JPH11204424A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize improvement in exposure accuracy in an aligner, by causing control means to carry out light exposure control by switching the gain of first light quantity measuring means to an optimum value in accordance with the quantity of incident light on the first light quantity measuring means. SOLUTION: A laser light source 1 is caused to oscillate a plurality of pulses with constant energy, and a light exposure is measured indirectly and directly by an optical measuring instrument 4 which is first light quantity measuring means, and a light exposure measuring instrument 10 which is second light quantity measuring means. From the result of measurement, an optimum gain in accordance with the transmittance and light condition of light quantity adjustment means 2 is selected and stored into a storage 12 in accordance with the light exposure of a wafer. In carrying out the exposure operation, control means 14 carries out light exposure control by immediately switching the gain of the optical measuring instrument 4 in accordance with the transmittance and lighting condition of the light quantity adjustment means 2. Thus, the S/N is improved and desired light exposure control accuracy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing semiconductor devices such as LSIs and liquid crystal substrates, and more particularly to an exposure apparatus having a function of measuring an exposure amount for controlling an exposure amount. Things.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, a reduction projection exposure apparatus (hereinafter, referred to as a stepper) reduces a circuit pattern on a reticle and projects it onto a wafer.
A commonly used exposure method forms a pattern image on the entire wafer surface by exposing another area while moving the wafer each time one exposure is completed, and repeating such exposure sequentially plural times. This is a step-and-repeat method.

[0003] The image quality of a pattern transferred onto a wafer surface is greatly affected by the performance of an illuminating device, for example, the amount of exposure light (exposure amount) on a surface to be irradiated and its fluctuation. Therefore, there has been proposed an exposure apparatus which performs control so that the irradiation light amount on a surface to be irradiated becomes a predetermined value. For example, Japanese Patent Application Laid-Open No. 4-48714
In the publication, an incident light beam is amplitude-divided into two light beams, and a beam splitter (light splitting member) that guides one of the light beams to a surface to be irradiated (reticle) and the other light beam to a photodetector is a light source. And in the optical path between the surface to be irradiated and the light beam passing through the beam splitter with a photodetector, the amount of irradiation on the surface to be irradiated, that is, the amount of exposure on the wafer surface There has been proposed an exposure apparatus which is controlled.

On the other hand, in recent years, in order to improve the productivity of a stepper, the sensitivity of a resist applied on a wafer surface has been increased. In the case of exposure using pulsed light, since energy per pulse varies, one exposure is performed by irradiating at least several tens of pulses in order to assure exposure unevenness and exposure accuracy. Therefore, if it is desired to perform exposure with a small exposure amount in order to correspond to a highly sensitive resist, it is necessary to reduce the exposure amount per pulse. For this purpose, there is a method of lowering the laser output or reducing the exposure light by the light amount adjusting means. Even when the exposure light is continuous light, there is a case where it is desired to reduce the light amount by the light amount adjusting means for the same reason.

[0005]

An optical measuring instrument for monitoring an exposure amount comprises a photodetector and an amplifier having a specific gain. Usually, this optical measuring instrument has only one fixed gain. When the gain is one step, when the amount of light incident on the photodetector decreases, the SN ratio deteriorates and the measurement accuracy decreases, so that there is a problem that desired exposure amount control accuracy cannot be obtained. An exposure meter that directly measures the amount of exposure light (exposure) on the surface to be irradiated has the same problem.

The present invention has been made in view of the above-mentioned problems in the conventional example, and has as its object to improve exposure accuracy in an exposure apparatus.

