JPS61236552A - Mask processing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the disclosure C. Prior art D. Problem to be solved by the invention E. Means for solving the problem F. Example F. Example of resist material F.2 Outline of the method of the present invention F3. Effects (Figs. 1.2 and 3) F4 Specific Example G Effects of the Invention A, Industrial Field of Application The present invention relates to transportable and conformable (image-fidelity) mask technology, and more specifically to one Embodiments relate to a method of enhancing the opacity of a novolak-based imaging mask. In another embodiment, the present invention relates to a method of making a portable, conformable mask that is entirely developable with water-soluble bases.

B. SUMMARY OF THE DISCLOSURE The mask processing method of the present invention enhances the opacity of novolak-based masks. The method involves applying an underlayer of deep UV resist sensitive to wavelengths in the range of 240 to 280 nm on the substrate, which can be either an aqueous base developable resist layer or an organic solvent developable resist layer, and then applying a novolak resin. The novolak resin based upper resist layer is imagewise exposed and then developed to form an imaging mask. then exposing the underlying resist layer to radiation having a wavelength in the range of about 280 to about 310 nm, followed by imagewise exposing the underlying resist layer through the imaging mask to ultraviolet light having a wavelength of 240 to 280 nm; The underlying resist layer is developed to form an image that corresponds to the image on the imaging mask.

An all-aqueous system is obtained if the substrate is provided with a bottom layer of water-soluble base-developable material and a top resist layer of water-soluble base-developable material thereon.

C0 Prior Art Transportable conformal mask (PCM) technology is known for forming high aspect ratio resist images that are insensitive to underlying surface irregularities. This technique is used in subtractive etch and exfoliation metallization methods. The basis of this technique, as disclosed in U.S. Pat. No. 4,211,834, is to use an image of the novolac resist as a mask when uniformly exposing the underlying deep ultraviolet (UV) resist with deep UV light. . An important aspect of PCM technology is that it is the only currently known method for forming high aspect ratio resist images of micron and sub-micron dimensions that is insensitive to surface irregularities without the use of reactive ion etching. The fact is that This technique is desirable because reactive ion etching processes are complex, costly, and difficult to maintain reproducible control.

Novolak resins mixed with certain sensitizers are useful in resist formulations and are used in PCM technology. These resists are used in the underlying layer as described in US Pat. No. 4,078,569. This patent discloses a resist that is sensitive to electron beams or deep ultraviolet light. A major limitation of PCM processes using novolak-based resists is that the novolak-based resists used are not completely opaque in the deep UV region.

Therefore, this material has a significant transmission of 1 at 240-280 nm.
Window 1 exists. The light transmitted through the novolac-based resist by this transmission window therefore limits the overall contrast required in the PCM manufacturing process. Therefore, 0.
Requires thin films thicker than 5 μm, which limits resolution. As a result, the aspect ratio also decreases, and interlayer adhesion is also adversely affected, making it difficult to select deep UV resists. When printing a PCM two-layer resist with an e-beam, a thin top layer reduces proximity effects, increasing resolution and allowing the formation of small features.

Two methods are currently used to overcome this drawback of two-layer resist masks in the PCM field. The first method is to carefully adjust the wavelength of the deep UV light to 24
It removes wavelengths larger than 0 nm. This method is limited to deep UV resists sensitive to wavelengths below 240 nm.

These deep UV resists sensitive below 240 nm are acrylate resins. The second method is 240-280
The solution is to add materials to the novolac resin that increase the opacity by nm.

The use of dielectric mirrors to filter out wavelengths above 240 nm has several drawbacks. Even using this radiation technique, the mirror efficiency is relatively low, so much of the available radiation is wasted, and the exposure time must be increased.Additionally, dielectric mirrors are expensive. Yes, it is too brittle to be used in the manufacturing process.

The second method, which involves adding materials to the novolac resin that absorb wavelengths of 240 to 280 nm, is less desirable than the first method. These additional materials degrade the properties of the resist paste. This is because such additives change the solubility and optical properties of the resist thin film.

