Method for fabricating a read sensor for a read transducer

A read sensor for a transducer is fabricated. The transducer has a field region and a sensor region corresponding to the sensor. A sensor stack is deposited. A hybrid mask including hard and field masks is provided. The hard mask includes a sensor portion covering the sensor region and a field portion covering the field region. The field mask covers the field portion of the hard mask. The field mask exposes the sensor portion of the hard mask and part of the sensor stack between the sensor and field regions. The sensor is defined from the sensor stack in a track width direction. Hard bias layer(s) are deposited. Part of the hard bias layer(s) resides on the field mask. Part of the hard bias layer(s) adjoining the sensor region is sealed. The field mask is lifted off. The transducer is planarized.

BACKGROUND

FIG. 1depicts a conventional method10for fabricating a magnetoresistive sensor in magnetic recording technology applications. The method10typically commences after a conventional magnetoresistive or tunneling magnetoresistive (TMR) stack has been deposited. The conventional read sensor stack typically includes an antiferromagnetic (AFM) layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. In addition, seed and/or capping layers may be used. The conventional magnetoresistive stack resides on an underlayer, which may be a substrate.

The conventional method10commences by providing a conventional mask for the read sensor, via step12. The mask provided is either a conventional hard mask or a conventional photoresist mask. The conventional photoresist mask covers the region from which the conventional magnetoresistive sensor is to be formed, as well as a portion of the transducer distal from the sensor termed the field region

The magnetoresistive structure is defined using the conventional mask, via step14. Step14typically includes ion milling the transducer. Thus, the portion of the magnetoresistive stack exposed by the conventional mask is removed. The magnetoresistive structure being defined may be a magnetoresistive sensor for a read transducer.

The hard bias material(s), such as CoPt, are deposited, via step16. In addition, seed and/or capping layers may be provided in step16. The hard bias material(s) and other layers are deposited while the conventional hard mask is in place. In addition, a shallow mill may be performed as part of providing the hard bias structure. A capping layer may be deposited after the shallow ion mill is completed. The capping layer typically includes a noble metal such as Ru and/or Ta.

The conventional mask may then be removed, via step18. For a conventional photoresist mask, step18may include performing a lift-off. For a hard mask, another process, such as ion milling may be used. A planarization such as a chemical mechanical planarization (CMP) is performed, via step20. The stripe height of the sensor is then defined, via step22. Note that in some instances, the stripe height may be defined in step22prior to the steps12-20. An insulator such as aluminum oxide is deposited on the transducer, via step24.

Although the conventional method10allows the conventional transducer to be fabricated, there are several drawbacks. The current trend in magnetic recording is to decreased track widths. The track width is approaching the sub-thirty micron range. At such low thicknesses, a conventional photoresist mask is consumed quickly in part because faceting of the photoresist mask may be significant at lower track widths. Thus, the desired track width may not be able to be achieved is a conventional photoresist mask is provided in step12. If a conventional hard mask is used instead, the hard mask may only be removed by a CMP and/or ion milling. This process may be difficult particularly for large areas for which the CMP capability may be limited and ion milling may be less effective. Further, the hard mask material may be stressful. A hard mask under stress may cause delamination of the magnetoresistive sensor film, particularly during the planarization in step20. Thus, the conventional method may not be capable of producing a read sensor at higher magnetic recording densities and the attendant lower track widths.

Accordingly, what is needed is a system and method for improving the fabrication of a magnetic recording read transducer.

