JPS63230889A - Production of substrate - Google Patents

Abstract

PURPOSE:To flatten the bottoms of grooves having different depths on a substrate by exposing a photosensitive resin layer on plural coating layers formed on the substrate, removing the resulting latent image and selectively etching the coating layers. CONSTITUTION:A coating layer 11 of aluminum oxide, a coating layer 12 of silicon oxide and a coating layer 13 of silicon nitride are successively formed on a glass substrate 10. The substrate 10 is dried and exposed to an atmosphere contg. an adhesion improver. A photosensitive resin layer 14 as a positive type resist layer is formed on the whole surface of the layer 13 by spin coating, dried and exposed to form latent image 16 having different depths in accordance with the intensity of light for exposure. The guide or pit parts are then dissolved by development to form a photosensitive resin film 17 having partially different thicknesses. The film 17 is baked and reactive ion etching is carried out in three stages with CF4+25%N2, CF4+40%N2 and CF4+25%N2 to form a groove 18a of a desired depth in the layers 13, 12 and groove 18b of a desired depth in the layer 13.

Description

[Detailed Description of the Invention] [-5! ! OBJECT OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of manufacturing a substrate particularly suitable for manufacturing a recording substrate such as an optical disk or a magneto-optical disk.

(Prior Art) Generally, recording media such as optical discs and magneto-optical discs use substrates on which spiral or concentric groove patterns are formed. The substrate 4 is made of plastic such as polycarbonate, acrylic, or epoxy, and is molded together with the groove-like pattern. This substrate is a support base for the recording medium, and has a function of transmitting light beams for recording and reading. In addition, the groove-like pattern formed on the substrate is a guide groove for optical servo (
It has the function of a guide groove (hereinafter referred to as a guide groove).

However, as described above, substrates made of plastics have problems in reliability as recording media.

In other words, the above-mentioned materials often undergo deformation, deterioration, etc., and are not reliable over the long term. Therefore, the use of glass as the material for the above-mentioned substrate is attracting attention as a means to solve such reliability problems. However, there are multiple steps to form guide grooves for optical servo on glass.

For this reason, when glass is used as the substrate material, the guide grooves are formed by the Fossipolymer method using an ultraviolet curing resin. However, the use of resin essentially results in a loss of reliability.

However, in recent years, with advances in etching technology, it is no longer necessarily possible to directly form guide grooves on a glass substrate, which has been extremely difficult in the past. In particular, dry etching is effective. An example of a method for forming guide grooves on a glass substrate by such dry etching is shown in FIG. First, 15 sheets of cleaned glass■
'' - is spin-coated with a positive resist ■ (see figure (a)).

Next, by light exposure method, width 0.5-1-, pitch 1-21
! Record the spiral guide groove of I & (b) in the same figure.
Then, using the remaining resist as a mask, dry etching is performed in a reactive gas (e.g., CHF) to a depth of approximately 0.5 to 1 - ω on the glass substrate. Etch the top ((d) in the same figure).

Thereafter, the resist that is no longer needed is removed by ashing with oxygen plasma (FIG. 4(e)).

On the other hand, in recent years, with the increase in information density and packaging, it has become necessary to form more complex grooves. That is, in addition to the above-mentioned guide grooves, it has become necessary to form bits for various formats. In this case, the guide groove is formed in a spiral or concentric shape with a depth λ: wavelength of the readout light source, n: refractive index of the substrate), and the bits for formatting 1 address, sector, synchronization signal, etc. have a depth λ/ 4n is formed in or between the guide grooves.

Incidentally, the formation of such guide grooves and bits of different depths on the same substrate has conventionally been carried out using plastic as the material of the substrate and by the method described below. According to this method, a stamper is first formed. In other words, a resist film is applied to a glass substrate with a film thickness of λ/4n, and then a high-precision cutting device is used to cut the resist film using two levels of laser light spots (modulated light source or dual source) using high recording power. Expose. After this, depending on the exposure intensity,
The above-mentioned stamper is formed by forming a guide groove part or a pit part by developing and eluting it, and then subjecting it to electrocution treatment, followed by nickel electroforming plating. Then, using this stamper, a large substrate made of plastic material having guide grooves and bits of different depths is made: jtW! e!
be done.

