KR20210109475A - Silicon etching solution, method for manufacturing silicon device using same, and substrate treatment method - Google Patents

Abstract

Provided is a silicon etchant capable of suppressing the influence of silicon crystal orientation and capable of uniform etching irrespective of the crystal orientation of single crystal grains in a polysilicon film. The silicon etching solution includes at least one compound selected from the group consisting of quaternary ammonium hydroxide, water, and compounds represented by the following formulas (1) and (2).

Description

Silicon etching solution, manufacturing method and substrate processing method of a silicon device using the etching solution

[0001] The present invention relates to a silicon etchant used in a surface treatment and an etching process for manufacturing various silicon devices. Further, the present invention relates to a method of manufacturing a silicon device using the etching solution. In addition, the present invention relates to a substrate processing method using the etching solution. Further, the substrate includes a semiconductor wafer, a glass substrate for a liquid crystal display device, a glass substrate for a plasma display, a glass or ceramic substrate for a magnetic or optical disk, a glass substrate for organic EL, a glass substrate for a solar cell, or a silicon substrate.

In consideration of the selectivity to a silicon oxide film and a silicon nitride film, alkali etching is sometimes used in a semiconductor manufacturing process using silicon. Here, selectivity refers to a property of exhibiting particularly high etching properties for a specific member. For example, when etching a substrate having a film different from the silicon film (eg, a silicon oxide film), only the silicon film is etched, and when the silicon oxide film is not etched, the selectivity to silicon is high. As the alkali, NaOH, KOH, and tetramethylammonium hydroxide (hereinafter also referred to as TMAH), which have low toxicity and are easy to handle, are used alone. Among them, TMAH has an etching rate for a silicon oxide film that is almost one order of magnitude lower than when NaOH or KOH is used, and is particularly preferably used when a silicon oxide film that is cheaper than a silicon nitride film is used as a mask material. .

BACKGROUND ART In semiconductor devices, the demand for etching is becoming stricter due to stacking of memory cells and densification of logic devices. In the etching, silicon etching with alkali exhibits crystal anisotropy, unlike etching in hydrofluoric acid-nitric acid aqueous solution. Crystal anisotropy refers to a property (anisotropy of etching) that causes a difference in etching rate depending on the crystal orientation of silicon. Using this property, alkali etching is used for processing a silicon device having a complex three-dimensional structure with respect to single crystal silicon. On the other hand, since polysilicon is composed of single crystal silicon particles (single crystal particles), if there is anisotropy in etching, the etching rate is different due to the difference in the crystal orientation in which the single crystal particles are exposed, and uniform etching cannot be performed and surface cracks are caused. It tends to occur, and in addition, there is a problem that, after etching, specific single crystal grains are difficult to be etched and may remain.

Recently, a process using silicon etching has been widely used in a semiconductor manufacturing process. As an example of the process, a charge accumulation type memory process will be described as an example. The charge accumulation type memory is, for example, as shown in FIG. 4, a substrate ( W), and its manufacturing process includes an etching process of the laminated film 91 . The etching includes a step of etching only polysilicon leaving the silicon oxide film, supplying an etching solution to the recessed portions 92 provided on the substrate W, and selectively etching the polysilicon films P1 , P2 , and P3 . At this time, the silicon oxide films O1, O2, and O3 are left without etching. The charge accumulation type memory operates as a memory by accumulating electric charges in a polysilicon film. The amount of accumulated electric charge depends on the volume of the polysilicon film. Therefore, it is necessary to strictly control the volume of the polysilicon film in order to realize the design capacity. However, as described above, if the etching rate is different depending on the crystal orientation of the single crystal grains, the polysilicon film cannot be etched uniformly, making it difficult to manufacture the device.

As described above, etching in hydrofluoric acid-nitric acid aqueous solution can be isotropically etched irrespective of the crystal orientation of silicon, and it is possible to uniformly etch single crystal silicon, polysilicon, and amorphous silicon. That is, the hydrofluoric acid-nitric acid aqueous solution does not exhibit crystal anisotropy in silicon etching. However, the hydrofluoric acid-nitric acid aqueous solution has a small etching selectivity between silicon and silicon oxide film, and cannot be used in the semiconductor manufacturing process in which the silicon oxide film remains as described above.

On the other hand, the alkaline etching solution has selectivity to the silicon oxide film and the silicon film, and selectively etches the silicon film. Regarding etching using alkali, Patent Document 1 discloses an etching solution for a silicon substrate for solar cells containing alkali hydroxide, water, and polyalkylene oxide alkyl ether. Patent Document 2 discloses an etchant for a silicon substrate for solar cells containing an alkali compound, an organic solvent, a surfactant, and water. In Patent Document 2, TMAH is exemplified as an example of an alkali compound, and polyalkylene oxide alkyl ether is exemplified as an organic solvent. However, the alkali compounds actually used are sodium hydroxide and potassium hydroxide.

Patent Document 3 discloses a developer containing quaternary alkylammonium hydroxide, a nonionic surfactant, and water. Although there are examples of polyalkylene oxide alkyl ethers as nonionic surfactants, nonionic surfactants with high surfactant activity, such as acetylene glycol-based surfinol (trade name), are actually used.

Non-Patent Document 1 describes a method capable of isotropically etching silicon by oxidizing the silicon surface by applying a voltage and dissolving the oxide film in an aqueous KOH solution.

Patent Document 4 discloses an etching solution containing water, quaternary alkylammonium hydroxide, and a water-miscible solvent, and as a water-miscible solvent, tripropylene glycol methyl ether and the like are described.

[Patent Document 1] Japanese Patent Laid-Open No. 2010-141139

[Patent Document 2] Japanese Patent Laid-Open No. 2012-227304

[Patent Document 3] International Publication No. 2017/169834

[Patent Document 4] Japanese Patent Laid-Open No. 2019-50364

[Non-Patent Document 1] Denso Technical Review, Yamashita et al. 2001, Vol. 6, No. 2, p. 94-99

By the way, in the etching liquid of patent document 1 and patent document 2, since NaOH and KOH are used as an alkali compound, the etching rate with respect to a silicon oxide film is high. Therefore, the silicon oxide film which should remain as a part of the mask material and pattern structure is also etched away, and only the polysilicon film cannot be etched selectively. In addition, since the etching liquid of Patent Documents 1 and 2 aims to increase crystal anisotropy and damage the surface, the polysilicon film cannot be etched uniformly. The developer of Patent Document 3 is not intended for precise etching of silicon, and therefore, the etching uniformity of the polysilicon film is not considered at all. In addition, nonionic surfactants that are actually used are surfinol, etc., which have high surface activity, cover the surface of the polysilicon film and rather damage polysilicon etching by alkali, and cannot etch the polysilicon film to a high degree. . Next, Non-Patent Document 1 can etch silicon isotropically, but since silicon is not directly dissolved, but an oxide film oxidized by voltage application is etched in an aqueous KOH solution, there is no etching selectivity between silicon and silicon oxide film. . In addition, the etching solution described in Patent Document 4 is a chemical solution capable of selectively removing silicon with respect to silicon-germanium, and there is no description about etching silicon isotropically.

Accordingly, an object of the present invention is to provide a silicon etchant capable of suppressing crystal anisotropy and capable of uniform etching regardless of the crystal orientation of single crystal grains in a polysilicon film. Moreover, in a preferable aspect of this invention, it aims at providing the method of adjusting the degree of influence on the etching rate by the crystal anisotropy at the time of silicon etching by adjusting the composition ratio of a silicon etching liquid.

MEANS TO SOLVE THE PROBLEM As a result of repeating earnest examination, the present inventors discovered that the said subject could be solved by making the silicon etching liquid containing quaternary ammonium hydroxide and water contain the compound represented by Formula (1) or Formula (2). .

That is, the first invention is

Isotropic comprising at least one compound selected from the group consisting of quaternary ammonium hydroxide, water, and compounds represented by the following formulas (1) and (2), and satisfying the following conditions 1 and 2 It relates to a silicon etchant.

R ¹ O-(C _m H _2m O) _n -R ² (1)

(Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,

m is an integer from 2 to 6, and n is from 1 to 3. However, R ¹ and R ² are not hydrogen atoms at the same time, and in the case of m=2, the sum of the number of carbon atoms (C ¹ ) ^{of n and R 1 and} the number of carbon atoms (C ^{2 ) of R 2} (n + C ¹ + C ^{2 )} ) is greater than or equal to 5.)

