JPH04151220A - Forming method for very finely processed core for injection molding - Google Patents

Abstract

PURPOSE:To process the depth and width of a desired channel with a high accuracy by forming a grating pattern composed of a first metal on a metal base, over which a second metal film is laminated, removing said grating pattern and the second metal film on the pattern by means of wet etching and forming a recessed and projected pattern of given depth composed of the second metal on the base. CONSTITUTION:A metal base 1 is coated with a first metal film 23, and then resist 24 is applied over the film to form a desired resist grating, and the first metal 23 is etched using said resist grating as a mask to complete a metal grating. The metal grating is coated with a second metal film 25 which is different from the grating pattern with the film thickness equivalent to the depth of recessed and projected pattern of a product. Then, a first metal mask and the second metal 25 on the mask are peeled off by the liftup method to form a grating pattern composed of the second metal 25. As for peeling liquid to be used at that time, the liquid melting the first metal 23 and provided with resistance to the second metal 25 is fit for the purpose. It is desirable in the above method that a third metal film 22 is applied for coating prior to forming the first metal film 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for making an injection molding core used for producing microfabricated plastic molded articles.

[Prior Art and its Problems] Conventionally, optical parts such as optical diffraction gratings whose surfaces are microfabricated have been manufactured using glass as a material and by the method shown in FIG. 2. That is, first, the organic material 3 is uniformly applied to one side of the base material 1 such as glass to a thickness of about 1 um, and is semi-cured by pre-baking (FIG. 2(a)). A lattice-shaped light shielding mask 5 is placed on the organic layer 3 and exposed to ultraviolet light (FIG. 2(b)). Next, in the case of a positive type organic material, for example, when it is developed with an alkaline developer, non-exposed areas are left (FIG. 2(C)) and a lattice is formed. The grid pattern formed as described above is used as a mask during vacuum deposition.

After that, the vacuum is transferred to a vapor deposition device, the vacuum is evacuated to a predetermined degree of vacuum, and a substance such as 5i027 is vapor-deposited to a predetermined thickness. film thickness) (Fig. 2(d)).

After 5i027 was deposited in the grating grooves 6 as described above, the organic layer 3 was peeled off to form the optical diffraction grating 8 shown in FIG. 2(e). As shown in FIG. 3, this optical diffraction grating 8 is supported inside a ring-shaped housing 9 and is manufactured as a product.

In this way, the method of forming the lattice pattern grooves 6 on the base material 1 through the organic material layer 3 and partially dissolving and removing this organic material layer 3 with a solvent requires manufacturing time, and it is difficult to simplify the manufacturing equipment. It is difficult and likely to be costly, and there are limits to the miniaturization of products.

On the other hand, if the optical diffraction grating could be manufactured by injection molding from synthetic resin, the manufacturing process would be simplified, the cost could be significantly reduced, and the manufacturing equipment would also be simplified.

However, a problem with the injection molding method is that for optical diffraction gratings, it is necessary to create grating grooves with a depth of about 0.3 periods with an accuracy of ±0.01 Yanagi, so injection molding cores that meet this accuracy Is required.

In order to maintain this accuracy, the width of the diamond blade is cut by cutting grooves with a slicer so that the width of the diamond blade is 20 mm.
One method is to set it on willow and cut it while controlling the depth of the lattice grooves.

However, with this method, it is difficult to control the groove depth, there are many variations in the depth dimension, and a considerably large number of tests are required to achieve a tolerance of ±0.0 uay, so it is difficult to say that it is very practical. Further, it cannot be applied to holograms having two-dimensional irregularities.

Therefore, as a method devised by the present inventors, as a method for creating a core having microfabrication, the method is almost the same as the conventional method, that is, the method (a) to (C) in FIG. 2 above.
A fine lattice pattern is formed using a resist, and then the resist surface on which the mask is formed is etched. In other words, the surface other than the mask is removed by etching, and after etching to a certain depth, the resist portion is removed using a resist stripper. death,
There is a method to create the desired injection molding core.

