Method for treating the etching solution

Abstract

The present etching system includes a processing tank with an etching solution containing silicon, a cooling tank, a pre-heating tank, a first pipe for transferring the etching solution from the processing tank to the cooling tank, a second pipe for transferring the etching solution from the cooling tank to the pre-heating tank, and a third pipe for transferring the etching solution from the pre-heating tank to the processing tank. The present method for treating the etching solution first performs an etching process using the etching solution, which is then cooled to a first temperature to form a silicon-saturated etching solution. After silicon-containing particles larger than a predetermined size are filtered out, the silicon-saturated etching solution is heated to a second temperature to form a non-saturated etching solution for performing another etching process later. The second temperature is preferably at least 10° C. higher than the first temperature.

Description

[0001] This is a Continuation of application Ser. No. 11 / 535,057 filed Sep. 25, 2006, which in turn is a Divisional of application Ser. No. 10 / 943,936. The disclosure of the prior applications is hereby incorporated by reference herein in its entirety.BACKGROUND [0002] (A) Field of the Invention [0003] The present invention relates to an etching system and method for treating the etching solution thereof, and more particularly, to an etching system and a method for treating the etching solution with a stable selectivity between silicon nitride and silicon oxide. [0004] (B) Description of the Related Art [0005]FIG. 1 to FIG. 3 show a method for fabricating a shallow trench isolation on a wafer 10 according to the prior art. The shallow trench isolation is widely used in the fabrication of the metal-oxide-semiconductor (MOS) transistor to form an electrical isolation between transistors. As shown in FIG. 1, the fabrication of the shallow trench isolation begins to form an oxide layer ...

AI Technical Summary

Benefits of technology

[0018] Compared with the prior art, the present invention possesses a steadier, smaller variation of the silicon concentration in the etching solution, and achieves a stable etching selectivity between the silicon nitride and silicon oxide. In addition, the present invention need not drain the used etching solution, which can reduce the cost of the etching process dramatically.

Problems solved by technology

For example, a 0.2 μm silicon particle remaining on the surface of wafer 10 will seriously cause integrated circuit fabricated by a 0.131 μm MOS fabrication process to fail.

However, if there were too many silicon particles, the filter 44 would easily fail due to the blocking of the silicon particles.

Therefore, the etching selectivity between silicon nitride and silicon oxide also changes with the processing time of the etching solution, which further increases the difficulty to control the process parameters, such as the etching time.

However, this treating method obviously reduces the efficiency of the etching solution.

Furthermore, completely renewing the phosphoric acid etching solution increases the consumption of phosphoric acid and raises the etching cost.

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