WO2016109958A1

WO2016109958A1 - Method for doping finfet

Info

Publication number: WO2016109958A1
Application number: PCT/CN2015/070309
Authority: WO
Inventors: 洪俊华; 吴汉明; 陈炯; 张劲
Original assignee: 上海凯世通半导体有限公司
Priority date: 2015-01-08
Filing date: 2015-01-08
Publication date: 2016-07-14
Also published as: KR20170103894A; KR101972365B1; CN107112239B; CN107112239A

Abstract

A method for doping a FinFET. The FinFET comprises a substrate (20) and fins (200) arranged in parallel on the substrate at intervals. Each fin comprises a top surface, a first side wall and a second side wall. The doping method comprises the following steps: T1, forming a doping layer on the top surface, the first side wall and the second side wall of each fin; and T2, implanting substrate elements into the top surface of the fin in the normal direction of the substrate (20) to reduce the concentration of doping elements in the top surface. Implantation saturation is realized through long-time ion implantation, and one process of substrate element implantation is added after implantation of the side wall is completed, thereby finally achieving uniform doping of the fin.

Description

FinFET doping method

Technical field

The present invention relates to a method of doping a FinFET, and more particularly to a method of doping a FinFET having a self-regulating function.

Background technique

As integrated circuits move from smaller 22nm technology nodes to smaller sizes, the process uses FinFET (Fin Field Effect Transistor, Fin is a fin, FinFET named according to the shape of the transistor and the fin similarity) structure, designed to reduce Channeling has an absolute advantage in suppressing subthreshold currents and gate leakage currents. As integration increases, it will be an inevitable trend for FinFET devices to replace traditional bulk silicon devices.

1 shows a portion of a FinFET structure (including two cells of 100 and 200), reference numeral 20 denotes a substrate, such as a silicon substrate, and reference numeral 22 denotes a shallow channel formed in the

substrate

20 or 20. In the shallow trench isolation region, the two Fins shown are indicated by

reference numerals

124 and 224 in Fig. 1, respectively.

In a FinFET structure, doping needs to be formed in a vertical Fin. Existing doping methods in the industry include growth and ion implantation. The growth method is feasible for P-type doping, but it encounters a dilemma when forming N-type doping. The N-type dopant source is more common in AsH3, and its toxicity is very large. Therefore, it is necessary to form an N-type doping by means of arsenic ion implantation. However, in practical applications, ion implantation faces three technical problems that need to be solved, namely, uniformity, amorphization and rounding.

1, uniformity (doping conformity)

Since Fin is of a vertical structure, in order to form doping in the sidewall, the direction of ion implantation must be at an angle to the length of Fin. Referring to FIG. 2 and FIG. 3, in order to achieve effective doping in the sidewalls of the Fin, the existing injection method usually adopts two injections, that is, the injection of the right side of Fin is completed according to the direction of the arrow shown in FIG. The injection to the left of Fin is then completed in the direction of the arrow shown in FIG. In this implant with an angle of inclination, the top of Fin is subjected to two ion implantations and no With the injection of the projected dose, this results in a severe non-uniformity of the doping amount between the top and side walls of each Fin.

Specifically, still referring to FIG. 2 or FIG. 3, in order to form doping on the sidewall of Fin, the direction of ion implantation must be at an angle to the normal direction of the substrate, except for 45°, Fin The doping amount on the top and side walls must be different. As the aspect ratio of the FinFET structure increases, the ratio of the height of the Fin to the distance between the two Fins increases, the angle of the ion implantation (the angle between the injection direction and the substrate normal) increases. The smaller the ion is injected into the top, the more ions will be injected into the sidewall, which exacerbates the unevenness of the top and sidewall doping doses of Fin itself. At present, this non-uniformity is extremely significant, even reaching a ratio of top to side doping dose of 20:1, and optimally, reaching 10:1. That is to say, the doping amount of the top is much larger than that of the sidewall, and this unevenness is extremely disadvantageous for the optimization of device performance.

