JP3472022B2 - How to make a photomask - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a photomask used when manufacturing a semiconductor device or the like by using a lithographic technique, and more particularly to a predetermined phase difference with respect to transmitted light during exposure. And a method for producing a phase shift mask that gives

[0002]

2. Description of the Related Art FIG. 1 shows an outline of a stepper used for exposure in a lithography process. The photomask 14 is set on the stepper, and the light emitted from the light source 11 is emitted by the fly-eye lens 13 and the condenser lens 14.
Is incident on the photomask 14 as parallel rays of light through the projection lens 15 and is focused on the wafer 16 through the projection lens 15.
As a result, the pattern formed on the photomask 14 is reduced and transferred to the resist applied on the wafer 16. Along with the recent sophistication of the demand for fine processing technology aiming at high integration of semiconductor devices, improvements have been made to the stepper optical system and photomask with the aim of improving pattern resolution and increasing the depth of focus of exposure. .

Among them, with respect to the photomask, a phase shifter is provided on a part of the mask pattern surface to invert the phase of a part of the optical image and superimpose it on the non-phase inversion part, thereby increasing the resolution. Phase shift masks have been developed that improve and increase depth of focus.

A Levenson mask is one of the phase shift masks. As a structure of the Levenson mask, for example, Japanese Patent Application Laid-Open No. 62-189468 discloses a substrate-engraved Levenson mask as shown in FIG. In FIG. 2, 21 is a quartz substrate, 22 is a light-shielding film, 2
Reference numeral 4 denotes a phase shifter, and the phase shifter 24 is formed by digging the quartz substrate 21 by a depth d according to a predetermined pattern.

FIG. 3 shows an outline of the manufacturing process of a substrate-engraved Levenson mask. First, the pattern of the resist 33 is formed every other one of the light transmitting portions 36 of the quartz substrate 31 on which the pattern is formed by the light shielding film 32. The phase shifter 34 is formed by etching the quartz substrate with reactive ions 37 or the like. Then resist 3
3 is removed to obtain a Levenson mask.

Further, by the same phase shifter structure and manufacturing method, a shifter edge type mask as shown in FIG. 4 is produced. In FIG. 4, 41 is a quartz substrate, 43 is a resist, 47 is a reactive ion, and 44 is a phase shifter.

In order to improve the resolving power and increase the depth of focus by using the phase shift mask, the optical images of the transmitted light are phase-inverted and superposed, and the phase difference provided by the phase shifter is set to about 180 degrees. It is necessary to adjust to the target value.

FIG. 5 shows the influence of the focus condition on the intensity distribution of the transmitted light. The vertical axis represents the intensity of the transmitted light, the horizontal axis represents the position on the wafer surface, 54 represents the phase shifter portion,
55 represents a non-shifter part. As shown in FIG. 5, when the phase difference deviates from the target value (180 degrees), a difference occurs between the light intensities that have passed through the adjacent apertures during defocusing during exposure. For this reason, in a portion where there is a focus shift in the exposure apparatus or a portion where there is a step on the substrate, the controllability of the pattern size becomes poor, which causes a deterioration in device characteristics. The phase difference provided by the phase shifter is mainly proportional to the substrate digging depth. Therefore,
In the photomask making process, highly accurate processing is required to bring the substrate engraving depth closer to the target value.

In order to adjust the substrate digging depth with high accuracy, the etching depth is measured during the shifter etching,
It is necessary to evaluate the difference from the target etching amount and then add a shifter etching. When a large pattern is measured, the change in the etching amount due to the pattern dependence of the etching rate (microloading effect) is not taken into consideration, and therefore the measurement of the phase difference includes a non-negligible error. Therefore, it is necessary to measure the phase difference of the fine pattern portion similar to the device pattern.
Such phase difference measuring methods include optical measuring methods, AF
M, a method using a contact type step measuring device, and the like.

