JP4052885B2 - V-groove manufacturing type manufacturing method, and V-groove structure article manufacturing method using the mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an array type multi-fiber optical connector for optical communication, a method for manufacturing an article having a plurality of V grooves, such as an optical reflecting surface (which returns incident light to the incident direction using two reflecting surfaces), and the method thereof. The present invention relates to a method for manufacturing a mold used in the manufacturing method.
[0002]
[Prior art]
In an array type multi-fiber optical connector for optical communication, in order to regularly connect and connect the tips of a plurality of optical fibers, alignment members in which V grooves for arranging the optical fibers one by one are formed in parallel with each other at an equal pitch are used. The As such an alignment member, a silicon (Si) substrate having a V-groove is used.
[0003]
As a method for forming a V groove in a silicon substrate, a resist pattern is formed on the surface of a Si (100) substrate by a photolithography method, and wet etching is performed with an alkali etching solution (KOH solution) using the resist pattern as a mask. In this etching, the silicon substrate is selectively etched due to the difference in the etching rate of the single crystal surface, and a (111) surface having a slow etching rate appears on the surface. As a result, a groove having a V-shaped cross section (V groove) is formed on the etched surface.
[0004]
[Problems to be solved by the invention]
Conventionally, wet etching processes have been performed in various forms. However, due to etching unevenness and difficulty in increasing the accuracy of the transferred pattern, the desired performance may not be obtained when a very high-precision fine three-dimensional shape is created by a wet process. It was. The method of performing wet etching on the surface of a silicon substrate using a resist pattern as a mask is difficult to control the amount of side etching and reduce in-plane variation, making it difficult to increase the accuracy of the pattern, and obtaining a highly accurate fine three-dimensional shape. Has been considered unsuitable.
[0005]
The present invention is a method of forming a V-shaped groove structure of precise three-dimensional structure by wet etching the silicon substrate, to provide a method of manufacturing a V-shaped groove structure article a V-shaped groove structure obtained by the method as a type It is the purpose.
[0006]
[Means for Solving the Problems]
The present invention is a method for manufacturing a mold for manufacturing an article having a periodic V-groove structure on the surface of a silicon substrate, and includes the following steps (A) to (D).
(A) a step of forming a film having resistance to an alkaline solution on the surface of a silicon substrate having a (100) plane;
(B) a photolithography process for forming a striped resist pattern having strip-shaped openings extending in parallel with each other on the film;
(C) a dry etching step of etching the film using the resist pattern as a mask to transfer the resist pattern to the film and exposing the silicon substrate in the resist pattern opening; and (D) removing the resist pattern; An anisotropic wet etching process in which the silicon substrate surface is wet etched with an alkaline etchant using the film pattern as a mask to form a V-shaped V-shaped groove.
[0007]
Examples of a film resistant to an alkaline solution are a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a laminated film of a silicon oxide film and a silicon nitride film, or a metal film. In particular, in the case of a silicon oxide film, a thermal oxide film formed by thermally oxidizing the (100) surface of a silicon substrate or a nitride film nitrided in a nitrogen atmosphere is preferable. In the case of a nitride film, an oxide film is desirably formed as an undercoat.
[0008]
If an attempt is made to form a pattern by etching such a film by a wet process, the wet etching becomes isotropic etching, and a reaction unevenness exists, so that a highly accurate pattern cannot be obtained. Therefore, by patterning such a film by dry etching according to the present invention, a mask with a highly accurate film pattern can be formed on the silicon substrate. This is because according to the dry etching method, it is possible to transfer with good verticality as compared with the case of transferring with the wet etching method.
[0009]
At this time, if the roughness of the resist surface is transferred to the pattern of the thermal oxide film or nitride film, it may cause a decrease in accuracy, so that the resist still remains when the film on the resist pattern opening is removed. Set conditions.
[0010]
In the step (D), since the film pattern is used as a mask, foreign substances adhering to the silicon substrate surface can be efficiently removed, etching unevenness is eliminated, and a highly accurate shape (line linearity, line width, groove) is obtained. Angle, groove depth, etc.) can be formed.
