Electrostatic Chuck Research Articles

A New Etch Planarization Technology to Correct Non-Uniformity Post Chemical Mechanical Polishing

The introduction of 3-D structures and new materials for advanced logic devices at extremely fine feature size presents challenges for within-wafer and wafer-to-wafer thickness uniformity control that is critical for yield and performance. For conventional chemical mechanical polishing technology, the typical thin film uniformity across the whole wafer may not meet the desired variation target of 2–3 nm $3{ {\sigma } }$ at some critical levels. Furthermore, wafer-to-wafer uniformity variation requires a wafer by wafer approach to uniformity correction. In this paper, a novel etch planarization technology is presented that combines a conventional production-proven etch process that is temperature sensitive with an inductively coupled plasma reactor equipped with a novel electrostatic chuck that provides die level thermal control. Improved process control enables cost effective uniformity improvements in excess of 85%.

Compliant electrostatic chuck with micropillar electrodes for handling of rough surfaces

Compliant electrostatic chuck with micropillar electrodes for handling of rough surfaces

Design space of electrostatic chuck in etching chamber**Project supported by the Ministry of Science and Technology of China (No. 2011ZX02403), and the National Natural Science Foundation of China (No. 51175284).

One of the core semiconductor devices is the electrostatic chuck. It has been widely used in plasma-based and vacuum-based semiconductor processing. The electrostatic chuck plays an important role in adsorbing and cooling/heating wafers, and has technical advantages on non-edge exclusion, high reliability, wafer planarity, particles reduction and so on. This article extracts key design elements from the existing knowledge and techniques of electrostatic chuck by the method proposed by Paul and Beitz, and establishes a design space systematically. The design space is composed of working objects, working principles and working structures. The working objects involve electrostatic chuck components and materials, classifications, and relevant properties; the working principles involve clamping force, residual force, and temperature control; the working structures describe how to compose an electrostatic chuck and to fulfill the overall functions. The systematic design space exhibits the main issues during electrostatic chuck design. The design space will facilitate and inspire designers to improve the design quality and shorten the design time in the conceptual design.

Study of Parameters Affecting the Electrostatic Attractions Force

This paper contains 2 main parts. In paper we simulated and studied three types of in various industries for suspension and handling of the semiconductor and glass and we selected evaluating the electrostatic force, which was comb pattern electrode. In the second part we investigated the parameters affecting the amount of electrostatic force such as the gap between surface and electrode (g), the electrode width (w), the gap between electrodes (t), the surface permittivity and electrode length improvement of adhesion force by changing these values Keywords—Electrostatic force, electrostatic adhesion, electrostatic chuck, electrostatic application in industry, Electroadhesive grippers.

Finite element analysis on factors influencing the clamping force in an electrostatic chuck

As one of the core components of IC manufacturing equipment, the electrostatic chuck (ESC) has been widely applied in semiconductor processing such as etching, PVD and CVD. The clamping force of the ESC is one of the most important technical indicators. A multi-physics simulation software COMSOL is used to analyze the factors influencing the clamping force. The curves between the clamping force and the main parameters such as DC voltage, electrode thickness, electrode radius, dielectric thickness and helium gap are obtained. Moreover, the effects of these factors on the clamping force are investigated by means of orthogonal experiments. The results show that the factors can be ranked in order of voltage, electrode radius, helium gap and dielectric thickness according to their importance, which may offer certain reference for the design of ESCs.

Addendum: Compliant electrostatic chuck based on hairy microstructure (2013 Smart Mater. Struct. 22 015019) and Electrostatic chuck consisting of polymeric electrostatic inductive fibers for handling of objects with rough surfaces (2013 Smart Mater. Struct. 22 095010)

The recent papers Saito et al 2013 Smart Mater. Struct. 22 015019 and Dhelika et al 2013 Smart Mater. Struct. 22 095010 described studies of an electrostatic chuck that mimics the structure of gecko-like toes. Earlier work published by the authors and other researchers is cited to further illustrate the origin and motivation of the research.

