JP2011086762A - Surface processing method, liquid composition for surface processing, and optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a surface processing method in which variation in quality is not easily generated and unevenness processing is carried out at high speed and which is superior in mass-productivity and cost reduction; a liquid composition for surface processing used therefor; and an optical device having a substrate processed by the surface processing method. <P>SOLUTION: The present invention relates to the surface processing method for forming unevenness on a surface of a workpiece, the surface processing method including: a particle layer-forming step of forming a particle layer 10 by coating the surface of the workpiece 20 with the liquid composition for surface processing which contains a particle group including first particles and second particles having lower etching resistance than the first particles and a binding agent; an etching step of forming the unevenness on the surface of the workpiece by subjecting the surface of the workpiece having the particle layer formed to etching processing; and a removing step of removing the particle layer after the etching process. Further, the present invention relates to the liquid composition for surface processing used for the surface processing method, and the optical device having the substrate obtained by the surface processing method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface treatment method for forming irregularities on the surface of an object to be processed by etching treatment, and a liquid composition for surface treatment used for this. The present invention also relates to an optical device having a substrate processed by the surface treatment method.

  Conventionally, in the field of optical devices such as solar cells, LEDs, flat panel displays, etc., in order to suppress the reflection phenomenon that occurs when the refractive index difference of the light transmitting interface is large, it is applied to the substrate surface through which light is transmitted by etching treatment. Processing which forms an unevenness is performed.

  On the other hand, in the field of semiconductor devices, for example, in order to suppress peeling of the thin film due to insufficient adhesion between the thin film and the substrate, a process of forming irregularities on the substrate surface with the aim of an anchor effect is performed. It is also done.

  Thus, in various fields, processing for forming irregularities on the surface of an object to be processed has been performed, and various proposals relating to irregularities have been made (for example, Patent Documents 1 to 5).

Japanese Patent Laid-Open No. 3-71677 JP 2000-261008 A JP 2005-277295 A JP 2007-27564 A JP-A-2005-279807 JP 2009-34630 A

  In the surface treatment method for performing the above-described uneven processing, etching is performed after particles having etching resistance are disposed on the surface of the object to be processed by dry or wet, or a film containing the particles is bonded to the surface of the object to be processed. We are processing.

  At this time, in any of the above methods, it is extremely difficult to cause the particles to exist in a single layer on the surface of the object to be processed, and usually the particles are partially overlapped. If etching is performed in this state, etching proceeds only in the gaps between the particles, so that only irregular irregularities and scattered irregularities are formed, resulting in variations in quality. . Specifically, for example, when the amount of particles is small, irregular irregularities are likely to be formed on the surface of the workpiece as shown in FIG. On the other hand, when the amount of particles is large, scattered irregularities are likely to be formed due to the overlapping of the particles as shown in FIG. Here, FIG. 4 and FIG. 5 are process diagrams for explaining the etching process in the conventional surface treatment method, where (A) shows before the etching process and (B) shows after the etching process. 4 and 5, 110 indicates an object to be processed, 111 indicates a particle layer, and 112 indicates particles.

  Although a method for removing such overlapping particles is also applied, the process becomes complicated and is not suitable for mass production and cost reduction.

  Accordingly, an object of the present invention is to provide a surface treatment method that is unlikely to cause variations in quality, and that can perform uneven processing at high speed, and that is excellent in mass productivity and cost reduction, and a liquid composition for surface treatment used therefor. It is to be. Moreover, the subject of this invention is providing the optical device which has the board | substrate processed by the said surface treatment method.

  The above problem is solved by the following means. That is,

<1>
A liquid composition for surface treatment for forming irregularities on the surface of an object to be treated,
A liquid composition for surface treatment comprising at least first particles, second particles having lower etching resistance than the first particles, and a binder.

<2>
When the etching resistance of the first particles is ER1, the etching resistance of the second particles is ER2, and the etching resistance of the binder is ER3, the relationship of the following formula (1) is satisfied. Liquid composition for surface treatment.
Formula (1): ER2 <ER1 and ER3 <ER1

<3>
The surface treatment liquid composition according to <1> or <2>, wherein the binder is water-soluble.

