Title of the invention: Device for measuring the gaseous contamination of a carrier for transporting semiconductor substrates and associated measurement method

[1] The present invention relates to a device and a method for measuring the gaseous contamination in a transport carrier for conveying and storing semiconductor substrates at atmospheric pressure.

[2] In the semiconductor fabrication industry, transport carriers such as FOUPs (Front

Opening Unified Pod) or RSPs (Reticle Storage Pod) make it possible to transport the substrates, such as semiconductor element wafers or photomasks, from one item of equipment to the other or to store the substrates between two fabrication steps.

[3] These transport carriers determine a confined space under atmospheric pressure, separated from the environment of use and of transport of the substrate, for the transport and storage of one or more substrates in clean rooms, in which the interior atmosphere is maintained with a very low contamination rate. These transport carriers are standardized elements, the opening and the closure of which can be managed automatically directly by the fabrication equipment.

[4] The transport carriers comprise a rigid peripheral casing, the aperture of which can be shut off by a removable door, a door seal being interposed between the door and the casing. However, the transport carrier is not totally airtight because breathing ports equipped with filters are provided in the casing or the door so as to allow equalizing of pressures between the interior and the exterior of the carrier.

[5] To further reduce the risks of contamination in the interior of these carriers, it is currently recommended to regularly purge the internal atmosphere of these carriers.

[6] The interior atmosphere of the carrier is important to control because it is directly linked to the production yield. However, the majority of the carriers on the market leak to a greater or lesser extent such that outside air can enter the carrier, notably at the door seal, and contaminate the substrates, in particular when the pressure in the interior of the carrier is lower than the exterior pressure and the outside air contains traces of corrosive gas and/or moisture. Equally, the substrates in the interior of the carriers may degas gaseous contaminants from preceding fabrication steps. The presence of corrosive gas and/or moisture in the interior of the transport carrier may then result in the reduction in the number of usable electronic chips on a wafer or may result in damage to a photomask, and this may have particularly detrimental consequences because the value of a mask is very high.

[7] Therefore, it is necessary for it to be possible to measure the level of gaseous contamination of a transport carrier in a simple manner in order to avoid damage to the substrates that it contains.

[8] A known solution consists in measuring the interior atmosphere of the carrier by taking a sample of gas through a breathing port. It is thus possible to measure the molecular contamination of the carrier without needing to open it.

[9] However, the aspiration of the interior atmosphere of the carrier for measurement may promote a compensatory intake of outside air through the leaky parts of the carrier, and notably through the door. This compensatory intake of outside air may contain traces of gaseous contaminants, and this may result in the contamination of the substrates and render the establishing of a reliable measurement of the contamination of the carrier difficult to implement.

[10] One of the aims of the present invention is therefore to propose an improved device and an improved method for measuring the contamination of a transport carrier for conveying and storing semiconductor substrates at atmospheric pressure.

[11] To that end, the subject of the invention is a device for measuring the gaseous contamination of a transport carrier for conveying and storing at least one semiconductor substrate at atmospheric pressure, said carrier comprising a door and a shell that can be closed by the door at a seal region, the carrier being provided with at least one breathing port, the measuring device comprising at least one analyser configured to measure the concentration of at least one gaseous contaminant, the measuring device comprising:

- an interface configured to be coupled to the transport carrier, said interface comprising a platform facing which the door of the transport carrier is intended to be coupled so as to provide a gap between the platform and the door,

- a measuring head connected to said at least one analyser and configured to be coupled in an airtight manner to one of the at least one breathing ports of the transport carrier,

- at least one injection nozzle configured to inject a controlled gas into the gap formed between the platform and the door, such that the controlled gas spreads out at least towards the seal region surrounding the door.

[12] The use of a platform on which the carrier is coupled so as to provide a gap facing leaky regions of the carrier, and of an injection nozzle configured to inject a controlled gas into the gap during a contamination measurement, makes it possible to reduce the risk of contamination of the substrates during a contamination measurement without needing to modify the carrier. In addition, this solution is simple to implement.

[13] The present invention may also relate to one of the following aspects, which may be considered separately or in combination to form new embodiments.

