JP2017118092A - Substrate processing apparatus, substrate processing method and etching liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate processing apparatus suppressing precipitation of silica, and to provide a substrate processing method and etching liquid.SOLUTION: A substrate processing apparatus includes a processing section, a circulation path, a heating section, and a first injection section. The processing section is supplied with etching liquid containing phosphoric acid and silica precipitation retardant, and removes a silicon nitride film from a substrate by bringing the substrate having a silicon nitride film on a surface into contact with the etching liquid. The circulation path circulates the etching liquid with respect to the processing section. The heating section heats the etching liquid. The first injection section is provided in the circulation path, and injects the silica precipitation retardant into the etching liquid.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a substrate processing apparatus, a substrate processing method, and an etching solution.

  In the manufacturing process of semiconductor devices, the etching process is an important process for pattern formation. Of the silicon nitride film and silicon oxide film formed on the substrate, the silicon nitride film is selectively etched to leave the silicon oxide film. Processing to be removed is requested. As a technique for performing such a selective etching process of a silicon nitride film, a process using a high temperature (140 ° C. to 180 ° C.) phosphoric acid aqueous solution as an etching solution is known.

  In a process that uses a high-temperature phosphoric acid aqueous solution, for example, a plurality of substrates on which a silicon nitride film and a silicon oxide film are formed are immersed in a processing tank that stores a high-temperature phosphoric acid aqueous solution. Etching process is performed. At this time, the silicon oxide film is etched although the amount is small due to the characteristics of the phosphoric acid aqueous solution. Therefore, for example, the etching selectivity of the silicon nitride film to the silicon oxide film is increased by adding a silicon compound to increase the silica concentration in the phosphoric acid solution. By increasing the etching selectivity of the silicon nitride film, the etching of the silicon oxide film can be suppressed.

  Usually, when a silicon nitride film is etched using an aqueous phosphoric acid solution, silica accumulates in the phosphoric acid. If the silica concentration in the etching solution is too low, the etching rate of the silicon oxide film increases, and the etching selectivity with respect to the silicon nitride film decreases. On the contrary, even if the silica concentration is too high, there arises a problem that it adheres to the treatment tank or clogs the filter. For this reason, when performing the etching process using phosphoric acid aqueous solution, various silicon type additives are used in order to adjust the silica concentration in phosphoric acid within an appropriate range according to the purpose of the process.

  In recent years, in a manufacturing process of a three-dimensional memory device, a laminated film in which silicon oxide films and silicon nitride films are alternately laminated on a wafer is formed. And in order to form a word line, a select gate, etc., it processes using the phosphoric acid previously adjusted to the predetermined silica density | concentration, The silicon nitride film is selectively removed among laminated films.

  However, in the case of a three-dimensional memory device, since the silicon nitride film has a large etching amount, the silica concentration is saturated during the phosphoric acid treatment, silica is deposited between the silicon oxide films, and a wiring layer is formed between the silicon oxide films. There was a problem that it was difficult to form. In the future, it is expected that the margin for silica deposition will become narrower due to the increase in the etching amount of silicon nitride film and the thinning of the silicon nitride film as the three-dimensional memory becomes highly stacked, and there is concern that the problem of silica deposition will become more serious Is done. For this reason, in order to manufacture a highly integrated three-dimensional memory with high yield, it is required to suppress silica precipitation.

Japanese Patent No. 4966223

  Provided are a substrate processing apparatus, a substrate processing method, and an etching solution for suppressing silica deposition.

  The substrate processing apparatus according to the present embodiment includes a processing unit, a circulation path, a heating unit, and a first input unit. The processing unit is supplied with an etchant containing phosphoric acid and a silica precipitation inhibitor, and contacts the substrate having a silicon nitride film on the surface with the etchant to remove the silicon nitride film from the substrate. The circulation path circulates the etching solution to the processing unit. The heating unit heats the etching solution. The first input unit is provided in the circulation path and inputs a silica precipitation inhibitor into the etching solution.

It is a figure of the substrate processing apparatus which shows 1st Embodiment. It is a flowchart of the substrate processing method which shows 1st Embodiment. It is a schematic sectional drawing of the semiconductor substrate for manufacturing a three-dimensional memory. It is explanatory drawing for demonstrating an example of an effect | action of 1st Embodiment. It is a graph which shows the 1st experiment example of 1st Embodiment. It is sectional drawing which shows the amount of silica precipitation in the 2nd experiment example of 1st Embodiment. It is a graph which shows the silica precipitation amount at the time of adding the aluminum compound as a silica precipitation inhibitor in the 2nd experiment example of 1st Embodiment. It is a graph which shows the silica precipitation amount at the time of adding a potassium compound as a silica precipitation inhibitor in the 2nd experiment example of 1st Embodiment. It is a graph which shows the silica precipitation amount at the time of adding a chloride compound as a silica precipitation inhibitor in the 2nd experiment example of 1st Embodiment. In the 3rd example of an experiment of a 1st embodiment, it is a graph which shows the dependence of the silica precipitation amount with respect to the addition concentration of an aluminum compound. In the 3rd example of an experiment of a 1st embodiment, it is a graph which shows the dependence of the silica precipitation amount with respect to the addition concentration of a chlorine compound. It is a figure of the substrate processing apparatus which shows 2nd Embodiment. In the experimental example of 2nd Embodiment, it is a graph which shows the correlation of an oxidizing agent and an etching rate. It is a figure of the substrate processing apparatus which shows 3rd Embodiment. It is a figure of the substrate processing apparatus which shows 4th Embodiment. In the substrate processing method which shows 4th Embodiment, it is a graph which shows the saturation dissolution concentration curve of the silicon | silicone before supply of a silica precipitation inhibitor. In the substrate processing method which shows 4th Embodiment, it is a graph which shows the saturation melt | dissolution density | concentration curve of the silicon | silicone after the supply of a silica precipitation inhibitor. It is a figure of the substrate processing apparatus which shows the modification of 4th Embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings. This embodiment does not limit the present invention.

(First embodiment)
(Substrate processing apparatus 1)
FIG. 1 is a diagram of a substrate processing apparatus 1 showing a first embodiment. The substrate processing apparatus 1 is a wet etching processing apparatus that selectively removes a silicon nitride film by immersing the substrate 2 having a silicon nitride film on the surface thereof in a solution containing phosphoric acid (hereinafter also referred to as a phosphoric acid solution). Can be used.

  As shown in FIG. 1, the substrate processing apparatus 1 includes a processing tank 11, which is an example of a processing unit, a circulation path 12, a heating unit 13, and a charging unit 14 (first charging unit). In addition, the substrate processing apparatus 1 includes a pump 15, a filter 16, and an intermediate tank 17.

