Abstract:
A method for producing a semiconductor element comprises the steps of: forming a plurality of grooves on a first surface of a semiconductor multi-layer structure along a first direction: forming a plurality of multi-element bars by cleaving the semiconductor multi-layer structure along a second direction; placing at least one of the plurality of multi-element bars on a support stage; and cleaving the at least one of the plurality of multi-element bars along the plurality of grooves by moving a pressure member in a longitudinal direction of the at least one of the plurality of multi-element bars while a constant load is applied by the pressure member to a second surface of the at least one of the plurality of multi-element bars, the second surface being opposite a third surface corresponding to the first surface of the at least one of the plurality of multi-element bars.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for producing a semiconductor element and a cleavage apparatus for use in the method. 
     2. Description of the Related Art 
     A conventional method for producing a semiconductor element (e.g., a semiconductor laser element) will be described with reference to FIGS. 5A through 5C. Initially, a semiconductor multi-layer structure  11  is provided as a semiconductor wafer  1  by successively laminating a plurality of semiconductor layers including an active layer. A plurality of grooves  15  to be used for cleavage (hereinafter referred to as cleavage grooves) are provided on the front surface of the semiconductor multi-layer structure  11  along a longitudinal direction of the cavity of a semiconductor laser element (direction X in FIG.  5 A). The grooves  15  are evenly spaced and parallel to each other. The active layer is provided about 4 μm below the front surface of the semiconductor multi-layer structure  11 . 
     Thereafter, a stripe-patterned electrode  13  is provided on the entire front surface of the semiconductor multi-layer structure  11  excluding the cleavage grooves  15 . A back electrode  12  is provided on the entire back surface of the semiconductor multi-layer structure  11 . The wafer  1  is cut into rectangles. A plurality of short scratches are provided at an edge of the rectangular semiconductor multi-layer structure  11  along the longitudinal direction of the cavity of a semiconductor laser element (direction X). The scratches are evenly spaced as shown in FIG.  5 A. 
     Thereafter, the integral of the semiconductor multi-layer structure  11 , the patterned electrode  13 , and the back electrode  12  is cleaved (first cleavage) in a direction perpendicular to the cleavage grooves  15  provided between the stripes of the patterned electrode  13 , using the scratches  14  as starting points of cleavage. Thereby, a plurality of multi-element bars  16  are obtained. The multi-element bar  16  has the back electrode  12   a  on the entire back surface of he bar-shaped semiconductor multi-layer structure  11  and plurality of patterned electrodes  13  separated by the cleavage grooves  15  on the front surface of the bar-shaped semiconductor multi-layer structure  11  as shown in FIG.  5 B. 
     Thereafter, referring to FIG. 5C, each multi-element bar  16  is cleaved (second cleavage) along the cleavage grooves  15 , resulting in a plurality of semiconductor laser elements  17 . Each semiconductor laser element  17  has the patterned electrode  13  on the front surface of the semiconductor multi-layer structure  11  and the back electrode  12   a  on the back surface of the semiconductor multi-layer structure  11 . When a voltage is applied between the patterned electrode  13  and the back electrode  12   a , laser light is emitted from a facet produced by the first cleavage. 
     The cleavage grooves  15  are, for example, scratches (grooves) formed mechanically by a diamond needle of a scriber or the like. In this case, there is a micro crack extending from the cleavage groove  15  inward the semiconductor multi-layer structure  11 . The micro crack reduces the strength of crystal. Therefore, when a load is applied from the back electrode  12   a  side to the cleavage groove  15  provided on the multi-element bar  16 , the multi-element bar  16  is easily cleaved along the micro crack having a lesser crystal strength. In order to conduct the second cleavage to the multi-element bar  16  on which the cleavage grooves  15  (scratches) are provided, a relatively small load is applied to the back electrode  12   a  in a longitudinal direction of the multi-element bar  16 . For example, a load is applied to the back electrode  12   a  by a roller being rotated and moved on the back electrode  12   a.    
