JPH0320463A - Reactive sputtering method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a sputtering method suitable for depositing a magnetic film on a magnetic disk medium using a magnetron-type reactive sputtering device, it is necessary to avoid In order to prevent the formation of an oxide film due to deposition, etc., in a magnetron-type reactive sputtering device, the gas pressure of oxygen, which is the sputtering gas, is set to a low gas pressure of 15 mTorr or less. Be careful to perform sputtering on the substrate.

[Industrial application field]

The present invention relates to a sputtering method suitable for depositing, for example, a magnetic film on a magnetic disk medium using a magnetron-type reactive sputtering device.

(Prior Art) An iron oxide type thin film magnetic recording medium is produced by an indirect method 7-Fe. 0
In the case of manufacturing by the sputtering method, an α-FezO3 film is formed on a nonmagnetic substrate using a reactive sputtering device, and then reduction and oxidation treatments are performed.

? Figure 3 shows a conventional high-frequency magnetron type reactive sputtering device suitable for such applications, with chamber 1
Inside, an Fe target 3 is placed adjacent to the magnet 2.
is disposed, and a non-magnetic substrate 4 is disposed facing the Fe target 3.

Then, while supplying oxygen as a reactive gas, Fe
A high frequency power source RF is connected between the target 3 and the non-magnetic substrate 4.
When connected, particles such as atoms or molecules ejected from the surface of the Fe target 3 react with oxygen molecules and adhere to the substrate 4 due to magnetron discharge, thereby forming a film.

Indirect method 1-Fe. To obtain the 0.0 sputtering medium, pure oxygen is thus supplied into the chamber 1 and the 0.0 sputtering gas is made to collide with the Fe target 3. Then, Fe and reactive gas 02 are combined on the Fe target 3, and α-
Fe. 0. As a result, it adheres to the non-magnetic substrate 4. At the same time, the Fe ejected from the Fe target 3 and the 02 sputtering gas combine in space to become αFe203, which is deposited on the nonmagnetic substrate 4.

Sputtering energy in a magnetron type speck device is concentrated in an annular shape, so as shown in FIG. 4, an erosion region 5 is formed in the center of the target 3 while sputtering is being performed, and a redeposition region 6 is formed outside of the erosion region 5. occurs.

Atoms or molecules of the target 3 that have been scattered from the erosion region 5 come back onto the target due to a reversal phenomenon and are deposited in regions other than the erosion region 5, forming a redeposition region 6 and forming a mass of oxide. becomes.

The oxide film 6 due to this redeposition etc. is easily peeled off. Further, since this oxide film 6 does not have magnetism, if particles ejected from the redeposition region 6 adhere to the nonmagnetic substrate 4, it may cause defects and cause a missing error.

Therefore, conventionally, when there is an opportunity to open the chamber to the atmosphere, the part of the redeposition area 6 that is likely to peel off is removed.
It was rubbed off mechanically.

However, if the high vacuum chamber is emptied and exposed to the atmosphere, the operating rate of the sputtering apparatus will be reduced, and scraping off the redeposition area may contaminate the inside of the chamber.

Therefore, the applicant of the present invention has filed a patent application in Japanese Unexamined Patent Publication No. 58-9221.
In the publication, a method was proposed in which a certain film was applied in multiple steps. FIG. 5 is a sectional view showing this method in the order of steps.

Although the nonmagnetic substrate 4 before a certain film is cleaned, it cannot be guaranteed to be completely cleaned. Therefore, as shown in (a), foreign matter 8 such as iron oxide lumps may adhere to the nonmagnetic substrate 4. When sputtering is performed for the first time on the substrate 4 where the foreign matter 8 is present, as shown in (b),
The result is magnetic #9a with foreign matter 8 mixed therein.

After the first layer of magnetic film 9a is deposited, cleaning is performed, but if the foreign matter 8 is removed at this time, a depression 10 will be created at the place where it fell off, as shown in (C), and if it does not fall off, Foreign matter 8 remains as is.

In the king of the eleventh magnetic film 9a shown in (C), (a) to (C
) By repeating sputtering and cleaning, a certain film operation is repeated, such as the 2N layer, the 3rd layer, the 4th layer, and so on.

