Metal working – Barrier layer or semiconductor device making
Reexamination Certificate
2001-02-27
2004-08-17
Fourson, George (Department: 2823)
Metal working
Barrier layer or semiconductor device making
C438S908000
Reexamination Certificate
active
06776805
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor manufacturing method which provides epitaxial growth and the like on the surface of a silicon substrate placed in, for example, a reaction chamber, by using reactive gas (corrosive gas).
2. Description of the Related Art
Manufacturing processes for providing a semiconductor circuit such as an LSI on a silicon substrate include selectively and epitaxially growing a silicon thin-film on the surface, providing a pattern comprising an SiO
2
film (silicon oxide) on the surface of a silicon substrate W, and epitaxially growing a silicon film in a region where the silicon is exposed, vapor-depositing a single-crystal silicon thin-film (epitaxial layer) having a predetermined concentration of impurity on a substrate for a MOS device comprising a silicon substrate having extremely low resistivity, and the like.
In these manufacturing processes, the silicon substrate is placed inside a process chamber and a reactive source gas is injected therein to grow the epitaxial layer on the substrate.
Other manufacturing processes using reactive gas include a variety of CVD processes for providing a thin-film on a substrate by the reaction of the reactive gas, and etching processes for providing micro-patterns, etc.
The reactive gas used in these semiconductor manufacturing apparatuses comprises a corrosive gas, such as ultra-high purity hydrogen chloride gas or ammonia gas. However, when the gas contains even a small amount of moisture, the metal components used in the apparatus (e.g. in the process chamber, gas supply system, gas discharge system, etc.) become susceptible to corrosion. This leads to hazardous pollution caused by metal (heavy metal) from the metallic sections. Consequently, there is a demand for a highly sensitive method for quantitative analysis of the moisture in corrosive gas inside the process chamber.
Conventionally, the only means of investigating the interrelation between processing conditions and heavy metal pollution, and the interrelation between processing conditions and the characteristics of the reactive gas processing, has been to feed back results obtained by directly analyzing a processed monitor wafer by using chemical analysis (atomic absorption spectrometry, radioactivation analysis, etc.), physical analysis (SIMS, TXRF, etc.), and electrical analysis (DLTS, SPV, lifetime, etc.).
In recent years, means for measuring the moisture content in reactive gas (corrosive gas) comprising a laser moisture measuring device which radiates laser light into the main body of a tube-like cell, connected to a process chamber, and measures the absorption spectrum of the transmitted light, has been proposed in, for example, Japanese Unexamined Patent Application, First Publication (Kokai), No. Hei 5-99845, Japanese Unexamined Patent Application, First Publication (Kokai), No. Hei 11-183366 and the like. Since the laser moisture measuring device can measure the gas without contact with the gas, it can measure even reactive gas with high precision. Therefore, it has become possible to measure the moisture content inside the process chamber even during processing.
However, the conventional semiconductor manufacturing technology described above does not address the following problems. During the actual processing, the moisture content inside the process chamber is not always constant in each process. Even when conditions are set after feeding back the results of analysis of the process monitor wafer, fluctuation in the moisture content causes variation in the characteristics of the reactive gas processing. For example, in the case of the selective epitaxial growth already mentioned, the moisture (absorbed moisture) of the SiO
2
film may be removed during pre-processing baking of the substrate, whereby the moisture content inside the process chamber increases. In this case, the moisture content increases during selective epitaxial growth, affecting the characteristics of the selectability of the selective growth and the selectively deposited film.
Furthermore, the moisture within the process chamber does not come only from the reactive gas pipes, and may be caused by atmosphere seeping in from other outside regions. This also increases the moisture content, making it difficult to determine the cause of fluctuations in the moisture content merely by measuring the moisture content in the process chamber. Nor is it clear what level of moisture content within the process chamber will make it possible to adequately control the effects of heavy metal pollution. For example, as shown in
FIG. 9
, an investigation of the relationship between the recombination lifetime and the moisture of discharged gas during the reaction reveals that the lower the moisture content, the longer the lifetime. However, there is a considerable difference between the average lifetime (solid line) and the maximum lifetime (broken line). This is due to spots of heavy metal pollution on the surface of the substrate.
SUMMARY OF THE INVENTION
The present invention has been realized after consideration of the above problems. It is an object of this invention to provide a semiconductor manufacturing method whereby reactive gas processing, such as selective epitaxial growth, can be carried out with high precision by correctly adjusting conditions during processing.
It is another object of this invention to provide a semiconductor manufacturing method and a semiconductor manufacturing apparatus which can restrict increases in the moisture content, prevent heavy metal pollution and the like, and investigate the correlation between moisture content in the process chamber and outside regions.
In order to solve the problems mentioned above, the semiconductor manufacturing method according to a first aspect of this invention provides a semiconductor manufacturing method which performs reactive gas processing, the reactive gas being fed into a reaction chamber, into which a substrate is placed, and reacting with the substrate. The method comprises measuring the moisture content in the reaction chamber, into which the substrate is placed, and in a gas discharge system of the reaction chamber, and adjusting conditions for processing the reactive gas based on the moisture content
In this semiconductor manufacturing method, the moisture content in the reaction chamber, into which the substrate is placed, and in a gas discharge system of the reaction chamber, is measured, and the conditions for processing the reactive gas are adjusted based on the moisture content. Therefore, it is possible to adjust the moisture content itself (correcting it to within an appropriate range) and conditions for film-formation, etching, and the like, based on the measurement of the moisture content during actual processing. This makes it possible to achieve highly precise and stable processing which takes into consideration the effects of moisture content on the characteristics of the reactive gas processing.
Preferably, in the semiconductor manufacturing method according to the first aspect of this invention, the conditions for processing the reactive gas should comprise conditions for heating the substrate prior to feeding the reactive gas into the reaction chamber.
In this semiconductor manufacturing method, the conditions for heating the substrate (baking conditions) are adjusted prior to feeding the reactive gas into the reaction chamber. Therefore, moisture in the substrate can be sufficiently removed prior to feeding the reactive gas into the reaction chamber, and the moisture content inside the reaction chamber can be adjusted to an appropriate level, and the like, thereby making the processing more stable.
The conditions for heating which are adjusted comprise at least one of the heating temperature of the substrate, the heating time of the substrate, and the amount of purge gas.
Preferably, in the semiconductor manufacturing method according to the first aspect of this invention, the conditions for processing the reactive gas should compr
Hasegawa Hiroyuki
Ishihara Yoshio
Masusaki Hiroshi
Yamaoka Tomonori
Estrada Michelle
Mitsubishi Materials Silicon Corporation
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