JPH11145107A - Surface treatment method for substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which enables selective etching of a predetermined film formed on the surface of a substrate, while maintaining a treatment solution made of an acid solution constantly in a boiling state by holding the treatment solution at a predetermined temperature and a predetermined acid concentration. SOLUTION: A treatment solution 14 in a treatment tub 10 is heated and constantly held in a boiling state by a constant-output heater 16 and 24, and the temperature of the treatment solution is detected by a temperature detector 34. On the basis of the detected temperature, the quantity of pure water 28 supplied from a pure water tub 30 to the treatment solution is controlled by a regulator 42, so that the treatment solution is held at a predetermined temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor wafer,
A method of immersing a glass substrate for a liquid crystal display device, a substrate such as an electronic component, etc. in a treatment solution composed of an aqueous solution of an acid such as a phosphoric acid aqueous solution to perform surface treatment, particularly, immersing the substrate in a treatment solution kept in a boiling state. The present invention also relates to a substrate surface treatment method for selectively etching a predetermined coating of two or more types of coatings formed on the surface of a substrate.

[0002]

2. Description of the Related Art A substrate, for example, a semiconductor wafer is immersed in a processing solution comprising an aqueous solution of an acid, for example, an aqueous solution of phosphoric acid, and a predetermined one of two or more kinds of coating films formed on the surface of the semiconductor wafer is obtained. Conventionally, when selectively etching a silicon nitride film out of a silicon oxide film (SiO ₂ film) and a silicon nitride film (Si ₃ N ₄ ), a schematic configuration is schematically shown in FIG. A surface treatment device as shown is used. This apparatus has a processing tank 10 in which a liquid inlet 12 is formed at the bottom and a phosphoric acid aqueous solution 14 is stored inside. A processing heater 10 is provided inside the processing tank 10.
6 are provided. Then, a plurality of semiconductor wafers to be processed are stored in a wafer holder (not shown), put into the processing tank 10 and immersed in the phosphoric acid aqueous solution 14.

[0003] The processing tank 10 is provided with an overflow liquid receiving portion 18 so that the phosphoric acid aqueous solution overflowing from the upper portion of the processing tank 10 flows into the overflow liquid receiving portion 18. A liquid circulation pipe 20 communicates with the inner bottom of the overflow liquid receiving portion 18, and the tip of the liquid circulation pipe 20 is connected to the liquid inlet 12 of the processing tank 10. A circulation pump 22, an in-line heater 24, and a filter 26 are interposed in the liquid circulation pipe 20.
0, the liquid can be circulated through the circulation path formed by the overflow liquid receiving portion 18 and the liquid circulation pipe 20. Overflow liquid receiver 18
Is provided with a discharge port at the other end of a pure water supply pipe 50 having one end communicating with the inner bottom of a pure water tank 30 in which pure water 28 is stored and having a fixed amount pump 32 interposed therebetween. Further, a temperature detector 34 is disposed inside the processing tank 10, and the temperature detector 3 is provided.
4 is connected to the temperature controller 52, and the temperature controller 52 is connected to the injection heater 16. Further, a temperature detector 54 is inserted in the middle of the liquid circulation pipe 20, and the temperature detector 5
4 is connected to a temperature controller 56, and the temperature controller 56 is connected to the in-line heater 24.

