Forming high aspect ratio patterning structure gas in oil car

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This application claims the priority benefit of China patent application serial No. 201611048184.4, filed Nov. 22, 2016. The entire contents of the above-mentioned patent application are hereby incorporated by reference herein and made a part of the specifications. FIELD OF THE INVENTION

Since the above requirements have exceeded traditional lithography processes limits, a new lithography process is needed. Generally, a tri-layer photoresist process is employed in the above high aspect ratio requirement, which is comprised of an injection barrier layer, a hard mask layer, and a photoresist layer. The pattern on the photoresist layer is successively transferred to the hard mask layer and the injection barrier layer by utilizing selection ratio change of etching among the photoresist layer, the hard mask layer and the injection barrier layer.

However, in the above prior art, when the ratio between the thickness of the injection barrier layer and the critical dimension is excessively large, a cone-shaped or a bowling-shaped photoresist etching morphology trends to be formed after etching, which will cause the insufficient of the selection ratio or larger critical dimension.

Therefore, how to solve the problem of the cone-shaped or the bowling-shaped photoresist etching morphology existed in the prior art, and to solve the problem of the generated burr on the pattern edge, so as to make the implanted ions be well distributed according to the design of the device, becomes an urgent issue to be solved.

To overcome the problems as mentioned above, it is an object of the present invention to provide a new method for forming high aspect ratio patterning structure to improve the photoresist morphology of the cone shaped or the bowling shaped and to further solve the problem of burrs on the pattern edge by utilizing a new process steps.

Step S 01: providing a semiconductor substrate, on which from bottom to top forming a dielectric film ashing stop layer and a combination mask layer in turn, wherein, the combination mask layer from bottom to top is comprised of a first photoresist layer, a first hard mask layer and a second photoresist layer in turn;

Preferably, in the Step S 02, a plasma etching process with a CF-based gas is employed to etch the first hard mask layer, and the morphology of the first hard mask layer is adjusted by adjusting the C/F ratio in the CF-based gas to adjust the final critical dimension.

Preferably, in the Step S 03, before the formation of the second hard mask layer, the height of the pattern sidewall is firstly adjusted by an anisotropic plasma etching process, while the second photoresist layer is completely consumed and removed; the reaction gases include oxygen or sulfur dioxide.

Preferably, in the Step S 05, a plasma etching process is employed to etch the first photoresist layer; the reaction gases include oxygen or sulfur dioxide; in the Step S 06, an isotropic plasma etching process is employed to remove the first hard mask layer and the second hard mask layer on the pattern; the reaction gases include sulfur hexafluoride or nitrogen trifluoride.

Concluded from the above technical solutions, the invention has disclosed a method for forming high aspect ratio patterning structure based on the tri-layer photoresist process. Firstly, forming a dielectric film ashing stop layer, a first photoresist layer, a first hard mask layer and a second photoresist layer on a semiconductor substrate in turn. After etching the first hard mask layer, a second hard mask layer having a high etch selectivity ratio with the first photoresist layer is formed on top surface and sidewall of the pattern by utilizing a low temperature chemical vapor deposition process, which can be a protect for the pattern sidewall during the later etching the first photoresist layer. So, the cone-shaped or the bowling-shaped photoresist morphology caused by plasma bombardment can be avoided. Therefore, the problems of the insufficient of selectivity ratio, burrs at the edge of the pattern and larger of the critical dimension can be solved, and the implanted ions can be well distributed according to the design of the device. BRIEF DESCRIPTION OF THE DRAWINGS