KR0155789B1 - Method of manufacturing solid-state image sensor - Google Patents

Abstract

A method for manufacturing a solid state imaging device is described. This is because the first and second conductivity type impurities are injected into the semiconductor substrate in the region where the channel region of the vertical transfer unit and the horizontal transfer unit are to be formed. A first step of forming a first doped well, a second step of forming an ion implantation prevention film on a semiconductor substrate exposing at least a first transfer type channel of the vertical transfer portion to a surface, and a second conductivity type on the entire surface of the resultant A third process of injecting impurities into a second doped well between the first conductive type transfer channel of the vertical transfer unit and a first doped well of a second conductive type formed below the third conductive type;

A fourth step of forming an insulating film on the transfer channel; And

And a fifth process of forming vertical transfer electrodes on the insulating layer on the transfer channel of the vertical transfer unit and forming horizontal transfer electrodes on the insulating layer on the transfer channel of the horizontal transfer unit. Therefore, the vertical transfer channel is formed on the second conductivity type well of higher concentration and the horizontal transfer channel is formed on the second conductivity type well of lower concentration, so that the vertical transfer portion ensures a high charge handling capacity. The horizontal transfer unit provides a simple and large-scale manufacturing process to ensure high charge transfer efficiency.

Description

Manufacturing method of solid state imaging device

1 is a cross-sectional view showing a portion of a CCD having a buried channel.

2 is a plan view showing a part of a CCD type solid state imaging device of a general IT system.

3A to 3C are cross-sectional views of a conventional case in which the vertical transfer unit and the horizontal transfer unit are formed by different processes in order to solve the above problems.

4 is a layout showing a mask pattern of a part of the CCD type solid-state imaging device of the IT system according to an embodiment of the present invention.

5A to 5C are cross-sectional views showing a vertical transfer unit and a horizontal transfer unit of the solid state imaging device manufactured by the method of an embodiment of the present invention.

6 is a potential distribution diagram of a transmission channel in an area connecting a vertical transmission unit and a horizontal transmission unit.

7A to 7C are cross-sectional views illustrating a method of manufacturing a solid-state imaging device according to an embodiment of the present invention.

8A to 8C are cross-sectional views illustrating a method of manufacturing a solid-state imaging device according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid state imaging device, and more particularly, to a method for manufacturing a CCD (Charge Coupled Device) type solid state imaging device of an IT (Interline Transfer) method.

CCD solid-state imaging devices, in particular, inter-line transfer type charge-coupled device solid-state imaging devices, include a light receiving and accumulating unit that receives and receives signal from an external optical system in a depletion state and generates and accumulates signal charges. It consists of a transmitter for transmitting to the output stage and a detector for detecting the transmitted signal charge and driving a voltage or current related to the amount of signal charge. In particular, the transfer section generally employs a buried channel CCD.

1 is a cross-sectional view showing a portion of a CCD having a buried channel, in which reference numeral 2 is an N-type semiconductor substrate, 4 is a P-type doping well, 6 is an N-type transfer channel, 8 is an insulating film, and 10 Denotes the transfer electrode.

P-type doping wells 4 formed on the N-type semiconductor substrate 2 are formed, and N-type transmission channels 6 are formed thereon. The transfer electrode 10 is formed on an insulating film 8 such as a coral film or a nitride film formed on the transfer channel.

At this time, the transmission device 10 is formed of a plurality of adjacent or overlapping electrodes, and the signal charges accumulated in the potential well formed under the one transfer electrode by the clock pulses applied to the electrodes, The transfer of signal charges takes place by moving to the potential well formed at the bottom. The series of transmission electrodes covering the transmission channel is composed of two or three or more electrodes combined according to the phase of the clock pulse to form one stage, and the signal charge is transferred from one stage to another during one cycle of the clock pulse. Move.

The movement of the signal charge corresponding to the clock pulse, i.e., the transfer is preferably performed without loss or addition of signal charge when moving from one stage to another stage, but in practice, the movement of the signal charge, between the transfer electrodes Due to the potential distribution and defects in the semiconductor substrate and the subsequent capture and release of charges, perfect transfer is not achieved.

