KR20000034225A - Method for manufacturing solid camera device - Google Patents

Abstract

PURPOSE: A method for manufacturing a solid camera device is provided to make the thickness of an insulator membrane between a first and a second polygates uniform for maintaining the breakdown voltage between the first and the second polygates. CONSTITUTION: A method for manufacturing a solid camera device includes a first to a sixth step. At the first step, an ONO layer(Oxide/Nitride/Oxide layer,32) is formed on a substrate(31). At the second step, a plurality of first polygates(33) are formed on the ONO layer(33). At the third step, a top oxide layer and a nitride layer adjacent to the both sides of each of the first polygates(33) are removed. At the forth step, a first oxide layer(34) is formed on the surface of the first polygates(33). At the fifth step, a plurality of second polygates(32) are formed on the first oxide layer(34) adjacent to the first polygates(33) and between the first polygates(33). At the sixth step, a second oxide layer(36) is formed on the surface of the second polygates(32).

Description

Manufacturing method of solid state imaging device

The present invention relates to a method for manufacturing a solid state image pickup device, and more particularly, to a method for manufacturing a solid state image pickup device for improving the operating characteristics of the device.

In general, the solid state image pickup device refers to a device for photographing a subject using an photoelectric change device and a charge coupled device to output an electrical signal.

Charge-coupled devices are used to transfer signal charges generated in photoelectric conversion devices in a particular direction using potential variations in the substrate.

The solid-state image pickup device is arranged in a matrix form at regular intervals and is formed between a plurality of photoelectric conversion regions for generating an image charge by converting a signal of light into an electrical signal and a photoelectric conversion region in a vertical direction, respectively. Vertical Charge Coupled Device (VCCD) for transferring the image charges generated in the photoelectric conversion region in the vertical direction, and Horizontal Charge Transfer Region (HCCD) for transferring the image charges transferred in the vertical direction in the horizontal direction : Horizontal CCD) and a floating diffusion region that senses the image charge transmitted in the horizontal direction and outputs it to the peripheral circuit unit.

In the solid state image pickup device, the double polygate serves as a charge coupling device, which reads and moves charges generated by light incident on a photodiode in a photoelectric conversion region. The process must maximize the charge transfer efficiency by minimizing capacitance while completely separating the polygates.

In the method of manufacturing a solid state image pickup device according to the related art, in the process of forming a double polygate of a solid state image pickup device, an ONO (Oxide / Nitride / Oxide) layer 12 is formed on a semiconductor substrate 11. Next, a first polycrystalline silicon and a first photosensitive film are formed on the ONO layer 12.

After selectively exposing and developing the first photoresist film so as to remain only at the site where the first polygate is to be formed, the first polycrystalline silicon is selectively etched using the selectively exposed and developed first photoresist film as a mask. A first polygate 13 is formed, and the first photosensitive film is removed.

As shown in FIG. 1B, a first oxide film 14 is grown on the surface of the first polygate 13.

In this case, since the growth rate of the oxide film is lower than that of other portions of the surface of the first polygate 13 by the nitride film of the ONO layer 12, the first polygate ( 13) The first oxide film 14 on both lower portions is formed very thin 14a.

As shown in FIG. 1C, a second polycrystalline silicon and a second photoresist film are formed on the entire surface, and the second photoresist film is selectively exposed and developed so as to remain only at the site where the second polygate is to be formed.

The second polycrystalline silicon is selectively etched using the selectively exposed and developed second photoresist film as a mask to form a first oxide film 14 between the first polygate 13 and adjacent to the first polygate 13. A plurality of second polygates 15 are formed thereon and the second photoresist film is removed.

Subsequently, a second oxide film 16 is grown on the surface of the second polygate 15.

However, in the conventional method of manufacturing a solid-state image pickup device, since the growth rate of the oxide film is lower than that of the other portions of the first polygate surface by the nitride film of the ONO layer, the first portions of the lower portions of both sides of the first polygate are lower. Since the oxide film is formed very thin, the breakdown voltage (BV) between the first and second polygates is lowered, thereby deteriorating the operating characteristics of the solid state imaging device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the method of manufacturing a solid state image pickup device for preventing the BV between the first and second polygates from lowering by uniformizing the thickness of the insulating film between the first and second polygates. The purpose is to provide.

1A to 1C are cross-sectional views illustrating a method of manufacturing a solid state image pickup device according to the related art.

2A to 2D are cross-sectional views illustrating a method of manufacturing a solid state image pickup device according to an exemplary embodiment of the present invention.

