TW519721B - Gradient barrier for copper back-end-of-line technology - Google Patents

Abstract

The present invention is directed to a structure of a gradient barrier layer. The gradient barrier with a composite structure of metal/metal salt of different composition/metal such as Ta/TaxN1-x/TaN/TaxN1-x/Ta (tantalum/tantalumx nitride1-x/tantalum nitride/tantalumx nitride1-x/tantalum) is proposed to replace the conventional barrier for copper metallization. The gradient barrier can be formed in a chemical vapor deposition (CVD) process or a multi-target physical vapor deposition (PVD) process. For CVD process, using the characteristics of well-controlled reaction gas injection, the ratio of tantalum (Ta) and nitrogen (N) can be modulated gradually to form the gradient barrier. For the multi-target PVD process, the gradient barrier is formed by depositing multi-layers of different composition TaxN1-x films. After subsequent thermal cycle processes such as metal alloy, the inter-layer diffusion occurs and a more smooth distribution of Ta and N is achieved for the gradient barrier. The advantages of forming the gradient barrier include a well-controlled process, a strong adhesion between via and landing metal, more uniform step coverage, and less brittle to reduce crack.

Description

519721 V. Description of the invention (1) 5 -1 Field of invention: The present invention relates to a method of forming a super large volume == a special technique (copper back end 〇f the (SI) rear copper Metal wire h / T.M /? Μ π Nitriding group / button (

Ta / TMh / TaN / TMh / Ta). 5-2 Background of the Invention: Shrinking, copper due to the low degree of integrated electricity, copper is very susceptible to the dielectric in the insulating material to form adjacent wires 1 di e 1 ectr Constant dimensional stress and electro-migration characteristics, the process is recognized as a high accumulation high interconnect process. However, including metal or non-metal, and the diffusion of copper to dielectric (IMD), such as oxidized stone, will form an inter-leve breakdown field. This causes the development of the barrier layer to be more metallic. Aluminum has a good impedance, which makes the steel metallization roads with good reliability and efficiency easily diffuse to a variety of materials and the dielectric constant of the material. For example, the leakage current between layers (inter-metal and reducing the internal IC, ILD) collapse field (difficult copper diffusion in the copper interconnect process) occurs. The first picture shows the copper metallization process application of integrated circuit. Contains The tens of nanometer (nm) tantalum nitride layer (TaN) 1 08 and the button metal layer (Ta) 11 0 barrier layer 'are sandwiched between the copper metal layer 112 of the dual surface structure and the oxidized stone. Gold 519721, description of the invention (2) _ Metallic = layer 10, and it is connected to the substrate 1QQ ^^ ~ '. The inner metal dielectric layer 106 is usually shaped / metal structure 110 and is used as a protective layer of nitride Silicon layer 丨 04. Must be two = present, on the substrate 1 00 • Copper barrier better barrier layer 'i nitride button 氮化' nitride giant is appropriate. Although the group metal and oxide-based dielectric Layer-adhesive copper seed (Copper seed) is a better material. 軚 I is usually formed on the nitrided surface layer to strengthen copper and nitride. In the traditional In the copper metal process, when an oxide-based dielectric is used = a metal dielectric layer, the tantalum nitride layer 108 of the barrier layer and copper gold = do not have significant adhesion problems. Therefore, The traditional resistance = 3 is used in the later copper metal wire technology (BEOL), the diffusion of ^ and 02, as shown by the arrow. The copper is made of ,,,,, and is not at a low level. The dielectric constant within the metal dielectric material system (low-k IMD), because the low dielectric constant material 210 has a larger thermal expansion coefficient, and the nitride button layer 108 and the copper landing pad 1 0 2 _ Poor adhesion, the interface 2 1 2 between the nitride button 108 and copper 102 is very weak and easy to separate, as shown in the second figure. In addition, the brittle nature of tantalum nitride is also easy to cause These factors can cause electrical discontinuities, and even more severely fail the reliability test, such as' Herma 1 cycle test (TCT) and stress migration test (SM). Therefore, in order to solve the problem of adhesion caused by the application of low dielectric constant materials, many methods have been developed, and the Ar-preciean technique is one of them.

