In this work, we characterize the in-plane and out-of-plane deformation of the dies following the imec die-to-wafer (D2W) bonding flow. By leveraging this result of alignment readout and leveling metrologies on scanner, we could improve the post-D2W bonding overlay performance through scanner precorrection for advanced packaging and heterogeneous integration system.

In this paper, a collective die-to-wafer bonding integration scheme will be investigated. Minimizing the difference between backside and frontside fingerprints using the ASML scanner is the primary goal of this study. In order to expose the wafer backside of the thinned wafer, requirements include aligning to marks present on wafer frontside, along with applying accurate corrections. In addition, the large errors introduced by temporary bonding need to be addressed. A grating mark with and without segmentation measured with ASML SMASH sensor using far infra-red wavelength, is capable addressing the detectability of wafer frontside marks through 50-um Si, and it is shown that we can detect misalignment errors of 200 nm and more.

In this work we demonstrate and report the capability of YieldStar and CDSEM to measure etch depths of metal in a data-driven approach. We find that both Yieldstar and CDSEM enable recess depth measurements with a precision of 0.5 nm over a range of 17 nm. Combining YieldStar and CDSEM (hybrid metrology) further improved prediction errors by 0.1 nm.

The grouping method assisted EPE-aware control method is being explored in a multi-feature dual layer Logic use case. EPE metric is estimated using angle resolved optical Scatterometry based overlay and electron beam-based metrology (large field of view SEM) for the reconstruction of edge-to-edge distance between the Metal and Via pattern. In the setup phase, EPE sensitivities to dose and focus have been derived using data from a FEM wafer. EPE-aware optimization, using scanner dose and overlay control sub-recipes, outperforms traditional optimization in simulations showing reduced EPE max per die. This improvement suggests a potential increase in device yield through the adoption of EPE-aware control strategies. To verify this performance improvement on wafers, an experiment is needed with minimal wafer to wafer and lot to lot variations which can be achieved by reducing time between lots and increasing the number of wafers measured.

Owing to photon shot noise and inhomogeneous distribution of the molecular components in a chemically amplified resist, resist patterns defined by extreme ultraviolet (EUV) lithography tend to suffer from stochastic variations. These stochastic variations are becoming more severe as critical dimensions continue to scale down, and can thus be expected to be a major challenge for the future use of single exposure EUV lithography. Complementing EUV lithography with directed self-assembly (DSA) of block-copolymers provides an interesting opportunity to mitigate the variability related to EUV stochastics. In this work, the DSA rectification process at imec is described for both line/space (L/S) and hexagonal contact hole (HEXCH) patterns. The benefits that rectification can bring, as well as the challenges for further improvement are being addressed based on the current status of imec’s rectification process.

For printing the most critical features in semiconductor devices, single exposure extreme ultraviolet (EUV) lithography is quickly advancing as a replacement for ArF immersion-based multipatterning approaches. However, the transition from 193 nm to 13.5 nm light is severely limiting the number of photons produced by a given source power, leading to photon shot noise in EUV patterns. In addition, inhomogeneous distribution of components inside conventional photoresists is adding to the printing variability, especially when critical dimensions continue to shrink. As a result, stochastic issues leading to rough, non-uniform, and potentially defective patterns have become a major challenge for EUV lithography. A promising solution for this top-down patterning approach is complementing it with bottom-up directed self-assembly (DSA) of block copolymers. In combination with 193i lithography, DSA of lamellae forming block copolymers has previously shown favorable results for defining dense line-space patterns using LiNe flow.1 In this study, we investigate the complementarity of EUV + DSA for rectification of pitch 28 nm line-space patterns. Roughness and defectivity are critical factors that need to be controlled to make these patterns industrially relevant. We look at the impact of DSA material and processing parameters on line edge roughness and line width roughness in order to identify and mitigate the origins of pattern roughness. On the other hand, we also assess the different types of defect modes that are observed by means of optical defect inspection and ebeam review, and study the root causes for their formation. To wrap-up, the benefits of 1X DSA versus 3X DSA are presented by comparing EUV + DSA to LiNe flow.

In this paper we have evaluated alignment and overlay for a Ruthenium Direct Metal Etch process. Depending on the integration strategy, line resistance and lithography requirements, a process with no remaining topography may be preferred from a lithography point of view, but due to the Ruthenium light absorption alignment and overlay through a thick Ruthenium layer will be challenging. In this paper we have studied the maximum thickness of Ruthenium for which the alignment sensor can still detect the alignment marks below and quantify the quality of diffraction-based overlay on an ASML YieldStar overlay metrology tool.

