WO1993011532A1

WO1993011532A1 - Dual-layer etch process

Info

Publication number: WO1993011532A1
Application number: PCT/US1992/010306
Authority: WO
Inventors: Alan L. Sidman
Original assignee: Digital Equipment Corporation
Priority date: 1991-11-25
Filing date: 1992-11-24
Publication date: 1993-06-10
Also published as: DE4294247T1; GB9314080D0; GB2267256A

Abstract

A method is disclosed for wet etching selectively a seed layer and an adhesion layer from the underlayer of a thin film head wafer. A first etch solution, which selectively etches the seed layer while not significantly etching the adhesion layer and the underlayer, is applied to the surface of the seed layer on the underlayer for a sufficient period of time to remove the seed layer that is exposed to the etch solution, thereby significantly etching the exposed surface of the seed layer while not significantly etching the adhesion layer. A second etch solution, which selectively etches the adhesion layer while not significantly etching the seed layer and the underlayer, is applied to the surface of the adhesion layer on the underlayer for a sufficient period of time to remove the adhesion layer that is exposed to the second etch solution, thereby significantly etching the exposed surface of the adhesion layer while not significantly etching the seed layer and the underlayer.

Description

DUAL-LAYER ETCH PROCESS

Background of the Invention

Thin film heads (TFHs) are used to transfer magnetic information to and from magnetic disks. The TFHs are sensitive electronic devices that are made to exacting dimensions and tolerances.

TFH wafers can be made with an underlayer which serves as a substrate. The substrate typically includes a series of layers. The top layer of the underlayers typically contains a metal, metal oxide or a polymer.

In creating conductor layers in a TFH, an adhesion layer is typically disposed by vacuum sputtering on the surface of the top underlayer. The adhesion layer is used to improve the adhesion between a conductive seed layer and the underlayer. The seed layer is deposited on the adhesion layer which typically has a thickness of about fifty to about three hundred angstroms. It can include reactive metals which have an affinity for oxygen. Such reactive metals can cause sufficient bonding to the underlayer which can contain a metal, metal oxide or a polymer. Chromium is a frequently used material for such an adhesion layer.

The seed layer, which is typically deposited by sequential vacuum sputtering on top of the adhesion layer, is made of a metal, such as copper. The seed layer metal has a low electrical resistivity, high electromigration resistance and must be compatible with the plating bath and process used to subsequently through-mask microplate the TFH conductor. The seed layer acts as a conductor to facilitate electrical contact and current flow during electrodeposition of a metal to form a device conductor metal layer. The metal layer is often formed from copper. Typically, the seed layer has a thickness of about one thousand to about two thousand angstroms.

Typically, after depositing the seed layer, the wafer is spin coated with a photoresist solution, baked to evaporate any solvents from the photoresist solution and patterned miσro-lithographically with a thin film head conductor or stud microcircuit pattern on a metal plate. The photoresist film is chemically modified at locations exposed to the ON light. The photoresist, where exposed, can be removed by a developer to produce a three-dimensional photoresist mask on top of the seed layer in the shape of the geometry exposed during the patterning process. The wafer is subsequently placed in a plating cell with a copper-bearing electrolyte to deposit a metal layer in those opened areas of the photoresist where the conductive seed layer is exposed to the plating cell.

The photoresist mask is stripped from the TFH wafer after the metal layer has been formed. The metal layer is isolated by removing the exposed seed layer and the underlying adhesion layer. The removal process for the seed and adhesion layers typically is by vacuum etching, such as ion milling or sputter etching. This process removes material from the exposed surface of the wafer. The length of time for etching must be long enough to remove the exposed seed layer and adhesion layer from all areas of the wafer, plus some over-etch because of the need for uniformity and reproducibility. The etching can be two to three times longer than would be required to remove the seed and adhesion layers from a perfectly flat surface because of shadowing phenomenon and etching non-uniformity across the vacuum chamber.

