Patent Publication Number: US-2017352574-A1

Title: Apparatus and method for treating wafer

Description:
BACKGROUND 
     Atomic layer etching (ALE) is an etching technique in semiconductor manufacture. ALE uses a sequence alternating between self-limiting chemical modification steps which affect the top atomic layers of the wafer, and etching steps which remove the chemically-modified areas, to allow the removal of individual atomic layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a schematic view of an apparatus in accordance with some embodiments of the present disclosure. 
         FIG. 2  is an enlarged sectional view of a portion of the wafer of  FIG. 1 . 
         FIG. 3  is a schematic view of an apparatus in accordance with some other embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     Reference is made to  FIG. 1 .  FIG. 1  is a schematic view of an apparatus  100  in accordance with some embodiments of the present disclosure. As shown in  FIG. 1 , the apparatus  100  for treating a wafer  200  is provided. The apparatus  100  includes a platen  110 , a chamber  120 , an etch gas supplier  130 , and a tilting mechanism  140 . The chamber  120  has at least one aperture  121 . The aperture  121  at least partially faces to the platen  110 . The platen  110  is configured to hold the wafer  200 , such that the wafer  200  at least partially faces to the aperture  121  of the chamber  120 . The etch gas supplier  130  is fluidly connected to the chamber  120 . The tilting mechanism  140  is coupled with the platen  110  for allowing the platen  110  to have at least one first degree of freedom to tilt relative to the aperture  121  of the chamber  120 . 
     In other words, the angle of the platen  110  relative to the aperture  121  of the chamber  120  is able to be adjusted by the tilting mechanism  140 . As shown in  FIG. 1 , the direction DA of the aperture  121  pointing towards the platen  110  forms an angle θ with the direction of the normal of the platen  110 . Since the wafer  200  is held by the platen  100 , the angle of the normal of the wafer  200  relative to the direction DA of the aperture  121  pointing towards the platen  110  is able to be adjusted by the tilting mechanism  140 . For example, in some embodiments, the wafer  200  is tilted by the angle θ relative to the direction DA of the aperture  121  pointing towards the platen  110 . In practical applications, the angle θ can be positive or negative. 
       FIG. 2  is an enlarged sectional view of a portion of the wafer  200  of  FIG. 1 . As shown in  FIGS. 1 and 2 , the direction DA of the aperture  121  pointing towards the platen  110  forms the angle θ with the direction of the normal of the wafer  200 . Moreover, the material  300  on the surface of the wafer  200  includes a surface portion  301  and side portions  302   a  and  302   b . The surface portion  301  connects the side portions  302   a  and  302   b . The surface portion  301  is substantially perpendicular to the normal of the wafer  200 , while the side portions  302   a  and  302   b  are substantially parallel with the normal of the wafer  200 . Practically, the surface portion  301  and the side portions  302   a  and  302   b  at least partially cover a protruding portion  201  of the wafer  200 , such as a semiconductor fin. 
     During the operation of the apparatus  100 , the etch gas supplier  130  supplies an etch gas into the chamber  110 . For instance, the etch gas can be an inert gas, such as argon or neon. The etch gas is ionized in the chamber  110 . Then, the ionized etch gas is directed through the aperture  121  of the chamber  110  and reaches the material  300  on the surface of the wafer  200 . The material  300  can be removed by bombardment with the ionized etch gas. 
     As mentioned above, the material  300  includes the surface portion  301  and the side portions  302   a  and  302   b . Since the wafer  200  is tilted by the angle θ relative to the direction DA of the aperture  121  pointing towards the platen  110 , both the surface portion  301  and the side portion  302   a  can be reached by the ionized etch gas. This means removal of both the surface portion  301  and the side portion  302   a  can be carried out accordingly. In this way, etching of the material  300  on the wafer  200  can be carried out by the apparatus  100  in a three-dimensional manner. 
