Patent Publication Number: US-2011059405-A1

Title: Substrate processing method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-205669, filed on Sep. 7, 2009; the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the invention relate generally to a substrate processing method. 
     2. Background Art 
     Manufacturing methods of semiconductor devices include many processes to deposit multiple substances as films onto a semiconductor wafer and pattern the films into desired patterns. To pattern the films, generally, a photosensitive substance called a resist is deposited onto the film to be patterned to form a resist film; and exposure of prescribed regions of the resist film is performed. Then, a resist pattern is formed by developing to remove the exposed portions or the unexposed portions of the resist film; and the film to be patterned is patterned by etching using the resist pattern as a mask. 
     Although ultra-violet light such as KrF excimer lasers and ArF excimer lasers is used as an exposure light source for better throughput, problems occur in which the resist pattern collapses as the semiconductor device is downscaled. Although there have been proposals (for example, JP-A 2007-123399 (Kokai)) to make the resist film thinner by introducing a multilayered resist process to reduce the defects caused by the resist pattern collapse, defects caused by resist pattern collapse have yet to be completely eliminated. 
     SUMMARY 
     According to an aspect of the invention, there is provided a substrate processing method, including: forming a resist film above a substrate; exposing the resist film; developing the resist film using a developing fluid after the exposing of the resist film; cleaning the resist film using a rinsing fluid after the developing of the resist film; and drying the resist film in a processing chamber after the cleaning of the resist film, inside the processing chamber being an atmosphere including an ion, the atmosphere including the ion being caused by introducing a gas including the ion produced externally to the processing chamber into the processing chamber. 
     According to another aspect of the invention, there is provided a substrate processing method, including: forming a resist film above a substrate; exposing the resist film; developing the resist film using a developing fluid after the exposing of the resist film; cleaning the resist film using a rinsing fluid after the developing of the resist film; and drying the resist film by blowing a gas including an ion onto the cleaned resist film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating the configuration of a substrate processing apparatus according to an embodiment of the invention; 
         FIGS. 2A to 2D  are schematic cross-sectional views illustrating a method for manufacturing a semiconductor device according to the embodiment of the invention; 
         FIGS. 3A to 3D  are schematic views illustrating a substrate processing method according to the embodiment of the invention; 
         FIG. 4  is a schematic cross-sectional view illustrating a state of a resist film being charged; 
         FIG. 5  is a schematic view illustrating a substrate processing method according to another embodiment of the invention; and 
         FIG. 6  is a schematic view illustrating a substrate processing method according to yet another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention will now be described with reference to the drawings. 
       FIG. 1  is a schematic view illustrating the configuration of a substrate processing apparatus according to an embodiment of the invention. The apparatus includes a processing chamber  20  capable of containing a semiconductor wafer W. Developing and rinsing are performed on the semiconductor wafer W in the processing chamber  20 . 
     A spin chuck  25  is provided in the processing chamber  20 . The spin chuck  25  is a vacuum chuck. A face (a back face) of the semiconductor wafer W on the side opposite to the processing surface is vacuum-attached to the upper face of the spin chuck  25 . The semiconductor wafer W is suction-held substantially horizontally on the spin chuck  25 . The spin chuck  25  includes a rotary shaft  26  extending downward. The rotary shaft  26  is linked to a not-illustrated motor. The spin chuck  25  receives a driving force of the motor and is rotatable around the rotary shaft  26 . 
     A nozzle  22  is provided above the spin chuck  25 . The nozzle  22  is opposable to the processing surface of the semiconductor wafer W suction-held by the spin chuck  25 . The nozzle  22  is connected to a not-illustrated developing fluid and/or rinsing fluid supply mechanism provided externally to the processing chamber  20 . A cup  21  surrounds below and around the spin chuck  25 . A not-illustrated liquid drainage mechanism is connected to a bottom portion of the cup  21 . 
     An ionizer  31  and a temperature/humidity adjustment apparatus  32  are provided externally to the processing chamber  20 . 
     The ionizer  31  includes, for example, an electro-discharge mechanism and produces ions by exposing a gas to electro-discharge. The ions produced in the ionizer  31  are sent to the temperature/humidity adjustment apparatus  32  with the gas (e.g., air). 
     The temperature/humidity adjustment apparatus  32  includes a gas transfer chamber, a heating unit, a humidification unit, and the like. The gas including the ions produced in the ionizer  31  is introduced into the gas transfer chamber. The heating unit includes a heater. The temperature in the gas transfer chamber is adjustable by controlling the electrical power supplied to the heater thereof. The humidification unit includes, for example, a mechanism having a heater immersed in water. The moisture evaporation amount in the gas transfer chamber, i.e., the humidity in the gas transfer chamber, is adjustable by controlling the electrical power supplied to the heater thereof. The gas including the ions adjusted to the desired temperature and humidity in the temperature/humidity adjustment apparatus  32  is introduced into the processing chamber  20 . 
