WO2013030451A1

WO2013030451A1 - Filter preunit

Info

Publication number: WO2013030451A1
Application number: PCT/FI2012/050828
Authority: WO
Inventors: Jarmo Maula; Touko Liikonen
Original assignee: Beneq Oy
Current assignee: Beneq Oy
Priority date: 2011-08-31
Filing date: 2012-08-29
Publication date: 2013-03-07
Anticipated expiration: 2014-02-28
Also published as: FI20115853A0

Abstract

The invention relates to a filter preunit for chemical vapour deposition processes. The unit is used to remove reaction residues from a residual gas flow. The filtering unit comprises at least two contact surfaces (24a, 24b), in connection of which the residual gas flow and reagent flow come into contact with each other, with at least one of the contact surfaces (24a, 24b) being movable to purify the contact surfaces from reaction residues grown on them.

Description

Filter Preunit

Background of the Invention

The object of the invention is a chemical vapour deposition process filter preunit in accordance with the preamble of claim 1.

For the background and prior art of the present invention, a reference is made to the following exemplary patents US 4,058,430 (Suntola), US 6,506,352 B1 (Lindfors et al.) and Fl 84,980 (Henttinen et al.). The former US patent is the basic patent of the ALE (Atomic Layer Epitaxy) method, subsequently commonly referred to as ALD (Atomic Layer Deposition). The second US patent represents a method and a device for removing materials from gas flows which are discharged, for example, from an ALD reactor, using a "sacrificial material".

In the above mentioned Fl patent Fl 84,980, there is shown a filter chamber including a rotatable mechanical flow-through filter and a related fixed scraper for cleaning reaction residues from the outer surface of the filter. In the said patent, there is also shown a post-reaction chamber where the particle size of the material to be filtered is increased before filtering by allowing the gas to be filtered to come into contact with a purifying reagent flow or, more commonly, a reagent flow. An often used reagent is water due to its good reactivity, easy availability, low cost and harmlessness. The materials to be filtered are led from the post-reaction chamber to the mechanical filter whereby all of the material to be filtered stresses the mechanical filter as the material passes through the filters.

The growing stress on the filter leads to retardation of the filtering action, an increased need for maintenance and cleaning, a loss of efficiency and, in extreme cases, to a failure of the apparatus.

The said Fl patent accurately describes especially the ALD method; however, the need for filtering is a common need for all chemical deposition processes such as, for example, Chemical Vapour Deposition (CVD) processes or plasma etching processes. In all such chemical vapour deposition processes, the exhaust gases have always at least some of the precursor left after the deposition action; these residual precursors have not reacted in the deposition process itself and are to be removed. In the CVD process, for example, precursor feed is never in perfect balance, and thus the CVD reactor exhaust or residual gas includes unreacted precursors or post-reaction products caused by them. In an ALD reactor, similarly, precursor agents are usually controlled in pulses to allow them to freely mix and react with each other only after the actual growth action. These various post-growth action reaction products are hereafter collectively referred to as "reaction residue" (other known international terms include "by-product" or "residue").

In the present application, the term "vapour" is commonly used to refer to a gaseous material, and the application uses the terms "vapour" and "gas" interchangeably.

If the process in question is a vacuum based or low pressure based flow solution from a processing apparatus to a filter, these reaction residues are especially harmful when reaching a vacuum pump that generates a vacuum. Even a slightest amount of reaction residue leads to dirt accumulation or growth inside the vacuum pump which, in the worst case scenario, may break the expensive pump only after a few weeks of use.

Despite the said Fl patent representing a solution that clearly improves the functioning of the filter, modern industrial scale chemical vapour deposition processes, such as, for example, ALD based protective coating processes or passivation processes, generate a large amount of exhaust gases thus subjecting the filters to a very high stress. In addition, especially the industrial vapour deposition apparatuses must be able to run several different, process chemically varying deposition actions during their operating life. This fact also adds to the performance requirements of filters. Further, numerous deposition processes take place in clean rooms which are often quite confined. Thus, any apparatuses used in them must be as small as possible, but without any compromises on performance requirements.

An object of the invention is to create a novel filter preunit to be used in the described very demanding operating environment, at the same time mostly avoiding the aforementioned drawbacks. A special object of the invention is to lengthen filter's operating life and maintenance interval, to decrease its required power and to improve the operational reliability and operating life of any post- filtering devices, including, for example, a possible vacuum pump, and to decrease their need for maintenance. Another object of the invention is to create a compact gas purifying apparatus to avoid any space related problems.

