JP5714348B2 - Method for vapor phase chemical etching of substrate - Google Patents

Description

  The present invention relates to a method for vapor-phase chemical etching of a substrate suitable for uniformly vapor-phase chemical etching of the upper surface and the outer peripheral surface of a substrate having a ground outer peripheral surface.

  Conventionally, chemical mechanical polishing (CMP) is known as a method for polishing the surface of a substrate such as a semiconductor or an optical element (see, for example, Patent Document 1). In CMP, a polishing body having a polishing cloth attached to a surface is placed on a disk-shaped surface plate, and then the object to be polished is rotated and pressed against the polishing body while rotating the substrate to be polished. Then, the surface of the substrate is mechanically polished by performing a relative motion such as rotating the substrate as an object to be polished on the polishing body. At this time, chemical polishing of the surface of the substrate is realized by supplying a polishing agent between the polishing body and the substrate to exert a chemical action by the polishing agent. As this abrasive, one having cerium oxide as a main component is generally used. By using CMP, for example, a convex portion having a diameter of about 10 nm can be almost removed.

  By the way, according to the technique disclosed in Patent Document 1, it is necessary to use cerium oxide known as a so-called rare metal as an abrasive. Cerium oxide is very expensive because its production country is limited. From the viewpoint of reducing the manufacturing cost, it is possible to flatten a convex part having a size larger than nanoscale without CMP. Proposal of a new method was desired. In addition, according to the disclosed technique of Patent Document 1, there is a problem that a convex part of the order of several nm of 10 nm or less, or a convex part of the order of 1 nm or less cannot be suitably polished. In particular, polishing in the order of several nanometers has a particularly strong demand in the case of application to a product that greatly deteriorates the quality when there are slight irregularities in the nanoorder, such as hard disks and optical disks, for example. In recent years, a polishing method capable of meeting this demand has been desired.

  For this reason, an etching method using near-field light has been proposed (see, for example, Patent Document 2). In this etching method using near-field light, by irradiating the substrate with light having a wavelength longer than the absorption edge wavelength of the etching gas molecules in the etching gas atmosphere, the nanoscale protrusions formed on the surface of the substrate are irradiated. It is characterized by selectively etching the nanoscale protrusions by generating near-field light and dissociating etching gas molecules through a non-adiabatic process based on the near-field light.

JP-A-11-129155 JP 2009-94345 A

Genichi Otsu, Kiyoshi Kobayashi "Nanophotonics Basics" Ohm, P141, P206-P208 (2006)

  By the way, according to the technique disclosed in Patent Document 2 described above, it is assumed that near-field light is generated based on light emitted from the outside. For this reason, for example, when etching is performed on a disk-shaped optical disc by the method disclosed in the cited document 2, minute unevenness formed on the upper surface of the optical disc irradiated with light can be removed, but grinding is performed. In some cases, light does not reach the chamfered portion formed by chamfering the corners between the side end surfaces, the side end surfaces and the top surface, and the side end surfaces and the bottom surface. As a result, the near-field light cannot be generated on the unevenness formed on the side end face or the chamfer portion, and etching by dissociating gas molecules cannot be realized. That is, not only the three-dimensional upper surface such as an optical disk or a substrate, but also the respective surfaces including the outer peripheral surface cannot be irradiated with light at the same time, so that the near-field light cannot be generated. There is a problem that uniform etching cannot be performed on all surfaces simultaneously.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to uniformly etch the upper surface and outer peripheral surface of a three-dimensional shape such as an optical disk or a substrate. It is an object of the present invention to provide a possible substrate etching method.

In the method for vapor phase chemical etching of a substrate according to claim 1, the substrate is placed in an etching gas atmosphere, and light having an absorption edge wavelength or more of gas molecules constituting the etching gas is incident on the substrate. The light is reflected between the substrate top surface and the substrate bottom surface, and the etching gas is dissociated based on the propagating light generated when the reflected light is emitted from the substrate to the outside. Etching the irregularities formed at a pitch below the diffraction limit of light and / or generating near-field light at least at the corners of the irregularities based on the propagation light, and based on the generated near-field light Etching is performed by dissociating the etching gas.