     The gas including the ions is introduced into the processing chamber  20  from the ionizer  31  via the temperature/humidity adjustment apparatus  32  by a not-illustrated blowing mechanism and then exhausted from the processing chamber  20  by a not-illustrated exhaust mechanism. Thereby, a gas atmosphere including the ions adjusted to the desired temperature and humidity can be maintained in the processing chamber  20 . 
     A method for manufacturing a semiconductor device according to this embodiment including developing and rinsing of the semiconductor wafer W will now be described. 
     As illustrated in  FIG. 2A , an antireflective film  12  is formed on the entire major surface of a substrate  11 . A resist film  13  is formed on the antireflective film  12 . These components are collectively referred to as the semiconductor wafer W. The substrate  11  is, for example, a silicon substrate. The substrate  11  includes a configuration in which films to be patterned such as an insulating film, a conductive film, a semiconductor film, etc., are formed on a silicon substrate. 
     Then, selective exposure is performed ( FIG. 2B ) in a not-illustrated exposure apparatus using a mask (reticle) to transfer the desired latent pattern image onto the resist film  13 . 
     After the exposure, the semiconductor wafer W is transferred into the processing chamber  20  illustrated in  FIG. 1  and suction-held by the spin chuck  25 . The semiconductor wafer W is suction-held by the spin chuck  25  in a state in which the resist film  13  faces upward. 
     Thereafter, the developing, rinsing, and spin drying processes illustrated in  FIGS. 3A to 3D  are performed. 
     First, as illustrated in  FIG. 3A , a developing fluid  3  is supplied from a developing fluid nozzle  22   a  onto the resist film in a state in which the spin chuck  25  holding the semiconductor wafer W is rotated, for example, at several ten to several thousand rpm. The semiconductor wafer W rotates with the spin chuck  25 ; and the developing fluid  3  supplied substantially in the center of the semiconductor wafer W spreads in the radial direction and spreads over the entire surface of the semiconductor wafer W. The developing fluid  3  includes, for example, TMAH (tetramethylammonium hydroxide). 
     By stopping the rotation of the spin chuck  25 , the developing fluid  3  exists in a state in which the developing fluid  3  swells up on the surface of the semiconductor wafer W due to surface tension as illustrated in  FIG. 3B . This state is maintained for the desired period of time. 
     The resist film  13  is selectively removed by the developing fluid  3  to pattern the resist film  13 . In the case where, for example, the resist film  13  is a positive type, the exposed portions are dissolved into the developing fluid  3  and the unexposed portions remain. The state after the developing is illustrated in  FIG. 2C . Alternatively, without stopping the rotation of the spin chuck  25 , the developing fluid  3  may be continuously supplied in the center of the rotating semiconductor wafer W to develop the resist film  13 . 
     Then, as illustrated in  FIG. 3C , a rinsing fluid  4  is supplied from a rinsing fluid nozzle  22   b  onto the semiconductor wafer W surface in a state in which the spin chuck  25  holding the semiconductor wafer W is rotated at, for example, several thousand rpm. The semiconductor wafer W rotates with the spin chuck  25 ; and the rinsing fluid  4  supplied substantially onto the center of the semiconductor wafer W spreads in the radial direction and spreads over the entire surface of the semiconductor wafer W. Purified water, for example, may be used as the rinsing fluid  4 . 
     After the cleaning, spin drying is performed to rotate the spin chuck  25  in a state in which the semiconductor wafer W is held as illustrated in  FIG. 3D . The spin drying causes the rinsing fluid  4  remaining on the semiconductor wafer W surface to move outward in the radial direction by centrifugal force to remove the rinsing fluid  4  from the semiconductor wafer W. 
     Collapse of the resist pattern had occurred easily during the spin drying. The inventor of the application focused on the charging of the resist film as one cause thereof. There is a tendency for the wafer surface or the resist film  13  to be positively charged as illustrated schematically in  FIG. 4  due to the series of wafer processing processes prior to the spin drying process; and it is considered that, in addition to the centrifugal force, effects of the repulsive force between the positive charges between adjacent resist films  13  during the spin drying cause the pattern collapse to occur easily. The semiconductor wafer W also may be easily charged during the spin drying by friction between the semiconductor wafer W and the gas (e.g., air) in the processing chamber  20 . 
     Therefore, in this embodiment, the atmosphere in the processing chamber  20  during the developing, the cleaning, and the spin drying is an ion atmosphere. Specifically, negative ions having a polarity opposite to the charge (the positive charge) of the semiconductor wafer W are produced in the ionizer  31  illustrated in  FIG. 1  as described above. A gas (e.g., air) including the negative ions is introduced into the processing chamber  20  via the temperature/humidity adjustment apparatus  32 . Thereby, a negative ion atmosphere is provided in the processing chamber  20 . 
