JPS6254440A - Exposure of semiconductor wafer - Google Patents

Abstract

PURPOSE:To sustain the stable exposure for a long time by a method wherein in case of opening a shutter, the power consumption of ultra-high pressure mercury lamp is controlled according to the fluctuation in the radiating light quantity of the mercury lamp while in case of closing the shutter, the mercury lamp is controlled to be supplied with specified level of power. CONSTITUTION:The exposed part of semiconductor wafer 2 is divided into multiple fine sections P arranged longitudinally and laterally so that individual section P of the fine sections may be successively shifted stepwise to the exposed position to be once stopped on the position for exposure. One time exposure is finished by opening and closing a shutter 11 to print a pattern on one fine section P of the semiconductor wafer 2. Through these procedures, in case of opening the shutter 11, the power consumption of ultra-high mercury lamp can be changed according to the fluctuation in the radiating light quantity of the mercury lamp while in case of closing the shutter 11, the fluctuation in the radiating light quantity of the mercury lamp can be automatically compensated to sustain the excellent exposure of the ultra-high pressure mercury lamp for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of exposing a semiconductor wafer using an ultra-high pressure mercury lamp.

[Prior art] General 1. In the manufacture of semiconductor devices such as ICs, LSIs, and 1LsIi, it is necessary to print a pattern on a semiconductor wafer made of silicon or the like through a photomask. Baking of such a pattern is performed, for example, to form a resist layer for etching. A method of exposure using light from a high-pressure mercury lamp is widely used.

A semiconductor wafer is usually circular and its entire surface is divided into micro areas arranged vertically and horizontally, and these micro areas are later divided into chips, each of which constitutes a semiconductor device. The size of a single semiconductor wafer is generally about 3 inches, 5 inches, or 6 inches in diameter, but as semiconductor wafer manufacturing technology advances, the size tends to increase.

In the exposure method that simultaneously exposes the entire surface of one semiconductor wafer and prints all minute areas at once, a high-output mercury lamp is required to expose a large area at once, which requires a large exposure device. However, since the exposed area for a single exposure is large, a fairly sophisticated technique is required to uniformize the illuminance in the exposed area of the conductor wafer.
As a result, it is difficult to adapt to the trend of increasing the size of semiconductor wafers.

For this reason, recently an exposure method (hereinafter also simply referred to as "step exposure method") has been developed, in which each of the minute areas arranged vertically and horizontally on a single semiconductor wafer is sequentially exposed one by one to form a C pattern. ) was proposed. According to such a step exposure method, it is only necessary to expose an area corresponding to one microscopic area in one exposure, which makes it possible to use a low-output mercury lamp or to make the exposure equipment more compact. In addition, since the area exposed at one time is small, it is easy to equalize the illuminance of the exposed area of the semiconductor wafer, which provides great benefits such as the ability to print patterns with high accuracy.
It is possible to perform f-cutting.

By the way, ultra-high-pressure mercury lamps do not blink repeatedly in short periods because the mercury gas enclosed in them condenses when turned off, so they are used in a state where they are kept on continuously. A shutter is used to limit the exposure time in order to carry out exposure with a predetermined foggy light, and while this shutter is closed, the next exposure of the semiconductor wafer is performed at the exposure position that is irradiated with light from the ultra-high pressure mercury lamp. It is necessary to step the semiconductor wafer so that the desired micro-area is located.

However, in this conventional exposure method, the light from the ultra-high pressure mercury lamp is not used for exposure while the shutter is closed, which wastes a lot of power, and the shutter is exposed to high temperatures. The damage to the shutter is thick and rough.

For this reason, there is a method of lighting an ultra-high-pressure mercury lamp in such a way that the power consumption of the ultra-high-pressure mercury lamp during the period when the shutter is closed is lower than the power consumption during the exposure period when the shutter is open. It is considered.

In this method, as the exposure processing of semiconductor wafers becomes faster, if the ultra-high pressure mercury lamp is repeatedly turned on many times in succession so that its power consumption changes at short time intervals, the lighting time of the ultra-high pressure mercury lamp can be reduced. As time passes, the amount of light emitted by the ultra-high pressure mercury lamp decreases due to factors such as wear of the electrodes and low light transmittance due to 7FSFjA\III adhesion to the tube wall, making it no longer possible to carry out exposure at the original exposure amount. It disappears.

