Semiconductor device manufacturing: process – With measuring or testing – Optical characteristic sensed
Reexamination Certificate
1999-12-08
2002-11-05
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
With measuring or testing
Optical characteristic sensed
C438S014000, C117S008000
Reexamination Certificate
active
06475815
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of measuring a temperature and a temperature distribution in a specified region of a chamber, to a method of taking samples for temperature measurement, and to a method for fabricating a semiconductor device by using the method of measuring a temperature.
The fabrication of semiconductor devices includes such processes as CVD, ion implantation, heat treatment (annealing), and plasma etching whereby a film is formed on a wafer, an impurity is introduced into the wafer, a diffusion layer is formed by activating the impurity, and the film formed is patterned. These processes should be performed under proper conditions determined individually, among which is a temperature. In particular, a temperature at a certain portion of a wafer placed in a chamber and a temperature distribution over a surface of the wafer are important parameters in controlling such processes as CVD and heat treatment.
To measure a temperature and a temperature distribution during the individual fabrication processes, various methods have been adopted conventionally.
For example, a thermocouple is mounted on a chamber for performing an RTA process as a rapid thermal anneal process or on a back surface of a wafer (TC wafer). There is also known a method of measuring a temperature in a chamber by optical measurement using the detection of an IR ray.
However, the conventional methods of measuring a temperature have the following disadvantages.
In the temperature measurement method using the TC wafer, for example, the temperature of the top surface of the wafer is unknown though the temperature of the back surface of the wafer can be detected. In addition, a temperature range that can be measured is limited so that measurement accuracy reportedly deteriorates when a certain high temperature is reached (500 to 600° C. or more).
On the other hand, the optical measurement is also disadvantageous in that accurate temperature measurement cannot be performed because of optical noise or the like produced under the influence of a plasma. Moreover, a temperature distribution over a surface of a wafer cannot be measured by merely detecting temperature values at a limited number of points.
In particular, it is difficult to perform highly reliable measurement with respect to a temperature distribution over a surface of a wafer even by using the TC wafer.
SUMMARY OF THE INVENTION
A first object of the present invention is to perform temperature measurement by focusing attention on the fact that the anneal-induced reordering process of a portion changed by ion implantation from a monocrystalline state to an amorphous region is dependent on temperature and on conditions during implantation, measuring the thickness of the amorphous region by using spectro ellipsometry or the like, and calculating a temperature from the measured thickness and thereby increase the accuracy of temperature measurement.
The present inventors have found, in an attempt to increase the accuracy of temperature measurement by using spectro ellipsometry, a close correlation between a process for increasing the accuracy of temperature measurement and an improvement in the configuration of the amorphous region. A second object of the present invention is to improve, based on the finding, conditions during preamorphous implantation which is performed for preventing channeling or as one of preliminary processes for a silicidation process.
A first method of measuring a temperature according to the present invention comprises the steps of: (a) doping an amorphous region formed in a semiconductor region of a substrate with oxygen; (b) heating the amorphous region for a given time and determining a reordering rate at which the amorphous region is recrystallized; and (c) determining a temperature of the amorphous region in the step (b) based on a relationship between the reordering rate of the amorphous region and a heating temperature, which has been prepared in advance.
In accordance with the method, the reordering rate during the heating of the amorphous region can be adjusted by adjusting the concentration of oxygen and temperature measurement can be performed in a desired temperature range.
The step (a) includes doping the amorphous region with oxygen such that a concentration of oxygen reaches a critical value for holding the reordering rate in the step (b) nearly constant from the initiation of the heating. Accordingly, the determination of the reordering rate, i.e., temperature measurement is performed with ease and high reliability. In
In the case where an oxide film is formed on the semiconductor region of the substrate before the step (a) is performed, the method may further comprise the step of forming, prior to the step (a), the amorphous region by implanting impurity ions into the semiconductor region.
In accordance with the method, the adverse effect of oxygen that has been knocked on by the implantation of impurity ions and entered the amorphous region can be circumvented.
Alternatively, the method further comprises the step of removing, prior to the process performed in the step (a), a natural oxide film on the semiconductor region therefrom under a reduced pressure and the step (a) is performed without exposing the substrate to an atmosphere and by holding the substrate under a reduced pressure after the step of removing the natural oxide film. Accordingly, the oxygen concentration can be adjusted reliably to a desired value.
The step (b) is performed by using spectro ellipsometric measurement of a thickness of the amorphous region, which enables in-line temperature measurement.
A second method of measuring a temperature according to the present invention comprises the steps of: (a) forming an amorphous region in a semiconductor region of a substrate by implanting therein ions of a IV group element; (b) heating the amorphous region for a given time and determining a reordering rate at which the amorphous region is recrystallized; and (c) determining a temperature of the amorphous region in the step (b) based on a relationship between the reordering rate of the amorphous region and a heating temperature, which has been prepared in advance.
In accordance with the method, the amorphous region can be formed without affecting the conductivity type of the semiconductor region.
The step (a) includes implanting Ge ions under such a condition that a dose is 1×10
15
atoms·cm
−2
or more, which provides a distinct boundary between the amorphous region and the crystal region in the semiconductor region and increases the accuracy and reliability of temperature measurement.
A third method of measuring a temperature according to the present invention comprises the steps of: (a) forming an amorphous region in a semiconductor region of a substrate by implanting therein ions of at least one of arsenic (As), phosphorus (P), a halogen element, and an inert gas element; (b) heating the amorphous region for a given time and determining a reordering rate at which the amorphous region is recrystallized; and (c) determining a temperature of the amorphous region in the step (b) based on a relationship between the reordering rate of the amorphous region and a heating temperature, which has been prepared in advance.
In accordance with the method, the accuracy and reliability of temperature measurement leading to an elongated maintenance period and a reduced number of semiconductor fabricating apparatus can be increased without using a corrosive gas such as GeF
4
.
A fourth method of measuring a temperature according to the present invention comprises the steps of: (a) forming a plurality of amorphous regions in a plurality of portions of a semiconductor region of a substrate by implanting ions therein under different conditions; (b) heating the plurality of amorphous regions for a given time and individually determining respective reordering rates at which the amorphous regions are recrystallized; and (c) determining respective temperatures of the amorphous regions in the step (b) which corre
Nambu Yuko
Shibata Satoshi
Malsawma Lex H.
Matsushita Electric - Industrial Co., Ltd.
Nixon & Peabody LLP
Smith Matthew
Studebaker Donal R.
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