     Japanese Laid-Open Publication No. 6-338662 discloses a method for forming scratches (grooves) as the cleavage grooves  15  on a semiconductor wafer in which semiconductor laser elements are provided. When the cleavage grooves  15  are formed mechanically used a scriber or the like, a plurality of cleavage grooves  15  need to be reliably provided from one edge to the other edge of the patterned electrode  13 . Such a process reduces working efficiency. 
     Further, the semiconductor wafer  1  is easily broken along the scratches which is being formed on the semiconductor wafer  1 . Breaks also easily occur along the scratches during the first cleavage in a direction perpendicular to the scratches. As a result, a yield of the semiconductor laser elements is lowered. 
     To address the above-described problems, the cleavage grooves  15  may be provided by etching. In this case, the front surface of the semiconductor wafer is first coated with a resist film, excluding portions thereof in which the cleavage grooves  15  will be provided. Such portions which has not been covered with the resist film are etched, resulting in the cleavage grooves  15  having a V-shaped cross-section as shown in FIG.  7 . In such a process, all the cleavage grooves  15  are formed at once. Therefore, the working efficiency of production of the cleavage grooves  15  is improved as compared with when the cleavage grooves  15  are formed mechanically using a scriber or the like as described above. 
     Japanese Laid-Open Publication No. 62-137894 discloses a cleavage apparatus  2  shown in FIG.  6 . In the cleavage apparatus  2 , etched grooves are provided as the cleavage grooves  15  on the multi-element bar  16 . The multi-element bar  16  is placed on a film  31 , and a sheet  34  is provided on the multi-element bar  16 . Further, the sheet  34  is covered with a film  32 . Thereafter, a load is applied via the film  31  to the multi-element bar  16  using a roller  33  so that the multi-element bar  16  is cleaved. 
     As described above, when the cleavage grooves  15  (etched grooves) are formed by etching, substantially no micro crack is generated inside the semiconductor multi-layer structure  11  unlike the scratches mechanically provided using a diamond needle or the like. Therefore, portions having low strength are not clearly provided inside the semiconductor multi-layer structure  11 . Therefore, when the multi-element bar  16  is subjected to the second cleavage, a greater load is required as compared with when the multi-element bar  16  has the cleavage grooves  15  mechanically formed. In this case, the multi-element bar  16  cannot be reliably cleaved (second cleavage) when a load applied by the roller  33  is relatively low. 
     In particular, in the apparatus  2 , the multi-element bar  16  is sandwiched by a pair of the films  31  and  32 , and is further held by a ring, thereby providing tension for the film  31 . A load is applied to the multi-element bar  16  using the roller  33 . Therefore, when the tension of the film  31  is changed, the load applied to the multi-element bar  16  is likely to be changed. Moreover, the film  31  or the multi-element bar  16  may be displaced due to the pressure caused by the roller  33 . The above-described reasons makes it difficult to apply a constant load to the multi-element bar  16 . It is also difficult to rotate the roller  33  smoothly while applying a constant load to the multi-element bar  16  sandwiched by a pair of the films  31  and  32 . 
     As described above, it is difficult to cleave the multi-element bar  16  sandwiched by a pair of the films  31  and  32  by applying a constant load to the multi-element bar  16 . 
     Japanese Laid-Open Publication No. 54-93356 discloses a cleavage method in which the cleavage grooves  15  having a V-shaped cross-section is formed by etching, and the insides of the cleavage grooves  15  are subjected to rough surface treatment, thereby providing micro cracks inside the semiconductor multi-layer structure  11 ; and thereafter, by rotating a roller, a load is applied to a surface (back surface) of the multi-element bar  16  opposite the surface on which the cleavage groove  15  are provided so that the multi-element bar  16  is cleaved (second cleavage). In such a method, the strength of the cleavage grooves  15  can be clearly distinguished from the strength of portions in which the cleavage grooves  15  are not provided. Therefore, a small load applied to the back surface causes the second cleavage in the multi-element bar  16 . 
