阅读说明：本技术 通过光刻胶生产三维结构 (Production of three-dimensional structures by means of photoresists ) 是由 詹斯·泰斯 法兰克·贝劳 于 2021-04-30 设计创作，主要内容包括：本发明涉及一种用于通过光刻胶生产三维结构,具体地用于产生处于微米到毫米范围内的台阶式结构的方法。寻找一种实现微机械和高性能电子结构的允许台阶式结构的基本上自由成型和高产出量生产的微结构的新的可能性的目的根据本发明通过以下得以实现：用第一光刻胶涂覆(3)铜包覆的衬底(1)至少一次,以产生限定高度的至少一个结构台阶,并且用第二光刻胶涂覆(3)所述第一光刻胶至少一次,以产生限定高度的至少一个另外的结构台阶,其中所述第一光刻胶和所述第二光刻胶具有不同光敏性和透射特性,通过用不同波长和辐射剂量进行曝光(4)并且在显影(5)之后,所述不同光敏性和透射特性使至少所述第一光刻胶和所述第二光刻胶的结构形成性区域(35；36)得以产生。所述结构形成性区域(35；36)彼此至少部分地重叠并且形成台阶式三维结构。(The invention relates to a method for producing three-dimensional structures by means of photoresists, in particular for producing stepped structures in the micrometer to millimeter range. The object of finding a new possibility to achieve a microstructure of a micromechanical and high-performance electronic structure that allows for a substantially free-form and high-throughput production of stepped structures is achieved according to the present invention by: a copper clad substrate (1) is coated (3) at least once with a first photoresist to produce at least one structural step of defined height and the first photoresist is coated (3) at least once with a second photoresist to produce at least one further structural step of defined height, wherein the first and second photoresists have different photosensitivity and transmission characteristics that enable structure forming regions (35; 36) of at least the first and second photoresists to be produced by exposure (4) with different wavelengths and radiation doses and after development (5). The structure-forming regions (35; 36) at least partially overlap each other and form a stepped three-dimensional structure.)

1. A method for producing a three-dimensional structure by means of a photoresist, the method having the steps of:

-providing a metal-clad substrate (1) to improve surface adhesion or adaptability for subsequent metal deposition and separation of structures (6; 71) from the substrate (1);

-coating (3) a copper clad substrate (1) at least once with a first photoresist to produce at least one structural step of defined height and coating (3) the first photoresist at least once with a second photoresist to produce at least one further structural step of defined height, wherein the first and second photoresists have different photosensitivity and transmission properties for patterning;

-exposing (4) the first photoresist in at least one structure forming region (35) of the first photoresist with exposure radiation (41) having a first wavelength range and a first radiation dose;

-exposing at least the second photoresist with an exposure radiation (42) having a second wavelength range and a second radiation dose in at least one structure forming region (36) of the second photoresist, wherein the structure forming regions (35; 36) of at least the first and second photoresists at least partially overlap each other;

-developing (5) at least one multilayer photoresist structure (6) from overlapping structure forming areas (35; 36; 37) of at least the first and second photoresists by developing non-structure forming exposed areas of the coatings (31; 32; 33; 34) of at least the first and second photoresists.

2. The method of claim 1, wherein the coating (3) of the first photoresist with the second photoresist is performed before the first structure-generating exposure (4) of the first photoresist and the structure-generating exposure (4) of the second photoresist.

3. The method according to claim 1, wherein the coating (3) of the first photoresist with the second photoresist is performed only after the structure-generating exposure (4) of the first photoresist, and the structure-generating exposure (4) of the second photoresist is performed after the coating (3) with the second photoresist.

4. A method according to claim 2 or 3, wherein coating (3) the second photoresist with a third photoresist is performed only after the structure-generating exposure (4) of the second photoresist, and coating (3) with a fourth photoresist or any further photoresist occurs after structure-generating exposure (4) of the third photoresist or any further previously applied photoresist.

5. The method according to any of claims 1 to 4, wherein at least the first or the second photoresist or further photoresists having more than one photoresist layer (31; 32; 33; 34) are applied on top of each other in order to produce a structural step of a desired defined height of the photoresist structure (6).

6. The method according to any one of claims 1 to 5, wherein the first and the second photoresist are selected in each case to have different sensitivities, so that the first and the second photoresist can be cured by different exposure radiation (41; 42) that does not react with the other respective photoresist.

7. The method of claim 6, wherein the first photoresist is sensitive to longer wavelength exposure radiation (41) having a higher exposure dose and is insensitive to shorter wavelength exposure radiation (42) having a lower exposure dose that the second photoresist reacts to, relative to an effective wavelength and exposure dose of the second photoresist, and the second photoresist is transparent and insensitive to the longer wavelength exposure radiation (42) and higher exposure dose of the first photoresist and is sensitive to exposure radiation (42) having a shorter wavelength relative to an effective wavelength and exposure dose of the first photoresist.

8. The method according to claim 6 or 7, wherein the different sensitivities of the first and second photoresists in a wavelength range between 375nm and 436nm differ by more than 20nm, preferably more than 30nm, and differ by between 10mJ/cm in applicable dose²And 2200mJ/cm²Preferably by a factor of more than 4.

