Michael N. Grimbergen

Photomask etch system and process for 10nm technology node and beyond

While the industry is making progress to offer EUV lithography schemes to attain ultimate critical dimensions down to 20 nm half pitch, an interim optical lithography solution to address an immediate need for resolution is offered by various integration schemes using advanced PSM (Phase Shift Mask) materials including thin e-beam resist and hard mask. Using the 193nm wavelength to produce 10nm or 7nm patterns requires a range of optimization techniques, including immersion and multiple patterning, which place a heavy demand on photomask technologies. Mask schemes with hard mask certainly help attain better selectivity and hence better resolution but pose integration challenges and defectivity issues. This paper presents a new photomask etch solution for attenuated phase shift masks that offers high selectivity (Cr:Resist > 1.5:1), tighter control on the CD uniformity with a 3sigma value approaching 1 nm and controllable CD bias (5-20 nm) with excellent CD linearity performance (<5 nm) down to the finer resolution. The new system has successfully demonstrated capability to meet the 10 nm node photomask CD requirements without the use of more complicated hard mask phase shift blanks. Significant improvement in post wet clean recovery performance was demonstrated by the use of advanced chamber materials. Examples of CD uniformity, linearity, and minimum feature size, and etch bias performance on 10 nm test site and production mask designs will be shown.

Model-based etch profile simulation of PSM films

For advanced binary and PSM mask etch, final profile control is critically important for achieving desired mask specifications. As an aid to attain profile control, an etch profile simulation method has been developed. The method starts with an initial photoresist profile and incorporates etch rate and directionality information to predict the final etch profile. In this paper, simulated results are compared to measured etch profiles for PSM substrates. The results highlight the importance and implications of incoming resist profile and etch selectivity on final profile.

Photomask etch: addressing the resist challenges for advanced phase-shift and binary photomasks

As lithography requirements mandate ever-thinner resist thickness, the need for in-situ monitoring has become more urgent. In this paper we present an in-situ optical methodology-based system to determine residual photoresist thickness during advanced photomask etch with < 1000 Å photoresist. Several types of phase-shift masks and photoresists were examined. A series of masks were etched to demonstrate the performance of the system. Results show an average accuracy of better than 2%, with a maximum absolute range of all tests within 8%.

Dry etching performance of advanced EUV mask blanks

Mask defectivity is often highlighted as one of the barriers to a manufacturable EUV solution. As EUV lithography matures, other components of mask making also emerge as key focus areas in the industry: critical dimension (CD) control, film variability, selectivity, and profile tolerance. Mask materials and specifications continue to evolve to meet the unique challenges of EUV lithography, creating the need for etch capabilities that can keep pace with the latest developments. In this study, the performance of a new EUV mask etch system will be evaluated using a variety of mask blanks to determine the relative performance of each blank type. Etch contributions to mean to target (MTT), CDU, linearity, selectivity, capping layer uniformity, line edge roughness (LER), and profile quality will be characterized to determine tool performance. The new system will also be used to demonstrate multilayer etching capabilities, important for opaque frame and alternating phase shift applications. A comprehensive summary of the etch performance of various EUV films and the readiness for manufacturing applications will be provided.

Plasma characterization of Tetra III chrome etch system

Both Langmuir probe and spatial optical emission spectroscopy (OES) measurements have been used to characterize the TetraTM chrome etch chamber. Langmuir data was measured over a range of process pressures between 1.5mT and 10mT and source powers between 150W and 500W. At 350W, the data show electron and ion densities near 1 x 109 cm-3 for Ar and for Cl2/O2 etch plasmas. Ion density trends with pressure were observed to be opposite for the two plasmas. The effect of the third electrode designed in the chamber was demonstrated to reduce ion density by more than an order of magnitude for Ar plasma and still lower for Cl2/O2 plasma. Electron temperature and plasma potential are also reduced. Radial OES measurements are reported with a new apparatus that yields direct spatial emission data. Spatial scans of infrared emission from atomic Cl were measured under a range of several chamber conditions already measured with the Langmuir probe. The scans showed that the emission uniformity above the mask can be adjusted to a flat profile by selection of the process condition.

Chrome etch solutions for 45-nm and beyond

Requirements to meet the 45nm technology node place significant challenges on Mask makers. Resolution Enhancement Techniques (RET) employed to extend optical lithography in order to resolve sub-resolution features, have burdened mask processes margins. Also, Yield compromises loom with every nanometer of error incurred on the Mask and the Device platforms. RET techniques, such as Optical Proximity Correction (OPC), require the Mask Etcher to achieve exceptionally tight control of Critical Dimensions (CD). This ensures OPC feature integrity on the mask and resultant image fidelity of OPC structures, as well as, subsequently high and sustainable yields. This paper talks about 45 nm Chrome etch challenges and how Applied Materials next generation mask etcher provides solutions to these challenges.

