Methods for cleaning semiconductor carrier devices

Abstract

Provided are a method for cleaning a semiconductor carrier device (100), comprising a first step (120) of exposing the semiconductor carrier device (100) to a warm gas (110) a second step (140) of exposing the semiconductor carrier device (100) to a cleaning fluid (112); and a third step (160) of exposing the semiconductor carrier device (100) to a warm gas (114), and method for cleaning a semiconductor carrier device (100), comprising a first step (220) of exposing the semiconductor carrier device (100) to a vacuum (222), a second step (240) of exposing the semiconductor carrier device (100) to a venting gas (224), and a third step (260) of exposing the semiconductor carrier device (100) to a vacuum (226) and a method of combination of them.

Description

[0001] Methods for cleaning semiconductor carrier devices

[0002] The present invention relates to methods for cleaning semiconductor carrier devices

[0003] Background

[0004] Semiconductor carrier devices such as FOUPs (Front Opening Unified Pods) are important in connection with wafer transport and contamination control within and outside of semiconductor fabrication plants, also known as fabs. The environment within the FOUP, the FOUP mini-environment, is responsible for isolating the wafers from the fab environment and at the same time transporting the wafers safely between tools and within the fab. Since the wafers are constantly exposed to a variety of processes and chemicals, the same chemicals are released from the wafers via outgassing processes. As a result, the FOUP walls absorb this gaseous material which gets embedded into the pores of the FOUP walls, on the inside as well as the outside of the FOUP. A deep cleaning of the FOUP(s) now becomes essential as contamination would adversely impact other wafers, for example such wafers which are subsequently transported or stored in such a FOUP, due to the emission of these substances from the FOUP. In this disclosure draft, two new approaches are suggested to deal with this problem. As will be seen from the disclosure, it is especially advantageous to combine the two new approaches, although even only performing any one of the new approaches leads to enhanced cleaning results over the prior art.

[0005] The same approaches could be used for cleaning other semiconductor carrier devices, such as, reticle pods, especially EUV pods.

[0006] Summary

[0007] The present invention addresses these problems by providing methods for cleaning semiconductor carrier devices. Embodiments and additional features are provided in the dependent claims and further discussed in the following description. According to a first aspect of the invention, there is provided a method for cleaning a semiconductor carrier device, comprising a first step of exposing the semiconductor carrier device to a warm gas, a second step of exposing the semiconductor carrier device to a cleaning fluid; and a third step of exposing the semiconductor carrier device to a warm gas. The warm gas provided in the first and the third step may be the same gas, but it is also conceivable to use different gases. The steps, especially all three steps, may be performed repeatedly.

[0008] This new method differs from prior art methods, which comprise only a wet cleaning step followed by a drying step, in that one extra step of drying (exposing to a warm gas) is performed before the wet cleaning step. This significantly increases the efficiency of the cleaning procedure, as will be explained in the following.

[0009] FOUPs are typically made of porous materials, for example polycarbonate materials. Contamination molecules, especially in the form of so called airborne molecular contamination AMC, enter these pores, and it requires energy in order for them to be able to diffuse out of the pores again. Providing warm clean dry air CDA as a first cleaning step, also referred to as drying, can effectively supply the required energy to enable molecules to diffuse out of the pores. The molecules thus diffused out of the FOIIP can then, with the second cleaning step, also referred to as wet cleaning, be effectively removed. This required energy is provided not only by the high temperature of CDA, but also by the physical force provided when CDA impinges on the contamination molecules within the pores. In addition, there are other contaminants than AMC that have more affinity to the surface and adhere to the surface. The first drying step provides enough energy for weakening or breaking these bonds between contamination and the surface. Then, In the next step of wet cleaning, the contamination can get removed efficiently. This force can be especially enhanced and / or directed or focussed onto an area of interest by providing the warm gas via nozzles directed at the semiconductor device in a desired angle. It is also possible to vary the angle of the nozzles in relation to the semiconductor carrier device during the first and / or third step. The third step, which again constitutes a drying, then effectively removes any remaining contaminants and / or cleaning fluids produced or used during the first two steps. Advantageously, the first step and / or the third step are performed for a time period ranging from 15 seconds to 20 minutes and / or wherein the temperature of the warm gas is in a range from ambient temperature, for example 15C ,20C or 25C, to 75C. The most beneficial time and temperature ranges will depend on the specific materials used for the semiconductor carrier device to be cleaned. The time and temperature can be adjusted for the first and third steps separately.

[0010] Advantageously, the second step is performed for a time period ranging from 40 seconds to 5 minutes and / or the temperature of the cleaning fluid is in a range from ambient temperature, for example 15C, 20C or 25C to 75C. Again, the most beneficial ranges will depend on the specific materials of the semiconductor carrier device to be cleaned.

[0011] According to a preferred embodiment, the warm gas used in the first and / or the third step is provided as a flow of clean dry air (CDA or XCDA) or Nitrogen or any other suitable gas or mixture of gases, and / or the cleaning fluid is provided as water, especially deionized water or any other suitable fluid.