When a semiconductor wafer is subjected to surface treatment by the apparatus having the structure shown in FIG. 3, a phosphoric acid aqueous solution 14 is heated to 150 ° C. by an injection heater 16 and an in-line heater 24.
It is heated to a temperature of about 180 ° C. Therefore, processing tank 1
Water evaporates from the phosphoric acid aqueous solution 14 in the
The phosphoric acid concentration of 4 increases. Therefore, pure water 28 is supplied from the pure water tank 30 through the pure water supply pipe 50 by the metering pump 32, and the pure water is supplied from the discharge port of the pure water supply pipe 50 to the phosphoric acid aqueous solution flowing into the overflow liquid receiving portion 18. Is continuously dropped. At this time, conventionally, the pure water supply pipe 50
A constant flow of pure water is passed through the inside of the processing tank, and pure water is constantly replenished in an amount substantially equivalent to the amount of water evaporated from the phosphoric acid aqueous solution 14 in the treatment tank 10. The temperature of the phosphoric acid aqueous solution 14 in the processing tank 10 is controlled by the temperature controllers 52 and 56 based on the detection signals sent from the temperature detectors 34 and 54, respectively. Is controlled by PID control so as to be maintained at a predetermined temperature.

When the silicon nitride film is selectively etched with respect to the silicon oxide film, the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film, that is, the selectivity becomes a problem. Further, the etching rate of the silicon oxide film or the silicon nitride film changes depending on the temperature of the phosphoric acid aqueous solution, and increases as the temperature of the phosphoric acid aqueous solution increases. The selectivity of the phosphoric acid aqueous solution at a certain temperature becomes maximum when the phosphoric acid aqueous solution is in a boiling state at the temperature, in other words, when the temperature is a phosphoric acid concentration at which the phosphoric acid aqueous solution has a boiling point. Therefore, the phosphoric acid aqueous solution 14 in the processing bath 10 is kept at a processing temperature appropriately selected in relation to the etching rate and the selectivity of the silicon nitride film, the concentration of the phosphoric acid aqueous solution, and the like.
So that the phosphoric acid aqueous solution is always kept at a boiling state at that temperature, that is, the phosphoric acid concentration is maintained such that the temperature becomes the boiling point of the phosphoric acid aqueous solution. It is important to perform a surface treatment on a semiconductor wafer.

[0006]

The phosphoric acid aqueous solution 14 in the treatment tank 10 is heated by the injection heater 16 and the in-line heater 24 to evaporate water, thereby increasing the concentration of phosphoric acid. In order to lower the concentration, pure water is replenished to the phosphoric acid aqueous solution from the pure water tank 30 through the pure water supply pipe 50 in the circulation path of the phosphoric acid aqueous solution. Therefore, the phosphoric acid concentration of the phosphoric acid aqueous solution 14 is determined by the evaporation amount of water from the phosphoric acid aqueous solution 14 and the replenishing amount of pure water. If the water evaporation amount and the replenishing amount of pure water are always equal, the phosphoric acid concentration of the phosphoric acid aqueous solution becomes , Will be kept constant.

On the other hand, the replenishment of pure water into the phosphoric acid aqueous solution removes the heat of the phosphoric acid aqueous solution, so that the temperature of the phosphoric acid aqueous solution decreases. When the temperature of the phosphoric acid aqueous solution decreases, the temperature detector 3
Temperature controllers 52, 5 based on the detection signals from 4, 54
The heaters 16 and 24 are controlled by 6 so that the amount of heat corresponding to the amount of heat removed from the aqueous phosphoric acid solution by the replenishment of pure water is given to the aqueous phosphoric acid solution, and the temperature of the aqueous phosphoric acid solution 14 in the processing tank 10 is maintained at a predetermined temperature. You.

However, in the conventional method of continuously replenishing a fixed amount of pure water to the phosphoric acid aqueous solution, the amount of water evaporated from the phosphoric acid aqueous solution 14 in the treatment tank 10 and the amount of pure water replenishment are not always equal. Absent. For this reason, even if the temperature of the phosphoric acid aqueous solution 14 in the treatment tank 10 is maintained at a predetermined temperature, the temperature does not always become the boiling point of the phosphoric acid aqueous solution. As described above, in the conventional method, it is difficult to perform the surface treatment of the semiconductor wafer while controlling the phosphoric acid concentration of the phosphoric acid aqueous solution such that the phosphoric acid aqueous solution is always kept in a boiling state at a predetermined temperature.

