Annealing process of germanium wafers

Abstract

The application belongs to the technical field of heat treatment, and discloses an annealing process of germanium wafer. The germanium wafer is placed on a quartz boat in sequence, and then the quartz boat is placed in a quartz tube; the quartz tube is sealed and vacuumized to a preset vacuum degree; the quartz tube is placed in an annealing furnace, the annealing furnace is started, and the temperature is raised to 630-700 DEG C for a period of time; the temperature rising rate is 1.0-1.2 DEG C / min; after the temperature holding is finished, the temperature is lowered; the temperature lowering rate is 1.0-1.2 DEG C / min. Through effective control of the annealing temperature, the temperature rising rate and the temperature lowering rate, the internal defects of the germanium wafer are greatly reduced after annealing.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology, specifically relating to the annealing process of germanium wafers. Background Technology

[0002] Germanium possesses a wide infrared transmission band (3~5μm and 8~12μm), high mechanical strength, and good chemical stability, making it the preferred material for lenses and windows in infrared thermal imaging systems. Germanium wafers exhibit semiconductor properties, playing a crucial role in the development of solid-state physics and solid-state electronics, and can be used to fabricate various transistors, rectifiers, and other devices.

[0003] The main method for preparing germanium single crystals is the Czochralski method. After preparation using the Czochralski method, further heat treatment of the germanium single crystal is a conventional process. Patent document CN113073386A discloses a heat treatment process for germanium single crystals, which involves sequentially performing a first isothermal stage, a first cooling stage, a second isothermal stage, and a second cooling stage in an inert atmosphere. The first isothermal stage involves heating to 750-850℃ and then holding it at that temperature for a certain time. The first cooling stage involves cooling to 450-550℃ at a certain rate. The second isothermal stage involves holding the temperature at 450-550℃ for a certain time, with the holding time in the second isothermal stage being longer than that in the first isothermal stage. The second cooling stage involves cooling to 20-30℃ at a certain rate. Patent document CN110952145A discloses a heat treatment method for improving internal stress and micro-defects in germanium single crystals, including the following steps: cutting the germanium single crystal to be annealed into appropriate lengths and marking them with numbers before placing them in a furnace; evacuating the furnace according to the equipment operating procedures and then filling it with argon gas, repeating this process twice; during the second filling with argon gas, maintaining the argon gas in the furnace chamber at atmospheric pressure and continuously introducing a certain flow rate of argon gas; heating the single crystal in an argon atmosphere; the heating and cooling process includes: heating from room temperature to 100℃ within 30 minutes; heating to 350℃ within 1 hour; heating to 450℃ within 1 hour; isothermal treatment, maintaining the temperature at 450℃ for 10 hours; and cooling naturally to 25℃ during the cooling stage.

[0004] Germanium single crystals are generally cylindrical and relatively thick. Wafers, on the other hand, are thinner, typically 280-320 μm. The annealing process differs depending on the crystal or wafer thickness; the annealing process for germanium single crystals is not suitable for germanium wafers. Currently, research on annealing processes for germanium wafers is rarely reported. Summary of the Invention

[0005] The purpose of this invention is to provide an annealing process for germanium wafers to eliminate internal defects in germanium wafers.

[0006] To achieve the above objectives, the present invention adopts the following specific technical solutions.

[0007] An annealing process for germanium wafers includes the following steps:

[0008] The germanium wafers were placed one by one on the quartz boat, and then the quartz boat was placed into the quartz tube;

[0009] After sealing the quartz tube, evacuate it to a level below the preset vacuum level;

[0010] Place the quartz tube in the annealing furnace, turn on the furnace, and heat it to 630~700℃ and hold it for a period of time; the heating rate is 1.0-1.2℃ / min.

[0011] After the heat preservation is completed, the temperature is lowered; the cooling rate is 1.0-1.2℃ / min.

[0012] Furthermore, in a preferred embodiment, the preset vacuum degree is 1×10⁻⁶. -4 pa.

[0013] Furthermore, in the preferred embodiment, the heat preservation time is 2 to 6 hours.

