EP2626140A1

EP2626140A1 - A method for non-drip dispensing of a liquid and a nozzle therefore

Info

Publication number: EP2626140A1
Application number: EP12154243.5A
Authority: EP
Inventors: Omar Fakhr; Kader Mekias
Original assignee: Suess Microtec Lithography GmbH
Current assignee: Suess Microtec Lithography GmbH
Priority date: 2012-02-07
Filing date: 2012-02-07
Publication date: 2013-08-14
Also published as: WO2013117633A1

Abstract

The invention relates to a method for non-drip dispensing of a liquid by means of a nozzle (1) onto a substrate (4), wherein said method comprises the following steps: dispensing the liquid from a first channel (2) of the nozzle onto the substrate, stopping dispensing the liquid and aspirating residual liquid via a second channel (3) of the nozzle. The invention also relates to a nozzle (1) for non-drip dispensing of a liquid onto a substrate (4). The nozzle comprises a first channel (2) adapted for dispensing the liquid and a second channel (3) adapted for aspiring residual liquid from an outlet end (5) of the nozzle.

Description

FIELD OF THE INVENTION

The invention relates to a method for non-drip dispensing of a liquid by means of a nozzle onto a substrate and a nozzle for non-drip dispensing of a liquid onto a substrate.

BACKGROUND OF THE INVENTION

Dispensing liquid onto a substrate is an important step in many fabrication processes, in particular in the production of computer chips or other logic devices. The physical and chemical properties of the liquid to be dispensed can largely vary. In particular, the viscosity plays an important role for the dispensing. Most of the photo-sensitive resists for the use in the micro-structure technology and the nanofabrication have a high viscosity which leads to high demands to the dispensing system, e,g, a spin coaster or a spray coaster, in particular to the nozzle of the dispensing system. Once a desired amount of liquid is dispensed to the substrate, a drop of residual resist at an outlet end of the nozzle can fall onto the substrate and can contaminate it. For preventing the drop from reaching the substrate, nozzles are known in the art which are sucking back the residual resist into the same channel which originally supplied the liquid. This backflow of liquid can cause two problems. Firstly, the liquid which is sucked back can comprise dirt particles from the ambient air contaminating the supply channel. Secondly, some liquids, in particular photo resists are sensitive to sudden pressure variations which appear during the back sucking of the liquid. Some sensitive liquids tend to outgas, especially nitrogen and in particular when they are close to the expiration date, creating gas bubbles in the supply line. These gas bubbles may be deposited onto the substrate during the next dispense leading to defects on the coated film on the substrate. These bubbles can even enlarge in a subsequent baking process. Thus, the dielectric strength of a coated insulation layer can be significantly decreased for example.
In addition, using the supply channel for aspirating residual liquid from the nozzle hardly removes any residues from the tip. These residues can begin to dry and can contaminate the next coating when little slugs of residues are dispensed together with fresh liquid.
In case that no backflow of the residual liquid is implemented in a coating system, the residual liquid is exposed to ambient conditions for a period of time which can influence the properties of the liquid. Even if the resist is viscous enough not to fall inherently onto the sample, the residual resist with changed properties is dispensed onto the next substrate together with fresh resist and the resulting coatings might not comply with the desired specifications.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for non-drip dispensing of a liquid by means of a nozzle onto a substrate and to provide a nozzle for non-drip dispensing of a liquid onto a substrate. This object is achieved with the features of the independent claims.
According to the invention, a method provides for non-drip dispensing of a liquid by means of a nozzle onto a substrate, wherein said method comprises the step of dispensing the liquid from a first channel of the nozzle onto the substrate, the step of stopping dispensing the liquid and the step of aspirating residual liquid via a second channel of the nozzle.
The liquid which is dispensed onto a substrate can be, for example, a protective coat, a photo-sensitive resist, an adhesion promoter or a barrier coat.
The substrate may be a semiconductor wafer, a substrate having magnetic properties or a glass substrate for example. The size of the substrate can vary from a few up to several hundreds of millimeters as in use at microchip mass production. The shape of the substrate can be of any form, e.g. round, rectangular or irregular.
The channel of the nozzle may have a cylindrical, a rectangular or a hexagonal profile for example. The two channels can be completely separated from each other or they can share a common sidewall. The step of dispensing the liquid can be performed by starting a pump in order to actively pump the liquid through the first channel or by opening a valve which is arranged above the nozzle and let the liquid flow through the first channel by gravitational force. The step of stopping the valve may be performed by shutting off the pump and / or by closing the valve. The step of aspirating the residual liquid via the second channel of the nozzle can be performed by applying a vacuum at the second channel from the end which is opposite to the end where the liquid is dispensed.
According to an embodiment of the invention, the first and the second channels can be arranged coaxially.
