JP2012033718A - Semiconductor device and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which has a highly-airtight cavity encapsulating an element region including elements and the like.SOLUTION: The semiconductor device manufacturing method comprises the steps of preparing a semiconductor substrate 10 on which an element region 11 including elements is formed, forming, on the semiconductor substrate 10, a resin layer 13 having a through hole 13A exposing the element region 11, subsequently forming a metallic thin film 14 extending from the resin layer 13 including a side wall 13W of the through hole 13A to cover a part of the semiconductor substrate 10, bonding a support member 15 so as to directly contact the metallic thin film 14, and encapsulating the element region 11 in a cavity 16 surrounded by the semiconductor substrate 10, the resin layer 13, the metallic thin film 14 and the support member 15. In the bonding step, bonded interfaces of the metallic thin film 14 and the support member 15 are bonded by using a surface activated bonding method in a vacuum.

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device in which an element formed on a semiconductor substrate is sealed and a manufacturing method thereof.

  In recent years, semiconductor devices in which elements such as MEMS (Micro Electro Mechanical Systems) and light receiving elements are sealed on a semiconductor substrate have been developed. In such a semiconductor device, a resin layer is formed on a semiconductor substrate so as to surround an element region where a MEMS or a light receiving element is formed. And a glass substrate is bonded on the resin layer through an adhesive made of resin. That is, the element region on the semiconductor substrate is sealed in a cavity surrounded by the semiconductor substrate, the resin layer, and the glass substrate. A semiconductor device having such a sealing structure is described in Patent Documents 1 and 2.

International Publication No. 2008/023824 International Publication No. 2008/023827

  However, in the conventional semiconductor device as described above, due to the roughness of the density of the resin layer and the unevenness of the surface of the resin layer, it passes between the resin layer and the glass substrate, or the adhesive and the glass substrate made of resin. As a result, there was a problem that external moisture entered the cavity. Alternatively, external moisture may penetrate and penetrate the resin layer itself that becomes the side wall of the cavity. Moisture that has entered the cavity may cause dew condensation and adversely affect light transmission, and may cause electrical or mechanical damage to the device.

The semiconductor device of the present invention has been made in view of the above-described problems, and includes a semiconductor substrate,
An element region including an element formed on a surface of the semiconductor substrate; a resin layer disposed on the semiconductor substrate having a through hole exposing the element region; and on the resin layer and in the through hole A metal thin film disposed on a side wall; a metal thin film formed on the resin layer; and a support directly bonded to the metal thin film, the semiconductor substrate, the resin layer, the metal thin film, and The element region is sealed in a cavity surrounded by the support.

  In addition, a method for manufacturing a semiconductor device according to the present invention provides a semiconductor substrate on which an element region including elements is formed and a support, and a resin layer having a through hole exposing the element region on the semiconductor substrate. Forming a metal thin film on the resin layer and on the side wall in the through hole, removing a contaminant on each surface of the metal thin film and the support in a vacuum, and vacuum A step of directly joining the metal thin film on the resin layer and the support.

  According to the present invention, the metal thin film formed on the resin layer and the support are directly joined, and the resin layer on the side wall of the cavity is covered with the metal thin film, so that the airtightness of the cavity is increased, and from the outside It is possible to prevent moisture from entering the cavity.

It is sectional drawing which shows the semiconductor device by embodiment of this invention. It is a top view which shows the semiconductor device by embodiment of this invention. It is sectional drawing which shows the manufacturing method of the semiconductor device by embodiment of this invention. It is sectional drawing which shows the manufacturing method of the semiconductor device by embodiment of this invention. It is sectional drawing which shows the manufacturing method of the semiconductor device by embodiment of this invention. It is the elements on larger scale explaining joining of the metal thin film of FIG. 5, and a support body. It is sectional drawing which shows the manufacturing method of the semiconductor device by embodiment of this invention. It is sectional drawing which shows the manufacturing method of the semiconductor device by embodiment of this invention. It is sectional drawing which shows the modification of the semiconductor device by embodiment of this invention.

  A schematic configuration of a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a completed semiconductor device.

  An element region 11 including elements and wirings is disposed on the surface of the semiconductor substrate 10 of the semiconductor device, and a pad electrode 12 connected to the element is disposed at an end of the semiconductor substrate 10. The semiconductor substrate 10 is made of, for example, a silicon substrate. The elements in the element region 11 include, for example, light receiving elements such as photodiodes and CCDs, but may include other electrical or mechanical devices such as MEMS. Hereinafter, the element region 11 will be described as including a light receiving element such as a photodiode or a CCD.

