JP2003050454A - Phase shifting mask and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase shifting mask capable of relatively easily suppressing size variation and dislocation of a pattern in projection exposure with an error in production nearly equal to that in the case of a conventional bored phase shifting mask by making the intensity of transmitted light from bored regions and that from unbored regions nearly equal to each other in a bored phase shifting mask. SOLUTION: The phase shifting mask is constructed in such a way that the maximum intensity of transmitted light from bored regions and that from unbored regions are made nearly equal to each other on an image surface by embedding absorbent media in the unbored regions to lower the intensity of transmitted light.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an IC, an LSI, a C.
It belongs to the field of photolithography technology used when manufacturing devices having submicron or quarter-micron patterns, such as CDs, liquid crystal panels, and thin-film magnetic heads, and is especially a super-solution for forming fine patterns. The present invention relates to a phase shift mask which is one of image technologies.

[0002]

2. Description of the Related Art Currently, semiconductor integrated circuits, liquid crystal display devices,
A photolithography process is generally used to manufacture a highly integrated device such as a thin film magnetic head.
As a device indispensable for this step, a substrate such as a silicon wafer or a glass plate on which a pattern drawn on a photomask or a reticle (the terms are used interchangeably in this application) is coated with a photoresist. There is a projection exposure apparatus that exposes on top.

The resolution R of the projection exposure apparatus is given by the following equation using the process constant k ₁ determined by the wavelength λ of the exposure light source, the numerical aperture (NA) of the exposure apparatus and the developing process.

[0004]

[Equation 1] In addition, the focal range in which a constant imaging performance can be maintained is called the depth of focus, and the depth of focus DOF is given by the following equation using the proportional constant k ₂ .

[0005]

[Equation 2] From both equations, it is desired to shorten the wavelength and raise the numerical aperture for further miniaturization, but there is a problem that it cannot be realized because the depth of focus becomes small. Further, it is difficult to shorten the wavelength because the transmittance of the glass material decreases as the wavelength advances.
A large NA also causes problems such as difficulty in designing and manufacturing a lens.

Therefore, a super-resolution technique (RET: Re) for reducing the size by reducing the value of the process constant k _1.
solution Enhancement Techn
Recently, the “logic” has been proposed. As one of such super-resolution techniques, there is a phase shift mask method that gives a desired shift amount to the phase of transmitted light with respect to a specific region on the mask. The phase difference is formed by a refractive index difference between the medium and air, such as depositing an appropriate medium in the target region or forming a step by digging (etching) the substrate.

FIG. 8A shows a typical digging type phase shift mask. In the figure, 90 is a mask substrate,
Quartz is generally used as a material. Reference numeral 91 is a light shielding portion, and chromium is usually used. Reference numeral 92 is one of the light-transmitting portions, and by digging the mask substrate, the phase of the light of the light-transmitting portion 93, which has no digging, is advanced to generate a phase difference. The simplest example of the digging type is to always set the phase difference between adjacent transparent portions to 1 by adjusting the digging depth in a mask that generates a normal line-and-space pattern.
When the angle is 80 °, the positive and negative of the projected complex amplitude shown in FIG. At this time, as shown in FIG. 8C, near the center of the light-shielding portion, the light intensity becomes substantially 0 mainly due to the interference of light from the adjacent light-transmitting portions.

When a narrow line width is exposed with a normal mask that does not use phase shift, the light from the light-transmitting portions on both sides is diffracted near the center of the light-shielding portion which should be the non-exposed portion, and these diffracted light is Since the phase difference is 0, they interfere and strengthen each other. As a result, the intensity of the non-exposed portion does not become 0, resulting in deterioration of contrast and inability to resolve. On the other hand, the phase shift mask uses the effect of such interference,
The resolvable line width can be reduced to about half that of a normal mask.

Incidentally, although referred to here as a dug portion and a non-dig portion, some of the phase shift masks are shown in FIG.
There is also a type called a dual trench that is dug in both as shown in. In this case as well, the phase difference of the light transmitted from the adjacent portion is 180 ° due to the difference in the depth of the dug. Therefore, FIG. 8 (e) is also essentially the same as FIG. 8 (a), and the shallow dug portion may be considered as the non-dig portion and the deep dug portion may be considered as the dug portion.

In addition, there is a shifter type phase shift mask shown in FIG. In this case, a medium that causes a phase shift of 180 ° is placed on every other transparent portion of the mask.

[0011]

However, in the conventional digging-type phase shift mask, the intensity of the transmitted light from the digging portion and the transmitted light from the non-drilling portion are different from each other, so that it is on the object to be processed. There was a problem that the pattern of (3) causes a position shift.

