Brandon M. Rawlings

High-throughput sequencing of the paired human immunoglobulin heavy and light chain repertoire

Each B-cell receptor consists of a pair of heavy and light chains. High-throughput sequencing can identify large numbers of heavy- and light-chain variable regions (VH and VL) in a given B-cell repertoire, but information about endogenous pairing of heavy and light chains is lost after bulk lysis of B-cell populations. Here we describe a way to retain this pairing information. In our approach, single B cells (>5 × 104 capacity per experiment) are deposited in a high-density microwell plate (125 pl/well) and lysed in situ. mRNA is then captured on magnetic beads, reverse transcribed and amplified by emulsion VH:VL linkage PCR. The linked transcripts are analyzed by Illumina high-throughput sequencing. We validated the fidelity of VH:VL pairs identified by this approach and used the method to sequence the repertoire of three human cell subsets—peripheral blood IgG+ B cells, peripheral plasmablasts isolated after tetanus toxoid immunization and memory B cells isolated after seasonal influenza vaccination.

Polymer-bound photobase generators and photoacid generators for pitch division lithography

The semiconductor industry is pursuing several process options that provide pathways to printing images smaller than the theoretical resolution limit of 193 nm projection scanners. These processes include double patterning, side wall deposition and pitch division. Pitch doubling lithography (PDL), the achievement of pitch division by addition of a photobase generator (PBG) to typical 193 nm resist formulations was recently presented.1 Controlling the net acid concentration as a function of dose by incorporating both a photoacid generator (PAG) and a PBG in the resist formulation imparts a resist dissolution rate response modulation at twice the frequency of the aerial image. Simulation and patterning of 45 nm half pitch L/S patterns produced using a 90 nm half pitch mask were reported.2 Pitch division was achieved, but the line edge roughness of the resulting images did not meet the current standard. To reduce line edge roughness, polymer bound PBGs and polymer bound PAGs were investigated in the PDL resist formulations. The synthesis, purification, analysis, and functional performance of various polymers containing PBG or PAG monomers are described herein. Both polymer bound PBG with monomeric PAG and polymer bound PAG with monomeric PBG showed a PDL response. The performance of the polymer bound formulations is compared to the same formulations with small molecule analogs of PAG and PBG.

RF Characterization of Magnetodielectric Material Using Cavity Perturbation Technique

Magnetodielectric (MD) materials find application in many areas of microwave engineering, and therefore, measurement of their dielectric and magnetic properties is very important. This paper presents a novel MD material characterization method using the cavity perturbation technique (CPT) with substrate-integrated waveguide (SIW) cavity resonators. Frequency dependent complex permittivity and permeability of MD material can be extracted with a single SIW cavity structure by inserting the sample material into different locations. The fundamental theory of CPT is explained and its analysis for SIW cavity is discussed. Cobalt nanoparticles are synthesized with a fluoropolymer matrix to realize the MD materials and their properties are measured in the frequency range 1-4 GHz. The effect of volume fraction and density of the synthesized MD materials on the dielectric and magnetic properties has been studied.

Photobase generator enabled pitch division: a progress report

Pitch division lithography (PDL) with a photobase generator (PBG) allows printing of grating images with twice the pitch of a mask. The proof-of-concept has been published in the previous paper and demonstrated by others. Forty five nm half-pitch (HP) patterns were produced using a 90nm HP mask, but the image had line edge roughness (LER) that does not meet requirements. Efforts have been made to understand and improve the LER in this process. Challenges were summarized toward low LER and good performing pitch division. Simulations and analysis showed the necessity for an optical image that is uniform in the z direction in order for pitch division to be successful. Two-stage PBGs were designed for enhancement of resist chemical contrast. New pitch division resists with polymer-bound PAGs and PBGs, and various PBGs were tested. This paper focuses on analysis of the LER problems and efforts to improve patterning performance in pitch division lithography.

Ultra-thin dual polarized millimeter-wave phased array system-in-package with embedded transceiver chip

A 16-element dual polarized phased array transmit/receive (Tx/Rx) System-in-Package (SiP) for 60 GHz applications is presented. Embedded die technology is used to achieve total module thickness of only 600 μm, improved first level interconnect density and better electrical performance. The dual polarized antenna architecture enables several configurations of the transmitter and receiver orientation without major impact on the signal to noise ratio (SNR). The proposed system was fabricated on a low loss multilayer organic package substrate, assembled and fully characterized. Single element and phased array performance was evaluated showing very good agreement with the simulation over the 60 GHz ISM band. Active measurements showing good steering and dual polarization characteristics were also performed.

