Process Control and Inspection of Resist & Organic Flex Circuits -Beltronics Inc.

Beltronics Inc. - Designers and Manufacturers of automated inspection equipment for leading semiconductor companies for over 20 years.

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Process Control and Inspection of Resist

To increase and maintain high yields, a production process should be continually monitored to rapidly detect, identify and eliminate any source of defects. Many metal defects originate as defects in the resist pattern prior to metal etch. Many high resolution resists have low contrast or are optically clear making it impossible to visually detect any defects. Figure 10a shows the reflected light image of a clear resist line pattern deposited on a non-planar metallic surface. The dark bands are due to changes in metal topology as described in the technical section. Beltronics has been able to induce fluorescence in many resists as shown in Figures 10b and 11b. Figure 10b reveals a line narrowing notch in one of the conductors. Figure 11b shows extraneous flakes of resist. Resist can be easily removed and reapplied prior to metal etch thereby effectively eliminating defects before they are fabricated.


Reflected Light image of clear resist deposited on non-flat substrate Figure 10a	Mscan detects notch defect in 12 micron line Figure 10b


Reflected light image of resist on flex Figure 11a	Mscan detects resist flakes Figure 11b

FLEX CIRCUITS

Process Control and Inspection of Organic Flex Circuits

Continuous monitoring of a production line can lead to the early detection and elimination of problems before part failure occurs. Figures 12a and 12b show the reflected light and Mscan images respectively, for a flex circuit in which the etch process is drifting out of specification. While the white light image looks perfect, the Mscan image clearly shows jagged edges. If such problems are not corrected, the process could continue to degrade until fatal shorts as shown in Figures 2a and 2b appear.


Reflected light image of resist on flex Figure 12a	Mscan etects resist flakes Figure 12b

Essential to the inspection of flex circuits is the ability to scan non-flat surfaces. Beltronics patented auto tracking system enables detection of extremely small defects on flex circuits at high scanning speeds. Mscan pixel size is adjustable down to 200 nanometres. Samples varying in height over 2000 microns can be tracked without loss in detection accuracy.

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