(Problems to be Solved by the Invention) By the way, as mentioned above, since the substrate formed by the stamper is made of plastic,
As mentioned above, there is a problem in reliability as a recording medium. For this reason, as described above, it is conceivable to use glass as the material of the substrate, but it has been extremely difficult to form guide grooves and pits of different depths on a glass substrate.

In order to solve the above-mentioned problem, the present applicant exposes a photosensitive resin layer in the exposure process with a view corresponding to the depth of the groove to be formed on the substrate, and in the latent image removal process, the depth of the groove is adjusted. However, further tests revealed that magneto-optical disks formed using this substrate tend to have high noise levels in the low frequency range. This is because when etching a substrate to a desired depth, the bottom of the groove is often not flat and has irregularities. To be more specific, in small-scale prototype production, etching conditions can be controlled within narrow limits and smoothing can be achieved;
However, under a mass production system (during mass processing), variations in unevenness within a magneto-optical disk within a lot become noticeable, reducing the noise level.

The present invention has been made in view of the above-mentioned problems, and
It is an object of the present invention to provide a method for manufacturing a substrate that can easily form grooves having sufficiently smooth surfaces on 145 different depths on a JI board with good productivity.

[Structure of the invention]

(Means for Solving the Problems)] In order to achieve the above-mentioned objects, the method for manufacturing a substrate of the present invention includes an etching process for etching a coating layer to a desired depth. It is characterized by comprising a plurality of etching processes in which at least a portion is selectively etched.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In an embodiment of the present invention, a coating layer is formed on a light-transmitting substrate by forming at least two or three layers to an optically desired thickness. The material of this coating layer is selected from a group of substances that make grooves easy to form by mutually having difficulty and ease of etching under certain conditions in the etching process for forming grooves in the layer.

That is, as shown in FIG. 5(a), on a plate or a certain deposited coating layer (1), another coating layer (2) is sequentially laminated, and then another coating layer (2) is laminated to finally form a layer. Provide a photosensitive resin layer ■ whose thickness varies depending on the depth of the groove 0 Then, repeat etching three times No. 5 Ij4 (b), (c),
(d) shows the respective etching steps), the grooves are completed. At this time, this etching process follows the following conditions:
That is, in the etching process shown in FIG. 5(b), the coating layer ■
The etching speed of the coating layer 0 is higher than that of the coating layer 0, and the fifth
In the etching process shown in Figure (C), the etching speed of coating layer 0 is
The etching speed is higher than that of the coating layers ■ and ■, as shown in Figure 5(d).
In the etching process shown in FIG.
C), the etching speed is greater than 8. In order to satisfy this condition, for example, the coating layer ■ should be
1. The coating layer 0 was made of Sin, and the coating layer (■) was made of Si and N.

The reactive io-etching method was selected as the etching method for each etching process, and each etching gas contained CF, + 25% N, and
Gas used in b) %CF, +40%ll2 (Fig. 5 (
The gas used in (c)), CF, +25%N (the gas used in FIG. 5(d)) may be selected.

(Function) In the substrate manufacturing method of the present invention, the photosensitive resin layer is exposed in the yl light process with an amount of light that corresponds to the depth of the groove to be formed on the transparent substrate. A latent image corresponding to the depth of the groove is obtained. Therefore, grooves with different depths can be easily formed in the light-transmitting substrate during the etching process. Furthermore, in the present invention, when forming grooves of various depths, it is necessary to select an etching method (etching gas, pressure) that does not etch portions that do not require groove formation or layers located at the bottom of the grooves. This makes it possible to obtain a flat groove shape without producing minute irregularities on the bottom.

(Example) Examples of the present invention will be described below with reference to the drawings.

First, an embodiment of the present invention will be described with reference to No. 1-.

In the 1st v4 (a), the code (10) has an outer diameter of 130 m+
+, a disk-shaped tempered glass substrate (7059°, product name manufactured by Corning Inc.) with an inner diameter of 15 mm and a thickness of 1.2 + s.
It is processed to have a flat surface with a surface roughness of 0.02 or less, and has been thoroughly cleaned. This tempered glass substrate (10)
250 layers of aluminum oxide are formed as a coating layer (11).

