Plasma etching method

Abstract

Provided is a plasma etching method with which it is possible to etch silicon at a high etching rate by using iodine fluoride in the presence of a carbon material or a silicon oxide material. This plasma etching method comprises an etching step for performing plasma etching of silicon in the presence of a carbon material or a silicon oxide material by using plasma obtained by converting an etching gas into plasma. The etching gas contains iodine fluoride and a hydrogen-containing compound. The hydrogen-containing compound is a compound that has a hydrogen atom in a molecule and does not have an oxygen atom in the molecule.

Description

Plasma Etching Method

[0001] The present disclosure relates to a plasma etching method.

[0002] In recent years, as represented by three-dimensional ICs, the stacking of semiconductor chips has been progressing. When stacking chips, in order to electrically connect the stacked chips, holes are formed in a silicon substrate (through-silicon via technology). When forming the holes, it is required to etch silicon at high speed, and currently the Bosch process is the mainstream as the processing method. In the Bosch process, sulfur hexafluoride (SF6) or the like is used as the etching gas. When silicon is etched with sulfur hexafluoride using a carbon material such as photoresist or amorphous carbon as a mask, it is possible to etch silicon at a high etching rate. However, since sulfur hexafluoride has a high global warming potential (GWP), a reduction in its usage amount is required. As etching gases with a low global warming potential, iodine fluorides such as iodine pentafluoride and iodine heptafluoride are known. For example, Patent Document 1 discloses a technique for plasma etching silicon using iodine fluorides such as iodine pentafluoride and iodine heptafluoride.

[0003] Japanese Patent Publication Gazette No. 177209 of 2008

[0004] However, as a result of the study by the present inventors, it has been found that when silicon is etched with iodine fluoride using a carbon material or a silicon oxide material as a mask, the etching rate of silicon may be insufficient. The present disclosure aims to provide a plasma etching method capable of etching silicon at a high etching rate using iodine fluoride in the presence of a carbon material or a silicon oxide material.

[0005] To solve the aforementioned problems, one aspect of the present disclosure is as follows: [1] to

[10] [1] A plasma etching method comprising an etching step of plasma etching silicon in the presence of a carbon material or a silicon oxide material using plasma obtained by plasmaizing an etching gas, wherein the etching gas contains iodine fluoride and a hydrogen-containing compound, and the hydrogen-containing compound is a compound that has a hydrogen atom in its molecule but does not have an oxygen atom in its molecule.

[0006] [2] The plasma etching method according to [1], wherein the hydrogen-containing compound is at least one of hydrogen gas, hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrocarbons, and halogenated hydrocarbons. [3] The plasma etching method according to [2], wherein the halogenated hydrocarbon is at least one of fluoromethane, difluoromethane, trifluoromethane, difluoroethylene, bromofluoroethylene, chlorofluoroethylene, pentafluoropropylene, hexafluorobutene, and heptafluorobutene.

[0007] [4] The plasma etching method according to any one of [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 [1] to [4], wherein the plasma etching is performed under a pressure of 0.2 Pa or more and 133.3 Pa or less. [6] The plasma etching method according to any one of [1] to [5], wherein the source power applied when the etching gas is plasma-generated is 3000 W or less.

[0008] [7] The plasma etching method according to any one of [1] to [6], wherein the member to be etched having silicon is placed on a lower electrode supporting the member to be etched, and the plasma etching is performed while applying a bias power of 0 W to 1500 W to the lower electrode. [8] The plasma etching method according to any one of [1] to [7], wherein the plasma etching is performed at a temperature of -100°C to 250°C.

[0009] [9] The plasma etching method according to any one of [1] to [8], wherein the etching gas further contains a fluorocarbon.

[10] The plasma etching method according to [9], wherein the fluorocarbon is at least one of tetrafluoromethane, hexafluoroethane, octafluorobutane, hexafluorobutadiene, and octafluorocyclobutane.

[0010] According to this disclosure, it is possible to etch silicon at a high etching rate using iodine fluoride in the presence of a carbon material or a silicon oxide material.

[0011] This is a schematic diagram of an example of a plasma etching apparatus illustrating one embodiment of the plasma etching method relating to this disclosure.

[0012] One embodiment of the present disclosure is described below. This embodiment is merely an example of the present disclosure, and the disclosure is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modified or improved forms may also be included in the present disclosure.

