In recent years, magnetic read and write devices have rapidly developed in high-recording density as the amount of handled information has increased. Along with this tendency, high-sensitivity and high-output magnetic heads have been requested. To meet the request, magnetic heads using giant magnetoresistive (GMR) films providing high-output have been developed and further improved. However, there is concern that even the magnetic heads using the GMR films lack output for a recording density of greater than 9.3×109 bits/cm2. Therefore, a magnetic head has been researched and developed which uses a tunneling magnetoresistive (TMR) element or CPP (Current Perpendicular to the Plane) GMR film allowing electric current to flow perpendicular to GMR surface, as the next-generation magnetoresistive element of the GMR film.
The magnetic head using the GMR film is largely different in structure from the magnetic head using the TMR film or CPP-GMR film. The former has a CIP (Current Into the Plane) structure which allows sensing current to flow in the direction parallel to the magnetoresistive film surface. The electrodes supplying the sensing current are provided on both sides of the magnetoresistive film. On the other hand, the latter has a CPP structure which allows the sensing current in a direction perpendicular to the film surface of the magnetoresistive film comprising the TMR film or CPP-GMR film. Therefore, the electrodes supplying the sensing current are provided to be laminated on the magnetoresistive film.
If a path which short-circuits upper and lower magnetic shields serving as electrodes exists in the magnetic head having the CPP structure, it forms a short-circuit for the sensing current. This poses a problem with a reduction in the signal of the magnetic head. In particular, when a short circuit is formed across an intermediate layer (a tunnel barrier layer or a current confined layer), the signal is significantly reduced.
A short circuit may be formed mainly at the following two places: (1) an end face of a magnetoresistive film perpendicular to a stacked surface, the end face forming a portion of a magnetic recording medium-facing surface; (2) an end face of a magnetoresistive film in contact with a refill film formed in an element height direction and in an track width direction.
The short circuit formed at (2) is formed in a process for forming the element height of the magnetoresistive film and a process for forming the track width. In the processes, an unnecessary region is removed by the Ar ion beam etching method. At this time, a phenomenon called re-adhesion occurs in which the etched material removed adheres to the side wall of the magnetoresistive film. The etched material is a metal laminated film, which is conductive, and so it can form a short circuit. As a method of preventing leakage of the sensing current due to the re-adhesion, Japanese Patent Publication No. 2003-86861 (“patent document 1”) discloses a method of preventing the short circuit by oxidizing the re-deposited material after the etching.
It is known that in the air-bearing surface lapping process of a magnetic head slider, the short circuit formed at (1) occurs when the air-bearing surface of the magnetoresistive film is lapped by using a plate embedded with minute diamond abrasive grains. In the air-bearing surface lapping process, the air-bearing surface is mechanically lapped for smoothing by the grinding operation of the hard grains and plastic flow operation. A metal element which forms a magnetic shield layer, a magnetoresistive film or a magnetic domain control film plastically flows to form a smear at an end face forming a portion of a magnetic recording medium-facing surface thereof. Since the smear is made of metal, it is conductive, which forms a short circuit for sensing current. A method of preventing short-circuit due to a smear is disclosed by Japanese Patent Publication No. 1999-175927 (“patent document 2”). This method involves removing a smear getting across a magnetoresistive film produced by mechanical lapping by plasma or ion-used dry etching after the mechanical lapping.
The method of removing the short-circuit formed at (1) is achieved not only by the dry etching method but also by applying the method described in patent document 1 used to remove the short-circuit formed at (2), to the magnetic recording medium-facing surface to form an oxidized layer on the air-bearing surface.
Japanese Patent Publication No. 2005-108355 (“Patent document 3”) describes a method of forming an oxidized layer on the air-bearing surface by using air, ion beams, ozone or the like in an air-bearing surface protection film forming process although the purpose of the method is as below. Even if a magnetoresistive element is placed high-temperature environment, the change of the resistance value of the magnetoresistive element before and after the placement is reduced to thereby enhance the stability of the characteristic relative to the high-temperature environment.
If dry etching is performed after the air-bearing surface lapping of the magnetic head slider, it is possible to remove the smear resulting from the plastic flow during the lapping. However, a damaged region produces the lowering of output or of withstand voltage. This damaged region is formed on an end face which forms a portion of the air-bearing surface of a magnetoresistive film, a magnetic domain control film, a refill film or a magnetic shield film. In addition, the damaged region is a region where a short-circuit or magnetically insensitive layer is formed at a portion of the air-bearing surface of a magnetoresistive film, a magnetic domain control film, a refill film or a magnetic shield film due to film quality alteration by the dry etching or to element interdiffusion with an adjacent film. In particular, if the tunnel barrier layer of a TMR film is damaged, the magnetoresistive effect of the TMR film is reduced to significantly lower output. Similarly, if the current confined layer of a CPP-GMR film is damaged, the magnetoresistive effect of the CPP-GMR film is reduced to significantly lower output.
On the other hand, when an oxidized layer is formed on a air-bearing surface by ozone exposure, air exposure, or oxygen ion beam bombardment, the damaged region may be removed in some cases. However, the oxidized layer formed on the air-bearing surface of a magnetic head cannot maintain sufficient corrosion resistance. Therefore, it is necessary to further form an air-bearing surface protection film after formation of the oxide film. Consequently, effective magnetic spacing is increased according to the thickness of the oxidized layer. This lowers read and write resolution when the magnetic head slider is caused to fly.
If the dry etching is not used in order not to form a damaged region on a air-bearing surface, it is impossible to remove a conductive smear formed by mechanical lapping, which significantly lowers signal.
Because of the problems described above, a method of manufacturing a high-recording density magnetic head at high-yields has not been realized under existing circumstances.