Patent Application
20080211115
The invention is related to an apparatus and a method of producing a semiconductor structure. More particularly, the invention is directed to an apparatus and a method wherein an insulating layer is fabricated on a silicon substrate.
An embodiment of the invention relates to a method of forming an insulating layer on a silicon substrate comprising the steps of: arranging the silicon substrate inside a process chamber; forming an oxide layer on the substrate's surface wherein an electrical field is applied and wherein an oxygen particles containing plasma is provided above the substrate's surface, the electrical field accelerating the oxygen particles in the direction of the surface wherein the oxygen particles penetrate inside the substrate and form said oxide layer; thereafter, modifying the stoichiometry of the oxide layer wherein a nitrogen particles containing plasma is provided above the substrate's surface; the electrical field accelerating the nitrogen particles in the direction of the surface wherein the nitrogen particles penetrate inside the oxide layer and modify the stoichiometry of the oxide layer; wherein the step of forming the oxide layer and the step of modifying the stoichiometry are carried out inside the same process chamber.
According to one aspect of the invention the step of forming the oxide layer and the step of modifying the stoichiometry of the oxide layer are carried out inside the same process chamber. By using the same process chamber for both steps the cost efficiency can be significantly enhanced compared to methods which carry out both steps in different process chambers.
Additionally, the method may be carried out at a relatively low temperature as the oxygen and nitrogen particles are accelerated in the direction of the surface by an electrical field.
Another embodiment of the invention is directed to an apparatus comprising a first process chamber and a second process chamber wherein the first process chamber is adapted to perform the following steps: forming an oxide layer on the substrate's surface wherein an electrical field is applied and wherein an oxygen particles containing plasma is provided above the substrate's surface, the electrical field accelerating the oxygen particles in the direction of the surface wherein the oxygen particles penetrate inside the substrate and form said oxide layer; and modifying the stoichiometry of the oxide layer wherein a nitrogen particles containing plasma is provided above the substrate's surface; the electrical field accelerating the nitrogen particles in the direction of the surface wherein the nitrogen particles penetrate inside the oxide layer and modify the stoichiometry of the oxide layer; and wherein the second process chamber is adapted to subject the insulating layer to a post-treatment procedure.
Furthermore, as an embodiment, the invention provides a semiconductor device comprising a silicon substrate and an insulating layer thereon. The insulating layer is made by using the method as discussed above.
In order that the manner in which the above-recited and other advantages of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The preferred embodiment of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout.
It will be readily understood that the process steps of the present invention, as generally described and illustrated in the figures herein, could vary in a wide range of different process steps. Thus, the following more detailed description of the exemplary embodiments of the present invention, as represented in
The present invention relates to a method for fabricating a semiconductor device. As an exemplary embodiment of the invention a fabrication of a gate stack layer for a field effect transistor is described hereinafter. The invention applies to other technologies as well.
As indicated by arrows 40 and 45, a substrate may be either processed in chambers 20 and 30 or 25 and 35 after inserting the substrate into the apparatus through access 50. The apparatus as shown in
In the following, the process steps for fabricating an insulating layer on a silicon substrate are explained with regard to chambers 20 and 30. Of course, chambers 25 and 35 could be used instead or simultaneously for processing further substrates in the same manner or using a different process.
Thereafter, the stoichiometry of the oxide layer is modified. A nitrogen particles containing plasma is provided above the substrate's surface. The electrical field accelerates the nitrogen particles in the direction to the surface such that the nitrogen particles penetrate inside the oxide layer and modify the stoichiometry. This second step is called “plasma nitridation” in
As both kinds of particles, i.e. the oxygen and nitride particles, are accelerated by an electric field versus the substrate, the oxidation and nitridation will take place at a relatively low temperature compared to other oxidation and nitridation methods. Preferably, the temperatures during oxidation and/or nitridation are below about 400° C.
Due to the acceleration of particles the method as described above allows the formation of an oxide layer at a temperature that is significantly lower than those otherwise necessary to form gate dielectrics such as a thermal oxide in a standard way. For example, a thermal oxidation usually requires an oxidation temperature of at least 700° C. in order to achieve a sufficient oxidation rate. In contrast thereto, the method described herewith provides a reasonable oxidation speed at a temperature of about 400° C. and below.
The sequence of process steps is briefly summarized below:
1) wafer in
2
a) O2 flow and pressure setup
2
b) O2 purge
2
c) strike oxygen plasma
2
d) plasma oxidation
3) RF or microwave power off
4) pump-down
6
a) N2 flow and pressure setup
6
b) N2 purge
6
c) strike nitrogen plasma
6
d) plasma nitridation
7) RF or microwave power off
8) equalize pressure and purge
9) wafer out
Process steps 2a)-2d) refer to the plasma oxidation whereas process steps 6a)-6d) refer to the plasma nitridation.
After removing the substrate from the first chamber 20 it is transferred to the second chamber 30 for a “thermal post processing step”. Inside the second chamber 30 the substrate and the insulating layer thereon are, for example, heated to a temperature of between about 700° C. and about 1100° C., preferably in oxygen atmosphere.
In
Instead, a structure as shown in
Furthermore, both steps, the plasma oxidation and plasma nitridation, could be combined in a single step, where the oxygen and nitrogen particles are introduced simultaneously into the chamber 20. During this step the formation of silicon oxide and silicon nitride takes place at the same time. The partial pressure ratio of the oxygen and nitrogen particles in the process chamber during that step can be used to adjust the stoichiometry of the resulting oxynitride layer, i.e., the ratio silicon to oxygen to nitrogen within the layer.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