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519721 V. Description of Invention (3)

The argon first ’then strengthens the adhesion’ so that argon generates a lot of). The main point of the mtcor-line processing process is to remove the formation of the group metal layer first to make the group metal layer. However, because the process conditions of the pre-treatment process at the bottom of the via are not a side effect, which leads to the formation of a reliable 310), the sidewall of the via (material re-deposition) 320 is thinner due to uneven copper, which increases. The electrical characteristics. Then the bottom part is shown when severe. Barrier thinning. Excessive etching. The bottom of the via hole is redeposited on the side wall or the chance of demineralization to a low dielectric discontinuity, and the lower one is changed. When the tantalum nitride sub-nitride button layer at the bottom of the via hole is also removed at the same time, or even nitrided completely The tantalum layer is removed and directly contacts the steel surface. The nitride button layer is very thin and often difficult to control. Therefore, for example, the material at the bottom of the micro trench is re-deposited and the resistance at the bottom of the trench is greater than the formation of the polar trench. 3 1 〇 The material is even a dielectric layer including its dielectric constant, and a dielectric layer with a greater dielectric constant After the removal of the layer 108, the thinning of the barrier layer caused by the trenches is marked as 330 and 340, respectively. Observing the lack of the above-mentioned prior art, the coefficient has a clement coefficient, good adhesion, and high ductility. In addition, the sound resistance of the step coverage is very necessary. The purpose and summary of the invention 5-3 In view of the above background of the invention, many of the traditional barrier layers

519721 V. Description of the invention (4) Disadvantages' The object of the present invention is to provide a method for forming a gradient barrier layer. Gradient barrier layer and metal salt / metal composite structure composed of “I”, for example, the synthesizing barrier layer of the same nitride group / group x / Ta) is applied to copper metal化 process. And instead of using conventional chemical vapor deposition technology (CVD) or physical vapor phase, "w retarding the early layer can be formed. Take the chemical vapor deposition process as an example, using the characteristics of the product: the gas, you can gradually adjust the components / τ uses the reaction example of the father to form a gradual barrier layer. The multiple: leather () two "prime (_ τΠ: deposition of a number of different composition of nitride button sound (X h), M later The diffusion of thermal cycling processes such as gold will cause the buttons to remove r τ, Α γ, and the inner interlayer lines, and the bands will become smoother; the distribution curve between prime Ta) and nitrogen (N), A gradual barrier lug is formed. The advantages of the J-Cutter and the K-Curve are easy to control the manufacturing process stoppage. The advantages of the second person and the “early-working early” include the better capacity of the step cover :: 丨 strong adhesion between the layer hole and the road metal, I force , And it is less brittle (large ductility) and not easy to break. Another method of the present invention is good: different! It provides a long-day surface forming a gradient barrier layer for copper metal deposition on The I_α method of the present invention has excellent performance; f 1 provides a good early resistance characteristic of forming a progressive barrier layer, which can prevent copper from diffusing outward. Another aspect of the present invention is a gradual layer. A square-shaped barrier layer [丄] provides an in-situ (in ~ sltu) formation method with tantalum / tantalum nitride / buttons of different compositions (519721

V. Description of the invention (5)

Ta / TaxN (x / TaN / TaxN (x / Ta)). According to the above-mentioned object, in a preferred embodiment, the present invention provides a gradient barrier layer, the structure of which includes a first metal layer, a metal salt composite layer of a plurality of different compositions; and Second metal layer. The first metal layer and the second metal layer are selected from the following: a button metal layer, a gold layer, and a tungsten metal layer. When the first metal layer and the second metal layer can be known metal layers, the plurality of metal salts having different compositions can be a plurality of different = nitrided group composite layers (Ta ^ -x), in which the element content (x) It varies between about 0.05 and 1. The plurality of nitrided button composite layers (T ~ N ·) of different compositions include at least a plurality of layers, a nitrided button layer, and a plurality of X h ΤχΛ-χ2 layers, where χι decreases from about 1 to 0.5 In the meantime, x2 is incremented between approximately 0 · 5 and 1. The total thickness of the first tantalum metal layer and the plurality of τ axl f ^ xi layers is about 10 to 100 angstroms. The thickness of the nitrided button layer (TaN) is between about ^ and 200 angstroms. And the plurality of layers and the second button metal are equal to about 100 to 2,000 angstroms. ≫ ^ ^ and In another embodiment of the present invention, the method of barrier layer on the substrate is also provided. The steps of the present invention are: m = layer on the substrate; On the composite layer. Different composition in chemical vapor deposition; gold to form the first metal layer. Then, "two) younger-reaction gas is passed in and reacted with the first reaction gas to form a second reaction gas. Several different metal salts

519721

Composite layer. Next, the introduction of the second reaction gas is stopped, and the first reaction gas is used to form a second metal layer. The method of the present invention further includes performing a loop process. # '5 ~ 4 发明 发明 描述 ·？ ★ Some embodiments of the present invention will be described in detail as follows. However, in addition to the detailed description, the present invention can also be widely implemented in other embodiments, and the scope of the present invention is not limited, which is subject to the scope of subsequent patents.

