JP2012186221A - Etching method, etching apparatus, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of concurrently satisfying a high etching selection ratio of a silicon nitride film to a silicon oxide film and a high etching rate of the silicon nitride film.SOLUTION: An etching method includes a preheat process that supplies heated HSOto a substrate in which a silicon nitride film and a silicon oxide film are exposed on its surface to heat the substrate and an etching process that then supplies mixed liquid of heated HSO, at least any one of HF, NHF and NHHF, and HO to the substrate.

Description

  The present invention relates to a technique for selectively etching a silicon nitride film with respect to a substrate on which a silicon nitride film and a silicon oxide film are exposed.

One of the processes for manufacturing a semiconductor device is a wet etching process in which a silicon nitride film formed on the surface of a substrate such as a semiconductor wafer is etched with an etching solution. In performing the wet etching process, there are many cases where the silicon nitride film has to be selectively etched without almost etching the silicon oxide film. In such a case, conventionally, a phosphoric acid solution (H ₃ PO ₄ ) was used. However, recently, it is necessary to provide a dedicated supply system for phosphoric acid, to prevent contamination of clean room atmosphere by phosphoric acid, and high-purity phosphoric acid is expensive. Then, an etchant that does not use phosphoric acid has been used.

Patent Document 1 describes an etching solution containing sulfuric acid, fluoride, and water as an example of an etching solution that does not use phosphoric acid. For the purpose of manufacturing an electronic device such as a semiconductor, It is also described that it is preferable to use hydrofluoric acid and ammonium fluoride as the fluoride. In an etching solution containing sulfuric acid, fluoride, and water, the ratio of the etching amount of the silicon nitride film to the etching amount of the silicon oxide film (hereinafter referred to as “the etching amount of hydrofluoric acid” in the etching solution is reduced). It is known that the “SiN / SiO ₂ selection ratio” can also be increased.

However, if the fluoride concentration in the etching solution is too low, the etching rate of the silicon nitride film becomes unacceptably low industrially. For this reason, it is difficult to achieve both a high SiN / SiO ₂ selection ratio and high productivity.

JP 2010-147304 A

  The present invention provides a technique that can achieve both a high etching selectivity of a silicon nitride film to a silicon oxide film and a high etching rate of the silicon nitride film.

The present invention provides a preheating step of heating the substrate by supplying heated H ₂ SO ₄ to the substrate with the silicon nitride film and the silicon oxide film exposed on the surface, and then heating the substrate to the heated H ₂ SO ₄ and an etching step of supplying a mixed liquid of at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O.

Further, the present invention is configured so that heated H ₂ SO ₄ can be supplied to a substrate holding unit that holds the substrate, and the substrate held by the substrate holding unit, and the heated H A chemical supply mechanism configured to supply a mixed liquid of ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O, and the chemical supply A preheating step of heating the substrate by supplying heated H ₂ SO ₄ to the substrate with the silicon nitride film and the silicon oxide film exposed on the surface by controlling the mechanism, and then heating the substrate to the heated H _An etching step of supplying a mixed liquid of ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ , and H ₂ O; Prepared To provide an etching apparatus.

Furthermore, the present invention is a storage medium for recording a computer-readable program that constitutes a control unit of an etching apparatus so that the etching apparatus can supply heated H ₂ SO ₄ to a substrate. Configured and configured to supply a mixed liquid of heated H ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O. When the computer executes the program, the control unit controls the etching apparatus so that the substrate with the silicon nitride film and the silicon oxide film exposed to the surface is heated to H _2. a preheating step of supplying SO ₄ to heat the substrate, then the substrate, and _H 2 _SO 4 which is heated, HF, NH ₄ F and N ₄ and at least one of HF _2, and the etching step of supplying a mixed liquid of H 2 _O, to the execution, provides a storage medium.

According to the present invention, the concentration of HF, NH ₄ F or NH ₄ HF _{2 in} the mixed liquid constituting the etchant is considerably reduced by preheating the substrate with heated H ₂ SO ₄ prior to the etching step. However, it is possible to minimize a decrease in the etching rate of the silicon nitride film.

