Patent Publication Number: US-2015079701-A1

Title: Semiconductor device manufacturing method and manufacturing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-191682, filed Sep. 17, 2013, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to semiconductor device manufacturing methods and manufacturing apparatuses. 
     BACKGROUND 
     Generally, a discrete semiconductor has a device structure formed in the thickness direction of a wafer. Thus, when discrete semiconductors are manufactured, it may be necessary to grind the backside of a wafer to make the wafer thinner while not applying pressure that causes the wafer to break or crack. However, as a wafer is made thinner there is a reduction in rigidity and the wafer may even warp or bend under its own weight. Such thin wafers are difficult to handle during subsequent manufacturing processes. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a semiconductor device manufacturing apparatus according to a first embodiment. 
         FIG. 2A  is a diagram of a semiconductor device manufacturing apparatus according to a comparative example. 
         FIG. 2B  is a partially-enlarged view showing a deformed state of a thin-sheet portion of a wafer. 
         FIG. 3  is a diagram of a semiconductor device manufacturing apparatus according to a second embodiment. 
         FIG. 4  is a plan view showing a plate in a semiconductor device manufacturing apparatus according to a third embodiment. 
         FIG. 5A  is a diagram illustrating an operation of a semiconductor device manufacturing apparatus according to a fourth embodiment. 
         FIG. 5B  is a diagram illustrating the operation of the semiconductor device manufacturing apparatus according to the fourth embodiment. 
         FIG. 6  is a diagram (part (a)) illustrating a semiconductor device manufacturing apparatus according to a fifth embodiment and a graph (part (b)) showing the in-plane distribution of hydraulic pressure with the location in a wafer plane on the horizontal axis and with the hydraulic pressure of a liquid on the vertical axis. 
     
    
    
     DETAILED DESCRIPTION 
     According to the exemplary embodiments, there is provided a semiconductor device manufacturing method and a manufacturing apparatus. 
     In an embodiment, a manufacturing apparatus includes a chuck for contacting a peripheral portion of a workpiece, such as a semiconductor wafer. The apparatus includes a nozzle to eject a process fluid (liquid or gas) toward a first surface while the workpiece is in contact with the chuck. The process fluid may be, for example, for cleaning, etching, or coating the workpiece or portions thereof. The apparatus also includes a plate having an opening configured such that a support fluid (liquid or gas) can be ejected toward a second surface of the workpiece while the workpiece is in contact with the chuck. In an example, the support fluid can be used to counteract a displacement (warpage) of the interior portion in the direction perpendicular to the plane of the workpiece due to, for example, gravity and/or hydrostatic pressure of the process fluid. 
     An example embodiment concerns a wafer processing technique in which a rim portion (peripheral portion) of the wafer is left with an original thickness (i.e., is not ground/thinned) while an interior portion of the wafers is ground/thinned. The interior portion is, in general, surrounded by the rim portion within the wafer plane. The peripheral portion is thus thicker than the interior portion in a direction perpendicular to the plane of the wafer. By leaving the rim portion with a thickness greater than the interior portion this technique improves rigidity of the entire wafer, even those portions which may have been thinned by grinding or the like, allowing the wafer to be handled in subsequent process steps without excessive warpage and/or breaking. This wafer processing technique is exemplary and is not required of all embodiments of the present disclosure. 
     In general, according to one embodiment, there is provided a semiconductor device manufacturing apparatus for processing a first surface of a thin-sheet portion other than a rim portion of a wafer with the rim portion thicker than the thin-sheet portion. The manufacturing apparatus includes chucks for holding the rim portion, a nozzle for ejecting a first fluid toward the first surface, and a plate provided with an ejection opening through which a second fluid is ejected toward a second surface of the thin-sheet portion. 
     In general, according to one embodiment, a semiconductor device manufacturing method is a method for processing a first surface of a thin-sheet portion other than a rim portion of a wafer with the rim portion thicker than the thin-sheet portion. The manufacturing method includes holding the rim portion, and ejecting a first fluid toward the first surface while ejecting a second fluid toward a second surface of the thin-sheet portion. 
