Semiconductor die and method of manufacturing the same

Abstract

The invention relates to a semiconductor die and a manufacturing method thereof. The present application relates to a semiconductor die (1) comprising a semiconductor body (10), in which a back side (10.2) of the semiconductor body (10) is structured with a plurality of openings (30) arranged in a repeating pattern (40) along a first axis (41) and along a second axis (42), having at least one of: i) a respective width (d41, d42) of a respective opening (30) compared to along the second axis (42); d42) along the first axis (41) is smaller; ii) the respective distance (s41, s42) between adjacent openings (30) is greater along the first axis (41) than along the second axis (42).

Description

Technical Field

[0001] This disclosure relates to a semiconductor die and a method for manufacturing a semiconductor die. Background Technology

[0002] A semiconductor die may include a semiconductor body on which a front-side metallization is disposed. Within the semiconductor body, for example, a device structure can be formed. Contact structures may be formed in the front-side metallization and connected to the device structure within the semiconductor body. Summary of the Invention

[0003] The embodiments of this application are intended to provide a beneficial semiconductor die.

[0004] In an embodiment of claim 1, the semiconductor die includes a semiconductor body and front-side metallization, wherein the back side of the semiconductor body is structured to have a plurality of openings. The openings extend vertically into the semiconductor body and are arranged in a repeating pattern laterally along a first axis and along a second axis, wherein...

[0005] i) The corresponding width of the corresponding opening is smaller along the first axis compared to along the second axis, and / or

[0006] ii) The corresponding distance between adjacent openings is greater along the first axis than along the second axis.

[0007] An opening on the back side can, for example, reduce the effective distance to a back contactor or mounting structure, such as the effective distance from a device structure or load terminal in the semiconductor body to the back metallization or mounting structure (e.g., a heatsink in a package). Reducing this effective distance can, for example, have thermal or electrical advantages, such as improving the on-resistance of devices formed in the die. This can even be applied to relatively thin dies, where further thinning of the die or wafer would at least mean additional processing efforts.

[0008] Thin dies can exhibit, for example, bifurcated warpage, such as asymmetrical bending along two different sides or axes of the die (greater bending along one side than the other). This warpage can be reduced by introducing anisotropy to the back side, i.e., by having anisotropic widths (characteristic i) and / or anisotropic arrangements (characteristic ii) of openings located on the back side. This can have advantages in die handling, such as further back-end processing for the wafer or die. When soldering the die, for example, reduced warpage at soldering temperatures can reduce solder gaps.

[0009] Embodiments and features are provided in the dependent claims and throughout the disclosure. Individual features will be disclosed, independent of any particular claim class; this disclosure relates to aspects of apparatus and devices, as well as methods and uses. If, for example, a die manufactured or used in a particular manner is described, this also discloses the corresponding manufacturing process or method of use. Generally, the approach of this application is to structure the back side of the die with a plurality of openings having anisotropic shapes and / or arrangements. Due to the anisotropy, more and / or larger openings per unit length can be introduced into the back side along a second axis compared to along a first axis; in other words, more semiconductor bulk material per unit length can be retained along the first axis compared to along the second axis.

[0010] The anisotropy of the shape of the corresponding opening (characteristic i) and the anisotropy of the arrangement of the openings (characteristic ii) can be combined or provided as alternatives. For the definition of anisotropy, a first axis and a second axis are referenced. These axes can respectively define the translational symmetry of the openings. In other words, multiple openings can be arranged in a first lateral direction parallel to the first axis to be translationally symmetric to each other, and multiple openings can be arranged in a second lateral direction parallel to the second axis to be translationally symmetric to each other.

[0011] The repeating pattern of openings arranged along the first and second axes can be a matrix pattern (rows along one axis, columns along the other). In an embodiment, the pattern is a regular pattern with a constant width and distance of openings along the first axis, and, unlike the first axis, a constant width and distance of openings along the second axis. Independent of these details, the first and second axes can, for example, be perpendicular to each other, and / or can be parallel to the respective sides (lateral edges) of the die or semiconductor body.

[0012] As seen in the plan view, the semiconductor body can, for example, have a rectangular shape, wherein a first side (first lateral edge) parallel to a first axis and a second side (second lateral edge) parallel to a second axis may be perpendicular to each other. While a square shape is also conceivable, embodiments involve shapes in which the first and second sides have different lengths, for example, the first side is longer than the second side, or vice versa.

