Alberto D. Dioses

New spin-on metal hardmask materials for lithography processes

Since the critical dimensions in integrated circuit (IC) device fabrication continue to shrink below 32 nm, multilayer stacks with alternating etch selectivities are required for successful pattern transfer from the exposed photoresist to the substrate. Inorganic resist underlayer materials are used as hard masks in reactive ion etching (RIE) with oxidative gases. The conventional silicon hardmask has demonstrated good reflectivity control and reasonable etch selectivity. However, some issues such as the rework of trilayer stacks and cleaning of oxide residue by wet chemistry are challenging problems for manufacturability. The present work reveals novel spin-on underlayer materials containing significant amounts of metal oxides in the film after baking at normal processing conditions. Such an inorganic metal hardmask (MHM) has excellent etch selectivity in plasma etch processes of the trilayer stack. The composition has good long term shelf life and pot life stability based on solution LPC analysis and wafer defect studies, respectively. The material absorbs DUV wavelengths and can be used as a spin-on inorganic or hybrid antireflective coating to control substrate reflectivity under DUV exposure of photoresist. Some of these metal-containing materials can be used as an underlayer in EUV lithography to significantly enhance photospeed. Specific metal hard masks are also developed for via or trench filling applications in IRT processes. The materials have shown good coating and lithography performance with a film thicknesses as low as 10 nm under ArF dry or immersion conditions. In addition, the metal oxide films or residues can be partially or completely removed by using various wet-etching solutions at ambient temperature.

Second-generation radiation sensitive developable bottom anti-reflective coatings (DBARC) and implant resists approaches for 193-nm lithography

We will discuss our approach towards a second generation radiation sensitive developable bottom antireflective coating (DBARCs) for 193 nm. We will show imaging results (1:1 L/S features down to 140 nm) for some first generation implant resist material based upon a fluorinated resins and also show relative implant resistance of these first generation fluorinated resists towards As implantation (15 KeV at 5x1015 dose with 20 x 10-4 amp). Also, discussed will be a second generation of implant resists based on a non-fluorinated resins. Surprisingly, we found that the nonfluorinated materials gave better implant resistance (~2-3 X1011 atoms/cm2) despite the higher atomic number of fluorine compared to hydrogen in the fluorinated implant materials (~2-5X1012 atoms/cm2). Finally, we will give an update on the lithographic performance of this second generation of implant resists.

Second-generation radiation sensitive 193-nm developable bottom antireflective coatings (DBARC): recent results

We will discuss our recent results using a second generation radiation sensitive developable 193 Bottom Antireflective coatings (DBARCs). These DBARC materials are made solvent resistant the application of a resist coating on top of them through a crosslinking mechanism that is reversible by acid catalyzed reaction upon exposure of the DBARC/resist stack. Typically this is done by crosslinking a copolymer containing a hydroxyl moiety with a polyfunctional vinylether during post applied bake. This DBARC approach, after exposure, allows for development of the stack in exposed areas down to the substrate eschewing the plasma etch breakthrough needed for conventional bottom antireflective coatings which are irreversibly crosslinked. We will give an update on the performance our latest 193 nm DBARC materials used with different Implant 193 nm resists when using a phase shift mask with off axis illumination.

Progress in spin-on metal oxide hardmask materials for filling applications

It is well known that metal oxide films are useful as hard mask material in semiconductor industry for their excellent etch resistance against plasma etches. In the advanced lithography processes, in addition to good etch resistance, they also need to possess good wet removability, fill capability, in high aspect ratio contacts or trenches. Conventional metal containing materials can be applied by chemical vapor deposition (CVD) or atomic layer deposition (ALD). Films derived from these techniques have difficulty in controlling wet etch, have low throughput and need special equipment. This leads to high costs. Therefore it is desirable to develop simple spin-on coating materials to generate metal oxide hard masks that have good trench or via filling performances using spin track friendly processing conditions. In this report, novel spin-on type inorganic formulations providing Ti, W, Hf and Zr oxide hard masks will be described. The new materials have demonstrated high etch selectivity, good filling performances, wet removal capability, low trace metals and good shelf-life stability. These novel AZ® Spin-on metal hard mask formulations can be used in several new applications and can potentially replace any metal, metal oxide, metal nitride or silicon-containing hard mask films currently deposited using CVD process in the semiconductor manufacturing process.