  The processing tank 11 includes an inner tank 111 and an outer tank 112. The inner tank 111 is formed in a box shape having an upper end opening 111a. The inner tank 111 is supplied with the phosphoric acid solution 3, that is, the etching solution. The inner tank 111 stores the supplied phosphoric acid solution 3. The inner tank 111 immerses (that is, contacts) the substrate 2 in the stored phosphoric acid solution 3. By being immersed in the phosphoric acid solution 3, the silicon nitride film of the substrate 2 is dissolved and removed in the phosphoric acid solution. The substrate 2 may be immersed in the phosphoric acid solution 3 using a substrate holding mechanism or a substrate lifting mechanism (not shown). The outer tub 112 surrounds the upper end portion of the inner tub 111 over the entire circumference. The outer tub 112 has an upper end opening 112 a that surrounds the upper end opening 111 a of the inner tub 111. The outer tank 112 collects the phosphoric acid solution 3 overflowed from the upper end opening 111 a of the inner tank 111. The processing tank 11 may be a batch type processing tank that simultaneously processes a plurality of substrates 2.

  The circulation path 12 causes the bottom of the outer tank 112 and the bottom of the inner tank 111 to be in fluid communication and causes the phosphoric acid solution 3 to circulate through the processing tank 11. The circulation path 12 returns the phosphoric acid solution 3 overflowed from the inner tank 111 and stored in the outer tank 112 to the inner tank 111 after removing the silicon nitride film. During the reflux process, the phosphoric acid solution 3 is processed by the heating unit 13, the charging unit 14, and the filter 16 so that the silicon nitride film can be removed again.

The pump 15 is provided in the circulation path 12. The pump 15 sucks the phosphoric acid solution 3 stored in the outer tank 112 to introduce the phosphoric acid solution 3 from the processing tank 11 into the circulation path 12.
Then, the pump 15 causes the phosphoric acid solution 3 introduced from the treatment tank 11 to flow back to the inner tank 111 through the circulation path 12.

  The intermediate tank 17 is provided in the circulation path 12 upstream of the pump 15. The intermediate tank 17 temporarily stores the refluxed phosphoric acid solution 3.

  The charging unit 14 is provided in the circulation path 12 so as to face the intermediate tank 17. The charging unit 14 charges, that is, adds the silica precipitation inhibitor 4 to the phosphoric acid solution 3 stored in the intermediate tank 17. The specific aspect of the injection | throwing-in part 14 is not specifically limited, For example, you may provide the weighing tank which weighs the quantity of the silica precipitation inhibitor 4, and the injection | throwing-in valve into which the measured silica precipitation inhibitor 4 is thrown in. . Further, the intermediate tank 17 may be provided downstream of the pump 15. Further, the charging unit 14 may be provided at a position facing the upper opening 112 a of the outer tank 112 so that the silica precipitation inhibitor can be charged into the phosphoric acid solution 3 stored in the outer tank 112. In this case, the intermediate tank 17 may be omitted.

  The phosphoric acid solution 3 is supplied from the supply valve 19 to the inner tank 111. The supply valve 19 may be installed so as to supply the phosphoric acid solution 3 to the outer tank 112, or may be installed so as to supply the phosphoric acid solution 3 in the path of the circulation path 12 or to the intermediate tank 17. .

  The silica precipitation inhibitor 4 suppresses the precipitation of silica on the substrate 2 accompanying the removal of the silicon nitride film. For example, the silica precipitation inhibitor 4 is used when a silicon nitride film is selectively removed from a laminated film of a silicon oxide film and a silicon nitride film by hot phosphoric acid treatment in a manufacturing process of a three-dimensional memory. Suppresses the precipitation of silica. The silica precipitation inhibitor 4 may have other purposes or effects.

The silica precipitation inhibitor 4 is a compound containing an element that is a cation having an ionic radius of 0.2 to 0.9 Å. The ionic radius is an ionic radius determined empirically from the sum of the anion and cation radii obtained from the lattice constant of the crystal lattice. The ion radius of the cation is 0.2Å or more and increases with the coordination number. A cation having an ionic radius of 1.0 mm or more is likely to be coordinated with water in phosphoric acid because of its large coordination number. Since water in phosphoric acid acts to remove the silicon nitride film, if it is coordinated to a cation, etching removal of the silicon nitride film is delayed. Furthermore, as shown in Equation 1, since the precipitation of silica is an equilibrium reaction that involves the generation of water, if a large amount of water is coordinated to the cation, the equilibrium is inclined so that the precipitation of silica is promoted. .

  From this, the silica precipitation inhibitor 4 may contain an element that becomes a cation having a hydration number of 0 to 3.5 in the phosphoric acid solution 3. When a cation having a hydration number greater than 3.5 is contained, a large amount of water in the phosphoric acid is hydrated to the cation, and the equilibrium reaction shown in Formula 1 is tilted to the right, and silica is likely to precipitate. End up.

For example, the silica precipitation inhibitor 4 may contain an oxide of any element of aluminum, potassium, lithium, sodium, magnesium, calcium, zirconium, tungsten, titanium, molybdenum, hafnium, nickel, and chromium. Further, the silica precipitation inhibitor 4 includes at least one of nitride, chloride, bromide, hydroxide, and nitrate of any of the elements instead of or in addition to the oxide of any of the elements. May be. For example, the silica precipitation inhibitor 4 contains at least one of Al (OH) ₃ , A1Cl ₃ , A1Br ₃ , A1 (NO ₃ ) ₃ , A1 ₂ (SO ₄ ) ₃ A1PO ₄ and A1 ₂ O _3. Also good. Further, the silica precipitation inhibitor 4 may contain at least one of KCl, KBr, KOH, and KNO ₃ . The silica precipitation inhibitor 4 may contain at least one of LiCl, NaCl, MgCl ₂ , CaCl ₂ and ZrCl ₄ .

  The filter 16 is provided in the circulation path 12 downstream of the charging unit 14 and the pump 15. The filter 16 removes foreign matters (insoluble substances) in the phosphoric acid solution 3 by filtering the phosphoric acid solution 3.

  The heating unit 13 is provided in the circulation path 12 downstream of the filter 16 and in the vicinity of the processing tank 11. The heating unit 13 heats the phosphoric acid solution 3 to a predetermined temperature. The phosphoric acid solution 3 heated by the heating unit 13 is discharged into the inner tank 111 by the discharge unit 113 provided in the inner tank 111. The heating unit 13 may be provided in the circulation path 12 upstream of the filter 16.

  According to the substrate processing apparatus 1, when the silica precipitation inhibitor 4 is added to the phosphoric acid solution 3 circulated through the circulation path 12 by the input unit 14, when the silicon nitride film of the substrate 2 is removed in the processing tank 11, Precipitation of silica can be suppressed.