Selective vacuum etch processes do not exist for TFH wafers for removal of adhesion and seed layers. Vacuum etching procedures, such as ion milling, can redeposit seed layer material elsewhere on the device. Transducer gap loss can be significant when removing the exposed seed layer and adhesion layer. Further, seed layer and adhesion layer materials that are not fully removed can lead to pole edge corrosion and electrostatic discharge through the head to the recording media or between layers of the thin film head. Electrostatic discharge at low amplitude can cause loss of recording area on recording media and electrostatic discharge at high amplitude can cause head crashes. Current processes have a low yield in a high vacuum system. The capital and maintenance costs for vacuum milling systems are high.

Another etch method is a patterning or defining etch method. In this method, an adhesion layer is disposed on the underlayer. A thick conductive metal layer is disposed on the adhesion layer directly without a seed layer. Photoresist is disposed on the metal layer and UV light is exposed to the photoresist through a micro-lithographical pattern of a thin film head conductor or stud microcirσuit. The photoresist film is chemically modified at locations exposed to the UN light. The photoresist, where exposed, can be removed by a developer to produce a photoresist mask on top of the metal layer in the shape of the geometry exposed during the patterning process. An etching solution is applied to the exposed metal layer thereby etching the metal layer through to the adhesion layer to form the TFH. The adhesion layer is removed by another etch solution.

The patterning or defining etch method has poor critical dimensioning which causes difficulty in etching the TFH coils to exacting tolerances. Typically, the metal layer is thick and requires substantial amounts of etching to form the coils. The gap loss between coils can be substantial on the order of twenty percent or more thereby preventing the formation of TFH heads with coils in close proximity to one another. Thus, a need exists for a method to etch a metal seed layer and a metal adhesion layer of a TFH wafer in a manner which overcomes or minimizes the above mentioned problems.

Sum ary of the Invention

The present invention relates to Applicant's discovery of both a first etch solution, which selectively etches a seed layer while not significantly etching an adhesion layer and underlayer, and a second etch solution, which selectively etches the adhesion layer while not significantly etching the seed layer on the top underlayer. Such maskless etches are used by applying a first etch solution to the surface of the seed layer for a sufficient period of time to remove the seed layer that is exposed to the first etch solution, thereby significantly etching the exposed surface of the seed layer while not significantly etching the adhesion layer. A second etch solution is applied to the surface of the adhesion layer for a sufficient period of time to remove the adhesion layer that is exposed to the second etch solution, thereby significantly etching the exposed surface of the adhesion layer while not significantly etching the seed layer and the underlayer to isolate thin film magnetic recording head conductor geometry.

The method of this invention which is a maskless isolation etching method has substantially higher material selectivity than the vacuum etching methods currently employed. The method can be used in the formation of coil winding or stud seed removal. The underlayer layer is substantially unaffected by the seed wet etch process. Gap loss between coils is reduced by about fifty percent as compared to the vacuum etching process, thereby having improved critical dimensioning. Also, edge corrosion caused by galvanic coupling between the magnetic pole layer and redeposited seed layer and adhesion layer residue is substantially eliminated. Redeposited seed layer material which can cause electrostatic discharge is minimized or eliminated. The seed layer can typically have a thickness of less than 500 angstroms, which is half the thickness of a typical TFH seed layer prepared by vacuum sputtering. The adhesion layer also acts as an added protective layer to the underlayers during seed layer etching.

Detailed Description of the Invention An adhesion layer is deposited on an underlayer of a TFH wafer by vacuum sputtering, as is known in the art. The adhesion layer is intended to improve the adhesion between the underlayer and a seed layer. The adhesion layer is made of a suitable metal for bonding to the top underlayer, such as chromium. The underlayer typically contains a metal, metal oxide or a polymer. The adhesion layer typically has a thickness in the range of between about 0.01 to about 0.02 microns. The seed layer, which can be selectively etched to produce microcirσuits on the TFH wafer, is deposited on top of the adhesion layer by vacuum sputtering in the same vacuum deposit run, as is known in the art. The seed layer is made of a suitable metal that can be bonded to the adhesion layer, such as copper. A suitable metal has a low electrical resistivity and a high electromigration resistance. The seed layer typically has a thickness in the range of between about 0.04 to about 0.06 microns.