However, an etching mask such as a resist remains in the mask during the phase shifter etching, and the optical phase difference measuring method means that the phase difference including the resist is measured. The error of was increasing.

A step difference is measured by an AFM or a contact type step measuring device including an etching mask such as a Cr light shielding film, and then the thickness of the Cr light shielding film measured in advance is subtracted to obtain a phase difference. Even in this case, since the etching amount of the Cr light-shielding film was unknown, an error occurred in the phase difference measurement value.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a phase shifter for a photomask in order to improve the resolution and depth of focus of an exposure optical image. It is an object of the present invention to provide a method for producing a photomask which enables highly accurate adjustment of the phase difference mainly determined by the etching depth when processing the.

[0013]

In the method for producing a photomask of the present invention, a predetermined phase difference is imparted to transmitted light at the time of exposure by controlling the digging depth of the surface of the transparent substrate. In the manufacturing method of the photomask to be generated, in addition to the area where the pattern used as the circuit of the element is arranged in the exposure area on the transparent substrate, the phase difference evaluation in which the pattern not used as the circuit of the element is arranged In the process of forming a region for etching and etching the surface of the transparent substrate,
At least one step of evaluating an error with respect to a target value of the phase difference by selectively removing a part of the etching mask in the phase difference evaluation region and measuring the phase difference with respect to transmitted light is provided. And

When the etching mask is an organic film, it is desirable to selectively remove a part of the etching mask by using a photo-assisted etching method, a laser ablation method or a focused ion beam.

In the case where the etching mask is a light-shielding or semi-transmissive film, the etching mask can be formed by using a photo-assisted etching method, a laser ablation method, or a focused ion beam without scraping the transparent substrate. It is desirable to selectively remove a part of

As the design rule of the pattern arranged in the phase difference evaluation region, it is desirable to use the same design rule as the pattern of the region used as the circuit of the element.

According to the method for producing a photomask of the present invention, a phase difference evaluation area is provided in the exposure area on the transparent substrate to evaluate the etching amount, and a phase difference evaluation pattern is arranged in this area. To do. During the process of etching the phase shifter on the substrate, the etching mask is selectively removed in a part of the phase difference evaluation region, and the phase difference with respect to the transmitted light is measured. Based on the measurement results thus obtained, the etching amount to be added, specifically, the etching time is determined. As described above, by repeating the steps of (1) etching the substrate, (2) selectively removing the etching mask in a part of the phase difference evaluation region, and (3) measuring the formed phase difference, It is possible to create a photomask (phase shift mask) with high phase difference accuracy by removing the influence of pattern dependence of the etch rate or fluctuations in the etch rate due to instability factors of the etching equipment and etching process. Become.

Further, when measuring the phase difference caused by the phase shifter portion, the phase difference with respect to the wavelength of the transmitted light actually used is directly measured by using an optical method, so that the etching deposit in the fine pattern is , The etching surface roughness, the phase difference including the effects of the waveguide effect,
The measurement can be performed directly without being affected by an etching mask such as a resist, and the phase difference accuracy caused by the phase shifter portion can be improved.

It is also possible to obtain the correlation between the phase difference and the step difference measured by the contact type step meter in advance and convert the phase difference from the step difference measured value. As an example of the optimum etching amount value, Japanese Patent Application No. 6-2221
90, the side wall of the light-shielding film and the side wall of the phase shifter are substantially aligned with each other, and the substrate engraving amount is changed alternately in the adjacent openings, the exposure wavelength is 248 nm, the quartz substrate is used. When the refractive index of 1. is set to 1.50, it is approximately 488 nm in the phase shifter part and 24 in the non-shifter part.
It is desirable to set it to 8 nm. If the phase shift mask is created according to this phase difference, the depth of focus of the exposure optical image can be increased. Further, in the phase shift mask having a shape in which the side wall of the phase shifter is hidden inside the side wall of the light-shielding film, it is desirable that the etching amount of the phase shifter portion be approximately 248 nm under the same conditions as described above. Even with this type of phase shift mask, the depth of focus of the exposure optical image can be increased if it is created in accordance with the phase difference as the target value. In the former (double-dip type), the desired etching depth is smaller than that in the latter because the phase advances due to the waveguide effect.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Example 1) FIG. 6 shows an example of an embodiment of the present invention. Figure 6
[FIG. 3] is an explanatory diagram of a Levenson mask forming process, and in this example, light having a wavelength of 248 nm is used as an exposure light source.

