Resist roughness Bi-modality as revealed by two-dimensional FFT 2D analysis

LER/LWR performance is currently considered as one of the major stumbling blocks complicating progress in the semiconductor technology. Line edge scans show that low frequency components clearly dominate the LER Power Spectral Density (PSD), thus implying a large characteristic length (>100-500 nm) phenomenon as the major LER source. Most of the theoretical analyses aimed to identify the origin of the LER were focused on the combined effect of exposure and CAR action statistics, and failed to explain the origin of this limit, which resulted in suggestions that there is more than just one phenomenon involved in LER generation. Depth profiling experiments were performed for a broad set of Polymer-PAG-Base combinations. Depth profiling PSD spectra have demonstrated that higher RMS values and correspondingly higher PSD amplitudes are associated with tighter PSD spectrum shifted towards lower frequencies (larger sizes of roughness features), which is very typical for all the cases investigated. The set of the PSD spectra obtained exhibit a pronounced bi-modal structure, indicating that there are at least two clearly noticeable independent roughness-controlling mechanisms.Defense Advanced Research Projects Agency (Air Force Contract FA8721-05-C-0002

Electron-beam Directed Materials Assembly

We have developed a processing method that employs direct surface imaging of a surface-modified silicon wafer to define a chemical nanopattern that directs material assembly, eliminating most of the traditional processing steps. Defining areas of high and low surface energy by selective alkylsiloxane removal that match the polymer period length leads to defect-free grating structures of poly(styrene-block-methyl methacrylate) (PS-b-PMMA). We have performed initial studies to extend this concept to other wavelengths beyond 157 nm. In this present paper, we will show that electron beam lithography can also be used to define chemical nanopatterns to direct the assembly of PS-b-PMMA films. Half-pitch patterns resulted in the directed assembly of PS-b-PMMA films. Electron beam lithography can also be used to prepare surfaces for pitch division. Instead of the deposition of an HSQ pinning structure as is currently done, we will show that by writing an asymmetric pattern, we can fill in the space with smaller lamellar period block copolymers to shrink the overall pitch and allow for 15-nm features.United States. Defense Advanced Research Projects AgencyUnited States. Air Force (Contract FA8721-05-C- 0002

Lithographically directed materials assembly

We have developed a processing method that significantly reduces the number of steps necessary to yield a surface that directs block copolymer assembly. This methodology employs a single resistless lithography step that directly changes the surface energy without requiring subsequent material deposition or plasma etching steps. The lithographically defined difference in surface energies acts as a template to direct diblock polymer self-assembly into low-defect periodic structures. Our newly developed lithographically directed self-assembly technique can produce sub-45 nm half pitch lines employing poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and interference lithography. Once assembled into periodic lines of alternating materials, the PMMA block can be removed and the resulting polystyrene features can be used as an etch mask to transfer periodic lines-and-spaces into a silicon substrate.Defense Advanced Research Projects Agency (Air Force Contract FA8721-05-C-0002

Polymer photochemistry at the EUV wavelength

The higher energy associated with extreme ultraviolet (EUV) radiation coupled with the high absorptivity of most organic polymers at these wavelengths should lead to increased excited state population and higher quantum yields of photoproducts. Polymers representative of those commonly employed in resists as well as some model polymers were selected for this study. Polymer photochemistry at EUV was catalogued as to the effect of absorbed 13.4-nm radiation on a polymer's quantum yield of chain scission (Φs) and crosslinking (Φx). In selected cases, the chain scission and crosslinking quantum yields were also compared to those previously determined at 157-, 193- and 248-nm. It was found that quantum yield values were over a magnitude greater at EUV relative to optical wavelengths.Intel Corporatio

PAG segregation during exposure affecting innate material roughness

We have developed an improved AFM-based technique to measure intrinsic material roughness (IMR) after base development. We have investigated the contribution of different polymeric PAGs to IMR. These polymeric PAGs include copolymers of several styrenic PAGs with hydroxystyrene. The IMR of these polymer-bound PAGs is reduced relative to that of their nonpolymeric counterparts with DUV exposure. Theses results represent further evidence for PAG segregation during the bake steps as being responsible for increased IMR in exposed resists, presumably by increasing the dissolution rate inhomogeneity on a nano-scale level. The work also shows that the effects of PAG segregation can be mitigated by employing polymer-bound PAGs. 2Lincoln LaboratoryIntel Corporatio