JP2005516119A - Tungsten deposition process by pulsed gas flow CVD. - Google Patents

Abstract

Embodiments of the invention relate to a process for forming a nucleation layer on a substrate disposed in a processing chamber. One embodiment includes introducing one or more of process gases, for example, each pulse includes a hydrogen-containing gas and a tungsten-containing gas. The hydrogen-containing gas and the tungsten-containing gas can be removed from the process chamber between pulses, by flowing a purge gas between them, and / or by pumping the chamber.

Description

Background of the Invention

Field of Invention
[0001] The present invention relates to processing of semiconductor substrates. More particularly, the present invention relates to an improved process for depositing a metal layer on a semiconductor substrate.

Explanation of related technology
[0002] The semiconductor processing industry continues to strive to further increase production yield while increasing the uniformity of the layers deposited on the larger surface area substrate. Also, due to these aforementioned factors, the degree of circuit integration per unit area of the substrate increases in combination with new materials. As circuit integration increases, there is a need for higher uniformity and process control for the physical and electrical properties of the deposited metal layer. Thus, nucleation with the material prior to layer formation has been found to be particularly beneficial.

  [0003] Nevertheless, an improved nucleation technique for depositing a metal layer is desired.

Summary of the Invention

  [0004] Embodiments of the invention relate to a process for forming a nucleation layer on a substrate disposed in a processing chamber. One embodiment includes introducing one or more process gas pulses, eg, each pulse includes a hydrogen-containing gas and a tungsten-containing gas. The hydrogen-containing gas and tungsten-containing gas can be removed from the processing chamber between pulses by flowing a purge gas between them and / or pumping the chamber.

  [0005] Another embodiment includes introducing a first set of one or more pulses and a second set of one or more pulses. Each pulse of the first set includes a first ratio of hydrogen-containing gas and tungsten-containing gas. Each pulse of the second set includes a second ratio of hydrogen-containing gas and tungsten-containing gas. The hydrogen-containing gas and the tungsten-containing gas may be flowed between each of the first pulse set and each of the second pulse set by flowing a purge gas therebetween and / or by pumping the chamber. It can be removed from the processing chamber.

  [0006] Yet another embodiment includes introducing a first set of one or more pulses and a second set of one or more pulses. Each pulse of the second set includes a first hydrogen-containing gas and a tungsten-containing gas. The first hydrogen-containing gas and the tungsten-containing gas are removed from the processing chamber between each of the first pulse sets by flowing a purge gas between them and / or by pumping the chamber. Can do. Each pulse of the second set includes a second hydrogen-containing gas and a tungsten-containing gas. The second hydrogen-containing gas and the tungsten-containing gas are removed from the processing chamber between each of the second pulse sets by flowing a purge gas between them and / or by pumping the chamber. Can do.

  [0007] So that the manner in which the above-described features, advantages, and objects of the present invention can be understood in detail, a book briefly summarized above by reference to embodiments of the invention shown in the accompanying drawings. The invention will be described in more detail.

  [0008] However, the accompanying drawings illustrate only typical embodiments of the invention and should not be considered as limiting the scope of the invention, which is not limited to other equivalents. It should be noted that embodiments having the following effects are allowed.

Detailed Description of the Preferred Embodiment

  [0024] Referring to FIGS. 1 and 2, an exemplary processing system 10 used to deposit a refractory metal film is shown according to one embodiment of the present invention. The system 10 is a parallel plate cold wall type chemical vapor deposition (CVD) system. The CVD system 10 has a processing chamber 12. A gas distribution manifold 14 is disposed in the processing chamber 12. The gas distribution manifold 14 disperses the deposition gas that travels into the processing chamber 12, and the deposition gas impinges on the wafer 16 mounted on the resistance heating susceptor 18.

  [0025] The processing chamber 12 may be part of a vacuum processing system having a plurality of processing chambers connected to a central transfer chamber (not shown) and operated by a robot (not shown). A substrate 16 is placed in the processing chamber 12 by a robot blade (not shown) through a slit valve (not shown) on the side wall of the processing chamber 12. The susceptor 18 is movable in the vertical direction by the motor 20. A substrate 16 is placed in the processing chamber 12 when the susceptor 18 is in a first position 13 opposite a slit valve (not shown). At position 13, the substrate 16 is initially supported by a set of pins 22 that penetrate the susceptor 18. Pin 22 is driven by a single motor assembly 20.

  [0026] When the susceptor 18 is at a processing position 32 opposite the gas distribution manifold 14, the pins 22 are retracted into the susceptor 18 so that the substrate 16 can be placed on the susceptor 18. When placed on the susceptor 18, the substrate 16 is attached to the susceptor by a vacuum clamping system shown as a groove 39. Alternatively, the substrate 16 may be attached to the susceptor by an electrostatic chuck, clamp ring, or other clamping system.

  When moved upward into the processing position 32, the substrate 16 contacts the purge guide 37 and centers the substrate 16 on the susceptor 18. The edge purge gas 23 is caused to flow through the purge guide 37 across the edge of the substrate 16 so that the deposition gas does not contact the edge and the back surface of the substrate 16. Also, a purge gas 25 is flowed around the susceptor 18 to minimize deposition on or near the susceptor 18. These purge gases are supplied from the purge line 24 and are also used to protect the stainless steel bellows 26 from being damaged by the corrosive gas introduced into the processing chamber 12 during processing.

