Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state – With a step of measuring – testing – or sensing
Reexamination Certificate
1995-09-12
2002-06-25
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
With a step of measuring, testing, or sensing
C117S086000, C438S005000, C438S007000, C438S265000, C438S267000, C438S286000, C438S293000
Reexamination Certificate
active
06409828
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to organometallic vapor phase epitaxy and more particularly to an apparatus and method for achieving a desired thickness profile in a semiconductor device using a flow-flange reactor.
BACKGROUND OF THE INVENTION
A commonly used epitaxial growth technique for gallium arsenide semiconductors is organometallic vapor phase epitaxy (OMVPE). The thickness profile of an epitaxial layer is an important factor to control during the OMVPE process. Often, an epitaxial layer with uniform thickness is desirable. In some circumstances, however, such as in fabricating a quantum well laser, a non-uniform thickness profile is desirable.
Reactor designs have been developed to aid in achieving the desired thickness profile. One widely used reactor is known as a flow-flange reactor. An example of a flow-flange reactor is the GS3200 manufactured by EMCORE of Somerset, New Jersey. In the EMCORE flow-flange configuration, the flow-flange of the growth chamber has three divided concentric sections, sometimes called gas dispersing rings, through which source gases are injected and dispersed. The three gas dispersing rings are also divided in half at the center such that Group III and Group V source gases may be separately injected. Typically, the Group III and dopant source gases are injected into one side of the three sections and Group V source gases are injected into the other side. The ratios of input flows of the Group III source gases on the three gas dispersing rings normally determine the thickness profile on the layer being epitaxially grown.
The standard procedure for adjusting the flow ratios of the Group III source gases to achieve a desired thickness profile is typically based upon trial and error and can become a costly process. With the standard procedure, an empirically known desirable set of input flow ratios is normally chosen. After analyzing results achieved with the empirically known set of input flow ratios, the set of ratios are then fine tuned until the desired thickness profile is achieved. It often takes ten or more iterations to achieve the desired thickness profile even when the initial settings achieve a thickness profile near the desired thickness profile.
In current practice, a fixed input flow ratio is often used for growing each layer on a wafer. One limitation of using a fixed input flow ratio is that the thickness profile may not be maintained when different growth conditions or source gases are used. Different source gases are normally used when different materials are to be grown or if unique properties of source materials are required. Because many different source gases and growth conditions are used for the growth of device structures, the current practice of using a fixed input flow ratio is inadequate. Moreover, different thickness profiles may be desirable for different layers of a multi-layer device structure such as in a quantum well laser.
SUMMARY OF THE INVENTION
Accordingly, a need has arisen for a method and apparatus for adjusting input flow ratios in a flow-flange reactor to achieve a desired thickness profile. A need has also arisen for a method and apparatus allowing different thickness profiles to be used for different layers of a semiconductor device.
One aspect of the invention is a method for adjusting input flow ratios in a flow-flange reactor to achieve a desired thickness profile. A target thickness profile is established. A first set of optimum input flow ratios is then determined in response to the target thickness profile. The first set of optimum input flow ratios is based upon a first plurality of sample thickness profiles and a first plurality of sets of sample input flow ratios, wherein each of the sample thickness profiles corresponds to one set of the first plurality of sets of sample input flow ratios. The input flow ratios of the reactor are then adjusted in response to the first set of optimum input flow ratios.
One important technical advantage of the present invention is that the disclosed method and apparatus allow the determination of a set of optimum input flow ratios with a smaller number of trials than with the conventional trial and error method. The present invention thus saves time and money in developing a manufacturing process for a specific device. Another important advantage of the present invention is that a set of optimum input flow ratios may be determined for each layer in a multiple layer device. By adjusting input flow ratios for each layer of the device, the desired thickness profile can be achieved for each level and varying thickness profiles can be used for different levels.
REFERENCES:
patent: 4579623 (1986-04-01), Suzuki et al.
patent: 5463977 (1995-11-01), Manada et al.
patent: 5472507 (1995-12-01), Yamaguchi
Emcore Technical update Dec. 1991.
Brady W. James
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
LandOfFree
Method and apparatus for achieving a desired thickness... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for achieving a desired thickness..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for achieving a desired thickness... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2964009