HO-(C ₂ H ₄ O) _p -H (2)

(In the above formula, p is in the range of 15 to 1000.)

Condition 1: 0.2 ≤ Etching rate ratio (R ₁₁₀ / R ₁₀₀ ) ≤ 1

Condition 2: 0.8 ≤ Etching rate ratio (R ₁₁₀ / R ₁₁₁ ) ≤ 4

(In the above, R ₁₀₀ represents an etching rate for 100 single crystal faces of _{silicon, R 110} represents an etching rate for 110 single crystal faces of _{silicon, and R 111} represents an etching rate for 111 single crystal faces of silicon.)

In the first invention, the concentration of quaternary ammonium hydroxide is 0.1 to 25% by mass, and the concentration of at least one compound selected from compounds represented by Formula (1) or (2) is 0.001 to 40% by weight It is preferable to be

In the first invention, the concentration of quaternary ammonium hydroxide is 0.5 to 25% by mass, and the concentration of at least one compound selected from compounds represented by Formula (1) or Formula (2) is 0.001 to 20% by weight It is preferable to be

_{The etching rate ratio (R 110} / R ₁₀₀ ) of the first silicon etching solution of the present invention is 0.3 to 1, and the etching rate ratio (R ₁₁₀ / R ₁₁₁ ) is preferably 0.8 to 3. When the etching rate ratio is in the above range, the etching rate becomes almost constant regardless of the crystal orientation, the surface cracks become small, and uniform etching becomes possible.

The second present invention is a substrate processing method for processing a silicon wafer and/or a substrate including a polysilicon film and an amorphous silicon film using the isotropic silicon etchant of the first present invention.

A third aspect of the present invention is a method of manufacturing a silicon device comprising a step of etching a silicon wafer, a polysilicon film, and an amorphous silicon film, wherein the etching is performed using the silicon etchant of the first present invention. am.

In the present invention, the etching rate ratio is the ratio of the etching rate with respect to the silicon substrate having different crystal orientations, condition 1 is the etching rate ratio of 110 and 100 surfaces (etch rate ratio (R ₁₁₀ / R ₁₀₀ )), condition 2 is the etching rate ratio (etch rate ratio (R ₁₁₀ / R ₁₁₁ )) of the 110 surface and the 111 surface. When the etching rate ratio is within the above range, it means that it is difficult to be influenced by the crystal orientation during etching. When the etching rate ratio of Conditions 1 and 2 is close to 1, it is difficult to be affected by the crystal orientation during etching, and etching can be performed more isotropically.

When at least one compound selected from the compounds represented by Formula (1) or Formula (2) is contained in a conventional silicon etchant containing quaternary ammonium hydroxide and water according to the study of the present inventor, as shown in FIG. Similarly, although the etching rate of silicon decreases, the difference in etching rate due to a difference in crystal orientation compared to a silicon etchant that does not contain at least one compound selected from the compounds represented by Formula (1) or Formula (2) was found to decrease. The silicon etching solution that does not contain at least one compound selected from the compounds represented by Formula (1) or Formula (2) has the highest etching rate in the order of 110 surfaces and 100 surfaces, and the etching rate of 111 surfaces is the slowest. Although the etching rate of each crystal plane is decreased by containing at least one compound selected from the compounds represented by the formula (1) or (2), the etching rate of 111 planes is reduced with respect to the decrease in the etching rates of 100 planes and 110 planes. Since the fall of the etching rate is small, the etching rate of each crystal plane approaches the same degree. At this time, by adjusting the addition amount of the quaternary ammonium hydroxide and at least one compound selected from the compound represented by the formula (1) or (2), the crystal orientation is less affected, and the silicon is more uniformly etched. It can be done with a silicon etchant that can do it.

The substrate processing method according to the first embodiment using the silicon etchant of the present invention,

a substrate holding process for holding the substrate in a horizontal form;

and supplying the isotropic silicon etchant of the present invention to the main surface of the substrate while rotating the substrate around a vertical rotation axis passing through the central portion of the substrate.

A substrate processing method according to a second embodiment using the silicon etchant of the present invention,

a substrate holding process for holding the plurality of substrates in an upright configuration;

and immersing the substrate in an upright form in the isotropic silicon etchant of the present invention stored in a treatment tank.

The etching rate of the silicon etchant of the present invention is hardly affected by the crystal orientation of silicon, and the etching process is isotropically irrespective of the crystal plane generated in the etching process surface of the polysilicon film or single crystal.

Further, by adjusting the composition ratio of the silicon etching solution, the etching rate can be adjusted with respect to the crystal orientation of silicon, and a silicon etching solution having a desired etching rate ratio can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the density|concentration of at least 1 type of compound selected from the compound represented by Formula (1) or Formula (2), and the etching rate of the silicon substrate of each crystal plane.
2 is a schematic top view of the substrate processing apparatus used in the first embodiment.
3 is a schematic cross-sectional view of a substrate processing unit used in the first embodiment.
4 : is a schematic sectional drawing which shows the board|substrate W used as an etching object.
5 is an example of an etching process flow in the first embodiment.
6 : is a schematic sectional drawing which shows the other board|substrate W2 used as etching object.
7 is a schematic top view of the substrate processing apparatus used in the second embodiment.
8 is a schematic cross-sectional view of a substrate processing unit used in the second embodiment.
9 is an example of an etching process flow in the second embodiment.

The isotropic silicon etching solution of the present invention contains at least one compound selected from the group consisting of quaternary ammonium hydroxide, water, and compounds represented by the following formulas (1) and (2), and also meets the following conditions 1 and 2 Satisfies.

R ¹ O-(C _m H _2m O) _n -R ² (1)

(Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,

m is an integer from 2 to 6, and n is from 1 to 3. However, R ¹ and R ² are not hydrogen atoms at the same time, and in the case of m = 2, the number of carbon atoms (C ¹ ) and R ^{2 of n and R 1} is the sum of the number of carbon atoms (C ² ) (n + C ¹ + C ^{2 )} ) is greater than or equal to 5.)

HO-(C ₂ H ₄ O) _p -H (2)

(In the above formula, p is in the range of 15 to 1000.)

Condition 1: 0.2 ≤ Etching rate ratio (R ₁₁₀ / R ₁₀₀ ) ≤ 1

Condition 2: 0.8 ≤ Etching rate ratio (R ₁₁₀ / R ₁₁₁ ) ≤ 4

(Wherein, R ₁₀₀ represents an etching rate for 100 surfaces of a silicon single crystal, R ₁₁₀ represents an etching rate for 110 surfaces of a _{silicon single crystal, and R 111} represents an etching rate for 111 surfaces of a silicon single crystal. The etching rate is the method described in Examples to be measured.)

As quaternary ammonium hydroxide, various quaternary ammonium hydroxide conventionally used as a component of a silicon etching liquid is used. Quaternary ammonium hydroxide is represented by ^{NR4 +} ·OH ^-. R is usually an alkyl group or an aryl group, and four R may be the same or different. Moreover, the alkyl group or the aryl group may have substituents, such as a hydroxyl group. Preferred quaternary ammonium hydroxides include quaternary alkyl ammonium hydroxide in which 4 R is an alkyl group, and an ammonium compound in which a hydroxyl group is bonded to an alkyl group of the quaternary alkylammonium hydroxide, such as trimethyl-2-hydroxyethylammonium hydroxide ( choline hydroxide), dimethylbis(2-hydroxyethyl)ammonium hydroxide, and methyltris(2-hydroxyethyl)ammonium hydroxide.

As the quaternary alkyl ammonium hydroxide, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide can be used without particular limitation. Among these quaternary alkyl ammonium hydroxides, quaternary alkyl ammonium hydroxides in which the alkyl group has 1 to 4 carbon atoms and all alkyl groups are the same are preferred. In particular, it is most preferable to use TMAH because of the high etching rate of silicon.

In addition, the concentration of quaternary ammonium hydroxide is also not particularly different from the conventional silicon etching solution, and if it is in the range of 0.1 to 25 mass %, an excellent etching effect can be obtained without causing crystal precipitation, which is preferable. Moreover, as for the density|concentration of quaternary ammonium hydroxide, it is more preferable that it is the range of 0.5-25 mass %.

The silicon etching solution of the present invention is characterized in that it contains at least one compound selected from compounds represented by the following formulas (1) and (2).

