JPS63265428A - Ashing method - Google Patents

Abstract

PURPOSE:To prevent adhesion onto a wall surface such as a treated-substrate opposed surface of a reaction product, to improve uniformity and ashing speed and to enable even sheet treatment by setting pressure where a solvent, etc., in a treated-surface coating film on a substrate to be treated are vaporized. CONSTITUTION:A flow-controlled ashing gas pressurized to a fixed pressure at the central section of a semiconductor wafer 18 placed onto a base plate 17 is allowed to flow out radially and uniformly from an outflow 13, and the semiconductor wafer 18 is ashed and treated. The pressure of a section to be treated, gas pressure in a chamber, is measured by a pressure gage 22 mounted onto the wall surface of the chamber at that time, the result of measurement is transmitted over a pressure controller 23 from the pressure gage 22, and the flow rate of the ashing gas is controlled so that an output from the pressure gage 22 is brought to a preset pressure value by the pressure controller 23. The discharge of the ashing gas after ashing treatment discharged from the inside of the chamber is adjusted by the pressure controller 23, thus pressing gas pressure in the chamber within a specified range. Accordingly, the treated surface of the semiconductor wafer 18 is pressed at fixed pressure, and a substance solvent, etc., having the low boiling point contained in the treated surface is not vaporized on ashing treatment, thus preventing the adhesion of the solvent, etc., in a resist onto the wall surface such as an opposed surface to the wafer 18.

Description

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

(Prior Art) Generally, fine patterns for semiconductor integrated circuits are formed by etching a base film formed on a semiconductor wafer using an organic polymer photoresist film formed by exposure and development as a mask. Therefore, the photoresist film used as a mask must be removed from the surface of the semiconductor wafer by an etching process. This means there is a good means of anisotropic etching.

However, there are problems with wafer damage and etching residue.

An ashing process is used to remove the photoresist film in such a case.

An example of this is disclosed in Japanese Unexamined Patent Publication No. 52-20766.

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

(Problems to be Solved by the Invention) When performing ashing using a gas containing ozone as an ashing gas using the above-described mechanism, in order to prevent decomposition of ozone in the flow path, the diffusion plate is cooled and the wafer, which is the substrate to be processed, is Ashing is performed by thermally decomposing the surface using high temperature. However, when this ashing step was performed, a considerable amount of deposits were observed on the surface of the diffusion plate facing the wafer. This causes contamination and decreases in throughput, and is not desirable as a clean solution for high integration.

The present invention has been made in response to the above-mentioned problems, and is an ashing device that prevents reaction products from adhering to the wall surface such as the surface facing the substrate to be processed, and enables single-wafer processing with improved uniformity and ashing speed. It provides:

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method in which the pressure of at least the part to be processed of the substrate to be processed is increased to a predetermined pressure at which the substance in the deposited film does not vaporize. It is characterized by ashing.

(Function) In the ashing method of the present invention, by setting a pressure that does not vaporize the solvent, etc. in the film deposited on the surface of the substrate to be processed, reaction products are formed on the wall surface such as the surface facing the substrate to be processed during ashing. This prevents the adhesion of ashing materials and also makes it possible to improve the ashing speed and uniformity.

The present inventors investigated why reaction products adhere to a wall surface such as a surface facing a substrate to be processed. First, the deposits were removed by various means, and as a result of analysis, it was found that the solvent in the resist was attached. As a result of detailed investigation into the cause of the adhesion of the solvent and the like in the resist, it was found that the adhesion occurs due to the vaporization of low boiling point substances such as the solvent contained in the film adhered to the substrate to be processed. It has also been found that the higher the pressure during treatment of this low boiling point substance, the faster the ashing rate becomes.

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

A manufacturing chamber 12 made of AQ and having a closed cylindrical shape is provided which can be moved up and down by an elevating mechanism 11. Konojo Chamber 1
An outlet 13, for example, a cylindrical nozzle with a diameter of about 8 mm, is provided near the center axis of the bottom surface of the ashing gas. On the surface of the bottom formed by the outlet 13, a heat-resistant glass disc 14 made of an insulating material and having a thickness of 5 mm is provided, for example. A lower chamber 15 is provided so as to airtightly engage with the upper chamber 12, and a disc-shaped mounting table 17 whose temperature can be freely controlled by a temperature control mechanism 16 is provided within the lower chamber 15. There is. On this mounting table 17 is a substrate to be processed, such as a semiconductor wafer 18.
will be installed. This wafer 18 is fixed by suction as necessary.