(Substrate processing method)
Next, a substrate processing method to which the substrate processing apparatus 1 of FIG. 1 is applied will be described. FIG. 2 is a flowchart of the substrate processing method according to the first embodiment. FIG. 3 is a schematic cross-sectional view of a semiconductor substrate 20 for manufacturing a three-dimensional memory. In the following substrate processing method, as an example, the semiconductor substrate 20 of FIG. 3 is processed. As shown in FIG. 3, the semiconductor substrate 20 has a laminated film 22 in which silicon oxide films 221 and silicon nitride films 222 are alternately laminated on a silicon substrate 21. In addition, the semiconductor substrate 20 has a trench 23 that penetrates the stacked film 22. 2, it is assumed that the phosphoric acid solution 3 is not stored in the treatment tank 11.

  From the initial state, first, the supply valve 19 of the substrate processing apparatus 1 supplies the untreated phosphoric acid solution 3 into the inner tank 111 of the processing tank 11 (step S1). The untreated phosphoric acid solution 3 is a phosphoric acid solution 3 in a state where a treatment necessary for removing the silicon nitride film 222 such as heating or addition of a silica precipitation inhibitor described later is not performed. The untreated phosphoric acid solution 3 supplied into the inner tank 111 overflows from the inner tank 111 and is stored in the outer tank 112. The untreated phosphoric acid solution 3 stored in the outer tank 112 is introduced into the intermediate tank 17 on the circulation path 12 by the suction force of the pump 15. The untreated phosphoric acid solution 3 introduced into the intermediate tank 17 is temporarily stored in the intermediate tank 17. The supply valve 19 may be installed so as to supply the phosphoric acid solution 3 to the outer tank 112, or may be installed so as to supply the phosphoric acid solution 3 in the path of the circulation path 12 or to the intermediate tank 17. .

  Next, the charging unit 14 adds the silica precipitation inhibitor 4 to the untreated phosphoric acid solution 3 stored in the intermediate tank 17 (step S2). At this time, the charging unit 14 has a concentration of the silica precipitation inhibitor 4 in the phosphoric acid solution 3 of 0.01 to 0.5 mol / L based on the detection result of the concentration meter 171 installed in the intermediate tank 17. Thus, the silica precipitation inhibitor 4 may be added to the phosphoric acid solution 3.

  Here, when the addition amount of the phosphoric acid solution 3 is less than 0.01 mol / L, it may be difficult to sufficiently suppress the precipitation of silica between the layers of the silicon oxide film 221. On the other hand, when the addition amount of the phosphoric acid solution 3 is more than 0.5 mol / L, the silica precipitation inhibitor 4 may remain between the silicon oxide films 221. Therefore, both the precipitation of silica and the remaining silica precipitation inhibitor 4 can be suppressed by setting the addition amount of the silica precipitation inhibitor 4 to 0.01 mol / L or more and 0.5 mol / L or less.

  Next, the filter 16 removes foreign matter from the phosphoric acid solution 3 to which the silica precipitation inhibitor 4 has been added (step S3).

  Next, the heating unit 13 heats the phosphoric acid solution 3 from which the foreign matter has been removed (step S4).

  Next, the pump 15 supplies the heated phosphoric acid solution 3 into the treatment tank 11 (step S5).

  Next, the silicon nitride film 222 is wet-etched by immersing the semiconductor substrate 20 in the heated phosphoric acid solution 3 in the processing bath 11 (step S6). At this time, the phosphoric acid solution 3 contacts each layer of the laminated film 22 through the trench 23 of the semiconductor substrate 20 and selectively removes the silicon nitride film 222. The phosphoric acid solution 3 used for the etching process overflows from the inner tank 111 and is stored in the outer tank 112.

  Next, the pump 15 sucks the phosphoric acid solution 3 stored in the outer tank 112 and returns it through the circulation path 12 (step S7). In the course of reflux, addition of a silica precipitation inhibitor (Step S2), removal of foreign matter (Step S3), heating (Step S4), and supply into the treatment tank 11 (Step S2) with respect to the phosphoric acid solution 3 S5) is performed again. Such various treatments to the phosphoric acid solution 3 accompanying the circulation of the phosphoric acid solution 3 may be repeated for the time required for wet etching. The addition of the silica precipitation inhibitor (step S2) may be omitted if the concentration of the silica precipitation inhibitor 4 in the phosphoric acid solution 3 is in the range of 0.01 mol / L to 0.5 mol / L. .

Next, the effect | action of the silica precipitation inhibitor 4 in the etching process (step S6) of FIG. 2 is demonstrated. FIG. 4 is an explanatory diagram for explaining an example of the operation of the present embodiment. The action shown in FIG. 4 is based on DFT (density functional theory) calculation (see J. Am. Chem. Soc. 2011, 133, 6613-6625). First, in the etching process (step S6) of the silicon nitride film 222, silanol Si (OH) ₄ is generated (step S61).

If the silica precipitation inhibitor 4 is not added to the phosphoric acid solution 3, the polymerization reaction between silanols proceeds to produce a reaction intermediate (step S62_1). The reaction rate constant in the production of the reaction intermediate is 6.6E + 11 / s, and the activation energy is 7 kJ / mol. Next, a dimer of silica (HO) ₃ Si—O—Si (OH) ₃ is generated based on the reaction intermediate (step S63_1). The reaction rate constant in the formation of the silica dimer is 1.4E + 4 / s, and the activation energy is 0 kJ / mol. Then, the silica dimer is polymerized to produce a silica polymer, and the produced silica polymer is deposited (step S64_1).

In contrast, in the present embodiment, after the silanol is generated (step S61), silanol by silica precipitation inhibitor 4 silicate ions Si _(OH) 3 O ionized ^- is generated (step S62_2) . And a reaction intermediate is produced | generated based on a silicate ion (step S63_2). The reaction rate constant in the production of the reaction intermediate is 1.6E + 7 / s, and the activation energy is 0 kJ / mol. Next, a transition state is formed (step S64_2). The reaction rate constant in the formation of the transition state is 1.6E + 7 / s, and the activation energy is 0 kJ / mol. Next, a dimer of silica is generated based on the transition state (step S63_1). The reaction rate constant in the formation of the silica dimer is 3.2E + 4 / s, and the activation energy is 56 kJ / mol. Thereafter, the silica polymer is precipitated as in the case where the silica precipitation inhibitor 4 is not added (step S64_1).

  As described above, when the silica precipitation inhibitor 4 is added, the reaction rate constant of the rate-determining reaction step with a high activation energy of the polymerization reaction is smaller than when the silica precipitation inhibitor 4 is not added. When the silica precipitation inhibitor 4 is added, it is considered that silica is difficult to polymerize and precipitate because silica tends to polymerize in an ionized state.

  Thus, it is kinetically clear that silica precipitation can be suppressed by adding the silica precipitation inhibitor 4.