FIG. 8B is a conceptual diagram used to explain the principle of the phase shift mask, and actually has a more complicated shape due to the structure in the depth direction due to the digging. Is known for rigorous calculations. In the non-drilled part, only the transmitted light that depends almost only on the width of the light-shielding part is reflected, but in the dug-down part, in addition to the transmitted light from the bottom side, the transmitted light from the side wall part and the transmitted light from the bottom side are reflected by the side wall. The mixed light and the like interfere with each other, and the result of the interference is the transmitted light from the dug portion. As a result, depending on the depth of the dug portion, the transmitted light from the dug portion has a smaller intensity than the transmitted light from the non- dug portion, and in the example described later, the intensity ratio is about 0.75. Become. This phenomenon may be called the waveguide effect.

The effect of this strength difference will be described with reference to FIG. In photolithography, a pattern is formed by transferring a projected intensity distribution onto a resist using a photosensitizer called a resist. For simplification, here, the transfer is assumed to occur only at the position where the intensity exceeds a certain threshold value, and the value indicated by TH in the figure is used as the threshold value. Further, assume that a positive resist is used, where the resist dissolves when the intensity exceeds a threshold.

Therefore, in this case, the regions L0, L1, L
The resist remains in the portions indicated by 2 and L3, and becomes a line by the subsequent etching. On the other hand, the areas S0, S1, S
In No. 2, the resist dissolves and becomes a space. Here, if the intensity of the transmitted light changes depending on the presence or absence of digging, the line width is almost constant, but the space width S1 is S0
Or S2 becomes larger. Therefore, there arises a problem that the position of the line is displaced even if the line width is as intended.

In order to reduce the waveguide effect, a method has been proposed in which the side wall is dug laterally as shown in FIG. 9 (a) so that it is located above the light-shielding portion to suppress the influence from the side wall. (For example, published patent 1998 1998 333
No. 316 publication and published patent 1999 No. 143048 publication). This method is effective for reducing the waveguide effect, but since the light-shielding portion is in a protruding form, there is a problem that damage there may be a problem and cleaning of the mask may be difficult.

As another method for reducing the waveguide effect, a method has been proposed in which the side wall of the dug portion is covered with a light shielding film as shown in FIGS. 2010 No. 512683 gazette and published patent Heisei 1
1 year No. 119411, etc.). This method can reduce the waveguide effect without causing a problem in supporting the light-shielding portion or cleaning the mask, but the light transmission region in the dug portion depends on the thickness of the light-shielding film formed on the side wall. It is difficult to control the thickness of the sidewall light-shielding film, but in recent years, MEF or MEEF (Mask (Mask), which is an amount indicating how much the manufacturing error of the mask is reflected in the error of the pattern size after projection exposure).
Error EnhancementFactor)
However, it is not based on the need to suppress the mask manufacturing error as much as possible. Furthermore, it is considered that there is a problem that the method of forming the light-shielding film on the side wall, which is significantly different from the conventional method, must be adopted as the manufacturing process.

As a similar method from the viewpoint of shielding the side wall of the dug portion, Japanese Patent Laid-Open No. 199919411 (1999).
Examples 6 and 7 of Japanese Patent Publication No. 7546 of Published Patent 2000
As disclosed in Japanese Patent Publication No. 5 and the like, there is a type in which a light-shielding portion for forming a line & space pattern and a light-shielding side wall are shared (see FIG. 9D). Although this method can also be expected to reduce the waveguide effect, there is a concern that mask manufacturing errors will increase, such as patterning by exposing the engraved and non-engraved parts coated with resists of different thicknesses at once. To be done.

Therefore, an object of the present invention is, in a digging-type phase shift mask, to make the intensity of the transmitted light from the digging portion and the intensity of the transmitted light from the non-drilling portion substantially equal to each other so that the pattern at the time of projection exposure is formed. It is to suppress the size variation and the position shift, and to achieve it easily and with the same manufacturing error as that of the conventional digging-type phase shift mask.

[0019]

In order to achieve the above object, a phase shift mask according to one aspect of the present invention is a medium that absorbs light of a certain wavelength on a substrate transparent to the light of a certain wavelength. And a light-transmitting portion through which light is transmitted, and a first light-transmitting portion of the light-transmitting portion is emitted from the second light-transmitting portion. In the digging type phase shift mask in which the substrate is digged so that the phase difference with the light is approximately 180 °, the intensity of the light emitted from the second light transmitting portion is reduced to The maximum value of the light intensity at the position corresponding to the first light-transmitting portion and the maximum value of the light intensity at the position corresponding to the second light-transmitting portion on the image plane on which the pattern drawn on the image is projected by the projection exposure system. Is characterized by substantially matching. Such reduction is performed, for example, by applying a medium that absorbs light of the wavelength to the second light transmitting portion to absorb the light. In such a phase shift mask, the maximum value of the light intensity of the light that has passed through the first and second light transmitting portions is substantially equal on the image plane projected by the projection exposure system, so that the position shift when the pattern is transferred is prevented. Can be prevented.

