JPH06103666B2 - Ashing 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.

(Prior Art) Generally, a fine pattern for forming a semiconductor integrated circuit is formed, for example, by using a photoresist film of an organic polymer formed by exposure and development as a mask and etching a base film of this mask. 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 for performing dry cleaning processes in semiconductor processes.

There is an ashing method in which oxygen atom radicals are generated by irradiating with ultraviolet rays, and the ashing process is performed in a batch process.

FIG. 5 shows an ashing device for generating oxygen atom radicals by irradiating such an ultraviolet ray. A large number of semiconductor wafers (2) are vertically arranged at a predetermined interval in the processing chamber (1). Ultraviolet rays from an ultraviolet arc tube (3) installed on the upper part of (1) are irradiated through a transparent window (4) such as quartz provided on the upper surface of the processing chamber (1), and the processing chamber (1) is irradiated. The filled oxygen is excited 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, in the conventional ashing method described above, the ashing speed is slow at 50 to 150 nm / min, and it takes a long time to process, so that, for example, a semiconductor wafer suitable for processing a large-diameter semiconductor wafer. There is a problem in that the single-wafer processing that processes one by one cannot be performed.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide an ashing method which has a high ashing speed of a photoresist film and can be used for single-wafer processing of large-diameter semiconductor wafers.

[Structure of Invention]

(Means for Solving Problems) The present invention provides an ashing method characterized by performing an ashing treatment with a mixed gas of an ashing gas and a nitrogen oxide gas.

(Function and effect) By performing ashing with a mixed gas of ashing gas and nitrogen oxide gas, high-speed ashing treatment can be performed, which is 2 to 3 times more than in the case of performing ashing treatment with ashing gas not mixed with nitrogen oxide gas. High-speed ashing processing becomes possible.

(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.
First, the configuration of the ashing device will be described.

A cylindrical upper chamber (5) having a U-shaped cross section is provided so as to be vertically movable by a lifting mechanism (not shown). The upper chamber (5) is provided with, for example, a glass flat plate (6) for allowing the ashing gas to flow out uniformly.
On the central axis of the flat plate (6), there is provided an outlet (7) having a diameter of, for example, 8 mm for letting out the ashing gas. A lower chamber (8) is provided so as to be engaged with the upper chamber (5), and a disk-shaped mounting table (on which a substrate to be processed, for example, a semiconductor wafer (9) can be mounted is provided in the lower chamber (8). 10) is provided. This table (10)
A heater (11) is installed inside the heater, and the heater (11) is provided outside the lower chamber (8) and has a temperature control mechanism (12).
Therefore, the temperature of the table (10) can be freely adjusted. A gas flow controller (1) is provided by a gas flow conduit (13) so that the ashing gas flows out to the surface of the semiconductor wafer (9) set on the mounting table (10).
Ozone generator (1) with oxygen source (15) via 4)
6) is provided. A nitrogen oxide gas flow conduit (17) is connected to the gas flow conduit (13), and the nitrogen oxide gas flow conduit (17) is connected via a gas flow controller (18) to nitrous oxide. It is connected to a nitrogen oxide gas generator (20) equipped with a supply source (19). Further, the gas flow conduit (13) is branched and connected to the air purging mechanism (21). Further, an exhaust mechanism (23) for exhausting the inside of the processing chamber (22) is provided at the bottom of the lower chamber (8) via an exhaust pipe (24). The ashing device is configured in this way.

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

The upper chamber (5) is raised by an elevating mechanism (not shown), the semiconductor wafer (9) is held by a transfer mechanism such as a hand arm (not shown), and a mounting table (10) provided in the lower chamber (8) is held. ) Is placed at a predetermined position above and is held, for example, sucked and held. Then, the upper chamber (5) is lowered by an elevating mechanism and airtightly connected to the lower chamber (8). At this time, the distance between the semiconductor wafer (9) mounted on the mounting table (10) and the flat plate (6) provided in the upper chamber (5) is preset to be, for example, about 0.5 to 20 mm. Therefore, the above distance is maintained during the airtight connection. Further, at this time, the heater (11) provided inside the mounting table (10) is provided outside the temperature control mechanism (1
The semiconductor wafer (9) is heated to about 300 ° C. because it was previously heated to about 150 to 500 ° C., for example, 300 ° C. by 2).

