Method for improving undercut flaw of phosphorosilicate glass

Abstract

The invention discloses an improvement method for the undercut defects of phosphorosilicate glass. The phosphorosilicate glass is formed in a process chamber by adopting the method of high density plasma chemical vapor deposition. The process chamber is connected with a gas pipeline used for the input of phosphorane gas, the gas pipeline is provided with a switching valve and a flow controller between the valve and the process chamber. In the improvement method, the residual phosphorane gas between the switching valve and the flow controller is pumped away before opening the switching valve. With the adoption of the method, the phosphorosilicate glass with uniform phosphorus content can be obtained in the process of subsequent sedimentation of the phosphorosilicate glass, thus avoiding the undercut defect occurring in the step of subsequent wet etching.

Description

technical field [0001] The invention relates to a manufacturing process in the field of semiconductors, in particular to a method for improving undercut defects in phosphosilicate glass. Background technique [0002] In 130nm and below technology, phosphosilicate glass (HDP-PSG) and undoped silica glass (USG) prepared by high-density plasma chemical vapor deposition process are widely used as pre-metal dielectric (PMD) of wafers. figure 1 It is a schematic diagram of the structure of the existing wafer. In the process of making the wafer through hole (via), a pad oxide layer 2, that is, undoped silicon glass, is deposited on the barrier layer 1 of the wafer at first; A layer of phosphosilicate glass 3 is deposited on the oxide layer; finally, a wet etching step is performed to form a via hole on the pre-metal dielectric for filling metal. The step of depositing phosphosilicate glass is carried out in the process chamber of high-density plasma, and the reaction gas generally...

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Problems solved by technology

[0003] However, in the above wet etching process, undercut defects often appear in phosphosilicate glass, such as figure 1 shown in

The study found that there is residual phosphine gas between the opening and closing valve of the phosphine gas delivery pipeline and the flow controller. After the opening and closing valve is opened, the new phosphine gas encounters the residual phosphine gas, causing gas burst problems , causing the concentration of phosphine gas in the process chamber to be instantly larger, resulting in a higher phosphorus content at the bottom of the phosphosilicate glass near the liner oxide layer

Moreover, the higher the phosphorus content in phosphosilicate glass, the greater the etching rate, so in the wet etching step, undercut defects often appear at the bottom of phosphosilicate glass

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