CN108231816A - Imaging sensor and the method for forming imaging sensor - Google Patents

Abstract

The present disclosure relates to an image sensor, which includes: a first photodiode for converting light in a first wavelength band, a first part of the first photodiode is formed of a first semiconductor material, a second part of the first photodiode formed in part of a second semiconductor material; and a second photodiode for converting light in a second wavelength band, the second photodiode formed of a second semiconductor material, wherein at least a portion of the first wavelength band has a wavelength greater than that of the For the wavelength of the second band, the energy band gap of the first semiconductor material is smaller than the energy band gap of the second semiconductor material. The present disclosure also relates to a method of forming an image sensor. The present disclosure can improve quantum efficiency and reduce crosstalk of light.

Description

Image sensor and method of forming image sensor

technical field

The present disclosure relates to the technical field of semiconductors, and in particular, to an image sensor and a method for forming the image sensor.

Background technique

The incident light may not be completely absorbed in the photodiode of the image sensor, and some light may pass through the photodiode. This will cause a decrease in quantum efficiency, and the part of the light that penetrates the photodiode may enter other photodiodes and cause light crosstalk.

Therefore, there is a need for new technology.

Contents of the invention

An object of the present disclosure is to provide a novel image sensor and a method of forming the image sensor.

According to a first aspect of the present disclosure, there is provided an image sensor, including: a first photodiode for converting light in a first wavelength band, a first part of the first photodiode is formed of a first semiconductor material, and the first photodiode A second portion of a photodiode is formed of a second semiconductor material; and a second photodiode for converting light in a second wavelength band, the second photodiode is formed of a second semiconductor material, wherein the light of the first wavelength band At least some of the wavelengths are greater than the wavelengths of the second band, and the energy band gap of the first semiconductor material is smaller than the energy band gap of the second semiconductor material.

According to a second aspect of the present disclosure, there is provided a method of forming an image sensor, comprising: forming a second portion of a first photodiode and a second photodiode in a semiconductor substrate, wherein the first photodiode is used for converting light of a first wavelength band, the second photodiode is used for converting light of a second wavelength band, the semiconductor substrate is formed of a second semiconductor material; The first portion of the first photodiode, wherein the first portion is formed of a first semiconductor material, wherein at least part of the wavelength of the first wavelength band is greater than the wavelength of the second wavelength band, and the first semiconductor material The energy band gap is smaller than the energy band gap of the second semiconductor material.

Other features of the present disclosure and advantages thereof will become apparent through the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, which constitute a part of this specification, illustrate the embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.

The present disclosure can be more clearly understood from the following detailed description with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram schematically showing the structure of an image sensor according to one embodiment of the present disclosure.

2 to 5 are diagrams schematically showing the structure of a first photodiode in an image sensor according to an embodiment of the present disclosure, respectively.

FIG. 6 is a diagram schematically showing the structure of an image sensor according to one embodiment of the present disclosure.

7 to 10 are schematic diagrams respectively showing cross sections of an image sensor at respective steps of an example of a method of forming an image sensor according to an exemplary embodiment of the present disclosure.

FIG. 11 is a schematic diagram schematically showing the structure of an image sensor according to one embodiment of the present disclosure.

12 to 14 are schematic diagrams each showing a cross-section of an image sensor at respective steps of an example of a method of forming an image sensor according to an exemplary embodiment of the present disclosure.

Note that in the embodiments described below, the same reference numerals may be used in common between different drawings to denote the same parts or parts having the same functions, and repeated descriptions thereof will be omitted. In this specification, similar reference numerals and letters are used to refer to similar items, therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

In order to facilitate understanding, the position, size, range, etc. of each structure shown in the drawings and the like may not represent the actual position, size, range, and the like. Therefore, the disclosed invention is not limited to the positions, dimensions, ranges, etc. disclosed in the drawings and the like.

Detailed ways

Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that relative arrangements of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present disclosure unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and in no way intended as any limitation of the disclosure, its application or uses.

Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods and devices should be considered part of the Authorized Specification.

In all examples shown and discussed herein, any specific values should be construed as illustrative only, and not as limiting. Therefore, other examples of the exemplary embodiment may have different values.

In the present disclosure, reference to "one embodiment" or "some embodiments" means that a feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment, at least some embodiments of the present disclosure. Thus, appearances of the phrase "in one embodiment" and "in some embodiments" in various places in this disclosure are not necessarily referring to the same embodiment or embodiments. Furthermore, features, structures or characteristics may be combined in any suitable combination and/or subcombination in one or more embodiments.

