Patent Publication Number: US-2021178522-A1

Title: Apparatus for etching thin layer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Korean Patent Application No. 10-2019-0166795, filed on Dec. 13, 2019, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which are incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an apparatus for etching a thin layer. More particularly, the present disclosure relates to an apparatus for etching and removing a thin layer formed on a substrate such as s silicon wafer. 
     BACKGROUND 
     Generally, semiconductor devices may be manufactured by manufacturing processes repeatedly performed on a silicon wafer. For example, a deposition process for forming a thin layer on a substrate, a photolithography process for forming a photoresist pattern on the thin layer, an etching process for patterning or removing the thin layer, etc., may be performed. 
     The etching process is classified into a dry etching process and a wet etching process. The wet etching process is classified into a single wafer type configured to process substrates piece by piece and a batch type configured to simultaneously process substrates. In a single wafer type etching apparatus, etchant is supplied on a rotating substrate, and the thin layer is removed through a reaction between the thin layer and the etchant. Etch residues and remaining etchant produced by the reaction is removed by the rotation of the substrate. 
     For example, when a thin layer including silicon nitride is formed on the substrate, the thin layer may be removed by etchant including phosphoric acid and water. In order to increase the speed of the reaction between the silicon nitride and the etchant, the etchant is heated and is then supplied on a central portion of the substrate. The etchant spreads from the central portion of the substrate toward an edge portion of the substrate by the rotation of the substrate. However, the temperature of the etchant may be lowered during the spreading, and thus, the etch rate may be decreased from the central portion of the substrate toward the edge portion of the substrate. Therefore, the thin layer on the substrate may not be uniformly removed. 
     SUMMARY 
     The embodiments of the present invention provide an apparatus for uniformly etching a thin layer on a substrate. 
     In accordance with an aspect of the present invention, an apparatus for etching a thin layer may include an etchant supply unit configured to supply an etchant onto a substrate to etch a thin layer formed on the substrate, a temperature measuring unit configured to measure a temperature of the substrate while an etching process is performed by the etchant, a laser irradiating unit configured to irradiate a first laser beam on a first portion including a central portion of the substrate and to irradiate a second laser beam in a ring shape on a second portion surrounding the first portion so that the temperature of the substrate is maintained at a predetermined temperature during the etching process, and a process control unit configured to control power of the first and second laser beams based on the temperature of the substrate measured by the temperature measuring unit to reduce a temperature difference between the first and second portions of the substrate. 
     In accordance with some embodiments of the present invention, the etchant supply unit may include an etchant supply nozzle configured to supply the etchant on the central portion of the substrate, a nozzle driving part configured to move the etchant supply nozzle in a horizontal direction, and an etchant heating part configured to heat the etchant at a predetermined temperature. 
     In accordance with some embodiments of the present invention, the laser irradiating unit may be disposed above the central portion of the substrate, and the etchant supply nozzle may be moved between the substrate and the laser irradiating unit by the nozzle driving part in the horizontal direction. 
     In accordance with some embodiments of the present invention, the etchant supply nozzle may be moved in the horizontal direction to be spaced apart from the substrate after the etchant is supplied in a predetermined amount on the central portion of the substrate. 
     In accordance with some embodiments of the present invention, the thin layer may include silicon nitride, and the etchant may include phosphoric acid and water. 
     In accordance with some embodiments of the present invention, the apparatus may further include a rotation driving unit configured to rotate the substrate. In such case, the etchant supply unit may supply the etchant in a predetermined amount on the central portion of the substrate, and the rotation driving unit may rotate the substrate so that the etchant spreads entirely on an upper surface of the substrate to form a liquid layer having a predetermined thickness. 
     In accordance with some embodiments of the present invention, the rotation driving unit may stop the rotation of the substrate so that the liquid layer is maintained by a surface tension. 
     In accordance with some embodiments of the present invention, the apparatus may further include a bowl unit configured to surround the substrate to collect the etchant. 
     In accordance with some embodiments of the present invention, the apparatus may further include a support unit configured to support the substrate, and the rotation driving unit may rotate the support unit. 
     In accordance with some embodiments of the present invention, the temperature measuring unit may include a thermal imaging camera disposed above the substrate. 
     In accordance with some embodiments of the present invention, the temperature measuring unit may include a plurality of infrared temperature sensors disposed under the substrate. 
     In accordance with some embodiments of the present invention, the apparatus may further include a support unit configured to support the substrate. In such case, the support unit may include a support head having a circular plate shape and support pins disposed on the support head to support edge portions of the substrate, and the infrared temperature sensors may be disposed on the support head. 
     In accordance with some embodiments of the present invention, the laser irradiating unit may include an adjustable ring mode (ARM) fiber laser device capable of controlling the power of the first and second laser beams. 