Furthermore, if the two injection parameters are not accurately controlled to be consistent, the doping on the two sidewalls of Fin will be uneven, which will affect the performance of the device.

2, amorphization (Amorphization)

The existing implantation method also suffers from the problem of amorphization. Since the energy of implanting ions is high, the depth at which ions are implanted is deep, which causes Fin to be amorphized, and the original single crystal structure is difficult to maintain. The performance of the device is also extremely disadvantageous.

3, rounded (Corner erosion)

Referring to FIG. 4, in addition to the problem of amorphization, the prior art high-energy implantation causes the two corners of Fin to be damaged by ions, and the damaged corners are shown in FIG. This structure is also detrimental to device performance.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the defect that the injection uniformity is poor when the Fin is doped by the ion implantation method in the prior art, and in particular, the unevenness of the top and sidewall of the Fin often exceeds 10:1. Providing a doping method of FinFET, which achieves saturation of implantation by ion implantation for a long time, and adds a substrate element (such as silicon or germanium) after the sidewall is completed. The process of implantation finally achieves uniform doping of Fin.

The present invention solves the above technical problems by the following technical solutions:

A FinFET doping method, the FinFET comprising a substrate and Fins disposed in parallel spaced apart on the substrate, each Fin comprising a top surface, a first sidewall and a second sidewall, wherein the doping method comprises The following steps:

T1, forming a doped layer in the top surface of the Fin, the first sidewall and the second sidewall;

T2, implanting a substrate element into the top surface of the Fin along a normal direction of the substrate to reduce the concentration of the doping element in the top surface.

Due to the vertical structure of Fin, the doping amount of the top surface is greater than the doping amount of the sidewall, which causes severe unevenness in top and sidewall doping. To this end, after the doping layer is completed, the implantation process of the substrate element is increased to reduce the concentration of the doping element in the top surface, thereby ensuring uniformity of doping of the top surface and the sidewall.

Preferably, the implantation depth of the substrate element in step T2 coincides with the depth of the doped layer.

Preferably, for each Fin, step T1 further comprises:

T11, injecting a doping element into the first sidewall and injecting into the top surface,

T12, implanting a doping element into the second sidewall and implanting into the top surface.

In the doping method, after the implantation doping of the first sidewall and the second sidewall is completed, since the top surface is subjected to two ion implantations, the doping amount in the top surface is inevitably larger than the doping amount of the sidewall. In order to reduce this non-uniformity, a process of vertical implantation is added after doping the two sidewalls of the Fin, and the substrate element is implanted into the top, since the implantation direction is along the normal direction of the substrate, The implantation of the substrate elements does not affect the doping on the two sidewalls of Fin, but only affects the doping of the top. After the substrate element is implanted, there are two cases: first, after the substrate element is implanted, a part of the doping element in the top is sputtered, thereby reducing the doping amount of the top portion, thereby reducing the doping concentration; Second, after the substrate element is implanted into the top, it is equal to increasing the dose of the substrate, and the concentration of the doping element is lowered. Thereby, it contributes to the uniformity of the top and side walls of the Fin.

Preferably, in step T11, a doping element is implanted into the first sidewall and implanted into the top surface until the dose of the doping element in the first sidewall reaches self-saturation, and/or, in step T12, the doping is performed. a dopant element is implanted into the second sidewall and implanted into the top surface until a dose of doping element in the second sidewall is self-saturated, wherein self-saturation is an implanted doping element and a sputtered doping element Equal dynamic equilibrium state.

