JP6782140B2 - Etching method and etching equipment - Google Patents

Description

The present invention relates to a substrate etching method and an etching apparatus. Examples of the substrate to be processed include a semiconductor wafer, a liquid crystal display device substrate, a plasma display substrate, an FPD (Field Emission Display) substrate, an optical disk substrate, a magnetic disk substrate, an optical magnetic disk substrate, and a photomask. Substrates such as substrates, ceramic substrates, and solar cell substrates are included.

In the manufacturing process of semiconductor devices, various silicon oxide films having different film qualities are formed on a silicon substrate. For example, examples of the silicon oxide film formed on the silicon substrate include a thermal silicon oxide film formed by thermal oxidation, a TEOS (Tetra Ethoxy Silane) film obtained by using a CVD method, and BSG (Boron Silicone) obtained by a CVD method. Examples thereof include a silicon oxide film containing a large amount of impurities such as a Grass) film, a PSG (Phospho Silane Glass) film, and a BPSG (Boron Doped Phospho Silane Glass) film. Further, during the manufacturing process of the semiconductor device, since the surface of the silicon substrate is chemically unstable, a natural oxide film is formed by the reaction with oxygen in the atmosphere.

Conventionally, wet etching based on hydrofluoric acid has been used for etching the various silicon oxide films. However, when the pattern formed with the high integration of semiconductor devices is miniaturized, there has been a problem that the pattern collapses due to the surface tension of water in wet etching. Further, in the formation of contacts on a silicon substrate, it is necessary to remove the natural oxide film on the bottom surface of the hole, but with the miniaturization of semiconductor devices, there has been a problem that the chemical solution cannot be sufficiently replaced at the time of washing with wet etching.

In order to solve such a problem of wet etching, there are a vapor phase etching technique using hydrofluoric acid vapor and a vapor phase etching technique using anhydrous hydrogen fluoride gas. Patent Document 1 describes a vapor phase etching technique using hydrofluoric acid vapor. Patent Document 1 describes that the exhaust flow rate in the processing chamber is controlled to increase the pressure at the time of etching in order to improve the uniformity of etching. After etching, the atmosphere in the processing chamber is replaced with an inert gas to stop the etching process on the entire surface of the substrate.

Further, Patent Document 2 describes a vapor phase etching technique using anhydrous hydrogen fluoride gas. Patent Document 2 describes anhydrous hydrogen fluoride gas in a predetermined mixing ratio with an inert gas while being held at a predetermined temperature of 80 ° C. to 120 ° C. and under a predetermined reduced pressure within the range of 12 Kpa to 40 Kpa. A method for etching a natural oxide film, which comprises exposing to a diluted reaction gas, is described. After the etching process, vacuum exhaust is performed and nitrogen gas is supplied after a predetermined time.

Japanese Unexamined Patent Publication No. 2013-149934 Japanese Unexamined Patent Publication No. 2008-34688

In the above-mentioned vapor phase etching technique using hydrofluoric acid vapor and the vapor phase etching technique using anhydrous hydrogen fluoride gas, fluorine remains on the surface of the silicon substrate after etching. When fluorine remains on the surface of silicon after etching the silicon oxide film, the residual fluorine reacts with silicon, causing defects in silicon or forming particles. Further, if fluorine remains after etching the silicon oxide film on the silicon serving as a gate, the fixed charge at the interface between the gate oxide film and the silicon formed thereafter increases, which adversely affects the electrical characteristics.

Therefore, in the present invention, in the manufacturing process of a semiconductor device, various silicon oxide films having different film qualities formed on a silicon substrate without leaving fluorine on the surface of the silicon after etching are uniformly vapor-phase etched on the entire surface of the substrate. It is an object of the present invention to provide an etching method and an etching apparatus.

The invention according to claim 1 for achieving the above object is an etching method for etching a substrate on which a silicon oxide film is formed, which comprises a depressurization step of depressurizing a processing chamber containing the substrate and a depressurization step. After that, an etching step containing hydrogen fluoride is supplied to the processing chamber to etch the silicon oxide film formed on the substrate, and after the etching step, steam is supplied to the processing chamber to supply the substrate. wherein a cleaning step of cleaning, after the pressure reduction step and before the etching step, to have a water film forming step of forming a water film on the surface of the substrate by supplying steam into the processing chamber to This is the etching method for the substrate. According to the etching method according to claim 1, since the cleaning step of supplying steam to clean the substrate is performed after the etching step, it is possible to suppress the residual fluorine on the surface of the substrate. Moreover, since the etching gas is supplied to the substrate on which the water film is formed on the surface, etching can be performed efficiently.