The object of the invention may be achieved by allowing a reagent to react before the actual mechanical filtering action with the vapour to be filtered in connection with at least two contact surfaces, of which at least one may be brought to move. Surprisingly, it has been observed that this way a significant portion of the reaction products do not stress the filter, usually based on a flow- through technique (also called a filtering section or a filtering apparatus), but the reaction products lead to reaction residue growth on especially the contact surfaces, the movement of which surprisingly prevents excessive reaction residue growth eventually interfering with the vapour flow on the surfaces and other susceptible parts of the apparatus. Another object of the invention may be achieved by integrating a preunit and a filtering apparatus into a purifying apparatus.

More specifically, the filter preunit and purifying apparatus of the invention are characterized by the features of the characterizing parts of claim 1.

Figures

In the following, the invention is described more closely by referring to the appended figures where:

• Figure 1 shows the application environment of the invention as a diagram;

• Figure 2 shows an embodiment of the preunit as a 3D projection;

• Figure 3 shows a detailed view of the contact surface and reagent feeds of the preunit as a 3D projection;

• Figure 4 shows semantically another embodiment of the contact surface and reagent feed of the preunit; and

• Figure 5 shows semantically a third embodiment of the contact surface and reagent feed of the preunit as a diagram.

Detailed Description of the Invention

Fig. 1 represents the typical application environment of a filter preunit

3a and a purification apparatus 3 using a block diagram representation.

From a source unit 1 , precursors, or source chemicals, are fed, preferably, as pulsed flows A and B to a vapour deposition tool, here an ALD unit, reactor 2 from which a residual gas flow C is discharged to the purification apparatus 3. In addition to an inert carrier gas, the residual gas flow C usually contains residues of reaction chemicals A and B which are, either after the reactor or already when reacting in the reactor, converted into reaction residue that subjects apparatuses to wear and tear; this reaction residue may be in gaseous, droplet or particle form or it may even have been accumulated as various layers or agglomerations within the apparatus. For this reason, the residual gas and reaction residues are sought to be removed as completely as possible from the residual gas flow C using the filter preunit 3a and filtering apparatus 3b in accordance with the present invention.

The purification apparatus 3 is thus comprised of two operational parts: a filter preunit 3a and a filtering apparatus 3b. When pursuing a compact structure, the filter preunit 3a and the filtering apparatus 3b may be preferably integrated into the casing of the same residual gas purifying purification apparatus 3; however, it is also possible to arrange the filter preunit 3a and the filtering apparatus 3b within different casings and to connect these devices using required assemblies. It is only required that the preunit 3a feeds prepurified residual gas to the filtering apparatus 3b.

To improve the efficiency of the purifying action, reagent R from a reagent container 5 is led to the purification apparatus 3. Flow D aspirated to a vacuum pump 4 is discharged from the filtering apparatus 3b. The object of an embodiment of the invention is to protect the expensive vacuum pumps 4 from reaction chemical residues A and B - thus, essentially, to increase the operating life of the pumps - that subject them to strong wear and tear and/or corrosion; in other words, to purify the residual gas flow C to a flow D that is as pure as possible. From the pump 4, a flow E2 is discharged either to open air or through a gas washer (not shown) to open air as a flow E1.

Fig. 2 shows in the form of a 3D cross section a purifying apparatus 3, the outer jacket of which comprises a vertical cylinder jacket 10 as well as a cover 11 a and a base 11 b. A residual gases C input assembly 13 is connected to the cover 1 1a of the vertical cylinder jacket 10, this assembly being normally heated to maintain the residual gas in gas form (the heating apparatus are not shown). Within the outer jacket 10, 1 1 a, 11 b of the purifying apparatus 3, the filtering apparatus section 3b according to Fig. 1 includes six, preferably identical, filter cartridges in the form of vertical cylinders (Fig. 2 only shows the filter cartridges 31 to 32) connected to drive elements, here gears 40, 41. The middle filter cartridge 31 has been placed essentially on the vertical center axis of the jacket 10 with the other filter cartridges around it, most preferably evenly distanced from each other.

In terms of vapour flow, the filter cartridges of the filtering apparatus 3b according to Fig. 2 are connected in parallel; in other words, both of them are fed from a first space 16a and they both feed a purified flow to a second space 16b. In the embodiment shown in Fig. 2, a flow is fed through the filter cartridges to their outer surfaces, with the filter cartridges feeding the purified flow through their inner space; in other words, the flow to be purified passes from the outer surface through the filter cartridge and onto its inner surface. Thus, the filtering effect of the filter cartridges is preferably based on flow-through where the material to be removed is at least partly stuck in the filter and the purified material, here gas, continues its flow in the process.