The key challenge to enable a good defectivity control for extreme ultraviolet (EUV) single expose at 32nm pitch is to understand what are the main drivers for defect generation. CD is one of the main contributors, and has many sources of variability (reticle, imaging, die layout, scanner). The paper will first discuss the quantification of defectivity sensitivity to CD, and identification of the main sources of CD variations (EUV flare, black border, etch, APC, mask bias etc...). All those effects do not have the same consequences on the defect level (only nanobridges will be considered as they are the main defect type). At this pitch, CD margin is becoming critical, an any small variation can lead to pattern collapse/bridge regime. In a second part, we will discuss the different options for a better CD control and evaluate their impact on the overall defectivity level (reticle, process and tool will be considered). An Intrafield CD uniformity improvement of 40% can lead to a defect density reduction by about 30%.

While the semiconductor industry has reached the high-volume manufacturing of the 7 nm technology node (N7), patterning processes for future technology nodes N5, N3 and even below, are being investigated and developed by research centers. To achieve the critical dimensions of gratings for these future technology nodes, we require multipatterning approaches, such as self-aligned double/quadruple/octuple patterning (SADP/SAQP/SAOP) and multiple litho-etch (LE) patterning, in combination with 193i lithography and even EUV lithography. These gratings need to be subsequently cut or blocked, which is typically done by one or more block masks. As the edge placement error (EPE) budget drastically decreases with decreasing critical dimensions, the standard LE block patterning scheme is not sufficient anymore. To relax the EPE budget, dedicated scaling boosters are required such as the self-aligned block scheme, which defines blocks in trenches, selectively to the neighboring trenches. In this work we explore the different multipatterning options for lines and blocks at pitches below 20 nm. As such, we will demonstrate and compare three different patterning options to enable 16 nm pitch gratings: 193i-based SAOP, EUV-based SADP and EUV-based SAQP. Finally, we will also elaborate on a self-aligned patterning scheme which does not define lines and blocks sequentially anymore but integrates them in a mixed mode. This patterning approach (SALELE) makes use of two LE masks and two self-aligned block masks. We will present its development status at relaxed pitch (28 nm) and discuss its advantages for future technology nodes.

Extreme ultraviolet (EUV) materials are deemed as critical to enable and extend the EUV lithography technology. Currently both chemically amplified resist (CAR) and metal-oxide resist (MOR) platforms are candidates to print tight features on wafer, however patterning requirements, process tonality (positive or negative), illumination settings and reticle tonality (dark or bright) play a fundamental role on the material performance and in consequence on the material choice. In this work we focus on the patterning of staggered pillars using a single EUV exposure, and this by looking at the lithographic and etching performance of CAR and MOR platforms, using metrics as process window, local critical dimension uniformity (LCDU), pillar edge roughness (PER), pillar placement error (PPE) and (stochastic) nano-failures. As a bright field reticle shows a lower aerial image contrast to print pillars compared to the aerial image of contact holes using a dark field reticle, we also investigate alternative patterning solutions such as the tone reversal process (TRP) to pattern pillars from contact holes.