The invention according to claim 2 is the etching method for a substrate according to claim 1 , wherein the etching gas is an etching mixed gas of hydrogen fluoride gas and steam. According to the etching method according to claim 2 , efficient etching is possible.

The invention according to claim 3 is the etching method according to claim 2 , wherein the etching gas has a ratio of the hydrogen fluoride gas to the water vapor of 10 to 60 vol. This is a substrate etching method characterized by being%.

The invention according to claim 4 is a method for etching a substrate according to the etching method according to claims 1 to 3 , wherein the substrate temperature in the etching step is 30 to 200 ° C.

The invention according to claim 5 is a substrate etching method according to claim 1 to 4 , wherein the degree of vacuum in the processing chamber in the etching step is 1 Pa to 100 Pa.

The invention according to claim 6 is an etching apparatus for etching a substrate on which a silicon oxide film is formed, a processing chamber having a processing space inside, a substrate holding means for holding the substrate in the processing space, and the processing. A decompression means that is connected to the bottom of the chamber to reduce the pressure in the processing space, a steam supply means that is connected to the upper part of the treatment chamber and supplies a second steam to the treatment space, and an upper portion of the treatment chamber. The control is provided with an etching gas supply means which is connected in communication and supplies an etching gas containing hydrogen fluoride to the processing space, and a control means for controlling the depressurizing means, the steam supply means, and the etching gas supply means. After depressurizing the processing space by the depressurizing means, the etching gas supply means supplies the etching gas to the processing space to etch the substrate, and then the steam supply means brings the processing space to the first. by supplying second steam have line cleaning process for cleaning the substrate, the etching gas supply means and the mixed gas piping to generate the etching gas by mixing the hydrogen fluoride gas first steam, the The control means is provided with a multiple valve for selectively supplying the first water vapor unit and the etching gas to the processing space through a mixed gas pipe, and the control means controls the multiple valve to perform the above-mentioned. After depressurizing the processing space by the depressurizing means, the first water vapor unit is supplied from the mixed gas pipe to the processing space to form a water film on the surface of the substrate, and the water film is formed. Later, the etching apparatus is characterized in that the etching gas is supplied from the mixed gas pipe to the processing space by controlling the multiple valve to etch the substrate . According to the etching apparatus according to claim 6 , since water vapor is supplied to clean the substrate after etching with the etching gas, residual fluorine on the surface of the substrate can be suppressed. Moreover, since the etching gas is supplied to the substrate on which the water film is formed on the surface, etching can be performed efficiently.

The invention according to claim 7 is the etching apparatus according to claim 6 , wherein the steam supply means supplies the second steam to the processing space without passing through the mixed gas pipe. It is an etching device. After supplying the etching gas, the etching gas may remain in the mixed gas pipe. Since the steam supply means supplies the second steam to the treatment space without passing through the mixed gas pipe, the steam that does not contain the residual etching gas can be supplied to the treatment space.

The invention according to claim 8 is an etching apparatus for etching a substrate on which a silicon oxide film is formed, a processing chamber having a processing space inside, a substrate holding means for holding the substrate in the processing space, and the processing. A decompression means that is connected to the bottom of the chamber to reduce the pressure in the processing space, a steam supply means that is connected to the upper part of the treatment chamber to supply a second steam to the treatment space, and an upper portion of the treatment chamber The control is provided with an etching gas supply means which is connected in communication and supplies an etching gas containing hydrogen fluoride to the processing space, and a control means for controlling the depressurizing means, the steam supply means, and the etching gas supply means. After depressurizing the processing space by the depressurizing means, the etching gas supply means supplies the etching gas to the processing space to etch the substrate, and then the steam supply means brings the processing space to the first. The cleaning process of supplying the steam of 2 to clean the substrate is performed, and the control means decompresses the processing space by the decompression means and then before supplying the etching gas to the processing space by the etching gas supply means. In addition, the etching apparatus is characterized in that the water vapor supply means is controlled to supply a second water vapor to the processing space to form a water film on the surface of the substrate. Since the etching gas is supplied to the substrate on which the water film is formed on the surface, etching can be performed efficiently.

The invention according to claim 9 is characterized in that, in the etching apparatus according to any one of claims 6 to 8 , a gas dispersion plate having a plurality of pores is provided on an upper portion of a substrate holding means in a processing chamber. It is an etching device.

