JP2001068448A - Etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching method wherein a fine pattern is formed safely on a silicon compound surface. SOLUTION: A thin liquid layer containing hydrofluoric acid and oxidizer is inserted between a silicon compound surface 1 and a window member 2 through which ultraviolet ray 11 is transmitted. The ultraviolet ray 11 is projected toward the silicon compound surface 1 through the window member 2 side, so that at least a part of the silicon compound surface 1 is oxidized and a silicon oxide generated therefrom is removed from the silicon compound surface 1 using the hydrofluoric acid contained in the thin liquid layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an etching method, and more particularly to an etching method for etching a silicon compound surface.

[0002]

2. Description of the Related Art Silicon carbide has features such as excellent heat resistance, radiation resistance, chemical resistance, and abrasion resistance, a wide band gap, and a high reflectance in the X-ray region. Have. For this reason, silicon carbide is expected to be applied to semiconductor devices and SR light gratings.

At present, silicon carbide substrates are often processed by a physical method such as diamond engraving or laser ablation. However, in order to form a fine pattern in a short time and with high accuracy, a chemical method is used. Application is mandatory. However, there are some problems in forming a fine pattern on a silicon carbide substrate in a short time and with high accuracy using a conventional chemical method.

For example, when pattern etching is performed using a reactive ion etching (RIE) method or the like, a resist having better chemical resistance than silicon carbide is required. However, such a resist is impractical. Further, when a photoelectrochemical (PEC) method is used, a resist is not necessary, but there is a problem in processing time and processing accuracy because of the direct drawing method.

[0005] In addition to the above method, the present inventors have developed a photochemical pattern etching method using an etchant gas such as ClF ₃ gas or NF ₃ gas as a chemical method. This method uses the radicals generated by photolysis of the etchant gas, silicon carbide on the surface of the silicon carbide substrate in which sublimate as SiF _n and CF _n or CN. According to this method,
Since the sublimation occurs only in the exposed portion of the laser light that is the surface excitation light, a desired pattern can be formed with high accuracy. However, this method requires dangerous gases such as ClF ₃ gas and NF ₃ gas.

[0006]

As described above, according to the conventional method, in order to form a fine pattern on a surface of a silicon compound substrate such as a silicon carbide substrate with high precision by a chemical method, it is necessary to use a ClF ₃ gas. And dangerous gas such as NF ₃ gas.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an etching method capable of forming a fine pattern on a silicon compound surface relatively safely.

[0008]

According to the present invention, there is provided a thin liquid layer containing hydrofluoric acid and an oxidizing agent between a surface of a silicon compound and a window member transmitting ultraviolet light. And irradiating the silicon compound surface with ultraviolet rays from the window member side to oxidize at least a part of the silicon compound surface, and generating silicon oxide by hydrofluoric acid contained in the thin liquid layer. An etching method characterized by removing from a silicon compound surface is provided.

In the etching method of the present invention, the oxidizing agent is
The active oxygen atom generated by the
Silicon compound consisting of silicon carbide
The bond is broken by photoexcitation of the compound surface.
Reaction with Si and C. With this reaction
SiO generated_TwoAnd CO_TwoOf oxides such as _Two
Such gases diffuse into the thin liquid layer. On the other hand, SiO_Twoetc
Is left on the surface of the silicon compound,
Easily removed. The etching method of the present invention
It is based on such a principle.

The etching of the silicon compound surface by the above-described method can be performed without using an oxidizing agent. However, when an oxidizing agent is used, highly active oxygen atoms can be generated very efficiently. . for that reason,
According to the method of the present invention, a sufficient etching depth can be easily realized.

As described above, in the method of the present invention, a liquid is used as an etchant. in this case,
The contact density between the surface of the silicon compound to be processed and the etchant can be further increased as compared with the case where a gas is used. Therefore, the etching rate can be improved.

According to the method of the present invention, a dangerous gas such as ClF ₃ gas or NF ₃ gas is not used for etching the silicon compound, but hydrofluoric acid is used instead. Hydrofluoric acid is relatively easy to handle as compared with the above gases, and therefore, according to the method of the present invention, it is possible to safely form a fine pattern on the surface of a silicon compound.