It is a schematic block diagram which shows one Embodiment of an etching apparatus. It is a schematic plan view of the etching apparatus shown in FIG. It is a schematic sectional drawing which shows an example of the structure of a board | substrate to be etched. It is a schematic sectional drawing which shows another example of the structure of a board | substrate to be etched.

  Hereinafter, preferred embodiments of the present invention will be described.

  First, the configuration of the wet etching apparatus will be described. The wet etching apparatus has a spin chuck 10 that rotates while holding a substrate, in this example, a semiconductor wafer W substantially horizontally. The spin chuck 10 includes a substrate holding unit 14 that holds the substrate in a horizontal posture by a plurality of holding members 12 that hold the peripheral edge of the substrate, and a rotation driving unit 16 that drives the substrate holding unit 14 to rotate. . Around the substrate holding unit 14, a cup 18 is provided for receiving the processing liquid scattered from the wafer W. The substrate holder 14 and the cup 18 are relatively movable in the vertical direction so that the wafer W can be transferred between the substrate transfer arm (not shown) and the substrate holder 14.

The wet etching apparatus further includes a chemical nozzle 20 for supplying chemical liquid to the wafer W. A chemical solution is supplied from the chemical solution supply mechanism 22 to the chemical solution nozzle 20. The chemical liquid supply mechanism 26 diluted at least one of a sulfuric acid supply system (first chemical liquid supply system) 30 and HF, NH ₄ F, and NH ₄ HF ₂ with water, here DIW (pure water). It has a supply system 40 (second chemical solution supply system) for supplying an aqueous solution (hereinafter referred to as “HF chemical solution supply system 40” for the sake of simplicity).

The sulfuric acid supply system 30 will be described. A circulation pipe 32 is connected to a sulfuric acid tank 31 for storing concentrated sulfuric acid (here, H ₂ SO _{4 having} a concentration of 98%, remaining water (H ₂ O)), and a pump 33 and a heater 34 are provided in the circulation pipe 32. Has been. Sulfuric acid is constantly circulated in the circulation pipe 32, and the sulfuric acid in the sulfuric acid tank 31 is maintained at a predetermined temperature, for example, 150 ° C or higher, preferably 170 ° C or higher, by being heated by the heater 34. The sulfuric acid temperature is preferably as high as possible as long as it does not cause a problem level of damage to the components of the sulfuric acid supply system 30. As an example, the temperature of sulfuric acid is 170 ° C. The sulfuric acid tank 31 is connected to the chemical solution nozzle 20 via a sulfuric acid pipe line 35, and an appropriate flow rate regulator such as a flow rate adjusting valve 36 and an on-off valve 37 are provided in the sulfuric acid pipe line 35. . The sulfuric acid stored in the sulfuric acid tank 31 is not limited to concentrated sulfuric acid (90% or more of H ₂ SO ₄ , remaining water), but dilute sulfuric acid (89% or less of H ₂ SO ₄ , remaining water). It may be. However, if the amount of water contained in dilute sulfuric acid increases, the boiling point decreases and it becomes difficult to use as a preheat liquid. Therefore, even when dilute sulfuric acid is used, it is preferable to increase the content of H ₂ SO ₄ . When dilute sulfuric acid is used, the water content in the HF chemical solution described later is reduced according to the water content in the dilute sulfuric acid.

The HF chemical solution supply system 40 will be described. The HF chemical tank 41 stores an aqueous solution in which at least one of HF, NH ₄ F, and NH ₄ HF ₂ is diluted with water (H ₂ O), here DIW (pure water). As a specific example of the HF chemical solution stored in the HF chemical solution tank 41, (a) an aqueous solution containing 30.8% NH ₄ HF ₂ and 8.9% HF by weight (provided by Stella Chemifa Corporation) A solution obtained by further diluting 250 to 500 times with water (pure water), and (b) an aqueous solution containing 7.1% by weight of NH ₄ HF ₂ and 15.4% of NH ₄ F Although the solution etc. which were further diluted 50-200 times with water (pure water) (equivalent to LAL500 provided by Stella Chemifa Corporation) can be illustrated, it is not limited to these. The HF chemical liquid tank 41 is connected to the chemical liquid nozzle 20 via an HF chemical liquid pipeline 42, and an appropriate flow rate regulator such as a flow rate adjustment valve 43, an on-off valve 44, and the like are connected to the HF chemical liquid pipeline 42. Is installed. The HF-based chemical liquid pipeline 42 merges with the sulfuric acid pipeline 35 at a junction near the chemical nozzle 20.

