JP2002110624A - Method and device for treating surface of semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide treatment method and device for achieving uniform treatment with a small consumption of treatment liquid, and for achieving uniform etching treatment, without roughness at a low etching rate, especially in the case of the etching treatment, when the surface of a semiconductor substrate is treated. SOLUTION: This device for treating the surface of the semiconductor substrate has a mist-generating device 11 that applies ultrasonic vibrations to the treatment liquid for changing into mist, a mist force-feeding device 12 that forcedly feeds generated mist 13, so that the generated mist 13 adheres onto the surface for the surface treatment of the semiconductor substrate, and a treatment tank 14 that carries the semiconductor substrate and performs surface treatment by the mist forcedly fed from the mist force-feeding device. In this case, for the particle size of the mist generated by the mist generating apparatus 11, 90% or higher a of the particle size is to be preferably within 6 to 12 μm. At the same time, the treatment liquid is preferably set to a fluoric acid solution A, and the surface treatment is preferably set as the etching one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating a surface of a semiconductor substrate, and more particularly to an etching process for a surface of the semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, in etching a semiconductor substrate with a hydrofluoric acid (HF) solution, the HF solution is adjusted to a certain concentration and temperature and then sent to a processing tank to be processed.
For example, in the case of the batch type, as shown in FIG. 10, an HF solution is put in a processing tank 110, and a plurality of semiconductor substrates W are vertically immersed in the HF solution at the same time.
The F solution is discharged, and pure water (DIW) is injected instead to perform rinsing.

In the case of a single wafer type, as shown in FIG. 11, one semiconductor substrate is placed on a turntable 120, and an HF solution is sprayed from above by a spray 121 for a predetermined time. After the lapse of time, pure water (DIW) is sprayed by the spray 122 to perform rinsing.

[0004]

However, in the case of the batch type, variations tend to occur in the concentration, temperature, flow rate, and the like in the tank, and processing unevenness tends to occur. In the case of single-wafer type,
Since a very small amount of the HF solution is applied to the substrate, it is very difficult to control the amount of drop, the concentration, the temperature, and the like. When the in-plane uniformity of the etching amount was measured for some of the slots, it was found that it was difficult to achieve the target value within 3%, as shown in FIG. In particular, in order to form a high dielectric constant film used for forming a gate electrode before a gate oxidation process of a recent miniaturized semiconductor element, a process of etching a very small amount of a very thin film uniformly in a substrate surface is desired. It is difficult to perform batch processing or single-wafer processing using an HF solution. That is, it is difficult to provide uniformity in the range of the etching amount of about 10 to 20 °, and the concentration, temperature,
There is a limit to flow control alone. Further, in the HF vapor (hydrofluoric acid vapor) method, since the temperature of HF increases, roughness is easily caused on the silicon surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor substrate having a high uniformity with low consumption of a processing solution in a surface treatment of a semiconductor substrate. An object of the present invention is to provide a processing method and an apparatus capable of performing an etching process.

[0006]

In order to solve the above-mentioned problems, the present invention employs the following means. According to a first aspect of the present invention, a surface treatment is performed by applying ultrasonic vibration to a treatment liquid to form a mist and adhere to the surface of the semiconductor substrate. In this case, it is preferable that 90% of the particle diameter of the mist is contained in 6 μm to 12 μm, and it is convenient that the treatment liquid is a hydrofluoric acid solution and the surface treatment is an etching treatment. The frequency of the ultrasonic vibration is preferably set to 500 kHz or more, and about 1 MHz is optimal.

According to a fourth aspect of the present invention, there is provided a surface treatment apparatus for a semiconductor substrate.
A mist generator that applies ultrasonic vibrations to the treatment liquid to form a mist, a mist pumping device that pressure-feeds the generated mist so as to adhere to the surface for surface treatment of the semiconductor substrate, And a treatment tank for performing a surface treatment by mist fed from the apparatus. In this case, it is preferable that 90% of the particle diameter of the mist generated by the mist generator is included in 6 μm to 12 μm, and the treatment liquid is a hydrofluoric acid solution and the surface treatment is an etching treatment. It is convenient.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a semiconductor substrate surface treatment apparatus according to the present invention will be described with reference to the drawings. FIG. 1 schematically shows a first embodiment of a semiconductor substrate surface treatment apparatus according to the present invention. As shown in the figure, the surface treatment apparatus 10 treats a plurality of semiconductor substrates (wafers) W at one time, and includes a mist generator 11, a mist pumping device 12 for pumping the generated mist, a semiconductor substrate And a treatment tank 14 that carries in W and performs surface treatment with the mist 13 pressure-fed from the mist pressure feeding device 12.

