A method for reducing the copper atomic content of a cavity

Abstract

The application provides a method for reducing the content of copper atoms in a cavity, and relates to the technical field of semiconductor processes, and is designed to solve the problems of high cost, more manpower and time occupied in the method for controlling copper pollution provided by related technologies. The method for reducing the content of copper atoms in the cavity comprises the following steps: heating the cavity to a preset temperature; introducing an oxygen-containing gas into the cavity, and reacting the oxygen-containing gas with copper atoms in the cavity to form copper oxide; and introducing a purge gas into the cavity, and using the purge gas to carry the copper oxide out of the cavity. The method for reducing the content of copper atoms in the cavity by using the chemical reaction between the oxygen-containing gas and the copper atoms at high temperature not only reduces the cost without replacing the expensive equipment components, but also saves manpower and time without regularly disassembling and cleaning the equipment components.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor process, in particular to a method for reducing copper atom content in a cavity. BACKGROUND

[0002] In a semiconductor manufacturing process, a vertical oxidation furnace is a key equipment for high-temperature processes (such as oxidation, diffusion and annealing, etc.). However, in the high-temperature processes, a quartz tube or other components inside the cavity will release trace amounts of copper atoms, and wafers using copper interconnection processes will also introduce some copper atoms into the cavity. These copper atoms present in the cavity will have a negative impact on the process of the vertical oxidation furnace. Therefore, in the vertical oxidation furnace process, strict control of copper contamination is the key to ensuring the structure and electrical properties of the device.

[0003] The method for controlling copper contamination provided by the related art mainly has the following two kinds: 1. Replace the original machine components with high-purity quartz components, use the low contamination of high-purity quartz material to reduce the release of copper atoms in high-temperature processes; 2. Disassemble the components in the vertical oxidation furnace, take them out and soak them in dilute nitric acid or dilute hydrochloric acid solution, and confirm the cleaning time according to different contamination levels, after cleaning, use deionized water to rinse thoroughly to remove residual chemical solution, and finally dry in a nitrogen-filled oven. Among them, the use of high-purity quartz material has high cost, and the use of regular cleaning technology needs to disassemble and install the components, which is complex to operate, not only occupies more manpower and time, but also has high cost, and also reduces the yield. SUMMARY

[0004] The purpose of the present application is to provide a method for reducing the copper atom content in a cavity, to solve the technical problems of high cost and occupation of more manpower and time in the method for controlling copper contamination provided by the related art.

[0005] The method for reducing the copper atom content in a cavity provided by the present application comprises:

[0006] warming the cavity to a preset temperature;

[0007] introducing an oxygen-containing gas into the cavity, and reacting the oxygen-containing gas with the copper atoms in the cavity to form copper oxide;

[0008] introducing a purge gas into the cavity to carry the copper oxide out of the cavity.

[0009] Further, before the step of introducing a purge gas into the cavity, the method further comprises:

[0010] stopping the introduction of the oxygen-containing gas, and reducing the temperature of the cavity from the preset temperature to the temperature of the machine.

[0011] Further, the cooling rate of the cavity is 5-10℃ / min.

[0012] Further, the preset temperature is 800-1000℃; and / or, the heating rate of the cavity is 5-10℃ / min.

[0013] Further, the oxygen-containing gas comprises oxygen with a purity of 99.99%.

[0014] Further, the flow rate of the oxygen-containing gas is gradually increased from an initial flow rate to a preset flow rate, and the flow rate of the oxygen-containing gas is increased by 1 slm every 30s.

[0015] Further, the initial flow rate is (5±0.002)slm, and the preset flow rate is 10-20slm.

[0016] Further, the cavity pressure during the reaction of the oxygen-containing gas with the copper atoms in the cavity to form copper oxides is normal pressure.

[0017] Further, the reaction time of the oxygen-containing gas with the copper atoms in the cavity is 5-10h.

[0018] Further, the cavity is a furnace tube of a vertical oxidation furnace.

[0019] The method for reducing the copper atom content of the cavity has the following beneficial effects:

[0020] In the method for reducing the copper atom content of the cavity, the chemical activity of the copper atoms in the cavity is increased by heating the cavity to a preset temperature; then, an oxygen-containing atmosphere is formed in the cavity by introducing an oxygen-containing gas into the cavity, so that the copper atoms adhering to the inner wall of the cavity can chemically react with oxygen atoms to form copper oxides in a suspended state; subsequently, the copper oxides formed in the cavity are carried out of the cavity by introducing a purge gas into the cavity, thereby achieving the purpose of reducing the copper atom content of the cavity.