However, in order to etch a metal core, it is necessary to control the power of the etching source, the gas used, the setting method of the substrate, the temperature conditions, etc. In addition, a question arises as to whether the dimensions and accuracy of the manufactured core can satisfy the molding conditions of an actual resin-molded microfabricated product.

Therefore, the present inventors have solved the above problem and developed a method that can accurately process the desired groove depth and width when dry etching the core surface using a fine resist pattern as a mask. Already suggested.

This involves forming a dielectric film or metal film on the surface of the base material with a thickness corresponding to the depth of the uneven pattern, and then
A predetermined resist pattern is formed using an organic resist. Etching is then performed using this resist pattern as a mask. At this time, the resist mask and the deposited film are etched separately, but the end point of etching is the base material or dielectric film (there is selectivity in the solubility of the etching gas or etching solution and the base material and film). It is for this reason.

According to the above process, first, the metal or dielectric substance is formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion blating, etc.) or chemical vapor deposition, and the thickness control of the vapor-deposited film at this time is determined. As is already well known, the accuracy is very good. However, major problems remain when etching the deposited film. This is because when creating a core by finding the two optimal conditions: the coating conditions for forming the deposited film and the etching conditions for etching, if one or both of the conditions change for some reason. The problem is that the desired lattice shape cannot be obtained. For example, when chromium (Cr) is vapor-deposited several times under the same coating conditions, then a resist pattern is formed, and chrome etching is performed, the resist pattern may be difficult to form in some cases, or when forming a mask. However, there is a problem in that side etching occurs during etching, making it impossible to obtain the desired lattice shape. This is because even if a film is formed under constant vapor deposition conditions, it may be difficult to etch or form a mask due to differences in the degree of contamination in the vacuum chamber, slight vapor deposition speed during Cr coating, etc. Therefore, at an experimental level, in some cases, it may be possible to form a lattice on only one or two out of several pieces, which poses a problem in manufacturing cores for mass production.

The present invention has been made in response to the above-mentioned conventional circumstances, and provides a method for creating an injection molding core that can accurately machine the desired groove depth and width using a lift-off method. The purpose is to provide.

[Means for Solving the Problems] The present invention provides a method for producing a microfabricated injection molding core having an uneven pattern on the surface of the base material, in which a lattice pattern made of a first metal is formed on a metal substrate. a step of depositing a second metal film on the lattice pattern with a thickness corresponding to the depth of the uneven pattern; a lattice pattern made of the first metal and a second metal film on the pattern; for injection molding with microfabrication, characterized by comprising the step of removing the second metal by wet etching using a stripping liquid to form an uneven pattern of a predetermined depth made of a second metal on the base material. This is how to create the core.

In the above method, if the third metal film is coated before forming the first metal film, the end point of etching when forming the metal lattice with the first metal film can be accurately set. This is a desirable method because it also prevents the base material from being corroded by the stripping solution during lift-off.

To create a microfabricated core for injection molding according to the present invention, first a metal grid is formed as a mask. The method for forming the metal lattice at this time is to first coat the first metal film. Regarding the film thickness, it is desirable to form the film in a range of 1,000 to 5,000 people. Next, a resist is applied onto the formed first metal film, and exposed and developed at a grating pitch tailored to the purpose to form a resist grating. By etching the first metal using this resist grid as a mask, a metal grid is completed. The etching method may be wet etching or dry etching.

A second metal film, which is different from the grid pattern, is coated on the metal grid with a film thickness corresponding to the depth of the concavo-convex pattern of the product. The method for coating the first metal and the second metal is either physical vapor deposition (vacuum vapor deposition, sputtering, ion blasting, etc.) or chemical vapor deposition.

Next, the first metal mask and the second metal on the mask are removed by a lift-off method to obtain a lattice pattern made of the second metal. Examples of the stripping solution used at this time include an alkaline solution, but any solution may be used as long as it dissolves the first metal and is resistant to the second metal, depending on the type of metal used. It is selected and used as appropriate.