     In accordance with some embodiments of the present invention, the apparatus may further include an infrared heater configured to heat the substrate. 
     In accordance with some embodiments of the present invention, the temperature measuring unit may include a thermal imaging camera disposed above the substrate, and the infrared heater may be disposed under the substrate. 
     In accordance with some embodiments of the present invention, the apparatus may further include a support unit configured to support the substrate. In such case, the support unit may include a support head having a circular plate shape and support pins disposed on the support head to support edge portions of the substrate, and the infrared heater may include a plurality of infrared lamps disposed on the support head. 
     In accordance with some embodiments of the present invention, a plurality of recesses may be formed in upper surface portions of the support head, the infrared lamps may be disposed in the recesses, and a plurality of windows may be disposed above the infrared lamps to cover upper portions of the recesses. 
     In accordance with some embodiments of the present invention, the temperature measuring unit may include a plurality of infrared temperature sensors disposed under the substrate, and the infrared heater may be disposed above the substrate. In such case, the apparatus may further include a support unit configured to support the substrate. The support unit may include a support head having a circular plate shape and support pins disposed on the support head to support edge portions of the substrate, and the infrared temperature sensors may be disposed on the support head. 
     The above summary of the invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The detailed description and claims that follow more particularly exemplify these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention can be understood in more detail from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view illustrating an apparatus for etching a thin layer in accordance with an embodiment of the present invention; 
         FIG. 2  is a plan view illustrating an etchant supply unit as shown in  FIG. 1 ; 
         FIG. 3  is an image illustrating a first laser beam and a second laser beam irradiated from a laser irradiating unit as shown in  FIG. 1 ; and 
         FIG. 4  is a schematic view illustrating an apparatus for etching a thin layer in accordance with another embodiment of the present invention. 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. 
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present invention are described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below and is implemented in various other forms. Embodiments below are not provided to fully complete the present invention but rather are provided to fully convey the range of the present invention to those skilled in the art. 
     In the specification, when one component is referred to as being on or connected to another component or layer, it can be directly on or connected to the other component or layer, or an intervening component or layer may also be present. Unlike this, it will be understood that when one component is referred to as directly being on or directly connected to another component or layer, it means that no intervening component is present. Also, though terms like a first, a second, and a third are used to describe various regions and layers in various embodiments of the present invention, the regions and the layers are not limited to these terms. 
     Terminologies used below are used to merely describe specific embodiments, but do not limit the present invention. Additionally, unless otherwise defined here, all the terms including technical or scientific terms, may have the same meaning that is generally understood by those skilled in the art. 
     Embodiments of the present invention are described with reference to schematic drawings of ideal embodiments. Accordingly, changes in manufacturing methods and/or allowable errors may be expected from the forms of the drawings. Accordingly, embodiments of the present invention are not described being limited to the specific forms or areas in the drawings, and include the deviations of the forms. The areas may be entirely schematic, and their forms may not describe or depict accurate forms or structures in any given area, and are not intended to limit the scope of the present invention. 
       FIG. 1  is a schematic view illustrating an apparatus for etching a thin layer in accordance with an embodiment of the present invention, and  FIG. 2  is a plan view illustrating an etchant supply unit as shown in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , an apparatus  100  for etching a thin layer may be used to remove a thin layer  12  formed on a substrate  10  such as a silicon wafer during a semiconductor manufacturing process. For example, the thin layer  12  including silicon nitride (Si 3 N 4 ) may be formed on the substrate  10 , and the thin layer etching apparatus  100  may supply an etchant  20  including phosphoric acid (H 3 PO 4 ) and water (H 2 O) on the substrate  10 , and may remove the thin layer  12  using etching reaction between the thin layer  12  and the etchant  20 . 
     In accordance with an embodiment of the present invention, the thin layer etching apparatus  100  may include a process chamber  102 , in which an etching process for removing the thin layer  12  is performed, and a support unit  110  configured to support the substrate  10  and a rotation driving unit  120  configured to rotate the support unit  110  may be disposed in the process chamber  102 . 
     For example, the support unit  110  may include a support head  112  having a circular plate shape and a plurality of support pins  114  disposed on the support head  112  to support edge portions of the substrate  10 . The support pins  114  may be arranged in a circular ring shape to support the edge portions of the substrate  10 . A plurality of support members  116  configured to support side portions of the substrate  10  may be respectively disposed on the support pins  114  during the rotation of the substrate  10 . The rotation driving unit  120  may include a rotation driving part  122  disposed under the support head  112  and including a motor for providing a rotational force and a rotating shaft  124  connecting the rotation driving part  122  to the support head  112 . 