Study on processing step uniformity tuning during FET fabrication and sensor wafer response as a function of chuck temperature adjustment

The effect of chuck temperature adjustment on critical dimension uniformity was studied for the shallow trench isolation etch process by introducing a temperature gradient in a multi-temperature-zone electrostatic chuck. It is shown that the initial radial critical dimension non-uniformity can be improved by a gradual temperature adjustment of the electrostatic chuck and results in the target specification values of uniformity, 3σ ≤ 1.5 nm, for a critical dimension of about 35 nm. Both temperature and RF sensor wafers were used to analyze the impact of an electrostatic chuck temperature gradient on process uniformity by utilizing their unique in situ spatial and temporal mapping capabilities. Thus, the across-wafer thermal sensitivity of the critical dimension was estimated for dense structures: a temperature change of 1 °C leads to a critical dimension change of ∼0.7 nm. The RF sensor wafer was also shown to have a clear response of RF current uniformity to the electrostatic chuck temperature gradient that suggests there could be other phenomena affecting critical dimension uniformity besides temperature itself. The pure temperature contribution to critical dimension change was found to be less than 0.3 nm/°C for the temperature range studied. Finally, a possible mechanism of critical dimension tuning is discussed and an assessment of each separate etch step’s sensitivity to the electrostatic chuck temperature gradient is performed.

The Optimization of Metal Hard-Mask Based All-in-One Etch

Metal hard-mask based all-in-one etch scheme has been extensively integrated with Cu interconnects for its significant improvement in terms of the line sidewall roughness, the reduction of ultra low-k material damage and the enhancement of lithography process window. In this paper, we investigated the trade-off relationship between electromigration (EM) and time-dependence break-down (TDDB) on one AMEC (Advanced Micro-fabrication Equipment Company) test vehicle. This etcher features the special switchable rf-power at bottom electrode. Results indicate the dynamic ESC (electrostatic chuck) is imperative to meet the quite different temperature demands between via etch and trench etch step, thus reducing the via encroachment on metal hard-mask while no metallic residue is detected at trench bottom. Meanwhile, the tunable edge ring coupled with the optimization of trench etch gases are also critical to deliver the on-target Rc and reliability performance. In brief, we successfully demonstrated the partial SAV (self-aligned via) could deliver the on-target WAT and reliability performance on AD-RIE.

Modeling of Electrostatic Chuck and Simulation of Electrostatic Force

Electrostatic chuck (ESC) is one of the key components in IC manufacturing process, which applies the principle of electrostatic adsorption to clamp the wafer on its surface. In such a system, electrostatic force is considered as one of the most important indicators. The method of modeling and simulation of electrostatic force by COMSOL software is proposed, and the accurateness is validated by comparing the results with those from reference. Then, the simulation of ESC in real manufacturing process is finished using the above method, which focuses on the effects of dielectric materials and voltage on electrostatic force. The research can offer references for the design of ESC, and it has significance to reduce experimental cost and improve the reliability of the equipment.

In-situ detection method for wafer movement and micro-arc discharge around a wafer in plasma etching process using electrostatic chuck wafer stage with built-in acoustic emission sensor

We report an electrostatic chuck (ESC) wafer stage with a built-in acoustic emission (AE) sensor for detecting anomalies occurring around a wafer during plasma etching. The built-in AE sensor detects acoustic waves caused by wafer movement and micro-arc discharge with high sensitivity, and identifies these anomalies based on the frequency characteristics of the waves. The results demonstrate the effectiveness of using an ESC wafer stage with a built-in AE sensor for in-situ anomaly detection, which can improve the production yield and overall equipment efficiency in large scale integrated circuit (LSI) manufacturing.

Detecting Arcing Events in Semiconductor Manufacturing Equipment

Bi-polar arcs require a high voltage difference between two closely spaced points. As an example, if there is excessive deposition or contamination on the deposition and or cover ring in a physical vapor deposition tool (PVD) tool, a DC bipolar arc can occur leading to ablation of underlying materials, wafer breakage, or chamber damage caused by the discharge. In some cases these incidents are not identified until numerous wafers have been processed. Therefore, it is essential to identify arcing at the time of the event. In this paper, we address arc detection in a PVD chamber. The electrostatic chuck (ESC) critical parameter(s) are captured with 1000 Hz sampling frequency and signal processing techniques such as FFT and wavelet transforms are used to improve the signal-to-noise ratio enhancing the ability to isolate arcs from raw data. This methodology can be implemented on other plasma chamber types.