     By performing the developing, the cleaning, and the spin drying in the negative ion atmosphere, the charge of the semiconductor wafer W can be neutralized and eliminated or reduced; and the pattern collapse of the resist film  13  during the spin drying can be suppressed. As a result, a resist pattern can be formed without defects over the entire surface of the semiconductor wafer W. 
     To prevent the pattern collapse during the spin drying due to the semiconductor wafer W being charged, it is sufficient for the ion atmosphere to be provided in the processing chamber  20  at least during the spin drying. However, by maintaining an ion atmosphere in the processing chamber  20  also during the developing and the cleaning (the rinsing), the charging of the semiconductor wafer W during the developing and the cleaning can be eliminated or reduced; and particles occurring in the processing chamber  20  during the developing and the rinsing can be suppressed from adhering to the semiconductor wafer W. 
     Also, because the developing, the cleaning, and the spin drying are performed continuously in the same processing chamber  20 , the processing can be performed efficiently by providing the ion atmosphere in the processing chamber  20  from the developing or cleaning process prior to the spin drying and maintaining the atmosphere through the spin drying. 
     As a comparative example that provides an ion atmosphere in the processing chamber  20 , it may be considered to provide, for example, needle-like electrodes in the processing chamber  20 , perform electro-discharge in the processing chamber  20 , and produce ions directly in the processing chamber  20 . However, in such a case, electrodes are provided in the processing chamber  20  which may cause the structure in the processing chamber  20  to be complex. Also, there is a risk of damage of the semiconductor wafer W due to irregular electro-discharge between the electrodes and the semiconductor wafer W. 
     Conversely, in this embodiment, the ion atmosphere is provided in the processing chamber  20  by producing ions externally to the processing chamber  20  and introducing the ions into the processing chamber  20 . To this end, it is unnecessary to newly provide electrodes in the processing chamber  20 ; and the structure of a conventional processing chamber, that is, a so-called developer, can be used as-is. Further, electro-discharging is not performed in the processing chamber  20 . Therefore, damage of the semiconductor wafer W due to irregular electro-discharge does not occur. 
     It is desired to control the temperature and the humidity in the processing chamber  20  at the desired values because the temperature and the humidity in the processing chamber  20  affect the film thickness of the resist film  13  and the uniformity in the surface during the developing. However, in the case where electro-discharge is performed in the processing chamber  20 , the temperature and the humidity in the processing chamber  20  fluctuates due to the effects of the electro-discharge; and the control thereof is unfortunately difficult. 
     Conversely, in this embodiment, the temperature and the humidity of the gas (e.g., air) are adjusted to the desired values by the temperature/humidity adjustment apparatus  32  in the state in which the ions are included; and the gas including the ions is then introduced into the processing chamber  20 . Therefore, the temperature and the humidity of the atmosphere in the processing chamber  20  have excellent controllability; and the processing quality can be improved. 
     In this embodiment, an air atmosphere including ions is provided in the processing chamber  20  during the developing and the rinsing. The atmosphere is adjusted to, for example, a temperature of 25° C. and a humidity of 40 to 50%. The atmosphere is adjusted during the spin drying to a higher temperature or a lower humidity than those of the developing and the rinsing. 
     After patterning the resist film  13  by performing the developing, the cleaning, and the drying described above, the films to be patterned or the substrate  11  are patterned by using the resist pattern as a mask as illustrated in  FIG. 2D  and performing etching of the antireflective film  12  and the substrate  11  itself or the films to be patterned on the surface layer thereof. 
     A substrate processing method according to another embodiment of the invention will now be described with reference to  FIG. 5 . In the embodiment illustrated in  FIG. 5 , the rinsing process and the drying process are performed simultaneously. 
     The semiconductor wafer W is rotated in the state of being suction-held by the spin chuck  25  described above. In such a state, the rinsing fluid  4  is supplied from a rinsing fluid nozzle  35  opposing the semiconductor wafer W onto the surface of the semiconductor wafer W; and similarly, a gas (e.g., air or nitrogen gas) including ions is blown from a blow nozzle  36  opposing the semiconductor wafer W onto the surface of the semiconductor wafer W. 
     Both the rinsing fluid nozzle  35  and the blow nozzle  36  move in a straight line in a surface direction of the semiconductor wafer W. Specifically, the rinsing fluid nozzle  35  supplies the rinsing fluid  4  onto the surface of the semiconductor wafer W while moving in a straight line in a direction A from the center of the semiconductor wafer W in the outer radial direction. Because the semiconductor wafer W is rotating, the rinsing fluid  4  is supplied to the entire surface of the semiconductor wafer W and cleaning is performed for the entire surface of the semiconductor wafer W. 
