JP5126938B2 - Removal method of organic coating - Google Patents

Description

  The present invention relates to a method for removing an organic film and a substrate, and in particular, a method for efficiently and selectively removing an organic film on an inorganic substrate without damaging the inorganic substrate itself under specific conditions, and the method. It is related with the board manufactured.

Conventionally, for example, a method of selectively removing an organic film (for example, a photoresist film) on an inorganic substrate (for example, SiO ₂ substrate) in supercritical water using a continuous reactor is known (for example, Patent Document 1 and Patent Document 2). In these conventional methods, usually, after raising the pressure to 22 MPa or more, the temperature is raised to 374 ° C. or more to generate supercritical water conditions, and the organic coating on the inorganic substrate is selectively removed under those conditions. ing. That is, as shown in the temperature rise-pressure line (2) in the water temperature-pressure diagram shown in FIG. 1, in a continuous supercritical water facility, the temperature rise is usually confirmed after confirming the airtightness of the process by pressure increase. Often done. C. In FIG. p. Indicates a critical point that becomes supercritical water. In the conventional method, both c. p. The condition of the supercritical water region exceeding the above is generated, and the organic film such as the photoresist film on the inorganic substrate made of the SiO ₂ substrate or the like is selectively removed under the condition.

Such a conventional method has the following problems.
For example, as shown in FIG. 2 showing the solubility characteristics of SiO ₂ in water, water having a constant pressure of about 20 MPa or more has a higher SiO ₂ dissolving power with increasing temperature, and has a peak near the critical point. , It has a characteristic that the dissolving power decreases rapidly. As a result of this characteristic, SiO ₂ is etched in the temperature rising process before the substrate reaches the supercritical water state. Furthermore, water up to the critical point is in a liquid phase and has a high hydrolysis power, and the organic coating is likely to be decomposed. Below the critical point, oxygen and water as oxidants are in a heterogeneous phase and are not suitable for uniform oxidation. As a result, during hydrolysis of the organic coating, SiO ₂ under the organic coating becomes a reducing atmosphere, and selective etching may occur due to deoxidation. Further, when cooling is performed while maintaining the pressure at the end of the operation, a liquid phase appears on the substrate, and SiO ₂ may be etched in the same manner as the temperature rises. Such a defect is caused by the condition of the aqueous phase in which SiO ₂ is easily etched in the process of reaching the supercritical water condition for selectively removing the organic film or in the cooling process after the selective removal. This is due to exposure.
Japanese Patent Laid-Open No. 11-274132 JP 2001-110711 A

  Accordingly, an object of the present invention is based on the above-described knowledge, and a method capable of efficiently and selectively removing an organic film on an inorganic substrate while avoiding undesirable etching of the inorganic substrate, and a method manufactured using the method. It is to provide a printed circuit board.

In order to solve the above-mentioned problem, the organic film removal method according to the present invention is a method in which the temperature in the reactor is set to 200 ° C. or more and 374 ° C. or less to raise the temperature of the water in the reactor to the boiling point or higher and then saturate. The method is characterized in that the pressure is increased so as not to reach the water phase side of the vapor, and the organic film on the inorganic substrate is selectively removed in the generated water vapor having a pressure of 10 MPa or more and less than 22 MPa. .

That is, in the process of generating steam conditions as the target conditions for selectively removing the organic film, first with water heated above the boiling point, and by boosting thereafter, water is saturated steam or superheated steam conditions Therefore, entering the water phase side from saturated steam is avoided. Therefore, the substrate is not exposed to the aqueous phase, and no problematic etching of the substrate occurs. In addition, here, “the temperature of the water is raised to the boiling point or higher” and “the pressure is increased so as not to reach the water phase side than the saturated steam” are defined as the process along the saturated vapor line in the process of reaching the predetermined condition. Means that it may be present. From the viewpoint of safety that it does not pass through the water phase region more reliably, it is preferable that all of them pass through the superheated steam region and reach a predetermined condition. That is, as shown by the characteristic line (3) in FIG. 1, it is preferable to increase the pressure after the temperature rise so as to reach a condition region where only an organic film such as a photoresist film can be selectively removed. In this method, the condition region where only the organic film can be selectively removed includes a water vapor region including a saturated vapor line and a supercritical water region as shown in FIG. 1, and preferably the superheated water vapor region is the target condition region. It is said.

