JP5550196B2 - Substrate etching method and sapphire substrate manufacturing method - Google Patents

Description

  The present invention relates to a substrate etching method for etching a sapphire substrate using an organic resist as a mask, and a method for manufacturing a sapphire substrate.

  In the field of manufacturing light emitting devices such as semiconductor lasers, sapphire substrates are widely used as substrates for growing GaN-based compound semiconductor crystals. It is known to form a fine concavo-convex shape on the surface of the sapphire substrate for the purpose of controlling the growth of the semiconductor crystal and improving the light extraction efficiency. Patent Document 1 listed below describes a method for etching the surface of a sapphire substrate on which a resist layer (etching mask) made of an organic material is formed by dry etching using a chlorine-based gas.

JP 2007-123446 A

  However, in dry etching using a chlorine-based gas as an etching gas, the ratio of the etching rate of the sapphire substrate to the resist layer (etching selection ratio) is low, and a resist layer having a thickness more than twice the etching amount is formed on the substrate. There was a need. Further, the increase in the thickness of the resist layer decreases the exposure accuracy of the resist layer, and it is difficult to form a fine resist pattern with high accuracy.

  In view of the circumstances as described above, an object of the present invention is to provide a substrate etching method and a sapphire substrate manufacturing method capable of enhancing the etching selectivity of a substrate with respect to an organic resist.

In order to achieve the above object, a substrate etching method according to an embodiment of the present invention includes a step of placing an aluminum compound substrate having an organic resist formed on a surface thereof in a vacuum chamber.
An organic member for forming plasma containing hydrocarbons is disposed in the vacuum chamber.
An etching gas is introduced into the vacuum chamber.
By forming plasma containing the hydrocarbon in the vacuum chamber, the surface of the substrate is etched using the organic resist as a mask.

A substrate etching method according to another aspect of the present invention includes a step of placing an aluminum compound substrate having an organic resist formed on a surface thereof in a vacuum chamber.
A gas for forming a plasma containing hydrocarbons is introduced into the vacuum chamber.
By forming plasma containing the hydrocarbon in the vacuum chamber, the surface of the substrate is etched using the organic resist as a mask.

In order to achieve the above object, a method for manufacturing a sapphire substrate according to an embodiment of the present invention includes a step of placing a sapphire substrate having an organic resist formed on a surface thereof in a vacuum chamber.
A hydrocarbon source for forming a plasma containing hydrocarbons is introduced or arranged in the vacuum chamber.
By forming plasma containing the hydrocarbon in the vacuum chamber, the surface of the substrate is etched using the organic resist as a mask.

It is a schematic block diagram of the etching apparatus demonstrated in the 1st Embodiment of this invention. It is a figure which shows the modification of the said etching apparatus. It is one experimental result explaining the effect | action of the etching method which concerns on the 1st Embodiment of this invention. It is a schematic block diagram of the etching apparatus demonstrated in the 2nd Embodiment of this invention. It is one experimental result explaining the effect | action of the etching method which concerns on the 2nd Embodiment of this invention. It is one experimental result explaining the effect | action of the etching method which concerns on the 3rd Embodiment of this invention.

A substrate etching method according to an embodiment of the present invention includes a step of placing an aluminum compound substrate having an organic resist formed on a surface thereof in a vacuum chamber.
A hydrocarbon source for forming a plasma containing hydrocarbons is introduced or arranged in the vacuum chamber.
By forming plasma containing the hydrocarbon in the vacuum chamber, the surface of the substrate is etched using the organic resist as a mask.

  In the substrate etching method, etching of an aluminum compound substrate proceeds by forming plasma containing hydrocarbons. On the other hand, the substrate etching method suppresses the progress of the etching of the resist by the plasma by depositing the hydrocarbon-based reactant derived from the hydrocarbon source generated by the plasma on the resist. Therefore, according to the above substrate etching method, the etching rate of the resist can be reduced, so that the etching selectivity of the substrate with respect to the resist can be increased, and fine irregularities are formed on the surface of the substrate without forming the resist thickly. A pattern can be formed.

  The aluminum compound that is a constituent material of the substrate includes aluminum oxide such as sapphire, aluminum nitride, and the like.

The plasma containing hydrocarbons is an etching gas plasma formed in the presence of a hydrocarbon source introduced, arranged or formed inside the vacuum chamber.
The hydrocarbon source introduced into the vacuum chamber includes gaseous organic substances. The hydrocarbon source disposed inside the vacuum chamber includes a bulk (solid) organic material and an organic film formed on the inner wall surface of the vacuum chamber and various components (such as a deposition plate and a stage). . Accordingly, during the etching of the substrate, a hydrocarbon-based reactant can be generated from the organic material by the plasma of the etching gas.