     Hereinafter, with reference to the drawings, example embodiments will be described. 
       FIG. 1  is a diagram illustrating a semiconductor device manufacturing apparatus according to a first embodiment. 
     As shown in  FIG. 1 , a semiconductor device manufacturing apparatus  1  according to the embodiment is an apparatus for performing wet processing on a wafer  100  in order to manufacture discrete semiconductor devices such as insulated gate bipolar transistors (IGBT) and vertical metal-oxide-semiconductor field-effect transistors (MOSFET), for example. The manufacturing apparatus  1  is a single-wafer processing apparatus, and is at least one of a wet-etching apparatus, a cleaning apparatus, or a coating apparatus, for example. 
     First, the wafer  100  to be processed by the manufacturing apparatus  1  will be described. 
     The wafer  100  is a silicon wafer, for example, on which semiconductor devices are to be formed. In the wafer  100 , a thin-sheet portion  101  is made thinner than an initial, original wafer thickness by grinding and a rim portion  102  as a peripheral edge portion of the wafer  100  is not ground and is left with the original wafer thickness. 
     The thin-sheet portion  101  is a portion other than the rim portion  102  of the wafer  100 , and has a thickness of 100 to 250 μm, for example. The rim portion  102 , in this example, has an annular shape, and is thicker than the thin-sheet portion  101 . With the rim portion  102  constituting a reinforcing portion, the entire of the wafer  100  has overall improved rigidity as compared to a wafer that having no rim portion. Inclusion of rim portion  102  can prevent wafer  100  from warping under its own weight. In wafer  100 , an upper surface  101   a  of the thin-sheet portion  101  is ground, and a lower surface  101   b  is not ground, for example. A back side grinding (BSG) tape  103  is attached to an entire lower surface of the wafer  100  including the lower surface  101   b.    
     A manufacturing apparatus  1  of an embodiment is provided with a plurality of chucks  11 . The chucks  11  hold the wafer  100  by the rim portion  102 , and the chucks  11  may be used to rotate the wafer  100 . The chucks  11  contact only the rim portion  102 , and do not contact the upper surface  101   a  and the lower surface  101   b  of the thin-sheet portion  101 . Thus, the upper surface  101   a  and the lower surface  101   b  of the thin-sheet portion  101  may be subjected to wet processing. The chucks  11 , in some embodiments, contact only a vertical surface (perpendicular to the wafer plane) of the rim portion  10 . The chucks  11  may be disposed so as to contact a periphery of wafer  100 . Chucks  11  may be referred to as chuck portions  11 . In some embodiments, wafer  100  may be held by a single chuck  11  which itself contacts different points of rim portion  102 . 
     The manufacturing apparatus  1  is also provided with a nozzle  12  for ejecting a liquid  105  toward the upper surface  101   a  of the thin-sheet portion  101 . The liquid  105  is a processing liquid for performing wet processing on the upper surface  101   a  of the thin-sheet portion  101 , and may be a chemical solution for cleaning the upper surface  101   a  of the thin-sheet portion  101 , such as dilute hydrofluoric acid (dHF), NC-2, SC-1, SC-2, or a sulfuric acid-hydrogen peroxide (H 2 O 2 ) mixture (SPM), for example, or may be a chemical solution for etching the upper surface  101   a , such as a mixed solution of nitric acid (HNO 3 ) and hydrofluoric acid (HF), or FEP, for example, or may be a chemical solution for rinsing the upper surface  101   a  such as de-ionized water (DIW), for example, or may be a resist material for forming a resist film on the upper surface  101   a.    