  Referring to FIGS. 1 and 3, deposition and carrier gases are supplied to the deposition zone of the processing chamber 12 via the gas line 19 to the manifold 14 in response to control of the valve 17. For this purpose, gas supply sources 31 and 33 are provided that are selectively placed in flow with the processing chamber 12 by the valve 17. More specifically, the valve 17 includes valves 17a, 17b, 17c, and 17d. A supply line 31a places the gas supply source 31 in communication with the valves 17a and 17b. A supply line 31b places the valve 17a in communication with the processing chamber 12. The supply line 31c puts the valve 17b into a flow state with the foreline 35. Supply line 33a places gas supply source 31 in communication with valves 17c and 17d. Supply line 33b places valve 17c in communication with process chamber 12. The supply line 33c puts the valve 17d into a flow state with the foreline 35. When the valve 17 a is operated, process gas from the gas supply source 31 enters the processing chamber 12. When the valve 17 c is operated, the process gas from the gas supply source 33 enters the processing chamber 12. When the valve 17b is operated, the process gas from the gas supply source 31 enters the foreline 35, and when the valve 17d is operated, the process gas from the gas supply source 33 enters the foreline 35.

  [0029] Referring again to FIGS. 1 and 2, during processing, the gas supplied to the manifold 14 is evenly distributed across the surface of the substrate 16, as indicated by arrows 27. Spent process gas and by-product gas are exhausted from the process chamber 12 by the exhaust system 36. The rate at which gas is released from the exhaust system 36 into the exhaust line is controlled by a throttle valve (not shown). During deposition, a second purge gas is introduced through a gas channel (not shown) in the susceptor 18. As previously described, supply line 38 directs purge gas toward the edge of substrate 16. An RF power source 48 may be coupled to the manifold 14 for plasma enhanced CVD (PECVD) or for cleaning the processing chamber 12.

  [0030] A throttle valve (not shown), a gas supply valve 17, a motor 20, a resistance heater coupled to the susceptor 18, an RF power supply 48, and other aspects of the CVD system 10 include a control line 44 (only partly). It is operated under the control of the processor 42. The processor 42 operates on a computer program stored on a computer readable medium such as the memory 46. A system controller 42 controls all operations of the CVD machine. The computer program includes an instruction set that commands timing, gas mixing, chamber pressure, chamber temperature, RF power level, susceptor position, and other parameters of a particular process, as described in more detail below. It describes. The processor 42 may also operate other computer programs stored on other memory devices including, for example, a floppy disk or other suitable drive.

  [0031] With reference to FIGS. 1 and 4, one exemplary use of the system 10 is to use a nucleation technique to nucleate the substrate 16 and the refractory metal layer using a refractory metal on the substrate 16. Depositing layers. To that end, the substrate 16 includes a wafer 50 having one or more layers shown as layer 52. As an alternative, there may be no layers on the wafer 50. Wafer 50 may be formed from any material suitable for semiconductor processing, such as silicon. Layer 52 may be formed from any suitable material including dielectric or conductive materials. The layer 52 may include a void 54 that exposes a region 56 of the substrate 16 or a layer 59 such as a titanium nitride layer located on the layer 52 and the wafer 50, as more clearly shown in FIG. .

  [0032] Referring to FIG. 5, one example of a refractory metal layer deposited according to one embodiment is a tungsten layer used to form a contact adjacent to a barrier layer 59 formed from titanium nitride TiN. It is. An adhesion layer 58 made of titanium Ti is deposited between the layer 52 and the barrier layer 59. Layers 59 and 58 match the profile of void 54 and cover region 56 and layer 52. At a location adjacent to the barrier layer 59 is a nucleation layer 60 formed from tungsten, as further described below. The nucleation layer 60 matches the profile of the layers 59 and 58 and thus the void 54 profile. A bulk deposition layer 62 made of tungsten is formed at a position adjacent to the nucleation layer. In this embodiment, a bulk deposited layer 62 is used to form contacts. The nucleation layer 60 acts to increase the step coverage of the resulting bulk deposited layer 62 and thus the resistivity of the resulting contact 63.

  [0033] Problems arise when the nucleation layer 60 is deposited. Specifically, as the aspect ratio of void 54 increases, it becomes more difficult to produce a nucleation layer with uniform thickness and acceptable compatibility.

[0034] Referring to FIGS. 6 and 7, in an extreme case, the pinch-off shown in the region 162a adjacent to the upper region 155 of the void 154 occurs. The pinch-off leaves the void 162b, resulting in a recessed profile of the nucleation layer 160. The recessed profile of the nucleation layer 160 is believed to arise from a concentration of gaseous material, referred to herein as a concentration boundary layer (CBL) 160c, that forms during the formation of the nucleation layer 160 proximate to the bottom 154a. It has been. CBL 160c is believed to arise from reactant by-products resulting from the formation of nucleation layer 160. Specifically, reaction by-products and outgassing from region 151 form a gaseous material that results in _CBL 160c of thickness t _CBL . Thickness t _CBL increases the distance, also called the diffusion length, which is the distance that the precursor must reach before reaching the region of void 154 where it is farthest from upper region 155 where nucleation occurs. is there. In this embodiment, the region farthest from the upper region 155 and where nucleation occurs is the surface 151a located in the vicinity of the lowermost part 154a. When the diffusion length is increased in this way, it takes more time to deposit the nucleation layer 160 on this region as compared to the nucleation time for deposition on the other region in the void 154, such as the upper region 155. The time will be longer. As a result, the nucleation layer 160 deposits in a region proximate to the upper region 155 much more quickly than the surface 151a proximate to the bottom 154a.