Figure 4A. In one embodiment, the present invention provides a gradient barrier. The focus of the present invention is to provide a heavy-layer barrier layer having a metal / metal salt of different composition / metal < a-type structure, such as a button / nitride button / button of different composition (xNl- x / TaN / TaxNi-x / Ta) structure to replace the traditional barrier layer: 4fin in steel metallization process. As shown in the figure, it has a substrate with a body structure of 410. Melic can be a substrate at any stage of the semiconductor process, for example, copper

400. For example, the section ^ 1 ^ 々 has a copper landing pad 410 at the bottom of 4 i 〇, and the inert layer of the wide lice silicon 43o is selectively formed on the copper landing pad in the incubator of the village 〇a〇. To maintain the electrical conductivity of copper. The double damascene structure is formed in white to prevent copper from moving from copper to Λ to apply the present invention.尨 person P pads 〇 extend the administration to; 丨 barrier layer 4 4 0 moxibustion, a mongolian layer 460 formed on the gradual barrier layer to complete g

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Double mosaic interconnects. It is necessary to stop the diffusion of the metal material between the 460 and the dielectric layer 440. The gradient barrier layer is sandwiched between the metal layer and electrically connected to the steel landing pad 4 1 0 to prevent the gradient barrier layer. 450 is a metal / salt / metal composite structure formed in sequence. First of all, a different and formed metal under the conductor structure (such as copper and gold with layer 7 is any layer with a greater ductility / 塾), * a gold dielectric layer with good adhesion In time, it will not be caused by the fact that the electrical constant material is used as the internal metal (titanium ta), tungsten (tungsten): genus; if not: the metal salt composite layer, which has better barrier properties, heart The "stop" layer material diffuses into the dielectric layer. Afterwards, a good crystal growth surface is formed for the metal material to deposit the metal layer on its rule; ^: the formed nitride group composite layer (TIM_χ composite layer) is sandwiched by the work: the same: the first is to avoid copper metal diffusion For the composite layer of Risi, the tantalum metal is ": the process is easy to control, so it is formed as gold u. Refer to the fourth figure B, which has a button / a different composition of nitride button / tantalum, namely Ta / TaxlIVxl / TaN / Tax2IVx2 / Ta structured barrier layer 45 °. The sum of the degree of the button metal layer and the first tantalum nitride layer (1 ^ and) of different composition is about 10 to 100 angstroms. , As shown in area I of the fourth figure, where the metal component (Ta) contained in TaJM varies with thickness