[Problem to be solved by the invention]

If sputtering is performed in multiple steps in this way,
As shown in FIG. 5(d), a plurality of magnetic films 9a, 9b,
The magnetic film 9 is constituted by 9c and 9d. and,
Even if the foreign matter 8... remains in each of the magnetic films 9a, 9b, 9c, 9d, the foreign matter 8... remains in the same place.
Since the probability of adhesion is extremely low, the deterioration of magnetic properties due to non-magnetic foreign matter 8 is only one-fourth, and it is almost impossible for the entire thickness of magnetic film 9 to become non-magnetic. Therefore, missing errors caused by partial inability to record/playback can be reliably prevented. However, in such a split sputtering method, it is not possible to prevent the foreign matter 8 from adhering to the non-magnetic substrate 4 before each sputtering operation.
This requires cleaning equipment, which is disadvantageous in terms of equipment and work efficiency, and productivity is poor. Furthermore, since the formation of an oxide film on the surface of the target 3 cannot be prevented as described above, periodic cleaning must be performed to remove the oxide film, which causes a decrease in efficiency.

The technical problem of the present invention is to solve such problems and to make it possible to prevent the formation of an oxide film due to redeposition on the target, which is the main cause of foreign matter adhering to the substrate. .

[Means to solve the problem]

The present invention is directed to a magnetron type reactive sputtering device, and when performing sputtering with this device,
Sputtering onto the substrate is performed by setting the gas pressure of oxygen, which is the sputtering gas, to a low gas pressure of 15 mTorr or less. Note that when manufacturing a magnetic film for a magnetic disk medium by the method of the present invention, an Fe target is used as the target.

[Effect]

In the reactive sputtering method according to the present invention, pure oxygen is supplied into a chamber, and the sputtering gas is made to collide with the Fe target. Then, Fe and the reactive gas 02 combine on the Fe target to form α-Fe,O, which adheres to the non-magnetic substrate or ejects Fe and O from the Pe target.
! The sputtering gas is combined with the sputtering gas in space to form α-Fe40. As a result, it adheres to the nonmagnetic substrate.

At this time, in the present invention, since the oxygen gas pressure is set to a low gas pressure of 15 mTorr or less, most of the oxygen is consumed for combination with Fe of the Fe target. As a result, there is insufficient oxygen to oxidize the surface of the Fe target, making it difficult to form an oxide film on the surface of the Pe target.

Furthermore, the particles that have returned to the redeposition region due to the reversal phenomenon are also in an oxygen-deficient state, so there is less oxide, and the formation of an oxide film due to redeposition is also suppressed.

In this way, by lowering the oxygen gas pressure, it is possible to suppress or prevent the formation of an oxide film on the target.

The invention according to claim 2 of the present invention is a method for removing and cleaning an oxide film when an oxide film is generated on the target, and when performing this cleaning, sputtering to the substrate is temporarily stopped. Then, increase the oxygen gas pressure to 1
The temperature is lowered to 5 mTorr or less, and only target sputtering is performed.

In this case, it is preferable to lower the oxygen gas pressure sufficiently to the extent that no oxide film is formed on the Fe target.

During cleaning, oxygen, which is a sputtering gas, collides with the Fe target and sputters the oxide film on the surface.
The oxide film is removed. In addition, sputtering is performed from the entire surface of the Fe target, but since the oxygen gas pressure is sufficiently low, oxygen combines with the sputtered Fe and α-Feg03
Therefore, it does not combine with the Fe of the Fe target to form an oxide film on the target surface.

When the sputtering gas pressure is lowered, the sputtering speed becomes faster, so that the oxide film can be efficiently removed by sputtering.

The substance that returns to the Fe target and deposits in the redeposition region due to the backflow phenomenon is also a compound in an oxygen-deficient state, and therefore does not become an oxide film.

[Example] Next, how the reactive sputtering method according to the present invention is actually implemented will be explained using an example.

A Pe-Co (20X) target was used as the target, and the sputtering power was set to 7K. Then, the oxygen flow rate was set to 40 sec, and the oxygen gas pressure was set to 20 mTorr.
, 15 mTorr, and 10 mTorr, and sputtering was performed on the alumite substrate. Next, after reducing in a reducing atmosphere such as hydrogen, 7-FezO. A magnetic disk medium consisting of a film was created.

FIG. 1 shows these γ-Fe. O. This is an example of recording/reproducing on a film and measuring the number of missing errors. The horizontal axis shows each oxygen gas pressure, and the vertical axis shows the number of missing errors.

Figure 1 (a) shows that the oxygen gas pressure is 20 mTorr → I
5mTorr→10a+Torr→15mTorr −
+20mTorr -+15mTorr -+10mT
This is a case where sputtering is performed by sequentially changing the values such as orr. When the oxygen gas pressure is as high as 20 mTorr, the number of missing errors is 200 per surface.
In contrast, in the case of 15 mTorr, 14
When it decreases to around 0 and decreases to lOmTorr,
The number has decreased to about 30. (b) and (C) are cases in which sputtering is performed with a constant oxygen gas pressure instead of changing the oxygen gas pressure continuously in this way. As shown in (C), when sputtering is performed at an oxygen gas pressure of 10 mTorr, the number of missing errors is reduced to about 5 per surface.