Some of these additives also reduce the lifetime of resist solutions used in thin film production.

PCM technology using polymethyl methacrylate (PMMA) as a deep UV photoresist and covering it with a novolak resist as a near UV photoresist is generally known, as disclosed in, for example, US Pat. No. 4,211,834. In this technique, a PCM resist is imagewise exposed and then an upper level novolak near-UV photoresist is developed. Since the top level novolac near-UV photoresist must act as a conformal contact mask during the subsequent exposure of the PMMA deep UV photoresist, the image areas of novolac resin remaining after development are P
It must strongly absorb wavelengths in the radiation range to which MMA is sensitive. This causes the underlying PMMA deep UV photoresist exposed through the novolac conformal mask to become the ultimate photoresist pattern on the underlying substrate.

Mr. Mashows and Mr. Willmott (March 1, 1984)
A paper presented at the 5PIE Conference on Optical Microlithography held in Santa Whale, California, USA on April 4-15, ``Stabilization of Single-Layer and Multilayer Resist Patterns for Aluminum Etching'' (Matthew
s and Wilmot'5tabilizat
ion of Single Lays a
ndmultilayer Re5ist Pet
terns t.

Alumimun Etc old ug Enylrom
ent' at theSPIE, Confer
ence；0ptical Microlithog
raphy m, 5anta C1ara, Ca1
ifornia.

March 14 15.1984) reported a modification of the PCM technique and that this modification was an improvement on the PCM technique described above.

In this variation, after developing the resist image on the top layer of novolak resist, but before exposing the top layer to deep UV radiation to transfer the pattern to the deep UV PMMA resist layer, a specific UV heat treatment step is used to develop the top layer. Novolac resin is cross-linked. This UV heat treatment step is 260 nm
Exposure to UV radiation with wavelengths between 520 nm and below and UV
Including heat treatment during exposure. This is followed by optional hard baking depending on the heat treatment temperature used during this exposure.

However, even such modifications have not been able to provide a PCM resist having all of the desired properties and characteristics. Furthermore, in this technique, PMMA is used as a lower layer, and an organic solvent is used to develop the lower layer. The combination of UV exposure with heat treatment results in the formation of a boundary layer that is insoluble in organic solvents, so prior to organic solvent development of the underlying PMMA layer, a method such as plasma etching is used to remove the insoluble boundary layer.
PCM technology cannot be used without the use of additional steps; the disadvantages remain of requiring a separate step to remove the insoluble boundary layer and requiring an organic solvent development step. Improvements in PCM technology are needed where the number of processing steps is minimal and all aqueous development is used.

D0 PROBLEM TO BE SOLVED BY THE INVENTION In view of the shortcomings of the prior art, it is an object of the present invention to increase the opacity of novolac resists so that high resolution images can be produced effectively.

In accordance with the present invention, the resolution of PCM masks is improved without the boundary layer residue created during conventional processing.

In accordance with the present invention, it is possible to use thinner imaging layers, thereby increasing overall resolution, and reducing costs by being developable with aqueous developers and eliminating the need for organic solvent recovery. , a PCM technology is provided that avoids environmental pollution problems and minimizes worker safety issues.

According to the present invention, a wide variety of different resist materials can be used in the manufacture of PCMs, providing greater latitude in the exposure and radiation that can be used for resist images in PCMs.

Means to Solve the E0 Problem Simply put, the present invention is based on the method of exposing and developing the upper resist layer based on the novolac resin in the exposure and development process of a two-layer mask containing a novolac resin as the upper layer. After that, and before exposing the lower deep UV resist layer, an intermediate treatment is performed to increase the opacity of the upper resist layer (image-forming resist layer).

