Bulk lifetime and surface recombination velocity measurement method in semiconductor wafers

Abstract

A noncontact and nondestructive measurement method is proposed to separately determine the bulk lifetime τb, and the front and backsurface recombination velocities S0 and Sw in the semiconductor wafer with different surface recombination velocities in the front and backsurfaces. The method is deduced based on a new analytical solution for photoconductivity decays derived for the wafer with different surface recombination velocities. The solution gives the expressions for a photoconductivity decay and a carrier profile under pulse laser excitation. The analytical relationship between the apparent (or effective) lifetime, S0, Sw, τb and a wafer thickness is given. The photoconductivity decay curve dependencies on various values of S0, Sw, and τb have been demonstrated. The algorithm is shown to separately extract τb, S0, and Sw. The algorithm is characterized by the measurement of two photoconductivity decay curves for pulse laser excitation on both surfaces of the wafer. The influence of the laser pulse width for the photoexcitation on the photoconductivity decays is discussed. The method can be readily applicable to noncontact photoconductivity decay measurement techniques using an electromagnetic wave such as a microwave.

Low surface recombination velocity in n-Si passivated by catalytic-chemical vapor deposited alumina films

“…The SiO 2 film thicknesses were measured to be 1.08 nm. The surface recombination at the interface between the film and n-Si was characterized by the initial decay in photoconductivity decay (PCD) curve measurements and also evaluated by S 0 determined by BS-PCD method from two PCD-curve measurements using contactless techniques [13][14][15][16]. In this experiment, the photoconductivity change was detected by a reflected 500 MHz electromagnetic wave.…”

Free Carrier Recombination Lifetime Calculation From Photoconductivity Decay Measurement in Non–passivated Silicon

“…6. Lifetime measurement results for samples [2][3][4][5][6][7] равновесных носителей заряда в объеме образца монокристаллического кремния.…”

“…В этом случае исполь-зование рекомендованных стандартом SEMI MF формул приводит к достаточно большой (до 20 %) систематической погрешности в оценке времени жизни свободных носителей заряда. [2][3][4][5]. Метод состоит в засветке образца излучением с энергией фотонов, превышающей ширину запрещенной зоны, и сня-тии кривой спада ФП после вы-ключения освещения.…”

“…Практически ни в одной работе, в которой проанализировано влияние поверхностной рекомбинации и приведены экспериментальные результаты, в том числе в [7,[11][12][13][14], не указано, в какой части релаксационной кривой определяли эффективное время жизни. В некоторых работах [4,15] максимальное эффективное временя жизни оценивают по котангенсу угла наклона асимптоты логарифма релаксационной кривой. При этом пред-полагают, что кривая становится линейной уже при t > 0,1τ, что в общем случае неверно.…”

Heat treatment in 110 °C liquid water used for passivating silicon surfaces

“…The passivation of semiconductor surfaces is important to achieve a long lifetime of photo-induced minority carriers, which is required for fabricating high-performance photosensors and photovoltaic devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Many famous passivation techniques have been developed for surface passivation, for example, formation of thermally grown SiO 2 layers [20], hydrogenation treatment [21,22], fieldeffect passivation caused by fixed charges in SiN or aluminum oxide [23,24], and high-pressure H 2 O vapor heat treatment [25][26][27][28][29].…”