JPS6120327A - Method for exposing material of semiconductor water by extra-high pressure mercury lamp - Google Patents

Abstract

PURPOSE:To prevent the failure in cooling of an extra-high pressure mercury lamp by increasing or decreasing the rotation velocity of a cooling fan according to switching of a high-power step and low-power step. CONSTITUTION:Exposure is effected by relatively combining the first high-power step A and second low-power step B, opening and closing operations of a shutter 4, and the step shift of the material 2 of semiconductor wafer. An interlocking switch 74 operates in connection with an interlocking switch 37 in a lighting circuit 3 and when a reference voltage Vref1 for high level is selected by the interlocking switch 37, a resistance for high level R1 is selected in the interlocking switch 74 to increase the output frequency of a variable frequency inverter 73. At this time, the rotation velocity of a fan motor 13 increases resulting in an increase in a quantity of cooling air. Consequently, failure in cooling of a mercury lamp can be prevented while keeping a difference between the power consumption of high level and that of low level large enough.

Description

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

[Background of the invention]

Generally, in manufacturing semiconductor devices such as IC, L8I, and ultra-L8I, it is necessary to print a pattern on a semiconductor wafer material (such as silicon) through a photomask. This kind of turn baking is often carried out in the process of forming, for example, a resist layer for etching. A method of exposing by irradiating light from a C ultra-high pressure mercury lamp is widely used.

Semiconductor wafers are usually circular in shape and are divided into micro areas arranged vertically and horizontally on the entire surface of the wafer, and these micro areas are later divided into chips, each of which constitutes a semiconductor chip. The size of a single semiconductor wafer is generally about 8 inches, 5 inches/inch, or 6 inches in diameter, but as semiconductor wafer manufacturing technology advances, there is a tendency for the size to increase. In the exposure method that simultaneously exposes the entire surface of a semiconductor wafer material and prints all microscopic areas at once, a high-output mercury lamp is required to expose a large area at once, which results in a large exposure device. Moreover, since the area exposed at one time is large, a considerably sophisticated technique is required to uniformize the illuminance in the exposed area of the semiconductor wafer material.

However, it is difficult to adapt to the trend of increasing the size of semiconductor wafers.

[Prior art]

For this reason, recently, an exposure method (hereinafter simply referred to as a "step exposure method") in which a pattern is sequentially printed by sequentially exposing each of micro areas arranged vertically and horizontally one by one on a single semiconductor wafer material. ) was proposed.

According to such a step exposure method, in one exposure, it is sufficient to expose an area equivalent to one minute area, which makes it possible to use a low-output mercury lamp, making the exposure device more compact. Moreover, since the area exposed at one time is small, it is easy to equalize the illuminance of the exposed portion of the semiconductor wafer, and other great benefits can be obtained.

In the end, it is possible to perform the tsuturn printing with high precision.

Therefore, when the mercury lamp is turned off, it is sealed and the mercury gas condenses into a round shape, and it is not possible to repeat blinking at short intervals. A shutter is used to limit the exposure time in order to perform the exposure at a predetermined amount, and while the shutter is closed, a minute area of the semiconductor quefer material to be exposed to the next exposure is located at the exposure position that is irradiated with light from the mercury lamp. It is necessary to move the mosquito semiconductor wafer material in steps (hereinafter simply referred to as "step movement") so that the mosquito semiconductor wafer material is positioned.

However, in such conventional exposure methods, the light from the 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, which can cause damage to the shutter. The problem is that it is large.

For this reason, a method can be considered in which the mercury lamp is turned on in such a manner that the power consumption of the mercury lamp during the period when the shutter is closed is smaller than the power consumption during the exposure period when the shutter is open.

