NL2003340C2 - Method of manufacturing a micro unit and micro unit for use in a microscope. - Google Patents

Description

P87953NL00

Title: Method of manufacturing a micro unit and micro unit for use in a microscope

The invention relates to a method of manufacturing a micro unit for use in a microscope, comprising the steps of providing a planar substrate supporting structure on which the micro unit is based.

Such a micro unit is e.g. known from the International publication 5 WO 2006/031104 disclosing a reactor for microscopy in the fields of analyzing heterogeneous catalysis, corrosion, chemical vapour deposition, materials science, biochemistry, biomedicine and electrochemistry. In principle, such reactors enable the imaging of chemical processes with high resolution, down to the atomic scale, i.e. circa 0.1 nm to circa 0.2 nm.

10 In realizing such a micro unit, an assembly step is performed for realizing a chamber in the micro unit for receiving the specimen to be inspected. Though such micro units operate properly, the manufacturing process might be enhanced in terms of ease of production. Further, the pressure in the chamber may vary in a restricted range, thereby limiting 15 potentially interesting applications.

It is an object of the invention to provide a method of manufacturing a micro unit for use in a microscope according to the preamble that is easier to produce. Thereto, the method according to the invention further comprises the steps of creating a chamber in the supporting structure for receiving a fluid 20 containing a specimen to be inspected, coating an inner surface of the chamber with a thin layer, and locally removing material from the exterior of the supporting structure until the thin layer is reached for forming a window segment that is at least partially transparent to a beam of radiation generated by the microscope.

25 By coating the inner surface of the chamber with a thin layer that forms a window segment when locally removing material from the exterior of 2 the supporting structure, a micro unit can be obtained that might be integrally formed with the supporting structure, thus eliminating the assemblage step wherein a chamber is formed. Since the chamber and the window segments can be formed in a single piece, using the internal coating process, the 5 production process of the micro unit simplifies considerably, thereby reducing manufacturing costs.

Further, since the micro unit can thus be manufactured using micro electromechanical system (MEMS) or micro system manufacturing techniques, including thin film technology and photolithographic processing technology, 10 any alignment of upper and lower windows can be performed with an accuracy that is much higher than is available when using conventional techniques. As an example, an accuracy of circa 0.1 micron can e.g. be reached, instead of circa 2 micron. Therefore, the lateral window size may be reduced from approximately 5 micrometer to approximately 1 micrometer, thereby 15 considerably increasing the rigidity of the window segment. Therefore, the window segment can withstand much higher pressures in the chamber, thereby facilitating a measurement at relatively high pressure while maintaining high resolution accuracy.

Further, the invention relates to a micro unit for use in a 20 microscope.

Other advantageous embodiments according to the invention are described in the following claims.

By way of example only, an embodiment of the present invention will now be described with reference to the accompanying figures in which 25 Fig. 1 shows a schematic cross sectional side view of a first embodiment of a micro unit according to the invention;

Fig. 2 shows a schematic top view of the micro unit of Fig. 1;

Fig. 3 shows a schematic perspective partial view of a second embodiment of a micro unit according to the invention; and.

3

Fig. 4 shows a flow chart of an embodiment of a method according to the invention.

The figures are merely schematic views of a preferred embodiment according to the invention. In the figures, the same reference numbers refer to 5 equal or corresponding parts.

Figure 1 shows a schematic cross sectional side view of a first embodiment of a micro unit 100 according to the invention. The micro unit 100 comprises a supporting structure 1, also called substrate, typically made of silicon of 0.5 mm thick. However, the substrate may also be made from other 10 materials, such as e.g. glass. Further, the substrate thickness might be smaller or larger than 0.5 mm. The substrate 1 is provided with a chamber 3, also called channel, which is arranged for receiving a specimen, in particular a fluid containing a chemically reacting substrate. As such, the micro unit is formed as a microreactor. The channel 3 comprises a multiple number of window 15 segments 13. In Fig. 1, two window segments 13 are shown that are provided in opposite wall sections 23 a,b. The window segments 13 are at least partially transparent to a beam of radiation E generated by a microscope, thereby enabling that the fluid containing a chemically reacting substance is inspected by the microscope, especially in a channel section 3a that is located near the 20 window segment 13. As an example, the beam of radiation E might be formed an electron beam or an X-ray beam. In the shown embodiments, the supporting structure 1 includes a viewing hole that is in line with the multiple number of window segments 13a-c.

