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Corrosion Free Cleaning Solution for GMR Head During Aqueous Fabrication Process

IP.com Disclosure Number: IPCOM000014534D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 4 page(s) / 67K

Publishing Venue

IBM

Abstract

GMR sensor corrosion during FAB aqueous processing condition is a prevailing problem. The charts below show the effect of water and ionic solution on the dissolution of various GMR sensor materials including Co, NiMn and Cu. The charts below show the sheet resistance measurements as a function of soaking time in DI water and in 0.01M NaHCO3 solutions. Sheet resistance increase correlates roughly to loss of material, and it is thus a rough gauge of severity of corrosion. As can be seen from these charts, NiMn corrodes rapidly in NaHCO3 solution, while relatively stable in DI water. Co corrodes quickly in NaHCO3 and DI water environment. Cu is relatively stable in both environments.

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  Corrosion Free Cleaning Solution for GMR Head During Aqueous Fabrication Process

   GMR sensor corrosion during FAB aqueous processing condition is a prevailing problem. The charts below show the effect of water and ionic solution on the dissolution of various GMR sensor materials including Co, NiMn and Cu. The charts below show the sheet resistance measurements as a function of soaking time in DI water and in 0.01M NaHCO3 solutions. Sheet resistance increase correlates roughly to loss of material, and it is thus a rough gauge of severity of corrosion. As can be seen from these charts, NiMn corrodes rapidly in NaHCO3 solution, while relatively stable in DI water. Co corrodes quickly in NaHCO3 and DI water environment. Cu is relatively stable in both environments.

000 50 100 150 200

Time, in Minutes

100A Co film on Glass

70 20 40 60 80 100 120 140

Time, in Minutes

100A NiMn film on Glass

1000

1000

800800

600600

400400

200200

DI only 100 us NaHCO3

DI Only 100 us NaHCO3

Sheet Resistance Change

Sheet Resistance

Sheet Resistance

0 20 40 60 80 100 120 140

Time, in minutes

100A Cu Film on Glass

12

11

10

DI Only 100 us NaHCO3

9

8

   In this invention disclosure, we identified a surfactant, Liquinox (Alkonox), that exhibited some corrosion inhibition properties for materials such as Co and NiMn. The charts below show that with NiMn in 0.01M NaHCO3, the corrosion rate is around 0.8 mA which corresponds to 160A/min. With the use of 0.1% Liquinox, the corrosion (blue triangle) dropped to 20A/min. On Co, the effect of Liquinox is more dramatic. The corrosion rate decreased from 200A/min. without Liquinox to less than 10A/min. Similar effect was observed on Cu (although data not shown).

   In addition, we also found that if we modify the detergent by removing the EDTA from the surfactant, the corrosion protection efficiency is further improved. The charts below showed that on NiMn, after removing EDTA from the liquinox, the overall corrosion current went from 0.8 mA to 0.05 mA, a factor of 16 decrease. With Co, the effect of EDTA removal is not as obvious.

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   To further enhance the corrosion inhibition effectiveness of the cleaning solution, we evaluated the effect of BTA for corrosion inhibition of various GMR sensor materials and found that 0.01% of BTA added to Liquinox solution can further reduce the corrosion rate by a factor of 5-10 depending on the metal. For instance, NiMn corrosion rate dropped from 160A/min. (0.8mA) to 2A/min (0.01mA), while for Co, the overall corrosion rate went from 200A/min (1 mA) to 1A/min (0.005 mA). Cu corrosion rate dropped from 4A/min. to below the instrument measurement limit.

NiMn in 0.01M NaHCO3 w/Various Additives, @ 0.15V

Co 0.01M NaHCO3 w/Various Additives, @...