Further, in the method of the present invention, the silicon compound surface and the window member are arranged such that a thin liquid layer containing hydrofluoric acid and an oxidizing agent is interposed therebetween. Such a structure can be formed, for example, by utilizing the capillary phenomenon. In this case, hydrofluoric acid and the oxidizing agent can be uniformly supplied to the entire surface of the silicon compound. Therefore, uniform etching can be performed. Further, in this case, since the necessary amount of hydrofluoric acid or the like is small, etching can be performed more safely.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a view schematically showing an apparatus used in an etching method according to one embodiment of the present invention. An apparatus 10 shown in FIG. 1 includes an ultraviolet source 12 such as an ArF excimer laser, a homogenizer 13, a mirror 14, a photomask 15 on which a predetermined pattern is formed,
And a mounting table (not shown) on which the is mounted horizontally.

This apparatus 10 has a thin liquid layer (not shown) formed by a capillary phenomenon in a gap between the window member 2 placed on the substrate 1 and the window member 2.
Is formed, and ultraviolet light is irradiated from above. That is, the apparatus 10 homogenizes the ultraviolet light (laser light) 11 output from the ultraviolet light source 12 by a homogenizer 13 such as a polyhedral prism, and changes the traveling direction of the ultraviolet light to a vertical direction by a mirror 14. The substrate 1 is irradiated from the window member 2 side through the mask 15.

According to one embodiment of the present invention, for example, the silicon compound surface is etched using the apparatus 10 shown in FIG. 1 by the following method.

First, a substrate 1 having at least one principal surface made of a silicon compound such as silicon carbide or silicon nitride is prepared. The substrate 1 is not particularly limited as long as at least one main surface is made of a silicon compound, and may be a substrate made of a silicon compound. The substrate 1 may be a substrate having a silicon compound layer on the surface. Here, it is assumed that the substrate 1 is a substrate made of a silicon compound.

Next, the silicon compound surface of the substrate 1 is
Drop an etchant containing hydrofluoric acid and an oxidizing agent
You. The oxidizing agent used for the etchant is H
_TwoO_Two, H _TwoSO_Four, HNO_Three, KNO_Three, KMnO_Four, K_TwoC
rO_Four, K_TwoCr_TwoO₇, Ag_TwoO and CuO etc.
be able to. These oxidizing agents may be used alone or in combination.
They may be used in combination.

Thereafter, the window member 2 is placed on the surface of the silicon compound of the substrate 1. The droplets of the etchant present on the silicon compound surface of the substrate 1 are spread between the substrate 1 and the window member 2 by capillary action. As a result, the etchant forms a very thin liquid film between the substrate 1 and the window member 2.

As described above, since the window member 2 comes into contact with the etchant, it is necessary to have resistance to the etchant. Further, as described later, since ultraviolet rays are irradiated from the window member 2 side, the window member 2 needs to transmit ultraviolet rays. Such materials include, for example, sapphire, quartz, synthetic quartz glass, calcium fluoride,
Examples thereof include magnesium fluoride and a transparent fluororesin plate such as FEP or PFA.

It is noted that, although slightly, quartz and synthetic quartz glass are placed in hydrofluoric acid, and calcium fluoride and magnesium fluoride are placed in water. Therefore, when the window member 2 made of these materials is used repeatedly, fine irregularities may be formed on the surface of the window member 2 that comes into contact with the etchant. However, since the etchant used here is a liquid, it will be described later. Excessive light scattering does not occur during UV irradiation.

Next, ultraviolet rays 11 are irradiated from the side of the window member 2 toward the substrate 1 using the apparatus 10 described above. As described above, since the thin liquid layer is interposed between the substrate 1 and the window member 2, the substrate 1 and the like are preferably arranged horizontally on a mounting table (not shown).

As the ultraviolet rays 11, for example, 30
Those having a wavelength of 0 nm to 120 nm can be used. In this wavelength range, each oxidant has light absorption and undergoes photolysis. However, it should be noted that since the absorption of hydrofluoric acid is 160 nm or less, the wavelength range where the etching efficiency is good is 300 nm to 160 nm.

The light source 12 for the ultraviolet light 11 is an ArF excimer laser, a KrF excimer laser,
r excimer laser, Kr excimer laser, F ₂ laser,
A laser using a nonlinear crystal that outputs ultraviolet laser light, X
Examples include an e ₂ ^* excimer lamp, a XeCl excimer lamp, an Ar excimer lamp, a Kr excimer lamp, a UV lamp, and the like.

The ultraviolet rays 11 are directed toward the substrate 1 from the window member 2 side.
Is irradiated, the above-described etching occurs selectively in the exposed portion. On the other hand, the above-mentioned etching does not occur in the unexposed portion. As a result, the photomask 1
A pattern corresponding to the pattern No. 5 is formed. According to the method according to the present embodiment, etching is performed as described above.

