JPH05303207A - Developer for lithography and lithographic process - Google Patents

Abstract

PURPOSE:To provide the developer for lithography which can form fine resist patterns all having different sizes and shapes in a designed manner and the lithograph. CONSTITUTION:This developer contains a surfactant having the ability to increase the dissolution of the resist in the resist regions which are to be dissolved away and are small in the area to be dissolved away on the resist layer formed at the time of forming the resist patterns having the different sizes or different shapes and this developer is used in at least a part in the formation of the resist patterns.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic developer and a lithographic process, and more particularly to a lithographic developer and a lithographic process suitable for an ultra high density integration process.

[0002]

2. Description of the Related Art In recent years, with the increase in density and miniaturization of semiconductor devices, it has become necessary to form a resist fine pattern with a process margin in the lithography process. Therefore, a photoresist having high resolution is used for pattern formation. These resists are of a positive type or a negative type, and pattern formation is usually performed with an alkaline developing solution, for example, a 2.38 wt% aqueous solution of tetramethylammonium hydroxide (hereinafter abbreviated as TMAH).

FIG. 11 shows a state in which the ratio of the dissolution rate of the resist exposed portion and the non-exposed portion, that is, the selection ratio of the resist to the developing solution has been improved as the resolution of the resist material has been increased. FIG. 11 shows the selection ratio of the dissolution rate of the exposed area and the unexposed area as a function of the TMAH concentration for resists having various resolutions. In the figure, the positive photoresist A has a resolution of 1.2 μm, the positive photoresist B is 0.8 μm, and the positive photoresist C is
Is 0.6 μm. As shown in the figure, it can be seen that the selection ratio of the resist increases exponentially as the resolution performance of the resist improves. That is, it is understood that realizing a high-resolution resist is equivalent to improving the selection ratio between the exposed portion and the non-exposed portion.

Attempts have also been made to increase the concentration of the developing solution in order to improve the developing ability, but in this case, the selection ratio between the exposed portion and the non-exposed portion of the resist is lowered, and the resolution performance of the resist is deteriorated. Will end up.

FIG. 12 shows a 0.55 μm line-and-space resist pattern formed by a conventional developer containing no surfactant. The exposure was performed with a g-line reduction projection exposure apparatus having a lens with a numerical aperture of 0.43. Since the wettability of the developing solution on the resist surface is poor, the trailing of the resist pattern and the occurrence of residue 1201 are observed after development. In order to suppress these phenomena, a developer containing a surfactant was used in part. However, with conventional surfactant-added developers, it is not possible to suppress the generation of this resist residue depending on the type of underlying substrate, and conversely, depending on the type of surfactant, addition of the surfactant reduces the sensitivity of the resist. Or, the exposure margin was reduced.

FIG. 13 shows the flatness of the surface after immersing the silicon wafer in a conventional developer containing no surfactant for 60 seconds by using the center line average roughness. It can be seen that the surface of the wafer dipped in the developing solution becomes very rough only by contacting the developing solution for a short time of 60 seconds, as compared with the wafer not dipped in the developing solution (reference). Further, if a semiconductor element is manufactured in such a surface state, its electrical characteristics are significantly deteriorated. FIG. 14 shows data obtained by fabricating a MOS transistor using this rough surface and examining the channel mobility.
Shown in. When the surface is roughened by touching the developer, the channel mobility is extremely deteriorated with respect to the reference value.

Further, when a surfactant in the developer is added, the surface roughness of silicon can be suppressed, but the surfactant is adsorbed on the silicon. FIG. 15 shows data obtained by observing the carbon 1s peak by X-ray photoelectron spectroscopy (XPS). The data from the silicon surface exposed to the developer with surfactant for 60 seconds showed a peak 1501 indicating the presence of surfactant. It was found that when the surfactant-added developer is used, the surfactant is adsorbed on the underlying substrate and is not removed by the usual washing process. When the surface active agent is adsorbed on the surface of the substrate, it causes carbon contamination, resulting in deterioration of film quality in the subsequent formation of various thin films. Further, when a surfactant that does not adsorb on the silicon surface is selected, the surface of the silicon becomes rough.

