JP2001155986A - Aligner, method for fabricating device and method for alignment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a highly accurate light exposure by detecting the intensity of X-rays stably. SOLUTION: The aligner for transferring a mask pattern to an wafer coated with resist comprises means for setting a light exposure based on the intensity of X-rays passed through a filter and the intensity of X-rays not passed through a filter wherein the filter is made of such a material as not causing chemical reaction in the exposure wavelength region of X-rays. Since a filter having high X-ray resistance and invariant film thickness can be employed, a highly accurate light exposure can be set without causing any measurement error even after long term use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for projecting and exposing a circuit pattern drawn on a mask onto a substrate such as a wafer, and more particularly to an exposure method based on the result of measuring the illuminance of irradiation light through a predetermined filter. And an exposure method capable of controlling exposure under optimum conditions.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of integrated circuits, uniformity of a resist line width after development has been required more and more. In order to achieve the uniformity of the resist line width, it is important to improve not only the uniformity of the mask line width and the stability of the developing conditions but also the uniformity of the exposure amount. If the amount of exposure of the resist per unit time at each position in the exposure area can be measured, the time corresponding to the amount of exposure at each position can be calculated. By exposing for a time corresponding to the exposure amount at each position, a constant exposure amount can be obtained in the exposure area. Therefore, in order to improve the uniformity of the exposure amount, it is necessary that the exposure intensity measurement on the wafer surface has sufficient reliability. Therefore, exposure intensity detection becomes an important problem.

Generally, the sensitivities of a resist and an exposure intensity detector do not match. However, when the X-ray spectrum is the same in the wafer plane, for example, in the case of light exposure or exposure using an X-ray tube, if a stable detector output is obtained at each point, exposure should be performed for a corresponding time. And a uniform exposure amount can be obtained.

However, in an exposure method in which synchrotron radiation is reflected by an X-ray mirror, there is generally a large difference in the absolute intensity and wavelength distribution of X-rays depending on the exposure position, and it is difficult to measure the intensity with a detector. . For example, when radiating light is enlarged by a mirror swing method, a fixed mirror, or the like, X-ray intensity measurement is performed ignoring the difference in wavelength distribution depending on the exposure position, and the intensity at each exposure position is determined based on the output of the detector. When the exposure time is determined, the exposure unevenness may be ±±% or more within the wafer surface. This is because the wavelength range felt by the detector and the resist is different.

Therefore, as a first conventional X-ray intensity measuring method, a resist is exposed and the X-ray intensity at each point is determined based on the result of the exposure.
The line intensity was being measured.

As a second conventional X-ray intensity measuring method, a method using a resist as a filter has been proposed. This is because in the first measurement, the X-ray intensity I1 transmitted through the first filter made of the same material as the mask substrate is used.
And in the next measurement, the first material of the same material as the mask substrate
The X-ray intensity I2 transmitted through the second filter made of the same material as that of the resist used is measured, and the intensity difference (I1-I2) is obtained at each point of the exposure area. Alternatively, the standardized intensity difference (I1 / I0-I2
/ I0) at each point of the exposure area. In general, it is considered that the sensitivity of the same type of resist is proportional to the amount of X-rays that contribute to exposure. In particular, in X-ray exposure, it is considered that the absorbed X-rays emit secondary electrons, which are sensitized to the resist. Therefore, it is considered that the sensitivity of the resist is approximately proportional to the amount of X-rays absorbed. Good.
Therefore, at each point of the exposure position, the absorption amount of the resist is determined from the difference between the first measurement and the next measurement, and the exposure intensity at each point on the wafer surface is calculated.

[0007]

However, the above-mentioned first conventional X-ray intensity measurement method, which is the first conventional X-ray intensity measurement method, has the following disadvantages. 1. The development conditions and reproducibility of the resist directly result in an error in the exposure time. 2. When the exposure wavelength changes due to the change in the orbit of the injected electrons or the contamination of the mirror and Be window, it is necessary to perform the test exposure each time.

