Abstract:
A semiconductor substrate rinsing method and apparatus. A wet processed substrate is spun to reduce the amount of process solution on the surface of the substrate. The concentration of the process solution on the surface of the substrate is reduced by applying a cleaning solution to the surface. The cleaning solution may be applied from nozzles on a supply member positioned across from the surface of the substrate. The nozzles may be angled to evenly distribute application of the cleaning solution on the substrate.

Description:
FIELD  
       [0001]     The present invention generally relates to semiconductor integrated circuit technology and, more particularly, to an apparatus and process for rinsing substrates.  
       BACKGROUND  
       [0002]     Semiconductor device fabrication involves many wet processing steps in which substrates are exposed to processing solutions, including various chemicals. For example, metal layers can be formed on substrates using deposition electrolytes in electrochemical or electroless processes. Similarly, deposited metal layers can be removed or planarized using chemical mechanical polishing or electropolishing, both of which processes typically use oxidizing solutions. Further, unwanted portions of masking layers can be removed by means of wet development processing, involving chemical solutions. Surfaces of substrates are “cleaned” or “polished” by means of removing a thin layer, such as an oxidized layer, using appropriate chemical solutions.  
         [0003]     After such wet processing steps, however, substrates need to be rinsed off, typically with de-ionized water (DI water), so that the chemical residues are removed from the substrate before a subsequent process step. Chemical residues left on the substrate would continue interaction with the substrate material, resulting in corrosion or defects that lower device performance or cause device failures.  
         [0004]     While it is important to clean or rinse chemical residues from substrates, it is also important, for productivity reasons, to do this process as quickly and with as little de-ionized water as possible. Therefore, in the semiconductor industry, there is always a need for more efficient rinsing or cleaning of substrates.  
       SUMMARY  
       [0005]     According to an aspect of the invention, a method is provided for rinsing a surface of a wafer using a cleaning solution. The surface of the wafer is treated using a process solution. The cleaning solution is applied to the surface to form a first mixture including a first concentration of the process solution. The wafer is spun to reduce an amount of the first mixture on the surface. The cleaning solution is applied to the surface to form a second mixture including a second concentration of the process solution, wherein the second concentration is less than the first concentration. The wafer is spun to remove the second mixture from the surface.  
         [0006]     According to another aspect of the invention, an apparatus is provided for rinsing a surface of a wafer using a rinsing solution after a wet process. The apparatus includes a solution supply member, a plurality of nozzles, and at least one moving mechanism. The solution supply member is positioned across from the surface of the wafer. The plurality of nozzles is disposed on the solution supply member and distributed to inject a substantially uniform amount of the rinsing solution onto both an edge region and a central region of the surface of the wafer. The at least one moving mechanism is configured to laterally move at least one of the wafer and the solution supply member as the solution is injected onto the surface of the wafer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     These and other aspects of the invention will be readily apparent from the following description and from the appended drawings (not to scale), which are meant to illustrate and not to limit the invention, and wherein:  
         [0008]      FIG. 1  is a schematic illustration of a wafer held by a wafer carrier after a process, wherein the surface of the wafer includes a film of a residual process solution in an embodiment;  
         [0009]      FIG. 2  is a schematic illustration of applying a rinsing solution to the surface of the wafer shown in  FIG. 1 ;  
         [0010]      FIGS. 3A and 3B  are schematic illustrations of rinsing solution jets impinging on the surface of the wafer as the wafer or the solution supply is moved laterally;  
         [0011]      FIG. 4  is a schematic illustration of a solution mixture formed on the surface of the wafer by the application of rinsing solution;  
         [0012]      FIG. 5  is a schematic illustration of another solution mixture formed on the surface of the wafer by the application of rinsing solution and spinning the wafer;  
         [0013]      FIG. 6  is a schematic illustration of the wafer after the rinsing process;  
         [0014]      FIG. 7  is a schematic illustration of the wafer after a drying process;  
         [0015]      FIGS. 8A and 8B  are schematic illustrations of an embodiment of a solution supply member;  
         [0016]      FIGS. 9A and 9B  are schematic illustrations of another embodiment of the solution supply member of the present invention;  
         [0017]      FIG. 10  is a schematic illustration of a rinsing station including the solution supply member of an embodiment; and  
         [0018]      FIG. 11  is a schematic illustration of a vertical system including a process station and a rinsing station, including the solution supply member of an embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0019]     The following detailed description of the preferred embodiments and methods presents a description of certain specific embodiments to assist in understanding the claims. However, one may practice the present invention in a multitude of different embodiments and methods as defined and covered by the claims.  