First, a light shielding film pattern is formed on a quartz substrate as follows. A substance sufficiently opaque to the exposure wavelength is formed into a film on the quartz substrate 61 by a method such as sputtering, and an etching mask material such as a resist is applied onto the quartz substrate 61 by a spin coater or the like, and an electron beam drawing apparatus or a laser drawing apparatus. After patterning is performed by using, etc., etching is performed to form a light shielding film pattern 62 as shown in FIG.

In addition to the pattern functioning as a device, this light-shielding film pattern includes at least one phase difference evaluation region. FIG. 7 shows an example of the phase difference evaluation area. In this example, the mask to be created is an exposure mask for forming a bit line of DRAM (dynamic RAM),
The line and space (L &
A pattern 76 based on S) was formed. In the pattern size for phase difference evaluation created in this example, the minimum pattern pitch on the mask is 1.44 μm (0.
36 μm). In this example, five patterns for evaluating the phase difference are arranged in the central portion and the peripheral portion of the mask substrate, respectively, in the portions where the device pattern 78 is not provided.

Next, an etching mask material such as a resist is applied over the entire surface of the mask substrate. In this example, an i-line resist was applied with a film thickness of 1 μm using a spin coater. Next, a pattern for processing the phase shifter of the Levenson mask is formed. As shown in FIG. 6B, this is a pattern 67 in which an opening area is arranged every other light transmitting portion of the light shielding film pattern 62, and the phase shifter portion 6 of the Levenson mask is formed.
The resist 63 of No. 4 is removed by a drawing technique such as electron beam drawing or laser drawing to expose the quartz substrate. In this example, drawing was performed using a laser drawing device.

Next, this mask substrate is etched to form a phase shifter 64. For the etching of the quartz substrate 61, methods such as wet etching, CDE (chemical dry etching), RIE (reactive ion etching) can be applied. In this example, a parallel plate type RIE using CF4 gas was used. A schematic diagram of the parallel plate type RIE used in this example is shown in FIG. This apparatus comprises a chamber 85, counter electrodes 86 and 87, a high frequency power supply 88, a reaction gas supply port 83, a vacuum pump 82 and the like. An exposure mask 89 is set between the opposing electrodes, a high frequency voltage is applied between the opposing electrodes while flowing a reaction gas, plasma 84 is generated, and the surface of the quartz substrate is etched. The etching conditions were that the flow rate of CF4 was 10 sccm, the gas pressure was 2 Pa, and the RF power applied to the electrodes was 0.28 W / c.
It was set to m ² . Under this condition, the etching rate of the quartz substrate was about 25 nm / min. As shown in FIG. 6C, the produced photomask is a photomask in which the side wall of the light shielding film and the side wall of the phase shifter are substantially aligned with each other and the amount of substrate engraving is alternately changed in the opening. Considering the exposure wavelength of 248 nm and the refractive index of quartz, the etching depth for obtaining the desired phase difference is approximately 240 nm, so the etching time was set to 9 minutes.