  In addition, from the viewpoint of effectively suppressing silica precipitation, the content ratio of the components of the etching solution in the treatment tank 11, that is, the weight concentration ratio, is phosphoric acid: 75 to 94% by weight, silica precipitation inhibitor: 0.01 to 3 It is preferable that they are 0.2 weight% (namely, 0.01-0.5 mol / L) and water: 2.8-24.9 weight%.

  Further, an etching solution containing 75 to 94% by weight of phosphoric acid, 0.01 to 3.2% by weight of a silica precipitation inhibitor and 2.8 to 24.9% by weight of water is directly applied to the treatment tank 11. You may supply.

(First Experiment Example)
Next, a first experimental example of the first embodiment will be described. FIG. 5 is a graph showing a first experimental example of the first embodiment.

In the first experimental example, a beaker containing a phosphoric acid solution containing 85% by weight of phosphoric acid was placed in an oil bath, and the phosphoric acid solution in the beaker was heated to 155 ° C. in the oil bath. At this time, the silica precipitation inhibitor was added and stirred in the beaker to which the substrate processing method of the present embodiment was applied. As the silica precipitation inhibitor, five types of compounds of Al (OH) ₃ , A1Cl ₃ , A1Br ₃ , A1 (NO ₃ ) ₃ , A1 ₂ (SO ₄ ) ₃ and A1PO ₄ were employed. These five types of compounds were added to phosphoric acid solutions in different beakers. On the other hand, the silica precipitation inhibitor was not added to the beaker to which the substrate processing method of the comparative example was applied. Then, the semiconductor substrate 20 was immersed in heated phosphoric acid for 15 minutes. After immersion, the semiconductor substrate 20 was rinsed with pure water for 60 seconds and dried, and then the semiconductor substrate 20 was observed with an SEM. FIG. 5 shows the amount of precipitated silica detected based on the observation result by SEM.

  As shown in FIG. 5, it was found that the amount of silica deposited was smaller when the silica precipitation inhibitor was added than when the silica precipitation inhibitor was not added.

  Thus, it is clear experimentally that the formation of silica can be suppressed by adding a silica precipitation inhibitor.

(Second experiment example)
Next, a second experimental example of the first embodiment in which the types of silica precipitation inhibitors are increased with respect to the first experimental example will be described. FIG. 6 is a cross-sectional view showing the amount of precipitated silica in the second experimental example.

In the second experimental example, in addition to the six types of aluminum compounds shown in the first experimental example, Al ₂ O ₃ is further employed as a silica precipitation inhibitor composed of an aluminum compound added to the phosphoric acid solution in the beaker. did. In the second experimental example, KCl, KBr, KOH, and KNO ₃ were employed as silica precipitation inhibitors made of potassium compounds. In the second experimental example, as the silica precipitation inhibitor consisting of chloride compound, and LiCl, and NaCl, and KCl, and MgCl _2, and CaCl _2, it was employed and ZrCl _4. In the second experimental example, the concentration of various silica precipitation inhibitors was unified to 0.1 mol / L.

  Then, in the second experimental example, after removing the silicon nitride film 222 (see FIG. 3) with a phosphoric acid solution in a beaker as in the first experimental example, as shown in FIG. The amount of silica 25 deposited in the vicinity of the trench 23 of the cavity 24 formed by the removal was calculated. The results are shown in FIGS.

  FIG. 7 is a graph showing the amount of silica deposited when an aluminum compound is added as a silica deposition inhibitor in the second experimental example. FIG. 8 is a graph showing the amount of silica deposited when a potassium compound is added as a silica deposition inhibitor in the second experimental example. FIG. 9 is a graph showing the amount of silica deposited when a chloride compound is added as a silica deposition inhibitor in the second experimental example.

  As shown in FIGS. 7 to 9, according to the second experimental example, when the concentration of the silica precipitation inhibitor is 0.1 mol / L, the silica precipitation inhibitor is used in any type of silica precipitation inhibitor. It was found that the amount of precipitated silica was reduced as compared with the case where no was added.

(Third experimental example)
Next, a third experimental example of the first embodiment in which the concentration of the silica precipitation inhibitor is changed will be described. In the third experimental example, the change in the amount of precipitated silica with the change in the concentration of the silica precipitation inhibitor was examined for several types of the silica precipitation inhibitors employed in the first experimental example. The results are shown in FIG. 10 and FIG.

  FIG. 10 is a graph showing the dependence of the silica precipitation amount on the addition concentration of the aluminum compound in the third experimental example. FIG. 11 is a graph showing the dependence of the amount of precipitated silica with respect to the addition concentration of the chlorine compound in the third experimental example.

  As shown in FIGS. 10 and 11, according to the third experimental example, when the concentration of the silica precipitation inhibitor is 0.01 to 3.2% by weight, any of the types in FIGS. 10 and 11 is used. Also in the silica precipitation inhibitor, it was found that the amount of precipitated silica was reduced as compared with the case where no silica precipitation inhibitor was added.

  As described above, according to the first embodiment, the silicon nitride film 222 in the laminated film 22 is etched using the phosphoric acid solution to which the silica precipitation inhibitor is added, so that the silica deposition accompanying the etching is performed. Can be suppressed. By suppressing the precipitation of silica, a three-dimensional memory with a high degree of integration can be manufactured with a high yield.

  Note that this embodiment can also be applied to process a substrate for a purpose other than a three-dimensional memory, such as a substrate for MEMS (Micro Electro Mechanical Systems).

(Second Embodiment)
Next, as a second embodiment, an embodiment in which a silicon nitride film is etched with an etchant containing an oxidizing agent will be described. In addition, in 2nd Embodiment, about the structure part corresponding to 1st Embodiment, the overlapping description is abbreviate | omitted using the same code | symbol. FIG. 12 is a diagram of the substrate processing apparatus 1 showing the second embodiment.

  As shown in FIG. 12, the substrate processing apparatus 1 of the second embodiment further includes a second input unit 140 in addition to the configuration of the substrate processing apparatus 1 of the first embodiment. The second charging unit 140 is provided in the circulation path 12 so as to face the intermediate tank 17. The second charging part 140 is adjacent to the charging part 14 in a direction (lateral direction in FIG. 12) perpendicular to the charging direction of the silica precipitation inhibitor 4.

  The second input unit 140 inputs the oxidant 40 into the phosphoric acid solution 3 stored in the intermediate tank 17. The specific aspect of the 2nd input part 140 is not specifically limited, For example, you may provide the weighing tank which weighs the quantity of the oxidizing agent 40, and the injection | throwing-in valve into which the measured oxidizing agent 40 is thrown in.

