Semiconductor device

Abstract

To provide a semiconductor device capable of suppressing reflection of light inside the device.SOLUTION: A semiconductor device includes: a semiconductor chip mounted on a wiring board; and a pincushion-like structure provided on a second face, of the semiconductor chip, on a side opposite a first side, the first side facing the wiring board. Needles of the pincushion-like structure each have a height of 1.0 μm or more and 2.0 μm or less, and the needles each have a width of 0.1 μm or more and 1.0 μm or less.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a semiconductor device.

Background Art

[0002] In recent years, the development of a micro LED display in which a plurality of LED (Light Emitting Diode) chips are arranged as pixels on a wiring board has been advanced.

[0003] For example, Patent Document 1 below discloses a display in which a light emitting unit including a plurality of LED chips is mounted on a wiring board. Patent Document 1 discloses providing a dark light absorption layer that absorbs light on the wiring board between adjacent light emitting units in order to suppress light interference between the light emitting units.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the dark light absorption layer suppresses light interference between the light emitting units by absorbing part of the light emitted from the light emitting units. Therefore, the display described in Patent Document 1 has reduced the light emission efficiency of the light emitting units. Therefore, in order to suppress light interference between adjacent LED chips without reducing the light emission efficiency, it has been required to suppress light reflection inside the device.

[0006] Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a novel and improved semiconductor device capable of suppressing light reflection inside the device.

Means for Solving the Problems

[0007] According to an aspect of the present invention, in order to solve the above problems, a semiconductor device is provided, which includes a semiconductor chip mounted on a wiring board and a needle mountain-like structure provided on a second surface opposite to a first surface of the semiconductor chip facing the wiring board, wherein the height of the needles of the needle mountain-like structure is 1.0 μm or more and 2.0 μm or less, and the width of the needles is 0.1 μm or more and 1.0 μm or less.

Effects of the Invention

[0008] As described above, according to the present invention, it is possible to suppress the reflection of light inside the device.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 6

Modes for Carrying Out the Invention

[0010] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0011] <1. Configuration of Semiconductor Device> First, with reference to FIGS. 1 and 2, the configuration of a semiconductor device according to an embodiment of the present invention will be described. FIG. 1 is a longitudinal sectional view showing the configuration of a semiconductor device 1 according to this embodiment. FIG. 2 is a longitudinal sectional view showing another configuration of the semiconductor device 1 according to this embodiment.

[0012] As shown in FIG. 1, the semiconductor device 1 includes a wiring substrate 300, bump electrodes 210, a semiconductor chip 200, and a needle-like structure 100. The semiconductor device 1 may be, for example, a micro LED display device in which a plurality of LED chips are mounted on the wiring substrate 300 in a two-dimensional array. The semiconductor chip 200 can control the light emission of each of the plurality of LED chips mounted on the wiring substrate 300.

[0013] The wiring substrate 300 is a substrate provided with wiring (not shown) for electrically connecting the semiconductor chip 200 mounted on the wiring substrate 300 and the plurality of LED chips. The wiring substrate 300 may be, for example, a glass substrate, a glass epoxy substrate, an epoxy substrate, a polyimide substrate, or a (meth)acrylic substrate, or may be a flexible substrate made of polyester or polyethersulfone. The wiring substrate 300 may be, for example, a pixel array substrate of a micro LED display device.

[0014] The bump electrode 210 is a conductive structure that electrically connects a wiring (not shown) provided on the wiring substrate 300 and a chip electrode (not shown) provided on the semiconductor chip 200. The bump electrode 210 is provided for each semiconductor chip 200 mounted on the wiring substrate 300. For example, the bump electrode 210 may be a metal electrode formed by plating or vapor deposition, a resin core electrode in which a resin core is covered with a metal film, a solder paste, or a solder ball. The shape of the bump electrode 210 may be a frustum shape, a column shape, a hemispherical shape, or a flattened spherical shape.

[0015] The semiconductor chip 200 is an IC (Integrated Circuit) chip in which an electronic circuit having an arithmetic function is formed on silicon. For example, the semiconductor chip 200 may be a control IC chip that controls the light emission of an LED chip that functions as a pixel of a micro LED display device. A chip electrode that is electrically connected to a wiring provided on the wiring substrate 300 via the bump electrode 210 is formed on the first surface S1 of the semiconductor chip 200 that faces the wiring substrate 300.