In an embodiment of the invention, the first and the second channels can be adjacent to each other.
In an embodiment of the invention, the first and the second channels can be separated from each other.
According to an embodiment of the invention, the method for non-drip dispensing of a liquid by means of a nozzle onto a substrate comprises the step of removing any residual liquid from the first channel and / or the second channel by means of a solvent or a cleansing liquid. The solvent may be an organic compound, e.g. acetone or isopropyl alcohol. The cleansing liquid may be a liquid comprising a solvent in combination with other active agents, e.g. bio-active agents. The step of removing any residual liquid may be performed by flushing the first and / or the second channel with the solvent or the cleansing liquid and aspirating the solvent or the cleansing liquid through the second channel after cleaning.
According to an embodiment of the invention, the method for non-drip dispensing of a liquid by means of a nozzle onto a substrate further comprises a step of adjusting or controlling the pressure difference between the first and the second channel. The pressure difference between the first and the second channel can be adjusted or controlled by means of a pump or a valve or by applying a suitably controlled vacuum. The pressure difference is applied when the liquid flows through the first channel or the residual liquid is aspirated via the second channel.
In an example of the invention, the step of dispensing and / or stopping the liquid can comprise a step of moving a valve member of a valve.
A valve member can be of rigid material, e.g. a metal or an alloy. The material of the valve member may be chemically resistant to the liquid that is dispensed, e.g. the material may be Polytetrafluoroethylene (PTFE). The valve member may open or close the valve in order to start or stop the dispensing of the liquid.
In an example of the invention, the valve member may comprise a membrane, preferably flexible or foldable, for opening and closing the valve by means of the applied pressure difference. The membrane may be of silicone or rubber, preferably chemically resistant to the liquid that is dispensed. The pressure difference between the first channel and the second channel may bend or reversibly deform the membrane, which can be connected to the first and / or the second channel. Bending or reversibly deforming the membrane may open or close the valve and the dispensing of the liquid may start or stop.
The invention also provides a nozzle for non-drip dispensing of a liquid onto a substrate, preferably for carrying out the method of any one of the preceding embodiments, comprising a first channel adapted for dispensing the liquid and a second channel adapted for aspiring residual liquid from an outlet end of the nozzle.
All features belonging to the embodiments which refer to the method for non-drip dispensing of a liquid by means of a nozzle onto a substrate also apply to all embodiments which refer to the nozzle for non-drip dispensing of a liquid onto a substrate.
According to an embodiment of the invention, the nozzle for non-drip dispensing of a liquid onto a substrate comprises a valve with a moveable valve member.
In an embodiment of the invention, the valve member comprises the first channel and / or the second channel.
According to an embodiment of the invention, the valve member is cone-shaped.
According to an embodiment of the invention, a valve seat is formed at an end of the first or the second channel.
The valve with the valve seat and the valve member may seal the nozzle at an outlet end. At an initial position, the valve member rests on the valve seat and the valve is closed, preventing the liquid from flowing out of the nozzle. When the valve member is moved away from the valve seat, the valve is opened and the liquid is dispensed onto the substrate. Bringing the valve member back in its initial position closes the valve and the dispensing is stopped.
According to an embodiment of the invention, the first and the second channel are adapted to be in fluid communication. The fluid communication of the first and the second channel may be realized by a single opening or a plurality of openings between both channels. After the dispensing of the liquid has stopped, residual liquid in the first channel as well as at the outlet end can be aspirated via the opening or the plurality of openings through the second channel.
Since no backflow of the liquid into the first channel occurs with said method for non-drip dispensing of a liquid by means of a nozzle onto a substrate and said nozzle for non-drip dispensing of a liquid onto a substrate, the amount of gas bubbles in the liquid in the first channel remains negligibly small. In addition, no residues of liquid are left, which can dry and crumble onto the substrate. In contrast to nozzle systems known in the art, in case of the present invention, the liquid is not sucked back into the supply channel and any outgassing of the liquid due to a sudden pressure difference is avoided. Further, the liquid to be dispensed is protected from atmosphere inside the nozzle when at idle. With the present invention, the nozzle can be cleaned in situ, i.e. without any additional device, and without affecting or contaminating the liquid by the solvent.
In the following, the invention will be described by means of particular embodiments and with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows a cross-section through a nozzle of a first embodiment;
Fig. 2 schematically shows a cross-section through a nozzle of a second embodiment similar to the first embodiment;
