header graphic bar

Magnetrons

A sputtering magnetron is a magnetic device that is used to enhance the sputtering process (thin film deposition).  Its magnetic field is used to produce “flux tunnels” which trap electrons and locally increase current density.  This higher volumetric density of trapped electrons results in greater localized ionization rates, which, consequently, produces “order of magnitude” improvements in sputter deposition rates.  

Inherently, these localized enhancements result in systemic inhomogenieties that manifest themselves as localized wear patterns in targets (material acting as the coating) and variations in thin film characteristics over the surface of the substrate (component receiving the coating).  Consequently, the shape, distribution, and characteristics of the magnetic field produced by the sputtering magnetron are pivotal to the success of the sputtering process; not only in the lab, but in production settings as well.

Dexter’s expertise in manipulating/enhancing magnetic field profiles results in magnetron designs focused on rectifying the shortcomings of OEM system.   A sputtering magnetron’s field characteristics can be tuned to:

1.       Improve Target Utilization

          a. Longer Production Runs
          b. Reduces Raw Material Consumption

2.       Improve Thin Film Uniformity

          a. Enhanced Product Functionality

3.       Improve Deposition Rates

          a. Higher Thru Put

 In some instances, all three enhancements can be incorporated into a single magnetron design. 

We have exhausted considerable efforts in developing our patented Quadrature technology for sputtering magnetrons.  By incorporating strategically placed/oriented magnetic components into conventional designs (no physical changes in size), magnetrons can be designed to sputter targets up to twice as thick as their OEM counterparts while maintaining/enhancing their performance characteristics.   Additionally, Quadrature technology allows for the sputtering of highly permeable magnetic targets, such as nickel or iron.  This may negate the need for full cathode or system upgrades.

In general, there are four types of sputtering magnetron configurations used in the market (there are other less utilized configurations which can also be utilized and optimized, if required).

Sweeping Planar

Dexter_Planar_Magnetron

These rectangular magnetrons are typically designed with a side-to-side sweeping motion which is exploited to enhance target utilization.  Sweeping can occur in any direction or combination of directions, but is usually limited to side-to-side.  Target utilization for this type of magnetron is superior to that of static planar units, but can still be limited by “cross corner” or “turn around” trenching.  Magnetic flux tunnel shaping can be incorporated to minimize or eliminate these production hindering features. Our patented Quadrature technology can also be integrated to:

 

  • Sputter Through Thicker Targets
  • Sputter Through Magnetic Targets
  • Increase Deposition Rates
  • Lower Operating Voltages/Power

Dexter_Rectangular_Planar_Contour

 

Dexter_Rotating_Planar_MagnetronDexter_TGun_Circular_Magnetron

Rotating Planar

These disk shaped magnetrons are typically designed with rotary motion which is exploited to enhance target utilization.  Motion can occur axially as well, but is usually limited to strictly rotation.  Target utilization for this type of magnetron is superior to that of static planar units, but can still be limited by trenching.  Magnetic flux tunnel shaping can be incorporated to eliminate severe trenching while enhancing deposition rates and maintaining/improving uniformity.  Our patented Quadrature technology can also be integrated to:

  • Sputter Through Thicker Targets
  • Sputter Through Magnetic Targets
  • Increase Deposition Rates
  • Lower Operating Voltages/Power

Dexter_Rotating_ Planar_Labeled_ Contour_ Image

 

Dexter_Rotating_Planar_Magnetron_Comparison

 

Rotatable

These sputtering magnetrons provide the greatest target utilization of all the configurations, but require cylindrically shaped targets.  Due to the availability of materials in this form factor, some sputtering applications cannot integrate this technology. 

Dexter_RMag_Rotatable_Magnetron

Like the sweeping or rotating planar magnetrons, this configuration is also prone to “trenching” at the turn arounds which limits utilization.  Flux tunnel shaping of the turn around sections as well as other dynamic modifications can be incorporated to enhance performance.