Electrostatic chuck consisting of polymeric electrostatic inductive fibers for handling of objects with rough surfaces

An electrostatic chuck (ESC) is a type of reversible dry adhesive which clamps objects by means of electrostatic force. Currently an ESC is used only for objects having flat surfaces because the attractive force is reduced for rough surfaces. An ESC that can handle objects with rough surfaces will expand its applications to MEMS (micro electro mechanical system) or optical parts handling. An ESC consisting of compliant electrostatic inductive fibers which conform to the profile of the surface has been proposed for such use. This paper aims at furthering previous research by observing the attractive force/pressure generated, both theoretically and experimentally, through step-by-step fabrication and analysis. Additionally, how the proposed fiber ESC behaves toward rough surfaces is also observed. The attractive force/pressure of the fiber ESC is theoretically investigated using a robust mechano-electrostatic model. Subsequently, a prototype of the fiber ESC consisting of ten fibers arranged at an angle is employed to experimentally observe its attractive force/pressure for objects with rough surfaces. The attractive force of the surface which is modeled as a sinusoidal wave with various amplitudes is observed, through which the feasibility of a fiber ESC is justified.

Detection of Micro-Arc Discharge Using ESC Wafer Stage With Built-In AE Sensor

An electrostatic chuck (ESC) wafer stage with a built-in acoustic emission (AE) sensor is developed to detect micro-arc discharge occurring around a wafer. The built-in AE sensor detects acoustic waves caused by anomalous discharge with high sensitivity. The results demonstrate the effectiveness of this novel ESC wafer stage for detecting micro-arc discharge occurring around a wafer and will contribute greatly to improving the production yield of semiconductor manufacturing.

Development of a nondeforming chucking technique for EUV lithography

Extreme ultraviolet (EUV) lithography has edged closer to practical use as the next-generation exposure technique for replicating 10-nm-order patterns. Since this replication takes place in a vacuum, the mask and wafer are usually clamped by electrostatic force. However, an electrostatic chuck has the following limitations: the force is smaller than the vacuum force, dust adheres to the tops of the chuck pins, and deformation occurs during chucking. The authors have developed a new nondeforming chucking technique that does not use electrostatic force or vacuum force and does not damage the contact surface. This paper describes the principle and features of this nondeforming chucking technique and evaluates the cooling temperatures required to solidify the freezing liquid and fix the quartz substrate using the finite element method. The various forces between the quartz specimen and the pin and the deformation of the quartz wafer due to chucking are also discussed. By lapping the pin tops after coating with oil repellent, the average shear strength of a 10-mm-square quartz specimen on a 0.5-mm-diameter, 2-mm-pitch pin chuck was increased to 5.1±0.9N/cm2, which is more than 1000 times for the acceleration force. The deformations after being fixed with the above pin chuck were less than ±0.15μm for a 100-mm-diameter, 1.2-mm-thick quartz wafer, with a maximum convex warpage of 8μm. It was concluded that the 6-mm-thick, 152-mm-square quartz mask with a thermal expansion coefficient of 5×10−9/K can be clamped without deformation at temperatures below 50°C using the new freezing pin chuck with the pitch of 2mm.

Development of a Predictive and Preventive Maintenance Demonstration System for a Semiconductor Etching Tool

Increasing yield, eliminating unexpected downtime, and reducing maintenance costs are some of the potential benefits that a predictive monitoring system can provide for semiconductor manufacturing. Prior to the implementation of a predictive based condition monitoring approach for critical semiconductor equipment and components, the technology requires further development and validation. A systematic approach for developing a predictive monitoring system is presented, including several key steps that include data pre-processing, feature extraction and selection, health assessment, and component lifetime prediction. The approach is demonstrated on a LAM 2300® Kiyo® conductor etch product, in which data was collected over an 8-month period from a GlobalFoundries Fab in Dresden, Germany. The methodology and predictive health models are demonstrated for an example component from the etching tool, the electrostatic chuck. Both trace signals and metrology data are evaluated for developing the health and prediction models for the electrostatic chuck. The health monitoring models provide a clear and increasing trend, in which the electrostatic health value can be tracked quite well over time. The systematic development framework shows promise and future works looks to further validate the prediction models, and in addition develop commercially viable implementation software from this work.