[0013] The plasma etching method according to this embodiment is a plasma etching method comprising an etching step of plasma etching silicon (Si) in the presence of a carbon material (C) or a silicon oxide material (SiO) using plasma obtained by plasmaizing an etching gas, wherein the etching gas contains iodine fluoride and a hydrogen-containing compound, and the hydrogen-containing compound is a compound that has a hydrogen atom (H) in its molecule but does not have an oxygen atom (O) in its molecule.

[0014] By using an etching gas containing iodine fluoride and a hydrogen-containing compound, it is possible to etch silicon at a high etching rate. The inventors deduce the reason for this as follows: When plasma etching is performed using an etching gas containing a hydrogen-containing compound, the iodine molecules (I2) generated from iodine fluoride react with the hydrogen-containing compound, thereby suppressing the reaction between iodine molecules and carbon or oxygen. As a result, inhibition of silicon etching by reaction products (carbon iodide or iodine oxide) between iodine molecules and carbon or oxygen becomes less likely. Therefore, according to the plasma etching method of this embodiment, it is possible to etch silicon at a high etching rate using iodine fluoride in the presence of a carbon material or a silicon oxide material.

[0015] Therefore, by applying the plasma etching method according to this embodiment to a semiconductor manufacturing process, it is possible to manufacture semiconductors with high productivity. Furthermore, since the plasma etching method according to this embodiment uses iodine fluoride, which has a low global warming potential, as the etching gas, it can contribute to the reduction of greenhouse gases.

[0016] The plasma etching method according to this embodiment will be described in more detail. Plasma etching according to this embodiment can be performed using a plasma etching apparatus. The plasma source in the plasma etching apparatus is not particularly limited, but examples include 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). The plasma etching apparatus shown in Figure 1, which will be described in detail later, is a plasma etching apparatus that uses ICP as a plasma source.

[0017] [Etching Gas] The etching gas contains iodine fluoride and a hydrogen-containing compound. The mixing ratio of iodine fluoride and the hydrogen-containing compound is not particularly limited, but the ratio of the hydrogen-containing compound content to the iodine fluoride content is preferably more than 0% by volume and 200% by volume or less.

[0018] If the ratio of hydrogen-containing compounds to iodine fluoride content exceeds 0 volume%, the reaction between iodine molecules and carbon or oxygen is suppressed by the hydrogen-containing compounds, making it possible to etch silicon at a high etching rate in the presence of carbon materials or silicon oxide materials. Furthermore, if the ratio of hydrogen-containing compounds to iodine fluoride content is 200 volume% or less, the etching of silicon by iodine fluoride proceeds sufficiently, making it possible to etch silicon at a high etching rate in the presence of carbon materials or silicon oxide materials.

[0019] The lower limit of the ratio of the hydrogen-containing compound content to the iodine fluoride content may be 30% by volume or more, or 50% by volume or more. The upper limit of the ratio of the hydrogen-containing compound content to the iodine fluoride content may be 100% by volume or less, or 150% by volume or less. The ratio of the hydrogen-containing compound content to the iodine fluoride content may be 30% by volume or more and 150% by volume or less, or 50% by volume or more and 100% by volume or less.

[0020] The etching gas may consist solely of iodine fluoride and hydrogen-containing compounds, but may also contain components other than iodine fluoride and hydrogen-containing compounds. Examples of components other than iodine fluoride and hydrogen-containing compounds include at least one of fluorocarbons and inert gases.

[0021] In other words, the etching gas may further contain fluorocarbons. When the etching gas contains fluorocarbons, the sidewall protection of the etching is improved (the sidewalls of the holes formed by etching tend to be formed substantially vertically). The type of fluorocarbon in the plasma etching method according to this embodiment is not particularly limited, but the fluorocarbon may be at least one of tetrafluoromethane (CF4), hexafluoroethane (C2F6), octafluorobutane (C3F8), hexafluorobutadiene (C4F6), and octafluorocyclobutane (C4F8).

[0022] Furthermore, as described above, the etching gas may also contain an inert gas. The type of inert gas is not particularly limited, but examples include helium (He), argon (Ar), neon (Ne), krypton (Kr), xenon (Xe), and nitrogen gas (N2). These inert gases may be used individually or in combination of two or more.

