US20110272287A1

US20110272287A1 - Method for patterning magnetic films

Info

Publication number: US20110272287A1
Application number: US12/776,010
Authority: US
Inventors: Elizabeth A. Duch; Ronald Goldblatt; David L. Rath; Lubomyr T. Romankiw; Xiaoyan Shao; Steven E. Steen; James Vichiconti
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 2010-05-07
Filing date: 2010-05-07
Publication date: 2011-11-10

Abstract

A method of patterning magnetic devices and sensors by double etching, which includes forming a layer of dielectric on a substrate; depositing a thin adhesion layer and a thin seed layer; applying a thin resist frame to pattern a structure; cleaning the metal surface to prepare for plating; electroplating to fill up the structure and the uncovered field area, which uses a paddle cell with a permanent magnet providing magnetic field to induce magnetic orientation; stripping the resist frame; etching the seed layer/adhesion layer exposed below the resist frame down to the dielectric surface; etching the rest of magnetic materials and the seed layer using electrolytic etching in the field; etching the adhesion layer in the field, and repeating the steps for building structures with multiple levels.

Description

TECHNICAL FIELD

This invention relates to the method of obtaining optimized magnetic orientation and undercut free patterning of magnetic films by a double etching approach, and particularly to a method of patterning magnetic devices and sensors by double etching.

BACKGROUND OF THE DISCLOSURE

Magnetic materials can be made to have preferred magnetic orientation induced by applying an external magnetic field during deposition. The deposition method includes but not limited to electrodeposition or physical vapor deposition. Obtaining a uniform and large enough field across large dimensions, such as 200 mm or 300 mm wafers, is one of the major challenges associated with building magnetic devices on 200 mm or 300 mm wafers. The shape anisotropy of a small patterned area demands additional field strength requirement in additional to the field requirement of a blanket symmetric film due to the demagnetization effect. By depositing a blanket film, or a film close to blanket continuity, the preferred magnetic orientation can be induced with a smaller magnetic field, which is more attainable and much less expensive.
U.S. Pat. No. 3,853,715 (“Elimination of Undercut In Anodically Active Metal During Chemical Etching”) describes a frame plating methodology to achieve magnetic orientation in a patterned structure. The method employed includes depositing a blanket seed layer, putting on frame resist for patterning, plating up the structure, block resist patterning to protect the structure, chemically etching away the rest, and stripping the resist. However, a drawback with this approach is the seed layer under the thin frame serves as a path for undercut during chemical etching of the remaining materials. The consequence of the undercut easily destroys the whole pattern by lifting the resist frame and etched away the wanted structure. The undercut also restricts the minimum dimension that can be built in this approach to be millimeters.
Accordingly, the present invention relates to an improved method, which includes double etching for manufacturing a device pattern, eliminates undercut issue, provides a reliable process to build devices ranging from nanometer size to tens of centimeters size range

SUMMARY OF THE DISCLOSURE

In accordance with the invention, the method includes in a series of steps patterns a magnetic structure by putting down a layer of dielectric as the substrate (step 1), depositing a thin adhesion layer and a thin seed layer (step 2), putting thin resist frame to pattern the structure (step 3), depositing up the structure and the field area (step 4), stripping the resist frame (step 5), etching the seed layer and the adhesion layer exposed below the resist frame down to the dielectric surface by sputter etch or reactive ion etch (step 6), etching the field magnetic materials by electrolytic etching where the device structures are typically isolated from the field (step 7), and etching the seed layer and adhesion layer in the field by sputter etch, and/or reactive ion etch (step 8).
Specifically, an aspect of the method of patterning magnetic devices and sensors by double etching includes:

- forming a layer of dielectric on a substrate;
- depositing a thin adhesion layer and a thin seed;
- applying a thin resist frame to pattern a structure;
- cleaning the metal surface to prepare for plating;
- electroplating to fill up the structure and the uncovered area, which uses a paddle cell with a permanent magnet providing magnetic field to induce magnetic orientation stripping the resist frame;
- etching the seed layer/adhesion layer exposed below the resist frame down to the dielectric surface by either reactive ion etch and/or physical sputtering etch;
- etching the rest of magnetic materials and the seed layer by electrolytic etching when the field is typically electrically isolated from the device structure.
- and etching the remaining adhesion layer in the field.

