A method for applying a structure onto a substrate

Abstract

The invention relates to a method for applying a structure (24) on a substrate (22), comprising the steps of: - Providing the substrate (22); - Depositing first material onto the substrate (22) such that the first material forms a contour line (30) of the structure (24) to be applied using a first deposition technique; - Depositing second material onto an area (34) of the substrate (22) surrounded by the contour line (30) such that the second material covers the area (34), thus forming the structure (24), using a second deposition technique. Furthermore, the invention relates to a substrate (22) with a deposited structure (24).

Description

[0001] A method for applying a structure onto a substrate

[0002] The present invention relates a method for applying a structure onto a substrate. Furthermore, the invention relates to a substrate with a deposited structure.

[0003] In many industrial processes, for example in semiconductor and / or OLED manufacturing, it is necessary to apply well-defined structures onto substrates.

[0004] The feature size of these structures typically ranges from a few micrometers to several millimeters or even centimeters.

[0005] It is highly desirable to deposit structures in this size-range by using wet film deposition techniques, which in general offer higher throughput speeds and lower costs than other well-known manufacturing methods such as physical or chemical vapor deposition (PVD, CVD).

[0006] In this context, inkjet printing is of great interest, because the drop-on-demand technology allows to selectively deposit material at desired positions and the printing layout can be changed easily.

[0007] One main challenge in wet layer deposition in general and inkjet printing in particular is the ink spreading on the substrate, which is directly linked to the wetting behavior.

[0008] If the surface tension of the ink is too high and / or the surface energy of the substrate surface is too low, wetting defects such as pinholes or wet film rupturing may occur.

[0009] If on the other hand the surface tension of the ink is too low and / or the surface energy of the substrate is too high, the ink might excessively spread, thereby distorting the printing pattern.

[0010] In consequence, it is particularly difficult to print patterns with feature sizes below 100 pm. Furthermore, even when printing larger patterns, the edge definition may suffer from imperfections caused by the aforementioned wetting phenomena. Common strategies to improve this situation are to apply heat to the ink and / or the substrate to quickly evaporate the ink solvents, to apply UV light to pin the ink on the substrate, and / or to influence the surface energy by pre-treating the substrate. However, these options do not always work and might result in undesired side effects. For example, when applying inkjet printing, heating the ink or substrate can result in increased evaporation at the nozzle plate, which can ultimately result in nozzle clogging.

[0011] Hence, there is a need for improving the process control for depositing structures from liquids onto substrates in general.

[0012] The object of the invention is solved by a method for applying a structure on a substrate, comprising the steps of:

[0013] Providing the substrate;

[0014] Depositing first material onto the substrate such that the first material forms a contour line of the structure to be applied using a first deposition technique;

[0015] Depositing second material onto an area of the substrate surrounded by the contour line such that the second material covers the area, thus forming the structure, using a second deposition technique.

[0016] For example, the substrate is a semiconductor or silicon wafer.

[0017] In one embodiment, the substrate provided at the beginning of the method is unprocessed. This means that the substrate has substantially no protrusions or depressions and is thus substantially flat at the beginning of the method.

[0018] Alternatively, the substrate provided at the beginning of the method is processed, which means that the substrate has protrusions or depressions and is thus pre-structured at the beginning of the method.

[0019] The main idea of the invention is to combine two complementary deposition technologies. By first depositing the contour line of the structure with a first highly precise deposition technique, a barrier is formed. This barrier confines the spreading area of the second material which is subsequently applied using a second deposition technique. Furthermore, the confinement allows depositing second material with increased wet film thickness which is beneficial to avoid pinhole formation or layer rupturing. The resulting structures have an improved edge definition and / or lower edge roughness compared to commonly printed layers without barrier.

[0020] In one embodiment of the method, the first deposition technique comprises a lithographic, particularly photolithographic step and / or is a nano or micro printing, stamping, imprinting and / or dispensing technique, in particular a microchannel particle deposition or a single-nozzle or multi-nozzle printing and / or dispensing technique, for example electro-static, capillary or aerosol jet printing or dispensing. This allows creating features smaller than 50 pm, particularly smaller than 10 pm, preferably smaller than 1 pm, with very precise edge definition.