Novel spin-on metal hardmask materials for filling applications

Hardmasks are indispensable materials during pattern transfer to the desired substrates in the semiconductor manufacturing process. Primarily there are two types of hardmask materials - organic and inorganic - and they can be coated onto substrates or underlying materials either by a simple spin-on process or by more expensive methods such as chemical vapor deposition (CVD), atomic layer deposition (ALD) and sputtering process. Most inorganic hardmasks such as SiO2, SiON, SiN and TiN are deposited using the CVD process. Future nodes require hardmasks with high etch resistance as the designs move from horizontal to vertical (3D). We have reported novel spin-on metallic hardmasks (MHM) with comparable or higher etch resistance than SiO2.1-2 In addition to high etch resistance, they are easy to remove using wet etch chemicals. The spin-on process offers high throughput and commonly used spin tracks can be utilized; thereby reducing overall process costs when compared with CVD. Via-fill performance is also an important attribute of hardmask materials for these future nodes. Organic spin-on materials, both siloxane- and carbon-based, are used in filling applications of deep via or deep trench fill, such as those found in LELE double-patterning schemes. Inorganic materials deposited by either chemical vapor deposition (CVD) or atomic layer deposition (ALD) have higher resistance to oxygenated plasma than organic materials, but are hindered by their poor filling performance. Therefore, novel tungsten (W) containing MHM materials having both good filling performance and higher resistance to oxygenated plasma than organic materials would be of value in some filling applications. The present paper describes specific metal oxides useful for filling applications. In addition to basic filling performance and etch resistance, other properties such as optical properties, outgas and shelf life via forced aging etc. will be discussed.

Radiation sensitive developable bottom anti-reflective coatings (DBARC): recent results

Second generation, radiation sensitive, developable 193 Bottom Antireflective coatings (DBARCs) are made solvent resistant through a crosslinking mechanism activated during post apply bake (PAB) that is reversible by acid catalyzed reaction upon exposure of the DBARC/resist stack. This allows coating the resists on the DBARC, after PAB, without dissolution of the antireflective coating. This DBARC approach avoids the plasma etch breakthrough needed for conventional bottom antireflective coatings which are irreversibly crosslinked, while maintaining excellent reflectivity control, typically lower than 1% on bare Si. We will give an update on the performance our latest 193 nm DBARC prototype materials used with different conventional alicyclic based 193 nm resists. For instance, using a binary mask with conventional illumination several of our prototype DBARC formulations were able to resolve 120 nm trench features with a 250 nm pitch.

Spin-on trilayer approaches to high NA 193nm lithography

New challenges face ArF bottom antireflection coatings (BARCs) with the implementation of high NA lithography and the concurrent increase use of spin-on hard masks. To achieve superior reflectivity control with high NA at least two semi-transparent ARC layers, with distinct optical indices, are necessary to effectively lower substrate reflectivity through a full range of incident angles. To achieve successful pattern transfer, these layers in conjunction with the organic resist, should be stacked with an alternating elemental composition to amplify vertical resolution during etch. This will circumvent the inherent low etch resistance of ArF resist and the decreasing film thicknesses that accompanies increasing NA. Thus, incorporating hard mask properties and antireflection properties in the same two layer system facilitates pattern transfer as a whole rather than just enhancing lithography. As with any material expected to exhibit multiple roles there is a delicate balance between optimizing materials with respect to one of its roles while not impairing its other roles. We will discuss some of these conflicts and present Si-BARCs and carbon rich underlayers which aim to balance these conflicts. In this paper we will explore simulations aimed at finding the best film thicknesses and optical indices, etch rate selectivity, and lithographic performance of high silicon content and high carbon content BARC materials designed to meet the demands of both high NA lithography and trilayer processing.

Process optimization consideration for 193nm developable bottom anti-reflective coatings (DBARCs)

Developable BARCs (DBARCs) are useful for implant layers because they eliminate the plasma etch step avoiding damage to the plasma sensitive layers during implantation. It is expected that DBARC will also be used for non-implant layers and double exposure technology. AZ has pioneered DBARC based on photosensitive cleave as well as crosslink/decrosslink mechanisms. In this paper, we focus on various processing factors for 193nm DBARC and discuss the influences of prewet, thickness, topography and substrates on lithographic performance. Prewet of DBARC before resist coating deteriorated performance, however, it was resolved by modifying DBARC formulations. The optimized DBARC showed both optical and lithographic performance comparable to conventional BARCs. DBARCs minimized reflection from the substrates and notching of patterns was improved observed on silicon oxide topography. This paper includes simulation, DBARC contrast curve analyses, and recent dry and immersion exposure results of DBARC.

Latest developments in photosensitive developable bottom anti-reflective coating (DBARC)

Developable bottom anti-reflective coatings (DBARC) are an emerging litho material technology. The biggest advantage of DBARC is that it eliminates the plasma etch step, avoiding damage to plasma sensitive layers during implantation. AZ has pioneered developable BARC based on photosensitive cleave as well as crosslink/decrosslink mechanisms. In this paper, we focus on the crosslink/decrosslink concept. DBARC/resist mismatching was corrected both from process and formulation sides. The optimized DBARC showed comparable lithographic performance as conventional BARCs. This paper provides the chemical concept of the photosensitive developable DBARCs, approaches for DBARC/resist matching and performance of photosensitive DBARCs for 248 nm and 193 nm exposures. Recent 193 nm immersion exposure results are also presented.