JP2015103788A - Semiconductor array substrate reuse method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an art to reuse a semiconductor substrate by separating a cover glass and the semiconductor substrate when malfunction which exceeds an allowable limit is found in a dam before cutting of a wafer.SOLUTION: A reuse method of a semiconductor element array substrate 2 comprises: a process of melting or destroying a dam 4 by irradiating laser beams 7 on a wafer-like member 1 on which a sensor substrate 6 which is provided with an on-chip color filter layer 3 composed of a color separation filter 3a and a microlens array 3b on an upper part of a semiconductor element array formed on a silicon wafer 10 and a cover glass 5 are bonded by a lattice-shaped dam 4 around the semiconductor element array 2a of the sensor substrate 6 at the lattice-shaped dam part 4 from the cover glass 5 side; a process of separating the cover glass 5 and the sensor substrate 6; and a process of removing the on-chip color filter layer 3 by performing ashing treatment and cleaning treatment on the sensor substrate 6.

Description

  The present invention relates to a solid-state imaging device, and in particular, from a solid-state imaging device substrate with a cover glass manufactured in a multifaceted manner with a wafer size, removing the cover glass in the wafer size and returning it to a semiconductor element array substrate before processing. About.

  A solid-state imaging device built in a digital camera or the like has a color separation filter and a microlens array (hereinafter collectively referred to as OCF: on-chip color filter,) on a large number of photoelectric conversion elements (CCD or CMOS) serving as a sensor body. Is made in a form corresponding to the photoelectric conversion element. A CCD or the like is manufactured by a wafer process using a silicon wafer, but the OCF process is a process similar to the wafer process as a post process completely independent of the above process.

  As shown in FIG. 2, the solid-state imaging device is manufactured in a multifaceted manner on a silicon wafer W having a diameter of about 30 cm, and finally cut into individual solid-state imaging devices 1. If the area for one solid-state imaging device is approximately 1 cm square including the periphery, several hundred solid-state imaging devices 1 can be obtained from one wafer W.

  Further, in the solid-state imaging device, not only the OCF layer is laminated on the photoelectric conversion element, but also the light receiving surface side on which light is incident needs to be sealed in order to improve the reliability of the entire element. For this purpose, a frame-shaped dam (spacer: barrier) 4 is formed using an organic material in a region avoiding the semiconductor element (light receiving) region 8 on the silicon substrate 10, and a cover glass 5 is formed on the dam 4. The light receiving region 8 is sealed by pasting (see also Patent Document 1, Patent Document 2, and FIG. 1).

  Each of the separated semiconductor devices is sealed with a cover glass. However, as shown in FIG. 2, in manufacturing, dams 4 are collectively formed in a lattice pattern on a line separating individual solid-state imaging devices 1 of the wafer W. Then, after being bonded to the cover glass of approximately the same size as the wafer W through the dam 4, the center of the dam 4 is cut with a dicing saw.

As a method for forming a dam on the wafer W in the prior art,
An uncured film is processed into the shape of a partition wall (frame shape) and placed between a substrate (hereinafter referred to as a sensor substrate) after forming an OCF layer and a cover glass, and then the film is cured and polymerized. There is a method of sticking together.

  Another method is a method using an adhesive layer containing a photocurable resin and a thermosetting resin, and after selectively forming the resin layer at the dam formation location, the predetermined area is exposed. The photocurable resin contained in the adhesive layer is cured. Then, there is a method of removing (developing) an uncured region of the photocurable resin to pattern the resin layer, and heat-curing the patterned dam layer to bond the sensor substrate and the cover glass.

  In the method including exposure and development, it is difficult to make the height of the partition wall higher than 50 μm. For dams with a height higher than this, a technology is known in which a photo-curing resin (or a resin that combines photo-curing properties and thermosetting properties) is printed by screen printing, and then the covering portion is fixed by photo-curing. Yes (see Patent Document 3).

