JP2796092B2 - Recording medium film manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a thin-film magnetic recording medium. It is conventionally known that a metal thin film has a higher recording density than a conventional iron oxide suspended in a binder. In order to obtain a high recording density, it is necessary to minimize the film thickness to, for example, less than 1,000 mm. Further, the coercivity Hc must be high enough to maintain a high density of flux reversals per inch. For example, 10,000 to 50,0 per inch
To maintain the integrated density of flux reversal, the coercivity is preferably between 600 and 2,000 (Oe). When the coercivity exceeds 2,000 Oe, it becomes difficult to both read and write data from the film using conventional single element read / write heads. To give a good output signal from the medium, for example, 40
It is necessary to have a high saturation magnetization Ms exceeding 0 emu / cc or preferably exceeding 800 emu / cc. Furthermore, high remanence Mr
And at least 80% hysteresis squareness S (S = Mr / M
s) It is necessary to have The strength of the magnetic field received by the disk read head is proportional to the product of the film thickness T and the remanence Mr. Generally, Mr · T must be greater than about 2 × 10 ⁻³ meu / cm ² to obtain a sufficiently strong output signal from the film. The above parameters are described in JK Howard's "Thin Films for Magnetic Record Technology: Review"
ing Technology: A Review), Journal of Vacuum Science and Technology, 1985. Typical films used for magnetic recording media are Co-Ni, Co
-Contains cobalt alloys such as Pt and Co-Ni-Pt. Many processes have been proposed for controlling the coercivity Hc, saturation magnetic Ms, and remanence Mr of such a film. For example, Opfe
r et al., "Thin-Film M
emory Disc Development), Hewlett-Packard Journal, 1985, states that Co-Pt
It is proposed that the coercivity of the film can be controlled by forming the film. The coercivity of the film depends on the thickness of the chromium underlayer. However, manufacturing processes involving the step of forming a chromium underlayer are relatively complex and expensive. According to Opfer's proposal, the coercivity can be controlled by changing the platinum concentration in the film. However, this suggests that if it is desired to use the same sputter device to form films of different coercivity, it is necessary to change the sputter target, That is generally inconvenient. According to Japanese Patent Application No. 171694/82 of Masahiro Yanagisawa, filed on September 30, 1982, controlling the coercivity of a Co-Pt-Ni film by changing the amount of nickel in the film. Is possible. However, this technique also requires changing the sputter target if it is desired to change the coercivity of the film. H, Maeda, "Correlatino Between the High Coercivit
y and Microstructures of Co-Ni Alloy Films),
The Journal of Applied Physics, 1982, discloses controlling the coercivity of a Co-Ni film by sputtering the film in an atmosphere containing argon and nitrogen. According to Maeda, the coercivity of the film is increased by increasing the nitrogen gas concentration in the sputter chamber to, for example, a concentration of about 24% by volume. However, this reduces the film saturation magnetic Ms. The present invention has been made in view of the above points,
A method of manufacturing a magnetic medium film having a controlled coercivity without affecting the other parameters such as the saturation magnetism and without changing the sputter target, eliminating the disadvantages of the prior art as described above. The purpose is to provide. In one embodiment of the recording medium of the present invention, a thin film recording medium is sputter-formed on a suitable substrate in an atmosphere containing a selected gas trace amount. The medium is typically an alloy containing cobalt and platinum. The coercivity of the medium is controlled by varying the amount of trace of a selected gas in the sputtering chamber during sputtering.