Under the present circumstances, if a hole pattern is formed using a resist having a resolving power of up to 0.6 μm (a line / space pattern can be formed with mask fidelity), the ability of the resist cannot be exhibited. FIG. 16 shows a cross-sectional photograph of a hole pattern when a conventional developer is used. Under the exposure condition (220 mJ / cm ² ) where a 0.8 μm size hole pattern is formed, 0.7 μm,
The 0.6 μm pattern is under exposure conditions. 0.7
Exposure conditions for forming a μm pattern (280 mJ / cm
^{In 2} ), the 0.8 μm pattern is overexposure condition
The 0.6 μm pattern is underexposed. That is, in the pattern itself having a small exposed area (for example, a hole pattern), the wettability of the developing solution is poor and it does not penetrate into the pattern, so that the resist performance cannot be sufficiently exhibited.

In order to improve the wettability of the developing solution, a developing solution containing a surfactant is used. FIG. 17 shows the relationship between the concentration of the surfactant added to the developer and the exposure threshold energy for hole pattern formation. The exposure threshold energy of the hole pattern means the exposure energy required for the bottom of the hole to reach the underlying substrate. Although the exposure threshold energy decreases when the concentration of the surfactant added to the developer is increased, the difference in the threshold exposure energy between different pattern sizes is the same as that before the addition of the surfactant.
That is, it has been impossible with the conventional surfactants to form fine hole patterns having different sizes under the same exposure condition with high accuracy.

FIG. 18 shows a cross-sectional photograph of the hole pattern formed by the surfactant-added developer shown in FIG. As shown in the figure, when the conventional surfactant is added, the side wall of the hole pattern has a curved shape. Further, when the amount of the surfactant added so far was increased in order to improve the wettability of the developing solution, deterioration of the pattern shape was observed.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is a lithographic developer capable of forming a fine resist pattern having all different sizes and shapes as designed. And to provide a lithographic process.

[0012]

The developer for lithography according to the present invention is used for forming a resist pattern having different sizes or different shapes with respect to a resist region to be dissolved and removed in the formed resist layer. And a surfactant having an ability to increase the dissolution of the resist in the resist region to be removed by dissolution.

According to the lithographic process of the present invention, when forming resist patterns having different sizes or different shapes, with respect to a resist region to be removed by dissolution of the formed resist layer, the dissolution removal with a small dissolution removal area on the surface of the resist layer is performed. It is characterized in that a lithographic developer containing a surfactant having an ability to increase the dissolution of the resist in the resist region to be used is used for at least a part of the formation of the resist pattern.

In the developing solution for lithography and the lithography process, the surfactant is, for example,
An amine-based surfactant having an ethylene-propyl block as a branched group, and a surfactant having an amine group, an ethylene oxide group, and a propyl oxide group as hydrophilic groups are preferable. Further, it is preferable to use a surfactant having a defoaming property.

Further, the concentration of the surfactant is 300 pp.
It is preferably m or more.

In the lithography process, the exposure of the resist may be carried out by using, for example, a g-line or i-line reduction projection exposure apparatus.

The surfactant adsorbed on the resist surface or the base substrate of the resist is preferably removed by ultrapure water containing 0.1 ppm or more of ozone,
In that case, the concentration of ozone in the ultrapure water is 2.0 p.
It is preferably pm or more.

The effect of the present invention is more remarkable when the size of the resist pattern is 0.5 μm or less.

[0019]

In this study, a developer containing a surfactant having the ability to enhance the dissolution of smaller resist patterns is used. Therefore, when a resist on which patterns having different sizes are projected by a drawing device is developed using this developing solution, the surfactant is adsorbed on the resist surface. Since the surfactant is present in a fine area where the liquid does not normally permeate, the development proceeds through the same process as the resist having a relatively large pattern area. Therefore, regardless of the pattern size and shape of the resist, fine patterns having different sizes and shapes are formed according to the design values, and it becomes possible to realize an LSI of higher density and higher speed.