Chrome etch challenges for 45 nm and beyond

Requirements to meet the 45nm technology node place significant challenges on Mask makers. Resolution Enhancement Techniques (RET) employed to extend optical lithography in order to resolve sub-resolution features, have burdened mask processes margins. Also, Yield compromises loom with every nanometer of error incurred on the Mask and the Device platforms. RET techniques, such as Optical Proximity Correction (OPC), require the Mask Etcher to achieve exceptionally tight control of Critical Dimensions (CD). This ensures OPC feature integrity on the mask and resultant image fidelity of OPC structures, as well as, subsequently high and sustainable yields. This paper talks about 45 nm Chrome etch challenges and how Applied Materials Tetra IITM etcher provides solutions to these challenges.

Photomask etch challenges for future technology nodes

Requirements to meet the 45nm technology node place many challenges on photomask makers. Resolution Enhancement Techniques (RET), employed to extend optical lithography in order to resolve sub-resolution features have burdened mask processes margins. Also, yield compromises rise with every nanometer of error incurred on the photomask (and device) platforms. As photomask costs rise, strict performance control is required for all photomask varieties utilized in the mask shop. Mask etching for future technology nodes, requires a system-level data and diagnostics strategy. This necessity stems from the need to control the performance of the mask etcher at increasingly stringent and diverse requirements of the photomask production environment. From etch applications perspective, alternating phase-shift masks (APSMs) and OPC masks pose key challenges. Specifically, the etcher needs to provide highly uniform CD performance across the entire active area of the photomask - for various feature sizes and load distributions, with no degradation to profiles. It is challenging to strike this balance, yet maintain adequate process window. Future etch systems require sensitive controls and knobs to provide this high precision and repeatable performance. Additionally, incoming variation in plate characteristics and quality necessitate tuning knobs capable of targeting the optimum performance across a diversity of applications.

Quartz etch solutions for 45-nm phase-shift masks

One means of extending the limits and lifetime of current lithography platforms for 45nm and beyond is the development of resolution enhancement techniques (RET) in the form of optical phase-shifting masks (PSM). By employing optical interference from 180° shifted lithography emission, PSM masks are able to enhance feature resolution at the wafer. This is particularly important for sub-wavelength features (i.e., features with critical dimensions less than the lithography wavelength) where line resolution can be severely degraded without such techniques. For these PSMs, the challenge is to provide highly uniform quartz etch performance across the entire active area of the mask for various feature sizes and local loads. Micro-loading (a.k.a. RIE lag or reactive ion etch lag) and phase angle range are key performance parameters to control. As the demands for these parameters tighten and mask costs rise, strict performance control is required for all PSM mask varieties utilized in the mask shop. In this paper we will discuss process results using Applied Materials next generation mask etch system in the area of APSM etch application. In particular, the discussion will focus on recent process results in phase uniformity and RIE lag for Quartz etch process. Feature profiles are also discussed with examples showing near vertical sidewalls and no micro-trenching.

Quartz etch challenges for 45 nm phase-shift masks

One means of extending the limits and lifetime of current lithography platforms for 45nm and beyond is the development of resolution enhancement techniques (RET) in the form of optical phase-shifting masks (PSM). By employing optical interference from 180° shifted lithography emission, PSM masks are able to enhance feature resolution at the wafer. This is particularly important for sub-wavelength features (i.e., features with critical dimensions less than the lithography wavelength) where line resolution can be severely degraded without such techniques. For these PSMs, the challenge is to provide highly uniform quartz etch performance across the entire active area of the mask for various feature sizes and local loads. Micro-loading (a.k.a. RIE lag or reactive ion etch lag) and phase angle range are key performance parameters to control. As the demands for these parameters tighten and mask costs rise, strict performance control is required for all PSM mask varieties utilized in the mask shop. In this paper we will discuss process improvements for the Applied Materials Tetra IITM chromeless phase lithography (CPL) etch application. In particular, the discussion will focus on recent process improvements in phase uniformity and RIE lag for our chrome hard mask CPL etch process. Results from modifications to the etch process are presented. Feature profiles are also discussed with examples showing near vertical sidewalls and no micro-trenching.