[0011]
In the photolithography step in step (B), the direction in which the strip-shaped opening of the resist pattern extends is parallel or perpendicular to the b-axis <010> of the silicon substrate, or parallel or perpendicular to the c-axis <001>. Like that.
[0012]
The b-axis <010> or c-axis <001> has been determined by various methods. As a new method, a resist having linear openings whose angles are slightly changed from each other on the surface of a silicon substrate having a (100) plane. A b-axis based on a step of forming a pattern, a wet etching step of etching the silicon substrate with an alkaline etchant using the resist pattern as a mask, and linearity of a linear pattern formed on the silicon substrate after the wet etching step The method provided with the crystal axis determination process which determines <010> or c-axis <001> can be mentioned.
[0013]
In this case, the linear opening provided in the resist pattern is changed in increments of 0.1 ° within an angle range of ± 1 °. The reason why the angle range to be changed is set to ± 1 ° is that the purchase specification of the silicon substrate is normally “± 0.5 °” as a standard.
[0014]
There are the following two methods for evaluating the linearity of a linear pattern formed on a silicon substrate by wet etching.
(1) Evaluation based on a dimensional difference between the width of the mask pattern and the width of the pattern actually formed on the silicon substrate.
(2) Evaluation by the difference in linearity between the mask pattern line and the pattern line actually formed on the silicon substrate. (If the angle deviates from the b-axis <010> or the c-axis <001>, the linearity deteriorates and the straight line becomes a stepped shape.)
[0015]
According to these methods, it is possible to determine with almost the same accuracy as in the case of X-ray measurement, and as a result, it is possible to determine the axis with an accuracy of ± 0.1 °.
In the case of X-ray measurement, there is a problem that an error in mounting the substrate on the jig is large.
[0016]
In the photolithography step in the step (B), it is preferable that the resist pattern is surface-cured by using ultraviolet light irradiation in combination with the resist post-baking. This suppresses thermal deformation of the resist and can be cured while maintaining the perpendicularity of the pattern edge, so that the line / space linearity is improved.
[0017]
After the dry etching step in step (C), it is preferable to provide an oxygen ashing step for removing organic substances attached to the exposed surface of the silicon substrate during the dry etching. In the dry etching in the step (C), a CxFy-based polymer adheres to the surface of the silicon substrate depending on the reactive gas species, the etching conditions, or the etching apparatus. Therefore, this polymer is removed by oxygen ashing.
[0018]
At this time, if the organic matter that could not be removed by oxygen ashing is left as it is, it acts as an etching blocker that hinders etching during etching with an alkali solution in the subsequent step, thereby causing uneven etching during wet etching with an alkali etching solution. Therefore, it is preferable to completely remove organic substances on the surface of the substrate by carrying out carros cleaning on the substrate. Carros cleaning is a cleaning method using a mixed solution of sulfuric acid and H ₂ O ₂ .
[0019]
During this oxygen ashing and carros cleaning, the surface of the silicon substrate is oxidized to form a silicon oxide thin film. This thin film has poor reactivity with alkali, for example, KOH, and causes etching unevenness. For this reason, it is preferable to provide a light etching step of removing the silicon oxide thin film formed on the exposed surface of the silicon substrate in this step by treating with a hydrofluoric acid solution for a short time after the oxygen ashing step and the carros cleaning.
[0020]
When the pretreatment by oxygen ashing and light etching is performed, impurities are eliminated on the surface of the silicon substrate when the silicon substrate is etched with an alkali solution, so that a uniform etching reaction is possible and a highly accurate fine three-dimensional shape can be obtained. . When the silicon substrate is subjected to alkali anisotropic etching using the resist pattern as a mask as in the prior art, (1) the resist is peeled off with an alkali etching solution, or (2) side adhesion with the alkali etching solution results in poor adhesion. As a result, there is a disadvantage that the groove width is widened.