In the method of Patent Document 3, a step of screen printing a photocurable resin layer in a frame shape to a step of curing a photocurable resin layer to a photocurable resin layer in a frame shape on a cured photocurable resin layer. The process of screen printing is repeated as many times as desired (until the dam has the desired thickness). Thereafter, the photocurable resin is cured after being covered with a cover glass.

JP 2008-40672 A Special table 2003-516634 gazette JP 2010-129643 A JP 2008-16667 A

  However, when the dam material is cured and the sensor substrate and the cover glass are fixed, bubbles may be generated in the dam. When cutting is performed when bubbles are generated, the inside of the solid-state imaging device and the atmosphere are communicated with each other, and the hermeticity inside the solid-state imaging device is impaired, and the reliability as the imaging device is reduced.

  When such an abnormality is found, the cover glass is peeled off from each individual solid-state imaging device, but the sensor substrate side is damaged if it is forcibly removed. Even if it is peeled off, it is not efficient to form a dam again and cover it with a cover glass. On the other hand, it is also difficult to remove the cover glass from the state where the cover glass is completely fixed before cutting.

  The present invention has been made in view of the above circumstances, and when an abnormality exceeding an allowable limit is found in the dam before cutting the wafer, the wafer size in which the OCF layer is removed by separating the cover glass and the sensor substrate. A method for regenerating a semiconductor device array substrate is provided.

According to a first aspect of the present invention for achieving the above object, an on-chip color filter layer comprising a color separation filter and a microlens array is provided on a semiconductor element array substrate in which a semiconductor element region is formed on a silicon wafer. A wafer-like member in which the sensor substrate and the cover glass are bonded to each other by avoiding the semiconductor element region of the sensor substrate by a lattice dam.
A process of melting or destroying the dam by irradiating a laser beam from the cover glass side to the lattice dam part,
A step of separating the cover glass and the sensor substrate;
In this method, the semiconductor element array substrate is reclaimed.

  The invention according to claim 2 is characterized in that after the cover glass and the sensor substrate are separated, an ashing process and a cleaning process are performed on the sensor substrate to remove the on-chip color filter layer. A method for reclaiming a semiconductor element array substrate according to Item 1.

  The invention described in claim 3 is the method for reclaiming a semiconductor element array substrate according to claim 1 or 2, wherein the dam is black.

According to the present invention, when a defect is found in a grid-like dam that bonds a sensor substrate and a cover glass, a wafer-sized semiconductor element array substrate before the on-chip color filter layer is formed can be obtained. .
In the invention of claim 3, if the dam is colored in black, the laser light absorption efficiency is high, so that the dam material can be heated, melted or destroyed in a short time. Reduction of the semiconductor element array substrate regeneration time can be expected.

(A)-(d) It is process drawing of the cross sectional view explaining the reproduction | regeneration process of the semiconductor element array substrate based on this invention. It is a figure of the top view of the wafer-like member with which the sensor substrate and the cover glass were joined by the grid | lattice-like dam.

Hereinafter, first, an outline of a solid-state imaging device and a manufacturing method thereof will be described with reference to FIG.
FIG. 1A is a cross-sectional view showing an outline of a basic structure of a solid-state imaging device according to the present invention.
1B to 1D are cross-sectional views illustrating a process of separating the cover glass.

  In the solid-state imaging device 1, a color filter 3 a and a microlens 3 b are further formed on a semiconductor element array substrate 2 in which a semiconductor element region (light receiving region) 8 such as a CCD sensor or a CMOS sensor is formed on a silicon wafer 10. Sensor substrate 6 and sealing cover glass 5. In the sensor substrate 6, wiring and the like connected to the light receiving region are drawn out to the back side of the silicon wafer through the substrate through via. Specifically, wiring connected to the light receiving region is formed on the surface portion of the sensor substrate, and a through via penetrating the sensor substrate is provided so as to connect to the wiring. The bottom surface of the through via is connected to the electrode pad (none is shown).

An OCF layer (On Chip Color Filter) 3 including a color filter 3a and a microlens 3b is provided on the photoelectric conversion element 2a on the surface side of the sensor substrate 6. The color filter 3a has, for example, three types of coloring filters corresponding to RGB.
FIG. 1 shows only three of several hundred solid-state imaging devices 1 on the silicon wafer 10 for convenience. The OCF layer 3 is formed corresponding to the millions of semiconductor elements 2a, and only the three color separation filters 3a and the microlenses 3b are shown.