As the etching gas, a chlorine-based gas such as Cl ₂ or BCl ₃ can be used. Chlorine radicals formed by the plasma react with the substrate surface to generate volatile substances such as AlCl. On the other hand, hydrocarbon-based reactants (CxHy (x and y are natural numbers)) are removed from the substrate surface by the sputtering effect of ions in the plasma while being deposited on the substrate without volatilization. By continuing the above process, the substrate can be etched while protecting the resist from etching.

  The plasma containing hydrocarbons may be formed by a plasma of a mixed gas of a chlorine-based etching gas and hydrogen or a hydrocarbon-based gas. Alternatively, the plasma containing hydrocarbons may be formed by a plasma of a mixed gas of a fluorocarbon-based or fluorohydrocarbon-based etching gas and hydrogen or a hydrocarbon-based gas.

The manufacturing method of the sapphire substrate which concerns on one Embodiment of this invention includes the process of arrange | positioning the sapphire substrate in which the organic resist was formed in the surface in a vacuum chamber.
A hydrocarbon source for forming a plasma containing hydrocarbons is introduced or arranged in the vacuum chamber.
By forming plasma containing the hydrocarbon in the vacuum chamber, the surface of the substrate is etched using the organic resist as a mask.

  According to the method for manufacturing a sapphire substrate, the etching rate of the resist can be reduced, and thus the etching selectivity of the substrate with respect to the resist can be increased. Thereby, while being able to reduce the thickness of a resist, the sapphire substrate by which the fine uneven | corrugated pattern was formed in the surface can be manufactured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a configuration diagram of an etching apparatus according to the first embodiment of the present invention. The etching apparatus 1 of this embodiment has a vacuum chamber 10. The vacuum chamber 10 is connected to a vacuum pump 15, and the inside can be reduced to a predetermined pressure.

Inside the vacuum chamber 10, a stage 11 that supports the substrate S and a counter electrode 12 disposed on the upper wall of the vacuum chamber 10 so as to face the stage 11 are installed. Further, a gas introduction pipe 13 for introducing an etching gas (etchant) into the vacuum chamber 10 is connected to the vacuum chamber 10. For example, a chlorine-based gas is used as the etching gas, and in this embodiment, BCl ₂ is used as the main gas.

  The stage 11 is connected to the ground potential, and the counter electrode 12 is connected to a high frequency power source 22 via a blocking capacitor 21. The counter electrode 12 is capacitively coupled to the stage 11 when a high frequency power of a predetermined frequency (for example, 13.56 MHz) is applied from the high frequency power source 22, and forms plasma P of etching gas.

  The plasma P is not limited to the above-described capacitively coupled plasma (CCP). For example, an inductively coupled plasma (ICP) in which a high-frequency coil (antenna) is installed instead of the counter electrode 12 is used. It may be.

  The substrate S is formed of an aluminum compound such as aluminum oxide or aluminum nitride. In this embodiment, a sapphire substrate is used as the LED (Light Emitting Diode) substrate. On the surface of the substrate S, a resist R made of an organic material patterned in a predetermined shape is formed. The resist R functions as an etching mask for forming a predetermined uneven pattern such as a dot shape or a stripe shape on the surface of the substrate S.

  In addition, a deposition preventing plate 14 is disposed inside the vacuum chamber 10. The deposition preventing plate 14 is installed so as to surround the periphery of the plasma forming space between the stage 11 and the counter electrode 12, and prevents the etching reaction product from adhering to the inner wall surface of the vacuum chamber 10.

  And the etching apparatus 1 of this embodiment has the organic member 31 arrange | positioned in the position which faces the formation space of the plasma P. FIG. In the example shown in FIG. 1, the organic member 31 is disposed on the upper surface of the stage 11 and formed in an annular shape surrounding the substrate S. The organic member 31 is not limited to being formed in an annular shape, and may be divided and arranged at a plurality of locations around the substrate S.

  As a constituent material of the organic member 31, various resin materials can be used. For example, polyimide (PI), polytetrafluoroethylene (PTFE), polyurea, or the like is used. Further, a bulk or a molded body formed of the same organic material as that of the resist R may be used as the organic member 31. As will be described later, the organic member 31 is used as a hydrocarbon source for forming a plasma P containing hydrocarbons.

  Next, a method for etching the substrate S using the etching apparatus 1 will be described.