In the present embodiment, the thickness of the thin liquid layer is usually in the range of 100 to 10 μm, preferably 50 to 50 μm.
２０20 μm. When the thickness of the thin liquid layer is within the above range, a sufficient amount of the etchant can be supplied to the surface of the substrate 1 and the ultraviolet light 1 in the thin liquid layer can be supplied.
1 can be suppressed, and the surface of the substrate 1 can be sufficiently photoexcited.

In this embodiment, the energy density of the ultraviolet rays 11 is preferably 100 mJ / cm ² or more, and more preferably 500 mJ / cm ² or more. In this case, highly active oxygen atoms can be sufficiently generated, and the surface of the substrate 1 can be sufficiently photoexcited.

In the present embodiment, it is preferable to appropriately select the ultraviolet light source 12 according to the composition of the thin liquid layer. For example, when the etchant contains hydrogen fluoride and water, it is preferable to use an ArF excimer laser or a Xe ₂ ^* excimer lamp as the ultraviolet light source 12. When the etchant contains hydrogen fluoride and hydrogen peroxide, the ultraviolet source 12 may be an ArF excimer laser, a KrF excimer laser, an Ar excimer laser,
It is preferable to use an r excimer laser, an F ₂ laser, a laser using a nonlinear crystal, a Xe ₂ ^* excimer lamp, a XeCl excimer lamp, an Ar excimer lamp, a Kr excimer lamp, a Hg lamp, a D ₂ lamp, or the like.

As described above, by appropriately selecting the ultraviolet light source 12 according to the composition of the thin liquid layer, excessive absorption of the ultraviolet light 11 in the thin liquid layer can be suppressed, and the surface of the substrate 1 can be sufficiently photoexcited. it can. That is, a high etching rate can be obtained.

As described above, in the method of the present embodiment, a liquid is used instead of a gas as an etchant, so that a high etching rate can be realized. Further, in the method of the present embodiment, since the etchant is formed as a thin liquid layer utilizing the capillary phenomenon,
The etchant can be uniformly supplied to the entire surface of the silicon compound. Therefore, uniform etching can be performed. Further, in this case, since the required amount of the hydrogen fluoride solution or the like is small, the etching can be performed more safely.

[0032]

Embodiments of the present invention will be described below.

Using the device 10 having the above structure,
The silicon compound surface was etched by the following method.

Example 1 First, hydrofluoric acid (H ₂ O: HF = 10: 1) was dropped on a SiC substrate 1, and a sapphire glass window member 2 was placed thereon. That is, a laminated body in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer made of hydrofluoric acid was formed by utilizing the capillary phenomenon.

Next, using an apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 was applied to this laminate from the sapphire glass window member 2 side in a direction perpendicular to the substrate surface at 400 mJ / cm.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 75 Å was achieved.

When KrF excimer laser light was irradiated instead of ArF excimer laser light, SiC
The surface of the substrate 1 was hardly etched.

Example 2 A mixed solution of hydrogen peroxide and hydrofluoric acid (H ₂ O ₂ : HF = 10:
1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, S
A laminated body was formed in which the iC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing hydrogen peroxide as an oxidizing agent.

Next, using an apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 of 256 mJ / cm was applied to the laminate from the sapphire glass window member 2 side in a direction perpendicular to the substrate surface.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 30 angstroms was realized.

(Example 3) A mixed solution of hydrogen peroxide solution and hydrofluoric acid (H ₂ O ₂ : HF = 10:
1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, S
A laminated body was formed in which the iC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing hydrogen peroxide as an oxidizing agent.

Next, using the apparatus 10 shown in FIG. 1, a KrF excimer laser beam 11 was applied to the laminate from the side of the sapphire glass window member 2 perpendicularly to the substrate surface at 400 mJ / cm.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 120 angstroms was realized.

Example 4 ArF Excimer Laser Light 1
Etching of the SiC substrate 1 was performed under the same conditions as in Example 1 except that the energy density of Example 1 was changed.
The relationship between the energy density of the ArF excimer laser beam 11 and the etching depth was examined. The etching of the SiC substrate 1 was performed under the same conditions as those described in Example 3 except that the energy density of the KrF excimer laser light 11 was changed, and the relationship between the energy density of the KrF excimer laser light 11 and the etching depth. Was examined. The result is shown in FIG.

