JPH07101684B2 - Ashing method and apparatus - Google Patents

Description

The present invention relates to an ashing method and an apparatus for removing a photoresist film or the like 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. Be seen.

Therefore, the photoresist film used as the mask needs to be removed from the surface of the semiconductor wafer after the etching process. As a process for removing the photoresist film in such a case, for example, an ashing process is performed.

This ashing process is also used for removing resist, cleaning silicon wafers and masks, removing ink, removing solvent residues, etc., and is suitable when performing dry cleaning process in a semiconductor process.

As an ashing device for removing the photoresist film, a device using oxygen plasma is generally used.

An ashing device for a photoresist film using oxygen plasma places a semiconductor wafer with a photoresist film in a processing chamber, converts the oxygen gas introduced into the processing chamber into a plasma by a high-frequency electric field, and is an organic substance due to generated oxygen atom radicals. The photoresist film is oxidized and decomposed into carbon dioxide, carbon monoxide, and water to be removed.

Further, there is an ashing device that generates an oxygen atom radical by irradiating with ultraviolet rays and performs the ashing process in a batch process.

FIG. 12 shows an ashing device for generating oxygen atom radicals by such ultraviolet irradiation. A large number of semiconductor wafers 2 are vertically arranged at a predetermined interval in the processing chamber 1, and an upper part of the processing chamber 1 is provided. Ultraviolet rays from the ultraviolet light emitting tube 3 installed in the processing chamber 1 are radiated through a transparent window 4 such as quartz provided on the upper surface of the processing chamber 1 to excite the oxygen filled in the processing chamber 1 to generate ozone. Then, oxygen atom radicals generated from this ozone atmosphere are caused to act on the semiconductor wafer 2 to perform an ashing process.

(Problems to be Solved by the Invention) However, among the conventional ashing devices described above,
In an ashing device that uses oxygen plasma, the semiconductor wafer is irradiated with ions and electrons that are accelerated by the electric field existing in the plasma, so if the integration is increased to 256K, 1M bits, the lead lines will be thinned. There is a problem in that the distance becomes narrower than the distance, and the semiconductor wafer is damaged by dielectric breakdown due to charge-up.

Further, in the ashing device using ultraviolet rays, damage to the semiconductor wafer is not given to the semiconductor wafer, but since the ashing speed is slow at 50 to 150 nm / min and it takes a long time to process, for example, in processing a large-diameter semiconductor wafer. Appropriate,
There is a problem that the single wafer processing for processing the semiconductor wafers one by one cannot be performed.

The present invention has been made in consideration of such a conventional situation, and has a high ashing speed without damaging the surface of a substrate to be processed, and can cope with, for example, single-wafer processing of large-diameter semiconductor wafers. A method and an apparatus therefor are provided.

[Structure of Invention]

(Means for Solving the Problems) One of the present invention is an ashing method for removing a film deposited on a surface of a substrate to be processed, which is placed in the processing chamber, by an ashing gas. A first step of generating ozone by an ozone generator provided, a second step of temporarily storing the ozone generated in the first step in a storage chamber provided outside the processing chamber, and a second step of The third step is that the ozone stored in the step 2 is pressure-fed to the processing chamber having the substrate to be processed heated by the heating means while adjusting the pressure.

Another aspect of the invention is an ashing device that removes a film deposited on the surface of a substrate to be processed, which is disposed in the process chamber, by an ashing gas, and a processing chamber including a heating unit that heats the substrate to be processed, An ozone generator provided outside the processing chamber, a storage chamber for temporarily storing ozone generated by the ozone generator provided between the ozone generator and the processing chamber, and the storage chamber It is provided with a pressurizing means for sending the stored ozone under pressure while adjusting the pressure of the stored ozone.

(Operation) The ashing gas for removing an unnecessary film on the surface of the substrate to be processed is temporarily stored in the storage chamber, and the stored gas is pressurized so that the ashing gas flows out to the substrate to be processed. It is possible to obtain an ashing method with a high value and a high speed processing.

Further, since the outflow amount of the ashing gas can be controlled in accordance with the processing process of the substrate to be processed, it is possible to process the substrate to be processed under optimum conditions.

(Example) Hereinafter, an example of the ashing method of the present invention will be described with reference to the drawings.

In the processing chamber 11, a mounting table 13 that holds the semiconductor wafer 12 by suction, such as by a vacuum chuck, is arranged. The mounting table 13 contains a heater 15 controlled by a temperature control device 14, and is configured to be movable up and down by an elevating device 16.