[0007]

According to the present invention, there is provided a light source for generating illumination light, a light amount adjusting means for adjusting the amount of light applied to an object to be illuminated, and a plurality of secondary light sources provided by the illumination light. At least one of a secondary light source forming unit for forming a light source, a first light amount measuring unit for indirectly measuring the irradiation light amount on the surface of the irradiation target, and a second light measuring unit for directly measuring the irradiation light amount on the surface of the irradiation target An exposure apparatus comprising: a light amount measurement unit; a calculation unit configured to calculate a measurement result; a storage unit configured to store measurement and calculation results; and a control unit configured to control an operation of each of the units. Has an amplifier having a plurality of different gains, and the control means switches the gain of the first light quantity measuring means to an optimum value in accordance with the quantity of light incident on the first light quantity measuring means to perform the exposure amount control. It is characterized by That.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exposure apparatus according to an embodiment of the present invention provides an exposure amount on a wafer surface indirectly or directly.
An optical measuring instrument for monitoring has a multi-stage gain,
The gain is switched in accordance with the amount of light incident on the photodetector. By using the above-described means, in the exposure amount measurement, a large signal amplitude can be obtained even with a small exposure amount, and the SN ratio can be improved. Therefore, highly accurate exposure amount control becomes possible.

By the way, the gain of the amplifier has a difference between the design value and the actual value due to variations in the constants of the electronic components constituting the circuit. There is also variation due to individual circuit differences. In the case where the optical measuring instrument has several gains, the continuity of the exposure amount is lost at the boundary where the gain is switched, which causes deterioration of the exposure amount control accuracy.

In order to solve such a problem, an exposure apparatus according to another embodiment of the present invention comprises an optical measuring device for monitoring an exposure amount on a wafer surface indirectly or directly in a plurality of stages. The actual gain is measured in advance, and at the time of measuring the exposure amount, each design gain value is corrected by calculation based on the measurement result. By taking the above-described means, the continuity of the exposure measurement can be maintained even when the gain of the optical measuring device is switched. Therefore, highly accurate exposure amount control becomes possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a semiconductor exposure apparatus according to one embodiment of the present invention. In FIG. 1, a light source 1 may be a laser light source that emits pulsed light or a mercury lamp that emits continuous light. The light source 1 is controlled in light amount and the like by a light source control unit 15. The light emitted from the light source is reduced by the light amount adjusting means 2 to an arbitrary light amount.

An optical measuring instrument (first light quantity measuring means) 4 comprises a photodetector 41, a gain switching means 42 and an amplifier 43. The photodetector 41 detects a light beam that has passed through the beam splitter 3 and indirectly detects an exposure amount on the surface of the wafer 7 described later.

Reference numeral 6 denotes a projection optical system which projects a circuit pattern on the reticle 5 on a wafer (substrate) 7 mounted on a wafer chuck 8 in a reduced size. 9 is a wafer stage. 10 is an exposure amount measuring device (second light amount measuring means)
The light receiving surface is set so as to be substantially coplanar with the wafer 7, and the exposure amount on the surface of the wafer 7 is detected.

Reference numeral 43 denotes an amplifier, which amplifies the output signal of the photodetector 41 and inputs the amplified signal to the arithmetic means 11. The amplifier 43 prepares an arbitrary number of amplifiers having different gains. Here, the gain of each amplifier is K0, K1, K2,. . .
Kn. Reference numeral 42 denotes an amplifier (gain) switching means for switching to a designated gain in accordance with a command from the control means 14.

The control means 14 controls each means.
The storage unit 12 stores measurement and calculation results, instruction contents from the control unit 14 to each unit, and the like. The input / output means 13 outputs information exchange between the control means 14 and other means, and the operator inputs necessary information to the control means 14.
It is for input to.

Next, a method of controlling the amount of exposure on the surface of the wafer 7 by the control means 14 of this embodiment will be described.
However, in the present invention, as described above, the exposure light can be applied to both pulsed light and continuous light, but here, the case of pulsed light will be described as an example to simplify the description. Further, the present invention provides an integrated amount (exposure amount) of irradiation light on an irradiation surface.
The present invention can be applied not only to the optical measuring device 4 for measuring indirectly, but also to the exposure measuring device for directly measuring. However, here, the former case will be described as an example.

