Furnace tube cleaning method

Abstract

The invention provides a furnace tube cleaning method which comprises the following steps: step 1, sealing a furnace tube, maintaining the temperature of the furnace tube at a preset cleaning temperature, and continuously introducing inert purging gas into the furnace tube; 2, ammonia gas cleaning, wherein ammonia gas is introduced into the furnace tube, and inert purging gas continues to be introduced; step 3, primary purging: stopping introducing the ammonia gas, and continuing to introduce the inert purging gas; step 4, oxidation purification: increasing the temperature of the furnace tube, introducing oxygen into the furnace tube, continuously introducing inert purging gas, and decomposing ammonia gas on the inner wall of the furnace tube into nitrogen and water vapor; and 5, secondary purging: stopping introducing the oxygen, and continuing to introduce the inert purging gas. According to the method, the copper ion pollution is removed, and meanwhile, the damage to the semiconductor device caused by ammonia gas residues is effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and in particular relates to a furnace tube cleaning method. Background Technology

[0002] In semiconductor manufacturing processes, the cleanliness of components such as vertical diffusion furnace tubes is crucial. Metal contamination, especially heavy metals like iron (Fe), nickel (Ni), and copper (Cu), can significantly reduce the electrical performance and yield of devices. Among these, copper is one of the most challenging contaminants due to its extremely high diffusion coefficient in silicon and silica. Summary of the Invention

[0003] The purpose of this invention is to provide a furnace tube cleaning method that achieves selective and efficient removal of copper ion contamination. Simultaneously, through optimized process parameters and steps, it effectively avoids damage to semiconductor devices caused by residual ammonia (dielectric layer damage, decreased gate oxide reliability). The technical solution adopted is as follows: A method for cleaning furnace tubes, specifically vertical furnace tubes, includes the following steps: Step 1: Seal the furnace tube, maintain the furnace tube temperature at the predetermined cleaning temperature, and continuously introduce inert purging gas into the furnace tube; Step 2, Ammonia cleaning: Ammonia gas is introduced into the furnace tube, and inert purging gas is continuously introduced. The ammonia gas reacts with copper ions on the inner wall of the furnace tube to form a gaseous copper ammonia complex. Step 3, First-level purging: Stop the flow of ammonia gas and continue to flow inert purging gas; Step 4, Oxidation purification: Increase the furnace tube temperature, introduce oxygen into the furnace tube, and continue to introduce inert purging gas. The ammonia on the inner wall of the furnace tube decomposes into nitrogen and water vapor. Step 5, Secondary Purging: Stop the oxygen supply and continue to supply inert purging gas.

[0004] Preferably, the volume concentration of ammonia in step 2 is 0.1% to 5%.

[0005] Preferably, the ammonia cleaning time is 0.5h to 4h.

[0006] Preferably, the first-stage purging time is 1 to 3 times the ammonia cleaning time.

[0007] Preferably, the volume concentration of oxygen in step 4 is 5%.

[0008] Preferably, the predetermined cleaning temperature in step 1 is 150℃~450℃.

[0009] Preferably, in step 4, the furnace tube temperature is increased to 400~600℃.

[0010] Preferably, the inert purging gas is nitrogen.

[0011] This invention is particularly applicable to the maintenance and cleaning of non-critical furnace tube process cavities (cavities that do not directly affect core electrical performance and mainly play an auxiliary, isolation and protection role).

[0012] Compared with the prior art, the advantages of the present invention are: It achieves selective and efficient removal of copper ion contamination, while effectively avoiding damage to semiconductor devices caused by residual ammonia through optimized process parameters and steps. Attached Figure Description

[0013] Figure 1 This is a flowchart of the furnace tube cleaning method. Detailed Implementation

[0014] The furnace tube cleaning method of the present invention will now be described in more detail with reference to the schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0015] like Figure 1 As shown, a furnace tube cleaning method, namely a vapor-phase cleaning method for removing copper ions from furnace tubes, includes the following steps: Step 1: Preparation.

[0016] The furnace door of the furnace tube is closed, the furnace tube temperature (temperature inside the furnace tube) is maintained at 300°C, and nitrogen (N2) is used as the purging gas and continuously introduced into the furnace tube.

[0017] Step 2: Ammonia cleaning.

[0018] Ammonia (NH3) is introduced into the furnace tube, and nitrogen (N2) is continued to be introduced. The ammonia reacts with copper ions on the inner wall of the furnace tube to form a gaseous copper-ammonia complex.