[14]- The platform comprises at least two spacers which are configured to offset the transport carrier from the platform in order to form the gap, the height of which is between 0.1 mm and 10 mm, notably 1 mm;

[15]- the flow rate of the controlled gas injected into the gap is between 1 and 20 L/min, notably between 1 and 10 L/min, notably 5 L/min, so as to fill the gap formed between the platform and the door with the controlled gas;

[16]- the controlled gas comprises one of the following gases:

- compressed dry air (CD A),

- extreme clean dry air (XCDA),

- nitrogen (N2);

[17] - at least one breathing port, such as at least two breathing ports, is provided in the door of said carrier;

[18]- at least one breathing port, such as at least two breathing ports, is provided in the shell of said carrier;

[19] - the injection nozzle is provided in the platform so as to face the centre of the door or in a region close to the centre of the door, for example within a radius of 5 cm around the centre of the door;

[20]- the interface comprises one or more injection rails extending facing the seal region at the perimeter of the door of the carrier;

[21]- the interface comprises positioning pins and the carrier comprises blind orifices which are complementary to the positioning pins and which are configured to receive the positioning pins of the interface;

[22]- the interface comprises at least one clamping mechanism configured to hold the carrier coupled to the interface.

[23] The present invention also relates to a method for measuring the gaseous contamination of a transport carrier for conveying and storing at least one semiconductor substrate at atmospheric pressure, said carrier comprising a door and a shell that can be closed by the door at a seal region, the carrier comprising at least one breathing port, said method comprising the following steps:

- a step of positioning the carrier on an interface of a measuring device, the measuring device comprising a platform which the door of the carrier is intended to come to face,

- a step of coupling the carrier to the measuring device in which a measuring head of the measuring device is coupled to one of the at least one breathing ports of the carrier,

- a step of injecting a controlled gas into a gap formed between the platform and the door such that the controlled gas spreads out at least towards the seal region surrounding the door,

- a step of aspirating gases from the carrier by way of the measuring device via the measuring head,

- a step of measuring the contamination of the gas aspirated via the measuring head by way of an analyser of the measuring device.

[24] Other features and advantages of the invention will become more clearly apparent upon reading the following description, which is given by way of illustrative and non-limiting example, and from the appended drawings, in which:

[25] [Fig 1] shows a schematic view of a measuring device and of a transport carrier according to a first embodiment;

[26] [Fig 2] shows a schematic view of a door of a carrier according to a first embodiment;

[27] [Fig 3] shows a schematic view of a platform of a measuring device;

[28] [Fig 4] shows a flow chart of the steps of a method for measuring the contamination according to the present invention;

[29] [Fig 5] shows a schematic view of a transport carrier coupled to a platform of a measuring device;

[30] [Fig 6] shows a schematic view of a measuring device and of a transport carrier according to a second embodiment;

[31] [Fig 7] shows a schematic view of a measuring device and of a transport carrier according to a third embodiment.

[32] In these figures, identical elements bear the same references.

[33] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment or that the features apply to a single embodiment. Individual features of different embodiments can also be combined or interchanged to provide other embodiments.

[34] The present invention relates to a device and a method for measuring the gaseous contamination of a transport carrier for conveying and storing semiconductor substrates at atmospheric pressure.

[35] Figure 1 shows a schematic view of a transport carrier 2 configured to be coupled to an interface 3 of a device 1 for measuring the contamination of the carrier 2, the measuring device 1 comprising a platform 5 for receiving the carrier 2. In the case of Figure 1, the platform is oriented horizontally, but other orientations are also possible.

[36] The carrier 2 is configured to receive at least one semiconductor substrate 6 such as a photomask or wafers so as to allow them to be conveyed and stored between the semiconductor fabrication steps and to avoid contamination of the substrates 6. The interior atmosphere of the transport carriers 2 is at the atmospheric pressure of air or of nitrogen or around atmospheric pressure, such that Pa +/- 5%Pa. Standardized side opening boxes of the FOUP (Front Opening Unified Pod) type or standardized side opening boxes of the MAC (Multi-Application Carrier) type or bottom opening boxes of the SMIF (Standard Mechanical InterFace) type or photomask transport boxes of the RSP (Reticle SMIF Pod) type are for example concerned. [37] The carrier 2 comprises a casing 4 formed by a removable door 4b and a rigid shell

4a that can be closed by the door 4b at a peripheral seal region 7. The door 4b and the shell 4a are for example made of plastics material. The door 4b is situated at the lower face of the carrier 2 and is configured to come to face the platform 5. As an alternative, the door 4b may be disposed differently, notably on a side of the carrier 2.