     Further, the manufacturing apparatus  1  is provided with a plate  13 . The plate  13  is arranged below the wafer  100  at a position opposite to the lower surface  101   b . The plate  13  is formed with an ejection opening  13   a  for ejecting a liquid  106  toward the lower surface  101   b . Since the BSG tape  103  is attached to the lower surface of the wafer  100  as described above, the liquid  106  contacts the BSG tape  103 , applying an upward force to the thin-sheet portion  101  via the BSG tape  103 . In the embodiment, the ejection opening  13   a  is formed only in one location where the liquid  106  is ejected vertically toward the center of the wafer  100 . The manufacturing apparatus  1  is also provided with a liquid supply apparatus  14  for supplying the liquid  106  to the ejection opening  13   a . The liquid  106  is a supporting fluid for supporting the wafer  100  against warpage, and is DIW, for example. Since the thin-sheet portion  101  is generally very thin and potentially fragile, it is usually not impossible to provide a support member that contacts the lower surface  101   b , and thus there is an unfilled space left below the thin-sheet portion  101  and the chuck  11  which may be filled with liquid  106  supplied by liquid supply apparatus  14  during processing steps of wafer  100 . 
     Next, the operation of the semiconductor device manufacturing apparatus  1  will be described. 
     As shown in  FIG. 1 , first, the chucks  11  contact the rim portion  102  of the wafer  100 , and rotate the wafer  100 . In this state, the liquid  105  is ejected from the nozzle  12  toward a central portion of the upper surface  101   a . Simultaneously, the liquid supply apparatus  14  ejects the liquid  106  through the ejection opening  13   a  in the plate  13  toward a central portion of the lower surface  101   b . For example, the flow rate or pressure of the liquid  106  can be set to be higher than the flow rate or pressure of the liquid  105 . 
     The liquid  105  contacts the central portion of the upper surface  101   a , spreading toward the rim portion  102  by the centrifugal force accompanying the rotation of the wafer  100 . Thus, the upper surface  101   a  is wet-processed by the liquid  105 . For example, the upper surface  101   a  is cleaned, etched, or rinsed by the liquid  105 . However, at this time, the hydraulic pressure of the liquid  105  and the weight of the liquid  105  accumulating on the thin-sheet portion  101  apply a downward force to the thin-sheet portion  101 . On the other hand, the liquid  106  ejected from the ejection opening  13   a  contacts the central portion of the lower surface  101   b , applying a hydraulic pressure to the lower surface  101   b  via the BSG tape  103 . Thus, an upward force is applied to the thin-sheet portion  101  to counter the downward force caused by liquid  105 . 
     According to the embodiment, the upward force applied to the thin-sheet portion  101  by the hydraulic pressure of the liquid  106  counteracts the downward force applied to the thin-sheet portion  101  by the hydraulic pressure and the weight of the liquid  105 , thus allowing the thin-sheet portion  101  to be supported without bringing a solid member into contact with the thin-sheet portion  101 . Thus, the thin-sheet portion  101  is prevented from warpage, and the thin-sheet portion  101  may be kept flat. As a result, by the force applied by the liquid  105 , the thin-sheet portion  101  may be prevented from warpage and a crack or a break in the thin-sheet portion  101  may be prevented. Further, it may be prevented that warpage of the thin-sheet portion  101  causes non-uniform distribution of the liquid  105  on the thin-sheet portion  101 , resulting in non-uniform processing with the liquid  105 . As a result, the yield of wet processing with the liquid  105  may be increased. 
     The type of the liquid  105  and a type of the liquid  106  may be chosen as desired. For example, liquid  105  and liquid  106  may be the same or different types and may be selected according to the wet processing to be carried out. For example, when a chemical solution for cleaning is used as the liquid  105 , the same chemical solution for cleaning may be used for the liquid  106  to clean the lower surface  101   b  simultaneously with the upper surface  101   a  of the thin-sheet portion  101 . Further, the physical properties such as viscosities and specific gravities of the liquids  105  and  106  may be made uniform (though this is not a necessity), thus facilitating the control of pressure. Alternatively, when a chemical solution for cleaning is used as the liquid  105 , pure water may be used for the liquid  106  to rinse the lower surface  101   b  to which the BSG tape  103  is attached, and to help prevent the chemical solution of the liquid  105  from leaking to the lower surface  101   b.    