[0013] The semiconductor body may include a semiconductor substrate and optionally one or more epitaxial semiconductor layers on the substrate. In the case of one or more epitaxial semiconductor layers, the upper side of the uppermost epitaxial semiconductor layer may form the "front side" of the semiconductor body, and the side of the semiconductor substrate opposite to the one or more epitaxial layers may form the "back side". Typically, the semiconductor body may be made of GaN or SiC, with specific embodiments involving a semiconductor body made of silicone (Si) (e.g., single-crystal silicon). The silicon material may extend from the back side of the semiconductor body upwards to the front side, for example, in a single-crystal silicon structure.

[0014] Typically, the shape and / or arrangement of the openings are considered in a plan view of the back side of the semiconductor body, i.e., viewed in the vertical direction. The thickness of the semiconductor body or metallization and / or the depth of the corresponding openings in the vertical direction, or "along the vertical direction," can be obtained, see below for further details. The vertical direction can be perpendicular to the first and second axes, for example, perpendicular to the first and second lateral directions.

[0015] From the back side of the semiconductor body, openings extend into the semiconductor body. The bottom of each opening may be vertically positioned inside the semiconductor body, i.e., vertically between the front and back sides. Specifically, on the back side (e.g., in a plane suitable for the back side), the shape and arrangement (e.g., width and spacing) of the openings can be obtained. The width of each opening can be obtained as its maximum width along its respective axis, i.e., a first width along a first axis and a second width along a second axis. The distances can be obtained as the minimum distances between adjacent openings (i.e., direct / nearest neighbor openings), i.e., a first distance along the first axis and a second distance along the second axis.

[0016] Typically, the corresponding opening, as seen in the plan view on the reverse side, can have, for example, a polygonal shape, such as having multiple edges or corners. Examples of polygonal shapes can be rectangular (e.g., square) or hexagonal shapes, but other polygons are also conceivable.

[0017] However, in the embodiments, the openings each have a circular shape, such as a shape without edges. The upper border of the corresponding opening on the back side can, for example, form a closed line that extends without corners (mathematically, it is differentiable at every point on the entire perimeter). Independent of these details, the circular shape can, for example, reduce the extension of areas with high stress concentration.

[0018] Openings with a circular shape can, for example, have a circular shape, that is, each having a uniform diameter. Anisotropy can then be introduced to the back side through the anisotropic arrangement of these circular openings (via feature ii only). However, in the embodiment, the openings each have an elliptical shape in the plan view of the back side.

[0019] Generally, when referring to "openings on the back side," this refers to openings that meet the criteria discussed in the relevant discussion, but it generally does not exclude other openings that do not meet the criteria. In other words, for illustration purposes, not all openings on the back side need to be elliptical in shape, as long as a subset of all openings on the back side forms a repeating pattern and the openings in this subset are elliptical in shape. However, in embodiments, the criteria discussed in the relevant discussion can be applied to all openings on the back side, so that, for example, all openings can be elliptical in shape.

[0020] Independent of these details, openings with an elliptical shape can have advantages, for example, in terms of electrical and mechanical properties, as the ellipse can, for example, reduce or "cancele" natural anisotropy due to its elongated shape. Referring to the ellipse formed by the corresponding opening, the first axis may correspond to the minor axis of the ellipse and the second axis may correspond to the major axis of the ellipse. Openings with an elliptical shape can be combined at different distances according to feature ii), or alternatively, can be provided in a pattern with the same distance along the first axis and along the second axis.

[0021] Typically, the device formed in a die can be, for example, an insulated gate bipolar transistor (IGBT). However, in embodiments, the device can be a transistor having, for example, a source region, a drain region, and a body region within a semiconductor body. Additionally, it may include a drift region between the body region and the drain region, which, for example, is made of the same doping type as the drain region but has a lower doping concentration. The source and drain regions, as well as the drift region (if present), can be made of a first doping type, while the body region can be made of a second doping type. In an exemplary embodiment, the first type is n-type and the second type is p-type.

[0022] Independent of a specific device type, trench structures can be provided on the front side of the semiconductor body. Typically, such trench structures can include, for example, columnar trenches, which may also be referred to as needle trenches. Columnar trenches can extend, for example, into the drift region of the device, and can respectively include columnar or needle-shaped field electrodes capacitively coupled to the drift region.