[38] The door 4b is provided at least with a first breathing port 9 and a second breathing port 11, each port comprising a through-orifice obstructed by a particle filter 12 and/or by a closure flap (not shown) preventing the entry of particles into the interior of the carrier 2. The breathing ports 9, 11 allow the transport carrier 2 to equalize the internal atmosphere with the exterior atmosphere.

[39] A purging gas may thus be injected into the carrier 2 at one breathing port 11, the surplus gas being discharged through another breathing port 9. In the example illustrated in Figure 2, the door 4b comprises four breathing ports 9, 11, 13, 15.

[40] One breathing port 9 is used as sampling port for sampling and analysing the internal atmosphere of the carrier 2. The other breathing port or ports 11, 13, 15 may therefore enable the introduction of gas into the carrier 2, notably for replacing the air sampled by the breathing/ sampling port 9.

[41] As shown in Figure 2, the door 4b may also comprise blind orifices 17, for example three blind orifices 17, which are intended to position the carrier 2 on the platform 5 of the device 1 for measuring the contamination.

[42] As shown in Figure 3, the platform 5 of the device 1 for measuring the contamination comprises positioning pins 19 which are complementary to the blind orifices 17 of the door 4b, the blind orifices 17 of the door 4b being configured to receive the positioning pins 19 when the carrier 2 is positioned on the platform 5.

[43] The platform 5 may also comprise spacers 21, notably four spacers 21, which are for example arranged at the corners of a square as in the exemplary embodiment in Figure 3 and against which the carrier 2, and notably the door 4b, comes to rest in the case of Figures 1 to 3. The spacers 21 are configured to create an offset between the carrier 2 and the platform 5, forming a gap of a height h of between 0.1 mm and 10 mm, notably equal to 1 mm as shown in Figure 5 in which the carrier 2 is coupled to the platform 5.

[44] As an alternative, the positioning pins 19 and the orifices 17 may also be configured to perform the function of spacers and to enable the creation of the gap between the platform 5 and the carrier 2 in the state when the carrier 2 is coupled to the platform 5.

[45] The platform 5 also comprises a measuring head 23 comprising an aspiration nozzle

25. The aspiration nozzle 25 may protrude above the platform 5 so as to allow coupling to the breathing port 9 when the carrier 2 is positioned on the platform 5 as shown in Figure 5. [46] As an alternative, the aspiration nozzle 25 may be movable in translation and be driven by a displacement device such as an electric or pneumatic ram. The displacement device is then configured to displace the aspiration nozzle 25 towards the carrier 2 positioned on the platform 5. This displacement brings about the coupling between the aspiration nozzle 25 and the breathing port 9.

[47] The coupling of the aspiration nozzle 25 and of the breathing port 9 enables an airtight connection between the interior of the carrier 2 and an aspiration line 27 connected to the aspiration nozzle 25.

[48] The aspiration line 27 is connected to an analyser 29 of the measuring device 1, comprising a sampling device 31, for example a diaphragm pump.

[49] The analyser 29 is configured to measure the concentration of at least one predefined contaminant, for example moisture, ammonia (NH3), ozone (O3), hydrofluoric acid (HF), hydrochloric acid (HC1), volatile organic compounds (VOC), sulfur-based compounds (SO2, H2S, etc.), nitrogen oxide (NOx), etc.

[50] The aspiration line 27 may comprise a valve 32 which allows or does not allow the passage of gas from the aspiration nozzle 25 to the analyser 29.

[51] As an alternative, the sampling device 31 may be external to the analyser 29 and be configured to aspirate the gases from the aspiration nozzle 25 to the analyser 29.

[52] In practice, the device 1 for measuring the contamination may comprise a plurality of analysers 29 which are connected to a common aspiration line, valves then allow or do not allow fluidic communication to be established between the common aspiration line and the different analysers 29.