The mist generating device 11 has an HF solution A inside.
Has an ultrasonic bath 15 made of PTFE (polytetrafluoroethylene) or quartz, etc., and an ultrasonic vibrator 16 which vibrates at 950 kHz in this example is attached to the bottom of the ultrasonic bath 15. Have been. Ultrasonic tank 1
When the ultrasonic vibrator 16 is operated by putting the HF solution A into the mist 5, the HF solution A is atomized and becomes a mist 13. Mist 13 caused HF solution A, also led to the mist pumping device 12 of PTFE or quartz or the like, the mist 13 guided is to the treatment tank 14 by an inert gas such as N ₂ is injected Is sent. Processing tank 14 also
Similarly, it is formed of a material which is not affected by HF, has a space in the center of the inside capable of accommodating a plurality of semiconductor substrates W at the same time, and a pipe 17 capable of supplying and draining pure water DIW is attached to the bottom.

The particle size of the mist 13 generated by the mist generator 11 is about 10 μm. The particle size distribution of the generated mist 13 was measured by a measuring device 30 as shown in FIG. The measuring device 30 has a frequency 9 at the bottom.
It has an ultrasonic bath 32 to which a 50 kHz ultrasonic vibrator 31 is attached, in which an HF solution is put. A pair of laser transmitting and receiving units 3 are provided on both sides of the upper opening of the ultrasonic bath 32.
3a and 33b were installed facing each other, the ultrasonic transducer 31 was operated, and the measurement was performed by using the particle size distribution measurement software for Windows NT (registered trademark).

As a result, as shown in FIG. 4, the particle size distribution was found to be 98% or more within 6 μm to 12 μm, show a sharp mountain-shaped distribution, and concentrate at about 10 μm. . As described above, the particle size of the mist is very uniform, and it can be said that the particle size is about 10 μm. In addition, as shown in FIG.
It becomes 99% or more in μm.

Further, it was examined whether or not the particle size of the mist is changed by the ultrasonic output. As shown in FIG. 5, the average value of the particle diameter was measured while changing the ultrasonic output to 200 W, 250 W, and 500 W. As a result, it was found that the particle size of the mist was constant irrespective of the change in the ultrasonic output. However, the amount of mist changes depending on the output. Subsequently, the relationship between the temperature of the HF solution and the particle size of the HF mist was examined. As shown in FIG. 6, the average value of the particle diameter was measured while changing the temperature of the HF solution in the ultrasonic bath 32 from 28 ° C. to 39 ° C. As a result, it was found that the particle size of the mist was constant regardless of the difference in the temperature of the HF solution.

Next, the operation of the surface treatment apparatus for a semiconductor substrate shown in FIG. 1 will be described. First, an HF solution A at normal temperature is stored in a mist generator 11 and an etching process is performed in a processing tank 14. Are carried in. When the ultrasonic vibrator 16 of the mist generator 11 is operated,
Mist 13 having a particle size of about 10 μm is generated. This mist 1
3 is directed to the mist pumping device 12, it is pumped to the treatment tank 14 by controlling the flow rate and temperature constant inert gas, e.g., N ₂ gas at the time management and a mass flow controller.

The mist 13 pressure-fed to the processing bath 14 adheres to the surface of the semiconductor substrate W carried into the processing bath 14. The particle size of the mist 13 is about 10 μm as described above.
However, when it adheres to the surface of the substrate W, it becomes thin and flat so that the surface becomes wet, and its thickness can be 1 μm or less. This has been confirmed experimentally. For example, when a mist of water droplets is attached to the surface of a wafer and when the wafer is immersed in water,
When the thickness of the water film adhering to the wafer surface was measured, it was 2.78 μm in the case of water immersion as shown in FIG.
In the case of water spray, the thickness is 0.802 μm, and in the case of mist formation, the water film can be thinned.

That is, even if an etching solution such as an HF solution is used instead of water, the liquid film can be made extremely thin by controlling the ultrasonic output. And when the etching amount is very small, for example, 10 °
Even in this case, it is easy to control the uniform etching of the surface.

FIG. 7 shows that the amount of etching varies depending on the concentration of the etching solution and the etching time. As described above, when the etching time and the etching amount are measured for two kinds of HF concentrations (0.5% and 0.25%) with the liquid film thickness of 1 μm or less, both have a linear relationship, and the etching amount is It turns out that control becomes easy. When the desired amount of etching is completed by controlling the concentration of the HF solution, the etching time, and the ultrasonic output,
The feeding of the mist 13 to the processing tank 14 is stopped, and pure water is supplied to the inside of the processing tank 14 for rinsing and draining, thereby completing the etching. According to this method, the amount of mist attached during etching can be extremely reduced as compared with the case where the mist is immersed.
The amount of HF solution used and the amount of pure water to be rinsed can also be reduced.