As shown in FIG. 1 , the image sensor of the present disclosure includes a first photodiode 10 and a second photodiode 20 . Wherein, the first photodiode 10 is used for converting the light of the first wavelength band, and the second photodiode 20 is used for converting the light of the second wavelength band. A first part 11 of the first photodiode 10 is formed from a first semiconductor material and a second part 12 thereof is formed from a second semiconductor material. The second photodiode 20 is formed of a second semiconductor material. Wherein, at least part of the wavelengths of the first waveband is greater than the wavelength of the second waveband, and the energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material.

In a semiconductor material with a smaller energy band gap, the minimum energy that electrons must obtain to be excited from the valence band to the conduction band is smaller, that is, the easier it is to be excited, and therefore the easier it is to absorb light entering it. For the same thickness of semiconductor material, a semiconductor material with a smaller energy band gap can generally absorb more light than a semiconductor material with a larger energy band gap. Since longer wavelength light is harder to absorb, fully absorbing longer wavelength light typically requires a thicker photodiode than shorter wavelength light. Therefore, in the image sensor according to these embodiments, a part of the photodiode for absorbing light with a longer wavelength is formed of a semiconductor material with a smaller energy bandgap, so that the photodiode is not increased (or is not increased too much) In the case of thickness, light with a longer wavelength can also be completely absorbed.

In the image sensor according to these embodiments, in some examples, the light of the first wavelength band converted by the first photodiode 10 may be red light, and the light of the second wavelength band used by the second photodiode 20 may be Green light and/or blue light; in some other examples, the light of the first wavelength band used for conversion by the first photodiode 10 may be infrared light, and the light of the second wavelength band used for conversion by the second photodiode 20 may be red light , green light and/or blue light; in still some examples, the light of the first waveband that the first photodiode 10 is used for conversion can be red light and infrared light, and the light of the second waveband that the second photodiode 20 is used for conversion Can be green light and/or blue light; In still some examples, the light of the first waveband that the first photodiode 10 is used for conversion can be infrared light, red light, green light and/or blue light, and the second photodiode 20 uses The light of the converted second wavelength band may be ultraviolet light. Those skilled in the art can understand that the above examples are only illustrative and not restrictive nor exhaustive, as long as all or part of the wavelengths in the first waveband are greater than the wavelengths in the second waveband.

In some embodiments, the first semiconductor material is silicon germanium (SiGe), and the second semiconductor material is silicon (Si). Those skilled in the art can understand that the first semiconductor material may include SiGe, GaAs, Pbs, PbSe, PbTe, GaSb, InN, etc., or any combination of two or more semiconductor materials. Those skilled in the art can also understand that any III group (boron group) element (B, Al, Ga, In, Tl), IV group (carbon group) element (C, Si, Ge, Sn, Pb), V group ( Nitrogen) elements (N, P, As, Sb, Bi) or the like can be used to form the first semiconductor material.

In some embodiments, as shown in FIG. 1 , the first portion 11 of the first photodiode 10 is closer to the surface of the image sensor for receiving light than the second portion 12 . The surface of the image sensor for receiving light may be the front side of the image sensor (for example, a front-illuminated image sensor) or the back side of the image sensor (for example, a back-illuminated image sensor).

In some embodiments, the structure of the first photodiode may be as shown in FIGS. 2 to 5 . Wherein, the first photodiode is formed by the first semiconductor material S1 and the second semiconductor material S2. Wherein, the second semiconductor material S2 (that is, the material that forms the second part of the first photodiode) is of the first conductivity type, and the first semiconductor material S1 (that is, the material that forms the first part of the first photodiode) can be the same as the first semiconductor material S1. The two semiconductor materials S2 are identically doped to the first conductivity type, or may be undoped semiconductor materials.

A region 30 of the second conductivity type is formed in the first semiconductor material S1 and/or the second semiconductor material S2 . For example, the region 30 of the second conductivity type can be formed only in the first semiconductor material S1 (as shown in FIG. In the second semiconductor material S2 (as shown in FIG. 4 ), it can also be formed in the first semiconductor material S1 and the second semiconductor material S2 (as shown in FIGS. 3 and 5 ) at the same time. For example, the region 30 of the second conductivity type may be formed from the upper surface, as shown in FIGS. 2 and 3 , or may be formed from the lower surface, as shown in FIGS. 4 and 5 . Although not shown in the drawings, those skilled in the art can understand that the boundary of the region 30 of the second conductivity type can also be just at the junction of the first semiconductor material S1 and the second semiconductor material S2 .