A light-transmitting portion and a light-shielding portion that determine a desired pattern to be transferred, and a phase shift mask in which the phase difference between the light emitted from the adjacent light-transmitting portions is substantially inverted.
A member for reducing the light intensity of the emitted light is arranged substantially parallel to the emission surface in the transparent portion corresponding to the stronger light intensity of the emitted light emitted from the adjacent transparent portions. . In such a phase shift mask, a member for reducing the light intensity reduces the intensity difference of the light emitted from the adjacent light transmitting portions.
The member that reduces the light intensity is a medium that absorbs light. The thickness of the medium is d, the absorption coefficient is κ, the wavelength used is λ, the circular constant is π, and the light is emitted from the adjacent light transmitting portions. If the intensity ratio of the emitted light is I = exp (-4πκd /
It is preferable that the relationship of λ) substantially holds. When such a relationship is satisfied, the deviation of the image plane of the pattern when the phase shift mask is used is within an allowable range of 10%.
It becomes the following.

According to another aspect of the present invention, in a manufacturing method, a medium which absorbs light having a certain wavelength is coated on a substrate which is transparent to light having a certain wavelength, and a transmitted light intensity is set to almost zero. And a light-transmitting portion through which light is transmitted. Of the light-transmitting portion, the first light-transmitting portion is formed by digging the substrate so that the phase difference from the light emitted from the second light-transmitting portion is approximately 180 °. What is claimed is: 1. A method for manufacturing a recessed phase shift mask, comprising a first step of dividing into at least one region sufficiently larger than a pattern size drawn on the mask, and a projection for each region. The second step of measuring the ratio of the maximum values of the light intensities at the positions corresponding to the first light transmitting portion and the second light transmitting portion on the image plane of the optical system, and to make the ratio approximately 1. The third step of determining the type and thickness of the absorptive medium applied to the second light-transmitting part, and the third step The absorbent medium which has been determined in step and a fourth step of applying at said thickness. This manufacturing method can provide a phase shift mask that exhibits the above-described operation. Further, such a method preferably includes a fifth step of inspecting the phase shift mask. This is because the effect of the phase shift mask can be confirmed.

The method according to another aspect of the present invention substantially reverses the phase difference between the light-transmitting portion and the light-shielding portion which determine the desired pattern to be transferred and the light emitted from the adjacent light-transmitting portion. The step of measuring the intensity ratio of the light emitted from the adjacent light-transmitting portions in the exposure using the digging-type phase shift mask, and the one having the higher intensity of the light in order to set the intensity ratio within the allowable range. A step of determining a thickness of a medium for reducing the intensity of the light, which is formed in the translucent part, and a step of forming the medium in the translucent part having a higher intensity of the light, The intensity difference of light emitted from the adjacent light transmitting portions of the phase shift mask is corrected. According to this method, it is possible to keep the light intensity difference between the light transmitting portions of the existing phase shift mask within the allowable range.

An exposure apparatus as still another aspect of the present invention has the above-mentioned phase shift mask, an illumination optical system for illuminating the pattern on the phase shift mask, and a projection optical system for projecting on the surface to be exposed. This exposure apparatus can also exhibit the function of the above-mentioned phase shift mask.

A device manufacturing method according to still another aspect of the present invention performs a step of projecting and exposing the object to be processed by using the above-described exposure apparatus, and performing a predetermined process on the object to be processed that has been projected and exposed. And steps. The claims of the device manufacturing method having the same operation as the above-described operation of the exposure apparatus extend to the devices themselves which are intermediate and final products. Further, such a device is, for example, L
Semiconductor chips such as SI and VLSI, CCD, LCD,
Includes magnetic sensors and thin film magnetic heads.

Other objects and further characteristics of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An exemplary exposure apparatus of the present invention will be described below with reference to the accompanying drawings. Here, FIG.
FIG. 3 is a schematic block diagram of the exposure apparatus 1 of the present invention. Figure 5
As shown in FIG. 1, the exposure apparatus 1 includes an illumination device 100, a mask 200, a projection optical system 300, a plate 400,
And stage 450.

