High-Precision Combinatorial Deposition of Micro Particle Patterns on a Microelectronic Chip

Figures & data

FIG. 1 Particle distribution in volume percent (% v/v); (a) wide distribution of larger SAC particles with a mean diameter of 15.6 μm; (b) narrow distribution of small SAC particles with a mean diameter of 2.3 μm.

FIG. 2 (top) CMOS chip with SAC particle deposition pattern with a total of 16,384 pixels on 1.28 × 1.28 cm²; (bottom) schematic deposition; two different kinds of particles are deposited on defined pixels consecutively.

FIG. 3 Principle of aerosol generation; particles are sucked out of a reservoir through an ejector, the aerosol is guided through a Teflon tube to the outlet, where the aerosol is brought into contact with the chip surface.

FIG. 4 Schematic geometry of aerosol outlet and CMOS chip position above the air stream for particle deposition.

FIG. 5 Simulation for the specific geometry as shown in Figure 4; (a) air velocity field; (b) electrostatic potential.

FIG. 6 Desired particle deposition pattern (a, left) and experimentally achieved pattern (a, right); (b) schematic of particle deposition on a chip; particles move towards the chip and are manipulated by electrical fields resulting from the voltage pattern on the chip surface to enable spatial defined particle deposition.

FIG. 7 Simulation detail of particle deposition on a chip; particles are 10 μm in diameter and feature a q/m value of –3^.10^–3 C/kg; (a) the voltage of the grid electrode is 0 V, several particles are deposited as contaminations on deactivated pixels; (b) voltage of the grid electrode is 30 V, excess particles are solely deposited on the grid electrode.

FIG. 8 Simulation of particle deposition on a chip; particle trajectories are represented as black lines, grayscale represents the electrical potential [V]; particle diameters are (a) 3 μm, (b) 5 μm, (c) 10 μm; with q/m value of –3^.10^–3 C/kg; in all cases no contamination on grounded pixels occurs.

FIG. 9 Simulation of particle deposition on a chip; particle trajectories are represented as black lines, grayscale represents the electrical potential [V]; particle diameters are (a) 3 μm, (b) 5 μm, (c) 10 μm; with q/m value of –3^.10^–2 C/kg; in (a, b) no contamination on grounded pixels occurs in contrast to (c).

TABLE 1 Stopping distance S for different particle diameters d with corresponding Knudsen number K_n and Cunningham correction factor C_c; initial velocity is v = 1m/s

d [μm]	Kn	Cc	τ[s]	Sv=1m/s [μm]
3	0.04	1.05	28^.10^–6	28
5	0.03	1.03	77^.10^–6	77
10	0.01	1.01	305^.10^–6	305

FIG. 10 Simulation of particle deposition on a chip; the electrostatic potential [V] is shown in grayscale, particle trajectories are shown as black lines; particles are 10 μm in diameter and possess a q/m value of –3^.10^–3 C/kg; (a) the voltage of the sieve is –1 kV, several particle trajectories end on the chip surface; (b) the voltage of the sieve is 0 V, only one single particle trajectory ends on the chip surface; (c) schematic of a particle in the electrical field resulting from the charge of the aerosol and the chip surface, acting as opposing electrodes.

FIG. 11 Simulation of particle deposition on a chip; the electrostatic potential [V] is shown in grey scale, particle trajectories are shown as black lines; particles are 5 μm in diameter and possess a q/m value of –3^.10^–3 C/kg; (a) one pixel with 100 V is neighbored by 0 V pixels; particles tend to be deposited on the middle of the 100 V pixel; (b) three adjacent pixels with 100 V are neighbored by 0 V pixels; particles are deposited equally distributed on the 100 V pixel in the center, particles deposited on the left and right 100 V pixel tend to be deposited on the side of the pixel, into direction of the center pixel.

FIG. 12 Four different deposition patterns of micro particles on each chip surface (checkerboard, 1 of 16, 1 of 36, 1 of 64). (a) high degree of contamination; particles with a wide size distribution and a mean diameter of 15.6 μm were used; (b) almost free of contamination; particles with a narrow size distribution and a mean diameter of 2.3 μm were used.

FIG. 13 Deposition on a chip (mean particle diameter 2.3 μm) exhibiting the effect described in the simulations in Figure 11; (a) single pixel with the pincushion effect visible; (b) in dependence of the voltage of directly surrounding pixels, particles either tend to be deposited in the center or on the side of the pixel; to guarantee isotropic central coverage of pixels, the same deposition pattern is produced by two consecutive deposition steps (c) and (d).