In some embodiments, the first conductivity type is P-type, and the second conductivity type is N-type, that is, an N-type region is formed in a P-type semiconductor material to form a photodiode. Those skilled in the art can understand that the first conductivity type can also be N-type, and the second conductivity type can also be P-type, that is, a P-type region is formed in an N-type semiconductor material to form a photodiode.

In some embodiments, as shown in FIG. 6 , the image sensor includes a first photodiode PD1 , a second photodiode PD2 , and a third photodiode PD3 . Wherein, the first photodiode PD1 is used for converting the light of the first wavelength band, the second photodiode PD2 is used for converting the light of the second wavelength band, and the third photodiode PD3 is used for converting the light of the third wavelength band. A first portion of the first photodiode PD1 is formed of a first semiconductor material SEM, and a second portion of the first photodiode PD1 is formed of a second semiconductor material (the portion in the semiconductor substrate SUB). Both the second photodiode PD2 and the third photodiode PD3 are formed of the second semiconductor material (in the semiconductor substrate SUB). Wherein, at least part of the wavelength of the first waveband is greater than the wavelength of the second waveband, at least part of the wavelength of the second waveband is greater than the wavelength of the third waveband, and the energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material.

In some embodiments, the color space of the image sensor is an RGB space, and the first photodiode PD1, the second photodiode PD2, and the third photodiode PD3 are used to convert red light, green light, and blue light, respectively.

In some embodiments, the image sensor further includes a photodiode located above the first photodiode PD1, the second photodiode PD2, and the third photodiode PD3 and covering the first photodiode PD1, the second photodiode PD2, and the third photodiode respectively. The first color filter CF1, the second color filter CF2, and the third color filter CF3 of the photodiode PD3. Wherein, the first color filter CF1, the second color filter CF2, and the third color filter CF3 are respectively used to transmit red light, green light, and blue light.

A method of forming an image sensor according to an embodiment of the present disclosure will be described below with reference to FIGS. 7 to 10 .

As shown in FIG. 7, the second portion of the first photodiode, the second photodiode, and the third photodiode are formed in the semiconductor substrate SUB formed of the second semiconductor material. Each photodiode may be formed by forming a region of the second conductivity type in the semiconductor substrate SUB of the first conductivity type. For example, the first region REG1 of the second conductivity type is formed in the semiconductor substrate SUB of the first conductivity type to form the second part of the first photodiode, and the second portion of the first photodiode is formed in the semiconductor substrate SUB of the first conductivity type. The second region REG2 of the second conductive type is formed to form a second photodiode, and the third region REG3 of the second conductive type is formed in the semiconductor substrate SUB of the first conductive type to form a third photodiode.

Next, forming a first portion of the first photodiode covering the second portion of the first photodiode over a second portion of the first photodiode, wherein the first portion of the first photodiode is formed of a first semiconductor material, and The energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material.

Specifically, as shown in FIG. 7 , firstly, a dielectric material layer L1 is formed on the semiconductor substrate SUB. The dielectric material layer L1 may be formed of silicon oxide, or may be formed of other dielectric materials such as silicon nitride. The dielectric material layer L1 can be formed by chemical vapor deposition (CVD), atomic layer deposition (ALD), thermal oxidation or other suitable means.

As shown in FIG. 8, the part of the dielectric material layer L1 covering the second part of the first photodiode is removed to form a gap as shown in FIG. 8 in the dielectric material layer L1, and the first photodiode is exposed in the gap. The second part of the diode exposes the semiconductor substrate SUB. The gap can be formed by photolithography plus etching, or by other means such as hard mask plus etching.

As shown in FIG. 9, the first semiconductor material SEM is filled in the formed gap as shown in FIG. across the first photodiode. Wherein, the energy band gap of the first semiconductor material is smaller than the energy band gap of the second semiconductor material. The first portion of the first photodiode may be formed through a chemical vapor deposition process, an atomic layer deposition process, or a molecular beam epitaxy (MBE) process, or the like. Preferably, the processing temperature for forming the first part is lower than 500° C., more preferably lower than 450° C., so as to avoid affecting the already formed devices, metal interconnection layers and the like.

