JPH09266157A - Reduction projection exposure method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent transfer failure of a pattern caused by the dust lying between a stage and a wafer without performing the inspection of the existence of adhesion of dust periodically. SOLUTION: A laser oscillator 5, which indicates every indication are 12 with laser beams, and a sensor 6, which measures the quantity of reflected laser beams, are provided. Here, the abnormal variation of height caused by a bulge 11 over the depth of focus of a projection lens is detected with a sensor 6, and an alarm is generated and concurrently the device is stopped, and the position of the indication area 12 where there is a bulge 11 is indicated on a position display 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction projection exposure method and apparatus for repeatedly irradiating an exposure light for each exposure light irradiation area to transfer a reticle pattern onto a semiconductor substrate.

[0002]

2. Description of the Related Art With the increase in the degree of integration of semiconductor devices, it is required to increase the numerical aperture of the projection lens of the reduction projection exposure apparatus of this kind, and in recent years, it has become possible to cope with a miniaturized pattern of 0.2 μm. It was However, as the numerical aperture increases, the depth of focus becomes shallower, and even a slight step on the semiconductor substrate (hereinafter simply referred to as a wafer) that is the work piece makes the pattern transfer unclear, resulting in a serious defect in quality. was there.

For this reason, not only measures for flattening the surface of the wafer to which the pattern is to be transferred but also improvement of the stage surface on which the wafer is placed have been taken on the apparatus side. However, there is a problem that cannot be solved by flattening technology and improvement of the device side. One of them is that minute dust adheres to the stage,
When a wafer is placed on it, the area of the wafer above the dust is curved so as to bulge upward, and there is a problem in use that the transferred pattern causes dimensional abnormality or pattern breakage. If the wafer including the transfer failure flows to the subsequent process, the subsequent process becomes a wasteful man-hour and the loss cost increases.

Conventionally, there has been no definitive means for dealing with this problem, and the flatness of the mounting surface of the stage and the presence or absence of dust have to be inspected periodically to deal with it.

[0005]

However, even if the flatness of the stage is periodically checked, dust adheres itself at random, and dust adheres during the check. Therefore, there is a problem in that a large amount of defective products are generated on the wafer subjected to the exposure processing during that time. Further, shortening the check interval does not completely eliminate the problem, but rather causes a new problem of not only increasing the number of inspection steps but also resting an expensive device.

A reduction projection exposure apparatus which solves the problem of dust adhesion is disclosed in Japanese Patent Laid-Open No. 63-129929. This apparatus is provided with a nozzle that blows high-pressure air on the back surface of the wafer, blows off dust adhering to the back surface of the wafer, and then lowers a suction table that holds the outer periphery of the wafer and places the wafer on the stage. However, it is difficult to solve the problem of dust adhesion with this device. After all, there is no guarantee that blown dust will be ejected outside the stage. Rather, there is a risk that the dust that has been blown will reattach to the stage, and the dust that originally attached to the stage cannot be removed. Furthermore, the problem is that there is no way to confirm that dust has not adhered to the stage.

Therefore, an object of the present invention is to provide a reduced projection exposure method capable of eliminating a pattern transfer defect caused by dust interposed between a stage and a wafer without regularly inspecting the presence or absence of dust adhesion. To provide the device.

[0008]

A feature of the present invention is that in a reduction projection exposure method in which exposure light is repeatedly irradiated for each irradiation region of one exposure light to transfer a reticle pattern onto a semiconductor substrate, a laser is applied for each irradiation region. Irradiate light, measure the amount of reflected light, and check the presence or absence of a bulge on the irradiated area based on the amount of light to determine whether or not the bulge is larger than a prescribed bulge. If the bulge is large, an alarm is issued and the exposure operation is performed. Is a reduction projection exposure method for stopping the exposure and displaying the position of the irradiation area having the bulge.

Another feature is that a laser light oscillator for irradiating the irradiation area with laser light, a sensor for measuring the amount of the laser light reflected from the irradiation area, and a measurement value of the sensor and a specified value are compared. Means for determining whether or not there is a bulge in the irradiation area and whether or not the bulge is larger than a prescribed bulge, and if the bulge is greater than the prescribed bulge, an alarm is issued and the exposure operation is stopped and the position of the irradiation area is determined. Is a reduction projection exposure apparatus.

[0010]

1 is a schematic sectional view showing a stage in a reduction projection exposure apparatus according to an embodiment of the present invention. As shown in FIG. 1, this reduction projection exposure apparatus includes a laser light oscillator 5 for irradiating a laser beam to an irradiation region 12 where the exposure light is irradiated in one shot, and a slit 7 for a laser beam reflected from the irradiation region 12. A sensor 6 which receives a laser beam through the laser beam and measures the amount of the laser beam, and the stage height is adjusted by the height adjusting unit 8 so that the sensor 6 is maximized.
z and the standard value are compared to determine whether or not there is a bulge 11 due to dust 10 in the irradiation region 12 and whether or not the size of this bulge 11 is larger than a prescribed bulge, and if the bulge 12 is a prescribed bulge. If it is larger, the control unit 2 is provided which operates the alarm device 1b, stops the exposure sequence operation, and displays the position of the irradiation region 12 having the bulge 11 on the stage 4 as a map on the position display unit 1a.