     However, in this case, the rough surface treatment is required after the cleavage grooves  15  have been provided by etching, thereby reducing working efficiency. Moreover, when the cleavage grooves  15  are subjected to the rough surface treatment, micro cracks are accidentally generated in portions other than the insides of the cleavage grooves  15 . The semiconductor multi-layer structure  11  may be broken at such portions. 
     Further, when the multi-element bar  15  is subjected to the first cleavage, the semiconductor multi-layer structure  11  is likely to be broken along the cleavage grooves  15  which are deep. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a method for producing a semiconductor element comprises the steps of: forming a plurality of grooves on a first surface of a semiconductor multi-layer structure along a first direction; forming a plurality of multi-element bars by cleaving the semiconductor multi-layer structure along a second direction; placing at least one of the plurality of multi-element bars on a support stage; and cleaving the at least one of the plurality of multi-element bars along the plurality of grooves by moving a pressure member in a longitudinal direction of the at least one of the plurality of multi-element bars while a constant load is applied by the pressure member to a second surface of the at least one of the plurality of multi-element bars, the second surface being opposite a third surface corresponding to the first surface of the at least one of the plurality of multi-element bars. 
     In one embodiment of this invention, the semiconductor multi-layer structure includes an active layer. 
     In one embodiment of this invention, the first direction is orthogonal to the second direction. 
     In one embodiment of this invention, the plurality of grooves are formed by etching. 
     In one embodiment of this invention, the multi-element bar is placed on the support stage via a support sheet. 
     In one embodiment of this invention, the support sheet includes polyvinyl chloride. 
     In one embodiment of this invention, the constant load is applied by the pressure member to the at least one of the plurality of multi-element bars via a protection sheet. 
     In one embodiment of this invention, the protection sheet includes a polyethylene terephthalate sheet, a surface of which is to be in contact with the pressure member is coated with a silicone resin. 
     In one embodiment of this invention, the support stage includes a rigid material. 
     In one embodiment of this invention, the rigid material includes at least one of a quartz, a glass, a metal, a stone, and a rigid plastic. 
     In one embodiment of this invention, a depth of the plurality of grooves is about 0.5 μm or more and about 5 μm or less from the first surface. 
     In one embodiment of this invention, a moving speed of the pressure member is about 10 mm/sec or more and about 100 mm/sec or less. 
     In one embodiment of this invention, the constant load applied to the at least one of the plurality of multi-element bars is about 5 N or more and about 20 N or less per multi-element bar. 
     According to another aspect of the present invention, a cleavage apparatus is provided for producing a semiconductor element using at least one multi-element bar, a plurality of grooves being provided in a predetermined direction on a first surface of the at least one multi-element bar. The apparatus comprises: a support stage for the at least one multi-element bar being provided; and a pressure member for applying a constant load to a second surface of the at least one multi-element bar, the second surface being opposite the first surface of the at least one multi-element bar, while the pressure member is moved in a longitudinal direction of the at least one multi-element bar. 
     In one embodiment of this invention, the at least one multi-element bar includes an active layer. 
     In one embodiment of this invention, the plurality of grooves are formed by etching. 
     In one embodiment of this invention, the support stage includes a rigid material. 
     In one embodiment of this invention, the rigid material includes at least one of the quartz, a glass, a metal, a stone, and a rigid plastic. 
     In one embodiment of this invention, a moving speed of the pressure member is about 10 mm/sec or more and about 100 mm/sec or less. 
     In one embodiment of this invention, the constant load applies to the at least one multi-element bars is about 5 N or more and about 20 N or less per multi-element bar. 
     In one embodiment of this invention, the pressure member does not rotate on the at least one multi-element bar. 
     In one embodiment of this invention, the pressure member is held by a spring, and the constant load is applied by the spring to the at least one multi-element bar. 
     Thus, the invention described herein makes possible the advantages of providing a method for producing a semiconductor element and a cleavage apparatus, in which a multi-element bar having shallow cleavage grooves formed by etching is efficiently and reliably cleaved into a plurality of semiconductor elements. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view showing a major portion of an exemplary apparatus for producing a semiconductor device according to the present invention. 
