JP2541443B2 - Wet etching apparatus and filter regeneration method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet etching apparatus used in semiconductor manufacturing and a method for regenerating a filter.

[0002]

2. Description of the Related Art In a conventional wet etching apparatus, as shown in FIG. 5, a wafer 33 supported by a carrier 32 is immersed in a processing solution in a processing tank 29, and a processing solution overflowing from the processing tank 29 is pumped by a pump 31. Through the filter 30, and the filter 30 captures particles in the treatment liquid.
The purified processing solution was circulated in the processing bath 29 to etch the wafer 33.

FIG. 6 is a diagram showing the relationship between the number of wafers processed in a conventional wet etching apparatus and the number of particles on the wafer surface.

A case will be described in which a phosphoric acid aqueous solution is used as a processing liquid and a silicon nitride film on a wafer is etched. When forming a silicon nitride film of 2000 angstrom on the surface of the wafer 33 in a phosphoric acid aqueous solution at a temperature of 150 ° C. in the processing bath 29, the wafer 33 is immersed for 60 minutes for etching. When the silicon nitride film is etched, particles are mixed in the processing liquid, and the number of particles increases as the number of processed wafers increases.
In particular, when the number of sheets exceeds 2500, the rate of increase of the party becomes high as is clear from FIG. In the case of FIG. 6, particles having a diameter of 0.3 μm or more are counted.

[0005]

When the number of particles increases, the particles adhere to the wafer surface to contaminate the wafer surface, which lowers the yield when manufacturing semiconductor elements on the wafer. In the apparatus, the filter was replaced before the number of processed wafers reached 2500. The replacement of the filter is performed approximately once every six months, and since the filter itself is expensive, there is a problem that the running cost increases.

An object of the present invention is to provide a wet etching apparatus and a filter regenerating method for regenerating and using the filter without replacing the filter itself.

[0007]

In order to achieve the above-mentioned object, a wet etching apparatus according to the present invention has an etching processing section, a filter regeneration section, and a flow path switching section,
A wet etching apparatus for immersing a material to be etched in a treatment liquid, capturing particles in the treatment liquid, and performing a wet etching treatment on the material to be etched by circulating a purified treatment liquid. It has a bath, a filter, and a pump, the treatment bath is filled with a treatment liquid for etching, the filter is for capturing particles contained in the treatment liquid, and the pump is for treatment. The treatment liquid overflowing from the bath is passed through the filter and circulated in the treatment bath, and the filter regenerating unit supplies the chemical liquid to the filter by the pump, dissolves and removes particles of the filter with the chemical liquid, and After the treatment, the filter and the pump are washed with pure water to regenerate the filter. , The processing liquid piping system and the chemical and pure water piping systems are switched and connected, and the processing liquid for disposal in the processing tank and the processed chemical liquid and waste water after filter regeneration are discarded in the disposal piping system. To do.

Further, it has a replenishing tank, and the replenishing tank supplies an unused processing liquid into the processing tank.

Further, a pressure sensor is provided, and the pressure sensor is installed in the flow paths on the primary side and the secondary side of the filter, and monitors clogging of the filter by the pressure difference between the pressure sensors.

The chemical solution is hydrofluoric acid, the treatment solution is phosphoric acid, and the material to be etched is a silicon nitride film.

A method of regenerating a filter of a wet etching apparatus according to the present invention is a method of regenerating a filter of a wet etching apparatus in which a chemical solution treatment and a cleaning treatment are performed to regenerate a filter for trapping particles in an etching treatment liquid. Therefore, the chemical treatment is a treatment of bringing the chemical into contact with the filter to dissolve and remove particles adhering to the filter with the chemical, and the cleaning treatment is a treatment of cleaning the filter in contact with the chemical with pure water. .

[0012]

When the silicon nitride (Si ₃ N ₄ ) film on the wafer is etched with phosphoric acid, the components of the particles adhering to the filter are Si-OP, and these are Si ₃
It was found to be the reaction product of N ₄ and phosphoric acid. It was also confirmed that this product was soluble in hydrofluoric acid (HF).