  The oxidant 40 is supplied into the processing tank 11 through the circulation path 12 and then promotes etching of the silicon nitride film 222 (see FIG. 3) in the processing tank 11. The silicon nitride film 222 is etched with water contained in the phosphoric acid solution 3. That is, an oxygen atom of a water molecule is bonded to a silicon atom in the silicon nitride film 222 to form a Si—O bond, and the Si—N bond in the silicon nitride film 222 is cut. By repeating this reaction, silanol is generated and etching of the silicon nitride film 222 proceeds.

  The oxidizing agent 40 has an oxidation-reduction potential of 1.0 V or higher, that is, a high oxidizing power. By having an oxidation-reduction potential of 1.0 V or higher, the oxidant 40 can oxidize silicon in the silicon nitride film 222 and break the Si—N bond. In the silicon nitride film 222 in which a part of the Si—N bond is cut by the oxidant 40, the bonding of oxygen molecules of water molecules contained in the phosphoric acid aqueous solution 3 is promoted. Thereby, the phosphoric acid aqueous solution 3 containing the oxidizing agent 40 has a higher etching rate of the silicon nitride film 222 than the phosphoric acid aqueous solution not containing the oxidizing agent 40. The oxidizing agent 40 may have other purposes or effects.

  The oxidizing agent 40 may be, for example, cerium (IV), manganese (VII), peroxomonosulfuric acid, peroxodisulfuric acid, hydrogen peroxide, ozone or perchloric acid. The oxidizing agent 40 is not limited to these as long as it is an oxidizing agent having a redox potential of 1.0 V or higher.

From the viewpoint of effectively suppressing the precipitation of silica and effectively improving the etching rate of the silicon nitride film 222, the content ratio of the components of the etching solution in the treatment tank 11 is phosphoric acid: 75 to 94% by weight, silica Precipitation inhibitor: 0.01 to 3.2% by weight (0.01 to 0.5 mol / L), oxidizing agent 0.01 to 2.0% by weight (0.01 to 0.2 mol / L), water: It is preferably 2.8 to 24.9% by weight.
Here, when the addition amount of the phosphoric acid solution 3 is less than 0.01 mol / L, the oxidizing agent 40 may be difficult to sufficiently accelerate the etching rate of the silicon nitride film 222. On the other hand, when the addition amount of the phosphoric acid solution 3 is more than 0.2 mol / L, the oxidant 40 may remain between the layers of the silicon oxide film 221. Therefore, the residual amount of the oxidant 40 can be suppressed while improving the etching rate of the silicon nitride film by setting the addition amount of the oxidant 40 to 0.01 mol / L or more and 0.2 mol / L or less.

  Also, 75 to 94% by weight of phosphoric acid, silica precipitation inhibitor: 0.01 to 3.2% by weight, 0.01 to 2.0% by weight of oxidizing agent, and 2.8 to 24.9% by weight of water. You may supply the etching liquid containing to the processing tank 11 directly.

(Experimental example)
Next, an experimental example of the second embodiment will be described. In this experimental example, with respect to the phosphoric acid solution in the beaker similar to the first experimental example of the first embodiment, the oxidation-reduction potential is +1.72 V as an oxidizing agent instead of the silica precipitation inhibitor. Cerium dioxide was added to 1.0 wt% (0.1 mol / L). Then, similarly to the first experimental example of the first embodiment, the silicon nitride film 222 was etched with a phosphoric acid solution in a beaker, and the etching rate was measured. Note that the etching rate was determined as a normalized etching rate with 1 being the case where no oxidizing agent was added. The result is shown in FIG.

  FIG. 13 is a graph showing the correlation between the oxidizing agent and the etching rate in the experimental example of the second embodiment. As shown in FIG. 13, according to the present experimental example, it was found that the etching rate can be improved by adding the oxidizing agent as compared with the case where the oxidizing agent is not added.

(Third embodiment)
Next, a single substrate processing apparatus will be described as a third embodiment. Note that, in the third embodiment, the same reference numerals are used for the components corresponding to the first and second embodiments, and redundant description is omitted. FIG. 14 is a diagram of the substrate processing apparatus 1 showing the third embodiment.

  In the first and second embodiments, the semiconductor substrates 20 are processed in batch mode. On the other hand, in the third embodiment, the semiconductor substrate 20 is processed in a single wafer type. In order to process the semiconductor substrate 20 in a single sheet form, the substrate processing apparatus 1 according to the third embodiment includes a substrate holding unit 101 and nozzles 102 </ b> A to 102 </ b> C instead of the processing tank 11 as a processing unit. Further, the substrate processing apparatus 1 of the third embodiment further includes a rotating shaft 103, a rotation driving unit 104, an arm 105, and liquid pipes 106A to 106A as constituent parts different from the first and second embodiments. C, flow control valves 107 </ b> A to 107 </ b> C, on-off valves 108 </ b> A to 108 </ b> C, and a cup 109.

  In the third embodiment, the phosphoric acid solution 3 is supplied to the intermediate tank 17 in advance. The heating unit 13 is provided in the intermediate tank 17 so as to heat the phosphoric acid solution 3 in the intermediate tank 17.

  The substrate holding part 101 has a horizontal disk shape, and has a plurality of chuck pins 101 a protruding upward on the outer peripheral edge of the upper surface thereof. By sandwiching the semiconductor substrate 20 with the plurality of chuck pins 101a, the substrate holding unit 101 holds the semiconductor substrate 20 substantially horizontally.

  The rotation shaft 103 extends downward from the central portion of the substrate holding unit 101 and is connected to the rotation driving unit 104 at the lower end thereof. The substrate holding unit 101 can rotate around the rotation shaft 103 by the driving force of the rotation driving unit 104.

  In order to supply the phosphoric acid solution 3 to the semiconductor substrate 20, the nozzle 102A communicates with the intermediate tank 17 through the fluid conduit 106A. The fluid conduit 106A is a part of the circulation path. In order to control the supply of the phosphoric acid solution 3, a flow rate adjusting valve 107A and an on-off valve 108A are arranged at a predetermined interval on the fluid conduit 106A. The nozzle 102A is fixed to an arm 105, and the arm 105 can be moved in the horizontal direction above the substrate holding unit 101 by a moving device (not shown). As the arm 105 moves toward the center of the semiconductor substrate 20, the nozzle 102 </ b> A faces the center of the semiconductor substrate 20. In a state of facing the central portion of the semiconductor substrate 20, the nozzle 102 </ b> A discharges the phosphoric acid solution 3 sent from the intermediate tank 17 onto the semiconductor substrate 20. When discharging the phosphoric acid solution 3, the rotation driving unit 104 rotates the semiconductor substrate 20 by rotating the substrate holding unit 101. By discharging the phosphoric acid solution 3 to the central portion of the semiconductor substrate 20 in a rotating state, the phosphoric acid solution 3 can be applied uniformly over the entire circumference of the semiconductor substrate 20. Thereby, the silicon nitride film 222 of the semiconductor substrate 20 can be removed with the phosphoric acid solution 3 uniformly and efficiently. The nozzle 102 </ b> A may discharge the phosphoric acid solution 3 obliquely toward the central portion of the semiconductor substrate 20 at a position facing the peripheral portion of the semiconductor substrate 20.