In the surface channel type charge coupling device that appeared in the early stages of CCD development, since the electric field in the direction of movement of the signal charge is strongly bound by the voltage applied to the transfer electrode, the interference electric field effect between the transfer channels becomes weak at the edge of the transfer electrode. In other words, if the speed of the transmission operation is increased, a large amount of signal charges remain without being transmitted, and thus the transmission efficiency cannot be increased.

However, in the buried channel charge coupling device in which the transmission channel is deeply formed into the semiconductor substrate, the interference electric field effect between adjacent transmission electrodes is increased, and the electric field is mainly distributed on the surface of the semiconductor substrate to trap or emit signal charges. Since it is less affected by the trap, the transmission efficiency can be maintained even if the transmission speed increases.

Therefore, in the buried channel charge coupling device, the factor which has the greatest influence on increasing the transfer speed as long as the mobility of the signal charge in the semiconductor substrate is allowed is the shape of the electric field formed in the transfer direction of the signal charge.

In the transfer channel of a charge-coupled element, when the charge is so small that it does not affect the potential of the transfer channel, i.e., when one electron is moved by an electric field applied in the transfer direction, the time t required for this transfer is Follow the same formula.

t = 1 / μ p2p1 (1 / Ey (y))

Here, Ey is an electric field component in a direction parallel to the trajectory of the charge, μ is the mobility of the charge in the semiconductor substrate, y is the displacement along the trajectory of the charge, p1 and p2 are the coordinates of the starting point and the arrival point, respectively. This equation can be approximated as

t L / (2μEymin) (Equation 2)

Where L is the movement distance of the charge and Eymin is the smallest value of the electric field components in the direction parallel to the charge trajectory.

As can be seen from the above equations, in order to reduce the transmission time of the signal charges, it is important to increase the smallest value of the electric field components in a direction parallel to the trajectory of the signal charges.

The smallest electric field component of the electric field component in the direction parallel to the trajectory of the signal charge appears at the lower part of the center of the transmission electrode, which is highly dependent on the depth of the transmission channel and the depth of the depletion region formed between the transmission channel and the doping well. . In other words, the deeper the depth of the transfer channel and the lower the impurity concentration of the doping well formed under the transfer channel, the deeper the boundary of the depletion region formed between the transfer channel and the doped well into the semiconductor substrate. Since it is greatly affected by the electric field interference between the transmission electrodes. Therefore, the transfer channel formed under the transfer electrode has a potential well having a predetermined potential gradient, whereby the movement speed of the signal charge is increased.

2 is a plan view showing a part of a CCD-type solid-state imaging device of a general IT method, where R1 is an optical diode that receives and contracts signal charges, R2 is a transmission channel of a vertical transmission unit, and R3 is a transmission channel of a horizontal transmission unit. A channel represents a transfer electrode of a vertical transfer unit, R5 represents a transfer electrode of a horizontal transfer unit, and R6 represents a detection stage.

According to the plan view of FIG. 2, as described above, the IT type CCD solid-state imaging device is composed of a light receiving and storing unit (photodiode), a transmitting unit (vertical transmitting unit and a horizontal transmitting unit), and a detection stage. In this case, the transmission unit is arranged in the column direction in the arrangement of the light receiving element, that is, the photodiode, and transmits the signal charge in the row direction by overlapping the vertical transfer unit for transmitting the signal charge in the column direction and the end of the vertical transfer unit. It can be seen that it consists of one or more horizontal transmission unit.

[Conditions of Horizontal Transmitter]

At every field period, the signal charges transferred from the light receiving and accumulating unit to the vertical transmission unit are transmitted simultaneously to one single horizontal transmission unit in every horizontal scanning cycle, and the horizontal transmission unit transmits signals from each column until the next horizontal scanning cycle. The charge is transferred step by step toward the detection stage.

In the case of the image pickup device corresponding to the NTSC method having about 250,000 effective pixels, the field period is 16.6 ms, which is 1/60 second, and the horizontal scanning period is 63.5 ms, which corresponds to 15.75 kHz. At this time, since the horizontal transmitter must output 553 signals in this period, the signal charge must be transmitted from one end to the other every approximately 115ns. While the vertical transfer unit transfers charges every 63.5 ms, the horizontal transfer unit operates about 550 times faster than that, so that the transfer efficiency is more serious in the horizontal transfer unit than in the vertical transfer unit.