9. The method of any of claims 6 to 8, wherein the third or further photoresist is selected to have a sensitivity such that the sensitivity is in a wavelength range between 248nm and 436nm, differs in wavelength from the wavelengths of the first and second photoresist by more than 20nm, preferably more than 30nm, and at between 10mJ/cm²And 2200mJ/cm²Preferably differing in applicable dose by more than a factor of 4 from the applied exposure dose of the first and second photoresists.

10. The method according to any one of claims 1 to 9, wherein during said developing (5) of at least said first and second photoresists, three-dimensional photoresist structures (6) of overlapping structure-forming regions (35, 36..) of at least said first and second photoresists remain on said substrate (1) and form photoresist gaps (61) between adjacent photoresist structures (6), said photoresist gaps being usable as cavities for filling with moldable material.

11. The method according to claim 10, wherein a metal or metal alloy is deposited into the photoresist gaps (61) between the photoresist structures (6).

12. The method according to claim 11, wherein at least one metal from the group comprising: copper, nickel, titanium, chromium, aluminum, palladium, tin, silver, and gold.

13. The method according to any of claims 1 to 12, wherein the photoresist structure (6) is produced in the form of an elongated or closed layer stack in order to mold different molded bodies.

14. The method according to any of claims 10 to 13, wherein resist removal (8) of the photoresist structure (6) is performed by a resist developer (81) after metal deposition (7) in the gaps (61) created between the photoresist structures (6) by development of at least the first and second photoresist, wherein a metal mold (72) remains on the metal layer of the metal-clad substrate (1).

15. A method according to claim 14, wherein a metal etch back (9) method of a metal layer (2) on the substrate (1) is performed by a metal etchant (91) at least in intermediate spaces between the metal structures (71) formed by the metal deposition (7).

16. The method according to claim 15, wherein the metal etch back (9) method with an etchant (92) suitable for metallizing the metal layer (2) of the substrate (1) is continued until the metal layer (2) of the substrate (1) is completely ablated, so that the metal structure (71) is singulated into the metal molding (72).

Technical Field

The invention relates to a method for producing a three-dimensional structure by means of a photoresist, in particular for producing a stepped structure from a photoresist or for molding a molded body by means of a stepped structure in the micrometer to millimeter range. The fields of use of the invention are in particular the electronics industry, printed circuit board packaging and chip packaging, the semiconductor industry and microtechnology, in particular microtechnology for producing micromechanical structures.

Background

Photoresist is used in the prior art for photolithographic patterning to produce structures in the micron and sub-micron range in microelectronics and microsystems technologies. The procedure is often performed by applying a layer of photoresist to the substrate or an already existing layer of circuit structure and subsequently exposing it to areas having a negative resist and which will remain as the surface of the structure, or to areas having a positive resist and which will be ablated. The non-resist areas during the subsequent development of the photoresist structure are removed as an uncured layer component and may subsequently be filled with electronic conductor structures and semiconductor structures or locally occupied by gate structures.

Such a procedure is described in "fabricating Planar Gunn diodes and HEMTs on InP substrates together on InP substrate" (IEEE Transactions on Electron Devices, Vol. 61, No. 8[2014] 2779-. The gate gap between the source and drain required for a gunn diode or HEMT (high electron mobility transistor) structure having a width of 1.5 to 2 μm in this context is created by an ablated photoresist structure. Because the thickness of the source and drain layers is small, only a photoresist layer having a thickness of about 0.1 μm is required. Photoresists for diode structures require different photoresist sensitivities due to different percentages of PMMA (poly methyl methacrylate) composition in order to achieve different ablation depths. With regard to the possibility of producing structures in which the layer thickness is of the order of magnitude or more of the structure width, the above-cited technical papers do not disclose suggestions or insights for a possible greater ablation depth at the energies and times required for their input.

Disclosure of Invention

The object of the present invention is to find a new possibility to realize microstructures of micromechanical and high-performance electronic structures that allow substantially free shaping of stepped, in particular overhanging, structures and that allow flexible, high-throughput production of complex shapes for forming metallic microstructures and conductive tracks.

According to the invention, the above object is achieved in a method for producing a three-dimensional structure by means of a photoresist, having the following steps:

-providing a metal-clad substrate (1) to improve surface adhesion or adaptability for subsequent metal deposition and separation of structures (6; 71) from the substrate (1);

-coating (3) a copper clad substrate (1) at least once with a first photoresist to produce at least one structural step of defined height and coating (3) the first photoresist at least once with a second photoresist to produce at least one further structural step of defined height, wherein the first and second photoresists have different photosensitivity and transmission properties for patterning;

-exposing (4) the first photoresist in at least one structure forming region (35) of the first photoresist with exposure radiation (41) having a first wavelength range and a first radiation dose;

-exposing at least the second photoresist with an exposure radiation (42) having a second wavelength range and a second radiation dose in at least one structure forming region (36) of the second photoresist, wherein the structure forming regions (35; 36) of at least the first and second photoresists at least partially overlap each other;

-developing (5) at least one multilayer photoresist structure (6) from overlapping structure forming areas (35; 36; 37) of at least the first and second photoresists by developing non-structure forming exposed areas of the coatings (31; 32; 33; 34) of at least the first and second photoresists.

