] Furthermore, as another example of carbon materials, components constituting a chamber for plasma etching can be cited. When the components constituting the chamber contain carbon and are disposed inside the chamber, silicon plasma etching is performed inside the chamber in the presence of the carbon material. Similarly, even if a component is not constituting the chamber, but carbon material is present inside the chamber, silicon plasma etching is also performed inside the chamber in the presence of the carbon material.

[0054] Furthermore, as another example of silicon oxide materials, components composed of quartz can be cited. Similar to another example of carbon materials, when a component composed of quartz is disposed inside the chamber, plasma etching of silicon is performed in the presence of silicon oxide materials.

[0055] [Plasma etching pressure]

[0056] In the plasma etching method of this embodiment, plasma etching can be performed at a pressure of 0.2 Pa or more and 133.3 Pa or less. At such pressures, fluorine radicals readily dissociate, and carbon iodides are less likely to form. The lower limit of the pressure can be 3 Pa or more, or 6.67 Pa or more. Furthermore, the upper limit of the pressure can be 16 Pa or less, or 40 Pa or less. Moreover, the pressure can be 3 Pa or more and 40 Pa or less, or 6.67 Pa or more and 16 Pa or less.

[0057] [Plasma etching temperature]

[0058] In the plasma etching method of this embodiment, plasma etching can be performed at a temperature of -100°C to 250°C. For example, the silicon-containing etched component can be controlled at a temperature within the above range for plasma etching. At the above temperature, the sidewall protection of the etched component becomes good. The temperature can be -100°C to 50°C or -100°C to 0°C.

[0059] [Source power of plasma etching]

[0060] In plasma etching apparatus, for example, an electric and magnetic field is formed by applying high-frequency source power to an RF (radio frequency) coil, thereby plasma can be generated by plasmaifying the etching gas.

[0061] In the plasma etching method of this embodiment, the source power is not particularly limited, and the source power applied when ionizing the etching gas can be 3000W or less. If the source power is as described above, the dissociation of iodine fluoride is promoted, thus enabling silicon to be etched at a higher etching rate. The source power can be more than 0W and less than 3000W, more than 1000W and less than 3000W, or more than 2000W and less than 3000W.

[0062] [Bias power of plasma etching]

[0063] In the plasma etching method of this embodiment, a silicon-containing component to be etched can be placed on a lower electrode supporting the component, and plasma etching is performed while applying a bias power of 0W or more and 1500W or less to the lower electrode. With the aforementioned bias power, the etching selectivity between the mask and silicon is excellent, and silicon can be etched at a high etching rate.

[0064] The bias power applied to the lower electrode can be greater than 0W and less than 1500W, greater than 0W and less than 300W, greater than 0W and less than 300W, greater than 0W and less than 100W, or greater than 0W and less than 100W.

[0065] The following is about the use Figure 1 The plasma etching apparatus shown illustrates an example of plasma etching of a silicon-containing component. Figure 1 The plasma etching apparatus is a plasma etching apparatus that uses ICP as the plasma source. First, for... Figure 1 The plasma etching apparatus will be described.

[0066] Figure 1 The plasma etching apparatus includes a chamber 1 for performing plasma etching inside, a lower electrode 2 supporting the etched component 20 inside the chamber 1, a bias power supply (not shown) for applying bias power to the lower electrode 2, an RF coil 15 forming an electric and magnetic field inside the chamber 1 for plasmaifying the etching gas, a source power supply (not shown) for applying high-frequency source power to the RF coil 15, a vacuum pump 13 for depressurizing the inside of the chamber 1, a pressure gauge 14 for measuring the pressure inside the chamber 1, a sensor 16 for acquiring plasma emission that occurs with the generation of plasma, and a spectrometer 17 for monitoring the time change of plasma emission by spectrorifying the plasma emission acquired by the sensor 16.

[0067] The etched component 20 is a silicon substrate on which a pattern of photoresist or silicon oxide is formed on its surface, the photoresist being formed of a carbon-containing material. As the sensor 16, for example, a CCD (charge-coupled device) image sensor can be used. However, instead of providing the sensor 16 and the beam splitter 17, an observation window can be provided in the chamber 1 to visually observe the interior of the chamber 1 and confirm the temporal changes in plasma emission.