[53] It should be noted that, in this case, there is no valve blocking the common aspiration line in order to avoid the analysers 29 being evacuated. Furthermore, the aspiration line 27 (or common aspiration line) may be connected to several aspiration nozzles 25. In this case, one or more X-way valves may be positioned so as to select the breathing port or ports to which the analyser or analysers 29 are fluidically connected.

[54] The platform 5 also comprises an injection nozzle 33 configured to inject a controlled gas into the gap formed between the platform 5 and the carrier 2. The controlled gas is for example compressed. A valve 36 may be disposed between the gas inlet 34 and the injection nozzle 33 in order to control the gas flow rate. The controlled gas corresponds, for example, to compressed dry air (CDA), extreme clean dry air (XCDA) or nitrogen (N2).

[55] In the case of Figure 3, the injection nozzle 33 is disposed at the centre of the platform 5 such that the gas is injected facing the centre of the door 4b and spreads out in the gap formed between the platform 5 and the door 4b over the entire area covered by the door 4b and in particular towards the seal region 7 and the breathing ports 11, 13, 15.

[56] The injection nozzle 33 may also be placed in a region close to the centre of the platform 5, for example within a radius of 5 cm around the centre of the platform 5.

[57] As an alternative, the number and the position of the injection nozzle or nozzles 33 may be different. In particular, a set of injection nozzles 33, for example in the form of injection rails, may be disposed facing the periphery of the door 4b, notably facing the seal region 7.

[58] An injection nozzle 33 may also be positioned facing a breathing port 11, 13, 15 in order to optimize the effectiveness of the compensation as shown in Figure 6. In addition, in the case of Figure 6, an analyser 29 is connected to two aspiration nozzles 25 via two different aspiration lines 27, two valves 32 which are respectively disposed in the two aspiration lines 27 make it possible to select the aspiration nozzle/nozzles which are fluidically connected to the analyser 29.

[59] According to another embodiment shown in Figure 7, the aspiration nozzles 25 and injection nozzles 33 may be combined to form aspiration/inj ection nozzles 40. The aspiration/inj ection nozzles 40 are connected, for the one part, to the analysers 29, and, for the other part, to the gas inlet 34. The establishing of fluidic communication between the aspiration/inj ection nozzles 40 and one or more analysers 29 or with the gas inlet 34 is controlled by valves 32 disposed in the lines 27 and valves 36 disposed between the gas inlet 34 and the lines 27.

[60] The device 1 for measuring the contamination may also comprise means for holding the carrier 2 on the platform 5 so as to allow the carrier 2 to be held in position on the platform 5 during the contamination measurement.

[61] According to one embodiment shown in Figure 3, the holding means are realized by a clamping device 35 comprising two grips which are arranged facing one another. The grips are mounted so as to be able to pivot between a holding position, for which pads bear against the shell 4a in order to hold the carrier 2 coupled to the platform 5, and a releasing position, in which the pads are moved away from the carrier 2. Other means of fastening, notably by snapfastening, can also be used.

[62] The different steps of a method for measuring the gaseous contamination of a transport carrier 2 using the measuring device 1 presented above will now be described on the basis of the flow chart in Figure 4. The order of the steps may be different from the order presented and certain steps may be simultaneous.

[63] The first step 101 relates to a step of positioning the carrier 2 on the interface 3 of the measuring device 1.

[64] In the case of Figures 1 to 3 and 5, the door 4b of the carrier 2 faces the platform 5 and the blind orifices 17 of the door 4b engage with the positioning pins 19. The carrier 2 also comes into contact with the spacers 21 so as to form a gap between the carrier 2 and the platform 5, and notably between the door 4b of the carrier 2 and the platform 5 as shown in Figure 5. The height h of the spacers 21 and therefore of the gap is between 0.1 mm and 10 mm, for example 1 mm.

[65] The second step 102 relates to a step of fastening the carrier 2 on the interface 3 of the measuring device 1. This fastening is effected for example by actuation of the grips of the clamping device 35.

[66] The third step 103 corresponds to a step of coupling between the measuring head 23 and the breathing port 9, the coupling being effected for example by interlocking engagement. A seal may be integrated into the measuring head 23 in order to improve the airtightness.

