DE10261845A1 - Process for treating a resist system and device therefor - Google Patents

Abstract

The invention relates to a method and a device for treating a resist system for the production of a semiconductor component, the resist system (1) having polar and / or charged components, characterized in that after the resist system (1) has been exposed to a substrate (2) the resist system (1) is exposed to an electrical field (10) to influence the movement of the polar and / or charged components of the resist system (1). The lateral diffusion of charged and / or polar components of the resist system can thus be reduced or prevented.

Description

The invention relates to a method according to the preamble of claim 1 and a device for performing the The method of claim 26.

In microelectronics, so-called chemically amplified Resist systems (chemical amplification resists, CAR) for various optical lithography process (wavelengths: 248nm, 193nm, 157 nm) in large Scope used. This is e.g. in Hiroshi Ito's article "Deep-UV resists: Evolution and status ", Solid-State Technology, July 1996, p. 164 ff. chemical increased Resists, especially with onium compounds as photo acid generators are also described in Reichmanis et al. "Chemically amplified resists: Chemistry and processes ", Advanced Materials for Optics and Electronics, Vol. 4, 83-93, 1994.

The resist systems can after the principle of acid catalytic Cleavage work. In the case of a positive resist, it is off a non-polar chemical group, for example a carboxylic acid tert-butyl ester group, in the presence of a photolytically generated acid (Photo Acid Generator: PAG; PAG) a polar carboxylic acid group educated.

Added bases can be the diffusion length the photo acid produced affect what affects both line roughness as well Have sensitivity of the resist system. In a subsequent development step the exposed resist film is treated with aqueous alkaline developer solutions, wherein the carbonic acid rich, polar areas are developed away and the unexposed resist areas are standing stay.

For the production of DRAMs by 2007 is likely Resist materials may be required, the structures up to one Size of 65 resolve nm can. For the 2016 will even be the resolution of 22 nm DRAM 1/2 pitch be necessary. With the currently used exposure wavelengths of 248 or 193 nm or also in the future wavelength used These structures can no longer be generated at 157 nm. For future lithography Therefore, optical lithography is used in the extreme generations shortwave range of about 13.4 nm (EUV) or even in the X-ray range advance.

Increase with decreasing structure size the requirements for the resist material used as well as what sensitivity as well as line roughness. In 2007, according to the today's planning only line roughness of less than 4 nm can be tolerated.

After exposure, the resist systems subjected to a thermal treatment (post exposure bake, PEB). The known chemically amplified resist systems (CAR) the problem is that the free positively charged parts of the resist system Diffuse (protons) isotropically through the resist system. This diffusion effect leads to Inaccuracies in the structures to be developed and leads significantly to line roughness.

It is known the diffusion of the restrict positive charged parts by adding bases to thus reducing the line roughness. The addition of bases has the consequence, however, that the exposure dose is increased must, so that the throughput of the plant is reduced.

With constant exposure dose and getting shorter exposure wavelengths the number of photons per exposure becomes smaller and smaller the number of photoacids produced. A loss of photoacids through added bases during of manufacturing further restrict the throughput of products (e.g. wafers).

The present invention lies the task is to create a method with which the lateral diffusion of charged and / or polar components of a resist system is reduced or prevented.

This object is achieved according to the invention solved a method with the features of claim 1.

In the method according to the invention becomes after the exposure of the resist system on a substrate, the resist system exposed to an electrical field. This will load on and / or polar components of the resist system exert a force such that the isotropic diffusion movement of the charged components a targeted movement due to the electric field is superimposed becomes. By choosing the field strength and / or field direction can the movement of the polar and / or charged particles are specifically influenced, so that the influence of diffusion e.g. can be reduced in the lateral direction.

It is advantageous if the electrical Field temporally and spatially is constant and homogeneous in the area of the resist system. Leave with it the polar and / or charged components of the resist system orient in a homogeneous manner in the resist system.

It is also advantageous to use the electrical Field has a predetermined gradient and / or as an electrical Alternating field is formed. Even leave with such training the movements of polar and / or charged components of the resist system in a targeted manner.