[0020]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the design fidelity of the line / space pattern of the resist exposed by the g-line reduction projection exposure apparatus having a numerical aperture of 0.43 and developed with the developing solution of this embodiment. The positive type resist (TSMR-V50: Tokyo Ohka Kogyo Co., Ltd.) used in this example has a resolution of 0.6 μm, but the type of resist is not particularly limited in the developing process using the developing solution of the present invention. ..

The surfactant used in this example is an amine-based antifoaming surfactant having an ethylene-propyl block as a chain group, but it has an ability to increase dissolution of smaller resist patterns. It may be any developer for lithography containing an activator. That is, when forming resist patterns having different sizes or different shapes, regarding the resist region to be dissolved and removed in the formed resist layer, the resist in the resist region to be dissolved and removed having a small dissolution and removal area on the resist layer surface is dissolved. Any surfactant may be used as long as it has an increasing ability.

The formation of hole patterns after the development process using these resists and a developing solution was observed with a scanning microscope.

FIG. 2 shows a transfer mask used for designing a hole pattern. The size of 1/5 on the mask 201 becomes the actual size. A positive type resist layer (TSMR-V50: Tokyo Ohka Kogyo Co., Ltd.) having a thickness of 1.26 μm was formed on an n-type (100) silicon substrate having a diameter of 5 inches. A g-line reduction projection exposure apparatus having a lens with a numerical aperture of 0.43 performed 5: 1 reduction projection of the test pattern 202 on the sample surface through the mask 201. With respect to the difference in the type of the resist patterning device, any other device may be used because it has no effect on the present invention.

Then, the sample was dipped in the developing solution of this embodiment for 70 seconds and washed with ultrapure water for 60 seconds to form a pattern. The pattern-to-pattern spacing is twice the pattern size. For example, in the case of holes having a size of 0.6 μm, the distance is 1.2 μm. Here, first, holes having a size of 1 μm to 0.6 μm were formed.

FIG. 3 shows the dependency of the exposure threshold energy of hole pattern formation on the concentration of the surfactant added. A significant decrease in threshold exposure energy was observed in small holes with increasing surfactant. That is, in the case of the 0.8 μm pattern, the dependency of the exposure threshold energy on the addition of the surfactant is hardly seen, but as the pattern size decreases to 0.7 μm or 0.6 μm, the threshold exposure increases with the increase of the surfactant concentration. The amount is significantly reduced. When the addition concentration of the surfactant was 300 ppm or more, hole patterns up to 0.6 μm could be formed under the same exposure conditions. This phenomenon is due to the ability of the developer used in the present invention to increase resist dissolution for patterns of smaller size.

Next, the cross section of the hole was observed with a scanning microscope to compare the developer of this example with a conventional surfactant-added developer. In FIG. 4, 0.8 μm, 0.7 μm,
A hole pattern profile of 0.6 μm is shown. With the conventional surfactant, the side wall of the hole pattern had a curved shape, but with the developer used in this example, the side wall of the hole pattern could have a sharp shape. This phenomenon is caused by the fact that the developing solution selectively penetrates into the fine area and the dissolution reaction product is rapidly diffused and removed from the resist surface. This occurs because development proceeds through the same process as a resist having a large pattern area.

Next, a reduction projection exposure apparatus using a g-line having a lens with a numerical aperture of 0.55 manufactured to form a high resolution pattern was used to form a hole pattern up to 0.4 μm. .. 0.6μm, 0.5μ in FIG.
The cross-sectional photograph of the hole pattern of m and 0.4 μm is shown. The exposure energy was 280 mJ / cm ² under the same exposure conditions.

As is apparent from the figure, by using the developing solution of this embodiment, 0.4 μm which could not be formed by the conventional method.
Up to the pattern, a good pattern profile could be accurately formed under the same exposure conditions. This phenomenon was achieved by a developing solution having an effect of increasing the developing ability for an ultrafine pattern that is hard to form.