[67] This step may be carried out simultaneously with steps 101 and 102, the clamping ensuring the coupling between the measuring head 23 and the breathing port 9. The coupling makes it possible to obtain an airtight connection between the interior of the carrier 2 and the measuring device 1.

[68] The fourth step 104 corresponds to a step of injecting a controlled gas via the injection nozzle or nozzles 33 into the gap formed between the platform 5 and the door 4b such that the controlled gas spreads out at least towards the seal region 7 surrounding door 4b.

[69] The controlled gas is, for example, compressed dry air (CD A), extreme clean dry air (XCDA) or nitrogen (N2). The flow rate of the injected gas is dependent on the height of the gap between the carrier 2 and the platform 5, should preferably be greater than the aspiration flow rate of the measuring head 23 and is for example between 1 L/min and 20 L/min, notably between 1 L/min and 10 L/min, for example 5 L/min for a gap of 1 mm. The flow rate is notably adjusted in such a way that the controlled gas spreads out in the entire gap and in particular facing the seal region 7, forming a blanket or cushion of controlled gas, such that the gas aspirated from the carrier 2, notably through the seal region 7, during the contamination measurement is predominantly, or even completely controlled gas.

[70]If the carrier 2 comprises several breathing ports 11, 13, 15 in addition to the breathing port coupled to the measuring head 23 and the breathing ports 11, 13, 15 are situated on the door 4b, the gas entering through the breathing ports 11, 13, 15 during the contamination measurement is then also controlled gas, that is to say a clean and/or dry gas injected through the injection nozzle or nozzles 33.

[71] This embodiment is particularly advantageous because it makes it possible to avoid having to obstruct or inject controlled gas into the breathing ports other than the breathing/sampling port coupled to the measuring head 23, so as to not introduce contaminants into the carrier 2 during the contamination measurement. The interface 3 is thus simplified considerably. It is nevertheless possible to inject controlled air via additional injection nozzles which are disposed facing the ventilation ports 11, 13, 15. [72] The fifth step 105 relates to the aspiration of gases from the carrier 2 by way of the measuring device 1 via the measuring head 23. The aspiration is carried out by sampling means 31 of the measuring device 1.

[73] The aspiration of the gases from the carrier 2 gives rise to a reduced pressure in the interior of the carrier 2 such that compensatory outside air is introduced into the carrier 2 via the breathing ports 11, 13, 15 and/or the seal region 7. This compensatory outside air corresponds in this case to the controlled gas injected in step 104.

[74] Thus, the air aspirated via the measuring head 23 is replaced in the carrier 2 by controlled gas such that the risk of introducing contaminants into the carrier 2 during the contamination measurement, notably via the seal region 7 which may be leaky, is significantly reduced.

[75] The sixth step 106 corresponds to the measurement of the contamination of the gas aspirated via the measuring head 23 by an analyser 29 of the measuring device 1. The measurement may relate to one or more contaminants.

[76] The measuring device 1 may comprise several analysers 29 which are associated with the measurement of different contaminants. The measurement of the contamination may be carried out for a predetermined time, for example 1 minute, and the level of contamination may be deduced from the evolution of the level of contamination during the predetermined time (the contaminant being diluted over time with the controlled gas introduced into the carrier 2 during the measurement).

[77] The sequencing of the steps 101 to 106 described above may also be condensed by carrying out several steps simultaneously. Step 103 can, for example, be simultaneous with step 101 or with step 102. Step 104 may be permanent and uncorrelated in relation to the measurement, notably it concerns compressed dry air (CDA) or extreme clean dry air (XCDA). Steps 104 and 105 may start simultaneously. Step 106 may start at the time of step 105 being carried out.

[78] Thus, the injection, during the contamination measurement, of controlled gas at the leaky regions of a carrier 2 such as the seal region 7 or the breathing ports 11, 13, 15 makes it possible to ensure the absence of introduction of contaminants during the measurement, making it possible to render the contamination measurement more reliable and especially to protect the substrates 6 during the contamination measurement. It is thus possible to measure the internal atmosphere of the carrier 2 without opening the carrier 2 and without risks of contamination, and therefore during production.