R ¹ O-(C _m H _2m O) _n -R ² (1)

In Formula (1), R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, m is an integer of 2 to 6, and n is 1 to 3. However, R ¹ and R ² are not hydrogen atoms at the same time. In addition, when m = 2, the sum (n + C ¹ + C ² ) of the number of carbon atoms (C ¹ ) ^{of n and R 1 and} the number of carbon atoms (C ^{2 ) of R 2} is 5 or more.

R ¹ is preferably a hydrogen atom or a methyl group, R ² is preferably a propyl group or a butyl group, and m is preferably 2 or 3.

When the compound represented by the formula (1) used particularly preferably in the present invention is specifically shown, ethylene glycol monobutyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, propylene Glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol dimethyl ether, triethylene Glycol monobutyl ether and tripropylene glycol monomethyl ether are mentioned. Among them, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, triethylene glycol monobutyl ether, tripropylene Glycol monomethyl ether is preferred.

HO-(C ₂ H ₄ O) _p -H (2)

In the above formula (2), p is in the range of 15 to 1000. In addition, p is an average value. Accordingly, the compound represented by the formula (2) may contain a small amount of a compound in which p is 14 or less or p is more than 1000. However, in the compound represented by Formula (2), the ratio of the compound where p is outside the said range is 2 % or less, Preferably it is 0 %. As for the compound represented by the said Formula (2) used especially preferably by this invention, all polyethyleneglycol whose p = 15-1000 in Formula (2) is mentioned. When p is less than 15, the effect of this invention does not appear, and when p exceeds 1000, the viscosity at the time of mixing becomes high and it becomes difficult to use. Among these polyethylene glycols, from the viewpoint of viscosity and handling, p = 30 to 500 are preferable. Although not limited, specifically, polyethylene glycol 1000 (p = about 22), polyethylene glycol 1500 (p = about 33), polyethylene glycol 1540 (p = 35), polyethylene glycol 2000 (p = 45) manufactured by Wako Pure Chemical Industries, Fujifilm. ), polyethylene glycol 4000 (p = 90), and polyethylene glycol 20000 (p = 450).

The compound represented by Formula (1) or Formula (2) may be used individually by 1 type, and may mix and use two or more things from which a type differs. For example, a mixture of propylene glycol monomethyl ether and propylene glycol monopropyl ether, a mixture of diethylene glycol ethyl methyl ether and polyethylene glycol 1000, and a mixture of polyethylene glycol 1000 and polyethylene glycol 4000 are mentioned.

When the compound represented by Formula (1) or Formula (2) is contained in a silicon etching solution containing quaternary ammonium hydroxide and water as described above, the difference in etching rate due to the difference in the crystal orientation of silicon is reduced. The silicon etching solution that does not contain the compound represented by Formula (1) or Formula (2) has the highest etching rate in the order of 110 surfaces and 100 surfaces, and the etching rate of 111 surfaces is the slowest. By containing the compound represented by Formula (1) or Formula (2), the etching rate of each crystal plane is lowered, but since the decrease in the etching rate of the 111 plane is small compared to the decrease in the etching rate of 100 planes and 110 planes, The etch rate can be approached to the same extent.

By containing at least one compound selected from the compounds represented by Formula (1) or Formula (2) and satisfying Conditions 1 and 2, crystal anisotropy at the time of silicon etching is suppressed, and etching is isotropically performed. and uniform etching processing is possible regardless of the silicon wafer, polysilicon film, or amorphous silicon film.

In order to satisfy the said conditions 1 and 2, content of at least 1 sort(s) of compound chosen from the compound represented by Formula (1) or Formula (2) may be adjusted. At this time, when the upper or lower limits of Condition 1 and Condition 2 are exceeded, even if etching can be performed uniformly with respect to an arbitrary crystal orientation, etching is unevenly performed in other crystal orientations, which is influenced by the orientation of single crystal grains in the polysilicon film means that it cannot be suppressed, and uniform etching cannot be performed.

Moreover, it is also possible to set it as the silicon etching liquid affected by the desired crystal orientation by adjusting content of the at least 1 sort(s) of compound chosen from the compound represented by Formula (1) or Formula (2).

The concentration of at least one compound selected from the compounds represented by Formula (1) or Formula (2) is preferably 40% by mass or less, more preferably less than 20% by mass, based on the total mass of the etching solution, 15 It is more preferable that it is less than mass %, and it is especially preferable that it is 10 mass % or less. Moreover, it is preferable that the density|concentration of at least 1 sort(s) of compound chosen from the compound represented by said Formula (1) or said Formula (2) is 0.001 mass % or more. If the concentration of the compound represented by the formula (1) or (2) is within the above range, the difference in etching rate depending on the crystal orientation is small, so the influence of single crystal grains in polysilicon is reduced and a uniform etching process is possible. becomes

The total concentration of at least one compound selected from quaternary ammonium hydroxide and the compound represented by Formula (1) or Formula (2) is preferably 45% by mass or less, more preferably 40% by mass or less, 35 It is more preferable that it is mass % or less, and it is preferable that it is 0.101 mass % or more, and, as for a lower limit, it is still more preferable that it is 0.501 mass % or more.

In addition, the mass ratio of quaternary ammonium hydroxide and at least one compound selected from the compound represented by Formula (1) or Formula (2) (quaternary ammonium hydroxide/the compound) is represented by Formula (1) 0.05-10 are preferable, as for a compound, 0.1-5 are more preferable, 0.5-1000 are preferable and, as for the compound represented by Formula (2), 1-500 are still more preferable.

Moreover, when using the compound represented by Formula (1) independently, 0.1-40 mass % is preferable on the basis of the mass of the whole etching liquid, and, as for the density|concentration, 0.1-20 mass % is more preferable. When using the compound represented by Formula (2) independently, 0.001-10 mass % is preferable on the basis of the mass of the whole etching liquid, and, as for the density|concentration, 0.001-5 mass % is more preferable.

When the compound represented by Formula (1) and the compound represented by Formula (2) are used together, the mass ratio (compound of Formula (1) / compound of Formula (2)) is preferably 0.05 to 2000, and 0.1 to 1000 This is more preferable, and it is preferable that the total amount exists in the said range.

In addition to at least one compound selected from the group consisting of quaternary ammonium hydroxide and the compound represented by the formula (1) or (2), a surfactant or the like may be added to the silicon etching solution as long as the object of the present invention is not impaired. However, since they may affect etching property, it is preferable to set it as 1 mass % or less, and it is more preferable that it is not contained. Therefore, it is preferable that the silicon etching solution substantially consists of water and at least one compound selected from quaternary ammonium hydroxide and a compound represented by Formula (1) or Formula (2), and the content of other components other than these is It is preferable to set it as 1 mass % or less, and it is more preferable that it is not contained. That is, it is preferable that the whole amount of remainder other than the quaternary ammonium hydroxide of a silicon etching liquid and at least 1 sort(s) of compound chosen from the compound represented by Formula (1) or Formula (2) is water.

The mechanism by which the influence of crystal anisotropy of silicon etching can be reduced by adding to the compound represented by Formula (1) or Formula (2) is not necessarily clear. However, the present inventors are considering as follows. The compound represented by the formula (1) or (2) can be considered as a nonionic surfactant having a relatively low surfactant activity. The compound represented by Formula (1) or Formula (2) has a surface active ability and is attached to the polysilicon surface to temporarily protect it. As a result, contact with the silicon surface of 110 and 100 surfaces with high etching rate and quaternary ammonium is inhibited, and etching is suppressed. However, since the surface active ability of the compound represented by Formula (1) or Formula (2) is relatively low, it is liberated from the silicon surface. As a result, the quaternary ammonium contacts the silicon surface and etching is performed. The adhesion of the compound represented by the formula (1) or (2) to the polysilicon surface and the glass are repeated, while the etching proceeds gently. On the other hand, although the compound adheres to the silicon surface on 111 surfaces, the atomic pore radius of 111 surfaces is small compared to 110 surfaces and 100 surfaces, and it is considered that the compound of formula (1) or (2) is difficult to penetrate. Therefore, the inhibition of the contact between the silicon surface and the quaternary ammonium is small compared with 110 and 100 surfaces, and it is considered that the degree of inhibition of etching is also reduced. As a result, although the etching rate becomes slow, it is thought that the influence of crystal orientation is reduced.

On the other hand, when a nonionic surfactant having high surfactant ability is used instead of the compound represented by Formula (1) or Formula (2), the surfactant strongly adheres to the polysilicon surface, and contact between the polysilicon surface and the etching solution This is inhibited, and etching becomes difficult to proceed.