Fig.3 schematically shows a cross-section through a nozzle of a third embodiment comprising openings between a first and a second channel;
Fig. 4 schematically shows a cross-section through a nozzle of a fourth embodiment comprising a flexible membrane as a valve member;
Fig. 5 schematically shows a cross-section through a nozzle of a fifth embodiment comprising an axially moveable valve member; and
Fig. 6 schematically shows a cross-section through a nozzle of a sixth embodiment comprising an axially moveable valve member.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 depicts an example of a nozzle 1 for non-drip dispensing of a liquid according to an embodiment of the invention. According to this embodiment, the nozzle 1 comprises a first channel 2 and a second channel 3 and a common outlet end 5. According to the invention, the liquid is supplied from a reservoir 13 via an optional valve 14 to the inlet end 15 of the nozzle 1 and via its first channel 2 to the outlet end 5 of the nozzle 1 and onto a substrate 4 as soon as the dispensing process has started. The second channel 3 is provided for aspirating residual liquid. According to this first embodiment, the first channel 2 is annularly arranged around the second channel 3; both channels are arranged coaxially to each other. The first channel 2 is longer than the second channel 3 so that the free outlet end 3a of the second channel 3 is located inside the first channel 2, i.e. at the end of the nozzle 1 where the liquid is dispensed and where the outlet end 5 is located. The substrate 4 is shown only in Fig. 1 (a) for reasons of clarity.
It is understood that the substrate 4 can be present all the time, in all embodiments.
The dispensing can be initiated by a pump or by opening a valve for providing the liquid from the reservoir 13, e.g. a disposable cartridge. The pump can be favorable in case where actively pumping the liquid is needed, whereas a valve without any other means may be sufficient in a case where the valve is arranged above the nozzle such that the gravitational force allows the liquid to flow downwards through the first channel 2. The liquid is guided through the first channel 2 and is dispensed out of the outlet end 5 of the nozzle onto the substrate 4. Both, the supply means and the reservoir are not shown in the figure.
When the dispensing is stopped, a drop can occur at the outlet end 5 (Fig. 1 (b)). The size, the shape of the drop and the time until the drop is about to fall, depend on the viscosity of the liquid. Before the drop can fall down, according to the invention, a vacuum is applied to the second channel 3 and any residues at the outlet end 5 and any residual liquid in the first channel 2 can be aspirated (in the Fig. upwards) via the second channel 3 to a non-shown waste reservoir or back to the liquid reservoir (Fig. 1 (c) and (d)). Subsequently, another substrate or another part of the substrate 4 can be coated.
According to an embodiment, a solvent or a cleansing liquid can be additionally provided via the second channel 3 in order to clean the second channel 3 and partially the first channel 2. Before the solvent or the cleansing liquid can drop onto the substrate 4, a vacuum is applied to the second channel 3 and the solvent or the cleansing liquid is aspirated via the second channel 3.
Fig. 2 schematically shows another embodiment of the invention, wherein the first channel 2, i.e. the channel which provides the liquid, is surrounded by the annularly-shaped second channel 3. The second channel 3 is longer than the first channel 2 such that the free end 2a of the first channel 2 is located inside the second channel 3, i.e. at the end of the nozzle where the liquid is dispensed and where the outlet end 5 is located. Both channels are arranged coaxially to each other.
When the dispensing is started, the liquid flows through the first channel 2 and is sprayed out of the outlet end 5 onto the substrate 4. Once the dispensing is stopped, a drop can occur at said end of said first channel 2 and / or the outlet end 5. Aspirating the residual liquid from the outlet end 5 and / or a part of the first channel 2 through the second channel 3 by means of the application of a pressure difference prevents any drop from falling onto the substrate 4. A solvent or a cleansing liquid may be additionally supplied through the second channel 3 afterwards for flushing the outlet end 5 and partially the first channel 2. Before the solvent or the cleansing liquid can drop onto the sample 4, a vacuum is applied to the second channel 3 and the solvent or the cleansing liquid is aspirated via the second channel 3.
Fig. 3 depicts a third embodiment of the invention, wherein the nozzle 1 comprises a first channel 2 surrounded by an annularly-shaped second channel 3; the first channel 2 is longer than the second channel 3 so that a free end 2b of the first channel 2 protrudes out of the second channel 3 at the side of the nozzle 1 where the liquid is dispensed. The end 3b of the second channel 3 at the free end of the nozzle 1 encloses the first channel 2 such that an inner part 6 of the nozzle and an outer part 7 of the nozzle are formed. The outer part 6 is the part where the free end 2b of the first channel 2 protrudes out of the second channel 3. At the inner part 7 of the nozzle 1, the first channel 2 comprises openings 8 such that the first channel 2 and the second channel 3 are in fluid communication. The openings 8 are preferably arranged at an angle less than 90° with respect to the axis of the first channel. The angle can be set such that the amount of liquid which unintentionally sips from the first channel 2 through the openings 8 into the second channel 3 during the dispensing is reduced to a minimum.