[0021]
The anisotropic wet etching step (D) is preferably performed by changing the concentration of the alkaline etching solution stepwise. For example, by increasing the concentration of the alkaline etching solution stepwise, as described in detail in the examples, the surface roughness close to a mirror surface can be obtained in the finishing stage while maintaining the etching rate high. become.
[0022]
Moreover, in order to perform the anisotropic wet etching process of a process (D) uniformly, it is preferable to perform ozone cleaning by excimer light before the anisotropic wet etching process. When the ozone cleaning is performed, the wettability of the silicon substrate surface is improved, and the wet etching easily proceeds without unevenness.
[0023]
The present invention also includes a method of manufacturing a V-groove structure article having a periodic V-groove structure on the surface of a substrate that is not a silicon substrate, using the mold manufactured by the above method, and including the following steps.
[0024]
(A) A curable material layer that is cured by light or heat is sandwiched between a flat surface of a target substrate on which a V-groove structure article is to be manufactured and a mold according to the present invention, and the material layer is cured to provide an in-plane direction. Forming a pattern of the material having a distribution in both the film thickness direction and
(B) A dry etching process in which the material pattern and the substrate are simultaneously dry etched to transfer the material pattern to the substrate to form a pattern having a periodic V-groove structure on the substrate surface.
[0026]
In the dry etching process in which the material pattern is transferred to the substrate, it is preferable to control at least one of the dry etching selectivity and the etching time, and to control the angle and / or depth of the resulting V-groove structure.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment will be described with reference to FIGS.
(A) A silicon substrate 20 having a (100) plane as a crystal plane and having a b-axis in an OF (orientation flat) portion is used. The OF portion is a notch in the outer peripheral portion that serves as the outer shape reference of the circular wafer of the silicon substrate 20.
[0030]
The surface of the silicon substrate 20 is thermally oxidized. At this time, a thermal oxide film (SiO ₂ ) 22 is formed on the silicon surface by introducing H ₂ gas and O ₂ gas and performing thermal oxidation at 1100 ° C.
[0031]
This substrate is cleaned, and the cleaning is performed in the order of CAROS cleaning, SC-1 cleaning, and excimer cleaning. Further, the substrate is subjected to OAP processing (resist adhesion improving processing). Here, as described above, the carros cleaning is a cleaning method using a mixed solution of sulfuric acid and H ₂ O ₂ , and the SC-1 cleaning is a cleaning method using a mixed solution of NH ₄ OH and H ₂ O ₂ . Excimer cleaning is a cleaning method in which excimer light is irradiated while flowing O ₂ gas to generate O ₃ to oxidize and remove organic substances on the substrate surface.
[0032]
(B) Next, a resist (manufactured by Tokyo Ohka Co., Ltd .: IP2250-13CP) is applied to the thermal oxide film 22 by 1.5 μm. As a coating method at this time, a spin coating method is used in order to eliminate variations in resist surface roughness. The spin coating condition is about 20 seconds at a rotation speed of 1200 rpm.
[0033]
Next, the resist is pre-baked at 100 ° C. for 3 minutes using a hot plate.
The pre-baked resist is irradiated with 220 mj of light using a mask in which the fine shape of the target line / space is patterned. If an optimal value is experimentally set based on the resist sensitivity, a more accurate pattern can be transferred.
[0034]
Next, the resist is developed (development time 38 s) and rinsed to form a resist pattern 24.
The resist pattern 24 is post-baked at 150 ° C. for about 3 minutes using a hot plate.
[0035]
(C) Next, dry etching is performed on the oxide film 22 using the resist pattern 24 as a mask and using an RIE apparatus with an upper electrode power of 1250 W and a lower electrode (RF) power of 200 W. As an example of the etching conditions, the etching gas is CF ₄ : 20 sccm, CHF ₃ : 10 sccm, Ar: 5 sccm, and the time is 3 minutes. At this time, the oxide film 22 in the opening of the resist pattern 24 is completely removed, and the resist pattern 24 remains.