     To be more specific, the side portion  302   a  forms a projected area P towards the aperture  121  of the chamber  120 . The size of the projected area P is related to the magnitude of the angle θ. In other words, the more the platen  110  is tilted by the tilting mechanism  140 , the larger the size of the projected area P of the side portion  302   a  will be. With a larger projected area P of the side portion  302   a  towards the aperture  121  of the chamber  120 , the side portion  302   a  is exposed to the ionized etch gas more readily, and the effectiveness of the etching of the side portion  302   a  of the material  300  by the ionized etch gas is correspondingly increased. 
     In addition, as shown in  FIGS. 1 and 2 , the apparatus  100  further includes a rotating mechanism  150 . The rotating mechanism  150  is coupled with the platen  110  for allowing the platen  110  to have at least one second degree of freedom to rotate relative to the aperture  121  of the chamber  120  either clockwise or anti-clockwise. To be more specific, during the operation of the apparatus  100 , the platen  110  is rotated about the normal of the platen  110  by the rotating mechanism  150 . In this way, the side portions  302   a  and  302   b  of the material  300  covering around the protruding portion  201  of the wafer  200  can be exposed to the ionized etch gas alternately. For instance, when the side portion  302   a  is at least partially exposed to the ionized etch gas, the side portion  302   b  on the other side of the protruding portion  201  is blocked from the ionized etch gas by the protruding portion  201 . However, after the platen  110  and thus the wafer  200  is rotated by the rotating mechanism  150  either clockwise or anti-clockwise, the side portion  302   b  on the other side of the protruding portion  201  will be turned and exposed to the ionized etch gas instead. As a result, etching of the side portion  302   b  can be carried out. Therefore, the side portions  302   a  and  302   b  of the material  300  covering around the protruding portion  201  of the wafer  200  can be exposed to the ionized etch gas alternately under the action of the rotating mechanism  150 . 
     In order to ionize the etch gas, the apparatus  100  includes at least one radio frequency generator  170 . As shown in  FIG. 1 , the radio frequency generator  170  is disposed at an end of the chamber  120  away from the aperture  121  and is coupled with the chamber  120 . In practical applications, the radio frequency generator  170  includes a radio frequency coil. When the etch gas supplier  130  supplies the etch gas into the chamber  110 , the radio frequency generator  170  operates to energize the etch gas. In this way, the etch gas is energized to form a plasma. The plasma is in fact a mixture of the etch gas ions and electrons. The etch gas in the form of plasma can remove the material  300  on the wafer  200  more readily. In some embodiments, the plasma can be inductively coupled plasma (ICP). In some other embodiments, the plasma can be capacitively coupled plasma (CCP). 
     In addition, the apparatus  100  further includes at least a pair of magnets  180  with opposite poles. The pair of magnets  180  is coupled with the chamber  120 . As shown in  FIG. 1 , the aperture  121  is substantially located between the pair of magnets  180 . The pair of magnets  180  generates a magnetic field over the aperture  121  of the chamber  120 . After the etch gas is energized to become the form of plasma by the radio frequency generator  170  as mentioned above, the etch gas in the form of plasma is influenced by the magnetic field when the plasma is directed towards the aperture  121  of the chamber  120 . Since the plasma is in fact a mixture of the etch gas ions and electrons, at least the electrically charged ions will be affected by the magnetic field and become effectively diverse. Afterwards, the etch gas ions will be directed to the material  300  on the wafer  200  as an ion beam. 
     In some embodiments, as shown in  FIG. 1 , the apparatus  100  further includes at least one grid  190  and a power supply  195 . In practical applications, the grid  190  at least partially covers the aperture  121  of the chamber  120 . The power supply  195  is configured to bias the grid  190  relative to the chamber  120 . During the operation of the apparatus  100 , the power supply  195  is turned on and thus the grid  190  becomes negatively charged while the chamber  120  positively charged. As a result, the positively charged ion beam of the etch gas will be accelerated towards the negatively charged grid  190 . Thus, the ion beam will be directed to bombard on the material  300  on the wafer  200  and remove the material  300  accordingly. 