         [0020]     An embodiment provides a method and apparatus for rinsing substrates, using a liquid such as DI water, or another liquid. In one embodiment, a substrate or wafer surface is contacted with a plurality of high velocity liquid jets or streams of a liquid, which are directed from a plurality of openings of a supply member. By moving at least one of the supply member and the wafer, every point on the wafer surface is contacted with the high velocity liquid jets. In a second embodiment, a wafer, which was previously treated with a liquid, is substantially drained by spinning the wafer one or more times at high speeds for a short period during the rinsing process. In a third embodiment, an embodiment of a supply member is provided. The openings of the supply member, which produce the high velocity liquid jets, are preferably distributed such that the coverage is substantially uniform. The substrate is typically dried before moving to the next processing step. Sometimes the rinsing and drying steps are performed in a processing module specifically designed for rinsing and drying the substrate.  
         [0021]     FIGS.  1  to  6  illustrate an exemplary rinsing process according to an embodiment, including liquid application and draining steps, upon a wet-processed wafer. In this embodiment, a rinsing process is performed using DI water to clean a wet-processed wafer.  FIG. 1  illustrates a wafer  100  held by a wafer carrier  102  for the rinsing process of this embodiment. The wafer  100  may be a wet processed wafer having a first film  104  of a process solution on a front surface  106  of the wafer  100 . The front surface  106  may be made of a metal, semiconductor, or a dielectric, or a combination of different materials, depending upon the stage of IC fabrication. The first film  104  may be formed of process solution and any byproduct left on the surface  106  of the wafer  100 . The wet process performed on the wafer  100  may be any electrochemical process or electroless process, or other deposition, removal or surface treatment process. The rinsing process of this embodiment cleans off the process solution film  104  so that the surface  106  can be further processed in a subsequent process step. The process solution forming the first film  104  may be an electrolyte or an electropolishing solution including various chemicals that are desirably removed from the surface  106  of the wafer  100  before a subsequent process step. In  FIG. 1 , the film  104  is illustrated with densely distributed dots representing chemicals or other materials that are desirably cleaned off using the process of this embodiment. In the figures, the density of the dots is gradually reduced to help visualization of the removal of such chemicals from the surface  106  during the rinsing process.  
         [0022]      FIG. 2  shows a liquid application step of this embodiment. In this step, jets of DI water or other rinsing solution depicted by arrows  108  are applied to the first film  104  on the front surface  106 . Jets  108  of DI water penetrate into the film  104  and impinge on the front surface  106  with high momentum. As the jets  108  are breaking the film  104  apart, the process solution forming the first film  104  begins mixing with the DI water. DI water jets  108  preferably penetrate below the fluid boundary layer substantially everywhere on the front surface  106 . As will be described below, this mixing, in turn, forms a mixture of DI water and the first film  104  or the chemicals of first film  104 , including constituents of the preceding wet process solution. In a preferred embodiment, a large number of jets  108 , typically from 50 to 150 jets for a 300-mm diameter wafer, are used to apply the DI water to the front surface  106 . As shown in  FIG. 2 , the jets  108  are preferably slanted at an angle so that they arrive at the front surface  106  under an impact angle (a i ) which is preferably 30°-60°. The diameter of the water jets is typically between 0.2 to 0.4 mm. The velocity of the jets  108  is preferably between 0.5 to 2.5 m/sec. The jets  108  may be directed from a supply member  200 ,  300 , as exemplified in  FIGS. 8A-9B .  
         [0023]     Referring to  FIG. 2 , in order to have full coverage on the front surface  106 , during the liquid application step, the wafer  100  is preferably rotated at rotational speeds ranging from 30 to 120 rpm, and reciprocated linearly in a horizontal dimension by about 2-4 mm at each 1 to 5 cycles per second. The jets  108  are preferably distributed such that the coverage on the front surface  106  is substantially uniform.  
         [0024]     As shown in  FIGS. 3A and 3B , in one embodiment, full coverage on the front surface  106  may be established dynamically by laterally moving the wafer  100  as the wafer  100  is rotated. Referring to  FIG. 3A , at a first lateral position and for a first predetermined number of rotations, the jets  108  impinge on spots denoted by ‘A’ on the front surface  106 . As shown in  FIG. 3B , at the end of the first predetermined number of rotations, the wafer  100  is laterally moved to a second lateral position in the direction of arrow ‘X’. At the second position, the jets  108  impinge on the spots denoted by ‘B’ adjacent the spots ‘A’ for a second predetermined number of rotations; thus, the front surface  106  is fully treated with the DI water. In other embodiments, the full coverage may be established by laterally moving the wafer  100  among more than two lateral positions. In one embodiment, the wafer  100  continuously oscillates between two lateral positions while it is rotated simultaneously.  
