JP2009206292A - Semiconductor substrate, and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a processing cycle time without lowering quality of division when a semiconductor substrate having a plurality of semiconductor elements formed is divided by semiconductor element to form individual semiconductor devices. <P>SOLUTION: On the semiconductor substrate 1, the plurality of semiconductor elements 2 each having constructed functional elements are formed in a grid shape, and on longitudinal and lateral separating lines 4 individually separating the plurality of semiconductor elements 2, grooves 3 are formed which are continuous except at parts corresponding to outer circumferential parts of the semiconductor elements 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor substrate having a partially thinned diaphragm structure or beam structure, represented by MEMS (Micro Electro Mechanical System), and a method for manufacturing a semiconductor device.

  A semiconductor pressure sensor or a MEMS acceleration sensor is a semiconductor device having a diaphragm structure or a beam structure that is partially thinned as typified by MEMS. In general, these sensors are manufactured by forming a plurality of sensors at the same time so as to have a diaphragm structure and a beam structure in a semiconductor wafer process, and then dividing them individually. For the division, a method of crushing by rotating an annular dicing saw with diamond or CBN particles fixed at a high speed is most commonly used. This processing is for removing crushing waste and suppressing frictional heat. It is performed while flowing cutting water. However, since the diaphragm structure and the beam structure are fragile structures, they may be destroyed by cutting water pressure.

  In recent years, laser beam machining has attracted attention as a dividing method that does not require cutting water. For example, Patent Document 1 discloses a method in which a modified region by multiphoton absorption is formed in a semiconductor wafer by laser light, and division is performed by cleavage starting from the modified region. Multiphoton absorption is a phenomenon in which absorption occurs in a material when the intensity of light is very large even when the energy of the photon is smaller than the absorption bandgap of the material, that is, when it is optically transmitted. This will be described below with reference to the drawings.

  10A and 10B are a plan view and a cross-sectional view schematically showing the separation line of the semiconductor substrate and its periphery. In the figure, 101 is a semiconductor substrate, 102 is a semiconductor element (semiconductor device) formed on the semiconductor substrate 101, and 104 is a separation line that separates the semiconductor substrate 101 for each semiconductor element 102.

  With respect to the semiconductor substrate 101, the condensing point of the laser beam 108 is aligned inside the substrate in the region of the separation line 104 to cause multiphoton absorption in a predetermined thickness direction, and this multiphoton absorption occurs continuously or intermittently. The laser beam 108 is scanned along the center of the separation line 104 so as to form a modified region 109 along the separation line 104 inside the substrate, and a cut portion (crack) starting from the modified region 109 110 is generated. In this way, by applying an external force to both sides of the separation line 104 simultaneously, the semiconductor substrate 101 can be easily broken even with a relatively small external force. When the semiconductor substrate 101 is thin, it can be naturally broken by the cut portion (crack) 110 without applying an external force.

  There is also a method of reducing the thickness of the processed portion by forming grooves on the separation line in advance by anisotropic etching or the like. For example, in the method disclosed in Patent Document 2, anisotropic etching is performed after an etching protective film is formed on a semiconductor substrate having an azimuth plane (100) so that vertical and horizontal separation line portions are exposed. . In this case, etching stops on the azimuth plane (111) and a V-groove having an inclination angle of 54.7 degrees is formed. By applying an external force to the semiconductor substrate so as to expand the V-groove, the V-groove is formed. The semiconductor substrate can be divided along the line, that is, along the separation line.

Patent Document 3 discloses that a continuous linear first groove and a dashed second groove are formed as scrub grooves on a surface portion of a semiconductor substrate. In Patent Document 4, as a method of dividing a substrate on which a plurality of semiconductor devices having a diaphragm are formed, one of the vertical and horizontal kerfs for division is a continuous kerf and the other is not. It is disclosed that a continuous kerf portion is formed. Patent Document 5 discloses that two grooves are formed on the separation line corresponding to each of the four sides of each semiconductor device.
Japanese Patent No. 3408805 JP 2001-127008 A JP 2004-186340 A Japanese Utility Model Publication No. 4-109537 JP 2004-165227 A

  However, in the laser processing method disclosed in Patent Document 1, when the semiconductor substrate 101 is thick, it cannot be divided by the modified region 109 by a single scan. It is necessary to arrange the regions 109 almost in series in the thickness direction, which leads to an increase in tact time for processing.