     FIGS. 2A through 2G are diagrams schematically showing a process for producing a semiconductor element according to the present invention. 
     FIG. 3A is a side view showing a multi-element bar in a process for producing a semiconductor element according to the present invention. 
     FIG. 3B is a perspective view showing a semiconductor element obtained by cleaving the multi-element bar shown in FIG.  3 A. 
     FIG. 4A is a side view showing a multi-element bar after improper cleavage. 
     FIG. 4B is a perspective view showing a semiconductor element obtained by the improper cleavage shown in FIG.  4 A. 
     FIGS. 5A through 5C are perspective views showing a process for a semiconductor element. 
     FIG. 6 is a diagram schematically showing a configuration of an exemplary apparatus for producing a semiconductor laser element. 
     FIG. 7 is a perspective view showing a major portion of the multi-element bar in which cleavage grooves are formed by etching. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the present invention will be described by way of illustrative examples with reference to the accompanying drawings. In the examples, a method for producing a semiconductor laser element and a cleavage apparatus will be described. In the method of the present invention for producing a semiconductor laser element, multi-element bars  16  are produced in a way similar to that of the conventional method for producing a semiconductor laser element as shown in FIGS. 5A through 5C. The method of the present invention differs from the conventional method shown in FIGS. 5A through 5C in that cleavage grooves  15  are not scratches mechanically formed, but are etched grooves formed by etching. The multi-element bars  16  are subjected to the second cleavage using a cleavage apparatus  100  shown in FIG.  1 . The direction along which the first cleavage is conducted is not necessarily orthogonal to the direction along which the second cleavage is conducted. The angle the two direction attain is designated to various values depending on the examples. 
     The multi-element bars  16  are, for example, about 30 mm long. The multi-element bars  16  are cleaved (second cleavage) into a plurality of semiconductor laser elements  17  having a cavity length of about 200 μm and a width of about 160 μm. The thickness of a semiconductor multi-layer structure  11  is about 100 μm. An active layer is positioned about 4 μm below the front surface of the semiconductor multi-layer structure  11 . The depth of the cleavage groove  15  provided at the stripes of the patterned electrode  13   a  is about 0.5 through 5 μm. The cleavage groove  15  are etched grooves formed by etching the front surface of the semiconductor multi-layer structure  11 . If the depth of the cleavage grooves  15  is more than about 5 μm, breaks occur from the cleavage grooves  15  which are the starting points of the first cleavage. If the depth of the cleavage grooves  15  is less than about 0.5 μm, a second cleavage described below cannot be achieved. 
     The cleavage apparatus  100  shown in FIG. 1 includes a disc-shaped support stage on which the multi-element bars  16  are placed and a pressing member  22  which is moved over the support stage  21  in parallel to at surface of the support stage  21 . 
     For example, the support stage  21  includes a rigid quartz plate. The front surface of the support stage  21  is mirror polished and horizontally held. The support stage  21  is not limited to a disc shape. 
     The pressure member  22  includes a stainless rod having a diameter of about 5 mm, for example. The pressure member  22  is provided over and parallel to the front surface of the support stage  21  while being biased downward by a spring or its own weight. The pressure member  22  is slid in a longitudinal direction of the multi-element bars  16  (along an edge formed by the first cleavage) over the full length of the multi-element bars  16 . 
     Using such an apparatus, the multi-element bars  16  are subjected to second cleavage. Referring to FIG. 2A, for example, a support sheet  23  of polyvinyl chloride having a thickness of about 70 μm and a ring film frame  25  are prepared. Referring to FIG. 2B, the support sheet  23  is attached to the ring film frame  25 . Referring to FIG. 2C, the multi-element bars  16  are placed on the support sheet  23 , and are evenly spaced in parallel. The multi-element bars  16  are placed on the front surface of the support sheet  23  in such a manner that a surface of the patterned electrode  13  contacts the front surface of the support sheet  23 . 