In the above-mentioned second conventional X-ray intensity measuring method, an intensity distribution corresponding to the sensitivity of the resist can be obtained. Reduced by the irradiation of rays,
Accurate X-ray intensity measurement was difficult. This is because the resist has a sensitivity to X-ray irradiation, so that a chemical change occurs in the resist due to X-ray irradiation, and the main chain and side chains of the resist molecules are cut off by X-rays, thereby reducing the molecular weight. Therefore, the scattering of the resist and the change in the film thickness caused the deterioration of the durability. Further, there is a disadvantage that the scattered resist adheres to surrounding members.

[0009]

According to the present invention, there is provided an exposure apparatus for setting an exposure amount based on the intensity of X-rays transmitted through a filter and the intensity of X-rays not passing through a filter. Wherein the filter is made of a material that does not cause a chemical reaction in the X-ray exposure wavelength region.

Preferably, the absorption coefficient of the filter is substantially proportional to the absorption coefficient of the resist within the exposure wavelength range, and the wavelength range of the exposure light is 0.2 to 1.5 nm. It is preferred to include.

Preferably, the filter does not have an absorption edge in the exposure wavelength range, and the filter preferably does not have an absorption edge in a wavelength range of 0.3 to 1.0 nm.

Further, the filters are Be, B, C,
Alternatively, it is desirable to be composed of an organic film.

Preferably, the X-ray intensity measurement is performed by an X-ray detector unit provided on a wafer stage for driving the wafer.

Further, based on the set exposure amount,
It is desirable to control the shutter.

Further, a device manufacturing method of the present invention includes a step of applying a resist to a wafer, a step of exposing a mask pattern to the wafer using the above-described exposure apparatus, and a step of developing the exposed wafer. It is characterized by the following.

Further, according to the exposure method of the present invention, the step of measuring the intensity of the X-ray without passing through a filter and the step of measuring the intensity of the X-ray through a filter made of a material which does not cause a chemical reaction in the exposure wavelength region of the X-ray are performed. And the step of setting an exposure amount based on the intensities of the two X-rays.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of the present invention will be described below.

The amount of resist absorption is given by the product of the film thickness t and the linear absorption coefficient μ (λ). Therefore, in order to produce a filter having the same absorption as the resist over the entire exposure wavelength range, the absorption coefficient μf (λ) is determined by the absorption coefficient μr of the resist.
A material having a constant μf (λ) / μr (λ) in relation to (λ) may be selected, and then a material may be selected so as to optimize the thickness of the filter.

Since the absorption in the X-ray region is caused by the X-ray absorption of the inner core electrons, the amount of X-ray absorption is determined by the element composition contained in the material. The absorption coefficient μ (λ) of the element is
In a wavelength region without an absorption edge, it is almost proportional to λ ³ .

On the other hand, since the resist is mainly composed of a polymer composed of light elements such as C, H, O and N, the absorption in the X-ray region is mainly determined by the absorption of these elements.
Since these light elements have no absorption edge at 2 nm or less, the absorption coefficient μr (λ) of the resist is almost proportional to λ ³ .

Therefore, in order to produce a filter having the same absorption characteristics as a resist, a filter made of an element having no absorption edge at 2 nm or less may be produced. Generally, the wavelength used for exposure is about 0.2 to 1.5 nm. Therefore, it is desirable to produce a filter made of an element having no absorption edge in this range. In addition, since the wavelength region used in particular is about 0.3 to 1.0 nm, it is desirable to produce a filter made of an element having no absorption edge in this range.

FIG. 2 is a graph showing the linear absorption coefficients of various substances and the linear absorption coefficient of a typical resist, PMMA. In FIG. 2, the horizontal axis is the wavelength, and the vertical axis is the linear absorption coefficient. Materials having no absorption edge in the exposure wavelength range include Be, C (diamond), B ₄ C, and polyimide. Although not shown in the figure, C, H,
The organic film composed of O and N has an absorption coefficient substantially similar to that of polyimide. These can be made to have the same absorption amount as the resist absorption amount by controlling the thickness. On the other hand, since Al has an absorption edge near 0.8 nm, it is difficult to have the same absorption as the resist even if the film thickness is controlled.

