DE10106861C1 - Production of fine resist structures in a photoresist layer during the manufacture of microelectronic components by applying a photoresist layer, applying and exposing 2 masks at different wavelengths and developing resist - Google Patents

Abstract

Production of fine resist structures in a photoresist layer (2) during the manufacture of microelectronic components comprises applying a photoresist layer; applying a first mask (1) having a first structure (5) transparent for a first wavelength ( lambda 1); irradiating the photoresist layer through the structure of the first mask with the wavelength ( lambda 1); removing the mask; applying a second mask having a second structure transparent for a second wavelength ( lambda 2); irradiating the photoresist layer through the structure of the second mask with the wavelength ( lambda 2); removing the second mask; and developing the resist layer. Preferred Features: The difference between the first and second wavelengths is at least 30 nm. The photoresist layer is heated treated after the first mask is applied and after the second mask is removed.

Description

The invention relates to a method for producing fine Resist structures in a deposited on a substrate Photoresist layer in the manufacture of microelectronic Components.

Such processes are microelectronic in the manufacture among other things for the production of fine Contact hole structures known. The photolithography is used here fie for transferring structures on a photo mask in an egg NEN photosensitive photoresist, for example on a Silicon wafer was applied. With the help of the photolithogra Fishing processes are made in the photoresist by the structure Exposure and subsequent development of relief structure Ren generated, which in turn as an etching mask for subsequent Serve as substrate etchings.

The optical transmission of the mask structures in the Re sist takes place via an optical lens system, whereby both the wavelength as well as the coherence of the light used (of radiation) as well as the numerical aperture of the lens significant influence on the resolution and the Have quality of structure transfer. With this over As a so-called process window, support is the leeway defines in which the photoresist layer from the focus plane of the lens system can drift without the structural quality activity is influenced. Such a drift can, for example due to slight temperature fluctuations, lens defects, Deflection of the wafer and other influences will call.

The following problems occur in the production of hole structures, which are present in the construction of semiconductor chips primarily as contact holes to active areas or electrodes of CMOS transistors:

• - In the manufacture of so-called iso contact hole structures isolated, so-called iso-contact holes on the mas ke depicted in the resist with a different diameter than tight, so-called dense contact holes, even if both contact hole types on the mask have the same diameter have.
• - With known methods, the process window is at the manufacturer position of iso contact holes much smaller than that in the manufacture of Dense contact holes. This means, that the "common" process window of Iso- and Dense- Contact hole structures in the manufacturing process through the small nere process window of the isocontact holes is determined.

So far, this problem has been countered by providing a so-called mask lead, which means that the hole structures on the mask are provided with a bias, which practically means that the diameter is greater than the desired one Nominal value is increased or decreased accordingly. Under the given optical boundary conditions, which are given by the wavelength used, the optics used and the coherence of the radiation used, iso-contact hole structures as well as dense contact hole structures with the same diameter can be imaged in the photoresist layer with the lead become. However, this method has the following disadvantages:

• - The respective lead must be em through elaborate learning cycles be found piric, and
• - Iso contact compared to Dense contact hole structures hole structures only with a significantly smaller process window (English: "depth of focus", abbreviated: DOF) shown be det.

A method for producing egg known from DE 25 43 553 A1 ner etching mask uses an applied on a carrier body tes organic resist material, which by high-energy Blasting is structured. Through electron radiation at least one structure and one by photon radiation further structure with radiation-specific developments generated. A high polymer resist material is used applies that ver under the influence of electron beams networks and under the influence of photon radiation depoly merized. In the proposed in this document Procedures are initially defined in the contact procedure reach the resist layer by ultraviolet light exposure depolymerized. Then with the help of the electron beam light the same resist layer at certain points wets. The depolymerized part of the Resist material removed. Then an etching process follows two material lying on top of each other on a carrier material layers are etched together. By a subsequent Development step becomes the unirradiated part of the resistma terials solved so that only those through the electrons beam exposure networked areas remain. By egg A subsequent etching process then only becomes the one above lying layer of material etched and finally the crosslink resist material removed. The be in this publication The known method described does not describe the method described in the steps proposed by this application at the same time dense vias and iso vias a microelectronic component can be produced.

EP 0962825 A1 describes a method for producing Pattern in a photoresist, which is a first at a first wavelength activatable component and a two component that can be activated at a second wavelength has, these wavelengths different from each other who are and the one photoactive component in the Ab sorption wavelength of the other photoactive component in the  Behaves essentially inert. After a structuring Be The photoresist is exposed in this document known methods the entire surface of the exposed Areas of photoresist with light of the other wavelength exposed so this surface in the case of a positive mus ter is difficult to solve in a developer or in Falling a negative pattern is easy in the developer to make solvable. In the subsequent development step this way you can create a pattern with high resolution form.

