Patent Application
20100006472
This application is based on and claims the benefit of French patent application Ser. No. 08/54,769, filed on Jul. 11, 2008, which is incorporated by reference herein in its entirety.
The present invention relates to a drain device for a transporting box used for the displacement of semiconductor substrates between the different stages in the production of semiconductor and microelectronic components, for example for the production of micro-electro-mechanical system (MEMS) or micro-opto-electro-mechanical system (MOEMS) components.
During production, the substrates, such as masks or slices of silicon 200 mm or 300 mm in diameter for example, are transported in transporting boxes which protect them against the pollution present in the atmosphere in clean rooms.
The transporting boxes have the advantage of being able to maintain a controlled atmosphere around the substrates, in which the presence of contaminating products is avoided as far as possible. For the transport of substrates in wafers 300 mm in diameter, one particular type of transporting box is used, known as an FOUP (“Front Opening Unified Pod”), comprising a sealed peripheral wall with a lateral input-output opening, which can be blocked by a door equipped with sealing means. In a transporting box, the wafers are stacked on top of each other in a sort of rack, which may also be referred to as a cassette or a basket. The basket containing up to 25 wafers is generally placed or held on the wall which constitutes the base of the transporting box.
The transporting box may be coupled to an input-output interface for the semiconductor component manufacturing equipment. The interface is a system allowing the transporting box to be positioned and its door to be opened. The interface usually comprises robotic means of activating the door to open and close the door of the transporting box. This interface (sometimes also known as a mini-environment), is usually known as an Equipment Front End Module, or EFEM.
Control of the contamination during the production of electronic chips is a major challenge for the semiconductor industry. The contamination may be caused by particles or gases, which cause corrosion or form crystals on the wafers for example. Contamination may have dramatic consequences for chip manufacturers since the performances of the chip will be severely reduced by these faults.
There are solutions to limit the contamination by installing drain systems in the substrate transporting boxes, advantageously using the vacuum or a neutral gas. However, these drain systems may only be used when the transporting box is detached from the equipment (US-2007-062,561; JP-2007-317 909), in other words when it is closed. This causes two problems.
The first problem concerns the duration of the draining operation, in other words the time to replace the contaminated atmosphere inside the transporting box with a clean neutral gas, for example nitrogen. Therefore, draining a closed transporting box requires the clean gas to be injected through drain ports which have the disadvantage of not being standard and which have a limited effect. It therefore takes more than 10 minutes to incompletely drain a box (R. Bernard and A. Favre: “Using numerical simulation to optimize 300 mm FOUP purging”, Solid State Techn., October 2003, p. 71). Furthermore, the vacuum process requires the transporting box to be placed in a vacuum and a return to atmospheric pressure progressively so as avoid the risk of damaging the box.
The second problem is that a transporting box containing the substrates may remain connected to the equipment for several hours. Even though it is possible to carry out a draining operation after having treated the entire batch of substrates contained in the transporting box, irreversible faults have already appeared.
The invention in one implementation encompasses a drain device for a transporting box with an input/output opening which a box door can block and which contains substrate wafers stacked based on parallel planes. The drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts. The drain device also comprises a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box.
The invention in another implementation encompasses a drain system of a transporting box, with an input/output opening which a box door can block and containing a stack of substrate wafers based on parallel planes, using a drain device for the transporting box. The drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box. The drain system comprises a chamber with at least one connection orifice to a transporting box equipped with a chamber door, and comprising means of activating the box door to open and close the door of the transporting box and means of activating the drain device to connect it to the transporting box.
In yet another implementation, the invention encompasses a drain method for a transporting box with an input/output opening which a box door can block and which contains substrate wafers stacked according to parallel planes, using a drain device for the transporting box. The drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box. The drain device is connected to the input/output opening of the transporting box. A purging gas is injected in the upper part of the volume of the drain device through the purging gas inlet orifice. The gas is inserted into the transporting box through openings, the median plane of which is parallel to the wafer planes and which connect with the upper part of the volume of the drain device. The gas is collected through openings, the median plane of which is parallel to the wafer planes and which connect with the lower part of the volume of the drain device. The gas is evacuated through the purging gas outlet orifice in the lower part of the volume of the drain device.
Other characteristics and advantages of the present invention will become apparent upon reading the following description of one embodiment, which is naturally given by way of a non-limiting example, and in the attached drawing, in which:
a, 2b and 2c show in diagram form the way in which a FOUP transporting box is connected to a drain system according to one embodiment of the invention,
a and 3b represent perspective views, of the two faces respectively, of a drain device according to one embodiment of the invention,
One embodiment of the present invention provides a device to effectively drain an FOUP transporting box, containing substrate wafers, while it is still connected to the equipment.
The invention also provides a drain device which can be adapted to all standard FOUP type transporting boxes.
A wafer is extracted or inserted into the transporting box approximately every 2 to 3 minutes. It is therefore a time constraint to carry out the draining operation as a background task during the treatment of a batch of substrates. The invention therefore also provides a draining method which can be used to obtain an efficient draining of a FOUP transporting box in under 3 minutes when it is connected to the equipment.
The present invention provides a drain device for a transporting box with an input/output opening which can be blocked by a box door and which contains substrate wafers stacked on parallel planes, comprising:
According to one preferential execution method, the dimensions of the openings in relation to the purging gas inlet orifice are such that the upper part of the drain device is in overpressure. It is understood that the total surface area of the connection openings between the upper part of the drain device and the transporting box must be sufficiently small.