         [0025]     As mentioned above, as the front surface  106  is treated with jets  108 , the process solution forming the first film  104  begins mixing with the DI water and forms a mixture of solutions on the surface  106  of the wafer  100 . As shown in  FIG. 4 , application of the DI water jets to the front surface  106  forms a second film  110  comprising a diluted mixture of the DI water and the process solution in the first film  104 . Although, in  FIG. 4 , the second film  110  is shown to be thicker than the first film  104  of  FIG. 1 , the second film  110  can be thinner or equal to the thickness of the first film  104 . According to this embodiment, the second film  110  is a mixture including DI water and the chemicals of the first film  104 . In this embodiment, the second film  110  is a dynamic environment where fresh DI water continuously arrives with the jets  108  and gets mixed with the existing mixture of process solution from the first film  104  and the already applied DI water, while at the same time the mixture is continuously drained by the motion of the wafer carrier  102  and the gravity. As a result, the amount of process solution or the concentration of the chemicals from the process solution in the second film  110  is continuously and significantly reduced as the jets  108  are applied to the front surface  106  for a predetermined time. In  FIG. 4 , dilution of the process solution in the DI water is represented by less densely distributed dots in the second film  110 .  
         [0026]      FIGS. 5 and 6  illustrate exemplary stages during the draining step of the rinsing process, according to an embodiment. During the draining step, the second film  110  is substantially drained one or more times by spinning the wafer  100  at higher speeds for a short period, preferably for about 0.5 to 3.0 seconds. The draining step may be performed by spinning the wafer  100  at high speeds for a short period and it will be understood that the short period of spinning may be performed more than once and also by accelerating and/or decelerating. The draining speed is preferably from 400 to 1200 rpm for a short period of time, preferably about 0.5 to 3.0 seconds and acceleration/deceleration from and to the rinsing speed is achieved preferably in less than 2 seconds.  
         [0027]     In one embodiment, the draining step and liquid application step can be applied sequentially to increase rinsing efficiency. In this embodiment, first the DI water jets are applied to the second film  110  shown in  FIG. 4  while the wafer  100  is rotated and laterally moved. Liquid application in this manner reduces the concentration of chemicals in the second film  110 . Second, the DI water jets are stopped and spinning of the wafer  100  is increased to draining speed (e.g., about 400-1200 rpm) for efficient draining of the diluted second film  110 , which reduces the amount of mixed solution on the surface  106  of the wafer  100 . As the spinning speed of the wafer  100  is reduced, an intermediate phase  110 ′ of the second solution  110  may be left on the front surface  106  of the wafer  100 , as shown in  FIG. 5 . The intermediate phase  110 ′ shown in  FIG. 5  is only an exemplary illustration and may be formed after one or more liquid application and draining steps. As shown in  FIG. 5  with the density of the dots in the intermediate phase  110 ′, the concentration of the process solution or the chemicals in DI water is highly reduced in the small volume of the intermediate phase  110 ′ in this stage. If the application of DI water to the intermediate phase  110 ′ and draining steps are repeated one or more times, a final phase  110 ″ of the second film  110  is obtained, as shown in  FIG. 6 . The final phase  110 ″ includes a volume of DI water with almost no process solution or chemicals in it. After this step, as shown in  FIG. 7 , the wafer  100  is dried to remove the final phase  110 ″ from the front surface  106 . The rinsing process of this embodiment removes the process solutions or the chemicals from wafer surface  106  in significantly shorter times and often with a smaller amount of DI water, which makes the rinsing more efficient.  