Advantageously, said coating said first photoresist with said second photoresist is performed before said first structure-generating exposure of said first photoresist and said structure-generating exposure of said second photoresist.

Alternatively, the coating of the first photoresist with the second photoresist is performed only after the structure-producing exposure of the first photoresist, and the structure-producing exposure of the second photoresist is performed after coating with the second photoresist.

In a further advantageous variant, the coating of the second photoresist with a third photoresist is performed only after the structure-producing exposure of the second photoresist, and the coating with a fourth photoresist or any further photoresist occurs after the structure-producing exposure of the third photoresist or any further previously applied photoresist.

In a preferred execution of the method, at least the first or the second photoresist or further photoresists having more than one photoresist layer are applied on top of each other in order to produce a structure step of the desired defined height of the photoresist structure.

Further, it is advisable that the first photoresist and the second photoresist are selected to have in each case different sensitivities, so that the first photoresist and the second photoresist can be cured by different exposure radiation that is not reacted by the other respective photoresist.

A preferred variant is that the first photoresist is sensitive to longer wavelength exposure radiation with a higher exposure dose and is insensitive to shorter wavelength exposure radiation with a lower exposure dose that the second photoresist reacts to, relative to the effective wavelength and exposure dose of the second photoresist, and that the second photoresist is transparent and insensitive to the longer wavelength exposure radiation and higher exposure dose of the first photoresist and is sensitive to exposure radiation with a shorter wavelength relative to the effective wavelength and exposure dose of the first photoresist.

The different sensitivities of the first and second photoresists in the wavelength range between 375nm and 436nm suitably differ by more than 20nm, preferably more than 30nm, and differ by between 10mJ/cm in applicable dose²And 2200mJ/cm²Preferably by a factor of more than 4.

The third or further photoresist is advantageously selected to have a sensitivity such that it is in the wavelength range between 248nm and 436nm, differs in wavelength from the wavelengths of the first and second photoresist by more than 20nm, preferably more than 30nm, and at between 10mJ/cm²And 2200mJ/cm²Preferably differing in applicable dose by more than a factor of 4 from the applied exposure dose of the first and second photoresists.

It has proven advantageous that during said developing at least said first and second photoresists, three-dimensional photoresist structures of at least overlapping structure-forming regions of said first and second photoresists remain on said substrate and form photoresist gaps between adjacent photoresist structures, said photoresist gaps being capable of functioning as cavities for filling with moldable material.

In this regard, a metal or metal alloy may be deposited into the photoresist gap between adjacent or surrounding photoresist structures.

At least one metal from the group comprising the following metals or alloys thereof is suitably used as the filling material for the cavity: copper, nickel, titanium, chromium, aluminum, palladium, tin, silver, and gold.

The photoresist structure is preferably produced in the form of an elongated layer stack spaced apart by gaps or a layer stack surrounded by gaps, in order to mold different molded bodies in the gaps.

The removal of the photoresist structure can suitably be performed by a resist developer after the metal deposition in the gaps created between the photoresist structures by development of at least the first and second photoresists, wherein the shaped metal molding remains on the metal layer of the metal-clad substrate.

The metal etch-back method of the metal layer on the substrate may advantageously be performed by a metal etchant at least in intermediate spaces between the metal structures formed by the metal deposition.

In a particularly advantageous application, the metal etch-back method with an etchant suitable for metallizing a metal layer of a substrate can be continued until the metal layer of the substrate is completely ablated, so that the metal structure is singulated into a metal molding.

The present invention shows the possibility of realizing micro-structures for micromechanical or high-performance microelectronic structures that allow substantially free-form stepped, in particular overhanging, structures and flexible, high-throughput production of complex shapes for forming metal micro-molded articles.

Drawings

Hereinafter, the present invention will be described more fully with reference to examples of embodiments and drawings. The figures show:

FIG. 1 shows a schematic diagram of a method for producing an advantageous stepped structure with different photoresist layers according to the present invention;

FIG. 2 shows a schematic diagram of a method for producing a further advantageous stepped structure with different photoresist layers according to the present invention;

FIG. 3 shows a schematic view of a further embodiment of a method according to the invention for producing a three-layer structure with at least two different photoresists;

FIG. 4 is a schematic illustration of a method according to the invention for continuing execution according to FIG. 3 to produce a six-layer structure having a total of at least three different photoresists;

fig. 5 continues the method according to the invention according to fig. 3 and 4, wherein the photoresist structure produced a plurality of times is used for producing a metal molded body and a singulation (detachment from the substrate) of the molded body is performed;

FIG. 6 is a schematic illustration of a further implementation of a method for producing a structure having at least two different photoresists according to the invention, wherein in each instance an exposure is performed on each of the different photoresists prior to exposure with the next photoresist;

fig. 7 continues advantageously from fig. 6 in accordance with the method of the invention, in which the resist structure produced a plurality of times is used for producing the metal structure, wherein the etch-back of the copper coating of the substrate can be carried out only for electrically isolating the individual metal structures or can be carried out before the metal mold body can be singulated (detached from the substrate);

FIG. 8 shows a schematic diagram of a further implementation of the method according to the invention for producing a thick photoresist layer, wherein separate exposures are performed on different photoresists and the gaps of the structure are filled with copper after development of the resist structure in order to obtain separate copper structures on the substrate after etch back of the metallization of the substrate (or of the substrate itself);

FIG. 9 is a selection of readily achievable cross-sections for a preferred photoresist structure for multiple production of microstructures using a limited number of different photoresist layers producible using a single combined development step.