<4>
A surface treatment method for forming irregularities on the surface of a workpiece,
p Particle layer formation in which a liquid composition for surface treatment containing at least first particles, second particles having lower etching resistance than the first particles, and a binder is applied to the surface of the object to be processed to form a particle layer Process,
An etching process is performed on the surface of the object to be processed on which the particle layer is formed, and an unevenness is formed on the surface of the object to be processed.
A removal step of removing the particle layer after the etching step;
A surface treatment method characterized by comprising:

<5>
When the etching resistance of the first particles is ER1, the etching resistance of the second particles is ER2, and the etching resistance of the binder is ER3, the relationship of the following formula (1) is satisfied. Surface treatment method.
Formula (1): ER2 <ER1 and ER3 <ER1

<6>
The surface treatment method according to <4> or <5>, wherein the binder is water-soluble.

<7>
The surface treatment method according to any one of <4> to <6>, wherein the etching treatment is a dry etching treatment.

<8>
In any one of <4> to <7>, the particle layer forming step is a step of forming the particle layer by applying the surface treatment liquid composition to the surface of the object to be processed by a spin coating method. The surface treatment method as described.

<9>
The surface treatment method according to any one of <4> to <8>, wherein the particle layer forming step is collectively performed on a plurality of the objects to be processed.

<10>
The surface treatment method according to any one of <4> to <9>, wherein the removing step is a step of removing the particle layer by applying a solvent that dissolves the binder.

<11>
<4> to <9>, wherein the removing step is a step of removing the particle layer by applying a solvent for dissolving the binder and rubbing with a rubbing member. Surface treatment method.

<12>
<4>-<11> The surface treatment method according to any one of <4> to <11>, wherein the surface of the object to be processed for forming irregularities is a light incident surface of an optical device.

<13>
<4>-<12> The optical device which has a board | substrate as a to-be-processed object surface-treated by the surface treatment method of any one of <12>.

  According to the present invention, it is possible to provide a surface treatment method that is unlikely to cause variations in quality and that can be unevenly processed at high speed and that is excellent in mass productivity and cost reduction, and a liquid composition for surface treatment used therefor. Can do. Moreover, according to this invention, the optical device which has a board | substrate processed by the said surface treatment method can be provided.

It is process drawing which shows the surface treatment method which concerns on embodiment. It is process drawing which shows the surface treatment method which concerns on embodiment. It is process drawing for demonstrating the etching process in the surface treatment method which concerns on embodiment, (A) shows before an etching process, (B) shows after an etching process. It is process drawing for demonstrating the etching process in the conventional surface treatment method, (A) shows before an etching process, (B) shows after an etching process. It is process drawing for demonstrating the etching process in the other conventional surface treatment method, (A) shows before an etching process, (B) shows after an etching process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is provided to the member which has the substantially the same function and effect | action through all the drawings, and the overlapping description may be abbreviate | omitted.

  FIG.1 and FIG.2 is process drawing which shows the surface treatment method which concerns on embodiment. FIG. 1 is a process diagram in perspective view, and FIG. 2 is a process diagram in FIG. FIGS. 3A and 3B are cross-sectional process diagrams for explaining the etching process in the surface treatment method according to the embodiment, in which FIG. 3A shows before the etching process and FIG. 3B shows after the etching process.

  In the surface treatment method according to the embodiment, first, a substrate to be processed 20 (object to be processed) is prepared as shown in FIGS. A plurality of substrates 20 to be processed are held on the holding substrate 30. Specifically, for example, the four substrates to be processed 20 having a rectangular planar shape are arranged in a grid of 2 × 2 and are held on one holding substrate having a rectangular planar shape. As a method for holding the substrate to be processed 20 on the holding substrate 30, for example, electrostatic adsorption or the like can be cited. In this way, for example, by holding a plurality of substrates to be processed 20 on the holding substrate 30 and forming the particle layer 10 described later on the plurality of substrates to be processed 20 in a lump, the working efficiency can be improved and reduced. Cost reduction is realized.