The present invention has been made in view of the above circumstances, and has been made on a surface of a substrate while maintaining a processing solution comprising an aqueous acid solution at a predetermined temperature and always in a boiling state. It is an object of the present invention to provide a method for treating a surface of a substrate, which can selectively etch a predetermined film among two or more types of films.

[0010]

The invention according to claim 1 is
A processing solution comprising an aqueous solution of an acid is heated by a heater to maintain the processing solution in a boiling state, and the substrate is immersed in the processing solution in a boiling state, and two or more types formed on the surface of the substrate In a method of treating a surface of a substrate for selectively etching a predetermined film among the films, a constant amount of heat is applied to the processing solution while the output of the heater is kept constant, and the processing solution is always kept in a boiling state. And the amount of pure water replenished to the processing liquid is controlled based on the detected temperature so that the temperature of the processing liquid is maintained at a predetermined temperature.

According to a second aspect of the present invention, in the method according to the first aspect, the heaters are provided only within a predetermined time from a point in time when the substrate is put into the processing liquid and within a predetermined time from a point in time when the processing liquid is replenished. The feature is to maximize the output.

According to a third aspect of the present invention, in the method according to the first or second aspect, the processing solution is a phosphoric acid aqueous solution, and the film formed on the surface of the substrate is a silicon oxide film and a silicon nitride film. And selectively etching the silicon nitride film.

According to the substrate surface treatment method of the present invention, a constant amount of heat is given to the processing liquid by the heater having a constant output, and the processing liquid is always kept in a boiling state.
That is, when the processing liquid is heated by the heater, the water evaporates from the processing liquid, the acid concentration of the processing liquid increases, and the boiling point of the processing liquid also increases accordingly. The temperature of the processing liquid is raised by a heater having a constant output that can raise the temperature of the processing liquid simultaneously, and the processing liquid is always kept in a boiling state. On the other hand, the temperature of the processing liquid is detected, and pure water is replenished to the processing liquid based on the detected temperature so that the temperature of the processing liquid is maintained at a predetermined temperature. That is, as described above, the temperature of the processing solution rises due to the increase in the acid concentration (boiling point increase) of the processing solution accompanying the evaporation of water from the processing solution. By detecting the rise and replenishing the processing liquid with pure water in an amount corresponding to the temperature rise, the temperature of the processing liquid falls and is maintained at the original predetermined temperature. Also at this time, since the processing liquid is kept in a boiling state, the predetermined temperature is the boiling point of the processing liquid, and the processing liquid is maintained at the original acid concentration such that the predetermined temperature becomes the boiling point. In this way, the processing liquid is maintained at a predetermined temperature and a predetermined concentration, and is constantly kept in a boiling state.

In the method according to the second aspect of the present invention, when the temperature of the processing liquid is greatly reduced instantaneously, such as when the substrate is put into the processing liquid or when the processing liquid is replenished, the processing is performed within a predetermined time from that point. Only the output of the heater is maximized, so that the temperature of the processing liquid quickly recovers. For this reason, it is possible to avoid a decrease in the etching rate of the film formed on the surface of the substrate.

In the method according to the third aspect of the present invention, the phosphoric acid aqueous solution is maintained at a predetermined temperature and a predetermined phosphoric acid concentration to be constantly kept in a boiling state, and the selectivity of the silicon nitride film to the silicon oxide film is increased. In this state, the silicon nitride film formed on the surface of the substrate is selectively etched.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic view showing an example of a schematic configuration of a surface treatment apparatus used for carrying out a substrate surface treatment method according to the present invention. In FIG. 1, components denoted by the same reference numerals as those used in FIG. 3 are the same as those in the conventional apparatus shown in FIG. 3, and the description thereof will be omitted.