The purification apparatus 3, its preunit part 3a, also includes a cylindrical contact surface 24a which leads to a lower first space 16a defined by the vertical jacket 10 and the base 11 b. Accordingly, a very compact structure and efficient use of space are achieved. The figure also shows a mobile, preferably frame-like, contact surface 24b, reagent feeds 23a, 23b of the reagent flow and a protrusion 25 in connection with the preunit 3a in accordance with Fig. 1.

The filter cartridges are rotated about their vertical center axes using a mechanism which comprises a central gear 40 and its rotation means 15. The vertical axis and a handle or a crank connected to it may act as the rotation means 15; it is only required that the person using the ALD tool rotates the handle or the crank occasionally, for example, every 5 minutes. Naturally, it is also possible to produce such a rotational force using, for example, an electric motor. The need for purification of the filters by rotation may, for example, be detected by detecting the pressure detected in the feed of the purification apparatus 3 using, for example, a manometer (not shown). A pressure increase indicates an increase in the resistance of flow in the purification apparatus, or a need for purification of the filter cartridges with a rotational motion. The rotational motion of the filter cartridges makes the outer perimeters and outer surfaces of the filter cartridges move against special scraper blades (not shown in Fig. 2). These scraper blades scrape reaction residues from the outer surfaces of the filters and thus improve the permeability of the filter and decrease the resistance of gas flow through the filter. By detecting pressure, the purifying action may also be fully automated using actuators apparent to those skilled in the art. Excessive rotation of the filters subjects the various structures of the apparatus to unnecessary wear and tear.

A gear 40 uses a gear 41 connected to the upper end of a filter cartridge 32, the gear 41 being fitted with bearings 18 to connect with an upper partition wall 17. An operation mechanism 40 to 41 is located in a second space 16b defined by a cover disk 11 a and the partition wall 17. This second space 16b gives onto an assembly 14 from which the filtered flow D is aspirated to a vacuum pump (not show in Fig. 2).

In the embodiment of Fig. 2, six filter cartridges are used; naturally depending on the process parameters, however, some other number of filter cartridges may be used, for example only one cartridge or even twenty cartridges.

The following provides, with reference to Figs. 2 to 5, a more specific explanation of the structure and operation of a preunit 3 which is a significant feature of the present invention comprised of contact surfaces 24a and 24b and reagent feeds 23a, 23b arranged in connection with the preunit.

In Fig. 2, reagent flow R is aspirated using the vacuum of the purification apparatus 3 at least partly through a rotating feedthrough 21 and a vertical pipe 20 to the reagent feeds 23a and 23b connected to the lower end of the vertical pipe 20. The reagent feeds 23a and 23b may be made of rigid pipe or, favourably, flexible elastic tube. In the embodiment of Fig. 2, there are two reagent feeds due to the symmetry; however, the apparatus may also include, for example, one, three or four reagent feeds.

In Fig. 2, the contact surface of the apparatus is comprised of two parts: a cylindrical contact surface 24a and a frame-like contact surface 24b. The reagent feeds 23a and 23b have been connected to the vertical pipe 20 and, at the same time, in connection with the contact surface 24b, which contact surface 24b is preferably frame-like. The vertical pipe 20 thus both leads to the reagent feeds 23a, 23b and rotates the contact surface 24b and the reagent feeds 23a, 23b. Reaction gases come into contact with each other in the reagent feeds 23 and 23b in connection with the contact surfaces 24a and 24b of the discharging reagent. The contact surface 24b is also referred to as a first contact surface, whereas the contact surface 24a is also called a second contact surface. After coming into contact with the reagent, the residual gases react and are converted, at least partly, to reaction residue which has at least partly grown to the contact surfaces 24a and 24b. In comparison to flow-through based filter solutions, the residual gas to be purified never flows through the surfaces of the contact surfaces 24a, 24b; thus, the clogging issues related to flow-through may largely be avoided when the gas purifying reaction is allowed to take place in connection with the contact surfaces. Especially, this solution affords a very favourable gas prepurifying before the actual, preferably flow-through based, filtering section 3b. With the preunit 3a, a substantially more pure flow reaches the filtering section 3b of the purifying apparatus 3 than without it. Accordingly, the stress on the filtering section 3b is essentially reduced and the overall need for maintenance of the purifying apparatus 3 is decreased and becomes more simple.

Without the purifying arrangement of the preunit 3a, a significant amount of reaction residues might accumulate within the preunit or the reagent feeds 23a and 23b might become more constricted or even totally clogged up. This essential drawback may be avoided by rotating the contact surface 24b. The contact surface 24b or the reaction residue grown on it, while in move, rubs against the contact surface 24a or the reaction residue grown on it, thus dislodging reaction residues from both the contact surface 24a and 24b.

