JP4709783B2 - Method for forming metal layer and method for manufacturing thin film magnetic head - Google Patents

Description

  The present invention relates to a method for forming a metal layer and a method for manufacturing a thin film magnetic head, and more particularly to a method for forming a write pole layer of a thin film magnetic head.

  2. Description of the Related Art Conventionally, a technique using a so-called three-layer resist structure in which a second photoresist layer is formed on an intermediate layer on a first photoresist layer to form a write pole layer of a thin film magnetic head is known. (See Patent Documents 1 and 2). The first photoresist layer is a layer that serves as a plating frame for the write pole layer and has a relatively large thickness. The second photoresist layer is formed thinner than the first photoresist layer in order to enable high-resolution exposure. Therefore, the second photoresist layer is exposed and developed using a predetermined mask, to create a photoresist pattern, when etching the intermediate layer as a mask, to form the desired openings in the intermediate layer with high precision Can do. Then the second photoresist layer is removed, as a mask, the intermediate layer, RIE when the first photoresist using (reactive ion etching) or the like is etched, vertical opening with high precision large photoresist thickness Can be formed. If a seed layer is provided in advance below the first photoresist layer, the metal layer can be produced by filling the opening of the first photoresist layer with a metal material using electroplating. Thereafter, the write pole layer having a desired shape is formed by trimming the metal layer using ion milling or the like. The method of forming the write pole layer using a three-layer resist structure, has attracted attention as a method of forming accurately write pole layer narrowing is underway in order to cope with high density recording.

  With reference to FIG. 3, a conventional method of forming a write pole layer will be described. After a read element (not shown) such as an MR (Magneto Resistance) element is formed on the wafer, first, as shown in FIG. 3A, a lower write magnetic pole layer 9 and a write gap that become a part of the write magnetic pole layer are formed. 10 and a seed layer 11 for electroplating for forming the write pole layer. Next, a first resist layer 112, an intermediate layer 114, and a second resist layer 115 to be a plating frame are formed as a three-layer resist. Next, in order to improve the adhesion with the seed layer 11, pre-baking is performed. Pre-baking is usually performed in a hot plate. Thereafter, the second resist layer 115 is exposed with deep ultraviolet light (DUV) or the like to produce a mask pattern.

Next, as shown in FIG. 3B, an opening 122 is formed in the intermediate layer 114 by reactive ion etching (RIE). Thereafter, the second resist layer 115 is removed. Next, as shown in FIG. 3C, an opening 123 is formed in the first resist layer 112 by RIE. Next, as shown in FIG. 3D, a metal layer 17 to be a writing element is formed in the opening 123 by electroplating. Thereafter, as shown in FIG. 3E, the intermediate layer 114 and the first resist layer 112 are removed by RIE, and the metal layer 17 is formed by ion milling milling as shown in FIG. Trim so that the line width becomes.
JP 2000-132812 A JP 2000-287376 A

  When the first resist layer is etched by RIE, the upper portion of the first resist layer is etched for a longer time. Since the reaction in the lateral direction cannot be suppressed even if the RIE anisotropy is increased, the opening 123 formed by etching has a shape in which the line width is wider toward the top of the first resist layer as shown in FIG. It was. Therefore, the metal layer obtained by plating also has a reverse taper shape with a thick upper part. The metal layer is further trimmed by ion milling, it is difficult to metal layer is milled to a desired shape to be formed in such a shape, the line width control of the write pole layer is deteriorated. As a result, the dimensional defect of the write pole layer and the write characteristics are deteriorated, and it becomes difficult to cope with the high recording density.

  There is another reason why the opening of the resist by etching spreads toward the top. This is because the concentration distribution of the residual solvent in the resist is different in the film thickness direction of the first resist layer. A positive resist is generally used in a process that requires fine processing such as manufacturing a write pole layer of a magnetic head. In the positive resist, but a resin and a photosensitive group is dissolved in an organic solvent, in order to improve the adhesion of the resist, after application of the resist, the solvent is evaporated by pre-baking. However, it is difficult to completely evaporate the solvent, and some of the solvent remains and segregates. Prebaking Because usually carried out in a hot plate, heat to the first resist layer is easily transferred from the substrate side, the lower portion of the first resist layer closer to the substrate is subjected to a greater thermal. As a result, evaporation of the solvent is also accelerated at the bottom of the first resist layer, the remaining solvent is relatively reduced in the first resist layer lower, relatively increased in the first resist layer upper. In the case of a thick film resist, uneven distribution of the resist material is likely to occur for this reason. The etching rate of RIE for the resist is basically the same as if the resist material is uniformly distributed, the etch rate as the residual solvent is more segregation increases. Accordingly, the etching rate is increased on the upper portion of the first resist layer, and the opening width of the upper portion is further increased in combination with the longer RIE treatment.