When the transmission efficiency of the horizontal transfer unit is lowered, problems such as blurring of the image in the horizontal direction and deterioration of the color signal level occur, resulting in poor image quality. Therefore, the photographing element needs to maintain high horizontal transmission efficiency.

Therefore, as described above, in order to increase the transmission speed of the horizontal transmission unit, the depth of the transmission channel is deep, and the impurity concentration of the doping well formed under the transmission channel is low so that the boundary of the depletion region formed between the transmission channel and the doping well is low. It can be seen that it must be forced to retreat deep into the board on the peninsula. That is, the horizontal transmission unit preferably has a deep transmission channel on the low concentration doping well.

[Conditions of Vertical Transmitter]

Since the vertical transfer unit is arranged in the column direction adjacent between the array of the light receiving and accumulating units (photodiodes), the vertical transfer unit reads the charge accumulated in the light receiving and accumulating unit, that is, transfers the accumulated signal charges to the vertical transfer unit all at once. It is easy to exchange charges with adjacent light receiving and accumulating units even during the transfer operation other than the above. In addition, the charge generated by the light in the vicinity of the vertical transmission part may be sucked into the vertical transmission part instead of being collected by the light receiving and accumulating part. Therefore, the vertical transmission part should be separated by a relatively high concentration of impurities to prevent this.

In addition, in order to increase the light sensitivity by increasing the area of the light receiving and accumulating portion, the width of the vertical transmission portion should be reduced. In order to ensure sufficient transmission capacity even at a narrow width, the transmission channel is formed shallow and depletion formed between the transmission channel and the doping well. Area boundaries should also be shallow.

Therefore, due to the factors listed above, it is preferable that the vertical transmission portion has a transmission channel of shallow depth on the high concentration doping well.

In general, since the horizontal transmission unit may occupy a sufficient space spatially and located outside the array of the light receiving unit, the horizontal transmission unit may be located in the same process as the process of forming the vertical transmission unit, although there are no limitations such as capacity limitation or mutual interference with pixels. By forming simultaneously, the problem of transmission efficiency due to the high-speed transmission is raised (as described above, the transmission speed of the horizontal transmission portion is almost 550 times the transmission speed of the vertical transmission portion).

That is, when the horizontal and vertical transmission units are formed in the same process as the vertical transmission unit, the vertical transmission unit is operated by a clock of a relatively slow frequency, so that sufficient transmission efficiency can be maintained, but the horizontal transmission unit is much faster than the vertical transmission unit. Since it must operate at a speed, the transmission efficiency is lowered, whereby the image quality can be lowered.

3A to 3C are cross-sectional views of a conventional case in which the vertical transfer unit and the horizontal transfer unit are formed by different processes in order to solve the problems as described above, and FIG. 3A is a cross-sectional view taken along the line AA ′ of FIG. 2. 3B is a cross-sectional view taken along the line BB 'of FIG. 2, and FIG. 3C is a cross-sectional view taken along the line CC' of FIG.

Numeral 12 denotes an N-type semiconductor substrate, 14 p-type first doping well, 16 p-type second doping well, 17 p-type third doping well, 18 n-type first transmission channel, 19 Denotes a second N-type transfer channel, 20 denotes a P ⁺ type isolation region, 22 denotes a vertical transfer unit and a vertical transfer electrode, and 24 denotes a horizontal transfer unit and a horizontal transfer electrode.

The vertical transfer unit formed by the conventional method includes a P-type first doping well 14 and a region in which the first doping well is formed by injecting P-type impurities into the N-type semiconductor substrate 12 in the region where the vertical transfer unit is to be formed. of the first N-type is formed by implanting impurities of the N type to a second doped well (16), a region to be the vertical transfer portion is formed of P ⁺ type is formed by re-implanting an impurity of P-type at a high concentration to the area to be vertical transfer portion Composed of a transfer channel 18 and vertical transfer electrodes 22, 22a, and 22b formed thereon with a dielectric insulating film on the semiconductor substrate on the first transfer channel, the dielectric insulating film being formed thereon (see FIGS. 3A and 3C). ,