[0021] This method of using an oxygen-containing gas to chemically react with copper atoms at high temperature to reduce the copper atom content not only reduces the cost of replacing expensive equipment components, but also eliminates the need to periodically disassemble and clean the equipment components, thereby saving manpower and time and reducing the impact on yield. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the following will briefly introduce the drawings needed to be used in the embodiments or related art descriptions. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0023] Figure 1 A flowchart of a method for reducing the copper atom content of a cavity provided by an embodiment of the present application is shown in FIG. 1.

[0024] Figure 2 A schematic diagram of the principle of a method for reducing the copper atom content of a cavity provided by an embodiment of the present application is shown in FIG. 2.

[0025] Figure 3 A flowchart of another method for reducing the copper atom content of a cavity provided by an embodiment of the present application is shown in FIG. 3.

[0026] Figure 4 A comparison chart of the copper atom content at different regions of a vertical oxidation furnace using and not using the method for reducing the copper atom content of a cavity provided by an embodiment of the present application is shown in FIG. 4, where Test-1 is data not using the above method and Test-2 is data using the above method. DETAILED DESCRIPTION

[0027] At present, copper contamination in a vertical oxidation furnace has a significant negative impact on its process. For example, in the oxidation process, copper atoms will enter the oxide layer and cause defects, resulting in a decrease in the density of the oxide layer, an increase in the leakage current, and a decrease in the insulation performance. In addition, copper atoms can catalyze or inhibit the oxidation reaction, resulting in uneven film formation rate, which reduces the uniformity of the oxide layer and degrades the quality of the oxide layer. In the diffusion process, the fast diffusion rate of copper atoms in silicon will result in uneven concentration of doping elements, which will adversely affect the performance of the device. In addition, if copper atoms diffuse to the PN junction region, it will also cause deep level traps, resulting in increased leakage current and degradation of junction characteristics. In the annealing process, copper atoms not only hinder the repair of lattice defects, but also reduce the activation efficiency of doping atoms, resulting in substandard electrical performance of the device.

[0028] Therefore, it is necessary to strictly control the copper contamination in the vertical oxidation furnace. The related technology uses high-purity quartz material to replace the original machine table components, which can reduce the release of copper atoms in high-temperature processes, but the cost is high. The periodic cleaning technology has the problems of complex operation and long cleaning period, which not only occupies more manpower and time, but also reduces the yield.

[0029] Therefore, the purpose of the present application is to provide a method for reducing the copper atom content of a cavity to solve the problems of high cost and occupation of more manpower and time in the method for controlling copper contamination provided by the related technology.

[0030] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0031] As shown in Figure 1 The embodiment provides a method for reducing the content of copper atoms in a cavity, which comprises the following steps:

[0032] S200: heating the cavity to a preset temperature.

[0033] By heating the cavity, the chemical activity of copper atoms can be increased, so that the stability of copper atoms attached to the inner wall of the cavity is reduced, and chemical reactions are more likely to occur. The cavity is heated from room temperature to a preset temperature.

[0034] S300: introducing an oxygen-containing gas into the cavity, and reacting the oxygen-containing gas with copper atoms in the cavity to form copper oxide.

[0035] After high-temperature heating in the above step, the chemical activity of copper atoms is increased. On this basis, by introducing an oxygen-containing gas into the cavity, the oxygen-containing gas can react with the above-mentioned copper atoms to generate copper oxide.

[0036] S500: introducing a purge gas into the cavity, and using the purge gas to carry the copper oxide out of the cavity.

[0037] After the chemical reaction between the oxygen-containing gas and the copper atoms, the generated copper oxide floats in the cavity in a suspended state. At this time, by introducing a purge gas into the cavity, the above-mentioned copper oxide can be carried out of the cavity by using the purge gas, so as to achieve the purpose of reducing the content of copper atoms in the cavity.

[0038] As can be seen, this method of using an oxygen-containing gas to react with copper atoms at high temperature to reduce the content of copper atoms not only reduces the cost without the need to replace expensive equipment components, but also saves manpower and time without the need to regularly disassemble and clean the components of the equipment, thereby reducing the impact on the yield.

[0039] In the embodiment, the cavity is a furnace tube of a vertical oxidation furnace. That is, the method for reducing the content of copper atoms in the cavity can reduce the content of copper atoms inside the furnace tube of the vertical oxidation furnace.

[0040] In other embodiments, the cavity can also be a furnace tube of a horizontal oxidation furnace.

[0041] In the embodiment, in step S200, the preset temperature is 800-1000°C.

[0042] This temperature can effectively increase the chemical activity of copper atoms attached to the inner wall of the cavity.

[0043] In the embodiment, in step S200, the heating rate of the cavity is 5-10°C / min.

[0044] By limiting the temperature rising rate of the cavity within the above range, on the one hand, the time-consuming process caused by too slow temperature rising can be avoided, and on the other hand, the cavity components can also be prevented from being subjected to greater thermal alternating loads caused by too fast temperature rising.