[0035] Referring to FIGS. 5 and 7, an exemplary process in which the disadvantages of CBL 160c are eliminated by the present invention involves the deposition of a refractory metal layer such as a tungsten layer. Therefore, nucleation of the substrate 16 starts, tungsten hexafluoride WF ₆ is used as a tungsten source, and any one of hydrogen molecules H ₂ , silane SiH ₄ , or diborane B ₂ H ₆ is used as a hydrogen source. Nucleation is defined by the following reaction equation.

(Chemical formula 1) WF ₆ + H ₂ → HF + W + H ₂

(Chemical formula 2) WF ₆ + SiH ₄ → HF + W + SiH ₄ + SiF _X

(Chemical Formula 3) WF ₆ + B ₂ H ₆ → HF + W + B _X F _Y + B _X H _Y
The nucleation layer 60 is formed from W on the right hand side of Reaction Schemes 1, 2, and 3 along with HF and is one of the by-products resulting from each of these reactions. Reaction 1 also has reaction by-products that contain H ₂ , which arises from an environment rich in hydrogen. Reaction 2 includes SiF _X and silane as additional byproducts, and Reaction Formula 3 includes B _X F _Y and B _X H _Y byproducts. This is the above-mentioned by-product, and is combined with the gas emission from the region 151 and the reaction generated from the impurities in the region 151 that generates the vapor phase CBL 160c. In other embodiments, other tungsten-containing gases such as tungsten carbonyl (W (CO) ₆ ) may be used.

[0036] Referring to FIGS. 1, 7, and 8, if the problems suffered by CBL 160c are not resolved, the by-products of the deposition process and the gases present may be present during nucleation to alleviate those problems. Periodically removed from the processing chamber 12. Specifically, at time t ₁ , first, a process gas is introduced into the processing chamber 12. Over time, the formation of the nucleation layer 160 continues, thereby increasing the concentration of by-products and increasing the amount of material outgassed from the region 151. Time t _2, the introduction of the process gas into the process chamber 12 is completed. Therefore, nucleation called nucleation time t _n occurs between times t ₁ and t ₂ . At the same time as the flow of the process gas is terminated to the time t ₂ to the processing chamber 12, its removal is carried out. This is done by introducing an inert purge gas such as Ar or N _2, or by reducing the pressure of the process chamber 12 at a high speed, or may be achieved by both. However, the desired result is that by time t ₃ , process gases, by-products and materials outgassing from region 151 that are believed to be due to the formation of CBL 160 c are removed from processing chamber 12. The time interval between t ₂ and _{t 3,} referred to as a removal time _{t r.} At time t ₃ , the process chamber 12 is pressurized once and process gas is introduced at time t ₄ to continue substrate nucleation.

[0037] during a given nucleation time t _n, the deposition rate D _R, together with the thickness of the layer, uniformity and compatibility of nucleation layer 60 is found to be controlled in response to the removal time t _r It was. Speaking in detail, as shown in the curve 163 of FIG. 9, the shorter the duration of t _r, by a reduction of the CBL, further increases the uniformity and compatibility of the thickness of the nucleation layer 60. However, as shown by curve 165 in FIG. 10, the shorter the duration of removal time _tr , the longer the deposition time required to achieve nucleation. Thus, during a given nucleation time t _n, removal time t _r, while maximizing uniformity and compatibility of the thickness of the nucleation layer may be optimized to achieve the maximum rate of deposition. Optimized duration of the removal time t _r, the aspect ratio of the void 54 shown in FIG. 5, deposition chemicals, process parameters, depends on a number of factors.

[0038] An exemplary process for nucleating a substrate in view of the advantages of the principles described above is described in terms of tungsten layer deposition with reference to FIGS. 1, 8, and 11. FIG. The instructions for performing the process for depositing the tungsten layer on the substrate 16 are stored as a computer readable program in the memory 46, which in step 300 is used by the processor 42 to place the substrate 16 at the processing location 32. Is operated by. In step 302, the substrate 16 is heated to an appropriate temperature. In this embodiment, the substrate 16 is heated to about 400 ° C., but the desired temperature may be in the range of about 200 ° C. to about 600 ° C., preferably about 350 ° C. to about 475 ° C., More preferably, it may be in the range of about 375 ° C to about 450 ° C. It has been found that deposition at low temperatures increases step coverage. However, if the temperature is too low, the stress of the film will be too high. It has also been found that higher substrate temperatures may increase erosion of the underlying layers by the tungsten-containing gas. In step 304, the chamber pressure is set to an initial pressure level of about 90 Torr, but may be in the range of 70-120 Torr. Thereafter, a hydrogen containing gas, such as silane SiH ₄ , is introduced into the processing chamber 12 so that the substrate 16 may soak in the processing chamber at an optional step 306. The soak time of the substrate 16 is about 15 seconds. However, the time range for the substrate 16 to soak silane may be in the range of 10-30 seconds. For this purpose, silane is introduced into the processing chamber 12 together with the carrier gas. The carrier gas may be argon (Ar), hydrogen gas (H ₂ ), nitrogen gas (N ₂ ), helium, other suitable gases, and combinations thereof. In one embodiment, the carrier gas comprises Argon introduced at a flow rate that is about 10 times or more the rate at which silane is introduced. In one example, Ar is introduced at a rate of about 1,000 standard cubic centimeters per second (sccm) and silane is introduced at a rate of about 100 sccm.
[0039] In step 308, the flow chamber pressure is established to be about 15 Torr and may range from 2 to 30 Torr. In step 310, a carrier gas is flowed into the processing chamber 12. Although any carrier gas may be used, in one embodiment, Ar and hydrogen molecules H ₂ are used, each of which is introduced into the processing chamber 12 at a rate in the range of 2000-6000 sccm, with 4000 sccm being exemplary Speed. Carrier gases Ar and H ₂ are introduced for about 10 seconds. However, the duration for which the carrier gas is introduced into the processing chamber 12 can range from 5 to 15 seconds. In one embodiment, steps 308 and 310 are both performed in which a carrier gas is flowed into the processing chamber to establish the desired chamber pressure.