[0023] The amount of inert gas used is not particularly limited, but the ratio of the inert gas content to the iodine fluoride content in the etching gas is preferably more than 0 volume% and 100 volume% or less. If the ratio of the inert gas content to the iodine fluoride content is more than 0 volume%, the plasma can be further stabilized. Also, if the ratio of the inert gas content to the iodine fluoride content is 100 volume% or less, the etching of silicon by iodine fluoride proceeds sufficiently, making it possible to etch silicon at a high etching rate in the presence of carbon material or silicon oxide material. The ratio of the inert gas content to the iodine fluoride content may be more than 0 volume% and 50 volume% or less, or more than 0 volume% and 20 volume% or less.

[0024] The amount of etching gas used in the plasma etching method according to this embodiment is not particularly limited, but for example, the total flow rate of etching gas to the chamber in which plasma etching is performed in a plasma etching apparatus should be adjusted according to the volume of the chamber, the exhaust capacity, and the pressure inside the chamber.

[0025] [Iodine Fluoride] The type of iodine fluoride used in the plasma etching method according to this embodiment is not particularly limited, but the iodine fluoride may be at least one of iodine pentafluoride (IF5) and iodine heptafluoride (IF7).

[0026] [Hydrogen-containing compounds] The type of hydrogen-containing compound used in the plasma etching method according to this embodiment is not particularly limited, as long as it is a compound that contains a hydrogen atom in its molecule but does not contain an oxygen atom. The hydrogen-containing compound may be at least one of hydrogen gas (H2), hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrocarbons, and halogenated hydrocarbons.

[0027] The hydrocarbon may be at least one of methane (CH4), ethane (C2H6), and propane (C3H8). The halogenated hydrocarbon may be at least one of fluoromethane (CH3F), difluoromethane (CH2F2), trifluoromethane (CHF3), difluoroethylene (C2H2F2), bromofluoroethylene (C2H2BrF), chlorofluoroethylene (C2H2ClF), pentafluoropropylene (C3HF5), hexafluorobutene (C4H2F6), and heptafluorobutene (C4HF7). Some of the above halogenated hydrocarbons have isomers, but any isomer can be used. For example, bromofluoroethylene may be 1-bromo-1-fluoroethylene or 1-bromo-2-fluoroethylene. Similarly, chlorofluoroethylene may be 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene.

[0028] [Carbon materials, silicon oxide materials] The plasma etching method according to this embodiment is a method for plasma etching silicon with iodine fluoride in the presence of a carbon material or a silicon oxide material. Examples of carbon materials include photoresists and amorphous carbon used as masks when etching a silicon-containing etchable member (e.g., a silicon substrate). Examples of silicon oxide materials include SiO2, SiON, SiOC, SiOCH, etc.

[0029] Another example of a carbon material is a component that makes up the chamber in which plasma etching is performed. If a component that makes up the chamber contains carbon and is placed inside the chamber, then plasma etching of silicon will be performed inside the chamber in the presence of the carbon material. Similarly, even if a component is not part of the chamber, if a carbon material is present inside the chamber, then plasma etching of silicon will be performed inside the chamber in the presence of the carbon material. Another example of a silicon oxide material is a component that is composed of quartz. Similar to the other example of a carbon material, if a component that is composed of quartz is placed inside the chamber, then plasma etching of silicon will be performed inside the chamber in the presence of the silicon oxide material.

[0030] [Pressure for Plasma Etching] In the plasma etching method according to this embodiment, plasma etching may be performed under a pressure of 0.2 Pa or more and 133.3 Pa or less. At the above pressure, fluorine radical dissociation is likely to occur, and carbon iodide is unlikely to be formed. The lower limit of the pressure may be 3 Pa or more, or 6.67 Pa or more. The upper limit of the pressure may be 16 Pa or less, or 40 Pa or less. The pressure may be 3 Pa or more and 40 Pa or less, or 6.67 Pa or more and 16 Pa or less.

[0031] [Plasma Etching Temperature] In the plasma etching method according to this embodiment, plasma etching may be performed at a temperature of -100°C to 250°C. For example, plasma etching may be performed by controlling the temperature of the etchable member having silicon to within the above range. At the above temperature, the protection of the sidewalls during etching is good. The temperature may be -100°C to 50°C, or -100°C to 0°C.

[0032] [Source Power for Plasma Etching] In a plasma etching apparatus, for example, by applying high-frequency source power to an RF (radio frequency) coil to form an electric field and a magnetic field, the etching gas can be converted into plasma and plasma can be generated.

