Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2000-08-01
2003-11-11
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S327000, C355S030000
Reexamination Certificate
active
06645701
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an exposure apparatus, exposure method, method of controlling substrate stage and method of controlling mask stage, and in particular to such apparatus and methods taking into consideration various temperature-related environmental factors of an exposure apparatus, such as the temperature changes with time which may occur in the exposure apparatus and the temperature gradients prevailing in the exposure apparatus.
Over the years, it has been continuously desired to achieve higher and higher complexity in semiconductor devices, which in turn has required higher accuracy in positioning of a photosensitized substrate and a mask in exposure apparatuses. One of the important factors affecting the accuracy in positioning of a mask and a photosensitized substrate is the ambient air temperature, which is one of the environmental factors affecting an exposure apparatus. Specifically, in an exposure apparatus including some kind of optical position measurement devices such as interferometers, instability in an ambient air temperature in the exposure apparatus may produce non-negligible air fluctuations in the optical paths of the interferometers and/or cause uneven heat expansions of various components in the apparatus such as a stage for carrying a mask and a stage for carrying a photosensitized substrate. For this reason, it has become common to house the entire exposure apparatus in a constant temperature chamber. In such a constant temperature chamber, one or more stream of temperature-controlled air is introduced therein so as to flow around the exposure apparatus, so that the apparatus may be kept at substantially a constant temperature. This may suppress undesirable temperature changes to a certain extent, which temperature changes may occur during exposure operations performed by the exposure apparatus.
However, this technique is insufficient for improving accuracy in positioning of a mask and a photo-sensitive substrate such as meets today's requirements.
By way of example, consider an exposure apparatus of the step-and-repeat type, in which a pattern formed on a mask is transferred onto a photosensitive substrate through a step-and-repeat exposure sequence. The exposure apparatus comprises a movable substrate stage for carrying a substrate, and the substrate stage is caused to wait at a predefined position, such as the loading position for loading on/off the substrate, for a time interval during which no exposure process is performed. Also, in an exposure apparatus of the type in which a photosensitized substrate and a mask are moved in synchronism by means of a substrate stage and a mask stage, the mask stage carrying the mask is generally caused to wait at a predefined position for a time interval during which no exposure process is performed.
In either case, the exposure apparatus produces more heat (per unit of time) during an exposure process than in a waiting interval prior to the commencement of the exposure process, so that the temperatures at regions near and around the exposure apparatus may not be stable until a substantial length of time, such as some tens of minutes to several hours, has elapsed from the commencement of the exposure process. As a result, the temperatures of some components of the exposure apparatus will often change with time during an exposure process, which leads to a substantial deviation in the measurements obtained from the position measurement systems used, between those obtained just after and those obtained several hours after the commencement of the exposure process. Apparently, such deviation will cause a deterioration in accuracy in the alignment established for an exposure operation, which may result in an exposure failure.
Further, the temperature distribution within the exposure apparatus is not uniform, especially around the substrate stage and/or the mask stage, because the exposure apparatus has several heat sources which produce temperature gradients. In addition, any changes in position of the substrate stage or the mask stage may vary the courses of the air streams flowing within the exposure apparatus, which may in turn lead to variations in temperature gradients within the exposure apparatus. Therefore, if the waiting positions for the substrate stage and the mask stage are defined without taking into consideration the temperature-related environmental factors within the exposure apparatus, the stability of an exposure process has to have certain limitations imposed thereon, such as possible occurrence of significant errors in the alignment accuracy due to temperature gradients.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide an exposure apparatus which is capable of suppressing any inconveniences which could be otherwise imposed by the temperature changes with time around the exposure apparatus.
It is another object of the present invention to provide an exposure method, in which the temperature at a region near at least one of a mask having a pattern formed thereon and a photosensitized substrate onto which the pattern of the mask is to be transferred by exposure is so adjusted that any inconvenience is avoided, which could be otherwise occur due to temperature changes with time around the exposure apparatus.
It is a further object of the present invention to provide a method of controlling a substrate stage in an exposure apparatus, in which the substrate stage is caused to wait at a position in the exposure apparatus at which stability against heat is obtained, so that the temperature gradients in the exposure apparatus and the effects of any changes in these temperature gradients may be minimized.
It is a yet further object of the present invention to provide a method of controlling a mask stage in an exposure apparatus, in which the mask stage is caused to wait at a position in the exposure apparatus at which stability against heat is obtained, so that the temperature gradients in the exposure apparatus and the effects of any changes in these temperature gradients may be minimized.
It is a still further object of the present invention to provide an exposure apparatus including a control system for a substrate stage, in which the substrate stage is caused to wait at a position in the exposure apparatus at which stability against heat is obtained, so that the temperature gradients in the exposure apparatus and the effects of any changes in these temperature gradients may be minimized.
It is a still further object of the present invention to provide an exposure apparatus including a control system for a mask stage, in which the mask stage is caused to wait at a position in the exposure apparatus at which stability against heat is obtained, so that the temperature gradients in the exposure apparatus and the effects of any changes in these temperature gradients may be minimized.
According to an embodiment of the present invention, there is provided an exposure apparatus for transferring a pattern formed on a mask onto a photosensitized substrate by exposure, comprising: a temperature measurement device for measuring temperature at a region near at least one of the mask and the photosensitized substrate; and a temperature adjustment device for comparing measurement data from the temperature measurement device with a preset desired value so as to adjust, prior to an exposure process, temperature at the region near at least one of the mask and the photosensitized substrate to an equilibrium temperature which would be established during an exposure process.
In the embodiment of the present invention described above, the exposure apparatus may further comprise a decision making device for determining, based on measurement results from the temperature measurement device and the equilibrium temperature, whether an exposure process is to be performed or not. In the case where the mask and the photosensitized substrate is held on respective stages each capable of two-dimensional movement, temperature adjustment ma
Ota Kazuya
Takagi Shin-ichi
Armstrong Westerman & Hattori, LLP
Huff Mark F.
Nikon Corporation
Sagar Kripa
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