FIG. 2 is a graph showing the relationship between the energy density of ultraviolet rays 11 and the etching depth in the etching method according to the embodiment of the present invention. In the figure, the horizontal axis indicates the energy density of the ultraviolet rays 11, and the vertical axis indicates the etching depth. Curve 21 shows data obtained when hydrofluoric acid and ArF excimer laser light were used as the etchant and the ultraviolet light 11, and the curve 22 was
The data obtained when a mixture of hydrogen peroxide and hydrogen fluoride and a KrF excimer laser beam are used as the etchant and the ultraviolet rays 11 are shown.

As is apparent from curves 21 and 22, hydrofluoric acid and Ar as etchant and ultraviolet light 11 were used.
As compared with the case where the F excimer laser beam was used, a larger etching depth could be obtained when a mixed solution of hydrogen peroxide and hydrogen fluoride and the KrF excimer laser beam were used as the etchant and the ultraviolet rays 11. That is, hydrogen peroxide is used as an oxidizing agent and ultraviolet rays 11
When a KrF excimer laser beam was used, a higher etching rate could be realized.

(Example 5) Concentrated sulfuric acid (9
5%) and a mixture of hydrofluoric acid (40%) (H _TwoS
O_Four: HF = 1: 1) was dropped, and further, quartz
The glass window member 2 was placed. That is, the capillary phenomenon is used.
The SiC substrate 1 and the quartz glass window member 2 are
Through a thin liquid layer of an etchant containing
A laminated body was formed.

Next, using the apparatus 10 shown in FIG. 1, the laminated body is subjected to K perpendicular to the substrate surface from the quartz glass window member 2 side.
The rF excimer laser beam 11 was irradiated with 10,000 shots at an energy density of 400 mJ / cm ² . As a result, an etching depth of 45 angstroms was realized.

Example 6 A mixed solution of pure water and hydrofluoric acid (40%) (H ₂ O: HF = 3:
1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, S
A laminated body in which the iC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing pure water as an oxidizing agent was formed.

Next, using an apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 was applied to the laminate from the sapphire glass window member 2 side perpendicular to the substrate surface at 650 mJ / cm.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 80 angstroms was realized.

(Embodiment 7) Nitric acid (60
%) And hydrofluoric acid (40%) (HNO ₃ :
HF = 1: 1) was dropped, and a transparent fluororesin window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminate was formed in which the SiC substrate 1 and the transparent fluororesin window member 2 were laminated via a thin liquid layer of an etchant containing nitric acid as an oxidizing agent.

Next, an ArF excimer laser beam 11 of 650 mJ / cm ² was applied to this laminate from the transparent fluororesin window member 2 side perpendicularly to the substrate surface using the apparatus 10 shown in FIG.
10000 shots at an energy density of As a result, an etching depth of 90 angstroms was realized.

Example 8 A mixture (HNO ₃ : HF = 1: 1) of an aqueous solution of potassium nitrate (1%) and hydrofluoric acid (40%) was dropped on the SiC substrate 1, and furthermore, The sapphire glass window member 2 was placed on the glass. That is, by using the capillary phenomenon, a laminate was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing potassium nitrate as an oxidizing agent.

Next, using an apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 of 650 mJ / cm was applied to the laminate from the sapphire glass window member 2 side in a direction perpendicular to the substrate surface.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 95 Å was achieved.

Example 9 A mixture (KMnO ₄ : HF = 1: 1) of an aqueous solution of potassium permanganate (1%) and hydrofluoric acid (40%) was dropped on the SiC substrate 1, and furthermore, The sapphire glass window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing potassium permanganate as an oxidizing agent.

Next, an ArF excimer laser beam 11 of 650 mJ / cm was applied to the laminate from the sapphire glass window member 2 side perpendicular to the substrate surface using the apparatus 10 shown in FIG.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 120 angstroms was realized.

Example 10 A mixture (K ₂ CrO ₄ : HF = 1: 1) of an aqueous solution of potassium chromate (1%) and hydrofluoric acid (40%) was dropped on a SiC substrate 1. Further, the sapphire glass window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminate was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing potassium chromate as an oxidizing agent.

Next, using the apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 of 650 mJ / cm was applied to the laminate from the sapphire glass window member 2 side in a direction perpendicular to the substrate surface.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 100 angstroms was realized.

