DRAWINGS
Example FIGS. 1A to 1E illustrate a method of forming a gate electrode of a semiconductor device, in accordance with embodiments.
Example FIGS. 2A and 2B are TEM photographs of variations in the micro tissue of a TiN layer before and after the spray of SiH4, in accordance with embodiments.
DESCRIPTION
As illustrated in example FIG. 1A, gate oxide layer 2 may be formed over silicon wafer 1, in accordance with embodiments. Polysilicon layer 3 may be formed over gate oxide layer 2. As illustrated in example FIG. 1B, TiN layer 4 may be formed over polysilicon layer 3. TiN layer 4 may be formed from Tetra Dimethyl Amino Titanium (DMAT) that is introduced into a chamber and thermally decomposed over the wafer. In embodiments, the wafer may be maintained at a temperature range between about 300° C. and about 500° C. and a working pressure within the chamber may be maintained between a range from about 1 Torr to about 10 Torr. TiN layer 4 may have an amorphous structure, in accordance with embodiments. A TiN layer may include Carbon, Oxygen, or other similar material caused by TDMAT (Tetra Dimethyl Amino Titanium), which may contribute to high resistivity.
As illustrated in example FIG. 1C, in order to remove the impurities (e.g. Carbon and/or Oxygen), a plasma treatment may be performed on TiN layer 4 to form plasma treated TiN layer 7, in accordance with embodiments. A plasma treatment may use H2/N2 gas plasma 5. In a plasma treatment, H2/N2 gas plasma is made and a negative bias is applied to the wafer, so that positive ions 6 (e.g. H+ and N2+ within the plasma) are projected into TiN layer 4. The incident ions may have a high kinetic energy. As these ions collide against the TiN layer, the amount of the impurities (e.g. Carbon and/or Oxygen) within the TiN layer may be reduced, which may reduce the resistivity of the TiN layer. In embodiments, the power applied to generate and maintain the plasma may be between approximately 500 W and approximately 1000 W.
In embodiments, an amorphous micro tissue may shift to crystalline TiN having a micro grain boundary due to the plasma treatment process. In embodiments, a TiN layer may be formed by Metal Organic Chemical Vapor Deposition (MOCVD). In embodiments, a thermal decomposition process of TDMAT and H2/N2 plasma treatment may be repeated a plurality of times. The thickness of a TiN layer may be increased according to the number times a thermal decomposition process and a plasma treatment are performed. For example, a TiN layer may have a thickness of approximately 30 Å when a thermal decomposition/plasma treatment is performed one time, while the thickness may be 60 Å if the thermal decomposition/plasma treatment is performed two times. The thickness of a TiN layer may be between approximately 30 Å and approximately 500 Å, in accordance with embodiments.
As illustrated in example FIG. 1D, a SiH4 gas 8 is sprayed on plasma-treated TiN layer 7 to form TiSiN layer 9, in accordance with embodiments. A wafer may be maintained at a temperature between approximately 300° C. and approximately 500° C., in accordance with embodiments. A SiH4 gas may be sprayed at the flow rate between approximately 10 sccm and approximately 5000 sccm for about 20 to 360 seconds, in accordance with embodiments. If the working pressure within the chamber is too low, TiSiN may not be generated effectively. If the working pressure within the chamber is too high, undesirable particles may be generated. Accordingly, the pressure of the chamber may be maintained between approximately 0.1 Torr and approximately 10 Torr.
During the formation of TiSiN layer 9, the entire TiN layer 7 may be converted to TiSiN layer (e.g. based on the spray conditions of SiH4), in accordance with embodiments. In embodiments, only a portion of TiN layer 7 may be converted to TiSiN (e.g. an upper portion). TiSiN layer 9 may have a thickness between approximately 30 Å and approximately 500 Å. In embodiments, the thickness of TiSiN layer 9 may be approximately the same as the thickness of TiN layer 7 before SiH4 is sprayed. TiSiN layer 9 may have an amorphous structure, which does not have a grain boundary, in accordance with embodiments. An amorphous structure without a grain boundary may prevent and/or minimize diffusion path for fluorine (F) to be formed (e.g. TiSiN layer 9 may have a relatively good diffusion prevention ability), in accordance with embodiments.
Example FIGS. 2A and 2B are TEM photographs of a MOCVD TiN before and after the spray of SiH4, in accordance with embodiments. Example FIG. 2A is a photograph of a micro-crystalline TiN before SiH4 is sprayed. Example FIG. 2B is a photograph of amorphous TiSiN (the black part) on an upper portion of a TiN layer after SiH4 is sprayed.
As illustrated in example FIG. 1E, WSix 10 may deposited by a CVD method using WF6 gas and SiH4 gas, in accordance with embodiments.
In embodiments, a TiSiN layer may be formed over a polysilicon layer, fluorine (F) generated when depositing WSix may be prevented and/or minimized from infiltrating into a gate oxide layer. Accordingly, it may be possible to prevent and/or minimize degradation of a gate oxide layer due to fluorine (F), in accordance with embodiments.
It will be obvious and apparent to those skilled in the art that various modifications and variations can be made in the embodiments disclosed. Thus, it is intended that the disclosed embodiments cover the obvious and apparent modifications and variations, provided that they are within the scope of the appended claims and their equivalents.
Patent Application
20080054381