     In some embodiments, the grid  190  may detachably cover the aperture  121  of the chamber  120 . In other words, in practical applications, when the grid  190  is detached optionally, the aperture  121  of the chamber  120  is fully opened. 
     In some embodiments, as shown in  FIG. 1 , the apparatus  100  further includes at least one linear motion mechanism  160 . In practice, the linear motion mechanism  160  is coupled with the platen  110  for allowing the platen  110  to have at least one third degree of freedom to move relative to the aperture  121  of the chamber  120 . To be more specific, the linear motion mechanism  160  is connected between the tilting mechanism  140  and the platen  110 . As shown in  FIG. 1 , the platen  110  is able to be moved linearly along at least a movement direction DM. In some embodiments, the movement direction DM is substantially perpendicular to the direction of the normal of the platen  110 . In this way, the wafer  200  held by the platen  110  can be moved linearly along the movement direction DM such that different portions of the wafer  200  can be exposed correspondingly to the aperture  121  of the chamber  120 . 
     On the other hand, the apparatus  100  further includes a reactive gas supplier  133  and a gas switch  138 . As shown in  FIG. 1 , the gas switch  138  fluidly connects the etch gas supplier  130 , the reactive gas supplier  133  and the chamber  120 . In practical applications, the reactive gas supplier  133  supplies a reactive gas into the chamber  110 . For instance, the reactive gas can be, for example, chlorine or fluorine. The reactive gas is then directed through the aperture  121  of the chamber  110  and reaches the wafer  200  to form, for example, an etch layer on the material  300 . The gas switch  138  is switchable between the fluid connection of the reactive gas supplier  133  with the chamber  120  and the fluid connection of the etch gas supplier  130  with the chamber  120 . In other words, when the reactive gas supplier  133  is fluidly connected with the chamber  120 , the etch gas supplier  130  and the chamber  120  will not be fluidly connected then. On the contrary, when the etch gas supplier  130  is fluidly connected with the chamber  120 , the reactive gas supplier  133  and the chamber  120  will not be fluidly connected then. As a result, formation of the etch layer and removal of the etch layer by the ionized etch gas can be carried out alternatively. That is, the apparatus  100  may perform atomic layer etching (ALE) or quasi-ALE on the material  300 , and the apparatus  100  may be, for example, an ALE or quasi-ALE tool. 
     To facilitate the operation of the apparatus  100 , in some embodiments, the apparatus  100  further includes a controller  175 . The controller  175  is configured to turn on the radio frequency generator  170  when the gas switch  138  is switched to fluidly connect the etch gas supplier  130  to the chamber  120  and turn off the radio frequency generator  170  when the gas switch  138  is switched to the fluid connection of the reactive gas supplier  133  with the chamber  120 . In this way, the radio frequency generator  170  functions when the etch gas supplier  130  is supplying the etch gas into the chamber  120  and is disabled when the reactive gas supplier  133  is supplying the reactive gas into the chamber  120 , making sure the proper operation of the apparatus  100 . 
     In a nutshell, the operation of the apparatus  100  comes as a repeated cycle with a sequence with at least the operations including the formation of the etch layer and the removal of the etch layer by the ionized etch gas. The formation of the etch layer may be performed in a temperature ranging from about 150 to about 400 degree Celsius and in a pressure ranging from about 0.1 to about 100 mT. The radio frequency generator  170  is turned off during the formation of the etch layer. The power supply  195  is turned off during the formation of the etch layer. The linear motion mechanism  160  is set static and the angle θ of the wafer  200  being tilted relative to the direction DA of the aperture  121  pointing towards the platen  110  is set to be substantially zero during the formation of the etch layer. 
     After the formation of the etch layer is completed, the removal of the etch layer by the ionized etch gas will then be in progress. The removal of the etch layer may be performed in a temperature ranging from about 50 to about 200 degree Celsius and in a pressure ranging from about 1 to about 100 mT. The radio frequency generator  170  is turned on to energize the etch gas during the removal of the etch layer. The power supply  195  is turned on such that the grid  190  is electrically charged during the removal of the etch layer. Meanwhile, both the linear motion mechanism  160  and the tilting mechanism  140  are set activated during the removal of the etch layer. 