When the dispensing is started, the liquid flows through the first channel 2 onto the substrate 4 (Fig. 3 (a) and (b)). As soon as the dispensing is stopped (Fig. 3 (c)), the liquid may form a drop which may fall onto the substrate 4. A vacuum can be applied to the second channel 3 resulting in aspirating any residual liquid from the first channel 2 through the openings 8 into the second channel 3 (Fig. 3 (d)). Additionally, a solvent or a cleansing liquid may be supplied through the first channel 2 and aspirated through the openings 8 into the second channel 3. According to the invention, the free end 2b of the first channel 2 where the fluid flows out of the nozzle 1 may be widened (as shown in Fig. 3) to ameliorate the dispensing of the liquid onto the substrate 4.
Fig. 4 schematically shows another embodiment of the invention, wherein a membrane 9 acting as a valve is arranged between the first channel 2 and the second channel 3. The first channel 2 is annularly surrounds the second channel 3; both channels are arranged coaxially to each other. The first channel 2 is longer than the second channel 3 so that the free end 3a of the second channel 3 is located inside the first channel 2, i.e. at the free end of the nozzle where the liquid is dispensed and where the outlet end 5 is located. The first channel 2 and the second channel 3 comprise said common outlet end 5 at the nozzle tip.
The membrane 9 can be flexible, e.g. a flexible or foldable ring, and an inner edge of the membrane 9 is fixedly mounted to the wall of the second channel 3. An outer diameter of the membrane 9 can be chosen in a manner that the membrane 9 may be in contact with the inner wall of the first channel 2 in order to form a valve member of a valve which prevents the liquid in the first channel 2 from flowing out of the first channel 2 (Fig 4 (a)). When a vacuum is applied to the second channel 3, the membrane 9, i.e. the valve member, is bent towards the inner part of the second channel 3 resulting in the valve to be opened (Fig. 4 (b)). A part of the liquid is sucked from the first channel 2 into the second channel 3. When the vacuum is stopped, the membrane 9 is not instantaneously relaxing back to its initial position. This period of time allows the liquid to flow from the first channel 2 and the second channel 3 out of the outlet end 5 onto the substrate 4 (Fig. 4(c)). As soon as the membrane 9 is relaxed back into its initial position, the valve starts closing (see arrows in Fig. 4 (d)). Depending on the viscosity, the liquid has already reached the substrate 4 or in case of very high viscosity, a drop is formed at the outlet end 5 which may still fall intentionally onto the substrate 4. When the valve is finally closed, any residual fluid can be aspirated via the second channel 3 by a vacuum (see arrow in Fig. 4 (e)) which is not sufficient to bend the membrane 9 towards the inner part of the second channel 3, but strong enough to aspirate the residual liquid.
Fig. 5 depicts another embodiment of the invention, wherein the end of the second channel 3 can be arranged in a moveable valve member 10 and an outlet end of the first channel 2 may be arranged as a valve seat 11 cooperating with the moveable valve member 10. Both ends are preferably arranged in the same direction, preferably in the flow direction of the liquid and preferably at the free end of the nozzle where the liquid is dispensed. The valve member 10 can be moved up and down in a vertical direction. The valve member 10 and the valve seat 11 form a valve which prevents the liquid from unintentionally flowing out of the nozzle 1. The first channel 2 annularly surrounds the valve member 10 so that the first channel 2 and the second channel 3 are arranged coaxially to each other. The free end of the valve member 10 pointing to the outlet end 5 of the nozzle 1 may be cone-shaped in order to provide for a sealing closure with an end of the first channel 2 which forms the valve seat 11. In an initial position (Fig. 5 (a)), the valve member 10 rests on the valve seat 11 and the liquid is enclosed in the first channel 2. When the valve member 10 is moved up, the valve opens and the dispensing of the liquid begins (Fig. 5 (b)). As soon as the valve member 10 is moved down and sits again on the valve seat 11 (Fig. 5 (c)), the liquid stops flowing out of the nozzle. Residual liquid can be aspirated through the second channel 3 (see arrows in Fig. 5 (d)). Additionally, a solvent or a cleansing liquid can be guided through the second channel 3 for cleaning the second channel 3 and the nozzle tip from residues and said solvent and or cleansing liquid can be aspirated via the second channel 3 before dripping onto the substrate 4. According to an embodiment, the second channel 3 may have multiple outlets 12 in order to accelerate the aspiration of any residual liquid and to homogeneously aspire the residual liquid.
Fig. 6 depicts another embodiment of the invention, wherein the moveabie valve member 10 can be height-adjusted with a height adjuster 16. For guidance of the moveable valve member 10, a valve member guide disk 17 is installed as a part of the nozzle 1. Screws 18 and corresponding nuts are used to connect the valve member guide disk 17 with other parts of the nozzle 1.
It is understood that the subject-matter of the present invention is not restricted to the case where the nozzle 1 is located above the substrate 4. As a further example, the nozzle 1 may be located under the substrate 4 so that the liquid is sprayed on the substrate 4 from below.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and non-restrictive; the invention is thus not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality and may mean "at least one".