  In the method disclosed in Patent Document 2, erosion of anisotropic etching is different from other portions at the portion where the vertical and horizontal V-grooves along the separation line intersect, and excessive etching is performed. Then, the etching does not stop at the azimuth plane (111), and the etching proceeds to the azimuth plane (211), for example. For example, if the V-groove is formed simultaneously with the step of forming a diaphragm structure that requires deeper etching than required for the V-groove, the intersection of the V-groove may be excessively etched and penetrate the semiconductor substrate. In this case, the strength of the semiconductor substrate is extremely deteriorated, and the semiconductor substrate is damaged during handling.

  In the method disclosed in Patent Document 3 or Patent Document 4, only one of the grooves in the vertical direction and the horizontal direction is a continuous groove, and the four sides of the semiconductor device to be divided are not uniform. Stress is concentrated on the side where the groove is formed, and the semiconductor device is damaged from the side. Further, since the continuous groove is formed in the state of the semiconductor substrate, the strength is extremely deteriorated, and the semiconductor substrate is damaged during handling.

  In the method disclosed in Patent Document 5, two grooves for division are formed corresponding to each of the four sides of the semiconductor device, that is, a continuous groove is not formed on the separation line. For this reason, the straightness of separation deteriorates, and the shape of the semiconductor device after division, particularly the dimensions of each side, becomes nonuniform. As a result, for example, the pick-up property with a collet picked up at the side of the semiconductor device in a later process is deteriorated, and the productivity is lowered.

  In view of the above problems, the present invention improves processing tact without reducing the quality of division when a semiconductor substrate formed with a plurality of semiconductor elements is divided into semiconductor elements to form individual semiconductor devices. With the goal.

  In order to solve the above-described problems, a semiconductor substrate according to the present invention includes a plurality of semiconductor elements in which functional elements are constructed in a grid shape, and the plurality of semiconductor elements are separated from each other in the vertical and horizontal directions. A continuous groove is formed on the separation line except for a portion corresponding to the outer peripheral portion of each semiconductor element. This is convenient when a part of the structure is thinned, for example, a diaphragm structure having a recess on the back side of each semiconductor element.

  A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device by dividing a semiconductor substrate in which a plurality of semiconductor elements each having a functional element built therein are formed in a grid pattern, for each semiconductor element. Forming a continuous groove by anisotropic etching on the vertical and horizontal separation lines separating the individual semiconductor elements, excluding a portion corresponding to the outer peripheral portion of each semiconductor element, and forming the grooves Forming a modified region in the substrate by irradiating a laser beam along each separated line and focusing on the inside of the substrate; and applying an external force to the semiconductor substrate in which the groove and the modified region are formed. And a step of dividing the semiconductor substrate along each separation line to form individual semiconductor devices.

  In the step of forming the modified region, the number of times of laser light scanning for the groove forming portion can be made smaller than the number of times of laser light scanning for the non-groove forming portion. When the step of forming the concave portion constituting the diaphragm structure is formed on the back side of each semiconductor element by anisotropic etching, the step of forming the groove can be performed simultaneously with the step of forming the concave portion.

  The semiconductor substrate of the present invention is on the vertical and horizontal separation lines that individually separate a plurality of semiconductor elements, except for the part corresponding to the outer peripheral part of each semiconductor element, that is, only in the vicinity of the outer peripheral part of the substrate. By forming a continuous groove, the substrate is thin at the groove part, and stress is easily concentrated when performing division by cleavage, etc. Compared to a semiconductor substrate without such a groove, Stable division with good straightness is possible. On the other hand, since the grooves are not continuously formed along the entire separation line, the strength and damage of the semiconductor substrate are unlikely to occur.

  In the method of manufacturing a semiconductor device according to the present invention, grooves are formed only in the vicinity of the outer peripheral portion of the substrate on each separation line of the semiconductor substrate as described above, that is, the formation of groove intersections that are extremely difficult to control etching is eliminated. Therefore, the groove can be formed very easily and stably. Further, when forming the modified region, the number of scans of the laser beam in the groove forming portion can be made smaller than that in the non-groove forming portion, and the total number of scans can be suppressed as compared with the case where no groove is formed. it can. Further, since the groove in the vicinity of the outer peripheral portion of the substrate is used as a starting point when dividing, the possibility of meandering of the dividing line and chipping of the semiconductor device after the division can be reduced as compared with the case where the groove is not formed. . By these things, it is possible to achieve stable division with good straightness and shortening of processing tact. The semiconductor device after the division is improved in quality and does not leave a trace of the groove, so that the area of the back surface of the device is not reduced, and the bonding area at the time of die bonding can be secured.

