JP2646413B2 - Projection exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Projection exposure method for projecting and exposing a substrate (wafer), especially semiconductor
After adjusting the temperature of the body substrate, step the pattern of the original
Projection exposure to semiconductor substrate by AND repeat method
The present invention relates to a shadow exposure method.

[0002]

2. Description of the Related Art In a projection exposure apparatus, a wafer carried in from outside the apparatus is transferred onto a wafer chuck via a wafer transfer system, is attracted to the wafer chuck, and is then projected. Exposed. In general, the temperature of a wafer is different from the chuck temperature when the wafer is loaded from outside the apparatus, but approaches the chuck temperature during wafer transfer mainly due to heat conduction with ambient air. FIG. 4A shows how the wafer temperature changes when a 6-inch wafer is carried into a conventional projection exposure apparatus. In FIG. 4A, it is assumed that a wafer having a temperature of 21.2 ° C. is carried in at time 0, and absorbed by a chuck having a temperature of 20 ° C. after about 20 seconds. The wafer being transported is about 0.
It was assumed that the temperature approached the ambient air temperature (20 ° C.) with a thermal resistance of 3 C / W, and approached the chuck temperature with a thermal resistance of 0.08 C / W after adsorption. On the other hand, it is known that the coefficient of linear expansion of a silicon wafer is 4.2 ppm / ° C. FIG. 4B shows the expansion and contraction of the wafer on the same time scale as FIG. 4A. The expansion and contraction of the wafer at 20 ° C. is shown as 0 ppm. In FIG. 4B , the temperature of the wafer at the time of chucking the chuck is about 0.5 ° C. higher than that of the chuck, and therefore, the wafer is sucked while being elongated by about 2.1 ppm. The temperature difference between the wafer and the chuck at the time of suction is determined mainly by the elapsed time after the wafer is loaded into the apparatus. Generally, a wafer transfer system transfers a wafer in a pipeline format. At this time, since the sequential transfer time is designed to be shorter than the exposure time for one wafer, the second and subsequent wafers wait at some stage on the transfer system. Therefore, the elapsed time of the first wafer and the elapsed time of the second and subsequent wafers are significantly different. In addition, a large-scale temperature control mechanism is required to keep the temperature of each part of the wafer transfer system uniform, for example, within a range of 0.5 ° C. Usually, there is a temperature difference of about 0.5 ° C. in each part in the transport system. Therefore, the temperature of each wafer at the time of chucking the chuck differs from one another depending on the ambient temperature during the transfer and the standby state of the wafer. As a result, the following three problems are caused. (1) Even if the magnification of the projection exposure system is strictly controlled, the size and the interval of the pattern actually projected and exposed differ from wafer to wafer due to thermal expansion (reduction) of the wafer. (2) During and immediately after the suction operation, stress is generated between the wafer that is going to have a size corresponding to the temperature and the chuck that is trying to keep the wafer at a certain size. For this reason, when the wafer is deformed by the suction operation or the suction force is weakened by a foreign substance or the like, the magnification changes during the exposure. (3) In the case of an apparatus that performs exposure by the step-and-repeat method, the step interval varies for each wafer.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object the purpose of step-and-repeat.
When exposing a semiconductor substrate by the
It is possible to adjust the temperature of the plate,
Prevents variations in plate deformation and improves pattern exposure accuracy
To provide a projection exposure method.

[0004]

According to the present invention, there is provided a substrate cassette (wafer cassette).
The semiconductor substrate (wafer) stored is transferred by the substrate transfer system.
The wafer is transferred onto a substrate chuck (wafer chuck)
After the substrate is sucked on the substrate chuck, the original
To the projection optical system for projecting the pattern
The semiconductor substrate adsorbed on the plate chuck is
Move by step and move by the XY stage
Step movement and illumination of the original by the illumination system are alternately repeated.
The semiconductor substrate by performing an exposure sequence
A projection for projecting and exposing the pattern of the original plate on
In the shadow exposure method, the base
Temperature controller for adjusting the temperature of the semiconductor substrate on a plate chuck
(Wafer temperature controller), and the substrate transfer system
The semiconductor substrate is placed on the substrate chuck from a plate cassette.
When transported, the semiconductor substrate on the substrate chuck is
Move to the air filter side by the XY stage
And by the temperature controller through the air filter
Adjusting the temperature of the semiconductor substrate;
Has a predetermined relationship with the temperature of the substrate chuck.
Later, the semiconductor substrate is adsorbed to the substrate chuck, and
Executing the exposure sequence on the projection optical system side
Features.

[0005]

According to the present invention , a transfer system is provided on a substrate chuck.
The semiconductor substrate transported by
The temperature is adjusted by moving to
Step and repeat on the projection optical system side
An exposure sequence according to a printing method is performed. That is,
According to Ming, the location where the temperature of the substrate is
Where the exposure sequence takes place will be separated
So, the temperature of the substrate by the temperature controller through the air filter
The possibility that the key affects the projection optical system can be reduced. Ma
In addition, the movement to the air filter side is
XY stay for step-moving the substrate on the substrate chuck
On the substrate chuck by the transfer system.
After the semiconductor substrate is transported, an exposure sequence for the substrate is performed.
The time until the start of the licensing can be shortened. For this reason,
According to the present invention, high-precision pattern exposure
Can be performed in

[0006]

FIG. 2A shows a wafer transfer sequence according to the present invention, and FIG. 2B shows a conventional wafer transfer sequence.
In the sequence of the present invention, first, a wafer is loaded (Step 1), and the rotation is corrected (Step 2). At the same time, forced air conditioning is performed to bring the wafer temperature closer to the reference temperature (step 3). Subsequently, chuck chucking for exposure is performed (step 4), exposure is performed (step 5), chuck chucking is released (step 6), and the wafer is carried out (step 7). The difference from the prior art is that forced air conditioning is performed before wafer suction for exposure (step 4).