Description of the symbols:

1 (Metal-clad) substrate

2 metal layer

3: coating

31. 32, 33 photoresist layer

34 final photoresist layer

35. 36, 37, 38 structural formation region

4: exposure to light

41 (of the photoresist layer 31) exposing radiation

42 (of the photoresist layer 32) exposure radiation

43 (of the photoresist layer 33) of an exposure radiation

44 (of the photoresist layer 34) of exposure radiation

5-development

51 developer

6 photoresist structure

61 (photoresist) gap

7 deposition of Metal

71 metal structure

72 (Metal) moulded body

8 resist removal

81 resist developer (resist stripping solution)

9 metal etch back

91 metal etchant (for Metal layer 2)

Etchant for partial metal layer etch back

Detailed Description

The method according to the invention for producing microstructures with a structure height (layer thickness) in the lower to higher micrometer range (1 μm to several hundred μm) in the basic variant according to fig. 1 comprises the following steps:

-providing a metallized substrate 1 (typically: a metal cladding, PVD metallization or metal deposition);

-coating 3 the metal clad substrate 1 at least once with a first photoresist to create at least one structural step defining a step height, and coating 3 the first photoresist at least once with a second photoresist to create at least one further structural step, wherein the first and second photoresists have different photosensitivity and transmission properties for patterning;

-subjecting the first photoresist to a first structure-generating exposure 4 with a first wavelength range and a first radiation dose;

-subjecting the second photoresist to a second structure-generating exposure 4 with a second wavelength range and a second radiation dose;

-developing 5 the multi-step photoresist structure 6 by ablating the non-structure forming exposed areas of the first and second photoresist.

In this respect, there is hardly any restriction on the kind of structural configuration in terms of the number, height and width of the edges. However, for the edge quality achievable at the end of the development process of the photoresist structure (which depends on the desired height of the structure step), the material of the photoresist should be selected on the basis of the spectral sensitivity of its material and the absorption/transmission properties of the processing beam by the photoresist utilized. In addition, there is a useful radiation output and radiation dose to achieve structure-generating exposures in as short an exposure time as possible within the sensitivity range of the photoresist used.

Fig. 1 shows the individual steps in a schematic cross-sectional view of a layer stack produced on a substrate 1. The substrate 1 is provided with a metal layer 2 (metal cladding layer) in sub-diagram 1 as a starting point for the generation of the desired microstructure. The metal layer 2 is mainly used to improve the surface adhesion for further coatings, subsequent metal deposition processes and processes for detaching the structure from the substrate 1.

Fig. 1, subfigure 2, shows the substrate 1 after being coated with a first photoresist 31 (e.g. a photopolymer a) having a layer thickness adapted to the desired height of the structure to be produced. If a defined uniform layer application cannot be done in one step, the required layer thickness can also be performed by multiple coats with the same photoresist 31, as will be shown more fully later (e.g. fig. 3 and 4).

The choice of the photoresist is substantially adapted to the final shape of the structure to be produced. The characteristics of the photoresist used for processing are wavelength dependent absorption/transparency and sensitivity (exposure dose). These characteristics must be adapted to each other appropriately for the respective structure.

As taken and illustrated in FIG. 1, for purposes of subsequent metal forming, for example, the creation of T-shaped structures from polymers requires a first photoresist (e.g., Hitachi (Hitachi) HM-40112) as the lower photoresist layer 31, which is reactive to relatively large wavelengths (e.g., 402nm) and requires a high exposure dose (e.g., 250 to 400mJ/cm at 405nm)²) To cure to the full depth of the photoresist layer 31. For example, the hitachi RY series, hitachi HM series, and DuPont (DuPont) WBR series, which have exposure wavelengths suitable for curing, are also suitable as the above-described kind of insensitive photoresist.

In contrast, when different cross-sectional dimensions and/or height dimensions are to be produced for the final shape of the structure, the overlying photoresist layer 32 requires significantly different characteristics. For the T-shaped protrusion selected in FIG. 1, a photoresist (e.g., Kolon Industries LS-8025) having a short wavelength (e.g., 375nm) is selected for the upper photoresist layer 32High absorption and high transparency to the long wavelength used for exposure of the first photoresist layer 31 and with as low exposure dose as possible (e.g. Kolon Industrial LS-8025: 35 to 50mJ/cm at 375nm²) To effect curing. For example, Hitachi RD series, Hitachi SL series, Asahi Kasei) AQ series and Kulon Industrial LS series are suitable as such highly sensitive photoresists.