[Problems to be Solved by the Invention] As described above, in the conventional semiconductor wafer exposure method, when exposing a semiconductor wafer using light emitted from an ultra-high pressure mercury lamp, the amount of light emitted from the ultra-high pressure mercury lamp is In order to compensate for changes, the amount of emitted light had to be measured manually and the input power to the ultra-high pressure mercury lamp had to be adjusted, which was cumbersome to operate.

In view of these problems, it is an object of the present invention to provide a semiconductor wafer exposure method that automatically compensates for fluctuations in the amount of emitted light from an ultra-high pressure mercury lamp and allows stable exposure over a long period of time. It is.

[Hand blowing to solve the problem] In order to achieve this objective, in this invention, when the shutter for opening and closing the light emitted from the ultra-high pressure mercury lamp is opened,
The power consumption of the ultra-high-pressure mercury lamp is increased or decreased to compensate for the fluctuations in the amount of light emitted by the ultra-high-pressure mercury lamp, and when the shutter is closed, a constant amount of power is applied to the ultra-high-pressure mercury lamp.

[Function] According to the present invention, when the shouter is opened, the power consumption of the ultra-high pressure mercury lamp is changed in accordance with the fluctuation in the amount of emitted light from the ultra-high pressure mercury lamp, so that even when the amount of radiation J changes over time, this The input power to the ultra-high-pressure mercury lamp is adjusted by A to compensate for the change, and the power consumption is adjusted to emit a constant amount of light.

Further, when the shutter is closed, since it is only necessary to keep the ultra-high pressure mercury lamp turned on, the ultra-high pressure mercury lamp is controlled to be driven using a constant electric power that keeps the ultra-high pressure mercury lamp turned on.

[Example] The present invention will be described in detail below based on one drawing. FIG. 1C is a diagram showing an exposure apparatus for explaining an embodiment of the semiconductor wafer exposure method according to the present invention. In this figure, l is an ultra-high pressure mercury lamp, 2 is a semiconductor wafer, and 3
is a photodetector, 10 is a lamp house, it is a shutter,
12 is a cooling fan, and 13 is a fan motor. 20
is an optical system, 21.22 is a mirror, 23 is an integrator, 24 is a filter, 25 is a condenser lens, 26
is a photomask, 27 is a reduction lens, and the reduction degree is l.
/10 to 115. 30 is a lighting circuit for the ultra-high pressure mercury lamp l, E is a commercial AC power supply, 31 is a rectifier/smoothing circuit, 32 is a switching circuit, 33 is a drive circuit, 34
35 is a pulse width modulation circuit, 35 is an amplifier circuit, 36 is a base 1$ voltage source, VR is a variable resistor for varying the reference voltage, 37a is an impark lance, 37b is a rectifier/smoothing circuit, 37c
3 is a starter, 3 is a power calculation circuit, and 39 is an ultra-high pressure mercury lamp voltage/current detection circuit.

In this exposure apparatus, power is constantly supplied to the ultra-high-pressure mercury lamp l to cause it to light continuously, and a lighting circuit section 30 is used to control the ultra-high-pressure mercury lamp l so that it has a power consumption waveform as shown in FIG. control the power supplied to the That is, the power consumption of the ultra-high pressure mercury lamp 1 is at a high level, for example, about 1.3 to 1.3 of the rated power consumption.
The first step A, in which the power consumption of one ultra-high pressure mercury lamp is at a level of about 2.5 f, is at a low level, for example, the rated power consumption or lower, which is periodically alternated. Repeat. In this first step A, the semiconductor wafer is exposed to light emitted from an ultra-high pressure mercury lamp l.

Regarding the lighting circuit section 30, this embodiment employs a switching regulator system that can be made smaller and lighter. The switching circuit 3 is configured so that the power corresponding to the voltage level of the X quasi-voltage source 36 is input to the ultra-high pressure mercury lamp l.
The second operation is controlled by negative feedback. , IQI, the repetition of the first step A and the second step B is based on the reference voltage source 3.
This is done by alternately changing the voltage levels of 6a and 36b in steps. Of course, the negative feedback circuit also switches between optical feedback for high levels and constant power for low levels.The output signal of this reference voltage source 36 is inputted to the pulse width modulation circuit 34 via the amplifier circuit 35, and The width is modulated, and the switching circuit 32 is caused to perform a switching operation according to the output signal of the reference voltage source 36 via the drive circuit 33. The output of this switching circuit 32 is boosted at a predetermined voltage ratio by an inverter transformer 37a, and is applied to the ultra-high pressure mercury lamp 1 via a rectifier/smoothing circuit 37b. The starter 37c is for applying a high voltage to the ultra-high pressure mercury lamp l at the time of starting lighting to start discharging.

