Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
1999-05-14
2001-10-16
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C250S216000
Reexamination Certificate
active
06303917
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to apparatuses and methods for monitoring radiant energy delivered to a substrate. The radiant energy can be generated by a laser or flash lamp, for example. The apparatuses and methods of the invention can be used to monitor radiant energy supplied to a substrate to anneal integrated devices or circuits formed thereon, or to expose a resist layer in the performance of photolithography. The apparatuses and methods can also be used to monitor radiant energy supplied to heat a substrate to form silicide contacts coupling source/drain or gate contacts to conductive metal lines or wiring. In addition, the apparatuses and methods can be used to monitor radiant energy that triggers a chemical reaction to deposit reactant products onto a substrate, or conversely, to remove material from a substrate, for example.
2. Description of the Related Art
FIG. 1
is a general diagram of a previous device
1
for monitoring the amount of energy delivered to a substrate
2
. The device
1
generally includes a laser
3
generating radiant energy
4
, a beam splitter
5
, optical element(s)
6
, a stage
7
, and an energy detector
8
. The radiant energy
4
, i.e., laser light, is supplied to the beam splitter which reflects a portion of the incident radiant energy
4
′ to the optical element(s). The optical element(s) includes one or more mirrors or lenses which modify the radiant energy
4
′ in some predetermined fashion. For example, the optical element(s) can be used to focus the radiant energy
4
′ onto the substrate, or to magnify or reduce the radiant energy's image field. The optical element(s) directs the light to the substrate which is positioned on the stage. A portion of the radiant energy
4
″ generated by the laser is transmitted through the beam splitter and impinges on the energy detector. The device
1
monitors the amount of radiant energy
4
′ supplied to the substrate by determining the amount of radiant energy
4
″ received by the energy detector.
The proper functioning of the device
1
depends upon the assumption that the radiant energy
4
″ tapped upstream along the optical path from the optical element(s), is related in a fixed manner to the amount of radiant energy
4
′ supplied to the substrate downstream along the optical path from the optical element(s). Although the amount of radiant energy
4
″ received by the energy detector may be related to the radiant energy
4
′ delivered to the substrate upon calibration of the device
1
and shortly thereafter, such relationship generally changes with time due to thermal or mechanical drifts of the optical element(s) or changes in the performance thereof. As a result, the actual amount of radiant energy
4
′ delivered to the substrate may be significantly different than expected, leading to over- or under-treatment of the substrate with the radiant energy
4
′ and consequent failure of the radiant-energy processing of the substrate. It would be desirable to overcome this disadvantage of previous devices and techniques used to monitor the radiant energy supplied to a substrate.
SUMMARY OF THE INVENTION
This invention has as its objects to overcome the disadvantages of previous devices and techniques as noted above, and does in fact overcome such disadvantages.
The invented apparatuses and methods can be used to monitor the radiant energy delivered to a substrate for treatment thereof. The apparatus can include a source for generating radiant energy. The source can be a laser or flash-lamp, for example. The apparatus also can include one or more optical elements such as a mirror(s), lens(es) or filter(s), for example, for modifying the radiant energy in a predetermined fashion. The apparatus includes an energy-tapping member which is positioned to receive the radiant energy from the optical element(s), and which divides the modified radiant energy into first and second portions. The first portion of radiant energy travels from the energy-tapping member to the substrate for treatment thereof. The apparatus also includes an energy sensor positioned to receive the second portion of the radiant energy from the energy-tapping member. The energy sensor generates a sensor signal indicative of the radiant energy supplied to the substrate, based on the second portion of radiant energy. Because the energy-tapping member is positioned downstream from the source and optical element(s) along the optical path traveled by the radiant energy, it should be appreciated that drift in the source or optical element(s) has no significant impact on the ability of the energy-tapping member and energy sensor to detect the radiant energy supplied to the substrate. Therefore, the apparatus can determine the amount of radiant energy supplied to the substrate with significantly greater accuracy as compared to previous devices.
The apparatus can further include a processing unit coupled to receive the sensor signal from the energy sensor. The processing unit can be implemented to relate sample data derived by sampling the sensor signal at a predetermined time increment, to energy data indicative of the first portion of radiant energy supplied to the substrate. The processing unit can use predetermined relationship data generated in a calibration mode of the apparatus to relate the sample data to corresponding energy data. In the operation mode, the processing unit uses the prestored relationship data to convert the sample data into energy data that indicates the radiant energy provided to the substrate over a predetermined time increment. The processing unit can use the energy data to generate a signal indicative of the radiant energy supplied to the substrate for corresponding sampling time increments. In addition, the processing unit can integrate the energy data to generate a signal indicative of the amount of energy supplied to the substrate in a single pulse or series of pulses of radiant energy generated by the source. The processing unit can also generate a display signal based on the energy data. The apparatus can include a display unit coupled to receive the display signal, to generate a visual display of the radiant energy supplied to the substrate, based on the display signal.
A method of this invention can include a step of generating and directing radiant energy to at least one optical element, and a step of modifying the radiant energy with the optical element. The method includes a step of dividing the radiant energy from the optical element into first and second portions. The first portion of the radiant energy travels to a substrate for treatment thereof. The method also includes a step of sensing the second portion of radiant energy, and generating a sensor signal indicative of the first portion of radiant energy supplied to the substrate, based on the sensed second portion of the radiant energy. The method can further include a step of integrating the sensor signal to generate a signal indicative of the amount of radiant energy supplied to the substrate. The method can also include a step of generating a display signal, based on the sensor signal, and a step of generating a visual display, based on the display signal.
These together with other features and advantages, which will become subsequently apparent, reside in the details of the invented apparatuses and methods as more fully hereinafter described and claimed, reference being made to the accompanying drawings, forming a part hereof wherein like numerals refer to like parts throughout the several views.
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patent: 4689482 (1987-08-01), Horikawa et al.
patent: 5004338 (1991-04-01), Morrow
patent: 5122635 (1992-06-01), Knodler et al.
patent: 5430816 (1995-07-01), Furuya et al.
patent: 5529630 (1996-06-01), Imahashi et al.
patent: 5580471 (1996-12-01), Fukumoto et al.
patent: 5581075 (1996-12-01), Naraki et al.
patent: 5751423 (1998-05-01), Traina et al.
patent: 5754571 (199
Jones Allston L.
Le Que T.
Ultratech Stepper, Inc.
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