A method for maintaining and restoring an MOCVD chamber

Abstract

The present invention relates to the field of LED chip technology, and more specifically to a method for maintaining and restoring an MOCVD chamber, comprising the following steps: S2: setting a reaction chamber temperature of 1000°C to 1200°C and a pressure of 150 Torr to 300 Torr for 30 to 60 minutes; S3: introducing triethylgallium and CP2Mg into the reaction chamber for 15 to 30 minutes; S4: introducing triethylgallium and CP2Mg into the reaction chamber for 60 to 90 minutes. The present invention has the beneficial effect of setting the baking temperature and time within a range suitable for removing impurities that are easily doped with Mg from a thin film in the reaction chamber. Therefore, the method of the present invention uses fewer steps and less time to further increase the Mg doping concentration in subsequently produced LED chips, thereby reducing the cost of producing LED chips and obtaining LED chips of the highest possible quality.

Description

Technical Field

[0001] The present invention relates to the technical field of LED chips, and in particular to a method for maintaining and restoring an MOCVD cavity. Background Art

[0002] An LED (Light Emitting Diode) is a solid-state semiconductor device that converts electrical energy into light. As a new type of light-emitting device, LEDs offer advantages such as high luminous efficiency, energy saving, long life, fast response time, and environmental friendliness, earning them the title of the most promising new generation light source.

[0003] LED chips typically include a substrate, an N layer, a multi-quantum well layer, and a P layer stacked in sequence. To improve the performance of LED chips, existing technologies typically dope the P layer with Mg. LED chips are typically formed in an MOCVD reaction chamber. During the LED chip formation process, a thin film made of a material similar to the LED chip forms on the reaction chamber walls. During the subsequent Mg doping process, Mg is also doped onto the thin film on the chamber walls, resulting in insufficient Mg doping concentration in the P layer. This insufficient Mg doping concentration leads to insufficient hole concentration in the P layer, which in turn reduces the LED chip's luminescence.

[0004] Referring to the method for recovering a light-emitting diode epitaxial growth reaction chamber and its epitaxial growth method disclosed in Chinese Patent Publication No. CN110739372A, thin films on the walls of the MOCVD reaction chamber can reduce the quality of LED chip growth, specifically affecting the doping of Mg into the P layer. Therefore, before each batch of LED chips is produced, the old thin film must be removed from the reaction chamber and a new thin film formed on the walls.

[0005] However, the Mg residue from the old film in the reaction chamber, after contact with the outside air, is difficult to remove. Existing techniques require extensive chamber baking and coating (i.e., growing a new film in the reaction chamber) to remove the old film and produce a high-quality new film, which consumes a lot of energy and time. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for maintaining and restoring an MOCVD cavity, thereby reducing the cost of maintaining and restoring the MOCVD cavity.

[0007] In order to solve the above technical problems, the present invention adopts a technical solution: a method for maintaining and restoring an MOCVD chamber, comprising the following steps:

[0008] S1: Use H2 and N2 as carrier gases in the MOCVD reaction chamber, set the reaction chamber temperature to 500°C-800°C, and continue for 45-120 minutes;

[0009] S2: Set the reaction chamber temperature to 1000°C-1200°C and the pressure to 150 Torr-300 Torr, and introduce 35,000-45,000 sccm of H2, 10,000-20,000 sccm of N2, and 50,000-60,000 sccm of NH3 into the reaction chamber for 30-60 minutes;

[0010] S3: H2, N2, and NH3 are used as carrier gases in the reaction chamber, and 750-1000 sccm of triethylgallium and 1000-2000 sccm of CP2Mg are introduced into the reaction chamber for 15-30 minutes;

[0011] S4: H2, N2, and NH3 are used as carrier gases in the reaction chamber, and 1500-2000 sccm of triethylgallium and 2000-4000 sccm of CP2Mg are introduced into the reaction chamber; this continues for 60-90 minutes;

[0012] S5: Resume work after completing MOCVD chamber maintenance.