Further, 520 layers of silicon oxide are continuously formed as a second covering layer (12) on this 1191 layer (11).

Furthermore, 700 layers of silicon nitride are continuously layered thereon as a third film layer (13).

After thoroughly drying this substrate (10), it is applied with an adhesion improver'svp gas (for example, OAP, a trade name of Tokyo Ohka Co., Ltd.), and the entire surface of the third coating layer (13) is coated with a spin code method. form a photosensitive resin layer (14) (λth
(Figure (b)), this photosensitive resin layer (14) is made of a positive resist (for example, OFI'R-800 (Tokyo Ohka Co., Ltd.)).
Co., Ltd. product name), etc.), negative resists (for example, LMR
16 (trade name of F6 Shiyakuhin Co., Ltd.), etc., but in this example, an example using a positive resist is shown. 0FP which is a positive resist as resin J11 (14)
R-800 (Tokyo Ohka Co., Ltd. Ws commercial name) Wo350
It was formed to a thickness of 0 people (7).

Thereafter, the photosensitive resin N (14) is dried at 90° C. for 30 minutes by a conventional method.

Then, using a high-precision cutting device similar to that used in the conventional standby production process for plastic substrates, a disc is cut using two levels of argon laser minute light spots (-modulated light source or dual light source) using high recording power. Expose while rotating.

Then, a latent image (16
) is formed, and then, depending on the exposure intensity, the guide groove portion or the bit portion is developed and eluted to form a photosensitive resin film (17) having partially different thicknesses.

After this, baking was performed at 130°C for 30 minutes, followed by parallel plate reactive ion etching! A groove is formed in the third coating layer to a desired depth by plasma etching, which generates plasma by introducing a gas containing CF and 25% N2 into a chamber of 4f (not shown). A coating layer thickness of 3) is formed.

(Fig. (6)) In the same chamber, a gas mixture of CF4 and 40% N was introduced to generate plasma, and grooves were formed in the second coating layer. Then, when etching is performed under the same conditions as No. 1Ii'11, a guide groove (18a) with a depth of λ/8n and a depth of λ/4 are formed.
bits (18b) of n (in this case, λ=830npeng,
A substrate having n=1.46) is formed.

(Fig. (g)) In other words, this board (10) has a spiral guide groove (18a) with a radius of 0.8 mm and a pitch of 1.6 mm and a width of 0.8 mm and a depth of 700 mm. formed to a depth of 1220 mm in places.
A preformat information bit (18b) is formed.

A recording layer and a reflective layer are laminated on the base Fi(10) thus obtained to form a recording medium. FIG. 2 is a diagram for explaining this. As shown in the figure, first, Tb, Fe,
250 Go ternary alloy layers are formed as recording layers (31). For this purpose, Tb,
Fe, Co ternary alloy target (composition Tb25a
t%, Fe65.5a t%, Co 9.5a t
%) is sputtered with Ar gas. Then, 350 AQNs are formed as an interference layer 32 on top of this. For this purpose, use AQ Tuttar and change the sputtering gas to 30%N.
A magnetron sputtering method using an Ar mixed gas containing . Further, 500 reflective layers (33) made of AQ are formed on the interference layer (32) by magnetron sputtering to form a magneto-optical recording medium (34).

With the above configuration, the recording layer (31) becomes a magnetic recording layer having an axis of easy magnetization in a direction perpendicular to the layer surface. Glass substrate (10)
(Irradiate laser light from 11 to heat one local area.

Based on the principle, the apparent (i'j
A recording medium with good characteristics, which has increased signal strength and significantly improved signal-to-noise level (S/N ratio), can be produced.

Thus, according to this embodiment, flat guide grooves with different depths and preformat bits can be formed on the entire surface of glass, translucent ceramics, etc. in the same process, resulting in high reliability. A method for manufacturing a recording medium will be explained.

In FIG. 3(a), the symbol (20) has an outer diameter of 130 m.