Here, the form of holding the substrate to be processed 20 with respect to the holding substrate 30 is not limited to the form of being arranged in a lattice shape as in the above form, and may be a form of arbitrarily arranging and holding.
In particular, for example, when the spin coating method is applied as the application of the surface treatment liquid composition, the planar shape of the holding substrate 30 and the arrangement position of the substrate 20 to be processed held by the holding substrate 30 are rotationally symmetric (or point symmetric). It is better to do so. As a result, in the spin coating method, the holding substrate 30 is stably rotated to prevent the substrate 20 to be detached from the holding substrate 30 and to form a uniform coating film (particle layer 10) of the liquid composition for surface treatment. Is realized.
Similarly, when the spin coating method is applied as the coating of the liquid composition for surface treatment, the plurality of substrates 20 to be processed are not disposed on the extended line from the rotation axis center of the holding substrate 30 to the outside. It is preferable to hold the substrate to be processed 20 with respect to the holding substrate 30 such that one substrate to be processed 20 is arranged. Thereby, the liquid composition for surface treatment which scatters outside by the centrifugal force as the holding substrate 30 rotates is applied to the coating film (particle layer 10) of the liquid composition for surface treatment formed on the substrate 20 to be processed. Adhering to the coating film is prevented from being uneven.
As described above, when the spin coating method is applied as the application of the liquid composition for surface treatment, from the above viewpoint, the four substrates to be processed are arranged in a lattice shape as the form in which the substrate to be processed 20 is held with respect to the holding substrate 30. The form of arranging and holding is most preferable.
In addition, the to-be-processed substrate 20 is not hold | maintained with respect to the holding substrate 30, for example, formation of the particle layer 10 etc. which are mentioned later collectively in the state which connected the end surface of the to-be-processed substrate 20 (for example, joining or adhesion | attachment). You may go.

  Here, there is no restriction | limiting in particular as the to-be-processed substrate 20, For example, the board | substrate comprised by a semiconductor (for example, silicon substrate), an electrically conductive material, an insulator, etc., the glass substrate used with a flat panel display, the said A functional layer (for example, a wiring layer, an insulating layer, or the like) may be formed on the substrate.

Next, as shown in FIG. 1B and FIG. 2B, for example, a liquid composition for surface treatment containing the particle group 11 is prepared, and the substrate 20 is held on the holding substrate 30. Then, the surface treatment liquid composition is applied to form the particle layer 10. Specifically, for example, the liquid composition for surface treatment is applied to the entire surface of each of the plurality of substrates to be processed 20 by spraying from the nozzle 31, and the holding substrate 30 holding the substrate to be processed 20 is rotated to form a coating film. The particle layer 10 is formed by a spin coating method for forming a thin film.
The application of the liquid composition for surface treatment is not limited to the spin coating method, and a well-known coating method may be adopted. However, the spin coating method can form a uniform coating film (particle layer 10) and rotate. This is an advantageous application method because the drying of the coating film is promoted.

By applying the surface treatment liquid composition, the particle layer 10 including, for example, the binder 12 and the particle group 11 is formed on the substrate 20 to be processed.
Here, the liquid composition for surface treatment includes, for example, the particle group 11 and a binder 12 and a solvent. The particle group 11 includes first particles 11A having etching resistance and second particles 11B having etching resistance lower than that of the first particles 11A. The details of the liquid composition for surface treatment will be described later.
The liquid composition for surface treatment should be prepared by mixing and dispersing with a stirring blade such as a dissolver that provides high-speed shearing because the particle group 11 is preferably dispersed uniformly in the liquid. Alternatively, it may be prepared by mixing and dispersing with a dispersing device such as an ultrasonic disperser.

  The thickness of the particle layer 10 to be formed is preferably 0.3 μm to 5 μm, for example, and more preferably 0.5 μm to 2 μm.

  Next, as shown in FIGS. 1C and 2C, with respect to the substrate 20 on which the particle layer 10 is formed (FIG. 3A), from the surface on which the particle layer 10 is formed. Etching is performed (FIG. 3B). This etching process is performed, for example, by arranging a plurality of holding substrates 30 holding a plurality of substrates 20 to be processed and collectively performing the holding substrates 30. In the embodiment, there is shown a form in which a plurality of substrates to be processed 20 are etched in a state where the substrates to be processed 20 are arranged in a lattice shape in a total of 3 × 3 × 9. In this way, by performing the etching process on the plurality of substrates to be processed 20 in a lump, work efficiency and cost reduction can be realized.

  When the etching process is performed, a region excluding a region covered with the first particles 11A having etching resistance constituting the particle layer 10 (a region where the first particles 11A are projected onto the substrate to be processed 20 when viewed from the etching direction). Then, while the surface of the substrate 20 to be processed is etched to form a recess, the surface of the substrate 20 to be processed is not etched in the region covered with the first particles 11A (see FIG. 3B).

  Specifically, when the etching process is performed, for example, the binder 12 constituting the particle layer 10 excluding the region covered with the first particles 11A is etched and etched more than the first particles 11A. The second particles 11B having low resistance are also etched.

  Thus, the etched region becomes a concave portion, and the non-etched region becomes a convex portion, and irregularities are formed on the surface of the substrate 20 to be processed. In addition, in the said area | region (area | region except the area | region covered with 11 A of 1st particle | grains) to be etched, the particle layer 10 is etched.