In a method described in US 5,422,205, with which transfer a microscopic pattern onto a substrate is a multi layer consisting of at least two layers gene film applied to a substrate. A first exposure step exposes the top layer of the multilayer film a first mask that bears a pattern that is the same or larger is larger than the microscopic pattern to be transferred. In egg In a second step, a second mask is positioned so that a main pattern on it is a transmission area of the top layer of the multilayer film overlaps, wherein this second mask with the microscope to be transferred main pattern and one next to the Main pattern lying additional pattern. In one second exposure step will be different than the top one Layer of the multilayer film exposed through the second mask. This known method can be advantageously used with a alternating phase shift mask with modified exposure combination.

The object of this invention is a generic method training for the production of fine resist structures in such a way that a precise transfer of the structures from the mask in the photoresist with a suitable for production Process window can be realized, with the manufacturing  of contact hole structures the goal is both iso-contact holes and dense contact at the same time holes with the same diameter in the resist sufficient process window from a production point of view to build.

This object is achieved with the features of claim 1 solved.

According to an essential aspect of the invention, the method according to the invention for producing fine resist structures in a photoresist layer applied to a substrate during the production of microelectronic components, the photoresist layer being exposed to a radiation source through a photomask and then exposed areas of the photoresist layer to form the resist structures following steps are developed:

• A) Apply a layer of photoresist with a positive Behavior when exposed to a first wavelength and with a negative behavior when exposed to a second wavelength, which is different from the first wavelength different;
• B) attaching a first mask with a first one for the first wavelength transparent structure over the photore sistschicht;
• C) first exposure of the photoresist layer through the first transparent structure of the first mask with the wavelength ge;
• D) removing the first mask;
• E) Apply a second mask with one for the second Wavelength transparent second structure above the photo resist layer;
• F) second exposure of the photoresist layer through the second transparent structure of the second mask with the second Wavelength;
• G) removing the second mask, and  
• H) Development of the resist layer, the second structure part of the first structure so that only the part of the first structure not overlaid by the second structure ten structure is developed, with simultaneous manufacture provision of dense contact holes and iso contact holes a microelectronic component of the first exposure step with a high resolution high exposure device numerical aperture and small first wavelength and the second exposure step with an exposure device low Resolution carried out with a larger second wavelength and the structure of the first mask to form a Dense contact hole structure in the photoresist layer is used.

Since in the method according to the invention first with the first mask only latent dense contact hole structures in the photoresist In principle, an iso / dense lead will be formed closed and the larger process window the Dense contact hole structures used. Furthermore, the production of the photo mask considerably simplified, since only one type of perforated structure must be formed on the first mask. This allows structures on the mask with a significantly higher Uniformity can be produced, which in turn improves quality improved the entire process. At the first exposure step becomes a latent image of the first, i.e. H. Dense- Contact hole structures created in the photoresist layer. Yet before development then in the second, uncritical Expose step the areas of the photoresist layer where no contact holes are to be created. At the The final development step is then only the contact holes visible as a relief structure in the photoresist second exposure step were not exposed.  

A particular advantage of the invention is that that for this second exposure step uncritical Be Use lighting equipment (second mask, exposure device) can be detected since the resolution requirement is lower. This makes it an inexpensive manufacturer achieved because it requires less investment and achieves a higher throughput.

A photoresist suitable for the photoresist layer has a first photoactive component, which in the first Be glowing step radiation of the first wavelength absorbed to solubility with the first wavelength exposed structures of the photoresist in the developer possible and at least one second photoactive component, what radiation of the second wavelength absorbs to da with an insolubility of be with the second wavelength light structure of the photoresist in the developer chen, with exposure to the first wavelength no photolysis of the second photoactive component and at exposure to the second wavelength, no photolysis the first photoactive component of the photoresist that may.

In practice, it is therefore required that the difference between the wel used in the first exposure step len length and that used in the second exposure step Wavelength is at least 30 nm. In principle, it can the first wavelength is at least 30 nm larger or smaller be smaller than the second wavelength. However, is preferred the first wavelength is at least 30 nm smaller than the two te wavelength.