A photoresist is then applied over the seed layer on the wafer. The photoresist can be applied by known techniques, such as spin coating. The TFH wafer can then be heated to a temperature and for a time to soft bake the photoresist.

The photoresist is then exposed to a collimated UV light source through a glass microcircuit pattern mask and is photolithographically patterned with the microcircuit pattern onto the photoresist film.

The TJV-modified portion of the photoresist film can be removed from the surface of the wafer by a suitable solvent, such as is known in the art. The unexposed photoresist film can remain as a three dimensional photoresist mask on top of the seed layer in the shape of the geometry exposed during the photolithographic patterning.

Following rinsing and plasma cleaning to remove organic residues of the UV-modified photoresist in the pattern, the wafer is placed in an acid copper sulfate plating cell with a copper-bearing electrolyte. Metal, such as copper, is electrodeposited only in those open areas of the wafer where the conductive seed layer is exposed to the plating bath. A conductive metal layer is formed by pattern plating through-mask up to a thickness, typically about two to about three microns, to provide proper coil resistance for the metal layer. The photoresist pattern film which was not TV- modified can then be removed from the surface of the wafer by a suitable solvent, such as is known in the art. A three dimensional TFH metal layer remains on top of the seed layer.

The surface of the metal layer and of the exposed seed layer on the wafer can be inspected for any residue of modified photoresist. This residue can possibly interfere with the etching of the seed layer, if it is not substantially removed. The inspection can be done with a suitable microscope. As an example, the microscope is set to dark field mode with low or medium magnification. The surface of the wafer is typically cleaned with a suitable substance to sufficiently remove any photoresist residue. In one embodiment, the suitable substance is oxygen plasma.

The seed layer material is etched with a first etch solution which can selectively etch the seed layer while not significantly etching the adhesion layer or the metal layer. Further, the first etch solution etches the seed layer at a rate that is appreciably constant. The amount removed can be controlled by exposure time. Even further, the first etch solution can repeatedly etch a series of TFH wafers with consistency and uniformity. Typically, the first etch solution is applied while the temperature is in the range of between about 20° and about 25°C. The first etch solution has a pH in the range of between about 4 and about 5.

As an example, the first etch solution is a solution of ammonium peroxydisulfate (also known as ammonium persulfate, (NH₄)₂S₂0₈) in deionized water solution. A suitable range of concentration of ammonium peroxydisulfate present in the solution can be typically in the range of between about 75 and about 125 grams per liter of deionized water solution. If the first etch solution is below the suitable range of concentration, the first etch solution will poorly clear the gaps in the seed layer. If the first etch solution is above the suitable concentration, the first etch solution will etch the seed layer too quickly. In a particularly preferred embodiment, one hundred grams of ammonium peroxydisulfate are dissolved per liter of deionized water. Preferably, the ammonium peroxydisulfate solution is made shortly before use, since it decays slowly at room temperature.

Alternatively, the first etch solution can contain other compositions to enhance etching. An example of a second composition in the first etch solution is a soluble chloride if a faster etch rate is desired. Examples of soluble chlorides are sodium chloride, potassium chloride, etc. A suitable range of concentration of chloride is in the range of about 50 to about 300 parts per million. The soluble chloride will accelerate the etching by about two to four fold. If the concentrations of chloride is greater than the suitable range, the rate of etching is too quick for isolation etching.

Another optional additive to the first etch solution to enhance etching is an anionic surfactant. The surfactant acts as a wetting agent. A suitable surfactant is an alkyl sulfonate and has a concentration of about fifty parts per million.