However, it has been found that such an exposure method has new problems. In other words, ultra-high pressure mercury lamps used as light sources for exposure usually need to be cooled.
If this cooling is insufficient, the envelope tube will deteriorate due to heat and may even cause a dangerous accident such as bursting.On the other hand, if the cooling is excessive, the mercury inside the envelope may condense. Normally, the cooling fan is rotated at a constant rotation speed so that the temperature of each part of the mercury lamp, such as the cap of the sealed tube, is always maintained within a certain temperature range when the lamp is lit. The mercury lamp is rotated to supply a constant amount of air into the lamp housing in which the mercury lamp is incorporated, thereby cooling the mercury lamp. However, with such a cooling means, it is difficult to properly cool the mercury lamp when the mercury lamp is turned on so that the power consumption varies between exposure and non-exposure. In other words, if you set the cooling air volume to a value suitable for when the light is on with high power consumption, for example, when the light is on with low power consumption, the cooling will be excessive and mercury inside the enclosure will condense. On the other hand, if you set the cooling air volume to a value suitable for when the lights are on with low power consumption, there will be insufficient cooling when the lights are on with high power consumption. This tends to cause early deterioration of the envelope tube due to overheating. On the other hand, it is possible to perform cooling by setting the cooling air volume to a value between the former and the latter, but in this case, the variable range of the power consumption of the mercury lamp cannot be made sufficiently large, and the level of If you change the duty ratio in the cycle of low power consumption and low power consumption, the required cooling conditions will change, making it impossible to achieve good cooling.In the end, the benefits of lighting with varying power consumption may not be sufficient. I can't get it.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and is capable of preventing insufficient cooling of an ultra-high pressure mercury lamp while making the difference between power consumption during exposure and power consumption during non-exposure sufficiently large. Therefore, it is an object of the present invention to provide a method for exposing semiconductor wafer materials using an ultra-high pressure mercury lamp, which can stably carry out exposure repeatedly performed at short time intervals over a long period of time at low cost.

[Structure of the invention]

The above object is to alternately repeat the first step in which the power consumption of the mercury lamp becomes high level and the second step in which the power consumption of the mercury lamp becomes low level while the ultra-high pressure mercury lamp is continuously lit. An exposure method in which a semiconductor wafer material is exposed to light emitted from the mercury lamp in a first step, the rotational speed of a cooling fan being increased or decreased in response to switching between the first step and the second step. A semiconductor sea urchin I material using an ultra-high pressure mercury lamp, characterized in that the mercury lamp is cooled in each step with a cooling air volume corresponding to the power consumption level of each of the first step and the second step. This is achieved by the following exposure method.

The present invention will be explained in detail below with reference to the drawings.

In one embodiment of the present invention, as shown in FIG. 1, for example, a mercury lamp 1 incorporated in an exposure apparatus for semiconductor wafer materials is constantly supplied with power to be in a continuous lighting state, and then, As shown in FIG. 2, an example of the power consumption waveform, by controlling the power supplied to the ultra-high pressure mercury lamp 1 by the lighting circuit unit 8, which will be described later, the power consumption of the mercury lamp 1 can be increased to a high level, for example, below the rated power consumption. The first step, where the power consumption level of the mercury lamp is approximately 1.8 to 2.5 times higher, and the second step B, where the power consumption of the mercury lamp is at a low level, for example, the rated power consumption or a level close to this, are synchronously alternately return &I,
In the first step, a semiconductor wafer material 2 is exposed to light emitted from a mercury lamp 1 . In FIG. 1, 8 is a lighting circuit for the mercury lamp l, lj is a shutter for blocking the light from the mercury lamp 1, 5 and 6 are reflectors, 7 is an integrator, 8 is a filter, 9 is a condenser lens, and 10 is a photo Mask, 11 is a reduction lens, a@
The grade is usually upper to higher grade. 1z is a cooling fan, 18
14 is a fan motor, and 14 is a fan motor drive circuit, the details of which will be described later.

The illustrated lighting circuit section 8 is an example of a case where a switching layer system is adopted, which allows for reduction in size and weight.
E is a commercial AC power supply, 81 is a rectifier/smoothing circuit, 82 is a switching circuit, 88 is a drive circuit, 84 is a nosol width modulation circuit, and 85 is an amplifier circuit.

86 is a reference voltage source, 87 is an interlocking switch, 88 is a power calculation circuit, and 89 is a voltage/current detection circuit for the mercury lamp 1.