  Here, as the etching process, both a wet etching process and a dry etching process are employed, but a dry etching process is preferably employed. Known dry etching processes include a reactive gas etching process in which etching is performed by exposing the substrate 20 to be processed in a reactive gas, and a reactive ion etching (RIE) in which reactive gas is ionized and radicalized by plasma to perform etching. The dry etching process is employed. A known apparatus is also used as an apparatus for performing the dry etching process.

On the other hand, the conditions for performing the dry etching treatment are appropriately set according to the thickness and type of the particle layer 10 (the type of the binder 12 and the type of the particle group). Is preferably adopted.
1) Dry etching can be performed using CF ₄ , C ₂ F ₆ , Cl _2, ClF ₃ or the like as a reactive gas.
2) As an etching method with strong anisotropy, it is preferable to use RIE or RIBE (reactive ion beam etching) using a gas such as SiCl ₄ + He or CH ₄ + He.
3) Depending on the type of etching gas, it may penetrate into the substrate to be processed and cause chemical and physical changes, so that the time during which the substrate to be processed is exposed to the etching gas can be optimized. .
4) If a part of the particle layer 10 remains after a desired uneven shape is obtained by etching, the residue is removed by introducing a gas such as ozone or oxygen and irradiating light such as ultraviolet rays. It is possible to employ an ashing method, or an ashing method in which oxygen gas is turned into plasma by a high frequency and the like, and the residue is removed using the plasma.

  In the etching process, the process of etching the particle layer 10 and the etching process of the substrate 20 to be processed may be performed successively by the etching process of the same technique, or separately by the etching processes of different techniques. May be.

Next, as shown in FIGS. 1D and 2D, the remaining particle layer 10 is removed from the substrate 20 to be processed. Specifically, for example, a solvent that dissolves the binder 12 by spraying from the nozzle 32 while rotating the holding substrate 30 (substrate 20 to be processed) (for example, when the binder 12 is water-soluble, warm water ( For example, warm water of 60 to 90 ° C., preferably 70 to 80 ° C.)) is applied, and the surface of the substrate 20 to be processed (the surface on which the particle layer 10 is formed) is slid by a non-illustrated rubbing member (for example, brush or blade). By rubbing, the particle layer 10 is removed. Further, the particle layer 10 can be efficiently removed by using an organic solvent other than warm water as a solvent for dissolving the binder 12. Examples of the method for applying the solvent include a method for applying the solvent by spraying from the nozzle 32, but the method is not limited to this, and an arbitrary method is adopted.
Adopting a method of removing the particle layer 10 by dissolving the binder 12 by applying a solvent is preferable from the viewpoint that the particle layer 10 can be easily removed. When the method of removing the particle layer 10 by rubbing is applied, the particle layer 10 can be removed more easily and quickly without remaining. The “solvent that dissolves the binder 12” means a solvent in which the binder 12 dissolves 10 wt% or more at 25 ° C.
Moreover, when removing the particle layer 10, by rotating the holding substrate 30 (the substrate to be processed 20), the solvent is scattered by the centrifugal force due to the rotation, and drying is promoted.

  The method for removing the remaining particle layer 10 is not limited to the above method, and for example, a method for removing the particle layer 10 by dry treatment such as oxygen plasma treatment may be employed.

  Through the above steps, the surface of the substrate to be processed 20 can be subjected to uneven processing.

  In the surface treatment method according to the embodiment described above, the particle group 11 including the first particles 11A having etching resistance and the second particles 11B having etching resistance lower than that of the first particles is dispersed and blended in the binder 12. The liquid composition for surface treatment is applied to the substrate 20 to be processed to form the particle layer 10, and the particle layer 10 (the first particles 11 </ b> A included therein) is used as an etching mask to form the particle substrate 10. Etching is performed on the surface.

  When the etching process is performed, the first particles 11A are not etched, whereas the second particles 11B having a lower etching resistance than the first particles 11A constituting the particle group 11 are etched, and the first particles that play the role of the etching mask itself. A gap between the particles 11A is secured. That is, even if the particle group 11 including the first particles 11A overlaps or is irregularly arranged on the substrate 20 to be processed, a region to be processed of the substrate 20 to be etched is secured, and the substrate 11 is irregular. The surface of the substrate to be processed 20 is subjected to unevenness processing while suppressing formation of unevenness with a small pitch or scattered unevenness. For this reason, an uneven | corrugated process is given to the surface of the to-be-processed substrate 20, without controlling especially the arrangement | positioning state of the particle group 11 (1st particle | grains 11A).