Referring to FIGS. 3 and 11, at step 312, a hydrogen-containing gas is flowed into the foreline 35, and at step 314, a tungsten-containing gas is flowed into the foreline 35. The rate at which the gas is flowed into the foreline 35 is such that the mixture of hydrogen-containing gas and tungsten-containing gas is purified so that the ratio of tungsten-containing gas to hydrogen-containing gas is in the range of 1: 1 to 5: 1. Adjusted. The hydrogen-containing gas may be introduced with a carrier gas such as hydrogen gas (H ₂ ), argon, nitrogen gas (N ₂ ), helium, other suitable gases, and combinations thereof. The tungsten-containing gas may be introduced with a carrier gas such as argon gas, nitrogen gas (N ₂ ), helium, other suitable gases, and combinations thereof. In one example, the hydrogen-containing gas used is silane SiH ₄ and the tungsten-containing gas used is tungsten hexafluoride WF ₆ . For about 5 seconds, silane is flowed at a rate of about 20 sccm and tungsten hexafluoride is flowed at a rate of about 40 sccm. In one embodiment, SiH ₄ is introduced with an H ₂ carrier gas and WH ₆ is introduced with an Ar carrier gas. The mixture of SiH ₄ and WF ₆ is flowed into the foreline 35 and then directed into the processing chamber 12 to avoid pressure spikes that can cause particulate contaminants. Specifically, the flow of SiH ₄ and WF ₆ is stabilized in the foreline 35, after which a mixture of SiH ₄ and WF ₆ is introduced into the processing chamber 12.

[0041] Referring again to FIGS. 1 and 11, in step 316, a mixture of SiH ₄ and WF ₆ is flowed or pulsed into the processing chamber 12 to nucleate the substrate 16 and tungsten. . Nucleation or pulsing is performed for a time sufficient to initiate nucleation of layer 160. The nucleation time or pulse time is typically in the range of about 0.1 to about 10 seconds, and is typically about 1.5 seconds. In step 318, the introduction of the SiH ₄ and WF ₆ mixture as a pulse into the processing chamber 12 is stopped before the t _CBL reaches a level that substantially prevents nucleation. In step 320, a mixture of SiH ₄ and WF _6, together with the gaseous by-products of the reaction of nucleation of SiH ₄ and WF _6, is removed from the process chamber 12. Removal of these gases is accomplished by reducing the chamber pressure, introducing purge gas while maintaining chamber pressure, or by both reducing the chamber pressure and introducing purge gas. It's okay. Typically, the removal step lasts 3-12 seconds. Exemplary purge gas, Ar, may be any inert gas such as N 2, or the _He,. One embodiment of the method of the present invention provides a gas for the nucleation reaction of SiH ₄ and WF ₆ along with a mixture of SiH ₄ and WF ₆ by reducing the chamber pressure to be in the range of about 1-3 Torr. Removing the by-products. Another embodiment of the method of the present invention involves removing gaseous by-products with a mixture of SiH ₄ and WF ₆ while maintaining chamber pressure. If the chamber pressure is maintained, step 310 need not be repeated unless the desired thickness of nucleation layer has been deposited by step 322. In yet another embodiment, the hydrogen-containing gas used is diborane B ₂ H ₆ .

  [0042] Referring to FIGS. 1, 5, and 11, in step 322, it is determined whether the nucleation layer 60 is of sufficient or desired thickness. This determination may be accomplished using any process known in the semiconductor industry. For example, spectroscopic measurements of the nucleation layer may be made. As an alternative, the thickness of the nucleation layer 60 may be calculated, i.e. modeled, using known flow rates and other operational features and deposition processes of the system 10. If the desired thickness of the nucleation layer 60 is achieved, the process proceeds to step 324 where the nucleation layer 60 is adjacent to the nucleation layer 60 using conventional CVD techniques, PVD techniques, or any other technique. Bulk deposition occurs to deposit the tungsten layer 62 at the locations. Bulk deposition is preferably performed by CVD techniques in a common chamber with the nucleation layer deposition or in a separate chamber of the common mainframe. After deposition of the bulk tungsten layer 62, the process ends at step 326. It should be understood that nucleation may occur in a common chamber, two different chambers or a common main frame, or two different chambers of different main frames.

  [0043] If, in step 320, it is determined that the nucleation layer is not of the desired thickness, the process proceeds to step 308 and steps 308, 310, 312 until the nucleation layer 60 obtains the desired thickness. 314, 316, 318, 320, and 322 are repeated. In this way, nucleation of the substrate 16 is achieved using a number of steps, i.e. using pulse nucleation techniques. The nucleation gas is pulsed into the processing chamber 12 for a few seconds and is quickly removed by rapidly depressurizing the processing chamber 12 or by introducing a purge gas. This step typically lasts about 3-12 seconds. It is believed that pulse nucleation techniques reduce the formation of concentration boundary layers resulting from outgassing during surface nucleation. Specifically, it is believed that the aforementioned outgassing may be substantially reduced by the diffusive flow of reactants used to nucleate the surface. Using this process has been found to reduce the adverse effects of the concentration boundary layer. In this process, the concentration boundary layer is made to form as large a size as possible while maintaining an appropriate diffusive flow of reactants used to nucleate the underlying surface of the concentration boundary layer. Thereafter, all of the process gas, reaction byproducts, and materials forming the concentration boundary layer are removed from the process chamber 12 by rapidly depressurizing the process chamber 12 or by introducing a purge gas therein. The This process is repeated until the nucleation layer 60 reaches an appropriate thickness. The tungsten nucleation layer has a step coverage of about 60% or more over a 0.17 μm plug with an aspect ratio of about 8: 1 or more compared to about 30% step coverage using the prior art. It has been found that the above process described in connection with FIG. 11 may be used.