Therefore, the filter is regenerated by bringing hydrofluoric acid into contact with the filter and dissolving and removing particles of the filter with the hydrofluoric acid. Further, the particles removed from the filter are discarded outside the tank without returning to the etching tank, so that the inside of the processing tank is cleaned.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a wet etching apparatus according to Embodiment 1 of the present invention.

In FIG. 1, the wet etching apparatus according to the present invention has an etching processing section, a filter regenerating section, and a flow path switching section.

The etching processing section includes a processing tank 8, a filter 9 and a pump 10. The processing tank 8 is composed of inner and outer double tanks 8a and 8b, and is a processing liquid L ₁ for etching.
Filled with the treatment liquid L ₁ from the upper edge of the inner tank 8a to the outer tank 8b.
The overflow processing solution L ₁ is circulated from the outer tank 8b to the inner tank 8a. In the embodiment, phosphoric acid is used as the processing liquid L ₁ , and the silicon nitride (Si ₃ N ₄ ) film on the wafer is etched.

The filter 9 is for trapping particles contained in the processing liquid L ₁ , and the pump 10 is for returning the processing liquid L ₁ overflowing to the outer tank 8b to the processing tank 8 through the filter 9. The filter 9 and the pump 10 are installed in series in the pipe P ₁ between the outer tank 8b and the inner tank 8a of the processing tank 8.

Further, a replenishment tank 13 is installed,
The unused processing liquid L ₁ therein is supplied into the inner tank 8a of the processing tank 8 through the valve 12 and the pipe 12a.

The filter regenerating section includes a chemical solution tank 11 and a pure water supply section 16. Chemical tank 11, liquid medicine L ₂ is filled, and with hydrofluoric acid (HF) as the chemical L _2. The chemical liquid tank 11 has one inlet and outlet connected to the downstream pipe P ₁ of the filter 9 and the other inlet and outlet connected to the upstream pipe P ₁ of the pump 10 via the pipes P ₂ and P ₃ . Further, the pure water supply unit 16 is connected to the upstream pipe P ₁ of the pump 10 via the pipe P ₄ .

The flow path switching section includes disposal pipes P ₅ , P ₆ , valves 1, 2, 3, 4, ₅ , ₆ , 7 and a valve control section 17. The discarding pipes P ₅ and P ₆ are connected to the downstream pipe P ₁ of the filter 9, respectively. The valve 1 has a filter 9
Is connected between the downstream side pipe P ₁ and the bottom of the inner tank 8 a of the processing tank 8, and the valve 2 is connected between the bottom of the outer tank 8 b and the upstream pipe P ₁ of the pump 10. The valve 3 is connected to the pipe P ₃ , the valve 4 is connected to the pipe P ₂ , the valve 5 is connected to the pipe P ₅ , the valve 6 is connected to the pipe P ₆ , and the valve 7 is connected to the pipe P ₄ .
The valve control unit 17 controls opening / closing of the valves 1 to 7 according to a sequence.

In the examples, the case where the silicon nitride film of the wafer as the material to be etched is subjected to the etching process using phosphoric acid will be described. As shown in FIG. 5, the wafer is supported by the carrier and accommodated in the inner tank 8a of the processing tank 8, and the wafer is immersed in the processing liquid L ₁ .

During wafer processing, the valves 1 and 2 are opened and the remaining valves 3 to 7 are closed according to a command from the valve controller 17. Then, the treatment liquid L ₁ in the treatment tank 8 is passed through the filter 9 by the pump 10 to capture the particles in the treatment liquid L ₁ by the filter 9, while the purified treatment liquid L ₁ is circulated in the treatment tank 8. Then, the silicon nitride film on the wafer is etched with the processing liquid L ₁ in the processing bath 8.

When the etching process is continuously performed and the number of processed wafers reaches a predetermined value, for example, 2500 as shown in FIG. 2, the filter 9 is clogged and the filter 9 needs to be regenerated. .

The method of reproducing the filter 9 according to the present invention will be described below. When the filter 9 is clogged, the wafer processing is stopped, and the valve 1 and the valve 2 are opened and the valve 3, the valve 4, the valve 6, and the valve 7 are closed according to the command of the valve control unit 17. Then, the valve 5 is opened and the inner and outer tanks 8a, 8a of the processing tank 8 are opened.
b and disposal from the disposal pipe P ₅ the processing liquid L ₁ in the pipe P _1.