     Thereafter, referring to FIG. 2D, a protection sheet  24  is provided in such a manner as to cover the entire multi-element bars  16  provided on the support sheet  23 , resulting in a state shown in FIG.  2 E. The protection sheet  24  is a relatively rigid polyethylene terephthalate (PET) sheet having a thickness of about 50 μm whose surface is coated with a silicone resin. The protection sheet  24  is provided over the multi-element bars  16  so that the surface of the protection sheet  24  which is coated with the silicone resin is positioned at the pressure member  22  side. Since, the protection sheet  24  is made of the relatively rigid material, the protection sheet  24  is substantially unbendable. Thereby, the multi-element bars  16  are held substantially horizontal. 
     Referring to FIG. 2F, the ring film frame  25  thus constructed is placed on the support stage  21 , preferably in such a manner that the cleavage grooves  15  are orthogonal to a direction along which the pressure member  22  is moved over the support stage  21 . The cleavage grooves  15  provided on the multi-element bars  16  are used for second cleavage. 
     The pressure member  22  is brought to an edge of each multi-element bar  16 . The pressure member  22  applies an appropriate predetermined load via the protection sheet  24  to the edge of the multi-element bar  16 . When the pressure member  22  is held with a spring, the load is generated by the spring. Referring to FIG. 2G, the pressure member  22  is horizontally translated in a longitudinal direction (along an edge formed by the first cleavage) of each multi-element bar  16  while being pressed on the multi-element bar  16 . The pressure member  22  contacts the multi-element bars  16  at at line substantially parallel to the cleavage groove  15 . The pressure member  22  is moved at a constant speed over the full length of the multi-element bars  16  in the longitudinal direction while applying a constant load to the multi-element bars  16 . The moving speed is, for example, about 10 mm/sec. 
     Referring to FIG. 3A, when the pressure member  22  passes above the cleavage grooves  15  provided on each multi-element bar  16 , the multi-element bar  16  is cleaved at the cleavage grooves  15 . The cleavage starts from the cleavage groove  15  and proceeds toward the back electrode  12   a  over the full thickness of the multi-element bars  16 , resulting in a flat facet. The cleavage is conducted successively at all the cleavage grooves  15 . The second cleavage of the multi-element bars  16  is completed. The resultant semiconductor laser element  17  having a predetermined size is shown in FIG.  3 B. In FIGS. 3A and 3B, reference numeral  19  indicates an active layer, and reference numeral  20  indicates a portion emitting laser light. Note that the surfaces of the multi-element bars  16  in which the cleavage grooves  15  are formed do not necessarily need to face the support stage  21 . The multi-element bars  16  may be placed on the support stage  21  in such a manner that the surfaces of the multi-element bars  16  on which the back electrode  12   a  are provided faces the support stage  21 . 
     The multi-element bars  16  placed on the support sheet  23  are covered with the protection sheet  24 . Therefore, the semiconductor laser elements  17  are prevented from flying off the support sheet  23  when the multi-element bars  16  are cleaved by the pressure member  22 . 
     The provision of the protection sheet  24  removes the necessity of application of an adhesive on the support sheet  23 . In this case, a surface of the laser element  17  on which the patterned electrode  13  is provided, facets obtained by the first cleavage, and facets obtained by the second cleavage are free from an adhesive which may obstruct a subsequent die bonding process or may impair laser oscillation. Further, it is possible to avoid a problem that the laser elements  17  are not separated when the support sheet  23  is expanded, since the facets obtained by the second cleavage are attached to each other via an adhesive. 
     The protection sheet  24  is removed. The support sheet  23  is expanded so that the gap between each semiconductor laser element  17  is increased. Thereby, a subsequent process is facilitated. Specifically, each semiconductor laser element  17  can be easily picked up. Thus, a plurality of semiconductor laser elements  17  which have predetermined size and whose facets obtained by the second cleavage are entirely flat are obtained. 