The exposure apparatus 1 of this embodiment is a projection exposure apparatus which exposes the circuit pattern formed on the mask 200 on the plate 400 by the step-and-scan method.
The present invention can apply a step-and-repeat method and other exposure methods. Here, in the step-and-scan method, the wafer is continuously scanned with respect to the mask to expose the mask pattern on the wafer, and after the exposure of one shot is completed, the wafer is step-moved to the exposure area of the next shot. This is a moving exposure method. The step-and-repeat method is an exposure method in which the wafer is moved stepwise for each batch exposure of a shot of the wafer to move the next shot to the exposure area.

The illuminating device 100 illuminates the mask 200 on which a circuit pattern for transfer is formed, and has a light source section 110 and an illuminating optical system 120.

The light source section 110 uses, for example, a laser as a light source. The laser is Ar with a wavelength of about 193 nm.
An F excimer laser, a KrF excimer laser having a wavelength of about 248 nm, an F ₂ excimer laser having a wavelength of about 153 nm, or the like can be used, but the type of laser is not limited to the excimer laser, and for example, a YAG laser may be used. However, the number of lasers is not limited. When a laser is used for the light source unit 110, it is preferable to use a light beam shaping optical system that shapes a parallel light beam from the laser light source into a desired beam shape or an incoherent optical system that makes a coherent laser light beam incoherent. . Further, the light source that can be used for the light source unit 110 is not limited to the laser, and one or a plurality of lamps such as a mercury lamp and a xenon lamp can also be used.

The illumination optical system 120 is an optical system that illuminates the mask 200 and includes a lens, a mirror, a light integrator, a diaphragm, and the like. For example, condenser lens,
The fly-eye lens, aperture stop, condenser lens, slit, and imaging optical system are arranged in this order. The illumination optical system 14 can be used regardless of on-axis light or off-axis light. The light integrator includes a fly-eye lens, an integrator configured by stacking two sets of cylindrical lens array (or lenticular lens) plates, and the like, but may be replaced with an optical rod or a diffractive element. In addition, the illumination optical system 120 includes the plate 400.
A masking blade or a scanning blade for changing the size of the upper transfer area may be provided.

The mask 200 of this embodiment will be described below with reference to FIG. The mask 200 includes a mask substrate 210, a transparent portion 220 and a transparent portion 240, and a light shielding portion 230.
A desired circuit pattern (or an image) to be transferred which is composed of and is formed, and is supported and driven by a mask stage (not shown).

In this embodiment, for example, quartz is used for the mask substrate 210. Quartz has a refractive index of 1.51 at a wavelength of 248 nm and has no absorption. Mask substrate 2
10 is placed in air (refractive index 1.00, no absorption). The material of the light shielding portion 230 is chrome, and its refractive index is 1.33 at a wavelength of 248 nm and its absorption coefficient is 2.16.
Is.

The diffracted light emitted from the mask 200 passes through the projection optical system 300 and is projected onto the plate 400. The plate 400 is an object to be processed such as a wafer or a liquid crystal substrate and is coated with a resist. Mask 200 and plate 4
00 has a conjugate relationship.

In the case of a scanning projection exposure apparatus, the mask 20
0 and plate 400 to scan mask 200
Pattern is transferred onto the plate 400. In the case of a stepper (step and repeat exposure type exposure apparatus), the exposure is performed with the mask 200 and the plate 400 kept stationary.

The projection exposure system 300 of this embodiment is a 1/4 reduction optical system generally used in a scanner, and has a numerical aperture (NA) of 0.
7. σ of the illumination system has σ = 0.3 which is suitable for the phase shift method and can be realized by a normal exposure apparatus.

The case where a 0.12 μm line-and-space pattern is formed on the resist will be described below. This condition is a region where resolution using a normal binary mask is difficult and a phase shift mask is required. 0.12 μm on the resist is 0.48 μm with the mask
corresponds to the pattern m. That is, on the mask 200, both the engraved part and the non-engraved part to be the light transmitting parts 220 and 240 have a width of 0.48 μm, and the light shielding part 230 also has a width of 0.48 μm. The thickness of chromium forming the light shielding portion 230 is about 100 nm.

In addition to the above conditions, the depth of the dug portion is 2
48 / (1.51-1.00) to 244 nm, that is, the geometrical optical phase difference between the engraved portion and the non-engraved portion is 1
When the intensity distribution by the conventional phase shift mask shown in FIG. 9A at 80 ° is calculated, the peak intensity ratio of the dug portion and the non-dig portion is about 0.749. At this time,
When the intensity distribution is sliced so that the line width is 0.12 μm, the space due to the non-engraved part is 0.136.
μm, the space due to the dug portion is 0.104 μm, which is 0.016 for a desired space width of 0.12 μm.
There is a deviation of μm. Generally, a deviation of 10% or more with respect to the desired value cannot be tolerated.