Next, as shown in FIG. 6D, a part of the etching mask 63 in the phase difference evaluation region is selectively removed to measure the phase difference. In this example, the resist on the phase difference evaluation pattern was removed by using the photo-assisted etching method. FIG. 9 shows a schematic view of the photo-assisted etching apparatus used in this example. This apparatus includes a chamber 95 having a quartz window 94, a light source 91, a condenser lens 96, an O
_{It is} composed of _two gas supply ports 93 and a vacuum pump 92. By setting the mask substrate 99 in the chamber 95 and focusing and irradiating light on a predetermined area on the resist while flowing O ₂ gas, the resist in the area to which the light is focused and irradiated is removed. In this example, the O ₂ gas pressure is 100 torr.
r, a Hg-Xe lamp (200 W, wavelength 200 nm to 450 nm) was used as a light source, and this was 200 μm in diameter.
It was focused to about m. The etching rate of the resist at this time was about 20 nm / min. The thickness of the resist at the time of resist coating was 1 μm, but at the time of phase shifter etching, the resist was also partially removed,
The resist thickness was about 600 nm. for that reason,
The etching time (laser light irradiation time) required to completely remove the resist was 30 minutes.

Next, the phase difference of the phase shifter 64 is measured using the phase difference evaluation pattern of the portion where the etching mask is removed. In this example, an optical phase difference measuring device was used for the phase difference measurement. FIG. 10 shows a schematic view of the optical phase difference measuring device used in this example. In this apparatus, the light generated by using the excimer laser light source 101 is converted into the prism 1
The light beam is separated into two light fluxes by 02 and these are separated by the photomask 10
The phase shifter unit 104 and the non-shifter unit 105 of No. 3 are made incident. When the two light fluxes transmitted through the photomask 103 are interfered with each other while mechanically scanning the phase modulation prism 106, the optical amplifier 1 responds to the phase change of the two light fluxes.
The interference intensity observed at 07 changes. The phase difference between the phase shifter portion 104 and the non-shifter portion 105 of the photomask 103 is obtained from the correlation between the change in the interference intensity and the phase modulation degree of the phase modulation prism 106. In this example, the wavelength of the excimer laser light source used was 248 nm.

When the phase difference of the photomask of FIG. 6 (d) was obtained by this apparatus, the error from the desired phase difference was 5 °. Converting this to a step of the quartz substrate, the error from the target value of the step is 7 nm. Therefore, an additional phase shifter process was further applied to this photomask. The equipment used for etching the quartz substrate is the same as in the previous time.
The parallel plate type RIE shown in Fig. 4, the etching conditions are the same as the previous time, the flow rate of CF4 is 10 sccm, the gas pressure is 2 Pa, and the RF power applied to the electrodes is 0.28 W / cm.
² Since the previous etching rate was 25 nm / min, this etching time was set to 15 seconds.

Next, the phase difference of this photomask is measured again. First, a part of the resist of the pattern portion where the resist has not been removed yet is selectively removed from the phase difference evaluation region on the photomask. In this example, FIG.
As shown in, the resist on the part adjacent to the pattern used for the previous phase difference measurement was removed. As in the previous case, the photo-assisted etching apparatus shown in FIG. 9 was used to remove the resist. The laser light irradiation time was set to 30 minutes as in the previous time, and the phase difference measuring device shown in FIG. 10 was used for the phase difference measurement, as in the previous time. As a result, an error of 1 ° from the desired phase difference was obtained. Since the error of the phase difference with respect to the target value was within the allowable range, the phase shifter etching process was completed.

Next, the etching mask is removed. In this example, the resist was oxidized and removed by a mixed solution of sulfuric acid and hydrogen peroxide by SH treatment. Further, in this example, the entire opening area of the photomask is etched by about one exposure wavelength. The target etching amount at this time is 2
It was 48 nm. Similar to the phase shifter etching, the parallel plate type RIE shown in FIG. 8 was used for this etching. CF4 was used as an etching gas, the reaction chamber gas pressure was 2 Pa, and the RF power applied to the electrodes was 0.2.
The etching time was 8 W / cm ² , and the etching time was 9 minutes and 30 seconds. As a result, a double engraved Levenson mask in which the engraving amount was alternately changed in the adjacent openings as shown in FIG. 14 was completed. In FIG. 14, 141 is a quartz substrate and 1 is a quartz substrate.
Reference numeral 44 represents a phase shifter portion (phase difference π portion), and 145 represents a non-shifter portion (phase difference 0 portion).