This opacity-promoting intermediate treatment may include exposing the exposed and developed upper imaging resist layer to radiation in the wavelength range of approximately 280 to 510 nm, or subjecting it to a heat curing treatment.
Or a combination thereof can be used. However, when a resist layer that can be developed with an organic solvent is used as the lower deep UV resist layer, a boundary layer that is insoluble in the organic solvent is generated as described above, which is undesirable. of radiation exposure is used. Lower deep U
If a water-soluble base-developable resist layer is used as the V-resist layer, it is also possible to use heat treatment instead of UV exposure, but the best results are obtained with UV exposure.

In the present invention, when a resist layer that can be developed with a water-soluble base is used as the lower deep UV resist layer, a resist mask that can be entirely processed with a water-soluble base is obtained. The upper and lower layers must each be sensitive to different wavelengths.

An example of a preferred method using exposure in the wavelength range of about 280 to about 310 nm as the opacity enhancement treatment is as follows.

(a) Forming an upper resist layer based on a novolac resin over a lower deep UV resist layer (developable with water-soluble base or organic solvent) that is sensitive to wavelengths in the range of about 240 to about 280 nm. (b) imagewise exposing the upper resist layer; (c) developing the upper resist layer to convert it into an imaged mask; and (d) having a wavelength in the range of about 280 to 510 am. exposing the imaging mask to radiation; (e) imagewise displacing the underlying resist layer through the imaging mask thus obtained in a range of about 240 to about 280 nm;
(f)) developing the lower resist layer to form an image conforming to the image of the imaging mask;

F. Examples Referring to FIGS. 1 to 3, 24 of the novolak resin
The light absorption effect on exposure to UV light with wavelengths from 0 to 280 nm is shown. Figure 1 is novolak resin, Figure 2
FIG. 3 shows the case where a sensitizer (described later) is further included. As can be seen from the graph, 280-310 according to the present invention
After UV exposure at wavelengths of nm, the thin film becomes significantly opaque, ie windowed, to wavelengths below 300 nm.

F. Examples of resist materials Suitable examples of water-soluble base-developable novolac resins that can be used in the present invention include, for example, phenol or alkyl (C, -06) substituted and halogen substituted phenols (
e.g. cresol), resorcinol, birogal and aldehyde or formaldehyde, acetaldehyde, acetone, acrolein, benzaldehyde, 1.3
．． Condensation products with aldehyde precursors such as 5-trioxane and novolak resins such as addition polymers of hydroxy styrene. A suitable water-soluble base developable resin has a molecular weight of about 300 to about 100,000, preferably 300 to 2
It has a molecular weight of 0,000.

Because the composition of the novolac resins that can be used to form the upper novolak-based resist layer used in these embodiments of the invention generally increases the sensitivity to exposing radiation, U.S. Pat. No. 304
/No. 1121, No. 3106465, No. 3201239
No. 2, for example as disclosed in No. 3,666,473.
．． 3. Generally contains a photosensitizer of the 1,2-diazonaphthoquinone-5-sulfonic acid type, such as 1-oxy-2-i)7zophthalene-5-sulfonic acid ester of 4-trihydroxybenzophenone. . This type of UV photoresist based on a suitable commercially available novolac is A21.
350 (Azoplate) (trade name of a resist consisting of novolak resin and diazoquinone photosensitizer sold by Azoplate) and HPR204 (Hund Chemical (trade name)
This is the trade name of a resist consisting of a novolak resin and a diazoquinone photosensitizer, sold by Hunt Chemical Co., Ltd. Other resists using different combinations of novolac resins and other photosensitizers can also be used in the present invention if desired. For example, in the example shown in Figure 2, U.S. Pat.
A novolak resin containing a 7:c polyolefin sulfone sensitizer was used, such as the polymethylallyl ether-methyl pentene sulfone bipolymer described in No. 398,001. A commercially available example of this class of novolac compositions is ggsooop (trade name for an electron beam resist consisting of novolac resin and poly-2-methyl pentane sulfone sold by Hitachi).