  The present invention has been made in view of such problems, and in particular, a method for forming a metal layer that can prevent deterioration in dimensional accuracy of a metal thin film due to the concentration distribution of a residual solvent in a resist. The purpose is to provide. It is another object of the present invention to provide a method of manufacturing a thin film magnetic head using such a metal layer forming method.

In order to solve the above problems, a metal layer forming method of the present invention includes a step of forming a seed layer on a base layer, and a step of forming a seed layer on the seed layer with a low residual solvent concentration at the top and a low residual solvent concentration at the bottom. Forming a first photoresist layer; forming a mask pattern layer having a first opening reaching the first photoresist layer on the first photoresist layer; and masking the mask pattern layer as a first photoresist layer are etched by reactive ion etching, the first photoresist layer, forming a second opening reaching the first through-opening and the communication, and the seed layer, first Forming a metal layer in the second opening by electroplating using the photoresist layer as a photoresist frame and the seed layer as an electrode, and forming a metal layer in the second opening It has a step of removing the first photoresist layer and mask pattern layer, an after. In the step of forming the first photoresist layer, the lower resist was applied on the seed layer and prebaked, and the upper resist having the same resin composition as the lower resist and higher viscosity than the lower resist was prebaked. Applying and pre-baking on the lower resist.

  The segregation of the residual solvent is suppressed as the residual solvent concentration of the first photoresist layer is reduced, and the etching rate is reduced accordingly. Conversely, the segregation of the residual solvent increases as the residual solvent concentration increases, and the etching rate also increases. Since the first photoresist layer is etched from the top, the top is etched for a longer time, and the etching tends to spread in the lateral direction (in the film surface direction) accordingly. However, in the present invention, since the residual solvent concentration is adjusted as described above, the cause of increase (decrease) in the etching rate due to the etching time and the factor of decrease (increase) in the etching rate due to the residual solvent concentration cancel each other. It becomes easier to form openings with a more uniform cross section in the film thickness direction of one photoresist layer.

  The thin film magnetic head manufacturing method of the present invention uses the above-described metal layer forming method for forming the write pole layer.

  As described above, according to the present invention can provide a method of forming a metal layer that makes it possible to prevent deterioration of the dimensional accuracy of the metal thin film due to the concentration distribution of the residual solvent in the resist. In addition, according to the present invention, it is possible to provide a method of manufacturing a thin film magnetic head using such a metal layer forming method.

  Hereinafter, an embodiment according to the method for forming a metal layer of the present invention will be described with reference to the step diagrams of FIGS. 1A to 1N and the flowchart shown in FIG. The following embodiments are directed to the write pole layer of a thin film magnetic head used in a hard disk device, but it goes without saying that the present invention can also be applied to a method of manufacturing a metal layer other than the write pole layer of a thin film magnetic head. The present invention is particularly suitable for manufacturing a metal layer having a large film thickness with respect to a planar dimension.

(Step S1) First, as shown in FIG. 1A, a base protective layer 2 made of Al ₂ O ₃ is formed on a substrate 1 made of Al ₂ O ₃ .TiC (aluminum titanium carbide). Next, the lower magnetic shield layer 3 made of NiFe is formed by electroplating. The lower magnetic shield layer 3 is a magnetic shield layer of the MR sensor 8 which is a reading element. An MR sensor 8 is formed on the lower magnetic shield layer 3 and its periphery is covered with an insulating layer 4 which is a non-conductive electrical protection layer made of Al ₂ O ₃ . Next, the first upper magnetic shield layer 5 made of NiFe is formed on the MR sensor 8. Further, a second upper magnetic shield layer 7 is formed on the first upper magnetic shield layer 5 via a shield isolation layer 6 made of Al ₂ O ₃ or Ru. The second upper magnetic shield layer 7 is made of a Co-based material having a large magnetic moment in order to enhance the magnetic shield effect. The second upper magnetic shield layer 7 is also used as a part of the write pole layer.

  (Step S2) Next, as shown in FIG. 1B, a lower write pole layer 9 made of NiFeCo is formed by sputtering as a part of the write element.

(Step S3) Next, as shown in FIG. 1C, a nonmagnetic material to be the write gap 10 is formed with a film thickness of about 0.1 μm. As the write gap 10, an oxide such as Al ₂ O ₃ or SiO ₂ or a metal such as Ru or W is used.