From the above results, with the developing solution of this embodiment, a fine pattern of 0.5 μm or less can be formed as designed even in the g-line reduction projection exposure apparatus, regardless of the resist pattern size and shape. Was confirmed.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS.
A description will be given using 10.

FIG. 6 is a conceptual diagram showing a method for producing ozone-added ultrapure water used in the ozone-added ultrapure water rinse cleaning of this embodiment. This device generates ozone by electrolysis of ultrapure water and dissolves it in ultrapure water. The ozone generator is a commercially available product, and no special measures are taken.
With this device, the ozone concentration in ultrapure water is adjusted to 0.01
It can supply accurately and stably up to 10 ppm.

In FIG. 7, a silicon wafer is immersed in the developing solution used in the present invention for 60 seconds, and then rinsed with water for 60 seconds.
It is the data which analyzed the carbon 1s peak obtained from the sample which carried out for 2 seconds, and the sample which carried out the ultrapure water rinse containing ozone of 2pppm for 60 seconds by X-ray photoelectron spectroscopy. Surfactant peak 70 from the silicon surface in ultrapure water rinse
1 is seen, but the surfactant peak 701 is not seen in the ultrapure water rinse containing 2 ppm of ozone. It was confirmed that the surfactant adsorbed on the silicon surface was decomposed and removed by rinsing with ozone ultrapure water at room temperature. The concentration of ozone added to ultrapure water is 0.1 ppm.
Even in such a case, it has been confirmed that the same effect can be obtained by setting the cleaning time to 10 minutes.

Next, the sample on which the thin film of the non-exposed positive resist was formed was immersed in the surfactant-added developer of the present invention for 60 seconds to adsorb the surfactant on the surface. Then 2pp
Ultrapure water treatment containing m of ozone was performed, and the contact angle of the ultrapure water on the sample surface was examined. FIG. 8 shows the relationship between the ozone ultrapure water cleaning time and the ability of removing the surfactant from the resist surface. Two
Before cleaning with ultrapure water containing ppm ozone, the contact angle is lower than that of the clean resist surface because the surface active agent is adsorbed on the resist surface. However, it was confirmed that by washing for 60 seconds or longer, the surfactant was completely removed, which was completely in agreement with the value of the contact angle on the clean resist surface.

FIG. 9 shows a resist pattern profile of 0.6 μm before and after cleaning with ultrapure water containing 2 ppm of ozone. 0.6 before and after cleaning with ultrapure water containing 2 ppm ozone
There is no difference in the resist pattern profile of μm. It was confirmed that there was no adverse effect such as deformation of the resist pattern due to ozone.

FIG. 10 shows a developing solution used in the present invention,
After immersing the silicon wafer in the conventional developer for 30 minutes,
The surface photograph after washing with ultrapure water containing 2 ppm of ozone is shown. It has been confirmed that the surface roughness of silicon is caused by immersion in a conventional developer containing no surfactant, but the surface roughness of silicon is not caused by the developer used in the present invention.

[0037]

According to the developing solution for lithography and the photolithography process of the present invention, it becomes possible to form all the fine resist patterns having different sizes and shapes as designed in the ultra high density integrated semiconductor process, It becomes possible to realize a higher density, higher speed LSI.

[Brief description of drawings]

FIG. 1 is a graph showing mask fidelity of a resist pattern developed by the developing solution of the present invention.

FIG. 2 is a schematic diagram showing a transfer mask used for designing a hole pattern.

FIG. 3 is a graph showing the dependency of the exposure threshold energy of hole pattern formation on the surfactant addition concentration in this example.

FIG. 4 shows 0.6 μm, 0.5 μm and 0.4 μm formed by a g-line stepper having an NA value of 0.43 and the developing solution of the present invention.
The photograph which shows the hole pattern profile of m.

FIG. 5: 0.6 μm, 0.5 μm, 0.4 μ formed by a g-line stepper having an NA value of 0.55 and the developer of the present invention.
The photograph which shows the hole pattern profile of m.