The more traces, the lower the coercivity,
The converse is also true. In one embodiment, a gas mixture having argon and a trace amount of nitrogen is introduced into the sputtering chamber, and the coercivity of the film is controlled by controlling the nitrogen concentration in the gas mixture. The gas mixture is typically less than 1% nitrogen and the coercivity of the resulting film decreases as the nitrogen concentration increases. Unlike the Maeda process described above, in the present invention, the magnetic film is formed using an alloy having a high intrinsic coercivity, for example, a Co-Pt base alloy. (As used herein, the intrinsic coercivity is the coercivity that the film would have if it did not contain nitrogen.) To control the coercivity, the alloy was sputtered to dope the alloy. A trace amount of nitrogen is introduced into the room. In contrast, in the case of Maeda, an alloy film is sputter-formed on a substrate in the presence of a high concentration of nitrogen. At this time, a large amount of nitrogen is introduced into the film to make the film finer. The structure is changed and the film coercivity is increased. In the present invention, film coercivity is reduced (rather than increased) by sputtering in the presence of nitrogen. These results are achieved without changing the film saturation magnetism. Importantly, because the coercivity of the film is controlled without changing the saturation magnetism, the film has a uniform high coercivity squareness and high saturation magnetism over the entire film surface. I have. In addition, the films exhibit high magnetic hysteresis loop squareness, and thus high remanence, so that high signal-to-noise ratios can be obtained from the films. In contrast, Maeda uses a high nitrogen concentration in the sputter chamber, thus reducing the saturation magnetism to a lower value than the saturation magnetism obtained with the present invention. Finally, it should be noted that after sputtering, it is not necessary to anneal the film formed in accordance with the present invention. In contrast, it is necessary to anneal the film formed using the method of Maeda in order to increase the saturation magnetism. According to another embodiment of the present invention, instead of sputtering in the presence of nitrogen (N ₂ ), ammonia (NH
_A gas as in ₃ ) is introduced into the sputtering chamber during sputtering. Sputtering in the presence of such gas traces reduces the film coercivity. According to another embodiment of the present invention, it is possible to control the coercivity of the film by changing the concentration of the trace amount of oxygen gas in the sputtering chamber. Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. Processes or methods according to the present invention include, for example, alloys based on cobalt and platinum, such as Co-Pt, Co-P
Provided is a thin film magnetic medium having an intrinsically high coercivity such as t-Ni, Co-Pt-Cr, Co-Pt-Pd. It is possible to easily change the coercivity of the film without reducing the saturation magnetism of the film and without the need to provide a chromium underlayer. In one embodiment, a film is sputtered on a substrate using an RF or DC magnetron sputtering apparatus. The sputtering is performed in an atmosphere containing argon and nitrogen. The gas pressure in the sputter chamber is typically between 5 and 70 mTorr, while the partial pressure of nitrogen in the sputter chamber is
Between 10 ^-4 and 10 ^-7 torr. Importantly, the concentration of nitrogen in the sputter chamber was determined in accordance with FIGS. 1a, 1b, 2,
And, as shown in the graph of FIG. 3, affects the coercivity of the resulting film. (The concentration of nitrogen in these figures is expressed as% by volume of the gas pressure in the sputter chamber.) The data shown in the graphs in FIGS. 1b, 2 and 3 were plated with NiP. Co on aluminum substrate
-It was obtained by forming an Ni-Pt alloy film to a thickness of about 700 mm by RF sputtering. The data shown in the graph in FIG.1a shows that C was formed on an aluminum substrate plated with NiP.
This was obtained by sputtering an o-Ni-Pt alloy film to a thickness of about 1,400 °. The film coercivity Hc decreases as the film thickness increases. Therefore, the coercivity shown in the graph of FIG. 1a is lower than the coercivity shown in the graph of FIG. 1b. Part of the reason is that the film of FIG. 1a is thicker than the film of FIG. 1b. The coercivity is also different because the film of FIG. 1a is sputter formed at a different pressure than the film of FIG. 1b. The effect of pressure on coercivity will be described below. The data in the graphs of FIGS. 1a and 1b were taken by sputter forming Co ₈₁ Ni ₉ Pt ₁₀ on a substrate at a power of 1.2 kW in argon and nitrogen atmospheres at a pressure of 10 and 20 mTorr, respectively. It is a thing. As can be seen from FIG. 1a, the coercivity of the resulting film increases as the nitrogen concentration in the gas mixture increases from 0% to 0.5%.
Reduced from 50 Oe to 300 Oe. In FIG. 1b, as the nitrogen gas concentration increases from 0% to 0.5%, the film coercivity becomes about 8%.