BRIEF SUMMARY OF THE INVENTION

A method for fabricating a read sensor on a substrate for a read transducer is described. The read transducer has a field region and a sensor region corresponding to the read sensor. The method includes depositing a read sensor stack including a plurality of layers on the substrate. A hybrid mask including a hard mask and a field mask is provided. The hard mask includes sensor portion covering the sensor region of read sensor stack and a field portion covering the field region of the read sensor stack. However, the hard mask exposes a first portion of the read sensor stack between the sensor portion and the field portion of the hard mask. The field mask covers the field portion of the hard mask. The field mask exposes the sensor portion of the hard mask on the sensor region and a second portion of the read sensor stack between the sensor region and the field region. The read sensor is defined from the read sensor stack in a track width direction. Defining the read sensor includes substantially removing the second portion of the read sensor stack. At least one hard bias layer is deposited. A portion of the hard bias layer resides on the field mask. A portion of the hard bias layer(s) adjoining the sensor region is sealed. The field mask is lifted off. The transducer is also planarized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3is an exemplary embodiment of a method100for providing magnetic recording transducer. For simplicity, some steps may be omitted. The method100is also described in the context of providing a single recording transducer. However, the method100may be used to fabricate multiple transducers at substantially the same time. The method100is also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method100also may start after formation of other portions of the magnetic recording transducer. For example, the method100may start after layers underlying the magnetoresistive sensor, such as a TMR sensor have been fabricated.

A read sensor stack is deposited on the substrate, via step102. The magnetoresistive layers may include a pinning layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. In addition, seed and/or capping layers may be used. The pinning layer may be an AFM or other layer configured to fix, or pin, the magnetization of the pinned layer. The pinned layer may be a synthetic antiferromagnetic (SAF) layer including magnetically coupled ferromagnetic layers separated by a nonmagnetic layer. The ferromagnetic layers may be termed pinned and reference sub-layers. The nonmagnetic spacer layer may be a conductive layer for a giant magnetoresistive structure, an insulator for a TMR structure, or may have another structure. The free layer is ferromagnetic and has a magnetization that is free to change in response to an external magnetic field, for example from a media. The free layer may have multiple sub-layers, as may the pinned and reference sub-layers. In addition, a capping layer may also be provided on the read sensor stack. Further, the transducer may be considered to have a sensor region, in which the magnetoresistive structure is to be formed, and a field region distal from the magnetoresistive structure.

A hybrid mask is provided on the read sensor stack, via step104. The hybrid mask includes a hard mask and a field mask. The hard mask includes sensor portion and a field portion. The sensor portion of the hard mask covers the sensor region of read sensor stack. The field portion of the hard mask covers the field region of the read sensor stack. Thus, the hard mask exposes a of the read sensor stack between the sensor and field portions of the hard mask. The field mask covers the field portion of the hard mask. The field mask exposes the sensor portion of the hard mask that is on the sensor region and a portion of the read sensor stack between the sensor region and the field region. In some embodiments, the portion of the read sensor stack exposed by the hard mask is the same as that which is exposed by the field mask. However, in other embodiments, the portions of the read sensor stack exposed by the hard mask and field mask differ. In some embodiments, the hard mask is formed of one or more of SiC, aluminum oxide, amorphous carbon, Ta, and tantalum oxide. In some embodiments, the field mask is formed from photoresist or an analogous material. The field mask has a sufficient thickness for the hard mask RIE, read read sensor milling, and lift off. For example, the thickness of a photoresist field mask may be approximately one micron or more in some embodiments. In some embodiments, providing the hybrid mask includes depositing a hard mask layer and providing a first mask on the hard mask layer. A first portion of the first mask covers the sensor portion of the hard mask. A second portion of the first mask covers at least a portion of the field portion of the hard mask. The first mask may include a bottom antireflective coating layer, such as an AR3 layer and a photoresist layer on the AR3 layer. In some embodiments, the pattern of the first mask is transferred to the hard mask layer, forming the hard mask. In some embodiments, another layer is provided on the hard mask layer. In some such embodiments, this layer is a Cr layer. In such embodiments, the pattern of the first mask is transferred to the additional layer. A photoresist layer may then be provided on the hard mask. The photoresist layer is then pattern to form the field mask that covers the field region, but exposes the sensor region. In some embodiments, the pattern of the field mask plus the portion of the first mask in the sensor region are transferred to the hard mask. In such embodiments, the portion of the underlying read sensor stack between the sensor region and the field region exposed by the hard mask and the field mask is the same. However, the hard mask covers the sensor region, while the field mask typically does not.