The horizontal transfer unit formed by the conventional method includes a P-type first doping well 14 and a region in which the first doping well is formed by injecting P-type impurities into the N-type semiconductor substrate 12 in the region where the horizontal transfer unit is to be formed. P-type third doping well 17 formed by re-injecting P-type impurities at low concentration into a region to be the horizontal transfer unit, and an N-type second formed by injecting N-type impurities into the region where the horizontal transfer unit is to be formed. A transfer channel 19 and a horizontal transfer electrode 24 formed on a semiconductor substrate on the second transfer channel (see FIGS. 3B and 3C),

In addition, according to the vertical and horizontal transfer units according to the conventional method, the final vertical transfer electrode 22a of the vertical transfer unit adjacent to the horizontal transfer unit for the purpose of smoothly transferring the signal charges from the vertical transfer unit to the horizontal transfer unit. The end of the second doped well is formed at the lower portion, and the second half of the lower portion of the vertical transfer electrode 22b immediately before the final vertical transfer electrode (the transmission channel of the portion adjacent to the final vertical transfer electrode) is denoted by N ⁻ . Type impurity was injected to reduce the impurity concentration of the first transport channel 18.

Therefore, the potential distribution in the transmission direction of the signal charges in the lower portion of the vertical transmission section adjacent to the horizontal transmission section is distributed to facilitate the transfer of the signal charges, thereby increasing the signal charge transmission efficiency from the vertical transmission section to the horizontal transmission section.

In the case of the vertical and horizontal transmission units according to the conventional method described above, in the horizontal transmission unit, the depth of the transmission channel is deep, the impurity concentration of the doping well located below is low, and the transmission efficiency of the signal charge is high, In the sending section, the depth of the residual channel is shallow, and the impurity concentration of the doping well located below is high, thereby achieving sufficient capacity for signal charge accumulation and electrical separation from adjacent light receiving and storing sections.

However, first. Since the first, second and third doping wells must be formed in different processes, three doping well formation processes must be performed, and the first and second transfer channels must be formed in different processes. The manufacturing process is complicated because the process of forming a transmission channel throughout the next system has to be performed.

Second, the shape of the potential distribution of the transfer channel from the vertical transfer unit to the horizontal transfer unit varies according to the position of the end of the third doped well, and the ends of the first transfer channel and the second transfer channel are transferred below the final vertical transfer electrode. There is no room for process variation because they must be formed to match each other in the channel.

That is, when the first transport channel, the second transport channel, the second doping well and the third doping well overlap or are spaced apart from each other (see also 3C), the vertical transport unit protrudes from the potential well formed in the horizontal transport unit. Potential barriers may also occur, hindering smooth signal transmission. Therefore, the ends of the first transport channel and the second transport channel must exactly match the bottom of the final vertical transfer electrode, and the ends of the second doped well and the third doped well must exactly match the bottom of the final vertical transfer electrode.

Accordingly, there is a need for a manufacturing method of a transmission section of a solid-state imaging device having both a vertical transmission section and a horizontal transmission section, while having a simple manufacturing process and a large process margin.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a solid-state imaging device having a large transfer capacity, a vertical transfer unit having high electrical separation from other elements, and a horizontal transfer unit having a high transfer efficiency of signal charges.

Another object of the present invention is to provide a manufacturing method having a simple manufacturing process and a large process margin.

In order to achieve the above objects, the manufacturing method of the solid-state imaging device according to the present invention,

The first and second conductivity type impurities are implanted into the semiconductor substrate in the region where the channel region of the vertical and horizontal transfer portions are to be formed, and thus the second conductivity type 1st process of forming a doping well;

A second step of forming an ion implantation prevention film on a semiconductor substrate at least exposing the transfer channel of the first conductivity type to a surface of the vertical transfer section;

A third process of injecting impurities of a second conductivity type into the entire surface of the resultant to form a second doped well between the transfer channel of the first conductivity type of the vertical transfer portion and the first doped well of the second conductivity type formed below; ;

A fourth step of forming an insulating film on the transfer channel; And

And a fifth process of forming vertical transfer electrodes on the insulating layer on the transfer channel of the vertical transfer unit and forming horizontal transfer electrodes on the insulating layer on the transfer channel of the horizontal transfer unit.