According to the present invention, it is possible to uniformly etch various silicon oxide films having different film qualities on the entire surface of the substrate without leaving fluorine on the surface after etching the silicon oxide film.

It is a side view which shows the schematic structure of the etching apparatus which concerns on Example. It is a flow chart which shows the flow of the process which concerns on Example. It is a graph which shows the fluorine removal by steam cleaning which concerns on Example. It is a graph of the etching rate with respect to the processing chamber pressure which concerns on an Example. It is a graph of the etching rate with respect to the substrate temperature which concerns on Example. It is a side view which shows the schematic structure of the etching apparatus which concerns on Example. It is a flow chart which shows the flow of the process which concerns on Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

FIG. 1 is a side view showing a schematic configuration of an etching apparatus 1 for carrying out the present invention. The etching apparatus 1 is a single-wafer etching apparatus that processes substrates W such as semiconductor wafers one by one. The etching apparatus 1 includes a processing chamber 2 for processing the substrate W, and a control unit 3 for controlling the operation of the apparatus provided in the etching apparatus 1 and the opening and closing of a valve.

In the processing chamber 2, a substrate holder 4 for holding the substrate W, a heating mechanism 5 built in the substrate holder 4 for heating the substrate W, and a gas located above the substrate holder 4 in the processing chamber 2 Installed in the dispersion plate 6, the exhaust pipe 7 communicated with the processing chamber 2 to reduce the pressure in the processing chamber 2, the vacuum pump 8 for reducing the pressure in the processing chamber 2 through the exhaust pipe 7, and the exhaust pipe 7. APC (Auto Pressure Control) valve 9, a pressure sensor 10 connected to the processing chamber 2, a first pipe 11 (mixed gas pipe) connected to the upper part of the processing chamber 2, and a steam supply source (not shown). The first water vapor flow rate controller 12 for supplying the generated first water vapor into the processing chamber 2, the hydrogen fluoride gas flow rate controller 13 for supplying the hydrogen fluoride gas into the processing chamber 2, and the first one. It is supplied from a multiple valve 14 having an on-off valve for supplying water vapor and hydrogen fluoride gas into the processing chamber 2, a second pipe 17 connected to the upper part of the processing chamber 2, and a steam supply source (not shown). It is provided with a second water vapor flow controller 15 and an on-off valve 16 for supplying the generated second water vapor into the processing chamber 2.

The processing chamber 2 has a cylindrical shape and has a processing space inside for processing the substrate W. A substrate holder 4 for holding the substrate W in a substantially horizontal posture is installed in the processing chamber 2. The substrate W is transported into the processing chamber 2 by a transport system (not shown) and placed on the substrate holder 4. The substrate W is heated to a predetermined temperature in the range of 30 ° C. to 200 ° C. by the heating mechanism 5 built in the substrate holder 4. As the heating mechanism 5, for example, a resistance heating type electric heater is used.

An exhaust pipe 7 is communicated with the bottom of the processing chamber 2 in order to reduce the pressure inside the processing chamber 2, and is exhausted by a vacuum pump 8 connected to the exhaust pipe 7. An APC valve 9 is connected to the exhaust pipe 7, and the APC valve 9 adjusts the pressure in the processing chamber 2 by adjusting the exhaust flow rate from the processing chamber 2. The degree of vacuum in the processing chamber 2 is monitored by the pressure sensor 10 connected to the processing chamber 2. The opening degree of the APC valve 9 is adjusted so that the monitored vacuum degree becomes a desired vacuum degree, and the pressure in the processing chamber 2 is adjusted. After the substrate W is held by the substrate holder 4, the vacuum pump 8 operates to start evacuation in the processing chamber 2. In the present embodiment, the means for depressurizing the inside of the processing chamber 2 is described by the vacuum pump 8, but the present invention is not limited to this, and for example, the exhaust gas from the factory utility can be used.

The first water vapor is supplied into the processing chamber 2 from the first pipe 11 which is communicated with the upper part of the processing chamber 2. The supply flow rate of the first steam is adjusted by the first steam flow controller 12, and the opening / closing valve of the multiple valve 14 is opened to supply the first steam into the processing chamber 2. The hydrogen fluoride gas supplied from the hydrogen fluoride supply source (not shown) is supplied into the processing chamber 2 by adjusting the supply flow rate by the hydrogen fluoride gas flow rate controller 13 and opening the opening / closing valve of the multiple valve 14. Will be done. The multiple valve 14 has a first water vapor on-off valve and a hydrogen fluoride gas on-off valve inside, and the valves can be opened and closed independently of each other. When both valves are opened, the first steam and hydrogen fluoride gas are mixed in the first pipe 11 which is the destination of the multiple valve 14. When any of the valves is opened, the multiple valve 14 supplies the first steam unit or the hydrogen fluoride gas unit to the first pipe 11.