Suitable materials that can be used as the lower deep UV resist layer used in the masks of the present invention are materials that are soluble in organic solvent developers and materials that are soluble in aqueous base developers.

More specifically, suitable examples of organic solvent developer developable resist materials that can be used in the present invention include polymethyl methacrylate (PMMA) polymers, polymethyl isopropenyl, poly-t-butyl methacrylate, and other polymers. Contains methacrylate copolymer.

Exemplary materials developable with aqueous base developers that can be used in the present invention as the underlying deep UV resist layer include methacrylate terpolymers such as terpolymers of methyl methacrylate, methacrylic acid, and methacrylic anhydride (see, e.g., U.S. Pat. No. 6,087,659). (disclosed), aliphatic imide polymers such as polydimethyl glutaimide, other acrylic acid polymers, polymethyl methacrylate-methacrylate acid polymers, itaconic acid polymers such as poly-dimethyl itaconic acid, and poly(hydroxystyrene). including.

If necessary, azide-polyvinyl phenol (for example, disclosed in U.S. Pat. Nos. 4,268,603, 4,148,655, etc.) (Hitachi Chemical
R9300ON and RE200ON sold by ),
Positive and negative resist materials such as 9Azoquino/Fenoliths or Novolac (A21350 from Azoplate) can be used.

When exposing the upper resist layer, the lower resist layer can be dyed, for example, with a dye, if necessary. Suitable properties of this dye include thermal stability and the ability to absorb the wavelength of the UV light used to expose the overlying resist. Suitable specific examples include coumarin dyes such as Coumarin 6, Coumarin 7 and Coumarin 30 sold by Kodak.

All of this invention can be developed with water-soluble base7. Suitable resist materials that can be used to form the upper resist layer in embodiments of the CP CM manufacturing method are polymeric materials that can be used in combination with sensitizers or photoactive components. Suitable polymeric materials may be novolacs, polymers based on polyvinyl phenol, or polymers that can be converted to polyvinyl phenol by irradiation or a combination of irradiation and heat treatment when a photoactive component is added to the polymer. These are sensitive to wavelengths in the range of about 300 to about 500 nm.

Particular examples include novolak resins sensitized with diazoquinone derivatives. Polyvinyl phenol and bis allyl
An example of a suitable resist material comprising an azide is U.S. Pat.
No. 268,603. Examples of polymers that convert to polyvinyl phenol upon irradiation and heat treatment in the presence of photoactive moieties of allyl onium salts are poly(P-tart-butoxycarbonyloxystyrene), poly(tert-butoxycarbonyloxystyrene), poly(tert-phthyl P-vinylbenzoate), Poly (P-
tert-butoxycarbonyloxy-2-methylstyrene), poly(t-butyl P-isoprophenyloxyacetate) and poly(t-butyl methacrylate), such as those disclosed in U.S. Pat. No. 4,491,628. .

Suitable resist materials for the underlayer that can be used in embodiments of the all aqueous developable PCM manufacturing method of the present invention are polymers selected from the following groups, or polymers containing at least a covalent portion thereof: These resist materials range from about 200 to about 500
Sensitive to UV wavelengths of nm.

(1) Contains a carboxylic acid group and can be methylated by irradiation.
Polymers that are developable with water-soluble bases, such as terpolymers of methacrylate, methacrylic acid, and methacrylic anhydride.

(2) Acid anhydrides in which the anhydride is hydrolyzed upon irradiation, or after irradiation, in the presence of an aqueous developer, the anhydride is hydrolyzed to yield acids such as methacrylic anhydride and acrylic anhydride copolymers. A polymer containing a chemical group.

(3) Polymers containing imide groups that become developable with water-soluble bases such as polyglutarimide and polymaleimide upon irradiation.

(4) By irradiation, O-nitrobenzaldehyde derivatives as disclosed in U.S. Pat. No. 4,491,628 undergo a Photo-Fries rearrangement.
rangement) and polymers capable of generating phenol or hydroxyl groups, such as onium salt-1t-Bog systems.

