JP2007305933A - Cleaning method, and processing apparatus of substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method of substrate in which resist having a hardened layer on the surface can be exfoliated using super-critical carbon dioxide as a medium. <P>SOLUTION: In the process for exfoliating resist on a semiconductor substrate, a hardened layer 70A on the resist surface is cracked by jetting carbon dioxide aerosol 71 to the resist 70 on the substrate 51, and then super-critical carbon dioxide 40 and additive are supplied into the same chamber 46 so that the resist 70 on the substrate is exfoliated thus cleaning the substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for cleaning a substrate using a supercritical carbon dioxide fluid. The present invention also relates to a processing apparatus for cleaning a substrate using a supercritical carbon dioxide fluid.

  Conventionally, wet cleaning has been performed for cleaning, etching, and resist removal in a semiconductor wafer process.

  Recently, in order to fabricate a hollow structure with a high aspect ratio such as MEMS (Micro Electro Mechanical System), a film having a hollow structure due to surface tension of a liquid such as a cleaning liquid or a drying liquid in a drying process after wet etching a sacrificial layer It has become clear that sticking occurs. For this reason, a supercritical carbon dioxide fluid is used for drying the hollow structure.

  However, since supercritical carbon dioxide has a low affinity with water, after wet etching, the etching solution must be replaced with a lower alcohol and then treated with a supercritical carbon dioxide fluid. For this reason, when processing is performed using a supercritical carbon dioxide fluid, a problem of complicated processes occurs.

  In order to solve such problems, a method has been proposed in which a small amount of chemical solution is added to supercritical carbon dioxide for treatment. According to this method, it becomes possible to perform wet etching and drying of the sacrificial layer by using a supercritical carbon dioxide fluid to which a chemical solution is added (see, for example, Patent Document 1).

On the other hand, recently, in a state-of-the-art CMOS LSI, a low dielectric constant film has been used in the wiring process. When such a low dielectric constant film is washed with a liquid, there arises a problem that the characteristics of the film deteriorate.
In order to prevent the deterioration of the low dielectric constant film, a cleaning method in which a small amount of chemical solution is added to supercritical carbon dioxide has been proposed (for example, see Patent Document 2).

A supercritical fluid has a characteristic that the fluid easily penetrates because the surface tension is zero in principle. Furthermore, it has the feature that the diffusion coefficient is large like gas, and the ability to transport substances is higher than gas because of its high density like liquid.
Further, in the supercritical state, the reactivity of the chemical solution is increased only by adding a trace amount of the chemical solution, which is advantageous for removing contamination. In addition, the supercritical fluid can remove contamination by the physical force of the fluid generated by volume expansion and contraction due to pressure change.

In the state-of-the-art CMOS LSI, along with higher integration and lower voltage of devices, ultra-shallow junctions are used for CMOS transistors. Along with this, it is required to minimize the substrate digging (recess) of the source / drain regions.
For example, in a CMOS transistor of 45 nm or more, the junction depth is 20 nm or less, and the ion implantation concentration peak (Rp) is 5 nm or less. For this reason, even if the substrate is dug about several nanometers, the impurity-implanted portion is consumed, causing variations in the threshold voltage (Vth) of the transistor and a decrease in drive current (Ids).
In particular, it is important to control the substrate excavation of the source / drain extension (S / D Extension).

  Here, the substrate excavation at the time of peeling the resist in the conventional CMOS transistor will be described.

FIG. 3A shows a state where a PMOS region and an NMOS region separated by an element isolation layer 82 made of a trench insulating film are formed on a silicon substrate 81. In the PMOS region and the NMOS region, a gate 85, a gate insulating film 84, and an offset spacer 86 are formed, respectively, and an SiO ₂ film 83 is formed as a protective film on the surface of the substrate 81.
Then, using the photoresist 91 formed on the PMOS region side as a mask, ion implantation is performed on the NMOS region side to form the source / drain extension portion 87.
Next, the photoresist 91 formed on the PMOS region side is removed by plasma oxygen ashing and sulfuric acid / hydrogen peroxide treatment.