[0013] The present invention has the beneficial effect of setting the baking temperature and time within a range suitable for removing impurities that are susceptible to Mg doping from the film in the reaction chamber. After removing these impurities, no further baking is required. Therefore, the method of the present invention utilizes fewer steps and less time to significantly increase the Mg doping concentration in subsequently produced LED chips, thereby reducing the cost of the LED chip production process and producing LED chips of the highest possible quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a characteristic curve diagram of hole concentration and depth of an LED chip in a comparative example according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the implementation methods.

[0016] The present invention provides a method for maintaining and restoring an MOCVD chamber, comprising the following steps:

[0017] S1: Use H2 and N2 as carrier gases in the MOCVD reaction chamber, set the reaction chamber temperature to 500°C-800°C, and continue for 45-120 minutes;

[0018] S2: Set the reaction chamber temperature to 1000°C-1200°C and the pressure to 150 Torr-300 Torr, and introduce 35,000-45,000 sccm of H2, 10,000-20,000 sccm of N2, and 50,000-60,000 sccm of NH3 into the reaction chamber for 30-60 minutes;

[0019] S3: H2, N2, and NH3 are used as carrier gases in the reaction chamber, and 750-1000 sccm of triethylgallium and 1000-2000 sccm of CP2Mg are introduced into the reaction chamber for 15-30 minutes;

[0020] S4: H2, N2, and NH3 are used as carrier gases in the reaction chamber, and 1500-2000 sccm of triethylgallium and 2000-4000 sccm of CP2Mg are introduced into the reaction chamber; this continues for 60-90 minutes;

[0021] S5: Resume work after completing MOCVD chamber maintenance.

[0022] As can be seen from the above description, the beneficial effect of the present invention is that the method of the prior art attempts to completely remove the old film on the wall of the reaction chamber, so the reaction chamber needs to be baked multiple times in the prior art, and the baking temperature cannot be set only within the range suitable for removing impurities that are easily doped with Mg.

[0023] In contrast, the present invention sets the baking temperature and time within a range suitable for removing impurities that are susceptible to Mg doping from the film in the reaction chamber. After removing these impurities, no further baking is performed. Therefore, the method of the present invention utilizes fewer steps and less time to significantly increase the Mg doping concentration in subsequently produced LED chips, thereby reducing costs and producing the highest quality LED chips.

[0024] Specifically, step S1 is to remove water and oxygen from the reaction chamber to prevent them from participating in subsequent reactions. The purpose of step S2 is to change the atmosphere in the reaction chamber while removing impurities from the film. After the atmosphere is changed, the reaction chamber can quickly and high-quality crystallize GaN into a film. S3 and S4 divide the doping of Mg in the film in the reaction chamber into two steps, thereby coordinating steps S1 and S2 to increase the Mg doping concentration in the film in a shorter time.

[0025] Furthermore, the step S1 specifically includes: using H2 and N2 as carrier gases in the MOCVD reaction chamber, setting the reaction chamber temperature to 500° C.-600° C., and continuing for 15-30 minutes;

[0026] The reaction chamber temperature was set to 700°C-800°C for 30-60 minutes.

[0027] As can be seen from the above description, dividing the steps of removing water and oxygen into the above two steps can enable water and oxygen to be removed more completely.

[0028] Furthermore, the step S1 specifically includes setting the MOCVD reaction chamber temperature to 500° C.-600° C. and the pressure to 200 Torr-400 Torr, and introducing 5000-10000 sccm of H2 and 5000-10000 sccm of N2 into the reaction chamber for 15-30 minutes;

[0029] The reaction chamber temperature was set at 700° C.-800° C. and the pressure was set at 200 Torr-400 Torr. 10,000-20,000 sccm of H 2 and 10,000-20,000 sccm of N 2 were introduced into the reaction chamber for 30-60 minutes.

[0030] As can be seen from the above description, the above arrangement provides a simple and efficient method for removing water and oxygen from the reaction chamber.

