The present invention generally relates to the electrochemical deposition of nickel iron on a work piece, and more particularly relates to the electroless deposition of nickel iron on a work piece utilizing a substantially alkali metal-free deposition solution.
Magnetoelectronics devices, spin electronics devices and spintronics devices are synonymous terms for devices that use the effects predominantly caused by electron spin. Magnetoelectronics effects are used in numerous information devices, and provide non-volatile, reliable, radiation resistant, and high-density data storage and retrieval. The numerous magnetoelectronics information devices include, but are not limited to, magnetic random access memory (MRAM), magnetic sensors and read/write heads for disk drives.
Generally, a magnetoelectronics information device is constructed with an array of magnetoelectronics elements (e.g., giant magnetoresistance (GMR) elements or magnetic tunnel junction (MTJ) elements) formed in a substrate that may also include a variety of semiconductor devices, such as, for example, MOSFETs. The magnetoelectronics elements are programmed by the magnetic field created from a current-carrying conductor. Typically, two current-carrying conductors, one formed underneath the magnetoelectronics element (the “digit line”) and one formed on top of the magnetoelectronics element (the “bit line”), are arranged in cross point matrix to provide magnetic fields for programming of the magnetoelectronics element.
Advanced semiconductor processes often use metal interconnects for the current-carrying conductors. One method of forming the metal interconnects is by a damascene or inlaid process during which a trench is patterned and etched in a dielectric layer, followed by the deposition of a metal layer, typically copper, within the trench. Flux concentrating systems often are formed proximate to the metal interconnect. Flux concentrating systems typically utilize cladding layers that are formed on three sides of the metal interconnect, leaving the side closest to the magnetoelectronics element without a cladding layer. In this manner, the cladding layers serve to concentrate the magnetic flux of the interconnect toward the magnetoelectronics element. Without cladding layers, high currents are required to achieve the desired magnetic field strength. These high currents may adversely affect nearby magnetoelectronics elements not being programmed. The cladding layers also serve to provide some shielding from external magnetic fields.
A frequently-used method for the fabrication of cladding layers includes the deposition of nickel-iron (NiFe) into a trench that has been etched in the dielectric layer that will be above or is below the magnetoelectronics element. NiFe is one of the more popular cladding materials because of its desirable soft magnetic properties. Typically, NiFe is deposited within the trench using plasma vapor deposition (PVD). However, the deposition of NiFe by PVD has proven unsatisfactory because the NiFe is not conformally deposited within the trench. Non-conformal deposition may result in the formation of voids within the trench.
Another method for depositing NiFe is electrodeposition (also known as electroplating). However, because of non-uniformities of electric current densities throughout the work piece during the electrodeposition process, which non-uniformities are particularly problematic in small-size features, it is difficult to obtain conformal sidewall coverage in the trenches. It also is difficult to obtain thicknesses suitable for the NiFe layer to serve as a layer.
In other applications, NiFe has been deposited by electrochemical deposition methods, such as electroless deposition Electroless deposition has been used successfully to achieve conformal deposition in features. However, electroless deposition methods typically utilize an electrochemical deposition solution that comprises a non-negligible amount of alkali metal ions, typically sodium (Na+) and potassium (K+) ions. Accordingly, such methods are undesirable for creating electronic devices, such as transistors, as even small amounts of Na+ or K+ ions in the devices can destroy them.
Accordingly, it is desirable to provide an improved method for depositing a NiFe layer for use in a flux concentrating system. In addition, it is desirable to provide a method for the electroless deposition of NiFe using an electrochemical deposition solution that is substantially alkali metal free. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
Turning now to the figures,
Referring to
Referring to
In one exemplary embodiment of the present invention, a first seed layer 42 next may be deposited overlying first conductive barrier layer 40 and within trench 36 using PVD, IMP, CVD or any other suitable technique known in the semiconductor industry. First seed layer 42 may be formed of copper (Cu), ruthenium (Ru), cobalt (Co), palladium (Pd) or any other suitable metal. Preferably, first seed layer 42 is formed of copper.
