CN115707527A - DK furnace tube cleaning method - Google Patents

Abstract

The invention relates to a method for cleaning a DK furnace tube, which belongs to the technical field of chip manufacturing and processing equipment, and includes the following steps: the first step: pickling the DK furnace tube, and the acid solution used is composed of deionized water, hydrofluoric acid and nitric acid ; The H2O:HF:HNO3 volume ratio of the acid solution is between 9:3:1 and 200:65:12. Step 2: Use UPW to flush, 10 minutes each time, 5 times, and drain the sewage after flushing. Step 3: After the DK furnace tube is rinsed, it is blown dry with N2, and the DK furnace tube is dried in the N2 cabinet for ≥ 12 hours. Step 4: The DK furnace tube is tested for acidity. Use PH test paper to test the acidity of the furnace tube. If the pH value is 7, the cleaning is completed. If the pH value is not 7, it is rinsed with UPW. Take it out and dry it again in an N2 cabinet for ≥12 hours. It has the characteristics of simple operation, thorough cleaning and good stability. The problem of difficulty in cleaning the furnace tube is solved.

Description

DK furnace tube cleaning method

technical field

The invention relates to the technical field of chip manufacturing and processing equipment, in particular to a method for cleaning a DK furnace tube.

Background technique

With the continuous development of chip manufacturing technology, the size of semiconductor silicon wafers is getting larger and larger, and the requirements for process technology are becoming more and more stringent, which puts forward higher requirements for the effect of regular cleaning of furnace tubes. Simple furnace tube cleaning can no longer meet the actual production application, especially for device products that have higher requirements for metal contamination. Usually chip manufacturing has to go through repeated processes such as cleaning process, diffusion process, implantation process, photolithography process, and etching process. After multiple film formations, the residual metal ions and polymer residues in the furnace tube accumulate If it is not removed regularly, it may form metal contamination and particle sources, thereby affecting process yield and product stability.

The impact of metal pollution on semiconductor devices is as follows: metal impurities are easy to accumulate at the Si-SiO2 interface, affecting the integrity of the gate oxide layer (Gate Oxide Integrity, referred to as GOI), reducing the oxide breakdown voltage (Oxidebreakdown voltage, referred to as BV- OX), causing the device to form leakage (Leakage). CMOS analog sensor (CMOSImagine Sensor, referred to as CIS) products are particularly sensitive to metal impurities, especially heavy metal impurities, which are prone to dark current (Dark current, referred to as DC), causing white spot defects (White Spot Defect).

Metal ions under high temperature conditions have a high diffusion coefficient in silicon and silicon dioxide, so after the furnace tube has been operated at high temperature for a long time, metal pollution (quartz or silicon carbide components) caused by the current process or metal pollution brought by the previous process It is easy to diffuse into the interior of the silicon wafer and is difficult to remove by cleaning, thus forming permanent defects. Therefore, the furnace tube machine must be cleaned regularly. Traditional furnace tube cleaning methods include: N2 cleaning. N2 at high temperature can remove small particles and organic residues in the furnace tube, but cannot remove metal ions.

Contents of the invention

The invention mainly solves the problem that metal ions cannot be removed in the prior art, and provides a DK furnace tube cleaning method, which has the characteristics of simple operation, thorough cleaning and good stability. The problem of difficulty in cleaning the furnace tube is solved. Improve the stability of semiconductor silicon wafer processing technology.

Above-mentioned technical problem of the present invention is mainly solved by following technical scheme:

A DK furnace tube cleaning method, comprising the following steps:

The first step: pickling of DK furnace tube, the acid solution used is composed of deionized water, hydrofluoric acid and nitric acid; the volume ratio of H2O:HF:HNO3 of the acid solution is between 9:3:1～200:65:12 between. The strong oxidizing property of HNO3 can oxidize metal atoms to ionic state and oxidize surface silicon atoms to silicon dioxide, and use HF to peel off metal impurities and silicon surface oxide layer, so as to obtain a clean furnace tube without metal and oxide contamination . The metal pollution in the furnace tube is removed through the redox reaction of nitric acid and hydrofluoric acid.

Step 2: Use UPW to flush, 10 minutes each time, 5 times, and drain the sewage after flushing.

Step 3: After the DK furnace tube is rinsed, it is blown dry with N2, and the DK furnace tube is dried in the N2 cabinet for a drying time of ≥12 hours.