The number of openings should preferably be at least equal to the number of wafers contained in the transporting box so as to direct the purging gas respectively towards each wafer. Transporting boxes may usually contain between 1 and 25 wafers.
According to a first embodiment of the invention, the openings are rectangular slots. Advantageously, the openings have a length of the same order of magnitude as the diameter of the substrate wafers. Preferably, the rectangular slots have a height of less than the distance separating two successive wafers, or around 10 mm, and the slots are preferably less than 3 mm high.
According to a second embodiment, the openings consist of aligned holes. Advantageously, the holes are aligned over a distance of the same order of magnitude as the diameter of the substrate wafers. The holes are preferably circular and have a diameter lower than the distance separating two successive wafers, and the holes preferably have a diameter of less than 2 mm.
According to one variant, the drain device comprises among other things a range of guides inserted between the openings. The number of guides is preferably at least equal to the number of wafers contained in the transporting box. These guides are used to direct the gas stream as close as possible to the wafers.
According to one execution method, the guides have a length of the same order of magnitude as the diameter of the substrate wafers.
According to another execution method of the invention, the guides are arranged in the planes of the wafers. Therefore, each guide is presented in the same plane as the wafer to which it corresponds. Advantageously, the end of each guide has a concave form which matches the form of the corresponding circular wafer.
Preferably, the drain device also comprises sealed connection means at the input/output opening of the transporting box.
The invention also provides a system for draining, using the drain device described previously, a transporting box with an input/output opening which can be blocked by a box door and containing a stack of substrate wafers. According to one embodiment of the invention, the drain system comprises a chamber, with at least one connection orifice to a transporting box equipped with a chamber door, and comprises means of activating the box door to open and close the transporting box door and means of activating the drain device to connect it to the transporting box.
The idea is to affix a drain device forming a door in the place of the door of the transporting box, and to use this drain device to inject a clean gas into the transporting box.
The drain system also comprises sealing means at the coupling zone of the connection orifice to the input/output opening of the transporting box.
The invention also provides a method for draining, using the drain device described previously, a transporting box with an input/output opening which can be blocked by a box door and containing substrate wafers stacked on parallel planes. According to one embodiment of the invention, the method includes the following stages:
Advantageously, the purging gas is injected into the upper part of the drain device at a pressure greater than 2 bars.
The drain method with the drain device according to one embodiment of the invention acts by forced convection between the substrate wafers. It is used to gain efficiency in relation to existing drain devices acting by diffusion. The draining operation is quicker: 1 minute instead of several minutes. After 1 minute of circulation of the purging gas at 50 slm, there remains on average less than 3.4% dioxygen in the transporting box.
This drain device and this drain method can be used with all FOUP type transporting boxes currently in service.
For an equivalent flow, the neutral gas enters the transporting box at a much lower speed than if the draining is carried out using drain orifices arranged in the back wall of the standard transporting boxes. For this reason, there are fewer particles detached and blown inside the transporting box. Furthermore, backscattering is not possible for these particles, therefore the wafers are protected against any risk of redeposition.
The draining operation may be used either at the end of the treatment before reclosing and disconnecting the transporting box, or as a background task during the treatment between two wafer transfer operations. The time required to reach a draining efficiency of greater than 90% is less than 2 minutes with a purging gas flow of 30 slm. This time is shorter than the duration passing between two wafer transfers.
A substrate treatment installation is shown in
a, 2b and 2c correspond to the successive stages of the coupling of a FOUP type transporting box to the drain device according to one embodiment of the invention.
a shows a drain system 20 according to one embodiment of the invention comprising a chamber 21 with sealed walls comprising at least one orifice 22 to allow the coupling of a transporting box 23. A basket 24 containing substrate wafers arranged horizontally is placed in the transporting box 23. The transporting box 23 comprises side walls 23a, a top wall 23b and a bottom wall 23c on which the basket rests 24. In one of the side walls 23a, there is an input/output opening blocked by a door 25. The door 25 is placed opposite the orifice 22 of the drain system 20. A drain device 26 according to one embodiment of the invention is placed in the lower part of the chamber 21. If the drain system 20 provides the functions of an EFEM module, it also comprises a second orifice 27 able to be connected to the loading/unloading lock for a substrate treatment installation.
Once the transporting box 23 is placed opposite the orifice 22 of the drain system 20, its door 25 is unlocked using means of activating the box door, then moved to the lower part of the chamber 21 for example, in order not to hinder the displacement of the wafers to the loading/unloading lock, as shown in
The drain device 26 is positioned by robotic means of activation in the place of the door 25 of the transporting box 23 in order to drain the transporting box 23 and the substrate wafers it contains, as shown in
A specific embodiment of the drain device according to the invention is represented in
The drain method will now be described in reference to
After flushing the wafers located in the top of the basket 56, the purging gas returns to the lower part 60 of the drain device volume 50, flushing the wafers located in the bottom of the basket 56, as shown by arrows 61 and 62. The purging gas then escapes through the outlet orifice 63.
The openings 54 are dimensioned in relation to the gas inlet orifice 52 in such a way that the upper part 53 of the drain device 50 is in slight overpressure, in order that the neutral and clean gas can enter homogeneously in the transporting box 51. The openings 54 may take the form of slots with a low height or a series of aligned holes with a low diameter, for example with a diameter of less than 2 mm. A low cross section for these openings 54 allows gas input with homogeneous distribution over the entire surface of the upper part 53 of the drain device 50.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08/54 769 | Jul 2008 | FR | national |