Above the mounting table 13, a cone-shaped cone portion 17a and a diffusion plate 17b arranged in the opening portion of the cone portion 17a and having a large number of small holes 17c as shown in FIG. 2 are formed. A gas outflow portion 17 is arranged, and this gas outflow portion 17 is cooled by cooling water or the like that circulates from a cooling device 18 in a pipe 18a arranged outside the cone portion 17a.

Further, below the processing chamber 11, an exhaust pipe 22 for exhausting exhaust gas generated by an oxidation chemical reaction with the film deposited on the surface of the semiconductor wafer 12 to the outside of the processing chamber 11, is provided. Is connected to the exhaust device 23.

On the other hand, above the gas outflow section 17, a gas storage section 31 is provided adjacent to the processing chamber 11 via a gas outflow valve 28. The gas storage unit 31 includes a gas storage chamber 30 for temporarily storing the ashing gas, and a piston 25 which is in close contact with the inner wall of the gas storage chamber 30 and which can be slid up and down by a drive unit 24. The storage room 30 is equipped with a cooling device as needed.

Further, on the side wall of the gas storage chamber 30, a flow path 30a communicating with the vacuum pump 26 via the vacuum valve 27 and a gas supply valve 2 are provided.
A gas flow rate controller 19 and a flow path 30b communicating with an ozone generator 20 connected to an oxygen supply source 21 via 9 are provided.

Next, an ashing process for removing the unnecessary photoresist film on the surface of the semiconductor wafer will be described.

First, the drive device 24 raises the piston 25 to make the space in the gas storage chamber 30 wide, the gas outflow valve 28 and the gas supply valve 29 are closed, and the vacuum valve 27 is opened to evacuate by the vacuum pump 26. The inside of the gas storage chamber 30 is placed in a reduced pressure vacuum state.

Next, the vacuum valve 27 is closed and the gas supply valve 29 is opened to supply the ashing gas whose ozone flow rate is controlled by the gas flow controller 19 from the ozone generator 20 to fill the gas storage chamber 30 with the ashing gas. To do.

On the other hand, the mounting table 13 is lowered by the elevating device 16 to provide a gap between the gas outflow part 17 and the arm of a wafer transfer device (not shown) and the like, and the semiconductor wafer 12 to be processed is
Is mounted on the mounting table 13 by this transfer device or the like and is suction-held.

After that, the mounting table 13 is raised by the elevating device 16, and the gap between the gas outflow portion 17 and the surface of the semiconductor wafer 12 is 0.5 to 2, for example.
Set to a predetermined interval of about 0 mm. In this case, the gas outflow portion 17 may be moved up and down by the lifting device.

Then, the heater 15 built in the mounting table 13 is installed in the temperature control device.
Controlled by 14, the semiconductor wafer 12 is heated to a range of about 150 to 500 ° C., for example, 300 ° C. After that, the following control is performed so that the ashing gas flow rate becomes a desired value.

That is, the gas outflow valve 28 is opened, and the driving device 24 lowers the piston 25 to, for example, a position near the broken line 25a to remove the ashing gas stored in the gas storage chamber 30 from the gas outflow portion 17.
Is forced to flow toward the semiconductor wafer 12. In this case, it goes without saying that the timing of forced outflow may be changed according to the treatment process.

On the other hand, the ashing gas containing ozone supplied from the oxygen supply source 21 and the ozone generator 20 is supplied to the gas flow controller 19
Is adjusted so that the flow rate is, for example, about 3 to 15 Sl / min (Sl is the flow rate at room temperature and atmospheric pressure), and is made to flow from the gas flow-out portion 17 toward the semiconductor wafer 12, and the exhaust device 23 is used to, for example, Evacuate so that the gas pressure is in the range of 200 to 700 Torr.

Then, between the gas outflow portion 17 and the semiconductor wafer 12, for example, as shown by an arrow in FIG. 3, a gas flow from the gas outflow hole 17c toward the semiconductor wafer 12 is formed.
The exhaust gas generated by the ashing treatment of 12 and the oxidation chemical reaction with the deposited film is exhausted from the exhaust pipe 22.

When the processing is completed, the gas outflow valve 28 is closed, the outflow of gas to the processing chamber 11 is stopped, and the piston 25 is raised by the drive device 24 to introduce the gas into the gas storage unit 31 and fill the gas storage chamber 30 with gas. The processed semiconductor wafer 12 is unloaded from the processing chamber 11, and the next semiconductor wafer 12 to be processed is loaded.

Here, it suffices that the vacuum pump 26 is operated at the time of the first process development to bring the gas storage chamber 30 into the depressurized vacuum state, and does not need to be operated each time the semiconductor wafer 12 is processed.