The read sensor is defined from the read sensor stack in the track width direction, via step106. The exposed portion of the read sensor stack is thus removed. Step106may include performing an ion mill. The read sensor may be a TMR junction, a GMR junction, or other sensor. The read sensor has junction angles at its base in the track width direction and a track width. In some embodiments, the track width is less than thirty nanometers.

At least one hard bias layer for a hard bias structure is deposited, via step108. Hard bias material(s) include those materials having a sufficiently high coercivity that normal operation of the magnetoresistive structure does not alter the magnetization (and thus the bias) of the hard bias materials. A portion of the hard bias material(s) is substantially adjacent to the magnetoresistive structure in the track width direction. An insulating layer may be deposited prior to the hard bias materials. In addition, seed and/or capping layers may also be provided in step108. The seed and/or capping layer(s) may each include sub-layers.

A portion of the hard bias layer(s) adjoining the sensor region is sealed, via step110. In some embodiments, sealing is accomplished by depositing one or more layers. For example, sealing the hard bias layer(s) may include depositing a bilayer including a Ta sub-layer and a Ru sub-layer on the Ta sub-layer. In another embodiment, the step of sealing the hard bias layer(s) may include depositing a trilayer including a Ru sub-layer sandwiched by two Ta sub-layers.

The field mask is lifted off, via step112. Thus the portion of the hard bias layer(s) on the field mask is removed. The transducer is planarized, via step114. Step114may include performing a CMP. In other embodiments, other mechanisms may be used to planarize the transducer. Thus, a portion of the hard bias structure as well as the hard mask is removed. The hard bias may thus be removed from the region on top of the read sensor. In some embodiments, a remaining portion of the hard mask is removed after the transducer is planarized. For example, an RIE appropriate for the hard mask maybe performed. Because the hard mask may be thinned in the planarization of step114, removal of the hard mask may be facilitated. Fabrication of the transducer may then be completed. For example, the stripe height (length perpendicular to the ABS) for the read sensor may be defined. A nonmagnetic gap, shields, and other structures may also be formed.

FIG. 3depicts the transducer130after the method100is completed. For clarity,FIG. 3is not to scale. In addition, only a portion of the transducer130is shown. The transducer is also described in the context of particular layers and structures. However, sublayers and/or substructures may also be provided. In the embodiment shown, the read sensor stack is a TMR stack and has been so labeled. The read transducer130includes a magnetoresistive sensor132S, remaining TMR stack132F, insulating layer134, hard bias structures136on underlying layers131. Thus, the underlying layers131may be termed a substrate. The transducer130includes field regions138and sensor region140in which the TMR sensor132S resides. Because they are in the field regions138, the remaining portions of the read sensor stack are labeled132F.

Using the method100, the transducer130having a magnetoresistive read sensor132may be formed. Because a hard mask is used in the sensor region140without a photoresist mask on this region140, a read sensor132S having the desired small track width may be fabricated. Because a field mask that can be lifted off or removed in some analogous, simple fashion, the hard bias material(s) may be more easily removed from the larger field regions138. Damage to the underlying layers132F and/or136may thus be reduced or avoided. Because the hard bias layer(s)136are sealed, oxidation and/or other issues with the hard bias layer(s)136may be mitigated or prevented. Further, planarizing the transducer, and the attendant thinning of the hard mask, may reduce stresses due to the hard mask. This may limit or prevent delamination of the TMR sensor132S during removal of the hard mask. Thus, the fabrication of the transducer130may be improved.

FIG. 4is a flow chart depicting another exemplary embodiment of a method150for fabricating a magnetic recording transducer.FIGS. 5-14depict ABS views of another exemplary embodiment of a magnetic recording transducer200during fabrication. Because the transducer200is being formed inFIGS. 5-13, the transducer200is denoted as transducer200A,200B,200C,200D,200E,200F,200G,200H,200I and200J inFIGS. 5,6,7,8,9,10,11,12,13and14, respectively. However, the transducer is simply referred to as the transducer200in the text. For clarity,FIGS. 5-14are not to scale. The method150is described in the context of the transducer200. For simplicity, some steps of the method150may be omitted. The method150is also described in the context of providing a single recording transducer200. However, the method150may be used to fabricate multiple transducers at substantially the same time. The method150and transducer200are also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method150also may start after formation of other portions of the magnetic recording transducer200. Further, the transducer may be considered to have a device region, in which the magnetoresistive structure is to be formed, and a field region distal from the magnetoresistive structure.