[0031] Furthermore, step S2.1 is included between S2 and S3;

[0032] S2.1: Use H2, N2, and NH3 as carrier gases in the reaction chamber, and introduce 2000-3000 seem of trimethylgallium into the reaction chamber for 30-60 minutes.

[0033] As can be seen from the above description, the above steps enable GaN to be grown on the cavity wall of the reaction chamber.

[0034] Furthermore, the S2.1 is specifically as follows: setting the reaction chamber temperature to 950°C-1150°C and the pressure to 150Torr-300Torr, introducing 15000-30000sccm of H2, 10000-20000sccm of N2, 30000-40000sccm of NH3 and 2000-3000sccm of trimethylgallium into the reaction chamber for 30-60 minutes.

[0035] As can be seen from the above description, the above arrangement provides a simple and efficient method for growing GaN.

[0036] Furthermore, step S2.2 is included between S2.1 and S3;

[0037] S2.2: Using H2, N2, and NH3 as carrier gases, introduce 1500-2000 sccm of trimethylgallium and 5500-8000 sccm of SiH4 into the reaction chamber for 30-60 minutes.

[0038] As can be seen from the above description, the above steps dope the Si element into the GaN thin film, so that sufficient Si can be doped into the LED chip formed subsequently.

[0039] Furthermore, the S2.2 is specifically as follows: setting the reaction chamber temperature to 900°C-1000°C and the pressure to 150Torr-300Torr, introducing 7500-15000sccm of H2, 7500-15000sccm of N2, 20000-30000sccm of NH3, 1500-2000sccm of trimethylgallium and 5500-8000sccm of SiH4 into the reaction chamber for 30-60 minutes.

[0040] As can be seen from the above description, the above arrangement provides a simple and efficient method for doping Si into GaN thin films.

[0041] Furthermore, the S3 is specifically as follows: setting the reaction chamber temperature to 900°C-1000°C and the pressure to 200Torr-400Torr, introducing 7500-15000sccm of H2, 7500-15000sccm of N2, 20000-30000sccm of NH3, 750-1000sccm of triethylgallium and 1000-2000sccm of CP2Mg into the reaction chamber for 15-30 minutes.

[0042] As can be seen from the above description, the above arrangement provides a simple and efficient method for doping Mg into GaN.

[0043] Furthermore, the S4 is specifically as follows: setting the reaction chamber temperature to 900°C-1000°C and the pressure to 200Torr-400Torr, introducing 7500-15000sccm of H2, 7500-15000sccm of N2, 20000-30000sccm of NH3, 1500-2000sccm of triethylgallium and 2000-4000sccm of CP2Mg into the reaction chamber; and continuing for 60-90 minutes.

[0044] As can be seen from the above description, the above arrangement provides a simple and efficient method for doping Mg into GaN.

[0045] Furthermore, step S4.1 is included between S4 and S5;

[0046] S4.1: Use nitrogen as the carrier gas in the reaction chamber and set the reaction chamber temperature to 650-850°C for 5-15 minutes.

[0047] As can be seen from the above description, the above configuration is for annealing the thin film on the reaction chamber.

[0048] Example 1

[0049] The MOCVD chamber maintenance and recovery method of this embodiment includes the following steps:

[0050] S1: Set the MOCVD reaction chamber temperature to 500°C and the pressure to 200-400 Torr. Introduce 5000-10000 sccm of H2 and 5000-10000 sccm of N2 into the reaction chamber for 15-30 minutes.

[0051] S2: Set the reaction chamber temperature to 700°C-800°C and the pressure to 200 Torr, and inject 10,000-20,000 sccm of H2 and 10,000-20,000 sccm of N2 into the reaction chamber for 35 minutes.