  That is, in the conventional organic film removal method, as described above, the supercritical water condition of 22 MPa or more and 374 ° C. or more was selected as the selective removal condition of the organic film. Even if not, it has been found that selective removal of the organic coating proceeds at a predetermined temperature or higher, and the method of the present invention has been completed. Then, by generating superheated water vapor and selectively removing the organic coating on the inorganic substrate in the superheated water vapor, it is possible to avoid exposure of the substrate to the aqueous phase. Can be prevented. In other words, as a selective removal condition of the organic film on the inorganic substrate, the superheated water condition can be set without setting the supercritical water condition. It is proposed that the organic film can be selectively removed. In this method, it is only necessary to realize the processing conditions for the selective removal of the organic film. For example, as shown by the characteristic line (1) in FIG. Can be achieved. In particular, in the case of a batch reactor or the like, the temperature increase / pressure increase process as shown in the characteristic line (1) is realistic.

In the organic film removal method according to the present invention as described above, the pressure of the generated water vapor is 10 MPa or more and less than 22 MPa as a treatment condition for selective removal of the organic film. In other words, this is the pressure condition before reaching the supercritical water, and by setting such conditions, the pressure specification of the processing apparatus can be kept low, and the apparatus and processing can be made cheaper accordingly.

  Further, the temperature of the generated water vapor can be 374 ° C. or lower. As described above, the selective removal of the organic coating proceeds even in a region where the pressure and temperature are below the supercritical water condition, so that the treatment at 374 ° C. or less is possible. By setting such conditions, the temperature specification of the processing apparatus can be kept low, and it is possible to reduce the cost of both the apparatus and the processing.

  In particular, if the temperature in the reactor is maintained at 200 ° C. or higher and 374 ° C. or lower and the pressure is equal to or lower than the saturated vapor pressure of water, including the startup, steady state, and shutdown, a superheated steam region that is relatively easily generated ( A saturated water vapor region may be included), and the organic film can be selectively removed while avoiding the problem of substrate etching.

  In the present invention, since the basic technical idea is not to expose the substrate to the aqueous phase when selectively removing the organic coating, the substrate is not exposed to the aqueous phase even when the temperature is lowered after the selective removal of the organic coating. Thus, it is preferable to prevent the substrate from being etched. For this purpose, it is preferable to lower the temperature after reducing the pressure to atmospheric pressure after the selective removal of the organic coating.

  In the present invention, either a continuous water flow system or a batch reactor (for example, an autoclave reactor) can be used. When a batch reactor is used, the entire reactor can be in a superheated steam state, a saturated steam part and an aqueous phase part are generated in the reactor, and an inorganic substrate is positioned in the saturated steam part. The organic film on the inorganic substrate can also be selectively removed.

  Examples of the inorganic substrate include a substrate made of silicon, glass, or ceramic, and examples of the organic coating include a photoresist film. In particular, efficient and selective removal of the photoresist film on the silicon substrate is actually required.

  Usually, stainless steel is often used as the material for the inner surface of the reactor. However, in the case of stainless steel, there is a risk that chromium may be eluted. It is preferably made of Ru, Rh, Pd, Os, Ir, Pt, or an alloy, oxide, or quartz thereof.

  Further, in the present invention, it is preferable to selectively remove the organic film on the inorganic substrate by adding an oxidant, which enables more efficient selective removal of the organic film. The oxidizing agent is preferably added to the reactor after conditions are satisfied, but it can also be added from the beginning.

  As the oxidizing agent to be added, for example, at least one selected from the group consisting of air, oxygen, hydrogen peroxide, and nitric acid can be used.

The oxygen partial pressure in the reactor is preferably 0.01 MPa or more and 2 MPa or less. That is, it is preferable to keep the water vapor pressure for selective removal of the organic film at an oxygen partial pressure that does not significantly affect the pressure.

In the present invention, it is preferable to confirm the progress of the treatment based on the CO or CO _{2 in} the exhaust from the reactor or the TOC concentration in the waste water. As a result, it is possible to confirm whether or not the predetermined processing has been completed. After completion of the predetermined process, the temperature may be lowered and cooled by the method described above.

  According to the organic film removal method of the present invention, it is possible to selectively and efficiently remove only the organic film without damaging the inorganic substrate itself so as not to be exposed to the aqueous phase. . In addition, the treatment can be performed even in a supercritical water state. As a result, there is no damage to the inorganic substrate itself, and it is possible to obtain a desired substrate in which only the organic coating is selectively removed as intended.