As described above, when the source / drain extension portion 87 is formed in the CMOS transistor, the NMOS region and the PMOS region are formed using the photoresist 91 as a mask.
At this time, when transistors with different threshold voltages (Vth) are mixedly mounted, the step of implanting ions using the photoresist 91 as a mask and the step of stripping the photoresist 91 are repeated many times.

Conventionally, plasma oxygen ashing and sulfuric acid / hydrogen peroxide treatment have been performed to remove the photoresist.
However, in this conventional process, although not shown, the surface of the silicon substrate 81 is oxidized. In particular, in the NMOS region that is not covered with the photoresist 91, the surface of the silicon substrate 81 is oxidized by about several nm.
Then, the oxide film is etched by the SC1 (ammonia / hydrogen peroxide) cleaning step before applying the next photoresist, and the oxidized portion of the silicon substrate 81 is scraped off.

FIG. 3B shows a state after performing plasma oxygen ashing and sulfuric acid / hydrogen peroxide treatment to remove the photoresist 91 and further performing a cleaning process.
As shown in FIG. 3B, the source / drain extension 87 in the NMOS region has been dug by the removal of the oxidized portion of the silicon substrate 81. In the figure, reference numeral 92 denotes an oxidized portion of the silicon substrate 81, which is left without being removed in the cleaning process because the insulating film 86 covering the gate electrode 85 is on the top.

  As described above, in the CMOS transistor, the substrate is dug when the resist is peeled off, which causes variations in threshold voltage (Vth) and a decrease in driving current (Ids).

  Furthermore, sulfuric acid / hydrogen peroxide used when the photoresist 91 is peeled off is not desirable from the viewpoint of global environmental load, and it is desired to reduce the amount of use.

  By the way, if the photoresist can be peeled off without using an oxidizing agent, it is possible to completely eliminate the substrate digging. For example, if the resist can be stripped using only an organic solvent, the substrate surface does not oxidize, and the substrate is not dug.

However, the photoresist ion-implanted at a high concentration has a hardened layer formed on the surface due to carbonization and alteration of the surface. And this hardened layer cannot be peeled only with an organic solvent.
Therefore, it is difficult to remove the photoresist ion-implanted at a high concentration only with an organic solvent.
Further, in the above-described method of adding a small amount of chemical solution to supercritical carbon dioxide and processing, it is possible to peel off the uncured portion inside the resist. However, the hardened layer formed on the resist surface cannot be peeled off by supercritical carbon dioxide to which a chemical solution is added.
Therefore, in the above-described method, the resist cannot be removed because supercritical carbon dioxide cannot penetrate into the resist due to the hardened layer on the resist surface.
In particular, peeling of a highly doped ion-implanted resist of about 1 × 10 ¹⁶ / cm ² is difficult only by supercritical processing.

  In contrast, if a large amount of fluoride is added, the resist whose surface is cured can be peeled off. However, in this case, the substrate is etched by the action of the fluoride, thereby eliminating the substrate excavation. The goal cannot be achieved.

  Therefore, a resist peeling method in which a laser is irradiated before supercritical processing to form cracks in the hardened layer on the resist surface, and then the supercritical fluid, gas, or liquid is used to infiltrate the fluid into the inside. Has been proposed (see, for example, Patent Document 3).

JP 2005-183749 A JP 2003-224099 A JP 2004-157424 A

  However, the above-described laser irradiation method requires an expensive laser light source, an optical mirror, an optical window, a lens, and the like, and further, the laser irradiation and subsequent fluid processing must be performed in a separate chamber. For this reason, the equipment cost and the processing cost accompanying board | substrate conveyance became large, and there existed a problem that it was not practical.

  In order to solve the above-described problems, the present invention uses a supercritical carbon dioxide fluid as a medium, and a substrate cleaning method capable of stripping a resist having a hardened layer on its surface at a relatively low cost. A processing apparatus for cleaning a substrate is provided.