Therefore, in the surface treatment method according to the embodiment, it is difficult for the quality to vary, and uneven processing can be performed at high speed, and high mass productivity and low cost are realized.
In particular, the surface treatment method according to the embodiment applies a water-soluble one as the binder 12, and applies warm water as a solvent for dissolving the binder 12, thereby reducing environmental burden and simplifying equipment. Thus, the formation and removal of the particle layer 10 can be performed quickly.

  In addition, by the surface treatment method according to the embodiment, the equivalent diameter of the concavo-convex shape after the surface treatment of the substrate to be processed 20 (object to be processed) is, for example, at least 60% of the total number in the case of a light incident surface of a solar cell. More preferably, at least 80% is in the range of 200 nm to 1000 nm. The equivalent diameter is obtained by measuring the surface shape of the concave portion of the surface with a contact type surface shape measuring device such as a surface roughness meter or a non-contact type surface shape measuring device such as AFM, so that a non-processed portion, that is, unevenness is formed. The area of the part surrounded by the part of 10% depth from the reference surface of the distance from the reference surface to the maximum depth of the processed part was obtained using a non-flat part as the reference surface, and the circle was calculated from this area value. The diameter is defined as the equivalent diameter. In this case, in the present invention, when the equivalent diameter is 10 nm or less, the recess is regarded as a flat portion on which no unevenness is formed, and is not counted as a recess. At this time, the number of the recessed portions to be measured is suitably at least 10, more preferably 50 or more, still more preferably 100 or more, and most preferably 500 or more. As a specific measuring method, for example, in the contour map of the shape measurement result measured in the non-contact mode by AFM, the depth z0 of the deepest portion is obtained, and the value of 10% of this z0 is 0.1 * z0. Then, the depth zij at each measurement position (i, j) is given by zij = zij−0.1 * z0. Using this zji, the contour map is displayed again and printed out, and the above-mentioned area can be obtained from this output map by a known method. In addition, it is also possible to perform data processing with digital data directly from the AFM measuring machine to obtain the area, and all existing methods can be used.

  Hereinafter, the details of the liquid composition for surface treatment applied to the surface treatment method according to the embodiment will be described. In the following description, reference numerals are omitted.

  The composition for surface treatment includes, for example, a binder, a particle group, and a solvent as necessary.

  The particle group includes first particles and second particles having lower etching resistance than the first particles. The particle group composed of these particles is not limited to these two types of particles, and may include other types of particles.

  Here, the first particles have etching resistance and are not etched by the etching process, whereas the second particles are particles etched by the etching process. Specifically, regarding the etching rate, for example, when the etching rate ER is “second particle etching rate / first particle etching rate”, it is preferable that ER> 5, and further ER> 10.

Further, when the etching resistance of the first particles is ER1, the etching resistance of the second particles is ER2, and the etching resistance of the binder is ER3, it is desirable to satisfy the relationship of the following formula (1). By satisfying this relationship, since the second particles are etched simultaneously with the binder or before the binder, the particle gap between the first particles generated by the etching of the second particles is easily maintained.
Formula (1): ER2 <ER1 and ER3 <ER1

  The first particle is not particularly limited as long as it has etching resistance, and examples thereof include inorganic particles, organic dye / pigment particles containing an inorganic element, latex particles and capsule particles containing an inorganic element. . Among these, as the first particles, inorganic particles are preferable from the viewpoints of etching resistance, availability, and handleability.

Examples of the inorganic particles include non-metallic materials such as titanium oxide, silica, calcium carbonate, and strontium carbonate, metals, and semiconductor materials. For example, the metal includes Cu, Au, Ag, Sn, Pt, Pd, Ni, Co, Rh, Ir, Al, Fe, Ru, Os, Mn, Mo, W, Nb, Ta, Bi, Sb, and Pb. Examples thereof include a single metal selected from the group or an alloy material composed of one or more of the metals selected from the group. Examples of the semiconductor include Si, Ge, AlSb, InP, GaAs, GaP, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, PbS, PbSe, PbTe, SeTe, and CuCl. Moreover, the microcapsule etc. which included these inorganic particles and used silica as the wall membrane material are mentioned.
Examples of organic dye / pigment particles containing inorganic elements include metal element-containing azo dye particles and metal element-containing phthalocyanine dye particles.
Examples of latex particles and capsule particles containing inorganic elements include particles in which acrylic latex is coated with colloidal silica, particles in which acrylic latex is coated in silicate, particles in which polystyrene latex particles are coated with silica, and the like.

