JPH02171290A - Information recording medium - Google Patents

Abstract

PURPOSE:To increase resistance to environments and at the same time, reduce required laser power for recording and deletion by specifying the flow ratio Q of hydrocarbon in an atmosphere of rare gas and hydrocarbon gas with Sb, Te, Ge alloy of specific composition as target, forming a recording layer using sputtering technique, and sandwiching the recording layer with dielectric films. CONSTITUTION:After air is exhausted from a container with pumps 18, 19, argon gas is introduced into the container from a gas line 20 and an SiO2 protecting film 14 is laminated on a substrate using sputtering technique. Next, air is exhausted from the container and CH4 gas is introduced into the container from a gas line 21 with argon gas so that the mixture ratio Q of CH4 gas is 5%<=Q<=35%. Then power is applied, for a specified time, to a sputtering source 24 where (SbTe1-x)y Ge1-y(0.05<=x<=0.7, 0.4<=y<=0.8) alloy is placed, while the substrate 12 is rotated. The amount of sputtered elements from the sputtering source is monitored with a monitoring device 25, and during this monitoring operation, power supply is adjusted. Consequently, a recording layer 13 is formed on the substrate 12. Furthermore, an SiO2 protecting film 14 is laminated on the recording layer 13 to form an information recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an information recording medium in which information is recorded by causing a change in atomic arrangement in a recording film by irradiation with light.

(Prior Art) Information recording media that utilize phase change caused by light beam irradiation have been developed as information recording media that can repeatedly record and erase information.

When recording information on such an information recording medium, first, the entire surface of the recording medium is irradiated with a light beam to bring the recording layer into a highly crystalline state (hereinafter referred to as a crystalline state). Next, in order to record information, the recording layer is irradiated with short, strong pulsed light to heat it and rapidly cool it, thereby bringing the recording layer into a state in which the atomic arrangement is disordered (hereinafter referred to as an amorphous state). When erasing recorded information, the recording layer is irradiated with long, weak pulsed light to heat it and slowly cool it to a crystalline state again. Since optical properties such as reflectance and transmittance change between the crystalline state and the amorphous state due to changes in atomic arrangement, information can be reproduced by detecting changes in these optical properties. ing.

The above-mentioned information recording medium targets Te,
A recording film containing Te and C is formed on a transparent resin such as PMMA or PMC and glass ink in an atmosphere containing hydrocarbons, and 5bTe'Gc is further produced by sputtering in an atmosphere containing hydrocarbons. Sb, Ge,
An information recording medium has been developed that has a recording film containing Te 2 C that has a long life even in a high temperature and humid environment.

(Problems to be Solved by the Invention) However, when forming a recording film containing Sb, Ge, Te, and C as described above by sputtering, the hydrocarbon flow rate g s
When x carbon (shi/k elementary cuff, hydrocarbon gas + rare gas) increases, the C content in the formed recording film increases and the optical absorption rate decreases, so the laser power during recording and erasing increases. This resulted in the problem that it became too large to be put to practical use.

An object of the present invention is to provide an information recording medium that has excellent environmental resistance and requires low laser power for recording and erasing information.

[Structure of the invention] (Means for solving the problem) Information description of the present invention 2. A medium is (SbTc+-8)yG
c l-(0,05≦x≦0.7, 0.4≦y≦0.8
) is used as a target, and the flow rate ratio of hydrocarbons is Q - carbon, 7 to 8, and rare gas + hydrocarbon gas is used as 5%≦Q≦35%, and sputtering is performed. What is the characteristic of the formed recording film?

A sectional view showing the structure of the information recording medium used in the present invention is shown in FIG.

Reference numeral 12 in FIG. 1 is a substrate made of glass or plastic material (for example, polymethyl methacrylate resin or polycarbonate resin), on which a recording layer 13 is formed which undergoes a layer change when irradiated with a light beam on this substrate 17f112. . Further, the recording layer 13 is sandwiched between dielectric films 14 on both sides.

Next, a method for manufacturing the information recording medium will be explained with reference to FIG. FIG. 2 is a side sectional view of a film forming apparatus used in the present invention.