The etching rate ratio (R ₁₁₀ / R ₁₀₀ ) is 0.3 to 1, and the etching rate ratio (R ₁₁₀ / R ₁₁₁ ) is preferably 0.8 to 3.5. When the etching rate ratio is in the above range, the etching rate becomes almost constant regardless of the crystal orientation, the surface cracks become small, and uniform etching becomes possible.

The silicon etching solution of the present invention can be easily prepared by mixing and dissolving a small predetermined amount of at least one compound selected from the compounds represented by the formula (1) or (2) in an aqueous solution of quaternary ammonium hydroxide at a predetermined concentration. can be manufactured. At this time, without directly mixing at least one compound selected from the compounds represented by formula (1) or formula (2), at least one selected from the compounds represented by formula (1) or formula (2) at a predetermined concentration in advance The aqueous solution of 1 type of compound may be adjusted, and this may be mixed.

The silicon etchant of the present invention has the advantages of a quaternary ammonium hydroxide aqueous solution-based silicon etchant, that is, it has low toxicity and is easy to handle. have an advantage In addition, as compared with the conventional quaternary ammonium hydroxide aqueous solution-based silicon etching solution, there is little variation in the etching rate for silicon due to the difference in crystal orientation. More specifically, when the etching process is performed under the same conditions, the polysilicon film has the characteristic that the influence of the orientation of single crystal grains can be suppressed. Therefore, the silicon etchant of the present invention is a semiconductor sensor (eg, a diaphragm of a semiconductor pressure sensor or a semiconductor acceleration sensor) for detecting various physical quantities such as valves, nozzles, printer heads, and flow rates, pressures and accelerations by silicon wet etching technology. It can be suitably used as an etchant when manufacturing various silicon devices, such as processing of cantilevers, etc.) and etching of polysilicon films and amorphous silicon films applied to various devices as a material such as a part of metal wiring and a gate electrode.

In the case of manufacturing a silicon device using the silicon etchant of the present invention, wet etching of silicon may be performed according to a conventional method. The method at this time is not particularly different from the case of using a conventional silicon etchant, for example, "a silicon wafer in which a necessary part of the silicon wafer is masked with a silicon oxide film or a silicon nitride film, etc." and dissolving unnecessary portions of the silicon wafer using a chemical reaction with the silicon etchant.

In a preferred embodiment of the present invention, when etching a laminate having recesses or through-holes penetrating a plurality of films in which a polysilicon film and a silicon oxide film are alternately stacked, the silicon etching solution is supplied with the silicon etching solution to the recesses or through-holes. It is used in the manufacture of a silicon device including a process of selectively etching a polysilicon film.

The temperature of the silicon etchant at the time of etching may be appropriately determined within the range of 20 to 95°C, in consideration of the desired etching rate, the shape and surface state of silicon after etching, productivity, and the like, and within the range of 30 to 60°C. it is preferable

For wet etching of silicon, only immersing the object to be etched in a silicon etching solution is sufficient, but it is also possible to employ an electrochemical etching method in which a constant potential is applied to the object to be etched.

Examples of the object to be etched in the present invention include silicon single crystal, polysilicon, and amorphous silicon, and among the objects, a non-object to be etched, such as a silicon oxide film or a silicon nitride film, may contain a metal such as aluminum. For example, a pattern shape is created by laminating a silicon oxide film, a silicon nitride film, and further a metal film on a silicon single crystal, a polysilicon or resist film is formed and applied thereon, and a metal part such as aluminum is covered with a protective film to form a silicon pattern a structure, etc. are mentioned.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a substrate processing method using the silicon etching solution of the present invention will be described in detail with reference to the accompanying drawings. Substrates include semiconductor wafers, glass substrates for liquid crystal display devices, glass substrates for plasma displays, glass or ceramic substrates for magnetic or optical disks, glass substrates for organic EL, glass substrates for solar cells, or silicon substrates.

Fig. 2 is a schematic view of the substrate processing apparatus 1 according to the first embodiment of the present invention as viewed from above.

As shown in FIG. 2 , the substrate processing apparatus 1 is a single-wafer apparatus that processes disk-shaped substrates W such as semiconductor wafers one by one. The substrate processing apparatus 1 has a load port LP holding a carrier C for accommodating the substrate W, and a plurality of processes for processing a substrate W conveyed from the carrier C on the load port LP. A unit 2, a transfer robot that transports the substrate W between the carrier C on the load port LP and the processing unit 2, and a control device 3 for controlling the substrate processing apparatus 1, have.

The transfer robot carries in and out of the substrate W with respect to the indexer robot IR and the plurality of processing units 2 that carry out the loading and unloading of the substrate W with respect to the carrier C on the load port LP. It includes a center robot (CR) to perform. The indexer robot IR transfers the substrate W between the load port LP and the center robot CR, and the center robot CR transfers the substrate W between the indexer robot IR and the processing unit 2 return the The center robot CR includes a hand H1 that supports the substrate W, and the indexer robot IR includes a hand H2 that supports the substrate W.

The plurality of processing units 2 form a plurality of towers TW arranged around the center robot CR in plan view. Each tower TW includes a plurality (eg, three) of processing units 2 stacked up and down. 2 shows an example in which four towers TW are formed. The center robot CR is also accessible to any tower TW.

3 is a schematic diagram horizontally viewed inside the processing unit 2 provided in the substrate processing apparatus 1 .

The processing unit 2 is a box-shaped chamber 4 having an interior space, and while maintaining a single substrate W horizontally in the chamber 4, a vertical rotation axis passing through the center of the substrate W is rotated around a vertical axis of rotation. It includes a spin chuck 10 to rotate, and a cylinder-shaped processing cup 20 surrounding the spin chuck 10 around a rotation axis.

The chamber 4 includes a box-shaped bulkhead 5 provided with a carry-in/out port 6 through which the substrate W passes, and a shutter 7 that opens and closes the carry-in/out port 6 .

The spin chuck 10 includes a disk-shaped spin base 12 maintained in a horizontal form, a plurality of chuck pins 11 for holding the substrate W in a horizontal form above the spin base 12, and a spin base ( A spin shaft extending downward from the central portion of 12, and a spin motor 13 for rotating the spin base 12 and the plurality of chuck pins 11 by rotating the spin shaft. The spin chuck 10 is not limited to a clamping chuck that contacts the outer circumferential surface of the substrate W with a plurality of chuck pins 11, and the back surface (lower surface) of the substrate W, which is a non-device forming surface, is used as a spin base ( 12) may be a vacuum chuck that holds the substrate W horizontally by adsorbing it on the upper surface.

The processing cup 20 includes a plurality of guards 21 for receiving the liquid discharged outward from the substrate W, and a plurality of cups 22 for receiving the liquid guided downward by the plurality of guards 21 . do. 3 shows an example in which two guards 21 and two cups 22 are installed.

The processing unit 2 includes a guard raising/lowering unit that lifts and lowers the plurality of guards 21 individually. The guard lifting unit positions the guard 21 at any position from the upper position to the lower position. The guard lifting unit is controlled by the control device (3). The upper position is a position where the upper end of the guard 21 is disposed higher than the holding position where the substrate W held by the spin chuck 10 is disposed. The lower position is a position where the upper end of the guard 21 is disposed below the holding position. The upper end of the guard ceiling circular shape corresponds to the upper end of the guard 21 . The upper end of the guard 21 surrounds the substrate W and the spin base 12 in a plan view.

When the processing liquid is supplied to the substrate W while the spin chuck 10 is rotating the substrate W, the processing liquid supplied to the substrate W is shaken off from the substrate W. When the processing liquid is supplied to the substrate W, the upper end of the at least one guard 21 is disposed above the substrate W. Therefore, the processing liquid, such as a chemical liquid, a rinse liquid, etc. discharged from the board|substrate W is received by the arbitrary guard 21, and is guided to the cup 22 corresponding to this guard 21. As shown in FIG.

The plurality of liquid discharging units includes a first chemical discharging unit 41 discharging a first chemical solution, a second chemical discharging unit 42 discharging a second chemical solution, and a rinsing solution discharging unit 43 discharging a rinsing solution. . Moreover, the gas discharge part which discharges several inert gas may be provided. Each of the plurality of liquid discharge units has a valve for controlling liquid discharge, and can start and stop liquid discharge. Each of the plurality of liquid discharging units has a driving mechanism, and can be driven between a processing position for discharging the liquid on the substrate and a standby position outside the substrate. The valve and the drive mechanism are controlled by the control device (3).