In this apparatus, one end communicates with the inner bottom of a pure water tank 30 in which pure water 28 is stored, and the other end of the pure water tank 30 is disposed in the overflow liquid receiving portion 18 and a pure water supply system in which a metering pump 32 is provided. A flow control valve 38 and a flow meter 40 are inserted in the pipe 36. Further, the temperature detector 34 disposed inside the processing tank 10 is connected to the flow controller 42, and the flow controller 42 is connected to the flow control valve 38. Further, an output adjuster 44 is connected to the injection heater 16 and the in-line heater 24. Other configurations are the same as those of the conventional device shown in FIG.

In order to perform a surface treatment on a substrate with the apparatus having the structure shown in FIG. 1, for example, in order to selectively etch a semiconductor wafer having a silicon oxide film and a silicon nitride film formed on its surface with a phosphoric acid aqueous solution, an output power is required. The output of the injection heater 16 and the in-line heater 24 is adjusted to be always constant by the controller 44, and the phosphoric acid aqueous solution 14 in the processing tank 10 is adjusted to a predetermined temperature of 150 ° C. to 180 ° C. by the injection heater 16 and the in-line heater 24. Allow to heat to temperature. The outputs of the heaters 16 and 24 at this time are set to such an extent that the amount of heat necessary to keep the phosphoric acid aqueous solution 14 in a boiling state is always given to the phosphoric acid aqueous solution. That is, the water content evaporates from the phosphoric acid aqueous solution and the phosphoric acid concentration increases,
Even if the boiling point of the phosphoric acid aqueous solution rises accordingly, the outputs of the heaters 16 and 24 are set to such an extent that the temperature of the phosphoric acid aqueous solution can be raised simultaneously to the increased boiling point. Further, the temperature of the phosphoric acid aqueous solution 14 in the processing tank 10 is detected by the temperature detector 34, and a detection signal is sent to the flow controller 42, and the flow controller 42 controls the flow control valve 38 based on the detection signal. For example, PID control is performed. Then, the flow rate of pure water supplied from the pure water tank 30 to the overflow liquid receiving portion 18 through the pure water supply pipe 36 so that the temperature of the phosphoric acid aqueous solution 14 in the treatment tank 10 is maintained at a predetermined temperature. The amount of pure water replenished per unit time to the phosphoric acid aqueous solution circulating in the circulation path is regulated.

As described above, the output of the injection heater 16 and the output of the in-line heater 24 are made constant by the output adjuster 44, and the temperature of the processing tank 10 is changed by the temperature detector 34.
The temperature of the phosphoric acid aqueous solution 14 is detected, and the flow controller 42 controls the flow control valve 38 to adjust the amount of pure water replenished per unit time so that the temperature of the phosphoric acid aqueous solution 14 is maintained at a predetermined temperature. By doing so, the phosphoric acid concentration of the phosphoric acid aqueous solution 14 is kept constant, and the phosphoric acid aqueous solution 14 is always kept in a boiling state. That is, water evaporates from the phosphoric acid aqueous solution 14 in the treatment tank 10, and the phosphoric acid aqueous solution 1
4, the boiling point of the phosphoric acid aqueous solution 14 rises, and the temperature of the phosphoric acid aqueous solution 14 rises accordingly. Therefore, the temperature rise of the phosphoric acid aqueous solution 14 corresponding to the evaporation of water from the phosphoric acid aqueous solution 14 is detected by a temperature detector. When the amount of pure water is detected in step 34 and added to the phosphoric acid aqueous solution in an amount corresponding to the temperature rise, the temperature of the phosphoric acid aqueous solution 14 is lowered and maintained at the original predetermined temperature. At this time, since the phosphoric acid aqueous solution 14 is kept in a boiling state, the predetermined temperature is the boiling point of the phosphoric acid aqueous solution 14, and the phosphoric acid aqueous solution 14 is maintained at the original phosphoric acid concentration such that the predetermined temperature becomes the boiling point. Becomes