After the substrate S having the resist R patterned in a predetermined shape on the surface is placed on the upper surface of the stage 11, the vacuum chamber 10 is driven at a predetermined pressure (for example, 5.0 × 10E−3 Pa−5 by driving the vacuum pump 15. X10E-4 Pa). Then, an etching gas (BCl ₃ ) is introduced into the vacuum chamber 10 through the gas introduction pipe 13. On the other hand, a high-frequency power is applied to the counter electrode 12 by the high-frequency power source 22, thereby forming an etching gas plasma P inside the vacuum chamber 10.

The radicals of the etching gas formed by the plasma react with the surface of the substrate S that is not covered with the resist R, and generate volatile substances such as AlCl and BO. The reaction formula is as follows.
BCl ₃ + Al ₂ O ₃ → AlCl ↑ + BO ↑ (1)
Thereby, the etching of the substrate S using the resist R as an etching mask proceeds.

  On the other hand, ions contained in the plasma P are biased toward the stage 11 and sputter the surface of the substrate S. At this time, the resist R is also etched by being sputtered by ions.

  In the etching apparatus 1 of this embodiment, the organic member 31 is disposed on the upper surface of the stage 11. The organic member 31 is disposed so as to face the formation space of the plasma P, and thus is sputtered by being attacked by the plasma P like the substrate S, and the sputtered particles are decomposed by the plasma P. Accordingly, the plasma P includes hydrocarbon-based reactants (CxHy (x and y are natural numbers)) that are decomposition products of the organic member 31. The hydrocarbon-based reactant is removed from the surface of the substrate S by the sputtering effect of ions in the plasma while being deposited on the surface of the substrate S without volatilizing.

  On the other hand, since the hydrocarbon-based reactant is also deposited on the surface of the resist R, it functions as a protective film that suppresses the progress of etching of the resist R. Thereby, since the etching rate of the resist R can be reduced, the etching selectivity of the substrate S with respect to the resist R can be increased, and a fine uneven pattern is formed on the surface without forming the resist R thick. A sapphire substrate can be manufactured.

  The hydrocarbon reactant generated by the plasma P includes not only the hydrocarbon component derived from the organic member 31 but also the hydrocarbon component derived from the resist R. In this embodiment, the organic member 31 that is a hydrocarbon source is provided separately from the resist R, so that the amount of hydrocarbon reactant generated is increased and the protective function of the resist R is obtained.

FIG. 3 is a result of an experiment showing the relationship between the etching rate of the substrate S and the etching selectivity with respect to the resist R (substrate etching rate / resist etching rate), and (A) shows the experiment when the organic member 31 is present. A result and (B) show an experimental result when there is no organic member 31, respectively. As experimental conditions at this time, the flow rate of BCl ₃ is 30 sccm, the process pressure is 0.5 Pa, the antenna power is 600 W, and the bias power is 60 W.

The etching rate and selectivity are higher when the organic member 31 is present than when the organic member 31 is absent. The reason why the etching rate is improved is that O of Al ₂ O ₃ is removed by the reducing action of BCl ₃ by B, but the same effect can be obtained with C as well. The reason for the improvement in the etching selectivity is that the etching rate of the resist R is lowered by the hydrocarbon-based reactant derived from the organic member 31.

  As described above, according to this embodiment, a desired uneven pattern can be formed on the surface of the substrate S without increasing the thickness of the resist R. Thereby, while being able to simplify a resist application | coating process, the material cost of a resist material can be reduced. Further, since the thickness of the resist R can be reduced, the exposure conditions can be easily adjusted, thereby improving the exposure accuracy. Furthermore, since the resist R having excellent pattern accuracy can be formed on the surface of the substrate S, a fine uneven pattern can be formed on the surface of the substrate S with high accuracy. Thereby, the performance of the device can be improved.

  The organic member 31 as the hydrocarbon source is not limited to being constituted by an independent member, and may be an organic film formed on the surface of the component in the vacuum chamber 10. FIG. 2 shows a configuration example of the etching apparatus 2 in which an organic film 32 as a hydrocarbon source is formed on the inner surface of the deposition preventing plate 14 facing the plasma P formation space. Also according to this configuration example, the same effects as those of the embodiment described with reference to FIG. 1 can be obtained.

<Second Embodiment>
FIG. 4 is a schematic configuration diagram of an etching apparatus 3 according to the second embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

In the etching apparatus 3 of the present embodiment, a mixed gas of a chlorine-based gas and a hydrocarbon-based gas is used as an etching gas. In particular, in the present embodiment, BCl ₃ is used as the chlorine-based gas, and methane (CH ₄ ) is used as the hydrocarbon-based gas. The hydrocarbon-based gas is used as a hydrocarbon source for forming a plasma P containing hydrocarbons.