It is particularly advantageous if the electric field is essentially perpendicular to the substrate is directed. This suppresses lateral diffusion of the charged and / or polar components of the resist system; the components are oriented essentially vertically, which is advantageous for producing sharp, vertical lines in the resist.

An advantageous reduction in the line roughness results if the field strength of the electric field is less than 10 ⁵ V / cm.

Another advantageous The resist system is designed during a thermal treatment (e.g. baking the resist system) the electrical Field exposed. It is advantageous if after the thermal treatment the electrical field is switched off and the resist system with a developer solution is treated.

Advantageously, exposure using a mask process or a direct write process, in particular an e-beam or ion beam method.

The method according to the invention is advantageous applicable when the resist system is a chemically amplified system is trained.

An advantageous embodiment of the method according to the invention uses a resist system with at least one polymer or copolymer with at least one acid labile Group. With such a resist system, structuring can surprisingly at wavelengths in the range of 0.1 to 150 nm. The acid labile Groups are split under the catalytic action of acid and release polar groups, which then increase the solubility of the polymer / copolymer in developers, e.g. aqueous effect alkaline developers.

It is advantageous if at least an acid labile Group is an ester group or a lactone group.

By using a copolymer with at least one maleic anhydride segment and at least one methacrylate segment can be a substrate even without chemical reinforcing agents in a lithography process with wavelengths be structured in the range from 0.1 to 150 nm. The resist system according to the invention shows a big one Process window, because there are no cross-links even with high exposure doses occur that lead to insolubility of resist. Even if you basically if the aim is to use small exposure doses, then the resist system according to the invention through the big Process window less sensitive to fluctuations in exposure.

It is particularly advantageous if a t-butyl methacrylate and / or a 2-ethoxyethyl methacrylate as the methacrylate segment is used.

The sensitivity of the resist system let yourself improve if a iodine and / or sulfur-containing photo acid generator as a chemical reinforcing agent is used.

In an advantageous embodiment of the resist system according to the invention, at least one photo acid generator has a perfluoroalkanesulfuonate anion of the form C _n F _{2n + 1-x} H _x SO ₃ ^- with n = 1, ..., 10.

Advantageously, at least one PAG an iodonium compound. It is particularly advantageous if at least one photo acid generator a di (tert-butylphenyl) iodonium triflate, Di (tert-butylphenyl) iodoniumhexaflat, Di (tert-butylphenyl) iodoniumnonaflat, Diphenyliodonium triflate, Diphenyliodoniumhexaflat or Diphenyliodoniumnonaflat having.

It is also advantageous if at least a photo acid generator a sulfonium compound, in particular a triphenylsulfonium triflate, Triphenylsulfoniumhexaflat or triphenylsulfonium nonaflate has.

The resist system according to the invention advantageously has a proportion of silicon, which leads to improved etch stability. Especially It is advantageous if the silicon in the form of a connection with a polymerizable carbon-carbon bond, in particular a trimethylallylsilane can be introduced into the resist system.

The sensitivity is increased if in the inventive method a resist system with a chemical reinforcing agent that at least contains an iodine and / or sulfur-containing photo acid generator used becomes.

The large process window is evident from the fact that the exposure dose in the lithography method according to the invention can be between 0.1 and 300 mJ / cm ² . Even massive overexposure (e.g. by a factor of 250) does not lead to crosslinking of the polymer in the resist system. It is particularly advantageous if the exposure dose during exposure is between 0.5 and 10 mJ / cm ² .

An embodiment of the method according to the invention can at wavelength from 0.1 to 150 nm become. This covers the EW area up to the X-ray area. Especially It is advantageous to use a wavelength of 13.4 nm to be used.

The task is also accomplished by a device solved with the features of claim 26.

By using an agent for generating an electrical field and at least one receiving means for a With a resist system it is possible to use the resist system suspend electrical field to the movement charged and / or to influence polar components of the resist system.

In an advantageous embodiment the means for generating an electric field is part of a Device for thermal treatment of the resist system, e.g. one Chamber for a baking step.

