JPS62238622A - X-ray exposure apparatus - Google Patents

Abstract

PURPOSE:To enable a width of resist pattern to be controlled to a target value, by variably controlling an amount of half shade on the surface of the resist based on the target value of the width of the resist pattern after development, and controlling an X-ray exposure so as to obtain a thickness of the residual resist film as previously set. CONSTITUTION:X-rays 2 from an X-ray source 1 are pseudoparallelized by a solar slit 3, selectively attenuated by X-ray absorbing patterns 5 of a mask 4 and reach resist 6 on a wafer. The mask pattern 5 is thereby transferred and exposed to the resist. Various set data such as a target width of the resist and a residuasl film thickness are stored in a memory 18. A CPU 17 determines an aperture ratio of the solar slit 3, a proximity gap and an X-ray exposure D so as to provide an amount of half shade of 0.2mum at maximum. Monitoring values detected by an X-ray detector 10 by means of an interface 16, a wafer chuck 8 is moved by a drive section 15 so as to obtain the X-ray exposure D and a period of time for which the resist is irradiated with the X-rays is controlled. According to such operations, a resist pattern having the target width of 0.50mum can be transferred with the residual film thickness as previously set.

Description

Detailed Description of the Invention [Field of Application in Industry A] The present invention relates to an X-ray exposure apparatus for manufacturing semiconductor devices, and in particular to an X-ray exposure apparatus for performing proximity exposure using pseudo-parallel X-rays.
It relates to a line exposure device.

[Prior Art] With the recent miniaturization of VLSIs, X-ray exposure is being considered in which a mask pattern is transferred onto a resist using X-rays instead of light.

For X-ray exposure, methods using divergent X-rays or pseudo-parallel X-rays have been proposed, but both are basically proximity exposures in which a mask pattern is transferred onto a resist on a one-to-one basis.

However, in conventional X-ray exposure equipment, due to limitations of the radiation source or the inability to use completely parallel X-rays, penumbra inevitably occurs at the edge of the transferred pattern during proximity exposure. As a result, the disadvantage is that the line width of the mask pattern and the line width of the resist after development do not necessarily match.

[Problems to be Solved by the Invention] An object of the present invention is to manage the final resist line width to a target value by controlling the exposure conditions in proximity exposure using pseudo-parallel X-rays. The aim is to provide an X-ray exposure system that can determine and automatically control optimal exposure conditions by providing specific conditions such as the target resist line width, mask used, and resist characteristics. An object of the present invention is to provide a line exposure device.

[Means for Solving the Problems] The X-ray exposure apparatus of the present invention performs proximity exposure using pseudo-parallel X-rays. A first control means that variably controls the amount of penumbra on the resist surface based on a target width value, and a second control means that controls the amount of X-ray irradiation so that a preset resist residual film thickness is achieved. It is equipped with

The first control means is a gap control means that variably controls the proximity gap, or changes the parallelism of the pseudo-parallel X-rays, for example, by converting solar slits with different aperture ratios, in order to control the amount of penumbra. It consists of means.

Further, the second control means includes means for controlling the X-ray irradiation time to the resist when the irradiation intensity of the X-ray source is controlled to be constant at a predetermined level; If the X-ray irradiation time is limited to a certain fixed time due to the throughput of the apparatus, for example, the apparatus includes means for variably controlling the X-ray irradiation intensity.

[Operation] When performing proximity exposure using pseudo-parallel X-rays, the difference between the line width of the mask pattern and the corresponding line width of the resist after development is mainly due to the size of the penumbra amount and the amount of X to the resist. It depends on the magnitude of the radiation dose. The amount of penumbra changes depending on the parallelism of the X-rays and the proximity gap, and the amount of X-ray irradiation to the resist influences the residual film rate of the resist and influences the resist line width.

In the X-ray exposure apparatus of the present invention, the first control means controls the penumbra amount based on the target resist line width, and at the same time, the second control unit controls the X-ray irradiation amount to the resist so that it becomes the target residual film thickness. The resist line width can be controlled with high accuracy by actively controlling the amount of penumbra and the amount of irradiation.

In order to further clarify the above-mentioned objects and features of the present invention, embodiments of the present invention will be described below with reference to the drawings.