Further, Be or C (diamond) is X
This material is used as a window of a line exposure apparatus and is known to have high radiation resistance. Polyimide is also an organic film having high radiation resistance.

As described above, the resist undergoes a chemical reaction upon irradiation with X-rays and has photosensitivity, so that the resist is deteriorated when used as a filter. Therefore, a material having no photosensitivity to X-rays, for example, an organic film which does not cause a chemical reaction even by X-ray irradiation can be used as the filter of the present invention. Further, for example, although not shown, an F element (absorption edge 1.8 nm) known as Teflon or the like is used.
The organic film containing the compound also has a high radiation resistance without an absorption edge at the exposure wavelength and can be used as a filter.

Next, a description will be given of the uneven exposure when the exposure time is determined based on the X-ray intensity distribution I (y) measured by the detector.

The resist absorption amount De (y) after exposure at the exposure position y is the resist absorption amount D per unit time.
(y) and the exposure time Te (y) at each point can be expressed by the following equation.

De (y) = D (y) × Te (y) (Equation 1) Here, the exposure position y indicates the coordinates of an arbitrary exposure point. Further, Te (y) is expressed by the following formula: Te (y) = C / I (y) where X-ray intensity data is I (y). Here, I (y) is a value obtained by calculation or measurement. The proportionality constant C is determined by the sensitivity of the resist, the target resist line width after exposure and development, the X-ray intensity at the time of exposure, and the like. Therefore, when the ratio D (y) / I (y) of the resist absorption amount and the X-ray intensity data is defined by R (y), and Equation 2 is substituted into Equation 1, De (y) = C × D (y) / I (y) = C × R (y). Further, when the exposure unevenness Err (y) is defined as a difference from the average exposure amount, Err (y) = (De (y) −De_a) / De_a = (R (y) −Re_a) / Re_a (Equation 3). Here, De_a and Re_a are De with respect to position y.
And Re. From the above, to reduce the exposure unevenness, the ratio R of the amount of resist absorption and the X-ray intensity data is required.
It can be seen that (y) should be kept constant. In the present invention, R (y) is made constant so that the X-ray intensity data I (y) is approximately proportional to the resist absorption amount D (y).

<Embodiment 1> FIG. 1 shows a first embodiment of the present invention.

The X-ray 10 is guided to an X-ray exposure device 12 through an X-ray extraction window 11 made of a Be film. The X-ray exposure apparatus 12 has a wafer stage 13 movable in an XY plane and an X-ray attached to a mask stage (not shown).
A line mask 14 and an exposure shutter 15 for determining an exposure time
Is installed. The exposure shutter has an opening at the center, and the exposure time of each part of the exposure can be adjusted by adjusting the moving speed of the shutter.

A wafer chuck 21 and an X-ray detector unit 22 are mounted on the wafer stage 13.
The X-ray detector unit 22 includes: a first filter 1;
It comprises a second filter 2 and an X-ray detector 3.

The first filter 1 is made of SiC of the same material as the mask substrate. The second filter 2
It is made of Be, has a thickness of 15 μm, and is movable. Since the X-ray detector unit 22 is attached to the wafer chuck, the X-ray detector unit 22 can move within the XY plane, and can measure the exposure intensity over the entire exposure area.

With the above configuration, measurement of the intensity distribution for measuring the exposure time of each portion of the exposure is performed. First, the X-ray detector unit 22 is moved within the exposure angle of view, and then the X-ray mask 14 is retracted from the exposure area. Therefore, the X-ray detector unit 22 can measure the X-ray intensity without being blocked by the pattern on the X-ray mask.

First, the second filter 2 is removed from the position where the exposure light of the X-ray detector is irradiated, and the X-ray intensity transmitted through the first filter is measured by the X-ray detector 3. Is set to X at a predetermined position y within the exposure angle of view
The line detector unit 22 is sequentially moved, and I1 (y) is measured.

Next, the second filter 2 is moved from the position of the X-ray detector and set so that the intensity of the X-ray transmitted through the first and second filters is measured. The X-ray detector unit 22 is sequentially moved to a predetermined position y within the exposure angle of view, and I2 (y) is measured. I1 (y) -I2 (y) is obtained from I1 (y) and I2 (y) obtained in this way, and is substituted into Equation 2 as I (y). To determine.