In the method of manufacturing a solid-state imaging device according to the present invention, the ion implantation prevention film is formed such that the semiconductor substrate of at least one region of the region where the final vertical transfer electrode of the vertical transfer portion adjacent to the horizontal transfer portion is to be formed is exposed to the surface. Preferably, the ion implantation prevention film is formed such that the semiconductor substrate of all regions except the region where the photodiode is formed is exposed to the surface among the regions where the vertical transfer unit and the photodiode are formed. do.

In the method of manufacturing a solid-state imaging device according to the present invention, one of the final vertical transfer electrodes adjacent to the horizontal transfer unit and the vertical transfer unit adjacent to the horizontal transfer unit and the horizontal transfer electrodes constituting the horizontal transfer unit is arranged to partially overlap each other. Preferably, the ion implantation prevention layer is formed to expose the semiconductor substrate of at least one region of the region where the final vertical transfer electrode is not overlapped with the horizontal transfer electrode to the surface.

In the method of manufacturing a solid-state imaging device according to an embodiment of the present invention, the first step is preferably performed by simultaneously implanting impurities of a first conductivity type and impurities of a second conductivity type, wherein It is preferable to use an impurity having a diffusion coefficient higher than that of the transport channel as an impurity constituting the doping well. Preferably, any one ion selected from phosphorus or arsenic is used as the impurity of the first conductivity type, and boron ions are used as the impurity of the second conductivity type.

In the method of manufacturing a solid-state imaging device according to another embodiment of the present invention, in the first step, the first doping well of the second conductivity type is first formed by injecting impurities of the second conductivity type, and then the first conductivity. It is preferable to proceed to the process of injecting the impurities of the type to form a transmission channel of the first conductivity type.

Therefore, according to the solid-state imaging device and the method of manufacturing the same according to the present invention, the vertical and horizontal transfer parts are processed in almost the same process except for the impurity implantation process for forming the second doped well while maintaining the electrical characteristics of the vertical and horizontal transfer parts. The manufacturing process is simple since no separate process is required for forming and electrically separating the side surfaces of the transmission channel. In addition, since the vertical and horizontal transmission units share the transmission channel, and form the second doping well only in the vertical transmission unit, the process margin is larger than in the conventional method.

The vertical transmission section forms a transmission channel on a high concentration and well-shielded doping well, eliminating mutual interference with water pipes and accumulators, and the horizontal transmission section forms a transmission channel on a lower concentration and deeper doping wells to speed up signal charges. To improve the picture quality.

In this case, an additional process for forming the above-mentioned doping wells is not necessary, and electrical characteristics are not influenced by process deviations that may exist in the manufacturing process.

In the lower part of the electrode at the output direction end of the vertical transfer unit adjacent to the horizontal transfer unit, a potential distribution for efficiently moving the signal electrons is generated, thereby speeding up the transfer of the signal electrons from the vertical transfer unit to the horizontal transfer unit. Eliminate vertical streaks on the screen, which may be caused by signal charges remaining at the end of the vertical transmitter.

Device separation between the transmission channel of the vertical transmission unit and the light receiving and accumulating unit is effectively achieved without any additional process.

Hereinafter, with reference to the accompanying drawings will be described in more detail the present description.

4 is a layout diagram showing a mask pattern of a part of the CCD type solid-state imaging device of the IT method according to an embodiment of the present invention, wherein P1 denotes a mask pattern for forming a photodiode for receiving and accumulating signal charges. , P2 denotes a mask pattern for forming a transfer channel of the vertical transfer unit and a horizontal transfer unit, P3 denotes a mask pattern for forming a vertical transfer electrode of the vertical transfer unit, P4 denotes a mask pattern for forming a horizontal transfer electrode of the horizontal transfer unit, and P5 Denotes a mask pattern for forming a second doped well. At this time, R1 represents a detection end region.

Referring to FIG. 4, the transmission channels (see P2) of the vertical transmission unit and the horizontal transmission unit are connected to each other, and the second doping well (see P4) has a photodiode arranged in a matrix shape. It can be seen that the columns are formed in all regions except the photodiode (see P1) and the transmission channel (see P2) among the regions where the vertical transfer unit is arranged.

At this time, the shape of the mask pattern (see P5) for forming the second doping well may be any shape as long as it includes a mask pattern (see P2) for forming the transmission channel of the vertical transfer unit. In an embodiment of the present invention, as shown in FIG. 4, the mask pattern P5 for forming the second doped well in all regions except for the region where the mask pattern P1 for forming the photodiode is disposed. Placed).