Compliant electrostatic chuck based on hairy microstructure

An electrostatic chuck (ESC) is a device used to clamp and transport flat-surfaced objects such as thin semiconductor wafers. Working by the principle of electrostatic force, its functionality is limited in handling objects with rough surfaces, as the attractive forces at work are significantly reduced. To improve this weak point, by employing 70 μm diameter polymer-based electrostatic inductive fibers with a conductive core, we develop a device prototype with an adhesional mechanism having a hairy microstructure with appropriate mechanical compliance. We theoretically and experimentally investigate how the prototype works, and how the fibers’ mechanical compliance affects the performance of ESC.

Analytical treatment of the deformation behavior of extreme-ultraviolet-lithography masks during electrostatic chucking

A new analytical approach is presented to predict mask deformation during electrostatic chucking in next-generation extreme-ultraviolet-lithography. Given an arbitrary profile measurement of the mask and chuck nonflatness, this method has been developed as an alternative to time-consuming finite element simulations for overlay error correction algorithms. We consider the feature transfer of each harmonic component in the profile shapes via linear elasticity theory and demonstrate analytically how high spatial frequencies are filtered. The method is compared to presumably more accurate finite element simulations and has been tested successfully in an overlay error compensation experiment, where the residual error y-component could be reduced by a factor of 2. As a side outcome, the formulation provides a tool to estimate the critical pin-size and -pitch such that the distortion on the mask front-side remains within given tolerances. We find for a numerical example that pin-pitches of less than 5 mm will result in a mask pattern distortion of less than 1 nm if the chucking pressure is below 30 kPa.

Residual Clamping Force and Dynamic Random Access Memory Data Retention Improved by Gate Tungsten Etch Dechucking Condition in a Bipolar Electrostatic Chuck

It was found that the residual clamping force of bipolar electrostatic chucks created by the residual charge between a wafer and an electrode would not only cause a wafer sticking problem but also degrade dynamic random access memory (DRAM) data retention performance. The residual clamping force and data retention fail bit count (FBC) of DRAM showed strong correlations to the gate tungsten etch dechucking process condition. Wafer sticking only degraded DRAM cell retention performance, and did not influence any in-line measurement or electrical parameters. Electrical characterization analysis of the FBC proved that the retention loss was mainly due to junction leakage rather than gate-induced-drain-leakage current. A new approach was proposed to suppress this leakage by introducing N2 gas instead of O2 to supply more plasma charges for neutralizing the wafer surface residual charges. The wafer shift dynamic alignment (DA) offset and retention FBC could be reduced by 50 and 40%, respectively. Poor data retention was suspected because of the compressive stress caused by wafer sticking DA shift resulting in a high electric field at the junction and an increase in junction leakage at the storage node.

Characterization of tunnel-oxide degradation due to plasma field oxide recess in flash memory devices

This paper presents the characterization of degradation of tunnel oxide during plasma recess of field oxide films for Shallow Trench Isolation (STI) in sub 30nm flash memory devices. Simple plasma charge damage monitor wafers with Metal-Oxide-Semiconductor (MOS) capacitor structures were used to analyze the mechanisms of degradation of tunnel oxide due to process-induced charging damage. We characterized the gate leakage currents and breakdown voltages of MOS capacitors with area antennas after performing the plasma process for field oxide recess of STI with various etching conditions in a dual-frequency capacitively coupled plasma reactor. The results showed that the degradation was strongly dependent on plasma non-uniformity, which could be improved by optimizing the radio-frequency and biasing power. Especially, we found that RF biasing power caused stress-induced leakage currents due to dielectric breakdown by the leakage current originating from the electrostatic chuck.

Particle protection capability of extreme ultraviolet lithography mask carriers based on the gap effect and filter effect

In extreme ultraviolet lithography, particle-free mask handling is a critical issue because the use of pellicles is impractical. We measured the long-term change in the number of particle adders on a mask blank during transfer processes using a reticle SMIF pod (RSP) and a dual pod, which consists of an outer pod and an inner pod that holds the mask. In the RSP, the number of particle adders during the transfer test of a load port in air to an electrostatic chuck chamber in vacuum decreased from 0.053/cycle to 0.032/cycle because of a clean-up during the pumping down and purging operations. However, the number of particle adders during vacuum transfer did not change with long-term use. Moreover, we found that particles were added by mask blank sliding on a robot hand during vacuum transfer. In contrast, for the dual pod, no accident was observed during the 2000-cycle transfer test, and the number of particle adders was 0.004/cycle. We confirmed that the filter effect and gap effect for protecting the mask from particles were effective. We concluded that the dual pod was a reliable mask carrier for vacuum transfer.