         [0028]     The liquid application step of the rinsing process may be performed using supply members described below. A supply member  200  to produce DI water jets, as described above, is exemplified in  FIG. 8A  in a top plan view and in  FIG. 8B  in a side view. In this embodiment, although supply members  200  are used with DI water, it is understood that supply members  200  can be used with any liquid or cleaning solution. A first side  202  of the supply member  200  includes a plurality of nozzles or openings  204  to produce DI water jets  206  that impinge on a surface  208  of a wafer  210  during the rinsing process. The wafer surface  208  may have a process solution film (not shown) to be cleaned using the supply member  200  and the process of this embodiment. While, in this embodiment, the distribution of the nozzles  204  is such that full coverage of the DI water jets  206  on the wafer surface  208  is obtained, still the coverage may not be uniform since the amount of fresh DI water received, for example, near the edge region E of the wafer is substantially less than the amount received near the central region C of the wafer. In one distribution example, the nozzles  204  are disposed on a first arm  212 A and a second arm  212 B of the supply member  200  and preferably slanted towards the edge of the wafer. In the illustrated distribution example, the first arm  212 A extends beyond the center of the wafer so that jets  206  from the nozzles  204  on the first arm  212 A cover an edge region E and a central region C of the surface  208  as the wafer is rotated. In the illustrated embodiment, the second arm  212 B only extends over an approximate border (dotted circle) between the edge and central regions so that the jets from the nozzles  206  on the second arm  212 B cover only the edge region E as the wafer is rotated. The addition of the second arm  212 B increases the number of jets treating the edge region E (two sets in region E vs. one set in region C), which is larger than the central region C; thus, in this embodiment, the rotating surface  208  is covered with better uniformity by the DI water jets  206 .  
         [0029]      FIGS. 9A-9B  show another embodiment of a supply member  300  having a first side  302  including a plurality of nozzles  304  for producing DI water (or other fluid) jets  306 . As shown in  FIG. 9B , the supply member  300  is positioned across from a surface  308  of a wafer  310 . In this embodiment, the supply member  300  includes a plurality of arms, including a primary arm  312 A, secondary arms  312 B and ternary arms  312 C. As in the previous embodiment, in this embodiment with the same principle, the nozzles  304  are distributed on the arms  312 A,  312 B,  312 C for coverage with substantial uniformity of the surface  308  by the DI water jets  306 . Accordingly, in this embodiment, the primary arm  312 A extends over an edge region E (largest region), a middle region M (smaller than E) and a central region (smaller than E and M). The secondary arms  312 B extend over the edge region E and the middle region M. The ternary arms  312 C extend over the edge region E. In this nozzle distribution configuration, as the wafer is rotated, the edge region E of the surface  308  is exposed to highest number of jets  306 ; the middle region M is exposed to fewer jets  306  than in the region E; and the central region C is exposed to the least number of jets  306 . In this embodiment, the supply member  300  preferably has about 30-50 nozzles for a 300 mm diameter wafer. The jets  306  are preferably slanted so that they arrive at the front surface  308  under an impact angle (α i ), which is preferably about 30°-60°. The diameter of the water jets  306  is preferably between 0.2 to 0.4 mm. The velocity of the jets  306  is preferably between 0.5 to 2.5 m/sec.  
         [0030]      FIGS. 10 and 11  illustrate two rinsing station embodiments, using at least one of the supply members  200 ,  300  described above.  FIG. 10  illustrates a single rinsing station  400  including a wafer holder  402  holding a wafer W to be rinsed using the supply member  300 . The wafer holder  402  is preferably moved (laterally moved and/or rotated) through a shaft  403  that is connected to a moving mechanism (not shown). A solution line  404  is preferably attached to the supply member  300  to provide a liquid, such as rinsing solution or DI water. The station  400  may be an integral part of an electrochemical, electroless or chemical mechanical polishing system. Alternatively, the station  400  may be located outside such systems.  
         [0031]      FIG. 11  shows a rinsing station  500  that is located over a process station  501  in a so-called vertical chamber arrangement. The rinsing station  500  also includes the supply member  300  for rinsing processed wafers. A solution line  504  is preferably attached to the supply member  300  to provide a liquid, such as rinsing solution or DI water. In the illustrated vertical chamber arrangement, a wafer W held by a wafer holder  502  can be processed in the process station  501  and rinsed in the rinsing station  500  by vertically moving the wafer W. In this embodiment, the wafer holder  502  can be moved vertically by extending or retracting the shaft  503 . The process station  501  may perform any of a variety of processes, such as electrochemical, electroless or chemical mechanical polishing processes. Flaps  506  between the two stations  500 ,  501  open to allow the wafer holder  502  to move between the stations  500 ,  501  and also close to seal the process station  501  when the rinsing station  500  is in use.  
         [0032]     In the systems of  FIGS. 8A-11 , one or more moving mechanisms (not shown) may rotate and/or laterally move the wafer W and/or supply member  300 . Rinsing solution is preferably delivered from a solution tank connected to the solution lines  404 ,  504 . In  FIGS. 10 and 11 , the solution line  404 ,  504  configurations are exemplary; it will be understood that they may be configured in various other ways.  
         [0033]     Although various preferred embodiments and the best mode have been described in detail above, those skilled in the art will readily appreciate that many modifications of the exemplary embodiment are possible without materially departing from the novel teachings and advantages of this invention.