40 is an inverter transformer, 41 is a UJI flow smoothing circuit.

4z is a starter. The reference voltage source 86 includes a high-level reference voltage Vrefl and a low-level reference voltage Vrefg, and an interlocking switch 87 allows only one of the reference voltages to be input to the amplifier circuit 35, and the input voltage is In other words, when the high-level reference voltage Vrefl is inputted, the power consumption is set to the first step A where the power consumption is at a high level.
When the low-level reference voltage Vref 2 is input, the power to be input to the mercury lamp 1 is adjusted by negative feedback control so that the power consumption is at a low level in the second step B. That is, in this example, the repetition of the first step person and the second step B is ! This is done by alternately selecting the high level reference voltage Vref1 and the low level reference voltage Vref2 using the dynamic switch 87.

In regulating the exposure amount, by appropriately setting the open time of the shutter 4, the semiconductor wafer material 2
Adjust the exposure amount at the exposed area to the required specified value. That is, the amount of exposure is determined by keeping the shutter 4 open for a set time while the mercury lamp 1 is turned on by the person in the first step where the power consumption is at a high level. In the second step B, in which the power consumption is set to a low level, the mercury lamp 5 is turned on, and during this time, the shutter 4 is gradually closed.

The repetition of the first step and the second step 7B, that is, the switching of the reference voltage Vrefl or the reference voltage Vref2 by the movement switch 37 in the lighting circuit section 8, is the same as the mode of step movement of the semiconductor wafer material 2. In relation to this, we will act in a manner that delays each other's actions. In other words, as shown in FIG.
The elements are sequentially moved in a stepwise manner to the non-original position and are once brought to rest at position 7 before exposure is performed. One exposure is completed by opening and closing the shutter 4, and a pattern is printed in one minute area P of the semiconductor wafer material.

Then, while the shutter 4 is closed, the micro area P to be next subjected to light calculation is moved step by step to the original position, and the exposure is repeated in the same manner.

In this way, the first step A and the second step B
, the opening/closing operation of the shutter 4, and the semiconductor wafer material 2
Exposure is performed by delaying the step movement of The cooling air volume for the first step person and the cooling air volume for the second step B are controlled to increase or decrease in accordance with the level of power consumption in each step in response to switching between step A and second step B. is set in an amount according to each power consumption, and an appropriate amount of cooling air is supplied into the lamp house 50 each time the first step B and the second step B are repeated to cool the mercury lamp 1. The appropriate cooling air volume in the first step A and the appropriate cooling air volume in the second step B differ depending on the specific structure of the lamp house 50 and other factors.

It is a good idea to conduct a simulation experiment in advance for each exposure apparatus to determine an appropriate cooling air volume.

To explain specifically, as shown in FIG.

The fan motor drive circuit 14 controls the rotational speed of the fan motor 18 as described above. The illustrated fan motor drive circuit 14 is a small I! ! ! Inono 9-2 performs quick reading control of fan motor using quantifiable one-round v iron
This is an example of a case where the data type is adopted. 71 is the power supply, 7z
is a rectifier/smoothing circuit, 78 is a variable frequency inverter, and this variable frequency inverter 78 has only one of the high bell resistor R1 or the low rail resistor R2 depending on the switching of the interlocking switch 174. The power supply Vcc is inputted via the resistor R1 or resistor R2 selected at this time.
A voltage with a frequency equal to the product of the resistance value of yC1 and the capacitance of one capacitor yC1 is applied to the fan motor 18, and the fan motor 1B rotates at a rotational speed corresponding to the frequency at that time.

In this example, the interlocking switch 74 operates in conjunction with the interlocking switch 87 in the lighting circuit section 8, and when the interlocking switch 87 selects the high-level reference voltage Vref 1, the slow-acting switch 74 operates in conjunction with the interlocking switch 87 in the lighting circuit section 8. 100 million resistance kL1 is selected, and conversely, the interlocking switch 87 selects the low level resistance Ili! ! When the I voltage Vrefg is selected, the low level resistor R is connected to the interlocking switch 74.
2 is selected. When the interlocking switch 74 selects the high bell resistor R1, the variable frequency inverter 78
The output frequency becomes large, and the rotational speed of the three-fan motor 1B becomes large, and the cooling air volume becomes large. On the other hand, when the low level resistor R2 is selected by the interlocking switch 74, the output frequency of the variable frequency converter 7B becomes low.