Around each photodiode, isolation structures I1, I2, such as deep trench isolation (DTI) structures, or shallow trenches, may then be formed surrounding the photodiode in whole or in part for isolating the photodiode from adjacent photodiodes. Isolation (STI) structure, etc., as shown in Figure 10. Afterwards, a filling layer L2 (for example, any suitable functional layer such as an anti-reflection layer, a high dielectric constant layer, a planarization layer, a spacer layer, etc.) formed by a dielectric material can be formed on the dielectric material layer L1, and then the filling layer L2 can be formed on the dielectric material layer L1. Color filters are formed on the layer L2, such as a first color filter CF1, a second color filter CF2, and a third color filter CF3 for the first photodiode, the second photodiode, and the third photodiode, respectively. Among them, the first color filter CF1, the second color filter CF2, and the third color filter CF3. are respectively located on the first photodiode, the second photodiode, and the third photodiode and respectively cover the first photodiode, the second photodiode, and the third photodiode. There are also light isolation structures I3 and I4 between the color filters. After that, the first microlens ML1, the second microlens ML2, and the second microlens ML1 covering the first color filter CF1, the second color filter CF2, and the third color filter CF3 are respectively formed on each color filter. Three microlenses ML3, thereby forming an image sensor as shown in FIG. 6 .

The material of each color filter is appropriately selected so that the first color filter CF1, the second color filter CF2, and the third color filter CF3 are respectively used to transmit the light of the first waveband, the light of the second waveband, and the light of the second waveband. Light of the third band. Therefore, the first photodiode is used to convert the light of the first wavelength band, the second photodiode is used to convert the light of the second wavelength band, and the third photodiode is used to convert the light of the third wavelength band. Wherein, at least part of the wavelength of the first wave band is greater than the wavelength of the second wave band, and at least part of the wavelength of the second wave band is greater than the wavelength of the third wave band. In some examples, the color space of the image sensor is the RGB space, the first color filter CF1, the second color filter CF2, and the third color filter CF3 are used to transmit red light, green light, and blue light respectively, and the A photodiode, a second photodiode, and a third photodiode are used to convert red light, green light, and blue light, respectively.

Those skilled in the art can understand that the isolation structures I1 and I2 for isolating photodiodes from adjacent photodiodes can also be formed before forming the dielectric material layer L1 , for example, to form an image sensor as shown in FIG. 11 .

As shown in FIG. 12, the second portion of the first photodiode, the second photodiode, and the third photodiode are formed in the semiconductor substrate SUB formed of the second semiconductor material. Then around each photodiode, an isolation structure I1, I2 is formed wholly or partially surrounding the photodiode for isolating the photodiode from adjacent photodiodes, such as a deep trench isolation (DTI) structure, or a shallow trench isolation (STI) structure, etc., as shown in Figure 12. Next, a dielectric material layer L1 is formed over the semiconductor substrate SUB. Then, the part of the dielectric material layer L1 covering the second part of the first photodiode is removed to form a gap as shown in FIG. 13 in the dielectric material layer L1, and the second part of the first photodiode is exposed in the gap. Part, that is, the semiconductor substrate SUB is exposed. As shown in FIG. 14, the first semiconductor material SEM is filled in the formed gap as shown in FIG. across the first photodiode. Wherein, the energy band gap of the first semiconductor material is smaller than the energy band gap of the second semiconductor material. Afterwards, a filling layer L2 formed of a dielectric material may be first formed on the dielectric material layer L1, and then the first color filters for the first photodiode, the second photodiode, and the third photodiode are formed on the filling layer L2. Filter CF1, second color filter CF2, and third color filter CF3, and first microlens ML1, second microlens ML2, and third microlens ML3, thereby forming an image sensor as shown in FIG. 11 .

The material of each color filter is appropriately selected so that the first color filter CF1, the second color filter CF2, and the third color filter CF3 are respectively used to transmit the light of the first waveband, the light of the second waveband, and the light of the second waveband. Light of the third band. Therefore, the first photodiode is used to convert the light of the first wavelength band, the second photodiode is used to convert the light of the second wavelength band, and the third photodiode is used to convert the light of the third wavelength band. Wherein, at least part of the wavelength of the first wave band is greater than the wavelength of the second wave band, and at least part of the wavelength of the second wave band is greater than the wavelength of the third wave band. In some examples, the color space of the image sensor is an RGB space, the first color filter CF1, the second color filter CF2, and the third color filter CF3 are used to transmit red light, green light, and blue light respectively, and the A photodiode, a second photodiode, and a third photodiode are used to convert red light, green light, and blue light, respectively.

Although the method for forming the image sensor shown in FIG. 6 is described above only in conjunction with FIGS. 7 to 10, and the method for forming the image sensor shown in FIG. 11 is described in conjunction with FIGS. 12 to 14, those skilled in the art can obtain the formation All image sensor methods described in this disclosure.