[0068] Furthermore, chamber 1 has an etching gas supply unit inside which etching gas is supplied. The etching gas supply unit includes an iodine fluoride gas supply unit 3 for supplying iodine fluoride gas, a hydrogen-containing gas supply unit 4 for supplying hydrogen-containing gas, an etching gas supply pipe 11 connecting the iodine fluoride gas supply unit 3 to chamber 1, and a hydrogen-containing gas supply pipe 12 connecting the hydrogen-containing gas supply unit 4 at the middle of the etching gas supply pipe 11.

[0069] Furthermore, when a mixture of iodine fluoride gas and hydrogen-containing compound gas is supplied as the etching gas, iodine fluoride gas is sent from the iodine fluoride gas supply unit 3 to the etching gas supply pipe 11, and hydrogen-containing compound gas is sent from the hydrogen-containing compound gas supply unit 4 to the etching gas supply pipe 11 via the hydrogen-containing compound gas supply pipe 12. As a result, the iodine fluoride gas and the hydrogen-containing compound gas are mixed in the middle of the etching gas supply pipe 11 to form a mixed gas, which is then supplied to the chamber 1 via the etching gas supply pipe 11.

[0070] When performing plasma etching using such a plasma etching apparatus, the component to be etched 20 is placed on the lower electrode 2 disposed inside the chamber 1. After the pressure inside the chamber 1 is reduced to more than 1 Pa and less than 50 Pa by the vacuum pump 13, etching gas is supplied to the inside of the chamber 1 through the etching gas supply unit. Furthermore, if a high-frequency (e.g., 13.56 MHz) source power is applied to the RF coil 15, an electric field and a magnetic field are formed inside the chamber 1, thereby accelerating electrons. These accelerated electrons collide with iodine fluoride molecules in the etching gas to generate new ions and electrons, resulting in a discharge and the formation of plasma. The generation of plasma can be confirmed using the sensor 16 and the spectrometer 17.

[0071] The amount of etching gas supplied to chamber 1 and the concentration of iodine fluoride in the etching gas (mixed gas) can be adjusted by controlling the flow rates of iodine fluoride gas and hydrogen-containing gas respectively using mass flow controllers (not shown) installed in the etching gas supply pipe 11 and the hydrogen-containing gas supply pipe 12.

[0072] Example

[0073] The following examples and comparative examples illustrate this disclosure in more detail.

[0074] (Example for reference)

[0075] Use and Figure 1 The plasma etching apparatus has a roughly the same structure. The RIE-200iP ICP etching apparatus manufactured by the company performed plasma etching on the component to be etched. The component to be etched consisted of a 30mm square polycrystalline silicon film with a side length of 30mm attached to a 300mm diameter crystalline silicon wafer. The polycrystalline silicon film was formed using a chemical vapor deposition method.

[0076] In addition, the internal volume of the chamber is 46,000 cm³. 3The etching gas is a mixture of iodine heptafluoride and argon. After adjusting the flow rate of iodine heptafluoride to 100 sccm and the flow rate of argon to 45 sccm using a mass flow controller, the two gases are combined downstream of the chamber to mix them, allowing the mixture to flow into the chamber. Here, sccm is the normalized volumetric flow rate (cm³) per minute at 0°C and 1 atmosphere. 3 ).

[0077] The internal pressure of the chamber was set to 6.67 Pa, the source power to 500 W, the bias power to 100 W, and the temperature of the component to be etched to 30 °C. The flow rates of iodine heptafluoride gas, argon gas, pressure, source power, and bias power were constantly monitored to ensure that the set values ​​matched the actual values. Plasma etching was then performed for 5 seconds. The results are shown in Table 1. Table 1 shows the polycrystalline silicon film thickness before etching, the film thickness after etching, and the etching rate.

[0078] It should be noted that the thickness of the polycrystalline silicon film is measured using... The company's reflectivity spectrophotometer F20 was used. Furthermore, the etching rate of the polycrystalline silicon film was calculated by subtracting the thickness after etching from the thickness before etching, and then dividing that by the etching time.