The invention is described below Reference to the figures of the drawings on several exemplary embodiments explained in more detail. It demonstrate:

1 a schematic representation of the known resist development process;

2 a schematic representation of an embodiment of the method according to the invention;

3a . 3b a representation of the diffusion behavior in the resist system without (a) and with an electric field (b).

4 schematic representation of an apparatus for performing the method according to the invention;

5 Contrast curves for different resist systems.

In 1 is a known method for creating structures on a substrate 2 , for example a wafer. The arrow on the left indicates successive process steps.

A substrate 2 is here with a chemically amplified resist system 1 lacquered and then with an exposure source 30 , which has a mask exposed. The mask structure is formed in the resist system 1 as a latent image of what is in 1 due to banding in the resist system 1 is indicated. Alternatively, the structure can be generated using direct writing methods, such as an e-beam or an ion beam method.

The resist system 1 the latent image of the mask is subjected to a thermal treatment step (PEB). During this step, the known processes result in an undesired isotropic diffusion of the polar acid (Photo Acid Generator: PAG; photo acid generator) with a polar carboxylic acid group. The isotropic diffusion is in 3a described in more detail.

After the thermal treatment step the resist system is treated with a development solution, in which here vertical structures are retained, but due to the lateral Share of the isotropic diffusion have a high line roughness.

The inventive method, which in 2 is shown schematically, should avoid this roughness.

The basic procedure corresponds to the procedure according to 1 , However, an electrical field is generated during the thermal treatment step of the PEB 10 applied to that perpendicular to the resist system 1 and to the substrate 2 stands. The electric field 10 is designed as a constant field with high homogeneity. The field direction can point up or down, which is symbolized here by an arrow.

The orientation of the electric field affects polar and / or charged components of the resist system 1 (eg PAG) exerted a force along the field lines so that the isotropic diffusion movement is superimposed by a vertical movement. As a result, the lateral movement is restricted.

In 3 this is shown schematically. 3a and 3b provide sections from an area of the resist system 1 in this 3a are the movements of the polar and / or charged components of the resist system 1 through circles 40 shown. The circles 40 are to be understood here as sectional representations, since the isotropic diffusion region is spherical.

This corresponds to the isotropic diffusion of the components, which has considerable lateral components. The line roughness, in 3a represented by the thick line on the left edge is high.

The application of an electric field according to the invention 10 causes the isotropic diffusion to drift the charged and / or polar components of the resist system 1 is superimposed. The movements of the components are shown in the two-dimensional representation of the 3b to a kind of ellipse 41 distorted. spatially the area has an ellipsoidal shape.

The vertical motion shares are now bigger than the lateral. The overlay this deformed diffusion area leads to the edge of exposed structures for a more effective overlap. this leads to that the line roughness, symbolized by the thick line Line on the left edge, is reduced.

In 4 is shown schematically an embodiment of a device according to the invention. In a thermal treatment device 20 is as a substrate 2 a wafer arranged. The substrate 2 is here with a resist system 1 coated, which has polar and / or charged components.

There is an agent in the thermal treatment device 50a . 50b to generate an electric field 10 arranged that essentially works like a capacitor. The substrate 2 with the resist system 1 is so between the capacitor plates 50a . 50b arranged that the field lines are perpendicular to the resist system 1 stand. If the capacitor plates 50a . 50b are sufficiently large, the electric field is homogeneous, so that the field lines lie parallel and produce the desired parallel drift movement, which in connection with 3b has been described. The field is in 4 oriented from top to bottom.

The following are resist systems 1 described, which can be used as embodiments in the inventive method and the inventive device. In principle, the method according to the invention can be carried out with all chemically amplified resist systems. In fol a reference is made to a group of resist systems.

The resist system described here has a polymer as part of the resist system, the polarity of which can be changed in a targeted manner is. The production of a polymer is described below, that alone or together with photo acid generators as a resist system is usable.

The polymer is synthesized using radical polymerization. To do this
20.27 g (206 mmol) maleic anhydride,
26.46 g (186 mmol) t-butyl methacrylate,
3.27 g (21 mmol) 2-ethoxyethyl methacrylate,
0.64 g (4 mmol) of α, α'-azoisobutyronitrile as radical initiator and
0.32 g (2 mmol) dodecyl mercaptan as chain regulator in
41.0 g (52 ml) of 2-butanone dissolved and heated to boiling (80 ° C.) under reflux for 3 hours. Then 4.0 g (5 ml) of methanol (for partial alcoholysis of the anhydride) are added and the reaction solution is refluxed for a further 24 hours (80 ° C.).