The second water vapor is supplied into the processing chamber 2 from the second pipe 17 which is communicated with the upper part of the processing chamber 2. The supply flow rate of the second steam is adjusted by the second steam flow controller 15, and the opening and closing valve 16 that can be opened and closed is opened to supply the second steam into the processing chamber 2. Although not shown, as the supply source of the first steam and the second steam, for example, a method of heating a tank storing pure water to vaporize it and pumping it with an inert gas such as nitrogen is used. A tank for storing pure water can be shared and supplied by switching between the first steam and the second steam, or tanks can be provided individually. Although not shown, a high-pressure cylinder of anhydrous hydrogen fluoride is used as the source of hydrogen fluoride gas.

Temperature control of the heating mechanism 5 of the etching device 1, flow rate control of the flow rate controllers 12, 13 and 15, opening / closing operation of the multiple valve 14, opening / closing operation of the opening / closing valve 16, exhaust operation of the vacuum pump 8, monitoring of the pressure sensor 10. The operation of each part such as the opening degree adjustment of the APC valve 9 is controlled by the control unit 3.

When the control unit 3 controls the multiple valve 14, the mixed gas of the first steam and the first steam / hydrogen fluoride gas is selectively supplied from the first pipe 11 into the processing chamber 2. The second steam is supplied from the second pipe 17 into the processing chamber 2. The first water vapor, the first water vapor / hydrogen fluoride gas mixed gas, and the second water vapor pass through the gas dispersion plate 6 and reach the substrate W. A plurality of gas dispersion plates 6 are used to uniformly supply the first water vapor introduced into the processing chamber 2, the mixed gas of the first water vapor and hydrogen fluoride gas, and the second water vapor onto the substrate W. An opening is formed. In the present embodiment, openings having an inner diameter of 0.1 mm are formed at intervals of 5 mm. The inner diameter and spacing of the openings are not limited to this. Further, the gas dispersion plate 6 may be installed in a plurality of stages.

The supply amount of hydrogen fluoride gas supplied for etching the silicon oxide film formed on the substrate W is 100 cc / min to 2000 cc / min, whereas the first water vapor to be mixed is 300 cc / min. 10000 cc / min is applied. In the substrate surface cleaning after etching the silicon oxide film, 300 cc / min to 10000 cc / min is applied as the supply amount of the second water vapor. Further, during the processing of the substrate W, the pressure in the processing chamber 2 is maintained at 1 to 100 Pa. The opening degree of the APC valve 9 is adjusted so that the pressure of the pressure sensor 10 becomes a predetermined pressure according to the supply amounts of the first steam, the mixed gas of the first steam and hydrogen fluoride gas, and the second steam. As a result, the pressure in the processing chamber 2 is controlled.

The first embodiment will be described with reference to the processing flow chart of FIG. The substrate W is transported into the processing chamber 2 by a transport system (not shown) and placed on the substrate holder 4 (step S1). After the substrate W is placed on the substrate holder 4, the substrate W is heated to a predetermined temperature in the range of 30 ° C. to 200 ° C. by the heating mechanism 5 built in the substrate holder 4.

After the substrate W is placed on the substrate holder 4, the vacuum pump 8 starts evacuation (step S2). Evacuation is performed until the pressure in the processing chamber 2 is about 0.1 Pa, and the air atmosphere in the processing chamber 2 is exhausted. The evacuation is determined by the capacity of the vacuum pump used and the permissible evacuation time, but the air atmosphere in the processing chamber 2 is exhausted and the inside of the processing chamber 2 becomes clean when the pressure is reduced as much as possible.

After the pressure in the processing chamber 2 reaches about 0.1 Pa, the first water vapor is supplied into the processing chamber 2 through the first pipe 11 (step S3). The supply flow rate of the first steam is adjusted to a predetermined flow rate by the first steam flow controller 12, and the valve of the multiple valve 14 is opened to be supplied from the first pipe 11 into the processing chamber 2. The opening degree of the APC valve 9 is adjusted by monitoring the pressure in the processing chamber 2 with the pressure sensor 10 so that the pressure in the processing chamber 2 becomes a predetermined degree of vacuum. The supply time of the first water vapor in step S3 is not particularly limited, but may be a time (for example, about 1 to 10 seconds) that allows a thin water layer to be formed on the entire surface of the substrate W.