  On the surface side of the sensor substrate 6, a columnar dam 4 made of a black resin is provided in addition to the OCF layer 3 so as to avoid the light receiving region 8. The dam 4 has a thickness (height) of several tens of μm, and is provided in a frame shape so as to surround the light receiving region. A transparent cover glass 5 is bonded and fixed to the upper surface of the dam 4. And the light reception area | region side of the sensor board | substrate 6 is sealed by installation of this cover glass 5. FIG.

The solid-state imaging device 1 is generally manufactured as follows.
First, a wafer-sized semiconductor element array substrate 2 is prepared in which a photoelectric conversion element 2a such as a CCD sensor or a CMOS sensor is formed on the front surface side of the silicon wafer 10 by a wafer process and an electrode pad is formed on the back surface side. One light receiving region 8 has millions of photoelectric conversion elements 2a.

  Next, the color filter 3 a and the microlens 3 b are formed on the surface side of the semiconductor element array substrate 2 by using a regular photolithography method. The color filter 3a and the microlens 3b are arranged and formed at positions corresponding to the photoelectric conversion elements 2a formed on the semiconductor element array substrate 2. The semiconductor element array substrate 2 on which the OCF layer 3 is formed is referred to as a sensor substrate 6.

The arrangement of the color filters 3a is, for example, an RGB Bayer arrangement, but these are not limited at all. The microlens 3b is for enhancing the light condensing property to the semiconductor element 2a, and can be omitted when the sensitivity of the semiconductor element 2a is sufficiently high even without a lens. Furthermore, when the surface unevenness of the semiconductor element array substrate 2 or the color filter 3a becomes a problem, a transparent surface smoothing layer (not shown) may be provided before forming them.

  Next, as shown in FIG. 2, the dam pattern 4 is formed on the surface side of the sensor substrate 6 so as to avoid the light receiving region 8 and to have a grid shape with a width of several tens of μm and a thickness of 20 to 50 μm. The dam 4 can be formed by applying a regular photolithography method from a photosensitive dry film or a liquid resist.

  Or it is formed by screen printing using black resin ink, but this is simple. The material of the dam 4 is preferably a liquid ink that contains an epoxy resin as a main component and contains a black filler, and is provided with thermosetting (further UV curable). After such a liquid ink is printed on the pattern of the dam 4, it is hardened by irradiation with heat or UV light.

  Examples of liquid inks include epoxy-urethane resins, isocyanate resins, and cyanoacrylate resins, in addition to epoxy resins as the main component. A photosensitive ink comprising a solvent-soluble resin having a relatively low molecular weight, a photopolymerizable monomer or oligomer, a photopolymerization initiator, and a solvent can also be employed.

  Alternatively, acrylic resin (20 parts by weight of methacrylic acid, 15 parts by weight of hydroxyethyl methacrylate, 10 parts by weight of methyl methacrylate, 55 parts by weight of butyl methacrylate is dissolved in 300 parts by weight of ethyl cellosolve, and 0.75% by weight of azobisnitrile in a nitrogen atmosphere. An acrylic resin obtained by adding a part and reacting at 70 ° C. for 5 hours can also be used.

  In addition, as a black pigment to be added, titanium black having a transmittance higher than that of carbon black in the near ultraviolet region of 350 nm to 400 nm and lower than that of carbon black in a visible light region of 600 nm or more can be suitably employed. Regardless of whether carbon black or titanium black is added, it is desirable that the reflectance in the visible wavelength region is less than 1.5% as the optical characteristics after the dam 4 is formed.

  Next, a wafer-sized cover glass 5 is brought into contact with the upper surface of the dam 4 and pressed to obtain a member (hereinafter referred to as a wafer-like member 1) having a structure shown in FIG. At this time, since the ink itself which is a material for forming the dam 4 has adhesiveness, the cover glass 5 can be bonded and fixed to the dam 4 without using any special adhesive. When the wafer-like member 1 including the cover glass 5 is cut along a dam 4 with a dicing saw, the solid-state imaging device 1 separated into individual pieces is obtained.

