Patent Publication Number: US-2006016561-A1

Title: Semiconductor etching apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims priority under 35 U.S.C. §119 from Korean Patent Application 2004-56176, filed on Jul. 20, 2004, the contents of which are hereby incorporated by reference in their entirety for all purposes as if fully set forth herein.  
     BACKGROUND AND SUMMARY  
      1. Technical Field  
      The present invention relates to a semiconductor etching apparatus capable of performing an entirely uniform etching on a wafer by controlling an etching rate on an edge of wafer and a flow of reactive gas.  
      2. Description  
      An etching technology to manufacture semiconductor devices is generally used to form a desired pattern from layer material formed on a semiconductor substrate, and an etching apparatus is needed for such a process.  
      In particular, an etching apparatus to form a pattern may be a plasma etching apparatus or dry etching apparatus, and such an etching apparatus is mainly used for a technology requiring a design rule under 0.15 μm.  
       FIG. 1  illustrates a dry etching apparatus. Referring to  FIG. 1 , a process chamber  10  includes an electrostatic chuck  11  on which a wafer W is mounted. A lower electrode  12  is provided below electrostatic chuck  11 . An upper electrode  13  is provided at a predetermined distance above electrostatic chuck  11 .  
      Reactive gas is supplied to the process chamber from above, or from a side of, process chamber  10  where upper electrode  13  is provided.  
      Under a state where wafer W is stably mounted on electrostatic chuck  11  of process chamber  10 , reactive gas is supplied into the process chamber, and also an RF bias is applied to lower electrode  12  and upper electrode  13 . Accordingly, plasma is generated on wafer W and this plasma collides with layer material of wafer W, performing an etching.  
      In the etching process of wafer W using plasma, an outer side or edge of the wafer W provided on electrostatic chuck  11  is surrounded by a focus ring  14  that is also generally referred to as a top ring, so that plasma can be concentrated and collected onto wafer W.  
      The most important issue in such an etching process is the uniformity of wafer etching.  
      Plasma generated by a supply of reactive gas and an applied RF bias is generally formed in an oval shape on the wafer W, and the vertical movement of the plasma ions colliding with the wafer W is satisfactory in the center of the wafer, but the collision angle becomes gradually more acute toward the edge of the wafer W, as shown in  FIG. 2  illustrating the collision of plasma on such an edge portion.  
      With reference to  FIG. 2 , an upper surface of electrostatic chuck  11  onto which wafer W is mounted has an outer diameter smaller than an outer diameter of wafer W, and is recessed toward the inside of electrostatic chuck  11  so as to have a stepped shape.  
      An edge ring  15 , formed of the same material as wafer W, is equipped within the stepped portion of electrostatic chuck  11 , and supports an edge surface of wafer W from beneath, together with electrostatic chuck  11 .  
      Focus ring  14  is provided outside of edge ring  15 . Focus ring  14  and edge ring  15  are mounted on a shadow ring  16  that is mounted at an outer circumference of an upper surface of lower electrode  12 .  
      However, plasma distributed in an oval shape on wafer W becomes slow and has an acute collision angle, particularly on an edge of wafer W, which causes the wafer W to have a slanted etching pattern as shown in  FIG. 3  and simultaneously not to be etched to a required depth, thus causing a lot of pattern defects, such as unopened trenches or holes, on an edge portion of wafer W.  
      Such defects lower the production yield of semiconductor devices and reduce the productivity and reliability of the resultant devices.  
      Accordingly, it would be desirable to provide a semiconductor etching apparatus exhibiting improved vertical collision characteristics of plasma ions on the edge of the wafer to produce a uniform etching rate on an entire surface of wafer. Furthermore, it would be desirable if the edge ring of the apparatus could be used when “flipped over,” thereby extending its useful life.  
      According to one aspect of the invention, a semiconductor etching apparatus includes an electrostatic chuck, an edge ring member and a spacer within a process chamber. A circumferal area of a top portion of the electrostatic chuck is recessed by a fixed distance down to a fixed depth to form a stepped-down ring mounting part. The edge ring member has an outer part and an inner part in one body. The outer part has a thickness greater than a height of a vertical surface of the ring mounting part of the electrostatic chuck, and the inner part is projected inwardly from an inner diameter surface of the outer part so as to be proximate to the vertical surface of the ring mounting part. An upper surface and a lower surface of the inner part are stepped upward and downward, respectively, by a same height from inner diameter upper and lower surfaces of the outer part. The spacer member has a ring shape, is disposed on a horizontal surface of the ring mounting part of the electrostatic chuck, is adapted to support a lower surface of the inner part of the edge ring member, and has a thickness that is the same as the height between the lower surface of the outer part and the upper surface of the inner part of the edge ring member.  
