Analyzing Thin Metal Films

Sputtered Neutral Mass Spectrometry is perfect for analyzing thin metal films where composition, thickness and interface condition can be determined. The example presented here, shows a magnetic film stack comprising Cr, Ni, Cu and Fe. Of the different methods of data storage, magnetic hard discs still offer highly economic means for high density rapid access. The continual move towards more and more compact read/write heads and more closely spaced data tracks has lead to a considerable development of magnetic materials and structures for this demanding application. Analysis of the metallic layer structures used in magnetic data storage is vital for both development and quality management with secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS) offering information on minor and major element composition respectively.


Both SIMS and SNMS use a concentrated, mono- energetic, chemically pure ion beam of typically 1-10 keV to sputter erode the surface under study. A small fraction of the sputtered material gets ionized due to the sputtering process itself and in SIMS, it is these ions that offer the sensitive information for which the technique is known. Being a mass spectrometry technique, all elements and isotopes may be detected, and in favorable conditions the detection limit can be in the low ppb region. However, because the ionization mechanism for SIMS takes place at the sample surface, it is very much dependent on the local chemistry and the ionized fraction can vary by several orders of magnitude. This makes SIMS ideal for trace analysis in materials of known matrix but quantification in materials of changing matrix can be complicated. SNMS overcomes the “matrix effect” by separating the sputtering and ionization events.

New Sputtering Target Innovations

Magnetron sputtering was initially developed using metal or alloy targets with materials having high electrical conductivity (e.g., Al, Ag, Au, Cu, Ti, Mo, etc.). In order to achieve acceptable deposition rates, the target material needed to be electrically and thermally conductive. Ceramic targets were developed for transparent conductive oxides (TCOs) and usually consisted of films made from compositions of ZnO:Al2O3 (2% wt) or In2O3:SnO2 (10% wt). However, as the name implies, the materials were fairly conductive and were suited for DC magnetron sputtering.

Pulsed-DC and RF magnetron sputtering allows for the deposition of materials with poor electrical conductivity. Semiconductor materials with better electrical conductivity can be sputtered with pulsed-DC power supplies, while insulating materials (mainly ceramics) require RF sputtering. The deposition rates for RF sputtering are generally much lower than with pulsed-DC. Also, pulsed-DC sputtering has a lower deposition rate than DC sputtering. New applications in photovoltaic, thermoelectric, storage, and semiconductor markets are spurring innovation in ceramic and semiconductor sputtering targets.

DC sputtering with metallic targets has fewer process problems since the metals are ductile and the materials feature high conductivity. Conversely, semiconductor and ceramic targets are more prone to process difficulties due to the brittle nature of the materials and the poor electrical and thermal conductivities. In order to achieve consistent sputtering over the life of the target, it is essential to have a well-sintered target material with high density. Voids and cracks in the material can propagate and lead to sputtering problems such as arcing, target cracking, and particle generation. Read More

Successful Large-Area Sputtering

Cylindrical rotating magnetrons can provide controlled reactive sputtering on both large areas and high-volume products, while also minimizing arcing and anode problems.

Magnetron sputtering, combined with an accurate control of process parameters and layer quality, has become one of the most important methods for depositing thin films. The technique involves bombarding a target surface, which is positioned on a magnetic tube, with an ionized gas. The gas causes metallic atoms to be ejected from the target and subsequently deposited on the substrate to be coated. In standard metallic sputtering, an inert gas, such as argon, is used. No chemical reaction occurs between the gas and the target particles, resulting in a coating on the substrate with a composition similar to the target material.

In a reactive sputtering process, at least one reactive gas (e.g., oxygen or nitrogen) is added. The reactive gas enhances the sputtering process on the target surface and also generates a chemical reaction with the target particles, forming a compound layer on the substrate. As a result, high-purity, uniform coatings can be achieved. Read More

Vacuum Coating by Sputtering

Vacuum coating by sputtering has established a leading position for the deposition of thin films because of its relatively easy scalability to high volumes and sizes, its good control of most layer characteristics, and its wide variety of available materials and possible coating stacks. The technology is commonly accepted and widely used in the architectural and automotive industries. In display and PV applications, however, the use of rotatable technology has been introduced more recently.

Within the large area coating business, the rotating cylindrical magnetron concept has proven to offer superior properties relative to the planar concept and to satisfy most industrial requirements. The geometry and sputter performance of rotating cylindrical sputter targets result in several advantages relative to planar sputter targets. Read More

What are Sputtering Targets?

A sputtering target is a material that is used to create thin films in a technique known as sputter deposition, or thin film deposition. During this process the sputtering target material, which begins as a solid, is broken up by gaseous ions into tiny particles that form a spray and coat another material, which is known as the substrate. Sputter deposition is commonly involved in the creation of semiconductors and computer chips. As a result, most sputtering target materials are metallic elements or alloys, although there are some ceramic targets available that create hardened thin coatings for various tools.