That is to say, for each Fin, the doping process of the two sidewalls is like this:

First, a doping element is implanted into the first sidewall and implanted into the top surface until the dose of the doping element in the first sidewall reaches self-saturation, wherein:

Part of the doping element is implanted into the first sidewall to form a doped layer;

After the doping element strikes the doped layer, the doping element in the doped layer is sputtered and the sputtered doping element is incident on the second sidewall of the adjacent Fin to form on the second sidewall of the adjacent Fin. Sedimentary layer,

Then, a doping element is implanted into the second sidewall and implanted into the top surface until the dose of the doping element in the second sidewall is saturated, wherein:

Part of the doping element is implanted into the second sidewall to form a doped layer;

After the doping element strikes the doped layer, the doping element in the doped layer is sputtered and the sputtered doping element is incident on the first sidewall of the adjacent Fin;

A portion of the doping element strikes the deposited layer to sputter the doping element in the deposited layer and the sputtered doping element is directed toward the first sidewall of the adjacent Fin.

Preferably, for each Fin, step T1 comprises:

Steps TP1 and TP2 are repeatedly performed until the dose of the doping element in the first sidewall and the second sidewall reaches self-saturation, and then step T2 is performed.

TP1, implanting a doping element into the first sidewall and injecting into the top surface;

TP2, implanting a doping element into the second sidewall and injecting into the top surface,

Among them, self-saturation is a dynamic equilibrium state in which the implanted doping element and the sputtered doping element are equal.

The doping conditions of the two sidewalls are as follows,

When injecting the first sidewall:

When injecting the second sidewall:

Preferably, the implantation direction of the doping element is at an angle of 2°-45° to the normal of the substrate, and/or

The doping element is arsenic, phosphorus or boron.

Preferably, the substrate element is silicon or germanium.

Preferably, the doping element has an implantation energy of 200 eV - 2 keV. When the doping element is arsenic, the implantation energy is 1 keV or less, and when the doping element is boron, the implantation energy is less than or equal to 300 eV.

The present invention also provides a method of doping a FinFET, the FinFET comprising a substrate and Fin disposed in parallel on the substrate, each Fin comprising a top surface, a first sidewall and a second sidewall, wherein the FinFET is characterized in that The doping method includes the following steps:

R1, forming a doped layer in the top surface of the Fin, the first sidewall and the second sidewall;

R2, implanting a substrate element into a top surface of the Fin in a direction almost parallel to the top surface to reduce a dose of the doping element in the top surface, wherein a direction almost parallel to the top surface indicates an implantation direction and the top The angle between the faces is greater than 0° and less than or equal to 5°.

In this technical solution, in order to solve the problem of uneven topping and sidewall doping of Fin, similarly, after the doping of Fin is completed, an implantation process of a substrate element is added, and an implantation direction almost parallel to the top surface is adopted. The substrate element is implanted into the top surface, and the doping element is sputtered to reduce the dose of the doping element in the top surface, thereby improving the doping uniformity of the top surface and the sidewall.

Preferably, for each Fin, step R1 further comprises:

R11, injecting a doping element into the first sidewall and injecting into the top surface,

R12, implanting a doping element into the second sidewall and implanting into the top surface.

Preferably, in step R11, a doping element is implanted into the first sidewall and implanted into the top surface until the dose of the doping element in the first sidewall reaches self-saturation, and/or, in step R12, the doping is performed. a dopant element is implanted into the second sidewall and implanted into the top surface until a dose of doping element in the second sidewall is self-saturated, wherein self-saturation is an implanted doping element and a sputtered doping element Equal dynamic equilibrium state.

Preferably, for each Fin, step R1 comprises:

Step RP1 and step RP2 are repeatedly performed until the dose of the doping element in the first sidewall and the second sidewall reaches self-saturation, and then step R2 is performed,

RP1, injecting a doping element into the first sidewall and injecting into the top surface;

RP2, implanting a doping element into the second sidewall and implanting into the top surface,

The doping element is arsenic, phosphorus or boron.

Preferably, the substrate element is silicon or germanium.

Based on the common knowledge in the art, the above various preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

The positive effects of the present invention are:

1. Decreasing the doping concentration of the top by increasing the vertical implantation of the substrate element after doping the sidewall of the Fin, or reducing the doping amount of the top by implanting the substrate element almost horizontally, thereby The doping of the top and side walls of the Fin is uniform.

