US-20260126722-A1 - EXPANDABLE NEGATIVE PHOTORESIST WITH SUSPENSION MATERIAL AND METHOD FOR REDUCING HORN SHAPES IN SPACER OXIDE USING EXPANDABLE NEGATIVE PHOTORESIST

US20260126722A1US 20260126722 A1US20260126722 A1US 20260126722A1US-20260126722-A1

Abstract

The present application discloses an expandable negative photoresist and a method for adjusting a profile of a spacer oxide using the expandable negative photoresist. The expandable negative photoresist includes a polymer material, a suspension material and a photoacid generator. The suspension material contains a plurality of expandable molecules. An expansion coefficient of the suspension material is greater than that of the polymer material.

Inventors

TZU-YU CHOU
Chih-Ying Tsai

Assignees

NANYA TECHNOLOGY CORPORATION

Dates

Publication Date: 20260507
Application Date: 20241211

Claims (9)

1 . A method for reducing a horn shape of a spacer oxide, comprising: providing an underlayer; forming a negative photoresist layer over the underlayer, wherein the negative photoresist layer comprises a polymer material, a suspension material containing a plurality of expandable molecules, and a photoacid generator (PAG); creating a patterned photoresist layer and an expandable layer over the underlayer through an exposure process and a developing process, wherein the expandable layer comprises a plurality of released expandable molecules, while the patterned photoresist layer is free of the released expandable molecules; depositing a spacer oxide layer that covers both the patterned photoresist layer and the expandable layer; and activating the released expandable molecules by a thermal process to expand the released expandable molecules outward, which in turn expands the spacer oxide layer outward, thereby reducing the horn shape of the spacer oxide to be formed in subsequent processes.
2 . The method of claim 1 , wherein each of the plurality of expandable molecules is chemically bonded to the polymer material of the negative photoresist layer through a chemical bond.
3 . The method of claim 2 , wherein an expansion coefficient of the suspension material is greater than that of the polymer material.
4 . The method of claim 3 , wherein a density of the suspension material is less than that of the polymer material.
5 . The method of claim 4 , wherein the polymer material of the negative photoresist layer includes poly(tert-butoxycarboxystyrene) (PBOCSt).
6 . The method of claim 5 , wherein the PAG includes triphenylsulfonium hexafluoroantimonate (Ph 3 SSbF 6 ).
7 . The method of claim 1 , wherein each of the plurality of released expandable molecules is separate from a polymer material of the patterned photoresist layer.
8 . The method of claim 1 , wherein a first sidewall of the expandable layer is coplanar with a first sidewall of the patterned photoresist, and a second sidewall of the expandable layer is coplanar with a second sidewall of the patterned photoresist.
9 . The method of claim 1 , wherein a method of photolytic bond cleavage is used to obtain the released expandable molecules.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation application of U.S. Non-Provisional application Ser. No. 18/934,430 filed Nov. 1, 2024, which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure relates to a negative photoresist and a method for adjusting a profile of a spacer oxide, and more particularly, to an expandable negative photoresist with a suspension material and a method for reducing horn shapes in spacer oxide using the expandable negative photoresist. DISCUSSION OF THE BACKGROUND Semiconductor devices are used in various electronic applications, including personal computers, cellular telephones, digital cameras, and other electronic equipment. Sizes of semiconductor devices are continuously decreasing to meet growing demands for computing power. However, such scaling down presents challenges that are becoming more frequent and impactful. Therefore, there are still challenges to improving quality, yield, performance and reliability while reducing complexity. Spacers and spacer oxides are commonly used in the manufacturing process of semiconductor devices to ensure correct distances between and functionality of components. With requirements for smaller line widths and spacings, such as critical dimensions (CD) less than 50 nm, and more complex fabrication processes, including pitch doubling and multiple patterning, ensuring the functional integrity of spacers while avoiding horn shapes remains an ongoing challenge. This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this Discussion of the Background section constitutes prior art to the present disclosure, and no part of this Discussion of the Background section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure. SUMMARY One aspect of the present disclosure provides an expandable negative photoresist comprising a polymer material, a suspension material, and a photoacid generator (PAG). The suspension material contains a plurality of expandable molecules. In some embodiments, an expansion coefficient of the suspension material is greater than that of the polymer material. In some embodiments, a density of the suspension material is less than that of the polymer material. In some embodiments, the expandable molecule is chemically bonded to the polymer material through a chemical bond. In some embodiments, the chemical bond is severed using a photolytic bond cleavage method. In some embodiments, the polymer material includes poly(tert-butoxycarboxystyrene) (PBOCSt). In some embodiments, the PAG includes triphenylsulfonium hexafluoroantimonate (Ph3SSbF6). Another aspect of the present disclosure provides a method for adjusting a profile of a spacer oxide, comprising providing a substrate, applying an underlayer over the substrate, forming a first photoresist layer over the underlayer, performing an exposure process on the first photoresist layer to create a second photoresist layer in the first photoresist layer, conducting a developing process on both the first and second photoresist layers to form a third photoresist layer and an expandable layer over the third photoresist layer, depositing a spacer oxide layer that covers both the third photoresist layer and the expandable layer, and performing a thermal process on the expandable layer, thereby adjusting the profile of the spacer oxide. The first photoresist layer comprises a first suspension material that contains a plurality of first expandable molecules, while the second photoresist layer comprises a second suspension material that contains a plurality of second expandable molecules. The expandable layer comprises the plurality of second expandable molecules. The thermal process is performed by activating the second expandable molecules in the expandable layer. In some embodiments, the first photoresist layer is a negative-tone photoresist. In some embodiments, the first suspension material is uniformly distributed throughout the first photoresist layer. In some embodiments, each of the plurality of first expandable molecules is chemically connected to a first polymer material in the first photoresist layer through a chemical bond. In some embodiments, an expansion coefficient of the first suspension material is greater than that of the first polymer material. In some embodiments, a density of the first suspension material is less than that of the first polymer material. In some embodiments, the first polymer material of the first photoresist layer includes poly(tert-butoxycarboxystyrene) (PBOCSt). In some embodiments, each of the plurality of second expandable molecules is separate from a second polymer material in the second photoresist layer. In some embodiments, an expansio