       FIG. 2A  is a diagram illustrating a semiconductor device manufacturing apparatus according to a comparative example.  FIG. 2B  is a partially enlarged view showing a deformed state of a thin-sheet portion of a wafer. 
     As shown in  FIG. 2A , in a manufacturing apparatus  9  according to the comparative example, a plate  13  and a liquid supply apparatus  14  (see  FIG. 1 ) are not provided, and a supporting liquid  106  (see  FIG. 1 ) is not ejected toward a lower surface  101   b.    
     Therefore, the thin-sheet portion  101  of a wafer  100  warps to be convex downward by the hydraulic pressure and the weight of a liquid  105 . Since the wafer  100  is provided with a thick rim portion  102 , thus achieving a certain degree of rigidity, the wafer  100  does not warp largely by its own weight. However, the thin-sheet portion  101  is thinner than the rim portion  102 , and therefore may warp significantly when a downward force is applied to a central portion of the thin-sheet portion  101  by the liquid  105 . This may cause a crack in the thin-sheet portion  101 , or cause a break in the thin-sheet portion  101 . Further, as shown in  FIG. 2B , the thin-sheet portion  101  warping to be convex downward causes the amount of the liquid  105  accumulating on the central portion of the thin-sheet portion  101  to be greater than the amount of the liquid  105  accumulating on a peripheral portion of the thin-sheet portion  101 , thus reducing the in-plane uniformity of processing. When the liquid  105  is an etchant, for example, etching at the central portion of the thin-sheet portion  101  may be relatively enhanced while etching at the peripheral portion is relatively suppressed. As a result, the yield of semiconductor devices may be reduced by the across-wafer process variation. 
     By contrast, according to the first embodiment, the liquid  106  is ejected from the opposite side of the liquid  105  with the thin-sheet portion  101  therebetween, whereby the thin-sheet portion  101  is supported by the liquid  106 , and may be prevented from warpage. 
       FIG. 3  is a diagram illustrating a semiconductor device manufacturing apparatus according to a second embodiment. 
     As shown in  FIG. 3 , in a manufacturing apparatus  2  according to the embodiment, a gas supply apparatus  24  is provided instead of the liquid supply apparatus  14  (see  FIG. 1 ). Thus, a gas  107  is jetted toward a lower surface  101   b  of a thin-sheet portion  101  of a wafer  100 . The gas  107  may be a nitrogen gas (N 2 ), for example. The gas  107  is jetted under conditions where the Bernoulli&#39;s effect is not substantial, in order to avoid a suction effect to be caused by flow of the gas  107 . 
     In this second embodiment, as in the first embodiment, the thin-sheet portion  101  is supported by the pressure of the gas  107 , and the thin-sheet portion  101  may be prevented from warpage. Further, the gas  107  may prevent a liquid  105  from leaking to the lower surface  101   b  side. Due to this, when a resist material is used as the liquid  105 , and a tape not resistant to an organic solvent is used as a BSG tape  103 , the resist material may be prevented from contacting the BSG tape  103 . Further, a gas may be jetted from a nozzle  12  instead of the liquid  105 . Due to this, the wafer  100  after wet processing may be dried. In this case, by using the gas  107  instead of the liquid  105  as a fluid for supporting the thin-sheet portion, both sides of the wafer  100  may be dried simultaneously. The configuration, operation, and effects other than those above in the second embodiment are otherwise similar to those in the first embodiment. 
       FIG. 4  is a plan view showing a plate in a semiconductor device manufacturing apparatus according to a third embodiment. 
     As shown in  FIG. 4 , in the manufacturing apparatus according to the third embodiment, a plate  33  is provided instead of the plate  13  (see  FIG. 1 ). In the plate  33 , a plurality of ejection openings  33   a  to  33   d  are formed. The ejection opening  33   a  is arranged at the center  34   a  of the plate  33 . The ejection openings  33   b  to  33   d  are arranged concentrically along imaginary concentric circles  34   b  to  34   d  with the center  34   a  as the center. 