First, the gain of the optical measuring device 4 is switched to an optimum gain in accordance with the exposure amount, and even when the light amount decreases,
A method for maintaining high exposure dose accuracy will be described. (1) The laser (light source 1) is caused to oscillate a plurality of pulses at a constant energy, and the optical measuring device 4 and the exposure measuring device 10 measure the exposure indirectly and directly. However, optical measuring device 4
The gain of the amplifier 43 is the reference gain (K0). The measurement is performed while changing the transmittance and the illumination conditions of the light amount adjusting means 2.
Performed several times with the same number of pulses. An average value of the measurement results is calculated, and the relationship between the exposure amount on the wafer and the output signal of the optical measurement device 4 as shown in FIG.

The relationship between the amount of exposure on the wafer and the output signal of the optical measuring device 4 (FIG. 2) is measured by oscillating a plurality of pulses, and is obtained from an average value of the results of a plurality of measurements. Therefore, it can be said that the measurement error due to energy variation per laser pulse is sufficiently small.

Further, in order to shorten the measurement time, the transmittance of the light amount adjusting means 2 is measured in advance before being incorporated in the apparatus, the measured value is inputted by the input / output means 13, and the control means 14 The relationship in FIG. 2 may be obtained by calculation.

(2) From the result of (1), an optimum gain is selected according to the exposure amount of the wafer. When the wafer exposure amount is small, a large gain is selected, and when it is large, a small gain is selected. As a result, a large signal amplitude can be obtained even with a small exposure amount, and the SN ratio can be improved.

(3) The optimal gain according to the transmittance of the light amount adjusting means 2 and the illumination conditions measured in (2) is stored in the storage device 12.

(4) When executing the exposure operation, the control means 14 immediately switches the gain of the optical measuring device 4 in accordance with the transmittance of the light amount adjusting means 2 and the illumination conditions, and controls the exposure amount.

Next, a method of correcting the gain of the optical measuring device 4 will be described. (1) The laser (light source 1) is caused to oscillate a plurality of pulses at a constant energy, and the optical measuring device 4 and the exposure measuring device 10 measure the exposure indirectly and directly. The measurement is performed a plurality of times with the same number of pulses by switching the gain of the optical measuring device 4 according to the transmittance of the light amount adjusting means 2 and the illumination conditions. An average value of the measurement results is calculated, and the relationship between the exposure amount on the wafer and the output signal of the optical measurement device 4 as shown in FIG.

(2) From the measurement results (FIG. 2),
4, an accurate gain (inclination of a straight line) is calculated and stored in the storage device 12.

(3) At the time of the exposure operation, the control means 14 corrects the measurement value of the optical measuring device 4 using the result and controls the exposure amount (the design gain value is determined by the actually measured gain value). Is corrected for).

Further, the gain measurement of the optical measuring device 4 may be performed by the optical measuring device 4 alone before being incorporated into the apparatus, and the measured gain value may be input by the input / output means 13.

By correcting the gain of the optical measuring device 4 by the above-described method, the continuity of the exposure measurement can be maintained even when the gain of the optical measuring device 4 is switched.

In the present invention, a secondary light source forming means using a fly-eye lens or a condenser lens is used instead of or in addition to the light quantity adjusting means 2 using an ND filter or the like. You can also. In this case, the light amount can be adjusted by changing the illumination condition of the secondary light source forming unit.

[0029]

Next, an embodiment of a device production method using the above-described exposure apparatus will be described.
FIG. 3 shows a micro device (a semiconductor chip such as an IC or an LSI,
2 shows a flow of manufacturing a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, and the like. In step 1 (circuit design), a device pattern is designed. Step 2 is a process for making a mask on the basis of the designed pattern. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 4 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern on the mask is printed onto the wafer by exposure using the exposure apparatus having the above-described exposure control apparatus. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the production method of this embodiment, it is possible to produce a highly integrated device at a low cost, which was conventionally difficult to produce.

[0032]

As described above, according to the present invention,
Since the gain of the amplifier is switched according to the amount of light incident on the optical measuring instrument, a large signal amplitude can be obtained even when the exposure amount is small, and the SN ratio can be improved. Further, if the gain of the actual optical measuring instrument is measured in advance and each gain value is corrected by calculation, the continuity of the exposure measurement can be maintained even when the gain is switched.