Page 12 519721 V. Description of the invention (8) ~~-and increase and decrease until the ratio of button to nitrogen (Ta / N) is 1. That is, Η is a decreasing number between 1 and 0.5. According to the second region j in the fourth diagram B, the thickness of the nitride button (TaN) is between about 100 and 200 Angstroms. The sum of the degrees of the button metal layer and another nitride button layer 2) with a different composition is about 100 to 200 angstroms, as shown in the fourth section of FIG. 4B. Among them, TaJw contains a metal component (Ta) from a button to nitrogen ratio (Ta / 〃N) of 1, which increases with increasing thickness until it is almost 100% nitrogen metal. That is, x2 is an incremental number between 0.5 and 0.5. The present invention provides a method for forming a stepped barrier layer 450. The gradient barrier layer can use chemical vapor deposition (cvd) or multi-standard (PVD) " ^ ° 14 ta = bismuth example, using the characteristics of the reactive gas that can be easily controlled, can be :: tune: button element (Ta) and nitrogen element rhenium, the ratio of the two in the same position: barrier layer. Referring to FIG. 4A again, the steps of the present invention include at least two :: 00s having a conductive structure 41 o thereon and an inner dielectric layer 440 thereon. Such as nitride stone Xi inert layer 43. It is selectively formed under the inner dielectric layer & to maintain the electrical conductivity of the conductive structure. Then use the transmission process: for example, self-pairing, first punish the layer hole, Λ y / wood double inlay process to form the double inlay and interstitial hole opening. The metal salt / gold / 'heart consisting of 4 channels: 519721 V. Description of the invention (9) Double-inlaid graphics on the substrate 400. In other words, by using the technique of #noting the corresponding gas, the first reaction gas is passed in, and the layer of the second metal is formed on the inner dielectric layer 440, and the double-inlaid trenches and vias are covered. Side walls and bottom. Then, the second gas introduced is gradually adjusted to form a plurality of metal salts with different compositions on the first metal layer. A second metal layer is formed on several metal salt composite layers having different compositions. The first and second metal reeds are used as the metal and the composition of the metal salt is a button element (Ta) and a nitrogen element. The first button metal layer is formed on the dielectric layer 440 by controlling the introduction of a reactive gas. Then, the flow of nitrogen gas is gradually adjusted, and a plurality of tantalum nitride layers (TaxN ^) of different compositions are formed on the first button metal layer. In addition, a plurality of tantalum nitride layers (TaxNi x) having different compositions may have a composition similar to that in FIG. 4B. That is, a nitrogen nitride button composite layer such as a region, t is formed by gradually increasing the nitrogen gas introduced. When the tantalum / nitrogen ratio approaches 丨, maintain the nitrogen flow rate until it reaches the preset thickness as shown in the second region. Then, the nitrogen flow rate is gradually reduced until it approaches zero, forming a complex .it layer such as the third region ..., V1. A second tantalum metal layer, which is "stopped from introducing nitrogen", is formed on several tantalum nitride layers (τ & λ_χ) of different compositions. After the defect, a copper layer-like conductive layer 460 is formed in a step-by-step barrier ^ dual-damascene interconnect structure. It must be "450" to form a conductor to prevent the conductor from dying. The same day guard can also use the barrier layer 420 of the present invention 440. Diffusion from the bulk structure 410 to the dielectric layer. In yet another embodiment, the metal / different alloys are formed using a physical vapor deposition (PVD) technique, and the shape of the metal salt / metal composite structure is gradually increasing. Layer 519721 V. Description of Invention (ίο) type barrier layer. Physical vapor deposition technology includes mul ti-target sputtering technology and metal ion plasma technology

(Ion metal plasma, IMP). At the same time, referring to the fourth A and the fifth A's, after the formation of the double-mosaic trench and the opening of the interstitial hole, a plurality of metal salt composite layers with different compositions are deposited. That is, the first metal layer 450a is formed on the dielectric layer 440. Then, a plurality of gold salt composite layers with different compositions are formed on the first metal layer, as shown in the figures 450b, 450c, 450d, 450e and 450f. Next, 450 g of a second metal layer was formed on a gold number salt composite layer having a different composition. Then, a copper metal layer conductor layer 460 is formed on the gradient barrier layer 450 to form a dual damascene interconnect structure.

The first and second metal layers are described as button metals, and the composition of the metal salt is group element (Ta) and nitrogen element (N). In a sputtering deposition process, a first target (containing 100% Ta) is used to form a wall-button metal layer on the dielectric layer 44. Then, a second target (containing about 85% Ta) is used to form a nitride group layer (TaxLx) of the first composition 9 on the first button metal layer. Subsequently, tantalum nitride layers of second and third compositions (containing about 65% and 450) of decreasing composition, respectively, are formed in sequence 450c and 450d on the first composition of nitride nitride layer 450b. After that, the tantalum nitride layers of the fourth and fifth compositions (containing about 65% and 85% Ta, respectively) with an increasing content of 45 0e, and 45 0 f are sequentially formed in the second composition on. Then, a second button metal layer 450 g is formed on the nitride button layer 45 0 f of the fifth composition. Then diffusion in the subsequent thermal cycling process, such as the second layer of the metal alloy process, will cause a smoother distribution curve between the tantalum element (T a) and the nitrogen element (N) to form a stepwise barrier layer 4 50, such as a dotted line 4 7 0 shown. Gradually