  [0044] In the process shown in FIG. 11, one or more steps may be performed simultaneously. For example, one embodiment includes performing steps 312, 314, and 320 simultaneously. While removing the hydrogen-containing gas, tungsten-containing gas, and by-products from the processing chamber, the hydrogen-containing gas and tungsten-containing gas are flowed to the foreline of the processing chamber.

[0045] Referring to FIG. 7, another process for forming a tungsten layer to increase step coverage is shown. One embodiment includes changing the ratio of hydrogen-containing gas to tungsten-containing gas between an early stage of nucleation and a later stage of nucleation. For example, one embodiment includes changing the ratio of silane (SiH ₄ ) and tungsten hexafluoride (WF ₆ ). Another embodiment includes changing the ratio of diborane (B ₂ H ₆ ) to tungsten hexafluoride.

[0046] Initial cycle, that consists of cycles after the pulse containing a large amount of hydrogen-containing gas, a layer of lower tungsten-containing gas, such as WF ₆ is considered to be prevented from being eroded. Moreover, it is thought that the step coverage of the formed film | membrane increases because a later cycle consists of a pulse containing a larger amount of tungsten containing gas than an initial cycle.

  [0047] To that end, the process shown in FIG. 12 includes steps 300, 302, 304, 306, 308, 310, 312, 314, 316, 318, 320, 322, 324, and 326 as shown in FIG. Each includes the same steps 400, 402, 404, 406, 408, 410, 412, 414, 416, 418, 420, 422, 424, and 426. Additional steps 411a and 411b are included in the process shown in FIG. 12 in view of the process when changing the ratio of tungsten-containing gas to hydrogen-containing gas.

  [0048] Referring to both FIG. 1 and FIG. 12, step 411a is performed after step 410. In step 411a, the processor 42 determines whether the ratio of the tungsten-containing gas to the hydrogen-containing gas has changed. If the ratio has not changed, in step 412 the flow of hydrogen-containing gas is resumed. If the ratio has changed, step 411b is executed and new flow rates for both the hydrogen-containing gas and the tungsten-containing gas are set. Thereafter, step 412 is performed and the remaining steps may be performed as described above with respect to FIG.

  [0049] In one embodiment, the hydrogen-containing gas and tungsten-containing gas in step 416 were flowed into the chaba at a first ratio of hydrogen-containing gas and tungsten-containing gas during one or more "cycles". Thereafter, a second ratio of hydrogen-containing gas and tungsten-containing gas less than the first ratio is flowed at the second ratio for one or more cycles. For example, the first ratio of hydrogen-containing gas and tungsten-containing gas may be about 1: 1 and the second ratio may be about 1: 4.

[0050] FIG. 13 illustrates another alternative process for forming a tungsten layer. The process shown in FIG. 13 is identical to steps 300, 502, 304, 306, 308, 310, 312, 314, 316, 318, 320, 322, 324, and 326 shown in FIG. 504, 506, 508, 510, 512, 514, 516, 518, 520, 522, 524, and 526. Additional steps 511a and 511b are included in the process shown in FIG. 13 in view of the process by which the hydrogen-containing precursor changes from a first hydrogen-containing gas to another hydrogen-containing gas. Or hydrogen-containing gas is used, hydrogen molecules _{H 2,} silane SiH _4, and including diborane _B 2 _{H 6,} not intended to be those limited.

[0051] For example, the use of SiH ₄ during initial nucleation may reduce the growth time and the time required to complete nucleation. However, the hydrogen molecule H ₂ may provide better step coverage than SiH ₄ . As a result, it may be beneficial to initiate nucleation with SiH ₄ as a hydrogen-containing precursor and complete nucleation with hydrogen molecules H ₂ .

[0052] In another example, the use of B ₂ H ₆ during initial nucleation may reduce the time required to complete nucleation due to higher reactivity than SiH ₄ . Thereafter, SiH ₄ and / or H ₂ may be used to complete nucleation during the later stages of nucleation.

  [0053] Referring to both FIG. 1 and FIG. 13, step 511a is performed after step 510. In step 511a, the processor 42 determines whether the same hydrogen-containing gas that is used during the pre-nucleation process is used. If the type of hydrogen-containing gas has not changed, in step 512, the flow of hydrogen-containing gas is resumed. If the type of hydrogen-containing gas has changed, step 511b is performed and a new supply of hydrogen-containing gas is used. Thereafter, step 512 is performed and the remaining steps are performed as described above with respect to FIG. In other embodiments, if the hydrogen-containing gas is changing, the ratio of the first hydrogen-containing gas to the tungsten-containing gas may change. Similarly, the ratio of the first hydrogen-containing gas and the tungsten-containing gas may vary.