The first water vapor passes through the plurality of openings of the gas dispersion plate 6 and is supplied to the entire surface of the substrate W. The first water vapor that reaches the entire surface of the substrate W forms a thin layer of water on the substrate W.

After the first steam is supplied for a predetermined time, the hydrogen fluoride gas flow rate controller 13 adjusts the hydrogen fluoride gas to a predetermined supply flow rate, and the valve of the multiple valve 14 is opened to open the multiple valve 14. It is mixed with the first water vapor in the first pipe 11 at the destination to become a mixed gas, which is supplied from the first pipe 11 into the processing chamber 2. The mixed gas supplied into the processing chamber 2 passes through the plurality of openings of the gas dispersion plate 6 and is uniformly supplied to the entire surface of the substrate W to etch the silicon oxide film formed on the substrate W (step S4). ). The supply flow rate of the first water vapor and hydrogen fluoride gas is predetermined depending on the silicon oxide film type to be etched. For example, in the case of etching the silicon oxide film as in the present embodiment, the supply flow rate of the first steam is set in the range of 300 cc / min to 10000 cc / min, and hydrogen fluoride mixed with the first steam is mixed. The gas supply flow rate is set to 100 cc / min to 2000 cc / min.

In the present embodiment, the first water vapor is supplied before the etching mixed gas is supplied. Therefore, since the water layer is formed on the substrate W before the hydrogen fluoride gas, which is the etching species of the silicon oxide film, reaches the substrate W, the etching can be started immediately. If the etching mixed gas is supplied to the substrate W in a state where the water film does not exist on the substrate W, the etching of the silicon oxide film of the substrate W cannot be started immediately. This is because when the silicon oxide film is etched with hydrogen fluoride gas, the hydrogen fluoride gas dissolves in water to dissociate and generate fluorine ions, and these fluorine ions contribute to the etching.

Immediately after the etching of the silicon oxide film by the mixed gas is completed, the first water vapor valve and the hydrogen fluoride gas valve of the multiple valve 14 are closed to stop the supply of the mixed gas. At the same time, the second steam is adjusted to a predetermined supply flow rate by the second steam flow controller 15, and the opening / closing valve 16 is opened to supply the second steam into the processing chamber 2 from the second pipe 17 (step S5). The second water vapor passes through the plurality of openings of the gas dispersion plate 6 and is supplied to the entire surface of the substrate W. Fluorine remaining on the surface of the substrate W is removed by supplying a second water vapor to the substrate W after etching the silicon oxide film and cleaning the substrate W. In the present embodiment, steam (second steam) for cleaning the substrate W from the second pipe 17 different from the first pipe 11 that supplies hydrogen fluoride gas into the treatment chamber 2 is introduced into the treatment chamber 2. We are supplying. If water vapor for cleaning the substrate W is to be supplied to the processing chamber 2 through the first pipe 11, the hydrogen fluoride gas remaining inside the first pipe 11 will be supplied to the processing chamber 2. In addition, it takes time to remove the fluorine remaining on the surface of the substrate W.

The first embodiment will be described with respect to the case where the silicon oxide film is a thermal oxide film. The substrate temperature was maintained at 50 ° C., the first steam was supplied to the processing chamber at a supply flow rate of 1000 cc / min for 5 seconds, and then hydrogen fluoride gas was supplied at a supply flow rate of 100 cc / min. The thermal oxide film was etched for 60 seconds by mixing with the steam of 1 and supplying the mixture to the treatment chamber. Immediately after etching, the surface of the substrate was washed for 240 seconds by setting the supply flow rate to 1000 cc / min. The degree of vacuum in the treatment chamber was controlled to 32 Pa from the time when the first steam was supplied to the treatment chamber until the treatment was completed. In order to compare and evaluate the amount of fluorine remaining on the surface of the substrate W after etching, a substrate W was also prepared in which the treatment was stopped by the end of etching without supplying the second water vapor under the above conditions.

FIG. 3 shows the result of evaluating the residual amount of fluorine in the substrate W treated under the above conditions. The residual amount of fluorine was measured by using commercially available ion chromatography. The horizontal axis shows the processing conditions. The untreated product that was not washed with the second steam is No, and the conditions for washing are indicated by H2O. The vertical axis shows the amount of detected fluorine. In the untreated case, the amount of fluorine detected was 33 ng, but it was not detected when washed with the second steam. From this result, it can be seen that a surface on which fluorine does not remain can be obtained by washing with a second steam after etching the thermal oxide film.