[0033] In the plasma etching method according to this embodiment, the magnitude of the source power is not particularly limited, but the source power applied when plasmaizing the etching gas may be 3000W or less. With the above source power, the dissociation of iodine fluoride is promoted, making it possible to etch silicon at a higher etching rate. The source power may be greater than 0W and less than or equal to 3000W, or between 1000W and 3000W, or between 2000W and 3000W.

[0034] [Bias Power for Plasma Etching] In the plasma etching method according to this embodiment, the member to be etched having silicon may be placed on a lower electrode supporting the member to be etched, and plasma etching may be performed while applying a bias power of 0W to 1500W to the lower electrode. With the above bias power, the etching selectivity between the mask and silicon is excellent, and the silicon can be etched at a high etching rate. The magnitude of the bias power applied to the lower electrode may be greater than 0W and 1500W or less, greater than 0W and 300W or less, greater than 0W and 300W or less, greater than 0W and 100W or less, or greater than 0W and 100W or less.

[0035] The following describes an example of performing plasma etching on a silicon-containing component using the plasma etching apparatus shown in Figure 1. The plasma etching apparatus in Figure 1 is a plasma etching apparatus that uses ICP as the plasma source. First, the plasma etching apparatus in Figure 1 will be described.

[0036] The plasma etching apparatus shown in Figure 1 comprises a chamber 1 in which plasma etching is performed, a lower electrode 2 that supports the etched member 20 inside the chamber 1, a bias power supply (not shown) that applies bias power to the lower electrode 2, an RF coil 15 that forms an electric and magnetic field inside the chamber 1 to plasmaize the etching gas, a source power supply (not shown) that applies high-frequency source power to the RF coil 15, a vacuum pump 13 that reduces the pressure inside the chamber 1, a pressure gauge 14 that measures the pressure inside the chamber 1, a sensor 16 that captures plasma emission generated in conjunction with plasma generation, and a spectrometer 17 that spectrally analyzes the plasma emission captured by the sensor 16 to monitor the temporal changes in plasma emission.

[0037] The etched member 20 is a silicon substrate on which a pattern of photoresist or silicon oxide is formed on its surface, and the photoresist is made of a carbon-containing material. For example, a CCD (Charge-Coupled Device) image sensor can be used as the sensor 16. However, instead of providing the sensor 16 and the spectrometer 17, a viewing window may be provided in the chamber 1, and the inside of the chamber 1 may be visually observed through the viewing window to confirm the temporal change in plasma emission.

[0038] Furthermore, the chamber 1 is equipped with an etching gas supply unit that supplies etching gas to the inside of the chamber 1. The etching gas supply unit includes an iodine fluoride gas supply unit 3 that supplies iodine fluoride gas, a hydrogen-containing compound gas supply unit 4 that supplies hydrogen-containing compound gas, an etching gas supply pipe 11 that connects the iodine fluoride gas supply unit 3 and the chamber 1, and a hydrogen-containing compound gas supply pipe 12 that connects the hydrogen-containing compound gas supply unit 4 to the middle part of the etching gas supply pipe 11.

[0039] When supplying a mixed gas of iodine fluoride gas and a hydrogen-containing compound gas as the etching gas, iodine fluoride gas is sent from the iodine fluoride gas supply unit 3 to the etching gas supply piping 11, and hydrogen-containing compound gas is sent from the hydrogen-containing compound gas supply unit 4 to the etching gas supply piping 11 via the hydrogen-containing compound gas supply piping 12. As a result, the iodine fluoride gas and the hydrogen-containing compound gas are mixed in the middle section of the etching gas supply piping 11 to form a mixed gas, which is then supplied to the chamber 1 via the etching gas supply piping 11.

[0040] When performing plasma etching using such a plasma etching apparatus, the workpiece to be etched 20 is placed on the lower electrode 2 located inside the chamber 1. After reducing the pressure inside the chamber 1 to 1 Pa or more and 50 Pa or less using a vacuum pump 13, etching gas is supplied to the inside of the chamber 1 by an etching gas supply unit. When high-frequency (for example, 13.56 MHz) source power is applied to the RF coil 15, an electric and magnetic field is formed inside the chamber 1, accelerating electrons. These accelerated electrons collide with iodine fluoride molecules in the etching gas, generating new ions and electrons, resulting in a discharge and the formation of plasma. The generation of plasma can be confirmed using a sensor 16 and a spectrometer 17.