[0021] For example, the first deposition technique can be a nano or micro stamping technique, in particular a microchannel particle deposition technique, comprising the following steps:

[0022] Providing the substrate;

[0023] Positioning a stamp on the substrate;

[0024] Injecting first material into the stamp;

[0025] Optionally curing the first material;

[0026] Peeling-off the stamp.

[0027] For example, the first material is ink. Accordingly, it is possible to use the first material for inkjet printing.

[0028] In an embodiment the first material is any material that can be used in lithographic, particularly photolithographic processes or in nano or micro printing, stamping, imprinting and / or dispensing processes. Therefore, a variety of materials can be used in the first deposition technique.

[0029] The second deposition technique can comprise a spray coating, particularly a masked spray coating process and / or is for example a multi-nozzle printing and / or dispensing technique such as inkjet printing. Spray coating and / or inkjet printing allows creating a thick and homogeneous infill layer. It is much faster than lithography and / or the nano or micro printing, stamping, imprinting and / or dispensing technique that is preferably applied for depositing the contour line.

[0030] In particular, the spray coating process comprises the steps of:

[0031] Providing a substrate with at least one contour line created by the first deposition technique;

[0032] Spray coating at least one area surrounded by the at least one contour line with a second material.

[0033] Optionally, the spray coating process can be extended to a masked spray coating process comprising the steps of:

[0034] Providing a substrate with at least one contour line created by the first deposition technique;

[0035] Providing a mask that covers the areas on the substrate not to be spray coated and that has at least one opening that does not cover at least a part of the substrate, wherein a contour of the at least one opening is substantially the same as a contour of at least one area of the substrate surrounded by the at least one contour line;

[0036] Spray coating the substrate through the at least one opening of the mask in the at least one area surrounded by the at least one contour line with a second material, particularly the substrate is not spray coated in the areas covered by the mask.

[0037] For example, the second material is a coating material. Accordingly, it is possible to use the second material for spray coating.

[0038] Particularly high throughput speeds and good precision can be achieved when applying combinations of capillary printing for manufacturing the contour line and inkjet printing for the subsequent second material deposition. In this context, it is conceivable that the second deposition technique is 10-200 times faster than the first deposition technique.

[0039] Particularly, the second material is ink. Accordingly, it is possible to use the second material for inkjet printing. In an embodiment the second material is any material that can be used in spray coating and / or inkjet printing processes. Therefore, a variety of materials can be used in the second deposition technique.

[0040] In one variant of the invention, the material deposited using the second deposition technique has a viscosity of 2-20 mPas. The relatively low viscosity enhances spreading of the second material and thus filling of the area defined by the contour line.

[0041] In comparison, the viscosity of the first material deposited using the first deposition technique to form the contour line can be significantly higher, in particular more than 20 mPas. The high viscosity is beneficial to reduce spreading of the first material on the substrate and thus to achieve a contour line with precise geometry. This is of course not limiting to the invention. It is also possible to apply the same first material and / or second material with the first and second deposition technique.

[0042] In one embodiment, the first deposition technique is a contactless deposition technique. Additionally or alternatively, also the second deposition technique is contactless. By avoiding any contact between the substrate and the deposition means, mechanical stress can be avoided during the second material deposition, which is in particular beneficial when using sensitive substrates, for example wafers such as semiconductor or silicon wafers or the like.

[0043] In another embodiment, the contour line is deposited such that it forms a liquid barrier which prevents the second material from spreading out of the area surrounded by the contour line.

[0044] The liquid barrier can be a mechanical barrier for the second material. In simplified terms, the height of the liquid barrier prevents second material from overflowing it.

[0045] Additionally or alternatively, the liquid barrier can be a surface energy barrier for the second material. For example, if the liquid barrier has a significantly lower surface energy than the substrate, the second material does not wet the liquid barrier surface. The low surface energy of the liquid barrier thus prevents the second material from wetting and / or overrunning it. On the contrary, it is also conceivable to manufacture the contour line such that it has a higher surface energy than the substrate surface. In this case, the second material wets the contour line and spreads along it. This can result in an improved second material distribution at the edge of the printed pattern and thus in a decreased edge roughness and / or better edge definition of the deposited wet film.