The material for the base material of the metal core for injection molding used in the method of the present invention is preferably one that has iron as its main component, and that is easy to process as a molding core and has satisfactory mechanical strength. You can use all of them.

Further, the first metal may be aluminum, but is not limited thereto.

As will be described later, since the deposition temperature when coating the second metal film is relatively high, it does not function as a mask at this time, melting or peeling, and does not peel off during lift-off. Any substance that can be removed with a liquid can be used.

For the second metal, cr, T;, cu, N +,
Examples include No, W, Ta, etc., but there is no particular limitation on the substance.A substance that is compatible with the base material, does not soak when the first metal is melted and peeled off, and has good durability during molding. You can use all of them.

Furthermore, the material of the third metal used when forming the third metal film prior to the formation of the first metal film is as follows:
Any material can be used as long as it has resistance to the stripping solution used during lift-off and is compatible with the base material. For example, it may be made of the same material as the second metal.

The target groove depth of the concavo-convex pattern lattice is determined by controlling the film thickness when coating the second metal.
This film thickness control is an extremely important factor. To control the film thickness during vapor deposition, as shown in the vacuum vapor deposition apparatus in FIG. Control the desired film thickness. Hey, in the diagram, 1
2 is a gas inlet, 14 is a shutter, 15 is a deposition source, 16
is an exhaust port.

The deposition temperature was set at 350°C because the primary purpose was to improve adhesion.
A temperature of .degree. C. or higher is preferable, and sputtering is preferable to vacuum deposition, and ion blating is preferable to sputtering. This is because, as already reported, the higher the kinetic energy of the vapor-deposited molecules, the more effective the adhesion is.

The resist mask used when forming the lattice made of the first metal is a previously reported resist, and is not particularly limited as long as it does not change or decompose when etching the first metal. As for the pattern formation method, for example, after applying an adhesion enhancer, the resist is made into a uniform thin film using a spin cord, and then prebaked in a super clean oven (resist semi-curing). At this time, the thickness of the resist is preferably in the range of 0.5 to 2.5 nm; if it exceeds 2.5 tiIIt, there will be problems with accuracy due to re-deposition during etching, and if it is less than 0.5111 nm, it will not work as a mask. None of these are preferred because they have no effect.

A mask plate (with a grid formed of chromium) cut into the desired microfabricated shape is placed on the resist surface formed as described above, and is irradiated with ultraviolet rays. As for the type of resist, this ultraviolet irradiation produces alkaline LS.
There are two types of resist: a positive resist, in which the irradiated portions of the resist are removed using an I developer, and a negative resist, in which the exposed portions are hardened and left behind, and it is best to use one depending on the grid formation conditions. Next, post-bake (resist complete hardening) is performed in a clean oven to make it ready for etching.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings. Note that in this example, the target lattice groove has a width of 2
A metal core with a thickness of 0.3 μm and a depth of 0.3 μm and mainly composed of iron was manufactured, and the formability of the optical diffraction grating was investigated. In addition, as a comparative experiment, we also investigated the molding strength of a core manufactured using a lift-off method using resist.

Example 1 Figure 1 shows an example of the method of the present invention in the order of steps.
The present embodiment will be explained based on the figure.

The surface of the metal base material 1 was cleaned with alcohol and set in a vacuum chamber. The vapor deposition method at this time is a vacuum vapor deposition method. Set the base material 1 at 400℃, and after exhausting, 2x
After confirming the degree of vacuum to lO-5 Torr, chromium (Cr) 22 was deposited to a film thickness of 150 mm.

After the base material was cooled, it was taken out after introducing into the atmosphere. Then,
Introduced into the vacuum chamber again, set the substrate at 100°C, evacuated, and confirmed the degree of vacuum to 2 x 10-5 Torr.
Aluminum (Ai>23) was deposited.At this time, AI!
The film thickness is 1500A. After the base material was cooled to near room temperature, it was taken out after being introduced into the atmosphere. A cross-sectional view of the base material formed as described above is shown in FIG. 1(a).

Next, as shown in FIG. 1(b), a resist 24 having a predetermined pattern is applied! 23.