  According to a second aspect of the present invention, there is provided a gas phase chemical etching method for a substrate according to the first aspect of the invention, wherein the substrate having a side end face is disposed in an etching gas atmosphere, and the light incident on the substrate is irradiated with the upper surface of the substrate. Guide to the side end surface while reflecting between the bottom surface of the substrate, etch the unevenness formed on the side end surface based on the propagation light emitted to the outside through the side end surface, and / or Based on the propagating light, near-field light is generated at least at the corners of the unevenness, and the etching gas is dissociated and etched based on the generated near-field light.

  According to a third aspect of the present invention, there is provided the method for vapor phase chemical etching of a substrate according to the first or second aspect, wherein the light is incident obliquely on the upper surface of the substrate through a prism.

  According to the present invention having the above-described configuration, near-field light can be generated not only on a three-dimensional top surface such as an optical disc or a substrate but also on each surface including an outer peripheral surface and a bottom surface. It is possible to perform uniform etching on all surfaces simultaneously.

It is a figure which shows the vapor phase chemical etching apparatus for performing the etching process to which this invention is applied. It is an enlarged view of the board | substrate as an etching object by this invention. It is a figure for demonstrating the relationship of the potential energy with respect to the internuclear distance of the gas molecule of etching gas. It is a figure for demonstrating the mechanism of an adiabatic process and a non-adiabatic process. It is a figure for demonstrating the case where near field light is generated based on the propagation light radiate | emitted outside from the outer peripheral surface. It is a figure for demonstrating the mechanism of the gaseous-phase chemical etching by a near field light. It is a figure for demonstrating the potential energy of a gas molecule when a gas molecule adsorb | sucks to the surface of a board | substrate. It is a figure for demonstrating the case where both the heat insulation process and the non-adiabatic process have arisen simultaneously.

  Hereinafter, embodiments for carrying out a gas phase chemical etching method of a substrate to which the present invention is applied will be described in detail with reference to the drawings.

  In the gas phase chemical etching method according to the present invention, an after-mentioned etching process is performed using a gas phase chemical etching apparatus 1 as described below.

  As shown in FIG. 1, the vapor-phase chemical etching apparatus 1 includes a chamber 11, a stage 13 disposed in the chamber 11, a gas supply pipe 23 connected to the chamber 11, and a chamber in the first embodiment. 11 and a light source 14 disposed outside.

  The stage 13 is a substrate on which the substrate 2 is placed. A prism 3 described later is placed on the upper surface of the substrate 2. The stage 13 may be provided with a position adjusting mechanism for adjusting the position and orientation of the substrate 2, a heating mechanism for heating the substrate 2, etc., and by controlling these, the surface of the substrate is etched. It becomes possible to control the reaction rate at the time of processing.

An etching gas for etching the surface of the substrate 2 is supplied from the gas supply pipe 23. Examples of the etching gas include chlorine-based gases such as Cl ₂ (chlorine), BCl ₃ (boron trichloride), and CCl ₄ (carbon tetrachloride), and silanes such as SiH ₄ (monosilane) and Si ₂ H ₆ (disilane). System gases. From the gas supply pipe 23, an inert gas such as N ₂ , He, or Ar may be supplied by mixing with the above-described etching gas.

  The light source 14 emits light having a predetermined wavelength based on control by a driving power source (not shown). The position of the light source 14 is adjusted so that the emitted light passes through a window 15 provided on the outer surface of the chamber 11 and is irradiated onto the substrate 2 on the stage 13. The light source 14 is composed of, for example, a laser diode. The light source 14 may include an optical system having a polarizing lens, a focusing lens, and the like in order to control the irradiation range of light irradiated on the substrate 2. The wavelength of light emitted from the light source 14 will be described later.

  The vapor-phase chemical etching apparatus 1 includes a pump 16 that sucks the gas in the chamber 11, a pressure sensor 17 that detects the pressure in the chamber 11, and a butterfly that opens and closes based on the chamber internal pressure detected by the pressure sensor 17. The valve 18 is provided, and these enable automatic control of the internal pressure in the chamber 11.