[0012] This is advantageously followed by a step of placing the carrier in a vacuum chamber that, for example, is operated in standard conditions with the standard recipe.

[0013] Advantageously, the method further comprises a step (especially a last step) of exposing the semiconductor carrier device to be cleaned to a purging gas, especially Nitrogen.

[0014] The same approach can be used for other carriers in the semiconductor industry such as reticle pods.

[0015] According to a second aspect of the invention, there is provided a method for cleaning a semiconductor carrier device, comprising a first step of exposing the semiconductor carrier device to a vacuum, a second step of exposing the semiconductor carrier device to a venting gas, and a third step of exposing the semiconductor carrier device to a vacuum.

[0016] Advantageously, the method according to the second aspect is preceded by a wet cleaning and drying, especially under standard conditions and recipe, and / or followed by a purging with a suitable purge gas, especially Nitrogen.

[0017] Taking into account the airborne property of AMC, it must be assumed that exposing semiconductor carrier devices to a vacuum within a vacuum chamber has a significant effect on removing contaminations. As the FOUR has a porous microstructure and molecules penetrate and get lodged in deep pores, it is not easy to remove them.

[0018] The second aspect of the invention provides a pulsed vacuum technique, in that the semiconductor carrier device is exposed to a vacuum, followed by an intermediate venting, for example at ambient pressure, and then to a further vacuum. The venting hereby constitutes a pulse-like change of pressure acting on the semiconductor carrier device. Hereby, physical forces to remove molecules from deep pores in the material of a semiconductor carrier device can be effectively generated. By providing such vacuum conditions, the molecules are pulled in a specific direction, but may still remain wedged or somehow lodged within the pores. With a rapid increase in pressure by venting, a further force, typically acting in a different direction, is imposed on the molecules which can effectively move them away from the area they were stuck in, thus dislodging or at least loosening them at their positions. Then, upon application of a further vacuum, the molecule or particle can be easily dislodged. The steps of this method, especially the pulse provided in connection with the venting step, can be repeated as many times as needed, and the venting time can vary.

[0019] The same approach can be used for other carriers in the semiconductor industry such as reticle pods.

[0020] Advantageously, the first step and / or the third step are performed for a time period ranging from 30 seconds to 600 seconds and / or wherein the minimum pressure provided in the vacuum is in a range from 0.0.010 kPa to 0.035 kPa. Also advantageously, the second step is performed for a time period ranging from 1 second to 60 seconds and / or wherein the maximum pressure during exposure of the semiconductor carrier device is ambient pressure. The vacuum and venting steps can be repeated as many times as needed or appears expedient.

[0021] Typically, the venting gas is provided as clean dry air (CDA or XCDA) or Nitrogen or any other suitable gases.

[0022] It is especially advantageous to expose the semiconductor carrier device to a purge gas, especially Nitrogen, especially after completion of the method steps.

[0023] According to a third aspect of the invention, there is provided a method for cleaning a semiconductor carrier device, comprising the features of the method according to the first aspect or one of its advantageous embodiments and the features of the second aspect or one of its advantageous embodiments. Combining the two methods as described, leads to especially advantageous cleaning results, wherein the two methods can be performed in any order, and any expedient number of times. After this combination, the carriers can be purged with nitrogen gas.

[0024] According to a fourth aspect of the invention, there is provided a device for implementing the method of any one, especially both, of the methods as described above. Such a device can especially be realized in the form of a semiconductor device cleaning station within a fab, comprising a wet cleaning station and a vacuum chamber. The wet cleaning station is typically provided with various nozzles for providing warm CDA used in the first and third steps, and deionised water used in the second step of the method according to the first aspect of the invention. The vacuum chamber is advantageously also provided with venting outlets adapted for implementation of rapid venting.

[0025] Utilising any one or both of the methods according to the invention enables a deeper cleaning of semiconductor carrier devices, for example of FOUPs made of polycarbonate (PC) material, compared to prior art cleaning methods. The methods according to the invention can also advantageously be used for cleaning other semiconductor carrier devices, such as reticle pods, especially EUV reticle pods.

[0026] To summarize an especially preferred embodiment of the first aspect of the invention, this comprises cleaning a semiconductor carrier device using a method including a drying step, followed by a wet cleaning step, followed by a drying step, followed by an exposure to a vacuum followed by a N2 purge.

[0027] To summarize an especially preferred embodiment of the second aspect of the invention, this comprises cleaning a semiconductor carrier device using a method including a wet cleaning step followed by drying step followed by an exposure to a vacuum followed by a venting step followed by a further exposure to a vacuum followed by a N2 purge.

[0028] The two preferred embodiments may be combined in order to provide an especially preferred cleaning method.

[0029] The invention will now be further described with reference to the appended Figures.