The first chemical liquid is a liquid containing at least one of chemical liquids (eg, hydrofluoric acid, buffered hydrofluoric acid, aqueous ammonia, etc.) capable of removing the natural oxide film of the substrate. In Fig. 3, it is denoted as DHF.

The second chemical is the silicon etchant of the present invention. In FIG. 3, it is denoted as TMAH COMPOUND.

The rinse solution supplied to the rinse solution discharge unit 43 is pure water (deionized water). The rinse liquid supplied to the rinse liquid discharge unit 43 may be a rinse liquid other than pure water. In FIG. 3, it is denoted as DIW.

4 is a schematic diagram showing an example of a cross section of the substrate W before and after the processing shown in FIG. 5 is performed.

The left side of FIG. 4 shows a cross section of the substrate W before the processing (etching) shown in FIG. 5 is performed, and the right side of FIG. 4 shows a cross section of the substrate W after the processing (etching) shown in FIG. 5 is performed. represents As shown on the right side of FIG. 4 , when the substrate W is etched, a plurality of recesses R1 concave in the plane direction of the substrate W (direction orthogonal to the thickness direction Dt of the substrate W) are recessed. It is formed on the side surface 92s of (92).

As shown in Fig. 4, the substrate W has a laminate film 91 formed on a base material such as a silicon wafer, and a thickness direction Dt of the substrate W from the outermost surface Ws of the substrate W (substrate W) W) includes a concave portion 92 concave in a direction orthogonal to the surface of the base material. The stacked film 91 includes a plurality of polysilicon films P1 , P2 , and P3 and a plurality of silicon oxide films O1 , O2 , and O3 . The polysilicon films P1 to P3 are an example of an object to be etched, and the silicon oxide films O1 to O3 are an example of an object to be etched. Silicon oxide is a substance that does not dissolve or hardly dissolves in an alkaline etching solution containing quaternary ammonium hydroxide.

The plurality of polysilicon films P1 to P3 and the plurality of silicon oxide films O1 to O3 are laminated in the thickness direction Dt of the substrate W such that the polysilicon films and silicon oxide films are alternately disposed. The polysilicon films P1 to P3 are thin films subjected to a deposition process for depositing polysilicon on the substrate W and a heat treatment process for heating the deposited polysilicon (see FIG. 4 ). The polysilicon films P1 to P3 may be thin films that have not been subjected to a heat treatment process.

As shown in FIG. 4 , the recess 92 penetrates the plurality of polysilicon films P1 to P3 and the plurality of silicon oxide films O1 to O3 in the thickness direction Dt of the substrate W. As shown in FIG. The side surfaces of the polysilicon films P1 to P3 and the silicon oxide films O1 to O3 are exposed at the side surface 92s of the recess 92 . The recessed part 92 may be any of a trench, a via hole, and a contact hole, and may be other than these.

Before the process (etching) shown in Fig. 5 is started, a native oxide film is formed on the surface layers of the polysilicon films P1 to P3 and the silicon oxide films O1 to O3. The two-dot chain line on the left side of FIG. 4 shows the outline of the native oxide film.

Hereinafter, an example of the processing of the substrate W performed by the substrate processing apparatus 1 will be described with reference to FIGS. 2 , 3 and 5 . In the substrate processing apparatus 1, the process after the start in FIG. 5 is performed.

When the substrate W is processed by the substrate processing apparatus 1, the carrying-in process of carrying in the substrate W into the chamber 4 is performed (step S1 of FIG. 5).

Specifically, in a state in which all the guards 21 are positioned at the lower positions, the center robot CR supports the substrate W with the hand H1 while the hand H1 enters the chamber 4 . . In addition, the center robot CR places the substrate W on the hand H1 on the plurality of chuck pins 11 with the surface of the substrate W oriented upward. Thereafter, a substrate holding process is performed in which the plurality of chuck pins 11 are pressed against the outer peripheral surface of the substrate W to maintain the substrate W in a horizontal form. The center robot CR places the substrate W on the spin chuck 10 and then takes out the hand H1 from the inside of the chamber 4 .

Then, the spin motor 13 is driven, and rotation of the substrate W is started (step S2 in Fig. 5). As a result, the substrate is rotated around a vertical axis of rotation passing through the center of the substrate.

Next, a first chemical solution supply process of supplying DHF, which is an example of the first chemical solution, to the upper surface of the substrate W is performed (step S3 in FIG. 5 ).

Specifically, the first chemical liquid valve of the first chemical liquid discharge unit 41 is opened to start discharging DHF. The DHF discharged from the first chemical liquid discharging unit 41 flows outward along the upper surface of the rotating substrate W after it collides with the central portion of the upper surface of the substrate W. As a result, a liquid film of DHF covering the entire upper surface of the substrate W is formed, and DHF is supplied to the entire upper surface of the substrate W. When a predetermined time elapses after the first chemical liquid valve is opened, the first chemical liquid valve is closed and the discharge of DHF is stopped.

Next, a first rinse solution supply process of supplying pure water, which is an example of a rinse solution, to the upper surface of the substrate W is performed (step S4 of FIG. 5 ).

Specifically, the rinse liquid valve of the rinse liquid discharge unit 43 is opened, and the rinse liquid discharge unit 43 starts discharging pure water. The pure water which collided with the upper surface central part of the board|substrate W flows outward along the upper surface of the rotating board|substrate W. DHF on the substrate W is washed by the pure water discharged from the rinse liquid discharge unit 43 and flows. Thereby, the pure liquid film which covers the whole upper surface of the board|substrate W is formed. When a predetermined time elapses after the rinse liquid valve is opened, the rinse liquid valve is closed and the discharge of pure water is stopped.

Next, a second chemical solution supply process of supplying a silicon etching solution as a second chemical solution to the upper surface of the substrate W is performed (step S5 of FIG. 5 ).

Specifically, the second chemical liquid valve of the second chemical liquid discharging unit 42 is opened, and the second chemical liquid discharging unit 42 starts discharging the etching solution. Before the discharging of the etching solution is started, the guard lifting unit may vertically move the at least one guard 21 in order to change the guard 21 that receives the liquid discharged from the substrate W. The etching solution collided with the center of the upper surface of the substrate W flows outward along the upper surface of the rotating substrate W. The pure water on the substrate W is replaced with the etching solution discharged from the second chemical solution discharging unit 42 . Thereby, the liquid film of the etching liquid which covers the whole upper surface of the board|substrate W is formed. When a predetermined time elapses after the second chemical liquid valve is opened, the second chemical liquid valve is closed and discharge of the etching liquid is stopped.

Next, a second rinse solution supply process of supplying pure water, which is an example of a rinse solution, to the upper surface of the substrate W is performed (step S6 of FIG. 5 ).

Specifically, the rinse liquid valve of the rinse liquid discharge unit 43 is opened, and the rinse liquid discharge unit 43 starts discharging pure water. The pure water which collided with the upper surface central part of the board|substrate W flows outward along the upper surface of the rotating board|substrate W. The etching solution on the substrate W is washed and flows by the pure water discharged from the rinse solution discharge unit 43 . Thereby, the liquid film of pure water which covers the whole upper surface of the board|substrate W is formed. When a predetermined time elapses after the rinse liquid valve is opened, the rinse liquid valve is closed and the discharge of pure water is stopped.

Then, a drying process of drying the substrate W by rotation of the substrate W is performed (step S7 in FIG. 5 ).

Specifically, the spin motor 13 accelerates the substrate W in the rotational direction, and a rotation speed ( For example, the substrate W is rotated at several thousand rpm). Thereby, the liquid is removed from the substrate W and the substrate W is dried. When a predetermined time elapses after the high-speed rotation of the substrate W is started, the spin motor 13 stops rotating. Thereby, rotation of the board|substrate W is stopped (step S8 of FIG. 5).

Next, a carrying-out process of carrying out the substrate W from the chamber 4 is performed (step S9 of FIG. 5 ).

Specifically, the guard lifting unit lowers all the guards 21 to the lower position. After that, the center robot CR moves the hand H1 into the chamber 4 . The center robot CR supports the substrate W on the spin chuck 10 with the hand H1 after the plurality of chuck pins 11 release the grip of the substrate W. Thereafter, the center robot CR takes out the hand H1 from the inside of the chamber 4 while supporting the substrate W with the hand H1 . The substrate W processed by this is carried out from the chamber 4 .