[Embodiment] FIG. 1 shows an embodiment of the present invention, and the exposure system includes an edge radiation source 1 that irradiates X-rays 2, and a gate that limits the parallelism of the irradiated X-rays 2 to within a predetermined parallelism range. a military equipment includes a solar slit 3 as a fixture and a mask 4 that performs proximity exposure of a pattern 5 made of an X-ray absorbing material on the surface of the resist 6 of the wafer 7 using pseudo-parallelized X-rays. The solar slit 3 can be exchanged with one with a different degree of parallelism using a slit exchanging unit 9.The wafer 7 is held by suction on a wafer chuck 8, and the wafer 7 is moved in a direction transverse to the irradiated X-rays by a drive unit 15 together with a mask 4 arranged in close proximity. The wafer and the mask can be moved vertically, and the control is performed by the drive control unit 14. The gap between the wafer and the mask is variable by the holding drive unit 11.
This control is performed by the gap control section 13. An X-ray detector 1o for detecting X-ray intensity is installed above the mask 4, and a gap sensor 12 for detecting the gap between the mask and the wafer is also provided. Detection data from these detectors and sensors is sent to the arithmetic processing unit (CPU) 17 via the interface 16, and is sent to the memory 18.
The slit exchange section 9, gap control section 13, drive control section 14, etc. are controlled by the CPU 17 based on setting information and program data given in advance to the CPU 17.

First, the principle of resist line width management used in the present invention will be described below.

Several methods have been proposed for pseudo-parallelizing unparalleled X-rays from an X-ray source, but here we will discuss
38, 59-127837, 60-34018
Line width control when using a method that combines an edge line source or a surface line source with a solar slit as disclosed in et al.

This method consists of the configuration shown in Fig. 2. First, among the X-rays 2 emitted in random directions from the edge ray source 1,
Only light having an incident angle of 00 or less that can pass through the solar slit 3 is irradiated onto the mask 4 . θ0 is defined as θo = tan-' (a/b) from the hole diameter a and thickness b of the solar slit 3, and the parallelism of the X-rays exiting the slit 3 is this angle θ. It will be kept below. A part of the X-rays irradiated to the mask 4 are absorbed by the X-ray absorption pattern 5 such as A of the mask 4.
The X-rays that are blocked by the pattern 5 and pass through the area without the pattern 5 selectively expose the resist 6 coated on the wafer 7 . In this case, in practice, the proximity gap P1
It is appropriate that θ0 be 5 to 40 μm and θ0 be 0.1 to 0.01 rad.

The exposed area of the resist 6 due to the X-rays that have passed through the area without the mask pattern 5 has an angle θ of the X-rays. A penumbra is generated at the edge based on the size Δ, and as shown in FIG. 3, the resist line width JlR becomes different from the mask line width of the mask pattern, as shown in FIG. The amount of penumbra Δ is Δ=P, @tanθ.

=P, ・a / b =P, ・SJ2 ・・(1) where 3℃ is the aperture ratio of the solar slit (
= a / b).

The main reason why the resist line width IR differs from the mask line width AM is the penumbra amount Δ, so by changing Pl and sa, fL
R can be controlled.

The difference in the resist line width after development with respect to the mask line width appears not only due to the penumbra amount Δ but also due to changes in the amount of X-ray irradiation to the resist, and this will be explained next with respect to a negative resist.

The residual film rate T of a negative resist is given by T; γ log (D/Do), where D is the actual amount of X-ray irradiation to the resist, and DO is the sensitivity of the resist, that is, the gelation reaction of the resist. The starting X-ray irradiation amount and γ are the γ value (resolution) of the negative resist. Normally, with negative resist, the residual film rate T is 0.
Choose 5 or more.

If the X-ray intensity distribution under mask pattern 5 is as shown in FIG. 4, the amount of X-ray irradiation is low.

When this point is reached, only the resist at positions where the X-rays are not blocked by the mask pattern 5 at all begins to remain after development, and the line width of the resist developed at this time becomes jlRI in FIG. With this irradiation amount, the resist in the penumbra (2Δ), which does not receive sufficient X-ray irradiation, has not yet reached a state where it will remain even after development.

X 11 Increase the amount of IM and that's it, L-Outside thread
The portions of the resist that receive only half the radiation dose compared to the portions where the rays are not blocked at all by the mask pattern, that is, the portions with an X-ray intensity of 0.5, receive an X-ray radiation dose of Do or more, and the resist is removed by development. It will remain as a film. The resist line width at this time is JZR2 in Figure 4.
And, the residual film rate T of the resist at the peak part is T=γ・log (2Do/Do): 0.3
It is represented by y.