[0079] [Table 1]

[0080]

[0081] (Comparative Example 1)

[0082] The crystalline silicon wafer with the polysilicon film bonded was replaced with a crystalline silicon wafer with an I-ray photoresist coating covering its entire surface. Except for this difference, plasma etching was performed in the same manner as in the reference example. Specifically, after coating the entire surface of the crystalline silicon wafer with I-ray photoresist, a polysilicon film was bonded onto the I-ray photoresist. As in the reference example, the thickness of the polysilicon film before and after etching was measured, and the etching rate of the polysilicon film was calculated. The results are shown in Table 1.

[0083] (Example 1)

[0084] A mixture of iodine heptafluoride, bromofluoroethylene, and argon was used as the etching gas, and plasma etching was performed in the same manner as in Comparative Example 1, except that the flow rate of iodine heptafluoride was 100 sccm, the flow rate of bromofluoroethylene was 40 sccm, and the flow rate of argon was 45 sccm. The results are shown in Table 1.

[0085] As shown in Table 1, the etching rate of the polycrystalline silicon film is higher compared to Comparative Example 1. This can be attributed to the suppression of carbon iodide formation, which hinders the etching of the polycrystalline silicon film, by bromofluoroethylene. Specifically, it can be assumed that the hydrogen atoms in bromofluoroethylene dissociate through plasma treatment, reacting with iodine molecules dissociated from heptafluoride to form hydrogen iodide, thus suppressing the formation of carbon iodides.

[0086] (Example 2)

[0087] A mixture of iodine heptafluoride, hydrogen bromide, and argon was used as the etching gas, and plasma etching was performed in the same manner as in Comparative Example 1, except that the flow rates of iodine heptafluoride, hydrogen bromide, and argon were 100 sccm and 45 sccm, respectively. The results are shown in Table 1.

[0088] As shown in Table 1, the etching rate of the polycrystalline silicon film is higher compared to Comparative Example 1. This can be attributed to the suppression of carbon iodide formation, which hinders the etching of the polycrystalline silicon film, by hydrogen bromide. Specifically, it can be assumed that the hydrogen atoms in hydrogen bromide dissociate through plasma treatment and react with iodine molecules dissociated from iodine heptafluoride to form hydrogen iodide, thus suppressing the formation of carbon iodides.

[0089] (Example 3)

[0090] Plasma etching was performed at a pressure of 13.33 Pa, except for this. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polycrystalline silicon film was higher compared to Example 2. This can be attributed to the increased dissociation of fluorine radicals in the plasma due to the increased pressure, which, in addition, activated the reaction between hydrogen and iodine atoms, thus suppressing the formation of carbon iodides that hinder the etching of the polycrystalline silicon film. It should be noted that the etching rate of the polycrystalline silicon film in Example 3 was also higher than that in Comparative Example 3 described later.

[0091] (Comparative Example 2)

[0092] Plasma etching was performed using sulfur hexafluoride gas instead of iodine heptafluoride gas, but otherwise the same procedure as in the reference example. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polycrystalline silicon film is lower compared to the reference example. This can be attributed to the lower fluorine content per molecule of sulfur hexafluoride compared to iodine heptafluoride, resulting in a lower density of fluorine radicals after plasma dissociation.

[0093] (Comparative Example 3)

[0094] Plasma etching was performed in the same manner as in Comparative Example 1, except that the iodine heptafluoride gas was replaced with sulfur hexafluoride gas. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polycrystalline silicon film is significantly higher compared to Comparative Examples 1 and 2.

[0095] The difference in etching rates between Comparative Example 2 and Comparative Example 3 can be attributed to the difference in the amount of fluorine radicals consumed in crystalline silicon and the i-ray photoresist. Crystalline silicon, being more reactive with fluorine radicals, consumes more fluorine radicals, resulting in a lower fluorine concentration around the polycrystalline silicon film. Conversely, the photoresist consumes fewer fluorine radicals, leading to an increased fluorine concentration around the polycrystalline silicon film. This results in the difference in etching rates.