Next, the valve controller 17 controls the valves 1, 2,
The valves 5, 6 and 7 are closed and the valves 3 and 4 are opened. Then, the pump 10 is driven to supply the chemical liquid L ₂ in the chemical liquid tank 11 to the filter 9 via the pipes P ₁ and P ₃ , and the filter 9
The chemical liquid L ₂ which has passed through the chemical liquid tank 1 through the pipes P ₁ and P _2.
Return to 1. The circulation of the chemical liquid L ₂ is performed for 5 to 60 minutes. Since the particles captured by the filter 9 come into contact with the chemical liquid L ₂ , the particles are dissolved and removed by the chemical liquid L ₂ , and the filter 9 is regenerated with the clogging removed.

Next, the valve 4 is closed and the valve 5 is opened while the pump 10 is still driven, and the chemical solution tank 11 and the pipes P ₁ , P ₂ and P are opened.
The chemical liquid L _{2 in 3} is discarded through the waste pipe P ₅ .

Subsequently, the valve control unit 17 closes the valves 3 and 5 and opens the valve 7, and pure water is supplied from the pure water supply unit 12 to the filter 9 and the pump 10 through the pipes P ₄ and P ₁ . After supplying and cleaning (5 to 60 minutes), the valve 6 is opened, and the waste water is discarded together with the chemical liquid through the waste pipe 6.

Finally, the valve control unit 17 opens the valves 1 and 2 and closes the valve 6. Then, the valve 12 of the replenishing tank 13 is opened to supply the unused etching processing liquid L ₁ into the processing tank 8.

When the pump 10 is driven in this state, the treatment liquid L ₁ in the treatment tank 8 is purified by passing through the filter 9.
Transition to a state in which wafer processing is possible.

FIG. 2 shows the relationship between the number of processed wafers and the number of particles on the wafer surface when the apparatus of the present invention shown in FIG. 1 is used. When the number of processed wafers reaches 2500, the filter 9 is regenerated, and after the regeneration is completed, the wafer processing is continued again. By regenerating the filter, the clogging is eliminated, and the particles removed from the filter are discarded without being returned to the processing tank, so a rapid increase in particles is suppressed, and the processing tank is suppressed. It is possible to achieve cleanliness. Further, since the particles that cause clogging of the filter are removed and the filter is regenerated and used without replacing the filter itself, the running cost can be reduced.

(Embodiment 2) FIG. 3 is a block diagram showing a wet etching apparatus according to Embodiment 2 of the present invention.

In Example 1, the number of particles in the processing tank 8 was periodically measured to determine the regeneration time of the filter. On the other hand, in this embodiment, since the filter regeneration time varies depending on the conditions of the etching process,
By detecting the pressure difference between the primary side and the secondary side of the filter, the regeneration time of the filter is determined in real time, and the regeneration of the filter is appropriately performed. That is, in the present embodiment, the piping P on the primary side and the secondary side of the filter 9 is used.
_The pressure sensors 14 and 15 are installed in ₁ respectively, and the pressure value detected by the two pressure sensors 14 and 15 is used as the valve control unit 17
Valve 1-7 when the pressure difference reaches a specific value.
Is controlled to open and close to regenerate the filter 9.

FIG. 4 shows the relationship between the number of processed wafers and the pressure difference detected by the two pressure sensors. In the filter 9, since the captured particles act as flow path resistance, a pressure difference occurs between the primary side and the secondary side, and the pressure difference is 1
Clogging occurs when the weight reaches kg / cm ² .

Therefore, it can be seen that if the filter 22 is regenerated when the pressure difference between the pressure sensors 14 and 15 reaches 1 kg / cm ² , particles on the wafer can be suppressed. Of course, the pressure difference differs depending on the filtration area of the filter 9 and the capacity of the pump 10, and therefore must be determined for each device.