Suitable photoresists for use in the invention described for example in EP 0 962 825 A1. The Soluble speed by exposure to the first wavelength  reacting first photoactive component in aqueous alkaline developers, for example, by acid catalysis based removal of hydrophobic groups at a base point Lymer of the photoresist through photolytic from the fotoak tive first component produced acid. Next the first photoactive component contains such a Fo toresist one or more other components (second com component) that absorb light of the second wavelength and thus making the photoresist layer insoluble. For example, substances are added to the photoresist the one after exposure to the second wavelength Networking of the photoresist, which thus in egg becomes insoluble in an alkaline developer.

He coated the substrates with the photoresist layer follows with usual production engineering methods, typi usually by spin coating followed by drying step on the hotplate, for example at 70 ° C to 160 ° C and for 30 to 180 seconds. The layer thicknesses of the photo lacquer coats depend on the requirements of the sub strat etching and are typically in the range of 50 nm up to 2 µm.

The first exposure step through the first mask, the uniform con. transparent for the first wavelength has clock hole structures, can either with a simple Chen chrome mask (COG: chrome-on-glass), a halftone Phase shift mask (HAT-PSM) or with an alternating one Phase mask. The one at the first exposure step The first wavelength used can be in the range of a few Na nomometers are up to 500 nm. Commonly used in production lines wavelengths used are: 436 nm, 365 nm, 248 nm, 193 nm, 157 nm. The first exposure step can also at other wavelengths, if necessary also by radiation from electrons or ions. Wesent Lich in the sense of the invention is only that the first wavelength  l1 for the first exposure step at least 30 nm larger or smaller than that in the second exposure step used wavelength is λ2 and that at the first exposure no photolysis of the second photoactive composition nenten takes place.

After the first exposure step and removing the first Mask can be a heat treatment step, e.g. B. in the range 80 ° C. up to 180 ° C for 30 to 180 seconds.

A second is used for the subsequent second exposure Mask used that exposes the photoresist layer allows in exactly those places where there is no contact hole structures should arise. It is in the sense of the Er irrelevant whether a simple chrome mask (COG: chrome-on-glass), a halftone phase shift mask (HAT-PSM) or an alternating phase mask is used. At the second exposure step, the second wavelength λ2 we few nanometers up to 500 nm. You can do the above mentioned, commonly used in production lines Wavelengths are used. In addition, the second Be clearing step but also with a different wavelength be carried out, if necessary also by irradiation with electrons or ions. Essential in the sense of the invention is that the second wavelength λ2 is at least 30 nm is larger or smaller than the first wavelength λ1 and that when exposed to the second wavelength in the second Exposure step no photolysis of the first photoactive Component of the photoresist takes place.

The photoresist layer can then be heat-treated about in the range of 80 ° C to 180 ° C, e.g. B. 30 to 180 seconds long.

Finally, the photoresist layer is placed in a suitable one Developed developer medium, using only the first exposure step  by exposure to the first wavelength exposed contact hole structures in the photoresist layer be formed.

The following is the manufacturing method of the present invention using an exemplary embodiment based on the drawing described in more detail, which relates to the application of the inventions method according to the invention in the production of fine contact aligns hole structures in a semiconductor wafer. The drawing Figures show in detail:

Figs. 1A to 1C are schematic cross sections of a microelectronic component illustrating individual steps of the invention Ver driving,

Fig. 2A schematically in a planar plan view of a in a layer applied to a substrate Fo toresistschicht with a first mask shown in FIG. 2B, in a first exposure step formed latent dense contact hole structural tur,

FIG. 2B schematically shows the for the first exposure step for exposure of the dense contact hole structures serving first mask,

Fig. 3A, in a schematic plan view of a plane with a second in Fig. 3B mask second exposure step executed,

Fig. 3B schematically shows the second mask used for the second exposure step, and

FIG. 4 is a schematic plan view showing latent dense contact hole structures and latent iso contact hole structures formed in the photoresist with the first exposure step according to FIGS. 2A and 2B and with the second exposure step according to FIGS. 3A and 3B.

Fig. 1A shows a schematic cross section through an Ab-section of a microelectronic device, wherein a was tet beschich to be patterned substrate 3 with a photoresist 2, which is, after exposure to a first wavelength λ1 indicates a positive response, that is, in Entwicklerme dium soluble and after a further exposure at a second wavelength λ2, which differs from the first wavelength, shows a negative behavior, that is to say, areas of the photoresist 2 which are already exposed at the wavelength λ1 are in the developer medium after exposure to the second wavelength λ2 again insoluble. A first exposure step with the wavelength λ1 is carried out according to FIG. 1A with a first photomask 1 , which has a first structure 5 which is transparent for the first wavelength λ1 (dense contact hole structure). Such a first mask 1 can be manufactured and positioned with high process reliability. The first exposure step results in exposure to the first wavelength λ1 in the first photoresist layer 2, first latent resist structures, the hatched areas denoted by 6 denoting the areas now soluble in the developer medium and the areas denoted by 10 being the insoluble areas non-transparent mask structures of the first mask 1 are covered areas.