[0096] The difference in etching rates between Comparative Example 1 and Comparative Example 3 can be attributed to the presence or absence of carbon iodides, which hinder the etching of the polycrystalline silicon film. In Comparative Example 1, carbon iodides, as products of the reaction between iodine and carbon dissociated from iodine heptafluoride plasma, hinder the etching of the polycrystalline silicon film. In Comparative Example 3, carbon iodides are not generated from sulfur hexafluoride. Therefore, it can be considered that the etching rate of Comparative Example 3 is higher than that of Comparative Example 1.

[0097] (Comparative Example 4)

[0098] A mixture of sulfur hexafluoride, bromofluoroethylene, and argon was used as the etching gas, and plasma etching was performed in the same manner as in Comparative Example 3, except that the flow rate of sulfur hexafluoride was 100 sccm, the flow rate of bromofluoroethylene was 40 sccm, and the flow rate of argon was 45 sccm. The results are shown in Table 1.

[0099] As shown in Table 1, the etching rate of the polycrystalline silicon film is lower compared to Comparative Example 3. This differs from Comparative Example 1, where sulfur hexafluoride does not generate etching-inhibiting components (carbon iodides) through the action of photoresist, thus eliminating factors that increase the etching rate of the polycrystalline silicon film. On the other hand, bromofluoroethylene generates deposited components such as CHx and CFx through plasma dissociation, which hinder etching. In Comparative Example 4, this effect can be considered significant.

[0100] (Comparative Example 5)

[0101] A mixture of sulfur hexafluoride, hydrogen bromide, and argon was used as the etching gas, and plasma etching was performed in the same manner as in Comparative Example 3, except that the flow rates of sulfur hexafluoride, hydrogen bromide, and argon were 100 sccm and 45 sccm, respectively. The results are shown in Table 1.

[0102] As shown in Table 1, the etching rate of the polycrystalline silicon film is lower compared to Comparative Example 3. This differs from Comparative Example 1, where, for sulfur hexafluoride, no etching-inhibiting component (carbon iodide) is generated through the action of the photoresist, thus eliminating factors that increase the etching rate of the polycrystalline silicon film. On the other hand, hydrogen atoms have the property of reacting with fluorine atoms to form hydrogen fluoride, leading to a decrease in the concentration of fluorine radicals. In Comparative Example 5, it can be assumed that this effect reduces the etching rate.

[0103] (Comparative Example 6)

[0104] The crystalline silicon wafer with a polycrystalline silicon film bonded to it was replaced with a crystalline silicon wafer with a silicon dioxide (SiO2) film deposited on its entire surface. Except for this difference, plasma etching was performed in the same manner as in the reference example. Specifically, after a silicon dioxide (SiO2) film was deposited on the entire surface of the crystalline silicon wafer, a polycrystalline silicon film was bonded onto the SiO2 film. As in the reference example, the thickness of the polycrystalline silicon film before and after etching was measured, and the etching rate of the polycrystalline silicon film was calculated. The results are shown in Table 1.

[0105] (Example 4)

[0106] A mixture of iodine heptafluoride, hydrogen bromide, and argon was used as the etching gas, and plasma etching was performed in the same manner as in Comparative Example 6, except that the flow rates of iodine heptafluoride, hydrogen bromide, and argon were 100 sccm and 45 sccm, respectively. The results are shown in Table 1.

[0107] As shown in Table 1, the etching rate of the polycrystalline silicon film is higher compared to Comparative Example 6. This can be attributed to the suppression of iodine oxide, a product of the reaction between silicon dioxide and iodine that hinders the etching of the polycrystalline silicon film, by hydrogen bromide. Specifically, it can be assumed that the hydrogen atoms in hydrogen bromide dissociate through plasma treatment and react with iodine molecules dissociated from iodine heptafluoride to form hydrogen iodide, thus suppressing the formation of iodine oxide, a product of the reaction with silicon dioxide.

[0108] (Example 5)

[0109] Plasma etching was performed at a pressure of 13.33 Pa, except for this, in the same manner as in Example 4. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polycrystalline silicon film is higher compared to Example 4. This can be attributed to the increased dissociation of fluorine radicals in the plasma due to the increased pressure, which in turn activates the reaction between hydrogen and iodine atoms, thus suppressing the formation of iodine oxide, a reactant of silicon dioxide, which hinders the etching of the polycrystalline silicon film.