FIG. 9 shows the measured etching amount of the surface of the semiconductor substrate W when the surface of the semiconductor substrate W is etched by the above-described method. As shown in the figure, it was proved that even a very small etching amount of about 3 ° can be uniformly etched. Therefore, 8 generated on the surface of the semiconductor substrate
An effective etching process can be performed even for a natural oxide film of about Å.

Next, a second embodiment of the present invention will be described. As shown in FIG. 2, a semiconductor substrate surface treatment apparatus 20 according to the second embodiment is configured in a single-wafer type, and includes a mist generator 21 and a mist pumping device 22 for pumping the generated mist. And a treatment tank 24 for carrying in the semiconductor substrate W and performing a surface treatment with the mist 13 pressure-fed from the mist pressure feeding device 22. Also, the processing tank 24
A rotary table 25 on which the semiconductor substrate W is placed is provided therein. Rotary table 28 for each semiconductor substrate
The only difference from the previous embodiment is that the semiconductor device is mounted on the substrate and etched, and the principle is completely the same.

In the above embodiment, the HF solution is mist-adhered to the substrate surface for etching the semiconductor substrate. However, if the SC-1 solution is mist-adhered, the particles adhering to the substrate surface are mist-formed. Can be cleaned, and using an ozone aqueous solution as a mist makes it possible to remove resist and attached organic substances.

[0020]

As described above, according to the present invention,
Since the treatment liquid is mist-formed by applying ultrasonic vibration, mist having a uniform particle diameter can be generated, and since the particle diameter is uniform and as small as about 10 μm, the treatment liquid is pumped to the treatment tank with a certain amount of inert gas. Mist can be deposited on the surface of the semiconductor substrate. Therefore, the amount of the processing liquid used can be reduced by half, and in the case of the etching process, even if the etching amount is minute,
In-plane uniform etching can be performed, and the amount of pure water used for rinsing can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a second embodiment of the present invention.

FIG. 3 is a diagram showing an apparatus for measuring a particle size distribution of mist.

FIG. 4 is a diagram showing a mist particle size distribution measured by the measuring device shown in FIG. 3;

FIG. 5 is a diagram showing the relationship between the particle size of the generated mist and the ultrasonic output.

FIG. 6 is a diagram showing the relationship between the temperature of the HF solution and the particle size of the generated mist.

FIG. 7 is a graph showing the relationship between the etching time and the etching amount in HF.
FIG. 6 is a diagram illustrating a result of measurement performed while changing the concentration of a solution.

FIG. 8 is a diagram showing measured values of the thickness of a water film on the wafer surface when the wafer is immersed in water and when water is sprayed.

FIG. 9 is a diagram showing a distribution of an etching amount on a surface of a semiconductor substrate.

FIG. 10 is a schematic view of a conventional batch etching apparatus.

FIG. 11 is a schematic view of a conventional single-wafer etching apparatus.

FIG. 12 is a diagram showing measured values of in-plane uniformity in the case of conventional immersion or spray etching.

[Explanation of symbols]

 10, 20 Surface treatment device for semiconductor substrate 11, 21 Mist generator 12, 22 Mist pumping device 13 Mist 14, 24 Processing tank A HF solution W Semiconductor substrate

Claims (6)

[Claims] 1. A method for treating a surface of a semiconductor substrate, comprising applying a supersonic vibration to the treatment liquid to form a mist and attaching the mist to the surface of the semiconductor substrate to perform the surface treatment. 2. The mist has a particle diameter of 90% of 6 μm.
The surface treatment method for a semiconductor substrate according to claim 1, wherein the thickness is included in a range of m to 12 μm. 3. The method according to claim 1, wherein the treatment liquid is a hydrofluoric acid solution, and the surface treatment is an etching treatment. 4. A mist generating device for applying ultrasonic vibration to a treatment liquid to form a mist, a mist pumping device for pressure-feeding the generated mist so as to adhere to the surface for surface treatment of the semiconductor substrate, and a semiconductor substrate. A treatment tank for carrying out a surface treatment by a mist carried in and fed from the mist pumping device, the surface treatment device for a semiconductor substrate. 5. The surface treatment apparatus for a semiconductor substrate according to claim 4, wherein 90% of the particle size of the mist generated by the mist generator is included in 6 μm to 12 μm. 6. The apparatus according to claim 4, wherein the treatment liquid is a hydrofluoric acid solution, and the surface treatment is an etching treatment.