  The substrate 2 to be planarized by the vapor-phase chemical etching method to which the present invention is applied is made of, for example, glass, aluminum, silicon, plastic such as polymethyl methacrylate resin (PMMA). . FIG. 2 shows an enlarged view of the substrate 2. The substrate 2 may be used as a recording medium substrate such as a magnetic disk substrate or an optical disk substrate, and is configured in a three-dimensional shape surrounded by an upper surface 2a, an outer peripheral surface 2b, and a bottom surface 2c. Among these, at least the outer peripheral surface 2b is usually ground. Further, the prism 3 is placed on the upper surface 2a of the substrate 2, but the shape thereof is not particularly limited, but light can be incident on the upper surface 2a of the substrate 2 at an angle. It needs to be shaped.

  Next, a gas phase chemical etching method to which the present invention is applied will be described. First, the substrate 2 to be etched is placed on the stage 13, and the prism 3 is placed on the upper surface 2 a of the substrate 2. Next, the inside of the chamber 11 is kept sealed, and controlled to a predetermined pressure and a predetermined temperature. Subsequently, an etching gas is supplied from the gas supply pipe 23. As an alternative to the prism 3, for example, a hemispherical lens may be placed. In any case, any configuration can be used as long as the optical path can be polarized to such an extent that light can be incident on the substrate 2 from an oblique direction.

  In this etching step, the substrate 2 is irradiated from the light source 14 through the prism 3 with propagating light having a wavelength that satisfies the following conditions in an etching gas atmosphere. As shown in FIG. 2, the light incident in the oblique direction from the upper surface 2a of the substrate 2 via the prism 3 is guided to the outer peripheral surface 2b while being reflected between the upper surface 2a and the bottom surface 2c. Then, the unevenness formed on the surface of the outer peripheral surface 2b is etched by dissociating the etching gas based on the propagating light emitted from the inside of the substrate 2 to the outside through the outer peripheral surface 2b. At the same time, near-field light is generated at least at the corners of the irregularities based on the propagation light, and etching is performed by dissociating the etching gas based on the generated near-field light.

  The wavelength of propagating light emitted from the light source 14 is longer than the absorption edge wavelength of the gas molecules of the etching gas. This is because the propagating light emitted from the light source 14 reaches the substrate while preventing the gas molecules of the etching gas in the gas phase away from the surface of the substrate 2 from dissociating.

  FIG. 3 shows the relationship of the potential energy with respect to the internuclear distance of the gas molecules of the etching gas.

  In etching the surface of the substrate 2 with the etching gas, it is necessary to generate radicals by dissociating a plurality of atoms constituting gas molecules of the etching gas. The energy for sufficiently separating the plurality of atoms constituting the gas molecule corresponds to the dissociation energy Eb.

  Here, when the gas molecules are dissociated by irradiation with light, the gas molecules are subjected to either an adiabatic process or a non-adiabatic process.

  The adiabatic process is a process in which the electrons of a gas molecule are directly transferred from the ground level to the excited level by irradiating propagating light having a light energy equal to or greater than the energy difference Ea between the ground level and the excited level of the gas molecule. It refers to the process of excitation. The gas molecules in which electrons are excited to the excited level can be dissociated in the direction P as shown in the figure.

  A non-adiabatic process (phonon-assisted process) refers to a process in which gas molecules are excited to a vibration level by near-field light and thereby dissociate gas molecules. At this time, the non-adiabatic process includes a process S1 in which gas molecules are excited in a multistage manner through a plurality of vibration levels to an excitation level, and a vibration level of an energy level equal to or higher than the dissociation energy Eb. It is classified into any one of the processes S2 excited in multiple steps. Gas molecules excited to an energy level or an excitation level equal to or higher than the dissociation energy Eb can be dissociated.

  The adiabatic process and the non-adiabatic process can be explained by a model in which bonds between atoms are replaced by springs as shown in FIG.

  In general, since the wavelength of propagating light is much larger than the size of the molecule, it can be considered that a spatially uniform electric field is generated by irradiation of propagating light at the molecular level. At this time, as shown in FIG. 4A, the plurality of electrons in the gas molecule vibrate with the same amplitude and the same phase by irradiation with the propagating light. Further, since the atomic nucleus in the gas molecule is heavier than the electron, it does not follow the vibration of the electron. As a result, only the electrons vibrate and the nuclei do not vibrate due to the irradiation of propagating light. Such a gas molecule excitation process that does not involve molecular vibration corresponds to an adiabatic process (see Non-Patent Document 1).