     The thin layer etching apparatus  100  may include an etchant supply unit  130  configured to supply etchant  20  onto the substrate  10  to etch the thin layer  12 . For example, the etchant supply unit  130  may include an etchant supply nozzle  132  configured to supply the etchant  20  on a central portion of the substrate, a nozzle driving part  134  configured to move the etchant supply nozzle  132  in a horizontal direction, and an etchant heating part  136  configured to heat the etchant  20  at a predetermined temperature. 
     Meanwhile, the thin layer  12  including the silicon nitride may be removed by a chemical reaction between the silicon nitride and the etchant  20  including phosphoric acid and water. Reaction formula between the thin layer  12  and the etchant  20  is as follows. 
       3Si 3 N 4 +4H 3 PO 4 +27H 2 O→4(NH 4 ) 3 PO 4 +9H 2 SiO 3  
 
     In the above reaction, a reaction speed may be increased by a temperature of the etchant  20 , and the etchant heating part  136 , for example, may heat the etchant  20  at a temperature of about  150 ° C., which is lower than a boiling point of the etchant  20 , in order to increase an etch rate of the thin layer  12 . 
     In accordance with an embodiment of the present invention, the etching process on the thin layer  12  may be performed in a puddle method. In particular, the etchant supply unit  130  may supply the etchant  20  in a predetermined amount on a central portion of the substrate  10 , and the rotation driving unit  120  may rotate the substrate  10  at a low speed to entirely spread the etchant  20  on an upper surface of the substrate  10  to form a liquid layer having a predetermined thickness thereon. That is, the etchant  20  supplied on the substrate  10  may spread from the central portion of the substrate  10  toward an edge portion of the substrate  10  by a centrifugal force, and the rotation driving unit  120  may stop the rotation of the substrate  10  after the etchant  20  sufficiently spreads towards the edge portion of the substrate  10 . The liquid layer may be maintained by a surface tension of the etchant  20 , and the etching process on the thin layer  12  may be performed for a predetermined time after the liquid layer is formed. 
     The temperature of the etchant  20  may be changed during the etchant  20  supplied on the substrate  10  spreads from the central portion of the substrate  10  toward the edge portion of the substrate  10 , and the etch rate of the thin layer  12  may thus be different for each portion of the substrate  10 . In accordance with an embodiment of the present invention, in order to solve the above described problem, the thin layer etching apparatus  100  may include a temperature measuring unit  140 , a laser irradiating unit  150 , and a process control unit  104 . The temperature measuring unit  140  is configured to measure the temperature of the substrate  10  during the etching process performed by the etchant  20 . In order to maintain the temperature of the substrate  10  at a predetermined temperature during the etching process, the laser irradiating unit  150  may irradiate a first laser beam  30  (shown in  FIG. 3 ) onto a first portion including the central portion of the substrate  10  and irradiate a second laser beam  32  (shown in  FIG. 3 ) having a ring shape onto a second portion surrounding the first portion. The process control unit  104  may control a power of the first laser beam  30  and a power of the second laser beam  32  based on the temperature measured by the temperature measuring unit  140  to reduce a temperature difference between the first and second portions of the substrate  10 . 
     For example, the temperature measuring unit  140  may include a thermal imaging camera  142  disposed above the substrate  10 , and the process control unit  104  may detect a temperature of the first portion of the substrate  10  and a temperature of the second portion surrounding the first portion from an image acquired by the thermal imaging camera  142 . 
     The laser irradiating unit  150  may be disposed above the central portion of the substrate  10 , and may provide the first laser beam  30  having a circular beam pattern corresponding to the first portion of the substrate  10  and a second laser beam  32  having a circular ring-shaped beam pattern corresponding to the second portion. For example, the laser irradiating unit  150  may include an adjustable ring mode (ARM) fiber laser device, which may control powers of the first laser beam  30  and the second laser beam  32 . 
       FIG. 3  is an image illustrating a first laser beam and a second laser beam irradiated from a laser irradiating unit as shown in  FIG. 1 . 
     Referring to  FIG. 3 , the process control unit  104  may control the power of the first laser beam  30  and the power of the second laser beam  32  based on the temperature of the substrate  10 . For example, the process control unit  104  may control the first laser beam  30  to have the same power as the second laser beam  32  as shown in  FIG. 3( a ) , or may selectively provide the first laser beam  30  or the second laser beam  32  as shown in  FIGS. 3( d ) and 3( e ) . Further, when the first portion and the second portion of the substrate  10  have different temperatures from each other, the second laser beam  32  may have a power greater than the first laser beam  30  as shown in  FIG. 3( b ) , or the first laser beam  30  may have a power greater than the second laser beam  32  as shown in  FIG. 3( c ) . 
     As described above, the power of the first laser beam  30  and the power of the second laser beam  32  are controlled based on the temperature of the first and second portions of the substrate  10 , and thus the temperature of the substrate  10  may be uniformly controlled at a predetermined temperature. Thus, the etch rate of the thin layer  12  may be uniformly controlled at the entire of the substrate  10 . 