  According to the substrate cleaning method of the present invention, in the step of removing the resist on the semiconductor substrate, a carbon dioxide aerosol is sprayed onto the resist on the substrate, and then a supercritical carbon dioxide fluid and an additive are supplied to the substrate. The resist is peeled off.

  The processing apparatus of the present invention is a processing apparatus for cleaning a substrate using a supercritical fluid, and includes at least one processing chamber for processing a substrate, a carbon dioxide supply unit, and an additive supply unit. At least one of the above has a carbon dioxide aerosol injection means in the processing chamber.

  According to the above-described substrate cleaning method of the present invention, it is possible to generate cracks in the cured portion formed on the resist surface on the substrate by spraying carbon dioxide aerosol. Thereafter, by supplying the supercritical carbon dioxide fluid and the additive, the supercritical carbon dioxide and the additive can penetrate into the resist from the crack portion, and the resist can be selectively and efficiently peeled off. .

  According to the above-described processing apparatus of the present invention, the carbon dioxide aerosol is sprayed onto the surface of the substrate to be cleaned in the processing chamber by including the carbon dioxide aerosol spraying means in at least one processing chamber. be able to. Then, after jetting the carbon dioxide aerosol, the substrate can be cleaned by supplying the supercritical carbon dioxide fluid and the additive into the processing chamber from the carbon dioxide supply means and the additive supply means.

  According to the above-described present invention, the resist having a hardened layer formed on the surface by ion implantation can be peeled off at low equipment costs and processing costs, and the substrate can be cleaned.

  First, an outline of the present invention will be described prior to the description of specific embodiments of the present invention.

  In a CMOS transistor, when a source / drain extension (S / D Extension) is manufactured, a PMOS region and an NMOS region are separately formed using a photoresist as a mask. Further, when transistors with different threshold voltages (Vth) are mounted together, ion implantation using a photoresist as a mask and stripping of the photoresist are repeated many times.

At this time, since the photoresist to be peeled is ion-implanted at a high concentration, a cured resist layer carbonized by ion implantation is formed on the surface of the resist. This resist hardened layer is very difficult to peel compared to the inside of the uncured photoresist.
For example, when a supercritical carbon dioxide fluid is supplied to remove the photoresist, an uncured portion can be removed. However, it is difficult to remove the cured resist layer only by treatment with a supercritical carbon dioxide fluid.
Therefore, when a hardened layer is formed on the surface of the photoresist to be peeled off, the fluid does not reach the inside of the resist that is not hardened.

Therefore, the present invention aims to solve the above-mentioned problems by injecting carbon dioxide (CO ₂ ) aerosol to break the cured film formed on the resist surface, and to supercritical dioxide dioxide to the inside of the resist. By reaching the carbon, the resist on the substrate is peeled off.

  The resist peeling method of the present invention will be described with reference to FIG.

First, as shown in FIG. 1A, a substrate 51 on which a resist film 70 is formed is accommodated in a processing chamber (chamber) 46, and CO ₂ aerosol 71 is sprayed from the nozzle 49 toward the resist film 70. .
At this time, the inside of the chamber 46 is at atmospheric pressure.

To generate the CO ₂ aerosol 71 with a strong impact force, the nozzle pressure must be relatively larger than the chamber pressure. That is, since the nozzle pressure is 5 MPa to 6 MPa equivalent to a normal cylinder pressure, it is desirable that the chamber pressure is a pressure lower than that, for example, atmospheric pressure.
When the pressure in the chamber 46 is 7.3 MPa or more, which is the critical pressure of carbon dioxide, the aerosol 71 is not generated. Therefore, the supply of the CO ₂ aerosol 71 is performed in a state where the chamber is at atmospheric pressure.

That is, the CO ₂ aerosol 71 is injected by releasing CO ₂ pressurized to, for example, 5 MPa to 6 MPa to atmospheric pressure.
At this time, CO ₂ aerosol particles 71 of about −80 ° C. are generated by the Joule-Thomson effect and adiabatic expansion by rapidly releasing the pressurized CO ₂ to atmospheric pressure.

