JP4250820B2 - Etching method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an etching method, and more particularly to an etching method for etching a silicon compound surface.
[0002]
[Prior art]
Silicon carbide is excellent in heat resistance, radiation resistance, chemical resistance, and wear resistance, has a wide band gap, and has a high reflectivity in the X-ray region. For this reason, silicon carbide is expected to be applied to semiconductor devices and SR light gratings.
[0003]
Currently, silicon carbide substrates are often processed by physical methods such as diamond engraving and laser ablation, but chemical methods are essential to form fine patterns in a short time and with high precision. It is. 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.
[0004]
For example, when pattern etching is performed using a reactive ion etching (RIE) method or the like, a resist having a chemical resistance better than that of silicon carbide is required. However, such a resist is unrealistic. In addition, when the photoelectrochemical (PEC) method is used, a resist is unnecessary, but since it is a direct drawing method, there is a problem in processing time and processing accuracy.
[0005]
In addition to the above method, the present inventors have used ClF as a chemical method._ThreeGas or NF_ThreeWe are developing a photochemical pattern etching method using an etchant gas such as gas. In this method, radicals generated by photolysis of an etchant gas are used to convert silicon carbide to SiF on the surface of a silicon carbide substrate._nAnd CF_nAlternatively, it is sublimated as CN. According to this method, since the sublimation occurs only in the exposed portion of the laser beam that is the surface excitation light, it is possible to form a desired pattern with high accuracy. However, this method is_ThreeGas or NF_ThreeYou need a dangerous gas like gas.
[0006]
[Problems to be solved by the invention]
As described above, according to the conventional method, in order to form a fine pattern with high accuracy by a chemical method on the surface of a silicon compound substrate such as a silicon carbide substrate, ClF_ThreeGas or NF_ThreeHazardous gas such as gas is necessary.
[0007]
The present invention has been made in view of the above problems, and an object thereof is to provide an etching method capable of forming a fine pattern on the surface of a silicon compound relatively safely.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a silicon compound surface from the window member side by interposing a thin liquid layer containing hydrofluoric acid and an oxidizing agent between the silicon compound surface and a window member that transmits ultraviolet rays. And at least a part of the surface of the silicon compound is oxidized by irradiating ultraviolet rays toward the surface, and the silicon oxide formed thereby is removed from the surface of the silicon compound with hydrofluoric acid contained in a thin liquid layer. An etching method is provided.
[0009]
The etching method of the present invention is a reaction between highly active oxygen atoms generated by photoexcitation of an oxidant and Si and C whose bonds are broken by photoexcitation of a silicon compound surface made of a silicon compound, for example, silicon carbide. Is used. SiO produced by this reaction₂And CO₂Of oxides such as CO₂Such gas diffuses into the thin liquid layer. On the other hand, SiO₂Etc. remain on the surface of the silicon compound, but are easily removed by hydrofluoric acid. The etching method of the present invention is based on such a principle.
[0010]
Although the etching of the silicon compound surface by the above-described method can be performed without using an oxidizing agent, when an oxidizing agent is used, highly active oxygen atoms can be generated very efficiently. Therefore, according to the method of the present invention, a sufficient etching depth can be easily realized.
[0011]
As described above, in the method of the present invention, a liquid is used as an etchant. In this case, compared with the case where gas is used, the contact density of the silicon compound surface which is a to-be-processed surface and an etchant can be raised more. Therefore, the etching rate can be improved.
[0012]
Further, according to the method of the present invention, ClF is used for etching a silicon compound._ThreeGas or NF_ThreeHazardous gas such as gas is not used and hydrofluoric acid is used instead. Since hydrofluoric acid is relatively easy to handle compared to the above gas, according to the method of the present invention, it is possible to safely form a fine pattern on the surface of the silicon compound.
[0013]
Furthermore, 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 capillary action. In this case, hydrofluoric acid and an oxidizing agent can be uniformly supplied to the entire silicon compound surface. Therefore, uniform etching can be performed. In this case, since the amount of hydrofluoric acid required is small, etching can be performed more safely.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings.
[0015]
FIG. 1 is a view schematically showing an apparatus used in an etching method according to an embodiment of the present invention. An apparatus 10 shown in FIG. 1 includes an ultraviolet ray 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 on which a substrate 1 is mounted horizontally ( (Not shown).