Various sensitizers can be used to enhance the photosensitivity of polymers suitable for use in the present invention. The use of sensitizers is not necessary in many cases. This is because, with the exception of the onium salt-1t-prog polymers of group (4), the water-soluble base-developable polymers are themselves photosensitive. In the case of the materials exemplified as all-aqueous resist systems, the range is about 280 to about 310.
The opacity of the upper resist layer can be improved by exposure to ultraviolet light at nm wavelength.

F2 Overview of the Method of the Invention Using the materials described above, mask materials that can be used in embodiments of the invention can be easily prepared.

Specifically, a substrate, such as a silicon oxide wafer, is first coated with a uniform layer of resist material for the underlying resist layer using conventional coating techniques such as spin coating.
It is coated to a thickness of 5 to about 5 μm, preferably 1 to 6 μm, and dried. This was followed by coating the lower resist layer with a resist layer for the upper layer material having a thickness of about 0.3 to about 1.5 μm, preferably 0.5 to 1.0 μm. A suitable technique for applying the top resist layer is spin coating and subsequent drying.

After the mask material of the present invention was formed, it was imagewise exposed to radiation to which the upper resist layer was sensitive using a chromium-coated glass mask as an image. The appropriate wavelength of the radiation used for this exposure is about 500 nm to about 45 nm.
0 nm or less, preferably 350 nm to 440 nm
The range is up to m. Suitable radiation sources that can be used for exposure to wavelengths in this range include mercury vapor lamps, mercury-xenon lamps, and the like.

Alternatively, the upper layer can be imagewise exposed to electron beam radiation or X-rays. If the upper and lower resist layers have different sensitivities to radiation, it is preferred to use electron beams or X-rays in this exposure step.

After exposing the upper resist layer, the mask material is adjusted to a pH of approximately 12.
Develop with an aqueous base developer having a molecular weight of from about 13 to about 13. Suitable examples of water-soluble base developers that can be used in the present invention include potassium hydroxide, sodium hydroxide, tetramethyl ammonium hydroxide, sodium silicate, sodium phosphate, and the like. These developers are Azoplate (Azoplate).
) as an AZ developer, and Shipley (5h
iplay) from Microborit (Microp)
orit) 2401. As a result of the exposure, the exposed areas of the upper resist layer become soluble in the aqueous base developer and are removed by contact with the developer, exposing the resist layer below these removed areas.

Naturally, the area removed by this development depends on whether the overlying resist layer is a positive resist or a negative resist.

As a result of this exposure and development of the upper resist layer, a mask image corresponding to the original resist image is formed in the upper layer and serves as a mask for the underlying resist layer underlying the upper layer.

In the next step, i.e. when it is desired to enhance the opacity to deep UV radiation of the resist image formed in the upper layer for masking the lower layer, e.g. a thin (e.g. less than about 1 μm thick) novolak is applied. At the step of using the top resist layer as a base, the resulting image mask is heated to approximately 20°C.
from about 280 to 320 n at a temperature between about 2006C and about 2006C.
m, preferably to radiation having a wavelength of 280 to 310 nm. For example, a full surface exposure is used. A suitable source for providing radiation in this wavelength range is a mercury-xenon lamp, a mercury vapor lamp. It has been found that this exposure renders the remaining image areas of the upper resist layer opaque to deep UV radiation, ie to radiation in the deep UV radiation region. A suitable exposure dose for this exposure step is from about 1 to about 20, preferably from 5 to 20 joules/cm2.

an initial exposure step for the purpose of opacity as described above;
That is, after approximately 280 to 310 radiation exposures, a second imagewise exposure step is performed. The radiation suitable for this exposure is the radiation to which the underlying resist layer is sensitive. For example, if the underlying resist layer is a deep UV resist layer, a suitable wavelength for the exposing radiation is in the range of about 200 to about 280 nm, preferably 200 to 240 nm. Suitable radiation sources with wavelengths in this range include mercury arc lamps and the like.