A stack for the read sensor is deposited, via step152. The magnetoresistive layers may include a pinning layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. In addition, seed and/or capping layers may be used. Examples of such layers are described above.

A hard mask layer is provided on the read sensor stack, via step154. Step154includes blanket depositing a hard mask layer such as SiC, amorphous carbon (e.g. sputtered carbon), aluminum oxide, Ta, and/or tantalum oxide on the read sensor stack. For the purposes of describing the method150, it is assumed that an SiC layer is used. In some embodiments, the step154includes depositing a hard mask layer having a thickness of not more than seventy nanometers. In another embodiment, the hard mask layer provided in step154has a thickness of not more than sixty nanometers. However, in other embodiments, other thicknesses of the hard mask layer may be used.

A Cr layer is deposited on the hard mask layer, via step156. In other embodiments, another layer may be used.

A first mask is provided, via step158. The first mask may include a BARC layer and a photoresist layer on the BARC layer. The first mask has a pattern that includes a first portion covering a sensor portion of the hard mask layer and a second portion covering at least a portion of the field region.

The pattern of the first mask is transferred to the Cr layer, via step160. Thus, the Cr is removed from a portion of the hard mask layer. The resist portion of the first mask may then be removed using a resist strip.FIG. 5depicts an ABS view of the transducer200after the exposed portion of the Cr is removed in step160. Thus, a sensor portion202and a field portion204of the transducer204are shown. The transducer200also includes a read sensor stack206on underlying layer(s) indicated as a substrate205. The substrate205may include underlying layers such as shield or insulating gap layers. Also shown are a capping layer207for the read sensor stack206and a hard mask layer208. In addition, the hard mask layer208is shown as being blanket deposited on the read sensor stack206. A Cr layer210that has been patterned is also shown. The first mask211is included. The first mask211includes an AR3 layer212and a photoresist layer214. The AR3 layer acts as a BARC layer for the photoresist layer214. The first mask211covers part of the field region204and the sensor region202.FIG. 6depicts the transducer200after the photoresist mask214is removed after the exposed portion of the Cr is removed. Thus, the AR3 layer212′ remains from the first mask211.

Another photoresist layer is provided, via step162. This photoresist layer is patterned to form a field mask, via step164. The field mask also covers the remaining portion212′ of the first mask211in the field region204. Further, the field mask covers the field portion of the hard mask layer207.FIG. 7depicts the transducer200after step164is performed. Thus, the field mask216is shown. In the embodiment shown, the field mask216extends beyond the first mask/BARC layer212′. However, in other embodiments, the field mask216may extend only to the edge of the first mask/BARC layer212′.

The pattern of the field mask216and remaining exposed portion of the first mask—the BARC layers212′ and Cr layer210′ in the sensor region202is transferred to the hard mask208, via step166. Thus, the exposed portion of the hard mask208between the field mask216and BARC layer212′/Cr210′ in the sensor region202is removed.FIG. 8depicts the transducer200after step166is performed. A portion of the hard mask layer208has been removed, hard mask208′. The hard mask208′ includes portions208S and208F in the sensor region202and the field region204, respectively. The hard mask208′ and the field mask216together form hybrid mask218. In some embodiments, any remaining portion of the first mask211, such as the BARC212′ as well as the Cr layer210′ may be considered part of the hybrid mask.

