Patent Application
20090047796
1. Field of Invention
The present invention relates to a semiconductor process. More particularly, the present invention relates to a method of manufacturing a dielectric layer.
2. Description of Related Art
Doping nitrogen into a dielectric film having a high dielectric constant (high-k) can prevent crystallization of the high-k films, reduce the equivalent of oxide thickness (EOT) and prevent boron penetration effectively, and the performance of semiconductor device can be thus improved.
Conventional method of doping nitrogen into a high-k film is performed by either thermal nitridation or plasma nitridation. The frequently occurred problem of the thermal nitridation is overdoping nitrogen into the interface between the high-k film and the substrate. The frequently occurred problem of the plasma nitridation includes plasma damage to the high-k film and too many unreactive bondings.
Nitridizing and optionally annealing plural high-k films layer-by-layer is performed to dope nitrogen into high-k films.
The invention can be more fully understood by reading the following detailed description of the embodiments, with reference made to the accompanying drawings as follows:
In
In
The steps of forming a high-k film, nitridizing the high-k film, and optionally annealing the high-k film are repeated for several times according to the process demand.
Finally, in
Each of these high-k films (110, 120, . . . , and 190) has various thickness of about 0.5 nm to about 2.0 nm. The material of these high-k films (110, 120, . . . , and 190) can be any silicate material or rare earth metal oxide, such as HfSiOx, HfO2, Ta2O5, ZrO2, or HfZrOx, HfLaOx, HfDyOx, HfScOx.
The substrate 100 above is maintained at a higher temperature for nitridation. According to an embodiment of this invention, the temperature of the substrate is maintained at a temperature higher than about 60° C., such as about 60° C. to about 300° C.
The pressure in the reactive chamber for nitridizing these high-k films (110, 120, . . . , and 190) is about 1 mTorr to about 1 Torr. The RF power of the low-power plasma above is about 200 W to 2000 W depends on the operation mode. For example, when the low-power plasma is applied in a continuous mode or in a pulse mode.
These high-k films (110, 120, . . . , and 190) are annealed under a dilute oxygen ambient having an oxygen concentration of less than 2% or in an inert ambient (e.g. N2). The temperature of annealing these high-k films (110, 120, . . . , and 190) is about 600° C. to about 1200° C. for about 10-3 seconds to about 1 hour depends on the method used. For example, when these high-k films (110, 120, . . . , and 190) are annealed by rapid thermal annealing, the annealing temperature ranges from about 600° C. to about 1050° C. with the duration ranging from 0.1 sec to 100 sec. When these high-k films (110, 120, . . . , and 190) are annealed by flash annealing, the annealing temperature ranges from about 800° C. to about 1200° C. with the duration ranging from 0.1 msec to 1 sec. When these high-k films (110, 120, . . . , and 190) are annealed by furnace annealing, the annealing temperature ranges from about 600° C. to about 900° C. with the duration ranging from 5 min to 1 hr.
Since these thin high-k films are formed and nitridized layer-by layer, the power of plasma used to nitridize these high-k films can be low to reduce the plasma damage and the nitrogen doping profile can be easily controlled. Moreover, these thin high-k films can be optionally annealed to reduce the number of dangling bonds (i.e. unreactive bonds); a higher boron penetration barrier is thus established. Therefore, the device performance can be improved by a dielectric layer made by these high-k films.
Those parameters described above can be easily optimized by a person skilled in manufacturing semiconductor integrated circuit according to the requirements of the products and many variations of the whole process. Hence those parameters described above are only exemplary of numerous embodiments that may be made of this invention. In short, it is the applicant's intention that the scope of this invention will be limited only by the scope of the appended claims.