Claims

A method for non-drip dispensing of a liquid by means of a nozzle (1) onto a substrate (4), said method comprising the following steps:
(a) dispensing the liquid from a first channel (2) of the nozzle (1) onto the substrate (4);

(b) stopping dispensing the liquid; and

(c) aspirating residual liquid via a second channel (3) of the nozzle (1).
The method of claim 1, wherein the first and the second channel (2 and 3, respectively) are coaxially arranged.
The method of claim 1 or 2, further comprising the following step:
removing any residual liquid from the first channel (2) and / or the second channel (3) with a solvent or a cleansing liquid.
The method of any of claims 1 to 3, wherein the steps of dispensing and / or stopping the liquid comprises a step of adjusting a pressure difference between the first and the second channel (2 and 3, respectively).
The method of any of claims 1 to 4, wherein the steps of dispensing and / or stopping the liquid comprise a step of moving a valve member (10) of a valve.
The method of claim 5, wherein the valve member comprises a membrane (9), preferably flexible or foldable, for opening and closing the valve by means of the applied pressure difference.
A nozzle (1) for non-drip dispensing of a liquid onto a substrate (4), preferably for carrying out the method of any one of the preceding claims, comprising:
(a) a first channel (2) adapted for dispensing the liquid; and

(b) a second channel (3) adapted for aspiring residual liquid from an outlet end (5) of the nozzle.
The nozzle (1) of claim 7, wherein the first and the second channel (2 and 3, respectively) are coaxially arranged.
The nozzle of claim 7 or 8, further comprising a valve with a moveable valve member (10).
The nozzle of claim 9, wherein the valve member (10) comprises the first and / or the second channel (2 and 3, respectively).
The nozzle of claim 9 or 10, wherein the valve member (10) is cone-shaped.
The nozzle of any of claims 9 to 11, wherein a valve seat (11) is formed at an end of the first or the second channel (2 and 3, respectively).
The nozzle of claim 9, wherein the valve member comprises a membrane (9).
The nozzle of claim 13, wherein the membrane (9) is flexible and / or foldable.
The nozzle of claim 7, wherein the first and the second channel (2 and 3, respectively) are in fluid communication.