Step 4: The DK furnace tube is tested for acidity. Use PH test paper to test the acidity of the furnace tube. If the pH value is 7, the cleaning is completed. If the pH value is not 7, it is rinsed with UPW. Take it out and dry it in the N2 cabinet again for ≥12 hours.

Preferably, the acid solution cleaning time for the DK furnace tube is 50-70 minutes.

Preferably, when the pickling process is halfway through, it is necessary to control the temperature of the mixed solution, and keep the temperature between 45°C and 55°C.

As preferably, the temperature is raised at a rate of 2 degrees Celsius/minute when the temperature is raised, and after the pickling process is completed, the temperature is lowered to normal temperature at a rate of 3 degrees Celsius/minute.

Preferably, after the temperature of the acid solution is kept constant, water vapor is added.

The present invention can achieve following effect:

The invention provides a DK furnace tube cleaning method, which has the characteristics of simple operation, thorough cleaning and good stability compared with the prior art. The problem of difficulty in cleaning the furnace tube is solved. Improve the stability of semiconductor silicon wafer processing technology.

Detailed ways

Below through embodiment, the technical solution of the invention is described further in detail.

Embodiment: a kind of DK furnace pipe cleaning method, comprises following operation steps:

The first step: pickling of DK furnace tube, the acid solution used is composed of deionized water, hydrofluoric acid and nitric acid; the volume ratio of H2O:HF:HNO3 of the acid solution is between 9:3:1～200:65:12 between. The acid solution cleaning time for the DK furnace tube is 60 minutes. Halfway through the pickling process, it is necessary to carry out constant temperature control on the mixed solution, and keep the temperature between 50 degrees. When the temperature of the acid solution is kept constant, make up the water vapor.

When heating up, the temperature is raised at a rate of 2 degrees Celsius/minute, and after the pickling process is completed, the temperature is lowered to normal temperature at a rate of 3 degrees Celsius/minute.

Step 2: Use UPW to flush, 10 minutes each time, 5 times, and drain the sewage after flushing.

Step 3: After the DK furnace tube is rinsed, it is blown dry with N2, and the DK furnace tube is dried in the N2 cabinet for a drying time of ≥12 hours.

Step 4: The DK furnace tube is tested for acidity. Use PH test paper to test the acidity of the furnace tube. If the pH value is 7, the cleaning is completed. If the pH value is not 7, it is rinsed with UPW. Take it out and dry it in the N2 cabinet again for ≥12 hours.

In summary, the DK furnace tube cleaning method has the characteristics of simple operation, thorough cleaning and good stability. The problem of difficulty in cleaning the furnace tube is solved. Improve the stability of semiconductor silicon wafer processing technology.

The above is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto, any changes or modifications made by those skilled in the art within the field of the present invention are covered by the patent scope of the present invention among.

Claims (5)

1. a DK furnace tube cleaning method is characterized in that comprising the following steps: The first step: pickling of DK furnace tube, the acid solution used is composed of deionized water, hydrofluoric acid and nitric acid; the volume ratio of H2O:HF:HNO3 of the acid solution is between 9:3:1～200:65:12 between; Step 2: Rinse with UPW, 10 minutes each time, 5 times, and drain the sewage after rinsing; Step 3: After the DK furnace tube is rinsed, it is blown dry with N2, and the DK furnace tube is dried in the N2 cabinet for ≥ 12 hours; Step 4: The DK furnace tube is tested for acidity. Use PH test paper to test the acidity of the furnace tube. If the pH value is 7, the cleaning is completed. If the pH value is not 7, it is rinsed with UPW. Take it out and dry it in the N2 cabinet again for ≥12 hours. 2. The method for cleaning the DK furnace tube according to claim 1, characterized in that: the acid solution cleaning time for the DK furnace tube is 50-70 minutes. 3. The method for cleaning the DK furnace tube according to claim 1, characterized in that: when the pickling process is halfway through, the mixed solution needs to be controlled at a constant temperature, and the temperature is kept between 45°C and 55°C. 4. DK furnace tube cleaning method according to claim 3, is characterized in that: heat up with the speed of 2 degrees Celsius/minute when heating up, after finishing pickling process, cool down to normal temperature with the speed of 3 degrees Celsius/minute . 5. The DK furnace tube cleaning method according to claim 3, characterized in that: when the temperature of the acid solution is kept constant, the water vapor is added.