[0019] That is, in step 2, a mixture of NH3 and N2 gas is introduced into the furnace tube.

[0020] The mixed gas consists of 1% NH3 by volume and 99% N2, with a total gas flow rate of 10 SLM, and is continuously introduced for 2 hours.

[0021] During this period, copper ions (copper or copper oxide) on the inner wall of the furnace tube react fully with NH3 to form a gaseous complex [Cu(NH3)4]. + And it is carried out by the airflow in step 3.

[0022] Step 3: Primary purging.

[0023] Stop the flow of ammonia (NH3) and continue to flow nitrogen (N2) to purge the inner wall of the furnace tube.

[0024] The furnace tube was continuously purged for 4 hours to remove most of the reaction byproducts and gaseous complexes.

[0025] The flow rate of nitrogen (N2) is 10 SLM.

[0026] Step 4: Oxidation purification.

[0027] Raise the furnace tube temperature to 500℃, introduce O2 into the furnace tube, and continue to introduce N2.

[0028] That is, in step 2, a mixture of O2 and N2 gas is introduced into the furnace tube.

[0029] The gas mixture consists of 5% O2 by volume and 95% N2 by volume.

[0030] The total gas flow rate is 5 SLM, and the treatment lasts for 30 minutes.

[0031] This step completely oxidizes and decomposes any NH3 molecules chemically adsorbed on the inner wall of the furnace tube, breaking them down into nitrogen and water vapor.

[0032] Step 4 is the key difference between this application and the conventional wisdom (that NH3 is unusable).

[0033] This step, through high-temperature oxidation, completely decomposes any trace amounts of ammonia (ammonia molecules) that may be adsorbed on the inner surface of the furnace tube into harmless nitrogen and water vapor, thus solving the core problem of ammonia as a pollutant.

[0034] Step 5: Secondary purging.

[0035] Stop introducing oxygen (O2) and continue introducing nitrogen (N2) to purge the inner wall of the furnace tube.

[0036] The purpose of step 5 is to remove the oxidation reaction byproduct H2 and to safely cool the furnace tubes.

[0037] The cleaning process ends when the furnace tubes naturally cool down to below 100°C.

[0038] This multi-step, closed-loop process design ensures that while leveraging the advantages of ammonia in efficiently complexing copper, it systematically eliminates potential risks, thereby enabling the technical solution to possess the novelty, inventiveness, and utility required for a patent.

[0039] Tests showed that the copper contamination (copper ion) level in the furnace tube decreased by more than 98%, and subsequent wafer monitoring tests revealed no electrical performance degradation caused by residual ammonia (NH3).

[0040] Furthermore, the copper ion removal rate of existing HCL purging methods (prior art) is only 25% in this embodiment.

[0041] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A method for cleaning furnace tubes, characterized in that, Includes the following steps: Step 1: Seal the furnace tube, maintain the furnace tube temperature at the predetermined cleaning temperature, and continuously introduce inert purging gas into the furnace tube; Step 2, Ammonia cleaning: Ammonia gas is introduced into the furnace tube, and inert purging gas is continuously introduced. The ammonia gas reacts with copper ions on the inner wall of the furnace tube to form a gaseous copper ammonia complex. Step 3, First-level purging: Stop the flow of ammonia gas and continue to flow inert purging gas; Step 4, Oxidation purification: Increase the furnace tube temperature, introduce oxygen into the furnace tube, and continue to introduce inert purging gas. The ammonia on the inner wall of the furnace tube decomposes into nitrogen and water vapor. Step 5, Secondary Purging: Stop the oxygen supply and continue to supply inert purging gas.

2. The furnace tube cleaning method according to claim 1, characterized in that, In step 2, the volume concentration of ammonia is 0.1% to 5%.

3. The furnace tube cleaning method according to claim 1, characterized in that, The ammonia cleaning time is 0.5h to 4h.

4. The furnace tube cleaning method according to claim 1, characterized in that, The first-stage purging time is 1 to 3 times the ammonia cleaning time.

5. The furnace tube cleaning method according to claim 1, characterized in that, The volume concentration of oxygen in step 4 is 5%.

6. The furnace tube cleaning method according to claim 1, characterized in that, The predetermined cleaning temperature in step 1 is 150℃~450℃.

7. The furnace tube cleaning method according to claim 1, characterized in that, In step 4, the furnace tube temperature is increased to 400~600℃.

8. The furnace tube cleaning method according to claim 1, characterized in that, The inert purging gas is nitrogen.

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