     In addition, the apparatus  100  further includes a cleaning gas supplier  136 . Similarly, the gas switch  138  fluidly connects the etch gas supplier  130 , the reactive gas supplier  133 , the cleaning gas supplier  136  and the chamber  120 . In practical applications, the cleaning gas supplier  136  supplies a cleaning gas into the chamber  110  in order to perform an in-situ cleaning process after the atomic layer etching. For instance, the cleaning gas can be, for example, nitrogen trifluoride (NF3) or tetrafluoromethane (CF4). To be more specific, the gas switch  138  is switchable between the fluid connection of the reactive gas supplier  133  with the chamber  120 , the fluid connection of the etch gas supplier  130  with the chamber  120 , and the fluid connection of the cleaning gas supplier  136  with the chamber  120 . In other words, when the reactive gas supplier  133  is fluidly connected with the chamber  120 , the etch gas supplier  130 , the cleaning gas supplier  136  and the chamber  120  will not be fluidly connected then. On the contrary, when the etch gas supplier  130  is fluidly connected with the chamber  120 , the reactive gas supplier  133 , the cleaning gas supplier  136  and the chamber  120  will not be fluidly connected then. Eventually, when the cleaning gas supplier  136  is fluidly connected with the chamber  120 , the etch gas supplier  130 , the reactive gas supplier  133  and the chamber  120  will not be fluidly connected. 
     Reference is made to  FIG. 3 .  FIG. 3  is a schematic view of an apparatus  100  in accordance with some other embodiments of the present disclosure. As shown in  FIG. 3 , the apparatus  100  includes at least one outer grid  191  and at least one inner grid  192 . The inner grid  192  is disposed between the outer grid  191  and the chamber  120  and corresponds to the aperture  121  of the chamber  120 . The inner grid  192  is substantially parallel and aligned with the outer grid  191 . The power supply  195  is configured to bias the outer grid  191  relative to the inner grid  192 . During the operation of the apparatus  100 , the power supply  195  is turned on and thus the outer grid  191  becomes negatively charged while the inner grid  192  positively charged. As a result, the positively charged ion beam of the ionized etch gas will be accelerated towards the negatively charged outer grid  191  after the etchant precursor deposition. Thus, the ion beam will be directed to bombard on the material  300  on the wafer  200  and remove the material  300  accordingly. Furthermore, the diameter of the inner grid  192  is in a range from about 2 to about 6 cm. In this way, the ion beam of the ionized etch gas will be focused by the inner grid  192  to have an diameter ranging from about 2 to about 6 cm as well. This control of the diameter of the ion beam of the ionized etch gas ensures that the ion beam distribution through the inner grid  192  is uniform and well-focused. Thus, the influence of overlapping between the ion beams is alleviated and the etching coverage is correspondingly achieved. In other words, the chance of local non-uniformity is reduced, facilitating both the vertical and horizontal scan of the wafer  200  to optimize the removal uniformity of the material  300 . 
     With reference to the apparatus  100  as mentioned above, some embodiments of the present disclosure further provide a method for treating the wafer  200 . The method includes the following operations (it is appreciated that the sequence of the operations and the sub-operations as mentioned below, unless otherwise specified, all can be adjusted according to the actual situations, or even executed at the same time or partially at the same time): 
     (1) tilting the wafer  200  at the angle θ relative to the aperture  121  of the chamber  120 ; and 
     (2) performing an etching treatment on the tilted wafer  200 . 