Reduced from 50 Oe to 220 Oe. Therefore, when forming a film, a selected amount of nitrogen is introduced into the sputtering chamber to reduce the film coercivity to a desired value. For example, it is desired to obtain a coercivity of 650 Oe and the total gas pressure in the sputter chamber is
At 20 mTorr, the gas in the sputter chamber is about 0.3
% Nitrogen and 99.7% argon. Importantly, coercivity is related to the total gas pressure in the sputter chamber. In particular, when the gas pressure is low, the coercivity decreases. (This result is described in, for example, "Corrosion-resistant Co-Pt thin-film medium for high-density recording (Corrosio
3−Resisting Co−Pt Thin Film Medium for High Dens
ity Recording) ", IEEE Transactions on Magnetics, 1983. Thus, the coercivity of the film of FIG. 1b, formed using a higher gas pressure than the pressure used to form the film of FIG. 1a, is also due to the given nitrogen concentration for this reason. On the other hand, it is much higher than the coercivity of the film of FIG. 1a. This effect is also shown in FIG. The data in the graph of FIG. 2 was obtained by sputtering a Co ₈₂ Ni ₉ Pt ₉ alloy on a substrate. The gas pressure in the sputter chamber was 20 mTorr. As can be seen, the coercivity of the film in FIG. 2 increases from about 1,120 Oe to 62% as the nitrogen concentration increases from 0% to 0.8%.
It has decreased to 0 Oe. Figure 3 shows the effect of nitrogen concentration giving the coercivity of _{Co 82 · 3 Ni 9 · 2} Pt 8 · 5 film. The two curves in FIG. 3 show the higher gas pressure (in this case, 40 mTorr)
Indicate that the films sputtered at a lower gas pressure (30 mTorr) have a greater coercivity than the films sputtered at a lower gas pressure (30 mTorr). At 40 mTorr, the coercivity of the film of FIG. 3 increases as the nitrogen concentration increases from 0% to 0.67%.
From 990 Oe to 680 Oe, while at 30 mTorr,
As the nitrogen concentration increases from 0% to 0.67%, the coercivity becomes
It has decreased from 940 Oe to 500 Oe. The intrinsic coercivity of the sputtered film also depends on the percentage of platinum in the film. In particular, films with higher concentrations of platinum generally have higher coercivity. Typical membranes used in accordance with the present invention have greater than 5% platinum on a molar basis. (The film of FIG. 2 has a lower platinum content than the film of FIG. 1b, but the coercivity of the graph in FIG. 2 shows the coercivity in FIG. 1b for a given nitrogen concentration. This is due to various differences in the sputtering equipment used to form the films of Figures 1b and 2. With reference to the present specification, By varying the concentration of the selected gas, in one embodiment, nitrogen, the coercivity of the resulting film is increased by the saturation magnetic Ms.
It will be readily appreciated by those skilled in the art that it can be changed without changing and without having to change the sputter target. FIG. 7 shows Co ₈₁ Ni ₉ Pt sputtered in the presence of different nitrogen concentrations.
_The saturation magnetic Ms for ₁₀ films is shown. The membrane in FIG.
Sputtered at 700 ° and at a pressure of 20 mTorr in the presence of an argon-nitrogen atmosphere. As will be appreciated, the saturation magnetism of the film is about 1,200 emu / cc and is not significantly reduced by the presence of nitrogen within a useful range of nitrogen concentrations (eg, less than 1%). As is well known in the art, the important index numbers used to evaluate a film are the hysteresis loop squareness S and the coercivity squareness S *, as defined below. Ideally, S = S * = 1. Films with high coercivity squareness S * provide good signal-to-noise ratio and good resolution, and films with high hysteresis squareness S provide strong output signals and therefore high signal-to-noise ratio I do. According to what we have learned, the hysteresis loop squareness S and the coercivity squareness S * are significantly improved by sputter forming in the presence of nitrogen. No. 6a
Figures 6b and 6b illustrate the hysteresis loop for a Co ₈₁ Ni ₉ Pt ₁₀ film sputtered to a thickness of 700 ° in the presence and absence of nitrogen, respectively. Without nitrogen, N = 0.67 and S * = 0.76, while in the presence of nitrogen, S = 0.84 and S * = 0.89. Therefore,
The film of FIG. 6a shows good hysteresis squareness and coercivity squareness. In another embodiment of the invention, oxygen is introduced into the sputtering chamber instead of nitrogen during sputtering. To our knowledge, oxygen also reduces the coercivity of the resulting film. The oxygen is typically provided by introducing steam having a partial pressure of less than 10 ^-4 Torr into the sputter chamber. Figure 4 shows Co ₈₁
The effect of oxygen on the coercivity of a 700 mm thick film of Ni ₉ Pt ₁₀ is shown. The film of FIG. 4 was sputtered in an atmosphere having a pressure of about 20 mTorr. The coercivity of the film of FIG. 4 decreases from 950 Oe to Oe as the oxygen concentration increases from 0% to about 0.5%. Therefore, in one embodiment, if it is desired to form a film with a coercivity of 650 Oe, a 700 膜 thick film of Co ₈₁ Ni ₉ Pt ₁₀ is treated with 0.33% oxygen.
