Effects of scaling the film thickness on the ferroelectric properties of SrBi2Ta2O9 ultra thin films

Abstract

We have investigated the effect of reducing the thickness of strontium bismuth tantalate film to as low as 25 nm on its ferroelectric characteristics. A degradation of ferroelectric properties such as significant reduction in remanent polarization is generally observed with reduction in film thickness, in particular below 100 nm. This has been overcome by using a modified deposition process sequence and a crystallization technique based completely on the rapid thermal annealing process. The resulting ultrathin films show good remanent polarization, low-voltage saturation, low leakage current, high breakdown strength, and good endurance. These films demonstrate the potential for scaling and are excellent candidates for several generations of ferroelectric random access memory applications.

Structural characteristics of SrTiO3 thin films processed by rapid thermal annealing

“…However, with the increase of annealing time, the surface roughness of thin films was improved with RMS decreasing from 6.2 to 4.6 nm. The dense, flat surface as well as low level of porosity on the surface was observed, which might lead to the improvement of electric properties [15].…”

“…In general, small grain size and dense surface are expected. According to Celinska [15], big grain size leads to rough surface, and for the films with a rough surface, as film thickness is reduced and approaches the film roughness, extremely high-field regions can exist in devices and lead to oxide breakdown.…”

Tunability and leakage currents of (Ba,Sr)TiO3 ferroelectric ceramics with various additives

“…Such charge inhomogenity considerably increases the hysteresis value. The horizontal parts on I (U ) dependencies or the negative differential resistance were observed on thin film samples [9,10], however the model description of this effect was not accomplished. The third part on the I (U ) characteristics is associated with the individual energetic distribution of the charge traps.…”

STRUCTURAL CHARACTERISTICS OF (Ba,Sr)TiO3 THIN FILMS BY RAPID THERMAL ANNEALING

“…12 In general, smaller grain size results in a denser and smoother surface, whereas big grain size leads to a rougher surface in which there exist extremely highfield regions that are easier to be electrically broken down. 13 In conventional annealing process, the thin film is crystallized in a long processing time with a low heating rate (1-10 • C/s), which causes a significant grain growth. With a rapid thermal annealing (RTA), Kosola 14 made strontium titanate thin films deposited by using the ALD method, crystallized with a fairly small grain size and flat surface.…”