[0045] In the embodiment, the oxygen-containing gas includes high-purity oxygen with a purity of 99.99%.

[0046] As shown in FIG. 1, after the high-purity oxygen is introduced into the cavity, the copper atoms attached to the inner wall of the cavity will chemically react with the oxygen, and the chemical reaction formula is as follows: Figure 2 2Cu + O2→ 2CuO↓ (1)

[0047] 4Cu + O2→ 2Cu2O↓ (2)

[0048] Among them, the generated copper oxide can be in a suspended state and float in the cavity, so that it can be carried out of the cavity under the action of the purge gas, which is nitrogen.

[0049] Preferably, the oxygen-containing gas introduced into the cavity is all oxygen with a purity of 99.99%. This setting makes the cavity have a high-purity oxygen atmosphere after the oxygen-containing gas is introduced into the cavity, so that the copper atoms attached to the inner wall of the cavity are completely surrounded by high-purity oxygen, which is beneficial to the chemical reaction of the copper atoms in the above formula (1) and formula (2).

[0050] In other embodiments, the oxygen-containing gas can also be H2O, and the chemical reaction formula occurring in the cavity is as follows:

[0051] 2Cu + 2H2O→ 2CuO + 2H2↑ (3)

[0052] In other embodiments, other inert gases can also be used as the purge gas.

[0053] In the embodiment, the flow rate of the oxygen-containing gas gradually increases from an initial flow rate to a preset flow rate, wherein the flow rate of the oxygen-containing gas is increased by 1 slm every 30 s.

[0054] In the initial stage, the oxygen-containing gas is introduced into the cavity at an initial flow rate; as the oxygen-containing gas continuously reacts with the copper atoms, the flow rate of the oxygen-containing gas gradually increases and eventually increases to a preset flow rate.

[0055]

[0056] ​The setting can first react the oxygen-containing gas with the copper atoms attached to the inner wall surface of the cavity to form copper oxide; as the reaction continues and the flow of the oxygen-containing gas increases, the copper atoms in the deep layer of the inner wall of the cavity can be exposed to more sufficient oxygen-containing gas for further reaction, thereby increasing the combination effect of copper atoms and oxygen-containing gas through the staged chemical reaction of copper atoms and oxygen-containing gas, thereby enhancing the oxidation of copper atoms in the cavity and improving the removal effect of copper atoms.

[0057] By setting the flow of the oxygen-containing gas to increase by 1 slm every 30 s, on the one hand, it can avoid the waste of the oxygen-containing gas due to the insufficient reaction of the previously introduced oxygen-containing gas with the copper atoms caused by the too fast increase of the flow of the oxygen-containing gas, and on the other hand, it can also avoid the low removal efficiency of the copper atoms caused by the too slow increase of the flow of the oxygen-containing gas.

[0058] In the embodiment, the initial flow is (5±0.002) slm, and the preset flow is 10-20 slm.

[0059] By setting the initial flow to the above value, it can avoid the too small initial flow to cause too little oxygen-containing gas to participate in the oxidation of copper atoms in the initial stage, thereby reducing the removal rate of copper atoms; by setting the preset flow in the above range, it can not only ensure the removal rate of subsequent copper atoms, but also avoid the waste caused by the too large flow.

[0060] In the initial stage of the introduction of the oxygen-containing gas into the cavity, the flow of the oxygen-containing gas will fluctuate by ±0.002 slm around the reference value of 5 slm due to the influence of pipeline, valve and other components. As the oxygen-containing gas is continuously introduced, its flow will tend to be stable and gradually increase to the preset flow.

[0061] Preferably, the preset flow is 15 slm.

[0062] In the embodiment, the cavity pressure for the reaction of the oxygen-containing gas with the copper atoms in the cavity to form copper oxide is normal pressure.

[0063] This setting not only ensures the smooth reaction of the oxygen-containing gas with the copper atoms in the high-temperature environment, but also saves the cumbersome steps of pressurizing or depressurizing the cavity, thereby further reducing the cost of controlling the copper contamination in the cavity.

[0064] The normal pressure refers to the state or environment under atmospheric pressure, which is represented by the standard atmospheric pressure, about 101.325 KPa.

[0065] In the embodiment, the reaction time of the oxygen-containing gas with the copper atoms in the cavity is 5-10 h.

[0066] By limiting the reaction time of the oxygen-containing gas and the copper atoms within the above range, on the one hand, the situation that the copper atoms removal effect is poor due to insufficient time can be avoided, on the other hand, when the reaction time of the oxygen-containing gas and the copper atoms is 10h, most of the copper atoms have been removed, at this time, the continuous reaction of the oxygen-containing gas and the copper atoms is stopped, and the energy waste caused by removing a small number of residual copper atoms can be avoided.