  (Step S4) Next, as shown in FIG. 1D, the write gap 10 as a base layer by sputtering, forming a film of the seed layer 11 a thickness of about 0.1 to 0.5 [mu] m. While seed layer 11 is an electrode layer for electroplating to form a write pole layer is the same even in the part of the write pole, a large Co-based material of the magnetic moment is used.

  (Step S5) Next, as shown in FIG. 1E, the first resist layer 12 serving as a resist frame of the write pole layer is formed on the seed layer 11 with a film thickness of several μm or more by using a spin coating method. Apply. After resist application, pre-baking is performed with a hot plate. Pre-baking is performed at a temperature range of 150 ° C. to 180 ° C. for a few minutes to a few dozen minutes.

(Step S6) Next, as shown in FIG. 1F, the surface of the first resist layer 12 is irradiated with ultraviolet rays (UV) from above the first resist layer 12. The wavelength of the ultraviolet rays is preferably about 220 to 320 nm, the output is preferably several mW / cm ² or more, and the irradiation time is preferably ten or more seconds. By irradiating with ultraviolet rays, the residual solvent concentration in the resist upper portion 12b can be reduced as compared with the resist lower portion 12a. Instead of ultraviolet rays, an electron beam (EB) may be used. In the case of an electron beam, the irradiation intensity (acceleration voltage) is preferably 100 kV or less, and the irradiation amount is preferably several μC / cm ² or more. Thus, the first photoresist layer 12 is partitioned into an upper resist portion 12b having a high solvent concentration and a lower resist portion 12a having a low solvent concentration. Actually, it is considered that the residual solvent concentration continuously changes in the first photoresist layer 12, and also continuously changes in the lower resist portion 12a and the upper resist portion 12b. It is thought that there is.

(Step S <b> 7) Next, a mask pattern layer (intermediate layer 14) having a first opening 22 reaching the first photoresist layer 12 is formed on the first photoresist layer 12. For this purpose, first, as shown in FIG. 1G, an intermediate layer 14 to be a mask layer of the first resist layer 12 is formed. The thickness of the intermediate layer 14 is desirably 50 nm or more. The intermediate layer 14 is formed of an oxide film such as SiO ₂ in addition to Al ₂ O ₃ .

  (Step S8) Next, as shown in FIG. 1H, a second resist layer 15 is applied on the intermediate layer 14 by spin coating and pre-baked. For the second resist layer 15, a photoresist corresponding to deep ultraviolet rays is used in order to obtain high resolution. In order to improve the resist adhesion of the second resist layer 15, the number of nm of the metal film is formed on the intermediate layer 14 may be coated with the second resist layer 15 thereon.

  (Step S9) Then, as shown in FIG. 1I, exposing the second photoresist layer 15 with deep UV and developed to pattern the second photoresist layer 15. The opening 21 formed by patterning substantially coincides with the planar shape of the metal layer 17 formed in a later process.

(Step S10) Next, as shown in FIG. 1J, the first opening 22 is formed in the intermediate layer 14 by RIE using the second photoresist layer 15 as a mask. As a reactive gas for RIE, a BCl ₃ or Cl ₂ gas is used. A first opening 22 is formed in the intermediate layer 14 immediately below the opening 21.

  (Step S11) Next, as shown in FIG. 1K, the second photoresist layer 15 is removed, and the intermediate layer 14 in which the first opening 22 is formed is exposed. Next, an intermediate layer 14 as a mask, by RIE using oxygen-based gas, a first photoresist layer 12 is etched, the first photoresist layer 12, communicates with the first opening 22, and the seed A second opening 23 reaching the layer 11 is formed. As a result of the irradiation of the upper resist portion 12b with ultraviolet light, the concentration of the dissolved solvent decreases, and the etching rate can be suppressed lower than that of the lower resist portion 12a. For this reason, it is possible to suppress the spread of the opening in the lateral direction of the resist and to form the second opening 23 having a wall shape closer to the vertical.

  (Step S12) Next, as shown in FIG. 1L, a metal layer 17 that becomes a part of the write pole layer is formed in the second opening 23 by electroplating. The etched photoresist layer 12 is used as a resist frame for electroplating, and the seed layer 11 is used as an electrode for electroplating. The plating film thickness needs to be about several μm. The metal layer 17 is formed of a material having a large magnetic moment, such as a NiFeCo system, in order to improve write characteristics such as overwrite characteristics.

(Step S13) Next, as shown in FIG. 1M, the intermediate layer 14 and the first resist layer 12 are removed by RIE. It is preferable to use a BCl ₃ or Cl ₂ gas when removing the intermediate layer 14 and an oxygen gas when removing the first resist layer 12. In order to remove the polymer, it may be removed with an organic solvent such as NMP (N-Methyl-2-Pyrolidone).

