TWI635566B - Method for filling trench with metal layer and semiconductor structure formed by using the same - Google Patents

Abstract

The present invention provides a method of filling a trench with a metal layer. A deposition machine is first provided and provides a substrate and a dielectric layer on the substrate, the dielectric layer comprising a trench. Next, a first deposition step is performed to fill the trench with a metal layer, and in the first deposition step, the temperature of the substrate gradually rises to a predetermined temperature. When the predetermined temperature is reached, a second deposition step is performed such that the metal layer fills the trench.

Description

Method for filling a trench with a metal layer and semiconductor structure formed by the method

The present invention relates to a method of filling a trench with a metal layer and a semiconductor structure formed by the method, and more particularly to a method for filling a trench with a metal layer with at least two deposition steps, and a method formed by the method A semiconductor structure.

In the modern information society, the microprocessor system consisting of integrated circuits has been widely used in all aspects of life, such as automatic control of household appliances, mobile communication devices, personal computers, etc., all of which have traces of integrated circuits. . With the increasing advancement of technology and the imagination of human society for electronic products, the integrated circuit has also developed in the direction of more yuan, more precision and smaller.

With the gradual decrease in the size of components, many problems have also been encountered in the fabrication of integrated circuits. For example, metal aluminum is a commonly used metal gate material. In the case of the existing gate last process, a dummy gate is usually formed first, followed by a dummy gate. The trench is removed to form a trench, and then the trench is filled with an aluminum layer to form a metal gate. However, due to the size reduction of the components, the filling ability of the aluminum layer is tested, for example, it is easy to form voids in the trench; in addition, the aluminum layer formed by the existing deposition process has a large grain size, too This results in surface roughness, so that the metal gate formed by the aluminum layer is easily spiked to the underlying barrier layer or even the work function metal layer (work function) Metal), which in turn reduces the quality of the components.

The present invention thus provides a method of filling a trench with a metal layer to overcome the above problems.

In accordance with an embodiment of the present invention, the present invention provides a method of filling a trench with a metal layer. A deposition machine is first provided and provides a substrate and a dielectric layer on the substrate, the dielectric layer comprising a trench. Next, a first deposition step is performed such that the trench fills a metal layer and the temperature of the substrate gradually rises to a predetermined temperature. When the predetermined temperature is reached, a second deposition step is performed such that the metal layer fills the trench.

According to another embodiment of the present invention, the present invention provides a semiconductor structure including a substrate, a dielectric layer, and an aluminum layer. The dielectric layer is disposed on the substrate and has a trench. The aluminum layer fills the trench, wherein the aluminum layer has a complex refractive index substantially greater than one.

The invention is characterized in that a three-layer deposition process is used, which can overcome the problems of the conventional metal layer filling the trench, and obtain a metal layer of better quality.

The present invention will be further understood by those skilled in the art to which the present invention pertains. The effect.

The invention provides a method for filling a trench with a metal layer, characterized in that it comprises at least two deposition steps, and with the temperature control of the deposition machine, the supply of the heat conduction gas and the adjustment of the deposition power, a hole filling capability can be obtained. A preferred metal layer.

Please refer to FIG. 1 and FIG. 2 for a schematic structural view of a deposition machine used in the present invention. As shown in FIG. 1, the deposition machine 300 of the present invention includes a cathode 302 and an anode 304, which are electrically connected to a bias voltage unit 306. The voltage required to deposit the process. A target 308 is provided on the surface of the cathode 302 as a pre-deposited metal layer material. Wafer 312 is disposed on a placement plane 316 on anode 304. As shown in FIG. 1, the anode 304 is also provided with a plurality of support pins 310 extending from the placement plane 316 to support the wafer 312 during transport. As shown in FIG. 2, the support post 310 can also be retracted into the anode 304 such that the wafer 312 can be placed on the placement plane 316. In a preferred embodiment of the invention, the anode 304 may also have the function of a heater that provides the temperature required for deposition and may provide a thermally conductive gas 314, such as argon (Ar). In one embodiment, the thermally conductive gas 314 can contact the back side of the wafer 312 via a hole 318 in the anode 304 of the heater plate such that the temperature of the heater plate can be transferred to the wafer 312 quickly and uniformly.