[0067] As shown in Figure 3 The embodiment provides another method for reducing the content of copper atoms in the cavity, which further comprises, before the step of introducing the purge gas into the cavity:

[0068] S400: stop introducing the oxygen-containing gas, and reduce the cavity from the preset temperature to the machine temperature.

[0069] After the reaction of the oxygen-containing gas and the copper atoms is completed, the oxygen-containing gas will no longer be introduced into the cavity, and at the same time, the cavity is reduced from the preset temperature to the machine temperature, on the one hand, the cooling process is used to slow down the continuous reaction of the oxygen-containing gas and the copper atoms, on the other hand, the normal operation of the vertical oxidation furnace is also avoided due to the too low temperature of the cavity.

[0070] It should be noted that in the semiconductor process, the machine temperature generally refers to a specific temperature range that needs to be maintained by the semiconductor manufacturing equipment during operation. For this embodiment, the machine temperature is the furnace temperature set by the vertical oxidation furnace during operation to meet the process requirements. Specifically, in this embodiment, the machine temperature is 650℃.

[0071] In the above step S400, the cooling rate of the cavity is 5-10℃ / min.

[0072] By limiting the cooling rate of the cavity within the above range, on the one hand, the situation that the cavity is cooled too fast and each component is subjected to a large thermal load and is broken can be avoided, on the other hand, the situation that the cavity is cooled too slowly and the time is too long can also be avoided.

[0073] It should be noted that the cooling process of the cavity can be realized by the cooling function of the vertical oxidation furnace itself, without relying on other cooling equipment.

[0074] Please continue to refer to Figure 3 In this embodiment, before the step of heating the cavity to the preset temperature, further comprising:

[0075] S100: check each component of the cavity to ensure that it is in a normal working state.

[0076] Through this step, the detection of the operation of the cavity can be realized, and the situation that the method for reducing the content of copper atoms in the cavity of the embodiment cannot be implemented due to the fault of the cavity can be prevented.

[0077] The following describes the application of the method for reducing the copper atom content in the cavity in a vertical oxidation furnace.

[0078] After the furnace tube of the vertical oxidation furnace is heated to 1000℃ and 99.99% pure oxygen is introduced into the furnace tube for 5h of O2 baking, it can be seen that the copper atom content in the vertical oxidation furnace is significantly reduced in the Top (top), Center (middle) and Bottom (bottom) three regions.

[0079] In summary, by using the above method for reducing the copper atom content in the cavity provided in the embodiment, not only high-cost equipment components do not need to be replaced, but also the number of copper atoms in the cavity can be significantly reduced in a short time, and the equipment components do not need to be disassembled and cleaned regularly, thereby greatly reducing the time cost and material cost, and the efficiency is higher.

[0080] In addition, the method for reducing the copper atom content in the cavity provided in the embodiment can be applied to various types of vertical oxidation furnaces, and does not involve harmful chemical liquids, and has wide applicability and good environmental protection.

[0081] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be subject to the scope defined by the claims.

[0082] Finally, it should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or action from another entity or action, and do not necessarily require or imply that these entities or actions exist in any such actual relationship or order. Moreover, the term "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or apparatus including the element.

[0083] In the above embodiments, the description of the orientation such as "upper", "lower" and the like is based on the drawings.

[0084] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of reducing the copper atomic content of a cavity, characterized by, The method comprises: warming the chamber to a preset temperature; introducing an oxygen-containing gas into the chamber, and reacting the oxygen-containing gas with copper atoms in the chamber to form copper oxide; stopping the introduction of the oxygen-containing gas, and reducing the temperature of the chamber from the preset temperature to a machine temperature at a rate of 5-10 ℃ / min; introducing a purge gas into the chamber to remove the copper oxide from the chamber by the purge gas; the preset temperature is 800-1000 ℃; and / or the rate of warming the chamber is 5-10 ℃ / min; and the oxygen-containing gas comprises oxygen with a purity of 99.99%.

2. The method of claim 1, wherein the copper atom content of the chamber is reduced by, The flow rate of the oxygen-containing gas is gradually increased from an initial flow rate to a preset flow rate, and the flow rate of the oxygen-containing gas is increased by 1 every 30 s slm .

3. The method of claim 2, wherein the copper atom content of the chamber is reduced by, The initial flow rate is (5±0.002) slm , and the preset flow rate is 10-20 slm .

4. The method of claim 1, wherein the copper atom content of the chamber is reduced by, The pressure of the chamber in the reaction of the oxygen-containing gas with the copper atoms in the chamber to form copper oxide is normal pressure.

5. The method of claim 1, wherein the copper atom content of the chamber is reduced by, The reaction time of the oxygen-containing gas with the copper atoms in the chamber is 5-10 h.

6. The method of claim 1, wherein the copper atom content of the chamber is reduced by, The chamber is a furnace tube of a vertical oxidation furnace.

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