The generated CO ₂ aerosol 71 is sprayed from the nozzle 49 and collides with the resist hardened layer 70A on the surface of the resist film 70 formed on the substrate 51, so that the resist hardened layer 70A is cracked by the impact force of the collision. Let

  Next, as shown in FIG. 1B, after the crack is generated in the resist hardened layer 70A, the supercritical carbon dioxide fluid 40 is supplied into the chamber 46 from the direction indicated by the arrow, for example. The supercritical carbon dioxide fluid 40 is mixed with a predetermined amount of additive.

  The supplied supercritical carbon dioxide fluid 40 can enter the resist interior 70B from a crack generated in the resist hardened layer 70A. For this reason, since the resist interior 70B is dissolved by the action of the additive, the cured resist layer 70A and the resist interior 70B can be simultaneously peeled off by supercritical carbon dioxide, as shown in FIG. The resist film 70 can be peeled off.

The above-described injection of the CO ₂ aerosol 71 can peel off particulate residues and fine particles adhering to the substrate by the impact force. However, when the substrate 51 is in close contact with the surface like the resist film 70, the impact force by the CO ₂ aerosol 71 cannot exceed the adhesion force of the resist film 70. For this reason, it is difficult to remove the resist film 70 only by the injection of the CO ₂ aerosol 71.
For this reason, in order to peel off the resist film 70, after the CO ₂ aerosol 71 is sprayed, a process for peeling off the resist film 70 with the supercritical carbon dioxide fluid 40 or the like is necessary.

When wet cleaning is used after the low-temperature aerosol 71 as a process for removing the resist film 70, the low-temperature aerosol 71 needs to be jetted with a chamber dedicated to gases such as CO ₂ , N ₂ , and Ar. On the other hand, since the wet cleaning tank is wetted with liquid, it cannot be performed in the same chamber, and the equipment cost and the processing cost associated with the substrate transport increase.

  Further, when gas cleaning is used as a process for removing the resist film 70, gas cleaning and spraying of the low temperature aerosol 71 can be performed in the same chamber, but the ability to dissolve the film resist is poor. The resist removal is difficult.

Therefore, as in the present invention, after the low-temperature aerosol 71 is jetted, the resist film 70 is stripped using the supercritical carbon dioxide fluid 40, so that both processes can be performed in the same chamber. It can be realized at low cost. Furthermore, by using the supercritical carbon dioxide fluid 40 as a medium, it is possible to clean the substrate with excellent resist stripping ability.
Therefore, the cleaning method of the present invention is highly effective in terms of both resist removal performance and cost.

  Next, a processing apparatus according to an embodiment of the present invention is shown in FIG.

The processing apparatus of FIG. 2 includes a processing chamber (chamber) 46, a carbon dioxide supply means 42 for supplying carbon dioxide (CO ₂ ) to the chamber 46, an additive supply means 45 for supplying an additive to the chamber 46, and a chamber. A dissolution tank 48 for dissolving the supercritical carbon dioxide supplied to 46 and the additive is provided.

The chamber 46 includes a substrate mounting portion having a built-in heater 52 for mounting the semiconductor substrate 51 to be processed, and a carbon dioxide supply nozzle 49 as a CO ₂ aerosol injection means. Further, a temperature raising means 56 is provided upstream of the chamber 46, and a temperature raising means 57 is provided downstream.

The carbon dioxide supply means 42 is composed of a CO ₂ cylinder containing carbon dioxide (CO ₂ ) liquefied by pressurization. The cylinder pressure is, for example, about 5.5 MPa to 6 MPa.
The carbon dioxide supply means 42 is provided with an open / close valve 58.
A main pipe 61 is connected to the carbon dioxide supply means 42. The main pipe 61 connects the carbon dioxide supply means 42 and a cooling means 53 for cooling and liquefying the CO ₂ gas. A main pipe 60 for generating a low temperature CO ₂ aerosol is branched from the main pipe 61.