The reaction solution is left on Cool down to room temperature and adds with vigorous stirring 35.0 g (27.5 ml) of 2-propanol. The solution obtained becomes within 30 Minutes with very strong mechanical stirring into a solution 10.5 g (13.1 ml) 2-butanone, 337.0 g (429 ml) 2-propanol and 329.0 g (329.0 ml) of water was added dropwise.

Here the polymer falls as a fine, white Powder from. You leave Stir for another 30 minutes and then sucks the solvent under a slightly reduced pressure over a G3 frit from.

The white precipitate comes with a solution from 16.0 g (20.0 ml) 2-butanone, 111.0 g (141 ml) 2-propanol and Washed 100.0 g (100 ml) of water and 72 hours at 80 ° C in a high vacuum dried. You get approx. 38 g (75% of theory) of fine, white powder as a reaction product. The analysis can be carried out by means of NMR, GPC or DSC.

A section of a structure is shown below as an example of a silicon-containing polymer of the resist system according to the invention:

Alternatively, a silicon-free polymer can be used:

Example 1 (resist system with polymer without PAG)

5 g of the polymer described above are dissolved in 209 g of 1-methoxy-2- dissolved propylacetate. The solution will be subsequently through a Teflon filter with 0.2 μm Pores pressure filtered. After a rest period of 24 hours is a first embodiment of the resist system ready for use. This first embodiment has no photo acid generator on.

The resist system is spun onto a silicon wafer (wafer) at 1000-5000 rpm and baked for 90 s at 130 ° C (PAB). The layer thickness of the resist system after spin-coating at 3000 rpm is approximately 110 nm. The exposure is carried out with EW light with a wavelength of 13.4 nm. The exposure dose D ₀ is 36.8 mJ / cm ² . After exposure, there is a further baking step, for 90 s at 130 ° C (PEB). The development takes place in a 2.38% tetramethylammonium hydroxide solution, then the wafer is rinsed with distilled water and dried.

The effectiveness of this resist system, even without photo acid generators, is shown 1 clear.

5 shows points of three contrast curves in which the film thickness in nm is plotted against the exposure dose in mJ / cm ² . The right curve ("without PAG") shows the measured values of Example 1. Even without a photo acid generator, exposure down to exposure doses down to 10 mJ / cm ^{2 is} possible. The sensitivity is therefore in a range that can be used in practice.

Example 2 (resist system with di (tert-butylphenyl) iodonium hexaflate as photo acid generator)

Basically, iodonium compounds have a structure (IR ₂ ) X, where R can be an organic radical, in particular an aryl group. X is a hydroxy group or a monovalent acid residue. Possible structures are, for example:

Whereby substituents R can also be arranged on such a structure:

Die Substituenten R können untereinander gleich oder identisch sein. Als Anion kann der Photosäuregenerator z.B. ein Perfluoralkansulfuonat der Form C_nF_2n+1–xH_xSO₃ ^– mit n=1,...,10 aufweisen.Straight or branched alkyl groups, such as, for example, -CH ₃ , C ₂ H ₅ , isopropyl or, can serve as substituents R.

The substituents R can be identical or identical to one another. As an anion, the photo acid generator can have, for example, a perfluoroalkanesulfuonate of the form C _n F _{2n + 1-x} H _x SO ₃ ^- with n = 1,... 10.

In the first exemplary embodiment, 50 mg of di (tert-butylphenyl) iodonium hexaflate [(tBu-Ph) ₂ J ⁺ , CF ₃ CHF CF ₂ SO ₃ ^- ] as the iodonium compound in 209 g of 1-methoxy- 2-propyl acetate dissolved.

The solution is then through a Teflon filter with 0.2 µm pores pressure filtered. After a rest period of 24 hours is a first embodiment of the resist system ready for use.

