JPH06103664B2 - Assing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to an ashing method for ashing a film deposited on a substrate to be processed.

(Prior Art) Generally, a fine pattern of a semiconductor integrated circuit is formed by etching a base film formed on a semiconductor wafer using a photoresist film of an organic polymer formed by exposure and development as a mask. Therefore, the photoresist film used as the mask needs to be removed from the surface of the semiconductor wafer by an etching process. This means includes a good means for anisotropic etching. However, there are problems of wafer damage and etching residue.

An ashing process is a process for removing the photoresist film in such a case.

An example thereof is disclosed in JP-A-52-20766.

According to this, a diffusion plate having a plurality of openings for diffusing and flowing out the ashing gas is brought close to the semiconductor wafer, and the ashing gas is caused to flow out onto the semiconductor wafer via the diffusion plate, Perform ashing processing.

(Problems to be Solved by the Invention) When ashing using a gas containing ozone as the ashing gas by the above mechanism, the diffusion plate is cooled to prevent decomposition of ozone in the flow path, and the wafer to be processed is a wafer. The ashing is carried out by thermal decomposition due to the high temperature of the surface of the. However, when this ashing process was performed, a considerable amount of deposits were found on the surface of the diffusion plate facing the wafer. This causes contamination and a decrease in throughput, and there is a problem that it is not desirable as a clean measure for high integration.

The present invention has been made in consideration of the above points, and a reaction product does not adhere to a wall surface of a surface of a substrate to be processed or the like, and an ashing apparatus that enables single-wafer processing with improved uniformity and ashing speed. Is provided.

[Structure of Invention]

(Means for Solving the Problems) The present invention is characterized in that the ashing is carried out under the condition that the pressure of at least the portion to be treated of the substrate to be treated is raised to a predetermined pressure at which the substance in the deposited film is not vaporized. And

(Operation) In the ashing method of the present invention, by setting a pressure that does not vaporize the solvent or the like in the film to be processed surface of the substrate to be processed, reaction products of It is possible to prevent the adhesion and improve the ashing speed and the uniformity.

The present inventors examined why the reaction product adheres to the wall surface such as the surface facing the substrate to be processed. First, the deposits were taken out by various means and analyzed, and as a result, it was found that the solvent and the like in the resist were deposited. As a result of detailed investigation of the cause of the solvent or the like in the resist, it was found that the low boiling point substance such as the solvent contained in the film deposited on the substrate to be processed was vaporized and deposited. It was also found that the ashing rate of this low boiling point substance increases as the pressure during treatment increases.

(Example) Hereinafter, an example in which the method of the present invention is applied to an ashing step of a semiconductor manufacturing process will be described with reference to the drawings.

An upper chamber 12 made of Al and having a cylindrical shape with a lid, which is vertically movable by an elevating mechanism 11, is provided. An outlet 13 for letting out the ashing gas, for example, a cylindrical nozzle having a diameter of about 8 mm is provided near the central axis of the bottom surface of the upper chamber 12. On the surface of the bottom surface formed by the outlet 13, a heat-resistant glass disk 14 made of, for example, an insulating material and having a thickness of 5 mm is provided. A lower chamber 15 is provided so as to be airtightly engaged with the upper chamber 12, and a disk-shaped mounting table 17 is provided in the lower chamber 15 so that the temperature can be controlled by a temperature control mechanism 16. A substrate to be processed, for example, a semiconductor wafer 18 is placed on the mounting table 17. This wafer 18 is adsorbed and fixed as necessary.

On the surface of the wafer 18, an ozone generator 20 provided with an oxygen supply source 19 so that the ashing gas flows out and a flow rate controller 21 for adjusting the supply flow rate of the ashing gas are provided.

In addition, the sealed portion formed by the upper chamber 12 and the lower chamber 15 has, for example, 1 to 10 ata without gas leakage, and is provided with a pressure gauge 22 and a pressure regulator 23 for pressurizing to a predetermined pressure. An exhaust mechanism 24 for discharging the ashing gas after the ashing process is connected to the pressure regulator 23.

