JPH01138638A - Production of information recording medium - Google Patents

Abstract

PURPOSE:To increase crystallization temp. and to improve the life of a recording film by specifying a film forming speed at the same relative flow rate of gaseous hydrocarbon in the case of forming the recording film by sputtering in an atmosphere of the gaseous hydrocarbon and inert gas. CONSTITUTION:After the inside of a vacuum chamber 1 is evacuated, gaseous Ar and gaseous CH4 are introduced into the chamber and electric power is supplied from a power supply 5 to a Te target 6 to form the optical recording film 9 which is a Te-C film on a substrate 8. The crystallization temp. can be increased by lowering the film forming speed even if the Q value of the relative flow rate of the gaseous CH4 is the same. The film forming speed by sputtering is, therefore, controlled to <=700Angstrom /min under the same flow rates of the gaseous CH4 and gaseous Ar at Q=(X/(X+Y))X100% where the flow rates of said gases are designated as X, Y. The crystallization temp. is thereby increased as high as possible while the degradation in the recording sensitivity and sputtering efficiency is prevented. The longer life of the recording film is thus obtd.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for manufacturing an information recording medium.

(Prior art) When sputter discharge is performed using Te as a target in an atmosphere of hydrocarbon gas (e.g., CH4 gas) and inert gas (e.g., Ar gas), a film containing Te, C, and H is obtained on the substrate. (hereinafter referred to as "rTe-C film"). Te-C
The film absorbs laser light and generates heat, melting and forming bits (holes).
is formed (M, Mashlta and N,
Yasuda.

Proceedings of' SP IE, 42
0. (1982)).

Therefore, digital information can be recorded with or without pits. On the other hand, to read information from the recording film, it is common to use reflection of laser light, but of course transmitted light may also be used. In any case, when the recording film is irradiated with continuously oscillated laser light, the light may be modulated by the depth of the pits.

Now, by changing the flow rate ratio of hydrocarbon gas and inert gas, the Te-C film obtained by the above method can be either amorphous, crystalline, or partially containing microcrystals, but maintaining an amorphous state as a whole. Can be done. That is, the flow rate of hydrocarbon gas is X1, the flow rate of inert gas is Y,
Q-fX/(X+Y)l If X100%, the state of the formed film strongly depends on the Q value.

By appropriately adjusting Q, it is possible to obtain an amorphous film with no diffraction intensity from a specific angle when examined by X-ray diffraction. At this time, in the Te-C film, Te clusters are mixed with C and H components, and insulating C and H components are mixed between the Te clusters. The Te-C film is
If the fine Te clusters do not aggregate, the amorphous state can be maintained. It is the C and H components that prevent the aggregation.

When having such a structure, the Te-C film is less likely to be oxidized than a single Te film even under high temperature and high humidity (65° C.-90%). This is because the Te film has no barrier against Te oxidation, whereas the Te--C film has C and H acting as a barrier to prevent Te oxidation.

When the reflectance of the recording film decreases due to oxidation, the S/N ratio deteriorates. Furthermore, unless it is completely oxidized, the oxide is transparent to laser beams with wavelengths in the infrared and near-infrared regions, so the film becomes a film with no reflectance, making it impossible to read information at all.

The same applies to writing information. If it is oxidized, the absorption rate will decrease, causing difficulties in writing. Oxidation is therefore unfavorable for both writing and reading information.

However, if Te is aggregated in the Te--C film, the oxidation rate will be about the same as that of the Te film. Therefore, maintaining the amorphous state of the Te--C film for as long as possible will maintain the information retention time as an optical recording film. Therefore, even if the temperature of the recording film increases during use, Te
There has been a desire for a film formation method in which the crystallization temperature of the -C film is made as high as possible.

(Problems to be Solved by the Invention) Conventionally, under the same film formation rate, there is a relationship between the Q value and the crystallization temperature as shown in Figure 2, so the crystallization temperature of the recording film is raised. Furthermore, in order to improve the oxidation resistance of Te, the Q value (relative ff1 of hydrocarbon gas) was increased.

