JPH06101426B2 - Ashing device - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial Application) The present invention relates to an ashing device for oxidizing and removing a photoresist film or the like deposited on a semiconductor wafer using ozone.

(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 done.

Therefore, the photoresist film used as the mask needs to be removed from the surface of the semiconductor wafer after the etching process.

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

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. 13 shows an ashing device for generating oxygen atom radicals by irradiating such an ultraviolet ray. In the processing chamber 1, a large number of semiconductor wafers 2 are vertically arranged at a predetermined interval, and the upper part of the processing chamber 1 is arranged. Ultraviolet rays from the ultraviolet arc tube 3 installed in the processing chamber 1 are irradiated 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,
The ashing apparatus using oxygen plasma has a problem of damaging the semiconductor wafer because the semiconductor wafer is irradiated with ions and electrons accelerated by an electric field existing in the plasma.

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 response to such conventional circumstances,
An object of the present invention is to provide an ashing device which does not damage a semiconductor wafer, has a high ashing speed of a photoresist film, and can perform an ashing process in a short time even in single-wafer processing of large-diameter semiconductor wafers. Is.

[Structure of the Invention] (Means for Solving the Problems) That is, according to the present invention, a semiconductor wafer having a photoresist film formed thereon is placed in an airtight processing chamber, and a processing gas is introduced into the processing chamber. In a single-wafer ashing device for removing the photoresist film, means for heating the mounting table to a predetermined temperature, means for mounting the semiconductor wafer on the mounting table, and mounting of the means are completed. The means for setting the reaction space by making the space between the mounting table and the gas outflow portion closely face each other at a predetermined distance later, means for outflowing the gas from the gas outflow portion after the setting of the means is finished, and the membrane Means for determining the end point after completion of removal of the gas, means for switching the gas flowing out from the gas outflow portion to the purge gas in accordance with the end point determination result of the means, and completion of switching of the purge gas by the means. Characterized by comprising a means for unloading the semiconductor wafer after from the mounting table.

(Operation) The ashing apparatus of the present invention is provided with a gas outflow portion that closely faces the semiconductor wafer in the processing chamber and causes the gas containing ozone to flow out toward the semiconductor wafer. By flowing out oxygen gas containing ozone, for example, from this gas outflow part, new ozone can be supplied to the surface of the semiconductor wafer, and the oxidation chemical reaction between the oxygen atom radicals and the film deposited on the semiconductor wafer is promoted. It is possible to obtain a high and uniform ashing speed.

Further, after heating the mounting table to a predetermined temperature, the semiconductor wafer is then mounted on the mounting table, and the mounting table and the gas outflow portion are closely opposed to each other at a predetermined distance. When the process is completed, the gas that flows out from the gas outflow section is switched to the purge gas, and when this switching is completed, a means for automatically carrying out a series of operations for unloading the semiconductor wafer from the mounting table is provided. The ashing process can be performed in time.

(Embodiment) An embodiment of the ashing device of the present invention will be described below with reference to the drawings.

FIG. 1 shows an ashing apparatus according to an embodiment of the present invention. In the ashing apparatus of this embodiment, a semiconductor wafer 12 is sucked and held in a processing chamber 11, for example, a vacuum chuck.
A mounting table 13 including 13a and the like is arranged.
3 has a heater 14a which is controlled by a temperature control device 14, and is configured to be vertically movable by an elevating device 15.

Above the mounting table 13, a cone-shaped cone portion 16a and a diffusion plate 16c arranged in the opening portion of the cone portion 16a and having a large number of small holes 16b as shown in FIG. The gas outflow part 16 is arranged, and the gas outflow part 16 is a cooling device.
It is cooled by a reaction gas temperature control device 17 including a pipe 17b arranged outside the cone portion 16a and circulating cooling water or the like.

Then, the gas outflow unit 16 is provided with a gas flow rate switching valve 18, a gas flow rate controller 19a, an ozone generator 19b, and an oxygen supply source.
A reaction gas supply device 19 composed of 19c and a gas flow rate controller 20
a, a purge gas supply device 20 including a purge gas supply source 20b
Connected to. An exhaust port is provided at the bottom of the processing chamber 11.
21 is provided, the exhaust port 21 monitors the concentration of, for example, carbon dioxide in the exhaust gas, and when this concentration becomes zero or less than a predetermined value, it is determined that the ashing process has ended It is connected to the device 22 and the exhaust device 23.

In addition, on both sides of the processing chamber 11, semiconductor wafers are provided via the processing chamber doors 24a and 24b by, for example, transfer arms 25a and 25b.
Transport devices 26a and 26b for transporting 12 are connected.

Further, the ashing device of this embodiment is provided with a control device 27 including, for example, a microcomputer, and the control device includes a vacuum chuck 13a, a temperature control device 14, an elevating device 15, and a reaction gas temperature control device. 17, gas flow path switching valve 18, reaction gas supply device 19, purge gas supply device 20, end point determination device 22, exhaust device 23, processing chamber doors 24a, 2
4b, which is connected to the transport devices 26a and 26b, controls these devices, for example, as follows to perform ashing.