The resist system is spun onto a silicon wafer (wafer) at 1000-5000 rpm and baked for 90 s at 130 ° C (PAB). The layer thickness of the resist system after spin-coating at 3000 rpm is approximately 110 nm. The exposure is carried out with EUV light of the wavelength 13.4 nm. The exposure dose D ₀ is 1.4 mJ / cm ² . After exposure, there is a further baking step, 90 s at 130 ° C (PEB). Development takes place in a 2.38% tetramethylammonium hydroxide solution, then the wafer is rinsed with distilled water and dried.

This will be a second embodiment of the resist system according to the invention manufactured.

Example 3 (resist system with triphenylsulfonium nonaflate as photo acid generator)

The photo acid generator can also have sulfonium compounds which basically have the form [R ₃ S] ⁺ X ^- . A possible structure is, for example, a triphenyl sulfonium (TPS):

The aromatic components can also have the substituents R listed in the example above.

A third exemplary embodiment of the resist system according to the invention is produced analogously to the example 2 However, instead of di (tert-butylphenyl) iodonium hexaflate, triphenylsulfonium nonaflate [Ph ₃ S ⁺ , CF ₃ (CF ₂ ) ₃ SO ₃ ^- ] is used as photo acid generator. In this exemplary embodiment, the exposure dose is 2.4 mJ / cm ² .

Example 4 (resist system with triphenylsulfonium nonaflate and base)

A fourth embodiment of the resist system according to the invention is produced analogously to Example 3 , however, an additional 3 mg triphenylsulfonium acetate is added to the solution as base. The exposure dose is 4.1 mJ / cm ² .

The contrast behavior of this embodiment is the middle curve in FIG 5 ("PAG + Base"). The sensitivity is also maintained by the addition of small amounts of base, even if the sensitivity is lower than in the left curve in 5 . d .H. when using a polymer according to the invention with PAG without base.

Example 5 (resist system with diphenliodonium triflate)

In a fifth embodiment, analog is used for example 2 produced a resist system, using diphenyliodonium triflate [Ph ₂ J ⁺ , CF ₃ SO ₃ ^- ] as the photoacid generator instead of the di (tert-butylphenyl) iodonium hexaflate. The exposure dose is 1.3 mJ / cm ² .

Example 6 (resist system with triphenylsulfonium triflate)

In a sixth exemplary embodiment, a resist system is produced analogously to Example 2, triphenylsulfonium triflate [Ph ₃ S ⁺ , CF ₃ SO ₃ ^- ] being used instead of the di (tert-butylphenyl) iodonium hexaflate as the photoacid generator. The exposure dose is 0.8 mJ / cm ² .

The left curve in 5 shows a contrast curve, which was determined with a resist system according to this embodiment. This makes it clear that the photo acid generator significantly improves the sensitivity, so that good results are achieved even with small exposure doses.

However, a much higher exposure dose of 250 mJ / cm ² can also be used. The resist system works even at these high doses without causing undesirable cross-linking.

Example 7 (resist system with triphenylsulfonium hexaflate)

In a seventh embodiment, analog is used for example 2 produced a resist system, using triphenylsulfonium hexaflate [Ph ₃ S ⁺ , CF ₃ CHF CF ₂ SO ₃ ^- ] as the photoacid generator instead of the di (tert-butylphenyl) iodonium hexaflate. The exposure dose is 1.6 mJ / cm ² .

The listed examples 2 to 7 show some combinations of photo acid generators. in principle are possible Permutations of the triphenylsulfonium, diphenyliodonium and di (tert-butylphenyl) iodonium salts of trifluorosulfonic acid (Triflate), the hexafluorosulfonic acid (Hexaflate) or nonafluorosulfonic acid (Nonaflate) suitable.

The embodiment of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable, which differ from the ver according to the invention drive and make use of the device according to the invention even in fundamentally different types.