[0016] The needle mountain-like structure 100 is provided in the semiconductor layer on the second surface S2 opposite to the first surface S1 of the semiconductor chip 200. The needle mountain-like structure 100 has a high aspect ratio and is a structure in which a plurality of steep convex structures (for example, needle-like structures) are two-dimensionally arranged. The needle mountain-like structure 100 having a steep convex structure reflects the incident light downward at the side surface of the convex structure. Therefore, the light reflected at the side surface of the convex structure is further reflected downward at the side surface of the opposing convex structure. Therefore, the light incident on the needle mountain-like structure 100 is confined in the space between the convex structures by multiple reflections between the convex structures, so that the needle mountain-like structure 100 can absorb most of the incident light in the semiconductor layer without reflecting it to the outside. Such a needle mountain-like structure 100 is also referred to as so-called black silicon. Thereby, the needle mountain-like structure 100 can suppress the reflection of light at the second surface S2 of the semiconductor chip 200.

[0017] Note that the details of the shape of the needle mountain-like structure 100 included in the semiconductor device 1 according to the present embodiment will be described later with reference to FIGS. 3 and 4.

[0018] In the above, the needle mountain-like structure 100 is provided on the second surface S2 of the semiconductor chip 200 that controls the light emission of each of the LED chips. However, the present invention is not limited to the above example. For example, as shown in FIG. 2, the needle mountain-like structure 100 may be provided on the LED chips 200R, 200G, and 200B that function as pixels of the micro LED display device.

[0019] The LED chips 200R, 200G, and 200B are each mounted on the wiring board 300 via bump electrodes 210, similarly to the semiconductor chip 200. Specifically, chip electrodes (not shown) are provided on the first surface S1 of the LED chips 200R, 200G, and 200B that faces the wiring board 300. The LED chips 200R, 200G, and 200B are electrically connected to the wiring of the wiring board 300 via the chip electrodes and the bump electrodes 210.

[0020] The LED chip 200R is, for example, a light-emitting diode that emits red light. The LED chip 200G is, for example, a light-emitting diode that emits green light. The LED chip 200B is, for example, a light-emitting diode that emits blue light. The micro LED display device can display a full-color image by using the LED chips 200R, 200G, and 200B.

[0021] The LED chips 200R, 200G, and 200B may be made of a compound semiconductor such as GaN, for example. Even when the LED chips 200R, 200G, and 200B are made of a compound semiconductor other than silicon, the needle mountain-like structure 100 can similarly absorb most of the incident light by the steep convex structure.

[0022] Note that the LED chips 200R, 200G, and 200B may be formed, for example, on a compound semiconductor layer laminated on a non-semiconductor substrate such as a sapphire substrate, a glass substrate, or a quartz substrate. In such a case, the LED chips 200R, 200G, and 200B can expose the compound semiconductor layer by peeling off the sapphire substrate laminated on the second surface S2 opposite to the first surface S1 provided with the chip electrodes. Thereby, the LED chips 200R, 200G, and 200B can form the hedgehog-like structure 100 on the exposed compound semiconductor layer.

[0023] According to the above configuration, the semiconductor device 1 according to the present embodiment can absorb the light incident on the hedgehog-like structure 100 provided on the second surface S2. Therefore, the semiconductor device 1 according to the present embodiment can suppress the reflection of the incident light.

[0024] <2. Details of the Hedgehog-Like Structure> Next, with reference to FIGS. 3 and 4, the details of the shape of the hedgehog-like structure 100 will be described. FIG. 3 is a schematic perspective view showing the details of the shape of the hedgehog-like structure 100. FIG. 4 is a longitudinal sectional view for explaining the dimensions of the convex structure 110 included in the hedgehog-like structure 100.

[0025] As shown in FIG. 3, the hedgehog-like structure 100 is provided on the second surface S2 of the semiconductor chip 200. The hedgehog-like structure 100 is configured by arranging a plurality of convex structures 110 extending in the normal direction of the second surface S2. The two-dimensional arrangement of the convex structures 110 may be a random arrangement or an arrangement having periodicity.

[0026] As shown in FIG. 4, the height h of the convex structure 110 may be 1.0 μm or more and 2.0 μm or less. The height h of the convex structure 110 is defined, for example, as the height from the flat portion existing between the convex structures 110 to the apex of the convex structure 110. When the height h of the convex structure 110 is 1.0 μm or more, the hedgehog-like structure 100 has a higher aspect ratio and can sufficiently confine the incident light in the space between the convex structures 110, so that the absorption rate of the incident light can be further improved. On the other hand, when the height h of the convex structure 110 is 2.0 μm or less, the hedgehog-like structure 100 can more easily form the convex structure 110, so that the manufacturing cost of the convex structure 110 can be reduced.