[0041] The supply amount of the etching gas to the chamber 1 and the concentration of iodine fluoride in the etching gas (mixed gas) can be adjusted by controlling the flow rates of the iodine fluoride gas and the hydrogen-containing compound gas respectively with mass flow controllers (not shown) installed in the etching gas supply pipe 11 and the hydrogen-containing compound gas supply pipe 12.

[0042] Examples and comparative examples are shown below to explain the present disclosure in more detail. (Reference Example) Using an ICP etching apparatus RIE-200iP manufactured by Sumco Corporation having substantially the same configuration as the plasma etching apparatus of FIG. 1, plasma etching of the etched member was performed. This etched member is a silicon wafer made of crystalline silicon with a diameter of 300 mm, on which a polysilicon film in a square shape with a side length of 30 mm is attached. The polysilicon film was formed by chemical vapor deposition.

[0043] Also, the internal volume of the chamber is 46000 cm 3 and the etching gas is a mixed gas of iodine heptafluoride gas and argon. After adjusting the flow rate of the iodine heptafluoride gas to 100 sccm and the flow rate of argon to 45 sccm by the mass flow controller, the pipes of both gases were joined on the downstream side of the chamber to mix the iodine heptafluoride gas and argon, and the mixed gas was circulated into the chamber. Here, sccm is the volume flow rate (cm 3 ) per minute standardized under the conditions of 0 °C and 1 atm.

[0044] With the internal pressure of the chamber at 6.67 Pa, the source power at 500 W, the bias power at 100 W, and the temperature of the etched member at 30 °C, the flow rates of the iodine heptafluoride gas, argon, pressure, source power, and bias power were constantly monitored, and plasma etching was performed for 5 seconds while confirming that there was no difference between the respective set values and execution values. The results are shown in Table 1. Table 1 shows the film thickness of the polysilicon film before etching, the film thickness after etching, and the etching rate.

[0045] Incidentally, the film thickness of the polysilicon film was measured using a reflectance spectroscopic film thickness meter F20 manufactured by Filmetrics. Also, the etching rate of the polysilicon film was calculated by subtracting the film thickness after etching from the film thickness before etching and dividing the result by the etching time.

[0046]

[0047] (Comparative Example 1) Plasma etching was performed in the same manner as in the reference example, except that the silicon wafer made of crystalline silicon to which the polysilicon film was attached was changed to a silicon wafer made of crystalline silicon coated with i-line photoresist over the entire surface. That is, the etched member was obtained by applying i-line photoresist over the entire surface of a silicon wafer made of crystalline silicon and then attaching a polysilicon film on the i-line photoresist. Similar to the reference example, the film thickness of the polysilicon film before etching and after etching was measured, and the etching rate of the polysilicon film was calculated. The results are shown in Table 1.

[0048] (Example 1) Plasma etching was performed in the same manner as in Comparative Example 1, except that a mixed gas of iodine heptafluoride gas, bromofluoroethylene, and argon was used as the etching gas. The flow rate of iodine heptafluoride gas 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.

[0049] As can be seen from the results shown in Table 1, the etching rate of the polysilicon film was higher compared to Comparative Example 1. This is presumably because the formation of carbon iodide, which inhibits the etching of the polysilicon film, was suppressed by bromofluoroethylene. That is, the hydrogen atoms contained in bromofluoroethylene are dissociated by plasma formation and react with iodine molecules dissociated from iodine heptafluoride to form hydrogen iodide, thus suppressing the formation of carbon iodide.

[0050] (Example 2) Plasma etching was performed in the same manner as in Comparative Example 1, except that a mixed gas of iodine heptafluoride, hydrogen bromide, and argon was used as the etching gas. The flow rate of iodine heptafluoride gas was 100 sccm, the flow rate of hydrogen bromide was 100 sccm, and the flow rate of argon was 45 sccm. The results are shown in Table 1.

[0051] As can be seen from the results shown in Table 1, the etching rate of the polysilicon film was higher compared to Comparative Example 1. This is thought to be because the formation of carbon iodide, which inhibits the etching of the polysilicon film, was suppressed by hydrogen bromide. In other words, it is thought that the hydrogen atoms in hydrogen bromide dissociated due to plasma formation and reacted with iodine molecules dissociated from iodine heptafluoride to form hydrogen iodide, thereby suppressing the formation of carbon iodide.