The photoresists are selected with mutually different parameters such that the exposure process with the exposure radiation 41 on the first structure-forming regions 33 of the photoresist layer 31 provided for curing (as shown in fig. 4) and the exposure process with the exposure radiation 42 on the second structure-forming regions 34 of the photoresist layer 32 selected for curing (as shown in fig. 5) is as far as possible restricted to the layer for which the exposure process is determined. This is important because, in particular, those parts of the structure-forming regions 33 and 34 of the photoresist layers 31 and 32 for which the two exposure radiations 41 and 42 are directed are only influenced by the exposure radiation 41 or 42 intended for them, so that a uniform degree of curing can be achieved in the respective structure-forming regions 33 and 34 of the first photoresist layer 31 and the second photoresist layer 32, respectively, which uniform degree of curing allows edge-specific, precise ablation of the uncured residual parts of the photoresist layers 31 and 32 in the subsequent development process according to sub-fig. 6 of fig. 1.

For the inverted T-shaped structure as shown in fig. 2, it is necessary to reverse the characteristics of the first photoresist layer 31 and the second photoresist layer 32 previously described with reference to fig. 1. The lower photoresist layer 31 requires a first photoresist (e.g., having a sensitivity of 30 to 50mJ/cm at 405nm) having a low exposure dose and a higher sensitivity to long wavelengths²Hitachi SL-1338). On the other hand, the upper photoresist layer 32 should have a second photoresist for high exposure dose and high transparency to long wavelengths (e.g., 180 to 300mJ/cm at 375nm)²Hitachi RY-5125).

All remaining sequences for performing the method according to fig. 2 remain unchanged from fig. 1. A first photoresist selected only for the shape of the structures, a second photoresist conforming to the latter and exposure radiation 41 and 42 selected to be suitable for the latter are varied. In principle, the material pairing of the photoresist layers 31 and 32 selected in fig. 1 can also be applied in the opposite way and can be cured with an adapted model of the exposure radiation 41 and 42 if the transparency of the second photoresist layer 32 in the wavelength range of the exposure radiation 41 for the first photoresist layer 31 permits.

The embodiments in fig. 1 and 2 (and all the following embodiment examples) reflect the substantial advantages and the heart of the method according to the invention, since the coating and exposure processes and the development process can be carried out in a uniform (i.e. not alternating) cycle, so that the coated substrate 1 need not be repeatedly changed to the specific process chamber it requires, and because of the economy of this method a large number of desired three-dimensional microstructures can be produced with high process throughput using the methods known from chip production.

Fig. 3 shows a further embodiment of a method according to the present invention using a first photoresist and a second photoresist different from the first photoresist. In this case, due to the desired structural height of the second photoresist, after the metal coating 2 (e.g., copper cladding) on the substrate 1 is coated with the lower photoresist layer 31, the photoresist layer 32 is applied twice, as shown in the steps of fig. 1 to 4. Such multiple coating before exposing the first and second photoresist to the exposure radiation 41 and 42 in successive exposure cycles is generally only possible under the following conditions: the two photoresist layers 32 (e.g., comprising Hitachi RY-5125) have sufficient transparency at the wavelength of the exposure radiation 41 (e.g., 405nm) used for the first photoresist (e.g., Hitachi SL-1338), and the latter can be at low exposure doses (e.g., at 30 to 50mJ/cm²Bottom) curing as schematically shown in figure 5. In sub-diagram 6 according to FIG. 3 with a second exposure radiation 42 (e.g. with 200 to 300mJ/cm at 375nm)²) After the exposure process is performed on the second photoresist (e.g., Hitachi RY-5125) of the two upper photoresist layers 32, the structure creation process and development process (corresponding to sub-diagram 6 in FIG. 2) can be terminated, or additional photoresist coatings can be used to create more complex shaped structures, as contemplated herein.

FIG. 4 shows a diagram of two additional structural steps for producing a desired structure3. The requirements may be the same when the desired structure is only of greater height. In fig. 4, subplot 7, which is numbered consecutively with reference to fig. 3, the further photoresist layer 33 is applied in a double manner in order to produce a further edge structure (structural step) in the case where the layer stack, which has been applied and exposed so far and comprises the lower photoresist layer 31 and the two upper photoresist layers 32 lying thereon, has not previously been subjected to a development process. Since a third photoresist (e.g., JSR THB-111N, 25mJ/cm at 355 nm) with a low exposure dose is to be selected²) So the multi-layer application is not dependent on the desired (rather low) structure height, but is required to prevent the influence on the photoresist layers 31 and 32 located therebelow. The wavelength used to cure the third photoresist must also be chosen differently than the first and second photoresists. However, if the exposure dose of layer 33 is low enough and the absorption is high enough, the same wavelength as used for layer 31 may be used. After two photoresist layers 33 have been applied, as shown in somewhat the same manner in FIG. 9, by having a short wavelength and low exposure dose for the third photoresist (e.g., 355nm at 25 mJ/cm)²(as described above)) or alternatively, 375nm at 35mJ/cm for the Kolon industry LS-8025²The lower exposure radiation 43 cures the two photoresist layers in the structure forming region 35.