Although the drawings of the present disclosure only schematically show the structure of the image sensor in the pixel area in the form of a cross-sectional view, those skilled in the art can obtain the overall structure and structure of the image sensor involved in the present disclosure based on the contents of the present disclosure. form method.

The word "A or B" in the specification and claims includes "A and B" and "A or B", and does not exclusively include only "A" or only "B", unless specifically stated otherwise.

In the specification and claims, the words "front", "rear", "top", "bottom", "above", "under", etc., if present, are used for descriptive purposes and not necessarily to describe a constant relative position. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the disclosure described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. Orientation operation.

As used herein, the word "exemplary" means "serving as an example, instance, or illustration" rather than as a "model" to be exactly reproduced. Any implementation described illustratively herein is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, the disclosure is not to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or detailed description.

As used herein, the word "substantially" is meant to include any minor variations due to defects in design or manufacturing, device or component tolerances, environmental influences, and/or other factors. The word "substantially" also allows for differences from a perfect or ideal situation due to parasitic effects, noise, and other practical considerations that may exist in an actual implementation.

The above description may refer to elements or nodes or features being "connected" or "coupled" together. As used herein, unless expressly stated otherwise, "connected" means that one element/node/feature is directly connected (or electrically, mechanically, logically, or otherwise) to another element/node/feature. direct communication). Similarly, unless expressly stated otherwise, "coupled" means that one element/node/feature can be directly or indirectly mechanically, electrically, logically or otherwise connected to another element/node/feature to Interactions are allowed even though the two features may not be directly connected. That is, "coupled" is intended to encompass both direct and indirect couplings of elements or other features, including connections utilizing one or more intervening elements.

In addition, certain terms may also be used in the following description for reference purposes only, and thus are not intended to be limiting. For example, the words "first," "second," and other such numerical terms referring to structures or elements do not imply a sequence or order unless clearly indicated by the context.

It should also be understood that when the word "comprises/comprises" is used herein, it indicates the presence of indicated features, integers, steps, operations, units and/or components, but does not exclude the presence or addition of one or more other features, whole, steps, operations, units and/or components and/or combinations thereof.

In this disclosure, the term "provide" is used broadly to cover all ways of obtaining an object, thus "provide something" includes, but is not limited to, "purchase", "preparation/manufacture", "arrangement/setup", "installation/ Assembly", and/or "Order" objects, etc.

Those skilled in the art will appreciate that the boundaries between the above-described operations are merely illustrative. Multiple operations may be combined into a single operation, a single operation may be distributed among additional operations, and operations may be performed with at least partial overlap in time. Also, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in other various embodiments. However, other modifications, changes and substitutions are also possible. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

In addition, implementations of the present disclosure may also include the following examples:

1. An image sensor, characterized in that, comprising:

a first photodiode for converting light in a first wavelength band, a first portion of the first photodiode is formed of a first semiconductor material, and a second portion of the first photodiode is formed of a second semiconductor material; and

a second photodiode for converting light in a second wavelength band, the second photodiode is formed of a second semiconductor material,

Wherein, at least part of the wavelengths of the first waveband are greater than the wavelengths of the second waveband, and the energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material.

2. The image sensor according to 1, wherein the first portion is closer to a surface for receiving light of the image sensor than the second portion.

3. The image sensor according to 1, further comprising:

a third photodiode for converting light in a third wavelength band, the third photodiode is formed of a second semiconductor material,

Wherein, at least part of the wavelengths of the second waveband are greater than the wavelengths of the third waveband.

4. The image sensor according to 3, wherein the first, second, and third photodiodes are used to convert red light, green light, and blue light, respectively.

5. The image sensor according to 3, further comprising:

first, second, and third color filters overlying and covering the first, second, and third photodiodes, respectively,

Wherein, the first, second, and third color filters are respectively used to transmit red light, green light, and blue light.

6. The image sensor according to 1, wherein both the first part and the second part are of the first conductivity type, and a second conductive type is formed in the first part and/or the second part. area of conductivity type.

7. The image sensor according to 6, wherein the first conductivity type is P-type, and the second conductivity type is N-type.

8. The image sensor according to 1, wherein the first semiconductor material is silicon germanium, and the second semiconductor material is silicon.