Generally, when a silicon oxide film is etched in a gas phase containing hydrogen fluoride, fluorine remains on the surface after etching. As mentioned earlier, residual fluorine can cause defects in silicon, form particles, and affect electrical properties. However, such a problem can be avoided by washing with the second steam as in the above-mentioned fluorine residual amount evaluation result.

Further, in the present embodiment, water vapor (second pipe) for cleaning the substrate W after etching is passed through a pipe (second pipe 17) different from the pipe (first pipe 11) for supplying the etching mixed gas. Water vapor) is supplied into the processing chamber 2. That is, the second water vapor is supplied into the processing chamber 2 without passing through the first pipe 11 (mixed gas pipe). As a result, it is possible to prevent the etching gas remaining in the pipe from being supplied into the processing chamber 2 when cleaning the substrate. Therefore, the atmosphere containing hydrogen fluoride in the treatment chamber 2 can be quickly replaced with water vapor. If the etching gas and the steam for cleaning the substrate W after etching are supplied into the processing chamber 2 through a common pipe, the silicon oxide film is etched with a mixed gas containing hydrogen fluoride gas, and then switched to steam. However, since the hydrogen fluoride gas in the piping flows out, the replacement efficiency of the atmosphere containing hydrogen fluoride in the processing chamber 2 deteriorates, and it takes time to remove the fluorine remaining on the surface of the substrate W.

Next, the etching rate when the thermal oxide film is etched in the present embodiment will be described. FIG. 4 shows the etching results when the pressure in the processing chamber 2 was changed and the hydrogen fluoride gas concentration was used as a parameter when the substrate temperature of the thermal oxide film was 170 ° C. and the supply flow rate of the first steam was 1500 cc / min. Is shown. The horizontal axis represents the pressure in the processing chamber 2, and the vertical axis represents the etching rate of the thermal oxide film. The etching rate was determined by measuring the film thickness before and after etching using an optical ellipsometer and determining the difference.

The higher the hydrogen fluoride gas concentration, the higher the etching rate of the thermal oxide film. Further, the etching rate also depends on the pressure in the processing chamber, and is larger when the pressure is high than when the pressure is low, and shows a maximum value at about 40 Pa. It is considered that the reason why the etching rate decreases when the pressure is low is that the probability that hydrogen fluoride gas, which is an etching species, reaches the surface of the thermal oxide film is not sufficient. Further, it is considered that the reason why the pressure exceeds 40 Pa and the etching rate is lowered is that the etching product generated by etching is not sufficiently detached from the substrate surface due to the high pressure.

From the results of this experiment, when the pressure inside the processing chamber 2 was 40 Pa, the hydrogen fluoride gas concentration was 52 vol. In%, an etching rate of about 90 nm / min can be obtained, and 40 vol. % Is about 80 nm / min, 25 vol. % Is about 60 nm / min, 10 vol. In%, an etching rate of about 10 nm / min was obtained. As described above, it can be seen that the etching rate can be controlled by changing the hydrogen fluoride gas concentration with respect to the thermal oxide film.

Next, the hydrogen fluoride gas concentration was adjusted to 15 vol. The etching rate when the temperature of the substrate W is changed by fixing it to% will be described. The pressure in the processing chamber 2 was 13.3 Pa. The results of the etching rate evaluated in FIG. 5 are shown. The horizontal axis represents the temperature of the substrate W, and the vertical axis represents the etching rate of the thermal oxide film. The results are shown when the temperature of the substrate W is 30 ° C, 80 ° C, 130 ° C, and 150 ° C. As the temperature of the substrate W increases, so does the etching rate. Etching with fluorine ions is the reaction rate-determining on the surface of the substrate W, and the higher the temperature, the higher the reaction rate. It can be seen that under this condition, the etching rate of the thermal oxide film can be controlled to about 3 to 20 nm by changing the temperature of the substrate W.

As a result of evaluating the etching rate of the thermal oxide film, it was found that the etching rate changes widely depending on the conditions of hydrogen fluoride gas supply flow rate, water vapor supply flow rate, processing chamber pressure, and substrate temperature. This indicates that it is possible to ideally etch various silicon oxide films having different film qualities formed in the manufacturing process of a semiconductor device by setting appropriate etching conditions. From the above experimental results, it can be seen that the etching rate of the thermal oxide film can be controlled to about 3 nm to 90 nm. For example, when etching a natural oxide film having a film thickness on the order of nm formed between processes of a semiconductor device, etching is performed under a low etching rate condition so that the etching is uniform and there is no damage to the substrate after etching. It becomes possible to do. Further, a dense silicon oxide film that is difficult to be etched, such as a thermal oxide film, can be etched uniformly and with high throughput by etching under a high etching rate condition. Further, since etching is performed in the vapor phase state, it is possible to etch the inside of a fine contact hole.