Incidentally, when the semiconductor wafer is put into the phosphoric acid aqueous solution 14 in the processing tank 10 or when the phosphoric acid aqueous solution is replenished into the processing tank 10, the phosphoric acid aqueous solution 1 is disturbed by disturbance.
If the temperature of 4 greatly decreases instantaneously, the etching rate of the silicon nitride film will decrease. For this reason,
When the temperature of the phosphoric acid aqueous solution 14 is instantaneously lowered due to the introduction of the wafer into the phosphoric acid aqueous solution 14 in the processing bath 10 or the replenishment of the phosphoric acid aqueous solution into the processing bath 10, the output controller 44.
It is preferable to adjust the output of the heaters 16 and 24 to the maximum value to heat the phosphoric acid aqueous solution 14. In this way, even if the temperature of the phosphoric acid aqueous solution 14 instantaneously decreases, the temperature of the phosphoric acid aqueous solution 14 recovers quickly, so that a decrease in the etching rate of the silicon nitride film can be avoided.

FIG. 2 shows an example of a temperature change state of the phosphoric acid aqueous solution 14 in the processing tank 10. First, a period T until the temperature of the phosphoric acid aqueous solution 14 reaches the set temperature from the start of the treatment.
1 controls the output of the heaters 16 and 24 to the maximum value by the output adjuster 44 to heat the phosphoric acid aqueous solution 14. And
After the temperature of the phosphoric acid aqueous solution 14 reaches the set temperature, a period T2 until a time t at which a wafer is loaded into the phosphoric acid aqueous solution 14 in the processing bath 10 or the phosphoric acid aqueous solution is replenished into the processing bath 10 is output. The heaters 16 and 2 are controlled by the controller 44.
The output of 4 is adjusted to the set value, and a constant amount of heat is continuously given to the phosphoric acid aqueous solution 14. Phosphoric acid aqueous solution 14 in processing tank 10
When a wafer is put into the tank or the phosphoric acid aqueous solution is replenished into the processing tank 10, the phosphoric acid aqueous solution 1
During the period T3 from the time when the temperature of the temperature controller 4 falls to the time when the temperature rises and reaches the set temperature again, the output controller 44 controls the heater 1
The output of 6, 24 is adjusted to the maximum value to give a large amount of heat to the phosphoric acid aqueous solution 14. In the period T4 after the temperature of the phosphoric acid aqueous solution 14 reaches the set temperature, the output of the heaters 16 and 24 is adjusted to the set value by the output adjuster 44, and a constant amount of heat is continuously given to the phosphoric acid aqueous solution 14.

During the process of increasing the temperature of the phosphoric acid aqueous solution 14 in the processing tank 10, the temperature of the phosphoric acid aqueous solution 14
When it enters (time point a), replenishment of pure water is started and the replenishment amount is gradually increased. Thereafter, when the temperature of the phosphoric acid aqueous solution 14 still rises and exits the proportional band P (time point b), the replenishing amount of pure water is maximized and kept constant. And the phosphoric acid aqueous solution 14
When the temperature of the phosphoric acid aqueous solution 14 falls within the proportional band P (time point c) in the process of further increasing the temperature, reaching the peak and then decreasing, the replenishment amount of pure water is gradually reduced. Thereafter, when the temperature of the phosphoric acid aqueous solution 14 still falls and goes out of the proportional band P (time point d), the replenishment of pure water is stopped. Some time after the replenishment of the pure water is stopped, the temperature of the phosphoric acid aqueous solution 14 starts to fall from rising to rising. Then, when the temperature of the phosphoric acid aqueous solution 14 rises and enters the proportional band P (time point a), replenishment of pure water is started again, and the replenishment amount is gradually increased. Thereafter, such a temperature change is repeated. In this case, since the phosphoric acid aqueous solution 14 in the treatment tank 10 is always kept in a boiling state, the temperature change of the phosphoric acid aqueous solution 14 in the steady state shown in FIG. Therefore, the temperature change of the phosphoric acid aqueous solution 14 shown in FIG. 2 indicates a change in the phosphoric acid concentration of the phosphoric acid aqueous solution 14. In other words, the replenishment of pure water lowers the phosphoric acid concentration of the phosphoric acid aqueous solution 14 (the boiling point of the phosphoric acid aqueous solution 14 drops).
Then, the temperature of the phosphoric acid aqueous solution 14 in the treatment tank 10 is lowered accordingly, and the replenishment of pure water is stopped. This increases the temperature of the phosphoric acid aqueous solution 14 in the treatment tank 10 accordingly.