As a result of this exposure, the underlying resist layer becomes developable in a developer. When the underlying resist layer is developable with a water-soluble base developer, suitable water-soluble base developers are those having a pH of 12.5 to 16.5. Exemplary water-soluble base developers that can be used include aqueous solutions of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, sodium chloride/silicate, and sodium silicate. Appropriate times and temperatures for this development are about 1 minute to about 10 minutes and about 10 degrees Celsius, respectively.
C to 25°C. If the underlying resist layer is developable with an organic solvent, suitable developers for use include those commonly used in the art. Suitable times and temperatures for this development are about 10 seconds to about 2 minutes and about 1 minute, respectively.
0'C to about 25°C.

As a result of the above-described processing, a mask is formed on the substrate.

Effect of F3 Exposure Referring to the drawings, the opacity (absorption E) achieved in an embodiment of the method of the invention using deep UV PCM technology, for example when using a novolac resin as the upper resist layer, is shown. Improvements are shown.

The data in FIG. 1 was obtained using a low power lamp (250 W) with fairly long exposure times, on the order of 5 to 50 minutes. However, using higher power lamp designs;
The processing time can be reduced by about 1/10. High speed exposure equipment is available which reduces processing time.

Figure 2 shows that a similar change can be induced thermally using a novolac-polyolefin sulfone sensitized resist. Therefore, heat treatment can be used instead of UV exposure, but the treatment time can be further reduced by combining UV exposure and heat treatment.

FIG. 6 shows a thin film of resist (0.5μ
Figure 3 shows the effect of the method of the invention on m).

When processing the novolak resist used in Figure 3 with a thickness of 0.5 μm as a mask (this intermediate processing uses a filter to remove wavelengths below 280 nm, at 60mW/cm
of acrylic terpolymer (conducted for approximately 3 minutes with a high-intensity UV source providing a radiation dose of
A deep UV resist consisting of methyl methacrylate, methacrylic anhydride and methacrylic acid in a 7015:15 ratio was exposed to radiation at wavelengths between 200 and 280 μm (see US Pat. No. 4,087,569). The resulting contrast of this exposure? : Measured by measuring the dissolution rate of the mask and non-mask portions of the thin film in a developer made of 2-ethoxymethanol. 280
Samples using masks that were intermediately treated with radiation at wavelengths between 310 nm and 310 nm showed an increase in contrast (ratio between exposed and unexposed areas dissolution) of 32 bands compared to untreated samples. 41A Resin), Figure 2 (Resin and Polyolefin Sulfone Sensitizer) and Figure 6 (Resin and Naphthoquinone Diazide Sensitizer) show that this effect is a result of the properties of the resin and that all Novolac-like resist systems It is thought that this can be said in general.

When implementing the above-described embodiments of the invention, the deep UV masking ability of the novolac resist is improved. This improvement occurs without changing the phosphorographic performance of the resist. This technique eliminates the need for expensive and inefficient dielectric materials used during the full exposure step of deep UV PCM fabrication methods using novolak overlayer resists.

Although embodiments of the present invention are specific to the examples and materials disclosed herein, the opacification by itself ranges from about 240 to about 2
It is applicable to any PCM technique that uses a novolak resist as a mask for exposure of an underlying resist layer sensitive to wavelengths between 80 nm.

When a novolac resin is used as the upper resist layer and the lower resist layer is an organic solvent developable resist layer such as polymethyl methacrylate, it is imagewise sensitive to radiation having wavelengths of about 240 to 280 nm. After exposure,
The resist material is developed with organic solvents without treating the material by additional steps such as thermal treatments such as soft baking or hard baking. This allows a submicron image with high resolution to be obtained. Therefore no intervening heat treatment is used. This is because it is known that if the heat treatment disclosed in the prior art is used at this stage, residual matter will be generated in the intermediate layer and the resolution will be deteriorated.