[0023] In an embodiment, the trench structure formed on the front side of the semiconductor body includes multiple longitudinal trenches. Compared to a lateral direction perpendicular to a longitudinal direction (i.e., a transverse direction), longitudinal trenches can, for example, have a significantly larger extension in said lateral direction (longitudinal direction). Typically, longitudinal and columnar trenches can be combined; for example, longitudinal trenches may include a gate electrode and columnar trenches may include a field electrode.

[0024] In an embodiment, the longitudinal groove has a longitudinal extension whose longitudinal direction forms an angle of up to 30° with the second axis, with an additional upper limit of, for example, up to 20° or 10°. In particular, the longitudinal direction may be parallel to the second axis. Arranging the longitudinal grooves at a small angle or even parallel to the second axis can, for example, allow for a certain "cancellation" of the anisotropy on the front side by introducing anisotropy to the back side.

[0025] In a plan view of the front side of a semiconductor body, longitudinal trenches can, for example, form a stripe pattern. Each longitudinal trench can form a straight line, such as parallel to each other. This trench pattern on the front side can correspond to a primitive pattern of a device, which includes, for example, multiple stripe-shaped primitives.

[0026] Independent of these details, in embodiments, the longitudinal trenches may each include: a field plate capacitively coupled to the drift region of the device. In other words, the respective longitudinal trench extends vertically into the drift region and includes a plate-shaped field electrode, wherein the field electrode may be coupled to the drift region via a field dielectric at the bottom and / or one or more sidewalls of the longitudinal trench.

[0027] Considering, for example, an arrangement where the drift region is located below the body region, the longitudinal trenches can extend to a relatively large depth within the semiconductor body, thus allowing for specific relevance to the cancellation achieved by the pattern on the back side. Typically, the corresponding longitudinal trenches can, for example, consist only of field plates, where the longitudinal field plates and longitudinal gate trenches can be arranged alternately in the lateral direction. Alternatively, the gate electrode can also be arranged above the semiconductor body, for example, as a planar gate. However, in embodiments, the longitudinal field plate trenches can additionally include a gate electrode, with the field plate, for example, arranged in the lower segment of the longitudinal trench and the gate electrode arranged in its upper segment.

[0028] In this embodiment, the semiconductor body has a thickness of up to 100 μm, with additional upper limits such as, for example, up to 50 μm, 40 μm, 35 μm, 30 μm, 28 μm, 26 μm, 24 μm, 22 μm, or 20 μm. Possible lower limits may be at least 10 μm, 15 μm, or 18 μm. This thickness is obtained vertically between the front and back sides of the semiconductor body, with the depth of openings on the back side and possible trench structures on the front side being, for example, neglected; in other words, this thickness is obtained laterally next to openings on the back side and laterally next to trenches on the front side.

[0029] In an embodiment, the depth of the corresponding opening on the back side has a ratio of at least 1:5 to the thickness of the remaining semiconductor body above the corresponding opening. Further lower limits can be, for example, at least 1:2, 1:1, 2:1, or 3:1, and possible upper limits are, for example, 10:1, 8:1, 6:1, 5:1, or 4:1. Specifically, this ratio can be obtained between the distance from the back side to the bottom of the opening and the distance from the bottom of the opening to the front side of the semiconductor body.

[0030] In an embodiment, the semiconductor body may be quite thick (e.g., 100 μm), and the opening may be quite deep (e.g., 90 μm). In this case, the ratio of the thickness of the semiconductor body to the thickness of the remaining semiconductor body above the corresponding opening may be 10:1.

[0031] In embodiments, the semiconductor die includes back metallization, i.e., back metallization is included on the back side of the semiconductor body. Typically, this can be, for example, aluminum back metallization, while embodiments of this application involve back metallization including a copper layer (e.g., a barrier layer, such as Ti / TiN, combining the copper layer and the semiconductor body). Depending on the material details, the back metallization can serve as, for example, an electrical contact with load terminals (e.g., drain terminals / regions) formed on the back side of the semiconductor body. Alternatively or additionally, it can provide a thermal connection to the package, or allow for “counteracting” the front metallization in relation to thermomechanically induced die bending.