  [0054] As described above, the processor 42 controls the operation of the system 10 according to the present invention. To that end, the processor 42 may include a single board computer (SBC), an analog / digital input / output board, an interface board, and a stepper motor controller board. The memory 46 may be of any type known to those skilled in the art including hard disk drives, floppy disk drives, RAID devices, random access memory (RAM), read only memory (ROM), and the like. The various components of the CVD system 10 are compliant with the Versa Modular European (VME) standard that defines board, card cage, and connector dimensions and types. The VME standard defines a bus structure having a 16-bit data bus and a 24-bit address bus.

  [0055] The computer program may be written in any conventional computer readable programming language, for example, 68000 assembly language, C, C ++, Pascal, Fortran, etc. Using a conventional text editor, the appropriate programming language is entered into a single file or multiple files and stored or embedded in a computer usable medium such as memory 46. If the input language is at a high level, it is compiled and the resulting compiler code is linked to the precompiled Windows library routine object code. To execute the linked and compiled object code, the system user calls the object code and causes the processor 42 to load the code into the memory 46. Thereafter, the processor 42 reads and executes the code and performs the tasks identified therein.

  [0056] The interface between the user and the processor 42 is via the CRT monitor 45 and the light pen 47 shown in FIG. The illustrated embodiment includes two monitors 45, one attached to the clean room wall for the operator and the other placed behind the wall for the service technician. The monitor 45 may display the same upper portion at the same time with only one light pen 47 operable. A light sensor at the tip of the light pen 47 detects the light emitted by the CRT display screen associated with the monitor 45. To select a particular screen or function, the operator touches a designated area of the display screen and presses the button on the pen 47. The touched area changes to the highlighted color or a new menu or screen is displayed confirming communication between the light pen and the display screen. Other devices such as a keyboard, mouse, or other pointing or communication device may be used in place of or in addition to the light pen 47 so that the user can communicate with the controller 42.

  [0057] Referring to FIGS. 1, 14, and 15, an exemplary block diagram of a hierarchical control structure of a computer program 70 stored in the memory 46 is shown. Using the light pen interface, the user enters the process set number and processing chamber number into the process selector subroutine 73 in response to a menu or screen displayed on the CRT monitor. A process set is a predetermined set of process parameters required to execute a particular process and is identified by a predetermined set number. The process selector subroutine 73 identifies (i) the desired processing chamber, and (ii) the desired set of process parameters required to operate the processing chamber for performing the desired process. Process parameters for performing a particular process relate to process conditions, eg, plasma conditions such as process gas composition and flow, temperature, pressure, RF power level and low frequency RF frequency, cooling gas pressure, and chamber wall pressure. . These parameters are given to the user in the form of a recipe and are entered using the interfaces of the light pen / monitors 45 and 47.

  [0058] The signal for monitoring the process is provided by the analog / digital input board of the system controller, and the signal for controlling the process propagates on the analog / digital output board of the CVD system 10. A process sequence subroutine 75 receives the specified processing chamber and set of process parameters from the process selector subroutine 73 and includes program code for controlling the operation of the various processing chambers. Since multiple users can enter process set numbers and process chamber numbers, or a single user can enter multiple process set numbers and process chamber numbers, the sequencer subroutine 75 is selected in the desired sequence. Operates to schedule processes. The sequencer subroutine 75 includes (i) monitoring the operation of the processing chamber to determine if the chamber is in use; and (ii) determining which process is running in the in-use chamber; , (Iii) performing a desired process based on the availability of the processing chamber and the type of process to be performed, including program code for performing. Conventional methods of monitoring the processing chamber, such as polling, can be used. When scheduling the process to be performed, the sequencer subroutine 75 takes into account other relevant factors as well as the current status of the processing chamber.

  [0059] When the sequencer subroutine 75 determines the next processing chamber and process set combination to be executed, the sequencer subroutine 75 passes the specific process set parameters to the chamber manager subroutines 77a-c, thereby determining the process set. Initiating execution, the chamber manager subroutines 77 a-c control a plurality of processing tasks in the processing chamber 12 in accordance with the process set determined by the sequencer subroutine 75. For example, the chamber manager subroutine 77a includes program code for controlling sputtering and CVD process operations in the processing chamber 12. The chamber manager subroutine 77 also controls the execution of various chamber component subroutines that control the operation of the chamber components necessary to execute the selected process set. Examples of chamber component subroutines are substrate positioning subroutine 80, process gas control subroutine 83, pressure control subroutine 85, heater control subroutine 87, and plasma control subroutine 90 in some embodiments.

  [0060] In operation, the chamber manager subroutine 77a selectively schedules or invokes process component subroutines depending on the particular process set being executed. Chamber manager subroutine 77a schedules process component subroutines in a manner similar to how sequencer subroutine 75 schedules the next processing chamber 12 and process set to be executed. Typically, the chamber manager subroutine 77a includes the steps of monitoring various chamber components, determining which components need to be operated based on the process parameters of the process set being executed, In response to the determining step, executing a chamber component subroutine.

  [0061] Referring to both FIGS. 1 and 15, the substrate positioning subroutine 80 includes program code for controlling the chamber components used to load the substrate into the susceptor 18. Optionally, the substrate positioning subroutine 80 may control the distance between the substrate 16 and the gas distribution manifold 14 by positioning the substrate 16 within the processing chamber 12. Once the substrate 16 is loaded into the processing chamber 12, the susceptor 18 is raised to the desired height of the processing chamber 12 after the susceptor 18 is lowered to receive the substrate. In this way, the substrate 16 is maintained at a first distance or distance from the gas distribution manifold 14 during the deposition process. The substrate positioning subroutine 80 controls the movement of the susceptor 18 in response to process set parameters related to the support height transferred from the chamber manager subroutine 77a.