     Referring again to  FIGS. 1 and 2 , the etchant supply nozzle  132  may be disposed under the laser irradiating unit  150 . That is, the etchant supply nozzle  132  may be moved in a horizontal direction between the substrate  10  and the laser irradiating unit  150  by the nozzle driving part  134 . For example, the nozzle driving part  134  may be connected to the etchant supply nozzle  132  through a nozzle arm  138 , and may rotate the nozzle arm  138  so that the etchant supply nozzle  132  is disposed above the central portion of the substrate. Also, the nozzle driving part  134  may rotate the nozzle arm  138  so that the etchant supply nozzle  132  is spaced apart from the substrate  10  after the etchant  20  is supplied on the substrate  10 . 
     In accordance with an embodiment of the present invention, the thin layer etching apparatus  100  may include a bowl unit  160  configured to surround the substrate  10  to collect the etchant  20 . For example, in order to remove reaction by-products and remaining etchant from the substrate  10  after the etching process, the rotation driving unit  120  may rotate the substrate  10  at a high speed, and the reaction by-products and the remaining etchant may be removed from the substrate  10 . The reaction by-products and the remaining etchant removed from the substrate  10  may be collected by the bowl unit  160 , and may be discharged through a discharge pipe (not shown) connected to the bowl unit  160 . 
     As shown in  FIG. 1 , the bowl unit  160  includes one bowl. However, as another example, the bowl unit  160  may include a plurality of bowls. For example, after the etching process is performed, a rinsing process for removing etch residues from the substrate  10  and a drying process for drying the substrate  10  may be performed. Also, the bowl unit  160  may further include a second bowl (not shown) configured to collect a rinsing liquid such as deionized water used for the rinsing process and a third bowl (not shown) configured to collect a drying liquid such as isopropyl alcohol used for the drying process. Also, although not shown in the figures, the thin layer etching apparatus  100  may further include a rinsing liquid supply unit configured to supply the rinsing liquid and a drying liquid supply unit configured to supply the drying liquid. 
     Meanwhile, in accordance with an embodiment of the present invention, the thin layer etching apparatus  100  may include an infrared heater  170  configured to heat the substrate  10  at a predetermined temperature. The infrared heater  170  may be disposed under the substrate  10  and may include a plurality of infrared lamps  172  disposed on the support head  112 . For example, the infrared heater  170  may include a plurality of infrared lamps  172  disposed in the support head  112 , and the support head  112  may include a plurality of quartz windows  174  configured to transmit infrared lights irradiated from the infrared lamps  172  towards a lower surface of the substrate  10 . Specifically, a plurality of recesses may be formed in upper surface portions of the support head  112 , and the infrared lamps  172  may be disposed in the recesses. In such case, the quartz windows  174  may be disposed above the infrared lamps  172  to cover upper portions of the recesses. 
       FIG. 4  is a schematic view illustrating an apparatus for etching a thin layer in accordance with another embodiment of the present invention. 
     Referring to  FIG. 4 , the thin layer etching apparatus  100  may include an infrared heater  180  configured to heat a substrate  10  and a temperature measuring unit  190  configured to measure the temperature of the substrate  10 . For example, the infrared heater  180  may include a plurality of infrared lamps  182  disposed above the substrate  10 , and the temperature measuring unit  190  may include a plurality of infrared temperature sensors  192  disposed under the substrate  10 , for example, on the support head  112 . 
     In accordance with the embodiments of the present invention as described above, the temperature of the first portion of the substrate  10  and the etchant  20  disposed thereon and the temperature of the second portion of the substrate  10  and the etchant  20  disposed thereon may be changed while supplying the etchant  20  on the substrate  10 . The difference between the temperature of the first portion and the temperature of the second portion may be reduced by the power control of the first laser beam  30  and the second laser beam  32 . 
     In particular, when the temperature of the second portion is lower than the temperature of the first portion, the power of the second laser beam  32  may be controlled to be greater than the power of the first laser beam  30 , and thus, the temperature of the substrate  10  and the etchant  20  may be uniformed. Further, when the temperature of the substrate  10  heated by the infrared heater  170  is higher than the temperature of the etchant  20 , the temperature of the first portion may be lower than the temperature of the second portion. In such case, the power of the first laser beam  30  may be controlled to be greater than the power of the second laser beam  32 , and thus, the temperature of the substrate  10  and the etchant  20  may be uniformed. As a result, the temperature of the entire substrate  10  and the etchant  20  may be uniformed, and the etch rate of the thin layer  12  may thus be uniformed. 
     Although the thin layer etching apparatus  100  has been described with reference to specific embodiments, it is not limited thereto. Therefore, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the present invention defined by the appended claims.