However, in this case, the optical recording sensitivity decreases, so it has not been possible to simultaneously prevent the crystallization of the recording film and maintain the recording sensitivity. Also, when the Q value becomes high, that is, when the flow rate of hydrocarbon gas becomes higher than that of inert gas,
Another drawback is that carbon can be deposited on the sputter target, impairing its sputtering efficiency, as shown in FIG. In the figure, the film formation rate is normalized by setting the film thickness after the first sputtering to 1.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides an information record containing carbon, hydrogen, and any one of metals, semimetals, or semiconductors, or alloys thereof. In a method for manufacturing an information recording medium in which a film is formed by sputtering in an atmosphere of hydrocarbon gas and inert gas, where the flow rate of hydrocarbon gas is X and the flow rate of inert gas is Y, Q-(X/ (X+Y)l xl
The sputtering film formation rate was 700 people/min under the same OO%.
A method for manufacturing an information recording medium is provided, which is characterized by the following features.

(Function) In the present invention, the crystallization temperature can be increased by slowing down the relationship between the Q value and the crystallization temperature. That is, Q
It is possible to increase the crystallization temperature and extend the life of the recording film while avoiding the drawbacks of decreased recording sensitivity and sputtering efficiency when the value increases.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

In the vacuum film forming apparatus shown in Fig. 1, the low vacuum valve 2
The vacuum chamber 1 was opened and the oil rotary pump 3 was used to roughly pump the inside of the vacuum chamber 1 from atmospheric pressure to 0.2 Torr. Next, after closing the valve 2, the high vacuum main valve 12 is opened, and the inside of the chamber 1 is pumped 5 x 10' using the cryopump 4.
Exhaust to Torr.

Next, IOSCCM of Ar gas and cH4 gas are introduced into the chamber 1 from the Ar gas introduction line 10 and the cH4 gas introduction line 11 through the respective mass flow controllers 20 and 21.

At this time, the main valve 12 is controlled so that the total gas pressure is 5
X 10' Torr. An ion gauge (not shown) is used to monitor whether the pressure inside the chamber 1 is maintained at this pressure for at least one minute. Once the pressure is stabilized, power of 100 W is supplied from the power supply 5 to the Te target 6.

Discharge is performed for 30 seconds with the shutter 13 on the target 6 closed, and when it is confirmed that the discharge state is stable (no flaking of the voltage and current value needles attached to the power supply 5), the shutter 13 is opened. A rotator 7 to which a previously cleaned polycarbonate (PC) substrate 8 is attached is rotated at 20 rpts to form an optical recording film 9 on the substrate.

The substrate may be polymethyl methacrylate (PMMA), polyolefin (PO), or glass as long as it is made of a transparent material that does not absorb at the wavelength of the laser used for optical recording. When used as an optical disc, a substrate on which guide grooves (pre-groups) are formed in advance may be used.

Now, the thickness of the film formed by sputtering is 200 to 300,
Film deposition rate is 250, 500, 700 and 1000 people/a
+1n. When the desired film thickness is reached, the shutter 13 is closed again. Next, the supply of electric power from the power supply 5 is stopped, the gas rotor 7 is stopped, and then the valves of the gas introduction lines 10 and 11 are closed. Next, the main valve 12 is fully opened to exhaust the air to 5 x 10' Torr.

Next, the valve 24 of the leak line 14 is opened, and N2 gas that has passed through a filter (not shown) is introduced into the chamber 1. After the pressure is returned to atmospheric pressure, the completed information recording medium 30 is taken out.

FIG. 2 shows the relationship between the Q value and the crystallization temperature of the Te--C film. At Q-20%, the crystallization temperature of the recording film at a deposition rate of 500 people/ff1in is 111°C, but when the deposition rate is reduced to 25%
When slowing down to 0 person/akin, the crystallization temperature rises to 126°C.

Considering the case of unidirectional crystallization temperature, Q-20%,
Crystallization temperature 126° at a deposition rate of 250 people/min
It can be seen that C is equivalent to that at a deposition rate of Q-35% and a deposition rate of 500 people/mln. This is CH4
This corresponds to reducing the flow rate by about 15% to obtain the same crystallization temperature.