Our patented Quadrature technology can also be integrated to:

  • Sputter Through Thicker Targets
  • Sputter Through Magnetic Targets
  • Increase Deposition Rates
  • Lower Operating Voltages/Power 

Dexter_Rotatable_Labeled_Contour_ Image

Static Planar

These sputtering magnetrons are utilized without motion.  The simplest configurations to integrate, these units can be shaped to any form, but are typically provided in a rectangular or disk shape.  Target utilization for this type of magnetron is poor but can typically be enhanced by magnetic flux profile shaping.  In addition, our patented Quadrature technology can also be integrated to:

  • Sputter Through Thicker Targets
  • Sputter Through Magnetic Targets
  • Increase Deposition Rates
  • Lower Operating Voltages/Power

When working with our engineering group, you might be asked:

1. What Type of magnetron is required?
    a. Static Planar
    b. Sweeping Planar
    c.  Rotatable Planar
    d. Rotatable

2. What type of material is being sputtered?
    a.  Magnetic
    b. Non-Magnetic

3.  If the material being sputtered is magnetic, do you have a hysteresis loop or magnetic material properties?

4.  How thick is the target material?

5.  What is the distance from the top of the magnetron to the back of the target material (TM-distance)? Can this be changed?  If so, what is the minimum/maximum distance)?

6.  What is the distance (range) from the top of the target to the substrate?

7.  What is the current utilization of your process? What is the minimum expected?

8.  What is the current uniformity of your process? What is the maximum deviation expected?

9.  Geometric considerations:
     a.  Static planar (length, width, thickness)?
     b. Sweeping planar (length, width, thickness, sweep distance)?
    c.  Rotating planar (diameter, thickness)?
    d. Rotatable (Target inside diameter, magnetron thickness, length)?

10.  Dynamic considerations:
       a.  Sweeping planar (sweep speed range)
       b. Rotating planar (RPM range)
       c.  Rotatable (RPM range)

11.  What is the goal of your redesign effort? (e.g. Enhanced utilization, improved uniformity, thicker targets, etc.)

12.  Target cooling method?
       a.  Magnetron exposed to or magnetron separated from cooling media

Sputtering magnetrons can be designed and manufactured using all of the major classes of magnet materials (Ceramic, NdFeB, SmCo, or Alnico).  However, greater than 90% of the magnetrons we produce today are designed and constructed from the rare-earth family of magnets – Neodymium Iron Boron (Nd-Fe-B) and Samarium Cobalt (Sm-Co).

Neodymium Iron Boron

Magnetrons produced from Nd-Fe-B provide the “biggest bang for the buck”.  This is the strongest grade of magnetic material and well is well suited for magnetron design and construction.  It is prone to corrosion, however, when submersed in liquids.  As such, for magnetrons exposed to the cooling media, either a hermetic seal will be required or Sm-Co materials should be utilized.  Additionally, these magnets have a typical  upper thermal limit of about 100°C in assembly (specialty higher thermal limit grades are available up to 200°C).

Samarium Cobalt

Magnetrons produced from Sm-Co are strong, corrosion resilient, and thermally superior to Nd-Fe-B versions.   This material costs between 2-3x as much as Nd-Fe-B versions.  Although not anti-corrosive, it is vastly superior to the Nd-Fe-B.  Its corrosion mode is “pitting”, which typically does not affect performance. Those magnetrons that are submersed in fluid should be constructed of Sm-Co materials.  A secondary barrier is recommended to protect the magnet bond lines, however.  Additionally, these magnets have a typical upper thermal limit of about 300°C in assembly.  Special mechanical considerations need to be addressed at these temperatures, however, to eliminate thermal expansion mismatch and unexpected stresses in the assembly.

