MONITOR WAFER AND METHOD OF USING THE SAME

A monitor wafer is provided. The monitor wafer includes a substrate and a cleaning layer. The cleaning layer is disposed on a bottom surface of the substrate. The cleaning layer is configured to remove particles from the substrate and/or a processing tool.

This application claims the benefit of People's Republic of China application Serial No. 202310065276.7, filed Jan. 13, 2023, the subject matter of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a monitor wafer and a method of using the same.

BACKGROUND

Particles may accumulate in a processing tool. For example, fall-on particles from the processing chamber of the processing tool and reaction byproduct residues from previous process may remain on a chuck. Such particles may contaminate the processes and/or lead to tool down or scrap, and thus should be removed. However, in order to remove the particles, the processing chamber must be opened and maintained. It is time consuming.

SUMMARY

This disclosure is focused on a time saving solution for the removal of the particles as described above.

This disclosure provides a monitor wafer. The monitor wafer comprises a substrate and a cleaning layer. The cleaning layer is disposed on -a bottom surface of the substrate. The cleaning layer is configured to remove particles from the substrate and/or a processing tool.

This disclosure also provides a method of using a monitor wafer. The monitor wafer comprises a substrate and a cleaning layer, and the cleaning layer is disposed on a bottom surface of the substrate. The method comprises following steps. First, the monitor wafer is transported into a processing tool. Then, a tool particle condition of the processing tool is monitored using the substrate of the monitor wafer. Particles are removed from the substrate and/or the processing tool using the cleaning layer of the monitor wafer. Monitoring the tool particle condition and removing the particles are conducted concurrently.

In this disclosure, a monitor wafer having a cleaning layer is used. As such, the particles can be removed when the regular monitor is conducted. The additional time required for the removal of the particles can thus be reduced significantly.

DETAILED DESCRIPTION

Various embodiments will be described more fully hereinafter with reference to accompanying drawings. The description and the drawings are provided for illustrative only, and should not result in a limitation. For clarity, the elements may not be drawn to scale. In addition, some elements and/or reference numerals may be omitted from some drawings. It is contemplated that the elements and features of one embodiment can be beneficially incorporated in another embodiment without further recitation.

One aspect of the disclosure is directed to a monitor wafer. Referring toFIGS.1A-1B, an exemplary monitor wafer100is shown, whereinFIG.1Ais a perspective view of the monitor wafer100, andFIG.1Bis a cross sectional view of the monitor wafer100. The monitor wafer100comprises a substrate102and a cleaning layer104. The cleaning layer104is disposed on a bottom surface of the substrate102. The cleaning layer104is configured to remove particles from the substrate102and/or a processing tool.

Specifically, the substrate102is a main portion for providing a monitoring function to the monitor wafer100. The substrate102can comprise Si. Other details of the substrate102can be similar to those of the monitor wafers typically used in semiconductor processes, and will not be repeated herein.

The cleaning layer104further provides a particle removing function to the monitor wafer100. The cleaning layer104can use a material satisfying at least one of the following characteristics: (1) stable in a temperature range from −20° C. to 450° C.; (2) moisture proofing; and (3) acid resisting, alkali resisting, and/or solvent resisting. More preferably, the cleaning layer104uses a material satisfying all of the characteristics (1) to (3) as described above. For example, the cleaning layer104can comprise polyimide or polyimide-based material. The polyimide-based material can be, for example, bio-based polyimide, such as a recyclable polyimide-based nanofiltration membrane generated by polycondensation of highly flexible 4,4′-diamino-3,3′-dimethyldiphenyl methane and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, but not limited thereto. Such a cleaning layer104can remove particles by a various mechanisms. For example, physical adhesion can be generated between the cleaning layer104and a chuck carrying the monitor wafer100, and thereby actively take away visible large particles from the chuck. In addition, surface polymer of the cleaning layer104has polarity, and thus surface adsorption and/or van der Waals Force can be generated to actively take away small particles.