  On the other hand, examples of the second particles include resin particles, and there is no particular limitation as long as a difference in etching resistance from the first particles can be obtained, but thermoplastic resin particles are preferable. Examples of the thermoplastic resin particles include acrylic resin particles, polyethylene resin particles, polypropylene resin particles, polyamide particles, polyimide particles, polyethylene terephthalate resin particles, polystyrene particles, and silicone resins.

  The average particle diameter of the first particles and the second particles may be the same, but the average particle diameter of the second particles is preferably larger than that of the first particles. Thereby, it becomes easy to ensure the particle | grain space | interval of the 1st particle | grains produced by the etching of 2nd particle | grains. The average particle size of the first particles and the second particles is preferably 0.1 μm to 1 μm, more preferably 0.2 μm to 0.5 μm. The average particle size is preferably in the above range from the viewpoint of thinning the particle layer to be formed.

  Here, the average particle diameter of a particle means the particle diameter obtained by a dynamic light scattering method, and the measuring method is as follows. In the dynamic light scattering method, it is possible to measure the particle size and particle size distribution in the submicron range or less, and the particles to be measured or dispersions thereof are dispersed by a known method such as ultrasonic irradiation in a medium. Then, after diluting it appropriately, a measurement sample is obtained. In the cumulative frequency curve of the particle size obtained by the dynamic light scattering method, the particle size having a cumulative frequency of 50% is defined as the average particle size, and the ratio of the 10% cumulative particle size to the 90% particle size is similarly determined. An example of a measuring apparatus that employs such a principle that can be used as an index of distribution is LB-500 manufactured by Horiba, Ltd.

  Moreover, it is preferable that the particle size distribution of a 1st particle and a 2nd particle is 2-50, More preferably, it is 2-10. By setting the particle size distribution in the above range, the maximum average particle size does not become too large, a flat particle layer is easily obtained, and uniform surface treatment is easily realized.

  Although there may be a difference in the blending amount of the first particles and the second particles, it is preferable that they are approximately the same.

  Here, when the particle layer is formed on the substrate to be processed, the coverage of the first particles functioning as an etching mask is preferably 20% or more and less than 90%, more preferably, the surface of the substrate to be processed. It is 30% or more and less than 80%, more preferably 40% or more and less than 70%. The coverage is selected according to the area ratio of a region where etching is performed to perform uneven processing.

  The coverage is the ratio of the first particles covering the substrate to be processed when the particle layer is formed on the substrate to be processed, that is, the area of the first particle projected onto the substrate when viewed from the etching direction. Indicates the percentage. This coverage is measured as follows. After bonding to the substrate to be processed, the surface can be observed using a scanning electron microscope or an optical microscope, and can be calculated from the projected area.

In addition, the specification of the unevenness processing of the surface of the substrate to be processed, that is, the diameter (equivalent diameter), depth, and processing area ratio of the surface unevenness after the etching process can be controlled by the coverage of the first particles, specifically, For example, it can be arbitrarily designed according to the blending amount, blending ratio, and average particle size of the first and second particles in the liquid composition for surface treatment.

  Examples of the binder constituting the liquid composition for surface treatment include a water-soluble polymer material and an organic solvent-soluble polymer material, and in particular, from the viewpoint of environmental load and simplification of equipment, it is water-soluble. Are preferred.

In addition, the binder is prepared by mixing a polymerizable monomer capable of forming the polymer material with other components constituting the particle layer to form a liquid composition for surface treatment, and after coating, a polymerization reaction by light or heat May be formed into a film, that is, a particle layer may be formed.
As an example of the polymerizable monomer, (meth) acrylic monomer, (meth) acrylic acid C1-C12 alkyl ester, and these and a known compound as a new acrylic modifier can be used in combination. it can. Examples of the acrylic modifier include carboxy-containing monomers and acid anhydride-containing monomers. These polymerizable monomer monomers can be polymerized by a known polymerization method, and can be appropriately selected from known materials such as an initiator, a chain transfer agent, an oligomer material, and a surfactant necessary for the polymerization. Examples of the polymerizable monomer include known epoxy monomers and isocyanate monomers.

  More specifically, examples of the binder include a glass transition temperature of −100 to 50 ° C., a number average molecular weight of 1,000 to 200,000, preferably 5,000 to 100,000, and a degree of polymerization of about A thing about 50-1000 is mentioned suitably. Examples of such include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, Examples include polymers or copolymers containing vinyl ether as a structural unit, polyurethane resins, various rubber resins, and modified polyvinyl alcohol having a weight average molecular weight of 100,000 or less.