Figure 2 shows a schematic top view of the micro unit 100, and 25 Figure 3 shows a schematic perspective partial view of an alternative embodiment of a micro unit 100 also including a multiple number of window segments 13. In order to provide the window segment 13 that is at least partially transparent to the microscope beam of radiation E, the micro unit 100 further comprises a thin layer 11 that is integrally formed with the window 30 segment 13. The thin layer 11 extends along an inner surface of the channel or 4 chamber 3, beyond the window segment 13. The thin layer 11 is typically made from SiN, SiC, SiC>2 and/or polycrystalline Si material and is typically circa 10 nm thick. However, also another thickness can be applied.

Preferably, the entire inner surface of the chamber 3 or 5 substantially the entire inner surface of the chamber 3, e.g. more than circa 50% or more than circa 90% is covered by the thin layer 11. The thin layer is locally integrally formed with a window segment to enable the microscope beam E, such as an electron beam, a light beam, an ion beam or an X-ray beam, to enter the chamber 3. In an embodiment according to the invention, 10 the thin layer 11 forms the window segment at locations where the supporting structure 1 has been removed to realize blind holes 25a,b. In principle, however, the window segment might not only include the thin layer 11 but also a further layer.

In the embodiments shown in Figures 1-3, the chamber includes a 15 pair of mutually facing wall sections, viz. a ceiling 4 and a floor 5 defining the cavity that forms the chamber or channel 3. Also the ceiling 4 and the floor 5 may be made from SiN or other thin film material, e.g. SiC,, SiOy and/or polycrystalline Si, having a typical thickness of e.g. 700 nm. Again, also another thickness can be applied. Further, the chamber includes a multiple 20 number of interconnecting members, also called pillars or supports 8 extending through the chamber and interconnecting said facing wall sections. By joining the ceiling 4 and the floor 5 via the supports 8 any bulging of the chamber ceiling 4 and floor 5 that might be induced by the application of a pressure in the chamber, is efficiently counteracted. As a result, the height of the chamber 25 or channel might be strongly reduced, e.g. to a value in a range from circa 0.1 micrometer to circa 1 micrometer. Decreasing the effective chamber height enables a higher density of molecules to be inspected while transparency requirements are maintained. Advantageously, decreasing the effective chamber height has a similar effect as increasing the inner pressure in the 5 chamber or replacing any gas containing the chemically reacting substance by a liquid.

As a result, a low pressure limit for gas-solid reactors for microscopy is relaxed. Since, according to an aspect of the invention, a higher pressure in 5 the chamber can be applied, even up to a range of circa 2 bar to circa 100 bar whereas a high resolution is maintained, thus enabling imaging of chemical processes with high resolution, down to the atomic scale, i.e. to a range of circa 0.1 to circa 0.2 nm. Further, by employing supports 8 interconnecting the mutually facing wall sections, a chamber height thinner than 1 micrometer 10 can be realized so that a sufficient transparency can be obtained in a robust micro unit that is relatively cheap and reliable.

In this respect, it is noted that the micro unit according to the invention, including the thin layer that is integrally formed with the window segment and extends along an inner surface of the chamber beyond the 15 window segment can in principle also be realized without the interconnecting members, e.g. when only moderate pressures will be applied in the chamber.

Due to a specific MEMS or micro system manufacturing technique, the supports may include a blind hole 16 a-e. By substantially evenly distributing the multiple number of interconnecting members 8 over the inner 20 surfaces of the mutually facing wall sections 4, 5 a relatively large pressure can be applied since the forces can then also be transmitted to wall sections in an evenly distributed manner.

Preferably, the interconnecting members 8 are designed to resist a pull force so that a relatively large internal pressure in the channel 3 can be 25 applied.

The one or multiple number of window segments can be comprised in the chamber ceiling 4 and/or chamber floor 5. By realizing window segments 13 in both the ceiling 4 and the floor 5, preferably in line, a transmission measurement can be performed. However, in principle, the one or more 6 window segments can also be realized in either the ceiling 4 or the floor 5, thereby allowing a reflection measurement.