In addition, voltage/Ti, current detection circuit 39 and power calculation circuit 38
is used for negative feedback control so that the power corresponding to the voltage level of the reference voltage 1; 3 and input to the amplifier circuit 35. In this *+X circuit 35, in the first step A, the output signal of the photodetector 3 is compared with the high level reference voltage vH which is the output signal of the reference voltage source 36b, and the emitted light from the ultra-high pressure mercury lamp 1 is compared. Negative feedback control is performed to maintain the value at a constant value.

In the second step B, the amplifier circuit 35 compares the output of the power calculation circuit 38 with the low-level reference voltage VL, and performs negative feedback control to maintain the power consumption in the ultra-high pressure mercury lamp l at a constant value. be done.

In order to regulate the amount of exposure to the semiconductor wafer 2, a shutter 11 is provided at the lower end of the lamp house IO.

By appropriately setting the time period during which the shutter 11 is open, the amount of exposure at the exposed portion of the main conductor wafer 2 is adjusted to a required specified value. That is, in the state where the ultra-high-pressure mercury lamp 1 is turned on in the first step A in which the power consumption is at a high level, the exposure amount is regulated by keeping the shutter 11 open for a set time. . Then, in the second step B in which the power consumption is reduced to a low level, a state is entered in which at least one ultra-high pressure mercury lamp 1 is lit, and the shutter 11 is closed during this time.

The first step A and the second step B are repeated at 11 times the step movement of the semiconductor wafer 2. That is, as shown in FIG. 3, the exposed portion of the semiconductor wafer 2 is divided into a large number of micro areas P arranged in rows and columns, and imt of these micro areas P are sequentially moved stepwise to the exposure position C.
Exposure is performed while the wafer is held still at that position. One exposure is completed by opening and closing the shutter 11, and a pattern is printed in one minute area P of the semiconductor wafer 2. Then, while the shirt tartar 11 is closed, the micro area Ptt is moved stepwise to the exposure position of the next minute area Ptt to be exposed, and the exposure is repeated in the same manner.

In this way, exposure is performed by linking step A and second step B of :4S1, the opening/closing operation of the shutter 11, and the step movement of the semiconductor wafer 2. Accordingly, regarding the decrease in the amount of emitted light, as described above, the amount of emitted light is controlled by the lighting circuit section 30 to be maintained at a constant value via the output signal of the photodetector 3. For example, as shown in FIG. 4, as a result of controlling the lighting of the ultra-high pressure mercury lamp l so that the power consumption gradually increases in the first step A, the amount of emitted light is maintained at a constant value, and the amount of emitted light decreases. Decrease over time is prevented.

FIG. 5 shows an example of a specific configuration of the ultra-high pressure mercury lamp 1, in which 101 is a quartz glass enclosure, 102A and 102B are bases, 103 and 104 are electrode bodies, and 105 and 10
6 are an anode body and a cathode body, respectively. Mercury is sealed inside the enclosure lot, and the amount of mercury sealed is such that the IR does not shrink by 7JI when the ultra-high pressure mercury lamp 1 is turned on in the second step B.

As shown in an enlarged view in FIG. 6, the anode body 105 includes a large-diameter cylindrical body 51 and a tip 53 that extends from the body 51 in a tapered shape and has a flat tip surface 52. On the other hand, the cathode body 10d is composed of a columnar part 61 and a tip part 62 extending from the columnar part 61 in the shape of a cone.

An example of a specific design of such an ultra-high pressure mercury lamp l is shown below.

(Rated power consumption) 500W (50V
, 10A) (Anode body shape) Outer diameter of body 51, 4.0-1 Diameter of tip surface 52 p22. Omm Opening angle α of tip 53 90 degrees (cathode body shape) Outer diameter D3 of columnar fi61 2.1111
■(Interelectrode pressure #) Ko, Og
tm (pressure inside the envelope when lit at rated power consumption) 13 atmospheres Semiconductor wafers were actually exposed using the above-mentioned method using an ultra-high pressure mercury lamp configured as described above under the following conditions. However, the desired exposure amount was stably obtained over a long period of about 400 hours, and the semiconductor wafer was successfully exposed.