Using the photomask having a phase error of 1 ° obtained in this example, NA = 0.5, σ = 0.3, wavelength 248.
When projected and exposed with an exposure device of 0.1 nm, 0.18 μmL
The depth of focus of the & S pattern was 1.5 μm.
When a photomask is prepared by conventional phase difference control based on etching rate and etching time, the accuracy of phase control is low, and it is difficult to prepare a photomask with a large depth of focus as described above. .

Next, in order to apply the photomask forming method according to the present invention to an actual device pattern, 1G-DRA
A memory cell portion wiring layer mask of M was prepared. L & S having a minimum line width of 0.15 μm was used for the phase difference evaluation region. When a phase shifter was formed on this photomask by the method of the present invention, a photomask having a phase error of 2 ° was obtained. As a result of projection exposure of this photomask with the above-mentioned exposure apparatus,
The wiring pattern could be resolved with high dimensional accuracy, and the electrical characteristics of the device could be improved. (Example 2) Next, a second example of the embodiment of the present invention will be described.

First, a light shielding film pattern is formed on a quartz substrate as follows. A material that is sufficiently opaque to the exposure wavelength is formed on a quartz substrate by a method such as sputtering, and an etching mask material such as a resist is applied on the quartz substrate by a spin coater, etc. After performing patterning by using, etching is performed (FIG. 6A).

In addition to the pattern functioning as a device, this light-shielding film pattern includes at least one phase difference evaluation region. In this example, the mask to be created is D
An exposure mask for forming an element isolation region of a RAM (dynamic RAM) was used, and a pattern based on line & space (L & S) was formed in the phase difference evaluation region. The pattern size of the phase difference evaluation region created in this example has a minimum pattern pitch of 1.44 μm on the mask (0.
36 μm). In this example, five phase difference evaluation patterns are arranged in the central portion and the peripheral portion of the mask substrate, respectively, in a portion where there is no device pattern (light transmitting portion) (FIG. 7).

Next, an etching mask material such as a resist is applied over the entire surface of the mask substrate. In this example, an i-line resist was applied with a film thickness of 1 μm using a spin coater. Next, an opening region for processing the phase shifter of the Levenson mask is formed on this mask substrate. This is a pattern in which openings are arranged every other light-transmitting portion of the light-shielding film pattern, and the resist of the phase shifter portion of the Levenson mask is removed by a drawing method such as electron beam drawing or laser drawing,
Expose the quartz substrate. In this example, drawing was performed using a laser drawing device (FIG. 6B).

Next, this mask substrate is etched to
Form a phase shifter. For etching the quartz substrate, methods such as wet etching, CDE (chemical dry etching) and RIE (reactive ion etching) can be applied. In this example, as in the first example, the parallel plate type RIE using CF4 gas shown in FIG. 8 was used. The etching condition is that the flow rate of CF4 is 10 scc.
m, gas pressure was 2 Pa, and RF power applied to the electrode was 0.28 W / cm 2. Under this condition, the etching rate of the quartz substrate was about 25 nm / min. The created photomask is a phase shift mask having a shape in which the side wall of the phase shifter is hidden inside the side wall of the light shielding film, and the etching depth for obtaining a target phase difference of 180 ° is an exposure wavelength of 248 nm and a refractive index of quartz. Considering the above, the etching time is set to 9 minutes because it becomes 248 nm.

The above steps are the same as those in the first example except for the device pattern, the shape of the formed phase shift mask, and the target phase difference. Next, using the partial resist stripping / retardation measuring device shown in FIG. 15, one etching mask (resist) in the retardation evaluation region was removed, and the retardation was measured.