  1. What type of utilization can I expect from these magnetrons?
  2. How does Dexter guarantee homogeneity across the length of long magnetrons?
  3. Will Dexter design my magnetron and let me manufacture it myself?
  4. How long will the design/prototype process take?
  5. What benefit can Quadrature have on my process?
  6. Can Quadrature be implemented into my magnetron configuration without changes the rest of my system?
  1. a.  Static Planar – typical utilization values are in the 10%-25% range.  Some configurations can be adjusted to reach 40%
    b. Sweeping Planar – typical utilization values are in the 20%-40% range.  With proper magnetic shaping, it can be adjusted to 50%-%60%
    c.  Rotating Planar – typical utilization values are in the 20%-40% range.  With proper magnetic shaping, it can be adjusted to exceed 50%
    d. Rotatable – Typical utilization values are in the 60%-75% range.  With proper shaping and dynamic integration, it can be designed to exceed 90%

2. Dexter checks and calibrates each of the permanent magnets used in the magnetron to within 1% of other equivalent magnets in the circuit.  This guarantees a consistent product throughout its length.

3. Although Dexter has a seasoned engineering staff, providing consultancy only services are not part of Dexter’s business models.  As such, Dexter will assist with the design of optimized magnetrons but will require purchase of the manufactured product as well.

4.  Typically, Dexter can design a magnetron for process enhancement within 2 weeks.  The prototype units can be manufactured an tested 6-8 weeks upon completion of the design.

5.  Quadrature magnets in a magnetron push more magnetic flux into the sputtering zone.  This increase in flux density allows for the sputter of thicker targets, the sputter of magnetic targets, increases in ionization/deposition rates, or reduction in process power.

6.  YES.  Most OEM magnetrons are not designed efficiently from a magnetic standpoint.  Quadrature magnets can be incorporated into most magnetrons without changing the envelope size.

Our design & development process is a collaborative effort between you and our engineering staff.  Our internally developed magnetron simulation software evaluates the magnetic flux tunnel’s interaction with the target and predicts utilization and uniformity characteristics.  Since we have magnetic machining capabilities in house and a large inventory of magnetic materials on-hand, design iterations and prototype units can be converted quickly and efficiently without weeks of delay waiting for magnetic materials to arrive. 

Since each sputtering system is unique, and the sputtering process is governed by multiple variables, including but not limited to:

  • system partial pressures
  • magnetic field profiles
  • electric field characteristics
  • gas distribution
  • target material characteristics
  • Source-to-substrate spacing

We have found that the most time efficient process for developing an enhanced sputtering magnetron solution involves establishing a baseline of performance for the existing (OEM) magnetron.  By magnetically modeling the existing magnetron and integrating that magnetic data into our software, program variables can be adjusted to match the your measured results (uniformity and utilization) for your existing process.  Once this baseline establishes the system and program parameters, we can focus on modifying the magnetic profile and predicting its resultant effect on the sputtering process. 

Using this method, we can model upwards of ten (10) three dimensional magnetron field profiles in a single day (dependent on model size and complexity).  This rapid turn around of analytical data allows us to evaluate numerous magnetic profiles in a very short amount of time, typically leading to first round solutions within one to two week’s time. The predicted sputtering data is shared with the customer and reviewed.  Once a magnetic solution is finalized and accepted by you, the prototype magnetron is mechanically configured and the design is placed to paper within another week’s time.

Once finalized, the initial prototype will be delivered to you for evaluation and validation within 6-8 weeks of your design approval.  Due to the large number of sputtering system geometries, we are unable to internally validate the magnetron performance and, as stated above, rely on a collaborative development effort.  Your test cycle will be used to evaluate the prototype’s functionality based on initially agreed upon performance targets. 

Although we make every attempt to account for cross variable interaction during the design phase, as with any multi-variant system, modifications to one variable of the equation (magnetics) can sometimes lead to unexpected changes in other system parameters.   As such, the quote for the design and prototype includes the costs associated with up to two more iterations (modeling and physical modifications to the prototype) to tune in its performance.   The prototype’s mechanical design/layout is configured in such a way as to allow these modifications to occur quickly.

If the intended design targets are not achieved after the first iteration, our engineers will begin tuning in our prediction program parameters to the latest set of your evaluation data and reconfiguring the magnetics for the next iteration.   Since we have magnetic machining capabilities in-house and a large inventory of magnetic materials on-hand, the prototype magnetron can quickly be modified to the next iteration.  The prototype magnetron should be returned to us for modification, where consequent iterations can be turned around within one to two weeks and returned to you for a repeat of the validation cycle.