JPH0323639A - Thin-film transistor - Google Patents

Abstract

PURPOSE:To obtain a thin-film transistor whose carrier mobility is not lowered, whose threshold voltage is not increased and whose element characteristic is good by using a polycrystalline semiconductor thin film which contains the specific number of fluorine atoms. CONSTITUTION:Fluorine atoms of 1X10<18> to 1X10<21>cm<-3> are contained both in polycrystalline Si thin films for source.drain region use and for channel region use and in a polycrystalline Si film for gate electrode use. The fluorine may be either in a molecule state or in an atom state; in the case of atoms, an ion state is included. In order to contain the fluorine, a thin-film transistor is formed, and, after that, the fluorine is introduced into the thin film by a method to implant F<+> ions or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film transistor using a polycrystalline semiconductor thin film.

[Summary of the invention]

The present invention provides a thin film transistor as described above, in which a polycrystalline semiconductor thin film has IXIO” to 1×IOz 1 piece cm −
By containing F in ', it is possible to provide a thin film transistor that has high device characteristics, does not deteriorate the characteristics of other semiconductor devices during manufacturing, and is relatively easy to manufacture.

[Conventional technology]

Recently, it has been considered to apply thin film transistors using polycrystalline semiconductor films such as polycrystalline Si thin films to three-dimensional LSIs.

However, in polycrystalline semiconductors, unsaturated bonds exist at grain boundaries, and these unsaturated bonds act as electrical barriers.

For this reason, in thin film transistors, there is a decrease in carrier mobility, an increase in dark value voltage, etc., and the device characteristics are poor.

One way to avoid this is to electrically inactivate the unsaturated bond by bonding hydrogen to the unsaturated bond (e.g.
LIETTERS, VOL. 9, N [L6, JUN
ε198Bj p. 287-289).

In addition, as another method, a method has been proposed in which the crystal grain size of polycrystalline St is increased to reduce grain boundaries and, as a result, unsaturated bonds are reduced (for example, rlEEE TRA
NSACTIONS ON EL[! CTRON DH
VICBS. VOL. 35, NiL? ．． JULY 19
88J p. 923-928).

Among the above two methods, a particularly promising method for implementing the former is, for example, a method using hydrogen in the plasma SjNll.

[Invention tries to solve it! IB) However, it is known that when hydrogen in plasma SiN@ etc. is bonded to the unsaturated bonds of polycrystalline Si, the hot carrier resistance of the MOSI transistor, which is formed in the lower layer of the polycrystalline Si thin film, deteriorates. (e.g. rll!EB
TRANSACTIONS ON I! LECTRO
NDI! VICI! S, VOL. 3G. Nl3. M
ARCH 1989J p. 529-533). Therefore, when trying to apply polycrystalline Si thin film transistors to LSI, there is a dilemma between improving the characteristics of the MILL} transistor due to hydrogenation and deteriorating the characteristics of the MOS} transistor formed in the lower layer of the polycrystalline SIN film due to hydrogenation. become. [Means for Solving the Problems] In the thin film transistor according to the present invention, the polycrystalline semiconductor thin film contains lxl01 to lx1021 eJ - "F. [Operation] In the thin film transistor according to the present invention, the polycrystalline semiconductor thin film contains
The unsaturated bonds in lII are inactivated, so there is no decrease in carrier mobility or increase in threshold implantation voltage. Furthermore, even if unsaturated bonds in the polycrystalline semiconductor thin film are inactivated, the hot carrier resistance of the transistor formed in the lower layer of the polycrystalline semiconductor ms does not deteriorate. Furthermore, there are various methods for incorporating F into a polycrystalline semiconductor thin film. [Example] An example of the present invention applied to a polycrystalline Si thin film transistor will be described below. In this example, both the polycrystalline Si thin film for the source/drain ttM region and the channel region, and the polycrystalline Sl film for the gate electrode have an F of 3.
Contains. F may be contained in either a molecular state or an atomic state, and the atomic state also includes an ionic state. Polycrystalline Sifl film or polycrystalline S
In order to incorporate F into the ill, F is introduced into these films after the formation of these films or after the formation of thin film transistors. As a method for introducing F into a polycrystalline sty film or a polycrystalline Si film, there is first a method of ion implantation of F+ ions. There is also a method in which a film containing F is deposited on a polycrystalline St thin film or a polycrystalline St film, and F is diffused in a solid phase by heat treatment. Possible examples of the F-containing film include W silicide obtained by decomposing WFh and F-containing stone. Alternatively, the wafer may be exposed to plasma containing fluorine ions. In this example, since the polycrystalline Sill film and the polycrystalline Si film contain F at the above concentration, the unsaturated bonds in these films are inactivated. (Effects of the Invention) The thin film transistor according to the present invention has high device characteristics because there is no decrease in carrier mobility or increase in dark value voltage. Furthermore, since the hot carrier resistance of the transistor formed in the lower layer of the polycrystalline semiconductor thin film does not deteriorate, the characteristics of other semiconductor elements are not deteriorated during manufacturing. Furthermore, since there are various methods for incorporating F into a polycrystalline semiconductor thin film, manufacturing is relatively easy.

Claims (1)

[Claims] A thin film transistor using a polycrystalline semiconductor thin film containing F of 1×10^1^5 to 1×10^2^1 cm^-^3.