[0036]
(D) Next, the substrate is subjected to O ₂ ashing treatment for 1 minute to remove the resist 24. By this treatment, the organic substance 26 centering on the CxFy polymer attached to the exposed surface of the silicon substrate 20 during the previous dry etching can also be removed.
[0037]
Next, carros cleaning is performed. This cleaning process completely removes the resist remaining on the substrate. Insufficient treatment here causes etching unevenness by acting as an etching blocker that hinders etching during etching with an alkaline solution in a subsequent step.
[0038]
(E) Next, etching (light etching) is performed with a 7% hydrofluoric acid aqueous solution for 2 minutes. By this process, the oxide thin film 28 formed on the exposed surface of the silicon substrate 20 during the previous O ₂ ashing and carros cleaning process is removed.
[0039]
Here, before proceeding to the next anisotropic wet etching process using a KOH solution, ozone cleaning using excimer light is performed. The silicon substrate surface after completion of the above step (E) is hydrophilic. If wet etching with the next KOH solution is performed in this state, the wettability is not good and unevenness occurs. In order to improve this, ozone cleaning is performed. When ozone cleaning is performed, the wettability of the silicon substrate surface is improved, and wet etching is performed quickly and uniformly. In addition, hydrogen gas is generated in the reaction of silicon and KOH as bubbles as shown in the following reaction formula.
_{Si + 2KOH + H 2 O =} K 2 SiO 3 + 2H 2
Since these bubbles inhibit the reaction, it is important to efficiently remove the bubbles in the form of microbubbles. For this reason, it is important to improve the wettability of the silicon substrate surface.
[0040]
(F) Next, etching is performed using a KOH solution as an etchant. This etching proceeds anisotropically, and a V-shaped groove 30 having a V-shaped cross section and extending in the direction perpendicular to the paper surface is formed. This etching is performed by changing the concentration of the KOH solution stepwise using an automatic KOH etching apparatus. Specifically, the etching solution temperature is 85 ° C. for 42 minutes, and the concentration is set as follows.
[0041]
(1) The KOH initial concentration is set to 13% for 13 minutes.
At this time, the etching rate of silicon is fast and is 2.0 μm / min. The etching amount by etching for 13 minutes is 26 μm. However, the surface roughness is large under these conditions.
[0042]
(2) As an intermediate step, the KOH concentration is automatically changed to 23% for 14 minutes.
At this time, the etching rate of silicon is 1.8 μm / min. The etching amount by etching for 14 minutes is 25 μm.
[0043]
(3) As a final step, the KOH concentration is automatically changed to 30%, and the process is performed for 15 minutes.
At this time, the etching rate of silicon is 1.6 μm / min. The etching amount by etching for 15 minutes is 24 μm.
[0044]
As a result, the total etching depth is 75 μm. Before and after changing the etching conditions, the concentration is gradually changed over about 5 minutes. Change the density with an automatic density controller.
[0045]
Further, in the automatic KOH etching apparatus, the silicon substrate is repeatedly moved up and down and rotated by a cam, and hydrogen gas (bubbles) generated on the surface of the silicon substrate is smoothly removed.
[0046]
When the KOH concentration is changed in this way, the reaction time is fast at low concentrations, so that the bubble residence time becomes longer and the bubbles become larger. For this reason, the surface reaction is inhibited by the bubbles, and the surface roughness becomes rough. Since the reaction is slow at high concentrations, it desorbs in the form of small bubbles. Therefore, the surface roughness is reduced. As a result, it is possible to obtain a surface roughness close to a mirror surface at the time of finishing while keeping the etching rate high.
[0047]
This alkali anisotropic etching is a uniform etching due to the effect of the pretreatment in the previous steps (D) and (E). This is different from the conventional method in which the silicon substrate is subjected to alkali anisotropic etching using the resist pattern as a mask. If the resist pattern is used as a mask during etching of the silicon substrate as in the prior art, the exposed silicon This is because the above pretreatment cannot be performed on the substrate surface.
