JPH05152551A - Manufacture of solid-state imaging device - Google Patents

Abstract

PURPOSE:To enhance mechanical strength of a CCD solid-state imaging device chip of back surface irradiation type. CONSTITUTION:A glass substrate 10 and a silicon substrate 11 are banded together. The silicon substrate 11 is grounded and etched to about 10mum thickness. A dispersion area 12 which is reverse conductive type, being contrary to the silicon substrate 11, is formed on the surface of silicon substrate 11. A transfer electrode 14, being the first layer, is farmed on the silicon substrate 11 with an oxidized film 13 in between. Further, a transfer electrode 16, being the second layer, is formed with an oxidized film 15 in between, A light beam irradiated arm the glass substrate 10 transmits through the glass substrate 10 and then absorbed in the silicon substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a backside illumination type solid-state image pickup device which receives light on the backside opposite to the device formation surface.

[0002]

2. Description of the Related Art A CCD solid-state image pickup device, which is widely used in image pickup devices such as television cameras, has a plurality of transfer electrodes formed in parallel on a semiconductor substrate, and information charges generated in the solid-state image pickup device by photoelectric conversion. Are stored and transferred in the channel region formed by the transfer electrode. In such a solid-state image pickup device, since the light from the subject is taken into the semiconductor substrate, securing an incident path of the light is one problem. Generally, in a CCD solid-state image sensor of frame transfer type or interline transfer type,
Light is taken into the semiconductor substrate through the openings provided in the gaps between the transfer electrodes or through the transfer electrodes themselves. In such a case, since the transfer electrode is provided on the side on which light is incident, it is limited to secure a wide incident path.

Therefore, it is considered that the light from the subject is received on the back side of the semiconductor substrate so that the light can be efficiently taken into the semiconductor substrate. FIG. 6 shows such a backside illuminated CCD solid-state imaging device. P
N-type diffusion region 2 in which a channel region forming an information charge transfer path is formed is formed on the surface of a silicon substrate 1 having a conductivity type of an oxide, and an oxide film (insulating film) 3 is formed on the diffusion region 2. A plurality of transfer electrodes 4 made of polycrystalline silicon are arranged in parallel with each other. On the transfer electrode 4 of the first layer, a transfer electrode 6 of the second layer is further arranged via an oxide film (insulating film) 5 so as to cover the gap of the transfer electrode 4. For example, a four-phase transfer clock is applied to these transfer electrodes 4 and 6, and the potential state in the channel region is changed in response to the transfer clock, whereby information charges generated in the channel region are accumulated and transferred. It

Here, the silicon substrate 1 has a thickness of 10 μm in the element region by providing a large recess on the back surface side.
It is formed as thin as possible, and as a result, information charges (usually carriers) generated by photoelectric conversion on the back surface side of the silicon substrate 1 are taken into the channel region before recombination. That is, the carriers and holes separated by the action of the light incident on the silicon substrate 1 recombine with the passage of time, so that the carriers are re-coupled so that the channel region for accumulating the carriers is close to the light incident region. The silicon substrate 1 is formed thin so that it can be stored as an information charge prior to bonding. Therefore, as shown by the arrow in the figure, when the back surface side of the silicon substrate 1 is irradiated with light from a subject and information charges are generated, the information charges are generated in the channel region formed in the diffusion region 2 on the front surface side of the silicon substrate 1. Are captured and accumulated.

Such a backside illumination type solid-state image pickup device is
For example, IEEE TRANSACTIONS ON E
LECTRON DEVICES, Vol ED-2
3, No. 11, November 1976, "A
Backside Illuminated 400x
400 Charge Coupled Device
For more information on Imager.

[0006]

However, since the silicon substrate 1 is formed thin, the mechanical strength of the chip is insufficient, and it becomes extremely difficult to handle it in the assembly process after element formation. Therefore, the manufacturing yield in the assembling process may be significantly reduced, which causes an increase in cost.

Further, when forming the recess on the back surface side of the silicon substrate 1, crystal defects, oxygen precipitation, etc. existing in the silicon to be removed by etching may be transferred to the active region of the silicon substrate 1, As a result, bit defects and uneven sensitivity may occur. Further, the etching process for forming the recess on the back surface side of the silicon substrate 1 also requires an extremely long time, resulting in an increase in cost.

Therefore, an object of the present invention is to simplify the manufacturing process of a backside illuminated CCD solid-state image pickup device.

[0009]

The present invention has been made to solve the above-mentioned problems, and is characterized by a plurality of hearts on one surface of a semiconductor substrate via a thin insulating film. A gate electrode is formed, and information charges generated in the substrate by light emitted from the other surface side of the semiconductor substrate are collected and transferred to a channel region formed on the one surface side of the semiconductor substrate. In a method for manufacturing a solid-state image sensor, a first substrate made of single crystal silicon that absorbs incident light and generates information charges by photoelectric conversion action, and a second substrate that contains silicon oxide that is transparent to the incident light as a main component. And a step of thinning the first substrate to a thickness that can guide the information charges generated on the other surface side of the substrate to the channel region before recombination. In the door.