[0038]

[Embodiment 1] FIG. 1 is a schematic sectional view for explaining a first embodiment of the present invention. In the figure, 210 is a mask substrate, 2
Reference numeral 20 is a dug portion of the light transmitting portion, and 230 is a light shielding portion, which are substantially the same as those shown in FIG. 9A. Reference numeral 240 denotes a non-digging portion of the light transmitting portion, 250 denotes an absorptive medium added on the non-digging portion of the light transmitting portion, and is made of the same chromium as the light shielding portion 230 here. In the conventional phase shift mask, the thickness of the absorptive medium 250 is 0.74 in terms of the intensity ratio between the dug portion and the non- dug portion.
It was decided to correct 9 only by the absorption of the non-digging part,
In this embodiment, it is about 3 nm. The thickness d is determined by the following formula, where I is the intensity ratio, κ is the absorption coefficient of the absorptive medium, λ is the used wavelength, and π is the circular constant.

[0039]

[Equation 3] FIG. 2 shows the image plane light intensity distribution by the mask of this embodiment together with the result of the conventional phase shift mask. In this embodiment, the strength ratio between the engraved portion and the non-engraved portion is improved to 0.877 while maintaining the effect as the phase shift mask. When the line width is 0.12 μm, the width of the space is 0.113 μm in the dug portion and 0.127 μm in the non- dug portion. This is a deviation of 0.07 μm from the desired width of 0.12 μm.
It is in the range of%.

Although the same chrome as the material of the light shielding portion is used as the absorptive medium 250 in this embodiment, any other material having absorptivity at the wavelength used can be used.
When using another material, it is necessary to change the thickness according to the absorption coefficient, but in implementing the present invention, the thickness d of the absorptive medium 250 (about 3 nm in this embodiment).
Is the thickness D of the light shielding portion 230 (about 100 nm in this embodiment)
It is preferable to use a material having a sufficiently small absorption coefficient, that is, a sufficiently large absorption coefficient. In that case, it is more preferable that the refractive index is close to 1.0.

The absorptive medium 230 for the light shield 230
It is not necessary for the absorption coefficient of the absorptive medium 250 for intensity correction of the light transmitting part to be significantly different, and the thickness d of 250 may simply be reduced. This is because when the thickness d is small, there is almost no phase delay with respect to air when passing through 230. Note that the complex refractive index of chromium at a wavelength of 248 nm is 1.3 + 2.1i, and if the thickness is 3 nm, the phase delay with respect to air is 1.3 °, which is sufficiently small. Further, if there is a condition that the allowable value of the width deviation is 5%, this has not been achieved in the present embodiment, but optimization is performed so that the width deviation becomes small with the thickness for correction by absorption only as an initial value. Just go. In the present embodiment, it is assumed that Formula 3 does not change depending on the allowable values of 10% and 5%. Formula 3 is valid when the width is sufficiently wide, and optimization is required based on Formula 3 when the width of the light transmitting portion is in the order of wavelength as in an actual phase shift mask.

[0042]

Second Embodiment In the phase shift mask 200 of the first embodiment,
Chromium was used as the absorptive medium 240 added to the non-drilled portion 240 to have a thickness of 3 nm, while the depth of the dug portion 220 was kept such that the geometrical optical phase difference was 180 °. There is. Generally, when a medium is added to the dug portion 220, the phase changes correspondingly and the effect as a phase shift mask decreases, but the thickness of chromium is 3 n.
The simple phase difference between air and m is (1.33-1.00)
It is only about × 3/248 to 0.003λ. On the other hand, the precision of the dug formation is 1 to 3 ° in phase angle and 0.003 to 0.008λ in terms of wavelength, and it can be said that the influence of the thickness of chromium is equal to or less than the precision of the dug formation.
Utilizing this fact, the existing conventional phase shift mask can be corrected.

FIG. 3 is a diagram for explaining a method of correcting a phase shift mask which is a second embodiment of the present invention. Figure 3
(A) shows a conventional phase shift mask 31. FIG. 3B shows a state in which the resist 32 is applied on the phase shift mask 31. FIG. 3C shows a state in which the non-engraved portion 34 is selectively exposed by performing exposure and development by a normal lithography method and leaving only the resist 33. After that, as shown in FIG.
The phase shift mask 200 is formed by depositing 5 to a desired thickness and finally removing the resist 33.