When the stage height z is adjusted so that the photocurrent from the sensor 6 is maximized, the comparison / determination unit 3 converts the amount of change Δz μm into a voltage signal and compares the voltage signal with a prescribed voltage to make a high level. A comparison circuit for outputting the voltage of, for example, a commercially available flip-flop circuit is provided. Further, it is desirable that the specified voltage is set to a voltage generated by the amount of change in height of the bulge 11 that can cover the focus advance of the projection lens in the exposure apparatus.

The control unit 2 operates the switching transistor which operates the alarm device 1b by the output voltage from the comparison / determination unit 3, and the position of the irradiation region 12 corresponding to the wafer map displayed on the display which is the position display unit 1a. , A switching transistor that operates a stop relay of a sequence circuit unit that controls the operation of the apparatus by the output voltage from the comparison and determination unit 3, and a stage 4 of the stage 4 when focusing. And a drive circuit section for driving the height adjusting section 8 for adjusting the height.

FIG. 2 is a flow chart for explaining an embodiment of the reduction projection exposure method of the present invention. next,
The exposure method of the present invention will be described by explaining the operation of the reduction projection exposure apparatus of FIG.

First, in step A of FIG. 2, the wafer 9 is placed on the stage 4 of the reduction projection exposure apparatus of FIG. 1 in which the reticle is set. Next, in step B of FIG. 2, the reticle pattern is aligned with the alignment mark. Thereafter, in step C, the laser beam is applied to the irradiation area 12 by the laser oscillator 5, and it is determined whether or not the light is reflected by the reflected light amount. If the light is in focus, the exposure is performed in step E. If the focus is not reached, the height adjustment unit 8 is operated by the control unit 2 in FIG. 1 to adjust the height of the stage 4 to bring it into focus.

Next, in step F of FIG. 2, the laser beam is irradiated onto the irradiation region 12 by the laser oscillator 5 of FIG. 1, and the stage height is adjusted until the amount of reflected light becomes maximum. If the amount of change Δzμm is within the standard value, it is determined in step H, and if all shots are not completed, another irradiation region is moved to the exposure position, and steps C to F are repeated. If the amount of change Δz exceeds the specified value in step F, a signal is transferred from the comparison / determination unit 3 of FIG. 1 to the control unit 2, and an alarm is generated and the operation of the apparatus is stopped in step G. At this time, since the position of the irradiation region 12 having the bulge 11 due to dust is displayed on the position display portion 1a of FIG. 1, the wafer 9 is removed in step I, and the stage 4 corresponding to the irradiation region 12 is removed. Clean the area.

In this way, the presence or absence of the bulge 11 due to dust is checked for each shot, and if there is the bulge 11 due to dust even in the one-shot area, the wafer is treated as a defective product and reconstructed or discarded. It is possible to prevent outflow to the subsequent process. In addition, since the location of the stage to which the dust adheres is immediately known, there is an advantage that the number of inspection steps for the presence or absence of dust can be eliminated.

In the embodiment of the present invention, the method of inspecting the presence or absence of the bulge due to dust by irradiating a single point with laser light in one irradiation area has been described. The points may be irradiated with laser light to inspect for the presence or absence of a bulge.

[0018]

As described above, according to the present invention, a laser light source for irradiating a laser beam for each irradiation area and a sensor for measuring the amount of reflected laser light are provided, and an abnormality due to a bulge exceeding the depth of focus of the projection lens is provided. The sensor detects the amount of change in height, generates an alarm, stops the device, and reconstructs or discards the wafer containing the irradiation area that causes transfer defects due to this abnormal bulge. There is an effect that a non-defective wafer can be always passed to the subsequent process without being raised.

Further, by providing a display section for displaying the position of the area having an abnormal bulge, a dusty portion of the stage can be found immediately, so that the wafer mounting surface of the stage is regularly arranged as in the conventional case. This eliminates the need for inspection, and has the effect of reducing inspection man-hours and improving the operating rate.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a stage in a reduction projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining an embodiment of a reduction projection exposure method of the present invention.

[Explanation of symbols]

 1a Position display part 1b Alarm device 2 Control part 3 Comparison judgment part 4 Stage 5 Laser oscillator 6 Sensor 7 Slit 8 Height adjustment part 9 Wafer 10 Dust 11 Swelling 12 Irradiation area

Claims (2)

[Claims] 1. A reduction projection exposure method in which exposure light is repeatedly applied to each irradiation area of one exposure light to transfer a reticle pattern onto a semiconductor substrate, and a laser beam is irradiated to each irradiation area and the amount of reflected light is measured. The presence or absence of a bulge on the irradiation area is checked by the amount of light to determine whether or not the bulge is larger than a prescribed bulge. If the bulge is large, an alarm is issued and the exposure operation is stopped and the irradiation with the bulge is performed. A reduced projection exposure method characterized by displaying the position of an area. 2. A laser light oscillator for irradiating the irradiation area with laser light, a sensor for measuring the amount of the laser light reflected from the irradiation area, and a swelling in the irradiation area by comparing a measured value of the sensor with a specified value. And a means for determining whether or not the bulge is larger than a prescribed bulge, and a means for issuing an alarm if the bulge is larger than the prescribed bulge, stopping the exposure operation, and displaying the position of the irradiation area. And a reduction projection exposure apparatus.