Depending on the nature of the thin film being created, sputtering targets can very greatly in size and shape. The smallest targets can be less than one inch (2.5 cm) in diameter, while the largest rectangular targets reach well over one yard (0.9 m) in length. Some sputtering equipment will require a larger sputtering target and in these cases, manufacturers will create segmented targets that are connected by special joints.

The designs of sputtering systems, the machines that conduct the thin film deposition process, have become much more varied and specific. Accordingly, target shape and structure has begun to widen in variety as well. The shape of a sputtering target is usually either rectangular or circular, but many target suppliers can create additional special shapes upon request. Certain sputtering systems require a rotating target to provide a more precise, even thin film. These targets are shaped like long cylinders, and offer additional benefits including faster deposition speeds, less heat damage, and increased surface area, which leads to greater overall utility.

The effectiveness of sputtering target materials depends on several factors, including their composition and the type of ions used to break them down. Thin films that require pure metals for the target material will usually have more structural integrity if the target is as pure as possible. The ions used to bombard the sputtering target are also important for producing a decent quality thin film. Generally, argon is the primary gas chosen to ionize and initiate the sputtering process, but for targets that have lighter or heavier molecules a different noble gas, such as neon for lighter molecules, or krypton for heavier molecules, is more effective. It is important for the atomic weight of the gas ions to be similar to that of the sputtering target molecules to optimize the transfer of energy and momentum, thereby optimizing the evenness of the thin film. Read More

Functional Thin Films and Sputtering Target Materials

Sputtering targets provide thin-film materials deposited by the sputtering method. Kobelco Research Institute, Inc. started the target material business in 1993 and its competitive strength exists in the approach of originally developing high- performance film-materials before providing the target-materials required to make the films. The research and development group of Kobe Steel is responsible for the development of original thin- films and has contributed to the steady growth of the business in cooperation with the Kobelco Research Institute, Inc. This article summarizes the developments, current statuses and futures of Al- Nd and Ag-Nd-Cu alloys, which have found lucrative applications in LCD panels and optical storage media respectively. Also described is the spray-forming process used in the production of Al-Nd alloy targets. Read More

Metal Targets during Sputtering

When a Cu surface is sputtered by ion bombardment under the condition that Mo atoms arrive at the Cu surface during sputtering an unexpected phenomenon can arise: the surface of the Cu target becomes covered with microscopic cones. The cone density increases with increasing flux density of arriving Mo atoms. When the cones are closely spaced they give the target a velvet-like black appearance. The result of dense cone coverage are a lower sputtering yield and a more oblique ejection of sputtered material. The cone tops seem to consist of Mo nuclei which are constantly replenished via surface migration and protect the underlying Cu from being sputtered. Read More

Alloy Sputtering Target

A sputtering target of platinum-cobalt alloy is disclosed which contains 10 to 55% by weight of platinum; 1 to 15% by weight of a first additional element selected from the group consisting of nickel and tantalum; no more than 1.5% by weight of a second additional element selected from the group consisting of boron, titanium, lanthanum, cerium, neodymium, beryllium, calcium, zirconium, and silicon; no more than 20% by weight of chromium; and balance cobalt. A method for manufacturing the sputtering target is also disclosed. In the method, a platinum-cobalt alloy containing specific ingredients in predetermined amounts is first prepared. Then, the platinum-cobalt alloy is subjected to hot plastic working with a thickness reduction of no less than 30%. Subsequently, the alloy thus hot worked is subjected to a cold plastic working with a thickness reduction of no less than 5% at a temperature less than the recrystallization temperature of the alloy. Read More

Composite Sputtering Target Structures

A target structure is provided for use in a magnetically enhanced diode sputter coating source having a sputtering target which at end-of-life has an eroded surface with a known shape.

The sputtering target has a non-sputtered profiled back surface conforming substantially in shape to the eroded surface at end-of-life.

A backing plate is bonded to the sputtering target which has a bonding surface complementary to the non-sputtered back surface of the sputtering target and is designed to mate therewith.

A method is provided for fabricating the target structure and bonding the sputtering target to the backing plate by isostatic pressing. Read More

Superhard Thin Film Coatings

As a result of increased requirements for abrasion resistant and protective thin film coatings, the hardness of thin film coatings has been steadily increasing over the past decade, due primarily to new materials, improved deposition processes and use of nanostructures and nanocomposites. Because it would not be possible to address all these materials, we will briefly describe the following broad categories, with emphasis on nanostructured thin films:

Binary thin films, including transition metal based materials, chromium-based materials, boron-based materials, carbon and diamond-based materials, tungsten and molybdenum based materials.
Ternary thin film materials
Quaternary and higher component thin film materials
Nanostructured materials
Wear resistant thin films are deposited by a wide variety of processes, but most often by physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques because they can be scaled up to industrial sizes and quantities. Read More