  A resin layer 13 having a through hole 13 </ b> A that exposes the element region 11 is disposed on the surface of the semiconductor substrate 10. When viewed from the direction perpendicular to the semiconductor substrate 10, the resin layer 13 is disposed so as to surround the periphery of the element region 11. The resin layer 13 is made of, for example, an organic resin such as acrylic, polyimide, or epoxy resin, preferably a photosensitive organic resin used in a photolithography process. Below, the resin layer 13 is demonstrated as what is photosensitive polyimide.

  A metal thin film 14 made of aluminum or a metal containing aluminum is disposed on the upper surface of the resin layer 13 and the side wall 13W inside the through hole 13A. Furthermore, the metal thin film 14 preferably extends continuously to a part on the semiconductor substrate 10 so as not to overlap with the element region 11. The metal thin film 14 may be made of a metal other than the above, for example, copper or a metal containing copper.

  Further, a substrate-like support 15 is bonded to the resin layer 13 via a metal thin film 14 on the resin layer 13. Below, the support body 15 demonstrates as what is a glass substrate which permeate | transmits light.

  On the other hand, a wiring 17 connected to the pad electrode 12 extends on the back surface and side surface of the semiconductor substrate 10. A protective layer 18 is connected to the wiring 17 through the protective layer 18 on the wiring 17. A bump electrode 19 is disposed.

  In this semiconductor device, an element region 11 including elements and the like is sealed in a cavity 16 surrounded by a semiconductor substrate 10, a resin layer 13, a metal thin film 14, and a support 15. Here, the metal thin film 14 on the upper surface of the resin layer 13 and the support 15 are directly bonded, and the bonding hands of the atoms on each surface are directly bonded to each other on the bonding surface of the metal thin film 14 and the support 15. The resin layer 13 that becomes the side wall 13W in the cavity 16 is covered with a metal thin film 14 that does not transmit moisture. Thereby, the airtightness of the cavity 16 becomes higher than that of the conventional example, and it is possible to prevent moisture from entering from the outside. Furthermore, when the metal thin film 14 extends continuously from a side wall 13W in the through-hole 13A to a part of the surface of the semiconductor substrate 10, the airtightness of the cavity can be improved more reliably.

  In addition, instead of the resin layer 13, a thick metal layer is formed, and a sealing structure with a cavity surrounded by the semiconductor substrate 10, the support 15 and the thick metal layer is conceivable. However, in order to realize this sealing structure, it is necessary to form a metal layer extremely thicker than a general wiring process in order to secure a sufficient height of the cavity. Cost increases significantly.

  Even if a thick metal layer is formed, an additional process such as CMP for flattening the irregularities on the surface of the metal layer is required. Further, the element in the element region 11 and the semiconductor substrate 10 are seriously affected by the heat treatment in the formation process of the thick metal layer and the heat treatment (for example, 400 ° C.) on the thick metal layer when the support 15 is bonded to the thick metal layer. There is a risk of serious damage.

  Hereinafter, a method for manufacturing the semiconductor device described above will be described with reference to the drawings. FIG. 2 is a plan view showing the method for manufacturing the semiconductor device, and shows a part of the wafer-like semiconductor substrate 10. 3-5 and FIG. 7-9 are cross-sectional views showing the method of manufacturing this semiconductor device, along the boundary between one semiconductor device and another semiconductor device adjacent thereto, that is, along the line AA in FIG. Shows the location. 6 (A) and 6 (B) are partial enlarged views for explaining the joining of the metal thin film 14 and the support 15 of FIG.

  First, as shown in FIGS. 2 and 3, a wafer-like semiconductor substrate 10 made of, for example, a silicon substrate is prepared. On the surface of the semiconductor substrate 10, an element region 11 including elements, an insulating film (not shown) such as a silicon oxide film, and a pad electrode 12 formed on the insulating film are formed. In addition, illustration of the pad electrode 12 is abbreviate | omitted in FIG.

  Next, as shown in FIG. 3, a photosensitive organic resin material is applied by, for example, spin coating to cover the surface of the semiconductor substrate 10, thereby forming a resin layer 13. According to the spin coating method, the resin layer 13 can be formed as flat as possible. The thickness T1 of the resin layer 13 is 90% or more of the height H of the cavity 16, for example, 5 μm to 50 μm (see FIG. 1). Here, the height H of the cavity 16 is the distance between the surface of the semiconductor substrate 10 and the surface of the support 15 that face each other. When an insulating film (not shown) such as a silicon oxide film is formed on the surface of the semiconductor substrate 10, the cavity height H is the distance between the surface of the insulating film and the surface of the support 15.

  Next, as shown in FIG. 4, the resin layer 13 is exposed and developed using a mask (not shown) to form a through hole 13 </ b> A that exposes the element region 11 in the resin layer 13. Thereafter, a metal thin film 14 covering the resin layer 13 is formed. The thickness T2 of the metal thin film 14 is 1/10 or less of the thickness T1 of the resin layer 13, and is 0.2 μm to 5 μm, for example.

