JP2012177775A - Processing method of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a substrate, by which a step of removing an unnecessary mask part can be eliminated and an unnecessary mask part is easily removed by using any force such as mechanical vibration or adhesive force.SOLUTION: The method includes: (a) forming a polycrystalline silicon film 1 on a substrate 2; (b) forming an opening 3 in the formed polycrystalline silicon film 1; (c) providing a groove part 4 in a periphery of the opening 3; (d) allowing etching to progress so as to form a cavity 5 and to deepen a groove in the groove part 4; and (e) removing a part of a mask unnecessary part 6 when the groove part 4 penetrates. However, technology of the prior arts can be used for a photoresist layer, a mask layer or formation of an opening by etching.

Description

  The present invention relates to a substrate processing method, and more particularly to a substrate processing method for removing unnecessary portions of a mask that are generated in the process of manufacturing a microlens array.

Microlenses are used to improve the light utilization efficiency of liquid crystal panels. One method of manufacturing a microlens is to obtain a lens by forming a hemispherical concave portion on a substrate using wet etching, filling the concave portion with a resin, molding it, and taking it out. As shown in FIG. 8, wet etching is performed by providing a mask layer 33 having an opening 34 on the substrate 30. However, as the etching progresses, a concavely curved cavity 31 is formed, and the mask layer 33 is not in close contact with the substrate 30. The unnecessary portion 32 is generated. As the cavity 31 becomes deeper, the surface of the cavity 31 becomes farther from the opening 34, and the etching solution is restricted by the unnecessary portion 32, so that the fluidity is deteriorated and it is difficult to reach the surface of the cavity 31. In addition, when a product (by-product) that is hardly soluble in water is generated by reaction with the etching solution, the opening 34 of the mask layer 33 may be blocked by the by-product.
As a result, the unnecessary portion 32 remains and the circulation of the liquid is hindered, and a concentration distribution is likely to be generated in and around the cavity 31, and in the vicinity of and around the etching surface. There was a problem.
In order to solve this problem, Patent Documents 1 and 2 as conventional techniques include a step of removing an unnecessary mask part in the middle of etching in order to improve shape controllability. That is, in order to improve the shape controllability, a step of removing the unnecessary mask portion is provided in the middle of the etching, and it is removed by applying mechanical vibration at high frequency or peeling off with an adhesive tape.

However, the conventional techniques disclosed in Patent Documents 1 and 2 may peel off a mask of a necessary part that should be left when an unnecessary part is removed. Further, the provision of the removing step may cause an increase in production cost or a decrease in productivity due to new equipment or chemicals.
The present invention has been made in view of such a problem, and provides a substrate processing method that reduces the unnecessary mask portion removal step and facilitates removal of the unnecessary mask portion even if the unnecessary mask portion remains. For the purpose.

In order to solve this problem, the present invention provides a substrate processing method for forming a concave curved surface on a substrate by etching, the first mask having a circular opening of a circular pattern, and the first mask. A second mask having a circular opening of concentric and large diameter with the circular opening of the mask, a polycrystalline silicon film is formed on the substrate surface, and the polycrystalline silicon film Forming a photoresist layer on the substrate, forming an opening corresponding to the circular opening in the photoresist layer using the first mask, and then performing etching to form an opening in the polycrystalline silicon film A photoresist layer is formed again on the polycrystalline silicon film in which the opening is formed, and an opening corresponding to the annular opening is formed in the photoresist layer using the second mask. Forming A second step of forming an annular groove corresponding to the annular opening in the polycrystalline silicon film by etching, and a polycrystalline silicon film in which the opening corresponding to the circular opening and the annular groove are formed And a third step of etching the substrate using as a mask.
When the concave curved surface is formed on the substrate by etching, a part of the polycrystalline silicon film used as a mask may remain as an unnecessary portion. This unnecessary portion has a problem of hindering the flow of the etching solution necessary for forming the concave curved surface. Therefore, in the present invention, a groove is formed around the circular opening of the polycrystalline silicon film, and as the etching proceeds, the groove is etched and penetrated to remove unnecessary portions around the circular opening. Thereby, the fluidity | liquidity of etching liquid can be improved.

According to a second aspect of the present invention, the diameter of the circular opening formed in the polycrystalline silicon film is φ, the selectivity between the substrate and the polycrystalline silicon film in the third step is α, the etching factor is ε, and the relative depth is When the upper limit of the height is D, the position x of the annular groove provided around the circular opening and the thickness t of the bottom of the annular groove are x ≦ (D / ε) φ, x / α ≦ t ≦ {(D / Ε) φ} / α is set so as to satisfy the relationship.
As for the position of the annular groove, if the position of the annular groove is too far from the circular opening, penetration occurs before the etching end spreads, and a pinhole is generated in the mask of the necessary part, and the desired concave curved surface. The shape cannot be obtained. Further, if penetration occurs after the etching edge has sufficiently spread, the relative depth becomes considerably large in the process, and the product may be clogged with the opening, so that the original purpose cannot be achieved. As for the thickness, if the thickness is too small, penetration occurs before the etching end spreads. If the thickness is too thick, the relative depth becomes considerably large, and the product may be clogged with the opening. Therefore, it is necessary to appropriately adjust the position of the annular groove and the thickness of the bottom.