A rotary pump 18 and a cryopump 19 are connected to the vacuum container 17 as exhaust ports, and A gas line 20, CH4 gas line 21, N
2 gas line 22. A support device 23 and a substrate 12 horizontally supported by the support device are provided in the upper part of the vacuum vessel 17.
It can be rotated around the axis. Furthermore, a 5bTeGe alloy is installed as a sputtering source 24 in the middle bottom of the vacuum chamber 17, facing the substrate 12, and a high frequency power source is connected to this sputtering source. Further, a monitor device 25 is installed above the sputter [24].

In order to manufacture an information recording medium having the cross-sectional structure shown in FIG. 1 using this apparatus, first, the rotary pump 18
0.2T of air inside the container.

Evacuate to rr, then 1X with cryopump 19
Evacuate to 10-Torr. Next, argon gas is introduced from the argon gas line 20 to maintain the pressure inside the vacuum container at 5×10 −3 Torr. And M.I.R.
A SiO2 sputtering source is installed, and power is applied. The sputtering of elements from the sputtering source is adjusted by the monitor device 25, and a SiO2 protective film is deposited on the substrate.

Next, the rotary pump 18 pumps the air inside the container to Q.
, evacuated to 2 Torr, and then evacuated to I x 10-5 Torr using the cryopump 19.

Next, argon gas is supplied to CH4 from the argon gas line 20.
CH4 gas is supplied from the gas line 21 at a CH4 mixing ratio Q of 5.
96≦Q≦35%, and the inside of the container is maintained at a predetermined pressure, for example, 5×10 −3 Torr. Then, while rotating the substrate 12, power is applied to the sputtering source 24 for a predetermined period of time. A monitor device 25 monitors elemental sputtering W from the sputtering source, and adjusts the power input to the sputtering source so that the monitored amount becomes a predetermined value. This forms a recording layer on the base E12. The film thickness is set to the specified film thickness (5000A
(below), film formation is stopped. Further, a SiO2 protective film is laminated on the recording film in the same manner as described above to form an information recording medium.

(Function) Since the recording film formed as described above contains C, it has excellent environmental resistance and shows little change in reflectance over time even under high temperature and high humidity conditions.

In addition to glass substrates, organic resin substrates such as PMMA and PMC can be used as substrates because of their particularly excellent oxidation resistance.

Furthermore, since the mixing ratio Q of hydrocarbons flowing in during sputtering is within the range of 5%≦Q≦35%, the a content of C becomes too high as a composition of the recording film to be formed. There is no. Therefore, the optical absorption rate does not decrease, and the laser power required for recording and erasing information can be small.

Also, the thickness of the recording film made of Sb, Gc, Te, C, and H is 1
When 00OA is used, as shown in Figure 3, the reflectance becomes a minimum value due to the multiple interference effect, so if the phase changes from an amorphous state to a crystalline state with this film thickness, the reflectance will increase. It was recognized and information was recorded.

In the information recording medium according to the present invention, since information is reproduced as a reflectance difference around 10 changes, it is advantageous that the reflectance difference before and after recording is generally large in the vicinity of the film thickness that gives an extreme value of interference. This limitation on the recording film thickness according to the present invention is due to the fact that the interference effect decreases as the film thickness increases and converges to a certain reflectance, and the laser power during recording increases as the film thickness increases. 5 from two conditions
000A or less is desirable. More preferably 3
00A to 1000A7><Appropriate. If it is less than 300A, there is a possibility that holes will be formed in the recording film due to laser irradiation.

(Experiment example) 1 Experiment 1- In this experiment, the recording film was formed by sputtering.

First, the rotary pump 18 pumps the air inside the container to zero.
It is evacuated to 2 Torr, and then evacuated to 1X10-'Torr using the cryopump 19. Next, argon gas is introduced from the argon gas rail 20 to maintain the pressure inside the vacuum container at 5×10 −3 Torr. Then, a substrate is installed, a 5io2 sputtering source is installed, and power is applied. The monitoring device 25 adjusts the sputtering amount of elements from the sputtering source, and a 5in2 protective film is laminated on the substrate.