[0048]
(G) Next, after carrying out 180-second carros cleaning, etching is performed with a 7% hydrofluoric acid aqueous solution for 20 minutes. By this treatment, the mask of the oxide film 22 remaining on the surface of the substrate 20 is removed.
[0049]
By using the method of the present invention, a concave portion of an inverted quadrangular pyramid surrounded by a (111) plane is formed on the surface of the silicon substrate, a reflective film is formed on the inner surface of the concave portion, and an optical having a concave reflecting surface of the inverted quadrangular pyramid. Parts can also be manufactured.
[0050]
Next, a method for transferring the V-groove formed in the silicon substrate to the final intended material other than the silicon substrate will be described with reference to FIG.
Here, the shape of the V-groove structure 30 of the mold 20a is formed such that the valley portion is formed in a V shape and the top portion of the peak portion between the V grooves 30 is a flat surface.
[0051]
(A) An appropriate amount of a curable material 34 that is cured by light or heat is dropped on the surface of the final substrate material 32 and the surface of the mold 20a, and the substrate material 32 and the mold 20a are aligned on the surface of the curable material. The substrate material 32 is, for example, a quartz glass substrate. At this time, it is important not to generate bubbles. At this time, the surface of the substrate material 32 is preferably subjected to a surface treatment for improving the adhesive strength, and the mold 20a is preferably subjected to a release treatment. When these treatments are performed, the mold 20a can be easily peeled after the curable material 34 is cured. An example of the surface treatment for improving the adhesive strength is a silane coupling treatment, and an example of the mold release treatment is a fluorine primer treatment.
Here, a transparent substrate is used as the substrate material 32.
[0052]
(B) Next, light is irradiated from the substrate material 32 side to cure the curable material 34. The curable material after curing is designated as 34a.
(C) The mold 20a is peeled from the cured curable material 34a. The shape transferred to the curable material 34a is an uneven surface with respect to the surface shape of the mold 20a, and a portion corresponding to the groove 30 becomes a ridge 30a having an inverted V-shaped cross section, and a valley is formed between the ridges 30a. A V-groove 30b having a flat surface is formed.
[0053]
(D) The curable material 34a and the substrate material 32 are simultaneously dry-etched to transfer the shapes 30a and 30b of the curable material 34a to the substrate material 32 that is the target material. The shapes 30a ′ and 30b ′ transferred to the substrate material 32 are basically shapes having irregularities opposite to the surface shape of the mold 20a. However, the dry etching selectivity, the etching end point, etc. are changed. Thus, the groove angle and the groove shape can be changed. The groove shape indicated by the solid line and the chain line in FIG. 3D indicates that the groove shape obtained is changed by changing such conditions.
[0054]
Further, as shown by the solid line in FIG. 3, if the etching is finished without etching until the curable material 34a completely disappears, the remaining curable material 34a is removed, and then the remaining curable material 34a is removed. As shown in (E), a V-groove structure in which the tops of the peaks between the V-grooves 30b ′ are flat surfaces is obtained. The flatness of the flat surface at the top of the peak is the flatness of the substrate material 32.
[0055]
【The invention's effect】
In the present invention, in order to manufacture an article having a periodic V-groove structure on the silicon substrate surface, a film such as a silicon oxide film is formed on the silicon substrate surface having the (100) plane, and a resist pattern is formed thereon. Then, after the resist pattern is transferred to the film by dry etching, the surface of the silicon substrate is alkali-etched by using the film pattern as a mask so that a V-shaped cross section is formed on the silicon substrate. A mask with a highly accurate coating pattern can be formed, and since the coating pattern is used as a mask, foreign substances adhering to the silicon substrate surface can be efficiently removed, etching unevenness is eliminated, and a highly accurate shape is obtained. Can be formed.
[Brief description of the drawings]
FIG. 1 is a process cross-sectional view showing the first half of a process of forming a V-groove in a silicon substrate in one embodiment.
2 is a process cross-sectional view showing the latter half of the same process for forming a V groove in the silicon substrate of the same example; FIG.