  More preferable binders include polyvinyl alcohol or derivatives thereof, cellulose derivatives (polyvinyl pyrrolidone, carboxymethyl cellulose, hydroxyethyl cellulose, etc.), natural polysaccharides or derivatives thereof (starch, xanthan gum, alginsan, etc.) that are readily water-soluble. Gelatin, water-dispersible urethane, acrylic polymer latex and the like are also included.

  The amount of the binder is appropriately set according to the dispersibility of the particle group. For example, the amount is preferably 5% by weight to 50% by weight, more preferably 10% by weight to 30% by weight with respect to the particle group. is there.

Other additives constituting the surface treatment composition include a dispersant that can stably disperse the particle group, and a surfactant and a solvent that adjust the viscosity and surface tension of the coating liquid during production, for example. Etc.
In particular, as the dispersant, phenylphosphonic acid, specifically “PPA” manufactured by Nissan Chemical Co., Ltd., α-naphthyl phosphoric acid, phenylphosphoric acid, diphenylphosphoric acid, p-ethylbenzenephosphonic acid, phenylphosphinic acid, aminoquinones, various Silane coupling agents, titanium coupling agents, fluorine-containing alkyl sulfates and alkali metal salts thereof can be used. In addition, nonionic surfactants such as alkylene oxide, glycerin, glycidol, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocyclics, phosphonium or sulfoniums, etc. Cationic surfactants, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester group, phosphate ester group, amino acids, aminosulfonic acids, sulfuric acid or phosphate esters of amino alcohol, alkyl Bedin type amphoteric surfactants and the like can also be used. As the dispersant, polyoxyethylene alkylphenyl ether, polyoxyalkylene block copolymer, polyoxyethylene alkylphenyl ether having a polymerizable unsaturated bond such as an allyl group, or the like may be selected. These dispersants (surfactants) are described in detail in “Surfactant Handbook” (published by Sangyo Tosho Co., Ltd.). These dispersants and the like are not necessarily 100% pure, and may contain impurities such as isomers, unreacted products, side reaction products, decomposition products, and oxides in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less. In the present invention, it is also preferable to use a combination of a monoester and a diester as described in the pamphlet of WO 98/35345 as a fatty acid ester.

The solvent constituting the surface treatment composition is selected from solvents that dissolve the binder in accordance with the binder type. Specifically, for example, when applying a water-soluble binder as a binder, it is preferable to apply an aqueous solvent as a solvent from the viewpoint of environmental load and simplification of equipment.
Examples of the aqueous solvent include water and lower alcohols (methanol, ethanol, butanol, isopropyl alcohol, etc.). As the solvent, water is most preferable.

In addition, the surface treatment method (liquid composition for surface treatment) which concerns on embodiment is applied suitably for the uneven | corrugated process mentioned below, for example.
1) In the field of optical devices such as solar cells, LEDs, flat panel displays, etc., in order to suppress the reflection phenomenon that occurs when the refractive index difference of the light transmitting interface is large, it is applied to the substrate surface through which light is transmitted by etching treatment. Concavity and convexity processing for forming concavities and convexities 2) In the field of semiconductor devices, in order to suppress peeling of the thin film due to insufficient adhesion between the thin film and the substrate, the concavity and convexity are formed on the substrate surface with the aim of anchor effect Uneven processing to be formed

  In particular, when applied to the field of optical devices, the surface (processing surface) of the workpiece (substrate) on which the irregularities are formed is preferably an optical device light incident surface. Thereby, the reflection phenomenon of the optical device is efficiently suppressed. And as mentioned above, the solar cell which has a board | substrate as the said to-be-processed object suitably is mentioned as a typical thing as an optical device provided with the to-be-processed object processed by the surface treatment method concerning embodiment. The solar cell includes a known configuration, for example, a substrate, a pair of electrodes, and a photovoltaic layer disposed between the pair of electrodes, in addition to the substrate processed by the surface treatment method according to the embodiment. The configuration.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention.

Example 1
-Preparation of liquid composition 1-
6 parts by weight of silica particles (first particle: SP-03F manufactured by Fuso Chemical Co., Ltd., average particle size 0.3 μm), acrylic resin particles (second particle: Soken) with respect to 100 parts by weight of PVA (made by Kuraray) 3% liquid MP1000 manufactured by Kagaku Co., Ltd., 4 parts by weight of an average particle diameter of 0.4 μm) and 0.5 parts by weight of a dispersant (2-ethylhexyl sulfosuccinate Na) are added and dispersed in a dissolver to obtain a liquid composition 1. It was.