     According to the embodiment, by ejecting a liquid  106  from the plurality of ejection openings  33   a  to  33   d , the liquid  106  may be ejected toward a plurality of areas on a lower surface  101   b  of a thin-sheet portion  101  as well as a central portion of the lower surface  101   b . Further, by making the ejection openings  33   a  to  33   d  different from each other in diameter, the flow rates of the liquid  106  ejected from the ejection openings  33   a  to  33   d  may be made different from each other. Alternatively, by providing appropriate adjustments on the lower surface side of the plate  33 , the pressures of the liquid  106  ejected from the ejection openings  33   a  to  33   d  may be made different from each other. By controlling the flow rates or pressures of the liquid  106  in this manner, the in-plane distribution of force the liquid  106  applies to the thin-sheet portion  101  may be optimized, and the shape of the thin-sheet portion  101  may controlled more precisely. The configuration, operation, and effects other than those above in the embodiment are otherwise similar to those in the first embodiment. 
       FIGS. 5A and 5B  are diagrams illustrating the operation of a semiconductor device manufacturing apparatus according to a fourth embodiment. 
     As shown in  FIGS. 5A and 5B , in a semiconductor device manufacturing apparatus  4  according to the embodiment, in addition to the configuration of the manufacturing apparatus  1  (see  FIG. 1 ) according to the first embodiment, a laser sensor  41  is provided. The laser sensor  41  is arranged above a wafer  100  at a position where laser light  109  is emitted toward a portion other than the center of a thin-sheet portion  101  from a direction perpendicular to an upper surface  101   a . In  FIGS. 5A and 5B , device components other than a nozzle  12 , a liquid  105 , the thin-sheet portion  101  of the wafer, and the laser sensor  41  are not specifically depicted for sake of clarity. 
     In the manufacturing apparatus  4 , the laser sensor  41  emits the laser light  109  toward the thin-sheet portion  101  (downward arrow), and measures the intensity of the laser light  109  reflected by the thin-sheet portion  101  (upward arrow). Thus, the laser sensor  41  calculates a reflectance R of the laser light  109 . The reflectance R is defined by R=Ir/Ii wherein Ii represents the amount of light of the laser light  109  emitted from the laser sensor  41  (downward arrow), and Ir represents the amount of light of the laser light  109  entering the laser sensor  41  (upward arrow). 
     As shown in  FIG. 5A , when the thin-sheet portion  101  of the wafer does not warp, when the laser light  109  emitted from the laser sensor  41  is incident on an upper surface  101   a  of the thin-sheet portion  101  from a direction normal to the upper surface  101   a , it is reflected vertically by the upper surface  101   a , and mostly reflects back towards the laser sensor  41 . Thus, the reflectance R is relatively high. 
     On the other hand, as shown in  FIG. 5B , when the thin-sheet portion  101  warps, the laser light  109  emitted from the laser sensor  41  is incident on the upper surface  101   a  from a direction inclined with respect to a normal  101   n  to the upper surface  101   a . Then, the laser light  109  is reflected in a direction inclined to the opposite side of the incident direction with respect to the normal  101   n , refracted by the surface of the liquid  105 , and thus travels in a direction deviating away from the direction toward the laser sensor  41 . Consequently, the light amount of the laser light  109  returning to the laser sensor  41  is relatively small, and the reflectance R is relatively low. 
     Accordingly, by calculating the reflectance R, it is possible to evaluate the amount of warpage of the thin-sheet portion  101 . Then, by feeding the evaluation results back to a liquid supply apparatus  14 , the thin-sheet portion  101  of the wafer may be kept flat by adjustments in fluid amounts, pressures, or types. Thus, even when the amount of warpage of the thin-sheet portion  101  differs because the thickness of the thin-sheet portion  101  differs from batch to batch, or the kind and ejection conditions of the liquid  105  differ, the amount of warpage is measured in situ (in-situ monitoring) and fed back, thereby being able to flatten the thin-sheet portion  101  with high precision. The configuration, operation, and effects other than those above in the embodiment are otherwise similar to those in the first embodiment. 