[0014] Furthermore, in a preferred embodiment, the method further includes a step of cleaning the germanium wafer before placing it into the quartz boat. Even more preferably, the cleaning method includes acid washing and water washing.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] (1) The operation process is simple.

[0017] (2) Annealing under vacuum conditions effectively prevents the wafer surface from being oxidized and does not introduce other impurities.

[0018] (3) After annealing, the defects inside the crystal are significantly reduced. Attached Figure Description

[0019] Figure 1 This is a Tencor image of a germanium wafer after pre-cleaning.

[0020] Figure 2 This is a Tencor image of the germanium wafer after annealing in Example 1.

[0021] Figure 3 This is a Tencor image of the germanium wafer after annealing in Example 2.

[0022] Figure 4 This is a Tencor image of the germanium wafer after annealing in Example 3.

[0023] Figure 5 The image shows the Tencor pattern of the germanium wafer after annealing, as shown in Comparative Example 1.

[0024] Figure 6 The image shown is a Tencor image of a germanium wafer after annealing, as shown in Comparative Example 2.

[0025] Figure 7 The image shows the Tencor pattern of the germanium wafer after annealing, as shown in Comparative Example 3.

[0026] Figure 8 The image shows the Tencor pattern of the germanium wafer after annealing, as shown in Comparative Example 4.

[0027] Figure 9 This is a Tencor image of a germanium wafer after annealing, as shown in Comparative Example 5.

[0028] Figure 10 The image shows the Tencor pattern of the germanium wafer after annealing, as shown in Comparative Example 6. Detailed Implementation

[0029] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] This invention provides an annealing process for germanium wafers, comprising the following steps:

[0033] The germanium wafers were placed one by one on the quartz boat, and then the quartz boat was placed into the quartz tube;

[0034] After sealing the quartz tube, evacuate it to the preset vacuum level;

[0035] Place the quartz tube in the annealing furnace, turn on the furnace, and heat it to 630~700℃ and hold it for a period of time; the heating rate is 1.0-1.2℃ / min.

[0036] After the heat preservation is completed, the temperature is lowered; the cooling rate is 1.0-1.2℃ / min.

[0037] In some specific embodiments, the preset vacuum degree is 1×10⁻⁶. -4 pa.

[0038] In some specific implementations, the heat preservation time is 2 to 6 hours, which can be 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0039] In some specific embodiments, the method further includes a step of cleaning the germanium wafer before placing it into the quartz boat. The cleaning method includes acid washing and water washing. The acid used for acid washing is sulfuric acid.

[0040] The technical solution of the present invention will be further described below through specific embodiments and comparative examples.

[0041] Before annealing, germanium wafers are pre-cleaned: concentrated sulfuric acid with a concentration of 95-98wt% is used as a cleaning agent to clean the germanium wafers. The acid treatment time is 30s, the rinsing time is 60s, the above process is repeated 3 times, and the wafers are spun dry for 600s.

[0042] After pre-cleaning, the Tencor pattern of the wafer is as follows: Figure 1 As shown, the number of bright spots before annealing was 4306.

[0043] Example 1

[0044] The annealing process for germanium wafers includes:

[0045] (1) Place the dried germanium wafers sequentially into a quartz boat, and then place the quartz boat into a quartz tube. Seal the quartz tube and evacuate it to a preset vacuum level of 1×10⁻⁶. -4 pa;

[0046] (2) Place the quartz tube into the annealing furnace, cover the furnace, and start the annealing process, which is divided into three stages:

[0047] The first stage is the heating program: the annealing furnace is heated from room temperature to 700℃ at a heating rate of 1℃ / min;

[0048] The second stage is the heat preservation process: heat preservation at 700℃ for 2 hours;

[0049] The third stage is the cooling process: after the heat preservation is completed, the temperature is reduced to room temperature at a rate of 1.2℃ / min.

[0050] Turn off the vacuum system, open the vacuum valve to purge the vacuum, open the furnace lid and remove the wafer.

[0051] Figure 2 This is a Tencor image of the wafer after annealing. There are 8 bright spots after annealing. (Comparison) Figure 1 and Figure 2 After annealing, the number of bright spots is significantly reduced.