  The cup 109 has a substantially cylindrical shape with an open upper end, and is provided around the substrate holding unit 101 so as to cover the substrate holding unit 101 from the side and below. The cup 109 communicates with the upstream end of the circulation path 12 through a through hole (not shown) provided in the bottom portion 109a. The phosphoric acid solution 3 discharged to the semiconductor substrate 20 moves to the outer peripheral edge of the semiconductor substrate 20 by centrifugal force due to the rotation of the semiconductor substrate 20, and then falls onto the bottom 109 a of the cup 109 from the outer peripheral edge. The dropped phosphoric acid solution 3 is recirculated in the circulation path 12 by the suction force of the pump 15, passes through the filter 16, and is then supplied to the intermediate tank 17. As in the second embodiment, the silica precipitation inhibitor 4 and the oxidizing agent 40 are supplied to the phosphoric acid solution 3 supplied to the intermediate tank 17. As a result, the silica precipitation inhibitor 4 and the oxidant 40 consumed by the reaction with the silicon nitride film 222 can be supplemented, and the phosphoric acid solution 3 can be reused for removing the silicon nitride film 222. The filter 16 may be disposed in the fluid conduit 106A, that is, the circulation passage so that the foreign matter in the phosphoric acid solution 3 can be removed in the fluid conduit 106A.

  In order to supply a chemical solution (cleaning solution) to the semiconductor substrate 20, the nozzle 102B communicates with a chemical solution supply source (not shown) through the fluid conduit 106B. In order to control the supply of the chemical solution, a flow rate adjustment valve 107B and an on-off valve 108B are arranged at a predetermined interval on the fluid conduit 106B. Similar to the nozzle 102 </ b> A, the nozzle 102 </ b> B is fixed to the arm 105 so as to face the central portion of the substrate holding unit 101. In order to remove the phosphoric acid solution 3 from the semiconductor substrate 20, the nozzle 102 </ b> B discharges a chemical solution to the semiconductor substrate 20 after removing the silicon nitride film 222. At this time, the phosphoric acid solution 3 can be efficiently removed by discharging the chemical solution while rotating the semiconductor substrate 20.

  In order to supply a rinsing liquid (for example, pure water) to the semiconductor substrate 20, the nozzle 102C is communicated with a rinsing liquid supply source (not shown) through the fluid conduit 106C. In order to control the supply of the rinsing liquid, a flow rate adjustment valve 107C and an on-off valve 108C are arranged at a predetermined interval on the fluid conduit 106C. Similar to the nozzle 102 </ b> A, the nozzle 102 </ b> C is fixed to the arm 105 so as to face the central portion of the substrate holding unit 101. In order to remove the chemical liquid from the semiconductor substrate 20, the nozzle 102 </ b> C discharges a rinsing liquid to the semiconductor substrate 20 after cleaning with the chemical liquid. At this time, the chemical liquid can be efficiently removed by discharging the rinse liquid while rotating the semiconductor substrate 20.

  In addition, you may control operation | movement of the rotation drive part 104, flow volume adjustment valve 107A-C, and on-off valve 108A-C by the control part not shown.

  Similarly to the second embodiment, also in the third embodiment, the deposition of silica can be suppressed by supplying the phosphoric acid solution 3 containing the silica precipitation inhibitor and the oxidizing agent to the semiconductor substrate 20 after heating. At the same time, the etching rate of the silicon nitride film 222 can be improved. Further, according to the third embodiment, the removal of the silicon nitride film 222 and the cleaning and rinsing after the removal can be completed with one substrate processing apparatus 1.

(Fourth embodiment)
Next, a substrate processing apparatus for processing a semiconductor substrate 20 with a phosphoric acid solution 3 in which silicon is dissolved will be described as a fourth embodiment. Note that in the fourth embodiment, the description of the components corresponding to the first embodiment will be omitted by using the same reference numerals. FIG. 15 is a diagram of the substrate processing apparatus 1 showing the fourth embodiment.

  As shown in FIG. 15, the substrate processing apparatus 1 according to the fourth embodiment further includes a third input unit 401, a first valve 402, and a discharge path 403 in addition to the configuration of the substrate processing apparatus 1 of FIG. 1. And a cooling tank 404, which is an example of a cooling unit, a supply unit 450, and a third valve 407. The supply unit 450 includes a precipitation inhibitor solution tank 451, a second valve 452, and a supply path 453.

  The third charging unit 401 is disposed to face the upper end opening 112 a of the outer tub 112. The third throwing part 401 throws silicon 5 into the outer tub 112 through the upper end opening 112a. For example, the silicon 5 introduced from the third introduction unit 401 may be in the form of a solution dissolved in a solvent, or may be in the form of a powder. By introducing the silicon 5, the silicon 5 is dissolved in the phosphoric acid solution 3 in the outer tank 112. The silicon 5 dissolved in the phosphoric acid solution 3 in the outer tank 112 is supplied into the inner tank 111, that is, the processing tank 11 through the circulation path 12 together with the phosphoric acid solution 3. Thereby, the processing tank 11 can remove the silicon nitride film 222 from the semiconductor substrate 20 with the phosphoric acid solution 3 in which the silicon 5 is dissolved. By using the phosphoric acid solution 3 in which the silicon 5 is dissolved, the etching selectivity of the silicon nitride film 222 with respect to the silicon oxide film 221 can be increased. The intermediate tank 17 and the first charging unit 14 may be omitted, and instead, the charging unit 401 may serve as the intermediate tank 17 and the first charging unit 14 instead.

  Here, in order to increase the etching selectivity of the silicon nitride film 222 to the silicon oxide film 221, the heating unit 13 heats the phosphoric acid solution 3 to the second temperature T2 that is the target of the phosphoric acid solution 3 in the processing bath 11. The second temperature T2 can also be referred to as a process temperature for processing the substrate 20 in the processing tank 11. The second temperature T2 is, for example, 150 ° C. or higher. When the temperature is 150 ° C. or higher, the saturated dissolution concentration of silicon 5 increases sharply as the temperature increases. Therefore, by treating the semiconductor substrate 20 with the phosphoric acid solution 3 having a temperature of 150 ° C. or higher, a large amount of silicon 5 can be dissolved in the phosphoric acid solution 3, so that silicon oxidation is suppressed while suppressing silica precipitation. The etching selectivity of the silicon nitride film 222 to the film 221 can be further increased. On the other hand, when the phosphoric acid solution 3 having the second temperature T2 is introduced into the discharge path 403 as it is after the substrate processing, the heat of the phosphoric acid solution 3 may damage the discharge path 403. It is desirable that the phosphoric acid solution 3 passing through the discharge path 403 is cooled so that the discharge path 403 is not damaged by the hot phosphoric acid solution 3. The cooling tank 404 is provided for cooling the phosphoric acid solution 3 passing through the discharge path 403.