  The chemical nozzle 20 is driven by the nozzle moving mechanism 50. The nozzle moving mechanism 50 includes a guide rail 51, a moving mechanism 52 with a built-in driving mechanism that can move along the guide rail 51, a base end of the nozzle moving mechanism 50 attached to the moving body 52, and a drug nozzle 20 held at the tip thereof. And a nozzle arm 53. The nozzle moving mechanism 50 can move the chemical nozzle 20 between a position just above the center of the wafer W held by the substrate holding unit 14 and a position just above the periphery of the wafer W. The chemical solution nozzle 20 can also be moved to a standby position outside the cup 18 in plan view.

  Further, the wet etching apparatus has a rinse nozzle 22 for supplying pure water (DIW) to the wafer W for rinsing processing, and an IPA nozzle 24 for supplying isopropyl alcohol (IPA) to the wafer W for drying processing. ing. DIW is supplied to the rinse nozzle 22 from a DIW supply source through a DIW pipe line 22c in which an appropriate flow rate regulator, for example, a flow rate regulating valve 22a and an on-off valve 22b are interposed. IPA is supplied to the IPA nozzle 24 from an IPA supply source through an IPA pipe 24c provided with a suitable flow regulator, for example, a flow regulating valve 24a and an on-off valve 24b. The rinse nozzle 22 and the IPA nozzle 24 are also attached to the nozzle arm 53. Therefore, the rinse nozzle 22 and the IPA nozzle 24 can also be moved between a position directly above the center of the wafer W held by the substrate holder 14 and a position directly above the periphery of the wafer W, and It can also be moved to a standby position outside the cup 18.

  The wet etching apparatus has a control unit 100 that controls the overall operation of the wet etching apparatus. The control unit 100 controls the operation of all functional parts of the wet etching apparatus (for example, the rotation drive unit 16, the valves 36, 37, 43, and 44 of the chemical solution supply mechanism 22 and the nozzle moving mechanism 50). The control unit 100 can be realized by, for example, a general-purpose computer as hardware and a program (such as an apparatus control program and a processing recipe) for operating the computer as software. The software is stored in a storage medium such as a hard disk drive fixedly provided in the computer, or is stored in a storage medium that is detachably set in the computer such as a CDROM, DVD, or flash memory. Such a storage medium is indicated by reference numeral 101. The processor 102 calls a predetermined processing recipe from the storage medium 101 based on an instruction from a user interface (not shown) or the like as necessary, and executes each processing component of the wet etching apparatus under the control of the control unit 100. It operates to perform a predetermined process.

  Although the illustrated substrate holding portion 14 of the spin chuck 10 is of a so-called mechanical chuck type in which the peripheral portion of the wafer W is held by the movable holding member 12, the present invention is not limited to this. It may be of a so-called vacuum chuck type that vacuum-sucks the central portion of the back surface of the. The illustrated nozzle moving mechanism 50 is a so-called linear motion type that translates the nozzle, but is a so-called swing arm type in which the nozzle is held at the tip of an arm that rotates about a vertical axis. It may be. In the illustrated example, the three nozzles 20, 22, and 24 are held by a common arm. However, they may be held by separate arms and moved independently.

  Next, a series of steps of a liquid processing method including an etching process performed using the wet etching apparatus will be described. In the series of steps described below, the control unit 100 controls each functional component of the wet etching apparatus so that various process parameters defined in the process recipe stored in the storage medium 102 are realized. It is executed by.

