Headway Technologies, Incorporated

Cherng Chyi Han

Min Li

Ru-Ying Tong

Cheng Tzong Horng

Mao-Min Chen

Yun-Fei Li

Kochan Ju

Simon H Liao

Hui-Chuan Wang

Yu-Hsia Chen

You Fong Zheng

Minghui Yu

Yimin Guo

Yue Liu

Pokang Wang

Jianing Zhou

Ruhang Ding

Zhigang Bai

Moris Musa Dovek

Chyu-Jiuh Torng

Yan Wu

Tong Zhao

Jiun-Ting Lee

Min Zheng

You Feng Zheng

A TMR (tunneling magnetoresistive) read sensor is formed in which a portion of the sensor stack containing the ferromagnetic free layer and the tunneling barrier layer is patterned to define a narrow trackwidth, but a synthetic antiferromagnetic pinning/pinned layer is left substantially unpatterned and extends in substantially as-deposited form beyond the lateral edges bounding the patterned portion. The narrow trackwidth of the patterned portion permits high resolution for densely recorded data. The larger pinning/pinned layer significantly improves magnetic stability and reduces thermal noise, while the method of formation eliminates possible ion beam etch (IBE) or reactive ion etch (RIE) damage to the edges of the pinning/pinned layer.

Reader sensor structure and its method of construction

A two part ion beam etch sequence involving low energy (&#x3c;300 eV) is disclosed for fabricating a free layer width (FLW) as small as 20-25 nm in a MTJ element. A first etch process has one or more low incident angles and accounts for removal of 70% to 100% of the MTJ stack that is not covered by an overlying photoresist layer. The second etch process employs one or more high incident angles and a sweeping motion that is repeated during a plurality of cycles. Sidewall slope may be adjusted by varying the incident angle during either of the etch processes. FLW is about 30 nm less than an initial critical dimension in the photoresist layer while maintaining a MR ratio over 60% and low RA (resistance&#xd7;area) value of 1.0 ohm-&#x3bc;m.

Two step method to fabricate small dimension devices for magnetic recording applications

A perpendicular magnetic recording (PMR) head is fabricated with a main pole shielded laterally by a pair of side shields, shielded above by a trailing shield and shielded optionally below by a leading shield. The shields and the seed layers on which they are formed are formed of materials having substantially the same physical characteristics including the same material composition, the same hardness, the same response to processes such as ion beam etching (IBE), chemical mechanical polishing (CMP), mechanical lapping, such as the slider ABS lapping, the same coefficient of thermal expansion (CTE) as well as the same B. Optionally, the trailing shield may be formed on a high Bseed layer to provide the write head with improved down-track performance.

Wrap-around shielded writer with highly homogeneous shield material

A three step ion beam etch (IBE) sequence involving low energy (&#x3c;300 eV) is disclosed for trimming a sensor critical dimension (free layer width=FLW) to less than 50 nm. A first IBE step has a steep incident angle with respect to the sensor sidewall and accounts for 60% to 90% of the FLW reduction. The second IBE step has a shallow incident angle and a sweeping motion to remove residue from the first IBE step and further trim the sidewall. The third IBE step has a steep incident angle to remove damaged sidewall portions from the second step and accounts for 10% to 40% of the FLW reduction. As a result, FLW approaching 30 nm is realized while maintaining high MR ratio of over 60% and low RA of 1.2 ohm-&#x3bc;m. Sidewall angle is manipulated by changing one or more ion beam incident angles.

Method to fabricate small dimension devices for magnetic recording applications

Improved CPP GMR devices have been fabricated by replacing the conventional seed layer (typically Ta) with a bilayer of NiCr on Ta, said seed being deposited on the NiFe layer that constitutes a magnetic shield. Additional improvement was also obtained by replacing the conventional non-magnetic spacer layer of copper with a sandwich structure of two copper layers with an NOL (nano-oxide layer) between them. A process for manufacturing the devices is also described.