To make the purifying action of the preunit more efficient, to the trajectory of the outer ends of the reagent feeds 23a, 23b and of the outer perimeter of the contact surface 24b one or more protrusions may further be arranged, for example, in the form of pins or other, for example, elongated protrusions 25, which the outer ends of the reagent feeds 23a, 23b and/or the contact surface 24b or at least their reaction residue growth hits, thus becoming efficiently dislodged. Preferably, the protrusions 25 have been connected to the contact surface 24a. The reagent feeds 23a and 23b and the contact surface 24b may be, at least partly, elastic such that they also bend while passing by the protrusions 25 and are also subjected to a purifying, mechanical, spring-like hitting motion. Thus, both the ends of the reagent feeds 23a and 23b and the contact surfaces 24a and 24b are subjected to purifying mechanical forces by the reaction residues. The ends of the reagent feeds 23a and 23b, in other words, their mouths or openings, may also be chamfered such that they come progressively into contact with the protrusions 25. This decreases the wear and tear of the ends of the reagent feeds 23a, 23b.

The rotation of the contact surface 24b and its connected parts, such as the reagent feeds 23a, 23b, may be arranged using either a freely rotating arrangement or, alternatively, so that the contact surface 24b and its connected parts are only allowed to rotate in limited fashion about the vertical pipe 20, for example, preferably 300° or 350°. In this connection, the term "rotating" is to be understood either as freely rotating or as having a limited rotational motion. The limited rotation simplifies the connection of the rotational feedthrough 21 as the connection may be made, for example, of flexible hose without the need for a fully rotational feedthrough.

In time, the said reaction residues dislodged by the above described purifying action are accumulated as layers on the base 11 b from where they are easily removed, for example, in connection with the scheduled maintenance of the apparatus 3 or through a purifying door or doors dedicated to this purpose

(not shown in Fig. 2).

In the embodiment of Fig. 2, the contact surface 24b and the reagent feeds 23a and 23b attached to the contact surface 24b are arranged to be movable, and contact surface 24a is fixed. It is obvious that to achieve the cleaning effect, contact surface 24a can also be arranged to be movable, while maintaining contact surface 24b and reagent feeds 23a and 23b fixed. Further, both contact surface 24a, and contact surface 24b with reagent feeds 23a and

23b, can be arranged to be movable relative to each other. It is also obvious that reagent could be fed from one outlet only to achieve the effect of the present invention.

In other words, what matters is the relative movement of the two contact surfaces (and the at least one reagent feed attached to one of the contact surfaces) relative to each other to achieve the appropriate cleaning effect of the filter preunit parts. The at least one reagent feed can be attached either to the moving contact surface or to the fixed contact surface. In case there are several reagent feeds, some or all of the reagent feeds can be connected to the fixed contact surface, or some or all of the reagent feeds can be contacted to the moving contact surface. For example, fig. 2 shows an embodiment where all of the reagent feeds (there two of them) are contacted to the moving contact surface.

Fig. 3 shows a detailed 3D partial enlargement view of the structure of the contact surfaces 24a, 24b of Fig. 2 and the reagent feeding solution 23a, 23b. The structure of the contact surface 24b is frame-like and consists preferably of stainless steel sheet strips cut to shape and fixed with screws to each other. As in Fig. 2, due to the 3D cross section of Fig. 3 it only shows half of the structure of the contact surface 24b essentially symmetrical with regard to the cross section surface in the figure. The contact surface 24b is connected to a vertical pipe 20 fitted to the rotating feedthrough 21 and through which the contact surface is being rotated. The vertical pipe 20 may also receive its rotational force from the rotational mechanism of the filtering apparatus 3b filter cartridges, or the rotational force may be arranged separately via either a hand crank, motor or some other actuator. Fig. 3 shows a manually operated turning handle 26 which is rotated to move the contact surface 24b and reagent feeds 23a, 23b. The vertical pipe 20 leads to the reagent feeds 23a, 23b which are also rotating with the rotating vertical pipe 20. During the rotation, the contact surface 24b rubs against the cylindrical contact surface 24a. To enhance the efficiency of the purifying action, the contact surface 24a may be fitted with elongated protrusions 25 or, for example, pins that also hit the contact surface 24b and/or the mouths of the reagent feeds 23a, 23b as they rotate past and over the protrusion 25.