Please refer to FIG. 3 to FIG. 6 , which are schematic diagrams showing a method for filling a trench with a metal layer according to the present invention. As shown in FIG. 3, a substrate 500 is first provided, such as a germanium substrate, a germanium-containing substrate, or a silicon-on-insulator (SOI) substrate. Connect A dielectric layer 502 is formed on the substrate 500, and a trench 504 is formed in the dielectric layer 502. It should be noted that the present invention may also have one or more layers of semiconductor structures between the substrate 500 and the dielectric layer 502, such as other dielectric layers or metal layers. Next, a barrier layer 506 may be selectively formed on the substrate 500, such as titanium/titanium nitride (Ti/TiN) or tantalum/tantalum nitride (Ta/TaN). The barrier layer 506 will overlie the surface of the trench 504 but will not fill the trench 504.

Next, as shown in FIG. 4, a first deposition process is performed to form a metal layer 508 on the surface of the barrier layer 506 in the trench 504. The metal layer 508 is preferably aluminum (Al), but other metal materials such as titanium (Ti), tantalum (Ta), tungsten (W), niobium (Nb), molybdenum (Mo), copper (Cu), Titanium nitride (TiN), titanium carbide (TiC), tantalum nitride (TaN), titanium tungsten (Ti/W) or composite metal layers such as titanium and titanium nitride (Ti/TiN), but not limit. In a preferred embodiment of the invention, the first deposition process is carried out in a deposition machine as shown in FIG. One feature of the present invention is that the first deposition process is heated from room temperature to a predetermined temperature, and the substrate 500 does not directly contact the anode 304 of the heating plate. In more detail, the substrate 500 is deposited as soon as it is placed on the support post 310 from room temperature, at which time the support post 310 is projected over the placement plane 316, so the substrate 500 (i.e., the wafer 312 of FIG. 1) There is no contact with the placement platform 316, but a gap. Although the anode 304 heating plate has a predetermined temperature, since the substrate 500 does not directly contact the placement platform 316, and the anode 304 of the heating plate does not provide the heat conduction gas 314, the two are not in a thermal equilibrium state, and therefore the substrate 300 The temperature does not rise immediately, but is gradually heated from room temperature to a predetermined temperature. It should be noted here that the room temperature of the present invention will vary with the environment of the machine, not a fixed value, and It may be related to the steps performed by the substrate 500 in the previous process. In general, room temperature will be less than 100 degrees Celsius, preferably less than 50 degrees Celsius, such as between 15 and 30 degrees. The predetermined temperature refers to a temperature at which the deposition machine is deposited in a steady state, for example, between 380 degrees Celsius and 420 degrees Celsius, preferably 400 degrees Celsius. In another embodiment of the invention, the bias supply unit 306 in the deposition station 300 in the first deposition step provides a first deposition power that is substantially between 10,000 watts and 15,000 watts.

Next, as shown in FIG. 5, when the substrate 500 reaches a predetermined temperature, a second deposition process is performed, and the trench 504 is gradually filled with the metal layer 508. One feature of the present invention is that the support post 310 will be retracted into the anode 304 during the second deposition process such that the substrate 500 is placed on the placement platform 316 (as shown in Figure 2). At this time, the anode 304 heating plate also provides a heat conducting gas 314 such as argon (Ar), which can uniformly transfer the predetermined temperature of the heating plate (for example, 400 ° C) to the substrate 500, at which time the substrate 500 and the anode 304 heating plate are thermally balanced. situation. In addition, the bias supply unit 306 in the deposition station 300 in the second deposition step provides a second deposition power. In a preferred embodiment of the invention, the second deposition power is less than or equal to the first deposition power. The second deposition power is, for example, between 2,000 watts and 10,000 watts.

Referring to FIG. 6 again, after the metal layer 508 fills the trench 504, a third deposition process may be performed to increase the thickness of the metal layer 508 on the substrate 500. The parameters of the third deposition process are substantially the same as those of the second deposition process. The difference is that the bias supply unit 306 in the deposition machine 300 in the third deposition step provides a third deposition work. Rate, in a preferred embodiment of the invention, the third deposition power will be greater than the second deposition power.

After the third deposition process is completed, a thermal reflow process may be selectively performed. No deposition is performed at this time, but only the anode 304 is maintained at a predetermined temperature, and the heat transfer gas 314 is also supplied for about 15 minutes.