[0046] Of course, the surface energy of the contour line and substrate can be tailored, for example by the choice of material and / or suitable surface treatment techniques, such as plasma or corona treatment.

[0047] In a further variant of the invention, the method comprises the additional step of drying the deposited first material forming the contour line, in particular prior to depositing the second material, and / or drying the deposited second material. The drying step can be a separate processing step. Alternatively, the first material and / or second material can be dried during application, for example by heating the substrate. In this way, higher throughput rates can be achieved.

[0048] In another embodiment, the contour line has a maximum height or average height of at least 100 nm, preferably at least 1 pm, in particular in a dried state. It has been found out that these heights are sufficient to achieve the aforementioned barrier effects.

[0049] A height ratio between a maximum height or an average height of the second material and a maximum height or an average height of the contour line can be at least 1 : 100, at least 1 : 10, at least 1 : 1 , at least 10: 1 , at least 50: 1 , at least 100: 1 , at least 1.000: 1 or at least 10.000: 1 .

[0050] The first material can be a silver material, in particular nanoparticle silver ink, or a photoresist material. These materials are well tested in many state of the art applications and are comparatively easy to process. Of course, also other materials are possible.

[0051] The object of the invention is also solved by a substrate with a deposited structure, comprising at least a first dam section and a second dam section, wherein the dam sections define at least part of a contour line of the deposited structure. The deposited structure furthermore comprises a layer of second material deposited within the contour line and covering an area extending between the first and second dam section. The advantages that were discussed for the method also apply for the substrate with the deposited structure.

[0052] Further advantages and features will become apparent from the following description of the invention and from the appended figures, which show a nonlimiting exemplary embodiment of the invention and in which:

[0053] Fig. 1 shows an ideal circular structure;

[0054] Fig. 2 shows an ideal rectangular structure;

[0055] Fig. 3 schematically shows a circular structure resulting from a conventional printing process;

[0056] Fig. 4 schematically shows a rectangular structure resulting from a conventional printing process;

[0057] Fig. 5 schematically shows a section of a substrate with a deposited structure according to the invention in a top view;

[0058] Fig. 6 schematically shows a cross section of the substrate and deposited structure of Fig. 5;

[0059] Fig. 7 schematically shows a cross section of a substrate with a deposited contour line;

[0060] Fig. 8 schematically shows the cross section of Fig. 7 with ink deposited onto an area surrounded by the contour line, wherein the contour line acts as mechanical liquid barrier;

[0061] Fig. 9 schematically shows the cross section of Fig. 7 with ink deposited onto an area surrounded by the contour line, wherein the contour line acts as surface energy liquid barrier; and

[0062] Fig. 10 schematically shows the cross section of Fig. 7 with ink deposited onto an area surrounded by the contour line, wherein the contour line acts as a wetting guide along which the ink can spread.

[0063] Fig. 1 shows an ideal circular structure 10 and Fig. 2 an ideal rectangular structure 12. The structures 10, 12, serve as examples of printing patterns that are intended for reproduction on a substrate surface by a wet film deposition technique. Fig. 3 schematically shows a circular structure 14 resulting from a conventional inkjet printing process with the printing pattern being the ideal circular structure 10 of Fig. 1.

[0064] Fig. 4 schematically shows a rectangular structure 16 resulting from a conventional inkjet printing process with the printing pattern being the ideal rectangular structure 12 of Fig. 2.

[0065] A comparison between the intended printing patterns and the actual printing results reveals that the deposited structures 14, 16 suffer from several imperfections.

[0066] The deposited circular structure 14 of Fig. 3 has a poor edge definition which is a direct result of the applied printing technique, in particular of the individual droplets being placed at different positions on the substrate by the inkjet.

[0067] Furthermore, the circular structure of Fig. 3 suffers from wetting defects 18 such as pinholes and layer rupturing.

[0068] The deposited rectangular structure of Fig. 4 has similar problems. It also suffers from a poor edge definition. In addition, ink spills 20 which are the result of excessive wetting affect the printed pattern.

[0069] Clearly, there is a need for a means to improve the quality of the deposited structures, which is also a focus of the present invention.