  When forming a recess that forms the diaphragm structure on the back side of each semiconductor element by anisotropic etching, it is sufficient to form a groove at the same time in the step of forming the recess. The process will not increase, and it will not increase costs or lead time.

Embodiments of the present invention will be described below with reference to the drawings.
1 is a plan view of a semiconductor substrate according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of the semiconductor substrate, FIGS. 3 and 4 are cross-sectional views taken along line AA ′ in FIG. It is -B 'sectional drawing.

  1 and 2, a semiconductor substrate 1 is made of Si single crystal, and a plurality of semiconductor elements 2 in which functional elements are constructed are formed in a grid pattern on one surface. The semiconductor element 2 shown in the drawing becomes a diaphragm pressure sensor (semiconductor device) after being divided. The semiconductor element 2 itself is made as thin as possible as a detection part, and a concave part 5 is formed on the back side, and these have a diaphragm structure. It is composed. An example of such a diaphragm pressure sensor is a microphone sensor. The diaphragm vibrates due to air oscillated by sound, and the displacement of the diaphragm changes the conductor capacitance between the passive diaphragm / vibrating diaphragm, thereby changing the vibration frequency and electric signal. Converted.

  The separation line 4 separating the plurality of semiconductor elements 2 is a divided region set for dividing each semiconductor element 2 and extends in the vertical direction and the horizontal direction so as to be orthogonal to each other. On each separation line 4, a continuous groove 3 is formed only in the vicinity of the substrate outer peripheral portion (substrate peripheral portion) except for the outer peripheral portion of each semiconductor element 2 on the back surface of the substrate opposite to the semiconductor element 2.

A method for manufacturing the semiconductor substrate 1 and the semiconductor device will be described.
As shown in FIG. 5A, an etching mask 6 is formed on a semiconductor substrate 1 (see FIG. 1) in which a plurality of semiconductor elements 2 are separated by separation lines 4 and formed in a grid shape. The etching mask 6 is formed, for example, by forming a silicon oxide film or the like by the CVD method and then patterning by a lithography technique so as to have openings in the regions where the recesses 5 and the grooves 3 are formed. Although not shown, an etching mask is left on the entire surface on which the semiconductor element 2 is formed.

  Next, as shown in FIG. 5B, the recess 5 and the groove 3 are formed by anisotropic etching. For the anisotropic etching, for example, a KOH solution or a TMAH (tetramethylammonium hydroxide) solution is used. At this time, since the groove 3 is formed only on the separation line 4 in the vicinity of the outer periphery of the substrate except for the outer periphery of each semiconductor element 2 as described above, there is no intersecting portion of the groove 3 and abnormal erosion caused by the intersection. Even if the recesses 5 having different etching depths are formed at the same time, the etching can be stopped at a desired depth. That is, the depth and width of the groove 3 can be determined by the opening width of the etching mask 6.

  After the etching is completed, the etching mask 6 is removed as shown in FIG. In this case, for example, a BHF solution is used, but the etching mask 6 may be left if there is no particular problem.

  After that, as shown in FIGS. 5D and 5E, the semiconductor substrate 1 is mounted on the expanded tape 7, and the laser beam 8 is focused along each separation line 4 and inside the semiconductor substrate 1. Then, a modified region 9 is formed inside the semiconductor substrate 1. At this time, the laser beam 8 is scanned along the longitudinal direction of the groove 3 while moving the focal point in the substrate thickness direction so that the microcracks generated from the modified region 9 propagate into the groove 3.

  Finally, as shown in FIG. 5 (f), by applying an external force F to the semiconductor substrate 1 in which the groove 3 and the modified region 9 are formed, that is, by applying an external force F that expands the expanded tape 7, The crack 10 starting from the modified region 9 formed along the separation line 4 is developed to divide the semiconductor substrate 1 to obtain individual semiconductor devices 11. If the above-mentioned microcracks have advanced to the groove 3 prior to the external force F, the external force F can be reduced and processing with smaller energy becomes possible.

  When the semiconductor substrate 1 is thick, as shown in FIGS. 6A and 6B, the laser beam 8 is scanned a plurality of times so that the modified regions 9 are aligned in the substrate thickness direction, thereby dividing the substrate. Can be easily. The laser beam 8 can be divided even if the number of times of scanning with the laser beam 8 is less than the portion where the groove 3 is not formed compared to the portion where the groove 3 is not formed.