Example 11 A mixed solution (K ₂ Cr ₂ O ₇ : HF = 1: 1) of an aqueous solution of potassium dichromate (1%) and hydrofluoric acid (40%) was placed on a SiC substrate 1. The sapphire glass window member 2 was placed thereon.
That is, by using the capillary phenomenon, a laminate was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing potassium dichromate as an oxidizing agent.

Next, an ArF excimer laser beam 11 of 650 mJ / cm was applied to the laminate from the sapphire glass window member 2 side perpendicularly to the substrate surface using the apparatus 10 shown in FIG.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 110 angstroms was realized.

Example 12 A mixed solution (A) of an aqueous solution of silver oxide (1%) and hydrofluoric acid (40%) was placed on a SiC substrate 1.
g ₂ O: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing silver oxide as an oxidizing agent.

Next, an ArF excimer laser beam 11 of 650 mJ / cm was applied to the laminate from the sapphire glass window member 2 side perpendicular to the substrate surface using the apparatus 10 shown in FIG.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 85 Å was achieved.

Example 13 A mixed solution (C) of an aqueous copper oxide solution (1%) and hydrofluoric acid (40%) was placed on a SiC substrate 1.
uO: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated via a thin liquid layer of an etchant containing copper oxide as an oxidizing agent.

Next, using an apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 was applied to this laminate from the sapphire glass window member 2 side perpendicular to the substrate surface at 650 mJ / cm.
10000 shots were irradiated at an energy density of ² . As a result, an etching depth of 55 Å was realized.

Example 14 A mixed solution of pure water and hydrofluoric acid (40%) (H ₂ O: HF = 3:
1) was dropped, and a synthetic quartz glass window member 2 was placed thereon. That is, by utilizing the capillary phenomenon, Si
A laminated body was formed in which the C substrate 1 and the synthetic quartz glass window member 2 were laminated via a thin liquid layer of an etchant containing pure water as an oxidizing agent.

Next, using the apparatus 10 shown in FIG. 1, the laminated body was irradiated with Xe ₂ ^* excimer lamp light 11 from the side of the synthetic quartz glass window member 2 perpendicularly to the substrate surface for 10 minutes. As a result, an etching depth of 30 angstroms was realized.

Example 15 A mixture (H ₂ O ₂ : HF = 3: 1) of aqueous hydrogen peroxide (30%) and hydrofluoric acid (40%) was dropped on the SiC substrate 1. Further, the synthetic quartz glass window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminate was formed in which the SiC substrate 1 and the synthetic quartz glass window member 2 were laminated via a thin liquid layer of an etchant containing hydrogen peroxide as an oxidizing agent.

Next, using the apparatus 10 shown in FIG. 1, 10 KrCl excimer lamp light (222 nm) 11 was applied to the laminate from the side of the synthetic quartz glass window member 2 perpendicularly to the substrate surface.
Irradiated for minutes. As a result, an etching depth of 60 Å was achieved.

Example 16 A mixture (H ₂ O ₂ : HF = 3: 1) of aqueous hydrogen peroxide (30%) and hydrofluoric acid (40%) was dropped on a SiN substrate 1, Further, the synthetic quartz glass window member 2 was placed thereon. That is, by using the capillary phenomenon, a laminate was formed in which the SiN substrate 1 and the synthetic quartz glass window member 2 were laminated via a thin liquid layer of an etchant containing hydrogen peroxide as an oxidizing agent.

Next, using the apparatus 10 shown in FIG. 1, an ArF excimer laser beam 11 was applied to this laminate at an energy density of 650 mJ / cm ² from the side of the synthetic quartz glass window member 2 for 10000 shots perpendicular to the substrate surface. Irradiated. As a result, an etching depth of 100 angstroms was realized.

Example 17 The relationship between the energy density of the ultraviolet rays 11 and the etching depth was examined by the following method.

First, hydrogen peroxide solution and 1
Liquid mixture with 5% hydrofluoric acid (H _TwoO_Two: HF = 10:
1) is dropped, and a sapphire glass window
Material 2 was placed. That is, using the capillary phenomenon, S
The iC substrate 1 and the sapphire glass window member 2 are
Through a thin liquid layer of an etchant containing sulfur as an oxidant
Thus, a laminated body was formed. Next, the device shown in FIG.
10, a sapphire glass window member
ArF excimer laser beam 11 perpendicular to the substrate surface from side 2
For 10,000 shots.