[0070] Figs. 5 and 6 schematically show a top view as well as a cross section of a substrate 22 with a deposited structure 24 according to the invention.

[0071] The deposited structure 24 comprises a first dam section 26 and a second dam section 28. Each dam section 26, 28 defines part of a contour line 30 of the deposited structure 24.

[0072] Preferably, the dam sections 26, 28 form a closed contour line 30. In other words, the dam sections 26, 28 are connected to each other such that they form a single line with no beginning and ending, similar to the contours depicted in Fig.1 and Fig. 2. Alternatively, the dam sections 26, 28 form an open contour line 30. In this case, the first and / or second dam section 26, 28 or connection between the dam sections 26, 28 is interrupted.

[0073] The deposited structure 24 furthermore comprises a layer 32 of second material applied within the contour line 30 and covering an area 34 extending between the first dam section 26 and second dam section 28. In a dried state, the layer is for example 3 pm thick.

[0074] The substrate 22 with the deposited structure 24 shown in Figs. 5 and 6 can be manufactured, with a method according to the invention. In the following, this method will briefly be explained.

[0075] In a first step, a substrate 22 is provided, for example a semiconductor wafer, in particular a silicon wafer.

[0076] In a second step, a first material is deposited onto the substrate 22 such that the first material forms a contour line 30 of the structure 24 to be applied using a first deposition technique.

[0077] The contour line 30 forms the first and second dam section 26, 28, as shown in Fig. 7.

[0078] In the example, the deposited first material is a photoresist material, in particular Sll-8 photo resist from Microchem Corp.

[0079] This is of course not limiting to the invention. Other materials are possible as well, for example silver materials, in particular nanoparticle silver inks or pastes with a silver content of e.g. 50 wt.%.

[0080] The first deposition technique with which the first material is applied is a nano or micro printing technique, in particular capillary printing. This technique allows printing highly precise line structures by guiding a single nozzle over the substrate 22 while ejecting the first material.

[0081] After deposition, the first material is dried and / or cured / hardened in a third processing step. In the non-limiting example, the deposited contour line 30 has a maximum height or an average height of -1 pm and a maximum width or average width of ~35 pm in a dried state (the figures are not drawn to scale).

[0082] This is of course not limiting to the invention. Also, thinner contour lines 30 can be applied, for example with a maximum width or average width of only a few pm and maximum height or average height of only 100-200 nm.

[0083] In a fourth processing step, second material in form of ink 36 is deposited onto an area 34 of the substrate surrounded by the contour line 30.

[0084] The ink 36 is deposited using a second, contactless deposition technique, in particular multi-nozzle inkjet printing with a piezoelectric printing head.

[0085] The ink 36 has a viscosity of 2-20 mPas, which is well suited for inkjet printing. Furthermore, due to the low viscosity, the ink 36 can easily spread and cover the area 34 surrounded by the deposited contour line 30, thereby forming the structure 24.

[0086] In the non-limiting example, a height ratio between a maximum height or an average height of the ink 36 and a maximum height or an average height of the contour line 30 is -50:1 (the figures are not drawn to scale).

[0087] This is of course not limiting to the invention. Also, higher or lower height ratios can be applied, for example with a height ratio of at least 1 :100, at least 1 :10, at least 1 :1 , at least 10:1 , at least 50:1 , at least 100:1 , at least 1.000:1 or at least 10.000:1.

[0088] Fig. 8 schematically shows the substrate 22 with the contour line 30 of Fig. 7 after deposition of the ink 36.

[0089] In the figure, the contour line 30 forms a liquid barrier 38 that mechanically prevents the ink 36 from spreading out of the area 34 surrounded by the contour line 30.

[0090] The invention is however not limited to gravity based ink confinement.

[0091] Fig. 9 schematically shows an alternative and / or additional strategy to ensure that the ink 36 stays at the intended position on the substrate 22, in particular within the deposited contour line 30. In the figure, the contour line 30 acts as a surface energy liquid barrier 38. This can be achieved by applying first materials with surface energies significantly lower than the substrate surface energy. In this case, it is energetically unfavorable for the ink 36 to cover the contour line 30 which thus acts as a liquid barrier 38.