      According to another aspect of the invention, the formation range of plasma formed on an upper surface of a wafer is extended through the edge ring member and the spacer member for extending an area outwardly, and simultaneously an electric field or magnetic field is in contact with such plasma, thereby accelerating a collision speed of plasma ions colliding with the wafer, at least at an edge of the wafer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
       FIG. 1  is a sectional view illustrating a side section part of a conventional etching apparatus;  
       FIG. 2  is an enlarged sectional view partially illustrating a collision state of plasma ions on an edge of a wafer in a conventional etching apparatus;  
       FIG. 3  is an enlarged sectional view partially illustrating a pattern defect example on an edge of a wafer in a conventional etching apparatus;  
       FIG. 4  is a sectional view of main components of a semiconductor etching apparatus according to a first exemplary embodiment;  
       FIG. 5  is a sectional view illustrating a separation state of the main components of  FIG. 4  according to a first exemplary embodiment;  
       FIG. 6  is a perspective view illustrating half sections of separated edge ring member and spacer member according to a first exemplary embodiment;  
       FIG. 7  is a sectional view illustrating a side section according to a second exemplary embodiment;  
       FIG. 8  is a plan view illustrating an installation structure of an electromagnet member according to a second exemplary embodiment;  
       FIG. 9  is a sectional view illustrating a side section according to a third exemplary embodiment;  
       FIG. 10  is a plan view illustrating an installation structure of a magnet member according to a third exemplary embodiment;  
       FIG. 11  is a perspective view according to a fourth exemplary embodiment; and  
       FIG. 12  is a sectional view illustrating a side part according to a fourth exemplary embodiment. 
    
    
     DETAILED DESCRIPTION  
      Hereinafter, exemplary embodiments will be described in detail with reference to FIGS.  4  to  12 . It will be understood by those skilled in the art that the present invention can be embodied in numerous different forms, and is not limited to the following described embodiments. The following various embodiments are exemplary in nature.  
      [First Exemplary Embodiment] 
       FIG. 4  is a sectional view of main components of a semiconductor etching apparatus according to a first exemplary embodiment.  FIG. 5  denotes an enlarged sectional view illustrating a separation state of the main components of  FIG. 4 , and  FIG. 6  designates a perspective view of an edge ring member and spacer member shown in  FIGS. 4 and 5 .  
      As shown in the drawings, according to a first exemplary embodiment, a circumferal area of an upper portion of an electrostatic chuck  110  on which a wafer is mounted is recessed by a fixed distance toward an inside thereof down to a predetermined depth to form a stepped-down ring mounting part  111 . The circumferal area of the upper portion of the electrostatic chuck  110  is understood to mean the area at the outer circumference of the electrostatic chuck  110  near its top surface. That is, as shown in  FIG. 4 , the outer circumference of the very top surface of the electrostatic chuck  110 , defined by the vertical surface  112 , is less than the circumference of the stepped-down base portion  113  of the ring mounting part  111 , defined by the vertical surface  119 .  
      In this arrangement, an upper surface of electrostatic chuck  110  is smaller than a diameter of a wafer W mounted on electrostatic chuck  110 .  
      An edge ring member  120  is provided at ring mounting part  111  so as to prevent etching of an edge of electrostatic chuck  110 . More particularly, edge ring member  120  and a spacer member  130  are mounted on base portion (horizontal surface)  113  of ring mounting part  111  formed at the circumferal area of the upper portion of electrostatic chuck  110 . Edge ring member  120  has a configuration where an outer part  121  and an inner part  122 , each being ring-shaped and having mutually different thicknesses, are connected in one body. Beneficially, edge ring member  120  comprises a same material as wafer W. Spacer member  130  supports side and lower surfaces of inner part  122  of edge ring member  120  so that edge ring member  120  always maintains a predetermined height.  