  The chlorine-based gas and the hydrocarbon-based gas are each controlled to a predetermined flow rate and introduced into the vacuum chamber 10 through the gas introduction pipe 13. The etching apparatus 3 forms plasma of the introduced etching gas by applying high frequency power to the counter electrode 12. As a result, the substrate S disposed on the stage 11 is etched using the resist R as a mask.

The reaction between the etching gas (BCl ₃ + CH ₄ ) and the substrate S is typically as follows.
Al ₂ O ₃ + BCl ₃ + CH ₄ → AlCl ↑ + BO ↑ + CO ↑ + CxHy ↓ (2)
In the reaction product of the formula (2), AlCl, BO and CO are volatilized, and CxHy is not volatilized and is deposited on the substrate S. The hydrocarbon-based reactant CxHy on the substrate S functions as a protective film that suppresses the progress of etching of the resist R, and lowers the etching rate of the resist R. Thereby, the etching selectivity of the board | substrate S with respect to the resist R can be improved.

FIG. 5 shows one experimental result showing the relationship between the ratio (%) of CH _{4 to} the etching gas (BCl ₃ + CH ₄ ), the etching rate, and the etching selectivity. As experimental conditions at this time, the total gas flow rate is 30 sccm, the process pressure is 0.5 Pa, the antenna power is 200 W, and the bias power is 40 W. As shown in FIG. 5, it was confirmed that as the ratio of CH ₄ in the etching gas increases, the etching selectivity of the substrate S to the resist R is improved while the etching rate is decreased. This is thought to be due to an increase in the production amount of the hydrocarbon-based reactant CxHy, which increases the protective effect of the resist R, but reduces the removal efficiency of the reactant CxHy on the substrate S by sputtering. From the result of FIG. 5, when considering the effectiveness and productivity of protecting the resist R, the ratio of CH _{4 to} the etching gas (BCl ₃ + CH ₄ ) can be 10% or more and 50% or less.

  Also in the present embodiment, the same operational effects as those of the first embodiment described above can be obtained. That is, according to the present embodiment, a desired uneven pattern can be formed on the surface of the substrate S without increasing the thickness of the resist R. Thereby, while being able to simplify a resist application | coating process, the material cost of a resist material can be reduced. Further, since the thickness of the resist R can be reduced, the exposure conditions can be easily adjusted, thereby improving the exposure accuracy. Furthermore, since the resist R having excellent pattern accuracy can be formed on the surface of the substrate S, a fine uneven pattern can be formed on the surface of the substrate S with high accuracy. Thereby, the performance of the device can be improved.

<Third Embodiment>
Subsequently, a third embodiment of the present invention will be described. In the present embodiment, the etching apparatus 3 shown in FIG. 4 is used as in the second embodiment. In the present embodiment, as an etching gas, a mixed gas of fluorohydrocarbon-based gas and hydrogen (H ₂₎ is used. Examples of the fluorohydrocarbon-based gas include CHF ₃ , CH ₂ F ₂ , and CH ₃ F. In this embodiment, CHF ₃ is used. Each of the above gases is used not only as an etching gas but also as a hydrocarbon source for forming a plasma P containing hydrocarbons.

  The fluorohydrocarbon gas and hydrogen are each controlled to a predetermined flow rate and introduced into the vacuum chamber 10 through the gas introduction pipe 13. The etching apparatus 3 forms plasma of the introduced etching gas by applying high frequency power to the counter electrode 12. As a result, the substrate S disposed on the stage 11 is etched using the resist R as a mask.

The reaction between the etching gas (CHF ₃ + H ₂ ) and the substrate S is typically as follows.
Al ₂ O ₃ + CHF ₃ + H ₂ → AlF ↓ + CO ↑ + CxHy ↓ (3)
In the reaction product of the formula (3), CO is volatilized, and AlF and CxHy are deposited on the substrate S without being volatilized. The ions in the plasma advance the etching of the substrate S by removing AlF on the substrate S by sputtering. Further, the hydrocarbon-based reactant CxHy on the substrate S functions as a protective film that suppresses the progress of etching of the resist R, and lowers the etching rate of the resist R. Thereby, the etching selectivity of the board | substrate S with respect to the resist R can be improved.