The main pipe 61 connects the cooling means 53 and the pressure raising means 43 and the temperature raising means 44 for bringing liquid carbon dioxide into a supercritical state. The pressure raising means 43 is constituted by a pressure raising pump, and the temperature raising means 44 is constituted by a line heater or the like.
Furthermore, branches from the main pipe 61, the main pipe 60 to generate the low-temperature CO ₂ aerosol, carbon dioxide release valve (pressure reducing valve) 50 is provided as means for generating CO ₂ aerosol. The main pipe 60 is connected to the carbon dioxide supply nozzle 49 in the chamber 46 via the pressure reducing valve 50.

A first switching valve 62 for switching the fluid flow is provided on the downstream side of the temperature raising means 44 in the main pipe 61. In the first switching valve 62, a bypass pipe 65 branches from the main pipe 61. The main pipe 61 connects the first switching valve 62 and the dissolution tank 48 to each other.
The bypass pipe 65 is connected from the first switching valve 62 to the second switching valve 64.

  The additive supply means 45 is provided with an open / close valve 59. A main pipe 69 is connected to the additive supply means 30. The main pipe 69 connects the additive supply means 45, the pressure raising means 54 and the temperature raising means 55 to each other and is connected to the dissolution tank 48.

The dissolution tank 48 has a confirmation window 48A for confirming whether carbon dioxide and the additive are mixed.
A pipe 61 that allows supercritical carbon dioxide to flow in and out and a pipe 69 that flows into the additive are connected to the dissolution tank 48.

A second switching valve 64 is provided on the downstream side of the dissolution tank 48. The second switching valve 64 is connected to a main pipe 61 from the dissolution tank 48 and a bypass pipe 65 from the first switching valve 62.
Further, in the second switching valve 64, a bypass pipe 66 is branched from the main pipe 61.

  A third switching valve 67 is provided on the downstream side of the temperature raising means 57. The third switching valve 67 is provided with a pressure adjustment valve 68 for controlling the pressure of the fluid flowing in the chamber 46.

  The bypass pipe 66 is connected from the second switching valve 64 to the third switching valve 67.

  A gas-liquid separation / recovery means for separating the additive from the supercritical carbon dioxide fluid discharged through the third switching valve 67 and recovering the separated additive is provided downstream of the third switching valve 67. 47 is provided.

Note that the number of chambers for processing a substrate is one in the processing apparatus of this embodiment, but the present invention is not limited to this, and a plurality of chambers may be used. When a plurality of chambers are provided, a chamber having a nozzle 49 for injecting CO ₂ aerosol and a chamber for supplying a supercritical carbon dioxide and an additive to process the substrate can be provided separately.

According to the processing apparatus of the above-described embodiment, the supercritical carbon dioxide fluid and the CO ₂ aerosol can be supplied from the same carbon dioxide supply means. For this reason, a processing apparatus can be comprised by one carbon dioxide supply means, and the expensive laser light source, optical mirror, optical window, lens, etc. which were required when performing laser irradiation become unnecessary.
Therefore, the configuration of the processing apparatus can be simplified, and a high effect can be obtained in terms of equipment cost.

  Next, a substrate processing method using the processing apparatus of the above-described embodiment will be described.

In the following description, the processing conditions of the semiconductor substrate 51 in the case where the semiconductor substrate 51 in which arsenic (As) ions are implanted at 1 × 10 ¹⁶ / cm ² after applying a resist as a sample are shown.

  First, after the above-described semiconductor substrate 51 to be processed is accommodated in the chamber 46, the lid is closed and the chamber 46 is sealed.