FIG. 15 is a conceptual diagram of the partial resist peeling / phase difference measuring device used in this example. An O ₂ gas supply port 163 and a vacuum pump 162 are connected to the sample chamber, an assist etching light source 161 is arranged outside a quartz glass window arranged on the upper surface of the sample chamber, and a side surface of the sample chamber is provided. The light sources for phase difference measurement 1 are respectively provided on the outer sides of the two quartz glass windows arranged in
58 and an optical amplifier 159 are arranged. Further, the phase modulation prism 15 is provided on the front surface of the phase difference measuring light source 158.
7 is a phase modulation prism 1 on the front surface of the optical amplifier 159.
56 are arranged respectively. A mask stage 15 holding a photomask 153 is provided inside the chamber.
2. A switching mirror 151b that irradiates the photomask 153 with light from the phase difference measurement light source 158 from the back surface side, and a switching mirror 151a that allows light transmitted through the photomask 153 to enter the optical amplification device 159 are arranged. Furthermore,
By moving the switching mirrors 151a and 151b, this apparatus can be switched so that the photomask 153 is irradiated with light from the light source 161 for assist etching from the front surface side.

Next, the usage of this device will be described. First, the photomask 153 is set in the partial resist peeling / phase difference measuring device. After moving the switching mirrors 151a and 151b out of the optical axis of the assist etching light source 161, the mask stage 152 is finely moved to irradiate the phase difference evaluation region of the exposure mask 153 with the assist etching light source 161 from the surface side. Align as you would. Next, O ₂ which is an etching gas is introduced into the chamber.
Let the gas flow. In this example, the pressure of O ₂ gas is 100 to
rr. In this state, the assist etching light source 1
61 is focused and irradiated on the exposure mask 153. In this example, the light source is a Hg-Xe lamp (200 W, wavelength 200
nm-450 nm) and this light is
The light was focused to about 00 μm. At this time, the resist etching rate was 20 nm / min, and the resist in the pattern portion was removed by the light irradiation time of 30 minutes.

Next, the gas supply and the focused irradiation light are stopped,
The switching mirrors 151a and 151b are moved to a position where the optical axis of the light source 161 for assist etching is blocked, and the switching mirrors 151a and 151b constitute a phase difference measuring system. That is, the light from the phase difference measurement light source 158 is
Switching mirror 151 via phase modulation prism 157
Light incident on the switching mirror 151b and reflected by the switching mirror 151b passes through the photomask 153,
The light that is incident on the laser light 1a and reflected by the switching mirror 151a is incident on the optical amplification device 159 via the phase modulation prism 156.

Next, the mask stage 152 is finely moved to
The phase shifter portion 154 and the non-shifter portion 155 on the mask are aligned with the phase difference inspection optical system. In this device, the light emitted from the phase difference measuring light source 158 is separated into two light fluxes by the phase modulation prism 157, and the two light fluxes are separated.
The third phase shifter unit 154 and the non-shifter unit 155 are made to enter. When the two light fluxes transmitted through the photomask 153 are interfered with each other while mechanically scanning the phase modulation prism 157, the interference intensity observed by the optical amplifier 159 changes with respect to the phase change of the two two light fluxes. . The phase difference between the phase shifter portion 154 and the non-shifter portion 155 of the photomask 153 is obtained from the correlation between the change in the interference intensity and the phase modulation degree of the phase modulation prism 157. In this example, the phase difference measuring light source 158 is an excimer laser light source, and the wavelength is 2
It was set to 48 nm.

As a result of the measurement, the phase difference of the phase shifter is 179.
A highly accurate photomask with a very small error from the target value (180 °) was obtained. In this example, the phase difference was within the allowable value of the error in one etching, so the phase shifter etching was completed.

Then, the resist was oxidized and removed by SH treatment to complete a photomask. The resist may be removed by an O ₂ asher using oxidation by O ₂ plasma instead of the SH treatment.