     The blow nozzle  36  blows the gas including the ions onto the surface of the semiconductor wafer W while moving in a straight line in the direction A to follow the movement of the rinsing fluid nozzle  35  in the direction A. In other words, the gas including the ions is blown onto the region cleaned with the rinsing fluid  4  to perform the drying of the semiconductor wafer W. 
     In this embodiment, a gas including negative ions having a polarity opposite to that of the charge (e.g., a positive charge) of the semiconductor wafer W is blown from the blow nozzle  36  onto the semiconductor wafer W. Thereby, the charge of the semiconductor wafer W can be neutralized and eliminated or reduced. Thereby, the pattern collapse of the resist film  13  during the drying can be suppressed; and a resist pattern can be formed without defects over the entire surface of the semiconductor wafer W. 
     In this embodiment as well, the temperature and the humidity of the processing chamber  20  are adjusted to the desired values during the developing, the rinsing, and the drying. However, the atmosphere thereof may not include ions. The gas including the ions supplied to the blow nozzle  36  is produced externally to the processing chamber  20  and sent to the blow nozzle  36  via a not-illustrated gas supply system. Accordingly, in this embodiment as well, the semiconductor wafer W is not damaged by irregular electro-discharge because electro-discharge is not performed in the processing chamber  20 . Further, the temperature and the humidity in the processing chamber  20  do not fluctuate due to effects of electro-discharge; the temperature and the humidity of the atmosphere in the processing chamber  20  have excellent controllability; and the processing quality can be improved. 
     Next,  FIG. 6  illustrates a substrate processing method according to yet another embodiment of the invention. 
     In this embodiment as well, the gas including the ions is blown onto the semiconductor wafer W to dry the semiconductor wafer W after the rinsing. 
     The gas including the ions is blown from a blow nozzle  38  toward the semiconductor wafer W. The blow nozzle  38  extends in a direction going into the page surface in  FIG. 6 . A gas outlet is made in a slit configuration in a lower end portion opposing the semiconductor wafer W. When the blow nozzle  38  moves in the direction A, the gas outlet moves in the direction A above the semiconductor wafer W in a state of opposing the semiconductor wafer W. The gas including the ions, rather than being blown perpendicularly to the processing surface of the semiconductor wafer W, is blown in a direction B obliquely downward from the blow nozzle  38  on the travel direction A side. 
     By moving the blow nozzle  38  in the direction A while blowing the gas including the ions in the direction B obliquely downward on the travel direction A side, the rinsing fluid  4  on the semiconductor wafer W is pushed by the gas blown from the blow nozzle  38  to flow toward the direction A. At this time, the semiconductor wafer W does not rotate and is stationary. 
     In the regions of the semiconductor wafer W surface where the blow nozzle  38  passes, the rinsing fluid  4  is pushed to the travel direction A side and removed. The longitudinal direction length of the blow nozzle  38  is not less than the diameter of the semiconductor wafer W. Therefore, by moving the blow nozzle  38  in the direction A from one end of the semiconductor wafer W to the other in the state of opposing the semiconductor wafer W, the rinsing fluid  4  existing on the entire surface of the semiconductor wafer W can be discharged from the semiconductor wafer W. 
     Here, variation in the fluid level on the both sides of the resist pattern occurs during the drying of the semiconductor wafer W even in the case where the semiconductor wafer W dose not rotate and no centrifugal force is generated. Therefore, it is considered that the pattern collapse easily occurs due to surface tension of fluid. 
     In this embodiment as well, a gas including negative ions having a polarity opposite to the charge (e.g., a positive charge) of the semiconductor wafer W is blown from the blow nozzle  38  onto the semiconductor wafer W. Thereby, the charge of the semiconductor wafer W can be neutralized and eliminated or reduced. Thereby, the pattern collapse of the resist film  13  during the drying can be suppressed; and a resist pattern can be formed without defects over the entire surface of the semiconductor wafer W. 
     Further, the gas including the ions supplied to the blow nozzle  38  is produced externally to the processing chamber  20  and sent to the blow nozzle  38  via a not-illustrated gas supply system. Accordingly, in this embodiment as well, the semiconductor wafer W is not damaged by irregular electro-discharge because electro-discharge is not performed in the processing chamber  20 . Also, the temperature and the humidity do not fluctuate in the processing chamber  20  due to effects of electro-discharge; the temperature and the humidity of the atmosphere in the processing chamber  20  have excellent controllability; and the processing quality can be improved. 
     Hereinabove, embodiments of the invention are described with reference to specific examples. However, the invention is not limited thereto. Various modifications are possible based on the technical spirit of the invention.