The TFH wafer can be rinsed with a pre-etch rinse of deionized water or other suitable solution to suitably prepare the surface of the seed layer for etching. Although not necessary, the wafer can be spun while being rinsed to enhance flow of the pre-etch rinse over the surface. In one embodiment, the wafer is spun for about fifteen seconds at a rate of about 40 revolutions per minute (rpm) while the wafer is rinsed with deionized water. The pre-etch rinse can be sprayed onto the surface from a single or multiple nozzle locations.

The first etch solution can be sprayed onto the wafer to etch the seed layer of the wafer. The surface of the wafer can then be sprayed with a single or multiple nozzle sprayer or other suitable device to suitably dispose the first etch solution onto the surface of the seed layer. In a preferred embodiment, the first etch solution is sprayed in a fine mist with a single nozzle sprayer from a point above the center of the wafer. Alternatively, the wafer can be disposed in a beaker or other container with the first etch solution in order to etch the seed layer.

The amount of first etch solution required to remove the exposed seed layer is dependent upon the amount of seed layer to be etched. For example, the seed layer can be exposed to the first etch solution for a suitable time, such as twenty seconds, to remove a seed layer having a thickness of five hundred angstroms. If the seed layer has a greater thickness, such as one thousand angstroms, the time of exposure of the first etch solution to the seed layer can be longer, such as forty seconds.

The first etch solution can be disposed on the wafer, while the wafer is spun to enhance the exposure of the solution to the exposed seed layer. A suitable rate of spinning is one that centrifugally forces the first etch solution to flow to the edges of the wafer. In one embodiment, the wafer is spun at a rate of about 40 rpm while the first etch solution is applied at a rate in the range of about ten to about fifty milliliters per second from a single nozzle sprayer for about twenty seconds.

The wafer should be washed with a suitable post first etch solution rinse in order to minimize further etσhing of the seed layer once the desired etch amount is achieved. This post first etch solution rinse can be deionized water or other suitable solution with which any remaining amounts of the first etch solution is removed or neutralized without appreciably harming the wafer. In a particularly preferred embodiment, deionized water is used. This rinse can be similarly applied with a sprayer as done with the pre-etch rinse. The wafer can be spun at a rate, such as 500 rpm to enhance the exposure of the rinse to the seed layer while sufficiently removing or neutralizing any first etch solution residue on the seed layer.

The atmosphere surrounding the wafer can then be purged with compressed dry air, dry nitrogen or other suitable gas to remove any atmospheric residues of the first etch solution. In one embodiment_r the atmosphere surrounding the wafer was purged with compressed dry air at about 34.475kPa (5psi) for three minutes while the wafer is spun at a rate of 2000 rpm. The adhesive layer is etched with a second etch solution which can selectively etch the adhesion layer material while not significantly etching the remaining exposed seed layer conductor or the underlayer. Further, the second etch solution etches the adhesion layer at a rate that is substantially constant. The thickness removed can be controlled by exposure time. Even further, the second etch solution can repeatedly etch a series of TFH wafers with consistency and uniformity. Typically, the second etch solution is applied while the temperature is in the range of between about 20° and about 25°C. The second etch solution has a pH in the range of between about 9 and about 10. As an example, the second etch solution is a solution of potassium ferricyanide (K₃Fe(CN)₆) and sodium hydroxide (NaOH) in a deionized water solution. A suitable concentration of potassium ferricyanide can be in the range of between about 100 and about 150 grams per liter of deionized water solution. A suitable concentration of sodium hydroxide can be in the range of between about 35 and about 50 grams per liter of deionized water solution. The ratio of the weight of potassium ferricyanide to the weight of sodium hydroxide is in a range of between about 2.75 to about 3.25. If the second etch solution is below the suitable range of concentration, the second etch solution will poorly etch the adhesion layer. If the second etch solution is above the suitable range of concentration, the second etch solution will etch the adhesion layer too quickly attacking the alumina gap layer contained in the underlayer. In a particularly preferred embodiment, the second etch solution is one hundred thirty seven grams of potassium ferricyanide and forty-five grams of sodium hydroxide per liter of deionized water with a weight ratio of 3.04 (137/45) .

