Precise Stress Control of Ta Absorber using Low Stress Alumina Etching Mask for X-Ray Mask Fabrication

Abstract

In the stress control of an X-ray mask absorber, the repeatability of control and stability are important. We found that the change in the stress in a Ta film resulting from annealing depends on the oxygen concentration in the film; the magnitude of the stress change is determined by the annealing temperature and time. Using this characteristic of Ta film, we have successfully controlled the stress in the Ta absorber to less than 5 MPa with good repeatability. In our mask fabrication process, Al2O3 film was used as an etching mask. We found that the Al2O3 film prevented the Ta absorber stress from changing in high-temperature atmospheres because the Al2O3 film prevented oxygen diffusion into the Ta film. Utilizing Al2O3 films, we succeeded in preventing changes in Ta absorber stress in the thermal processes after Ta stress control, such as frame bonding and resist baking. Consequently, we were able to precisely control the Ta absorber stress in X-ray masks with good repeatability and stability in a realistic X-ray mask fabrication process.

Stress Reduction of Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> by Inhibiting Oxygen Diffusion

“…According to a report, the stress-change in air is much larger than that in nitrogen, 13) which has been explained by oxygen diffusion into Ta film. [13][14][15] The stresschange is increased with annealing temperature and time, and is directly proportional to the diffused oxygen content in Ta film. 13) Additionally, the large distance of oxygen diffusion into Ta film is understood to be due to the high diffusion rate of oxygen along the grain boundaries of the Ta.…”

“…[13][14][15] The stresschange is increased with annealing temperature and time, and is directly proportional to the diffused oxygen content in Ta film. 13) Additionally, the large distance of oxygen diffusion into Ta film is understood to be due to the high diffusion rate of oxygen along the grain boundaries of the Ta. 13,15,16) In this paper, we investigated the effect of oxygen diffusion on the stress-hysteresis behavior of Ge 2 Sb 2 Te 5 , as shown in Fig.…”

“…13) Additionally, the large distance of oxygen diffusion into Ta film is understood to be due to the high diffusion rate of oxygen along the grain boundaries of the Ta. 13,15,16) In this paper, we investigated the effect of oxygen diffusion on the stress-hysteresis behavior of Ge 2 Sb 2 Te 5 , as shown in Fig. 2.…”

Sputter deposition and annealing of Ta, TaSix and TaBx composite films and their application in next generation lithography masks

“…XRD analysis was not performed on Ta 5 B. Previous work 4,5,13 has shown that ␤-Ta films deposited at low pressures had a fibrous, dense structure, while films deposited at higher pressures were less dense with an open columnar structure. Oxygen diffusion along grain boundaries and eventually into the grains, resulted in an observed change of stress in the compressive direction.…”

Development of x-ray mask fabrication process using w-sputtering

“…X-ray lithography using synchrotron radiation (SR) is a promising technology for fabricating ultra large scale integration (ULSI) devices with dimensions less than 0.1 p.m, because it has a superior characteristics such as high resolution and throughput [1][2][3][4][5]. Since the current x-ray lithography is a proximity printing system, x-ray mask is the most critical element in this technology.…”