  (Step S14) Next, as shown in FIG. 1N, by ion milling, the metal layer 17 is trimmed to a desired write width, to form a write pole layer 18.

  As described above, in the present invention, the residual solvent concentration of the resist is high at the bottom of the resist and low at the top of the resist so that more residual solvent is segregated at the bottom of the resist and segregation is reduced at the top of the resist. I have control. If the residual solvent is segregated at the lower part of the resist, the etching rate of the resist is increased, and the lateral etching can be promoted. If the amount of segregation of the remaining solvent at the upper part of the resist is reduced, the etching at the upper part of the resist is suppressed, and the etching in the lateral direction is also restricted. In this embodiment, in order to control the residual solvent concentration in this way, ultraviolet irradiation or electromagnetic wave irradiation is performed from the upper side of the resist. This effectively removes the residual solvent from the top of the resist, limits segregation, and suppresses the etching rate on the top of the resist. As a result, it becomes easy to make an opening having a uniform cross section in the resist film thickness direction as compared with the conventional case, and a metal film with a small line width difference in the film thickness direction can be formed. For this reason, the line width controllability of the write magnetic pole layer is improved, and it becomes easy to cope with the higher recording density.

  It should be noted that other methods can be used as long as the residual solvent concentration can be controlled to be large at the bottom of the resist and small at the top of the resist. As an example, as an alternative to the above-described steps S5 and S6, a lower resist is applied on the seed layer and prebaked, and then an upper resist having the same resin composition as the lower resist and a higher viscosity than the lower resist is prebaked. It may be coated on the lower resist and prebaked. This also reduces the concentration of the dissolved solvent in the upper part of the first resist layer. In general, a resist is formed of a resin, a photosensitive agent, and an organic solvent, and is adjusted to a desired viscosity by diluting with a solvent. The amount of solvent in the high-viscosity resist is less than the amount of solvent in the low-viscosity resist (state where the solvent density is low and the resin density is high). Therefore, using a high-viscosity resist with a low solvent density (high resin density) as the upper resist and covering the lower resist, the movement of the solvent in the lower resist is blocked by the resin, preventing the solvent from volatilizing from the lower resist. Will increase further. The composite resist layer thus obtained can be used as the first resist layer to perform the above-described step S7 and subsequent steps. In this embodiment, since the number of resist layers is arbitrary, a metal thin film with higher accuracy can be formed by sequentially forming three or more resists.

It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a step figure explaining one embodiment of the formation method of the metal layer of the present invention. It is a flowchart explaining one Embodiment of the formation method of the metal layer of this invention. It is a step figure explaining one Embodiment of the formation method of the metal layer of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Underlayer protection layer 3 Lower magnetic shield layer 4 Insulating layer 5 First upper magnetic shield layer 6 Shield separation layer 7 Second upper magnetic shield layer 8 MR sensor 9 Pole layer 10 Write gap 11 Seed layer 12 First Resist layer 12b Upper resist portion 12a Lower resist portion 14 Intermediate layer 15 Second resist layer 17 Metal layer 18 Write pole layer 21 Opening 22 First opening 23 Second opening

Claims (4)

Forming a seed layer on the base layer;
Forming a first photoresist layer on the seed layer with a lower residual solvent concentration and a lower residual solvent concentration;
Forming a mask pattern layer having a first opening reaching the first photoresist layer on the first photoresist layer;
Using the mask pattern layer as a mask , the first photoresist layer is etched by reactive ion etching , and the second photoresist layer reaches the seed layer in communication with the first opening. Forming an opening of
Forming a metal layer in the second opening by electroplating using the first photoresist layer as a photoresist frame and the seed layer as an electrode;
Removing the first photoresist layer and the mask pattern layer after forming the metal layer in the second opening;
I have a,
The step of forming the first photoresist layer includes:
Applying a lower resist on the seed layer and pre-baking;
An upper resist having the same resin composition as that of the lower resist and having a viscosity higher than that of the lower resist is applied onto the pre-baked lower resist, and prebaked.
That it contains, method for forming the metal layer. The step of forming the mask pattern includes:
Forming an intermediate layer on the first photoresist layer;
Forming a second photoresist layer on the intermediate layer;
Patterning the second photoresist layer;
Forming the first opening in the intermediate layer using the patterned second photoresist layer as a mask;
Removing the second photoresist layer to expose the intermediate layer in which the first opening is formed;
The method for forming a metal layer according to claim 1, comprising: The method for forming a metal layer according to claim 2 , wherein the intermediate layer is an oxide film. Method of manufacturing a thin film magnetic head used for forming the magnetic layer write method for forming a metal layer according to any one of claims 1 to 3.

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