[0110] (Comparative Example 7)

[0111] Plasma etching was performed in the same manner as in Comparative Example 6, except that the iodine heptafluoride gas was replaced with sulfur hexafluoride gas. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polycrystalline silicon film is significantly higher compared to Comparative Examples 2 and 6.

[0112] The difference in etching rates between Comparative Example 2 and Comparative Example 7 can be attributed to the difference in the amount of fluorine radicals consumed in crystalline silicon and silicon dioxide. Crystalline silicon, being more reactive with fluorine radicals, consumes more fluorine radicals, resulting in a lower fluorine concentration around the polycrystalline silicon film. Conversely, silicon dioxide, with its lower fluorine radical consumption, exhibits a higher fluorine concentration around the polycrystalline silicon film. This difference in etching rates leads to the difference in etching rates.

[0113] (Comparative Example 8)

[0114] A mixture of sulfur hexafluoride, hydrogen bromide, and argon was used as the etching gas, and plasma etching was performed in the same manner as in Comparative Example 7, except that the flow rates of sulfur hexafluoride, hydrogen bromide, and argon were 100 sccm and 45 sccm, respectively. The results are shown in Table 1.

[0115] As shown in Table 1, the etching rate of the polycrystalline silicon film is lower compared to Comparative Example 7. This differs from Comparative Example 6, where, for sulfur hexafluoride, no etching-inhibiting component (iodine oxide) is generated through its reaction with silicon dioxide, thus eliminating factors that could increase the etching rate of the polycrystalline silicon film. On the other hand, hydrogen atoms have the property of reacting with fluorine atoms to form hydrogen fluoride, leading to a decrease in the concentration of fluorine radicals. In Comparative Example 8, it can be assumed that the etching rate was reduced through this interaction.

[0116] Explanation of symbols

[0117] 1··· Chamber

[0118] 2. Lower electrode

[0119] 3. Iodine Fluoride Gas Supply Department

[0120] 4. Hydrogen-containing compound gas supply department

[0121] 11. Piping for Etching Gas Supply

[0122] 12. Piping for supplying hydrogen-containing compounds

[0123] 13··· Vacuum Pump

[0124] 14. Pressure gauge

[0125] 15···RF Coil

[0126] 16··· Sensors

[0127] 17···Spectrum Splitter

[0128] 20···Etched components.

Claims

1. A plasma etching method comprising an etching step of performing plasma etching of silicon in the presence of a carbon material or a silicon oxide material using plasma obtained by plasmaifying an etching gas. The etching gas contains iodine fluoride and hydrogen-containing compounds. The hydrogen-containing compound is a compound that has hydrogen atoms in its molecule but no oxygen atoms in its molecule.

2. The plasma etching method according to claim 1, wherein the hydrogen-containing compound is at least one of hydrogen, hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrocarbons, and halogenated hydrocarbons.

3. The plasma etching method according to claim 2, wherein the halocarbon is at least one of monofluoromethane, difluoromethane, trifluoromethane, difluoroethylene, bromofluoroethylene, chlorofluoroethylene, pentafluoropropylene, hexafluorobutene, and heptafluorobutene.

4. The plasma etching method according to any one of claims 1 to 3, wherein the iodine fluoride is at least one of iodine pentafluoride and iodine heptafluoride.

5. The plasma etching method according to any one of claims 1 to 3, wherein the plasma etching is performed at a pressure of 0.2 Pa or more and 133.3 Pa or less.

6. The plasma etching method according to any one of claims 1 to 3, wherein the source power applied when plasmaifying the etching gas is 3000W or less.

7. The plasma etching method according to any one of claims 1 to 3, wherein the etched component having the silicon is placed on a lower electrode supporting the etched component, and the plasma etching is performed while applying a bias power of 0W or more and 1500W or less to the lower electrode.

8. The plasma etching method according to any one of claims 1 to 3, wherein the plasma etching is performed at a temperature above -100°C and below 250°C.

9. The plasma etching method according to any one of claims 1 to 3, wherein the etching gas further contains a fluorocarbon compound.

10. The plasma etching method according to claim 9, wherein the fluorocarbon compound is at least one selected from tetrafluoromethane, hexafluoroethane, octafluorobutane, hexafluorobutadiene, and octafluorocyclobutane.

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