That is, as also shown in the flowchart of FIG. 3, first, the set temperature of the temperature control device 14 is set to a predetermined value of, for example, about 150 ° C. to 500 ° C. (a), and the temperature rise of the mounting table 13 is started ( b).

When the temperature of the mounting table 13 reaches the set temperature (c), one of the processing chamber doors 24a and 24b, which is the loading side, is opened, and one of the transportation devices 26a and 26b, which is the loading side, is activated. Then, the semiconductor wafer is transferred by the transfer arms 25a and 25b.
12 is mounted on the mounting table 13 and suction-held by the vacuum chuck 13a (d).

As the transport system, a step motor or the like is used as a power source,
It is possible to conveniently use a transfer device in which the belt serves as a power transmission unit from the step motor to the transfer arm installed on the transfer path for holding the wafer. That is, the movement of the wafer placed on the transfer arm toward the processing chamber is started by a signal input to the step motor from a push button or the like, and a photocoupler or the like mounted on the side of the transfer path for position detection is started. It is possible to detect the stop position by the sensor and mount the wafer at a predetermined position on the mounting table. After that, the transfer arm immediately starts moving outward from the processing chamber, detects the initial position by a photocoupler or the like attached to a position different from the photocoupler on the side of the transfer path, and stops at the same time. The processing chamber door can be closed by an air cylinder or the like.

Next, the mounting table 13 is raised by the elevating device 15, and the gap between the gas outflow portion 16 and the surface of the semiconductor wafer 12 is, for example, 0.5 to 20 m.
The reaction space is set at a predetermined interval of about m (e).

This lifting mechanism uses an air cylinder as a power source,
It is possible to conveniently use a lifting device that uses a mounting table-air cylinder connecting rod guided by a linear bearing or the like as a power transmission means from the air cylinder to the wafer mounting table. That is, when the processing chamber door is closed, a signal from the door opening / closing air cylinder causes the wafer mounting table to start to rise. In order to obtain a predetermined distance between the wafer and the gas diffusion plate, it is possible to raise the wafer mounting table by the stroke length of the air cylinder for raising and lowering the wafer mounting table predetermined and then stop it.

After this, the gas flow path switching valve 18, the reaction gas supply device 19,
Operate the exhaust device 23 to remove the semiconductor wafer from the gas outlet 16.
A reaction gas such as oxygen gas containing ozone is caused to flow toward 12 at a predetermined flow rate of, for example, about 3 to 15 / min, and the gas pressure in the processing chamber 11 is set to 700 to 200To by the exhaust device 23, for example.
Evacuate to within the range of rr (f).

Then, the ashing process is performed, and it is determined whether or not the ashing process is completed based on the components of the exhaust gas measured by the end point determination device 22 (g).

For example, a method of detecting the concentration of a specific component such as carbon dioxide in the exhaust gas by infrared absorption analysis or the like can be used for determining the end point of this ashing. In other words, the ashing end point determination can be performed by comparing the carbon dioxide concentration with zero or a constant value close to zero with a comparator.

When it is determined that the ashing process is completed, the gas flow path switching valve 18 is switched, the purge gas supply device 20 is operated, and the purge gas such as nitrogen gas is caused to flow from the gas outlet 16 toward the semiconductor wafer 12. (H).

Next, when the purging is completed by a preset time or the like (i), the mounting table 13 is lowered by the elevating device 15 according to the same control method as when the mounting table is raised, the vacuum chuck 13a is cut off, and the processing is performed. Room doors 24a, 24b, transfer device 2
The unloading side of 6a and 26b is operated to unload the semiconductor wafer 12 from the mounting table 13 to the outside of the processing chamber 11 (j).

Then, when continuously processing the next semiconductor wafer, the above-described operations below the placement of the semiconductor wafer are repeated,
When all the processing is completed (k), the operation is completed (l).

In the processing step described above, a large number of small holes 16b in the gas outlet 16 are provided.
The gas flowing out from the diffuser plate is shown by the arrow in Fig. 4.
A gas flow from the central portion of the semiconductor wafer 12 to the peripheral portion is formed between the semiconductor wafer 12 and 16c.

Here, ozone is heated and decomposed by the heated semiconductor wafer 12 and the atmosphere around it, and a large amount of oxygen atom radicals are generated. Then, the oxygen atom radicals react with the photoresist film deposited on the surface of the semiconductor wafer 12, ashing is performed, and the photoresist film is removed.

The life of ozone generated by the ozone generator 19b is
As shown in the graph of FIG. 5 in which the vertical axis is the ozone decomposition half-life and the horizontal axis is the temperature of the gas containing ozone, the life of ozone decreases rapidly as the temperature increases.
Therefore, it is preferable that the temperature of the gas outlet 16 is about 25 ° C. or lower, while the temperature of the semiconductor wafer 12 is heated to about 150 ° C. or higher. Therefore, in this embodiment, the control device 27 controls the reaction gas temperature control device 17 so that the temperature of the gas outflow portion 16 is maintained at about 25 ° C. or lower.

