A contact-lens-shaped IC chip technology

Abstract

We report on novel contact-lens-shaped silicon integrated circuit chip technology for applications such as forming a conforming retinal prosthesis. This is achieved by means of patterning thin films of high residual stress on top of a shaped thin silicon substrate. Several strategies are employed to achieve curvatures of various amounts. Firstly, high residual stress on a thin film makes a thin chip deform into a designed three-dimensional shape. Also, a series of patterned stress films and ‘petal-shaped’ chips were fabricated and analyzed. Large curvatures can also be formed and maintained by the packaging process of bonding the chips to constraining elements such as thin-film polymer ring structures. As a demonstration, a complementary metal oxide semiconductor transistor (CMOS) image-sensing retina chip is made into a contact-lens shape conforming to a human eyeball 12.5 mm in radius. This non-planar and flexible chip technology provides a desirable device surface interface to soft tissues or non-planar bio surfaces and opens up many other possibilities for biomedical applications.

Silicon-Based Micromachining Process for Flexible Electronics

“…Wu et al (2016) employed this release process to fabricate a silicon-based flexible imager [26][27][28][29][30][31][32][33], and Figure 11 shows the process flow to release an imager from the carrier substrate and the fabricated mounted monocentric imager. Sevilla et al used this release process to fabricate a silicon-based flexible FinFET.…”

“…Liu et al employed this process to fabricate a spherical flexible CMOS retina chip. They thinned the backside Si to a thickness of around 50 μm by mechanical lapping, and after that a dry etching such as XeF 2 or RIE is used to etch the Si substrate down to around 10μm thickness and remove the surface micro-crack damages induced during the lapping process [33].…”

Measuring plastic deformation in epitaxial silicon after thermal oxidation

“…These plastic deformations are not completely understood yet. Some effects of residual stress in MEMS include damage [1], warpage [2], reduced sensitivity of ultrasonic sensors [3], and buckling [4].…”

Design and fabrication of silicon-tessellated structures for monocentric imagers

“…In addition to the motivation to achieve a miniature monocentric imager, curved silicon structures can enable a variety of applications in flexible electronics and the Internet of Things [13][14][15] . Therefore, we seek to address the challenge of developing a lowcost, CMOS-compatible process for silicon-based flexible electronics by demonstrating a miniature hemispherical curved silicon substrate for monocentric imagers.…”