9. A method of forming an image sensor, comprising:

A second part of the first photodiode and a second photodiode are formed in the semiconductor substrate, wherein the first photodiode is used to convert light of a first wavelength band, and the second photodiode is used to convert light of a second wavelength band light, the semiconductor substrate is formed from a second semiconductor material; and

forming a first portion of the first photodiode covering the second portion over the second portion, wherein the first portion is formed from a first semiconductor material,

Wherein, at least part of the wavelengths of the first waveband are greater than the wavelengths of the second waveband, and the energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material.

10. The method according to 9, wherein forming the first portion over the second portion comprises:

forming a layer of dielectric material over the semiconductor substrate;

removing a portion of the layer of dielectric material overlying the second portion to expose the second portion; and

The first portion is formed on the exposed second portion.

11. The method according to 9, wherein the first portion is formed by chemical vapor deposition, atomic layer deposition, or molecular beam epitaxy.

12. The method according to 11, characterized in that the processing temperature for forming the first part is lower than 500°C.

13. The method according to 11, characterized in that the processing temperature for forming the first portion is lower than 450°C.

14. The method according to 9, further comprising:

forming a third photodiode in a semiconductor substrate, wherein the third photodiode is used to convert light of a third wavelength band, the semiconductor substrate is formed of a second semiconductor material,

Wherein, at least part of the wavelengths of the second waveband are greater than the wavelengths of the third waveband.

15. The method of 14, wherein the first, second, and third photodiodes are used to convert red, green, and blue light, respectively.

16. The method according to 14, further comprising:

forming first, second, and third color filters covering the first, second, and third photodiodes, respectively, over the first, second, and third photodiodes,

Wherein, the first, second, and third color filters are respectively used to transmit red light, green light, and blue light.

17. The method according to 9, wherein both the first part and the second part are of the first conductivity type, and the first part and/or the second part are formed with a second conductive type. type of area.

18. The method according to 17, wherein the first conductivity type is P-type, and the second conductivity type is N-type.

19. The method according to 9, wherein the first semiconductor material is silicon germanium, and the second semiconductor material is silicon.

Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only, rather than limiting the scope of the present disclosure. The various embodiments disclosed herein can be combined arbitrarily without departing from the spirit and scope of the present disclosure. Those skilled in the art will also appreciate that various modifications may be made to the embodiments without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims (10)

1. An image sensor, characterized in that, comprising: a first photodiode for converting light in a first wavelength band, a first portion of the first photodiode is formed of a first semiconductor material, and a second portion of the first photodiode is formed of a second semiconductor material; and a second photodiode for converting light in a second wavelength band, the second photodiode is formed of a second semiconductor material, Wherein, at least part of the wavelengths of the first waveband are greater than the wavelengths of the second waveband, and the energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material. 2. The image sensor according to claim 1, wherein the first portion is closer to a surface for receiving light of the image sensor than the second portion. 3. The image sensor according to claim 1, further comprising: a third photodiode for converting light in a third wavelength band, the third photodiode is formed of a second semiconductor material, Wherein, at least part of the wavelengths of the second waveband are greater than the wavelengths of the third waveband. 4. The image sensor of claim 3, wherein the first, second, and third photodiodes are used to convert red light, green light, and blue light, respectively. 5. The image sensor according to claim 3, further comprising: first, second, and third color filters overlying and covering the first, second, and third photodiodes, respectively, Wherein, the first, second, and third color filters are respectively used to transmit red light, green light, and blue light. 6. The image sensor according to claim 1, wherein both the first part and the second part are of the first conductivity type, and the first part and/or the second part are formed with A region of the second conductivity type. 7. The image sensor according to claim 6, wherein the first conductivity type is P-type, and the second conductivity type is N-type. 8. The image sensor according to claim 1, wherein the first semiconductor material is silicon germanium, and the second semiconductor material is silicon. 9. A method of forming an image sensor, comprising: Forming a second part of the first photodiode and a second photodiode in the semiconductor substrate, wherein the first photodiode is used to convert light in a first wavelength band, and the second photodiode is used to convert light in a second wavelength band light, the semiconductor substrate is formed from a second semiconductor material; and forming a first portion of the first photodiode covering the second portion over the second portion, wherein the first portion is formed from a first semiconductor material, Wherein, at least part of the wavelengths of the first waveband are greater than the wavelengths of the second waveband, and the energy bandgap of the first semiconductor material is smaller than the energy bandgap of the second semiconductor material. 10. The method of claim 9, wherein forming the first portion over the second portion comprises: forming a layer of dielectric material over the semiconductor substrate; removing a portion of the layer of dielectric material overlying the second portion to expose the second portion; and The first portion is formed on the exposed second portion.