Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2001-04-04
2004-10-26
Rodriguez, Paul (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S019000, C700S077000, C700S121000, C165S206000
Reexamination Certificate
active
06810298
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a temperature adjustment apparatus in, e.g., an alignment stage apparatus such as an exposure apparatus or a high-precision processing apparatus requiring precise alignment, an exposure apparatus having the temperature adjustment apparatus, and a semiconductor device manufacturing method.
BACKGROUND OF THE INVENTION
A projection exposure apparatus (e.g., a stepper or the like) used in photolithography for manufacturing a semiconductor element, liquid crystal display element, or the like, transfers at a high precision a pattern formed on a master such as a reticle or photomask onto a substrate such as a wafer or glass plate coated with a photoresist via a projection optical unit. For this purpose, very high imaging characteristics are demanded for the projection optical unit, and a high measurement precision is demanded for, e.g., a laser interferometer for measuring the alignment of a stage which supports a substrate such as a master or wafer.
The imaging characteristics of the projection optical unit and the measurement precision of the laser interferometer are greatly influenced by changes in apparatus and ambient temperatures. The laser interferometer causes fluctuations of a laser beam upon a change in ambient temperature, degrading the measurement precision.
At the same time, a member holding a mirror as a measurement target of the laser interferometer deforms owing to the temperature change, the relative alignment of a substrate and the mirror serving as an alignment reference change, and the measurement precision decreases. Recently, demands have arisen for an alignment precision of a nanometer (nm) order. For example, even if a 100-mm thick low-temperature thermal expansion member (thermal expansion coefficient: 1×10
−6
) deforms by 100 nm upon a temperature change of 1° C., and the air temperature on the laser path of the laser interferometer changes by 1° C., the alignment measurement value may change by 100 nm depending on conditions. Hence, the temperatures of the building components of the projection exposure apparatus and its ambient temperature must be kept constant.
In a conventional projection exposure apparatus, a temperature rise of the apparatus by a heating member such as an exposure light source or a driving motor for driving a stage degrades the measurement precision of, e.g., the laser interferometer for measuring the stage alignment and the imaging characteristics of the projection optical unit.
In some cases, a temperature change of air changes the ambient temperature of the projection exposure apparatus, degrading the imaging characteristics of the projection optical unit. To prevent this, global air-conditioning is generally performed in which the projection exposure apparatus is stored in an environment control chamber, and temperature-controlled air is supplied into the chamber.
An exposure apparatus requiring precise temperature management undergoes temperature management by a combination of global air-conditioning and a method of directly supplying a temperature-controlled coolant such as air or water to a portion to be cooled. For example, to keep the measurement precision of the laser interferometer constant, air controlled to a predetermined temperature in a predetermined direction is supplied into a local space in the optical path of a laser beam between the laser interferometer and a mirror for reflecting a laser beam from the laser interferometer. To recover and remove heat generated by, e.g., a driving motor for driving a reticle stage or wafer stage, a cooling circulation pipe surrounds the driving motor, and a coolant such as water, air, or an inert liquid is circulated from an external temperature adjustment apparatus to the circulation pipe.
The temperature is controlled by setting a temperature sensor at or near a portion to be temperature-controlled, changing the flow rate or temperature of a coolant on the basis of an output from the temperature sensor, and adjusting the heat recovery amount (see Japanese Patent Laid-Open Nos. 7-302124 and 7-302747).
FIG. 14
is a view schematically showing an example of the driving device of an alignment stage in a conventional exposure apparatus. A wafer
501
is held by a top plate
503
of an alignment stage via a wafer chuck
502
. A pattern formed on a master (not shown) such as a reticle is transferred onto the wafer
501
by irradiation light from an illumination optical unit (not shown) via a projection lens (not shown). The alignment stage aligns the wafer by relatively moving linear motors made up of a movable element
505
to which permanent magnets
506
are fixed and a stationary element
507
in which a plurality of coils
508
are buried, in accordance with driving signals from a controller
511
and driver
512
. The movable element
505
is guided by hydrostatic bearings
524
and connected to linear motors
526
for vertical movement. The top plate
503
is set via the movable element
505
and linear motors
526
. The stationary element
507
has a plurality of coils
508
and is constituted by a jacket structure so as to flow a coolant for recovering heat generated by the coils
508
.
A mirror
504
is attached to the top plate
503
, and the alignment of the top plate
503
is measured by an alignment measurement unit
516
such as a laser interferometer fixed to an alignment position where the unit
516
faces the mirror
504
. A measurement value from the alignment measurement unit
516
is sent to the controller
511
. The controller
511
controls the energization amount to the coil
508
of each linear motor via the driver
512
on the basis of the measurement value, drives and controls the linear motor, and drives and aligns the alignment stage at a high precision.
The stationary element
507
is connected to a coolant pipe
518
for circulating a coolant temperature-managed by a cooling unit
517
, in order to prevent heat generated by each coil
508
upon driving the linear motor from conducting to air or a member and increasing the temperatures of the top plate
503
and wafer
501
. The temperature-managed coolant drains heat generated by the coil
508
and is recovered by the cooling unit
517
outside the driving device. To compensate for the temperature, a temperature control unit
513
receives temperature data from a temperature measurement unit
515
for outputting temperature data measured by a temperature sensor
514
set on the movable element
505
, and instructs the cooling unit
517
to control the temperature or flow rate of the coolant so as to minimize temperature changes of the movable element
505
and top plate
503
. In addition, the temperature control unit
513
supplies to the linear motors via the coolant pipe
518
a coolant which is managed in temperature and adjusted in flow rate by the cooling unit
517
. The temperature-managed coolant absorbs heat generated by the linear motor stationary element
507
, and suppresses temperature changes of the movable element
505
, top plate
503
, and wafer
501
.
In this prior art, to precisely manage the temperatures of a plurality of heating portions, {circle around (1)} a necessary amount of coolant temperature-controlled in accordance with the respective heating portions is supplied to the heating portions, or {circle around (2)} a coolant of the same temperature is supplied to all the heating portions after the flow rate is secured such that the coolant temperature after absorbing heat generated by all the heating portions is equal to or smaller than the allowable rise temperature of the apparatus. In {circle around (1)}, the pipe for supplying the coolant is complicated. Particularly to manage the temperature of the wafer stage or the like, problems such as a load resistance to driving due to the pipe rigidity and a location ensured to lay out the pipe must be solved. For example, to individually control the temperatures or flow rates of the respective linear motors when the linear motors have different driving patterns, the num
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