Sputtered on the substrate at a pressure of 20 mTorr in an atmosphere of 99.67% argon. It should be noted that although it is possible to control the film coercivity by sputtering in the presence of oxygen, oxygen does not improve hysteresis squareness as much as nitrogen. In another embodiment, both oxygen and nitrogen are present in the sputtering chamber during sputtering. In this embodiment, oxygen is typically provided by the decomposition of water vapor. Fifth
The curves 1 and 2 in the figure show the nitrogen required in the sputtering chamber to produce a film having a coercivity of 650 Oe as a function of the respective concentrations of water vapor and hydrogen detected in the sputtering chamber after sputtering. Indicates the amount. (The hydrogen detected in the sputter chamber was generated from the portion of water vapor that was decomposed into hydrogen and oxygen during sputtering.) The data shown in the graph of FIG. - nitrogen - are those taken by sputtering a thickness of Co ₈₁ Ni ₉ Pt ₁₀ film of 700Å in an atmosphere of water vapor. In the film of FIG. 5, when the hydrogen concentration is between 0.5% and 0.95% and the water vapor concentration is between 0.2% and 0.28%, the coercivity of 650 Oe is obtained when the nitrogen concentration is between 0.66% and 0.87%. Is possible. Because both hydrogen and nitrogen can reduce the coercivity of the resulting film, the presence of more oxygen in the sputter chamber will form a film with a given coercivity. Require less nitrogen and vice versa. Therefore, when the concentration of hydrogen and water vapor is high, a low concentration of nitrogen (0.55%) is required to obtain a coercivity of 650 Oe, while a low concentration of hydrogen and water vapor results in a higher concentration of nitrogen (0.87%). )
Is required. However, the present inventors have found that when the water vapor concentration in the sputtering chamber exceeds 1%, the coercivity of the resulting film cannot be controlled by changing the nitrogen concentration. It is. As described above, the specific embodiments of the present invention have been described in detail. However, the present invention should not be limited to these specific embodiments, and various modifications may be made without departing from the technical scope of the present invention. Is of course possible. For example, Ni
Instead of using a P-plated aluminum substrate, it is also possible to use other substrates, including a NiP substrate coated with a non-ferromagnetic film such as chromium or other metal or insulator. Substrates having glass, silicon, polymer, or ceramic materials can also be used. Further, an inert gas other than argon can be present in the sputtering chamber. Also, using this method, for example,
It is also possible to form a film having a coercivity range of 600 to 2,000 Oe. Further, in some embodiments,
Instead of forming a cobalt-platinum based alloy on the substrate, it is also possible to sputter another intrinsically high coercivity cobalt or iron based alloy on the substrate in the presence of nitrogen gas. is there.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a and 1b are graphs showing the effect of nitrogen concentration in a sputtering chamber on the coercivity of a Co ₈₁ Ni ₉ Pt ₁₀ film, FIG.
