A polarization-sensitive laser-light-scattering method is developed for simultaneous in situ measurements of properties (size, size dispersion, density, and refractive index) of particulates formed in processing plasmas. The developed system is applied to observe the growth processes of particulates in a range of their size larger than about 10 nm in rf silane plasmas. A size, a size dispersion (logarithm of a standard deviation of size), a density, and a refractive index of particulates in the plasmas are found to be 10–200 nm, about 0.1, 107–109 cm−3 and about 3–5i, respectively. The former three of such values agree fairly well with ones deduced from scanning electron microscopic (SEM) observation. These particulates grow through three phases of nucleation and initial growth, rapid growth, and growth saturation. Coexistence of two size groups of particulates with narrow size dispersions during and after the rapid growth phase verified by the SEM observation may be explained by a model taking into account coagulation between oppositely charged particulates.

Growth kinetics of particles above 10 nm in size in silane RF discharges has been extensively studied and fairly well clarified. Moreover, recent developments of new measurement methods for particles below 10 nm in size have led to a rapid advance in understanding the growth processes of small particles. Such previous studies are reviewed with the accent on their initial growth phase corresponding to a particle size range below 10 nm. The notable effect of pulse modulation of the RF discharges of suppressing particle growth is also described. Both the growth of particles and their suppression by the modulation can be explained by a model taking into account the production of key radicals (highly reactive neutral radicals of SiH2 having a high production rate), particle growth reactions initiated by the key radicals and particle diffusion in the radical production region.

Growth processes of particles in a cluster-size range below a few nm in size in low pressure and low power SiH4 rf discharges are studied using the new method, in which the threshold photoemission method is coupled with the microwave interferometry, for measurements of their size and density. The density of particles is above 1010 cm−3 and much exceeds that of positive ions, the result of which shows that most of them are neutral. The particles grow mainly around the plasma/sheath boundary near the powered electrode and their size growth rate is 3.4–4.4 nm/s, being much higher than a film growth rate of 0.064–0.12 nm/s. These features strongly indicate that their growth is due to deposition of polymerized species, originated from short lifetime SiH2 radicals, on them, while coagulation between particles becomes appreciable after a time when their density reaches about 1011 cm−3. Moreover, the pulse modulation of rf discharge is found to be effective in reducing the density of cluster-size particles. The reduction can be explained by a model taking account of diffusion of the polymerized species through the radical production region, where the particles nucleate and grow.

Growth processes of particles in high frequency silane plasmas are studied as a parameter of discharge frequency (3.5–28 MHz) or by modulating the amplitude of discharge voltage (125–275 V). Except for the 28 MHz case, particles tend to grow through three phases of nucleation and subsequent initial growth, rapid growth, and growth saturation. A detailed study for 6.5 MHz explains the following features: morphology of particles shows that coagulation of particles plays a crucial role in the rapid growth phase; a coagulation rate of 200 s−1 observed in the rapid growth phase is extremely high compared to a thermal collision rate of 5 s−1 between particles; coagulation almost stops when decreasing the discharge power by about one-fourth at the middle of the rapid growth phase; two size groups of particles with narrow size dispersions coexist during and after the rapid growth phase. For 28 MHz, while, as compared to 6.5 MHz, particles appear early after the initiation of discharge and their density is high by about two orders, their growth rate in the subsequent phase is quite low. To properly explain most rapid growth features, a model, taking into account coagulation between oppositely charged particles, is proposed.

Nucleation and subsequent initial growth processes of particles in rf silane plasmas are investigated using a newly developed photoemission method. In this method, electrons produced due to interactions of particles with photons (photodetachment, photoionization) are measured. Since threshold energies for the interactions are dependent on particle size, size ranges of the detected particles are determined by wavelengths of the irradiated light. Using this method, small particles such as SinHx (n≲10), SinHx (n≲200) and SinHx (n≳20) can be detected. The experiments show that even in a very early phase of their growth, particles nucleate and grow principally around the plasma/sheath boundary near the rf electrode, where short lifetime radicals are produced actively. This suggests that the short lifetime radicals are the key species contributing to the particle nucleation and its subsequent initial growth processes. Moreover, it is found that small particles exist even in the bulk plasma. Since some of them are considered to be neutral, they are likely to be transported to the substrate on the grounded electrode.