[0052] (Example 3) Plasma etching was performed in the same manner as in Example 2, except that the pressure was 13.33 Pa. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polysilicon film was higher than in Example 2. This is thought to be because the increase in pressure increased the amount of fluorine radicals dissociated in the plasma, and in addition, the reaction between hydrogen atoms and iodine atoms was activated, which suppressed the formation of carbon iodide that inhibits the etching of the polysilicon film. Furthermore, the etching rate of the polysilicon film in Example 3 was also higher than that of Comparative Example 3, which will be described later.

[0053] (Comparative Example 2) Plasma etching was performed in the same manner as in the reference example, except that 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 polysilicon film was lower compared to the reference example. This is thought to be because sulfur hexafluoride has a lower fluorine content per molecule compared to iodine heptafluoride, resulting in a lower density of fluorine radicals after plasma dissociation.

[0054] (Comparative Example 3) Plasma etching was performed in the same manner as in Comparative Example 1, except that 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 polysilicon film was significantly higher compared to Comparative Examples 1 and 2.

[0055] The difference in etching rates between Comparative Example 2 and Comparative Example 3 is thought to be due to the difference in fluorine radical consumption between crystalline silicon and i-line photoresist. Crystalline silicon consumes a large amount of fluorine radicals because its reaction with fluorine radicals is active, thus decreasing the fluorine concentration around the polysilicon film. On the other hand, photoresist consumes less fluorine radicals, so the fluorine concentration around the polysilicon film increases. As a result, a difference in etching rates occurs.

[0056] The difference in etching rates between Comparative Example 1 and Comparative Example 3 is thought to be due to the presence or absence of carbon iodide, which inhibits the etching of the polysilicon film. In Comparative Example 1, carbon iodide, a reaction product of iodine dissociated from iodine heptafluoride in plasma and carbon, inhibits the etching of the polysilicon film. However, in Comparative Example 3, carbon iodide is not generated from sulfur hexafluoride. Therefore, it is thought that the etching rate was higher in Comparative Example 3 than in Comparative Example 1.

[0057] (Comparative Example 4) Plasma etching was performed in the same manner as in Comparative Example 3, except that a mixed gas of sulfur hexafluoride, bromofluoroethylene, and argon was used as the etching gas. 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.

[0058] As can be seen from the results shown in Table 1, the etching rate of the polysilicon film was lower compared to Comparative Example 3. This is because, unlike Comparative Example 1, sulfur hexafluoride does not generate etching-inhibiting components (carbon iodide) due to the action of the photoresist, and therefore there is no factor that improves the etching rate of the polysilicon film. On the other hand, bromofluoroethylene generates deposition components such as CHx and CFx through plasma dissociation, which are factors that inhibit etching. It is thought that this effect was particularly pronounced in Comparative Example 4.

[0059] (Comparative Example 5) Plasma etching was performed in the same manner as in Comparative Example 3, except that a mixed gas of sulfur hexafluoride, hydrogen bromide, and argon was used as the etching gas. The flow rate of sulfur hexafluoride was 100 sccm, the flow rate of hydrogen bromide was 100 sccm, and the flow rate of argon was 45 sccm. The results are shown in Table 1.

[0060] As can be seen from the results shown in Table 1, the etching rate of the polysilicon film was lower compared to Comparative Example 3. This is because, unlike Comparative Example 1, sulfur hexafluoride does not generate etching-inhibiting components (carbon iodide) due to the action of the photoresist, and therefore there is no factor that improves the etching rate of the polysilicon film. On the other hand, hydrogen atoms have the property of reacting with fluorine atoms to form hydrogen fluoride, which leads to a decrease in the concentration of fluorine radicals. In Comparative Example 5, it is thought that the etching rate decreased due to this action.

[0061] (Comparative Example 6) Plasma etching was performed in the same manner as in the Reference Example, except that the crystalline silicon wafer to which the polysilicon film was attached was changed to a crystalline silicon wafer with a silicon dioxide (SiO2) film deposited over its entire surface. That is, the material to be etched was a crystalline silicon wafer with a silicon dioxide (SiO2) film deposited over its entire surface, and then a polysilicon film attached on top of the silicon dioxide (SiO2) film. As in the Reference Example, the film thickness of the polysilicon film before etching and after etching were measured, and the etching rate of the polysilicon film was calculated. The results are shown in Table 1.