The wafer W to be processed has an SiN film (silicon nitride film) and an SiO ₂ film (silicon oxide film) exposed on the surface (“surface” includes the inner surface of a hole or a recess formed in the wafer). The SiN film needs to be selectively removed. As a cross-sectional structure of the wafer W to be processed, as schematically shown in FIG. 3A, a SiO ₂ film and a SiN film, which are thermal oxide films, are laminated on a silicon substrate (Si), An example in which a trench is formed is illustrated. In this case, the SiN film is selectively etched from the state shown in FIG. 3A to the state shown in FIG. As another cross-sectional structure of the wafer W to be processed, as shown schematically in FIG. 4, both the SiO ₂ film and the SiN film are exposed on the upper surface of the wafer W, which is the surface of the wafer W. It may be.

  First, the wafer W having the cross-sectional structure as described above is loaded into a wet etching apparatus by a transfer arm (not shown) and held on the substrate holding unit 14 of the spin chuck 10.

[Preheating process]
Next, the chemical nozzle 20 is moved directly above the center of the wafer W by the nozzle moving mechanism 50. Further, the rotation driving unit 16 rotates the wafer W at a predetermined rotation number, for example, 100 rpm. In this state, the flow rate adjustment valve 36 of the sulfuric acid supply system 30 is adjusted to a predetermined opening and the on-off valve 37 is opened, whereby concentrated sulfuric acid heated from the chemical nozzle 20 to a predetermined temperature, for example, 170 ° C., has a predetermined flow rate, for example. 1 L (1000 mL) / min is supplied to the center of the wafer W, and the supplied concentrated sulfuric acid diffuses to the peripheral edge of the wafer by centrifugal force. At this time, concentrated sulfuric acid does not effectively attack both the SiN film and the SiO ₂ film on the surface of the wafer W, and acts exclusively as a heating medium for heating the wafer W. The supply of concentrated sulfuric acid is continued for a predetermined time, for example, 10 seconds, whereby the wafer W is preheated.

[Etching process]
Next, while the wafer is continuously rotated and the supply of concentrated sulfuric acid by the sulfuric acid supply system 30 is continued, the flow rate adjustment valve 43 of the HF chemical solution supply system 40 is adjusted to a predetermined opening and the on-off valve 44 is be opened. As a result, the HF chemical solution (which is at normal temperature) flows through the HF chemical solution supply line 42, merges with the concentrated sulfuric acid flowing through the sulfuric acid line 35, and mixes the concentrated sulfuric acid and the HF chemical solution. Is supplied to the chemical nozzle 20 as an etchant. As an example, the HF chemical solution is an aqueous solution obtained by further diluting an aqueous solution containing 30.8% NH ₄ HF ₂ and 8.9% HF by weight 500 times with pure water, and the flow rate of concentrated sulfuric acid. Is 1 L / min, and the flow rate of the HF chemical is 250 mL / min. The temperature of the etching solution obtained by mixing the concentrated sulfuric acid and the HF chemical solution rises to, for example, 207 ° C. due to the heat generated by the mixing, and such a high temperature etching solution is located above the center of the wafer. To the wafer W. This etching process is continued for a predetermined time, for example, 60 seconds. After completion of the preheating process, the supply of concentrated sulfuric acid by the sulfuric acid supply system 30 is once stopped, and then, at the start of the etching process, supply of concentrated sulfuric acid from the sulfuric acid supply system 30 and HF from the HF chemical solution supply system 40 are performed. You may start supplying the chemicals at the same time. The composition of the mixed liquid obtained as a result of mixing the sulfuric acid and the HF chemical solution is not limited to that specified from the above mixing ratio, and is, for example, 50% by weight and H ₂ SO ₄ is 50 to 90%. Preferably 60 to 80%, HF component (sum of contents of HF, NH ₄ F and NH ₄ HF ₂ ) is 0.5% or less, preferably 0.1% or less, and H ₂ O is 5 to 50% Preferably, it can be 10 to 30%.