A 5 inch diameter (SbO,
3TeO,7) o,sGcO,2 was provided as a sputtering source, and the inside of the container was 1X1O-6.
To "I exhausted the gusset. Then A" Gaff, 10 S C
Introducing CM and CH4 gas 3SCCM to 5X10-3T
The total pressure was adjusted to orr. Using a thoroughly cleaned disc-shaped caponate substrate with an outer diameter of 130 mm and a plate thickness of 1.2 mm as a substrate, the amount of sputtering was monitored by a monitor while rotating this Ml at 6 Orpm, and the power input to the sputtering source was controlled. A recording layer was formed by depositing each element until the total film thickness was 100 OA.

Further, a 5i02 protective film is laminated on the recording film in the same manner as described above to form an information recording medium.

Using this information recording medium in a recording/reproducing device, the speed of 1800 rp
The recording frequency was 3.7 MHz.

When a laser beam with a recording pulse width of 50 msec was irradiated, a C/N of 30 dB was obtained at a recording power of 7 mW at a location corresponding to a linear velocity of 5.5 m/sec.

-Experiment 2- Here, changes in the atomic arrangement of the recording film due to light beam irradiation were confirmed.

A beam focused to a beam diameter of 1 μm was applied to the recording film formed in Experiment 1.
When pulsed light of mW 15 μs was irradiated, the reflectance of the irradiated area changed (unrecorded area). Next, when pulsed light of 13 mW and 300 ns was applied, it was confirmed that the reflectance of the irradiated area returned to its original value (recording area).

Next, in order to compare the crystalline state of the unrecorded area and the recorded area, the diffraction pattern was observed using a transmission electron microscope.

When the protective layer was peeled off from the sample and the state of the recording layer was observed from a diffraction pattern, a halo pattern characteristic of amorphous materials was observed in the areas not irradiated with laser light. Moreover, in the unrecorded part of the laser beam irradiated part, diffraction rings and spots indicating a crystal structure were observed, and in the recorded part, a halo pattern peculiar to an amorphous substance near the unirradiated part was observed.

-Experiment 3- Here, the change in reflectance over time was fixed at 11!11, and the stability of the recording state was evaluated.

The mixture ratio Q of hydrocarbons is 096. 596. We made 3 types of 35% and 100% in an environment of 65℃ and 9096RH.
After exposure for 0 hours, the ratio (Rt/Rl) between the initial reflectance (R1) and the reflectance over time (Rt) was plotted against the exposure time (FIG. 4).

As can be seen from Figure 4, the reflectance gradually decreases in samples with Sb, Ge, and Te compositions, but with Sb, Ge, Tel:C
It can be seen that the decrease in reflectance over time is slow in the sample to which .

[Effects of the Invention] As detailed above, the present invention exhibits stable characteristics even under high temperature and humidity, has a relatively high optical absorption rate, and requires low laser power to record and erase information. It is possible to provide an information recording medium that can withstand practical use.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the layer structure of the information recording medium used in the present invention, Fig. 2 is a side cross-sectional view of the film forming apparatus, and Fig. 3 shows the correlation between the film thickness and reflectance of the recording film. The graph shown in FIG. 4 is a graph showing the reflectance ratio (Rt/R1) over time. 12...Substrate 13...Recording layer 14...Dielectric layer

Claims (1)

[Claims] In an information recording medium in which information is recorded and erased by causing a change in atomic arrangement in a recording layer by irradiation with a light beam, the recording layer serves as a sputtering source (Sb_xTe_1_-
_x)yGe_1_-_y(0.05≦x≦0.7, 0
．． 4≦y≦0.8), and in a mixed atmosphere of rare gas and hydrocarbon gas, the mixture ratio of hydrocarbons Q (Q = hydrocarbon gas / [hydrocarbon gas + rare gas]) is set. 5%≦Q≦
1. An information recording medium characterized in that the recording film is formed by sputtering at a concentration of 35%, and both sides of the recording film are sandwiched between dielectric layers.