     In the cleavage apparatus of the above-described example, control of the load applied by the pressure member  22  is a key factor in second cleavage in which the multi-element bar  16  is reliably cleaved into the semiconductor laser elements  17  and flat facets are obtained. As described in the DESCRIPTION OF THE RELATED ART section, the crystal strength of the shallow cleavage grooves  15  formed by etching cannot be clearly distinguished from the crystal strength of portions in which the cleavage grooves  15  are not provided. The cleavage grooves  15  require a greater load for cleavage as compared with scratches mechanically formed by a scriber or the like. Moreover, the pressure member  22  needs to be continuously and reliably moved on the entire back surface of the multi-element bar  16 . 
     When the pressure member  22  is continuously moved in a longitudinal direction of the multi-element bar  16 , an applied load is designated to be greater than the crystal strength of the cleavage grooves  15  and less than the crystal strength of portions in which the cleavage grooves  15  are not provided. If the applied load is less than the crystal strength of the cleavage grooves  15 , the multi-element bar  16  is not cleaved even when the pressure member  22  reaches directly above the cleavage grooves  15 . In this case, substantially no semiconductor laser elements  17  are obtained. If the applied load is greater than the crystal strength of the portions in which the cleavage grooves  15  are not provided, the semiconductor laser elements  17  are smaller than the desired size or damaged, thereby significantly reducing yield upon the second cleavage. The applied load is determined depending on the material and thickness of the support sheet  23  and the protection sheet  24 , the crystal strength and crystal direction and cavity length, width, thickness, and the like of the semiconductor laser elements to be obtained by the second cleavage. An experiment which the inventors have conducted demonstrated that when the applied load was about 5 N or more and about 20 N or less for each multi-element bar  16 , the multi-element bars  16  were stably cleaved (second cleavage) into the semiconductor laser elements  17 . 
     The translation speed of the pressure member  22  is preferably about 10 mm/sec or more. If the speed is more than about 100 mm/sec, the applied load which contributes to the cleavage of the cleavage groove  15  is reduced. In this case, a greater applied load is required. In addition, the quick movement of the pressure member  22  causes the following problem. When the pressure member  22  is translated to be brought in the vicinity of above the cleavage groove  15 , cleavage is started. However, the pressure member  22  is quickly moved away from the cleavage groove  15 . The cleavage may be stopped halfway. The multi-element bar  16  is dragged in the direction of the translation of the pressure member  22 , so that the remaining cleavage is forcedly completed. In this case, referring to FIGS. 4A and 4B, facets obtained by the cleavage are curved in the vicinity of the back surface of the multi-element bar  16  (convex facet portion  17   a  and concave facet portion  17   b ). Such facets depart from the desired facets which are flat. When the resultant semiconductor laser element  17 ′ is incorporated into an optical apparatus and is mounted on an appropriate substrate of the optical apparatus by die bonding, the position of the front surface of the semiconductor laser element  17 ′ is not aligned with the position of the back surface of the semiconductor laser element  17 ′. A position of laser emission is likely to be shifted from the desired position. Moreover, the convex facet portion  17   a  is broken off the semiconductor laser element  17 ′ during assembly of an optical apparatus. Such a broken piece is likely to be attached to a laser oscillation facet, thereby preventing emission of laser light. 
     The support stage  21  needs to be sufficiently rigid so a to keep the position of the multi-element bar  16  from being lowered by depression of the support stage  21  caused by a load applied by the translating pressure member  22 . The material of the support stage  21  is not limited to the quartz plate, but may be a glass plate, a metal plate, a stone plate, a rigid plastic plate, or the like. Further, the surface of the support stage  21  on which the multi-element bars  16  are placed is preferably flat like a mirror so that a load is evenly applied by the translating pressure member  22  to the entire multi-element bar  16 . 
     The support sheet  23  is provided so that the semiconductor laser elements  17  are prevented from being scattered when the multi-element bars  16  are cleaved (second cleavage). The support sheet  23  has preferably a small level of elasticity so that the load applied by the pressure member  22  is not dispersed and the multi-element bars  16  are not significantly sunk, whereby the multi-element bars  16  are reliably supported by the support stage  21 . For example, the thickness of the support sheet  23  is about 70 μm which is relatively thin. 