Alternatively, the second etch solution can contain other additive to enhance etching. An example of a third additive in the second etch solution is an anionic surfactant as described above in the first etch solution.

The second etch solution can be sprayed onto the wafer at a rate and amount to sufficiently etch the adhesion layer of the wafer. The surface of the wafer can be sprayed with the second etch solution by a suitable device similar to the device used to dispose the first etch solution onto the surface of the spinning wafer. As a caution, the first etch solution and second etch solution should be applied separately and well isolated from one another. A possible danger of forming hydrogen cyanide gas exists if the two solutions are mixed. In one embodiment, the wafer is spun at a rate of about 300 rpm while the second etch solution is applied at a rate in the range of between about ten to about fifty milliliters per second from a single nozzle sprayer for about twenty seconds. Alternatively, the adhesion layer can be etched by submerging the wafer in the second etch solution. The wafer can be placed on a wafer holder and then disposed in the second etch solution. The wafer and wafer holder can be gently agitated to circulate the second etch solution. In one embodiment, a wafer is disposed in a second etch solution for sixty seconds to etch a two hundred angstrom adhesion layer. The amount of second etch solution to suitably remove the exposed adhesion layer is dependent upon the amount of adhesion layer to be etched. For example, the adhesion layer can be exposed to the second etch solution for a suitable time, such as sixty seconds, to remove an adhesion layer having a thickness of two hundred angstrom. If the adhesion layer has a greater thickness, the time of exposure to the second etch solution is longer. The wafer should be washed with a suitable rinse to minimize further etching of the adhesion layer once the desired etch amount is achieved. This rinse can be deionized water or other suitable solution with which any remaining amounts of second etch solution is removed or neutralized. In a preferred embodiment, deionized water is used. The rinse can be similarly applied with the sprayer as done during the pre-etch rinse and post first etch solution rinse. The wafer can be similarly spun at a rate to remove the rinse while sufficiently removing or neutralizing any residue on the adhesion layer.

This invention can be used with an automatic controller -system to automatically sequence the steps of this method. The invention will now be further and more specially described by the following example. All parts and percentages are by weight unless otherwise specified. Example

A thin film head wafer was prepared with a chromium adhesion layer having a thickness of two hundred angstroms. The adhesion layer was deposited by sputtering on underlayers of alumina, hard-baked photoresist and nickel-iron alloy. A copper seed layer was deposited on the adhesion layer by sputtering having a thickness of five hundred angstroms.

The wafer was spin coated with an AZ positive photoresist solution from American Hoechst. The wafer was heated to a temperature of 90°C for thirty minutes to sufficiently evaporate the solvent from the photoresist.

A patterned glass plate mask was disposed above the photoresist film. The photoresist film was exposed to a TJV collimated light as the light passed through the patterned glass plate.

The unmodified portion of the photoresist film was removed from the surface of the wafer by a solution of an AZ positive photoresist alkaline developer from American Hoechst. After removing the modified photoresist film, the wafer was cleaned with an oxygen plasma for five minutes with one hundred percent oxygen at 750 Watts. Following rinsing and plasma cleaning to remove organic residues of the UV-modified photoresist in the pattern, the wafer was placed in an acid copper sulfate plating cell with a copper-bearing electrolyte. The copper was electrodeposited only in those open areas of the wafer where the conductive seed layer is exposed to the plating bath to form a conductive metal layer with a thickness of three microns. The remaining unmodified photoresist is then removed by an organic solvent. After removing the unmodified photoresist film, the wafer was cleaned with an oxygen plasma for five minutes with one hundred percent oxygen at 750 Watts. The wafer was then placed on a spindle and spun at a rate of 40 rpm. The wafer was thoroughly rinsed with deionized water by spraying for 15 seconds. A 0.44M solution of ammonium peroxydisulfate (Reagent Grade from Fisher Scientific) in deionized water which had a pH of 4 was then sprayed with a single stream at the center of the wafer at a rate of 30 milliliters per minute for 20 seconds while at a temperature of 23°C. The wafer was spun at a rate of 40 rpm, as the ammonium peroxydisulfate was sprayed. The exposed five hundred angstrom copper seed layer was etched to the adhesion layer.