FIG. 3 is a process cross-sectional view illustrating a method for transferring a V-groove formed on a silicon substrate to a material for final use other than the silicon substrate.
[Explanation of symbols]
20 Silicon substrate 20a Type 22 Thermal oxide film 24 Resist pattern 30 V groove 32 Substrate material for final use 34 Curable material

Claims (12)

A method for manufacturing a mold for manufacturing an article having a periodic V-groove structure, comprising the following steps (A) to (D).
(A) a step of forming a film having resistance to an alkaline solution on the surface of a silicon substrate having a (100) plane;
(B) a photolithography process for forming a striped resist pattern having strip-shaped openings extending in parallel with each other on the film;
(C) a dry etching step of etching the film using the resist pattern as a mask to transfer the resist pattern to the film and exposing the silicon substrate in the resist pattern opening;
(D) An anisotropic wet etching process in which, after removing the resist pattern, the silicon substrate surface is wet etched with an alkaline etchant using the film pattern as a mask to form a V-shaped V-shaped groove.   2. The mold manufacturing method according to claim 1, wherein the film is a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a laminated film of a silicon oxide film and a silicon nitride film, or a metal film.   The mold manufacturing method according to claim 2, wherein the film is a thermal oxide film formed by thermally oxidizing the (100) surface of the silicon substrate or a nitride film nitrided in a nitrogen atmosphere.   In the photolithography step in step (B), the direction in which the strip-shaped opening of the resist pattern extends is parallel or perpendicular to the b-axis <010> of the silicon substrate, or parallel or perpendicular to the c-axis <001>. Item 4. A method for producing a mold according to any one of Items 1 to 3. The mold manufacturing method according to claim 4, wherein the b-axis <010> or the c-axis <001> is determined by the following method.
Forming a resist pattern having linear openings whose angles are slightly changed from each other on a silicon substrate surface having a (100) plane;
A wet etching step of etching the silicon substrate with an alkaline etchant using the resist pattern as a mask, and a b-axis <010> or a c-axis based on the linearity of the linear pattern formed on the silicon substrate after the wet etching step Crystal axis determination step for determining <001>.   6. The method for producing a mold according to claim 1, wherein in the photolithography step in step (B), the resist pattern is surface-cured by using ultraviolet light irradiation in combination with post-baking of the resist.   The method for producing a mold according to any one of claims 1 to 6, further comprising an oxygen ashing step for removing organic substances attached to the exposed surface of the silicon substrate during the dry etching after the dry etching step in the step (C). .   8. The light etching process according to claim 7, further comprising a light etching process for removing the silicon oxide thin film formed on the exposed surface of the silicon substrate in the oxygen ashing process by a short time treatment with a hydrofluoric acid solution after the oxygen ashing process. Mold manufacturing method.   9. The mold manufacturing method according to claim 1, wherein the anisotropic wet etching step of step (D) is performed by changing the concentration of the alkaline etching solution stepwise.   10. The mold manufacturing method according to claim 1, wherein after the step (C) is finished, the silicon substrate is subjected to ozone cleaning before the anisotropic wet etching step of the step (D). A method for producing a V-groove structure article having a periodic V-groove structure on the surface of a substrate that is not a silicon substrate, using the mold produced according to any one of claims 1 to 10, and comprising the following steps.
(A) A curable material layer that is cured by light or heat is sandwiched between a flat surface of a target substrate on which a V-groove structure article is to be manufactured and the mold, and the material layer is cured to form an in-plane direction and a film. Forming a pattern of the material having a distribution in both thickness directions; and (B) transferring the material pattern to the substrate by simultaneously dry-etching the material pattern and the substrate to periodically form the substrate surface. A dry etching process for forming a pattern having a V-groove structure.   The method for manufacturing a V-groove structure article according to claim 11, wherein in the dry etching step, at least one of a dry etching selectivity and an etching time is controlled to control an angle and / or a depth of the V-groove structure.

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