[0016]
The apparatus 10 is an apparatus that forms a thin liquid layer (not shown) by a capillary phenomenon in a gap with the window member 2 placed on the substrate 1 and irradiates ultraviolet rays from the upper part. That is, the apparatus 10 homogenizes the ultraviolet rays (laser light) 11 output from the ultraviolet ray source 12 with a homogenizer 13 such as a polyhedral prism, and then changes the traveling direction downward in the vertical direction by the mirror 14. The substrate 1 is irradiated from the window member 2 side through the mask 15.
[0017]
According to one embodiment of the present invention, for example, the silicon compound surface is etched by the following method using the apparatus 10 shown in FIG.
[0018]
First, a substrate 1 having at least one main 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.
[0019]
Next, an etchant containing hydrofluoric acid and an oxidizing agent is dropped onto the surface of the silicon compound of the substrate 1. The oxidizing agent used in the etchant is H₂O₂, H₂SO_Four, HNO_Three, KNO_Three, KMnO_Four, K₂CrO_Four, K₂Cr₂O₇, Ag₂O, CuO, etc. can be mentioned. These oxidizing agents may be used alone or in combination.
[0020]
Thereafter, the window member 2 is placed on the silicon compound surface of the substrate 1. Etchant droplets 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 thin liquid layer that is an extremely thin liquid film between the substrate 1 and the window member 2.
[0021]
Thus, since the window member 2 is in contact with the etchant, it is necessary to have resistance to the etchant. Further, as will be described later, since ultraviolet rays are irradiated from the window member 2 side, the window member 2 needs to transmit ultraviolet rays. Examples of such materials include sapphire, quartz, synthetic quartz glass, calcium fluoride, magnesium fluoride, or transparent fluororesin plates such as FEP and PFA.
[0022]
Note that quartz and synthetic quartz glass are placed in hydrofluoric acid, while 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, the etchant used here is a liquid and will be described later. Excessive light scattering does not occur during UV irradiation.
[0023]
Next, the apparatus 10 is used to irradiate the substrate 11 with ultraviolet rays 11 from the window member 2 side. As described above, since the thin liquid layer is interposed between the substrate 1 and the window member 2, it is preferable that the substrate 1 and the like are arranged horizontally on a mounting table (not shown).
[0024]
Moreover, as the ultraviolet rays 11, for example, those having a wavelength of 300 nm to 120 nm can be used. In this wavelength range, each oxidant has light absorption and undergoes photolysis. However, since the absorption of hydrofluoric acid is 160 nm or less, it should be noted that the wavelength range with good etching efficiency is 300 nm to 160 nm.
[0025]
As such a light source 12 of the ultraviolet ray 11, ArF excimer laser, KrF excimer laser, Ar excimer laser, Kr excimer laser, F₂Lasers, lasers using nonlinear crystals that output ultraviolet laser light, Xe₂ ^*Examples include an excimer lamp, a XeCl excimer lamp, an Ar excimer lamp, a Kr excimer lamp, and a UV lamp.
[0026]
When the ultraviolet rays 11 are irradiated toward the substrate 1 from the window member 2 side, the above-described etching is selectively generated in the exposure portion. On the other hand, the etching does not occur in the unexposed area. As a result, a pattern corresponding to the pattern of the photomask 15 is formed on the surface of the substrate 1. According to the method of the present embodiment, etching is performed as described above.
[0027]
In the present embodiment, the thickness of the thin liquid layer is usually in the range of 100 to 10 μm, and preferably in the range of 50 to 20 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 excessive absorption of the ultraviolet rays 11 in the thin liquid layer can be suppressed, so that the substrate 1 Can be sufficiently photoexcited.
[0028]
In this embodiment, the energy density of the ultraviolet ray 11 is 100 mJ / cm.²Preferably, it is 500 mJ / cm.²More preferably. In this case, highly active oxygen atoms can be sufficiently generated, and the surface of the substrate 1 can be sufficiently photoexcited.
[0029]
In the present embodiment, it is preferable to appropriately select the ultraviolet ray source 12 according to the composition of the thin liquid layer. For example, when the etchant contains hydrogen fluoride and water, an ArF excimer laser or Xe is used as the ultraviolet source 12.₂ ^*It is preferable to use an excimer lamp. In the case where the etchant contains hydrogen fluoride and hydrogen peroxide, the ultraviolet source 12 can be an ArF excimer laser, a KrF excimer laser, an Ar excimer laser, a Kr excimer laser, F₂Laser, laser using nonlinear crystal, Xe₂ ^*Excimer lamp, XeCl excimer lamp, Ar excimer lamp, Kr excimer lamp, Hg lamp, or D₂It is preferable to use a lamp or the like.