Abstract: Wet nanoscale etching of silicon is very dependent to surface reactive sites like step edges, defect densities, and crystallographic planes [1]. Ultra-pure water (UPW) used during rinsing and drying steps is etching silicon in the sub-nanometer range furthermore this silica residues will cause ring shape drying marks on the surface [2-3]. In this paper drying marks are characterized by physical and chemical characterization techniques to evaluate the silicon etching process. The conversion of the silicon hydrogen bond to silicon hydroxide is investigated on different crystal orientations to monitor the reactivity of the surface. Experiment & Measurement: The p-type (100) and (111) 200 mm silicon wafers (SunEdison) used had a resistivity of 1-5 Ω.cm. The samples were cleaned with an HF/HCl mixture to obtain a hydrophobic surface with a contact angle of around 70◦. Atomically smooth silicon (111) was prepared by a NH4F (Sigma-Aldrich 99%) etching process in a closed oxygen free etching cell [4]. Double side polished silicon (100) and (111) wafer were used as a crystal in attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to monitor the hydrogen termination. The 3D profile of the WM formed after evaporation of a UPW sessile droplet was measured using a KLA-Tencor High Resolution Profilometer [3]. Results & Discussion:The impact of the crystal orientation on the WM residue is studied by comparing the results of droplet drying on p-type Si (100) versus (111) in the dark (40% relative humidity). Although AFM analysis confirms a smooth surface finish (RMS = 0.2 nm) for the HF treated (100) and (111) surface, no clear atomic planes are observed. Fig. 1 shows the etch rate of silicon in the dark under clean room conditions. The etch rate is calculated based on residue volume (measured by profiliometry) divided by the droplets initial wetting area, and evaporation time. Fig. 2 shows the decrease in the amplitude of the silicon hydride peak, measured by ATR-FTIR spectroscopy, as a function of time (the rate of decrease is faster in the Si (100), case as might be expected). The fact that hydride termination of the surface disappears only slowly gives information about the etching mechanism, that will be discussed in the proceeding. The higher stability of the (111) surface is attributed to the higher number of back-bonds for Si-surface atoms in case of (111) (with 3 back-bonds) versus the (100) case (with 2 back-bonds). The experimental result confirms the chemical dissolution process but a difference in surface stability is observed. WM formation was studied in the dark since previous work [3] showed that light increases the etch rate markedly, thus complicating the interpretation. In order to investigate the impact of surface morphology on WM formation, atomically smooth surfaces were prepared by immersing a p-type Si (111) substrates (miscut angle <0.07º) in oxygen free NH4F. The results are shown in Figure 3. By comparing the result of HF-pretreated and NH4F-pretreated surfaces it is clear that the atomically smooth surface shows reduced reactivity compared to the rough HF last surface. Due to lower step edge density the chemical reactivity of the surface decreases and WM residue formation is suppressed. Conclusion: This study showed the effect of surface imperfections on dissolution process by WM formation. It is shown that the silicon (111) dissolution process decreased in case of atomically smooth surface. The dissolution can be further suppressed by performing rinsing and drying process in dark ambient. References [1] M. Hines et al., Int. Rev. Phys. Chem. 20, (2001) 645. [2] T. Miura et al., J. Appl. Phys. 79, (1995) 4373. [3] A.H. Tamaddon et al. solid state phenomena, 219 , (2014) 89. [4] P. Allongue et al., Electrochimica Acta 45, (2000) 4591. Figure 1

Wetting and drying in wet cleaning process received a lot of attention to meet the requirements of advanced technology nodes. Drying performance is evaluated by the number of watermarks produced during the rinsing and drying steps. Watermarks appear by evaporation of a very small sized water droplet remaining at the end of the drying step. In this article the influence of relative humidity and oxygen concentration of ambient on formation of different watermark shapes is studied by evaporation of ultra-pure water droplet on HF-last silicon surfaces. A qualitative model is presented taking into account: evaporation and gas-ambient (O2) exchange, chemical reactions forming the residue species starting from dissolved O2 and Si, transport of species by diffusion and evaporation driven convective radial outward flow. The watermarks are subdivided in two components: an outer ring shaped component and a more or less flat residue bed inside the ring. The experimental results showed a transition between ring shape to somehow uniform circular shape of watermark (bed part) by increasing the relative humidity of ambient. The low humidity resulted in the shorter drying time and in the smallest drying residue, consisting mainly of a ring-shaped component, which is in agreement with the model.

The wet cleaning process plays an important role in advanced semiconductor industry. Particularly when bare silicon areas are exposed, wafer drying can result in undesired watermark (WM) residues on the surface [1-2]. In principle there are three components effecting the formation, shape and size of WM. 1) composition of the ambient like oxygen concentration, relative humidity and temperature affect WM formation [3]. 2) liquid: factors such as pH and the amount of dissolved species inside the liquid influence the WM composition. 3) substrate: for silicon for instance: surface passivation is important for WM formation [2]. WMs are composed of silica that is formed during the drying process by oxidation of the silicon surface [1]. Therefore when studying WM formation it is important to understand the mechanism (s) of silicon oxidation and the dissolution.

In immersion lithography, the probability to leave water on a photoresist (PR) increases with the scan speed. After wet processes, in general, liquid droplets may remain on the substrates. The evaporation of these droplets coupled with the leaching of the PR produces defects. These drying defects may affect the resolution of the subsequent lithographic exposure. Beyond lithography, this interaction droplet-PR is of great interest in ink-jet printing technology. Indeed, contrast and resolution depend on the pattern left after the evaporation of sessile droplets. Here, we analyze the drying speed of a sessile water droplet on a PR substrate with the aim to characterize the resulting drying marks by the dynamics of their formation and by their typical ''crater'' topography. First, we focus our study on the drying dynamics of an evaporating sessile droplet and its drying patterns left on the PR; second, we show that the contact line motion is the key feature in the generation of surface defects with a strong interaction fluid/surface despite the hydrophobicity.