[0052] S3: Set the reaction chamber temperature to 1000°C and the pressure to 150 Torr-300 Torr, and introduce 35,000-45,000 sccm of H2, 10,000-20,000 sccm of N2, and 50,000-60,000 sccm of NH3 into the reaction chamber for 30-60 minutes;

[0053] S4: Set the reaction chamber temperature to 950°C-1150°C and the pressure to 150 Torr, and introduce 15,000-30,000 sccm of H2, 10,000-20,000 sccm of N2, 30,000-40,000 sccm of NH3, and 2,000-3,000 sccm of trimethylgallium into the reaction chamber for 30-60 minutes;

[0054] S5: Set the reaction chamber temperature to 900°C and the pressure to 150 Torr-300 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 1500-2000 sccm of trimethylgallium, and 5500-8000 sccm of SiH4 into the reaction chamber for 30-60 minutes;

[0055] S6: Set the reaction chamber temperature to 900°C and the pressure to 200 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 750-1000 sccm of triethylgallium, and 1000-2000 sccm of CP2Mg into the reaction chamber for 15-30 minutes;

[0056] S7: Set the reaction chamber temperature to 900°C and the pressure to 210 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 1500-2000 sccm of triethylgallium, and 2000-4000 sccm of CP2Mg into the reaction chamber; continue for 60 minutes;

[0057] S8: Use nitrogen as the carrier gas for the reaction chamber and set the reaction chamber temperature to 650-850°C for 5-15 minutes. After completing the MOCVD chamber maintenance, resume operation.

[0058] Example 2

[0059] The MOCVD chamber maintenance and recovery method of this embodiment includes the following steps:

[0060] S1: Set the MOCVD reaction chamber temperature to 600°C and the pressure to 400 Torr, and introduce 10,000 sccm of H2 and 10,000 sccm of N2 into the reaction chamber for 15-30 minutes;

[0061] S2: Set the reaction chamber temperature to 800°C and the pressure to 400 Torr, and inject 10,000-20,000 sccm of H2 and 10,000-20,000 sccm of N2 into the reaction chamber for 60 minutes.

[0062] S3: Set the reaction chamber temperature to 1200°C and the pressure to 300 Torr, and introduce 35,000-45,000 sccm of H2, 10,000-20,000 sccm of N2, and 50,000-60,000 sccm of NH3 into the reaction chamber for 50 minutes.

[0063] S4: Set the reaction chamber temperature to 1100°C and the pressure to 300 Torr, and introduce 15,000-30,000 sccm of H2, 10,000-20,000 sccm of N2, 30,000-40,000 sccm of NH3, and 3,000 sccm of trimethylgallium into the reaction chamber for 30-60 minutes;

[0064] S5: Set the reaction chamber temperature to 900°C-1000°C and the pressure to 150 Torr-300 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 2000 sccm of trimethylgallium, and 7500 sccm of SiH4 into the reaction chamber for 30 minutes;

[0065] S6: Set the reaction chamber temperature to 1000°C and the pressure to 400 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 900 sccm of triethylgallium, and 2000 sccm of CP2Mg into the reaction chamber for 20 minutes;

[0066] S7: Set the reaction chamber temperature to 1000°C and the pressure to 400 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 2000 sccm of triethylgallium, and 4000 sccm of CP2Mg into the reaction chamber; continue for 80 minutes;

[0067] S8: Use nitrogen as the carrier gas for the reaction chamber and set the reaction chamber temperature to 850°C for 5 minutes. After completing the MOCVD chamber maintenance, resume operation.

[0068] Example 3

[0069] The MOCVD chamber maintenance and recovery method of this embodiment includes the following steps:

[0070] S1: Set the MOCVD reaction chamber temperature to 550°C and the pressure to 300 Torr, and introduce 7500 sccm of H2 and 7500 sccm of N2 into the reaction chamber for 22 minutes.

[0071] S2: Set the reaction chamber temperature to 750°C and the pressure to 300 Torr, and inject 15,000 sccm of H2 and 15,000 sccm of N2 into the reaction chamber for 30-60 minutes.

[0072] S3: The reaction chamber temperature was set at 1100°C and the pressure was set at 220 Torr. 40,000 sccm of H2, 15,000 sccm of N2, and 55,000 sccm of NH3 were introduced into the reaction chamber for 45 minutes.