Therefore, according to the present invention, it is possible to improve the exposure amount measurement accuracy by adding only a small amount of functions to the existing functions, thereby achieving high-precision exposure amount control. Can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a semiconductor exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a wafer exposure amount and an output signal of an optical measuring instrument in a semiconductor exposure apparatus.

FIG. 3 is a diagram showing a flow of manufacturing a micro device.

FIG. 4 is a diagram showing a detailed flow of a wafer process in FIG. 3;

[Explanation of symbols]

1: light source, 2: light intensity adjusting means, 3: beam splitter,
4: optical measuring instrument, 41: amplifier, 42: gain switching means, 43: amplifier, 5: reticle, 6: projection optical system,
7: Wafer, 8: Wafer chuck, 9: Wafer stage, 10: Exposure amount measuring instrument, 11: Operation means, 12: Storage means, 13: Input / output means, 14: Control means, 15: Light source control means.

Claims (6)

[Claims] 1. A light source for generating illumination light, at least one of a light amount adjusting means for adjusting an irradiation light amount to an object to be irradiated and a secondary light source forming means for forming a plurality of secondary light sources from the illumination light, First light quantity measuring means for indirectly measuring the irradiation light quantity on the irradiated body surface, second light quantity measuring means for directly measuring the irradiation light quantity on the irradiated body surface, and arithmetic means for calculating the measurement result; In an exposure apparatus having storage means for storing measurement and calculation results and control means for controlling the operation of each means, the first light quantity measurement means has an amplifier having a plurality of different gains, and the control means An exposure apparatus for controlling an exposure amount by switching a gain of said first light amount measuring means to an optimum value in accordance with an amount of incident light on said first light amount measuring means. 2. The control means causes each of the light quantity measuring means to measure the irradiation light quantity on the surface of the object to be irradiated a plurality of times while changing the setting of the light quantity adjusting means and / or the secondary light source forming means in advance. Based on the measurement result, the calculation unit calculates the optimum gain and the respective gain correction values of the first light amount measurement unit with respect to the irradiation light amount, stores the information in the storage device, and stores the information in the exposure operation. Immediately responds to the amount of irradiation on the surface of the object to be irradiated,
2. An exposure apparatus according to claim 1, wherein the exposure amount control is performed by switching the gain of said light amount measuring means to an optimum value and correcting each gain value. 3. An accurate gain value measurement of the first irradiation light quantity measuring means is performed by the first irradiation light quantity measuring means alone before mounting the exposure apparatus, and the measured value is inputted to the storage means by the input means. The control means causes the calculation means to calculate a correction value for each gain value from the measured value,
2. The exposure apparatus according to claim 1, wherein each exposure value is controlled by correcting each gain value based on the calculation result. 4. The storage means stores an optimum gain of the first light quantity measuring means with respect to an irradiation light quantity in correspondence with the illumination condition and / or a setting state of the light quantity adjusting means. In the exposure operation, the exposure amount control is performed by immediately switching the gain of the first irradiation light amount measurement unit to an optimum value according to the illumination condition and / or the setting state of the light amount adjustment unit. Item 4. The exposure apparatus according to any one of Items 1 to 3. 5. A light source for generating illumination light, at least one of a light amount adjusting means for adjusting an irradiation light amount to an object to be irradiated and a secondary light source forming means for forming a plurality of secondary light sources from the illumination light, First light quantity measuring means for indirectly measuring the irradiation light quantity on the irradiated body surface, second light quantity measuring means for directly measuring the irradiation light quantity on the irradiated body surface, and arithmetic means for calculating the measurement result; In an exposure apparatus having storage means for storing measurement and calculation results and control means for controlling the operation of each means, the second light quantity measurement means has an amplifier having a plurality of different gains, and the control means An exposure apparatus for controlling an exposure amount by switching a gain of the second light amount measuring unit to an optimum value in accordance with an amount of light incident on the second light amount measuring unit. 6. A device manufacturing method, comprising manufacturing a device using the exposure apparatus according to claim 1.