Fabrication method of semi-floating gate transistor

Abstract

The invention relates to a manufacturing method of a semi-floating gate transistor. In the manufacturing method, a gate dielectric material layer, a first floating gate material layer and a mask material layer are sequentially formed, and then the patterned mask material layer is used as a mask and the gate dielectric material layer is used as a barrier to etch the first floating gate material layer. The floating gate material layer is used to form the second opening defining the contact window setting area on the semiconductor substrate, and then the mask material layer and the gate dielectric material layer located in the contact window setting area are removed by using a maskless method to form a semi-floating gate. Compared with the method of using the mask structure obtained by multi-layer coating to make the contact window, the manufacturing method of the present invention is more convenient, and the contact window is obtained directly after etching in a maskless manner, without further processing. Removing the mask material can reduce the influence of the original oxide layer, and help to make a good contact between the subsequently formed semi-floating gate and the semiconductor substrate, thereby helping to improve device performance and facilitate mass production.

Description

technical field [0001] The present invention relates to the technical field of semiconductors, and in particular, to a method for fabricating a semi-floating gate transistor. Background technique [0002] Semiconductor memories are used in various electronic fields. Among them, a non-volatile memory (Non Volatile Memory, NVM) can store data for a long time in the case of power failure. Floating Gate Transistor (FGT) is a mainstream non-volatile memory device. In general, floating gate transistors have a stacked gate structure comprising a floating gate (floating gate) and a control gate (control gate) at least partially covering the floating gate, wherein the floating gate is surrounded by an insulating dielectric , by applying a high voltage to control the carriers to pass through the gate insulating layer in the way of tunneling (Fowler-Nordheim) or hot carrier injection, thereby changing the amount of stored charge in the floating gate, the threshold voltage of the tran...

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Problems solved by technology

However, in this process, since the contact window 10a is very small (for example, 0.05 μm wide), the requirements for the photolithography process are very high. Usually, an immersion photolithography machine is used, and at least two layers of anti-reflection are formed by a multi-layer coating process. layer and photoresist layer to make a mask; in addition, oxygen atoms are introduced during the process of removing the mask after etching, which causes a layer of native oxide (native oxide) to grow easily on the substrate surface in the contact window area, which It will affect the contact between the semi-floating gate formed at the contact window and the substrate, which will affect the performance of the device, which is not good for mass production

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