  The metal thin film 14 is formed on the entire surface of the resin layer 13 and the semiconductor substrate 10 in the through hole 13A by, for example, sputtering, and then partially removed by exposure and development using a mask (not shown). Then, patterning is performed so as to expose the element region 11.

  That is, the metal thin film 14 covers the upper surface of the resin layer 13 and the side wall 13W inside the through hole 13A. Preferably, the metal thin film 14 is formed so as to continuously extend from the side wall 13 </ b> W onto a part of the semiconductor substrate 19 (however, a portion not overlapping with the element region 11).

  Next, as shown in FIG. 5, a resin layer 13 and a support 15 made of a glass substrate having a thickness of, for example, 200 μm to 600 μm are bonded together with a metal thin film 14 interposed therebetween. At that time, the metal thin film 14 and the support 15 are directly bonded to each other without interposing a resin adhesive or the like therebetween. Below, the joining method using the surface activation joining method is demonstrated as a joining method which implement | achieves this direct joining.

  In the atmosphere, the surfaces of the metal thin film 14 and the support 15 serving as the bonding surfaces are covered with contaminants (water molecules and organic molecules) that hinder the bonding. Therefore, after removing such contaminants, the bonds between the atoms on the surfaces of the metal thin film 14 serving as the bonding surface and the support 15 are directly bonded to strengthen the bonds between the two atoms.

  In order to remove contaminants on the surfaces of the metal thin film 14 and the support 15, sputter etching using an ion beam or plasma is used. Since each surface after sputter etching is in a state where it easily reacts with surrounding gas molecules, an inert gas such as argon is used for the ion beam. This contaminant removal process is performed in the vacuum chamber 40 in a vacuum state. At each surface of the metal thin film 14 and the support 15 after removal of contaminants, atoms with bonds are exposed, so that the bonding force with other atoms is high, that is, an activated state. .

Thereafter, in the vacuum chamber 40 in a vacuum state, the activated metal thin film 14 and the surfaces of the support 15 are opposed to each other so as to be in direct contact with each other, and pressure bonding is performed at a relatively low heating temperature (for example, about 100 ° C. or less). To do. Thereby, both strong joining can be obtained. In this case, the degree of vacuum of the vacuum chamber 40 is preferably (about 10 ⁻⁵ Pa).

  In this way, the resin layer 13 and the support 15 are bonded to each other through the metal thin film 14, so that the element region 11 is sealed by being surrounded by the semiconductor substrate 10, the resin layer 13, the metal thin film 14, and the support 15. 16 is formed.

  In the above process, before the metal thin film 14 and the support 15 are joined, the metal thin film 14 has irregularities reflecting the irregularities on the surface of the resin layer 13 as shown in FIG. However, as shown in FIG. 6B, when the support 15 is pressure-bonded to the metal thin film 14, the elasticity of the resin layer 13 and the metal thin film 14 of 1/10 or less of the thickness T <b> 1 of the resin layer 13. Due to the thinness, the metal thin film 14 is deformed so as to reflect the flatness of the surface of the support 15 and is in close contact with the support 15. At that time, the resin layer 13 functions as a buffer layer that absorbs stress when the metal thin film 14 is deformed. In FIGS. 6A and 6B, the surface of the support 15 facing the metal thin film 14 is simplified and extremely flat, but may actually have irregularities. Even in this case, the metal thin film 14 is deformed so as to reflect the unevenness of the surface of the support 15 and is in close contact with the support 15.

  The side wall 13W in the cavity 16 is covered with such deformation of the metal thin film 14, strong direct bonding between the metal thin film 14 and the support 15 by the surface activated bonding method described above, and the metal thin film 14 that does not transmit moisture. Due to this synergistic effect, the airtightness of the cavity 16 can be reliably increased as compared with the conventional example. Furthermore, when the metal thin film 14 is formed to extend from the side wall 13W onto a part of the surface of the semiconductor substrate 10, the airtightness of the cavity can be improved more reliably.

  Furthermore, according to the above process, since it is not necessary to form a thick metal layer in order to ensure a sufficient height H of the cavity 16, it is possible to avoid an increase in time and cost in the manufacturing process such as a long sputtering process. Further, there is no need for an additional step such as CMP for flattening the irregularities on the surface of the metal layer.

  Further, since the thickness T2 of the metal thin film 14 of the present embodiment is as thin as 1/10 or less of the thickness T1 of the resin layer 13, it avoids long-time high-temperature heat treatment necessary for the thick metal layer forming process. it can. Moreover, since the metal thin film 14 can be bonded to the support 15 at a relatively low heating temperature from room temperature as described above, the high-temperature heat treatment necessary for bonding the support 15 to a thick metal layer is performed. Can be avoided. Therefore, it is possible to avoid serious damage to the elements in the element region 11 and the semiconductor substrate 10 due to the heat treatment.