[0062] (Example 4) Plasma etching was performed in the same manner as in Comparative Example 6, except that a mixed gas of iodine heptafluoride, hydrogen bromide, and argon was used as the etching gas. The flow rate of iodine heptafluoride gas was 100 sccm, the flow rate of hydrogen bromide was 100 sccm, and the flow rate of argon was 45 sccm. The results are shown in Table 1.

[0063] As can be seen from the results shown in Table 1, the etching rate of the polysilicon film was higher compared to Comparative Example 6. This is thought to be because hydrogen bromide suppressed the formation of iodine oxide, a reaction product of silicon dioxide and iodine that inhibits the etching of the polysilicon film. In other words, it is thought that the hydrogen atoms in hydrogen bromide dissociated due to plasma formation and reacted with iodine molecules dissociated from iodine heptafluoride to form hydrogen iodide, thereby suppressing the formation of iodine oxide, a reaction product with silicon dioxide.

[0064] (Example 5) Plasma etching was performed in the same manner as in Example 4, except that the pressure was 13.33 Pa. The results are shown in Table 1. As can be seen from the results in Table 1, the etching rate of the polysilicon film was higher compared to Example 4. This is thought to be because the increase in pressure increased the amount of fluorine radicals dissociated in the plasma, and in addition, the reaction between hydrogen atoms and iodine atoms was activated, which suppressed the formation of iodide oxide, a reaction product of silicon dioxide that inhibits the etching of the polysilicon film.

[0065] (Comparative Example 7) Plasma etching was performed in the same manner as in Comparative Example 6, except that 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 polysilicon film was significantly higher compared to Comparative Examples 2 and 6.

[0066] The difference in etching rates between Comparative Example 2 and Comparative Example 7 is thought to be due to the difference in fluorine radical consumption between crystalline silicon and silicon dioxide. Crystalline silicon consumes a large amount of fluorine radicals because its reaction with fluorine radicals is active, thus decreasing the fluorine concentration around the polysilicon film. On the other hand, silicon dioxide consumes less fluorine radicals, so the fluorine concentration around the polysilicon film increases. As a result, a difference in etching rates occurs.

[0067] (Comparative Example 8) Plasma etching was performed in the same manner as in Comparative Example 7, except that a mixed gas of sulfur hexafluoride, hydrogen bromide, and argon was used as the etching gas. The flow rate of sulfur hexafluoride was 100 sccm, the flow rate of hydrogen bromide was 100 sccm, and the flow rate of argon was 45 sccm. The results are shown in Table 1.

[0068] As can be seen from the results shown in Table 1, the etching rate of the polysilicon film was lower compared to Comparative Example 7. Unlike Comparative Example 6, sulfur hexafluoride does not generate etching-inhibiting components (iodine oxide) through interaction with silicon dioxide, so there is no factor that improves the etching rate of the polysilicon film. On the other hand, hydrogen atoms have the property of reacting with fluorine atoms to form hydrogen fluoride, which leads to a decrease in the concentration of fluorine radicals. In Comparative Example 8, it is thought that the etching rate decreased due to this action.

[0069] 1... Chamber 2... Lower electrode 3... Iodine fluoride gas supply unit 4... Hydrogen-containing compound gas supply unit 11... Etching gas supply piping 12... Hydrogen-containing compound gas supply piping 13... Vacuum pump 14... Pressure gauge 15... RF coil 16... Sensor 17... Spectrometer 20... Material to be etched

Claims

1. A plasma etching method comprising an etching step of plasma etching silicon in the presence of a carbon material or a silicon oxide material using plasma obtained by plasmaizing an etching gas, wherein the etching gas contains iodine fluoride and a hydrogen-containing compound, and the hydrogen-containing compound is a compound that has a hydrogen atom in its molecule but does not have an oxygen atom in its molecule.

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

3. The plasma etching method according to claim 2, wherein the halogenated hydrocarbon is at least one of fluoromethane, 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 under 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 the etching gas is converted into plasma is 3000 W or less.

7. The plasma etching method according to any one of claims 1 to 3, wherein the member to be etched having silicon is placed on a lower electrode supporting the member to be etched, and the plasma etching is performed while applying a bias power of 0 W to 1500 W 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 of -100°C or higher and 250°C or lower.

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

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

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