[0032] In one embodiment, the backside metallization fills the openings, for example, completely fills the openings, and covers the backside of the semiconductor body between the openings. In another embodiment, the backside metallization only partially fills the openings, but still covers the backside of the semiconductor body between the openings. In both embodiments, in a plan view of the backside, the backside metallization can form a continuous layer, for example, completely covering the backside of the semiconductor body.

[0033] The thickness of the back metallization can be at least 2 μm and / or at most 10 μm. This thickness is achieved between the openings, i.e., from the back side of the semiconductor body to the side of the back metallization opposite to the semiconductor body.

[0034] In this embodiment, the depth of the corresponding opening is at least 10 μm, with a further lower limit of, for example, at least 12 μm or 14 μm. Possible upper limits could be 90 μm, 80 μm, 50 μm, 20 μm, 18 μm, or 16 μm, wherein the opening in the exemplary embodiment has a depth of approximately 15 μm. As discussed above, this depth can be obtained vertically between the back surface of the semiconductor body and the bottom of the corresponding opening.

[0035] In one embodiment, a method of manufacturing a semiconductor die includes structuring the back side of a semiconductor body by forming a plurality of openings. These openings may be arranged in a repeating pattern along first and second axes, for example having an anisotropic shape (characteristic i) and / or spacing (characteristic ii), as detailed above. The openings can be formed, for example, by dry etching. Attached Figure Description

[0036] The following describes a semiconductor die and its manufacturing process in more detail with the aid of exemplary embodiments. Individual characteristics can also be relevant in different combinations.

[0037] Figure 1 The semiconductor die is shown in a vertical cross-section;

[0038] Figure 2 A schematic plan view showing an opening located on the back side of the semiconductor body;

[0039] Figure 3 An alternative embodiment with an opening located on the back side of the semiconductor body is shown in a schematic plan view;

[0040] Figure 4 Another alternative embodiment of the opening located on the back side of the semiconductor body is shown in the schematic plan view;

[0041] Figure 5 The schematic cross-section illustrates the device structure within the semiconductor body;

[0042] Figure 6 This shows a semiconductor body with back-side metallization;

[0043] Figure 7a -c illustrates some manufacturing steps;

[0044] Figure 8 Summarize some manufacturing steps in the flowchart. Detailed Implementation

[0045] Figure 1 The semiconductor die 1 is shown in a vertical cross-section, the cross-sectional plane being parallel to the vertical direction 140 and the first lateral direction 141. The semiconductor die 1 includes a semiconductor body 10, which, in the illustrated example, is made of single-crystal silicon. On the front side 10.1 of the semiconductor body 10, a front metallization 20 is arranged, as shown, including: a wiring layer 21, for example made of aluminum (e.g., AlCu); and a top layer 22. In this example, the top layer 22 is made of copper.

[0046] An insulating layer 25 may be disposed between the semiconductor body 10 and the front metallization 20, and a sandwich dielectric 26 may be disposed between the wiring layer 21 and the topmost metallization layer 22. The topmost metallization layer 22 may be contacted during subsequent bonding and packaging processes, for example, by wire or clip bonding. In alternative embodiments not shown here, the front metallization 20 may include only the topmost metallization layer or may include more than one wiring layer.

[0047] Reference Figure 6 The device 60 formed in the semiconductor die 1 is discussed in more detail. It includes a trench structure 50 with longitudinal trenches 51 on the front side 10.1 of the semiconductor body 10. These trenches 51 have a length extension perpendicular to the plane of the drawing (i.e., in the longitudinal direction 55).

[0048] The back surface 10.2 of the semiconductor body 10 is structured to have a plurality of openings 30. The openings 30 extend from the second side 10.2 into the semiconductor body 10 in a vertical direction 140 (extending in this direction, but not upward to its first side 10.1). In the example shown, the openings 30 are filled with a back surface metallization 80, which also covers the back surface 10.2 between the openings 30.

[0049] Figure 2 A schematic plan view is shown, i.e., the rear face 10.2 viewed in the vertical direction 140. This illustration shows the arrangement of the openings 30 in the repeating pattern 40 (i.e., along the first axis 41 and along the second axis 42). Only a small portion of the rear face 10.2 is shown, and the pattern 40 continues in the first lateral direction 141 and also in the second lateral direction 142.