[0030] Figure 1 shows a schematic diagram illustrating an embodiment of the first aspect of the invention,

[0031] Figure 2 shows a schematic diagram illustrating an embodiment of the second aspect of the invention, and

[0032] Figure 3 shows a schematic diagram illustrating an embodiment combining the first aspect of the invention and the second aspect of the invention.

[0033] In Figure 1 , a region of a surface of a FOUR is schematically shown and designated 100. On the microscopic scale shown, contamination molecules 104 are shown trapped in pores 102 of the FOUR surface 100. Further contamination molecules 104 are shown adhering to the surface 100. In a first cleaning step 120, a warm gas flow 110 is blown onto the surface 100. This weakens the adhering bonds of the molecules 104 adhering to surface 100. Also, the warm gas flow can displace contamination molecules 104 from the pores 102, in which they are trapped.

[0034] In a subsequent second cleaning step 140, a fluid 112 such as water, especially deionised water, is directed to the surface 100. This leads to an effective removal of molecules, whose adhering bonds have been weakened in step 120, but which are still adhering to surface 100, by the fluid 112.

[0035] In a third step 160, the fluid 112 still adhering to the surface 100, which can contain contamination molecules 104, can effectively be removed by providing a further warm gas flow 114.

[0036] In Figure 2, a region of a surface of a FOUR is again schematically shown and designated 100. Again, on the microscopic scale shown, contamination molecules 104 are shown trapped in pores 102 of the FOUR surface 100. Further contamination molecules 104 are shown adhering to the surface 100.

[0037] In a first step 220, a vacuum 222 is applied to the surface 100, or, in other words, the surface is subjected to a vacuum. This can be effected, for example, by placing the carrier in a suitable vacuum chamber (not shown). This can lead to a weakening of adhering bonds of molecules 104 to the surface 100. In a subsequent step 240, the surface 100 is subjected to a vent 224, for example implemented by activation of a suitable venting valve (not shown). Hereby, adhering bonds of molecules 104 to surface 100 can be further weakened, and / or molecules trapped in pores 102 of the surface 100 can be displaced within the pores 102, such that, in a third step 260, in which a further vacuum 226 is applied, the molecules still adhering to surface 100 or still present in pores 102 can be effectively removed from the surface 100.

[0038] Figure 3 shows a schematic diagram illustrating a combination of the cleaning steps as described in Figures 1 and 2. Here, a contaminated carrier is provided in a step 300. This contaminated carrier is subjected to the cleaning steps 120, 140, 160, as described in connection with Figure 1 , and then to the cleaning steps 220, 240 and 260, as described in connection with Figure 2. These steps are followed by a purge step 320, in which the carrier is subjected to a purge gas such as Nitrogen. Following this purge step 320, a cleaned carrier is provided for further use, for example within a fab environment, in a step 340.

Claims

Claims1 . Method for cleaning a semiconductor carrier device, comprising a first step of exposing the semiconductor carrier device to a warm gas a second step of exposing the semiconductor carrier device to a cleaning fluid; and a third step of exposing the semiconductor carrier device to a warm gas.

2. The method according to claim 1 , wherein the first step and / or the third step are performed for a time period ranging from 15 seconds to 20 minutes and / or wherein the temperature of the warm gas is in a range from ambient temperature to 75C.

3. The method according to claim 1 or 2, wherein the second step is performed for a time period ranging from 40 seconds to 5 minutes seconds and / or wherein the temperature of the cleaning fluid is in a range from ambient temperature to 75C.

4. The method according to any one of the preceding claims, wherein the warm gas is provided as clean dry air (CDA or XCDA) or Nitrogen or any other gases, and / or the cleaning fluid is provided as water, especially deionized water or any other fluids.

5. The method according to any one of the preceding claims, further comprising a step of exposing the semiconductor carrier device to a vacuum chamber and then a purging gas, especially Nitrogen.

6. Method for cleaning a semiconductor carrier device, comprising a first step of exposing the semiconductor carrier device to a vacuum, a second step of exposing the semiconductor carrier device to a venting gas, and a third step of exposing the semiconductor carrier device to a vacuum.

7. The method according to claim 6, wherein the first step and / or the third step are performed for a time period ranging from 30 seconds to 600 seconds and / or wherein the minimum pressure provided in the vacuum is in a range from 0.010 kPa to 0.035 kPa.

8. The method according to claim 6 or 7 wherein the second step is performed for a time period ranging from 1 second to 60 seconds and / or wherein the maximum pressure during exposure of the semiconductor carrier device is ambient pressure.

9. The method according to any one of claims 6-8 wherein the venting gas is provided as clean dry air (CDA or XCDA) or Nitrogen or any other gases.

10. The method according to any one of claims 6-9, further comprising a step of exposing the semiconductor carrier device to a purging gas, especially Nitrogen.11 . Method for cleaning a semiconductor carrier device, comprising the features of any one of claims 1 -5 and any one of claims 6-10 or a combination of them.

12. Device for implementing the method of any one of the preceding claims.

Images