FIG. 6 shows one experimental result showing the relationship between the flow rate (sccm) of H ₂ of the etching gas (CHF ₃ + H ₂ ), the etching rate, and the etching selectivity. As experimental conditions at this time, the flow rate of CHF ₃ is 50 sccm, the process pressure is 0.3 Pa, the antenna power is 350 W, and the bias power is 250 W. As shown in FIG. 6, it was confirmed that as the ratio of H ₂ in the etching gas increases, the etching selectivity of the substrate S to the resist R is improved while the etching rate is decreased. This is thought to be due to an increase in the production amount of the hydrocarbon-based reactant CxHy, which increases the protective effect of the resist R, but reduces the removal efficiency of the reactant CxHy on the substrate S by sputtering. From the results of FIG. 6, when considering the effectiveness and productivity of protecting the resist R, the flow rate of H ₂ can be set to 20 sccm or more and 40 sccm or less. Further, the ratio of H _{2 to} the etching gas (CHF ₃ + H ₂ ) can be 10% or more and 50% or less.

  Also in the present embodiment, the same operational effects as those of the first embodiment described above can be obtained. That is, according to the present embodiment, a desired uneven pattern can be formed on the surface of the substrate S without increasing the thickness of the resist R. Thereby, while being able to simplify a resist application | coating process, the material cost of a resist material can be reduced. Further, since the thickness of the resist R can be reduced, the exposure conditions can be easily adjusted, thereby improving the exposure accuracy. Furthermore, since the resist R having excellent pattern accuracy can be formed on the surface of the substrate S, a fine uneven pattern can be formed on the surface of the substrate S with high accuracy. Thereby, the performance of the device can be improved.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, in the first embodiment described above, the organic members 31 and 32 as the hydrocarbon source are formed on the upper surface of the stage 11 or the inner surface of the deposition preventing plate 14, respectively, but the arrangement example of the organic members is not limited to the above example. . For example, the inner surface of the vacuum chamber exposed to the plasma forming space, the periphery of the fixing portion for fixing the counter electrode, and the organic member on the surface of the tray when the substrate S is placed on the tray. May be arranged or formed.

Moreover, in the above 2nd Embodiment, although mixed gas of chlorine gas and hydrocarbon gas was used as etching gas, you may comprise etching gas with the mixed gas of chlorine gas and hydrogen. Similarly, in the above third embodiment, a mixed gas of a fluorohydrocarbon gas and hydrogen is used as an etching gas, but a fluorocarbon gas (CF ₄ , C ₃ F ₈ ) is used instead of the fluorohydrocarbon gas. , C ₄ F _8, etc.) may be replaced with hydrogen and a hydrocarbon gas (CH _4, etc.) may be used. Even with these etching gases, the same effects as described above can be obtained.

DESCRIPTION OF SYMBOLS 1, 2, 3 ... Etching apparatus 10 ... Vacuum chamber 11 ... Stage 12 ... Counter electrode 13 ... Gas introduction pipe 14 ... Deposition plate 15 ... Vacuum pump 31, 32 ... Organic member P ... Plasma R ... Resist S ... Substrate

Claims (6)

An aluminum compound substrate on which an organic resist is formed is placed in a vacuum chamber,
An organic member for forming a plasma containing hydrocarbons is disposed in the vacuum chamber;
Introducing an etching gas into the vacuum chamber;
A substrate etching method in which the surface of the substrate is etched using the organic resist as a mask by forming plasma containing the hydrocarbon in the vacuum chamber. The substrate etching method according to claim 1,
The etching gas includes a chlorine-based gas. An aluminum compound substrate on which an organic resist is formed is placed in a vacuum chamber,
To form a hydrocarbon, a plasma containing a chlorine or fluorine, introduced a hydrocarbon gas, a gas containing chlorine or fluorine in the vacuum chamber,
A substrate etching method in which a plasma containing the hydrocarbon and chlorine or fluorine is formed in the vacuum chamber to etch the surface of the substrate using the organic resist as a mask. An aluminum compound substrate on which an organic resist is formed is placed in a vacuum chamber,
Introducing a mixed gas of fluorocarbon-based or fluorohydrocarbon-based etching gas and hydrogen or hydrocarbon-based gas into the vacuum chamber;
A substrate etching method for etching the surface of the substrate using the organic resist as a mask by forming plasma of the mixed gas in the vacuum chamber . A substrate etching method according to any one of claims 1 , 3 and 4 , comprising:
The substrate etching method is a substrate etching method, wherein the substrate is an aluminum oxide substrate or an aluminum nitride substrate. A sapphire substrate with an organic resist formed on the surface is placed in a vacuum chamber,
Introduction or placing the hydrocarbon source for forming a plasma containing a hydrocarbon into the vacuum chamber,
Introducing a gas containing chlorine or fluorine into the vacuum chamber;
A method for manufacturing a sapphire substrate, wherein a plasma containing the hydrocarbon and chlorine or fluorine is formed in the vacuum chamber to etch the surface of the substrate using the organic resist as a mask.

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