Next, the opening / closing valve 58 is opened, and carbon dioxide is supplied from the carbon dioxide supply means 42.
The supplied carbon dioxide is cooled by the cooler 53 and passes through the bypass pipe 60 in a pressurized state of 5.5 MPa to 6 MPa, which is the same pressure as the cylinder pressure, and is filled up to the pressure reducing valve 50.
By opening the pressure reducing valve 50 to atmospheric pressure, the carbon dioxide in a pressurized state becomes aerosol particles of about −80 ° C. due to the Joule-Thomson effect and adiabatic expansion. Then, aerosol particles are ejected from the nozzle 49 toward the substrate 51.

At this time, the entire surface of the substrate 51 can be processed by relatively moving the nozzle 49 and the substrate 51 in the xy direction at, for example, about 200 mm / s.
For example, when processing is performed at a scanning speed of 100 mm / s, processing of the entire surface of a 200 mm diameter wafer is completed in about 1 minute.

By making the distance between the nozzle 49 and the substrate 51 in the chamber 46 close to about 10 mm, it is possible to effectively generate a crack in the resist hardened layer.
However, as the distance between the nozzle 49 and the substrate 51 becomes shorter, the collision force of the aerosol particles increases and the pattern formed on the semiconductor substrate 51 may be destroyed. For this reason, the distance between the nozzle 49 and the substrate 51 may be longer than the above in consideration of the vulnerability of the pattern formed on the substrate 51.
Moreover, a high effect is acquired by performing the angle of the nozzle 49 and the board | substrate 51 at an angle of 45 degrees, for example.

The carbon dioxide supply nozzle 49 is configured so as to be relatively movable in the xy direction as described above, but is further configured to be relatively movable in the vertical direction with respect to the substrate 51. It may be configured.
By being configured to move in the vertical direction in this way, it is possible to adjust the collision force of the aerosol particles and to raise the nozzle 49 so as not to disturb the flow of supercritical carbon dioxide. Become.

  After the above-described aerosol injection process is completed, the pressure reducing valve 50 is completely closed.

Next, the carbon dioxide supplied from the carbon dioxide supply means 42 is cooled by the cooler 53 to be in a liquid state. Then, the carbon dioxide in the liquid state is pressurized to 7.3 MPa or more by the pressure raising means 43 and further heated to 31.1 ° C. or more by the temperature raising means 44 to be in a supercritical state.
At this time, carbon dioxide supplied for a while is separated from the gas and liquid by the first switching valve 62 and the second switching valve 64 through the first bypass pipe 65 and the second bypass pipe 66. -Discharge to collection means 47.

Thereafter, the first switching valve 62 is switched to the dissolution tank 48 side, and supercritical carbon dioxide is supplied to the dissolution tank 48 through the main pipe 61. Then, the supercritical carbon dioxide supplied to the dissolution tank 48 is discharged to the gas-liquid separation / recovery means 47 through the second bypass pipe 66.
Then, the pressure of the supercritical carbon dioxide fluid is controlled by the pressure control valve 68 so as to be a desired pressure, for example, 10 to 20 MPa.

  At this time, when the pressure in the dissolution tank 48 and the second bypass pipe 66 becomes equal to or higher than a certain pressure, the pressure regulating valve 68 is opened and supercritical carbon dioxide is discharged to the gas-liquid separation / recovery means 47. As described above, by appropriately discharging the fluid filled in the dissolution tank 48 through the second bypass pipe 66, the pressure and temperature in the dissolution tank 48 can be kept constant.

  Next, the opening / closing valve 59 is opened, and an additive such as an organic solvent such as an organic solvent is supplied from the additive supply means 45. The supplied additive is adjusted to a predetermined pressure and temperature by the pressure raising means 54 and the temperature raising means 55 and supplied to the dissolution tank 48. And in the dissolution tank 48, it adds in the ratio of about 1-5 vol% with respect to the supercritical carbon dioxide fluid already heated and pressurized.

As an additive, a co-solvent such as an organic solvent can be used. As the organic solvent, at least one selected from methanol, ethanol, isopropyl alcohol, propylene glycol, ethylene glycol, N-methylpyrrolidone, propylene carbonate, ethylene carbonate, and trifluoroacetic acid can be used.
Moreover, these organic solvents may be added singly in the supercritical carbon dioxide fluid, or may be added in combination.