  During the etching process, the chemical solution nozzle 20 may be moved in the radial direction of the wafer by the nozzle moving mechanism 50 and may be reciprocated (scanned) once or a plurality of times between the upper portion of the wafer center and the upper portion of the wafer peripheral portion. . In the etching process, since the temperature of the wafer W is lower than the temperature of the supplied etching solution, the wafer is cooled by the wafer in the process of diffusing from the central portion of the wafer W to the peripheral portion. Etching conditions may be different between the peripheral portion (etched with a low-temperature liquid) and the peripheral portion (etched). In addition, while the wafer central portion is etched with a fresh unreacted liquid, the peripheral portion is etched with a liquid containing a reaction product, and the etching conditions may be different. By moving the chemical nozzle 20 as described above, it is possible to solve the above problems and perform processing with higher in-plane uniformity. When the chemical solution nozzle 20 is scanned, for example, the first nozzle in which the etchant falls (collises) at the center of the wafer at the start of the etching process, that is, the supply position of the etchant is at the center of the wafer. From the position (the chemical nozzle 20 is directly above the center of the wafer W), first, the chemical nozzle 20 is placed at the second nozzle position where the etching solution falls to a position radially inward from the peripheral edge of the wafer by a predetermined distance (for example, 10 mm). Next, the chemical liquid nozzle 20 is moved to a third nozzle position where the etching liquid falls to a position radially outward from the wafer center by a predetermined distance (for example, 15 mm), and then the second nozzle position and the third nozzle position are moved. The chemical nozzle can be reciprocated between the nozzle positions. The operation of returning the chemical nozzle 20 to the third nozzle position instead of the first nozzle position results in an excessive etching amount at the center of the wafer when the chemical nozzle 20 is returned to the first nozzle position. In such a case, if there is no such problem, the chemical nozzle may be returned to the first nozzle position. Further, it is possible to eliminate the waste of the etching solution by moving the chemical nozzle 20 to the second position without moving the chemical nozzle 20 to the peripheral edge of the wafer. However, the chemical nozzle 20 is moved to the peripheral edge of the wafer. It does n’t matter. Further, when performing scanning, the chemical nozzle can be moved at a constant speed, for example, 5 to 30 m / sec.

[Rinse process]
Next, the supply of the mixed liquid (mixed acid) composed of concentrated sulfuric acid and HF chemical solution from the chemical nozzle 20 is stopped, and DIW is supplied from the DIW nozzle 22 to the center of the wafer while the wafer continues to rotate. . Thereby, the mixed liquid and etching residue remaining on the wafer surface are removed. The DIW may be room temperature, but the rinse time can be shortened by using, for example, hot DIW at 80 ° C.

[Drying process]
Next, the supply of DIW from the DIW nozzle 22 is stopped, and the IPA is supplied from the IPA nozzle 24 to the center of the wafer while the rotation of the wafer is continued. This replaces DIW remaining on the wafer surface with IPA. Next, the rotation speed of the wafer is increased and the supply of IPA is stopped, and the IPA on the wafer surface is removed. In this drying step, dry air may be supplied or N ₂ gas may be supplied to accelerate the drying of the wafer. Further, spin-drying (shake-off drying) may be performed immediately after the rinsing process without replacing DIW with IPA.

  Thus, a series of liquid processing is completed. The processed wafer W is unloaded from the wet etching apparatus by a transfer arm (not shown).

Next, the result of the test for confirming the effect of the above embodiment will be described. A semiconductor wafer having an exposed SiN film and SiO ₂ film on the surface was prepared, and wet etching was performed. The flow of the etching process is as described in the above-described embodiment (provided that conditions 1 and 2 do not have a preheating step). The preheating process was performed by discharging concentrated sulfuric acid (concentration 98%) heated to 170 ° C. from the chemical nozzle to the center of the wafer for 10 seconds at a flow rate of 1 L / min while rotating the wafer W at 100 rpm. . The preheating process was performed only in the case of condition 3. In the etching process, concentrated sulfuric acid (concentration 98%) heated to 170 ° C. is supplied to the chemical nozzle at a flow rate of 1 L / min while rotating the wafer W at 100 rpm. Aqueous solution diluted to 500 times (for conditions 1) and 500 times (for conditions 2 and 3) is supplied to the chemical nozzle at a flow rate of 250 mL / min, and a mixed liquid of concentrated sulfuric acid, LAL5000 and pure water is 1250 mL / min. The wafer was supplied from the chemical nozzle to the wafer at a flow rate of 60 seconds. The temperature of the mixed liquid discharged from the chemical nozzle was 207 ° C. In the etching process, the chemical nozzle is scanned, and the chemical nozzle is moved from the first nozzle position (above the center of the wafer) to the second nozzle position (10 mm inside from the wafer periphery) and then the third nozzle. The position was returned to the position (15 mm outside from the wafer center), and then reciprocated between the second nozzle position and the third nozzle position.