The cleaning layer104can be disposed on the whole bottom surface of the substrate102. Herein, the term “top surface” is referred to a surface of the substrate102that is corresponding to a surface of a wafer to be treated in the processing tool, and the term “bottom surface” is referred to a surface opposite to the top surface. It is contemplated that, in the processing tool, the top surface of the monitor wafer typically faces a processing source, such as but not limited to a target, an etchant, a plasma source, a polishing machine, and so on. In some embodiments, the cleaning layer104has a thickness from 20 μm to 40 μm.

FIGS.2A-2Bshow another exemplary monitor wafer100′, whereinFIG.2Ais a perspective view of the monitor wafer100′, andFIG.2Bis a cross sectional view of the monitor wafer100′. The monitor wafer100′ is different from the monitor wafer100in that the monitor wafer100′ further comprises another cleaning layer106disposed on a top surface of the substrate102. Similar to the cleaning layer104, the cleaning layer106can be disposed on the whole top surface of the substrate102. Other details of the cleaning layer106are similar to those of the cleaning layer104, and will not be repeated herein.

Another aspect of the disclosure is directed to a method of using a monitor wafer. The monitor wafer can be the monitor wafer100or the monitor wafer100′ as described above. The monitor wafer can comprise a substrate102and a cleaning layer104disposed on a bottom surface of the substrate102. The substrate102can comprise Si. The cleaning layer104can comprise polyimide or polyimide-based material. The cleaning layer104can be disposed on the whole bottom surface of the substrate102. The monitor wafer100′ may also be used, and it comprises another cleaning layer106disposed on a top surface of the substrate102. Other details of the monitor wafer will not be repeated herein.

For convenience, the following illustration will use the monitor wafer100as an example. Referring toFIG.3, the method comprises following steps. First, the monitor wafer100is transported into a processing tool200. Then, a tool particle condition of the processing tool200is monitored using the substrate102of the monitor wafer100. Particles are removed from the substrate102and/or the processing tool200using the cleaning layer104of the monitor wafer100. Monitoring the tool particle condition and removing the particles are conducted concurrently.

More specifically, the processing tool200can comprise a processing path210as indicated by arrows and a processing chamber220. The processing chamber220comprises, for example, a processing source222and a chuck224. The processing source222can be but not limited to a target, an etchant, a plasma source, a polishing machine, and so on. The chuck224can be a magnetic chuck or a vacuum chuck. It should be understood that the details of the processing tool200described herein and shown inFIG.3are for illustrative only, and should not result in a limitation.

Transporting the monitor wafer100into the processing tool200can be transporting the monitor wafer100into the processing chamber220of the processing tool200along the processing path210of processing tool200.

In a condition that the processing tool200comprises the processing path210and the processing chamber220, monitoring the tool particle condition of the processing tool200can comprise monitoring a particle condition of the processing path210and a particle condition of the processing chamber220. The tool particle condition, as well as the particle condition of the processing path210and the particle condition of the processing chamber220, can comprise a particle type, a particle amount, and a particle distribution. The particles are, for example, fall-on particles from the processing chamber and/or reaction byproduct residues remained on the chuck from previous process, but not limited thereto.

In some embodiments, the method can further comprise monitoring defects of the monitor wafer100and/or the processing tool200other than the particles using a defect scanning tool.

In removing the particles from the processing tool200and/or the substrate102, the cleaning layer can remove particles by at least one of adhesion, adsorption, or van der Waals Force. In some embodiments, removing the particles can comprise applying an energy to the cleaning layer104. The additional energy may be beneficial for increasing the adsorption effect of the cleaning layer104.

In summary, various mechanisms such as adhesion, adsorption, van der Waals Force, and so on are used in the disclosure to remove particles when the regular monitor is conducted. As such, the additional time required for the removal of the particles can be reduced significantly. It is estimated 5 that, compared to removing particles by opening and maintaining the process chamber, using the monitor wafer according to the disclosure to remove particles can save about 19.5 days of idle time per year. It is beneficial for extending PM (preventive maintenance) cycle and increasing up-time.