In addition, it is preferable that the end of the mask pattern P5 is disposed to be included in a mask pattern adjacent to the mask pattern for forming the horizontal transfer electrode (see P4) among the mask patterns for forming the vertical transfer electrode (see P3). Arrow).

5A to 5C are cross-sectional views showing the vertical image pickup unit and the horizontal transfer unit manufactured by the method of the embodiment of the present invention, and the AA 'line and the CC' line of FIG. 4 are cut out, respectively.

According to the cross-sectional views, the P-type first doping well 32 formed in the vertical transfer unit N-type semiconductor substrate 30, the N-type transmission channel 34 formed in the first doping well, and the first doping well and the transfer And a P + type second doping well 36 formed in a shape surrounding the transfer channel between the channels and vertical transfer electrodes 38 and 38a formed on the transfer channel, wherein the horizontal transfer unit is formed on the N type semiconductor substrate 30. The P-type first doped well 32 is formed, the N-type transfer channel 34 formed in the first doped well, and the horizontal transfer electrode 40 formed on the transfer channel.

At this time, the first doping well 32 and the transmission channel 34 is formed to be connected to each other in the vertical transmission unit and the horizontal transmission unit, the second doping well 36, the end thereof is adjacent to the horizontal transmission unit It is formed to be positioned below the transfer electrode of the vertical transfer part, that is, the final vertical transfer electrode 38a.

In addition, the transfer channel 34 is formed deeper in the horizontal transfer unit than in the vertical transfer unit, and the final vertical transfer electrode 38a and the horizontal transfer electrode 40 are formed to partially overlap each other.

The fraudulent second doping well 36 is formed to serve to electrically separate the side of the transmission channel 34 of the vertical transmission portion from other elements, and thus is formed to have a width larger than the width of the transmission channel.

FIG. 6 illustrates potential distribution in a transmission channel in an area connecting the vertical transmission unit and the horizontal transmission unit in FIG. 6, and specifically illustrates the potential distribution in the AA ′ line of FIG. 5C.

According to the potential distribution diagram, the potential of the area connecting the vertical transfer unit and the horizontal transfer unit in the solid state imaging device manufactured according to the embodiment of the present invention is formed to have a constant slope so as to improve the transfer efficiency of the signal charges. .

Therefore, according to the solid state imaging device manufactured according to one embodiment of the present invention,

First, the vertical transfer portion has a large storage capacity of signal charges due to a shallow transmission channel and a high concentration of second doping wells formed below the transmission channel.

Secondly, the vertical transfer unit can easily achieve electrical separation from other devices even if the device isolation region is not formed separately by the high concentration of the second doping well formed on the lower side and the side of the transmission channel.

Third, since the transmission efficiency is improved by a transmission channel having a deep depth and a low concentration of the first doping well formed under the transmission channel, the transmission speed of the signal charge is large.

7A to 7C are cross-sectional views illustrating a method of manufacturing a solid state imaging device according to an exemplary embodiment of the present invention, and are taken along line AA ′ of FIG. 4.

8A to 8C are cross-sectional views illustrating a method of manufacturing a solid state imaging device according to an exemplary embodiment of the present invention, and the line BB ′ of FIG. 4 is cut out.

Hereinafter, a method of manufacturing a solid-state imaging device according to an embodiment of the present invention will be described in more detail with reference to FIGS. 7A to 7C and 8A to 8C.

First, FIGS. 7A and 8A illustrate a process of forming the first doped well 32 and the transfer channel 34, which are formed on the first conductive semiconductor substrate 30. The first process of forming the first ion implantation prevention layer 35 having a shape that exposes the region where the planar transmission channel is to be formed on the surface (see mask pattern P2 in FIG. 4), and the second conductivity type impurities in the resultant. A second process of implanting ions to form the first doping well 32 and a third process of forming a transport channel 34 by implanting impurity ions of a first conductivity type into the resultant are performed.

In this case, since the first doping well 32 and the transmission channel 34 are formed using the same ion implantation prevention layer (in the present invention, the first ion implantation prevention layer is used), alignment errors can be eliminated. In addition, the first doping well 32 has a low impurity concentration and is formed so that the junction position with the semiconductor substrate is located deep in the semiconductor substrate. To move fast.