     To be more specific, concerning the wafer  200  disposed with the protruding portion  201 , there exists at least a part of the surface of the protruding portion  201  projecting no area towards the aperture  121  of the chamber  120  before the wafer is tilted. However, after the wafer  200  is tilted at the angle θ relative to the aperture  121  of the chamber  120 , the surface of the protruding portion  201  of the wafer  200  projecting no area towards the aperture  121  before the wafer  200  is tilted will be exposed towards the aperture  121 . As a result, during the etching treatment, apart from the surface of the wafer  200  substantially facing the aperture  121  already before the wafer  200  is tilted, the surface of the wafer  200  projecting no area towards the aperture  121  before the wafer  200  is tilted also faces the aperture  121 . Therefore, after the wafer  200  is tilted at the angle θ relative to the aperture  121  of the chamber  120 , the etching treatment on the surface of the wafer  200  projecting no area towards the aperture  121  before the wafer  200  is tilted can be performed. In other words, the etching treatment on the tilted wafer  200  can be performed by the apparatus  100  in a three-dimensional manner. In practical applications, the angle θ can be positive or negative. 
     In order to perform the etching treatment on various portions of the wafer  200 , the method for treating the wafer  200  further includes the following operation: 
     (3) rotating the tilted wafer  200 . 
     In this way, after the tilted wafer  200  is rotated either clockwise or anti-clockwise, various portions of the wafer  200  are alternatively exposed towards the aperture  121  of the chamber  120 . For instance, a surface of the protruding portion  201  of the tilted wafer  200  originally located at the back of the protruding portion  201  will be exposed to the aperture  121  of the chamber  120  instead after the rotation of the tilted wafer  200 . As a result, the etch treatment on the tilted wafer  200  in the three-dimensional manner can be performed accordingly. 
     On the other hand, in order to facilitate scanning the wafer, the method for treating the wafer  200  further includes the following operation: 
     (4) moving the wafer  200  along at least one linear direction, i.e., the movement direction DM as mentioned above. 
     With the movement of the wafer  200  relative to the aperture  121  of the chamber  120 , different portions of the wafer  200  can be exposed correspondingly to the aperture  121  of the chamber  120 . Thus, the portion of the wafer  200  where the etching treatment is performed can be conveniently controlled. 
     In some embodiments, before the etching treatment, a surface of the wafer  200  is exposed to at least one reactive gas to form an etch layer on the surface of the wafer  200 , and the etching treatment removes the etch layer from the surface of the wafer. Therefore, the method for treating the wafer  200  further includes the following operation: 
     (5) exposing a surface of the wafer to at least one reactive gas to form an etch layer on the surface of the wafer. 
     That is, the method for treating the wafer  200  includes performing an atomic layer etching (ALE) or quasi-ALE process on the wafer  200 . Furthermore, in some embodiments, the operations of performing the etching treatment and exposing the surface of the wafer to the reactive gas are performed in the same process chamber where at least the platen  110  and the chamber  120  are contained. 
     According to various embodiments of the present disclosure, since the wafer can be tilted relative to the direction of the aperture pointing towards the platen by the tilting mechanism, both the surface portion and the side portion of the material on the wafer can be reached by the ionized etch gas. This means removal of both the surface portion and the side portion of the material can be carried out accordingly. In this way, atomic layer etching of the material on the wafer can be carried out by the apparatus in a three-dimensional manner. 
     According to various embodiments of the present disclosure, the apparatus for treating the wafer is provided. The apparatus includes the platen, the chamber, the etch gas supplier and the tilting mechanism. The chamber has the aperture at least partially facing towards the platen. The etch gas supplier is fluidly connected to the chamber. The tilting mechanism is coupled with the platen for allowing the platen to have the first degree of freedom to tilt relative to the aperture of the chamber. 
     According to various embodiments of the present disclosure, the apparatus for treating the wafer is provided. The apparatus includes the platen, the chamber, the etch gas supplier and the rotating mechanism. The chamber has the aperture at least partially facing towards the platen. The etch gas supplier is fluidly connected to the chamber. The rotating mechanism is coupled with the platen for allowing the platen to have at least two degree of rotational freedom. 
     According to various embodiments of the present disclosure, the method for treating the wafer is provided. The method includes tilting the wafer and performing the etching treatment on the tilted wafer. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.