The read sensor is defined from the read sensor stack206in a track width direction, via step168. In some embodiments, the read sensor may also be defined in the stripe height direction. Step168may include performing an ion mill. Thus, a portion of the read sensor stack206between the sensor region202and the field region204is removed. Also in step168any remaining portion of the first photoresist layer214(shown inFIG. 5only) on the sensor region202is consumed. In the embodiment shown, the first photoresist layer214is consumed previously.FIG. 9depicts the transducer200after step168is performed. Thus, the sensor206S has been formed. Because of the hard mask208S, the track width of the sensor206S may be small, including in the sub-thirty micron range. In addition, a portion of the read sensor stack206F covered by the field mask216and portion208F of the hard mask208F remains in the field204.

One or more hard bias layers are deposited, via step170. In some embodiments, the hard bias layer(s) are blanket deposited.FIG. 10depicts the transducer200after step170is performed. A portion of the hard bias layer(s) are on the field mask216of the hybrid mask218, a portion of the hard bias layer(s) would be between the field region204and the sensor region202, and a portion of the hard bias layer(s) would be on the sensor region202.

A first Ta layer is deposited, via step172. A Ru layer is deposited on the first Ta layer, via step174. A second Ta layer is deposited on the Ru layer, via step176. Thus, the three layers form a sealing layer. In other embodiments, other layer(s) may be deposited to seal the hard bias layers. A sacrificial aluminum oxide layer on the second Ta layer, via step178.FIG. 10depicts the transducer100after step178is performed. Thus, hard bias layer(s)220are shown. In addition, a sealing layer222that would include the Ta/Ru/Ta trilayer is also depicted. Sacrificial aluminum oxide layer224that covers the portion of the transducer200depicted. In some embodiments, the sacrificial layer may be thinner on the sidewalls of the hybrid mask218due to the shadowing effect.

The field mask216is lifted off, via step180. In addition, the BARC layer212′ is removed from the field region204, via step182.FIG. 11depicts the transducer200after step182is performed. Thus, the field mask216and BARC214′ have been removed. Portions of the hard bias220, sealing layer(s)222, and sacrificial aluminum oxide layer224on the field mask216have been removed. Thus, only hard bias layer(s)220′, sealing layer(s)222′, and sacrificial layer224′ remain.

A remaining portion of the Cr layer210′ is removed, via step184. In some embodiments, a portion of the hard mask208′ is also removed. Further, the portion of the hard bias layer(s)220′ may be removed.FIG. 12depicts the transducer200after step184is performed. Thus, the Cr layer210has been removed. The hard mask208″ remains, but has been thinned. More specifically, the hard mask208S′ and208F′ have been thinned. The may reduce the stress in the hard mask208F′ and208S′. Thus, delamination of the sensor stack206F and the sensor206S in subsequent steps may be reduced. Further, adjusting of the thickness of the sacrificial layer224′ may allow the hard mask thickness208F′ and208S′ to be thinned to the desired thickness in step184. Thus, the process margins for a subsequent planarization may be improved.

The transducer is planarized, via step186. In some embodiments, step186includes performing a CMP.FIG. 13depicts the transducer200after step186is performed. In the embodiment shown, a portion of the hard mask208F″ in the field region remains. However, in another embodiment, the hard mask208″ may be completely removed. Thus, in some embodiments, any hard mask208″ remaining is optionally removed, via step188.FIG. 14depicts the transducer200after step186or188has been performed. Thus, the hard mask208″ has been completely removed. Fabrication of the transducer200may then be completed. Using the method150, the transducer200having a magnetoresistive read sensor206S may be formed. Use of the hybrid mask218may facilitate fabrication of the transducer. Because the hard mask208S of the hybrid mask218is used in the sensor region202without a photoresist mask on this region202, a read sensor206S having the desired small track width may be fabricated. Because a field mask216that can be lifted off or removed in some analogous, simple fashion, the hard bias material(s)220may be more easily removed from the larger field regions204. Damage to the underlying layers2206F and206S may thus be reduced or avoided. Because the hard bias layer(s)220are sealed using sealing layer(s)222, oxidation and/or other issues with the hard bias layer(s)220may be mitigated or prevented. Further, planarizing the transducer, and the attendant thinning of the hard mask208′″, may reduce stresses due to the hard mask208″. This may limit or prevent delamination of the TMR stack206F and206S Thus, the fabrication of the transducer200may be improved.