In the first embodiment, the number of particles on the wafer is periodically measured, and the filter 9 is regenerated when the number of particles starts to increase. However, according to the present embodiment, the number of particles on the wafer is increased in advance. Since it is possible to measure the pressure difference that starts to be measured and automatically regenerate the filter 9 before the pressure that starts to increase, it is possible to reduce the time required to regularly measure the number of particles on the wafer. Have.

[0037]

As described above, the present invention dissolves and removes particles adhering to a filter by injecting a chemical solution into an etching solution circulation line having a filter and a pump, and then washing the filter and the like with pure water. In order to
The clogged filter can be regenerated, the filter need not be replaced, and the running cost can be kept low. Further, since the etching liquid circulation line including the filter is washed with pure water, the chemical liquid for dissolving particles is not mixed into the etching liquid during the next etching process, and the etching process can be performed normally. .

Further, when the filter is regenerated, the treatment liquid in the treatment tank is discarded and the unused treatment liquid is supplied, so that the inside of the treatment tank can be cleaned.

Further, by monitoring the pressures on the primary side and the secondary side of the pressure sensor with the pressure sensor, the regeneration time of the filter can be determined and the regeneration of the filter can be appropriately executed, and the automatic regeneration of the filter can be performed. Can be achieved.

Further, paying attention to the fact that the particles attached to the filter are the reaction products of Si ₃ N ₄ and phosphoric acid. Since these particles are dissolved with hydrofluoric acid, the particles can be reliably removed from the filter. The filter can be regenerated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment according to the present invention.

FIG. 2 is a diagram showing the relationship between the number of processed wafers and the number of particles on the wafer surface in Example 1.

FIG. 3 is a configuration diagram showing a second embodiment according to the present invention.

FIG. 4 is a diagram showing a relationship between the number of processed wafers and a pressure difference of a pressure sensor in the second embodiment.

FIG. 5 is a configuration diagram showing a conventional example.

FIG. 6 is a diagram showing a relationship between the number of processed wafers and the number of particles on the wafer surface in a conventional example.

[Explanation of symbols]

 1 to 7 valves 8 processing tank 9 filter 10 pump 11 chemical liquid tank 12 valve 13 replenishment tank

Claims (5)

(57) [Claims] 1. An etching treatment section, a filter regeneration section, and a flow path switching section are provided, the material to be etched is immersed in the treatment solution, particles in the treatment solution are captured, and a purified treatment solution is obtained. A wet etching apparatus that circulates and wet-etches a material to be etched, wherein the etching processing section has a processing tank, a filter, and a pump, and the processing tank is filled with a processing liquid for etching. The filter is for trapping particles contained in the treatment liquid, and the pump is for circulating the treatment liquid overflowing from the treatment tank through the filter to the treatment tank. The chemical solution is supplied to the filter by the pump, the particles of the filter are dissolved and removed by the chemical solution, and the filter and the pump are purified by pure water after the treatment. The filter is used to clean and regenerate the filter, and the flow path switching unit connects the filter and pump by switching between the processing liquid piping system and the chemical liquid and pure water piping system, and discarding in the processing tank. A wet etching apparatus, which disposes a treatment liquid for use, a treated chemical liquid after filter regeneration and waste water in a waste pipe system. 2. The wet etching apparatus according to claim 1, further comprising a replenishing tank, wherein the replenishing tank supplies an unused processing liquid into the processing tank. 3. A pressure sensor is provided, the pressure sensor being installed in the flow paths of the primary side and the secondary side of the filter, and monitoring the clogging of the filter by the pressure difference between the pressure sensor and the pressure sensor. The wet etching apparatus according to claim 1 or 2, which is characterized in that. 4. The wet solution according to claim 1, wherein the chemical liquid is hydrofluoric acid, the treatment liquid is phosphoric acid, and the material to be etched is a silicon nitride film. Etching equipment. 5. A filter regeneration method for a wet etching apparatus which performs a chemical treatment and a cleaning treatment to regenerate a filter for trapping particles in an etching treatment liquid, wherein the chemical treatment involves bringing the chemical into contact with the filter. A method of regenerating a filter in a wet etching apparatus, characterized in that the particles adhering to the filter are dissolved and removed with a chemical liquid, and the cleaning process is a process of cleaning the filter in contact with the chemical liquid with pure water.