2. The doping dose of the sidewall is self-saturated when the doping of the sidewall of the Fin is performed. It is ensured that the doping at each position of each side wall is uniform, and that the doping of the two side walls of each Fin is also uniform.

3. Since the implantation energy of the doping element is controlled below 2 keV, that is, low energy implantation, the implantation depth of the doping element is shallow, and the damage to Fin is also small, which is favorable for the maintenance of the single crystal structure and improves the circle. The phenomenon of the angle reduces the wear on the Fin.

DRAWINGS

Figure 1 is a schematic diagram of Fin in the prior art.

Figure 2 is a schematic view of the injection of a side wall of Fin.

Figure 3 is a schematic view of the injection of the other side wall of Fin.

Fig. 4 is a schematic view showing the wear of the two end angles of Fin in the prior art.

5 to 7 are schematic views of implantation according to Embodiment 2 of the present invention.

Figure 8 is a schematic view showing the injection of Embodiment 4 of the present invention.

detailed description

The invention is further illustrated by the following examples, which are not intended to limit the invention.

Example 1

In the doping method of the FinFET according to the embodiment, the FinFET includes a substrate and Fins disposed in parallel on the substrate, and each Fin includes a top surface, a first sidewall, and a second sidewall, and the doping method Includes the following steps:

T1, forming a doping layer in the top surface, the first sidewall and the second sidewall of the Fin, and the doping layer can be realized by an existing process. Due to the vertical structure of the Fin, the doping layer is doped in the top surface. The concentration is necessarily greater than the doping concentration of the doped layer of the sidewall.

T2, injecting silicon element into the top surface of Fin along the normal direction of the substrate to reduce the concentration of doping elements in the top surface. Wherein, the implantation depth of the silicon element is consistent with the depth of the doped layer, so that the concentration of the doping element in the top surface can be effectively reduced.

Example 2

In this embodiment, the structure of the FinFET is the same as that of Embodiment 1. Referring to FIGS. 5-7, the substrate is denoted by 100 and Fin is denoted by 200. The doping method comprises the following steps:

For each Fin 200:

Referring to FIG. 5, a doping element is implanted into the first sidewall and implanted into the top surface until a dose of doping element in the first sidewall reaches self-saturation, wherein the doped layer of the top surface is represented by 302, The doped layer of the sidewall is indicated at 301.

Referring to FIG. 6, a doping element is implanted into the second sidewall and implanted into the top surface until the dose of the doping element in the second sidewall is self-saturated, and the doping layers of the top surface and the sidewall remain Indicated by 302 and 301. In order to form doping in the sidewall, the implantation direction of the doping element must be at an angle to the normal of the substrate, then the top surface is implanted twice, resulting in more doping elements on the top surface. Doping elements in the sidewalls. The implantation energy of the doping element is 1 keV.

Referring to FIG. 7, after the implantation of the doping element is completed, silicon element is implanted into the top surface of Fin along the normal direction of the substrate to reduce the concentration of the doping element in the top surface. The reduction in concentration is achieved by sputtering doping elements and increasing the substrate material.

Example 3

The basic principle of Embodiment 3 is the same as that of Embodiment 2, except that:

In this embodiment, instead of using two injection methods, ion implantation of the first sidewall and the second sidewall is sequentially performed multiple times by multiple injections until the dose of the doping element in the two sidewalls reaches Saturated, then perform vertical silicon implants.

Reference is made to Example 2 where the rest are not mentioned.