Further, the micro unit may include an input port 6 and an output port 7, also called inlet and outlet, for flowing the fluid into and from the 5 channel 3, respectively. In principle, the micro unit may include a single port for allowing the fluid to flow into and from the channel. 17. The channel structure extending between the inlet 6 and the outlet 7 has a substantially elongated form, thereby providing an elegant design providing inflow and outflow regions as well as an inspection region including the viewing hole 2 10 with the window segments 13.

In addition, the micro unit optionally includes electrical contact pads 15 as well as a heating element 14 interconnecting the electrical contact pads 15 for the purpose of heating the unit to a desired temperature range.

During use of the micro unit 100, a solid specimen is deposited on 15 the window segments, inside the channel, typically some kind of nanoparticles. Then, a gaseous and/or liquid environment that is different from the environment outside in terms of pressure, temperature and/or molecular species is flown to the channel 3, e.g. by applying a pressure difference between the inlet and the outlet. As a result, the fluid contains a chemically 20 reacting substance, e.g. a solid specimen. If desired, the specimen and its environment are brought to a higher temperature employing the heating element 14 to accelerate an expected chemical or physical reaction. In the channel a chemical reaction or physical transformation may take place to be monitored by use of a microscope, quite often in vacuum.

25 Figure 4 shows a flow chart of an embodiment of the method according to the invention. The method is used for manufacturing a micro unit for use in a microscope. The method comprises the steps of providing 200 a planar substrate supporting structure, creating 210 a chamber in the supporting structure for receiving a fluid containing a specimen to be 30 inspected, coating 220 an inner surface of the chamber with a thin layer, and 7 locally removing 230 material from the exterior of the supporting structure until the thin layer is reached for forming a window segment that is at least partially transparent to a beam of radiation generated by the microscope.

During the process of manufacturing the micro unit, a planar 5 substrate, such as a semiconductor or glass wafer, is provided typically having a thickness of circa 0.5 mm. By using micro electro mechanical system (MEMS) surface micromachining techniques and/or semiconductor fabricating techniques, such as a photolithographic wafer stepper technique, e.g. a sacrificial etching process, the chamber 3 may be created serving as a room 10 that may receive a fluid including a specimen such as a chemically reacting substance. In this way a chamber 3 might be realized that is integrally formed with the supporting structure 1. In a first stage of the manufacturing process, the chamber 3 may include one or a multiple number of apertures, also called access holes 9, so that a region near window segments 13 to be realized is 15 easily accessible from outside. The access holes 9 might also have been used for creating the chamber 3 in the supporting structure 1. Via the at least one access hole 9 at least a part of the chamber’s inner surface is coated with a thin layer 11. Optionally, said chamber’s inner surface is deposited with a stop layer 12 prior to coating the surface with the thin layer 11. Typically, the thin 20 layer comprises SiN and the stop layer 12 typically contains SiÜ2. The thin layer is e.g. 10 nm thick. Further, the stop layer 12 has e.g. a typical thickness of circa 150 nm. However, also other thicknesses may be chosen. After applying the coating process(es), the access holes 9 may be sealed, e.g. by inserting plugs 10 a-c.

25 The thin layer 11 and the stop layer 12 can be deposited using a conformal technique such as low-pressure chemical vapour deposition (LPCVD) or atomic layer deposition (ALD). Any fluid required for coating may enter the chamber 3 interior through the access holes 9 that have typically been used in a surface machining step to etch away a sacrificial layer. The 30 plugs 10 might be made by a combination of nonconformal thin film deposition 8 technique such as plasma enhanced chemical vapour deposition (PECVD), by photolithography and by etching.

It is noted that instead of using at least one access hole 9 for coating the chamber’s inner surface, in principle, also other holes providing access to 5 the chamber 3 can be used, e.g. the inlet 6 and/or the outlet 7 that enable a fluid to flow into and from the chamber 3, respectively, during normal use of the micro unit 100.

Further, after application of the coating process(es), material is locally removed from outside the supporting structure 1, thus obtaining a blind 10 hole 25a,b, until the thin layer 11 is reached. Preferably, opposite areas of the floor and the ceiling are removed, including the stop layer, thereby exposing the window segments 13. After the removal process, the blind hole 25a,b extends to the thin layer 11 and the thin layer 11 locally forms a window segment 13 separating the blind hole 25 and the chamber 3. The window 15 segments are typically circular in shape and may have a diameter ranging e.g. from circa 1 to circa 10 microns. The window segment 13 is at least partially transparent to a beam of radiation generated by a microscope. When a stop layer 12 has been coated, said stop layer 12 might assist in the process of removing the material from the supporting structure 1. The removal process 20 can be performed using a micromachining process or a lithographic process followed by an etching step.