After spraying with the ammonium peroxydisulfate solution, the wafer was spun at 500 rpm, while it was thoroughly rinsed with deionized water for sixty seconds. The atmosphere surrounding the wafer was purged with compressed dry air gas at 34.5 kPa (5psi) for three minutes while the wafer was spun at a rate of 2000 rpm for four minutes. The wafer was then spun at 300 rpm and sprayed with a single stream of second etch solution at the center of the wafer at a rate of 20 milliliters per minute for 60 seconds. .The second etch solution contained forty-five grams of sodium hydroxide (Reagent Grade from Fisher Scientific) and one hundred thirty- seven grams of potassium ferricyanide (Reagent Grade from Fisher Scientific) per liter of deionized water. The exposed two hundred angstrom chromium adhesion layer was removed, thereby significantly exposing the underlayer while not etching the seed layer and underlayer significantly.

The wafer was rinsed thoroughly with deionized water for 215 seconds while the disk was spun at 500 rpm. The atmosphere surrounding the water was purged with compress dry air at five pounds per square inch while the wafer was spun at a rate of 2000 rpm for four minutes.

The gap loss was about 650 angstroms versus an expected 1500 angstroms for a vacuum sputtered wafer. The measured pole to coil resistance was 1.20 X 10¹¹ ohms. After exposure to a temperature of 150°C and a humidity of ninety percent for thirty six hours, there was no noticeable pole edge corrosion, and the TFH wafer functioned without failure even without passivation. Effect of the Invention:

Thin film head wafers can be produced by vacuum etching procedures, eg., ion milling. But these procedures cause excessive transducer gap loss when removing exposed seed layer and adhesion layer. Incompletely removed seed layer and edge layer materials cause pole edge corrosion and electrostatic discharge (ESD) through the head to the recording media. ESD causes loss of useful recording area. Selective vacuum etch processes do not exist for thin film head wafers. Vacuum milling systems can be used where available, for producing thin film heads but are very expensive to install and maintain.

The above described invention teaches a dual layer etch process which overcomes the disadvantages of the prior art. In the present invention, the adhesion layer and the seed layer are processed without vacuum milling or vacuum etching of the prior art.

A first etch solution, eg., ammonium peroxy disulphate of suitable concentration selectively etches the seed layer but not significantly the underlayer. A second solution, eg., Potassium ferricyanide and sodium hydroxide in deionized water, selectively etches the adhesion layer but not significantly the second layer and the underlayer. The result is a significant and desired etching of the exposed surface of the adhesion layer, but not significantly etching the seed layer and the underlayer. Thus, thin film heads may be produced with the required dimensions and characteristics more economically than by known prior art methods.

Equivalents

Those skilled in the art will recognize, or be able to ascertain using . no more than routine experimentation, many equivalents to the specific embodiments of the invention described specifically herein. Such equivalents are intended to be encompassed in the scope of the claims.

Claims

A method for maskless wet etching a metal seed layer and a metal adhesion layer from an underlayer of a substrate of a thin film head wafer, comprising the steps of: a) applying a first etch solution, which selectively etches the seed layer while not significantly etching the adhesion layer and the underlayer, to the surface of the seed layer for a sufficient period of time to selectively remove the seed layer exposed to the first etch solution, thereby significantly etching the exposed surface of the seed layer while not significantly etching the adhesion layer; and b) applying a second etch solution, which selectively etches the adhesion layer while not significantly etching the seed layer and the underlayer, to the surface of the adhesion layer for a sufficient period of time to remove the adhesion layer exposed to the second etch solution, thereby significantly etching the exposed surface of the adhesion layer while not significantly etching the seed layer and the underlayer to form a thin film head wafer.