[0052] Example 2

[0053] The annealing process for germanium wafers includes:

[0054] (1) Place the dried germanium wafers sequentially into a quartz boat, and then place the quartz boat into a quartz tube. Seal the quartz tube and evacuate it to a preset vacuum level of 1×10⁻⁶. -4pa;

[0055] (2) Place the quartz tube into the annealing furnace, cover the furnace, and start the annealing process, which is divided into three stages:

[0056] The first stage is the heating program: the annealing furnace is heated from room temperature to 630℃ at a heating rate of 1.2℃ / min;

[0057] The second stage is the heat preservation process: heat preservation at 630℃ for 6 hours;

[0058] The third stage is the cooling process: after the heat preservation is completed, the temperature is reduced to room temperature at a rate of 1℃ / min.

[0059] Turn off the vacuum system, open the vacuum valve to purge the vacuum, open the furnace lid and remove the wafer.

[0060] Figure 3 This is a Tencor image of the wafer after annealing. The number of bright spots after annealing is 15.

[0061] Example 3

[0062] The annealing process for germanium wafers includes:

[0063] (1) Place the dried germanium wafer into a quartz boat, and then place the quartz boat into a quartz tube. Seal the quartz tube and evacuate it to the preset vacuum level of 1×10⁻⁶. -4 pa;

[0064] (2) Place the quartz tube into the annealing furnace, cover the furnace, and start the annealing process, which is divided into three stages:

[0065] The first stage is the heating program: the annealing furnace heats the temperature from room temperature to 680℃ at a heating rate of 1.1℃ / min;

[0066] The second stage is the heat preservation process: heat preservation at 680℃ for 4 hours;

[0067] The third stage is the cooling process: after the heat preservation is completed, the temperature is reduced to room temperature at a rate of 1.1℃ / min.

[0068] Turn off the vacuum system, open the vacuum valve to purge the vacuum, open the furnace lid and remove the wafer.

[0069] Figure 4 This is a Tencor image of the wafer after annealing. The number of bright spots after annealing is 59.

[0070] Comparative Examples 1-6

[0071] The only difference between Comparative Example 1 and Example 1 is that the heating rate is 1.3℃ / min.

[0072] The only difference between Comparative Example 2 and Example 1 is that the heating rate is 0.9℃ / min.

[0073] The only difference between Comparative Example 3 and Example 1 is that the holding temperature reached is 710°C.

[0074] The only difference between Comparative Example 4 and Example 1 is that the holding temperature reached was 620°C.

[0075] The only difference between Comparative Example 5 and Example 1 is that the cooling rate is 1.3℃ / min.

[0076] The only difference between Comparative Example 6 and Example 1 is that the cooling rate is 0.9℃ / min.

[0077] Figures 5-10 The images show the Tencor patterns of the wafers obtained after annealing in Comparative Examples 1-6. As can be seen from the images, the number of bright spots is relatively large, at 3174, 2071, 3207, 3274, 2912, and 021 respectively.

[0078] It can be determined through Examples 1-3 and Comparative Examples 1-6 that the annealing process provided by the present invention has an excellent effect on eliminating internal defects in germanium wafers.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An annealing process for germanium wafers with a thickness of 280-320 μm, characterized in that, Includes the following steps: The germanium wafers were placed one by one on the quartz boat, and then the quartz boat was placed into the quartz tube; After sealing the quartz tube, evacuate it to a level below the preset vacuum level; Place the quartz tube in the annealing furnace, turn on the annealing furnace, heat to 630~700℃ and hold for 2~6 hours; the heating rate is 1.0-1.2℃ / min. After the heat preservation is completed, the temperature is lowered; the cooling rate is 1.0-1.2℃ / min.

2. The annealing process as described in claim 1, characterized in that, The preset vacuum level is 1×10⁻⁶. -4 pa.

3. The annealing process as described in claim 1 or 2, characterized in that, Also includes: The step of cleaning the germanium wafers before placing them on the quartz boat.

4. The annealing process as described in claim 3, characterized in that, The cleaning methods include acid washing and water washing.

Images