Example 4

The basic principle of Embodiment 4 is the same as that of Embodiment 2, and the injection of silicon element is added after the implantation of the doping element is completed, the difference being the injection direction, specifically:

First, doping elements are first implanted according to FIGS. 5 and 6 to form doped layers on the top surface and the sidewalls. Referring to FIG. 8, silicon elements are implanted into the top of Fin in a direction almost parallel to the top surface. In the face to reduce the dose of the doping element in the top surface, in this embodiment, the direction parallel to the top surface is The injection direction is at an angle of 2° to the top surface. Thus, the injection of silicon element sputters a part of the doping element in the top surface, which reduces the doping amount of the top surface, thereby improving the doping uniformity of the top surface and the sidewall.

Effect Example 1

First, the implantation of As is performed. The injection direction is 10° from the normal direction of the substrate, the implantation energy is 250 eV, and the initial implantation dose is 7.5e16 cm ^-2 , but is doped to the first sidewall from saturation. The doping amount in the second sidewall was 2.58e15 cm ^-2 , and the doping amount at the top was 2.13e16 cm ^-2 .

Next, 5e15 cm ^-2 of silicon was vertically implanted at a potential of ¹ keV to the top surface (due to the vertical implantation, so that the sidewalls were not affected), and the dose of As in the top surface was reduced to 1.54e16 cm ^-2 due to sputtering.

It can be seen that the ratio of the top surface and the side wall is divided to obtain a uniformity ratio of the top surface and the side wall of about 5:1, which is greatly improved compared to the prior art 10:1. .

Effect Example 2

First, the implantation of As is performed, the injection direction is 20° with the normal direction of the substrate, the implantation energy is 250 eV, the initial implantation dose is 7.5e16 cm ^-2 , and the first sidewall and the doping are self-saturated. The doping amount in the two sidewalls was 3.33e15 cm ^-2 , and the doping amount in the top surface was 1.83e16 cm ^-2 .

Next, 5e15 cm ^-2 of silicon was vertically implanted at a potential of ¹ keV to the top surface (due to the vertical implantation, so that the sidewalls were not affected), and the dose of As in the top surface was reduced to 1.22e16 cm ^-2 due to sputtering.

It can be seen that the ratio of the top surface and the side wall is divided to obtain a uniformity ratio of the top surface and the side wall of about 3.7:1, which is greatly improved compared to the prior art 10:1. .

Effect Example 3

First, the implantation of As is performed in the same manner as in the second embodiment, and the silicon element is vertically implanted into the top surface of the Fin along the normal direction of the substrate. The difference from the effect example 2 is that the amount of silicon to be implanted is 1.25e16cm ^-2, under the influence of sputtering, the final dose of doping: the top surface: 6.7642e15cm ^-2, side walls: 3.3339e15cm ^-2. Thus the doping dose ratio of the top and side walls is about 2:1.

Effect Example 4

The doping of Fin is still referred to the effect of Embodiment 2, that is, the implantation of As element until self-saturation, and then different from the above three effect embodiments, the injection of silicon element is not along the normal direction, but is almost along Parallel to the plane of the substrate, in the embodiment of the present invention, the implantation direction of the silicon element is 2° to the plane of the substrate, the energy is 1 keV, and the amount of silicon element is 8e16 cm ^-2 , in such a nearly parallel substrate At the angle, silicon will hit the top surface of Fin, and some silicon will enter the top surface of Fin. A part of silicon will cause As in Fin to be sputtered, thereby reducing the doping concentration of As in the top surface. The doping doses in the top and side walls are: top surface: 1.2786e16cm ^-2 , side wall 3.3289e15cm ^-2 . The ratio of top surface to side wall is 3.84:1.

From the four effect embodiments, the uniformity of doping on the top and side walls is significantly improved over the prior art.

In the interest of clarity of the various aspects of the invention, the various parts of the figures are not drawn to scale. The effect data of all effect examples were simulated using MATLAB (a computational simulation software).

While the invention has been described with respect to the preferred embodiments of the present invention, it is understood that the scope of the invention is defined by the appended claims. A person skilled in the art can make various changes or modifications to the embodiments without departing from the spirit and scope of the invention, and such changes and modifications fall within the scope of the invention.