And an ozone generator (16) equipped with an oxygen supply source (15)
Ozone is generated by the gas flow controller (14), and the ozone is introduced into the gas flow conduit (13) at a set flow rate of 5 to 20 l / min, for example, 15 l / min. Further, a nitrogen oxide gas generator (20) equipped with a nitrous oxide supply source (19) is used to generate an unstable nitrogen oxide gas such as nitric oxide, nitrogen dioxide, or dinitrogen tetraoxide. The gas flow controller (14) conducts the gas to the gas flow conduit (13) at a set flow rate of 50 to 500 ml / min, for example, about 250 ml / min. The nitrogen oxide gas generating means at this time is, for example, an AC power supply is connected to two electrodes facing each other with a slight gap, and a high voltage is applied to the electrodes by the power supply, and the two electrodes are connected to each other. The nitrous oxide supply source (19) is used to conduct nitrous oxide to generate an unstable nitrogen oxide gas such as nitrogen dioxide or nitrous oxide. The generated nitrogen oxide gas such as nitrogen dioxide or dinitrogen tetraoxide is introduced into the gas flow conduit (13) and mixed with ashing gas containing ozone to form dinitrogen pentaoxide. Then, the ashing gas mixed with the nitrogen oxide gas, that is, dinitrogen pentoxide is mounted on the mounting table (10) through the outflow port (7) having a diameter of 8 mm provided on the flat plate (6), and the semiconductor wafer (9 ) And the ashing process is performed. At this time, a film, such as Cl, deposited on the surface of the semiconductor wafer (9) by the reaction of oxygen radicals O ( ¹ D) generated by heating the ashing gas mixed with the nitrogen oxide gas, that is, dinitrogen pentoxide.
HmOn is decomposed into carbon dioxide and water vapor, but in the case of only ozone ashing, the semiconductor wafer (9) is produced by the reaction of oxygen radicals O ( ³ P) generated by heating ozone.
The same effect can be obtained by decomposing a film, such as ClHmOn, deposited on the surface into carbon dioxide and water vapor. However, since oxygen radicals O ( ¹ D) and O ( ³ P) are more reactive than O ( ¹ D), ashing gas containing the above nitrogen oxide gas, that is, ashing with dinitrogen pentoxide is more preferable. A higher ashing speed can be obtained. FIG. 2 is a graph showing changes in the ashing rate due to changes in the flow rate of nitrous oxide. This is the characteristic when the semiconductor wafer (9) is heated to 300 ° C and the ozone flow rate is set to 15 l / min. From this graph, it can be seen that mixing nitrogen oxide gas with ozone increases the ashing speed. It is understood that the optimum flow rate of nitrous oxide is 250 to 300 ml / min.

The ashing speed on the surface of the semiconductor wafer (9) is shown in FIG. This shows the ashing rate due to the change in the dinitrogen monoxide flow rate when the ozone flow rate was set to 15 l / min while the semiconductor wafer (9) was heated to 300 ° C. From this graph, it can be seen that when nitrogen oxide gas is mixed with ozone, the ashing speed also increases at each part of the surface of the semiconductor wafer (9), but when the flow rate of dinitrogen monoxide reaches about 1000 ml / min, the semiconductor wafer (9 ) It is clear that the optimum flow rate of nitrous oxide is about 250 ml / min because the peripheral area becomes slower than the ozone ashing rate.

When the ashing process of the semiconductor wafer (9) is completed as described above, the exhaust mechanism (23) exhausts the exhaust gas in the processing chamber (22) through the exhaust pipe (24). At the same time, from the air purge mechanism (21) through the gas flow conduit (13) to the processing chamber (2
2) Purge air inside.

Next, another embodiment will be described with reference to FIG. A substrate to be processed, for example, a semiconductor wafer (26) can be held, for example, sucked and held, on an upper surface of a mounting table (25) which is connected to an elevating mechanism and a temperature control mechanism (not shown) and is configured to be capable of elevating and controlling temperature. A lid (27) is provided on the upper part so as to engage with such a mounting table (25), and in order to make the inside airtight at the time of this engagement, a Teflon-based rubber packing (28 ) Is provided. This lid (27) and mounting table (2
An internal processing space is formed by the engagement of 5).