According to a third aspect of the present invention, the etching is performed by isotropic etching.
Etching includes anisotropic etching and isotropic etching. In the case of the present invention, isotropic etching is preferable because a concave curved surface is formed on the substrate. Isotropic etching is convenient for forming a concave curved surface because etching proceeds at the same speed in all directions.

  According to the present invention, productivity is improved by eliminating the step of removing unnecessary mask portions. In addition, even when removing unnecessary mask parts using mechanical vibration or adhesive force, it can be easily removed and does not adhere to the substrate without adversely affecting the portion of the mask that is adhered to the substrate. Unnecessary portions of the mask can be easily and reliably removed by applying high frequency vibration.

It is a figure explaining the process of forming the concave curved surface to a board | substrate by wet etching using the manufacturing method of the board | substrate of this invention, (a) is a figure which forms a silicon film on a board | substrate surface, (b) is opening. The figure to form, (c) is a figure which forms an annular groove part, (d) is a figure which forms a cavity, (e) is a figure which removes a mask unnecessary part. It is a figure which shows typically an example of the photomask for photoresist exposure, (a) is a figure of the mask which forms opening, (b) is a figure of the mask which forms an annular groove part. It is a figure which shows the formation process of the mask layer which has an annular groove part around an opening, (a) is a figure which forms a silicon film on a substrate surface, (b) is a figure which forms an opening, (c) is an annular groove part FIG. (A) is a figure which shows what position should provide an annular groove part, and should have thickness of a bottom part, (b) is a figure explaining an etching factor. It is a figure which shows the effect which reduces the increase in the relative depth accompanying progress of an etching. (A) is a figure which shows a comparative example and (B) shows Example 1. FIG. (A) is a figure which shows the mask layer which concerns on Example 2, and the mode of etching, (B) is a figure which shows the mask layer which concerns on Example 3, and the mode of etching. It is a figure explaining the process of forming the concave curved surface to the board | substrate by the conventional wet etching.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is a diagram illustrating a process of forming a concave curved surface on a substrate by wet etching using the substrate manufacturing method of the present invention. A mask A (first mask) (see FIG. 2) having a circular opening 8 of a circular pattern, and a mask B (concentric with the circular opening 8 of the mask A and having an annular opening 9 having a large diameter) (Second mask) (see FIG. 2), and (a): the polycrystalline silicon film 1 is formed on the substrate surface 2. (B): A polysilicon layer is formed by forming a photoresist layer on the polycrystalline silicon film 1, forming an opening corresponding to the circular opening 8 in the photoresist layer 1 using the mask A, and performing etching. An opening 3 is formed in the film 1. (C): A photoresist layer is again formed on the polycrystalline silicon film 1 in which the opening 3 is formed, and an opening corresponding to the annular opening 9 is formed in the photoresist layer 1 using the mask B, and then etching is performed. As a result, an annular groove 4 corresponding to the annular opening 9 is formed in the polycrystalline silicon film 1. (D): The cavity 5 is formed by etching the polycrystalline silicon film 1 and the substrate 2 in which the opening 3 corresponding to the circular opening 8 and the annular groove 4 are formed. (E): Since the annular groove portion 4 penetrates, a part of the mask unnecessary portion 6 is removed. A known technique can be used to form a photoresist layer, a mask layer, an opening by etching, and the like.

FIG. 2 is a diagram schematically showing an example of a photomask for photoresist exposure. FIG. 3 is a diagram showing a process of forming a mask layer having a groove around the opening.
The case where two photomasks are used is shown. The pattern of each mask is formed by arranging a plurality of openings 8 and 9 shown in FIG. 2 as one pattern. Thereby, the concentric annular groove 4 around the opening 3 can be formed. By using concentric circles, when the unnecessary mask portion 6 isotropically expands by isotropic etching, the annular groove portion 4 penetrates at the same timing, so that the detachment occurs smoothly. Further, because of the isotropic shape, the shape does not change even after the circulation of the liquid during etching or the penetration 3 occurs and the opening 3 spreads, and the uniformity of the shape is maintained.