  However, when bubbles are generated inside the dam 4 in the bonding process, there is a possibility that the inside of the image sensor communicates with the atmosphere by the bubbles themselves or the divided bubbles. Therefore, when air bubbles are detected in the inside of the lattice-like dam, it is necessary to take measures at the wafer-like member 1 stage.

  The present invention depends on where and how much of the bubble in question is detected in the lattice dam. If a considerable number of defective products are expected after cutting, the cover glass 5 once bonded is peeled off. In this case, the original semiconductor element array substrate 2 without the OCF layer 3 is restored and recreated. At this time, it is desirable to remove only the dam 4, but it is difficult to remove the entire OCF layer 3.

Hereinafter, the specific method is demonstrated using FIG.1 (b)-(d).
First, the lattice dam 4 is irradiated with laser light 7 from the cover glass 5 side to melt or break the dam 4 to facilitate separation of the cover glass 5 and the sensor substrate 6 (FIG. 1B). .
By selectively irradiating only the dam 4 portion made of an epoxy material or an acrylic material with a high-power laser 7 using a mask, the dam 4 is broken and the connection can be released. Thereafter, the wafer-size cover glass 5 can be removed relatively easily (see FIG. 1C and Patent Document 4).

  If a rework-type material is used for the dam material, the adhesive strength is lowered and the dam material is easily removed when the temperature of the dam is raised to about 200 degrees by laser irradiation. The rework type material can be obtained in either a thermosetting type or an ultraviolet curable type. It is effective to keep the dam black for temperature rise.

  Next, the sensor substrate 6 from which the cover glass 5 has been removed is covered with the remainder or residue of the dam 4, OCF, etc., but it is necessary to remove these organic materials. These can be removed by decomposition using a strong acid or strong alkali solution, or a combination of swelling and polishing with an organic solvent. Alternatively, if it is composed of a reworkable material, it can be easily dissolved and removed with methanol or the like after the temperature is raised.

In addition to the above wet process, the OCF layer 3 and the like can be similarly removed by subjecting the sensor substrate 6 to ashing and cleaning. Plasma ashing is an apparatus that generates a reactive gas plasma such as oxygen plasma from the photoresist remaining on the substrate, and decomposes and removes the organic photoresist into CO ₂ and H ₂ O in the gas phase. is there.
Any step or a combination of these steps may be used, but finally, the semiconductor element array substrate 2 with no contamination can be regenerated by washing and drying (FIG. 1D).

1. Solid-state imaging device (wafer-like member)
DESCRIPTION OF SYMBOLS 2 ... Semiconductor element array substrate 2a ... Photoelectric conversion element 3 ... OCF layer 3a ... Color filter layer 3b ... Micro lens 4 ... (Lattice-like) dam 4 '... Broken dam 5 ... Cover glass 6 ... Sensor substrate 7 ... Laser light 8: Light receiving region (semiconductor element region)
10. Silicon wafer W: Wafer-sized semiconductor element substrate or wafer-like member

Claims (3)

A sensor substrate having an on-chip color filter layer composed of a color separation filter and a microlens array on a semiconductor element array substrate on which a semiconductor element region is formed on a silicon wafer, and a cover glass include the sensor by a lattice dam. A wafer-like member bonded to avoid the semiconductor element region of the substrate,
A process of melting or destroying the dam by irradiating a laser beam from the cover glass side to the lattice dam part,
A step of separating the cover glass and the sensor substrate;
A method for reclaiming a semiconductor element array substrate, characterized by comprising:   2. The semiconductor element array substrate according to claim 1, wherein after the cover glass and the sensor substrate are separated, the sensor substrate is subjected to an ashing process and a cleaning process to remove the on-chip color filter layer. Playback method.   3. The method of reclaiming a semiconductor element array substrate according to claim 1, wherein the dam is black.