Protective film agent for laser dicing and wafer processing method using the protective film agent

Abstract

A protective film agent for laser dicing according to the present invention comprises a solution having, dissolved therein, a water-soluble resin and at least one laser light absorber selected from the group consisting of a water-soluble dye, a water-soluble coloring matter, and a water-soluble ultraviolet absorber. The protective film agent is coated on a surface of a wafer, which is to be processed, and is then dried to form a protective film. Laser dicing through the protective film produces chips from the wafer. As a result, deposition of debris can be effectively prevented on the entire face of the chips, including their peripheral edge portions.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a protective film agent for use in laser dicing which applies a laser beam to a predetermined region of a wafer, such as a semiconductor wafer, to carry out predetermined processing, and a processing method by laser dicing using the protective film agent. [0003] 2. Description of the Related Art [0004] As is well known among those skilled in the art, a wafer formed in a semiconductor device manufacturing process has a laminate, which comprises an insulating film and a functional film stacked on the face of a semiconductor substrate, such as silicon, partitioned by a lattice of scheduled division lines, called streets. Respective regions partitioned by the streets define semiconductor chips such as IC's or LSI's. That is, a plurality of semiconductor chips are obtained by cutting the wafer along the streets. An optical device wafer has a laminate, which comprises a gallium nitride-based comp...

AI Technical Summary

Benefits of technology

[0012] It is an object of the present invention, therefore, to provide a protective film agent for laser dicing, which can form a protective film having high adhesion to the face of a wafer, and being capable of effectively preventing deposition of debris on the entire face of chips, including their peripheral edge portions, in producing the chips from the wafer by laser dicing, and also to provide a method for processing the wafer with the use of the protective film agent.

[0022] The protective film agent for laser dicing according to the present invention contains the water-soluble laser light absorber in addition to the water-soluble resin. Thus, a protective film, which is formed on the face of the wafer by coating and drying the protective film agent, shows high absorption of laser light and, when irradiated with laser light, is promptly thermally decomposed to be laser-processed along the street lines. Hence, peeling of the protective film, which occurs under the pressure of a vapor, etc. of the thermal decomposition product of the substrate upon exposure to laser light, can be effectively prevented. Furthermore, the water-soluble dye, etc., which are used as the water-soluble laser light absorbers, all have high affinity for the wafer face. Thus, the adhesion of the protective film has been enhanced, and peeling of the protective film from the wafer face, particularly, in the vicinity of the street lines is effectively suppressed. Accordingly, the protective film is formed by the protective film agent of the present invention, and laser dicing is performed by irradiation with laser light, whereby the deposition of debris can be effectively prevented throughout the faces of the diced chips.

Problems solved by technology

Thus, the wafer has posed the problems that when the wafer is cut into semiconductor chips by the cutting blade (cutting edge), flaws, scratches or chipping occurs, causing the peeling of the insulating film required of circuit elements formed on the faces of the chips.

When laser light is applied along the streets of the wafer, however, the new problem has arisen that the laser light is absorbed, for example, into the silicon substrate, and its thermal energy leads to the melting or thermal decomposition of silicon, thus generating a silicon vapor, etc., which are condensed and deposited on the faces of the chips.

The resulting condensation deposit (debris) of the silicon vapor, etc. markedly deteriorates the quality of the semiconductor chips.

With the foregoing methods, however, it is still impossible to prevent the deposition of debris completely, and the problem occurs that debris deposits on peripheral edge portions of the chips, in particular.

As a result, debris deposition occurs at the peripheral edge portions of the chip faces.

The problem also exists that the adhesion of the protective film to the wafer face is so low that the protective film is prone to peel off.

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