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 6-inch semiconductor wafer 12 is heated to 300 ° C. with the distance between the gas outlet 17 and the semiconductor wafer 12 as a parameter. 4 shows changes in the ashing speed of the ashing device of this embodiment in the case of performing. 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 16 is several.
mm, and by setting the flow rate of the gas containing ozone within the range of about 2 to 40 Sl (Sl is the flow rate at room temperature and atmospheric pressure), it is possible to perform high-speed ashing with an ashing speed of 1 to several μm / min. .

Further, the mounting table 13 is heated to a predetermined temperature, then the semiconductor wafer 12 is mounted on the mounting table 13, and the mounting table 13 and the gas outflow portion 16 are closely opposed to each other at a predetermined interval, and then the gas outflows. A gas containing ozone is caused to flow out from the section 16, and when the processing is completed, the gas to be flowed out from the gas outflow section 16 is switched to a purge gas, and when this switching is completed, the semiconductor wafer 12 is placed on the mounting table.
Since a series of operations to be carried out from the top 13 is automatically performed, the processing time for one semiconductor wafer 12 can be set to about 60 seconds, and even a large-diameter semiconductor wafer can be reliably processed in a short time by single-wafer processing. You can ash.

In this embodiment, the gas outflow portion 16 is configured by arranging the diffusion plate 16c having a large number of small holes 16b in the opening of the cone-shaped cone portion 16a, but the present invention is not limited to this embodiment. For example, the diffuser plate 16c may be a diffuser plate 30c having a plurality of concentric circular slits 30b as shown in FIG. 7, and a sintered body such as metal or ceramic as shown in FIG. A diffuser plate 31c, a diffuser plate 32c having a linear slit 32b as shown in FIG. 9, a diffuser plate 33c having small holes 33b of different sizes as shown in FIG.
As shown in Fig. 11, the diffusing plate 3 provided with spiral slits 34b
4c etc. may be used. In addition, the cone-shaped cone portion 16a,
It goes without saying that the columnar portion 35a and the like as shown in FIG. 12 may have any shape.

Furthermore, in this embodiment, the case of using a photoresist film as the ashing target has been described, but what kind of ashing target is applicable as long as it can be applied to various things such as ink removal and solvent removal and can be removed by oxidation. 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.

[Advantages of the Invention] As described above, in the ashing apparatus of the present invention, the semiconductor wafer is not damaged, and the ashing speed is uniform and high, so that the semiconductor wafer can be loaded from the mounting table to being unloaded. Since a series of operations is automatically performed, even a large-diameter semiconductor wafer or the like can be reliably ashed in a short time by single-wafer processing.

[Brief description of drawings]

FIG. 1 is a block diagram showing an ashing device according to an embodiment of the present invention, FIG. 2 is a bottom view showing an essential part of FIG. 1, and FIG.
A flowchart showing the operation of the ashing device shown in the figure,
FIG. 4 is an explanatory diagram showing the flow of a gas containing ozone, FIG. 5 is a graph showing the relationship between ozone half-life and temperature, and FIG.
FIG. 7 is a graph showing the relationship between the ashing rate, the flow rate of gas containing ozone, and the distance between the gas outflow portion and the semiconductor wafer. FIGS. 7 to 11 are bottom views showing modifications of the gas outflow portion shown in FIG. FIG. 12 is a vertical sectional view showing a modified example of the gas outflow portion, and FIG. 13 is a configuration diagram showing a conventional ashing device. 11 ... Processing chamber, 12 ... Semiconductor wafer, 13 ... Mounting table, 14
...... Temperature control device, 15 …… Elevating device, 16 …… Gas outflow part, 18 …… Gas flow path switching valve, 19 …… Reaction gas supply device, 20 …… Purge gas supply device, 22 …… End point determination device,
23 ... Exhaust device, 24a, 24b ... Processing chamber door, 26a, 26b ...
… Conveyor, 27 …… Control device.

Claims (2)

[Claims] 1. A single-wafer ashing apparatus which is placed in an airtight processing chamber and introduces a processing gas into a semiconductor wafer having a photoresist film formed thereon to remove the photoresist film. A means for heating the mounting table to a predetermined temperature, a means for mounting the semiconductor wafer on the mounting table, and a predetermined interval between the mounting table and the gas outflow portion after the mounting of the means is completed. A means for setting a reaction space in close proximity to each other, a means for causing the gas to flow out from the gas outlet after the setting of the means is completed, a means for determining an end point at which the removal of the film is completed, A means for switching the gas flowing out from the gas outflow portion to a purge gas in accordance with the end point determination result, and carrying out the semiconductor wafer from the mounting table after the switching of the purge gas by the means is completed. And an ashing device. 2. The ashing device according to claim 1, wherein the purge gas is nitrogen gas.