Hereinafter, the present invention will be described in detail together with preferred embodiments with reference to the drawings.
In the present invention, as described above, basically, the inorganic substrate itself is not exposed to the aqueous phase, and the condition region where only the resist shown in FIG. 1 can be selectively removed is reached. In FIG. 1, a more optimal and relatively narrow target processing area is shown. However, the processing possible area in the present invention is, for example, as shown in FIG. it is possible to the side of the processing area, this area also includes the saturated vapor line (where desirably superheated steam region). And a region shown in area and 1 shown in FIG. 3, in the present invention, it is possible selective removal of the organic coating in supercritical water area by the remote low pressure (less than 22 MPa) area is understood The

In order to confirm that this low pressure region is a region where only the organic film can be selectively removed without damaging the substrate, the removal performance of the organic film (photoresist film) on the silicon (SiO ₂ ) substrate. A confirmation test was performed under each condition shown in Table 1. As a result, even if the pressure is less than 22 MPa, it is possible to selectively remove only the organic coating without damaging the silicon substrate if the temperature is raised to a predetermined temperature, particularly under conditions of 10 MPa or more and less than 22 MPa. It was confirmed.

Example 1
As shown in FIG. 4, a continuous reactor was used and a method of increasing the pressure after raising the temperature was performed. In order to prevent the etching of SiO ₂ of the silicon substrate 41 during the temperature rising process, nitrogen 4 supplied through the compressor 12 in the apparatus (if the cylinder is sufficiently high in pressure, it does not need to go through the compressor 12. (Preferably) or purged with air 3, heated to 200 ° C. or higher by the preheater 13 and the heater 15, and then fed into the reactor 14. In order to prevent the pressure in the reactor 14 from increasing and reaching the saturated vapor pressure by the supply, the opening of the pressure control valve 17 is set to 100% so that the pressure in the reactor 14 is 0.5 MPa or less. When the temperature exceeds 374 ° C. due to the supply of heated water and the heater 15, the set value of the pressure control valve 17 is increased to 20 MPa at a rate of 1 MPa / min while continuing the supply of heated water and the operation of the heater 15. The pressure control valve 17 is PID controlled so that the pressure in the reactor becomes 20 MPa (control system C01, PI controller). With this starting method, the substrate does not come into contact with the liquid phase through the line (3) in FIG. 1, and the target temperature and pressure can be reached while preventing excessive etching of SiO ₂ . After the target condition is achieved, the organic coating is selectively removed by supplying hydrogen peroxide 2 or air 3. The end of the removal process is performed under predetermined conditions (reaction time 30 minutes or CO in the exhaust gas 31 separated by the gas-liquid separator 18 by the sensor S3: 1000 ppm or less, or CO2: 1% or less, or the sensor S4 in the waste water 32. TOC: 100 ppm or less), and after reaching the predetermined condition, the pressure is reduced and then cooled. At this time, the superheated steam condition is maintained by temperature and pressure. While continuing the supply of heated water and the operation of the heater 15 of the reactor, the set value of the pressure control valve 17 is reduced to atmospheric pressure at a rate of 1 MPa / min. Thereafter, the supply of water, the preheater 14 and the heater 15 of the reactor are stopped, and the inside of the reactor 14 is purged with nitrogen 4 or air 3 while the inside of the reactor 14 is at 100 ° C. or higher. To dry. The reactor is opened when the reactor is cooled, and the substrate 41 from which the organic coating has been removed is taken out. In the substrate obtained by such a method, the substrate itself was not damaged, and only the organic film was efficiently and selectively removed.

In order to monitor the etching of SiO ₂ , it is also effective to take the following measures as shown in FIGS.
(1) A pot 19 is provided in the middle of the pipe between the water preheater and the reactor (preferably a pipe route having a height lower than that of the preheater 13 and the reactor 14 and having no liquid pool in the middle). A sensor S1 (conductivity meter, liquid level meter, hygrometer) that detects the state of water in the pot 19 is provided to detect the liquid level or to generate an alarm or liquid when the relative humidity reaches a predetermined value or higher. Increase the output of the preheater 13 (control system C11), reduce the reactor pressure (control system C12), or supply air or nitrogen until the surface is no longer detected or the relative humidity falls below the specified value Is provided (control system C13) or water supply amount is reduced (control system C14).
(2) A sensor S2 (conductivity meter, liquid level meter, hygrometer) that detects whether or not there is a liquid phase under the substrate 41 installed in the reactor 14 is provided to detect the liquid level or the relative humidity is When the value exceeds the specified value, the preheater output is increased (control system C21) until the alarm is generated, the liquid level is not detected, or the relative humidity is lower than the specified value. Means to increase (control system C25), reduce reactor pressure (control system C22), increase air or nitrogen supply (control system C23), or reduce water supply (control system C24) Is provided.
(3) The temperature / pressure data of the saturated vapor pressure curve is incorporated in the control system in advance, and the control system C11, C12, C21, C22, C25 means that the pressure is below the predetermined value of the saturated vapor pressure of the temperature. Is used.

