METHOD FOR PROVIDING A MAGNETIC RECORDING TRANSDUCER USING A CHEMICAL BUFFER
A method for fabricating a magnetic recording transducer is described. The magnetic recording transducer has an underlayer and at least one layer on the underlayer. The layer(s) are capable of including an aperture that exposes a portion of the underlayer. The method includes providing a neutralized aqueous solution having a chemical buffer therein. The chemical buffer forms a nonionic full film corrosion inhibitor. The method also includes exposing a portion of the magnetic recording transducer including the layer(s) to the neutralized aqueous solution including the chemical buffer. In one aspect this exposure occurs through a chemical mechanical planarization.
This application is a divisional of U.S. patent application Ser. No. 13/801,408, filed on Mar. 13, 2013, which is hereby incorporated by reference in its entirety.
BACKGROUNDConventional magnetic recording heads can be fabricated in a number of ways.
Although the conventional method 10 can be used to form the conventional transducer, there are drawbacks.
Accordingly, what is needed is an improved method for fabricating a magnetic recording transducer, including a magnetoresistive sensor.
SUMMARYA method for fabricating a magnetic recording transducer is described. The magnetic recording transducer has an underlayer and at least one layer on the underlayer. The layer(s) are capable of including an aperture that exposes a portion of the underlayer. The method includes providing a neutralized aqueous solution having a chemical buffer therein. The chemical buffer forms a nonionic full film corrosion inhibitor. The method also includes exposing a portion of the magnetic recording transducer including the layer(s) to the neutralized aqueous solution including the chemical buffer. In one aspect this exposure occurs through a chemical mechanical planarization.
2A-2C are diagrams depicting a conventional read transducer 50 as viewed from the air-bearing surface (ABS) during fabrication. The conventional read transducer 50 is formed using the conventional method 10. Thus, the conventional read transducer 50 includes a shield 52 and a sensor 60 having an AFM layer 62, a pinned layer 64, a tunneling barrier layer 66, and a free layer 68. Aluminum oxide refill 54 and Ru cap 70 are also shown. Note that the Ru cap 70 may be made of Ru layers that are deposited at different times. Thus,
The method 100 may also commence after formation of other portions of the magnetic recording transducer. For example, the method 100 may start after the underlayer and at least one layer on the underlayer are fabricated. The underlayer may be an aluminum oxide refill, while the layer may be a Ru layer. However, other underlayers and/or layers are possible. Further, the layer and underlayer may each be a multilayer, alloy, or have another structure. The underlayer may also reside on other layers. During fabrication, the layer may have an aperture formed therein. For example, a Ru layer may have an aperture formed therein during planarization such as a CMP. Such an aperture exposes part of the underlayer.
A neutralized aqueous solution having a chemical buffer therein is provided, via step 102. The chemical buffer is for forming a nonionic full film corrosion inhibitor. This nonionic full film corrosion inhibitor forms a full film on the layer(s) of the magnetic transducer exposed to the solution. For example, step 102 may include neutralizing a solution and introducing nonionic surfactant(s). In some embodiments, therefore, step 102 is performed by introducing one or more additives to a solution. The additives may be used to provide the chemical buffer as well as to neutralize a non-neutral solution. In some embodiments, the additive(s) include at least one amine. In other embodiments, the additive(s) include at least one polyoxyethylated nonionic surfactant. The polyoxyethylated surfactants may reduce the surface tension, function as full film corrosion inhibitors and neutralize the solution. Examples of the polyoxyethylated surfactant include but may not be limited to alkylphenols having a hydrophobic tail portion including less than fifteen C—C chains and fatty alcohol ethoxylates also having a hydrophobic tail portion that includes less than the fifteen C—C chains. The tail portions of the alkylphenols and the fatty alcohol ethoxylates may differ, but each is desired to have less than fifteen C—C chains. The concentration of the chemical buffer is desired to be in the semi-micelle range. Thus, not all of the chemical buffer forms micelles in the solution. Instead, at least part of the chemical buffer forms the nonionic full film corrosion inhibitor. Examples of the amine(s) include but may not be limited to quaternary ammonium salt(s). Note that in some embodiments, the amine(s) may bubble in the water. Other water soluble nonionic surfactants with hydroxyl groups or polyoxyethylene chains may also be used to inhibit corrosion. In still other embodiments, some combination of these additives and/or other additives may be used.