  An example of forming the mask layer will be described with reference to FIG. A known technique can be used for forming a photoresist layer, a mask layer, an opening by etching, and the like. (A): Polycrystalline silicon film 1 is formed on glass substrate 2. (B): A photoresist layer is formed on the polycrystalline silicon film 1 (not shown), and an opening is formed in the photoresist using the mask A (FIG. 2A). Then, the polycrystalline silicon film 1 is etched to form an opening 3 in the polycrystalline silicon film 1, and then the photoresist is removed. (C) A photoresist layer is again formed on the polycrystalline silicon film 1 from which the photoresist has been removed (not shown), and alignment is performed using the mask B (FIG. 2B). An annular opening is formed concentrically around the opening in the photoresist. The mask is provided with alignment marks for aligning the masks A and B. Then, the polycrystalline silicon film 1 is etched to form a concentric annular groove 4 around the opening 3 in the polycrystalline silicon film 1, and then the photoresist is removed.

  FIG. 4 is a diagram showing at what position the annular groove portion is provided and how much the bottom portion is to be thickened. As for the position, if the position of the annular groove portion 4 is too far from the opening 3, penetration occurs before the etching end spreads, and a pinhole is generated in the mask of the necessary portion, and a desired concave curved surface shape is obtained. I can't. Further, even if penetration occurs after the etching edge has sufficiently spread, the relative depth becomes so large that the product may clog the opening and the original purpose cannot be achieved. As for the thickness, if the thickness is too small, penetration occurs before the etching end spreads, and if it is too thick, the relative depth becomes considerably large, and the product may be clogged with the opening. As described above, it is necessary to appropriately adjust the position of the annular groove and the thickness of the bottom.

FIG. 4A shows the relationship that the position of the annular groove 4 and the thickness of the bottom t should satisfy. For example, in order to make the relative depth 2 or less, the annular groove 4 is positioned at position p (distance from the mask opening end), When the thickness t, the opening diameter φ, and the selection ratio α are set, the following relationship is shown.
p ≦ 2φ
p / α ≦ t ≦ 2φ / α
More generally, when relative depth D and etching factor ε, p ≦ (D / ε) · φ
p / α ≦ t ≦ (D / ε) · (φ / α)
1) Since the etching end position (x = c) is equal to the depth in the case of isotropicity, the relative depth D = c / φ
2) To form a spherical surface with D ≦ 2, when the annular groove portion penetrates, the etching end (x = c) needs to be inside the position 2φ, and the etching end needs to be on the outer periphery from the annular groove portion.
3) Therefore, the following is performed. Let annular groove part position p be the above-mentioned range a (0-2phi). The film thickness t of the annular groove is set so that the film penetrates when the etching end is in the range b (p to 2φ).
4) Since the annular groove is etched by c / α at the selection ratio α, the following relationship is required. That is, when the position p of the annular groove, the film thickness t, the opening diameter φ, and the mask / substrate selection ratio α, p ≦ 2φ, p / α ≦ t ≦ 2φ / α

FIG. 4B is a diagram for explaining the etching factor.
When the depth of the cavity 5 is c, the opening diameter of the cavity 5 is b, and the diameter of the opening 3 is a, the etching factor can be expressed as c / {(ba) / 2}.

FIG. 5 is a diagram showing the effect of reducing the increase in relative depth with the progress of etching. As an example, the case where p = 10 μm, t = 20 nm, φ = 10 μm, and α = 1000 is shown.
The dotted line 10 shows the effect of reducing the relative depth. Practices 10 and 12 show the necessary relationship between t and p. As an example, p = 10 μm, t = 20 nm, φ = 10 μm, and α = 1000 are shown. In the comparative example 11, the relative depth increases in proportion to the spread of the etching end (x = c), whereas in the example, the relative depth increases until the annular groove 4 penetrates, but the position c = 20 μm. The annular groove 4 penetrates. As a result, a part of the unnecessary mask portion is removed, φ is expanded to 30 μm, and the relative depth is reduced from 2 to 0.7. Thereafter, as the etching progresses, the relative depth increases. However, in Comparative Example 11, the relative depth is 2 or less in the etching diameter R (R = φ + 2x) range up to 50 μm. It becomes up to 130μm and spreads more than twice. In addition, the result of shaking t and p was graphed. For example, if P = 20 μm, both the spread of φ and the reduction width of the relative depth are increased to 50 μm and 0.4, respectively. When T = 10 nm, since the penetration is quick, an increase in the relative depth at the initial stage of etching is reduced. For example, when the annular groove portion 4 is provided at a position of 20 μm, it is necessary to at least make the thickness 20 to 40 nm in order to make the relative depth 1-2.