Thereafter, the base material on which the resist pattern has been formed is placed in an etching bath and subjected to wet etching to form an aluminum grid as shown in FIG. 1(C). After wet etching is completed,
The resist pattern is peeled off and transported to a vacuum deposition tank for the first
Set the coated surface on the vapor deposition source side as shown in Figure (d).

Next, the substrate temperature was set to 400°C, and 2×1O-5
Evacuate to Torr, and as shown in Figure 1(e), Cr
25 is deposited to the desired depth. In Honjitsu Zetsubaku, it was set at 3,000 people (0.3 Korea). After cooling the base material, air was introduced into the base material and the base material was taken out.

Next, A123 was peeled off to produce an injection molding core as shown in FIG. 1(f).

Comparative Example 1 The surface of a metal base material was cleaned with alcohol, and 150 people vapor-deposited base Cr in the same manner as in Example 1.

Next, a resist is formed on the Cr in a predetermined pattern.

The resist pattern surface was set on the vapor deposition source side, the substrate temperature was set at 100° C., and the vacuum was evacuated to 2×10 −5 Torr.

Next, in this comparative example, 3000 coats were applied to the desired CR thickness (lattice depth). After introducing the atmosphere, take it out,
The resist was peeled off to obtain a core similar to that shown in FIG. 1(f).

Next, the cores obtained in Examples and Comparative Examples were installed in an injection molding machine, and their moldability and lattice strength were examined. For moldability, four samples were made for each number of moldings using the cores obtained from each piece, and those with moldability abnormalities in all four were evaluated as ×, and those with no abnormality in all four were evaluated. ○
And so. In addition, the lattice strength was determined by checking the lattice condition of the core under a microscope after each molding cycle to check for peeling of the lattice.

When lattice peeling was observed, it was rated as X, and when no peeling was observed, it was rated as 0. The results are shown in Table-1.

Table 1 In the lattice produced in Comparative Example 1, since the base material temperature during Cr deposition was low, the lattice peeled off as the number of moldings increased.

In particular, about 50% of the lattice was removed when molding was performed ioooo times. No abnormality was observed in Example 1.

[Effects of the Invention] As explained above, according to the method for producing an optical diffraction grating core for injection molding of the present invention, the desired groove depth and width can be formed with high precision, and the core has excellent shape and moldability. and
Furthermore, compared to optical diffraction gratings manufactured using conventional methods, the manufacturing time can be greatly shortened and manufacturing equipment can be simplified.

[Brief explanation of drawings]

FIG. 1 is a process diagram of an embodiment of the method of the present invention, FIG. 2 is a process diagram of an example of a conventional method for producing an optical diffraction grating, and FIG.
The figure is a sectional view showing a conventional method of supporting an optical diffraction grating during commercialization, and FIG. 4 is a schematic diagram of a vacuum evaporation apparatus used in an example of the method of the present invention. 1.11... Base material 3... Organic layer 5.
... Lattice pattern mask 6 ... Lattice groove 7 ... 31
02 8... Optical diffraction grating 9... Housing 10... Chamber 12... Gas inlet 13... Crystal resonator monitor 15... Evaporation source 22, 25-(:, r 24...・Resist pattern 14...Shutter 16...Exhaust port 23...8β

Claims (2)

[Claims] (1) A method for producing a microfabricated injection molding core having an uneven pattern on the surface of the base material, which includes the step of forming a lattice pattern made of a first metal on a metal base material, and the step of forming a lattice pattern made of a first metal on the lattice pattern. Depositing a second metal film with a thickness corresponding to the depth of the uneven pattern, and wet etching the lattice pattern made of the first metal and the second metal film on the pattern using a stripping solution. 1. A method for producing a microfabricated injection molding core, comprising the step of removing and forming an uneven pattern of a predetermined depth made of a second metal on a base material. (2) The microfabrication method according to claim 1, further comprising the step of forming a third metal film resistant to a stripping liquid on the entire surface of the base material prior to forming the lattice pattern made of the first metal. How to make a core for injection molding.