When a novolac is used for the upper resist layer and the lower resist layer is a water-soluble base developable resist layer, the material does not require additional processing such as heat treatment (it can be developed immediately, but if necessary The imagewise exposed imaging material is subjected to a temperature of 100°C to about 200°C, preferably 1
Baking heat treatment can be performed at a temperature of 20 to 150°C for about 1 to 10 minutes, preferably 5 to 10 minutes. Instead of full UV exposure curing for opacification, an intermediate plasma curing process can also be used in combination with a heat treatment. This process is described in U.S. Patent No. g4187331, 198
1st Annual Journal of Vacium Science and Technology (J, Vac.

Set, & Teeh, ) 19:1127 J. Moran (J, Moran) and G. Tiller (G.
This is known as a plasma hardening treatment of a resist layer, as disclosed in a paper by John Taylor.

U.S. Pat. No. 4,187,331 for plasma curing techniques
See also US Pat. No. 4,253,388. Because the mask layer is typically 1.0 microns or less thick, plasma curing methods are more effective for embodiments of the present invention than curing methods reported in the literature.

F4 Specific Examples In the following description, all parts, percentages, ratios, etc. are by weight unless otherwise specified.

Example 1 Si with a thermally grown oxide layer 5000^ thick
Fill the wells with acrylic terpolymer resist (methyl
terpolymer of methacrylate, methacrylate anhydride and methacrylic acid in a molar ratio of 70:15:15), followed by a 0.5 nm layer of diazoquinone-novolak photoresist,
Bake at 6C for 30 minutes. Upper layer Regis 1
- Patterned by exposure using a GCA60DO step-and-repeat camera (commercially available from OCA Corporation). The resist was then developed in a 0.2N aqueous solution of OH for 1.5 minutes at a temperature of 23°C. 280 of this pattern masking layer
UV treatment at a wavelength of 310 nm was carried out using a Microlide with a 280 nm cutoff filter.
te) 100m (Fusion Semiconductor
Fusion Semiconductor
orSystems Inc.). This UV treatment time is 800 seconds.

Following this, the underlying deep UV resist was exposed to light at wavelengths between 2[]0 and 240 nm using the camera described above and exposed to a dilute solution of tetramethylammonium hydroxide (approximately 1% by weight).
I developed it inside. Submicron (0.8 micron) images of good quality were obtained.

Comparative Example 1 For the same Si wafer processed as in Example 1, except without using the 280-310 nm UV exposure process, resolution was limited to about 1, 2 or 1.1 μm. There were almost no 1 micron images, and no submicron images were obtained.

Example 2 A Si Ueno Y 1.7 μm acrylic terpolymer with a thermally grown oxide layer of 5000 μm thickness was coated as described in Example 1 and baked at 200°C. Each layer of urethane was coated with a layer of diazoquinone/novolac photoresist as in Example 1. The novolak photoresist layer was imagewise exposed using a Kasper contact aligner (NUV) at a dose of 75 mJ/cm2 and developed in a 0.20 N KOH aqueous developer.

The wafer with a patterned developed novolak resist layer was then exposed to a 280 nm light source (Optical Associates, Inc.) with a 280 nm cutoff filter.
) using 300 nm radiation (35 mw/a
m2) for 600 seconds to render the novolak resin image opaque to the 240-280 nm region.

One of the wafers thus obtained was thermally treated at 150°C for 10 minutes, and the other wafer was similarly heat-treated and then further heat-treated at 180°C for 5 minutes.

The bottom resist layer is then passed through the patterned top novolac resist to a 230 nm dielectric Q? ! ,
Microlite 1 using '
Exposure was performed using a 00m radiation source at a wavelength of 200-250 nm with an exposure dose of 1500 mJ/Cm2. The acrylic terpolymer resist layer of each of the samples thus obtained was then diluted with a 1:1.15 (by volume) solution of 0.52N tetramethyl ammonium hydroxide (Allied Corp.
Developed with Acculith LMI600 manufactured by Oration). Clear images with no interlayer residue were obtained in each case.