2. A method of claim 1 wherein the seed layer comprises copper.

3. A method of claim 2 wherein the adhesion layer comprises chromium, wherein the first etch solution comprises an ammonium peroxydisulfate solution, wherein the ammonium peroxydisulfate solution has a concentration in the range of between about 75 grams and 125 grams per liter of solution.

4. A method of claim 3 wherein the second etch solution comprises a potassium ferricyanide and sodium hydroxide solution, wherein the potassium ferricyanide has a concentration in the range of between about 100 grams and 150 grams per liter of solution.

5. A method of claim 4 wherein the sodium hydroxide has a concentration in the range of between about 35 grams and about 50 grams per liter of solution.

6. A method for maskless wet etching a copper seed layer and a chromium adhesion layer from a thin film head wafer, comprising the steps of: a) applying an ammonium peroxydisulfate solution to the surface of the copper seed layer of the thin film magnetic recording head wafer for a sufficient period of time to remove the copper seed layer that is exposed to the ammonium peroxydisulfate solution, said ammonium peroxydisulfate solution thereby sufficiently etching the exposed surface of the copper seed layer while not significantly etching the adhesion layer; and b) applying a potassium ferricyanide and sodium hydroxide solution to the surface of the chromium adhesion layer of the thin film magnetic recording head wafer for a sufficient period of time to remove the adhesion layer that is exposed to the potassium ferricyanide and sodium hydroxide solution, said potassium ferricyanide and sodium hydroxide solution thereby significantly etching the exposed surface of the chromium adhesion layer while not significantly etching the seed layer and the underlayer to form a thin film head wafer.

7. A method of Claim 6 wherein the ammonium peroxydisulfate has a concentration of about 100 grams per liter of solution wherein the potassium ferricyanide has a concentration of about 137 grams per liter of solution.

8. A method of Claim 7 wherein the sodium hydroxide has a concentration of about 45 grams per liter of solution.

9. A thin film magnetic recording head made with a thin film head wafer formed by a method of Claim 1.

10. A method for forming a thin film head wafer, comprising the steps of: a) depositing on a top underlayer, wherein the underlayer includes a metal, metal oxide or polymer or combination thereof, an adhesion layer, wherein the adhesion layer comprises a reactive metal which has an affinity for oxygen to cause sufficient bonding to the oxide contained in the underlayer; b) depositing on the adhesion layer a seed layer, wherein the seed layer can sufficiently bond to the adhesion layer; c) depositing a photoresist on the surface of the adhesion, wherein when exposed to a UV light source through a photolithographic screen pattern, thereby modifying the photoresist to form the pattern in the photoresist; d) exposing the photoresist to the UV light source through the photolithographic screen pattern to form the pattern in the photoresist; e) removing the UV light modified photoresist from the seed layer, thereby exposing a portion of the seed layer to the atmosphere; f) plating the exposed seed layer with a metal to form a conductive TFH metal layer; g) removing the remaining photoresist from the surface of the wafer; h) applying a first etch solution, which selectively etches the seed layer while not significantly etching the adhesion layer, to the surface of the seed layer for a sufficient period of time to selectively remove the seed layer exposed to the first etch solution, thereby significantly etching the exposed surface of the seed layer while not significantly etching the adhesion layer; and i) applying a second etch solution, which selectively etches the adhesion layer while not significantly etching the seed layer and the underlayer, to the surface of the adhesion layer for a sufficient period of time to remove the adhesion layer exposed to the second etch solution, thereby significantly etching the exposed surface of the adhesion layer while not significantly etching the seed layer and the underlayer to form a thin film head wafer thereby forming a thin film head wafer.