Process of octagonal pole for microwave assisted magnetic recording (MAMR) writer

A microwave assisted magnetic recording (MAMR) writer structure having a spin transfer oscillator (STO) self aligned to an adjoining octagonal shaped portion of a write pole along an air bearing surface (ABS), comprising:

• (a) an octagonal write pole formed on a substrate, comprising:
• (1) a lower portion including a leading edge of the octagonal write pole and two lower sections of write pole sidewalls formed at a first angle with respect to a plane that is perpendicular to the substrate and to the ABS such that the width of the leading edge is less than the distance between two ends of the two lower sections that are a first distance from the substrate in a down track direction;
• (2) a middle portion including two middle sections of write pole sidewalls each having a first end connected to an end of an upper sidewall section at a first corner, and a second end connected to an end of a lower sidewall section at a second corner, said middle sections of sidewalls each form a second angle with respect to a plane that is perpendicular to the substrate and to the ABS and a distance between second corners along a second plane parallel to the ABS is greater than a distance between first corners along a first plane parallel to the ABS;
• and
• (3) a top portion including a trailing edge of the octagonal write pole and two upper sidewall sections that extend in a down track direction from two ends of the trailing edge such that an end of each upper sidewall section opposite the trailing edge connects with an end of a middle sidewall section at a first corner;
• and
• (b) a STO with a lower surface that contacts the trailing edge of the octagonal write pole, a top surface, and two sidewalls that connect the top surface with the bottom surface and are formed coplanar with the upper sidewall sections of the top portion of the octagonal write pole, said STO is comprised of a field generation layer (FGL), non-magnetic spacer, and spin injection layer (SIL) that are sequentially formed on the trailing edge.

A method of forming a MAMR writer structure having a spin transfer oscillator (STO) self aligned to an adjoining top portion of an octagonal shaped write pole along an air bearing surface (ABS), comprising:

• (a) providing a write pole portion of a main pole layer formed on a substrate and within an insulation layer wherein the write pole has a trapezoidal shape at the ABS in which a leading edge that interfaces with the substrate has a smaller width in a cross track direction than a trailing edge which is formed coplanar with a top surface of the insulation layer, said trailing edge has a first width and is connected to the leading edge by two sidewalls;
• (b) depositing a STO stack of layers on the main pole layer and on the top surface of the insulation layer, said STO stack has a planar top surface;
• (c) forming a photoresist feature on the STO stack, said photoresist feature has two sidewalls formed essentially vertical to the STO top surface, a second width less than the first width in a cross track direction, and is aligned above the trapezoidal shaped write pole at the ABS;
• (d) performing a first ion beam etch (IBE) step to remove exposed regions of the STO stack, a top portion of the write pole below the exposed STO regions, and a top portion of the insulation layer to form a STO structure and an underlying top portion of the write pole having a second width and self aligned to the STO structure;
• said top portion has two sidewalls coplanar with said photoresist feature sidewalls and each of two sidewalls has an end formed at a first corner that is on a first plane which includes a top surface of the insulation layer;
• (e) performing a second IBE step with a sweeping motion that trims the second width of the photoresist feature and of the top write pole portion including trailing edge to a pole width, forms sloped sidewalls on a middle portion of the write pole wherein each of two sloped sidewalls has a first end at a first corner and a second end at a second corner where a distance between second corners is greater than a distance between first corners, and lowers the top surface of the insulation layer to a second plane that includes said second corners;
• (f) sequentially depositing a dielectric layer and an etch stop layer on the insulation layer and photoresist feature, and on the sidewalls of the photoresist feature and on top and middle portions of the write pole wherein a top surface of an adjacent section of the etch stop layer formed above the insulation layer is substantially coplanar with the top surface of the STO structure;
• (g) performing a third IBE step to remove portions of the dielectric layer and etch stop layer thereby exposing the photoresist feature;
• (h) removing the photoresist feature and performing a chemical mechanical polish (CMP) kiss lap process to form a top surface of the STO structure that is coplanar with the top portion of adjacent sections of the etch stop layer;
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• (i) depositing a trailing shield on the top surface of the STO structure, adjoining sections of dielectric layer, and on adjacent sections of the etch stop layer.