The effect of the present invention will be described with reference to FIG.

X focused and expanded by two Pt mirrors
FIGS. 3 and 4 show an error Err (Equation 3) between the exposure amount absorbed by the resist and the measurement by the X-ray detector when the resist is collectively irradiated through the Be window. FIG. 3 shows an error when the output of the X-ray detector is used as X-ray intensity data I (y). FIG. 4 shows a case where data (I1 (y) -I2 (y)) obtained by a difference method using a Be having a film thickness of 15 μm for the filter 2 of the present invention is used as X-ray intensity data I (y). Is the error of

The calculation condition is that the electron energy is 585 Me
The radius of SR generator as V and X-ray source is 0.593m
And In this case, the peak of the exposure wavelength is 0.65 nm. X-rays condensed and expanded by two mirrors (both the first and second mirrors are Pt mirrors) are converted into a 20 μm thick B-ray.
e. Exposure is performed through a 2 μm-thick SiC mask membrane. As an X-ray detector, GaAsP (Au 9 nm,
The airside layer is 0.5 μm and the diffusion layer is 2.7 μm).

The exposure setting error when the exposure is set by directly using the output result of the X-ray detector is -4% to 1% as can be seen from FIG. On the other hand, when the exposure is set based on the output result of the X-ray detector using the above-described filter, as can be seen from FIG. 4, the exposure setting error is -0.2% to 0.1%. Within the range. That is, according to the present invention, it can be seen that the exposure setting error is improved by one digit or more compared to the conventional method.

According to the above-described embodiment, by using a filter having a large radiation resistance and a constant film thickness,
It is possible to set the exposure amount with high accuracy and without causing a measurement error even when used for a long time. In addition, by using a material having an absorption coefficient in the exposure wavelength range that is substantially proportional to the absorption coefficient of the resist as a filter, the exposure amount can be set with high accuracy.

<Embodiment 2> If the spectral sensitivity of the detector has no wavelength dependency and the absorption coefficient between the resist and the resist equivalent filter 2 is proportional, the resist equivalent filter 2
If the thickness is optimally selected, the exposure setting error is essentially zero.

However, in practice, the spectral sensitivity of the GaAsP detector has a wavelength dependence, and the absorption coefficients of the resist and the filter 2 corresponding to the resist are not completely proportional, but have a wavelength dependence. Therefore, the exposure setting error does not become zero.

Therefore, in this embodiment, a third wavelength correction filter is provided to correct these wavelength dependencies.

FIG. 5 shows that the first filter is SiC having a thickness of 2 μm, the second filter is Be having a thickness of 5 μm, and the third filter is a B filter having a thickness of 5 μm.
The exposure setting error obtained using e is shown. According to FIG. 5, the error is improved near the position of Y15 mm as compared with the case of FIG.

Further, the intensity of X-rays may change during the intensity distribution measurement. In that case, the intensity of the X-ray or the accumulated current at the time of the intensity distribution measurement may be measured, and the intensity distribution measurement value may be corrected based on the measured value.

<Embodiment of X-ray Exposure Apparatus> Next, an embodiment of an X-ray exposure apparatus using the above-described X-ray detector unit will be described.

FIG. 6 is a block diagram of the X-ray exposure apparatus of the present invention.

The SR light 62 emitted from the SR generator 61 as an X-ray source enters a mirror 63a installed at a predetermined position from a light emitting point. The sheet-shaped SR light 62 emitted from the SR generator 61 is enlarged by the mirror 63a and the mirror 63b. Although two mirrors are shown in the figure, two or more mirrors or one convex mirror may be used for the purpose of expanding the sheet-like SR light. The SR light 64 reflected by the mirror passes through a transmission mask 67 of an original plate in which a pattern made of an X-ray absorber is formed on an X-ray transmission film, and then has a desired pattern shape. Coated substrate 6
8 (wafer). The wafer 68 is held by the wafer chuck 69 of the wafer stage described above, and the wafer chuck 69 is mounted on a main stage (not shown).