As the additive concentration of the above-mentioned additive, it is preferable to add in a range of 1 vol% or more and 10 vol% or less in a supercritical carbon dioxide fluid at 60 ° C. and 25 MPa.
When the concentration of the additive is lower than the above range, the resist film provided on the semiconductor substrate 51 cannot be removed, and the processing capability is reduced. Further, when the temperature is higher than the above range, the resist film provided on the semiconductor substrate 51 is uniformly formed because the supercritical carbon dioxide cannot be dissolved in the supercritical carbon dioxide fluid and the supercritical carbon dioxide and the additive are phase-separated. It cannot be washed.

The supercritical carbon dioxide fluid and additive supplied to the dissolution tank 48 are not uniformly mixed for a while from the start of mixing. For this reason, the phase of the supercritical carbon dioxide and the phase of the chemical solution are separated inside the dissolution tank 48, and the interface between the two phases can be confirmed from the confirmation window 48A.
The second switching valve 64 remains switched to the second bypass piping 66 side until it is confirmed that the supercritical carbon dioxide and the additive are uniformly mixed.
Then, the fluid in the dissolution tank 48 is discharged to the gas-liquid separation / recovery means 47 through the second bypass pipe 66.

After confirming from the confirmation window 48A that the supercritical carbon dioxide fluid and additive are well dissolved and in a homogeneous phase, the second switching valve 64 is switched to dissolve the additive in the supercritical carbon dioxide. Fluid is supplied to the chamber 46.
At this time, similarly to the dissolution tank 48 described above, the pressure and temperature in the chamber 46 can be kept constant by opening and closing the pressure regulating valve 68.

  In order to remove the resist film provided on the semiconductor substrate 51, it is preferable to adjust the temperature in the chamber 46 to a range of 35 ° C. to 80 ° C. and a pressure of 10 MPa to 30 MPa.

Thus, by supplying the supercritical carbon dioxide fluid mixed with the additive to the chamber 46, the resist on the semiconductor substrate 51 can be treated with supercritical carbon dioxide.
The cleaning time of the substrate 51 with the supercritical carbon dioxide fluid in which the additive is dissolved is, for example, about 5 minutes.

  Thereafter, the open / close valve 59 is closed to stop the supply of the additive, and the first switching valve 62 is switched to the first bypass piping 65 side. Thereby, the supercritical carbon dioxide fluid in which the additive in the processing chamber 46 is dissolved can be replaced with the supercritical carbon dioxide fluid not containing the additive, and the surface of the substrate 51 can be rinsed quickly.

  Finally, the second switching valve 64 is switched to the second bypass piping 66 side, the first switching valve 62 is switched to the dissolution tank 48 side, and the additive component remaining in the dissolution tank 48 is removed from the gas-liquid It is discharged to the separation / collection means 47.

The fluid discharged to the gas-liquid separation / recovery means 47 returns to the atmospheric pressure, so that the carbon dioxide becomes a gas from the supercritical state. The gaseous carbon dioxide and the liquid additive can be separated, and the additive can be recovered as an exhaust liquid. At this time, the resist component removed and extracted by the supercritical fluid in the chamber 46 is dissolved or accompanied by the additive and accumulated in the gas-liquid separation / recovery means 47 together with the additive.
On the other hand, carbon dioxide discharged as a gas is discharged as a waste gas. The discharged carbon dioxide can be recondensed and recovered.
In addition, the collected chemical solution and carbon dioxide can be recycled to be usable and reused.

According to the substrate processing method described above, the resist can be selectively and efficiently removed by processing the substrate in supercritical carbon dioxide after the CO ₂ aerosol injection at normal pressure.
Further, in the above process, the substrate is not eroded or etched, so that the reliability of the transistor can be improved and the yield of the semiconductor device can be improved.