  The dissolution concentration of silicon 5 in the phosphoric acid solution 3 is higher than the first saturated dissolution concentration S1 corresponding to the target first temperature T1 of the phosphoric acid solution 3 in the discharge path 403, and the phosphoric acid solution in the treatment tank 11 It is lower than the second saturated dissolution concentration S2 corresponding to the target second temperature T2. The first temperature T1 can also be referred to as a target temperature for cooling the phosphoric acid solution 3 by the cooling tank 404. The second temperature T2 can also be referred to as a target temperature for heating the phosphoric acid solution 3 by the heating unit 13. The first temperature T1 may be a temperature of 80 ° C. or less, for example.

  By making the dissolution concentration of silicon 5 higher than the first saturation dissolution concentration S1 and lower than the second saturation dissolution concentration S2, the dissolution concentration of silicon 5 can be increased while suppressing the precipitation of silicon 5. Thereby, the etching selectivity of the silicon nitride film 222 to the silicon oxide film 221 can be further increased.

  Note that the third charging unit 401 may load the silicon 5 into the inner tank 111. Further, as a method for dissolving silicon 5 other than introducing silicon 5 by the third injection unit 401, for example, by selectively removing the silicon nitride film 222 from the semiconductor substrate 20 with the phosphoric acid solution 3 in the processing bath 11. The silicon contained in the removed silicon nitride film 222 may be dissolved in the phosphoric acid solution 3. In this case, in the next processing of the semiconductor substrate 20, the semiconductor substrate 20 can be processed with the phosphoric acid solution 3 in which silicon is dissolved.

  The discharge path 403 is in communication with the circulation path 12. The discharge path 403 includes a discharge path 403 a on the upstream side of the cooling tank 404 and a discharge path 403 b on the downstream side of the cooling tank 404. The cooling tank 404 itself may constitute a part of the discharge path 403. For example, the discharge path 403 discharges the phosphoric acid solution 3 used a predetermined number of times for processing the semiconductor substrate 20 to the outside of the substrate processing apparatus 1. On the discharge path 403, the 1st valve 402, the cooling tank 404, and the 3rd valve 407 are arrange | positioned in order from the upstream.

  The first valve 402 can open and close the upstream discharge passage 403a. By opening the first valve 402, the phosphoric acid solution 3 is introduced into the upstream discharge path 403a. The first valve 402 and the other valves 407 and 452 may be electromagnetic valves, for example.

  The cooling tank 404 stores the phosphoric acid solution 3 introduced into the upstream discharge path 403a by the first valve 402 until the time required for cooling elapses. The cooling tank 404 cools the stored phosphoric acid solution 3 to the first temperature T1. By cooling the phosphoric acid solution 3, damage to the downstream discharge path 403b due to heat of the phosphoric acid solution 3 can be avoided. The specific mode of the cooling method of the cooling tank 404 is not particularly limited. For example, the cooling tank 404 may cool the phosphoric acid solution 3 by heat exchange with a refrigerant such as water or gas.

  The third valve 407 can open and close the discharge path 403 b on the downstream side of the cooling tank 404. The third valve 407 opens after the time required for cooling has elapsed since the introduction of the phosphoric acid solution 3 into the cooling tank 404. Accordingly, the third valve 407 introduces the phosphoric acid solution 3 in the cooling tank 404 that has been cooled to the first temperature T1 into the discharge path 403b on the downstream side.

  The supply unit 450 supplies the silica precipitation inhibitor 4 to the phosphoric acid solution 3 passing through the downstream discharge path 403b. By supplying the silica precipitation inhibitor 4, silica precipitation in the downstream discharge path 403 b can be suppressed, and clogging of the discharge path 403 can be prevented.

  In the example shown in FIG. 15, the supply unit 450 supplies the silica precipitation inhibitor 4 to the phosphoric acid solution 3 in the cooling tank 404. Specifically, the precipitation inhibitor solution tank 451 stores a solution of the silica precipitation inhibitor 4 at the upstream end of the supply path 453. The downstream end of the supply path 453 is connected to the cooling tank 404. The second valve 452 can open and close the supply path 453 between the precipitation inhibitor solution tank 451 and the cooling tank 404. By opening the second valve 452, the silica precipitation inhibitor 4 in the precipitation inhibitor solution tank 451 is introduced into the cooling tank 404 by the supply path 453.

  The silica precipitation inhibitor 4 is supplied to the phosphoric acid solution 3 through the discharge path 403 when the temperature of the phosphoric acid solution 3 is higher than the third temperature T3 corresponding to the saturated dissolution concentration of the silicon 5. The third temperature T3 is higher than the first temperature T1 and lower than the second temperature T2. In the example shown in FIG. 15, the temperature of the phosphoric acid solution 3 introduced into the cooling tank 404 is higher than the third temperature T3 until the heat exchange with the refrigerant (not shown) sufficiently proceeds in the cooling tank 404. high. The supply unit 450 supplies the silica precipitation inhibitor 4 to the phosphoric acid solution 3 before the temperature of the phosphoric acid solution 3 introduced into the cooling tank 404 reaches the third temperature T3 by cooling. For example, the supply unit 450 supplies the silica precipitation inhibitor 4 to the introduced new phosphoric acid solution 3 at the timing when the new phosphoric acid solution 3 is introduced into the cooling tank 404 as the first valve 402 is opened. May be.

  By supplying the silica precipitation inhibitor 4 to the phosphoric acid solution 3 when the temperature is higher than the third temperature T3, precipitation of silicon 5 can be avoided in advance. The supply unit 450 may supply the silica precipitation inhibitor 4 to the upstream discharge path 403a. Even in this case, since the silica precipitation inhibitor 4 can be supplied to the phosphoric acid solution 3 when the temperature of the phosphoric acid solution 3 is higher than the third temperature T3, the precipitation of the silicon 5 can be avoided in advance.

  FIG. 16A is a graph showing a saturated dissolution concentration curve Cb of silicon 5 before the supply of the silica precipitation inhibitor 4 in the substrate processing method showing the fourth embodiment. In FIG. 16A, the horizontal axis represents the temperature of the phosphoric acid solution 3, and the vertical axis represents the saturated dissolution concentration of the silicon 5. Further, in FIG. 16A, the dissolution concentration of silicon 5 dissolved in the phosphoric acid solution 3 at the second temperature T2 is shown by a solid bar graph to which reference numeral 5 is attached. As shown by the solid bar graph, the dissolution concentration of silicon 5 in this embodiment is higher than the first saturation dissolution concentration S1 at the first temperature T1, and the second saturation dissolution concentration at the second temperature T2. Lower than S2.