Further, in this example, the entire mask was wet-etched with a dilute hydrofluoric acid solution. As a result of performing the treatment for 2 minutes with a solution having a concentration of 10%, only the quartz substrate was etched by about 20 nm without etching the Cr light shielding film. As a result, a Levenson mask was completed in which the side wall of the phase shifter was hidden inside the side wall of the light shielding film.

Using the photomask having a phase difference of 179 ° obtained in this example, NA = 0.6, σ = 0.3, wavelength 24
Projection exposure with an exposure device of 8 nm gave 0.15 μm
A depth of focus of 0.9 μm was obtained in the L & S pattern. Incidentally, in the conventional photomask produced by the phase difference control based on the etching rate and the etching time, the precision of the phase control is low, and it is difficult to produce a photomask having a large depth of focus.

Next, in order to apply the photomask forming method of this example to an actual device pattern, a memory cell portion wiring layer mask of 1G-DRAM was formed. L & S having a minimum line width of 0.15 μm was used for the phase difference evaluation region. When a phase shifter was formed on the photomask by the method of this example, a photomask having a phase difference of 179 ° was obtained. As a result of projection exposure of this photomask with the exposure apparatus shown in FIG.
The wiring pattern could be resolved with high dimensional accuracy, and the electrical characteristics of the device could be improved. (Regarding Other Application Examples of the Present Invention) The effects of the present invention are not limited to the examples described above. For example, the shape of the phase difference evaluation region and the method of arranging it on the photomask are not limited to the example shown in FIG. 7. Further, the mask to be created is not limited to the Levenson mask of the type as shown in the first example (FIGS. 6 and 14) or the second example. For example, a shifter edge mask as shown in FIG. 13 (here, , 131 is a quartz substrate, 137 is a shifter pattern, and 134 is a phase shifter), and the like can be applied to all photomasks that change the phase by etching the substrate itself.

Even if the etching apparatus for etching the phase shifter is attached, the parallel plate type RI used in the above example is used.
The etching apparatus is not limited to the E apparatus (FIG. 8), and other etching apparatuses such as a magnetron RIE apparatus and an ECR-RIE apparatus can be used.

The apparatus used for selective removal of the etching mask of the phase difference evaluation pattern portion is not limited to the photo-assisted etching apparatus (FIG. 9) used in the above example, and the height shown in FIG. A laser ablation method using an output pulse laser (here, 115 is a chamber, 111 is a light source, 116 is a condenser lens, 114 is a quartz window, 119 is a protective plate, and 113 is a photomask),
Alternatively, the IBAE method (ion beam assisted etching, where 125 is a chamber, 12
9 is FIB (focused ion beam), 124 is plasma,
123 represents a photomask) or the like can also be used.

The number of times the phase shifter is etched and the phase difference is measured is two and one in the above example, but the phase difference of the phase shifter is necessary to obtain the target resolving power and the depth of focus. If it is within the allowable range of phase error, it may be larger or smaller than this.

Regarding the method of measuring the phase difference of the phase shifter,
In addition to the method of observing the intensity change by interfering the two light fluxes shown in the above example (FIGS. 10 and 15), an apparatus as shown in FIG. 16 is used to change the focal position of the image of the photomask. A method of observing and observing the difference in light intensity (here, 201
Is a CCD camera, 202 is an objective lens, 203 is a photomask, 204 is a condenser lens, and 205 is an optical amplification device).

[0050]

According to the method for producing a phase shift type photomask of the present invention, the phase difference of the formed phase shifter is precisely measured during the step of etching the substrate, and the etching conditions are finely adjusted. Can be adjusted,
A phase shift mask with high dimensional accuracy can be easily and reproducibly created. As a result, the effect of significantly improving the depth of focus of the exposure optical image was achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of a projection exposure apparatus.

FIG. 2 is a diagram for explaining the shape of a substrate digging type Levenson mask.

FIG. 3 is a diagram illustrating a conventional Levenson mask manufacturing process.