On the upstream side of the mask 67, a shutter 65 for controlling the exposure time over the entire exposure area is provided. The shutter 65 has two movable light shielding plates. The two light shielding plates are driven by a shutter drive unit (not shown) controlled by a shutter control unit 70.

The shutter control unit 70 controls the shutter drive unit based on the exposure amount set by using the above-mentioned X-ray detector unit,
Is driving.

A beryllium film (not shown) is located between the mirror 63 and the shutter 65. The mirror side of the beryllium film is in an ultra-vacuum, and the shutter side is in a reduced pressure He.

By using the exposure apparatus of this embodiment, it is possible to obtain an exposure apparatus compatible with high speed and high precision.

<Embodiment of Device Manufacturing Method> Next, an embodiment of a method of manufacturing a semiconductor device using the above-described exposure apparatus will be described.

FIG. 7 shows a manufacturing flow of a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.
In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. 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). . In step 6 (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. 8 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. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. 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 manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which has been conventionally difficult to manufacture.

[0055]

According to the exposure apparatus of the first aspect of the present invention, it is possible to use a filter having a high resistance to X-rays and a constant film thickness. It is possible to set an exposure amount that does not cause a measurement error.

According to the exposure apparatus of the second aspect,
By using a material whose absorption coefficient within the exposure wavelength range is substantially proportional to the absorption coefficient of the resist as a filter, it is possible to set the exposure amount with high accuracy.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 is a diagram showing an absorption coefficient;

FIG. 3 shows uneven exposure when the output of an X-ray detector is used as it is.

FIG. 4 shows uneven exposure according to the first embodiment.

FIG. 5 shows exposure unevenness according to a second embodiment.

FIG. 6 is an embodiment of an X-ray exposure apparatus.

FIG. 7 is a flow chart of manufacturing a semiconductor device.

FIG. 8 is a wafer process flow diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st filter 2 2nd filter 3 X-ray detector 10 X-ray 11 X-ray extraction window 12 X-ray exposure apparatus 13 Uha stage 14 Mask 15 Shutter 21 Wafer chuck 22 X-ray detector unit

Claims (10)

[Claims] 1. An exposure apparatus for transferring a mask pattern onto a resist-coated wafer, comprising: means for setting an exposure amount based on the intensity of X-rays transmitted through a filter and the intensity of X-rays not passing through a filter. An exposure apparatus, wherein the filter is made of a material that does not cause a chemical reaction in the X-ray exposure wavelength region. 2. The exposure apparatus according to claim 1, wherein the absorption coefficient of the filter is substantially proportional to the absorption coefficient of the resist within the exposure wavelength range. 3. The exposure wavelength range is from 0.2 to 1.5 n.
The exposure apparatus according to claim 2, wherein the exposure apparatus includes a wavelength of m. 4. The filter according to claim 1, wherein the filter has no absorption edge within the exposure wavelength range.
An exposure apparatus according to any one of claims 1 to 3. 5. The filter according to claim 1, wherein the filter has a thickness of 0.3 to 1.0 nm.
The exposure apparatus according to claim 4, wherein the exposure apparatus does not have an absorption edge in the wavelength region of (1). 6. The exposure apparatus according to claim 1, wherein the filter is made of Be, B, C, or an organic film. 7. The exposure apparatus according to claim 1, wherein the X-ray intensity measurement is performed by an X-ray detector unit provided on a wafer stage that drives the wafer. 8. The exposure apparatus according to claim 1, wherein a shutter is controlled based on the set exposure amount. 9. A step of applying a resist to a wafer, a step of exposing a mask pattern to the wafer using the exposure apparatus according to any one of claims 1 to 8, and a step of developing the exposed wafer. A device manufacturing method, comprising: 10. A step of measuring the intensity of X-rays without passing through a filter, and a step of measuring the intensity of X-rays through a filter made of a material that does not cause a chemical reaction in an exposure wavelength region of X-rays. Setting an exposure amount based on the intensities of the two X-rays.