(Time interval wI of first step A) Approximately 400 times 5
eC (time interval of second step B) approximately 400m5
ec (power consumption for the first step A) initially is 70
After 400 hours at 0W, it increased almost linearly to reach IKW.

(Power consumption in second step B) 400 from the beginning
The power was kept constant at 500W until the time elapsed.

According to the above embodiment, the following effects are achieved.

During the period when the synchrotron radiation of the ultra-high pressure mercury lamp is not used for exposure, the ultra-high pressure mercury lamp is turned on in the second step in which the power consumption of the ultra-high pressure mercury lamp is at a low level, thereby significantly reducing the power wasted by the ultra-high pressure mercury lamp. It can be made smaller and can prevent overheating damage to the shutter. Moreover, the ultra-high-pressure mercury lamp can be designed in a size that corresponds to the average value of the high-level power consumption in the first step and the low-level power consumption in the second step. In the first step, the power consumption of the ultra-high pressure mercury lamp is at a high level, so that the necessary exposure amount can be obtained at this time. Therefore, exposure of semiconductor wafers can be performed using a smaller ultra-high pressure mercury lamp, and as a result, the volume occupied by the exposure equipment is reduced, and the cost required for maintenance of clean rooms and the like is reduced, resulting in a significant reduction in the manufacturing cost of semiconductor devices. It becomes possible to do so.

Hereinafter, the semiconductor wafer exposure method according to the present invention has been described based on the configuration example shown in FIG. Configuration of circuit section 30, exposure optical system 2
Various changes can be made to the configuration of 0. for example, ! In order to compensate for fluctuations in the amount of emitted light from the high-pressure water lamp and obtain a constant light source, the high-level reference voltages V and l in Step A 3 are varied over time without using a photodetector. You may let them. This method is effective in preventing the amount of emitted light from an ultra-high pressure mercury lamp from decreasing over time.

Furthermore, this semiconductor wafer exposure method can also be applied to cases where exposure methods other than the step exposure method are employed.

[Effects of the Invention] As is clear from the explanation in J-2, according to the present invention, when the shutter is opened, f of the amount of emitted light from the ultra-high pressure mercury lamp is reduced.
By changing the power consumption of the ultra-high-pressure mercury lamp according to 97 hours, and driving the ultra-high-pressure mercury lamp with constant power when the shutter is closed, the ultra-high-pressure mercury lamp can be lit continuously, and when the shutter is open, the ultra-high-pressure mercury lamp can be turned on continuously. Since it is possible to automatically correct changes in the amount of radiation from high-pressure mercury lamps,
It can be carried out over long periods with good exposure using an ultra-high pressure mercury lamp.

[Brief explanation of drawings]

FIG. 1 is an exposure diagram for explaining an embodiment of a semiconductor wafer exposure method according to the present invention. Figure 2 is a diagram showing an example of the power consumption waveform of an ultra-high pressure mercury lamp, Figure 3 is an explanatory diagram showing a part of the exposed area of a semiconductor wafer, and Figure 4 is a diagram showing an example of the power consumption waveform of an ultra-high pressure mercury lamp. FIG. 5 is a diagram showing how the power consumption of a high-pressure mercury lamp gradually increases over time, FIG. 5 is a diagram showing an example of an ultra-high-pressure mercury lamp, and FIG. 6 is an enlarged view of the main part thereof. In the figure. l: Ultra-high pressure mercury lamp 2: Semiconductor wafer 3: Photodetector
10: Lamp house 20: Optical system 30
:Lighting Circuit Department, 10:Fan Motor Drive Circuit Department Agent For Patent Attorney 1) Haru Kitatake Figure 2 Figure 3

Claims (2)

[Claims] (1) A method in which a semiconductor wafer is exposed to light emitted from an ultra-high-pressure mercury lamp while the ultra-high-pressure mercury lamp is continuously lit. A semiconductor device characterized in that the power consumption of the ultra-high pressure mercury lamp is increased or decreased to compensate for the fluctuation in the amount of emitted light of Wafer exposure method. (2) A photodetector detects fluctuations in the amount of emitted light from the ultra-high pressure mercury lamp, and the power consumption of the ultra-high pressure mercury lamp is increased or decreased in accordance with the detection result. Exposure method for semiconductor wafers.