The present invention is characterized in that CO ₂ aerosol particles are jetted as pretreatment means for facilitating a fluid such as carbon dioxide or a chemical solution to reach the inside of the resist.
The pretreatment means may be performed in the same chamber as the chamber in which the supercritical carbon dioxide treatment is performed, or may be performed in a different chamber.
In particular, the effect of the pretreatment can be maximized by performing the pretreatment means in the same chamber as the chamber in which the supercritical carbon dioxide treatment is performed. Then, the resist can be stripped and the substrate can be cleaned at low cost both in equipment cost and processing cost.

  Furthermore, in the present invention, since a substance other than carbon dioxide and an organic solvent is not used for cleaning the substrate, it is possible to provide a method for manufacturing a semiconductor substrate with less environmental burden.

  In the above-described embodiment, the dissolution tank 48 for dissolving the additive in supercritical carbon dioxide is used. However, the dissolution tank 48 can be used instead of the dissolution tank 48. By mixing the additive into supercritical carbon dioxide by in-line injection, the dissolution tank 48 becomes unnecessary, and the configuration of the processing apparatus can be simplified.

  The present invention is not limited to the above-described configuration, and various other configurations can be employed without departing from the gist of the present invention.

It is a schematic diagram explaining the washing | cleaning method of the board | substrate of this invention. It is a block diagram showing one form of the processing apparatus which concerns on this invention. It is a schematic diagram which shows the peeling method of the resist in the conventional CMOS transistor.

Explanation of symbols

40 Supercritical carbon dioxide fluid, 42 Carbon dioxide supply means, 43, 54 Pressure increase means, 44, 52, 55, 56, 57 Temperature raising means, 45 Additive supply means, 46 Processing chamber (chamber), 47 Gas-liquid separation Collection means, 48 dissolution tank, 48A confirmation window, 49 carbon dioxide supply nozzle, 50 carbon dioxide release valve (pressure reducing valve), 51 semiconductor substrate, 53 cooling means, 58, 59 on-off valve, 60 bypass piping, 61, 65, 69 Main piping, 62 First switching valve, 64 Second switching valve, 66 Bypass piping, 67 Third switching valve, 68 Pressure regulating valve, 70 Resist film, 70A Resist hardened layer, 70B Resist inside, 71 Carbon dioxide aerosol , 81 substrate, 82 a shallow trench, 83 SiO ₂ film, 84 gate insulating film, 85 gate, 86 an offset space Sir, 87 source / drain extensions (S / D Extension), 91 photoresist 92 oxide film

Claims (8)

In the process of peeling the resist on the semiconductor substrate,
A method for cleaning a substrate, comprising: spraying carbon dioxide aerosol onto the resist on the substrate, then supplying a supercritical carbon dioxide fluid and an additive to peel the resist on the substrate.   The method for cleaning a substrate according to claim 1, wherein a crack is generated on the surface of the resist by spraying carbon dioxide aerosol.   The substrate cleaning method according to claim 1, wherein the injection of the carbon dioxide aerosol and the supply of the supercritical carbon dioxide fluid and the additive are performed in the same processing chamber.   The method for cleaning a substrate according to claim 1, wherein the additive is an organic solvent.   The organic solvent is at least one selected from methanol, ethanol, isopropyl alcohol, propylene glycol, ethylene glycol, N-methylpyrrolidone, propylene carbonate, ethylene carbonate, and trifluoroacetic acid. Substrate cleaning method. In a processing apparatus for cleaning a substrate using a supercritical fluid,
Having at least one processing chamber for processing the substrate, carbon dioxide supply means, and additive supply means;
At least one of the processing chambers has a carbon dioxide aerosol injection means in the processing chamber.   The processing apparatus according to claim 6, wherein a pipe communicating with the carbon dioxide aerosol injection unit is branched from a pipe communicating the carbon dioxide supply unit and the processing chamber.   The processing apparatus according to claim 7, wherein a pipe communicating with the carbon dioxide aerosol injection means has a carbon dioxide release valve as the carbon dioxide aerosol generation means.

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