[0073] S4: The reaction chamber temperature was set at 1050°C and the pressure was set at 220 Torr. 15,000-30,000 sccm of H2, 10,000-20,000 sccm of N2, 30,000-40,000 sccm of NH3, and 2,500 sccm of trimethylgallium were introduced into the reaction chamber for 45 minutes.

[0074] S5: Set the reaction chamber temperature to 950°C and the pressure to 150 Torr-300 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 1700 sccm of trimethylgallium, and 6000 sccm of SiH4 into the reaction chamber for 45 minutes;

[0075] S6: Set the reaction chamber temperature to 900°C-1000°C and the pressure to 200 Torr-400 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 870 sccm of triethylgallium, and 1500 sccm of CP2Mg into the reaction chamber for 22 minutes;

[0076] S7: Set the reaction chamber temperature to 950°C and the pressure to 300 Torr, and introduce 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 1700 sccm of triethylgallium, and 3000 sccm of CP2Mg into the reaction chamber; continue for 75 minutes;

[0077] S8: Use nitrogen as the carrier gas for the reaction chamber and set the reaction chamber temperature to 750°C for 10 minutes. After completing the MOCVD chamber maintenance, resume operation.

[0078] Comparative Example

[0079] Please refer to Figure 1 This comparative example compares two groups of LED chips. The first group of LED chips is formed in a reaction chamber treated by a conventional reaction chamber maintenance recovery method, and the second group of LED chips is formed in a reaction chamber treated according to Example 3 of the present invention.

[0080] Test the first group of LED chips and average the test data to get Figure 1 The dashed curve in the middle.

[0081] Test the second group of LED chips and average the test data to get Figure 1 The solid curve in the middle.

[0082] The difference between the conventional reaction chamber recovery method after maintenance and the third embodiment of the present invention is that steps S3 to S7 are replaced by:

[0083] The reaction chamber temperature was set at 950°C and the pressure was 220 Torr. 15,000-30,000 sccm of H2, 10,000-20,000 sccm of N2, 30,000-40,000 sccm of NH3, and 2,500 sccm of trimethylgallium were introduced into the reaction chamber for 45 minutes.

[0084] The reaction chamber temperature was set at 950°C and the pressure was 220 Torr. 15,000-30,000 sccm of H2, 10,000-20,000 sccm of N2, 30,000-40,000 sccm of NH3, 2,500 sccm of trimethylgallium, and 3,000 sccm of CP2Mg were introduced into the reaction chamber for 45 minutes.

[0085] The reaction chamber temperature was set at 950°C and the pressure was 220 Torr. 15,000-30,000 sccm of H2, 10,000-20,000 sccm of N2, 30,000-40,000 sccm of NH3, and 2,500 sccm of trimethylgallium were introduced into the reaction chamber for 45 minutes.

[0086] The reaction chamber is subjected to a process of mass-producing the first group of LED chips without placing a substrate.

[0087] Figure 1 The horizontal axis represents the depth of the P-type GaN layer of the LED chip, and the vertical axis represents the hole concentration corresponding to a certain depth of the P-type GaN layer.

[0088] observe Figure 1 It is not difficult to see that the LED chip produced using the reaction chamber processed in Example 3 of the present invention has an increased Mg doping concentration, which results in an increased hole concentration in the LED chip.

[0089] However, the time taken to process the reaction chamber in the third embodiment is less than that taken in the conventional technology.