[0030]
Thus, by appropriately selecting the ultraviolet ray source 12 according to the composition of the thin liquid layer, excessive absorption of the ultraviolet ray 11 in the thin liquid layer can be suppressed, and the surface of the substrate 1 can be sufficiently photoexcited. That is, a high etching rate can be obtained.
[0031]
As described above, in the method of the present embodiment, a liquid, not a gas, is used as an etchant, so that a high etching rate can be realized. Moreover, in the method of this embodiment, since an etchant is formed as a thin liquid layer using a capillary phenomenon, an etchant can be uniformly supplied to the whole silicon compound surface. Therefore, uniform etching can be performed. Further, in this case, since a necessary amount of a hydrogen fluoride solution or the like is small, etching can be performed more safely.
[0032]
【Example】
Examples of the present invention will be described below.
[0033]
Using the apparatus 10 having the above-described structure, the silicon compound surface was etched by the following method.
[0034]
Example 1
First, hydrofluoric acid (H₂O: HF = 10: 1) was dropped, 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 through a thin liquid layer made of hydrofluoric acid was formed by utilizing a capillary phenomenon.
[0035]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is applied to the laminated body from the sapphire glass window member 2 side perpendicular to the substrate surface at 400 mJ / cm.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 75 angstroms could be realized.
[0036]
In addition, when the KrF excimer laser beam was irradiated instead of the ArF excimer laser beam, the surface of the SiC substrate 1 was hardly etched.
[0037]
(Example 2)
A mixed liquid of hydrogen peroxide and hydrofluoric acid (H₂O₂: HF = 10: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body in which the SiC 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 was formed.
[0038]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is applied to this laminated body from the sapphire glass window member 2 side in a direction perpendicular to the substrate surface at 256 mJ / cm.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 30 angstroms could be realized.
[0039]
(Example 3)
A mixed liquid of hydrogen peroxide and hydrofluoric acid (H₂O₂: HF = 10: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body in which the SiC 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 was formed.
[0040]
Next, using the apparatus 10 shown in FIG. 1, 400 mJ / cm of KrF excimer laser light 11 is applied to the laminate from the sapphire glass window member 2 side perpendicular to the substrate surface.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 120 angstroms could be realized.
[0041]
(Example 4)
Except that the energy density of the ArF excimer laser beam 11 is changed, the SiC substrate 1 is etched under the same conditions as shown in Example 1, and the relationship between the energy density of the ArF excimer laser beam 11 and the etching depth is investigated. It was. Further, the SiC substrate 1 is etched under the same conditions as described in Example 3 except that the energy density of the KrF excimer laser beam 11 is changed, and the relationship between the energy density of the KrF excimer laser beam 11 and the etching depth. I investigated. The result is shown in FIG.
[0042]
FIG. 2 is a graph showing the relationship between the energy density of the ultraviolet light 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 ray 11 and the vertical axis indicates the etching depth. A curve 21 shows data obtained when hydrofluoric acid and ArF excimer laser light are used as the etchant and ultraviolet ray 11, and a curve 22 shows the hydrogen peroxide and hydrogen fluoride as the etchant and ultraviolet ray 11. The data obtained in the case of using a mixed solution and KrF excimer laser light are shown.
[0043]
As is apparent from the curves 21 and 22, as compared with the case where the hydrofluoric acid and ArF excimer laser light are used as the etchant and the ultraviolet ray 11, a mixed liquid of hydrogen peroxide and hydrogen fluoride and the KrF excimer are used as the etchant and the ultraviolet ray 11. When laser light was used, a larger etching depth could be obtained. That is, when hydrogen peroxide was used as the oxidizing agent and KrF excimer laser light was used as the ultraviolet ray 11, a faster etching rate could be realized.
[0044]
(Example 5)
On the SiC substrate 1, a mixture of concentrated sulfuric acid (95%) and hydrofluoric acid (40%) (H₂SO_Four: HF = 1: 1) was added dropwise, and the quartz glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the quartz glass window member 2 were laminated through a thin liquid layer of an etchant containing sulfuric acid as an oxidizing agent.
[0045]
Next, using the apparatus 10 shown in FIG. 1, 400 mJ / cm of KrF excimer laser light 11 is applied to the laminate from the quartz glass window member 2 side perpendicular to the substrate surface.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 45 angstroms could be realized.
[0046]
(Example 6)
On the SiC substrate 1, a mixture of pure water and hydrofluoric acid (40%) (H₂O: HF = 3: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated through a thin liquid layer of an etchant containing pure water as an oxidizing agent.