Example 2
As shown in FIG. 6, the autoclave type continuous reactor was used to carry out a method of increasing the temperature and pressure. In the batch reactor 51, the temperature of the water in the sealed container is raised by the heater 15, and the internal pressure increases as the temperature rises (line (1) in FIG. 1). If there is a sufficient amount of water to generate a liquid phase (water phase) below the critical point, the pressure becomes the saturated vapor pressure, and the pressure is determined by the amount of charged water above the critical point. In the initial stage of temperature increase, the temperature and pressure are increased according to the saturated vapor pressure, so that the gas phase and the liquid phase coexist in the reactor. When the substrate is set on the liquid phase side, SiO ₂ is etched by dissolution as in the conventional method. By installing on the gas phase side, etching under conditions below the critical point can be avoided, and the target temperature and pressure can be reached. After securing the treatment time, the container can be opened after cooling, but in order to suppress condensation on the substrate, the humidity is detected with a hygrometer S at 374 ° C or lower, and the pressure is reduced when the relative humidity is 90% or lower. (Control system C31) and it is preferable to remove the water in the container. The installation position of the hygrometer is above the water surface to be initially filled. In addition, the temperature / pressure data of the saturated vapor pressure curve can be incorporated in the control system in advance, and can be replaced with a means for reducing the pressure so that the pressure becomes 90% or less of the saturated vapor pressure of the temperature (control system C32).

  In addition, as shown in FIG. 7, in order to suppress the dew condensation on a board | substrate with a continuous type apparatus and a batch type apparatus, the board | substrate 41 is directly heated with the heater 61, and the temperature and pressure conditions of the board | substrate surface are less than saturated vapor pressure The heater output can also be controlled (control system C41), or the relative humidity is less than 100% (control system C42).

  The organic film removal method according to the present invention is applicable to any application that requires selective removal of an organic film on an inorganic substrate, and is particularly suitable for selective removal of a photoresist film on a silicon substrate. It is a thing.

It is a temperature-pressure characteristic figure which shows the example of the temperature rising / pressure | voltage rise process in this invention. It is a temperature-solubility characteristic view showing the dissolution characteristic of SiO _{2 in} a silicon substrate. It is a temperature-pressure diagram which shows the area | region in which the removal process of the organic film in this invention is possible. FIG. 2 is an equipment system diagram of the apparatus used in Example 1. FIG. 3 is an equipment system diagram of another apparatus that can be used in the first embodiment. It is explanatory drawing which shows the reactor used in Example 1, and its each state. It is a schematic sectional drawing of the reactor which shows the improvement form in Example 1,2.

Explanation of symbols

1 Water 2 Hydrogen peroxide 3 Air 4 Nitrogen 11 Pump 12 Compressor 13 Preheater 14 Reactor 15 Heater 16 Cooler 17 Pressure regulating valve 18 Gas-liquid separator 19 Pot 31 Exhaust 32 Drainage 41 Substrate 51 Batch reactor 61 heater

Claims (6)

  By raising the temperature in the reactor to 200 ° C. or more and 374 ° C. or less to raise the water in the reactor to the boiling point or more, the pressure was increased so as not to reach the water phase side than saturated steam, and 10 MPa was produced. A method for removing an organic film, wherein the organic film on the inorganic substrate is selectively removed in water vapor having a pressure of less than 22 MPa.   The method for removing an organic film according to claim 1, wherein a batch reactor is used and the entire reactor is brought into a superheated steam state.   A batch type reactor is used, a saturated water vapor part and an aqueous phase part are generated in the reactor, an inorganic substrate is positioned in the saturated water vapor part, and an organic film on the inorganic substrate is selectively removed. The method for removing an organic film according to claim 1.   The method for removing an organic film according to claim 1, wherein the inorganic substrate is made of silicon, glass, or ceramic.   The method for removing an organic film according to claim 1, wherein the organic film is a photoresist film.   The method for removing an organic film according to any one of claims 1 to 5, wherein an oxygen partial pressure in the reactor is 0.01 MPa or more and 2 MPa or less.

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