The method of filling a trench with a metal layer provided by the present invention is characterized in that at least two deposition steps are used. First, the metal layer 508 is formed at a slowly rising temperature in the first deposition process, and the thermal budget of the metal layer 508 can be reduced. Therefore, the metal layer 508 near the barrier layer 506 can be obtained with a smaller particle size. The small, better quality metal layer 508 avoids the phenomenon that the conventional metal layer 508 penetrates the barrier layer 506. On the other hand, in the second deposition process, the hole filling ability of the metal layer 508 can be increased due to the lower deposition power, and voids in the trench 504 can be avoided. Finally, in the third deposition process, the metal layer 508 has been perfectly filled into the trench 504, so that higher deposition power can be performed to increase the throughput of the process. In a preferred embodiment of the present invention, the thickness of the metal layer 508 formed by the first deposition process is about 1/2 of the thickness of the metal layer 508 formed by the second deposition process and the third deposition process. .

In another embodiment of the present invention, the first deposition process, the second deposition process, and the third deposition process may also be managed through a time mode, such as setting in the deposition machine 300: when the first deposition The process enters the second deposition process after a first predetermined time, and enters the second deposition process after a second predetermined time. The three deposition process, when the third deposition process passes a third predetermined time, enters the thermal reflow process.

As described above, the present invention can provide a method of forming a metal layer 508 of a better quality, having a smaller particle size and a smoother surface, particularly for metallic aluminum, which can be reflected in its complex refractive index. For example, the complex refractive index of the aluminum layer may be above 1, for example greater than 1.5, or even greater than 1.7. It should be noted that the measurement reference of the complex refractive index preferably means that a barrier layer of, for example, 80 angstroms is formed on the bulk wafer, and then formed by the deposition method described above. An aluminum layer of 3,000 angstroms to 4,000 angstroms is then measured by a KLA-Tensor model of the ASET-F5X machine with a wavelength of 436 mils.

The method for filling a trench with a metal layer provided by the present invention can be applied to any process that requires filling a trench into a metal layer, such as various damascene processes, capacitor processes, or even various planar transistors or non-planar electrodes. Metal gate process for non-planar transistors. Please refer to FIG. 7 to FIG. 11 , which are schematic diagrams showing the steps of a method for fabricating a metal gate according to the present invention. As shown in Fig. 7, a substrate 400 is first provided, such as a germanium substrate, a germanium containing substrate or a germanium insulating substrate. The substrate 400 has a plurality of shallow trench isolation (STI) 401 thereon. A transistor 402 is formed in the active region surrounded by the shallow trench isolation 401, such as a P-type transistor or an N-type transistor.

In an embodiment of the present invention, as shown in FIG. 7, the transistor 402 includes a dielectric layer 404, a high dielectric constant layer 405, an etch stop layer 407, a sacrificial gate 406, and a cap layer 408. A sidewall 410, a light doped drain (LDD) 412, and a source/drain 414. In a preferred embodiment of the present invention, the dielectric layer 404 is a germanium dioxide layer, and the high dielectric constant layer 405 has a dielectric constant of greater than about 4. It may be a rare earth metal oxide layer or a lanthanide metal oxide layer, for example. Hafnium oxide (HfO ₂ ), hafnium silicon oxide (HfSiO ₄ ), hafnium silicon oxynitride (HfSiON), aluminum oxide (aluminum oxide, Al ₂ O ₃ ), Lanthanum oxide (La ₂ O ₃ ), lanthanum aluminum oxide (LaAlO), tantalum oxide (Ta ₂ O ₅ ), zirconium oxide (ZrO ₂ ), zirconium oxychloride (zirconium silicon oxide, ZrSiO ₄ ), hafnium zirconium oxide (HfZrO), yttrium oxide (Yb ₂ O ₃ ), yttrium silicon oxide (YbSiO), zirconium aluminate (zirconium aluminate, ZrAlO), hafnium aluminate (HfAlO), aluminum nitride (AlN), titanium oxide (TiO ₂ ), zirconium oxynitride (ZrON), hafnium oxynitride (hafnium oxynitride, HfON), zirconium silicon oxynitride (ZrSiON) Hafnium silicon oxynitride (hafnium silicon oxynitride, HfSiON), tantalum oxide bismuth strontium _{(strontium bismuth tantalate, SrBi 2 Ta} 2 O 9, SBT), lead zirconate titanate _{(lead zirconate titanate, PbZr x Ti} 1-x O 3, PZT) or barium strontium titanate (Ba _x Sr _1-x TiO ₃ , BST), but not limited to the above. The etch stop layer 407 includes a metal layer or a metal nitride layer, such as titanium nitride (TiN). The sacrificial gate 406 is, for example, a polysilicon gate, but may be a composite gate composed of a polysilicon layer, an amorphous Si or a germanium layer. The cap layer 408 is, for example, a tantalum nitride layer. The sidewall spacer 410 may be a composite film layer structure, which may include high temperature oxide (HTO), tantalum nitride, hafnium oxide or nitrogen formed using hexachlorodisilane (Si ₂ Cl ₆ ). Huayu (HCD-SiN). The lightly doped drain 412 and the source/drain 414 are formed with a suitable concentration of dopant. Then, a contact etch stop layer (CESL) 403 and an inter-layer dielectric (ILD) 409 are formed on the substrate 400 to cover the transistor 402.