In one embodiment of the present invention, when the semiconductor substrate is N-type conductive, the first doping well is formed by implanting P-type impurities such as, for example, boron (B) ions, and the transport channel is formed of, for example, phosphorus. It was formed by implanting N-type impurities such as (P) and arsenic (As) ions.

Since the first doped well 32 is to be formed under the transport channel 34, it is generally preferable that the implantation energy of impurities for forming the first doped well is higher than the implantation energy of impurities for forming the transport channel. Do. However, in an embodiment of the present invention in which boron is used as an impurity for forming a first doping well and phosphorus or arsenic is used as an impurity for forming a transport channel, the boron ion has a diffusion coefficient greater than that of phosphorus or arsenic ions. Therefore, even if impurities are implanted with the same implantation energy, the first doped well is formed under the transport channel.

In addition, in the case of implanting the impurity ions for forming the first doped well 32, the impurity may be implanted perpendicularly to the surface of the semiconductor substrate, but the first doped well may be widely spread under the transfer channel to the side of the transfer channel. In order to electrically separate the lower portion of the transport channel to form a wider, the impurity may be injected by adjusting the incident angle.

In the manufacturing method according to an embodiment of the present invention, the first doped well 32 and the transfer channel 34 are sequentially formed by a two-step ion implantation process, but impurities and transfer for forming the first doped well are performed. Of course, the first doping well and the transmission channel may be simultaneously formed by implanting impurities for channel formation.

In FIGS. 7A and 8A, the first doping well 32 is formed to electrically separate the semiconductor substrate and the transfer channel and serve as a ground for determining the potential of the transfer channel. 34) is formed for the transmission of signal charges.

7B and 8B illustrate a process of forming the second doped well 36, which exposes at least the transfer channel 34 to the surface on the semiconductor substrate 30 (mask of FIG. 4). Pattern (P5)) A first process of forming the second ion implantation prevention layer 35 and a second process of forming a second doped well 36 in the vertical transfer part by injecting impurities of a second conductivity type into the resultant. Proceeds to.

The second doped well 36 is formed to completely surround the side of the transfer channel so that the side of the transfer channel 34 does not contact the semiconductor substrate 30. In order to make it shallow and to secure the electrical separation of the side of the transport channel, the impurity of a concentration higher than the impurity concentration of the first doping well is implanted to form a shape surrounding the transport channel and the first doping well and surrounding the side of the transport channel. In order to facilitate the movement of the signal charges from the vertical transfer unit to the horizontal transfer unit (described in FIGS. 5C and 6), the ends thereof are formed below the vertical transfer electrode adjacent to the horizontal transfer unit. do. The mask pattern for forming the second doped well is as described with reference to FIG. 4.

Since the second doped well 36 is not formed in the horizontal transfer unit, the depth of the transmission channel of the horizontal transfer unit is maintained as shown in FIG. 8A.

According to the manufacturing method according to the embodiment of the present invention, since the vertical transfer part may include a transmission channel having a shallow depth and a doping well that completely surrounds the transmission channel with high impurity concentration by the second doping well. The accumulation of signal charges is large and it is possible to strengthen the electrical separation from other elements (eg photodiodes). In addition, since the second doping well is not formed, the horizontal transfer unit may include a deep transmission channel and a doping well having a low impurity concentration, thereby increasing the transmission channel.

In the conventional method, the element isolation region 20 is formed on the side of the transmission channel 18, as shown in FIG. 3A, in order to secure the electrical separation between the transmission channel and another element (for example, a photodiode). In the present invention, since a separate process for device isolation is not necessary, the manufacturing process is simplified.

In addition, in the conventional method, the first, second and third doped wells and the first and second transfer channels were formed by different processes, but in the present invention, except for the ion implantation process for forming the second doped well, The process for forming the direct transfer unit and the process for forming the horizontal transfer unit may be simultaneously performed. Therefore, the manufacturing process is much simpler than in the conventional method.

In addition, if the end of the second doping well 36 is disposed so as to be positioned below the final vertical transfer electrode, the movement of the signal charges from the vertical transfer unit to the horizontal transfer unit is made much better. In addition, the marginal problem of the process (in the conventional method, the ends of the first and second doping wells have to be coincident with the ends of the first and second doped wells) are solved.