      Outer part  121  of edge ring member  120  has a thickness that is greater than a height of a vertical surface  112  of ring mounting part  111  formed at the circumferal area of the upper surface of electrostatic chuck  110 . An inner diameter of outer part  121  is equal to or greater than an inner diameter of ring mounting part  111 . Inner part  122  of edge ring member  120  is formed being projected inwardly from an inner diameter surface of outer part  121  so as to be proximate to vertical surface  112  of ring mounting part  111 . An upper surface and a lower surface of inner part  122  are stepped downward and upward, respectively, by the same height from inner diameter upper and lower surfaces of outer part  121 .  
      In other words, in forming outer part  121  and inner part  122  of edge ring member  120 , a predetermined length is extended inwardly from an inner diameter surface of outer part  121 , and a thickness of the formed length is reduced both downward and upward by an equal height from an upper surface and a lower surface of outer part  121 , respectively, and thus inner part  122  is formed with a reduced thickness. That is, a height between an upper surface of outer part  121  of edge ring member  120  and an upper surface of inner part  122  is equal to a height between a lower surface of outer part  121  and a lower surface of inner part  122 .  
      Furthermore, the height from a lower surface of outer part  121  to an upper surface of inner part  122  is the same as the height of vertical surface  112  of ring mounting part  111 . Also, inner part  122  of edge ring member  120  has such a diameter that an inner diameter surface of inner part  122  is proximate to and almost in contact with vertical surface  112  of ring mounting part  111  of electrostatic chuck  110 .  
      In edge ring member  120 , beneficially a width of outer part  121  is between 8.0˜14.0 mm and a width of inner part  122  is between 0.5˜2.5 mm.  
      In inner part  122  of the edge ring member  120 , the upper surface and the lower surface are processed to have a mirror-like finish, and in outer part  121 , the upper surface and the lower surface are processed roughly by a lapping process.  
      Meanwhile, spacer member  130 , provided at the lower surface of the inner part  122  of the edge ring member  120 , has a thickness corresponding to a stepped height between outer part  121  and inner part  122  of edge ring member  120 , and has a flat bottom so as to be mounted on base portion  113  of ring mounting part  111  of the electrostatic chuck  110 .  
      Spacer member  130  is formed in such a size that an inner diameter surface can become proximate to vertical surface  112  of the ring mounting part  111  of electrostatic chuck  110 , and beneficially a width of the spacer member  130  may be in a range from 0.2˜2.5 mm.  
      A focus ring  140  is provided outside of edge ring member  120 . Focus ring  140  and edge ring member  120  are mounted on a shadow ring  150  that is mounted at an outer circumference of electrostatic chuck  110  at a portion beneath the ring mounting part  111 .  
      [Second Exemplary Embodiment] 
       FIGS. 7 and 8  illustrate a second exemplary embodiment, and in the following described exemplary embodiments, like reference symbols are used for like components.  
      As in the first exemplary embodiment, a circumferal area of an upper portion of an electrostatic chuck  110  on which a wafer is mounted is recessed by a fixed distance toward an inside thereof down to a predetermined depth to form a stepped-down ring mounting part  111 . That is, as shown in  FIG. 4 , the outer circumference of the very top surface of the electrostatic chuck  110 , defined by the vertical surface  112 , is less than the circumference of the stepped-down base portion  113  of the ring mounting part  111 , defined by the vertical surface  119 .  
      In this arrangement, an upper surface of electrostatic chuck  110  is smaller than a diameter of a wafer W mounted on electrostatic chuck  110 .  
      Edge ring member  120  is provided on ring mounting part  111  so as to prevent etching of an edge of electrostatic chuck  110 . More particularly, an edge ring constructed of edge ring member  120  and spacer member  130  are mounted in ring mounting part  111  formed at a circumferal area of the upper surface of electrostatic chuck  110 , and such a configuration is the same as the above-described first exemplary embodiment.  
      That is, edge ring member  120  has a configuration wherein outer part  121  and inner part  122 , each being ring-shaped and having mutually different thicknesses, are connected in one body, and spacer member  130  supports side and lower surfaces of inner part  122  of edge ring member  120  so that edge ring member  120  always maintains a predetermined height.  