The invention is not restricted to the embodiments described herein. It will be understood that many variants are possible.

It is noted that the micro unit according to the invention can be 25 applied for inspecting, via a microscope, a specimen that is present in the chamber. As an example, the specimen to be inspected includes a fluid containing a chemically reacting substance. However, the micro unit might also find application in other fields, e.g. in the field of micro electron sources.

It is further noted that other materials can be used for realizing 30 structure elements indicated above. As an example, other thin film material 9 components can be used for forming the thin layer that is integrally formed with the window segment and extends along an inner surface of the chamber beyond the window segment.

The thin layer coated inside the chamber can not only be used for 5 creating a window segment. The thin layer may also serve as a surface modification for further functionalities, such as a catalytic function for accelerating a chemical process. As a further example, a hydrophobic functionality might thus be realized. As such, the thin layer may also have the function of protecting the reactor interior from an attack by chemical 10 substance, promoting chemical reactions in the interior, e.g. by catalytic action and/or attracting or repelling specific substance, e.g. for promoting hydrophobicity. Also, the thin layer may serve as a protection layer. In addition, a further coating layer, e.g. a second thin layer, might be deposited in the chamber at least partially covering the thin layer. Here, the same 15 technique can be used as employed for depositing the thin layer. The further coating layer may include a desired physical and/or chemical functionality, e.g. for fulfilling one or more of the above-mentioned functions.

Other such variants will be obvious for the person skilled in the art and are considered to lie within the scope of the invention as formulated in the 20 following claims.

Claims (17)