The above steps are repeated for building structures with multiple layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the disclosed process flow of the present disclosure.

FIG. 2 illustrates the patterning results from a prior art method.

FIG. 3 illustrates examples of structures that can be made with the disclosed methodology together with a planar view of a typical electrical isolated device structure.

DETAILED DESCRIPTION OF THE DISCLOSURE

A more complete appreciation of the disclosure and many of the attendant advantages will be readily obtained, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.
FIG. 1 illustrates a double etch patterning process flow. This methodology completely eliminates undercut issue and provides a reliable process to build devices ranging from nanometer size to tens of centimeters size range. Etching steps 6 and 8 can be chemical etching or dry etching processes, including but not limited to plasma etch, sputter etch, reactive ion etch, and chemical etch.
Etching step 7 uses electrolytic etching, which uses electrical current to dissolve the unwanted film in a sodium chloride solution, which does not attack the desired device structure due to electrical isolation of the device structure and the unwanted magnetic film in the field.
This invention discloses a few major improvements over the existing methodology. More specifically, it patterns a magnetic structure by:

- 1. Forming a layer of dielectric on the substrate, which includes silicon oxide, silicon oxynitride, low-k dielectric, and a polymer such as a polyimide, or resist;
- 2. Depositing an adhesion layer and a seed layer, which may include Ta, TaN, Ti, TiN, Cr, or the combinations thereof as the adhesion layer and a thin layer of metallic film from various deposition techniques, such as Ni, Fe, Co, Cu, and alloys thereof;
- 3. Applying a thin resist frame to pattern the structure;
- 4. Cleaning of metal surface to prepare for plating;
- 5. Electroplating to fill up the structure and the uncovered field area, which uses a paddle cell with a permanent magnet providing magnetic field to induce preferred magnetic orientation;
- 6. Stripping the resist;
- 7. Etching the seed layer/adhesion layer exposed below the resist frame down to the dielectric surface by sputtering etch and/or reactive ion etch;
- 8. Etching the remainder of magnetic materials and the seed layer, in which electrochemical etching is used since the typical device features are well isolated from the field; and
- 9. Etching the adhesion layer either by sputtering or reactive ion etch.

The above steps are repeated for building structures with multiple layers.
In a preferred embodiment, suitable substrates may include but they are not limited to: silicon, quartz, glass, sapphire, metal, gallium nitride, gallium arsenide, germanium, silicon-germanium, indium-tin-oxide, alumina (Al₂O₃), and plastic. The substrate may be rigid or flexible.
In another preferred embodiment, the dielectric layer may be silicon oxide, silicon oxynitride, low-k dielectric, and a polymer such as a polyimide, or resist
In another preferred embodiment, the thin adhesion layer may include but it is not limited to Ta, TaN, Ti, TiN, Cr, and combinations of thereof.
In another preferred embodiment the seed layer may include but is not limited to Ni, Co, Fe, Cu, Ru, Rh, Zn, Ag, Au and the alloys thereof. The seed layer is typically deposited to a thickness from about 5 nm to about 500 nm. The layer may be deposited by PVD, CVD, ALD or by electroless deposition techniques
In another preferred embodiment, the electroplating can be carried out using an anode such as Pt, Ti or other soluble metals such as Ni, Co, Fe, Cu and the alloys thereof, and a cathode, which is the wafer substrate to be plated with a conductive seed layer.
In another preferred embodiment, the electroplating is generally carried out employing a current density of about 1 to about 100 milliamps/cm², more typically about 1 to about 50 milliamp/cm²and even more typically about 5 to about 20 milliamps/cm². Also, the electroplating is generally carried out at temperatures of about 10° C. to about 80° C.
The general dimensions for electroplating are between about 10 nm and about 10 cm. The aspect ratio is from about 0.5 to about 10.
In another preferred embodiment, the etching of adhesion layer and seed layer may include conventional dry etching for example, sputtering, reactive ion etching, ion beam etching and/or plasma etching.
The electrolytic etching utilizes an electrical current to dissolve the electrically connected metal film, with the metal film being the anode, and a counter electrode of Pt, Ti, Cu, Ni, steel, or other conductive materials being the cathode. A typical electrolytic etch solution is sodium chloride with pH range of −1 to 3. The etching solution provides sufficient conductivity, and can be made to be aggressive toward the specific metal dissolution. Any other desired chemical may be used for the etching treatment.
Obviously, numerous modifications and variations of the disclosure are possible in light of the above disclosure. It is therefore understood that within the scope of the appended claims, the disclosure may be practiced otherwise than as specifically described herein.

