Semiconductor device manufacturing: process – Including control responsive to sensed condition – Optical characteristic sensed
Reexamination Certificate
1999-10-27
2002-05-28
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
Optical characteristic sensed
C438S016000, C356S908000
Reexamination Certificate
active
06395563
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for manufacturing a semiconductor device and a method of manufacturing the same. More particularly, it relates to property control of a surface of a semiconductor layer and a film formed thereon in a manufacturing process performed by using a clustered manufacturing device in an atmosphere insulated from an external space.
As the packaging density of a semiconductor integrated circuit has increased in recent years, miniaturization and higher performance have been required of an element composing a MOS device, such as a transistor. However, the miniaturization of an element such as a transistor should not reduce the reliability of the whole device. Therefore, both miniaturization and increased reliability are required of each component of an element such as a transistor.
In particular, a gate insulating film (gate oxide film), which is an essential component of a MOS device, has rapidly been reduced in thickness. It is expected that an extremely thin insulating film with a thickness of 4 nm or less will be used in the twenty-first century. Since the properties of the gate insulating film are said to determine the properties of the MOS transistor and the electric properties of a semiconductor integrated circuit, the formation of an insulating film with excellent properties has been in great demand.
It has been proved that the properties of an insulating film are largely dependent on the surface state of a semiconductor layer before the insulating film is formed thereon. Accordingly, there has been studied a cleaning method for improving the properties of the semiconductor layer or the like. For example, it has been reported that the use of a cleaning method (pregate cleaning process) which minimizes the undulations of a surface of a Si substrate allows the formation, on the laboratory level, of a high-quality gate oxide film with an extremely small thickness of about 1.2 nm.
There has also been reported a clustered manufacturing device which allows sequential process steps from pregate cleaning to gate insulating film formation to be performed without exposing wafers to an atmosphere and thereby prevents the formation of a natural oxide film and the deposition of a contaminant resulting from exposure to the atmosphere (Document 1: Schuegraf et. al., IEEE/International Reliability and Physics Symposium 97, p. 7). It has been proved that a high-quality gate insulating film can be formed by the manufacturing process using the clustered manufacturing device. The use of the clustered manufacturing device is particularly desirable in the step of forming a gate insulating film having a reduced thickness of 4 nm or less.
On the other hand, property control of the gate insulating film in a MOS device has been performed conventionally by forming an element such as a MOS capacitor or MOS transistor and analyzing the electric properties of the element. If any trouble occurs in the step of forming the gate insulating film, the procedure is followed in which the trouble is found by evaluating the electric properties of the MOS capacitor or the like that has been formed previously, diagnosing the cause of the trouble, and practicing a troubleshooting method. As a result, a large quantity of gate insulating films with degraded electric properties are formed consecutively till the trouble is found, which reduces production efficiency.
If an ellipsometer used conventionally for measuring a film thickness in the manufacturing process is used to measure the thickness of a thin film, it does provide a measured value, but the minimum film thickness that can be measured with reliability is on the order of 10 nm. It can hardly be said that a film thickness smaller than 10 nm is measurable with sufficiently high accuracy. Thus far, a reliable evaluation method which is usable for an extremely thin film with a thickness of about 4 nm or less in the manufacturing process has not been established yet.
Although the electric properties of a MOS capacitor or the like formed on a wafer are measured after a large number of sequential process steps were performed with respect to the wafer in the process using the clustered manufacturing device described above, there is no method of controlling the condition of the wafer in the course of the process steps. Despite the fact that a high-quality gate insulating film is formable on the laboratory level, there is no guarantee, under present circumstances, that high-quality gate insulating films can be formed in the process of mass-producing MOS devices even by using the clustered manufacturing device.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a method of manufacturing a semiconductor device incorporating an optical evaluation method which can provide sufficient reliability and accuracy in measuring the properties of an extremely thin film.
A second object of the present invention is to provide a method and device for manufacturing a semiconductor device which allow optical measurement of the properties of an insulating film, especially the thickness thereof, and provide a method of property control in sequential process steps from pregate cleaning to insulating film formation, which are performed by using a clustered manufacturing device.
A device for manufacturing a semiconductor device of the present invention is a clustered device comprising: a plurality of processing rooms for processing a wafer having a semiconductor region; a shared container enclosing a space containing the plurality of processing rooms such that the space is held in an atmosphere disconnected from an external space; transporting means for transporting the wafer within the shared container; and optical measuring means for optically evaluating a surface state of the wafer being disposed at any site in the shared container.
The arrangement allows optical evaluation of the surface state of a wafer in a situation unaffected by a natural oxide film formed on the wafer or contamination deposited thereon by exposing the wafer to the external space. By thus optically evaluating the surface state of the wafer after the removal of the film or after the formation of the film, the thickness of an oxide film or the like can be measured with high accuracy. Since the wafer need not be extracted, for optical evaluation, to the outside of the shared container, the process of manufacturing a semiconductor device can be controlled properly by using in-line evaluation without adversely affecting the wafer in the manufacturing process.
In the device for manufacturing a semiconductor device, the optical measuring means can be comprised of: a first light source for generating exciting light; a second light source for generating measuring light; a first light guiding member for intermittently irradiating the semiconductor region of the wafer in the shared container with the exciting light generated from the first light source; a second light guiding member for irradiating the semiconductor region with the measuring light generated from the second light source; reflectance measuring means for measuring the reflectance of the measuring light with which the semiconductor region is irradiated; a third light guiding means for causing the measuring light reflected by the semiconductor region to be incident upon the reflectance measuring means; and change calculating means for receiving an output of the reflectance measuring means and calculating a change rate of reflectance of the measuring light by dividing the difference between the reflectances of the measuring light when the semiconductor region is irradiated and not irradiated with the exciting light by the reflectance of the measuring light when the semiconductor region is not irradiated with the exciting light.
This achieves the following effect. When the semiconductor region is irradiated with the exciting light guided by the first light guiding member, carriers in the semiconductor region are excited to produce an electric field. Under the influe
Fourson George
Garcia Joannie Adelle
Nixon & Peabody LLP
Robinson Eric J.
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