The life of the ozone generated by the ozone generator 20 depends on the temperature, and the vertical axis indicates the ozone decomposition half-life, and the horizontal axis indicates the temperature of the gas containing ozone. The higher the value, the faster the decomposition of ozone, and the shorter its life becomes. Therefore, in the ashing treatment performed by utilizing the oxidation reaction by the oxygen atom radicals generated by the decomposition of ozone, the gas temperature is preferably heated to about 150 ° C to 500 ° C.

On the other hand, the temperature of the opening of the outflow section 17 N gas is preferably not more than about 25 ° C., the gas outlet portion 17 are cooled by the cooling device 18 to 25 ° C. or less.

In the graph of FIG. 6, the vertical axis is the ashing speed, the horizontal axis is the flow rate of the gas containing ozone, and the distance between the gas outflow portion 17 and the semiconductor wafer 12 is a parameter. 4 shows changes in the ashing speed of the semiconductor wafer 12. The ozone concentration is adjusted to about 3 to 10% by weight. As can be seen from this graph, in the ashing apparatus of this embodiment, the distance between the semiconductor wafer 12 and the gas outflow portion 17 is set to several mm, and the gas flow rate containing ozone is set to the range of 2 to 40 Sl / min. High-speed ashing processing with a speed of 1 to several μm / min can be performed.

In this way, since ashing is performed without using plasmaized ashing gas, highly integrated ashing processing can be performed without damage even with highly integrated 256 Kbit, 1 Mbit, and 2 Mbit.

Further, since the gas flow rate can be controlled by controlling the gas pressure, high-speed ashing processing can be performed.

In this embodiment, the gas outflow portion 17 is composed of the diffusion plate 17b having a large number of small holes 17c as shown in FIG. 2, but the present invention is not limited to this embodiment, and for example, The gas outlet 17 may be composed of a diffusion plate 77b having a plurality of concentric slits 77c as shown in FIG. 7, and is made of a sintered body such as metal or ceramic as shown in FIG. Diffusing plate 87b, diffusing plate 97b with linear slits 98c arranged radially as shown in FIG. 9, diffusing plate 107b with small holes 107c of different sizes as shown in FIG.
Diffusion plate with spiral slit 117c as shown in FIG.
You may comprise 117b etc.

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

Further, in this embodiment, the processing chamber 11 and the gas storage unit 31 are provided adjacent to each other, but the processing chamber 11 and the gas storage unit 31 may be provided separately as shown in FIG. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

〔The invention's effect〕

As described above, according to the present invention, the ashing corresponding to the processing process can be performed without damaging the substrate to be processed, and the asching speed is high. Can be done.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an ashing device according to an embodiment of the present invention, FIG. 2 is a bottom view of a gas outflow portion of FIG. 1, and FIG. 3 is a gas outflow of FIG. Of the gas flow in the section, Fig. 4 shows the first
FIG. 6 is a configuration diagram showing another embodiment of the figure, FIG. 5 is a graph showing the relationship between the half-life of ozone and temperature used in FIG.
FIG. 7 is a graph showing the relationship between the ashing rate in FIG. 1, the flow rate of gas containing ozone, and the distance between the gas outflow portion and the semiconductor wafer. FIGS. 7 to 11 are views showing modified examples of the gas outflow portion in FIG. FIG. 12 is a block diagram showing a conventional ashing device. 11 …… Processing chamber, 12 …… Semiconductor wafer 13 …… Mounting table, 15 …… Heater 17 …… Gas outflow part, 17b …… Diffusion plate 22 …… Exhaust pipe, 25 …… Piston 27 …… Vacuum valve, 28 …… Gas outflow valve 29 …… Gas supply valve, 30 …… Gas storage chamber 31 …… Gas storage unit

Claims (2)

[Claims] 1. An ashing method for removing a film deposited on the surface of a substrate to be processed placed in a processing chamber by an ashing gas, wherein ozone is generated by an ozone generator provided outside the processing chamber. The first step, the second step of temporarily storing the ozone generated in the first step in the storage chamber provided outside the processing chamber, and the ozone stored in the second step by the heating means. An ashing method comprising a third step of adjusting the pressure and sending the pressure to the processing chamber having the heated substrate to be processed. 2. An ashing apparatus for removing a film deposited on the surface of a substrate to be processed, which is disposed in the processing chamber, by an ashing gas, the processing chamber including a heating means for heating the substrate to be processed,
An ozone generator provided outside the processing chamber, a storage chamber for temporarily storing ozone generated by the ozone generator provided between the ozone generator and the processing chamber, and the storage chamber An ashing device comprising: a pressurizing unit that adjusts the pressure of the stored ozone and pressure-feeds it to the processing chamber.