Seed/AFM combination for CCP GMR device

Patterned, longitudinally and transversely antiferromagnetically exchange biased GMR sensors are provided which have narrow effective trackwidths and reduced side reading. The exchange biasing significantly reduces signals produced by the portion of the ferromagnetic free layer that is underneath the conducting leads while still providing a strong pinning field to maintain sensor stability. In the case of the transversely biased sensor, the magnetization of the free and biasing layers in the same direction as the pinned layer simplifies the fabrication process and permits the formation of thinner leads by eliminating the necessity for current shunting.

Patterned, synthetic longitudinally exchange biased GMR sensor

By using a free layer that includes a NiFe layer containing between 65 and 72 atomic percent iron, an improved CPP GMR device has been created. The resulting structure yields a higher CPP GMR ratio than prior art devices, while maintaining free layer softness and acceptable magnetostriction. A process for manufacturing the device is also described.

Free layer for CPP GMR having iron rich NiFe

An improved seed/AFM structure is formed by first depositing a layer of tantalum on the lower shield. A NiCr layer is then deposited on the Ta followed by a layer of IrMn. The latter functions effectively as an AFM for thicknesses in the 40-80 Angstrom range, enabling a reduced shield-to-shield spacing.

Process of manufacturing a seed/AFM combination for a CPP GMR device

One of the major requirements for higher frequency extendability is to reduce yoke length and inductance in order to have fast saturation. This has been accomplished by using a design that provides a cavity in the lower pole piece inside which is located at least two coils, one on top of the other. A process for manufacturing the device is also described.

High data rate writer with low resistance coil and short yoke

Method for fabricating a patterned, synthetic transverse exchange biased GMR sensor

A method for forming a planar GMR read-head having a narrow read gap, a narrow track-width and being well insulated from its lower shield. The method requires the formation of a planarized bottom magnetic shield in which concave regions, symmetrically disposed about a track-width region, are filled with a layer of dielectric to provide added insulation. The dielectric filled shield is planarized and an additional planar dielectric layer, a thin planar GMR sensor layer and a planar PMGI layer of uniform thickness is formed on it. A layer of photoresist is deposited on the PMGI layer and a bi-layer lift-off stencil of uniform height above the GMR layer and symmetric overhang regions is formed. The uniformity of the lift-off stencil, which is a result of the planarity of the layers on which it is formed, allows the deposition of conductive lead and biasing layers with controlled overspread.

Method to make planarized GMR head for high track density

Method for fabricating a patterned, synthetic transversely exchanged biased GMR sensor

Present processes used for planarizing a cavity filled with a coil and hard baked photoresist require that a significant amount of the thickness of the coils be removed. This increases the DC resistance of the coil. In the present invention, CMP is terminated as soon as the coils are exposed, allowing their full thickness to be retained and resulting in minimum DC resistance. Application of this process to the manufacture of a planar magnetic write head is described.

Low DC coil resistance planar writer

Present processes used for planarizing a cavity filled with a coil and hard baked photoresist require that a significant amount of the thickness of the coils be removed. This increases the DC resistance of the coil. In the present invention a layer of alumina is deposited onto the surface of the excess photoresist, following which CMP is initiated. The presence of the alumina serves to stabilize the photoresist so that it does not delaminate. CMP is terminated as soon as the coils are exposed, allowing their full thickness to be retained and resulting in minimum DC resistance. Application of this process to the manufacture of a two coil planar magnetic write head is described.

Short yoke length planar writer with low DC coil resistance

A problem associated with current bottom spin valve designs is that it is difficult to avoid magnetic charge accumulation at the edge of the sensor area, making a coherent spin rotation during sensing difficult to achieve. This problem has been eliminated by introducing an exchange coupling layer between the free layer and the ferromagnetic layer that is used to achieve longitudinal bias for stabilization and by extending the free layer well beyond the sensor area. After all layers have been deposited, the read gap is formed by etching down as far as this layer. Since it is not critical exactly how much of the biasing layers (antiferromagnetic as well as ferromagnetic) are removed, the etching requirements are greatly relaxed. Whatever material remains in the gap is then oxidized thereby providing a capping layer as well as a good interface for specular reflection in the sensor region.

Growing community of inventors

San Jose, CA, United States of America

Cherng Chyi Han