At the time of exposure shown in FIG. 3C, a resist pattern may be generated in the states shown in FIGS. 3D and 3E depending on the difference in exposure amount, alignment accuracy, and the like. When the absorptive medium is deposited as it is, in addition to the formation of the side wall at the boundary with the light shielding portion in FIG. 3D, the absorptive medium is also deposited on the light shielding portion. In FIG. 3E, a gap is created at the boundary with the light shielding part. Both are not preferable from the viewpoint of adjusting the strength ratio between the dug portion and the non-dug portion, but in the state of FIG. 3D, the sidewall is formed by using a sputtering method or the like having a high straightness. It can be suppressed, and the thickness deposited on the light-shielding portion is smaller than the thickness of the entire light-shielding portion, and the influence is small. Therefore, it can be considered that the resist patterning has a line width margin equivalent to the width of the chrome of the light shielding portion, and it is understood that the addition of the absorbing medium is easy.

The procedure of the actual correction method will be described with reference to FIG. First, the entire correction process will be outlined with reference to FIG.

In order to form a desired line width by photolithography, a conventional digging-type phase shift mask 31 is used.
Are produced (step 1002). This may have already been produced. After the inspection similar to normal mask fabrication such as defect inspection was performed, it was provisionally decided (however,
Exposure is performed under practical (experimental) exposure conditions (step 100
4) Based on the result of the direct measurement by the measurement of the aerial image or the difference in the space width due to the actual baking on the resist, the intensity ratio of the digging portion opening and the non-digging portion opening is calculated (step 1006). The absorptive medium to be added to the opening of the non-drilled portion and its thickness are determined so that the intensity ratio appearing in this measurement approaches 1.0 (step 1008). afterwards,
The process is completed after the process of adding the absorptive medium (step 1010) and the inspection (step 1012) (step 101).
4).

In the inspection, the absorbing medium adding step 1010 is performed.
It is confirmed whether the absorptive medium is added as designed on the mask that has passed through. This is because defects are often a problem in the forming method using etching as in the present embodiment, and the performance designed using simulation may not be exhibited. Also, you may actually try exposure to confirm the performance by inspection.

When measuring the intensity ratio, the intensity ratio may be different depending on the measuring position. In such a case, the mask may be divided into sections, and the intensity ratio may be corrected for each section.

FIG. 4B shows the absorbing medium added to the non-drilled portion opening so that the intensity ratio of the dugout portion opening and the non-drilled portion opening in the above-mentioned correction step is close to 1.0, and its absorbing medium. It is a flow chart which showed the process of determining thickness in detail.

First, it is assumed that the intensity ratio of the digging portion opening and the non-digging portion opening of the phase shift mask to be corrected is known. On the other hand, a database containing the refractive index and the absorption coefficient for the wavelength used in the exposure is prepared for various media applicable to the process of adding the absorptive medium, and one of them is extracted (step 1016). ). Next, when this medium is used, the thickness required to correct the intensity ratio is calculated from Equation 3 (step 1018), and the intensity distribution simulation is performed based on this based on the mask structure (step 1020). The simulation here is performed under one condition such as the point of defocus 0, and it is determined whether or not the thickness of this medium is acceptable with respect to the preset allowable value of the intensity ratio (step 1022). In general, a sufficient strength ratio correction cannot be performed with a thickness that considers only absorption, so the thickness is changed to make a loop (steps 1024, 10).
20).

When the intensity ratio falls below the allowable value (step 1022), simulation of general image characteristics such as defocus pair line width and positional deviation is performed (step 102).
6) If the result can be approved (step 102)
8) The medium and the thickness are adopted (step 1008), and if there is a problem, the medium may be changed and the same flow may be performed again (step 1016).

Here, the flow chart is advanced for one medium, but in practice, it is naturally possible to proceed in parallel for an arbitrary number of media and finally select one medium.

The mask stage supports the mask 200 and is connected to a moving mechanism (not shown). The mask stage and the projection optical system 300 are provided on, for example, a stage barrel surface plate supported by a base frame placed on a floor or the like via a damper or the like. The mask stage may have any configuration known in the art. The moving mechanism (not shown) is composed of a linear motor or the like, and the mask 200 can be moved by driving the mask stage in the XY directions. The exposure apparatus 1 scans the mask 200 and the plate 400 in a synchronized state by a control mechanism (not shown).

The projection optical system 300 has an aperture stop for focusing on the plate 400 the diffracted light that has passed through the pattern formed on the mask 200. The projection optical system 300 includes an optical system including only a plurality of lens elements, an optical system including a plurality of lens elements and at least one concave mirror (catadioptric optical system), a plurality of lens elements and at least one kinoform. An optical system having a diffractive optical element such as, an all-mirror type optical system, or the like can be used. When correction of chromatic aberration is required, a plurality of lens elements made of glass materials having different dispersion values (Abbe values) may be used, or the diffractive optical element may be configured to generate dispersion in the direction opposite to the lens element. To do.