The above results show that when UV exposure is combined with subsequent heat treatment to improve the opacity of the novolac resin resist to UV light, the underlying acrylic terpolymer resist layer can be developed clearly and is non-staining. The results show that residual liquid at the boundary can be clearly removed by developing the lower acrylic terpolymer deep UV resist layer with a water-soluble base developer.

Comparative Example 2 A polymethyl methacrylate (PMMA) resist layer was used on the Si wafer instead of the acrylic terpolymer resist layer as the lower resist layer, and PMMA was
Heat at 0°C for 30 minutes, then remove the diazoquinone from the top.
A layer of novolak resist was applied. A layer of novolac resist on each of the Si substrates was then imagewise exposed and developed as described in Example 2.

One 31 wafer (sample 1) developed in this way was
A second 31 wafer (
Sample 2) at 150°C for 10 minutes, followed by 180”
Thermal treatment was performed at C for 5 minutes.

The underlying PMMA resist layer was then exposed through the patterned novolac resin as described in Example 2 using a Microlite 100m radiation source at a dose of 1500 mJ/am and a wavelength of 260 nm. .

The PMMA resist layer of sample 1 exposed in this way was
Methyl isobutyl ketone (MIBK) for 5 seconds
) to remove the exposed areas of PMMA. However, boundary residue remained in the image area between the PMMA layer and the novolac layer.

Developed with MIBK for another 25 seconds (residues on the border could not be removed even with 7. Inglobil Alcohol (IPA)
It was found that the boundary residue could not be removed even if it was used as a cleaning solution.

For Sample 2, the exposed PMMA resist layer was also developed as described above in MIBK for 90 seconds to remove the PMMA, but extremely high levels of boundary residue still remained.

Example 6 A Si wafer coated with the same resist as described in Comparative Example 2 was prepared and the procedure of Comparative Example 2 was followed without heat treatment after the initial imagewise exposure/development step of Comparative Example 2. Ta. 2
After the second imagewise exposure step, a UV exposure process of 80 to 310 nm is carried out, followed by the development of PMMA'lfMI.
The test was carried out in BK for 90 minutes, and a clear image with no border residue was obtained. Novolak resist layer pattern is not removed;
It was left covered, but some deformation of the image occurred.

If the procedure described above for this example was used, except that a mixed solvent of acetone, inglovil alcohol, and water (60:40:3 parts by volume) was used in place of MI BK, the novolak resist layer Butter removed and PMM
It was possible to obtain an image with no boundary residue in the A resist.

Effects of the G1 Invention According to the present invention, submicron high resolution can be achieved,
Manufacturing techniques using PCM techniques can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the absorption rate of novolak resin and wavelength when the irradiation time is changed. FIG. 2 is a graph showing the relationship between absorption rate and wavelength of a resist made of a novolac resin and a polyolefin sulfone sensitizer. 6th
The figure is a graph of absorption versus wavelength for a novolac photoresist comprising a novolac resin and a diazoquinone sensitizer. Applicant Inter + 7 Town Kuya Birenes Machines Corporation Agent Patent Attorney Yamamoto
Jin Rou (1 other person) Effects of the present invention Figure 1 λ (-w) Figure 2

Claims (1)

Scope of Claims: (a) Forming on a substrate a lower resist layer that is sensitive to ultraviolet light with a wavelength of about 240 to about 280 nm and is developable with a water-soluble base or an organic solvent, and an upper resist layer based on a novolac resin. (b) imagewise exposing said upper resist layer; (c) developing said upper resist layer to convert it into an imaging mask; and (d) forming a lower resist layer developable with an organic solvent. (e) subjecting the imaging mask to at least one of exposure to ultraviolet light having a wavelength of about 280 to about 310 nm and heat treatment, provided that no heat treatment is used for use; (f) developing the lower resist layer to form an image that corresponds to the image on the imaging mask; Mask processing method including