It is a disc-shaped alkali-free glass substrate (Nmu 40. trade name of HOYA Co., Ltd. II) with an internal fi of 15 and a thickness of 1.2. processed,
and has been thoroughly cleaned. On this substrate, 520 layers of silicon oxide are formed as a first covering layer (21) by high wave magnetron sputtering. Further on top of that, a second covering layer (22) of silicon nitride with a thickness of 70% is applied.
0 people piled up.

After sufficiently drying this substrate (20), it is placed in an atmosphere of an adhesion improver (for example, OAP: Tokyo Ohka Co., Ltd. 11! trade name), and the entire surface of the second coating W (22) is coated with a normal coating using a spin code method. Forming a photosensitive resin layer (23) (third
(Figure (b)), this photosensitive resin layer (23) is a positive resist (for example, 0FPR-800 Tokyo Ohka Co., Ltd. I).
), negative resists (such as Fuji Yakuhin (trade name)
fB Co., Ltd. LMR16 (trade name) may be used, but in this example, an example using a positive resist is shown. In other words, according to this example, this photosensitive resin layer (23) 0FPR-800 is a positive resist.
(trade name of Tokyo Ohka Co., Ltd. !l!) was formed to a thickness of 3,500 people.

Thereafter, the photosensitive resin m12 is dried at 90° C. for 30 minutes by a conventional method.

Then, patterns (24a) of chrome (usually black in color) with different film thicknesses depending on the guide grooves of different depths and pits for preformat information to be formed on the covering layers (21) (22). The photosensitive resin M (2
3) to form a latent image (25) (Fig. f53 (c)).

For this exposure, contact exposure (allanite: PLA-521F; trade name, manufactured by Canon Inc.) using ultraviolet light as a light source was used.

Next, by developing with a special developer (NMD-3; trade name manufactured by Tokyo Ohka Co., Ltd.) and washing, the portion that has become a latent image is removed. That is, depending on the density of the latent image, in other words, depending on the amount of light transmitted through the exposure mask (24), the photosensitive resin layer (23
) is formed with a pattern (26) of holes, e.g., through holes or recesses (FIG. 3(d)); this pattern (15)
Since a latent image is formed in a short exposure time of about 1 second, a higher throughput is guaranteed compared to cutting using a rotary force t using a laser beam used in one embodiment.

After that, baking was performed at 130°C for 30 minutes.

Next, in a chamber of a parallel plate type reactive ion etching device (not shown), grooves are formed in the second coating layer by plasma etching, in which a gas containing 25% N added to CF4 is introduced to generate plasma. is the desired depth λ/8n: f5
2 coating layer thickness) is formed (3rd w4(e))
.

Into the same chamber, a gas containing 40% 1!2 of CF was introduced to generate plasma, and grooves were formed in the first coating layer to a desired depth of λ/4n.
:Thickness of the first and second coating layers) is formed. (Figure 3(f)).

When etching is performed in the same chamber under the same conditions as the first time, the guide groove (27) with a depth of λ/8n and the bit (27b) with a depth of λ/4n (in this case, λ=830n)
m, n = 1.46) is formed. (
Figure 3 (g)).

Thereafter, the remaining photosensitive resin layer (23) is removed and cleaned using oxygen plasma. (3rd +m (h)).

That is, on this substrate (20), a guide groove (27a) #t is formed in a spiral shape with a pitch of 1.6 mm and a width of 0.8 um and a depth of 700 mm in the range of half fi 30a to 60 mm, with a depth of 1 in some places.
220 bits for preformat information (27b)
is formed.

A recording layer and a reflective layer are laminated on the substrate (20) thus obtained to form a recording medium. FIG. 4 is a diagram for explaining this. As shown in the figure, Tb is first deposited on the substrate obtained by the above-mentioned process.

A Fe, Co ternary alloy layer is formed as the recording layer 22 by 250 people. For this purpose, 35% of Si and N4 are deposited as an interference layer (42) on top of this by magnetron sputtering.
A zero-person magnetron sputtering method is used. In addition, A
500 reflective layers (43) made of G were formed to form a magneto-optical IIjt medium (44).

With the above configuration, the recording layer (41) becomes a magnetic recording layer 1 having an axis of easy magnetization in the direction perpendicular to the film surface. Glass substrate (20
) side to heat one local area by irradiating laser light.