(b) shows the case where the oxygen gas pressure was set to 20+wTorr and sputtering was performed in four parts according to the method explained in FIG. 5, and about seven l7 sing errors occurred.

In this way, by the method of the present invention, the oxygen gas pressure can be reduced to 10 mT.
orr and sputtering with a fixed gas pressure causes fewer ξ-twisting errors than the conventional four-split sputtering method, and is extremely effective.

In the case of the conventional 4-part sputtering method, the oxygen gas pressure is 29a
Even at Torr, the number of missing errors is about 7, so lowering it to about 15 mTorr is even more effective.

In the example, the oxygen gas pressure was lowered only to 10+sTorr in consideration of the magnetic properties, but if sputtering to the substrate is stopped and the target surface is cleaned, the oxygen gas pressure may need to be lowered further. Good.

For example, when the substrate was removed and idle sputtering was performed for 5 minutes at 5 mTorr, most of the iron oxide deposited on the surface of the Fe target was removed, and cleaning was effectively performed.

As the sputtering atmosphere, in addition to supplying only pure oxygen as described above, it is also possible to use a mixed gas of Ar+Oz. In this case as well, if the O2 partial pressure is lowered by the method of the present invention, the same effect as in the case of sputtering with pure oxygen alone can be expected.

FIG. 2 shows an example in which an Ar+Og mixed gas is used and the 02 partial pressure is varied, the horizontal axis shows each 02 partial pressure, and the vertical axis shows the number of missing errors.

(C) is Ot partial pressure 5*Torr equivalent to 0. -10s
ccm. ．． This is a case of long sputtering with Ar-30sec, and due to lack of oxygen for sputtered Fe particles,
It becomes a metal film of Fe, and no magnetism is obtained. the result,
Cannot be used as a magnetic recording medium.

(b) is 0.0% equivalent to Ot partial pressure of 10 mTorr. -203
This is a case of sputtering with CCll SAr-20sec, and about 190 sputtering errors occurred.
As shown in (a), compared to 275 missing errors when sputtering only Ox in an atmosphere of 20 s+Torr, the effect of suppressing missing errors is apparent.

As is clear from this, even in a mixed atmosphere with Ar, the effect of lowering the oxygen gas pressure is recognized. However, as shown in (d), 0. Only 10s+Torr
Compared to the number of missing errors in the atmosphere of Ar
In the case of a mixed atmosphere with oxygen, the effect of reducing oxygen gas pressure is not significant.

〔Effect of the invention〕

As described above, according to the present invention, in a magnetron-type reactive sputtering apparatus, the gas pressure of oxygen, which is a sputtering gas, is set to a low gas pressure of 15 mTorr or less to perform sputtering on a substrate, thereby preventing oxidation of the target. can be suppressed,
It is possible to prevent foreign matter from adhering to the substrate, and to obtain a highly reliable magnetic recording medium with few missing errors. In addition, if an oxide film is generated on the target by sputtering the substrate, stop sputtering the substrate, sufficiently lower the oxygen gas pressure to 15 mTorr or less, and perform blank sputtering on the target.
The oxide film on the target can be spun and removed for effective cleaning.

[Brief explanation of the drawing]

Figure 1 is a diagram comparing the characteristics of a magnetic recording medium manufactured by the method of the present invention and a magnetic recording medium manufactured by a conventional method. Figure 2 shows the case where 02 + Ar mixed gas is used as the sputtering gas. FIG. 2 is a diagram comparing the characteristics of magnetic recording media between the method of the present invention and the conventional method. FIG. 3 is a diagram showing a reactive sputtering apparatus, FIG. 4 is a diagram showing the surface condition of a target, and FIG. 5 is a sectional view showing a conventional four-split sputtering method. In the figure, l is chamber, 2 is magnet, 3 is F
e target, 4 is a non-magnetic substrate, 5 is an erosion area, 6 is an oxide film (redeposition area), 8 is a foreign substance, 9a, 9b... are magnetic films, 10 is a depression after the foreign substance falls off, respectively. show. 4th town

Claims (2)

[Claims] 1. A reactive sputtering method characterized in that sputtering is performed on a substrate using a magnetron-type reactive sputtering apparatus, with the gas pressure of oxygen, which is a sputtering gas, being set to a low gas pressure of 15 mTorr or less. 2. In a magnetron-type reactive sputtering device, if an oxide film forms on the target during sputtering on a substrate, the sputtering on the substrate is stopped, the oxygen gas pressure is lowered to 15 mTorr or less, and only sputtering is performed on the target. A reactive sputtering method characterized by cleaning the target.