  FIG. 6A shows a portion where the groove 3 is formed, and the modified regions 9a and 9b are formed by setting the number of scans of the laser light 8 twice. FIG. 6B shows a non-formed portion of the groove 3, and the modified regions 9 a, 9 b, 9 c are formed with the number of scans of the laser light 8 being three.

According to the configuration of the semiconductor substrate 1 and the manufacturing method of the semiconductor device 11 described above, the following effects can be obtained.
By forming the continuous groove 3 only on the separation line 4 in the vicinity of the outer peripheral portion of the semiconductor substrate 1, the substrate is thin at the groove 3 portion, so that stress is easily concentrated when dividing by cleavage or the like. Compared with the case where the grooves 3 are not formed, stable division with good straightness is possible. On the other hand, since the groove 3 is not continuously formed along the entire separation line 4, the strength degradation and breakage of the semiconductor substrate 1 are unlikely to occur.

  When the groove 3 is formed, it does not have a groove crossing portion that is extremely difficult to control the etching, so that abnormal erosion during etching as in the case of having a groove crossing portion does not occur and can be formed very easily and stably. Processing tact can be shortened. Furthermore, since the formation of the modified region 9 at the later stage facilitates the formation of cracks, for example, the V-groove shape may not be very difficult to control etching, and stable etching can be performed very easily.

  Even when the modified region 9 is formed, the number of scans of the laser beam 8 for the groove forming portion can be made smaller than that for the non-groove formed portion. Processing tact can be shortened.

  Since the groove 3 is a starting point in the division, there is an effect of having the modified region 9, and the meandering of the divided lines and the semiconductor device 11 after the division are compared with the case where the groove 3 is not formed. The possibility of chipping can be reduced, and division with excellent straightness can be easily performed, and the quality of the semiconductor device 11 is improved. The trace of the groove 3 does not remain in the semiconductor device 11, and the area of the back surface of the device does not decrease.

If the groove 3 is formed simultaneously with the anisotropic etching step for forming the recess 5, there is no particular increase in the number of steps, and an increase in cost and lead time can be avoided.
The thickness of the semiconductor substrate 1 is determined according to the diameter of the semiconductor substrate 1 and the thickness required for the semiconductor device 11 after division, and the depth of the groove 3 also depends on the thickness of the semiconductor substrate 1. It is decided.

For example, when the semiconductor device is a microphone sensor, the Si single crystal substrate is Φ4 to 12 inches and the thickness is 100 to 1000 μm, the planar size of the target semiconductor device is about 1 to 200 mm ² , and the finished thickness is about 10 to 900 μm. If there is, the thickness of the planar diaphragm (semiconductor element 2 here) is about 1 to 5 μm on the passive side and about 1 to 5 μm on the vibration side. Therefore, the recess 5 is formed by etching so as to have such a thickness. Can do. The planar size of the recess 5 is about 0.5 to 150 mm ² . The groove 3 has a width of about 20 to 500 [mu] m (preferably narrow to improve the number of chips taken), and a depth of about 10 to 890 [mu] m (preferably deep to facilitate separation and division, but unnecessary. To the extent that no substrate cracking occurs).

  Although the dimension range does not partially overlap with the example of the microphone sensor described above, when the semiconductor substrate 1 has a diameter of 3 to 12 inches, a thickness of 25 to 725 um, and a separation line width of 5 to 200 um, the groove 3 has a width of 5 Good results were obtained when formed at ˜200 μm and depth ˜195 μm. When the thickness of the semiconductor substrate 1 was 300 μm, good results were obtained by scanning the laser beam 8 0 to 10 times (the number of scans is small for the groove forming portion).

FIG. 7 shows the semiconductor device 11 divided from the semiconductor substrate 1. A semiconductor element 2 and a recess 5 are formed in the semiconductor substrate 1 ′.
FIG. 8 shows a state where the semiconductor device 11 is mounted on the mounting substrate 13. The semiconductor device 11 and the mounting substrate 13 are bonded with a die bond material 14 as is generally done. Since the trace of the groove 3 is not left on the semiconductor substrate 1 ′, that is, the outer shape of the semiconductor device 11 is the same as the conventional one, the bonding area at the time of die bonding can be ensured similarly to the conventional case, Die bonding is possible.

