Method and device for removing pollution from a confined environment

1. A method for decontaminating an unsealed enclosed environment ( 1 ) comprising an inner space ( 2 ) delimited by a wall ( 3 ) having a natural leak ( 4 ), comprising the following steps:

the unsealed enclosed environment ( 1 ), having its natural leak ( 4 ), is placed within a sealed decontamination chamber ( 5 ) comprising means for introducing gas ( 6 ) and means for pumping out gas ( 7 , 8 ),

the gas contained within the decontamination chamber ( 5 ) is pumped out by adjusting the pressure drop within the decontamination chamber ( 5 ) in such a way so that the difference in pressure between the interior and exterior of the unsealed enclosed environment ( 1 ) is at all times less than the difference in pressure that would cause mechanical warping that would damage the wall ( 3 ) of the unsealed enclosed environment ( 1 ).

2. A method according to claim 1 , wherein a step of raising pressure is comprised, during which the increase in pressure within the decontamination chamber ( 5 ) is adjusted so that the difference in pressure between the interior and exterior of the unsealed enclosed environment ( 1 ) is at all times less than the difference in pressure that would cause mechanical warping that would damage the wall ( 3 ) of the unsealed enclosed environment ( 1 ).

3. A method according to claim 1 , wherein the variation in pressure within the decontamination chamber ( 5 ) is controlled by following a theoretical curve of pressure versus time.

4. A method according to claim 1 , wherein the variation in pressure within the decontamination chamber ( 5 ) is controlled by following a signal given by at least one sensor detecting warping in the wall ( 3 ) of the unsealed enclosed environment ( 1 ).

5. A method according to claim 1 , wherein to adjust the change in pressure within the decontamination chamber ( 5 ), the pumping capacity of the pumping means ( 7 , 8 ) is varied, by controlling their rotational velocity, and/or by controlling a variable conductance ( 12 ) of the pumping means, and/or a gas flow entering the decontamination chamber ( 5 ) is varied by controlling the means for introducing gas ( 6 ).

6. A method according to claim 1 , further comprising a step of purging, said step of purging comprising at least one operation of filling with purging gas, during which a purging gas is introduced into the decontamination chamber ( 5 ).

7. A method according to claim 6 , wherein the sub of purging further comprises at least one purging gas pumping operation during which the mixture of the gas present in the decontamination chamber ( 5 ) is extracted therefrom.

8. A method according to claim 7 , wherein the purging gas filling and pumping operations are performed simultaneously, with a pumping flow rate less than the injection flow rate.

9. A method according to claim 7 , wherein multiple purging gas filling and pumping operations are performed in succession.

10. A method according to claim 6 , wherein multiple purging steps, comprising purging gas filling and pumping operations, alternate with pumping steps.

11. A method according to claim 6 , wherein the purging gas filling operation comprises an overpressure period, during which the decontamination chamber ( 5 ) is kept at a pressure greater than atmospheric pressure, before being returned to atmospheric pressure.

12. A method according to claim 6 , wherein the purging gas is nitrogen.

13. A method according to claim 6 , wherein the purging gas is synthetic air.

14. A method according to claim 6 , wherein the purging gas is introduced into the unsealed enclosed environment ( 1 ), and extracted therefrom, through the filters ( 35 ) that said environment comprises.

15. A method according to claim 1 , wherein the unsealed enclosed environment ( 1 ) being a photomask equipped with its film ( 3 ), the purging gas is introduced and extracted through the low-conductance filters separating the film from the active part of the mask.

16. A method according to claim 1 , wherein the unsealed enclosed environment ( 1 ) is a closed atmospheric transport pod.

17. A method according to claim 16 , wherein the transport pod contains semiconductor substrate wafers ( 100 ).

18. A method according to claim 1 , wherein low pressures, of about 10 −2 to 10 −3 Torr, are achieved within the decontamination chamber ( 5 ).

19. A method according to claim 1 , wherein the gases pumped are analyzed, and the pumping step is halted once the level of pollution inside the sealed decontamination chamber ( 5 ) becomes less than a preset value.

20. A device for decontaminating an unsealed enclosed environment ( 1 ), comprising:

a decontamination chamber ( 5 ) capable of containing the unsealed enclosed environment ( 1 ),

means for introducing gas ( 6 , 13 ), capable of producing a gas injection flow within the decontamination chamber ( 5 ),

pumping means ( 7 , 8 ), capable of pumping the gases out of the decontamination chamber ( 5 ),

wherein:

the pumping means ( 7 , 8 ) have a variable pumping capacity,

command means ( 14 ) are provided to adjust the pumping capacity and adjust the gas injection flow,

means for controlling the difference in pressure between the interior and exterior of the unsealed enclosed environment ( 1 ) are provided,

the command means ( 14 ) adjust the pumping capacity and/or the gas injection flow so that the difference in pressure between the interior and exterior of the unsealed enclosed environment ( 1 ), determined by the means for controlling the difference in pressure, is at all times less than the difference in pressure that would cause mechanical warping that would damage the wall ( 3 ) of the unsealed enclosed environment ( 1 ).

21. A device according to claim 20 , wherein the means for controlling the difference in pressure comprise a theoretical curve of pressure versus time, saved in the memory ( 14 b ) of the command means ( 14 ), and which the command means ( 14 ) follow in order to vary the pumping capacity and/or gas injection flow over time.

22. A device according to claim 20 , wherein the means for controlling the difference in pressure comprise at least one warping sensor ( 15 ), adapted to measure the warping of the wall ( 3 ) of the unsealed enclosed environment ( 1 ), and providing a signal for controlling the variation in pressure within the decontamination chamber ( 5 ).

23. A device according to claim 20 , further comprising means for heating the unsealed enclosed environment ( 1 ).

24. A device according to claim 20 , wherein the means for introducing gas ( 6 , 13 ) comprise a source of purging gas, this gas being nitrogen or synthetic air.

25. A device according to claim 20 , further comprising pumped gas analysis means ( 11 ).

26. A device according to claim 25 , wherein the analysis means ( 11 ) comprise means for ionizing the pumped gases, means for identifying the ionized gases by measuring an ion parameter, and means for performing an operation on the measured parameters.

27. A device according to claim 25 , wherein the pumping and purging steps are automated and are triggered by reading signals from the pumped gas analysis means ( 11 ) and/or a warping sensor ( 15 ).

28. A device according to claim 20 , wherein the decontamination chamber ( 5 ) is of dimensions slightly greater than those of the unsealed enclosed environment ( 1 ).

29. A device according to claim 20 , further comprising measuring means ( 10 ) for measuring the change in pressure within the decontamination chamber ( 5 ).

30. A device according to claim 20 , wherein the pumping means ( 7 , 8 ) comprise a primary pump ( 8 a ) and a secondary pump ( 8 b ), and capable of establishing a vacuum of

about 10 −2 to 10 −3 Torr within the decontamination chamber ( 5 ).