      Outer part  121  of the edge ring member  120  has a thickness that is greater than a height of vertical face  112  of ring mounting part  111  formed at the circumferal area of the upper portion of electrostatic chuck  110 . An inner diameter of the outer part  121  is equal to or larger than an inner diameter of ring mounting part  111 . Inner part  122  of edge ring member  120  is formed being projected inwardly from an inner diameter surface of outer part  121  so as to be proximate to vertical surface  112  of ring mounting part  111 . An upper part and a lower part of inner part  122  are stepped upward and downward, respectively, by the same height from inner diameter upper and lower surfaces of the outer part  121 . In other words, the height between the upper surface of outer part  121  and the upper surface of inner part  122  of edge ring member  120  is equal to the height between a lower surface of outer part  121  and a lower surface of inner part  122 .  
      Furthermore, the height from a lower surface of the outer part  121  to an upper surface of the inner part  122  is equal to the height of the vertical surface  112  of the ring mounting part  111 . Also, inner part  122  of edge ring member  120  has such a diameter that an inner diameter surface of inner part  122  is proximate to and almost in contact with vertical surface  112  of ring mounting part  111  of electrostatic chuck  110 .  
      Beneficially, the width of outer part  121  of edge ring member  120  is between 8.0˜14.0 mm, and the width of inner part  122  is between 0.5˜2.5 mm.  
      An upper surface and a lower surface of inner part  122  of edge ring member  120  are processed to have a mirror-like finish, and an upper surface and a lower surface of outer part  121  are processed roughly by a lapping process.  
      Meanwhile, pacer member  130  is formed as a flat plate to be mounted on a horizontal surface of ring mounting part  111  in electrostatic chuck  110 , with a thickness corresponding to the height of a step between outer part  121  and inner part  122  of edge ring member  120 . In spacer member  130 , an inner diameter surface is formed having a size sufficient to be proximate to vertical surface  112  of the electrostatic chuck  110 . Beneficially, spacer member  130  may have a width of 0.2˜2.5 mm.  
      A focus ring  140  is provided outside of edge ring member  120 . Focus ring  140  and edge ring member  120  are mounted on a shadow ring  150  that is mounted at an outer circumference of electrostatic chuck  110  at a portion beneath the ring mounting part  111 .  
      The configuration of the edge ring member  120  and the spacer member  130  provided at the ring mounting part  111  of the electrostatic chuck  110  is the same as that of the first exemplary embodiment. However, the second exemplary embodiment includes an electromagnet member  200  provided in particular on an upper outer wall of process chamber  100 , where electromagnet member  200  is formed by winding a conductive coil around a ring-shaped core of magnetic material (e.g., iron).  
      As shown in  FIG. 8 , electromagnet member  200  is obtained by winding an electromagnetic coil  210  having a ring-shaped iron core shape several times, and is provided in a shape surrounding an outer surface of process chamber  100 . Electromagnet member  200  is fixed to an outer wall of process chamber  100  at a position higher than the plasma formation height in process chamber  100 .  
      When a power source is applied to such electromagnet member  200  so that current flows in the direction indicated by the arrows in the drawing, the electric field has a downward direction according to the Faraday principle, thus the collision speed of plasma ions formed on wafer W is increased.  
      At this time, plasma ions are accelerated and so an etching characteristic is improved not only in the center but also at an edge of wafer W.  
      In other words, the plasma formation range is further increased by edge ring member  120 , and also an electric field is in contact with plasma so that plasma is accelerated toward a wafer, thereby an etching having a sufficient vertical depth can be performed in particular on the edge of wafer W.  
      [Third Exemplary Embodiment] 
       FIGS. 9 and 10  illustrate the configuration of a third exemplary embodiment of the invention.  
      Beneficially, electrostatic chuck  110 , ring mounting part, vertical surface  112 , edge ring member  120  (including outer part  121  and inner part  122 ), spacer member  130 , focus ring  140 , and shadow ring  150  have the same configurations and characteristics as described above in detail with respect to the first and second exemplary embodiments. Accordingly, a detailed discussion of these elements will not be repeated again here.  
      However, in the third exemplary embodiment, a plurality of magnet members  300  are provided along an upper portion of an outer wall of process chamber  100  at a position higher than a plasma formation area.  