  However, in addition to forming the above-described grooves 3 in the semiconductor substrate 1 before division, continuous grooves may be formed on the vertical and horizontal separation lines except for the portions corresponding to the corner portions of the respective semiconductor elements 2. . In this case, although notched portions that are traces of the grooves 3 remain on each side of the back surface of the divided semiconductor substrate 1 ′ but do not remain in the corner portions, the area of the back surface of the device is not reduced, and an adhesion area can be secured. .

  Even in this configuration, no groove crossing portion that is extremely difficult to control the etching occurs, so that the groove can be formed very easily and stably. In addition, since the grooves on each separation line are almost entirely continuous in a straight line, when the modified region that is the starting point for division is formed by laser light, the number of times the laser light is scanned for the groove forming portion is set. Even if it is less than the other parts, it is possible to stably perform division with excellent straightness, and it is possible to shorten the machining tact. Since it is only necessary to form the groove at the same time in the step of forming the recess 5, the number of steps for forming the groove is not increased, and the cost is not increased and the lead time is not increased.

  In the above embodiment, the diaphragm structure is formed in the semiconductor substrate 1 and the semiconductor device 11, but it is needless to say that the diaphragm structure is not necessary. The semiconductor substrate 1 may also be a compound semiconductor substrate in addition to a silicon substrate.

  For example, when an acceleration sensor is manufactured as the semiconductor device 11, as shown in FIGS. 9A and 9B, the recess 5 ′ is formed on the upper surface of the semiconductor substrate 1, and the semiconductor element 2 is installed in the opening. The groove 3 is formed on the lower surface of the semiconductor substrate 1. The effects of the subsequent steps and the grooves 3 are the same as described above.

  According to the present invention, when a semiconductor substrate on which a plurality of semiconductor elements are formed, for example, a silicon substrate or a compound semiconductor substrate, is divided into semiconductor devices corresponding to the respective semiconductor elements, the processing cost is not increased and the processing quality is not lowered. The processing tact can be improved, and is particularly useful for manufacturing a MEMS sensor or the like having a diaphragm structure.

The top view of the semiconductor substrate of one embodiment of the present invention The top view which expands and shows a part of the semiconductor substrate A-A 'sectional view of the semiconductor substrate in FIG. B-B 'sectional view of the semiconductor substrate in FIG. Sectional drawing which shows the manufacturing method of the semiconductor device of one Embodiment of this invention Sectional drawing which shows a part of manufacturing method of the same semiconductor device in detail Plan view and sectional view of the semiconductor device Sectional drawing which shows the state which mounted the semiconductor device in the semiconductor substrate Sectional drawing which shows the manufacturing method of the semiconductor device of other embodiment of this invention Plan view and sectional view showing a conventional semiconductor substrate and its dividing method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Semiconductor element 3 Groove 4 Separation line 5 Concave part 6 Etching mask 7 Expanding tape 8 Laser beam 9, 9a, 9b, 9c Modified area 10 Crack 11 Semiconductor device 12 Concave part 13 Mounting board 14 Die bond material

Claims (5)

  A plurality of semiconductor elements in which functional elements are constructed are formed in a grid shape, and a portion corresponding to the outer peripheral portion of each semiconductor element is formed on vertical and horizontal separation lines that individually separate the plurality of semiconductor elements. A semiconductor substrate, wherein a continuous groove is formed except for.   2. The semiconductor substrate according to claim 1, wherein the semiconductor substrate has a diaphragm structure provided with a recess on the back side of each semiconductor element.   A method of manufacturing a semiconductor device by dividing a semiconductor substrate on which a plurality of semiconductor elements each having a functional element are formed in a grid shape, and separating the plurality of semiconductor elements individually. Forming a continuous groove by anisotropic etching on a separation line in each direction except for a portion corresponding to the outer peripheral part of each semiconductor element, and along each separation line in which the groove is formed and on the substrate A step of forming a modified region inside the substrate by irradiating a laser beam with a focus on the inside, and applying an external force to the semiconductor substrate on which the groove and the modified region are formed, and applying the semiconductor substrate to each separation line And a step of forming individual semiconductor devices by dividing the semiconductor device.   4. The method of manufacturing a semiconductor device according to claim 3, wherein, in the step of forming the modified region, the number of times of laser beam scanning with respect to the groove forming portion is smaller than the number of times of laser light scanning with respect to the non-groove forming portion.   A step of forming a recess constituting the diaphragm structure on the back side of each semiconductor element by anisotropic etching, wherein the step of forming a groove is performed simultaneously with the step of forming the recess. A method for manufacturing a semiconductor device according to claim 3.

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