[0050] The openings 30 each have a width d obtained along the first axis 41. 41 and the width d obtained along the second axis 42 42 The width d of the corresponding opening 30 41 Less than its width d 42 In other words, the opening 30 has a larger extension along the second axis 42 compared to the opening along the first axis 41. Figure 2 In the embodiments, the openings 30 have a circular shape without corners, that is, an elliptical shape in this example.

[0051] like Figure 2 As indicated in the diagram, the second axis 42 and the second lateral direction 142 are parallel to the longitudinal direction 55 defined by the trench structure formed on the vertically opposite front sides of the semiconductor body 10 (see [reference]). Figure 1 and 5 (Comparison). Figure 2 In the embodiment illustrated in the figure, different widths d41 d 42 Anisotropy is introduced to the back face 10.2, wherein the distance s between adjacent openings 30 is... 41 s 42 The first axis 41 and the second axis 42 are equal.

[0052] Figure 3 An alternative embodiment is shown. The distance s obtained along the first axis 41 between adjacent openings 30 41 Greater than the distance s obtained along the second axis 42 between adjacent openings 30 42 In other words, the openings 30 are arranged closer to each other along the second axis 42 compared to along the first axis 41. Again, the second axis 42 and the second lateral direction 142 are parallel to the longitudinal direction 55 of the groove structure on the vertically opposite front.

[0053] exist Figure 4 In this embodiment, the opening 30 does not have a circular shape, but instead has a polygonal shape, i.e., a hexagonal shape in this example. The opening 30 is stretched along the second axis 42, and the width d obtained along the first axis 41 is... 41 The width d obtained along the second axis 42 is smaller than 42 Furthermore, compared to along the first axis 41, they are arranged closer to each other along the second axis 42, thus reducing the distance s. 41 Greater than distance s 42 .

[0054] Although only oval, circular, and hexagonal shapes are illustrated Figures 2 to 4 However, this disclosure is not limited to these shapes of opening 30, and other shapes such as triangles, squares, rectangles, rhombuses, pentagons or shapes with more than five corners are conceivable.

[0055] in addition, Figures 2 to 4 The centers of the shapes exemplarily shown in the opening 30 all form a rectangular pattern. This disclosure should not be construed as limiting in this respect, and the centers of the shapes can also be arranged in different patterns, for example, in which the centers in one row staggered relative to the centers in the next row (e.g., the centers arranged in a hexagonal pattern). It can be readily understood that in the staggered arrangement of the centers of the shapes of the opening 30, the distance s 41 and s 42 One of them can be negative (for example, shapes arranged in one row can interweave with shapes arranged in the next row).

[0056] Figure 5The illustration shows a possible device 60 formed in a semiconductor die 1. In the example shown, device 60 is a vertical FET. It includes a source region 61, a body region 62, and a drain region 63, with a drift region 66 disposed between the body region 62 and the drain region 63. In the example shown, the source region 61, drift region 66, and drain region 63 are n-doped, the drift region 66 has a lower doping concentration than the drain region 63, and the body region 62 is p-doped.

[0057] The device 60 includes a trench structure 50 having a plurality of longitudinal trenches 51, each longitudinal trench 51 having a corresponding length extension in the longitudinal direction 55 (perpendicular to the plane of the drawing). In the lower section region, each trench 51 includes a field plate 65, which is capacitively coupled to the drift region 66. In the upper section region, corresponding gate electrodes 69 capacitively coupled to the main body region 62 are arranged.

[0058] Figure 5 The illustration shows an exemplary device. Alternatively, the field plate and gate electrode can be arranged, for example, in separate trenches (alternatingly arranged in separate trenches in the first lateral direction 141). As an alternative to the field plate in the longitudinal trench, columnar field electrodes in columnar trenches can be provided. Furthermore, the FET is merely an exemplary device; alternatively, an IGBT, for example, can be provided.

[0059] Figure 6 A semiconductor body 10 with an opening 30 on its back side 10.2 is shown. The back side 10.2 is covered by a back side metallization 80, which fills the opening 30. According to an embodiment, the openings 30 each have a depth 130 of 10-20 μm, wherein the thickness 110a retained above the respective opening 30 is approximately 3-6 μm. The back side metallization 80 has a thickness 180 of 2-10 μm, wherein the thickness 110 of the semiconductor body 10 is approximately 20 μm in this example.