  [0062] Process gas control subroutine 83 has program code for controlling process gas composition and flow rates. The process gas control subroutine 83 controls the open / close position of the safety shut-off valve and increases / decreases the mass flow controller to obtain a desired gas flow rate. The process gas control subroutine 83, like all chamber component subroutines, is invoked by the chamber manager subroutine 77a and receives process parameters associated with the desired gas flow rate from the chamber manager subroutine 77a. Typically, the process gas control subroutine 83 opens the gas supply line and (i) reads the required mass flow controller and (ii) the desired flow rate received from the chamber manager subroutine 77a. And (iii) adjusting the flow rate of the gas supply line as necessary. In addition, the process gas control subroutine 83 includes steps for monitoring the gas flow in preparation for unsafe flow and for operating a safety shut-off valve when an unsafe condition is detected.

  [0063] In some processes, an inert gas, such as helium He or argon Ar, is flowed into the processing chamber 12 to stabilize the chamber pressure before the reactive process gas is introduced. For these processes, the process gas control subroutine 83 is programmed to include a step for flowing an inert gas through the processing chamber 12 for the time required to stabilize the chamber pressure. Thereafter, the steps described above are executed.

  [0064] The pressure control subroutine 85 includes program code for controlling chamber pressure by adjusting the opening size of a throttle valve (not shown) in the exhaust system (not shown) of the processing chamber 12. The opening size of the throttle valve (not shown) is set to control the chamber pressure to a desired level with respect to the total process gas flow rate, the size of the processing chamber, and the pump set point pressure of the exhaust system. When the pressure control subroutine 85 is called, the target level is received as a parameter from the chamber manager subroutine 77a. The pressure control subroutine 85 operates to measure the chamber pressure by reading one or more conventional pressure manometers connected to the chamber, compares the measured value with the target pressure, and stores the corresponding pressure. The PID (proportional, integral and derivative) values are obtained from the pressure table and the throttle valve is adjusted accordingly. Alternatively, the pressure control subroutine 85 may adjust a throttle valve (not shown) to adjust the chamber pressure.

  [0065] The heater control subroutine 87 includes program code for controlling the current to the heating unit used to heat the substrate 16. The heater control subroutine 87 is also called by the chamber manager subroutine 77a to receive target or set point temperature parameters. The heater control subroutine 87 measures temperature by measuring the voltage output of a thermocouple located at the pedestal 18. The heater control subroutine 87 also compares the measured temperature with the set point temperature and increases or decreases the current applied to the heating unit to obtain the set point temperature. The temperature is obtained from the measured voltage by looking up the corresponding temperature in the stored conversion table or by calculating the temperature using a fourth order polynomial. If the embedded loop is used to heat the susceptor 18, the heater control subroutine 87 gradually controls the increase / decrease of the current applied to the loop. In addition, a built-in failsafe mode may be included to detect process safety compatibility and may interrupt the operation of the heating unit if the processing chamber 12 is not properly set.

  [0066] In some embodiments, the processing chamber 12 is equipped with an RF power source 48 that is used for chamber cleaning or other operations. If a chamber clean plasma process is used, the plasma control subroutine 90 includes program code for setting the frequency RF power level applied to the process electrodes in the chamber 12. Similar to the chamber component subroutine described above, the plasma control subroutine 90 is called by the chamber manager subroutine 77a.

  [0067] The process parameters described above are exemplary as well as the process gases listed above. It should be understood that the processing conditions may be varied as needed. For example, the present invention has been described as depositing a tungsten layer adjacent to a layer of TiN. However, this process is equally effective when depositing a tungsten layer adjacent to the titanium Ti layer or directly on the wafer surface. This process may also be used to nucleate another other metal layer. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

  [0068] While embodiments of the invention have been described above, other and further embodiments of the invention may be devised without departing from the basic scope thereof. , Determined by the claims.

1 is a longitudinal cross-sectional view of one embodiment of a simplified chemical vapor deposition (CVD) system according to one embodiment of the present invention. FIG. 2 is a longitudinal cross-sectional view of one embodiment of a resistance heating susceptor used in the processing chamber of FIG. 1 for securing a substrate disposed in the processing chamber. It is a simplified top view which shows the connection of the gas supplied to the CVD system shown to the upper part of FIG. FIG. 2 is a detailed cross-sectional view of the substrate shown above FIG. 1 before the nucleation of the refractory metal layer and the substrate. FIG. 5 is a detailed cross-sectional view of the substrate shown in the information of FIG. 4 after nucleation and bulk deposition of a refractory metal layer, according to one embodiment of the present invention. FIG. 2 is a detailed cross-sectional view of a substrate showing the adverse effects of nucleation by prior art nucleation techniques. 2 is a detailed cross-sectional view of the substrate shown above FIG. 1 showing the generation of a concentration boundary layer during nucleation of the refractory metal layer and the substrate. 2 is a graph showing the relationship between the by-product concentration and time in the processing chamber shown in FIG. 4 is a graph showing the relationship between the concentration boundary layer thickness and the time required to remove process gas and by-products from the processing chamber according to the present invention. 4 is a graph illustrating the relationship between the deposition rate of a refractory metal nucleation layer on a substrate and the time required to remove process gases and by-products from the processing chamber according to the present invention. 6 is a flow chart illustrating a process for depositing the refractory metal layer shown in FIG. 5 according to one embodiment of the invention. 6 is a flowchart illustrating a process for depositing the refractory metal layer shown in FIG. 5 according to a first alternative embodiment of the present invention. 6 is a flowchart illustrating a process for depositing the refractory metal layer shown in FIG. 5 according to a second alternative embodiment of the present invention. FIG. 4 is a simplified diagram of a system monitor used in connection with the CVD system shown above FIGS. 1-3 in a multi-chamber system. FIG. 2 shows an exemplary block diagram of a hierarchical control structure of system control software used to control the system shown above FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Processing system, 12 ... Treatment chamber, 14 ... Gas distribution manifold, 16 ... Substrate, 17 ... Valve, 18 ... Susceptor, 19 ... Gas line, 20 ... Motor, 22 ... Pin, 31, 33 ... Gas supply source, 31a ˜31c, 33a˜33c ... supply line, 35 ... fore line, 39 ... groove, 42 ... processor, 44 ... control line, 46 ... memory, 48 ... RF output source, 50 ... wafer, 52 ... layer, 54,154 162b ... Void, 56 ... Covering region, 58 ... Adhesive layer, 59 ... Barrier layer, 60, 160 ... Nucleation layer, 62 ... Bulk deposition layer, 63 ... Contact, 160c ... Concentration boundary layer (CBL)