On the surface of the lid (27) facing the wafer (26), a quartz glass window (29) made of a transparent material having a larger area than at least the wafer (26) is provided in parallel with the wafer (26). Has been. Above the quartz glass window (29), a plurality of ultraviolet lamps (30) arranged so as to cover the entire surface of the wafer (26) are arranged in parallel with the quartz glass window (29). A gas supply pipe (31) is connected to the lateral portion of the lid (27), and the gas supply pipe (31) is provided with an oxygen generator having an oxygen supply source via a gas flow rate controller (not shown). It is connected to. Furthermore, the gas supply pipe (3
In 1), a nitrogen oxide gas generator equipped with a dinitrogen monoxide supply source is connected via a gas flow rate controller (not shown). Furthermore, the gas supply pipe (31) is branched and connected to an air purging mechanism (not shown). The gas supply pipe (31) connected to each of these mechanisms is provided with the lid (2
The ashing gas can be supplied to the surface of the wafer (26) through a plurality of openings (32) having a diameter of, for example, 1 mm provided on the periphery of the wafer (26).

Further, an exhaust pipe (33) is connected to a lateral portion of the lid (27), and the exhaust pipe (33) is connected to an exhaust mechanism (not shown) for exhausting the processing space.

An ashing process is performed by the ashing device configured as described above. First, the mounting table (25) is lowered by driving the elevating mechanism, and is not shown at a predetermined position on the upper surface of the mounting table (25). A substrate to be processed, for example, a semiconductor wafer (26) is transferred and placed by a transfer mechanism, for example, a hand arm. Then, the mounting table (25) is lifted and engaged so that the distance between the lid (27) and the wafer (26) is about 0.1 to 0.5 mm, and further the packing (28) acts to move the inside of the processing space. Keep tightly closed. Already at this time the table (25)
The temperature is controlled to about 350 ° C. by the temperature control mechanism, and the wafer (26) placed above is heated to about 350 ° C. by the heat of the mounting table (25).

Next, ozone is generated by an ozone generator equipped with an oxygen supply source, and a set flow rate of 5-20 l / min is set by a gas flow rate controller.
For example, about 10 l / min is supplied to the gas supply pipe (31). Further, a nitrogen oxide gas generator equipped with a dinitrogen monoxide supply source generates nitrogen oxide gas such as NO _x , and a gas flow rate controller sets a set flow rate of 50 to 500 ml / min such as 250 ml.
The gas is supplied to the gas supply pipe (31) at a rate of about / min and mixed with the ozone. Then, the mixed gas is provided with a plurality of openings (32).
From the UV lamp (30) to the surface of the wafer (26) mounted on the mounting table (25) and, for example, at a wavelength of 25
An ashing process is performed by irradiating the surface of the wafer (26) with a 4 nm ultraviolet ray through a transparent quartz glass window (29). At this time, the mixed gas supplied to the surface of the wafer (26) is excited by the ultraviolet rays, and the heat of the wafer (26) in a high temperature state further generates oxygen atom radicals. This oxygen atom radical is deposited on the surface of the wafer (26), for example ClHm.
Decomposes On into carbon dioxide and water vapor. In this case, by using ultraviolet rays together with the ashing treatment with the mixed gas, it becomes possible to generate oxygen atom radicals having a stronger oxidizing action, and a higher ashing rate can be obtained as compared with the ashing treatment with the mixed gas or ozone alone. Obtainable.

The exhaust gas after the ashing process is exhausted through the exhaust pipe (33).

As described above, according to this embodiment, by mixing the nitrogen oxide gas with the ashing gas and irradiating the mixed gas with ultraviolet rays to excite it, only the mixed gas or,
Oxygen atom radicals having a stronger oxidizing action can be generated as compared with ashing treatment using only ozone, and high-speed ashing treatment can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an ashing device for explaining an embodiment of the method of the present invention, and FIGS. 2 and 3 are ashing when nitrogen oxide gas is mixed with ashing gas. FIG. 4 is a graph showing speed, FIG. 4 is an explanatory view of another embodiment of the method of the present invention, and FIG.
The figure is a block diagram of a conventional ashing device. 9, 26 ... Wafer, 16 ... Ozone generator, 18 ... Gas flow controller, 19 ... Nitrous oxide supply source, 20 ... Nitrogen oxide gas generator, 30 ... UV lamp.

Claims (4)

[Claims] 1. An ashing method characterized by performing an ashing treatment with a mixed gas of an ashing gas and a nitrogen oxide gas. 2. The ashing method according to claim 1, wherein the nitrogen oxide gas is dinitrogen pentoxide. 3. The ashing method according to claim 1, wherein the mixed gas is a mixed gas of ozone with nitric oxide, nitrogen dioxide or dinitrogen tetraoxide. 4. The ashing method according to claim 1, wherein the mixed gas is irradiated with ultraviolet rays.