In this way, the resist line width changes as the amount of X-rays irradiated onto the resist increases or decreases. Furthermore, as is clear from FIG. 4, since the resist line width also changes depending on the amount of penumbra, the line width of the resist can be further controlled by increasing or decreasing the amount of X-ray irradiation along with the penumbra amount Δ.

There are factors that affect the resist line width in addition to the penumbra amount Δ and the X-ray irradiation amount. For example, the resist line width ℃R is determined by the mask contrast β (X-ray transmission intensity in the area without mask pattern / transmitted through the mask pattern). 7.5rE21 which is also related to X-ray intensity)! , "The X-ray intensity distributions are shown for cases where R is ?n and 5, respectively. In the case of irradiation dose 2 Do, when β = 20, the resist line width is jZRll, and when β = 5, ILR12>fLR□1. .

When the mask contrast β changes in this way, the line width of the resist changes, so consider the change in the mask contrast β when the effective wavelength of the X-ray changes due to a change in the radiation source or dirt, etc. It is preferable to give a correction value to control the line width of the resist.

As described above, in the case of proximity exposure using pseudo-parallel X-rays, the line width of the resist after development is equal to the line 1jly of the mask.
, X-ray irradiation amount D, mask contrast β, proximity gap P1, slit aperture ratio SJ2, etc. have a complex influence. For example, in the case of a negative resist, penumbra amount Δ=Pyo・2
, the γ value of the resist is γ, and when 2Δ≦ILM, the line width ILM of the resist after development can be expressed as a function of these factors as shown in the following equation.

IIR= fz(J2v, Δ, 1/β, Do/D)・
(2) Another important requirement for an exposure apparatus is the wafer processing capacity per unit time, that is, the throughput, which is mainly determined by the exposure time t. on the other hand,
When the aperture ratio SL of the solar slit is reduced, the amount of X-rays passing through the solar slit decreases, and the amount of X-rays irradiated to the wafer decreases.
Linear density becomes smaller.

Therefore, the exposure time t can be expressed as a function of the irradiated X-ray dose and SfL as follows.

t=fs(D, 5JZ)...(3) From this,
In addition to the resist pattern shape, it is also possible to take into account the throughput and control the resist line width using the exposure time t as a control parameter.

In other words, in the X-ray exposure apparatus according to the present invention, when a target resist line width and specific conditions such as the corresponding mask and resist characteristics are given as set values, the optimum values of other exposure conditions corresponding to the target resist line width and other specific conditions such as the characteristics of the corresponding mask and resist are given as set values. is determined by calculation and exposure is performed.

When determining the optimal exposure conditions, the conditions may be determined based on data obtained through experiments, simulations, etc., or may be calculated using a function determined by analysis or an approximate expression thereof.

When determining the optimal exposure conditions, there is a degree of freedom in how to select specific conditions to input.If the mask and resist to be used have been determined, it is possible to set the resist line width target value and residual film rate setting value after development. An example of control in which the optimal penumbra amount and X-ray irradiation amount are determined by input will be described below.

As an example, the mask contrast β = 10, the resist line width is 0.45 to 0.50 μm for the mask line width of 045 μm.
m as a target, and using a resist with a γ value of 1.5, the remaining film rate T
When transferring a resist pattern of = 0.53, the aperture ratio SL and proximity gap P1 of the solar slit are set and controlled so that the penumbra amount Δ is 0.1 to 0.2 μm, and the X-ray irradiation amount is is T=y・log
CD/Do) to T=0.53. Due to γ=1.5, D=2.25D0 is controlled.

This will be explained below.

In FIG. 1, X-rays 2 emitted from a line source 1 pass through a solar slit 3 at an incident angle θ. Pseudo-parallelization is achieved within Here θ. is θ using the hole diameter a and thickness b of the solar slit 3. = tan-' (a/b). The pseudo-parallelized X-rays are selectively attenuated by the X-ray absorption pattern 5 of the mask 4 and are exposed to the resist 6 on the wafer.
The transfer exposure of the mask pattern is completed.

The procedure for this exposure is as follows.

(1) First, as in the above example, β=10, ILM=0.
Setting data of 45 μm, y=i, s, resist sensitivity Do, resist line width (max) as a drift value of 0.50 μm, and residual film rate T=0.53 are stored in the memory 18.