  After that, as shown in FIG. 7, a part of the region along the dicing line DL of the semiconductor substrate 10 is etched to form a window 10 </ b> A that penetrates the semiconductor substrate 10 and exposes a part of the pad electrode 12. In the example shown in the figure, the window 10A is partially opened in a square shape in the planar direction of the semiconductor substrate 10, for example, but is formed so as to extend in a street shape along the dicing line DL. Also good.

  Next, an insulating film (not shown) is formed so as to cover the back and side surfaces of the semiconductor substrate 10. Further, a wiring 17 is formed so as to extend from the back surface to the side surface of the semiconductor substrate 10 and to be connected to the pad electrode 12 through the insulating film.

  Next, as shown in FIG. 8, using a dicing blade or the like, a cut is formed from the resin layer 13 in the window 10A to the middle of the support 15 in the thickness direction along the entire dicing line DL. Thereafter, a protective film 18 made of polyimide or the like is formed to cover the back surface of the semiconductor substrate 10 including the inside of the window 10. Further, a bump electrode 19 connected to the wiring 17 is formed on the back surface of the semiconductor substrate 10 through an opening provided in a part of the protective film 18.

  Finally, dicing is performed along the dicing line DL. In this dicing, the protective film 19 and the resin layer 13 are cut so that the resin layer 13 and the protective film 18 covering the edge of the pad electrode 12 remain, and the pad electrode 12 is not exposed. In this way, the semiconductor substrate 10 and the like are separated into the semiconductor device of FIG.

  Needless to say, the present invention is not limited to the above-described embodiment, and modifications can be made without departing from the scope of the invention.

  In the above embodiment, the support 15 has been described as a glass substrate. However, other than this, a semiconductor substrate such as a silicon substrate or a gallium / arsenic substrate may be used as the support 15. The metal thin film 14 is not limited to the above-described aluminum or copper, and for example, gold, platinum, silver, tin, lead, or zinc can be used. Even in these cases, the surface activated bonding method can be used for bonding the metal thin film 14 and the support 15. Thereby, the airtightness of the cavity 16 becomes high like the said embodiment.

  As a modification of the above embodiment, as shown in FIG. 9, a window 10 </ b> A is not formed in the semiconductor substrate 10, and instead of the wiring 17, a through electrode that penetrates the semiconductor substrate 10 and is connected to the pad electrode 12. 27 may be formed, and a bump electrode 19 connected to the through electrode 27 may be formed on the back surface of the semiconductor substrate 10.

DESCRIPTION OF SYMBOLS 10 Semiconductor substrate 10A Window 11 Element area | region 12 Pad electrode 13 Resin layer 13W Side wall 13A Through-hole 14 Metal thin film 15 Glass substrate 16 Cavity 17 Wiring 18 Protective film 19 Bump electrode 27 Through-electrode DL Dicing line

Claims (10)

A semiconductor substrate;
An element region including an element formed on the surface of the semiconductor substrate;
A resin layer disposed on the semiconductor substrate with a through hole exposing the element region;
A metal thin film disposed on the resin layer and on the sidewall in the through hole;
A support directly bonded to the metal thin film on the resin layer,
A semiconductor device, wherein the element region is sealed in a cavity surrounded by the semiconductor substrate, the resin layer, the metal thin film, and the support.   The semiconductor device according to claim 1, wherein the metal thin film is disposed so as to extend from a side wall in the through hole onto a part of the semiconductor substrate.   3. The semiconductor device according to claim 1, wherein a thickness of the metal thin film is equal to or less than one-tenth of a thickness of the resin layer.   The semiconductor device according to claim 1, wherein the support is a glass substrate.   The semiconductor device according to claim 1, wherein the metal thin film contains aluminum or copper. Preparing a semiconductor substrate on which an element region including elements is formed, and a support;
Forming a resin layer having a through hole exposing the element region on the semiconductor substrate;
Forming a metal thin film on the resin layer and on the side wall in the through hole;
Removing contaminants on each surface of the metal thin film and the support in vacuum;
And a step of directly bonding the metal thin film on the resin layer and the support in a vacuum.   The method of manufacturing a semiconductor device according to claim 6, wherein the metal thin film is formed to extend from a side wall in the through hole to a part of the semiconductor substrate.   8. The method of manufacturing a semiconductor device according to claim 6, wherein the thickness of the metal thin film is equal to or less than one tenth of the thickness of the resin layer.   The method of manufacturing a semiconductor device according to claim 6, wherein the support is a glass substrate.   10. The method for manufacturing a semiconductor device according to claim 6, wherein the metal thin film contains aluminum or copper.

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