[0092] In Figs. 8 and 9, the ink 36 is confined to the area 34 surrounded or enclosed by the contour line 30.

[0093] Consequently, the risk of ink spills 20 (e.g. shown in Fig. 4) is reduced. Due to the confinement, it is also possible to apply thicker ink wet films which is also beneficial to reduce or avoid wetting defects 18 (e.g. shown in Fig. 3).

[0094] The edge definition of the deposited structure is improved compared to conventionally printed patterns, because the highly precise first deposition technique defines the edge structure.

[0095] Fig. 10 schematically shows a further alternative strategy to deposit structures 24 with improved edge definition.

[0096] In this case, the contour line 30 is deposited from a first material that has a significantly higher surface energy than the substrate surface. The ink 36 therefore wets the contour line 30 and spreads along it homogeneously, thereby reducing or avoiding rough edge structures.

[0097] In an optional fourth processing step, the ink 36 is dried, thus forming the layer 32.

[0098] The invention is not limited to the first deposition technique being a nano or micro printing technique, in particular a capillary printing technique. For example, the first deposition technique can comprise a lithographic, particularly photolithographic step and / or can be a nano or micro stamping, imprinting and / or dispensing technique.

[0099] Particularly, the invention is not limited to the second deposition technique being an inkjet printing technique and / or the second material being ink (36). For example, the second deposition technique can comprise a spray coating, particularly a masked spray coating process, and / or the second material can be a coating material. In summary, the method according to the invention combines the advantages of the different applied material deposition techniques, which results in an improved quality of the deposited structures 24. For example, compared to conventional inkjet printing, the edge roughness can be reduced from + / -10 pm to only + / -1 pm. The maximum layer thickness can be improved compared to conventional single nozzle capillary printing from -1 pm to -10 pm. Furthermore, the processing time can be significantly reduced compared to conventional single nozzle capillary printing, for example from -1500 s to -10 s for depositing a 1x1 mm2square structure filled with a 1 pm thick layer.

Claims

Claims1. A method for applying a structure (24) on a substrate (22), comprising the steps of:Providing the substrate (22);Depositing first material onto the substrate (22) such that the first material forms a contour line (30) of the structure (24) to be applied using a first deposition technique;Depositing second material onto an area (34) of the substrate (22) surrounded by the contour line (30) such that the second material covers the area (34), thus forming the structure (24), using a second deposition technique;- wherein the first deposition technique is electro-static printing, capillary or aerosol jet printing, or dispensing.

2. The method according to claim 1 , wherein the second deposition technique comprises a spray coating, particularly a masked spray coating process and / or is a multi-nozzle printing and / or dispensing technique, for example inkjet printing.

3. The method according to claim 1 or 2, wherein the second material is ink (36).

4. The method according to any of the preceding claims, wherein the material deposited using the second deposition technique has a viscosity of 2-20 mPas.

5. The method according to any of the preceding claims, wherein the first and / or second deposition technique is a contactless deposition technique.

6. The method according to any of the preceding claims, wherein the contour line (30) forms a liquid barrier (38) that prevents the second material from spreading out of the area (34) surrounded by the contour line (30).

7. The method according to any of the preceding claims, further comprising the step of drying the deposited first material forming the contour line (30), in particular prior to depositing the second material, and / or drying the deposited second material.

8. The method according to any of the preceding claims, wherein the contour line (30) has a maximum height or an average height of at least 100 nm, preferably at least 1 pm, in particular in a dried state.

9. The method according to any of the preceding claims, wherein a height ratio between a maximum height or an average height of the second material and a maximum height or an average height of the contour line is at least 1 :100, at least 1 :10, at least 1 :1 , at least 10: 1 , at least 50: 1 , at least 100: 1 , at least 1.000: 1 or at least 10.000:1.

10. The method according to any of the preceding claims, wherein the first material of the contour line (30) is a silver material or a photoresist material.

11. A substrate (22) with a deposited structure (24), comprising at least a first dam section (26) and a second dam section (28), wherein the dam sections (26, 28) define at least part of a contour line (30) of the deposited structure (24); and a layer (32) of second material deposited within the contour line (30) and covering an area (34) extending between the first dam section (26) and second dam section (28).

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