[0047]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 80 angstroms could be realized.
[0048]
(Example 7)
Mixed liquid (HNO on nitric acid (60%) and hydrofluoric acid (40%) on SiC substrate 1_Three: HF = 1: 1) was added dropwise, and the transparent fluororesin window member 2 was placed thereon. That is, using a capillary phenomenon, a laminated body 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.
[0049]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the transparent fluororesin window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 90 angstroms could be realized.
[0050]
(Example 8)
A mixed solution (HNO of potassium nitrate aqueous solution (1%) and hydrofluoric acid (40%) on the SiC substrate 1_Three: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, 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 nitrate as an oxidizing agent.
[0051]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 95 angstroms could be realized.
[0052]
Example 9
Mixed liquid (KMnO) of potassium permanganate aqueous solution (1%) and hydrofluoric acid (40%) on SiC substrate 1_Four: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body in which the SiC substrate 1 and the sapphire glass window member 2 were laminated through a thin liquid layer of an etchant containing potassium permanganate as an oxidizing agent was formed.
[0053]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 120 angstroms could be realized.
[0054]
(Example 10)
A mixed solution (K) of an aqueous potassium chromate solution (1%) and hydrofluoric acid (40%) on the SiC substrate 1₂CrO_Four: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, 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 chromate as an oxidizing agent.
[0055]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 100 Å could be realized.
[0056]
(Example 11)
Mixed liquid (K) of aqueous potassium dichromate (1%) and hydrofluoric acid (40%) on SiC substrate 1₂Cr₂O₇: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the sapphire glass window member 2 were laminated through a thin liquid layer of an etchant containing potassium dichromate as an oxidizing agent.
[0057]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 110 angstroms could be realized.
[0058]
Example 12
A mixed solution (Ag) of an aqueous silver oxide solution (1%) and hydrofluoric acid (40%) on the SiC substrate 1₂O: HF = 1: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using a capillary phenomenon, a laminated body 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 was formed.
[0059]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 85 angstroms could be realized.
[0060]
(Example 13)
A liquid mixture (CuO: HF = 1: 1) of an aqueous copper oxide solution (1%) and hydrofluoric acid (40%) is dropped on the SiC substrate 1, and a sapphire glass window member 2 is placed thereon. I put it. That is, using a capillary phenomenon, a laminated body 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 was formed.
[0061]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is 650 mJ / cm perpendicular to the substrate surface from the sapphire glass window member 2 side.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 55 angstroms could be realized.
[0062]
(Example 14)
On the SiC substrate 1, a mixture of pure water and hydrofluoric acid (40%) (H₂O: HF = 3: 1) was dropped, and a synthetic quartz glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body was formed in which the SiC substrate 1 and the synthetic quartz glass window member 2 were laminated through a thin liquid layer of an etchant containing pure water as an oxidizing agent.
[0063]
Next, using the apparatus 10 shown in FIG. 1, Xe is vertically applied to the laminated body from the synthetic quartz glass window member 2 side to the substrate surface.₂ ^*Excimer lamp light 11 was irradiated for 10 minutes. As a result, an etching depth of 30 angstroms could be realized.
[0064]
(Example 15)
A mixed liquid (H) of hydrogen peroxide (30%) and hydrofluoric acid (40%) on the SiC substrate 1₂O₂: HF = 3: 1) was added dropwise, and the synthetic quartz glass window member 2 was placed thereon. That is, using a capillary phenomenon, a laminated body 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.
[0065]
Next, using the apparatus 10 shown in FIG. 1, this laminated body was irradiated with KrCl excimer lamp light (222 nm) 11 for 10 minutes perpendicularly to the substrate surface from the synthetic quartz glass window member 2 side. As a result, an etching depth of 60 angstroms could be realized.
[0066]
(Example 16)
A mixed liquid (H) of hydrogen peroxide (30%) and hydrofluoric acid (40%) on the SiN substrate 1₂O₂: HF = 3: 1) was added dropwise, and the synthetic quartz glass window member 2 was placed thereon. That is, using a capillary phenomenon, a laminated body in which the SiN substrate 1 and the synthetic quartz glass window member 2 were laminated through a thin liquid layer of an etchant containing hydrogen peroxide as an oxidizing agent was formed.
[0067]
Next, using the apparatus 10 shown in FIG. 1, ArF excimer laser light 11 is applied to the laminated body from the synthetic quartz glass window member 2 side perpendicularly to the substrate surface at 650 mJ / cm.²Was irradiated with 10,000 shots at an energy density of. As a result, an etching depth of 100 Å could be realized.