A photoresist is applied to the plate 40. The photoresist coating process includes a pretreatment, an adhesion improver coating treatment, a photoresist coating treatment, and a prebake treatment. Pretreatment includes washing, drying and the like.
The adhesion improving agent coating treatment is a surface modification treatment (that is, hydrophobic treatment by applying a surfactant) for enhancing the adhesion between the photoresist and the base, and HMDS (Hexamet).
An organic film such as hyl-dilazane) is coated or steamed. Pre-baking is a baking (baking) process, but it is softer than that after development and removes the solvent.

The plate 400 is supported by the wafer stage 450. Since the stage 450 may have any configuration known in the art, detailed description of its structure and operation will be omitted here. For example, stage 45
0 is a plate 400 in the XY directions using a linear motor.
To move. The mask 200 and the plate 400 are, for example, synchronously scanned, and the positions of a mask stage and a wafer stage 450 (not shown) are monitored by, for example, a laser interferometer, and both are driven at a constant speed ratio. The stage 450 is provided, for example, on a stage surface plate supported on a floor or the like via a damper, and the mask stage and the projection optical system 300 are, for example, a base on which the lens barrel surface plate is placed on the floor or the like. It is provided on a lens barrel surface plate (not shown) supported on the frame via a damper or the like.

In the exposure, the light flux emitted from the light source section 110 illuminates the mask 200 by the illumination optical system 120, for example, Koehler illumination. Translucent part 220 of mask 200
Since the light intensities of the lights emitted from the light emitting devices 240 and 240 are substantially equal to each other on the plate 400 or within the allowable range, the pattern transfer to the resist is performed with high accuracy and a high quality device (semiconductor element, LCD element, image pickup element (CCD) Etc.), a thin film magnetic head, etc.) can be provided.

Next, with reference to FIGS. 6 and 7, an embodiment of a device manufacturing method using the above-described exposure apparatus 1 will be described. FIG. 6 is a flowchart for explaining the manufacture of devices (semiconductor chips such as IC and LSI, LCDs, CCDs, etc.). Here, manufacturing of a semiconductor chip will be described as an example. In step 1 (circuit design), the device circuit is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured. In step 3 (wafer manufacturing), 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 a lithography technique using the mask and the wafer. Step 5
(Assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and an assembly process (dicing, bonding),
It includes steps such as packaging (chip encapsulation). In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 7 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. Step 13
In (electrode formation), electrodes are formed on the wafer by vapor deposition or the like. In step 14 (ion implantation), ions are implanted in the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the exposure apparatus 1 exposes the circuit pattern of the mask onto the wafer. By the phase shift mask 200, it is possible to transfer a pattern having high resolution and reduced positional deviation onto a wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. Step 19
In (resist stripping), the resist that has become unnecessary after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. According to the manufacturing method of this embodiment, it is possible to manufacture a higher quality device than the conventional one.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications and changes can be made within the scope of the gist thereof.

With the above correction method, even when a simple conventional digging-type phase shift mask is used, the widths of the digging part opening and the non-digging part opening are made substantially the same, and high resolution and high accuracy are achieved. Projection exposure becomes possible.

As described above, according to the present embodiment, even if the conventional phase shift mask that does not require a complicated manufacturing process is used, the problem of the space width difference and the gap can be reduced to a practical level. It is possible to perform projection exposure with high resolution and high accuracy. Further, it is possible to provide a method for easily correcting the existing phase shift mask.

[0063]

According to the present invention, in the digging-type phase shift mask, the intensity of the transmitted light from the digging portion and the intensity of the transmitted light from the non-digging portion are made substantially equal to each other, and the pattern of the pattern at the time of projection exposure is changed. It is possible to provide a phase shift mask that can suppress a size variation and a positional shift relatively easily and with a manufacturing error comparable to that of a conventional digging-type phase shift mask.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a phase shift mask which is a first embodiment of the present invention.

FIG. 2 is a graph comparing the image plane light intensity distribution when the phase shift mask according to the first embodiment of the present invention is used with that of the conventional phase shift mask.

FIG. 3 is a schematic cross-sectional view showing a method for correcting a phase shift mask which is a second embodiment of the present invention.

FIG. 4 is a flow chart for explaining a method of correcting a phase shift mask which is a second embodiment of the present invention.

FIG. 5 is a schematic block diagram of an exposure apparatus of the present invention.

FIG. 6 is a flowchart for explaining a device manufacturing method having an exposure step of the present invention.

7 is a detailed flowchart of step 4 shown in FIG.

FIG. 8 is a sectional view showing a conventional phase shift mask.

FIG. 9 is a sectional view showing a conventional phase shift mask.