FIG. 6 is a conceptual diagram showing a method for producing ozone-containing ultrapure water.

FIG. 7 is an XPS spectrum showing that the surfactant is removed from the silicon surface by washing with ozone ultrapure water.

FIG. 8 is a graph showing that the surfactant is removed from the resist surface by ozone ultrapure water cleaning by contact angle measurement.

FIG. 9 is a photograph showing a 0.55 μm line and space pattern after washing with ozone ultrapure water. (A) Before cleaning (b) After cleaning

FIG. 10 is a photograph showing a roughened state of the silicon surface by the developing solution of this example and the conventional developing solution. (A) Conventional developer (b) Developer of this embodiment

FIG. 11: TMAH of selectivity of resist to developer
The graph which shows concentration dependence.

FIG. 12: 0.55 μm formed by a conventional developer
A photo showing the line and space pattern.

FIG. 13 is a graph showing changes in the center line average roughness of the silicon surface due to immersion in a developing solution.

FIG. 14 is a graph showing deterioration of MOSFET channel mobility due to a developer.

FIG. 15 is an XPS spectrum showing adsorption of a surfactant on the surface of a silicon wafer.

FIG. 16 is a photograph showing a hole pattern profile with a conventional developer.

FIG. 17 is a graph showing the dependence of the exposure threshold energy of hole pattern formation in a conventional developer on the concentration of a surfactant added.

FIG. 18 is a photograph showing a hole pattern formed by the developer containing the surfactant shown in FIG.

[Explanation of symbols]

 201 Mask 202 Test pattern 701, 1501 Surfactant peak 1201 Hem, residue

Claims (14)

[Claims] 1. When forming resist patterns having different sizes or different shapes, with respect to a resist region to be dissolved and removed in the formed resist layer, a resist region to be dissolved and removed having a small dissolved and removed area on the resist layer surface is formed. A lithographic developer comprising a surfactant having the ability to increase the dissolution of a resist. 2. The developer for lithography according to claim 1, wherein the surfactant is a defoaming surfactant. 3. The lithographic developer according to claim 1, wherein the surfactant is an amine-based surfactant having an ethylene-propyl block as a chain group. 4. The lithographic development according to claim 1, wherein the surfactant is a surfactant having an amine group, an ethylene oxide group and a propyl oxide group as hydrophilic groups. liquid. 5. The lithographic developer according to claim 1, wherein the concentration of the surfactant is 300 ppm or more. 6. When forming resist patterns having different sizes or different shapes, with respect to a resist region to be dissolved and removed in the formed resist layer, a resist region to be dissolved and removed having a small dissolved and removed area on the surface of the resist layer is formed. A lithographic process, characterized in that a lithographic developer containing a surfactant having the ability to increase the dissolution of the resist is used for at least part of the formation of the resist pattern. 7. The lithography process according to claim 6, wherein the surfactant is a defoaming surfactant. 8. The lithographic process according to claim 6, wherein the surfactant is an amine-based surfactant having an ethylene-propyl block as a branching group. 9. The lithography process according to claim 6, wherein the surfactant is a surfactant having an amine group, an ethylene oxide group and a propyl oxide group as hydrophilic groups. 10. The concentration of the surfactant is 300 ppm.
The lithographic process according to any one of claims 6 to 9, which is the above. 11. The resist pattern has a size of 0.
11. The lithographic process according to claim 6, wherein the thickness is 5 μm or less. 12. The exposure of the resist is performed by g-line or i-line.
The lithographic process according to claim 6, wherein the lithographic process is performed using a line reduction projection exposure apparatus. 13. The method according to claim 6, wherein the surface active agent adsorbed on the resist surface or the base substrate of the resist is removed by ultrapure water containing 0.1 ppm or more of ozone. The lithographic process of paragraph 1. 14. The concentration of ozone in the ultrapure water is 2.
The lithographic process according to claim 13, wherein the lithographic process is 0 ppm or more.