Etching Characteristics of The B and N Co-Doped Amorphous Carbon Films through Nitrogen Concentration Control for Use as Hardmasks

The challenge to overcome the limits of semiconductor chip shrinkage continues. Shorter-wavelength light sources, such as extreme ultraviolet (EUV), are being utilized to maximize resolution. The use of shorter-wavelength light sources leads to a decrease in the depth of focus (DOF), and consequently, a proportional reduction in the thickness of the photoresist (PR) layer. This limitation in PR layer thickness may lead to a failure in fulfilling its intended role as a mask in the etching process following lithography, risking complete loss or compromise during etching and potentially causing a deterioration in pattern quality. To address the previously mentioned issues, a sacrificial layer called the hard mask is applied between the component to be patterned and the PR. Amorphous carbon is the material that can most effectively meet various characteristics required for use as a sacrificial layer. Various approaches have been attempted to enhance etch selectivity and improve pattern quality in the etching process by altering the properties of this material. While there have been numerous studies analyzing the characteristics by doping different elements into the amorphous carbon layer, the focus has predominantly been on research related to individual elements.<br/>We aimed to investigate how characteristics change from the perspective of etch resistance when boron & nitrogen co-doping is applied, rather than when individual dopants are applied separately. B & N co-doped amorphous carbon (a-BCN) hardmask were obtained by adjusting the nitrogen content in an amorphous carbon film supplied with sufficient boron, using the DC sputter process. The composition of the hardmask film was analyzed through XPS analysis. Subsequently, films deposited under various conditions were evaluated for their relationship with dry etching performance. In particular, we analyzed the relationship between the etching gas and the a-BCN hardmask structure in the ternary system from both physical and chemical reaction perspectives. We figured out that increased nitrogen in the film alters its density and structure, impacting physical etching processes. Additionally, DFT calculations show that higher nitrogen content increases the probability of chemical etching reactions with fluorine. The details of the physical and chemical reaction mechanisms of etching in a-BCN will be discussed in detail. Based on the implementation results of the ternary system in the hardmask, we would like to discuss the changes in etching characteristics from both physical and chemical perspectives.