FIG. 6 is a diagram showing the mask layer and the state of etching in Example 1 and the comparative example. FIG. 6A shows a comparative example, and FIG.
In the comparative example of FIG. 6A, a polycrystalline silicon film 1 having a thickness of 400 nm was formed on a quartz glass substrate 2. A photoresist layer was formed on the polycrystalline silicon film 1 and an opening with an opening diameter φ = 10 μm was formed in the photoresist using the mask A (FIG. 2A). Openings 3 were formed in the polycrystalline silicon film 1 by dry etching (FIGS. 6A to 6A).
After the above steps, in Example 1 of FIG. 6B, a photoresist layer is further formed thereon, mask B (FIG. 2B) is used for alignment, and openings 3 are formed in the photoresist. An annular opening was formed concentrically around the center. An annular groove 4 was formed in the polycrystalline silicon film 1 by dry etching (FIGS. 6B to 6A). At this time, the position p of the annular groove portion was set to 10 μm, the thickness t was set to 20 nm, and the groove width was set to 1 μm.
Wet etching was performed on the mask. A hydrofluoric acid aqueous solution was used as an etching solution. When the selectivity α was about 10 ³ and the etching factor ε was about 1 and the depth was etched by 20 μm, the mask layer was etched by 20 nm, the annular groove 4 penetrated and the opening expanded to 30 μm. Thereafter, etching was continued to obtain a recess having a depth of 60 μm and a diameter of 130 μm. There is no need to provide a step of removing the unnecessary mask portion.

FIG. 7A is a diagram showing the mask layer according to the second embodiment and the state of etching, and FIG. 7B is a diagram showing the mask layer according to the third embodiment and the state of etching.
In FIG. 7A, the annular groove 4 is provided on the outer periphery from the first embodiment. The position p = 20 μm. In FIG. 7 (B), the annular groove parts 4 and 4a were provided in two places, and the thickness of the bottom part was thickened to the outer periphery. At this time, the annular groove width 4a was narrowed toward the outer periphery, so that the thickness was increased toward the outer periphery due to the micro loading effect.

The shape of the comparative example and the example was observed. Using an electron microscope, the surface state on the surface side where the concave portion was provided was observed and evaluated according to the following four criteria.
A: The concave surface has a spherical shape, and no unintentional irregularities due to variations in the etching rate at each part are observed.
A: Almost no unintentional irregularities due to variations in etching rate at each part are observed.
(Triangle | delta): Existence of the unintentional unevenness | corrugation by the dispersion | variation in the etching rate in each site | part is recognized.
X: The presence of unintentional irregularities due to variations in the etching rate at each part is remarkably required.

As a result of the observation, the following results were obtained, and it was found that a desired shape was easily obtained in the examples.
Example 1
Example 2 ○
Example 3
Comparative example ×
This is because the provision of the annular groove around the opening removes part or all of the unnecessary portion of the mask during the etching, thereby reducing the increase in relative depth as the etching progresses. This is probably because a uniform concentration distribution was generated and the influence of a product (by-product) that was hardly soluble in water could be suppressed.
Moreover, in each Example, the removal process of a mask unnecessary part is not provided, but it is thought that it is a result which shows the possibility of productivity improvement.

DESCRIPTION OF SYMBOLS 1 Polycrystalline silicon film, 2 board | substrate, 3 opening, 4 annular groove part, 5 cavity, 6 mask unnecessary part, 8 mask A opening, 9 groove part opening, 10 graph of relative depth 2, 11 comparative example graph, 12 relative depth 1 graph, 13 to 16 Example graph, 30 substrate, 31 cavity, 32 mask unnecessary portion, 33 mask layer, 34 opening

Japanese Patent Laid-Open No. 2007-175813 JP 2008-058836 A

Claims (3)

A substrate processing method for forming a concave curved surface on a substrate by etching,
Preparing a first mask having a circular opening of a circular pattern and a second mask having an annular opening having a large diameter and concentric with the circular opening of the first mask;
A polycrystalline silicon film is formed on the substrate surface, a photoresist layer is formed on the polycrystalline silicon film, and an opening corresponding to the circular opening is formed in the photoresist layer using the first mask. A first step of forming an opening in the polycrystalline silicon film by performing etching after forming;
A photoresist layer is again formed on the polycrystalline silicon film in which the opening is formed, and etching is performed after an opening corresponding to the annular opening is formed in the photoresist layer using the second mask. A second step of forming an annular groove corresponding to the annular opening in the polycrystalline silicon film,
A third step of etching the substrate using a polycrystalline silicon film having an opening corresponding to the circular opening and the annular groove formed as a mask;
A substrate processing method characterized by comprising: The opening diameter of the circular opening formed in the polycrystalline silicon film is φ, the selectivity between the substrate and the polycrystalline silicon film in the third step is α, the etching factor is ε, and the upper limit of the relative depth is D When the position x of the annular groove provided around the circular opening and the thickness t of the bottom of the annular groove x ≦ (D / ε) φ
x / α ≦ t ≦ {(D / ε) φ} / α
The substrate processing method according to claim 1, wherein the substrate processing method is set so as to satisfy the above relationship.   2. The substrate processing method according to claim 1, wherein the etching is performed by isotropic etching.

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