[0060] Figure 7a -c illustrates some manufacturing steps. Figure 7a In this process, front-side metallization 20 has been formed on the front side 10.1 of the semiconductor body 10. Figure 7b In the subsequent steps shown, openings 30 230 are formed on the back surface 10.2 by dry etching 235. To define the shape and arrangement of the openings 30, a mask (not shown) can be formed and structured on the back surface 10.2. After removing the mask, back surface metallization 80 can be deposited, see [reference needed]. Figure 7c The metal fills the opening 30 and covers the back side 10.2 between the openings 30.

[0061] Figure 8The flowchart summarizes some manufacturing steps. After forming a 300-sided metallization on the semiconductor substrate, an opening 230 can be formed on the back side. Subsequently, a back side metallization 310 can be deposited.

Claims

1. A semiconductor die (1), comprising: Semiconductor body (10); Front-side metallization (20) is located on the front side (10.1) of the semiconductor body (10); The back surface (10.2) of the semiconductor body (10) is structured to have a plurality of openings (30), which extend into the semiconductor body (10). The plurality of openings (30) are arranged in a repeating pattern (40) along the first axis (41) and along the second axis (42). It has at least one of the following: i) Compared to the width (d) of the corresponding opening (30) along the second axis (42), 41 d 42 Smaller along the first axis (41), ii) The corresponding distance (s) between adjacent openings (30) compared to along the second axis (42). 41 s 42 (41) is larger along the first axis.

2. The semiconductor die (1) as claimed in claim 1, wherein the opening (30) has a circular shape in a plan view of the back side (10.2) of the semiconductor body (10).

3. The semiconductor die (1) as claimed in claim 2, wherein the opening (30) has an elliptical shape in a plan view of the back side (10.2) of the semiconductor body (10).

4. The semiconductor die (1) as claimed in any of the preceding claims, wherein a trench structure (50) is formed on the front side (10.1) of the semiconductor body (10), the trench structure (50) comprising a plurality of longitudinal trenches (51) parallel to each other, wherein the longitudinal direction (55) of the longitudinal trenches (51) forms an angle of up to 30° with the second axis (42).

5. The semiconductor die (1) as claimed in claim 4, wherein the longitudinal direction (55) of the longitudinal trench (51) is parallel to the second axis (42).

6. The semiconductor die (1) as claimed in claim 4 or 5, wherein the longitudinal trenches (51) each include a field plate (65) that is capacitively coupled to a drift region (66) of a device (60) formed in the semiconductor die (1).

7. The semiconductor die (1) as claimed in any of the preceding claims, wherein the semiconductor body (10) has a thickness (110) of up to 100 μm between the front side (10.1) and the back side (10.2).

8. The semiconductor die (1) as claimed in any of the preceding claims, wherein the depth (130) of the corresponding opening (30) has a ratio of at least 1:1 and at most 10:1 to the thickness (110a) of the remaining semiconductor body (10a) above the corresponding opening (30).

9. The semiconductor die (1) as described in any of the preceding claims, comprising: Backside metallization (80) is located on the backside (10.2) of the semiconductor body (10).

10. The semiconductor die (1) of claim 9, wherein the back metallization (80) fills the opening (30) and covers the back side (10.2) of the semiconductor body (10) between the openings (30).

11. The semiconductor die (1) of claim 9, wherein the back metallization (80) forms a layer covering the back side (10.2) of the semiconductor body (10) and only partially fills the opening (30).

12. The semiconductor die (1) as claimed in any one of claims 9 to 11, wherein the thickness (180) of the back metallization (80) between the openings (30) is at least 2 μm and at most 30 μm.

13. The semiconductor die (1) as described in any of the preceding claims, wherein the depth (130) of the corresponding opening (30) is at least 10 μm and at most 90 μm.

14. The semiconductor chip of claim 1, wherein the semiconductor body has a thickness of up to 50 μm between the front and back sides.

15. A method of manufacturing a semiconductor die (1) as described in any of the preceding claims, the method comprising: -The back surface (10.2) of the semiconductor body (10) is structured by forming (230) the plurality of openings (30).

16. The method of claim 15, wherein the opening (30) is formed (230) by dry etching (235).

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