Magneto-optical recording and reproduction are performed by detecting reflected light and reading signals due to the magnetic Kerr effect. Based on this principle, the interference layer (42) and reflective layer (43), which increase the Kerr effect of light, increase the apparent signal strength and significantly improve the signal-to-noise level (S/N ratio). A recording medium with good characteristics can be produced.

Thus, according to this embodiment, flat guide grooves with different depths and preformat bits can be formed on the entire surface of glass, translucent ceramics, etc. in the same process, resulting in high reliability. It becomes possible to mass produce substrates for recording media.

〔Effect of the invention〕

As explained above, according to the method for manufacturing a substrate of the present invention, grooves with flat bottoms having different depths can be easily formed on a transparent substrate.

[Brief explanation of drawings]

1(a) to 5151(h) are simplified process diagrams showing one embodiment of the present invention, FIG. 2 is a simplified cross-sectional diagram of a recording medium obtained by one embodiment, and FIG. 3(0) to 5151(h) FIG. 3(h) is a simplified process diagram showing another embodiment of the present invention, FIG. 4 is a simplified cross-sectional diagram of a recording medium obtained by another embodiment, and FIG. 5 is a detailed explanation of the present invention. Simplified process diagram for the process, Figure 3156 (
a) to FIG. 6(a) are simplified process diagrams for explaining a conventional method of manufacturing a recording medium. (10), (20)...Glass substrate (transparent substrate) (11)...Aluminum oxide (third coating layer) (12), (21)...Silicon oxide (second coating layer) Covering layer) (13), (22)...Silicon nitride CM
Upper coating layer) (14), (23)...Photosensitive resin layer (24)...Exposure mask (25)...Latent image agent Patent attorney Noriyuki Noriyuki Chika Norio Ogo Figure 5 Figure 2 Figure 4 Figure 6

Claims (1)

[Scope of Claims] (1) A first step of forming a plurality of coating layers on a substrate; a second step of forming a photosensitive resin layer on the top layer of the plurality of coating layers; A third step of exposing the resin layer to light, a fourth step of removing the latent image on the exposed photosensitive resin layer, and a fifth step of etching the coating layer to a desired depth. The method for manufacturing a substrate comprising: the fifth step comprises a plurality of etching steps for selectively etching at least a portion of the covering layer. (2) The plurality of etching steps include a first etching condition that makes it difficult to etch a second coating layer counted from the top layer of the plurality of coating layers. a second coating layer counted from the top layer of the plurality of coating layers is easily etched, but a third coating layer counted from the top layer and the top layer are easily etched; a second etching step comprising second etching conditions such that etching is difficult; and a third coating layer counting from the top layer of the plurality of coating layers and a second coating layer counting from the top layer. The substrate according to claim 1, further comprising at least a third etching step comprising a third etching condition that is difficult to eat with respect to the third coating layer. Production method. (3) The third step is a step of exposing using a black mask having recesses or holes having a depth corresponding to the desired depth of the grooves to be formed in the plurality of covering layers. A method for manufacturing a substrate according to claim 1. (4) The method of manufacturing a substrate according to claim 1 or 2, wherein the plurality of etching steps are dry etching. (5) The method for manufacturing a substrate according to claim 1, wherein the substrate is a light-transmitting substrate. (6) The method for manufacturing a substrate according to claim 5, wherein the light-transmitting substrate is an inorganic substrate. (7) The method of manufacturing a substrate according to claim 1, wherein the first step is a step of forming a layer made of silicon nitride as the uppermost layer. (8) The method of manufacturing a substrate according to claim 7, wherein in the first step, a layer made of aluminum oxide is formed under the layer made of silicon oxide. (9) In the first etching process, C
3. The method of manufacturing a substrate according to claim 2, wherein the etching step is performed using an etching gas containing F_4 gas as a main component. (10) The second etching step is an etching step using an etching gas mainly composed of CF_4 gas to which H_2 gas is added.
2. Method for manufacturing the substrate described in Section 1. (11) The third etching step is an etching step using an etching gas mainly composed of CF_4 gas to which N_2 gas is added.
2. Method for manufacturing the substrate described in Section 1.