(2) Next, based on the setting conditions in (1) above, the arithmetic processing unit 17 calculates the penumbra amount (max) 0.2 μm and the X-ray irradiation amount D = 2.25D o, and the penumbra amount is The opening of the solar slit 3 has a maximum diameter of 0.2 μm.
e' /I L -F-! Jp p) >
Niji -J',--,-/rs
l-At t6 h A) The actual amount of X-ray irradiation is determined from among the combinations, and the set value of the sensitivity Do of the resist used.

(3) The gap controller 13 controls the mask 4 and the wafer 7 via the drive unit 11 while feedbacking the output of the gap sensor 12 via the interface 16 so that the P8 value obtained in (2) above is achieved. Set the proximity gap between

(4) The solar slit 3 having the aperture ratio S° C. determined in (2)′ is selected and set in the slit replacement section 9.

(5) Detection values of the X-ray detector 10 are transferred to the interface 16
The wafer chuck 8 is moved by the drive unit 15 via the drive control unit 14 so that the amount of X-ray irradiation determined in (2) is achieved while monitoring via .

Through the above operations, a resist pattern with a target line width of 0.50 μm is transferred at the set remaining film rate.

Although the above embodiments have been described using negative resists, similar control is possible for other types of resists by using corresponding analytical formulas and simulation results.

In addition, in the above-mentioned embodiment, the parallelism θ0 of the pseudo-parallel X-rays,
In other words, if the aperture ratio Sl of the solar slit is decreased,
The X-ray intensity passing through the solar slit is naturally attenuated. Therefore, in order to secure the same irradiation amount, the exposure time t must be relatively long, but if the exposure time t is fixed in advance in relation to throughput, the above equation (3) should be taken into account. Determine the exposure time t determined from the throughput, XR, X, β, Do, etc. (1
) to (3) can be used to calculate the penumbra amount Δ and the irradiation amount, and by controlling the X-ray intensity by, for example, the aperture ratio SfL of the solar slit so that the irradiation amount is equal to the exposure time t, a similar target can be obtained. Line width resist patterns can be transferred with priority given to throughput.

Furthermore, the present invention can be widely applied to proximity exposure using pseudo-parallel X-rays, and pseudo-parallelization is not limited to the combination of a tube X-ray source and a slit, but can also be applied to other types of exposure using, for example, SOR. It is similarly applicable to the pseudo-parallel X-ray method.

[Effects of the Invention] As described above, according to the present invention, the amount of penumbra and the amount of X-ray irradiation induced in proximity exposure using pseudo-parallel X-rays can be optimally controlled under given conditions. Thus, the resist line width can be controlled and managed to a target value, and the resist line width can always be managed to have a constant relationship with the line width of the mask pattern.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is a conceptual diagram of proximity exposure using pseudo-parallel X-rays, Fig. 3 is a cross-sectional view showing the relationship between a mask pattern and a resist pattern, and Fig. 4 is a A diagram showing the X-ray intensity distribution directly below the mask pattern,
FIG. 5 is a diagram showing changes in X-ray intensity distribution due to mask contrast. 1: Edge radiation source 2: X-ray 3: Solar slit 4: Mask 5: Mask pattern 6: Resist 7: Wafer 8: Wafer chuck 9: Solar slit exchange unit 10: X-ray detector 11: Wafer and mask holding/ Drive section 12: Gap sensor 13: Gap control section 14: Drive control section 15: Drive section 16: Interface 17: Arithmetic processing section 18: Memory. Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] 1. The X-rays from the X-ray source are passed through a pseudo-collimating means to be collimated within a preset parallelism range, and then a mask pattern is formed on the resist surface of the wafer using a proximity exposure method. X exposed to
In the line exposure device, the first step is to variably control the amount of penumbra on the resist surface based on the target value of the line width of the resist after development.
control means and X so that the set resist residual film thickness is achieved.
An X-ray exposure apparatus comprising: second control means for controlling radiation dose. 2. The X-ray exposure apparatus according to claim 1, wherein the first control means includes gap control means for variably controlling the proximity gap. 3. The X-ray exposure apparatus according to claim 1, wherein the first control means includes means for changing the degree of parallelism of the pseudo-parallelization means. 4. The X-ray exposure apparatus according to claim 1, wherein the second control means includes means for variably controlling the irradiation time to the resist while keeping the irradiation intensity of the X-ray source constant. 5. The X-ray exposure apparatus according to claim 1, wherein the second control means includes means for variably controlling the irradiation intensity of the X-ray source while keeping the X-ray irradiation time to the resist constant.