As described above, in the preferred embodiment of the present invention, the silicon etchant described above is applied to the polysilicon films P1 to P3 (see Fig. 4) and to the silicon oxide films O1 to O3 different from the polysilicon films P1 to P3 ( 4) is supplied to the exposed substrate W.

In this embodiment, DHF, which is an example of an oxide film removing liquid, is supplied to the substrate W, and the native oxide films of the polysilicon films P1 to P3 are removed from the surface layers of the polysilicon films P1 to P3. Thereafter, the etching solution is supplied to the substrate W, and the polysilicon films P1 to P3 as etching objects are selectively etched. The native oxide films of the polysilicon films P1 to P3 are mainly composed of silicon oxide. The etching liquid is a liquid that etches the polysilicon films P1 to P3 with little or no etching of silicon oxide. This is because hydroxide ions react with silicon, but do not react or hardly react with silicon oxide. Accordingly, by removing the native oxide film of the polysilicon films P1 to P3 in advance, the polysilicon films P1 to P3 can be etched efficiently.

In the present embodiment, the etching objects P1 to P3 that have been subjected to a heat treatment process of heating the deposited polysilicon are etched with an alkaline etching solution. Heating the deposited polysilicon under appropriate conditions increases the particle size (grain size) of the polysilicon. Therefore, compared to the case where the heat treatment process is not performed, the silicon single crystal included in the etching objects P1 to P3 is enlarged. This means that the number of silicon single crystals exposed on the surfaces of the etching objects P1 to P3 decreases and the influence of anisotropy increases. Therefore, by supplying an etching solution containing at least one compound selected from quaternary ammonium hydroxide, water, and a compound represented by Formula (1) or Formula (2) to these etching objects P1 to P3, The effect of anisotropy can be effectively reduced.

6 is another example of the processing of the substrate W2 performed by the substrate processing apparatus 1 . In the example shown in FIG. 6, the state in which the process (etching) shown in FIG. 5 was performed with respect to the board|substrate W2 which has fin-shaped Si protrusion is shown. When the processing of the substrate W2 having the fin-shaped Si protrusions as shown in FIG. 6 is performed, as shown on the left side of FIG. 6 , variations in the etching amount occur due to the crystal anisotropy during silicon etching in the related art. The right side of Fig. 6 shows a cross section of the substrate W2 after the treatment with the etching solution of the present invention has been performed. 6 , when the substrate W2 is etched, the crystal anisotropy at the time of etching the fin-shaped Si protrusions of the substrate W2 is suppressed, and isotropic etching can be performed. In addition, the dotted line in FIG. 6 shows the shape before a process.

In the present embodiment, the processing unit 2 may include a blocking member disposed above the spin chuck 10 . The blocking member includes a disk portion disposed above the spin chuck 10 and a cylindrical portion extending downward from the outer periphery of the disk portion.

Next, a second embodiment will be described.

The main difference between the second embodiment and the first embodiment is that the substrate processing apparatus 101 is a batch type apparatus that processes a plurality of substrates W at once.

7 is a schematic plan view showing the layout of the substrate processing apparatus 101 according to the second embodiment of the present invention. 8 is a schematic diagram showing the processing unit 102 provided in the substrate processing apparatus 101 according to the second embodiment of the present invention. 7 to 9 , the same reference numerals as those in FIG. 1 are attached to the same components as those shown in FIGS. 1 to 5 , and descriptions thereof will be omitted.

As shown in FIG. 7 , the substrate processing apparatus 101 is roughly divided into a control unit 3 , a cassette holding unit 93 , a shape conversion unit 94 , and a processing unit 102 , and a cassette holding unit 93 , a shape The conversion unit 94 and the processing unit 102 are controlled by the control unit 3 . In the cassette holding unit 93 , a cassette 90 accommodating a plurality of substrates W stacked in a horizontal form with a main surface in a vertical direction is held. In the shape conversion unit 94, the plurality of substrates W before processing are unloaded from the cassette 90, and at the same time the shape of the plurality of substrates W is converted to an upright shape with the main surface facing the horizontal direction, and the plurality of substrates W ) is transmitted to the processing unit 102 . Further, the plurality of substrates W after processing by the processing unit 102 are transferred from the processing unit 102 to the shape conversion unit 94 in an upright form, and the plurality of substrates W have a planar main surface. ) direction, the plurality of substrates W are collectively returned to the cassette 90 of the cassette holding portion 93 .

The processing unit 102 includes a main conveying mechanism 121 , a transfer part cleaning unit 122 , a first chemical processing unit 123 , a second chemical processing unit 124 , and a drying processing unit 125 , , the first chemical processing unit 123 , the second chemical processing unit 124 , the drying processing unit 125 , and the transfer material cleaning unit 122 are arranged in this order in FIG. 7 . The first chemical processing unit 123 includes a first chemical solution tank 231 in which a predetermined chemical solution is stored, a first rinse solution tank 232 in which a rinse solution is stored, and a first rinse solution tank 231 in the first chemical solution tank 231 ( 232 , a first lifter 233 for collectively transporting the plurality of substrates W is provided. Like the first chemical processing unit 123 , the second chemical processing unit 124 also includes a second chemical liquid tank 241 in which a predetermined chemical is stored, a second rinse liquid tank 242 in which a rinse liquid is stored, and a second chemical liquid tank ( A second lifter 243 for collectively transferring the plurality of substrates W from the 241 to the second rinsing liquid tank 242 is provided.

The main conveying mechanism 121 includes a transfer unit 211 for supporting and lifting and lowering the plurality of substrates W, and transfers the transfer unit 211 to the transfer unit cleaning unit 122 , the first chemical processing unit 123 , and the second transfer unit 211 . A transfer unit moving mechanism 212 that moves between the chemical processing unit 124 and the drying processing unit 125 is provided. The dissimilar material 211 includes a pair of support arms 213 disposed at intervals, an arm driving unit for changing the distance between the pair of support arms 213, and a pair of support arms 213 for vertically elevating and lowering the pair of support arms 213 . An arm lift is provided. A support member 214 is provided at a lower portion of each support arm 213 , and a plurality of grooves are formed in the support member 214 at a constant pitch from the tip of the support arm 213 toward the base. The arm driving unit changes the distance between the pair of support members 214 by rotating each support arm 213 about an axis parallel to the axis from the tip of the support arm 213 to the base. .

In the substrate processing apparatus 101 , a plurality of substrates W are conveyed into the processing unit 102 in an upright form in which the main surface is stacked in parallel from the tip of the support arm 213 toward the root by the shape conversion unit 94 , , an edge of the substrate W is disposed in the groove and supported by a pair of support members 214 . The interval between the pair of support members 214 is a width when the plurality of substrates W are clamped by the pair of support members 214 (a width smaller than the diameter of the substrate W, hereinafter referred to as the “napping width”). ') and the width at which the plurality of substrates W are released by the pair of support members 214 (the width greater than the diameter of the substrate W, hereinafter referred to as "release width") It's arbitrary.

The foreign material cleaning unit 122 has two cleaning tanks 221 arranged vertically below the pair of supporting members 214 . In each cleaning tank 221 , a nozzle for ejecting a cleaning liquid and a nozzle for ejecting nitrogen gas are provided. When cleaning the transfer member 211 , a pair of support members 214 (and a part of the support arm 213 ) are respectively disposed in the two cleaning tanks 221 . And after the support member 214 is cleaned by the cleaning liquid, the cleaning liquid adhering to the support member 214 is removed by the nitrogen gas (that is, the support member 214 is dried).

When the substrate (W) is processed by each chemical processing unit (123, 124), the transfer part (211) for holding the plurality of substrates (W) is disposed above the chemical liquid tank (231, 241), the chemical liquid tank (231, The first lifter 233 and the second lifter 243 in 241 move upward. The first lifter 233 and the second lifter 243 are provided with a plurality of jaws for supporting the upright substrate W from below, and after the substrate W comes into contact with the jaws, The plurality of substrates W are transferred from the transfer portion 211 to the first lifter 233 and the second lifter 243 by the distance between the pair of support members 214 being widened to the release width. In the chemical processing units 123 and 124 , the first lifter 233 and the second lifter 243 are lowered to place a plurality of substrates W in the chemical bath 231,241, and the chemical treatment is performed on the plurality of substrates. (W) is performed in batches.