In the above-described embodiment, the flow rate control valve 38 is controlled by the flow rate regulator 42 based on the temperature of the phosphoric acid aqueous solution 14 detected by the temperature detector 34, and the pure water supply pipe 36 Overflow liquid receiving part 18 through
Although the flow rate of the pure water supplied into the inside is adjusted, an opening / closing control valve is used instead of the flow control valve 38, and a time during which the opening / closing control valve is opened within a unit time by the controller (the unit time , The amount of pure water replenished to the phosphoric acid aqueous solution per unit time may be adjusted.

[0025]

According to the method for treating the surface of a substrate according to the first aspect of the present invention, while maintaining a treatment solution comprising an aqueous solution of an acid at a predetermined temperature and at a predetermined acid concentration and always in a boiling state, Surface treatment can be performed, so that a predetermined coating of two or more types of coatings formed on the surface of the substrate can be selectively etched with a large selection ratio.

In the method according to the second aspect of the present invention, when the temperature of the processing liquid is greatly reduced instantaneously, such as when the substrate is put into the processing liquid or when the processing liquid is replenished, the temperature of the processing liquid is rapidly increased. Therefore, a decrease in the etching rate of the film formed on the surface of the substrate can be prevented.

According to the method of the present invention, the selectivity of the silicon nitride film to the silicon oxide film is increased.
The silicon nitride film formed on the surface of the substrate can be selectively etched.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a schematic configuration of a surface treatment apparatus used to carry out a substrate surface treatment method according to the present invention.

FIG. 2 is a diagram illustrating an example of a state of a temperature change of a phosphoric acid aqueous solution in a processing tank when a substrate surface treatment method according to the present invention is performed.

FIG. 3 is a schematic view showing an example of a schematic configuration of a conventional surface treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Processing tank 12 Liquid inlet at the bottom of processing tank 14 Phosphoric acid aqueous solution 16 Injection heater 18 Overflow liquid receiving part 20 Liquid circulation pipe 22 Circulation pump 24 In-line heater 26 Filter 28 Pure water 30 Pure water tank 32 Metering pump 34 Temperature detector 36 Pure water supply pipe 38 Flow control valve 40 Flow meter 42 Flow controller 44 Output controller

Claims (3)

[Claims] 1. A treatment solution comprising an aqueous solution of an acid is heated by a heater to maintain the treatment solution in a boiling state, and the substrate is immersed in the boiling treatment solution to form two or more types formed on the surface of the substrate. In a surface treatment method for a substrate, which selectively etches a predetermined coating of coatings of a higher type, a constant amount of heat is applied to the processing liquid while the output of the heater is kept constant, so that the processing liquid is always brought into a boiling state. Maintaining the temperature of the processing solution, and controlling the replenishment amount of pure water to the processing solution based on the detected temperature so that the temperature of the processing solution is maintained at a predetermined temperature. Processing method. 2. The substrate surface according to claim 1, wherein the output of the heater is maximized only within a predetermined time from the time when the substrate is introduced into the processing liquid, and within a predetermined time from the time when the processing liquid is replenished. Processing method. 3. The processing liquid is a phosphoric acid aqueous solution, the coating formed on the surface of the substrate is a silicon oxide film and a silicon nitride film, and the silicon nitride film is selectively etched. Item 3. The method for treating a surface of a substrate according to Item 2.