Figure graph showing the effect of nitrogen concentration in the sputtering chamber which gives the coercivity film of Co ₈₂ Ni ₉ Pt _9, FIG. 3 is Co _{82 · 3} Ni
Graph showing the effect of nitrogen concentration in the sputtering chamber to provide a coercivity of _{9 · 2} Pt _{8 · 5,} the concentration of the fourth figure of the sputtering chamber that gives the coercivity film of Co ₈₁ Ni ₉ Pt ₁₀ oxygen FIG. 5 is a graph showing the amount of nitrogen required to obtain a coercivity of 650 Oe as a function of the concentration of water vapor in the sputtering chamber. FIGS. 6a and 6b are graphs respectively. Graphs showing hysteresis loops of Co ₈₁ Ni ₉ Pt ₁₀ sputtered in the presence and absence of nitrogen, FIG. 7 shows Co ₈₁ Ni ₉ P
graph showing the effect of the concentration of the sputtering chamber of nitrogen to give the saturated magnetic film of t _10, it is.

Continuation of front page (72) Inventor Tu Chang United States, California 95070, Saratoga, Paramount drive 13254 (56) References JP-A-61-142523 (JP, A) JP-A-61-194625 (JP, A) JP-A-61-250827 (JP, A) JP-A-60-124021 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/66 G11B 5/85

Claims (1)

(57) [Claims] In a method of manufacturing a recording medium film, when forming an alloy film having platinum and cobalt on a substrate by sputtering, the method includes a selected gas having at least one of nitrogen and oxygen, and has a coercivity of the alloy film. Introducing a reducing atmosphere into the sputtering chamber, wherein the coercivity of the resulting film varies depending on the concentration of the selected gas in the atmosphere. 2. In the method of manufacturing a recording medium film, when forming an alloy film containing platinum and cobalt on a substrate by sputtering,
At least one of nitrogen and oxygen is introduced into the sputtering chamber at a concentration of less than 2% in the sputtering chamber, and the coercivity of the resulting film is the amount of at least one of the nitrogen and oxygen introduced into the sputtering chamber. Characterized in that it varies depending on the method. 3. 3. The method according to claim 2, wherein said alloy film contains another metal, and said alloy film has an intrinsic coercivity of more than 650 Oe. 4. 3. The method according to claim 2, wherein argon is present in said sputtering chamber. 5. 3. The method of claim 2, wherein said nitrogen has a partial pressure between 10 ^-4 and 10 ^-7 Torr. 6. 3. The method according to claim 2, wherein said oxygen is introduced into said sputtering chamber in the form of water vapor. 7. 7. The method according to claim 6, wherein the water vapor is 10 ^-4.
A method comprising having a partial pressure of less than Torr. 8. 3. The method of claim 2, wherein said alloy film has at least 5% platinum. 9. 3. The method according to claim 2, wherein when introducing the nitrogen, a gaseous compound containing nitrogen is introduced, and the gaseous compound is decomposed during a sputtering process. 10. 3. The method according to claim 2, wherein when introducing the oxygen, a gaseous compound containing oxygen is introduced, and the gaseous compound is decomposed during a sputtering process. 11. 3. The method of claim 2, wherein said alloy film is sputter-formed on a layer of a non-ferromagnetic metal. 12. 3. The method of claim 2, wherein said alloy film is sputter formed on a layer of an electrically insulating material. 13. In a method for manufacturing a recording medium film,
When sputter-forming an alloy film having a specific coercivity exceeding 0 Oe, the coercivity of the alloy film is reduced by introducing a selected gas into a sputtering chamber, and the coercivity of the alloy film is set to The method varies depending on the amount of the selected gas introduced into the sputter chamber, wherein the selected gas comprises oxygen or nitrogen. 14． 14. The method of claim 13, wherein said alloy film is based on cobalt. 15. In the method of manufacturing a magnetic recording medium film, when an alloy film having a specific coercivity exceeding 650 Oe is formed on a substrate by sputtering, a selected gas is introduced into a sputtering chamber, and the coercivity of the alloy film is set in the sputtering chamber. Varying depending on the amount of the selected gas introduced into the sputtering chamber, the selected gas having oxygen or nitrogen and having a concentration in the sputtering chamber of less than 2%. A method characterized by the following.