When the treatment with the chemical is completed, the first lifter 233 and the second lifter 243 rise and then move upwards of the rinse liquid tanks 232 and 242 . Then, as the first lifter 233 and the second lifter 243 descend, the plurality of substrates W are disposed in the rinse liquid tanks 232 and 242, and the treatment with the rinse liquid is performed on the plurality of substrates W. is performed collectively for When the treatment with the rinsing liquid is completed, the first lifter 233 and the second lifter 243 are raised, and the substrate W is disposed above the rinsing liquid tanks 232 and 242 . In this case, the transfer part 211 is also disposed above the rinse liquid tanks 232 and 242 , and the plurality of substrates W are positioned between the pair of support members 214 having the gaps widened by the release width. After the distance between the pair of support members 214 is narrowed to the pinching width, the first lifter 233 and the second lifter 243 are lowered by the first lifter 233, the second lifter 243, and the transfer member. A plurality of substrates W are transferred to the portion 211 .

Specifically, all the substrates W included in one batch are transferred to the first lifter 233 of the first chemical processing unit 123 by the main conveying mechanism 121 , and in the first chemical tank 231 . It is immersed in the 1st chemical|medical solution. For example, the first chemical solution is diluted hydrofluoric acid (DHF). The first chemical solution may be a liquid containing at least one of chemical solutions capable of removing the native oxide film of the substrate (eg, hydrofluoric acid, buffered hydrofluoric acid, aqueous ammonia, etc.). All of the substrates W included in one batch immersed in the first chemical solution are moved upward of the first rinse solution tank 232 by the first lifter 233 , and 1 Immerse in rinse aid. The first rinse solution is pure water (deionized water). A rinse solution other than pure water may be used. All the substrates W included in one batch immersed in the first rinse liquid are transferred by the first lifter 233 to the main conveying mechanism 121, and the second chemical processing unit 124 is 2 is transferred to the lifter 243 . The second chemical is the silicon etchant of the present invention. In Fig. 8, it is denoted as TMAH COMPOUND. All the substrates W included in one batch transferred to the second lifter 243 are immersed in the etching solution in the immersion tank 103 of the second chemical tank 241, and then are taken out from the immersion tank 103 ( Step S13) of Fig. 9). All the substrates W included in one batch unloaded from the immersion tank 103 are immersed in the second rinse solution tank 242 . The second rinse solution is pure water (deionized water). The second rinse liquid may be a rinse liquid other than pure water. All the substrates W included in one batch transferred to the second lifter 243 are dried in the drying processing unit 125 by the main conveying mechanism 121 .

8 is a diagram for explaining the chemical liquid tank 241 of the chemical liquid treatment tank 124 of the processing unit 102 . 8 includes a processing unit 102 that simultaneously supplies an alkaline etching solution corresponding to the second chemical solution to the plurality of substrates W. In FIG. The processing unit 102 includes an immersion tank 103 into which a plurality of substrates W are simultaneously loaded while storing the etchant, and an overflow tank 104 for receiving the etchant flowing from the immersion tank 103 . .

In addition to the immersion tank 103 and the overflow tank 104 , the processing unit 102 includes a lower position in which a plurality of substrates W are immersed in the etching solution in the immersion bath 103 , and a plurality of substrates W are immersed. and a second lifter 243 that moves up and down while simultaneously holding the plurality of substrates W between the upper positions positioned above the etching solution in the tank 103 .

The processing unit 102 includes two chemical liquid nozzles 109 provided with a second chemical liquid discharge port 47 for discharging an alkaline etching liquid corresponding to the second chemical liquid, and a drain pipe 116 for discharging the liquid in the immersion tank 103 . include When the chemical nozzle 109 discharges the etchant, the etchant is supplied into the immersion tank 103 and at the same time an upward flow is formed in the etchant in the immersion tank 103 . In addition, when the drain valve 117 interposed in the drain pipe 116 is opened, the liquid in the immersion tank 103 , such as an etching solution, is discharged to the drain pipe 116 . The upstream end of the drainage pipe 116 is connected to the bottom of the immersion tank 103 .

The overflow tank 104 includes a common pipe 110c for guiding the etching solution in the overflow tank 104 toward the two chemical solution nozzles 109 , and the etching solution supplied from the common pipe 110c to the two chemical solution nozzles 109 . It is connected to the chemical|medical solution piping 110 including the two branch piping 110b which guide each through the return piping 115. As shown in FIG. The upstream end of the return pipe 115 is connected to the overflow tank 104 , and the downstream end of the return pipe 115 is connected to the chemical liquid valve 114 . The etchant overflowing from the immersion tank 103 to the overflow tank 104 is sent back to the two chemical liquid nozzles 109 by a pump 113 disposed downstream of the chemical liquid valve 114, and at the same time, the two chemical liquid nozzles 109 ) is filtered by the filter 111 before reaching. The processing unit 102 may include a temperature controller 112 that changes the temperature of the etching liquid in the immersion tank 103 by heating or cooling the etching liquid.

When the empty immersion tank 103 is filled with the etching solution, the chemical solution valve 65 interposed in the pipe 63 that supplies the etching solution to the overflow tank 104 is opened, and the etching solution stored in the tank 62 is pumped ( 64) to the overflow tank 104. Next, the chemical liquid valve 114 interposed in the common pipe 110c is opened. Thereby, the etching liquid in the overflow tank 104 is sent into the common pipe 110c, is supplied to the two chemical liquid nozzles 109 through the two branch pipes 110b, and is immersed in the two chemical liquid nozzles 109. It is discharged into the tank (103). And when the middle ear of the immersion tank 103 is filled with the etching solution, the chemical liquid valve 65 is closed and the supply of the etching solution from the tank 62 to the immersion tank 103 is stopped. The chemical liquid valve 65 may be closed except when filling the empty immersion tank 103 with an etching liquid.

A liquid mixture of quaternary ammonium hydroxide and a compound represented by the formula (1) or (2) is stored in the tank 62 , and the quaternary ammonium hydroxide and the compound are provided by a chemical valve interposed in the pipe 78 . 79 is opened and may be supplied as a mixed liquid in the tank 62, or may be supplied individually. In addition, the tank 62 may be supplied with an inert gas by opening the valve 73 interposed in the pipe 72 . Thereby, the upper space of the inert gas tank 62 can be filled, and it can suppress that the mixed liquid stored in the tank 62 and oxygen come into contact.

9 is a process diagram showing an example of a flow from supplying a new etching solution until the used etching solution is discharged from the immersion tank 103 . An operation to be described later is executed by the control device 3 controlling the substrate processing apparatus 101 . That is, the control device 3 is programmed to perform the following operations on the substrate processing apparatus 101 . Hereinafter, reference is made to FIGS. 8 and 9 .

The etching liquid supplied to the immersion tank 103 of the processing unit 102 is stored in the tank 62 . After that, the chemical liquid valves 65 and 114 are opened, and the etchant is supplied from the tank 62 to the overflow tank 104 by driving the pump 64 . The etchant supplied to the overflow tank 104 opens the chemical liquid valve 114 connected to the common pipe 110c, and is sent into the common pipe 110c. The etching solution in the common pipe 110c is supplied to the two chemical solution nozzles 109 through the two branch pipes 110b, and supply of the etching solution from the two chemical solution nozzles 109 to the immersion tank 103 is started (Fig. Step 9 S11). When the middle ear of the immersion tank 103 is filled with the etching liquid, the chemical liquid valve 65 is closed and the supply of the etching liquid from the tank 62 to the immersion tank 103 is stopped.

After the supply of the etching solution, the second lifter 243 descends from the upper position to the lower position while maintaining the plurality of substrates W in an upright state. Thereby, all the board|substrates W included in one batch are immersed in the etching liquid of the immersion tank 103 in an upright state (step S12 of FIG. 9). Accordingly, the etching solution is simultaneously supplied to the plurality of substrates W, and the object to be etched such as the polysilicon films P1 to P3 (see Fig. 4) is etched. When a predetermined time elapses after the second lifter 243 is moved to the lower position, the second lifter 243 rises to the upper position.

This sequence of flows is repeated for each batch. That is, when all the substrates W included in one batch are taken out of the immersion tank 103 (step S13 in FIG. 9 ), similarly to the above, all the substrates W included in the other batch are transferred to the immersion tank 103 . It is etched by being immersed in the etchant inside. And when the number of times or usage time of the etchant in the immersion tank 103 reaches the upper limit, the etchant in the immersion tank 103 is replaced with a new etchant.