Claims

A FinFET doping method, the FinFET comprising a substrate and Fin disposed in parallel on the substrate, each Fin comprising a top surface, a first sidewall and a second sidewall, wherein the doping method comprises The following steps:

T1, forming a doped layer in the top surface of the Fin, the first sidewall and the second sidewall;

T2, implanting a substrate element into the top surface of the Fin along a normal direction of the substrate to reduce the concentration of the doping element in the top surface.
The doping method according to claim 1, wherein the implantation depth of the substrate element in step T2 coincides with the depth of the doped layer.
The doping method according to claim 1, wherein for each Fin, step T1 further comprises:

T11, injecting a doping element into the first sidewall and injecting into the top surface,

T12, implanting a doping element into the second sidewall and implanting into the top surface.
The doping method according to claim 3, wherein in step T11, a doping element is implanted into the first sidewall and implanted into the top surface until a dose of doping element in the first sidewall reaches Self-saturating, and/or, in step T12, implanting a doping element into the second sidewall and implanting into the top surface until a dose of doping element in the second sidewall reaches self-saturation, wherein self-saturation is The implanted doping element and the sputtered doping element are equal in dynamic equilibrium state.
The doping method according to claim 3, wherein for each Fin, step T1 comprises:

Steps TP1 and TP2 are repeatedly performed until the dose of the doping element in the first sidewall and the second sidewall reaches self-saturation, and then step T2 is performed.

TP1, implanting a doping element into the first sidewall and injecting into the top surface;

TP2, implanting a doping element into the second sidewall and injecting into the top surface,

Among them, self-saturation is a dynamic equilibrium state in which the implanted doping element and the sputtered doping element are equal.
Doping method according to any one of claims 1 to 5, characterized in that the doping element The injection direction of the element is between 2° and 45° from the normal of the substrate, and/or

The doping element is arsenic, phosphorus or boron, the substrate element is silicon or germanium, and/or

The doping element has an implantation energy of 200 eV - 2 keV.
A FinFET doping method, the FinFET comprising a substrate and Fin disposed in parallel on the substrate, each Fin comprising a top surface, a first sidewall and a second sidewall, wherein the doping method comprises The following steps:

R1, forming a doped layer in the top surface of the Fin, the first sidewall and the second sidewall;

R2, implanting a substrate element into a top surface of the Fin in a direction almost parallel to the top surface to reduce a dose of the doping element in the top surface, wherein a direction almost parallel to the top surface indicates an implantation direction and the top The angle between the faces is greater than 0° and less than or equal to 5°.
The doping method according to claim 7, wherein for each Fin, step R1 further comprises:

R11, injecting a doping element into the first sidewall and injecting into the top surface,

R12, implanting a doping element into the second sidewall and implanting into the top surface.
The doping method according to claim 8, wherein in step R11, a doping element is implanted into the first sidewall and implanted into the top surface until a dose of a doping element in the first sidewall reaches Self-saturating, and/or, in step R12, implanting a doping element into the second sidewall and implanting into the top surface until a dose of doping element in the second sidewall reaches self-saturation, wherein self-saturation is The implanted doping element and the sputtered doping element are equal in dynamic equilibrium state.
The doping method according to claim 8, wherein for each Fin, step R1 comprises:

Step RP1 and step RP2 are repeatedly performed until the dose of the doping element in the first sidewall and the second sidewall reaches self-saturation, and then step R2 is performed,

RP1, injecting a doping element into the first sidewall and injecting into the top surface;

RP2, implanting a doping element into the second sidewall and implanting into the top surface,

Among them, self-saturation is a dynamic equilibrium state in which the implanted doping element and the sputtered doping element are equal.
The doping method according to any one of claims 7 to 10, wherein the implantation direction of the doping element is between 2 and 45 degrees from the normal of the substrate, and/or

The doping element is arsenic, phosphorus or boron, the substrate element is silicon or germanium, and/or

The doping element has an implantation energy of 200 eV - 2 keV.