1. Werkwijze voor het vervaardigen van een micro eenheid in een microscoop, omvattende de stappen van: het verschaffen van een planaire, substraat ondersteunende structuur; het creëren van een kamer in de ondersteunende structuur voor het 5 ontvangen van een fluïdum omvattende een monster ter inspectie; het aanbrengen van een dunne laag op een binnenoppervlak van de kamer; en het locaal verwijderen van materiaal vanuit het uitwendige van de ondersteunende structuur totdat de dunne laag wordt bereikt voor het 10 vormen van een raamsegment dat ten minste gedeeltelijk transparant is voor een stralingsbundel die door de microscoop wordt gegenereerd.A method for manufacturing a micro unit in a microscope, comprising the steps of: providing a planar, substrate-supporting structure; creating a chamber in the supporting structure for receiving a fluid comprising a sample for inspection; applying a thin layer to an inner surface of the chamber; and locally removing material from the exterior of the supporting structure until the thin layer is reached to form a window segment that is at least partially transparent to a radiation beam generated by the microscope. 2. Werkwijze volgens conclusie 1, waarbij de stap van het creëren het gebruik van een sacrificial etsproces omvat.The method of claim 1, wherein the step of creating comprises using a sacrificial etching process. 3. Werkwijze volgens conclusie 1 of 2, waarbij de dunne laag SiN, SiC,Method according to claim 1 or 2, wherein the thin layer of SiN, SiC, 4. Werkwijze volgens één der voorgaande conclusies 1-3, voorts omvattende de stap van het aanbrengen van een stoplaag op het binnenoppervlak van de kamer vóór het aanbrengen van de dunne laag.A method according to any one of the preceding claims 1-3, further comprising the step of applying a stop layer to the inner surface of the chamber before applying the thin layer. 5. Werkwijze volgens één der voorgaande conclusies 1-4, waarbij het 20 proces van het aanbrengen van een laag wordt uitgevoerd door gebruikmaking van een opening van de kamer die wordt verzegeld na de stap van het aanbrengen van een laag.5. Method as claimed in any of the foregoing claims 1-4, wherein the process of applying a layer is carried out by using an opening of the chamber which is sealed after the step of applying a layer. 6. Micro eenheid voor gebruik in een microscoop, omvattende een planaire, substraat ondersteunende structuur, komvattende een kamer voor 25 het ontvangen van een monster ter inspectie, waarbij de kamer een raamsegment omvat dat ten minste gedeeltelijk transparant is voor een stralingsbundel die door de microscoop wordt gegenereerd, en waarbij de micro eenheid voorts een dunne laag omvat die integraal is gevormd met het raamsegment en zich uitstrekt langs een binnenoppervlak van de kamer, voorbij het raamsegment.6. Micro unit for use in a microscope, comprising a planar, substrate supporting structure, comprising a chamber for receiving a sample for inspection, the chamber comprising a window segment that is at least partially transparent to a radiation beam passing through the microscope is generated, and wherein the micro unit further comprises a thin layer integrally formed with the window segment and extending along an inner surface of the chamber beyond the window segment. 7. Micro eenheid volgens conclusie 6, waarbij in hoofdzaak het gehele binnenoppervlak van de kamer door de dunnen laag is bedekt.The micro unit of claim 6, wherein substantially the entire inner surface of the chamber is covered by the thin layer. 8. Micro eenheid volgens conclusie 6 of 7, waarbij de ondersteunende structuur, omvattende de kamer, integraal is gevormd.The micro unit of claim 6 or 7, wherein the support structure comprising the chamber is integrally formed. 9. Micro eenheid volgens één van de voorgaande conclusies 6-8, gevormd als een microreactor voor gebruik in een microscoop, waarbij het monster ter inspectie een fluïdum omvat dat een chemisch reagerende 10 substantie omvat.9. A micro unit according to any one of the preceding claims 6-8, formed as a microreactor for use in a microscope, wherein the sample for inspection comprises a fluid comprising a chemically reacting substance. 10. Micro eenheid volgens één van de voorgaande conclusies 6-9, waarbij de kamer een paar onderling toegekeerde wandsecties en een meervoudig aantal onderling verbindende delen omvat, waarbij genoemde delen zich door de kamer uitstrekken en genoemde toegekeerde wandsecties onderling 15 verbindt.10. A micro unit according to any one of the preceding claims 6-9, wherein the chamber comprises a pair of mutually facing wall sections and a plurality of mutually connecting parts, wherein said parts extend through the chamber and mutually connect said facing wall sections. 11. Micro eenheid volgens één van de voorgaande conclusies 6-10, waarbij het meervoudig aantal onderling verbindende delen in hoofdzaak evenredig verdeeld zijn over de binnenoppervlakken van de onderling toegekeerde wandsecties.A micro unit according to any one of the preceding claims 6-10, wherein the plurality of interconnecting parts are substantially evenly distributed over the inner surfaces of the mutually facing wall sections. 12. Micro eenheid volgens één van de voorgaande conclusies 6-11, waarbij de onderling verbindende delen ontworpen zijn om bestand te zijn tegen een trekkracht.The micro unit according to any of the preceding claims 6-11, wherein the interconnecting parts are designed to withstand a tensile force. 13. Micro eenheid volgens één van de voorgaande conclusies 6-12, waarbij het raamsegment is omvat in een eerste wandsectie van het paar 25 onderling toegekeerde wandsecties.13. A micro unit according to any one of the preceding claims 6-12, wherein the window segment is included in a first wall section of the pair of mutually facing wall sections. 14. Micro eenheid volgens één van de voorgaande conclusies 6-13, omvattende een tweede raamsegment dat is omvat in een tweede wandsectie van het paar onderling toegekeerde wandsecties.A micro unit according to any one of the preceding claims 6-13, comprising a second window segment that is included in a second wall section of the pair of mutually facing wall sections. 15. Micro eenheid volgens één van de voorgaande conclusies 6-14, waarbij de kamer een invoeropening en een uitvoeropening omvat om het fluïdum respectievelijk in en uit de kamer te laten stromen.The micro unit according to any of the preceding claims 6-14, wherein the chamber comprises an inlet port and an outlet port for flowing the fluid into and out of the chamber, respectively. 15 SiOa en/of poly kristallijn Si materiaal omvat.SiOa and / or poly crystalline Si material. 16. Micro eenheid volgens één van de voorgaande conclusies 6-15, 5 waarbij het raamsegment ten minste gedeeltelijk transparant is voor een stralingsbundel die door de microscoop wordt gegenereerd.A micro unit according to any one of the preceding claims 6-15, wherein the window segment is at least partially transparent to a radiation beam generated by the microscope. 17. Micro eenheid volgens één van de voorgaande conclusies 6-16, waarbij de kamer een in hoofdzaak langwerpige vorm heeft.The micro unit of any one of the preceding claims 6-16, wherein the chamber has a substantially elongated shape.