     When a load is applied by the pressure member  22  to the multi-element bars  16 , the multi-element bars  16  are sunk a certain amount into the support sheet  23 . The multi-element bars  16  are stabilized by the rigid support stage  21  and is no longer sunk. Since the applied load is absorbed by the support sheet  23 , the multi-element bars  16  is not damaged. Further, the semiconductor laser elements  17  after the second cleavage are prevented from being scattered or shifted, since the semiconductor laser elements  17  are fixed to the support sheet  23 . 
     The protection sheet  24  provided on the multi-element bars  16  are preferably coated with silicone resin at least one the surface thereof which is pressed by the pressure member  22 . In this case, the coefficient of kinetic friction between the pressure member  22  and the protection sheet  24  is significantly small, even when the pressure member  22  is not a roller having rotation mechanism. Therefore, one of the pressure member  22  and the protection sheet  24  can be translated while a great load is stably applied to the multi-element bars  16 . Conversely, when the pressure member  22  is a roller which rotates on its own axis, the protection sheet  24  may get entangled with the rotating roller when a great load is applied. Alternatively, the roller is rotated but may be moved nowhere. In this case, a constant load is unlikely to be reliably applied. Further, vibration occurs in the translating roller depending on the condition of an engagement mechanism of a rotating portion and a supporting portion of the roller. Such vibration is likely to cause variations in the applied load. The roller needs to be well maintained in order to achieve a constant load and a constant speed. The use of roller is not suited for mass production. 
     The pressure member  22  is not limited to a specific material, shape, and the like as long as the pressure member  22  can apply a constant and great load and can move at a constant speed over the multi-element bar  16 . Further, the direction along which the pressure member  22  is moved is not limited to a longitudinal direction of the multi-element bar  16 , but may be any direction as long as the pressure member  22  can apply a constant load to the multi-element bar  16 . 
     The coefficient of kinetic friction between the pressure member  22  and the protection sheet  24  varies depending on the materials thereof (see, e.g., “Mechanical Property of Plastics”, FIGS. 16.15 at page 223, published by Nikkan Kogyo Shinbunsha). Preferably, the coefficient of kinetic friction between the pressure member  22  and the protection sheet  24  is about 0.1 or less. 
     The protection sheet  24  is made of a polyethylene terephthalate (PET) sheet which is a relatively rigid resin sheet. Therefore, a load is reliably applied to the multi-element bar  16  by the pressure member  22 . 
     Due to the interposition of the protection sheet  24 , the multi-element bars  16  and the pressure member  22  do not contact with each other. Therefore, even when a great load is applied, the semiconductor laser elements  17  are prevented from being scattered and being damaged. 
     The protection sheet  24  provided on the multi-element bars  16  is preferably extended from widthwise edges of the multi-bars  16 , keeping the horizontal state rather than bending along the edges. In this case, since a step of the protection sheet  24  at the widthwise edge of the multi-element bar  16  positioned upstream of the translation is reduced. Therefore, when the pressure member  22  is moved from the upstream edge of the multi-element bar  16 , the semiconductor laser element  17  positioned at the upstream edge is substantially not damaged. 
     In the second cleavage method and apparatus of the above-described examples, the second cleavage is conducted at the cleavage grooves  15  which are shallow grooves formed by etching. It is apparently understood that the second cleavage method and apparatus of the above-described examples are also preferable for the cleavage using the scratches mechanically formed by a scriber or the like described in the DESCRIPTION OF THE RELATED ART section or for separation of the multi-element bar  16  half broken by dicing. The method for producing a semiconductor element and the cleavage apparatus of the present invention may be applied to any semiconductor element such as a memory device, light-emitting device, light-receiving device, and a semiconductor integrated circuit, as well as a semiconductor laser element. 
     As described above, in the method for producing a semiconductor and the cleavage apparatus of the present invention, a multi-element bar having cleavage grooves formed by etching can be cleaved efficiently and reliably into a plurality of semiconductor elements. Moreover, the cleavage can be achieved by sliding a pressure member having no roller mechanism over the multi-element bar. The mechanism of the cleavage apparatus can be significantly simplified. 
     Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.