Further, for the example shown in FIG. 4, it is assumed that when the structure forming region 38 is smaller than the structure forming region 37 of the photoresist layer 33, so as to use a third photoresist (e.g., JSR-THB-111N: [ e.g., 25mJ/cm at 355nm, 25 mJ/cm)²]) The same additional photoresist applies the final photoresist layer 34 in a manner that provides a further gradual change in the profile of the desired structure according to sub-fig. 10.

However, if the size of the structure-forming region 38 of the final resist layer 34 is large, i.e., has an overhang with respect to the structure-forming region 37 (not shown in FIG. 4), a fourth resist (e.g., JSR ARX series, 15mJ/cm at 248nm, 15 mJ/cm) must be selected²) The fourth photoresist also has a different wavelength (at least with respect to the third photoresist of layer 33) and needs to be of the same wavelengthA small radiation dose is used for curing in order to prevent damage to the underlying photoresist layers 31, 32, and 33 outside the structure forming regions 35, 36, and 37.

After the final photoresist layer 34 has been cured (as shown in sub-diagram 11 of fig. 4) by means of exposure radiation 44 which, in the first example described above, can correspond to the exposure radiation 43 of the smaller structure-forming regions 38, the joint development process of all photoresist layers 31 to 34 is carried out in accordance with sub-diagram 12 by means of a common developer 51 (for example, an alkaline developer (sodium carbonate, potassium hydroxide, tetramethylammonium hydroxide, etc.) or an organic developer (1-methoxy-2-propyl acetate, cyclopentanone, etc.)) after which the desired structures 6 remain.

Fig. 5 shows a preferred application of the structure 6 produced in the method according to fig. 3 and 4, wherein it is assumed that the multiple production of the structure 6 is performed on the substrate 1 occupied by the metal layer 2. Such a cross section of the substrate 1 is shown in fig. 5, subfigure 13, in which a metal deposition 7 (of copper, nickel, chromium, tin, palladium, silver, gold or alloys thereof, for example) is carried out in each case between two adjacent structures 6 until the photoresist gap 61 is completely filled. In order to protect the metal deposit 7 during the subsequent etch-back process, it may be advantageous to choose a substrate 1 that is soluble in organic solvents and thus not corrosive to the metal of the metal deposit 7. For this purpose, it is useful to incorporate an additional thin separation layer (not shown here) made of polymer between the substrate 1 and the metal layer 2.

Sub-diagram 14 of fig. 5 shows the next step of the molding metal deposition 7 between the structures 6 revealing photoresist layers 31 to 34 (only specified in fig. 4 and 5). The structure 6 utilized in this case as a negative mold for shaping the metal deposit 7 is dissolved away for this purpose, since the resist developer 81 acts on the structure-forming regions 35 to 38 of the photoresist layers 31 to 34 in the method step of the resist removal 8 and at the same time the photoresist structure 6 between the photoresist gaps 61 filled with metal is dissolved. Thereafter, the metal deposit 7, which is molded into the photoresist gap 61 and is still fixedly connected to the substrate 1 via the metal layer 2 of the substrate 1, remains on the metal-clad substrate 1.

If metal deposit 7 as metal structure 71 (designated only in sub-diagram 16) remains fixedly bonded to substrate 1 but electrically isolated from each other, metal etch back 9 is performed to a limited extent so that only the metal cladding layer of substrate 1 is ablated by resist developer 81 (e.g., iron (III) chloride or copper (II) chloride with hydrogen peroxide for copper, iron (III) chloride or nitric acid with hydrochloric acid for nickel, ammonium hydroxide with hydrogen peroxide and methanol for silver, dilute nitric acid for tin, etc.). The result is schematically shown in fig. 5, subfigure 15.

If a single-cut metal structure 71 is desired, the process of metal etchback 9 is longer and/or continued with an etchant (as described above) specifically adapted to the material of metal layer 2 of substrate 1 until metal structure 71 is detached from substrate 1 as a single metal mold 72, as shown in sub-diagram 16.

In six sub-figures, fig. 6 shows a further example for producing a simple photoresist structure 6, where only two photoresist layers 31 and 32 are needed to produce a T-shaped structure 6 having the following dimensions: width b: 100 μm, height h: 83 μm, support width s: 50 μm, support height (h-t): and 45 μm.

The procedure differs from the embodiment according to fig. 1 and 2 in that according to fig. 2 a first photoresist (for example for the relatively short wavelength of 365nm for the i-line of a mercury vapor lamp) is used]Optimized dupont hitachi RY-5545), the resulting photoresist layer 31 is exposed (e.g., first with exposure radiation 41 adapted thereto [ e.g., 240mJ/cm at 375nm, 240 mJ/cm) in the structure forming region 35 corresponding to sub-fig. 3, before performing coating 3 according to sub-fig. 4 with a second photoresist sensitive to relatively large wavelengths (e.g., hitachi SL-1333 at 405nm), after coating 3 with optimized dupont hitachi RY-5545)²])。

If a photoresist layer 32 is applied, it is then exposed with exposure radiation 42 (e.g., 30mJ/cm at 405nm) in structure-forming regions 36 according to sub-diagram 5²) And (6) exposing. Subsequently, the joint development process 5 is performed with a selected resist developer 81 (e.g., an alkaline solution based on sodium carbonate, sodium hydroxide, potassium carbonate, or potassium hydroxide).