As shown in FIG. 8, a planarization process, such as a chemical mechanical polish (CMP) process or an etch process or a combination of the two, is performed to sequentially remove portions of the inner layer. The electrical layer 409, a portion of the contact hole etch stop layer 403, a portion of the sidewall spacer 410, and completely remove the cap layer 408 until the top surface of the sacrificial gate 406 is exposed. Next, a wet etch process and/or a dry etch process is performed to remove the sacrificial gate 406, the etch step stops at the etch stop layer 407, and a trench 416 is formed in the first transistor 402.

As shown in FIG. 9, a work function metal layer 418 is formed over the substrate 400. The work function metal layer 418 can be adjusted by the type of transistor 402. If the transistor 402 is a P-type transistor, the work function metal layer 418 is, for example, nickel (Ni), palladium (Pd), platinum (Pt), bismuth (Be), iridium (Ir), yttrium (Te), yttrium. (Re), ruthenium (Ru), rhenium (Rh), tungsten (W), molybdenum (Mo); tungsten, tantalum, molybdenum, tantalum (Ta), titanium (Ti) nitride; tungsten, tantalum, titanium carbonization Or titanium aluminide (TiAlN), tantalum aluminide (TaAlN), and the like. If the transistor 402 is an N-type transistor, the work function metal layer 418 is, for example, titanium aluminide (TiAl), zirconium aluminide (ZrAl), tungsten aluminide (WAl), tantalum aluminide (TaAl) or tantalum aluminide. (HfAl), etc., but not limited to the above. In other embodiments of the present invention, before the success function metal layer 418 is formed, it is also optional. A bottom barrier layer (not shown) is formed selectively, such as a tantalum nitride (TaN) layer.

As shown in FIG. 10, a selective barrier layer 420 and a metal layer 422 are integrally formed on the substrate 400. The metal layer 422 of the present invention is formed by forming the metal layer 508 as described above (as shown in FIGS. 3 to 6), so that a metal layer 422 of a better quality can be obtained. Finally, as shown in FIG. 11, a planarization process is performed to remove the metal layer 422, the barrier layer 420, and the work function metal layer 418 outside the trench 416, such that the work function metal layer 418, (the barrier layer 420) And the metal layers together form a metal gate 424 to form a transistor structure having a metal gate of the present invention.

In summary, the present invention provides a method of filling a trench with a metal layer, and a semiconductor structure formed by the method. This method can be applied to processes such as metal gates. The invention is characterized in that a three-layer deposition process is used, which can overcome the problems of the conventional metal layer filling the trench, and obtain a metal layer of better quality.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