The contact surface 24b is preferably frame-like to prevent the reaction residue growing on it from creating heavy, large agglomerations, as the surface area available for growth is small. The contact surface 24b may also be a partly or fully threadlike structure, for example, it may consist of a steel thread 1 mm in thickness (not shown in the figure), or, alternatively, it may consist of a completely uniform sheet (not show in the figure), a perforated sheet (not show in the figure), or it may be, for example, paddle wheel like comprising, for example, four contact surface parts arranged to a 90° angle in relation to each other (not shown in the figure).

According to the semantic Fig. 4, the reagent feeding solution 23c may also be implemented to be in connection with a fixed cylindrical part 24a of the contact surface. In this embodiment, the frame-like contact surface 24a rotated about its axis 20a, while moving, purifies by scraping both itself as well as the end of the reagent feeding pipe 23c and the contact surface 24a. The part 13 represents the residual gas input assembly to the preunit. There maybe one or more reagent feeding pipes 23c in connection with the contact surface 24a, either in the jacket or in connection with the upper or lower edge of the contact surface 24a.

In accordance with Fig. 5, the motion of the contact surface 24c may be achieved by other means than rotational motion, too. In Fig. 5, the contact surface 24c moves reciprocatingly in a piston-like manner, up and down in the figure, in the inner space created by the contact surface 24a and guided by an axis 20a, thus scraping the reaction residues from itself and the contact surface 24a and the mouth of reagent feed 23c. The reciprocating, or piston-like, motion may be achieved in several ways, for example, hydraulically, by using a pinion rack or an electrical or magnetic actuator 26, or the motion may be brought about by utilizing a crank mechanism and the rotational motion of the filtering apparatus 3b filter cartridges (the crank mechanism is not shown).

As described above, the apparatus according to the invention is also suited to be used in connection with other chemical deposition processes, for example, CVD or plasma etching processes, which generate reaction residues which must be filtered or removed from the gas flow for various reasons. It is apparent that the gas flows may be brought about by using a positive pressure pump or pumps arranged in the beginning of the flow or by using a vacuum pump or pumps arranged to the end of the flow or by using combinations of such pumps.

It is apparent to those skilled in the art that as technology evolves, the basic idea may be fulfilled in various ways. Thus, the invention and its embodiments are not limited by the above described examples, but they may vary within the scope of claims.

Claims

1. A filter preunit (3a) for chemical vapour deposition processes, which

preunit is used to remove reaction residues from a residual gas flow, the preunit (3a) comprising at least two contact surfaces (24a, 24b, 24c), in the vicinity of which the residual gas flow (C) and reagent flow (R) have been arranged to come into contact with each other and at least one of which is arranged to be moved to purify the contact surfaces (24a, 24b, 24c) from reaction residues grown on them, characterized in that the mouth of at least one of the reagent feeds (23a, 23b) in connection with the first contact surface (24b) or the reaction residue grown on it has been arranged to hit the second contact surface (24a) or the reaction residue grown on if while at. the same time purifying the mouth/mouths of the reagent feed/feeds (23a, 23b) through the action of the relative motion of the first (24b) and the second (24a) contact surfaces.

2. The preunit according to claim 1 , characterized in that the said relative motion is a rotational motion.

3. The preunit according to claim 1 , characterized in that the said relative motion is a reciprocating motion.

4. The preunit according to anyone of claims 1 to 3, characterized m that the first contact surface (24b) or the reaction residue grown on it has been arranged to hit the protrusions (25). arranged in connection with the second contact surface (24a) by the action of the said relative motion.

5. The preunit according to anyone of claims 1 to 4, characterized in that at least one of the contact surfaces (24a, 24b) is a frame-like or a threadlike structure.

6. The preunit according to anyone of claims 1 to 5, characterized in that the first contact surface (24b) is mobile and the other contact surface (24a) is immobile.

7. The filter preunit according to anyone of claims 1 to 6, characterized in that the preunit (3a) feeds prepurified residual gas to the filtering apparatus 3b, which apparatuses (3a, 3b) are integrated into a compact purifying apparatus within a common outer jacket (10, 1 a, 1 1 b).

8. The filter preunit according to claim 7, characterized in that the filtering apparatus (3b), to which the filter preunit feeds prepurified residual gas, is a flow-through based filtering apparatus.

9. The filter preunit according to claim 7 or claim 8, characterized in that the filtering apparatus, to which the filter preunit feeds prepurified residual gas, has been fitted with several cylindrical filter cartridges (31 , 32) rotated via drive elements.

10. The filter preunit according to anyone of claims 7 to 9, characterized in that in the filtering apparatus, to which the filter preunit feeds prepurified residual gas, the middle filter cartridge (31) has been placed essentially on the vertical center axis of the jacket (10), with the other filter cartridges around it.