The test results are shown in Table 1 below. “Etching uniformity” is based on the etching amount measured at a plurality of locations on the wafer, based on the formula “[((maximum value of etching amount−minimum value of etching amount) / (average value of etching amount × 2)). )] × 100 ”.

The difference between Condition 1 and Condition 2 is only the dilution rate of LAL5000. The condition 2 has a lower concentration of LAL5000 (that is, the concentrations of NH ₄ HF ₂ and HF in the etching solution are lower). Due to this difference, the SiN / SiO ₂ selection ratio was higher in the condition 2, while a decrease in the etching rate of the SiN film was observed. This result is as taught by prior art documents. The difference between condition 2 and condition 3 is only the presence or absence of the preheating step. In condition 3 with the preheating process, the etching rate of the SiN film was considerably higher than in condition 2. In condition 3, compared with condition 2, the SiN / SiO ₂ selection ratio was also high, and the etching uniformity of the SiN film was also high.

From the above test results, it can be seen that by providing a preheating step, a relatively high SiN film etching rate can be ensured even if the concentration of the HF chemical solution is lowered in order to increase the SiN / SiO ₂ selection ratio. It was. In addition, it is confirmed that by providing a preheating step, the SiN / SiO ₂ selectivity and SiN film etching uniformity increased by lowering the concentration of the HF chemical solution, or at least having no adverse effect did it.

As is clear from the above test results, according to the above embodiment, by providing a preheating step for preheating the wafer with concentrated sulfuric acid heated prior to the etching step, the etching rate of the SiN film in the etching step can be increased. Can be increased. For this reason, even if the concentration of the HF-based chemical used in the etching process in order to increase the SiN / SiO ₂ selection ratio is lowered, it is possible to suppress a decrease in the etching rate of the SiN film and suppress a decrease in throughput. Concentrated sulfuric acid has a boiling point higher than that of pure water, so it can be supplied to the wafer at 100 ° C. or higher, and can be supplied to the wafer at a considerably high temperature if it is below the endurance temperature of the supply piping system. it can. For this reason, a wafer can be heated efficiently. Moreover, since concentrated sulfuric acid is one component of the etching solution used in the etching process, there is no need to provide a dedicated heating means (heating lamp, heater, etc.) or a dedicated heating fluid supply system for the preheating process, It is possible to shift directly from the preheating process to the etching process without interposing an intermediate process (for example, a rinsing process for removing sulfuric acid).

In the above embodiment, the substrate to be processed is a semiconductor wafer. However, the substrate is not limited to this. Other types of substrates having a SiN film and a SiO ₂ film, for example, a substrate for an FPD (flat panel display). Or a substrate for MEMS (microelectromechanical system).

DESCRIPTION OF SYMBOLS 10 Spin chuck 14 Substrate holding | maintenance part 16 Rotation drive part 20 Chemical solution nozzle 26 Chemical solution supply mechanism 30 1st chemical solution supply system (sulfuric acid supply system)
40 Second chemical supply system (HF chemical supply system)
100 Control Unit 101 Storage Medium

Claims (13)