In order to produce a particularly high width b while having a small support width s,it may be desirable to use a photoresist layer 31 with particularly high sensitivity. An example of such a photoresist is AZ 125nXT, which requires 1500mJ/cm for thicker layers starting from 70 μm²To 2200mJ/cm²The curing is carried out at a dose of (a). Thus, the upper photoresist layer 32 can be exposed with a dose four times smaller but significantly higher than usual in order to enhance the stability of this upper photoresist layer 32 and enable a larger overhang than the lower photoresist 31. In this example, structure-forming region 36 (formed from Hitachi SL-1333 resist) may be at about 150mJ/cm²Instead of 30mJ/cm²And (6) exposing. In contrast, the dose used to expose the lower photoresist layer 31 is ten times to almost fifteen times its amount, so that a dose less than one tenth of the dose used for the upper photoresist layer 32 has no significant effect on the unexposed regions (outside the structure-forming regions 35) of the lower photoresist layer 31.

In each case, the exposure dose of the lower to upper photoresist layers 31, 33 and 32, 34, respectively, should differ by a factor of four or more. This prevents undesired exposure of the respective other photoresist layers 32, 34 and 31, 33 outside the structure-forming regions 35, 36 that have been exposed. Since the exposure dose is substantially determined by the sensitivity of the selected resist, the smaller the factor of the dose difference can be chosen, the farther apart the wavelengths to which the respective resist is sensitive.

Fig. 7 shows a continuation of the method of fig. 6 for producing a metal structure 72 on the substrate 1 for producing a robust conductive trace for a power electronic device or a refined conductive trace with enhanced mechanical stability. The intersecting photoresist structures 6 on the substrate may also be cured by exposure such that the gaps 61 are released by the intersection-structure-forming regions 35 and 36 for metal deposits 71 having a square, rectangular, parallelogram, rhomboid, hexagonal, or base area in the range of oval to circular.

To illustrate this method embodiment, fig. 7 shows a cross-section of a metal-clad substrate 1 with a metal layer 2 (e.g., copper). A metal (as a layer of, for example, copper, nickel, chromium, tin, palladium, silver, gold, or alloys thereof) is deposited in the gaps 61, which are created between the photoresist structures 6 according to sub-diagram 6 of fig. 6. Thus, the gap 61 is completely filled and the metal deposit 7 is thus correspondingly molded by using the structure of the gap 61 as a preform. According to fig. 8, during resist removal 8, photoresist structure 6 is completely dissolved away by resist developer 81 (e.g., potassium carbonate), and metal etching 9 is then performed on metal layer 2 by applying etchant 92 (as described above) which is suitably adapted for partial metal etch back of metal layer 2 between metal structures 71. Thus, the substrate 1 remains with the metal structure 71 in a particular shape, the remainder of the metal layer 2 acting as an adhesion promoter.

In the method variant shown in fig. 8, the significant feature of the structure generation is the generation of a particularly high T-shaped photoresist structure 6, in which the ratio of the support height (h-T) to the overall height h is about one, and therefore an overhang of the structure-forming region 36 of the second photoresist is formed over the structure-forming region 35 of the first photoresist, and in order to save time, the photoresist structure 6 will be generated from as few photoresist layers 31 and 32 as possible. In this example, the size of the stepped T-resist structure 6 is assumed to be h 155 μm, b 90 μm, s 60 μm, and (h-T) 75 μm.

For this purpose, a photoresist layer 31 (of relatively large wavelength (e.g. 405nm) and high exposure dose (e.g. 350 mJ/cm) produced by a first photopolymer (e.g. DuPont WBR-2075 or Hitachi HM-40112)²At 405 nm)) is applied to the metal layer 2 of the metal-clad substrate 1. For the second overhanging structure step, it is necessary to coat 3 with two identical photoresist layers 32, and to use a second photoresist (e.g. asahi AQ-4088) which is highly absorbing for short wavelengths (e.g. 365nm) and highly transparent for long wavelengths used for the exposure of the first photoresist layer 31 and has the lowest possible exposure dose (e.g. 80 mJ/cm)²At 375 nm). Wavelength pairing of 405nm and 355nm may also be used, as long as a suitable light source is available in the exposure apparatus (not shown), in this case, for example, JSR THB-111N (25 mJ/cm at 355 nm)²Small exposure dose) may be used as the second resist.