Dynamics of the evaporative drying of ultrapure water (UPW) droplets on a hydrophobic Si surface in a controlled ambient is studied. A quantitative study of the watermarks (WM) residue volume and mass is performed from low to high ambient humidity. The effects of oxygen in the gas phase and dissolved O2 concentration in UPW are investigated for different levels of ambient humidity. The shape of the drying residue on surface is studied to estimate the mechanism of residual colloids/particles deposition in presence of different ambient conditions. Our quantitative study on WM formation in different ambient humidity showed a linear increase in drying residue mass as a function of the initial UPW droplet volume.

Although evaporation as a pure bulk phase transformation is well understood, when one adds solutes to the liquid, or brings the liquid into contact with a substrate, we obtain a new and rich variety of possible behaviors that we can access experimentally to better understand the drying dynamics of residual water droplets. Evaporation of sessile droplets with a small contact angle (below 90°) is studied here extensively on silicon substrates. We focused our work on the origin of the creation of watermarks on silicon wafers. A thorough understanding of droplet evaporation is of vital importance for examining the drying rate, the flow patterns observed inside drying drops, and the residual deposits. The concentration of each potential dissolved species (e.g. silica or silicic acid) can also be predicted and confronted to their solubility. We developed a theoretical model to predict the evaporation rate and the behavior of submillimetric droplets taking into account the characteristics of the ambient and the substrate during the drying process. We discuss also the topology of watermarks on silicon wafers in the case of a predominant evaporation phenomenon.

Evaporation of sessile droplets with a small contact angle (below 90 degrees) is studied here extensively on silicon substrates. We focused our work on the origin of the creation of watermarks on silicon wafers. A thorough understanding of droplet evaporation is of vital importance for examining the drying rate, the flow patterns observed inside drying drops, and the residual deposits. The concentration of each potential dissolved species (e. g. silica or silicic acid) can also be predicted and confronted to their solubility. We developed a theoretical model to predict the evaporation rate and the behavior of millimetric droplets taking into account the characteristics of the ambient and the substrate during the drying process. We discuss also the topology of watermarks on silicon wafers in the case of a predominant evaporation phenomenon. (C) 2012 The Electrochemical Society. All rights reserved.

With the downscaling of devices, due to device geometry shrinkage, the total number of cleaning steps has increased dramatically. As a result, the number of drying cycles after cleaning has increased as well. As the device shrinks with the integration density increase, it is noteworthy that a perfect drying efficiency is mandatory to obtain a high performance device [. Basically, the mechanism of wafer drying in semiconductor industry can be explained as: first reducing the amount of liquid on the wafer surface by mechanical forces. There are some approaches for removing the liquid such as spinning, high pressure gas blowing by nozzle or air-jet, vertical withdrawal from the liquid bath, using surface gradient tension and so on [2]. Second: if the mechanical forces in the liquid removal part are not sufficient for drying and some droplets or a thin liquid layer remain on the wafer surface, complete drying will be achieved by evaporation of the remaining layer on the wafer. After this evaporation step, known as state transformation, the wafers will be completely dried. Evaporation of the remaining liquid layer is the main mechanism for generating drying defects (watermarks, residues, particles, and etc.)[3]. In this study, we propose a new methodology for semiconductor wafer drying based on a high-pressure gas flow. In comparison to conventional drying tools, the new drying set up combines high speed drying (wafer drying time down to 2 sec at 150mm.s-1) and a low number of added drying defects.

Evaporation of unpinned sessile droplets with small contact angles (below 90°) is studied here extensively. We focused our work on the constant contact-angle mode in which the contact area of the droplet on the substrate decreases. A thorough understanding of droplet evaporation is of vital importance for examining the drying rate, the flow patterns observed inside drying drops, and the residual deposits. The concentration of each potential dissolved species (e.g. silica or silicic acid) can also be predicted and confronted to their solubility. We developed a theoretical model to predict the evaporation rate and the behavior of millimetric droplets taking into account the characteristics of the ambient and the substrate during the drying process. We discuss also the topology of watermarks on silicon wafers in the case of a predominant evaporation phenomenon.

A spiral antenna operating at 24 GHz designed for scientific and medical (ISM) band is reported. The procedure is fully compatible with standard CMOS fabrication process. The fabrication has been achieved on silicon substrates using a bulk micromachining technique. To improve the radiation efficiency and to minimize transmission loss, a silicon-based membrane has been employed on silicon substrates. To optimize the occupied area of the antenna a square spiral structure is selected rather than the circular one. The simulation results show a good matching and wide bandwidth operation of the spiral antenna.