Next, a method of ashing a semiconductor wafer by the above ashing apparatus will be described.

The upper chamber 12 is raised by the elevating mechanism 11, and a mounting table installed in the lower chamber 15 by a transfer mechanism (not shown).
A substrate to be processed, for example, a semiconductor wafer 18 is automatically transferred to and placed on a predetermined position on the substrate 17. The wafer 18 can be manufactured with reproducible elements having the same characteristics by aligning the orientation flat of the wafer 18 if necessary.

Next, the upper chamber 12 descends and is connected to the lower chamber 15 to set the inside of the processing chamber in a sealed state to form a reaction chamber. At this time, for example, the disk 14 formed of glass is
The position is set so as to be spaced from the surface of the semiconductor wafer 18 by, for example, about 0.5 to 20 mm. At this time, the center of the tip of the outflow port 13 is provided so as to be located on the central axes of the mounting table 17 and the semiconductor wafer 18 to enable uniform processing over the entire surface of the wafer 18.

The center position of the semiconductor wafer 18 is aligned by a center alignment mechanism (not shown), and the center of the mounting table 17 and the center of the semiconductor wafer 18 are aligned by a transfer mechanism (not shown) such as a hand arm. That is, the center of the outlet 13 and the center of the wafer 18 are adjusted to be coaxial.

Then, the ashing gas generated by the ozone generator 20 provided with the oxygen supply source 19 is adjusted by the flow rate controller 21 so that the flow rate becomes, for example, about 2 to 40 Sl / min (flow rate in normal temperature and normal pressure), and the outlet port. The semiconductor wafer is diffused by a diffusion plate (not shown) 13 from the outflow port 13 provided at the center of the disk 14.
18 Runs out towards the surface. Further, the wafer 18 has already been heated by the temperature control mechanism 16 to a range of, for example, about 150 to 300 ° C. by the heater provided inside the mounting table 17.

Semiconductor wafer mounted on the mounting table 17 through the outlet 13
The ashing gas whose pressure is adjusted to a predetermined pressure and whose flow rate is adjusted is uniformly discharged radially from the central portion of the semiconductor wafer 18.
Performs 18 ashing processes.

At this time, the pressure gauge 22 provided on the wall surface of the chamber measures the pressure of the portion to be treated, for example, the gas pressure in the chamber, and the measurement result is sent from the pressure gauge 22 to the pressure regulator 23 as, for example, an electric signal. The flow rate of the ashing gas is adjusted and controlled so that the pressure gauge 22 output is at the set pressure value. Then, the pressure of the ashing gas discharged from the chamber after the ashing process is adjusted by the pressure controller 23 to increase the gas pressure in the chamber to a range of, for example, about 1 to 10 ata. This is a pressure range where an ashing speed of 1 μm / min, which is considered to be necessary for single-wafer processing, is secured and handling of high-pressure gas equipment is not possible. At the same time, the flow rate of the ashing gas is constantly adjusted by the flow rate controller 21 so that it does not change due to changes in the gas pressure in the chamber. Therefore,
The ashing gas in the chamber during the ashing process is pressurized to a predetermined pressure at a predetermined flow rate suitable for the ashing process due to the above-described functions of the flow rate controller 21 and the pressure controller 23.

As a result, the surface to be processed of the semiconductor wafer 18 is pressed to a predetermined pressure, so that the low boiling point substance solvent or the like contained in the photoresist film or the like on the surface to be processed is not vaporized during the ashing process, and the wafer 18 It is possible to prevent the solvent or the like in the resist from adhering to the wall surface such as the surface facing the. In other words, the resist is a mixture of organic polymer and solvent, so the empirical formula of Clapeyron's formula From P: pressure, T: temperature, and A, B: constants, it will vaporize in proportion to the pressure. Therefore the second
As shown in the figure, the higher the pressure is, the smaller the vaporization amount of the solvent or the like in the resist becomes, but if the pressure is too high, the apparatus becomes expensive because it becomes a high pressure gas equipment. Therefore, industrially, the treatment pressure is preferably 10ata or less.