As shown in fig. 1, after coating 3 with the lower photoresist layer 31, in this case, exposure 4 is similarly performed in the desired structure-forming region 35 (fig. 2), suitably with an exposure radiation 41 selected for the first photoresist, before performing the second and third coating 3 with two similar photoresist layers 32 (according to fig. 3 and 4, including the second photoresist). According to fig. 8, sub-diagram 5, exposure 4 is then performed in the provided structure forming region 36 with exposure radiation 42 suitable for the second photoresist. Next is a joint development 5 of all photoresist layers 31 and 32 (fig. 6). As described in the previous examples with reference to fig. 5 and 7, metal deposition 7 is performed in gaps 61 between photoresist structures 6, thereby molding metal structures 71 (e.g., layers comprising copper, nickel, chromium, tin, palladium, silver, gold, or alloys thereof) at photoresist structures 6. After resist removal 8 by resist stripping liquid 81 (e.g. by a 10% potassium hydroxide solution), the electrically conductive connection formed by metal layer 2 of substrate 1 remains between metal structures 71 (according to fig. 8). In order to remove the latter and obtain the metal structures 71 as fixed structures on the substrate 1, a metal etch-back 9 (sub-diagram 9) is performed with an etchant 92 specifically adapted to the metal layer 2 (e.g. copper (II) chloride together with hydrogen peroxide for Cu; a mixture of 5% nitric acid/65% phosphoric acid/5% acetic acid and water for Al; dilute nitric acid for Sn) for partially ablating the metal layer 2 only between the desired metal structures 71.

Fig. 9 again shows a particularly advantageous photoresist structure 6 according to the method step of development 5. To clarify the example already described above, the dimensioning to be adjusted is indicated in fig. 1.

The photoresist structure 6 shown in sub-diagram 1 of fig. 9 is preferably designed for producing a metal structure 71 or a metal molding 72 and typically has dimensions h-30-1000 μm and (h-t) -10 μm-900 μm, wherein its width b and support width s can in practice optionally be selected, but in each case depends on the height and spacing of the structure and on the stability of the resist. Creating multiple similar layers 31 and 32, respectively, allows the structure height of each structure step to be increased to a maximum of 1000 μm when only two different photoresists are used. The individual photoresist layers 31, 32 may sometimes have a significantly smaller height (e.g., at most 76 μm for the Hitachi SL series, at most 112 μm for the Hitachi HM-40112, and at most 240 μm for the Dupont WBR series), and must be stacked, with exceptions (e.g., at most 1000 μm for MicroChem SU-8), where a larger structural step can be achieved with only one photoresist layer 31. Since various dry film resists are produced only in a certain layer thickness (e.g., the hitachi HM series of 56 μm, 75 μm, and 112 μm), it may be necessary in some cases to produce the desired layer thickness by laminating multiple thin resist layers 31, 32. In this case, as in each other case, the exposure dose has to be adapted to the respective layer thickness and layer configuration in order to obtain optimum results after development of the photoresist structure 6.

Fig. 9, sub-diagram 2, illustrates such a photoresist structure 6 that is preferably provided for producing a metal structure 71 or metal mold 72 with a larger gradation or protrusion (overhang) of the capping surface (not shown) when the structural steps of the structure forming region 36 of the lower photoresist layer 31 have a larger height and when the structure forming region 36 of the upper photoresist layer 32 has a larger overhang.

The metal structure 71 may be used to mechanically stabilize the conductive traces on the flexible substrate 1. By appropriate selection of the structure 6 in terms of height, width and overhang, it is possible to improve the mechanical stability under repeated loading and at the same time reduce the amount of material required for coating/deposition (electroplating) of the metal structure 71. This extends the service life of the metal bath used for depositing the metal layer. At the same time, by varying the size ratio of metal structure 71, the mechanical and electrical properties can be selectively adapted to the respective requirements.

The metal molded body 72 is mainly used as a micromechanical element or a constituent member that can be mass-produced by the technique used here.

Sub-fig. 3 of fig. 9 shows a particular layer configuration specifically oriented to have a high width to support width ratio, similar in size to sub-fig. 1 and 2. In this way, the production of the metal structure 71 is improved, in particular with regard to mechanical stability and adhesion to the flexible substrate 1.

With the present invention, it is possible to achieve a cost-effective and high-yield production of microstructures from a photoresist or a metal with reproducible accuracy and a limited number of method steps in one or several cycles. Thus, mass production with conventional techniques of the semiconductor industry and the printed circuit board industry (but where the height dimensions of the resulting structures are significantly larger than those in conventional circuit and wafer chip fabrication cycles) is possible with reproducible edge quality and accuracy for relatively fine sharp-edged stepped bodies. By combining photoresist layers 31 to 34 comprising several different photoresists of different curing sensitivities, a layer stack can be assembled which can be partially machined in successive exposure cycles with different exposure wavelengths and/or exposure doses, but the photoresist structure 6 can be formed in each case in a joint development process. In this way, particularly high process economics can be achieved in the production of 3D microstructures in the micrometer range of one to three digits.

When adapting the method according to the invention to steppers in the semiconductor industry, it is possible to increase the width of the resist structures to be produced further to approximately 150nm, and the structure height may go into the millimeter range, since conventional mercury vapor lamps in the semiconductor industry provide filters for the wavelengths used there (365nm, 405nm, 436 nm). In addition, various laser sources (solid-state lasers or laser diodes) with wavelengths of 355nm, 375nm or 405nm may also be used. This method can also be applied to resists in the deep UV range, which are exposed with wavelengths of 248nm (KrF laser) and 193nm (ArF laser).