Next, a modified example of the first embodiment will be described with reference to FIG. FIG. 6 is a side view showing a schematic configuration in which the gas supply system of the etching apparatus 1 is modified. Except for the gas supply system, all have the same configuration as that of the first embodiment. In this modification, the first pipe 11 is a supply pipe for hydrogen fluoride gas alone. The hydrogen fluoride gas flow rate controller 13 is the same as that of the first embodiment, but an on-off valve 20 is interposed in the first pipe 11 in order to stop the supply of hydrogen fluoride gas.

In recent years, the miniaturization of semiconductor devices has progressed, and devices having a gate length of 10 nm or less have been developed. In the manufacture of such state-of-the-art semiconductor devices, it is desired to control the etching of the monatomic layer. In this modification, such monatomic layer etching is possible.

This modification will be described with reference to the processing flow chart of FIG. 7. The substrate W is transported into the processing chamber 2 by a transport system (not shown) and placed on the substrate holder 4 (step S71). After the substrate W is placed on the substrate holder 4, the substrate W is heated to a predetermined temperature in the range of 30 ° C. to 200 ° C. by the heating mechanism 5 built in the substrate holder 4.

After the substrate W is placed on the substrate holder 4, the vacuum pump 8 starts evacuation (step S72). Evacuation is performed until the pressure in the processing chamber 2 is about 0.1 Pa, and the air atmosphere in the processing chamber 2 is exhausted. It is desirable to reduce the pressure as much as possible as in the first embodiment.

After the pressure in the processing chamber 2 reaches about 0.1 Pa, water vapor is supplied into the processing chamber 2 through the second pipe 17 (step S73). The flow rate controller 15 adjusts the supply flow rate of water vapor to a predetermined flow rate, and the opening / closing valve 16 is opened to supply the water vapor into the processing chamber 2. The opening degree of the APC valve 9 is adjusted by monitoring the pressure in the processing chamber 2 with the pressure sensor 10 so that the pressure in the processing chamber 2 becomes a predetermined degree of vacuum.

The water vapor introduced into the processing chamber 2 passes through the plurality of openings of the gas dispersion plate 6 and is supplied to the entire surface of the substrate W. The water vapor that reaches the entire surface of the substrate W forms a thin layer of water on the substrate W. The supply flow rate and supply time of the water vapor to be supplied depend on the film quality and film thickness of the silicon oxide film to be etched, but the supply flow rate is 300 cc / min to 10000 cc / min and the supply time is 1 to 10 seconds. .. By this step, a water film having a constant thickness is formed on the surface of the substrate W, and it becomes a solvent in which hydrogen fluoride gas, which will be described later, is dissolved.

The supply of steam is stopped by closing the on-off valve 16. After that, the flow controller 13 adjusts the hydrogen fluoride gas to a predetermined supply flow rate, and the opening / closing valve 20 is opened to supply the hydrogen fluoride gas into the processing chamber 2 through the first pipe 11. The hydrogen fluoride gas introduced into the processing chamber 2 passes through the plurality of openings of the gas dispersion plate 6 and is supplied to the entire surface of the substrate W. The hydrogen fluoride gas that reaches the entire surface of the substrate W dissolves in the water film formed in advance, dissociates to generate fluorine ions, and etches the silicon oxide film. After the supply for a predetermined time, the supply of hydrogen fluoride gas is stopped by closing the on-off valve 20. The film thickness of the silicon oxide film to be etched is determined by the concentration of the hydrogen fluoride gas supplied and the supply time. That is, the etching in this modification is an etching method in which a hydrogen fluoride gas having a predetermined concentration is dissolved in a water film formed in advance to etch a silicon oxide film. By using this method, it is possible to etch the monoatomic layer by controlling the amount of water film formed and selecting the hydrogen fluoride gas concentration.

After the etching step for a predetermined time, the opening / closing valve 16 is opened to supply water vapor into the processing chamber 2 (step S75). The water vapor passes through the plurality of openings of the gas dispersion plate 6 and is supplied to the entire surface of the substrate W. Fluorine remaining on the surface of the substrate W is removed by supplying water vapor to the substrate W after etching the silicon oxide film and cleaning the substrate W as in the first embodiment.