By the way, at a deposition rate of 1000 people/min, Q-20
%, the crystallization temperature is 100°C or less. However, since the heat resistant temperature of the organic substrate normally used is around 80° C., the crystallization temperature of the recording film itself needs to be as high as possible.

As a guideline, a temperature of 100℃ or higher is desirable, so 700 people/
A film formation rate of mln or less is effective.

FIG. 3 shows the write characteristics of recording films formed under conditions of -20, 50 and 100%. Writing is at wavelength 830
The pulse width is 60n5e by a nm semiconductor laser.
I went as c. Further, writing and reading were performed by rotating a 1.2U thick PC board with a guide groove at 185 rpm.

Looking at this, Q-20% has the highest recording sensitivity, and as the Q value increases, the sensitivity at the writing threshold decreases.

In this figure, the degree of modulation is given by the B/A value in the reproduced waveform illustrated in FIG.

FIG. 5 shows the results of an accelerated life test under high temperature conditions (65° C.-90%). Information bit error rate (BER, BitE error rate) is used as a change measurement item.
) was selected and the change in BER over time was investigated.

When oxidation progresses, even locally, the area around the pits or the recording film becomes transparent. This may cause distortion of the reproduced waveform, or areas that are not originally pits may be detected as pits, causing BE
Bring about a change in R. Therefore, the change in BER is considered to be due to oxidation of the recording film, and in the case of a Te--C film, the aggregation of Te clusters and progress of crystallization as described above.

Looking at this, the Q-20 mentioned above had the best recording sensitivity.
%, when comparing recording films with a film formation rate of 1000.700.500 and 250 people/win, the recording film with a film formation rate of 250 Å/min has the smallest change in BER. In other words, it can be seen that the slower the film formation rate, the longer the life.

Note that the present invention is not limited to the above embodiments. In addition to Te, Se is used as a metal in the recording film.

B15Ges Sb, Sns In,, S% AS%
Pb or Ag can be used. This is because a recording film made of these metals has sufficient writing sensitivity even with a semiconductor laser of low output, and is therefore suitable for a consumer information recording medium such as the present invention.

Further, in the above embodiment, CH4 gas was used as the hydrocarbon gas, but other alkane gases such as C2H6 and C3HB, alkene gases such as C2H4, and alkyne gases such as C2H2 may be used to form a Te-C film in the same way. can be formed.

[Effects of the Invention] As described above, according to the present invention, it is possible to increase the crystallization temperature and extend the life of the recording film while preventing a decrease in recording sensitivity and sputtering efficiency.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a vacuum film forming apparatus according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between Q value and crystallization temperature, and Fig. 3 is a graph showing recording sensitivity for each Q value. 4 is a graph of the reproduced waveform, FIG. 5 is a graph showing the accelerated lifetime for each film deposition rate, and FIG. 6 is a graph showing the change in the sputtering film deposition rate for each Q value. 1... Vacuum chamber, 8... PCU board, 9... Te-C film, 10... Ar gas introduction line, 11...・CH4 gas introduction line. Applicant's agent Patent attorney Takehiko Suzue Figure 1 0 20 40 60 80
Figure 3

Claims (6)

[Claims] (1) A method for manufacturing an information recording medium in which an information recording film containing carbon, hydrogen, and any one of metals, semimetals, or semiconductors, or alloys thereof is formed by sputtering in an atmosphere of hydrocarbon gas and inert gas. In, when the flow rate of hydrocarbon gas is X and the flow rate of inert gas is Y, Q={X/
A method for manufacturing an information recording medium, characterized in that the sputtering film formation rate is 700 Å/min or less under the same condition of (X+Y)}×100%. (2) The metal, semimetal or semiconductor is Te, Se, G
The method according to claim 1, wherein the material is e, Bi, Sb, In, Ag, S, As or Pb. (3) The method according to claim 1, wherein the hydrocarbon gas is an alkane gas, an alkene gas, or an alkyne gas. (4) The method according to claim 1, wherein the information recording film is an amorphous film having a crystallization temperature or an amorphous film partially containing microcrystals. (5) The method according to claim 4, wherein the crystallization temperature is 50°C or more and 400°C or less. (6) The method according to claim 1, wherein the Q is 10% or more.