300‧‧‧Sedimentation machine

302‧‧‧ cathode

304‧‧‧Anode

306‧‧‧ bias supply unit

308‧‧‧ Target

310‧‧‧Support column

312‧‧‧ wafer

314‧‧‧heat conducting gas

316‧‧‧Placement platform

318‧‧‧ hole

400‧‧‧Base

402‧‧‧Optoelectronics

403‧‧‧Contact hole etch stop layer

404‧‧‧ dielectric layer

405‧‧‧High dielectric constant layer

406‧‧‧sacrificial gate

407‧‧‧etch stop layer

408‧‧‧ cover

409‧‧‧Interlayer dielectric layer

410‧‧‧ Sidewall

412‧‧‧Lightly doped bungee

414‧‧‧Source/Bungee

416‧‧‧ Ditch

418‧‧‧Work function metal layer

420‧‧‧Barrier layer

422‧‧‧metal layer

424‧‧‧Metal gate

500‧‧‧Base

502‧‧‧ dielectric layer

504‧‧‧ Ditch

506‧‧‧ barrier layer

508‧‧‧metal layer

Fig. 1 and Fig. 2 are schematic views showing the structure of a deposition machine used in the present invention.

3 to 6 are schematic views showing a method of filling a trench with a metal layer according to the present invention.

7 to 11 illustrate steps of a method of fabricating a metal gate of the present invention. schematic diagram.

Claims (20)

A method of filling a trench with a metal layer, comprising: providing a deposition machine; providing a substrate and a dielectric layer on the substrate, the dielectric layer comprising a trench; performing a first deposition step to fill the trench And entering a metal layer, wherein the temperature of the substrate gradually rises to a predetermined temperature in the first deposition step; and when the predetermined temperature is reached, performing a second deposition step, so that the metal layer fills the trench. A method of filling a trench with a metal layer as described in claim 1, wherein in the first deposition step, the temperature of the substrate is gradually increased from room temperature to the predetermined temperature. A method of filling a trench with a metal layer as described in claim 1 wherein the second deposition step is performed at the predetermined temperature. A method of filling a trench with a metal layer as described in claim 1 wherein the machine comprises a heater. A method of filling a trench with a metal layer as described in claim 4, wherein when the first deposition step is performed, the heating plate has the predetermined temperature, and the substrate and the heating plate have a gap therebetween. A method of filling a trench with a metal layer as described in claim 4, wherein the heating plate does not provide a heat conducting gas when the first deposition step is performed. A method of filling a trench with a metal layer as described in claim 4, wherein when the second deposition step is performed, the heating plate has the predetermined temperature and provides a heat transfer gas. A method of filling a trench with a metal layer as described in claim 1, wherein the deposition power of the first deposition step is substantially greater than the deposition power of the second deposition step. A method of filling a trench with a metal layer as described in claim 1, wherein the deposition power of the first deposition step is substantially equal to the deposition power of the second deposition step. The method of filling a trench with a metal layer as described in claim 1, further comprising: after the second deposition step, performing a third deposition step to increase a thickness of the metal layer, wherein the third deposition The deposition power of the step is substantially greater than the deposition power of the second deposition step. A method of filling a trench with a metal layer as described in claim 10, wherein the deposition machine comprises a heating plate, and in the third deposition step, the heating plate has the predetermined temperature and provides a heat conduction gas. A method of filling a trench with a metal layer as described in claim 1 wherein the predetermined temperature is substantially between 380 degrees Celsius and 420 degrees Celsius. A method of filling a trench with a metal layer as described in claim 1 wherein the predetermined temperature is substantially 400 degrees Celsius. The method of filling a trench with a metal layer as described in claim 1, wherein before the performing the first deposition process, forming at least one barrier layer on the trench, the barrier layer comprising titanium/nitrogen Titanium (Ti/TiN) or tantalum/tantalum nitride (Ta/TaN). A semiconductor structure comprising: a substrate; a dielectric layer disposed on the substrate, the dielectric layer having a trench; and an aluminum layer filling the trench, wherein the aluminum layer has a complex refractive index substantially greater than 1.5 . The semiconductor structure of claim 15 further comprising at least one barrier layer disposed between the dielectric layer and the aluminum layer. The semiconductor structure of claim 16, wherein the barrier layer comprises titanium/titanium nitride or tantalum/niobium nitride. The semiconductor structure of claim 15, wherein the semiconductor structure It is a transistor and the aluminum layer is part of the gate of the transistor. The semiconductor structure of claim 18, wherein the transistor further comprises a gate dielectric layer disposed between the aluminum layer and the substrate, and a source/drain electrode disposed on both sides of the aluminum layer In the substrate. The semiconductor structure of claim 15, wherein the aluminum layer is formed by filling a trench with a metal layer as described in claim 1 of the patent application.