W wafer 1 Etching device 2 Processing room 3 Control unit 4 Substrate holder 5 Heating mechanism 6 Gas dispersion plate 7 Exhaust piping 8 Vacuum pump 9 APC valve 10 Pressure sensor 11 1st piping 12 1st water vapor flow controller 13 Hydrogen fluoride gas flow controller 14 Multiple valve 15 Second steam flow controller 16 Open / close valve 17 Second piping

Claims (9)

In an etching method for etching a substrate on which a silicon oxide film is formed,
A decompression step of decompressing the processing chamber accommodating the substrate and
After the decompression step, an etching step of supplying an etching gas containing hydrogen fluoride into the processing chamber to etch the silicon oxide film formed on the substrate, and an etching step.
After the etching step, a cleaning step of supplying water vapor to the processing chamber to clean the substrate, and
A method for etching a substrate, which comprises a water film forming step of supplying water vapor to the processing chamber to form a water film on the surface of the substrate after the depressurizing step and before the etching step . In the etching method according to claim 1 ,
A method for etching a substrate, wherein the etching gas is an etching mixed gas of hydrogen fluoride gas and water vapor. In the etching method according to claim 2 , the etching gas has a ratio of the hydrogen fluoride gas to the water vapor of 10 to 60 vol. A method of etching a substrate, which is characterized by being%. The etching method according to any one of claims 1 to 3 , wherein the substrate temperature in the etching step is 30 to 200 ° C. The etching method according to any one of claims 1 to 4 , wherein the degree of vacuum in the processing chamber in the etching step is 1 Pa to 100 Pa. An etching device that etches a substrate on which a silicon oxide film is formed.
A processing room with an internal processing space and
A substrate holding means for holding the substrate in the processing space and
A decompression means that is connected to the bottom of the processing chamber to reduce the pressure in the processing chamber.
A steam supply means connected to the upper part of the treatment chamber and supplying a second steam to the treatment space,
An etching gas supply means connected to the upper part of the processing chamber to supply an etching gas containing hydrogen fluoride to the processing space.
A control means for controlling the decompression means, the steam supply means, and the etching gas supply means is provided.
After depressurizing the processing space by the depressurizing means, the control means supplies the etching gas to the processing space by the etching gas supply means to etch the substrate, and then the steam supply means performs the processing space. by supplying a second steam have line cleaning process of cleaning the substrate,
The etching gas supply means includes a mixed gas pipe that mixes the first steam and hydrogen fluoride gas to generate the etching gas.
A multi-valve for selectively supplying the first steam unit and the etching gas to the processing space through the mixed gas pipe is provided.
By controlling the multiple valve, the control means supplies the first steam alone from the mixed gas pipe to the processing space after depressurizing the processing space by the depressurizing means to the surface of the substrate. A water film is formed to form a water film, and after the water film is formed, the etching gas is supplied from the mixed gas pipe to the processing space by controlling the multiple valve to etch the substrate. Etching device characterized by. The etching apparatus according to claim 6 .
The etching apparatus, wherein the steam supply means supplies the second steam to the processing space without passing through the mixed gas pipe. An etching device that etches a substrate on which a silicon oxide film is formed.
A processing room with an internal processing space and
A substrate holding means for holding the substrate in the processing space and
A decompression means that is connected to the bottom of the processing chamber to reduce the pressure in the processing chamber.
A steam supply means connected to the upper part of the treatment chamber and supplying a second steam to the treatment space,
An etching gas supply means connected to the upper part of the processing chamber to supply an etching gas containing hydrogen fluoride to the processing space.
A control means for controlling the decompression means, the steam supply means, and the etching gas supply means is provided.
After depressurizing the processing space by the depressurizing means, the control means supplies the etching gas to the processing space by the etching gas supply means to etch the substrate, and then the steam supply means performs the processing space. A second steam is supplied to the substrate to perform a cleaning process for cleaning the substrate.
The control means controls the steam supply means after decompressing the processing space by the depressurizing means and before supplying the etching gas to the processing space by the etching gas supply means to provide a second processing space. An etching apparatus characterized in that a water film is formed by supplying water vapor to form a water film on the surface of the substrate. In the etching apparatus according to any one of claims 6 to 8 .
An etching apparatus characterized by having a gas dispersion plate having a plurality of pores in the upper part of a substrate holding means in a processing chamber.

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