FIG. 1 shows a change in the temperature of the loaded wafer (a) and a change in the size of the wafer (b) in the present invention.
Is shown taking a case of a 6-inch wafer as an example. FIG. 1 (b)
In the table, the change from the wafer size at 20 ° C. is shown as a ratio. At time 0, the wafer loaded at a temperature of 21.2 ° C. approaches the air temperature around the transfer system of 20 ° C. with a thermal resistance of 0.3 C / W during the transfer and while the wafer rotation is being corrected. Twenty seconds after the loading, the wafer is fed onto the chuck for projection exposure, moved to just below the forced air conditioner, and air-cooled to 20.05 ° C. Chuck temperature is 20 ℃
And has a sufficiently large heat capacity. During air conditioning, the wafers are cooled with a low thermal resistance of 0.04 C / W and about 1.3
It reaches the target temperature in seconds. Since the temperature difference is 0.05 ° C., the change from the reference size is about 0.2 ppm. When the wafer is sucked for exposure, the wafer has a substantially standard size, so that no stress is accumulated during the suction. The size change of the wafer is 0.1 ppm or less.
Further, even if the history of the wafer during transfer is different and the temperature of the wafer when transferred onto the chuck varies, the temperature of the wafer is adjusted to the chuck temperature by air conditioning. There is no variation in temperature and no variation in size.

FIG. 3 shows the configuration of the present invention. In the figure, 3 is a reticle, 5 is a wafer, 1 is an illumination system for irradiating exposure light, 2 is an alignment scope for measuring a displacement between the wafer 5 and the reticle 3, and 4 is a pattern of the reticle 3 on the wafer 5. A projection lens 7 for projecting the wafer 5, an XY stage 7 for moving the wafer 5, a wafer cassette 9 for accommodating the wafer, a wafer transfer system 10, and an apparatus base 8. As a newly added part in the present invention, 1
1 is a wafer temperature controller, 12 is a duct, 13 is an air filter, 14 is a wafer temperature sensor, and 15 is a chuck temperature sensor.

Immediately after the wafer is placed on the chuck on the XY stage from the wafer transfer system, the wafer moves immediately below the air filter before suction, and the temperature is adjusted here. This temperature control is based on the chuck temperature monitored by the temperature sensor 15 and the temperature sensor 1.
4 is controlled so as to minimize the difference from the wafer temperature monitored. As the temperature sensor 14, a non-contact infrared sensor or the like can be considered. In any case, when the temperature difference becomes equal to or less than a predetermined threshold value, the wafer is sucked, and the process proceeds to the next exposure sequence.

If a preliminary rough temperature control mechanism is provided inside the wafer transfer system 10, the time required for the temperature control of the present invention can be reduced.

[0011]

As described above , according to the present invention,
Semiconductor substrate transferred by the transfer system on the substrate chuck
First moves to the air filter side and the temperature is adjusted,
After that, the projection optical system side
Exposure sequence by step-and-repeat method
Is performed. That is, according to the present invention, the temperature control of the substrate
Exposure sequence is performed on the place and substrate
Since the place will be separated, air filter
Temperature control of the substrate by the temperature controller via
Can be reduced. Also, to the air filter side
Move the substrate on the substrate chuck to the projection optical system.
Carrying is performed by the XY stage that moves the step
The semiconductor substrate is transferred onto the substrate chuck by the system
To the start of the exposure sequence for the substrate
You can shorten the time. For this reason, according to the present invention, highly accurate
High-throughput pattern exposure
You.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are graphs showing a change in wafer temperature and a change in size of a semiconductor exposure apparatus according to the present invention with respect to an elapsed time after loading of the wafer;

FIGS. 2A and 2B are flowcharts of an exposure sequence according to an embodiment of the present invention and a conventional technique, respectively.

FIG. 3 is a configuration diagram of a semiconductor exposure apparatus provided with an air conditioner according to the present invention.

FIGS. 4A and 4B are graphs respectively showing a change in wafer temperature and a change in wafer size with respect to an elapsed time after a wafer is carried in a conventional semiconductor exposure apparatus;

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-158626 (JP, A) JP-A-58-119638 (JP, A) JP-A-59-155842 (JP, A) JP-A-55-155842 43844 (JP, A) Japanese Patent Laid-Open No. 55-93224 (JP, A) Japanese Patent Publication No. 87-13661

Claims (1)

(57) [Claims] 1. A projection optical system which transports a semiconductor substrate housed in a substrate cassette onto a substrate chuck by a substrate transport system, adsorbs the semiconductor substrate on the substrate chuck, and projects a pattern of an original plate. Moving the semiconductor substrate adsorbed on the substrate chuck by an XY stage, and performing an exposure sequence in which the step movement by the XY stage and the illumination of the original plate by an illumination system are alternately repeated, thereby performing each of the steps on the semiconductor substrate. In a projection exposure method of sequentially projecting and exposing the pattern of the original plate on an area, a temperature controller for adjusting the temperature of the semiconductor substrate on the substrate chuck via an air filter is provided, and the substrate transport system transfers the substrate cassette from the substrate cassette. When the semiconductor substrate is transported onto the substrate chuck, the semiconductor on the substrate chuck The substrate is moved to the air filter side by the XY stage, the temperature of the semiconductor substrate is adjusted by the temperature controller via the air filter, and the temperature of the semiconductor substrate is a predetermined temperature with respect to the temperature of the substrate chuck. A projection exposure method comprising: adsorbing the semiconductor substrate to the substrate chuck after the relationship is established; and executing the exposure sequence on the projection optical system side.