[0010]

According to the present invention, the device forming substrate has a two-phase structure of a thin silicon substrate and a thick glass substrate, so that the light is incident from the back surface side while maintaining the mechanical strength of the chip. It is possible to reduce the distance between the region where the light is absorbed and the region where the information charges are accumulated. Further, since the silicon substrate can be thinly formed before forming each transfer electrode, the manufacturing process is greatly simplified.

[0011]

1 to 5 are cross-sectional views in order of steps, illustrating a method for manufacturing a solid-state image sensor according to the present invention. First, as shown in FIG. 1, a quartz substrate (glass substrate) 10 that is transparent to incident light and a silicon substrate 1 that absorbs light and performs photoelectric conversion.
1 and 1 are attached and integrated. This bonding method can be performed by applying hydrophilic treatment to each of the substrates 10 and 11 and then bringing them into close contact with each other, and further performing heat treatment at 700 ° C. or higher. According to the hydrophilic treatment and the heat treatment, the hydroxyl groups (—OH) attached to the surfaces of the substrates 10 and 11 are hydrogen-bonded to each other by the hydrophilic treatment, and the hydroxyl groups hydrogen-bonded by the heat treatment are H ₂ O. Since it causes dehydration condensation, sufficient strength can be obtained as a substrate for forming a solid-state imaging device.

Then, the silicon substrate 11 side is polished and finally subjected to etching to finally set the thickness of the silicon substrate 11 to about 10 μm as shown in FIG. The silicon substrate 11 can take in carriers generated near the surface on the quartz substrate 10 side into a channel region formed on the opposite surface before recombination and can sufficiently absorb incident light. Formed to a thickness. The quartz substrate 10 is formed to have a thickness of about 500 μm.

Subsequently, as shown in FIG. 3, an N type diffusion region 12 for forming a channel region is formed on the surface of the silicon substrate 11 of P type conductivity type. Further, as shown in FIG. 4, polycrystalline silicon is laminated with an oxide film 13 interposed therebetween, and a predetermined pattern is transferred to this to form the transfer electrode 14.
To form. Then, polycrystalline silicon is laminated again on the transfer electrode 14 via the oxide film 15, and as shown in FIG.
The transfer electrode 16 of the second layer is formed in the region covering the gap of the transfer electrode 14 of the first layer. The manufacturing process of the transfer electrodes 14 and 16 is the same as that of the conventional solid-state imaging device shown in FIG.

The solid-state image sensor thus obtained is
Since the substrate has a two-layer structure of the quartz substrate 10 and the silicon substrate 11, the light incident from the quartz substrate 10 side is
The light passes through the quartz substrate 10, reaches the silicon substrate 11, and is absorbed by the silicon substrate 11. That is, silicon oxide (Si
Since the quartz substrate 10 containing O ₂ ) as a main component is optically transparent to visible light (including infrared light), the incident light is transmitted through the silicon substrate 11 without being absorbed. .. On the other hand, the silicon substrate 11 absorbs the irradiated light and photoelectrically converts the light to generate carriers that become information charges. Therefore, the glass substrate 10 allows the silicon substrate 11
Mechanical strength is imparted to the chip without affecting the incidence of light on the chip, which simplifies the handling of the chip during the manufacturing process.

[0015]

According to the present invention, since the mechanical strength of the chip of the backside illumination type solid-state image pickup device can be increased, the handling in the manufacturing process is facilitated and the manufacturing yield can be improved. Furthermore, since it is not necessary to perform a long etching process for thinning the substrate, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first step of a method for manufacturing a solid-state image sensor according to the present invention.

FIG. 2 is a cross-sectional view showing a second step of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 3 is a cross-sectional view showing a third step of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 4 is a cross-sectional view showing a fourth step of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 5 is a cross-sectional view showing a fifth step of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 6 is a cross-sectional view showing a conventional backside illumination type solid-state imaging device.

[Explanation of symbols]

 10 glass substrate 1, 11 silicon substrate 2, 12 diffusion region 3, 5, 13, 15 oxide film 4, 6, 14, 16 transfer electrode

Claims (3)

[Claims] 1. A plurality of gate electrodes are formed on one surface of a semiconductor substrate via a thin insulating film, and information charges generated in the substrate by light emitted from the other surface side of the semiconductor substrate are formed. A method of manufacturing a solid-state imaging device, which collects and transfers and outputs to a channel region formed near the surface on one surface side of a semiconductor substrate, which is made of single crystal silicon that absorbs incident light and generates information charges by photoelectric conversion. A step of bonding a first substrate and a second substrate containing silicon oxide as a main component, which is transparent to the incident light, and the information generated on the other surface side of the first substrate A method of manufacturing a solid-state image sensor, comprising: a step of thinning electric charges to a thickness capable of leading to the channel region before recombination. 2. A first substrate and a second substrate are brought into close contact with each other,
The method for manufacturing a solid-state image pickup device according to claim 1, further comprising a step of performing heat treatment to bond both substrates. 3. The method for manufacturing a solid-state imaging device according to claim 1, wherein the first substrate bonded to the second substrate is cut from the front surface side and then etched to obtain a predetermined thickness. ..