A portion of the magnetic recording transducer the layer(s) is exposed to the neutralized aqueous solution including the chemical buffer, via step 104. In some embodiments, the neutralized aqueous solution is a planarization solution. In such embodiments, step 104 may include performing a CMP using a slurry containing the solution formed in step 102.
Because the layer(s) are exposed to the solution in step 104, a nonionic full film corrosion inhibitor may be formed on the magnetic recording transducer. Stated differently a layer of the nonionic full film corrosion inhibitor may be formed on the surface of the portion of the magnetic transducer being fabricated. If step 102 includes using the solution as part of a CMP slurry, the mechanical action of the CMP may still remove portions of the layer as well as the underlayer. However, the nonionic full film corrosion inhibitor may reduce or prevent chemical interactions between the underlayer or layer and the remainder of the solution. As a result, the hydration of the underlayer and resulting removal of portions of the underlayer may be reduced or prevented. Corrosion may also be inhibited. Consequently, damage to other components covered by the underlayer may be diminished or eliminated. For example, corrosion of a magnetoresistive sensor may be addressed. In addition, the layer(s) may be held in the solution in step 104 prior to a post CMP clean. Because of the nonionic full film corrosion inhibitor and the neutral pH of the solution, damage to the layer(s) may also be prevented while they remain in this solution. Thus, yield for fabrication methods employing the method 100 and performance of magnetic recording transducer so formed may be enhanced.
The non-neutral aqueous solution is neutralized, via step 112. Step 112 may include providing additive(s) such as KH2PO4 and/or NaOH to the non-neutral solution. In other embodiments, the polyoxyethylated nonionic surfactants described above may be used to neutralize the solution. The solution formed is desired to have a pH close to 7.0. In some such embodiments, the pH of the solution is in the 6.5-7.5 range.
At least one additive for the chemical buffer is introduced to the solution, via step 114. The additives may include one or more of the polyoxyethylated nonionic surfactants, amines, and/or other additives described above.
The transducer 150 is being exposed to the solution 160 in the step 104. For example, the solution 160 may be used for a CMP. The transducer 150 may also remain immersed in the solution prior to a post CMP clean. In addition, an aperture 156 has been formed in the upper layer 154. Thus, without more, the underlayer 152 would be exposed to the solution. However, because the solution was prepared using the method 100 and/or 110, a nonionic full film corrosion inhibitor layer 166 has been formed. In the embodiment shown in
Using the method 100 and/or 110, performance and fabrication of the magnetic transducer 150 may be enhanced. The magnetic transducer 150 may undergo a CMP, be held in solution prior to a post CMP clean, or undergo other processing that exposes the underlayer 152 to the ambient. However, because the solution 160 is neutral, the underlayer 152 may be less likely to be dissolved in the solution 160. Because of the presence of the chemical buffer 162 and formation of the nonionic full film corrosion inhibitor layer, corrosion of portions of the transducer 150 including but not limited to the layers 152 and 154 may be reduced or eliminated. Thus, fabrication of the magnetic transducer 150 may be improved.