The above operation was performed using ArF excimer laser light 1
A plurality of times were performed while changing the energy density of No. 1 and the etching depth obtained for each was examined. The result is shown in FIG.
Shown in

FIG. 3 is a graph showing the relationship between the energy density of ultraviolet rays and the etching depth. In the figure, the horizontal axis indicates the energy density, and the vertical axis indicates the etching depth. A straight line 30 indicates the data obtained in Example 17, and straight lines 31 and 32 indicate Comparative Examples 1 and 2 described later.
Shows the data obtained in.

As shown in FIG. 3, according to the seventeenth embodiment,
A sufficient etching depth was able to be realized with a relatively low energy density.

(Comparative Example 1) A SiC substrate was housed in a chamber, and the inside of the chamber was controlled to a ClF ₃ atmosphere of 5 Torr. Next, S through a window provided in the chamber.
Kr of 50 mJ / cm ² parallel to the surface of the iC substrate
Irradiation with F excimer laser light caused photolysis shown by the following reaction formula.

ClF ₃ → Cl ^* + 3F ^* At this time, the substrate surface was excited by simultaneously irradiating the substrate surface with 10,000 shots of KrF excimer laser light at 20 Hz. The exposed portions on the substrate surface excited as described above were reacted with radicals generated by the photolysis of ClF ₃ to etch the exposed portions on the substrate surface.

The above operation is performed by irradiating Kr onto the substrate.
The etching was performed a plurality of times while changing the energy density of the F excimer laser light, and the etching depth obtained for each was examined. As a result, as shown by the straight line 31 in FIG. 3, a high energy density was required to realize a sufficient etching depth.

(Comparative Example 2) A SiC substrate was housed in a chamber, and the inside of the chamber was controlled to an NF ₃ atmosphere of 200 Torr. Next, Xe ₂ ^* lamp light was irradiated through a window provided in the chamber, and KrF excimer laser light was irradiated perpendicularly to the surface of the SiC substrate at 10,000 Hz at 20 Hz.

The above operation was performed a plurality of times while changing the energy density of the KrF excimer laser beam, and the etching depth obtained for each was examined. As a result, as shown by a straight line 32 in FIG. 3, a high energy density similar to that of Comparative Example 1 was required to realize a sufficient etching depth.

[0078]

As described above, according to the method of the present invention, ClF ₃ gas or N
Hazardous gases such as F ₃ gas is not used, the hydrogen fluoride solution is used instead. Therefore, according to the method of the present invention, it is possible to form a fine pattern on the surface of the silicon compound relatively safely.

That is, according to the present invention, there is provided an etching method capable of forming a fine pattern on a silicon compound surface relatively safely.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an apparatus used for an etching method according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the energy density of ultraviolet rays and the etching depth in the etching method according to the embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the energy density of ultraviolet rays and the etching depth in the etching methods according to examples and comparative examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Window member 10 ... Device 11 ... Ultraviolet light 12 ... Ultraviolet light source 13 ... Homogenizer 14 ... Mirror 15 ... Photomask 20, 21, 30-32 ... Straight line

Claims (6)

[Claims] 1. A thin liquid layer containing hydrofluoric acid and an oxidizing agent is interposed between a surface of a silicon compound and a window member that transmits ultraviolet light, and ultraviolet light is directed from the window member side toward the silicon compound surface. Irradiation oxidizes at least a part of the silicon compound surface, and removes a silicon oxide generated thereby from the silicon compound surface with hydrofluoric acid contained in the thin liquid layer. Method. 2. The etching method according to claim 1, wherein the surface of the silicon compound contains one of silicon carbide and silicon nitride. 3. The oxidizing agent is H ₂ O ₂ , H ₂ SO ₄ , HN
O ₃ , KNO ₃ , KMnO ₄ , K ₂ CrO ₄ , K ₂ Cr ₂ O ₇ ,
_3. The etching method according to claim 1, further comprising at least one compound selected from the group consisting of Ag2O and CuO. 4. The etching method according to claim 1, wherein the thin liquid layer is formed by utilizing a capillary phenomenon. 5. The method according to claim 1, wherein the ultraviolet light has a wavelength of 300 to 120 nm.
The etching method according to any one of claims 1 to 4, wherein the etching method has the following wavelength. 6. The window member is made of sapphire, quartz, synthetic quartz glass, calcium fluoride, magnesium fluoride,
The etching method according to any one of claims 1 to 5, wherein the etching method is made of a material selected from the group consisting of a transparent fluorine resin.