Synthesis of magneto-dielectrics from first principles and antenna design

Magneto-dielectric materials have been spotlighted as a new opportunity for effective antenna size reduction in many recent studies. In this paper, we start from first principles to describe the methodology used to synthesize the magneto-dielectric material. A combination of Bruggemans effective medium model and Sihvola and Lindell model are used to find the right mixture of cobalt particles and fluoropolymer material for the effective antenna miniaturization. A three pole Lorentzian dispersion model is derived for fitting extracted material properties of magneto-dielectric composite material. The material properties are extracted using a cavity perturbation technique with substrate integrated waveguide cavity resonator. The Kramers-Kronig relations are used to demonstrate that the extracted material properties from the method are causal in this paper. A 900MHz PIFA on magneto-dielectric material substrate is designed, fabricated and measured. A 7.4% bandwidth and 61.7% radiation efficiency for the antenna were obtained. Human body effect to antenna was studied and Specific Absorption Rate (SAR) was calculated. The simulation results show that magneto-dielectric material can reduce the effect of human body on antenna performance and the magnetic loss enables a decrease in the SAR of the antenna.

Self-aligned patterning on a flexible substrate using a dual-tone, thermally activated photoresist

The fabrication of electronic devices on flexible substrates represents an opportunity for the development of flexible display technologies, large area devices, and roll-to-roll manufacturing processes. Traditional photolithography encounters alignment and overlay limitations when applied to flexible substrates. One solution to the overlay challenges is imaging of two device layers in a single lithographic exposure. To enable the simultaneous patterning of two device layers, a new photoresist system was developed. Prior work on dual-tone photoresists introduced formulations capable of storing two independent images, but the reported systems are incompatible with the reactive ion etch processes commonly used today. This paper describes a dual-tone photoresist system that maintains the ability to store two independent latent images, distinguished by the incident exposure light wavelength, simultaneously remaining compatible with reactive ion etch image transfer processes.

High aspect ratio patterning of photosensitive polyimide with low thermal expansion coefficient and low dielectric constant

Abstract. A photosensitive polyimide system based on amine catalyzed imidization of a precursor poly(amic ester) is described. The material is based on the meta ethyl ester of pyromellitic dianhydride and 2,2’ bis(trifluoromethyl)benzidine. It acts as a negative tone resist when formulated with a photobase generator. The material exhibits a dielectric constant of 3.0 in the gigahertz range, a coefficient of thermal expansion of 6±2  ppm/K, and can be patterned to aspect ratios of >2 when formulated with a highly quantum efficient cinnamide type photobase generator.

Directly patternable dielectric based on fluorinated polyimide

A photosensitive polyimide system based on amine catalyzed imidization of a precursor poly(amic ester) is described. The material is based on the meta ethyl ester of pyromellitic dianhydride and 2,2’ bis(trifluoromethyl)benzidine and acts as a negative tone resist when formulated with a photobase generator. The material exhibits a dielectric constant of 3.0 in the GHz range, a coefficient of thermal expansion of 6±2 ppm/K, and can be patterned to aspect ratios of greater than 2 when formulated with a high efficiency cinnamide type photobase generator.

Efficient and scalable single mode waveguide coupling on silicon based substrates

One of the key challenges in Silicon based optical interconnect system remains to be the efficient coupling of optical signals from the submicron size on-chip waveguides to standard single mode (SM) fibers with low insertion loss (IL) and relaxed alignment tolerance. Large optical alignment tolerance allows optical connectors to be attached to on-chip waveguides passively using standard semiconductor pick-and-place assembly tools that have placement accuracies of 10- 15μm. To facilitate the assembly, optical fiber coupling elements need to be modular and compact. They have to also have low profile to avoid blocking air flow or mechanical interference with other elements of the package. In this paper we report the development of a two-dimensional (2D) SM optical fiber coupling architecture that consists of Si based photonic lightwave circuit (PLC) substrate and a high-density micro-lensed fiber optic connector. The system is compact, efficient and has large optical alignment tolerance. At 1300nm an insertion loss of 2.4dB and 1.5dB was measured for the PLC module and the fiber optic connector, respectively. When the PLC module and connector was aligned together, a total insertion loss of 7.8dB was demonstrated with x,y alignment tolerance of 40μm for 1dB optical loss. The SM optical coupling architecture presented here is scalable, alignment tolerant and has the potential to be manufactured in high volume. To our knowledge, such a system has not been reported in the literature so far.