  On the other hand, since the near-field light sharply decreases as the spatial electric field gradient moves away from the object surface, it can be considered that a spatially nonuniform electric field is generated at the molecular level. At this time, as shown in FIG. 4B, the plurality of electrons in the gas molecules vibrate differently due to irradiation with near-field light. In addition, the nucleus also vibrates due to the vibration of the plurality of electrons. As a result, the gas molecules can be excited to the vibration level. This corresponds to a non-adiabatic process. Such a process related to molecular vibration in the gas molecule excitation process corresponds to a non-adiabatic process.

  In the present invention, propagating light is emitted from the outer peripheral surface 2b to the outside as shown in FIG. 5, and at least a corner of the convex portion 4 in the process of passing this propagating light through the convex portion 4 formed on the outer peripheral surface 2b. Near-field light is generated in the part. Here, the corner portion where the near-field light is generated by irradiating the propagating light to the convex portion 4 is a sharpened portion 43 corresponding to the tip of the convex portion 4 as shown in FIG. When near-field light is selectively generated in the sharpened portion 43, the etching gas molecules 51 are dissociated by the generated near-field light, and radicals 52 are generated. The radical 52 is selectively generated only in the vicinity of the sharpened portion 43 where the near-field light is generated. Then, the generated radical 52 selectively reacts with the sharpened portion 43 closest to the radical 52. As a result, the sharpened portion 43 is etched by the activity of the radicals 52 as shown in FIG. When the sharpened portion 43 is etched, a sharpened portion 43 ′ is further formed in the convex portion 42, but near-field light is selectively generated in this way, and the etching gas molecules 51 are dissociated. Thus, the radical 52 can be selectively formed in the vicinity of the sharpened portion 43 ′. As a result, the sharpened portion 43 ′ is etched by reacting with the radical 52.

  Further, the corner portion where the near-field light is generated includes not only the sharpened portion but also any corner portion constituting the concave portion 5 and the convex portion 4. The concave portion 5 is also included in the corner portion, and near-field light is generated as shown in FIG. 6B, and the concave portion 5 is smoothed by the radical 52 generated based on the generated near-field light. Will be.

  As described above, the generation of near-field light in the local region of the outer peripheral surface 2 b of the substrate 2, the radical activity due to the dissociation of the etching gas molecules 51, and the reaction of the sharpened portion 43 are repeatedly performed. As shown in FIG. 6C, by etching the corners, the surface can be smoothed and the surface roughness can be reduced.

  Note that the above-described etching using near-field light can be similarly realized not only on the outer peripheral surface 2b but also on the upper surface 2a or the bottom surface 2c. For example, light incident on the substrate 2 may be emitted from the top surface 2a as shown in FIG. 5 in the process of being guided to the outer peripheral surface 2b while reflecting the top surface 2a and the bottom surface 2c from each other. is there. Near-field light is generated at least at the corners of the convex portion 4 in the process in which the propagating light emitted from the upper surface 2a passes through the convex portion 4 formed on the upper surface 2a. Due to the generated near-field light, the etching gas molecules are dissociated into radicals, and the upper surface 2a can be flattened by the same mechanism as described above. Similarly, the lower surface 2c can be flattened.

  In addition to the non-adiabatic process described above, the present invention may dissociate gas molecules into radicals based on the adiabatic process described below. Since the light source 14 emits light having a wavelength longer than the absorption edge wavelength of the gas molecules as described above, the gas molecules are not dissociated in the gas phase. However, when gas molecules are adsorbed on any one or more of the upper surface 2a, the outer peripheral surface 2b, and the bottom surface 2c of the substrate 2, energy is given to the gas molecules due to the interaction between the substrate 2 and the gas molecules as shown in FIG. As a result, the excitation level of the gas molecule decreases as shown in the direction Q, and the energy difference from the ground level to the excitation level decreases. For this reason, even if the surface of the substrate 2 is irradiated with propagation light having a wavelength longer than the absorption edge wavelength of the gas molecules, the gas molecules adsorbed on the surface of the substrate 2 can be dissociated through an adiabatic process. It becomes.