[Explanation of symbols]

1 Exposure device 200 Mask or reticle 210 mask substrate 220 Engraved part of translucent part 230 Shading section 240 Non-engraved part of the translucent part 250 Absorbent medium added to non-dug 300 Projection optical system

Claims (9)

[Claims] 1. A substrate transparent to light of a certain wavelength,
A medium that absorbs light of the wavelength is applied, and a light-shielding portion having a transmitted light intensity of approximately 0 and a light-transmitting portion that transmits light are formed.
In the digging-type phase shift mask, in which the substrate is digged so that the first light-transmitting portion has a phase difference of about 180 ° with respect to the light emitted from the second light-transmitting portion, among the light-transmitting portions. By reducing the intensity of the light emitted from the second light-transmitting portion, a pattern corresponding to the first light-transmitting portion is formed on the image plane on which the pattern drawn on the phase shift mask is projected by the projection exposure system. And the maximum value of the light intensity at the position corresponding to the second light-transmitting portion is made to substantially coincide with each other. 2. A substrate transparent to light of a certain wavelength,
A medium that absorbs light of the wavelength is applied, and a light-shielding portion having a transmitted light intensity of approximately 0 and a light-transmitting portion that transmits light are formed.
In the digging-type phase shift mask, in which the substrate is digged so that the first light-transmitting portion has a phase difference of about 180 ° with respect to the light emitted from the second light-transmitting portion, among the light-transmitting portions. The intensity of the light emitted from the second light transmitting portion is reduced by applying and absorbing a medium that absorbs the light of the wavelength to the second light transmitting portion, and the pattern drawn on the phase shift mask is reduced. On the image plane projected by the projection exposure system, the maximum value of the light intensity at the position corresponding to the first light-transmitting portion and the maximum value of the light intensity at the position corresponding to the second light-transmitting portion are made to substantially match. Characteristic phase shift mask. 3. A phase shift mask, which substantially reverses the phase difference between the light-transmitting portions and the light-shielding portions that determine a desired pattern to be transferred, and the light emitted from the adjacent light-transmitting portions, A phase shift characterized in that a member for reducing the light intensity of the emitted light is arranged substantially parallel to the emission surface in the transparent portion corresponding to the one having a higher light intensity of the emitted light emitted from the matching transparent portion. mask. 4. The member for reducing the light intensity is a medium that absorbs light, the thickness d of the medium, the absorption coefficient κ, the used wavelength λ, the circular constant π, and the adjacent light transmitting portions. Let I be the intensity ratio of the emitted light emitted from I = exp (-4π
The phase shift mask according to claim 3, wherein the relationship of κd / λ) is substantially established. 5. A substrate transparent to light of a certain wavelength,
A medium that absorbs light of the wavelength is applied, and a light-shielding portion having a transmitted light intensity of approximately 0 and a light-transmitting portion that allows light to pass therethrough. Of the light-transmitting portions, the first light-transmitting portion is the second light-transmitting portion. A method for manufacturing an engraving type phase shift mask in which the substrate is engraved so that the phase difference from the light emitted from the transparent portion of the mask is approximately 180 °, and the method is based on the pattern size drawn on the mask. First step of dividing into at least one area, which is sufficiently large, and light intensity at a position corresponding to the first light transmitting portion and the second light transmitting portion on the image plane of a projection optical system with respect to each area. A second step of measuring the ratio of the maximum values of the absorptive values, and a third step of determining the absorptive medium to be applied to the second light transmissive portion and the thickness thereof so that the ratio becomes approximately 1. A fourth step of applying the absorptive medium having the thickness determined in the third step. Production methods that. 6. The method of claim 5, further comprising a fifth step of inspecting the phase shift mask. 7. A light-transmitting portion and a light-shielding portion that determine a desired pattern to be transferred, and a digging-type phase shift mask in which a phase difference between lights emitted from adjacent light-transmitting portions is substantially inverted are used. A step of measuring the intensity ratio of the light emitted from the adjacent light-transmitting portions in the exposure, and the light-transmitting portion having the higher light intensity so as to set the intensity ratio within an allowable range, A step of determining a thickness of a medium that reduces the intensity of light, and a step of forming the medium in the light-transmissive portion having a higher light intensity, and the adjacent light-transmissive portions of the phase shift mask. Method to correct the intensity difference of the light emitted from the section. 8. An exposure comprising the phase shift mask according to claim 1, an illumination optical system for illuminating a pattern on the phase shift mask, and a projection optical system for projecting on a surface to be exposed. apparatus. 9. A device manufacturing method comprising: a step of exposing a substrate with a device pattern using the exposure apparatus according to claim 8; and a step of performing a predetermined process on the exposed substrate.