The first mask 1 is then removed and, if appropriate, a heat treatment step is applied, which can last for 30 to 180 seconds in the temperature range from 80 ° C. to 180 ° C.

Fig. 1B is in accordance subsequently positioned a second photo mask 4 on the photoresist layer 2 having a transparent to the second wavelength λ2 second structure 7, and then the photoresist layer 2 exposed in a second exposure step through the second photomask 4 having the second wavelength λ2. This creates in the photoresist layer 2 two te latent resist structures 8 which, since the photoresist with the properties mentioned is used for the photoresist layer 2 , after exposure to the second wavelength λ2 become insoluble in the developer medium again, so that in this way Part of the areas 6 previously formed in the first exposure step according to FIG. 1A are masked, that is to say become insoluble again in the developer. As mentioned, the second wavelength λ2 used in the second exposure step according to FIG. 1B differs from the first wavelength λ1 by at least 30 nm.

The second mask 4 is then removed and optionally a heat treatment step in the temperature range from 80 to 180 ° C. is carried out for 30 to 180 seconds.

Development is then carried out so that, according to FIG. 1C, the regions 6 formed in FIG. 1A and not made insoluble again according to FIG. 1B are dissolved and contact hole structures 9 are formed in the resist layer 2 .

It should be mentioned that it is irrelevant for this invention whether a simple chrome mask, a halftone phase shift mask or an alternating phase mask is used for the first mask 1 and the second mask 4 . The exposure with the first wavelength λ1 can take place in a wavelength range from a few nanometers to 500 nm. The exposure with the second wavelength λ2 can also take place in a wavelength range from a few nanometers to 500 nm. The only important thing is that the two wavelengths λ1 and λ2 differ in such a way that they cause the intended positive and negative behavior in the photoresist. The difference between the two wavelengths λ1 and λ2 is at least 30 nm.

Referring to Figs. 2 to 4 in manufacturing a fei ner contact hole structures will now be described in a semiconductor wafer dishes tes embodiment, the underlying inventive procedure described above with reference to FIGS. 1A-1C.

A substrate 3 , which can be a silicon wafer with, for example, a 500 nm thick silicon oxide layer, is coated with a photoresist layer 2 in the spin coating process. After drying on the hotplate (60 seconds at 110 ° C), a photoresist layer 2 of z. B. 450 nm thickness. A first mask 1 shown in FIG. 2B is positioned over the photoresist layer 2 . The first exposure step is then carried out using a 248 nm exposure device (numerical aperture is 0.63 NA). The first mask 1 is a chrome-on-glass mask, the contact hole structures 5 of which have a diameter of 170 nm and a grid of 340 nm. In this case, as shown in FIG arise. 2A regular latent contact hole structures 6 having a diameter of 170 nm, which are arranged in a grid of 340 nm, so that the intermediate spaces 10 is also 170 nm measured.

Mask 1 is then removed and heat treatment is carried out on the hotplate at 110 ° C. for 60 seconds.

The photoresist layer 2 on the wafer 3 is then exposed with a 365 nm exposure device (numerical aperture is 0.60 NA) through a second chrome-on-glass mask 4 , which has, for example, the structure 7 shown in FIG. 3B. The smallest hole size, that is to say the region 11 of this second mask 4, is 340 nm and the smallest grid is 680 nm. In the second exposure step, the exposure dose is 320 J / m ² . In this case, the area designated in FIG. 3A with the number 8 arises in the photoresist layer 2, which leaves an iso-contact hole and various other dense contact holes free and covers the other areas of the photoresist layer 2 .

Thereafter, the second mask 4 is removed and a further heat treatment is carried out on the hotplate at 130 ° C. for 60 seconds and then the photoresist layer 2 in an aqueous alkaline developer (0.26 N tetramethylammonium hydroxide in water), for. B. Developed for 40 seconds. 4, both the se contact hole structures 6 (Dense) and the iso contact hole structures 6 (iso), which all have the same diameter of 170 nm, are formed in the photoresist layer 2 according to FIG. 4. The result of the method according to the invention shown in FIG. 4 was confirmed with an SEM measurement.