1

resist system

2

substratum

10

electrical field

20

contraption for thermal treatment

30

exposure source

40

isotropic diffusion

41

of electric field superimposed diffusion

50a,

b Means for generating an electric field,

capacitor plates

Claims (27)

Method for treating a resist system for the production of a semiconductor component, the resist system having polar and / or charged constituents, characterized in that after the resist system has been exposed ( 1 ) on a substrate ( 2 ) the resist system ( 1 ) an electric field ( 10 ) to influence the movement of the polar and / or charged components of the resist system ( 1 ) is suspended. A method according to claim 1, characterized in that the electric field ( 10 ) constant in time and space and in the area of the resist system ( 1 ) is homogeneous. A method according to claim 1, characterized in that the electric field ( 10 ) has a predetermined gradient and / or is designed as an alternating electrical field. Method according to at least one of the preceding claims, characterized in that the electrical field ( 10 ) essentially perpendicular to the substrate ( 2 ) is aligned. Method according to at least one of the preceding claims, characterized in that the field strength of the electric field ( 10 ) is less than 10 ⁵ V / cm. Method according to at least one of the preceding claims, characterized in that the resist system ( 1 ) during a thermal treatment, in particular a baking step, the electric field ( 10 ) is suspended. A method according to claim 6, characterized in that after the thermal treatment the electric field ( 10 ) is switched off and the resist system is treated with a developer solution. Method according to at least one of the preceding Expectations, characterized in that the exposure with a mask process or a direct writing process, in particular an e-beam or ion beam process he follows. Method according to at least one of the preceding claims, characterized in that the resist system ( 1 ) is designed as a chemically reinforced system. Method according to at least one of the preceding claims, characterized in that the resist system ( 1 ) has at least one polymer or copolymer with at least one acid-labile group. A method according to claim 10, characterized in that at least one acid labile Group of the resist system an ester group or a lactone group is. A method according to claim 10 or 11, characterized by a resist system ( 1 ) with a copolymer with at least one maleic anhydride segment and at least one methacrylate segment. Procedure according to claim 12, characterized in that that the methacrylate segment is a t-butyl methacrylate and / or a 2-ethoxyethyl methacrylate is. Method according to at least one of the preceding claims, characterized by a resist system ( 1 ) with at least one iodine and / or sulfur-containing photo acid generator as a chemical reinforcing agent. A method according to claim 14, characterized in that at least one photo acid generator has a perfluoroalkanesulfuonate anion of the form C _n F _{2n + 1 - x} H _x SO ₃ ^- with n = 1, ..., 10. Procedure according to claim 15 or 16, characterized in that that at least one photo acid generator has an iodonium compound. Method according to at least one of claims 14 to 16, characterized in that at least one photoacid generator a di (tert-butylphenyl) iodonium triflate, di (tert-butylphenyl) iodonium hexaflate, di (tert-butylphenyl) iodonium nonaflate, Diphenyliodonium triflate, Diphenyliodoniumhexaflat or Diphenyliodoniumnonaflat having. Method according to at least one of the preceding Expectations, characterized in that at least one photo acid generator has a sulfonium compound. A method according to claim 18, characterized in that at least one photo acid generator a triphenylsulfonium triflate, triphenylsulfonium hexaflate or triphenylsulfonium nonaflate having. Method according to at least one of the preceding Expectations, characterized by a share of silicon. Procedure according to claim 20, characterized in that that the silicon is in the form of a compound with a polymerizable Carbon-carbon bond, in particular a trimethylallylsilane can be introduced into the resist system. Method according to at least one of the preceding claims, characterized in that the polymer prior to the application of the resist system ( 1 ) with a chemical reinforcing agent, which is mixed at least one iodine and / or sulfur-containing photo acid generator. Method according to at least one of the preceding claims, characterized in that the exposure dose during exposure is between 0.1 and 300 mJ / cm ² . Method according to at least one of the preceding claims, characterized in that the exposure dose during exposure is between 0.5 and 10 mJ / cm ² . Method according to at least one of the preceding Expectations, characterized in that the wavelength at exposure 0.1 up to 150 nm, in particular 13.4 nm. Device for carrying out the method according to claim 1, characterized by a means for generating an electric field ( 10 ) and at least one receiving means for a substrate ( 2 ) with a resist system ( 1 ). Apparatus according to claim 27, characterized in that the means for generating an electric field ( 10 ) Part of a device for thermal treatment of the resist system ( 1 ) is.