How Can You Tell When a Gold or Platinum Target Needs to Be Replaced?

During routine technical support, users often ask us, “How long can a gold or platinum target be used before it needs to be replaced?” As VPI application engineers, our recommendation is: Do not judge target life solely by operating time or the number of sputtering cycles. The primary criteria should be the target’s erosion condition and remaining thickness. The following guidelines may also help.

Inspect the Target Surface First

During magnetron sputtering, concentrated erosion zones in the form of rings, triangles, or other patterns typically develop on the target surface. This is normal. Pay particular attention to the following conditions:

• The erosion groove has become very deep, with significant localized thinning of the target.

• Pinholes or through-holes have appeared on the target surface.

• The target holder, backing plate, or bonding layer beneath the target is visible.

• The target shows cracks, warping, delamination, or abnormal burn marks.

• Erosion is concentrated on one side, resulting in clearly uneven wear.

For the thin gold and platinum targets commonly used in VPI systems, the target should be replaced immediately once a hole appears. Continued use may cause the target holder or backing plate to be sputtered, contaminating the deposited film and potentially damaging the sputtering source.

For thicker magnetron sputtering targets, the remaining thickness at the deepest point of erosion can be measured. As a general engineering guideline, replacement should be scheduled when the erosion depth approaches 75% of the target’s original thickness. However, the specific replacement criterion should always be determined according to the equipment model, target structure, and VPI technical requirements.

Monitor Persistent Changes in the Process

As a target approaches the end of its service life, the following symptoms may occur:

• More time is required to achieve the target film thickness under the same process parameters.

• The deposition rate displayed by the thickness monitor continues to decline.

• The plasma distribution becomes uneven.

• The current or voltage becomes difficult to stabilize.

• Frequent arcing occurs during sputtering.

• Film uniformity or batch-to-batch repeatability deteriorates.

These symptoms should only be used as supplementary indicators. Insufficient vacuum, changes in argon flow, chamber contamination, target-surface contamination, or an aging quartz crystal in the thickness monitor can cause similar problems. We therefore recommend checking the condition of the equipment first and then confirming the target’s actual degree of erosion.

Do Not Compare Gold and Platinum Targets Based Solely on Operating Time

Platinum generally has a lower sputtering rate than gold. At the same current and sputtering time, a platinum film may be thinner than a gold film. Therefore, the longer deposition time required for platinum does not necessarily indicate that the target has deteriorated.

A more reliable approach is to establish separate historical process baselines for gold and platinum targets, then compare their deposition rates, film thicknesses, and discharge conditions under identical process parameters.

Recommendations from VPI Application Engineers

Laboratories can perform the following checks regularly:

1. Photograph and document the erosion pattern on the target surface.

2. Check for holes, cracks, or exposure of the backing plate.

3. Measure the erosion-groove depth on thicker targets.

4. Compare deposition rates and film thicknesses under the same process conditions.

5. Record abnormal arcing, current fluctuations, and changes in film uniformity.

   
   

In simple terms: inspect the target surface, measure the remaining thickness, check the deposition rate, and observe the discharge condition. A target must be replaced if it has been perforated or the backing plate is exposed. If deposition slows down or the discharge becomes unstable, both the target condition and the overall equipment status should be evaluated.

Important: Always switch off the sputtering power supply before replacing a target. Do not begin replacement until the system has been safely shut down, vented, and allowed to cool completely.

Because the target-head structure, target dimensions, and cooling method vary among VPI models, please provide the equipment model, photographs of the target surface, and recent process parameters to a VPI application engineer if you are unsure whether the target needs to be replaced.