      Here, each magnet member  300  is formed of mutually corresponding N and S poles. The magnet members  300  are arrayed in the same sequence along an outer wall of the process chamber  100  so that the N pole of each magnet is disposed closer to the S pole, than the N pole, of the preceding magnet as one proceeds circumferentially along the outer wall of process chamber  100 .  
      A magnetic force having a downward direction is formed by a magnetic field generated between the N and S poles, and this magnetic force is contacted with the plasma in process chamber  100 . Accordingly, the magnet members  300  are provided to accelerate plasma ions toward wafer W according to the Faraday principle, in similarity to the second exemplary embodiment.  
      At this time, the magnetic field formed on a peripheral portion of the outer wall of process chamber  100  is greater than the magnetic field formed in a center of process chamber  100 . Thus, the plasma on an edge of wafer W can be made to be more vertically aligned than in the example shown in  FIG. 2  above.  
      Furthermore, a formation range of the plasma is extended further by edge ring member  120 , and when the magnetic field is in contact with the plasma, plasma ions are accelerated toward the wafer W so as to perform an etching having a vertical profile and sufficient depth.  
      Meanwhile, a primary magnetic field is formed in each magnet member  300  due to its N pole and S pole, but a parasitic magnetic field also may be formed due to the effects of adjacent magnet members  300 . The magnetic field formed in a particular magnet member  300  due to adjacent magnet members  300  has a direction opposite to the primary magnetic field formed in the particular magnet member  300  itself. Thus it may be most desirous to make the magnet members  300  have a distance great enough to reduce or eliminate the influence of the magnetic field formed in adjacent magnet members  300 .  
      [Fourth Exemplary Embodiment] 
       FIGS. 11 and 12  illustrate the configuration of a fourth exemplary embodiment.  
      Beneficially, electrostatic chuck  110 , ring mounting part, vertical surface  112 , edge ring member  120  (including outer part  121  and inner part  122 ), spacer member  130 , focus ring  140 , and shadow ring  150  have the same configurations and characteristics as described above in detail with respect to the first and second exemplary embodiments. Accordingly, a detailed discussion of these elements will not be repeated again here.  
      However, the fourth exemplary embodiment includes a plurality of electromagnet members  400  having a rectangular shape provided along an outer wall of process chamber  100  centering on a plasma formation area.  
      Electromagnet member  400  is formed by winding an electromagnetic coil onto an iron core of a rectangular ring shape, and such electromagnet members  400  are equipped along an outer wall of process chamber  100  so that a middle height portion of the electromagnet member  400  is positioned at a plasma formation area of the process chamber  100 .  
      When a power source is applied to the electromagnet member  400  of rectangular shape, an electric field is in contact with the outer side of the plasma through the electromagnet member  400 , and plasma ions are accelerated toward wafer W.  
      That is, when plasma ions are accelerated and collide with wafer W at an edge of wafer W, the verticality of the etched pattern is improved and the pattern can be formed to a sufficient depth.  
      According to exemplary embodiments described above, a structural improvement of an edge ring can extend a formation range of plasma formed on a wafer W such that a collision angle of plasma on an edge of wafer W has an almost vertical property, to thereby in turn improve the verticality of an etched pattern and simultaneously accelerate a collision speed of plasma at least at an edge of wafer thereby obtaining a sufficient etching to a depth required for the vertical property to prevent an error, such as a non-opening problem.  
      As described above, according to exemplary embodiments, an edge ring member formed of the same material as wafer W is extended further to the outside of the wafer, thus a formation range of plasma formed on the wafer W is also extended, to thereby increase the verticality of the collision angle through plasma ions and to simultaneously accelerate a collision speed of plasma ions at least at an edge of wafer W by a contact between a downward electric field or magnetic field and plasma ions. Accordingly, the verticality of the pattern formed at an edge of wafer W is improved, and at the same time, the etching can be performed to a required depth with a precise pattern.  
      Accordingly, an entirely uniform etching efficiency on a wafer W is obtained and productivity increases, enhancing reliability for products with economical advantages.  
      It will be apparent to those skilled in the art that modifications and variations can be made in the present invention without deviating from the spirit or scope of the invention. Thus, it is intended that the present invention cover any such modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Accordingly, these and other changes and modifications are seen to be within the true scope of the invention as defined by the appended claims.