7C and 8C illustrate a process of forming the vertical transfer electrode 38 and the horizontal transfer electrode 40, which are formed on the semiconductor substrate 30 on which the transfer channel 34 is formed, such as an oxide film or the like. On the first process and resultant of forming an insulating film, such as a nitride film, a conductive material such as polysilicon is deposited / patterned (see mask patterns P3 and P4 in FIG. 4) and the vertical transfer electrode 38 and horizontal The second process of forming the transfer electrode 40 is performed.

In one embodiment of the present invention, the semiconductor substrate is made of N-type, but it is a matter of course that the effect of the present invention can be achieved as it is even if it is made of P-type. In this case, when the conductivity type of the semiconductor substrate is changed from N type to P type, the conductive type of the transmission channel, the first doping well and the second doping well should also be changed to correspond thereto.

Therefore, according to the solid-state imaging device and the method of manufacturing the same according to the present invention, the vertical and horizontal transfer parts are processed in almost the same process except for the impurity implantation process for forming the second doped well while maintaining the electrical characteristics of the vertical and horizontal transfer parts. The manufacturing process is simple since no separate process is required to form and electrically split the side of the transmission channel. In addition, since the vertical and horizontal transmission units share the transmission channel, and only the vertical transmission unit forms the second doping well, the process margin is larger than in the conventional method.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit to which the present invention belongs.

Claims (10)

First and second impurities are injected into the semiconductor substrate in the region where the channel region of the vertical transfer unit and the horizontal transfer unit are to be formed, and the first doping well of the second conductive type located below the transfer channel Forming a first step; A second step of forming an ion implantation prevention film on a semiconductor substrate at least exposing the transfer channel of the first conductivity type to a surface of the vertical transfer section; A third process of injecting impurities of a second conductivity type into the entire surface of the resultant to form a second doped well between the transfer channel of the first conductivity type of the vertical transfer portion and the first doped well of the second conductivity type formed below; ; A fourth step of forming an insulating film on the transfer channel; And a fifth process of forming vertical transfer electrodes on the insulating film on the transfer channel of the vertical transfer part and forming horizontal transfer electrodes on the insulating film on the transfer channel of the horizontal transfer part. . The solid state image pickup device according to claim 1, wherein the ion implantation prevention film is formed to expose a surface of the semiconductor substrate in at least one region of the region where the final vertical transfer electrode of the vertical transfer unit adjacent to the horizontal transfer unit is to be formed. Method of manufacturing the device. The method of claim 2, wherein the ion implantation prevention film is formed in a shape that exposes the surface of the semiconductor substrate in all regions except the region where the photodiode is formed, the vertical transfer portion and the photodiode is formed on the surface. A solid state imaging device manufacturing method. The solid state imaging device of claim 1, wherein a final vertical transfer electrode adjacent to the horizontal transfer unit and one of the horizontal transfer electrodes constituting the horizontal transfer unit are partially overlapped. Way. The solid state imaging device of claim 4, wherein the ion implantation prevention layer is formed to expose a semiconductor substrate in at least one region of a region where a final vertical transfer electrode that is not overlapped with a horizontal transfer electrode is formed on a surface thereof. Way. The method of manufacturing a solid state image pickup device according to claim 1, wherein the first step is performed by simultaneously implanting impurities of the first conductivity type and impurities of the second conductivity type. 7. A method according to claim 6, wherein the diffusion coefficient of the impurity of the second conductivity type is larger than the diffusion coefficient of the impurity of the first conductivity type. 8. The solid state imaging according to claim 7, wherein the first step is performed by using any one of phosphorus or arsenic as the impurity of the first conductivity type and using boron ions as the impurity of the second conductivity type. Method of manufacturing the device. 2. The method of claim 1, wherein the first step includes implanting impurities of the second conductivity type to form first doping wells of the second conductivity type, and then implanting impurities of the first conductivity type to implant the first conductivity type. A method of manufacturing a solid-state imaging device, characterized in that it proceeds to the step of forming a transmission channel. The method of claim 1, wherein the second doping well is formed by injecting impurities having a concentration higher than that of the impurities constituting the first doping well.