Claims (20)

A process for forming a nucleation layer on a substrate disposed in a processing chamber, comprising:
Introducing one or more pulses, each having a hydrogen-containing gas and a tungsten-containing gas, into the processing chamber;
Removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber between the pulses;
Including the process.   The process of claim 1, further comprising introducing the hydrogen-containing gas and the tungsten-containing gas into a foreline while removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber.   The process of claim 1, wherein removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber comprises reducing the pressure in the processing chamber.   The process of claim 1, wherein removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber comprises introducing a purge gas into the processing chamber while maintaining a pressure in the processing chamber.   The process of claim 1, wherein removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber comprises introducing a purge gas into the processing chamber while reducing the pressure in the processing chamber.   The process of claim 1, further comprising depositing a bulk layer on the nucleation layer in the same processing chamber or in different processing chambers. A process for forming a nucleation layer on a substrate disposed in a processing chamber, comprising:
Introducing a first set of one or more pulses, each having a first ratio of a hydrogen-containing gas and a tungsten-containing gas, to the processing chamber;
Introducing one or more second sets, each having a second ratio of the hydrogen-containing gas and the tungsten-containing gas, into the processing chamber;
Removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber between each of the first pulse sets and between each of the second pulse sets;
Including the process.   The process of claim 7, wherein the second ratio of the hydrogen-containing gas and the tungsten-containing gas is less than the first ratio.   The process of claim 7, further comprising introducing the hydrogen-containing gas and the tungsten-containing gas into a foreline while removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber.   The process of claim 7, wherein removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber comprises reducing the pressure in the processing chamber.   The process of claim 7, wherein removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber comprises introducing a purge gas into the processing chamber while maintaining a pressure in the processing chamber.   The process of claim 7, wherein removing the hydrogen-containing gas and the tungsten-containing gas from the processing chamber comprises introducing a purge gas into the processing chamber while reducing the pressure in the processing chamber.   8. The process of claim 7, further comprising depositing a bulk layer on the nucleation layer in the same processing chamber or in different processing chambers. A process for forming a nucleation layer on a substrate disposed in a processing chamber, comprising:
Introducing a first set of one or more pulses, each having a first hydrogen-containing gas and a tungsten-containing gas, into the processing chamber;
Removing the first hydrogen-containing gas and the tungsten-containing gas from the processing chamber during each of the first pulse sets;
Introducing a second set of one or more pulses each having a second hydrogen-containing gas and the tungsten-containing gas into the processing chamber;
Removing the second hydrogen-containing gas and the tungsten-containing gas from the processing chamber during each of the second pulse sets;
Including the process.   The process of claim 14, wherein the first hydrogen-containing gas comprises silane and the second hydrogen-containing gas comprises hydrogen gas.   During each of the first pulse sets, introducing the first hydrogen-containing gas and the tungsten-containing gas into the foreline while removing the first hydrogen-containing gas and the tungsten-containing gas from the processing chamber. And further comprising removing the second hydrogen-containing gas and the tungsten-containing gas from the processing chamber during each of the second pulse sets while removing the second hydrogen-containing gas and the tungsten-containing gas from the processing chamber. The process of claim 14, further comprising introducing a gas into the foreline.   The step of removing the first hydrogen-containing gas and the tungsten-containing gas from the processing chamber includes reducing the pressure of the processing chamber, and the second hydrogen-containing gas and the tungsten-containing gas from the processing chamber. The process of claim 14, wherein the step of removing comprises reducing the pressure in the processing chamber.   The step of removing the first hydrogen-containing gas and the tungsten-containing gas from the processing chamber includes introducing a purge gas into the processing chamber while maintaining a pressure in the processing chamber, The process of claim 14, wherein removing the hydrogen-containing gas and the tungsten-containing gas comprises introducing the purge gas into the processing chamber while maintaining a pressure in the processing chamber.   The step of removing the first hydrogen-containing gas and the tungsten-containing gas from the processing chamber includes introducing a purge gas into the processing chamber while reducing the pressure in the processing chamber. The process of claim 14, wherein removing the two hydrogen-containing gases and the tungsten-containing gas comprises introducing a purge gas into the processing chamber while reducing the pressure in the processing chamber.   15. The process of claim 14, further comprising depositing a bulk layer on the nucleation layer in the same processing chamber or different processing chambers.

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