A neutralized aqueous solution having a chemical buffer therein is provided, via step 202. The chemical buffer forms a nonionic full film corrosion inhibitor. This nonionic corrosion inhibitor would form a full film on the upper layer. This full film may be a monolayer of the chemical additive. In some embodiments, step 202 is performed by introducing one or more polyoxyethylated nonionic surfactants and/or amines. Such surfactants may both neutralize the solution and allow for formation of the nonionic full film corrosion inhibitor. The polyoxyethylated surfactant may include but may not be limited to alkylphenols having a hydrophobic tail portion including less than fifteen C—C chains and fatty alcohol ethoxylates also having a hydrophobic tail portion that includes less than the fifteen C—C chains. The tail portions of the alkylphenols and the fatty alcohol ethoxylates may differ, but each is desired to have less than fifteen C—C chains. Examples of the amine(s) include but may not be limited to quaternary ammonium salt(s). The concentration of the chemical buffer is desired to be in the semi-micelle range. Thus, not all of the chemical buffer forms micelles in the solution. Instead, at least part of the chemical buffer forms the nonionic full film corrosion inhibitor.
In step 204, a CMP is performed on the magnetic recording transducer 250 using the neutralized aqueous solution provided in step 202. For example,
Claims
1. A method for fabricating a magnetic recording transducer having an underlayer at least one layer on the underlayer and a structure under the underlayer, the at least one layer capable of including an aperture that exposes a portion of the underlayer, the method comprising:
- providing a neutralized aqueous solution having a chemical buffer therein, the chemical buffer for forming a nonionic full film corrosion inhibitor, the nonionic full film corrosion inhibitor including a monolayer of at least a portion of the chemical buffer, the nonionic full film corrosion inhibitor inhibiting removal of the portion of the underlayer exposed by the aperture by forming the nonionic full film corrosion inhibitor on at least the aperture; and
- exposing a portion of the magnetic recording transducer including the at least one layer to the neutralized aqueous solution including the chemical buffer, corrosion of the structure being inhibited by inhibition of removal of the portion of the underlayer by the nonionic full film corrosion inhibitor.
2. The method of claim 1 wherein the underlayer further includes aluminum oxide.
3. The method of claim 2 wherein the layer includes Ru.
4. The method of claim 1 wherein the neutralized aqueous solution includes a chemical mechanical planarization (CMP) solution.
5. The method of claim 1 wherein the step of providing the neutralized aqueous solution having the chemical buffer therein further includes:
- neutralizing a non-neutral aqueous solution; and
- providing at least one additive for the chemical buffer after the step of neutralizing the non-neutral aqueous solution.
6. The method of claim 5 wherein the non-neutral aqueous solution is either an acidic aqueous solution or a basic aqueous solution.
7. The method of claim 1 wherein the step of providing the neutralized aqueous solution having the chemical buffer therein further includes:
- providing at least one additive for the chemical buffer to a non-neutral aqueous solution; and
- neutralizing the non-neutral aqueous solution after the step of providing the at least one additive.
8. The method of claim 7 wherein the non-neutral aqueous solution is either an acidic aqueous solution or a basic aqueous solution.
9. A method for fabricating a magnetic recording transducer including a magnetoresistive sensor, an aluminum oxide layer adjacent to the magnetoresistive sensor and a Ru layer on the aluminum oxide layer, the method comprising:
- providing a neutralized aqueous solution having a chemical buffer therein, the chemical buffer for forming a nonionic full film corrosion inhibitor, the chemical buffer including at least one of at least one amine and at least one polyoxyethylated nonionic surfactant, the at least one polyoxyethylated surfactant including at least one of alkylphenols having a first hydrophobic tail portion including less than fifteen C—C chains and fatty alcohol ethoxylates having a second hydrophobic tail portion including less than the fifteen C—C chains, the at least one amine includes at least one quaternary ammonium salt; and
- performing a chemical mechanical planarization (CMP) using the neutralized aqueous solution as at least part of a slurry, the CMP capable of forming an aperture in the Ru layer and exposing a portion of the aluminum oxide layer under the aperture.
Type: Application
Filed: Nov 2, 2015
Publication Date: Feb 25, 2016
Inventors: MASAHIRO OSUGI (SUNNYVALE, CA), LILY YAO (HAYWARD, CA), MING JIANG (SAN JOSE, CA), GUANGHONG LUO (FREMONT, CA), WAI-MING J. KAN (SAN RAMON, CA)
Application Number: 14/929,754