[0027] Also, the width w of the convex structure 110 may be 0.1 μm or more and 1.0 μm or less. The width w of the convex structure 110 is defined, for example, as the total width of the convex structure 110 at the position of half the height of the convex structure 110 (in other words, the width corresponding to the half-value width when the convex structure 110 is regarded as one peak). When the width w of the convex structure 110 is 0.1 μm or more, the hedgehog-like structure 100 can more easily form the convex structure 110, so that the manufacturing cost of the convex structure 110 can be reduced. On the other hand, when the width w of the convex structure 110 is 1.0 μm or less, the hedgehog-like structure 100 has a higher aspect ratio and can reflect the incident light downward at the side surface of the convex structure 110, so that the absorption rate of the incident light can be further improved.

[0028] Furthermore, the interval g between the convex structures 110 may be 0.1 μm or more and 2.0 μm or less. The interval g between the convex structures 110 is defined, for example, as the interval between the convex structures 110 at the position of half the height of the convex structure 110. When the interval g between the convex structures 110 is 0.1 μm or more, the hedgehog-like structure 100 can more easily form the convex structure 110, so that the manufacturing cost of the convex structure 110 can be reduced. On the other hand, when the interval g between the convex structures 110 is 2.0 μm or less, the hedgehog-like structure 100 can sufficiently confine the incident light in the space between the convex structures 110, so that the absorption rate of the incident light can be further improved.

[0029] The needle-like structure 100 with a plurality of convex structures 110 arranged in such a shape can have a light absorption rate in the visible light band of 95% or more. The light absorption rate of the needle-like structure 100 in the visible light band can be measured, for example, by normal reflectance measurement.

[0030] Note that the shape of the tip of the convex structure 110 is not particularly limited. The shape of the tip of the convex structure 110 may be a flat surface or a curved surface, or may be an acute-angled shape with a ridge line or a vertex protruding. Regardless of the shape of the tip, the needle-like structure 100 can improve the absorption rate of incident light by setting at least the height and width of the convex structure 110 within the above ranges. Further, the needle-like structure 100 can further improve the absorption rate of incident light by setting the interval between the convex structures 110 within the above range.

[0031] <3. Method for forming the needle-like structure> Subsequently, with reference to FIGS. 5A to 5D, a method for forming the needle-like structure 100 provided on the semiconductor chip 200 will be described. FIGS. 5A to 5D are longitudinal sectional views for explaining each step of the method for forming the needle-like structure 100.

[0032] First, as shown in FIG. 5A, a semiconductor chip 200 made of silicon (Si) is prepared. The second surface S2 of the semiconductor chip 200 is a semiconductor layer made of Si.

[0033] Note that when the semiconductor chip 200 is a laminate of a non-semiconductor substrate and a semiconductor layer, and the second surface S2 on which the needle-like structure 100 is to be formed is the non-semiconductor substrate, a step of peeling the non-semiconductor substrate existing on the second surface S2 from the semiconductor layer may be performed prior to this step. According to this, the semiconductor chip 200 can expose the semiconductor layer on the second surface S2.

[0034] Next, as shown in FIG. 5B, anisotropic etching Et is performed on the second surface S2 of the semiconductor chip 200. When forming the needle-shaped structure 100 in the semiconductor layer made of Si, for the anisotropic etching Et, reactive ion etching (RIE) using a mixed gas of SF6 / O2 is used. In reactive ion etching, the Si exposed on the second surface S2 is etched by the SF6 plasma.

[0035] At this time, by controlling the etching conditions such as the flow rate of the mixed gas and etching the Si exposed on the second surface S2 unevenly, as shown in FIG. 5C, recesses 120H are randomly formed on the second surface S2. Further, on the tip of the convex portion 110A between the recesses 120H, a SiO2 film 130 generated by the reaction of the etched Si and O2 radicals is deposited. Since the deposited SiO2 film 130 functions as a protective film for etching by the SF6 plasma, the etching of the convex portion 110A is suppressed, and thus the etching into the recesses 120H further proceeds.

[0036] Therefore, as shown in FIG. 5D, as the anisotropic etching Et proceeds, the etching into the recesses 120H where the SiO2 film 130 is not deposited selectively proceeds, and thus a convex structure 110 with a high aspect ratio is formed.