An ozone generator 112G equipped with an oxygen supply source 19 and a flow rate regulator 21 for adjusting the supply flow rate of the ashing gas are provided so that the ashing gas flows out onto the surface of the wafer 18.

In addition, the sealed portion formed by the upper chamber 12 and the lower chamber 15 is, for example, 1 to 10 ata, and there is no gas leakage.
A pressure gauge 22 and a pressure regulator 2 are used to pressurize to a predetermined pressure.
3 is provided. An exhaust mechanism 24 that exhausts the ashing gas after the ashing process is connected to the pressure regulator 23.

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

The upper chamber 12 is raised by the lifting mechanism 11.

A substrate to be processed, such as a semiconductor wafer 18, is automatically transferred to a predetermined position on a mounting table 17 provided in the lower chamber 15 by a transfer mechanism (not shown).

Place it. By aligning the orientation flat of the wafer 18 as necessary, devices with the same characteristics can be manufactured with good reproducibility.

Next, the upper chamber 12 is lowered to lower the lower chamber 1.
5 to form a reaction chamber by setting the inside of the processing chamber in a sealed state. At this time, for example, a disk 1 made of glass
4 is, for example, 0.5 to 20+m from the 18th surface of the semiconductor wafer.
Set the positions so that they are spaced a certain distance apart. Also,
At this time, the center of the tip of the outlet 13 is located on the center axis of the mounting table 17 and the semiconductor wafer 18, so that uniform processing can be performed over the entire surface of the wafer 18.

The semiconductor wafer 18 is aligned by a center alignment mechanism (not shown).
The center of the mounting table 17 and the semiconductor wafer 18 are aligned and placed using a transport mechanism (not shown), for example, a hand arm. That is, adjustment is made so that the center of the outlet 13 and the center of the wafer 18 are coaxial.

Then, the ashing gas generated by the ozone generator 2° equipped with the oxygen supply source 19 is adjusted by the flow rate regulator 21 so that the flow rate is, for example, about 2 to 40 SQ/win (flow rate converted to normal temperature and normal pressure). It is diffused by a diffusion plate (not shown) of the outlet 13 and flows out from the outlet 13 provided at the center of the disk 14 toward the surface of the semiconductor wafer 18 . Further, the wafer 18 is heated to a temperature of, for example, 150 to 300 by a heater installed in the mounting table 17 by the temperature control mechanism 16.
It is heated to a range of about ℃.

The ashing gas, which is pressurized to a predetermined pressure and whose flow rate is adjusted, is uniformly flowed out radially from the center of the semiconductor wafer 18 placed on the mounting table 17 through the outlet 13, thereby performing an ashing process on the semiconductor wafer 18. .

At this time, a pressure gauge 22 provided on the wall of the chamber measures the pressure of the part to be processed, for example, the gas pressure in the chamber, and the measurement result is sent from the pressure gauge 22 to a pressure regulator 23 as, for example, an electrical signal. The flow rate of the ashing gas is adjusted and controlled so that the output of the pressure gauge 22 reaches the set pressure value. and.

By adjusting the amount of ashing gas discharged from the chamber after the ashing process using the pressure regulator 23, the gas pressure in the chamber is increased to a range of, for example, about 1 to 10 ata. This is a pressure range that ensures the ashing speed IIjM/in, which is considered necessary for single wafer processing, and does not require handling of high-pressure gas equipment. At the same time, the flow rate of the ashing gas is constantly adjusted by the flow rate regulator 21 so that it does not change due to changes in the gas pressure within the chamber. Therefore, during the ashing process, the ashing gas in the chamber is pressurized to a predetermined pressure at a predetermined flow rate suitable for the ashing process by the above-described functions of the flow rate regulator 21 and the pressure regulator 23.