The above description shows that the method according to the invention has the following main advantages:

• - Different contact hole sizes (diameter) from Dense contact holes and isocontact holes are avoided;
• - The structuring first exposure with the first waves length λ1, which defines the critical contact hole size, is on a high-resolution exposure device, the one has a high numerical aperture and a small wavelength, performed during the second exposure step with the second wavelength λ2 on an exposure device with ge lower resolution and longer wavelength can be.

If, for example, the first exposure step, as described above, is carried out on a 248 nm exposure device with the numerical aperture 0.63 in order to produce the contact hole structures 6 with a diameter of 170 nm in a grid of 340 nm, the second can Exposure is carried out on an i-line stepper (365 nm) with a numerical aperture of 0.60, since with this exposure, in this example, only a resolution of 340 nm with a grid of 680 nm is required. By using an inexpensive exposure device for the second exposure step, this can be done at relatively low cost.

The method according to the invention thus enables a combination nation of a photoresist with the described properties with a double exposure at different wavelengths gene that dense contact hole structures and iso contact hole structures are formed in the resist at the same time critical first exposure step with the wavelength λ1 there are only dense contact hole structures on the photomask are located. This causes a disturbing iso / dense lead avoided, and the process window in production enlarged.

Claims (7)

1. A method for manufacturing fine resist patterns in egg ner applied to a substrate (3) photo-resist layer (2) of microelectronic in the preparation components, said photoresist layer (2) exposed to a radiation source by ei ne photomask and then exposed portions of the photoresist layer to form the Resist structures are developed, comprising the following steps:

• A) applying a photoresist layer ( 2 ) with a positive behavior when exposed to a first wavelength (λ1) and with a negative behavior when exposed to a second wavelength (λ2), which differs from the first wavelength;
• B) applying a first mask ( 1 ) with a first structure ( 5 ) transparent to the first wavelength (λ1) over the photoresist layer ( 2 );
• C) first exposure of the photoresist layer ( 2 ) through the first transparent structure ( 5 ) of the first mask ( 1 ) with the wavelength (λ1);
• D) removing the first mask ( 1 );
• E) applying a second mask ( 4 ) with a second structure ( 7 ) transparent to the second wavelength ( 2 ) over the photoresist layer ( 2 );
• F) second exposure of the photoresist layer ( 2 ) through the second transparent structure ( 7 ) of the second mask ( 4 ) with the second wavelength (λ2);
• G) removing the second mask ( 4 ), and
• H) Developing the resist layer (2), wherein the second structure (7) overlies a portion of the first structure (5) so on, that only is not developed (7) superimposed on part of the first structure from the second structure, wherein

for the simultaneous production of dense contact holes and iso contact holes in a microelectronic component, the first exposure step (C) with a high-resolution exposure device with a high numerical aperture (NA) and a small first wavelength (λ1) and det second exposure step (F) with an exposure device lower resolution is carried out with a larger second wavelength (λ2) and the structure of the first mask ( 1 ) is used to form a den se contact hole structure in the photoresist layer ( 2 ). 2. The method according to claim 1, characterized in that for the photoresist layer ( 2 ), a resist material with a first photoactive component, which absorbs radiation of the first wavelength (λ1) in the first loading step (C), in order first to have a solubility of the first To allow wavelength (λ1) exposed first structure ( 5 ) in the developer, and is used with at least one second photoactive component, which in the second exposure step (F) absorbs radiation of the second wavelength (λ2), thereby insolubility of the with the second wavelength (λ2) exposed second structure ( 7 ) where it overlaps the first structure ( 5 ) in the developer, and that when exposed to the first wavelength (λ1) no photolysis of the second photoactive component and when exposed to the second wavelength (λ2) no photolysis of the first photoactive component of the photoresist takes place. 3. The method according to claim 1 or 2, characterized, that the difference between the first wavelength (λ1) of the first exposure step (C) and the second wavelength (λ2) of the second exposure step (F) be at least 30 nm wearing. 4. The method according to any one of claims 1 to 3, characterized in that after step (B) a heat treatment of the photoresist layer ( 2 ) is carried out. 5. The method according to any one of claims 1 to 4, characterized in that after step (G) a heat treatment of the photoresist layer ( 2 ) is carried out. 6. The method according to any one of claims 1 to 5, characterized in that the structure of the first mask ( 1 ) with a diameter of the contact holes of 170 nm and a grid of 340 nm and the structure of the second mask ( 4 ) for a minimum contact hole size of 340 nm and for a smallest grid of 680 nm. 7. The method according to any one of claims 1 to 6, characterized, that the numerical aperture of the first exposure device 0.63 NA and the first wavelength (λ1) 248 nm and that the numerical aperture of the second exposure device 0.60 NA and the second wavelength (λ2) is 365 nm.