At this time, the rotational speed of the fan motor 18 becomes small, and the amount of cooling air becomes small.

When actually designing an exposure apparatus, the time from when the output frequency of the variable frequency inverter 78 changes until the cooling air volume near the mercury lamp 1 changes correspondingly, and the voltage level of the reference voltage source 86 are considered. It is preferable that the difference in time from when the mercury lamp 1 changes to when the power consumption of the mercury lamp 1 changes correspondingly and the temperature of each part of the mercury lamp 1 changes to be substantially equal to the time difference. There is no practical problem as long as the time difference is such that the temperature of each part is within the allowable temperature range.

FIG. 4 shows an example of a specific configuration of the mercury lamp 1.

101 is an enclosure made of quartz glass; 102. A and 102B are bases, 108 and 104 are 9L noodles, respectively, 105.
106 are positive body and #polar body, respectively. Mercury is sealed inside the envelope 101, and the amount of mercury sealed is as follows.

The amount is such that mercury does not condense when the mercury lamp 1 is turned on in the second step B.

As shown in an enlarged view in FIG. 5, the anode body 105 includes a large-diameter cylindrical Q-body portion 51, and a tip portion F18 that extends from the island portion 51 in a tapered shape and has a flat tip surface 52. On the other hand, the pole body 106 is constituted by.

Similarly, as shown in an enlarged view in FIG. 5, it is composed of a columnar portion 61 and a cone-shaped tip portion 62 extending from the columnar portion 61.

An example of a specific design of such a mercury lamp 1 is shown below.

Rated power consumption 500W (fiOV, l0A)
Outer diameter D of anode body shape body 51 D14.0 Diameter of tip face 52 D22.0 Opening angle of tip end 58 0 90 degrees Outer diameter of cathode body shape columnar part 61 D32.0 Distance between electrodes WaL 8. O
Pressure inside the enclosure when lighting at rated power consumption
When a semiconductor wafer material was actually exposed to light under the following conditions using a mercury lamp with a pressure of 18 atmospheres and the method described above, the initial exposure amount remained stable for a long period of about 400 hours. It was possible to perform good exposure processing of the semiconductor wafer material.

Time interval of the first step person: Approximately 400nnec Second
The time interval of step B was approximately 400 m5ec, and the power consumption in the first step A was kept constant at 600 W.

Power consumption in second step B The power was kept constant at 400W.

The rotational speed of the cooling fan 71z in the first step A is 8000 rpm The rotational speed of the cooling fan 12 in the second step B ZOOOrpm The method of the present invention has been explained above based on the nine examples shown in FIG. The invention method is not limited to the above configuration example, and the configuration of the lighting circuit section 8 for lighting the mercury lamp 1,
The configuration of the optical system for light and the configuration of the 77mm monitor drive circuit 14 for driving the fan motor 18 can be modified in various ways. For example, (a) a photocoupler or other switching means may be used instead of mechanical contacts such as the interlocking switches 87 and 74.

(b) What is the control method for the rotational speed of the cooling fan 12?

It may be selected as appropriate depending on the characteristics of the fan motor 18 used, and in addition to the control method using one frequency, the rotation speed may be controlled by changing the voltage using, for example, a triac, a transformer, or a variable resistor.

(c) The configuration of the fan motor drive circuit 14 and the components of the lighting circuit section 8 may be partially shared (1゜ [Actions and Effects of the Invention]) As described in detail above, the present invention Depending on the method, the following effects can be achieved.

