Method and apparatus for conditioning the atmosphere in a...

Coating processes – Measuring – testing – or indicating

Reexamination Certificate

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C427S248100, C118S715000, C118S663000, C118S696000, C118S708000

Reexamination Certificate

active

06316045

ABSTRACT:

The present invention relates to methods and apparatus for pumping gases out from a process chamber such as a process chamber used in manufacturing semiconductor electronic components.
BACKGROUND OF THE INVENTION
In manufacturing semiconductor electronic components, an important step consists in treating a semiconductor substrate in a controlled atmosphere at very low pressure, e.g. for depositing layers of various materials by plasma deposition.
In industrial production, substrates in the form of wafers are conditioned and brought successively into a process chamber through an airlock or through a transfer chamber. In the process chamber, the atmosphere must be controlled very accurately, in particular to avoid the presence of any impurity or of any pollution.
Progress made in recent years in the semiconductor industry is essentially related to the increase in the integration of electronic circuits into components of a few square millimeters in area, defined on silicon wafers that are increasingly large.
Numerous (up to 400) technological steps are required to make such circuits, and, during the process, the pressure in the process chamber is subjected to sudden variations between various steps during which the pressure must be controlled and set to appropriate values.
Generating the low-pressure controlled-atmosphere in the process chamber requires the use of effective pumping systems. Such a system generally comprises a primary pump whose outlet is connected to atmosphere and whose inlet is connected to the outlet of a secondary pump such as a turbomolecular pump whose inlet is connected to the process chamber.
The process steps in the process chamber require the presence of special gases, and, by acting on the substrate, they generate gaseous compounds that must be removed. As a result, the pumping system must pump a variable atmosphere containing gaseous compounds that must be treated by gas treatment apparatus in order to deliver to atmosphere only compounds that are inoffensive.
Currently, pumping and gas treatment systems are situated remote from process chambers, i.e. they are connected to process chambers via long and costly pipes that are over ten meters long.
The reason behind that distance and those pipes is that current pumping and gas treatment systems are heavy and voluminous, and they give rise to adverse effects such as vibrations that it is essential to avoid in the process chamber.
Currently, an electronic component factory is therefore designed in a building having at least two levels, the upper level containing the process chamber(s), and the lower level containing the pumping and gas treatment apparatus. Pipes interconnect the two levels to convey the vacuum.
The pipes which are essential in known structures suffer from several drawbacks:
the pipes themselves generate vibrations;
the pipes constitute a large surface area on which the pumped gases can deposit in the form of particles; particles deposited in that way can backscatter from the pipe into the process chamber, thereby increasing the contamination of the chamber during subsequent steps of the process;
the pipes require major mechanical support means;
to reduce the deposits in the pipes, it is possible to provide temperature control, but such control is extremely costly and very difficult to implement;
a monitoring and control system that is complex to implement must be provided for reasons of safety in the event of leakage, since the pumped gases are harmful; and
the considerable amount of space needed requires large facilities and large floor areas for the factories; their cost is very high; losses from the cold line are non-negligible.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to integrate in the immediate vicinity of the process chamber the various elements making up the vacuum line, thereby eliminating the problems due to the piping. An object is thus to design a system that can be connected directly to the process chamber, thereby making it possible to direct the effluent as quickly as possible to the gas treatment apparatus, thereby improving the effectiveness thereof.
But the problem is then that the immediate proximity of the active members of the vacuum line constitutes an increased risk of polluting the process chamber, it being possible for the pollution to be, in particular, chemical, thermal, or mechanical. For example, the proximity of the process chamber gives rise to deposits of particles on the active members of the vacuum line, such as the pumps or the valves, thereby increasing the risk of pollution by backscattering towards the process chamber.
For this reason, the invention aims both to reduce the cost of the installations by avoiding the presence of pipes between the process chamber and the pumping and gas treatment apparatus, and also to reduce the risks of polluting the process chamber.
Another object of the invention is to facilitate adapting the pumping system to various process chamber structures, by optimizing the effectiveness of the process control in the process chamber.
Another object of the invention is to improve the effectiveness of the gas treatment in order to eradicate or to reduce appropriately any discharge to the atmosphere of toxic matter.
Another object of the invention is to make it possible to dispose the pumping means in the immediate vicinity of the process chamber, in particular by reducing the size of said means.
To achieve these objects and others, the invention provides a method of conditioning the atmosphere in a process chamber for treating a substrate, in which method:
the gases are pumped out from the process chamber by means of a primary pump and of at least one secondary pump;
the pumping speed is adjusted so as to maintain the pressure adapted to each treatment step in the process chamber;
the extracted gases are analyzed upstream from the primary pump; and
the result of the analysis of the extracted gases is used to adjust the pumping speed as a function of the pumped gases, so as to determine the variation in the pressure inside the process chamber during the stages of the treatment.
In an advantageous implementation, to adjust the pumping speed as a function of the extracted gases, a pre-recorded transfer function is used which, for each gas mixture present in the process chamber during the treatment, represents the relationship between the pumping speed, the flow rate, and the resulting pressure in the process chamber.
By improving the control over the pumped gases, it is advantageously possible to make provision for said at least one secondary pump to be connected to the process chamber via a pipe of length shorter than three meters.
For example, said at least one secondary pump may be adjacent to the process chamber.
Preferably, in the invention, the gas treatment function is integrated into the pumping line by:
treating the gases downstream from the primary pump; and
analyzing the gases at the outlet of the primary pump so as to determine their nature and their state and so as to adapt the pumping parameters, constituted by the temperature of the primary pump, the injection of dilution gas into the primary pump, and the speed of the primary pump, in order to optimize the effectiveness of their treatment.
Preferably, the gases are also analyzed on exiting from the treatment so as to adapt the treatment as a function of the result of said analysis. It is possible to interrupt the pumping in the event that a treatment defect is detected by said analysis of the gases exiting from the treatment.
In order to make it easier to adapt the pumping means to various process chamber structures, it is advantageously possible to make provision to cause the pumping speed to vary during a prior training step in the presence of at least some of the gas mixtures that can be present during the treatment steps in the process chamber, and the resulting pressure in the process chamber is measured to determine said transfer function.
The invention also provides apparatus for conditioning the atmosphere in a process chamber for tr

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