Next, in accordance with another exemplary embodiment of the present invention, as illustrated in
A NiFe cladding layer 46 then is deposited using electroless deposition The electroless deposition process utilizes an electroless deposition solution that is substantially alkaline metal-free. As used herein, the term “substantially alkali metal-free” deposition solution (or component thereof) or a deposition solution (or component thereof) “substantially free from alkali metal ions” means that the concentration of alkali metal ions in the deposition solution (or component thereof) is sufficiently low such that, upon deposition of NiFe cladding layer 46, the concentration of alkali metal ions in an insulating material layer proximate to the NiFe layer, such as dielectric layer 34, is no greater than 1×1012 atoms/cm2. In this manner, the concentration of alkali metal ions in the insulating material layer does not compromise the physical, chemical and/or electrical properties of the devices formed in semiconductor work piece 30. In a preferred embodiment of the present invention, the alkali metal ion concentration in an insulating material layer proximate to the NiFe layer, such as dielectric layer 34, is no greater than 1×1011 atoms/cm2. NiFe cladding layer 46 has a nickel concentration in the range of about 70 to about 90 atomic weight percent and a ferrous iron concentration in the range of about 10 to about 30 atomic weight percent, with an amount of boron and/or phosphorous that enhances the magnetic properties of the cladding layer. In one embodiment of the invention, the concentration of boron and/or phosphorous in NiFe cladding layer 46 is about 1 to about 15 atomic weight percent. In a preferred embodiment of the present invention, NiFe cladding layer 46 has a nickel concentration in the range of about 75 to about 78 atomic weight percent and a ferrous iron concentration of about 16 to about 18 atomic weight percent with about 5 to about 9 atomic weight percent of boron and/or phosphorous. In a more preferred embodiment of the invention, NiFe cladding layer 46 has a nickel concentration of about 75 atomic weight percent and a ferrous iron concentration of about 18 atomic weight percent with about 7 atomic weight percent of boron and/or phosphorous.
The electroless deposition solution is formulated from a source of nickel ions and a source of ferrous iron ions. The source of nickel ions may comprise nickel sulfamate, nickel chloride, nickel sulfate, and/or any other suitable nickel ion source. The source of ferrous iron ions may comprise iron sulfamate, iron chloride, iron sulfate, and/or any other suitable ferrous iron ion source. The electroless deposition solution may also be formulated from one or more complexing agents. The complexing agent may include glycine, tartaric acid, malic acid, citric acid, ammonium tartrate, ammonium citrate, ammonium acetate, acetic acid and/or any other suitable complexing agent known for use in electroless deposition processes. In a preferred embodiment of the present invention, the electroless deposition solution is formed from two complexing agents, glycine and tartaric acid. The electroless deposition solution also is formulated using one or more reducing agents. The reducing agent may include dimethylaminoborane (DMAB), morpholine borane (MPB), glyoxylic acid, ammonium hypophosphite and/or any other suitable reducing agent known for use in electroless deposition processes. In a preferred embodiment of the present invention, the electroless deposition solution is formulated using DMAB. The reducing agent and/or the complexing agent preferably contributes boron and/or phosphorous to NiFe cladding layer 46 to enhance the magnetic properties of the cladding layer, as described above.
In one exemplary embodiment of the present invention, to control the rate at which NiFe is deposited, the pH of the electroless deposition solution may be maintained in the range of about 7.5 to about 9.5. In a preferred embodiment of the present invention, the pH of the electroless deposition solution is in the range of about 7.8 to about 8.2. Thus, the electroless deposition may also be formulated using a pH adjusting agent to adjust the pH of the solution accordingly. Suitable pH adjusting agents may include electronic-grade tetramethylammonium hydroxide (TMAH), ammonium hydroxide, and/or any other suitable pH adjusting agent known for use in electroless deposition processes. In a preferred embodiment of the present invention, the electroless deposition solution is formulated utilizing TMAH as the pH adjusting agent.