[0068]
(Example 17)
The relationship between the energy density of the ultraviolet ray 11 and the etching depth was examined by the following method.
[0069]
First, a mixed solution of hydrogen peroxide and 15% hydrofluoric acid (H₂O₂: HF = 10: 1) was dropped, and a sapphire glass window member 2 was placed thereon. That is, using the capillary phenomenon, a laminated body in which the SiC 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 was formed. Next, using the apparatus 10 shown in FIG. 1, this laminate was irradiated with 10,000 shots of ArF excimer laser light 11 perpendicularly to the substrate surface from the sapphire glass window member 2 side.
[0070]
The above operation was performed a plurality of times while changing the energy density of the ArF excimer laser beam 11, and the etching depth obtained for each was examined. The result is shown in FIG.
[0071]
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. Moreover, the straight line 30 shows the data obtained in Example 17, and the straight lines 31 and 32 show the data obtained in Comparative Examples 1 and 2 described later, respectively.
[0072]
As shown in FIG. 3, according to Example 17, a sufficient etching depth could be realized with a relatively low energy density.
[0073]
(Comparative Example 1)
The SiC substrate is accommodated in the chamber, and the interior of the chamber is 5 Torr of ClF._ThreeControlled to atmosphere. Next, 50 mJ / cm parallel to the surface of the SiC substrate through a window provided in the chamber.²The photodecomposition shown in the following reaction formula was caused by irradiation with KrF excimer laser light.
[0074]
ClF_Three→ Cl^*+ 3F^*
At the same time, the substrate surface was excited by irradiating 10,000 shots of KrF excimer laser light at 20 Hz perpendicular to the surface of the substrate. The exposed portion of the substrate surface thus excited and ClF_ThreeThe exposed portion of the substrate surface was etched by reacting with radicals generated by photodecomposition.
[0075]
The above operation was performed a plurality of times while changing the energy density of the KrF excimer laser beam irradiated toward the substrate, and the etching depth obtained for each was examined. As a result, as shown by a straight line 31 in FIG. 3, a high energy density was required to achieve a sufficient etching depth.
[0076]
(Comparative Example 2)
A SiC substrate is accommodated in a chamber, and the chamber is filled with NF of 200 Torr._ThreeControlled to atmosphere. Next, through the window provided in the chamber, Xe₂ ^*While irradiating with lamp light, 10000 shots of KrF excimer laser light were irradiated at 20 Hz perpendicular to the surface of the SiC substrate.
[0077]
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 as a straight line 32 in FIG. 3, the same high energy density as in Comparative Example 1 was required to achieve a sufficient etching depth.
[0078]
【The invention's effect】
As described above, according to the method of the present invention, ClF is used for etching a silicon compound._ThreeGas or NF_ThreeHazardous gas such as gas is not used, instead a hydrogen fluoride solution is used. 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.
[0079]
That is, according to the present invention, there is provided an etching method capable of forming a fine pattern on the 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 an etching method according to an 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 etching methods according to examples and comparative examples of the present invention.
[Explanation of symbols]
1 ... Board
2 ... Window member
10 ... Device
11 ... UV
12 ... UV source
13 ... Homogenizer
14 ... Mirror
15 ... Photomask
20, 21, 30 to 32 ... straight line

Claims (3)

A thin liquid layer formed by utilizing capillary action containing hydrofluoric acid and an oxidizing agent is interposed between the surface of a silicon compound composed of one of silicon carbide and silicon nitride and a window member that transmits ultraviolet light. 300 from the window member side toward the silicon compound surface  nm ~ 120  nm By irradiating with ultraviolet rays having a wavelength of at least a part of the silicon compound surface is oxidized, and the silicon oxide formed thereby is removed from the silicon compound surface with hydrofluoric acid contained in the thin liquid layer. An etching method characterized by the above. The oxidizing agent is a group consisting of H ₂ O ₂ , H ₂ SO ₂ , H ₂ SO ₄ , HNO ₃ , KNO ₃ , KMnO ₄ , K ₂ CrO ₄ , K ₂ Cr ₂ O ₇ , Ag ₂ O, and CuO. 2. The etching method according to claim 1, comprising at least one kind of compound selected from the above.   2. The etching method according to claim 1, wherein the window material is made of a material selected from the group consisting of sapphire, quartz, synthetic quartz glass, calcium fluoride, magnesium fluoride, and transparent fluororesin.

Images