Claims

1. A method of patterning magnetic devices and sensors by double etching, which comprises:

forming a layer of dielectric on a substrate;

depositing a thin seed layer or a combination of adhesion layer and seed layer;

applying a thin resist frame to pattern a structure;

cleaning the metal surface to prepare for plating;

electroplating to fill up the structure and the uncovered field area, which uses a paddle cell with a permanent magnet providing magnetic field to induce magnetic orientation stripping the resist frame;

etching the seed layer/adhesion layer exposed below the resist frame down to the dielectric surface;

etching the rest of magnetic materials and the seed layer by electrolytic etch.; and

etching the adhesion layer in the field.

2. The method of claim 1, above steps are repeated for a multiple level build.

3. The method according to claim 1, wherein the substrate is selected from the group consisting of silicon, quartz, glass, sapphire, metal, gallium nitride, gallium arsenide, germanium, silicon-germanium, indium-tin-oxide, alumina, and plastic.

4. The method according to claim 1, wherein the dielectric layer is selected from the group consisting of silicon oxide, silicon oxynitride, low-k dielectric, and a polymer such as a polyimide, or resist;

5. The method according to claim 1, wherein the thin adhesion layer is selected from the group consisting of Ta, TaN, Ti, TiN, Cr, combinations thereof.

6. The method according to claim 1, wherein the thin seed layer is selected from Ni, Fe, Co, Cu, Ru, Rh, Ag, Ag, Zn, and the alloys thereof.

7. The method according to claim 1, wherein the thin seed layer/adhesion layer has a thickness from about 5 nm to about 500 nm.

8. The method according to claim 1, wherein the thin seed layer/adhesion layer is deposited by PVD, CVD, or by electroless techniques.

9. The method according to claim 1, wherein the cleaning before electrodeposition can be ashing in reducing gas, such as forming gas, ammonia, or hydrogen, or chemical cleaning, such as acid rinse, or physical clean, such as sputtering etch.

10. The method according to claim 1, wherein the electroplating is carried out employing a current density of about 1 to about 100 milliamps/cm².

11. The method according to claim 1, wherein the electroplating is carried out at temperatures of about 10° C. to about 80° C.

12. The method according to claim 1, wherein the electroplating is carried out employing a current waveform of about 5 to about 20 milliamps/cm².

13. The method according to claim 1, wherein the electroplating is carried out by a paddle cell with a magnetic field applied during the deposition.

14. The method according to claim 1, wherein the seed layer/adhesion layer etching is carried out by dry etching, sputtering etch, reactive-ion etching (RIE), wet-chemical etching, or ion-beam etching.

15. The method according to claim 1, wherein the electrolytic etching uses external current/potential supply to dissolve the metal film in contact with the power, with the metal film being electrically connected to the anode (or positive potential), and a counter electrode connected to the cathode. The solution can be sodium chloride with pH range between −1 to 3 or any other desired chemicals specific to the metal to be etched.

16. The method according to claim 1, wherein the electrolytic etching uses a current density range between 10 milliamps to 10 amps.