The above-described components of the electroless deposition solution may be combined in any suitable order by any convenient method of mixing, such as, for example, by rapidly stirring with a mechanical stirrer or by agitating with a mechanical agitator. In one exemplary embodiment of the present invention, the electroless deposition solution may be formulated using nickel ions present in a concentration in the range of about 2.0 to 3.0 grams/liter, preferably about 2.2 to about 2.4 grams/liter, ferrous iron ions present in a concentration in the range of about 0.25 to about 0.40 grams/liter, preferably about 0.32 to about 0.36 grams/liter, glycine present in a concentration in the range of about 2.0 to about 10 grams/liter, preferably about 4.0 to about 5.0 grams/liter, tartaric acid present in a concentration in the range of about 20.0 to about 40.0 grams/liter, preferably about 25.0 to 30.0 grams/liter, DMAB present in a concentration in the range of about 1.5 to about 6.0 grams/liter, preferably 1.8 to about 2.2 grams/liter, and a 25% solution of TMAH present in an amount sufficient to adjust the pH of the electroless deposition solution to within a range of about 7.5 to about 9.5, preferably within a range of about 7.8 to about 8.2.
Referring again to
In another exemplary embodiment of the present invention, as illustrated in
In one exemplary embodiment of the present invention, a second seed layer 50 next may be deposited overlying second barrier layer 48 and within trench 36. Second seed layer 50 may be formed of copper (Cu), ruthenium (Ru), cobalt (Co), palladium (Pd) or any other suitable metal. Preferably, second seed layer 50 is formed of copper. Second seed layer 50 may be formed using PVD, IMP, CVD or any other suitable technique known in the semiconductor industry. It will be appreciated that second conductive barrier layer 48 and second seed layer 50 can each be grown to a thickness suitable for the size of trench 36.
Next, as illustrated in
In one exemplary embodiment of the present invention, work piece 30 then may be subjected to an annealing process to stabilize conductive interconnect 52. Work piece 30 may be annealed at an anneal temperature in the range of about 100 to about 500° C., preferably in the range of about 200 to about 300° C. More preferably, the anneal temperature is about 250° C. Work piece 30 may be annealed for a period in the range of about 15 minutes to about one hour. Preferably, work piece 30 is annealed for about 30 minutes.
Referring to
A portion of dielectric layer 114 may be removed by patterning and etching to form one, or more than one, trench 116 within dielectric layer 114. Trench 116 is proximate to field regions 118. It will be appreciated that trench 116 may be of any length and height suitable to form an operative cladded conductor, as described in more detail below. Dielectric layer 114 may be etched utilizing standard etching techniques such as, for example, dry etch in plasma.
The method further utilizes the steps described above with reference to
Referring to
Next, as illustrated in
Referring now to
After the deposition and anneal of conductive interconnect 136, any excess metal overlying field regions 118, including conductive interconnect 136, second seed layer 134, second conductive barrier layer 132, first NiFe cladding layer 126, first activation layer 124, first seed layer 122 and first conductive barrier layer 120, and any other metallic layer, such as a second cladding layer, that has deposited overlying work piece 100 and within trench 116, may be removed from field regions 118 using any suitable process known in the semiconductor industry, such as by chemical mechanical planarization (CMP), dry or wet etching, or the like.
In one exemplary embodiment of the present invention, referring to
Next, a second or “top” NiFe cladding layer 140 then is deposited overlying second activation layer 138 by electroless deposition using the electroless deposition solution disclosed above. Second NiFe cladding layer 140 may have the same composition and be formed from the same materials as described above for first NiFe cladding layer 126 and NiFe cladding layer 46. The deposition of NiFe using the above-described electroless deposition solution is selective to metal, that is, it will deposit on the activated copper layers but will not deposit on dielectric material layer 114. In this manner, a self-aligned second NiFe cladding layer 140 may be deposited overlying copper interconnect layer 136 to form a bit line 142 without the need for an additional masking and patterning step. Because second NiFe cladding layer 140 is self-aligned, shorting of bit line 142 with an adjacent bit line due to a common electrical contact from a misaligned top cladding layer is unlikely to occur.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.