Explanation of symbols for main parts of the drawings

31: semiconductor substrate 32: ONO layer

33: first polygate 34: first oxide film

35: second polygate 36: second oxide film

In the method for manufacturing a solid state image pickup device of the present invention, in the process of forming a double polygate of a solid state image pickup device, forming an ONO layer on a substrate, forming a plurality of first polygates on the ONO layer, 1, removing a top oxide film and a nitride film of the ONO layer adjacent to both sides of the polygate, growing a first oxide film on the surface of the first polygate, between the first polygate and adjacent to the first polygate. And forming a plurality of second polygates on the first oxide film, and growing a second oxide film on the surface of the second polygate.

Referring to the accompanying drawings, preferred embodiments of the method for manufacturing a solid-state imaging device according to the present invention as described above in detail as follows.

2A to 2D are cross-sectional views illustrating a method of manufacturing a solid state image pickup device according to an exemplary embodiment of the present invention.

In the method of manufacturing the solid state image pickup device according to the embodiment of the present invention, as shown in FIG. 2A, in the process of forming a double polygate of the solid state image pickup device, the ONO layer 32 is formed on the semiconductor substrate 31. The first polycrystalline silicon and the first photosensitive film are formed on the ONO layer 32.

After selectively exposing and developing the first photoresist film so as to remain only at the site where the first polygate is to be formed, the first polycrystalline silicon is selectively etched using the selectively exposed and developed first photoresist film as a mask. A first polygate 33 is formed and the first photosensitive film is removed.

As shown in FIG. 2B, a second photoresist film is coated on the ONO layer 32 including the first polygate 33, and the second photoresist film is removed only at portions adjacent to both sides of the first polygate 33. It is selectively exposed and developed as much as possible.

Thereafter, the top oxide film and the nitride film of the ONO layer 32 are selectively etched using the selectively exposed and developed second photoresist film as a mask, so that the ONO layers adjacent to both sides of the first polygate 33 are selectively etched. After removing the top oxide film and the nitride film of (32) (41), the second photosensitive film is removed.

At this time, the top oxide film, the nitride film, and the lower oxide film of the ONO layer 32 are selectively etched using the second photoresist film as a mask, so that the semiconductor substrate 31 of the portions adjacent to both sides of each of the first polygates 33 is removed. It can also be exposed.

As shown in FIG. 2C, a first oxide film 34 is grown on the surface of the first polygate 33.

At this time, since the first oxide film 34 is grown while the top oxide film and the nitride film of the ONO layer 32 adjacent to both sides of the first polygate 33 are removed, the entire surface of the first polygate 33 surface is grown. The oxide film growth rate is the same, so that the thickness of the first oxide film 34 on the surface of the first polygate 33 is uniform (34a).

As shown in FIG. 2D, a second polycrystalline silicon and a third photoresist film are formed on the entire surface, and the third photoresist film is selectively exposed and developed so as to remain only at the site where the second polygate is to be formed.

The second polycrystalline silicon is selectively etched using the selectively exposed and developed third photoresist layer as a mask to form a first oxide layer 34 adjacent to the first polygate 33 and adjacent to the first polygate 33. A plurality of second polygates 35 are formed thereon and the third photoresist film is removed.

Subsequently, a second oxide layer 36 is grown on the surface of the second polygate 35.

Since the first oxide film is grown in a state where the top oxide film and the nitride film of the ONO layer adjacent to both sides of the first polygate are removed, the solid-state imaging device of the present invention makes the thickness of the insulating film between the first and second polygates uniform. In addition, the BV between the first and second polygates is prevented from being lowered, thereby improving the operating characteristics of the solid state image pickup device.

Claims (2)

In the process of forming a double polygate of a solid state image pickup device, Forming an ONO layer on the substrate; Forming a plurality of first polygates on the ONO layer; Removing a top oxide film and a nitride film of the ONO layer adjacent to both sides of the first polygate; Growing a first oxide film on the surface of the first polygate; Forming a plurality of second polygates between the first polygates and on a first oxide film adjacent to the first polygates; And growing a second oxide film on the surface of the second polygate. In the process of forming a double polygate of a solid state image pickup device, Forming an ONO layer on the substrate; Forming a plurality of first polygates on the ONO layer; Etching the ONO layers adjacent to both sides of each of the first polygates; Growing a first oxide film on the surface of the first polygate; Forming a plurality of second polygates between the first polygates and on a first oxide film adjacent to the first polygates; And growing a second oxide film on the surface of the second polygate.