[0090] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for maintaining and restoring an MOCVD chamber, characterized in that: The steps include: S1: Use H2 and N2 as carrier gases in the MOCVD reaction chamber, set the reaction chamber temperature to 500°C-800°C, and continue for 45-120 minutes; S2: Set the reaction chamber temperature to 1000°C-1200°C and the pressure to 150 Torr-300 Torr, and introduce 35,000-45,000 sccm of H2, 10,000-20,000 sccm of N2, and 50,000-60,000 sccm of NH3 into the reaction chamber for 30-60 minutes; S3: H2 and N2 are used as carrier gases in the reaction chamber, NH3 is used as the reaction gas in the reaction chamber, and 750-1000 sccm of triethylgallium and 1000-2000 sccm of CP2Mg are introduced into the reaction chamber for 15-30 minutes; The step S3 specifically includes setting the reaction chamber temperature to 900° C.-1000° C. and the pressure to 200 Torr-400 Torr, introducing 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 750-1000 sccm of triethylgallium, and 1000-2000 sccm of CP2Mg into the reaction chamber for 15-30 minutes; S4: H2 and N2 are used as carrier gases in the reaction chamber, NH3 is used as the reaction gas in the reaction chamber, and 1500-2000 sccm of triethylgallium and 2000-4000 sccm of CP2Mg are introduced into the reaction chamber; the reaction continues for 60-90 minutes; The step S4 specifically includes setting the reaction chamber temperature to 900° C.-1000° C. and the pressure to 200 Torr-400 Torr, introducing 7500-15000 sccm of H2, 7500-15000 sccm of N2, 20000-30000 sccm of NH3, 1500-2000 sccm of triethylgallium, and 2000-4000 sccm of CP2Mg into the reaction chamber; and continuing the process for 60-90 minutes. S5: Resume work after completing MOCVD chamber maintenance.

2. The MOCVD chamber maintenance and recovery method according to claim 1, characterized in that: Specifically, S1 includes: using H2 and N2 as carrier gases in the MOCVD reaction chamber, setting the reaction chamber temperature to 500° C.-600° C., and continuing for 15-30 minutes; The reaction chamber temperature was set to 700°C-800°C for 30-60 minutes.

3. The MOCVD chamber maintenance and recovery method according to claim 2, characterized in that: The step S1 specifically includes setting the MOCVD reaction chamber temperature to 500° C.-600° C. and the pressure to 200 Torr-400 Torr, and introducing 5000-10000 sccm of H2 and 5000-10000 sccm of N2 into the reaction chamber for 15-30 minutes; The reaction chamber temperature was set at 700° C.-800° C. and the pressure was set at 200 Torr-400 Torr. 10,000-20,000 sccm of H 2 and 10,000-20,000 sccm of N 2 were introduced into the reaction chamber for 30-60 minutes.

4. The MOCVD chamber maintenance and recovery method according to claim 1, characterized in that: Also included is step S2.1 between S2 and S3; S2.1: Use H2 and N2 as carrier gases and NH3 as reaction gas in the reaction chamber, and introduce 2000-3000 sccm of trimethylgallium into the reaction chamber for 30-60 minutes.

5. The MOCVD chamber maintenance and recovery method according to claim 4, characterized in that: The S2.1 is specifically as follows: setting the reaction chamber temperature to 950°C-1150°C and the pressure to 150Torr-300Torr, introducing 15000-30000sccm of H2, 10000-20000sccm of N2, 30000-40000sccm of NH3 and 2000-3000sccm of trimethylgallium into the reaction chamber for 30-60 minutes.

6. The MOCVD chamber maintenance and recovery method according to claim 4, characterized in that: Also included is step S2.2 between S2.1 and S3; S2.2: Use H2 and N2 as carrier gases and NH3 as reaction gas in the reaction chamber, and introduce 1500-2000 sccm of trimethylgallium and 5500-8000 sccm of SiH4 into the reaction chamber for 30-60 minutes.

7. The MOCVD chamber maintenance and recovery method according to claim 6, characterized in that: The S2.2 is specifically as follows: setting the reaction chamber temperature to 900°C-1000°C and the pressure to 150Torr-300Torr, introducing 7500-15000sccm of H2, 7500-15000sccm of N2, 20000-30000sccm of NH3, 1500-2000sccm of trimethylgallium and 5500-8000sccm of SiH4 into the reaction chamber for 30-60 minutes.

8. The MOCVD chamber maintenance and recovery method according to claim 1, characterized in that: Also included is step S4.1 between S4 and S5; S4.1: Use nitrogen as the carrier gas in the reaction chamber and set the reaction chamber temperature to 650-850°C for 5-15 minutes.

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