(1) During the period when the radiant light of the mercury lamp is not used, the mercury lamp is turned on in the second step in which the power consumption of the mercury lamp is at a low level, so that the power wasted by the mercury lamp can be significantly reduced. In addition, it is possible to prevent overheating damage to the shutter, and the mercury lamp is used as a secondary lamp.
In addition, since the power consumption of the mercury lamp is high in the first step, it is not possible to obtain the necessary exposure amount at this time. Therefore, the exposure of semiconductor wafer materials can be performed using a smaller mercury lamp, and as a result, the volume occupied by the exposure equipment becomes smaller, and the cost required for maintenance of clean rooms and the like is reduced, which ultimately leads to a significant reduction in the manufacturing cost of semiconductor devices. It becomes possible to do so.

(2) By controlling the rotational speed of the cooling fan to increase or decrease in response to switching between the first step and the second step, each time the first step and the second step are repeated, In order to cool the mercury lamp with the cooling air volume according to the power consumption level of each of the first step and the second step, the mercury lamp is In the first step, where each part is always maintained within a suitable temperature range and therefore the power consumption is at a high level, overheating damage to the enclosure etc. does not occur, and in the second step, where the power consumption is at a low level. mercury does not condense inside the envelope, and as a result, the difference between the high level of power consumption in the first step and the low level of power consumption in the second step is made sufficiently large, while preventing poor cooling of the mercury lamp. As a result, it is possible to perform exposure repeatedly at short time intervals stably over a long period of time at low cost.

(8) Since the cooling air volume is adjusted by changing the rotational speed of the cooling fan, the range in which the cooling air volume can be adjusted is wide, and therefore the cooling air volume can be easily adapted to large changes in the power consumption of mercury lamps. Moreover, it is possible to adjust the cooling air volume without causing the mechanical movement that occurs when adjusting the cooling air volume by opening and closing operations such as a Danopper. be able to.

(4); Since the rotational speed of the cooling fan can be controlled by controlling the rotational speed of the fan motor used in combination with the cooling fan, cooling can be achieved by using a simple fan motor drive circuit. The rotational speed of the fan can be easily made to follow each of the first step and the second step with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing an example of an exposure apparatus;
FIG. 2 is an explanatory diagram showing an example of the waveform of power consumption of a mercury lamp that changes due to repetition of the first step and the second step, FIG. 8 is an explanatory diagram showing a part of the exposed portion of the semiconductor wafer material, FIG. 4 is an explanatory diagram showing an example of a mercury lamp, and FIG. 5 is an explanatory diagram showing an enlarged main part of the mercury lamp shown in FIG. 1...Mercury lamp 2...Semiconductor Unino\-Material 8...I lighting circuit section 4...Shutter 5.
6...Reflection @7...Integrator 8...Filter 9...Condenser lens 10゛°゛Photomask 11°°° Small convergence lens 12-1.77 for cooling 18...Fan motor 14. ...Fan motor drive circuit 81...Rectifier/smoothing circuit 82...Switching circuit 88...Drive circuit 84...Pulse width modulation circuit 85...Amplification circuit 86...Reference voltage source B
7... Interlocking switch 88... Power calculation circuit 89.
...Voltage/current detection circuit 40... Inverter transformer 41... Rectification/smoothing circuit 4 Z 00. Starter Vrefl...
High level reference voltage Vref 2...Low level reference voltage 71...Power supply 7z...II current/smoothing circuit 7B...Variable frequency Inno-Tough 4...Interlocking switch R,... Resistor for high level... Resistor for low level Vcc = power supply C1°°°''7 de79101
・=・Enclosure 10ZA, 102JB ・, -Base 105... Anode body 106... Polar Body Science 2 Decoy 3 Decoy Year 5 Figure

Claims (1)

[Claims] 1) While the ultra-high pressure mercury lamp is continuously lit, the first step in which the power consumption of the mercury lamp becomes high and the second step in which the power consumption of the mercury lamp becomes low are repeated alternately. The exposure method comprises exposing a semiconductor wafer material to light emitted from the mercury lamp in the step, the rotational speed of a cooling fan being increased or decreased in response to switching between the first step and the second step. A method for exposing a semiconductor wafer material using an ultra-high pressure mercury lamp, characterized in that the mercury lamp in each step is cooled with a cooling air volume corresponding to the level of power consumption in each of the first step and the second step.