  If the silica precipitation inhibitor 4 is not supplied to the phosphoric acid solution 3 passing through the discharge path 403, the dissolution concentration of the silicon 5 is set to the first saturation dissolution concentration as shown by the broken line bar graph denoted by reference numeral 5 in FIG. It is necessary to make S1 or less. This is because when the dissolution concentration of silicon 5 is made higher than the first saturation dissolution concentration S1 without supplying the silica precipitation inhibitor 4, the dissolution concentration exceeds the first saturation dissolution concentration S1 as the phosphoric acid solution 3 is cooled. This is because the silicon 5 is deposited in the discharge path 403.

  On the other hand, in this embodiment, by supplying the silica precipitation inhibitor 4 to the phosphoric acid solution 3, it is possible to suppress the precipitation of the silicon 5 accompanying the cooling of the phosphoric acid solution 3. For example, as shown in FIG. 16B described later, the silica precipitation inhibitor 4 suppresses the precipitation of the silicon 5 by increasing the saturation dissolution concentration curve of the silicon 5. Since precipitation of silicon 5 can be suppressed, the dissolution concentration of silicon 5 can be set to a value S3 larger than the first saturation dissolution concentration S1, as shown by a solid bar graph in FIG. 16A. Thereby, the etching selectivity of the silicon nitride film 222 with respect to the silicon oxide film 221 can be increased, and the deposition of silicon 5 in the discharge path 403 can be suppressed.

  FIG. 16B is a graph showing a saturated dissolution concentration curve Ca of silicon 5 after supplying the silica precipitation inhibitor 4 in the substrate processing method according to the fourth embodiment.

  In the fourth embodiment, the silica precipitation inhibitor 4 is supplied to the phosphoric acid solution 3 when the temperature of the phosphoric acid solution 3 is higher than the third temperature T3 corresponding to the saturated dissolution concentration S3 of the silicon 5. When the silica precipitation inhibitor 4 is supplied to the phosphoric acid solution 3 when the temperature is higher than the third temperature T3, the silicon 5 is precipitated when the phosphoric acid solution 3 is cooled to the third temperature T3 in the cooling tank 404. It can be prevented from starting. The reason is that, for example, as shown in FIG. 16B, the saturation dissolution concentration curve is increased from Cb to Ca by the addition of the silica precipitation inhibitor 4, so that the saturation dissolution concentration at the third temperature T3 can be increased from S3 to S30. It depends. The increase in the saturation solubility curve from Cb to Ca is supported by the results shown in FIGS. 5, 7, 8, 9, 10, and 11. Therefore, when the silica precipitation inhibitor 4 is supplied to the phosphoric acid solution 3 when the temperature is higher than the third temperature T3, the precipitation of the silicon 5 can be avoided in advance.

  As described above, according to the fourth embodiment, the etching selectivity of the silicon nitride film 222 to the silicon oxide film 221 can be increased in the processing tank 11, so that the processing efficiency of the semiconductor substrate 20 can be improved. it can. Moreover, clogging of the discharge path 403 can be prevented by avoiding the precipitation of silicon 5 in advance.

  FIG. 17 is a diagram of the substrate processing apparatus 1 showing a modification of the fourth embodiment. In FIG. 15, an example in which the deposition of silicon 5 is avoided has been described. On the other hand, in this modification, the precipitation of silicon 5 is eliminated afterwards.

  Specifically, as shown in FIG. 17, in the substrate processing apparatus 1 of the present modification, the supply unit 450 supplies the silica precipitation inhibitor 4 to the phosphoric acid solution 3 passing through the downstream discharge path 403b. In the phosphoric acid solution 3 downstream of the cooling tank 404, silicon 5 deposited by cooling in the cooling tank 404 is present. However, in this modification, the precipitated silicon 5 can be dissolved by the silica precipitation inhibitor 4 immediately after that. Thereby, the deposition of the silicon 5 can be eliminated afterwards to prevent the discharge passage 403 from being clogged.

  Note that the fourth embodiment may be appropriately combined with the second embodiment or the third embodiment.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Substrate processing apparatus 11 Processing tank 12 Circulation path 13 Heating part 14 Input part

Claims (7)

An etching solution containing phosphoric acid and a silica precipitation inhibitor is supplied, and a processing unit that contacts the substrate having a silicon nitride film on the surface to the etching solution to remove the silicon nitride film from the substrate;
A circulation path for circulating the etching solution to the processing unit;
A heating unit for heating the etching solution;
A substrate processing apparatus comprising: a first input unit that is provided in the circulation path and inputs the silica precipitation inhibitor into the etching solution. A discharge path for discharging the etching solution;
The processing unit removes the silicon nitride film from the substrate with the etching solution in which silicon is dissolved,
The dissolution concentration of the silicon with respect to the etching solution is higher than the first saturated dissolution concentration corresponding to the first temperature that is the target of the etching solution in the discharge path, and is the target of the etching solution in the processing unit. The substrate processing apparatus according to claim 1, wherein the substrate processing apparatus is lower than a second saturated dissolution concentration corresponding to the second temperature.   The substrate processing apparatus of Claim 2 provided with the supply part which supplies the said silica precipitation inhibitor to the etching liquid which passes along the said discharge path. Supply an etching solution containing phosphoric acid and a silica precipitation inhibitor in the processing section,
A substrate processing method for removing a silicon nitride film from the substrate by bringing a substrate having a silicon nitride film on the surface into contact with the etching solution supplied into the processing section. Silicon is dissolved in the etching solution,
In the processing section, the silicon nitride film is removed from the substrate with the etching solution in which the silicon is dissolved,
The etching solution is discharged through the discharge path,
The dissolution concentration of the silicon with respect to the etching solution is higher than the first saturated dissolution concentration corresponding to the first temperature that is the target of the etching solution in the discharge path, and is the target of the etching solution in the processing unit. The substrate processing method according to claim 4, wherein the substrate processing method is lower than a second saturated dissolution concentration corresponding to the second temperature. Supplying the silica precipitation inhibitor to the etching solution passing through the discharge path;
The substrate processing according to claim 5, wherein the supply of the silica precipitation inhibitor to the etching solution passing through the discharge path is performed when the temperature of the etching solution is higher than a third temperature corresponding to the saturated dissolution concentration of the silicon. Method. An etching solution for removing silicon nitride,
An etching solution containing 75 to 94% by weight of phosphoric acid and 0.01 to 3.2% by weight of a silica precipitation inhibitor, wherein the silica precipitation inhibitor is aluminum, potassium, lithium, sodium, magnesium, calcium, An etching solution comprising at least one compound selected from the group consisting of oxides, nitrides, chlorides, bromides, hydroxides and nitrates of any of zirconium, tungsten, titanium, molybdenum, hafnium, nickel and chromium.

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