At this time, in order to dissociate the gas molecules adsorbed on the surface of the exposed portion 4 of the substrate 2 through an adiabatic process, when the dissociation energy of the gas molecules of the etching gas is defined as Eb, 0.5 × Eb or more It is preferable to irradiate light having a wavelength having light energy. Thereby, it becomes possible to dissociate the gas molecules adsorbed on the upper surface 2a, the outer peripheral surface 2b, and the bottom surface 2c of the substrate 2 through an adiabatic process. However, in this case, since the number of gas molecules dissociated through the heat insulation process on the surface of the substrate 2 is stochastically small, the light intensity of the propagating light to be irradiated is increased in order to increase the etching rate. . Also, the gas molecules adsorbed on the surface of the substrate 2 in terms of dissociating through the adiabatic process, the absorption edge wavelength of the etching gas when the _{λ 1, (λ 1 + λ} 1/10) or less of light having a wavelength If the irradiation is performed, the etching rate can be further increased.

An example of the wavelength for realizing such a phenomenon is, for example, when Cl ₂ is used as the gas molecule of the etching gas, since the absorption edge wavelength of the Cl ₂ gas molecule is 400 nm, the wavelength is longer than this. What is necessary is just to irradiate the propagation light of wavelength, such as 403 nm and 408 nm. Such a wavelength is emitted from an InGaN laser or the like.

  As described above, according to the present invention, near-field light can be generated not only on a three-dimensional upper surface 2a such as an optical disk or a substrate but also on each surface including the outer peripheral surface 2b and the bottom surface 2c. It is possible to perform uniform etching on all surfaces simultaneously.

  The present invention is not limited to the case where all of the upper surface 2a, outer peripheral surface 2b, and bottom surface 2c are etched, and only the outer peripheral surface 2b is etched based on the propagation light emitted from the outer peripheral surface 2b. Of course, it is good also as a form to do. In addition to the outer peripheral surface 2b, it is a matter of course that only the top surface 2a or the bottom surface 2c may be etched based on the propagation light emitted from the top surface 2a or the bottom surface 2c.

  Moreover, in the above-described embodiment, the case where both the heat insulation process and the non-adiabatic process occur has been described. However, the present invention is not limited to this, and any one of the processes may be generated. Of course.

  However, it is more desirable that both the above-described heat insulation process and non-adiabatic process occur simultaneously. The reason for this is that, as shown in FIG. 8 (a), the entire surface 2d of the substrate 2 can be scraped in the depth direction by the heat insulation process, and as shown in FIG. By the heat insulation process, it becomes possible to generate near-field light on the minute unevenness generated on the scraped surface 2e and etch it. As a result, both polishing in the depth direction and removal of surface irregularities can be realized simultaneously.

  Furthermore, in the present invention, not only the ground side end face, but also the chamfer portion irregularities obtained by chamfering the corners of the side end face and the top face and the side end face and the bottom face can be etched as well. is there.

DESCRIPTION OF SYMBOLS 1 Gas-phase chemical etching apparatus 2 Substrate 2a Upper surface 2b Outer peripheral surface 2c Bottom surface 3 Prism 4 Protrusion 11 Chamber 13 Stage 14 Light source 15 Window 16 Pump 17 Pressure sensor 18 Butterfly valve 23 Gas supply pipe

Claims (3)

Place the substrate in the etching gas atmosphere,
Incident light in the substrate above the absorption edge wavelength of gas molecules constituting the etching gas,
The incident light is reflected between the substrate top surface and the substrate bottom surface,
The etching gas is dissociated based on propagating light generated when the reflected light is emitted from the substrate to the outside, and the unevenness formed at a pitch below the diffraction limit of light is etched on the emission surface.
And / or generating near-field light in at least the corners of the unevenness based on the propagating light, and dissociating and etching the etching gas based on the generated near-field light. Phase chemical etching method. A substrate having side end faces is placed in an etching gas atmosphere,
Guiding the light incident on the substrate to the side end surface while reflecting between the substrate upper surface and the substrate bottom surface,
Based on the propagating light by being emitted to the outside through the side end surface, the unevenness formed on the side end surface is etched,
And / or near-field light is generated in at least corners of the unevenness based on the propagation light, and the etching gas is dissociated and etched based on the generated near-field light. A method for vapor phase chemical etching of a substrate as described. The method for vapor phase chemical etching of a substrate according to claim 1 or 2, wherein the light is incident obliquely on the upper surface of the substrate through a prism.