As a result, the surface to be processed of the semiconductor wafer 18 is pressurized to a predetermined pressure, so that low boiling point substances such as solvents contained in the photoresist film, etc. on the surface to be processed are not vaporized during the ashing process, and the wafer 18 6 In other words, since the resist is a mixture of an organic polymer and a solvent, the empirical formula of Clapeyron's formula PoceXP (A-co+zya, ts
) P: pressure, T: temperature, A, B: constants,
It vaporizes in proportion to the pressure. Therefore, as shown in FIG. 2, the higher the pressure, the less the amount of vaporization of the solvent, etc. in the resist, but if the pressure is too high, it becomes a high-pressure gas device, which increases the cost of the device. Therefore, industrially, the processing pressure is preferably 10 ata or less.

Further, as shown in FIG. 3, in order to ensure an ashing rate of 1 pm/win 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.

The ashing gas discharged by the pressure regulator 23 is decomposed by an ozone decomposer (not shown).

It is discharged from the exhaust mechanism 24.

With this, the ashing process for the semiconductor wafer 18 is completed.
Flow rate regulator 21. The pressure inside the chamber is returned to atmospheric pressure by the pressure gauge 22 and the pressure regulator 23, the upper chamber 12 is raised by the lifting mechanism 11, and the wafer is transported to the next process by a transport mechanism (not shown).

Although glass was used as the material for the disk 14 in the above embodiment, any heat-resistant glass may be used, quartz glass may also be used, and the disk 14 only needs to be larger than the semiconductor wafer. The wafer facing surface 13 is smaller in size than the wafer.

In addition, in the above embodiment, the case of a photoresist film was explained as an ashing target, but it can be applied to various things such as ink removal and solvent removal, and any ashing target can be used as long as it can be removed by oxidation. The ozone-containing gas is not limited to oxygen; any gas that does not react with ozone, particularly an inert gas such as Nz*Ar, No, etc., can be used by containing ozone.

In the above embodiment, an example applied to the processing of semiconductor wafers was explained, but it can be applied to any ashing process, such as a photomask provided on a glass substrate, a printed circuit board, or an amorphous silicon film deposited. There is no need to explain it.

As described above, according to this embodiment, the semiconductor wafer is placed with its center aligned with the center of the mounting table, and the wafer is pressurized in a closed chamber to prevent vaporization of the solvent, etc. in the wafer. The ashing gas can be uniformly discharged onto the wafer from the outlet provided on the central axis of the wafer, thereby preventing the occurrence of contamination and increasing the ashing speed.

〔Effect of the invention〕

As explained above, according to the present invention, by performing ashing while applying pressure on at least the surface of the substrate to be processed to a pressure that does not vaporize the solvent, etc. in the deposited film, the ashing material can be removed from the substrate. It is possible to perform clean single-wafer ashing with improved ashing speed and uniformity by preventing adhesion to wall surfaces such as opposing surfaces.

[Brief explanation of drawings]

FIG. 1 is an elliptical diagram of the ashing device in the ashing method of the present invention, FIG. 2 is a graph showing the relationship between the temperature of the substrate to be processed and the amount of vaporization from the film deposited on the substrate in the ashing device of FIG. 1, and FIG. The figure is a graph showing the relationship between the gas pressure in the reaction chamber and the ashing rate in FIG. 1. In fig. 12... Upper chamber 13... Outlet 14... Disc plate 15... Lower chamber 17... Mounting table 18... Semiconductor wafer patent applicant
Tokyo Electron Ltd. Figure 1: Plate temperature T”C Figure 2

Claims (3)

[Claims] (1) When ashing the film deposited on the substrate to be processed using ashing gas, the pressure of at least the part to be processed of the substrate to be processed is increased to a predetermined pressure at which the substance in the deposited film does not vaporize. This ashing method is characterized by ashing in a closed state. (2) The ashing method according to claim 1, wherein the set pressure is 1 to 10 ata. (3) The ashing method as set forth in claims 1 and 2, wherein the pressure setting means for the processing target portion adjusts the flow rate of the ashing gas.