Specifically, the drain valve 117 is opened, and the etching liquid in the immersion tank 103 is discharged to the drain pipe 116 (step S14 in FIG. 9 ). When the middle of the immersion tank 103 is empty, a new etching solution is supplied to the immersion bath 103 (step S11 in FIG. 9 ).

[Example]

Hereinafter, the present invention will be described in more detail by way of Examples, but the present invention is not limited to these Examples.

Example 1

A silicon etching solution having the composition shown in Table 1 was prepared using tetramethylammonium hydroxide (TMAH) as the quaternary ammonium hydroxide and ethylene glycol monobutyl ether as the compound represented by the formula (1).

<Evaluation of surface cracks of silicon substrates in each crystal orientation>

The silicon etchant heated to a liquid temperature of 40°C was ventilated by flowing _{N 2 gas until the dissolved oxygen concentration decreased to a certain concentration value.} The etching rate of silicon was measured. The target silicon substrate is a silicon substrate (100 plane, 110 plane, 111 plane) of each crystal orientation, and a natural oxide film is removed with a chemical solution. The etching rate is measured by measuring the weight of the silicon substrate before and after etching on the silicon substrate (100, 110, 111) of each crystal orientation, and converting the etching amount of the silicon substrate from the weight difference before and after processing, divided by the etching time saved by _{Next, the etching rate ratios (R 110} / R ₁₀₀ ) and (R ₁₁₀ / R ₁₁₁ ) of the silicon substrates (100, 110, 111) of each crystal orientation were calculated. In addition, the surface state of the silicon substrates (100 faces, 110 faces, 111 faces) of each crystal orientation was observed and evaluated according to the following criteria. A result is shown in Table 2.

<Evaluation criteria for surface cracking of silicon substrates in each crystal orientation>

5 ... No white turbidity is seen on the wafer surface, and it is a mirror surface.

3 ... A small amount of cloudiness is seen on the wafer surface, but it is a mirror surface.

1 ... The surface of the wafer is completely cloudy, but the mirror surface remains.

0 ... The wafer surface is completely cloudy, and the mirror surface is lost due to severe surface cracks.

When the evaluation results of 100 faces, 110 faces, and 111 faces were 3 or more, and the total was 11 or more, the crystal orientations were also uniformly etched and good isotropy was exhibited.

<Evaluation of the selectivity between silicon and silicon oxide film and silicon nitride film>

The silicon etchant heated to a liquid temperature of 40℃ was _{ventilated by flowing N 2} gas until the dissolved oxygen concentration decreased to a certain concentration value, and then ventilated the silicon oxide film and silicon nitride film. The etching rates of the silicon oxide film and the silicon nitride film were measured at 40°C. The etching rate is determined by measuring the film thicknesses before and after etching of the silicon oxide film and the silicon nitride film with a spectroscopic ellipsometer, converting the etching amount of the silicon oxide film and the silicon nitride film from the difference in film thickness before and after processing, and dividing by the etching time saved Next, the etching rate ratio (R ₁₀₀ / silicon oxide film) (R ₁₀₀ / silicon nitride film) with the silicon substrate (100 surfaces) was calculated and evaluated according to the following criteria. A result is shown in Table 2.

<Evaluation criteria for selectivity between silicon and silicon oxide film and silicon nitride film>

Selectivity between silicon and silicon oxide film (Si (100 planes) / SiO ₂ )

A: 1000 B: 700 or more and less than 1000 C: 500 or more and less than 700 D: less than 500

Selectivity between silicon and silicon nitride film (Si (100 planes) / SiN)

A: 1000 B: 700 or more and less than 1000 C: 500 or more and less than 700 D: less than 500

It was set that B or more showed favorable selectivity. Here, the selectivity (Si (100 surface) / SiO ₂ ) of potassium hydroxide (KOH), which is an inorganic alkali, is about 250, and it is classified as D as the evaluation criterion.

Examples 2 to 32

The evaluation was carried out in the same manner as in Example 1 except that the silicon etching solution having the composition shown in Table 1 was used as the silicon etching solution. In addition, "Choline" in the table represents trimethyl-2-hydromethylethylammonium hydroxide (choline hydroxide). A result is shown in Table 2.

Comparative Examples 1 to 9

Evaluation was carried out in the same manner as in Example 1 except that the silicon etching solution did not contain at least one compound selected from the compounds represented by Formula (1) or Formula (2), and a silicon etching solution having the composition shown in Table 1 was used. . A result is shown in Table 2.

Further, for Example 1 and Comparative Example 1, the surface Ra values (unit: nm) of the silicon substrates (100 faces, 110 faces, 111 faces) of each crystal orientation were measured, and the results are shown in Table 3. The surface Ra value is a value observed at a viewing angle of 175 μm using a 50x lens of an optical coherence microscope for 100, 110, and 111 surfaces. From Table 2, it can be seen that the evaluation result of the surface state and the surface Ra value match. In addition, a polycrystalline silicon plate was separately prepared and etched in the same manner as above, and the surface Ra value was measured at a viewing angle of 1.5 μm using an atomic force microscope (AFM).

Table 1

Table 2

Table 3

1, 101: substrate processing apparatus
2, 102: processing unit
3: control unit
4: chamber
10: spin chuck
11: chuck pin
12: spin base
13: spin motor
20: processing cup
21: guard
22: cup
41: first chemical liquid discharge unit
42: second chemical liquid discharge unit
43: rinse liquid discharge part
47: chemical discharge port
62: tank
91: laminated film
92: Yobu
93: cassette holding part
94: state conversion unit
103: immersion bath
104: overflow jaw
109: chemical liquid nozzle
110: chemical liquid pipe
111: filter
112: thermostat
113: pump
114: chemical liquid valve
121: main conveying mechanism
123: first chemical processing unit
124: second chemical processing unit
233: first lifter
243: second lifter
R1: recess
P1, P2, P3: polysilicon film
O1, O2, O3: silicon oxide film
LP: load port
IR: Indexer Robot
CR: Center Robot
H1 (H2): Hand

Claims (6)

Isotropic comprising at least one compound selected from the group consisting of quaternary ammonium hydroxide, water, and compounds represented by the following formulas (1) and (2), and satisfying the following conditions 1 and 2 silicon etchant.
R ¹ O-(C _m H _2m O) _n -R ² (1)
(Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
m is an integer from 2 to 6, and n is from 1 to 3. However, R ¹ and R ² are not hydrogen atoms at the same time, and in the case of m=2, the sum of the number of carbon atoms (C ¹ ) ^{of n and R 1 and} the number of carbon atoms (C ^{2 ) of R 2} (n + C ¹ + C ^{2 )} ) is greater than or equal to 5.)
HO-(C ₂ H ₄ O) _p -H (2)
(Wherein, p is an integer from 15 to 1000.)
Condition 1: 0.2 ≤ Etching rate ratio (R ₁₁₀ / R ₁₀₀ ) ≤ 1
Condition 2: 0.8 ≤ Etching rate ratio (R ₁₁₀ / R ₁₁₁ ) ≤ 4
(In the above, R ₁₀₀ represents an etching rate for 100 single crystal faces of _{silicon, R 110} represents an etching rate for 110 single crystal faces of _{silicon, and R 111} represents an etching rate for 111 single crystal faces of silicon.) The method according to claim 1, wherein the concentration of the quaternary ammonium hydroxide is 0.1 to 25% by mass, and the concentration of at least one compound selected from the compounds represented by the formula (1) or (2) is 0.001 to 40% by mass. isotropic silicon etchant. A method of processing a substrate by etching a silicon wafer and/or a substrate comprising a polysilicon film and an amorphous silicon film using the isotropic silicon etching solution according to claim 1 or 2. A method of manufacturing a silicon device comprising a step of etching a silicon wafer, a polysilicon film, and an amorphous silicon film, wherein the etching is performed using the isotropic silicon etchant according to claim 1 or 2 . a substrate holding process for holding the substrate in a horizontal form;
A substrate processing method comprising: a processing liquid supplying step of supplying the isotropic silicon etchant according to claim 1 or 2 to the upper surface of the substrate while rotating the substrate around a vertical rotation axis passing through the central portion of the substrate. a substrate holding process for holding the plurality of substrates in an upright configuration;
A substrate processing method comprising the step of immersing the substrate in an upright form in the isotropic silicon etchant according to claim 1 or 2 stored in a processing tank.

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