Method and device for real time control of the thickness of an integrated circuit layer

摘要

The layer which requires measuring is deposited on an underlying layer, and the method is carried out in the course of an operation of (A) etching the substrate of integrated circuit incorporating the layers. The method includes the further steps: (B) the follow-up of advancement of etching front of each layer of integrated circuit, by the intermediary of a line of optical emission spectrum of the reaction products of etching for at least one spectral component of underlying layer; (C) establishing the amplitude distribution as a function of time of optical emission of the reaction products of etching; (D) the determination of amplitude transition of optical emission at the time of passage of etching front of the measured layer to the underlying layer; (E) the calculation of thickness of measured layer by correlating the transition of amplitude and the distribution. The spectral component of underlying layer is an emission line wavelength characteristic of the layer. The measured layer is the second layer of silicon dioxide (SiO2), the underlying layer is a stop layer of silicon nitride (Si3N4), and the spectral component is the line of silicon nitride at 405 nm. The correlation is proportional to the time of etching separating the emission amplitude at the start of etching, which constitutes a reference amplitude, by an increase of 50% of the reference amplitude over the distribution. The calculation of thickness is effected on the basis of a linear relationship of the etching time and the calculated thickness. The follow-up of advancement of etching front is effected by means of a monochromator. The device for measuring the layer thickness comprises: an etching reactor with an optical window allowing observation of etching products; a monochromator with the wavelength centered on a characteristic value of underlying layer and allowing the delivery of values of emission amplitude of etching products; the means for computing the temporal position when the etching front reaches the underlying layer, and the effective thickness of measured layer by use of linear relationship.