A preheating step of heating the substrate by supplying heated H ₂ SO ₄ to the substrate with the silicon nitride film and the silicon oxide film exposed on the surface;
Thereafter, an etching step of supplying a mixed liquid of heated H ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O to the substrate;
An etching method comprising: The preheating step is performed by supplying the heated H ₂ SO ₄ to the center of the substrate while rotating the substrate around a vertical axis in a horizontal posture,
The etching method according to claim 1, wherein the etching step is performed by supplying the mixed liquid to the substrate while rotating the substrate around a vertical axis in a horizontal posture.   The etching method according to claim 2, wherein the etching step is executed while reciprocating a supply position of the mixed liquid to the substrate a plurality of times between a substrate central portion and a substrate peripheral portion.   The etching method according to claim 3, wherein the etching step is performed while reciprocating a supply position of the mixed liquid to the substrate a plurality of times between a substrate center and a substrate periphery.   In the etching step, the supply position of the mixed liquid to the substrate is reciprocated a plurality of times between a position away from the substrate center by a predetermined distance in the radial direction and a position away from the substrate periphery by a predetermined distance in the radial direction. The etching method according to claim 3, which is performed. 4. The etching method according to claim 2, wherein the supply of the heated H ₂ SO _{4 in} the preheating step and the supply of the mixed chemical solution in the etching step are performed by the same chemical nozzle. The etching process maintains the supply of the heated H ₂ SO _{4 to} the chemical nozzle in the preheating process, while adding HF, NH to the heated H ₂ SO ₄ supplied to the chemical nozzle. The etching according to claim 6, wherein the etching is performed by discharging the mixed chemical obtained by mixing at least one of ₄ F and NH ₄ HF ₂ with H ₂ O from the chemical nozzle. Method. The etching method according to claim 1, wherein a temperature of the heated H ₂ SO ₄ is 150 ° C. or higher. The etching method according to claim 8, wherein a temperature of the heated H ₂ SO ₄ is 170 ° C. or higher. A substrate holder for holding the substrate;
Heated H ₂ SO ₄ can be supplied to the substrate held by the substrate holder, and the heated H ₂ SO ₄ , HF, NH ₄ F, and NH ₄ HF ₂ can be supplied. A chemical supply mechanism configured to be able to supply a mixed liquid of at least one of the above and H ₂ O;
Controlling the chemical supply mechanism,
A preheating step of heating the substrate by supplying heated H ₂ SO ₄ to the substrate with the silicon nitride film and the silicon oxide film exposed on the surface;
Thereafter, an etching step of supplying a mixed liquid of heated H ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O to the substrate;
A control unit that causes
Etching device equipped with. The substrate holding unit is configured to hold the substrate in a horizontal posture,
The etching apparatus further includes a rotation driving unit that rotates the substrate holding unit around a vertical axis,
The etching apparatus according to claim 10, wherein the control unit is configured to control the rotation driving unit so that the substrate holding unit holding the substrate rotates in the preheating step and the etching step. The chemical solution supply mechanism includes a first chemical solution supply system configured to supply the heated H ₂ SO ₄ , and at least one of HF, NH ₄ F, and NH ₄ HF ₂ A second chemical solution supply system configured to be able to supply H ₂ O, the first chemical solution supply system and the second chemical solution supply system are connected to a common chemical solution nozzle, A first chemical supply system supplies the heated H ₂ SO ₄ to the chemical nozzle and the second chemical supply system is H and at least one of HF, NH ₄ F and NH ₄ HF ₂ and H The first state in which ₂ O is not supplied to the chemical nozzle, the first chemical supply system supplies the heated H ₂ SO ₄ to the chemical nozzle, and the second chemical supply system HF, NH ₄ F and N The etching apparatus according to claim 10 or 11, configured to be switchable between at least one of H ₄ HF _{2 and} a _{second state} in which H ₂ O is supplied to the chemical nozzle. . A storage medium that records a computer-readable program that forms a control unit of an etching apparatus, the etching apparatus being configured to supply heated H ₂ SO ₄ to a substrate, and A chemical supply mechanism configured to supply a mixed liquid of heated H ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O. And when the computer executes the program, the control unit controls the etching apparatus,
A preheating step of heating the substrate by supplying heated H ₂ SO ₄ to the substrate with the silicon nitride film and the silicon oxide film exposed on the surface;
Thereafter, an etching step of supplying a mixed liquid of heated H ₂ SO ₄ , at least one of HF, NH ₄ F, and NH ₄ HF ₂ and H ₂ O to the substrate is performed. Let the storage medium.

Images