-Particle layer formation-
Next, after spraying the liquid composition 1 on a 120 mm square silicon substrate, it was spin-coated at 4000 rpm for 2 minutes. Thereby, a particle layer having a dry film thickness of 1 μm was formed.

-Etching treatment-
Next, the silicon substrate on which the particle layer is laminated is first subjected to reactive ion etching treatment using an oxygen-containing gas for 200 seconds, and the region other than the region covered with the silica particles of the particle layer (the acrylic layer of the particle layer). Resin particles and binder) were removed.
Next, using the remaining particle layer (silica particles) as a mask, dry etching was performed at 150 W for 100 seconds in the presence of SF ₆ gas.

-Particle layer removal process-
Next, the remaining particle layer was removed by rubbing with a brush while applying warm water at 80 ° C. to the particle layer forming surface of the silicon substrate.

-Surface observation of silicon substrate-
When the treated silicon substrate surface was observed with a scanning electron microscope and AFM, the diameter of the silicon substrate surface (equivalent diameter of at least 60% based on the total number of irregularities on the silicon substrate surface) was 0.2 to An uneven structure of 0.5 μm and a depth of 0.1 to 0.4 μm was observed. Furthermore, when the reflectance of the treated silicon surface was measured, the reflectance was 0.5% or less in the wavelength range of 350 to 600 nm, which can be greatly improved compared to the reflectance of 15 to 30% for the untreated material. It was.
The same result was obtained even when the same process as described above was performed a plurality of times. In addition, when four silicon substrates were arranged in a square lattice and the same treatment was performed on the four substrates at the same time, the same result was obtained.

(Comparative Example 1)
In the liquid composition, a comparative liquid composition was prepared in the same manner as the liquid composition 1 except that the acrylic resin particles were not blended, and the silicon substrate was treated in the same manner as in Example 1 except that this was used. It was.
Then, when the same treatment as described above was performed a plurality of times, only a few percent of the whole was etched, resulting in a silicon substrate on which a sufficient uneven structure was not formed. When the reflectance of this silicon substrate was measured, it was 10% or more.

10 Particle layer 11 Particle group 11A First particle 11B Second particle 12 Binder 20 Substrate 30 Holding substrate 31, 32 Nozzle

Claims (13)

A liquid composition for surface treatment for forming irregularities on the surface of an object to be treated,
A liquid composition for surface treatment comprising at least first particles, second particles having lower etching resistance than the first particles, and a binder. The etching resistance of the first particles is ER1, the etching resistance of the second particles is ER2, and the etching resistance of the binder is ER3. Liquid composition for surface treatment.
Formula (1): ER2 <ER1 and ER3 <ER1   The surface treatment liquid composition according to claim 1, wherein the binder is water-soluble. A surface treatment method for forming irregularities on the surface of a workpiece,
A particle layer forming step of forming a particle layer by applying a liquid composition for surface treatment containing at least first particles, second particles having lower etching resistance than the first particles, and a binder to the surface of the object to be processed. When,
An etching process is performed on the surface of the object to be processed on which the particle layer is formed, and an unevenness is formed on the surface of the object to be processed.
A removal step of removing the particle layer after the etching step;
A surface treatment method characterized by comprising: The etching resistance of the first particles is ER1, the etching resistance of the second particles is ER2, and the etching resistance of the binder is ER3. Surface treatment method.
Formula (1): ER2 <ER1 and ER3 <ER1   The surface treatment method according to claim 4, wherein the binder is water-soluble.   The surface treatment method according to claim 4, wherein the etching process is a dry etching process.   The said particle layer formation process is a process of apply | coating the said liquid composition for surface treatment to the said to-be-processed object surface by a spin coating method, and forming a particle layer. Surface treatment method.   The surface treatment method according to any one of claims 4 to 8, wherein the particle layer forming step is collectively performed on a plurality of the objects to be processed.   The surface treatment method according to claim 4, wherein the removing step is a step of removing the particle layer by applying a solvent that dissolves the binder.   The surface according to any one of claims 4 to 9, wherein the removing step is a step of removing the particle layer by applying a solvent for dissolving the binder and rubbing with a rubbing member. Processing method.   The surface treatment method according to any one of claims 4 to 11, wherein the surface of the object to be processed for forming irregularities is a light incident surface of an optical device.   The optical device which has a board | substrate as a to-be-processed object surface-treated by the surface treatment method of any one of Claims 4-12.

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