FIG. 4 is a diagram illustrating a step of creating a shifter edge mask.

FIG. 5 is a diagram illustrating a relationship between a phase difference error of a Levenson mask and a light intensity difference.

6A to 6F are views for explaining a Levenson mask manufacturing process according to the present invention, and FIGS. 6A to 6F show the order of processes for adjusting the amount of the phase shifter.

FIG. 7 is a diagram showing an example of a phase difference evaluation area.

FIG. 8 is a diagram showing a structure of a parallel plate type RIE.

FIG. 9 is a diagram showing the structure of an optically assisted etching apparatus.

FIG. 10 is a diagram showing an example of an optical phase difference measuring device.

FIG. 11 is a view showing the structure of a laser ablation device.

FIG. 12 is a diagram showing a structure of IBAE.

FIG. 13 is a diagram illustrating a step of forming a shifter edge mask according to the present invention.

FIG. 14 is a diagram illustrating a process of making a double-ditch Levenson mask according to the present invention.

FIG. 15 is a schematic view of a partial resist peeling and phase difference measuring device according to the present invention.

FIG. 16 is a schematic view of another example of the optical phase difference measuring device.

[Explanation of symbols]

11, 91, 101, 111 ... Light source, 12 ... Fly-eye lens, 13 ... Condenser lens, 14, 89, 99, 103, 113, 123 ... Photomask, 15 ... Projection lens , 16 ... Semiconductor wafer, 21, 31, 41, 61, 71, 131, 141, ...
Quartz substrate, 22, 32, 62, 72 ... Shading film, 24, 34, 44, 64, 134 ... Phase shifter, 33, 43, 63, 73 ... Resist (etching mask), 36 ... -Light transmitting part, 37, 47 ... Reactive ion, 54, 104, 144, 154 ... Phase shifter part, 55, 105, 145, 155 ... Non-shifter part, 67, 137 ... Shifter Pattern, 76 ... Retardation evaluation pattern, 77 ... Retardation evaluation region, 78 ... Device pattern, 82, 92 ... Vacuum pump, 83 ... Reactive gas supply port, 84, 124 ... Plasma, 85, 95, 115, 125 ... Chamber, 86, 87 ... Counter electrode 88 ... High frequency power supply, 93, 163 ... O ₂ gas supply port, 94, 114 ... Quartz window, 96, 16 ... Condensing lens, 102 ... Prism, 106 ... Phase modulation prism, 107 ... Optical amplifying device, 119 ... Adhesion prevention plate, 129 ... FIB, 151a, 151b ... Switching mirror, 152 ... Mask stage, 153, 203 ... Photomask, 156, 157 ... Phase modulation prism, 158 ... Phase difference measuring light source, 159 ... Optical amplification device, 161 ... assist etching source, 162 ... vacuum pump, 163 ... O ₂ gas supply port, 201 ... CCD camera, 202 ... objective lens, 204 ... condenser lens, 205 ... light source.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-200149 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03F 1/00-1/16 H01L 21 / 027

Claims (2)

(57) [Claims] 1. A method of manufacturing a photomask, wherein a predetermined phase difference is generated with respect to transmitted light at the time of exposure by controlling a digging depth of the surface of the transparent substrate. in, provided with a phase difference evaluation region arranged a pattern not used as a circuit element, the design rule for the pattern that is disposed on the phase difference evaluation area, design Le pattern region used as a circuit element
In the middle of the step of etching the surface of the translucent substrate, the etching mask in the area for evaluating the phase difference is selectively removed to measure the phase difference with respect to the transmitted light. And a step of evaluating an error of the phase difference with respect to a target value at least once. 2. A step of applying a resist on a substrate, a step of exposing and transferring a pattern to the resist using the photomask prepared by the method of claim 1, and a step of developing the exposed resist. And a step of forming a positive or negative pattern on the surface of the substrate, and a step of etching the substrate having the pattern formed on the surface.