Further, as shown in FIG. 3, in order to secure an ashing speed of 1 μm / min or more, which is considered necessary for single-wafer processing, it is preferable that the gas pressure in the reaction chamber is 1 ata or more.

Then, the ashing gas discharged by the pressure controller 23 is decomposed by an ozone decomposer (not shown) and discharged from the exhaust mechanism 24.

With the above, the ashing process of the semiconductor wafer 18 is completed, the pressure inside the chamber is returned to the atmospheric pressure by the flow rate controller 21, the pressure gauge 22 and the pressure controller 23, and the upper chamber 12 is raised by the elevating mechanism 11 and is not shown. The wafer is transferred to the next process by the transfer mechanism.

Although the material of the disk 14 in the above-described embodiment is glass, the heat-resistant glass may be used, and quartz glass may be used. Also, the disk 14 need only be larger than the semiconductor wafer,
Further, the surface of the outlet 13 facing the wafer is smaller than the size of the wafer.

Further, in the above embodiment, the case of the photoresist film was described as the ashing target, but it can be applied to various things such as ink removal and solvent removal, and what is the ashing target as long as it can be removed by oxidation. However, the ozone-containing gas is not limited to oxygen, but a gas that does not react with ozone, particularly an inert gas such as N ₂ , Ar, or Ne, can be used by containing ozone.

Further, in the above-mentioned embodiment, the embodiment applied to the processing of the semiconductor wafer has been described, but in the ashing step, it can be applied to any of the photomask provided on the glass substrate, the printed board, the deposited amorphous silicon film, and the like. Needless to say.

As described above, according to this embodiment, the semiconductor wafer is mounted with its center aligned with the center of the mounting table, and the wafer is pressurized in a closed chamber to prevent evaporation of solvent and the like in the wafer. The ashing gas can be made to uniformly flow out onto the wafer from the outflow port provided on the central axis of the wafer, contamination can be prevented, and the ashing speed can be increased.

〔The invention's effect〕

As described above, according to the present invention, at least the pressure of at least the surface to be processed of the substrate to be processed is ashed while being pressurized to a pressure at which the solvent or the like in the deposited film is not vaporized. It is possible to prevent adherence to the wall surface such as the facing surface, and perform clean ashing for single-wafer processing with improved ashing speed and uniformity.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ashing device in the ashing method of the present invention, and FIG. 2 is a graph showing a relationship between a temperature of a substrate to be processed and a vaporization amount from a film to be deposited on the substrate to be processed in the ashing device of FIG. 1, FIG. 3 is a graph showing the relationship between the gas pressure in the reaction chamber of FIG. 1 and the ashing speed. In the figure, 12 ... upper chamber, 13 ... outlet 14 ... disk, 15 ... lower chamber 17 ... mounting table, 18 ... semiconductor wafer

Front Page Continuation (72) Inventor Keisuke Shikaki 1-226-2 Nishishinjuku, Shinjuku-ku, Tokyo Within Tokyo Electron Co., Ltd. (72) Inzo Inouzo Sato, Shinjuku-ku, Tokyo 1-226-2 Tokyo Electron Internal Examiner Kazutomo Nakanishi

Claims (3)

[Claims] 1. When ashing a film deposited on a substrate to be processed with an ashing gas, a pressure of at least a portion to be treated of the substrate to be treated is set to a predetermined pressure at which a substance in the film deposited is not vaporized. An ashing method characterized by ashing under pressure. 2. The ashing method according to claim 1, wherein the set pressure is 1 to 10 ata. 3. The ashing method according to claim 1 or 2, wherein the pressure setting means of the portion to be processed adjusts the flow rate of the ashing gas.