       FIG. 6  is a diagram having a portion (a) illustrating a semiconductor device manufacturing apparatus according to a fifth embodiment.  FIG. 6  also includes a portion (b) that is a graph showing the in-plane distribution of hydraulic pressure with the location in a wafer plane on the horizontal axis, and with the hydraulic pressure of a liquid  106  on the vertical axis. 
     As shown in portion (a) of  FIG. 6 , in a semiconductor device manufacturing apparatus  5  according to the fifth embodiment, a plate  33  like the one described in the third embodiment is provided. The plate  33  is formed with a plurality of ejection openings  33   a  to  33   d  in concentric arrangements. Further, in the manufacturing apparatus  5 , a plurality of laser sensors  41  like that described with respect to the fourth embodiment is provided. Moreover, in the manufacturing apparatus  5 , a hydraulic pressure control apparatus  51  for controlling the pressures of the liquid  106  that is supplied to the ejection openings  33   a  to  33   d  independently from each other is provided between a liquid supply apparatus  14  and the plate  33 . The hydraulic pressure control apparatus  51  may control the flow rates instead of the pressures of the liquid  106 . Furthermore, a controller  52  connected to all the laser sensors  41  and the hydraulic pressure control apparatus  51  is provided. In the manufacturing apparatus  5 , the position of a nozzle  12  may be movable in a radial direction of the wafer  100 . 
     In the manufacturing apparatus  5 , the nozzle  12  can move in the radial direction of the wafer  100 , thus changing the distribution of force applied by the liquid  105  to the wafer  100  and changing the warping state of the thin-sheet portion  101 . On the other hand, in the manufacturing apparatus  5 , the laser sensors  41  determine reflectances R at portions of the thin-sheet portion  101 , and output the reflectances R to the controller  52 . The controller  52  evaluates the state of warpage of the thin-sheet portion  101 , then determines the pressure distribution of the liquid  106  based on this, and outputs a control signal to the hydraulic pressure control apparatus  51 . Based on the control signal transmitted from the controller  52 , the hydraulic pressure control apparatus  51  controls individual hydraulic pressures of the liquid  106  that is supplied to the ejection openings  33   a  to  33   d  in the plate  33 . Thus, the pressure distribution of the liquid  106  may be controlled in real time based on the output of the laser sensors  41  and other input variables. For example, as shown in portion (b) of  FIG. 6 , in accordance with the movement of the nozzle  12 , the peak of the hydraulic pressure distribution of the liquid  106  may be moved. 
     By dynamically controlling the pressure distribution of the liquid  106  in this manner, an upward force applied by the liquid  106  to the thin-sheet portion  101  is continuously adjusted to balance against a downward force applied by the liquid  105  to the thin-sheet portion  101 . Thus, the manufacturing apparatus  5  is able to keep the thin-sheet portion  100  flat with high precision. The configuration, operation, and effects other than those above in the fifth embodiment are otherwise similar to those in the first embodiment. 
     In any of the embodiments, the liquid  105  may be replaced with a gas, and the liquid  106  may also be replaced with a gas. That is, a combination of a fluid ejected toward the upper surface  101   a  of the thin-sheet portion  101  and a fluid ejected toward the lower surface  101   b  may be chosen as desired. “Fluid” in this context includes a liquid or a gas and mixed phases thereof. The embodiments have shown the example in which the processing liquid  105  is ejected toward the upper surface  101   a  of the thin-sheet portion  101 , and the supporting liquid  106  is ejected toward the lower surface  101   b  of the thin-sheet portion  101 , but the scope of the present disclosure is not limited to this arrangement. For example, the upper and lower relationship may be reversed. Further, it should be noted the disclosed embodiments may be combined with each another for implementation. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.