[0037] Through the above steps, a needle-shaped structure 100 including a convex structure 110 with a high aspect ratio is formed on the second surface S2 of the semiconductor chip 200. Note that for the LED chips 200R, 200G, and 200B made of compound semiconductors, by changing the etching gas and etching conditions, it is also possible to form the needle-shaped structure 100 in the same manner as silicon.

Example

[0038] Hereinafter, with reference to the examples, the needle-shaped structure 100 included in the semiconductor device 1 according to the present embodiment will be specifically described. Note that the examples shown below are merely examples, and the needle-shaped structure 100 included in the semiconductor device 1 according to the present embodiment is not limited to the following examples.

[0039] (Example) First, a semiconductor chip with an electronic circuit formed on the surface of a silicon substrate was prepared. Subsequently, reactive ion etching was performed on the back surface of the semiconductor chip opposite to the surface (i.e., the surface where the silicon substrate was exposed). For the reactive ion etching, SF6 / O2 = 21 / 11 sccm was used as the etching gas, and the RF (Radio Frequency) power was set to 700 W. By performing the reactive ion etching, a mountain-like structure of needles was formed on the back surface of the semiconductor chip. Four samples with a mountain-like structure of needles formed on the back surface of the semiconductor chip were fabricated.

[0040] (Evaluation) Next, the mountain-like structure of needles formed on the back surface of the semiconductor chip was observed using a scanning electron microscope (SEM). One of the SEM observation results is shown in FIG. 6. FIG. 6 is an SEM image of the mountain-like structure of needles formed on the semiconductor chip according to the example, observed at a magnification of 10,000 times.

[0041] From the SEM observation results, the height, width, and the interval between the convex structures of the mountain-like structure of needles were visually measured at 5 points per sample. The average value of the 5 measurement results for each sample is shown in Table 1.

[0042] Also, by performing specular reflectance measurement on the back surface of the semiconductor chip of each sample, the light absorption rate of the mountain-like structure of needles was measured. The light absorption rate of the mountain-like structure of needles was 95% in the visible light band, respectively.

[0043] [Table 1]

[0044] As shown in FIG. 6, it can be seen that the semiconductor chip according to the example has a mountain-like structure in which a plurality of steep needle-like convex structures stand due to reactive ion etching.

[0045] Also, as shown in Table 1, for the semiconductor chip according to the embodiment, since the height of the convex structure of the needle mountain-like structure is 1.0 μm or more and 2.0 μm or less, and the width of the convex structure is 0.1 μm or more and 1.0 μm or less, it is possible to increase the light absorption rate in the visible light band to 95% or more. Further, for the semiconductor chip according to the embodiment, since the interval between the convex structures of the needle mountain-like structure is 0.1 μm or more and 2.0 μm or less, it is possible to further increase the light absorption rate in the visible light band.

[0046] (Appendix) As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that these also belong to the technical scope of the present invention.

[0047] For example, in the above embodiment, the needle mountain-like structure 100 is provided on the second surface S2 of the semiconductor chip 200, but the present invention is not limited to such an example. For example, the needle mountain-like structure 100 may be provided on the first surface S1 opposite to the second surface S2 of the semiconductor chip 200, or may be provided on at least one or more side surfaces of the semiconductor chip 200. Even in such a case, the needle mountain-like structure 100 can suppress the reflection of incident light.

Explanation of Reference Numerals

[0048] 1... semiconductor device, 100... needle mountain-like structure, 110... convex structure, 200... semiconductor chip, 210... bump electrode, 300... wiring board, S1... first surface, S2... second surface

Claims

1. A semiconductor chip mounted on a wiring board, A hedgehog-like structure provided on a second surface opposite to a first surface of the semiconductor chip facing the wiring board, Comprising, The height of the needles of the hedgehog-like structure is 1.0 μm or more and 2.0 μm or less, and the width of the needles is 0.1 μm or more and 1.0 μm or less. A semiconductor device.

2. The distance between the needles is 0.1 μm or more and 2.0 μm or less. The semiconductor device according to claim 1.

3. The light absorption rate of the hedgehog-like structure in the visible light band is 95% or more. The semiconductor device according to claim 1 or 2.

4. The semiconductor chip is an IC chip or an LED chip. The semiconductor device according to claim 1 or 2.

5. The hedgehog-like structure is provided on a semiconductor layer exposed on the second surface of the semiconductor chip. The semiconductor device according to claim 1 or 2.

6. The semiconductor chip is electrically connected to the wiring board through a chip electrode provided on the first surface and a bump electrode provided on the wiring board. The semiconductor device according to claim 1 or 2.

Images