Page 15 519721 V. Description of the invention (11) " 一 " ---, the structure of the barrier layer is shown in FIG. 5B, which has f ^ similar to that in FIG. 4B. It must be emphasized that the number of nitrided button composite layers with different compositions is unique in Asia and Africa and is not limited by the five layers in this embodiment. The gradient barrier layer provided by the present invention has a metal / metal composite of different composition = / t composite structure, for example, tantalum / nitride button of different composition / axNl-x / TaN / TaxN (X / Ta) The structure can replace the traditional barrier for copper metallization process. The advantages of the incremental barrier include: easy! Manufacturing process conditions, strong adhesion between the interlayer hole and the landing metal, better step coverage, and less brittle (large ductility) difficult to break . The above are merely preferred embodiments of the present invention, and are not intended to limit the scope of patent application for the present invention; all other equivalent changes or modifications made without departing from the spirit disclosed by the present invention shall be included in the following Within the scope of patent application. Θ 519721 BRIEF DESCRIPTION OF THE DRAWINGS The objects, features, and advantages of the present invention are detailed from the following detailed description and drawings. The description clearly shows: — The first picture is a cross-sectional view of the traditional barrier layer to avoid copper diffusion; the second picture is a cross-sectional view of the adhesion problem between the traditional barrier layer at the bottom of the via and the contact metal; the third This is a cross-sectional view of the side effect of the traditional barrier layer using argon pre-processing technology. ^ Figure A is a cross-sectional view of the present invention forming a progressive barrier layer; Figure B is a first view of the present invention. A cross-sectional view of a gradient barrier structure of an embodiment; FIG. 5A is a cross-sectional view of a gradient barrier structure of another embodiment of the present invention; and a fifth B is a fifth A of the present invention Figure is a cross-sectional view of a gradient barrier structure after thermal cycling. The main part of the symbol: 100 substrate

Page 519721 Brief description of the diagram 102 Copper implantation 104 Silicon nitride layer 106 Oxidized dielectric layer 108 Tantalum nitride layer 110 Group metal layer 112 Copper metal layer 210 Dielectric layer of low dielectric constant material 212 Nitriding Interface separation between tantalum and copper 310 Micro-ditch 320 Re-deposition of the material at the bottom of the via 330 330 Thinning of the trench 340 Nitrogen button layer at the bottom of the trench is completely removed 400 Substrate 410 Conductive structure 420 Barrier layer 430 Inert layer 440 Dielectric layer 450 Gradual barrier layer 45 0a First metal layer 45 0b First nitride group layer 45 0c Second nitride group layer 45 0d Third nitride layer 45 0e Fourth group Nitriding group layer 45 0 f Tantalum nitride layer of fifth composition

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Claims (1)

519721 6. Scope of patent application 1. A step-type barrier layer having a structure including: a first metal layer; a metal salt composite layer of a plurality of different compositions; and a second metal layer. 2. For example, the gradient barrier structure of the first patent application range, wherein the first metal layer is selected from the following, a group of metal layers, a titanium metal layer, and a crane metal layer. 3. The gradient barrier structure of item 1 in the scope of the patent application, wherein the metal salt formed above includes at least a button element (Ta) and a nitrogen element (N). 4. For example, the gradient barrier structure of the patent application No. 3, wherein the metal salt composite layer of the plurality of different compositions includes at least, a nitride group composite layer (T ax Ν1- χ), wherein the group element content (X) varies between about 0.5 to 1. 5. For example, the gradient barrier structure of item 3 of the patent application scope, wherein the plurality of metal salt composite layers of different composition mentioned above include at least, a plurality of Taxl lVxl layers, a nitride group layer, and a plurality of Tax2 5_1 之间。 Ni_x2 layer, where X1 decreases between about 1 to 0.5, and x2 increases between about 0.5 to 1. 6. The gradient barrier layer structure according to item 5 of the patent application scope, wherein the first metal layer is a group of metal layers, and the group of metal layers and the plurality of metal layers are Page 20 519721 VI. Patent application scope First metal layer 1 2. The method of forming a gradient barrier layer on a substrate as described in item 11 of the patent application scope, wherein the above-mentioned formation of the plurality of different composition of the The step of the metal salt composite layer at least includes passing a second reaction gas with a different flow rate and reacting with the first reaction gas to form the metal salt composite layers with different compositions. 1 3. The method for forming a gradient barrier layer on a substrate according to item 12 of the scope of patent application, wherein the step of forming the second metal layer at least includes stopping the introduction of the second reaction gas, The first reaction gas is used to form the second metal layer. 14. The method for forming a gradient barrier layer on a substrate according to item 10 of the scope of patent application, wherein the first metal layer is a group of metal layers. 1 5. The method for forming a gradient barrier layer on a substrate according to item 14 of the scope of patent application, wherein the above-mentioned step of forming the metal salt composite layer of the plurality of different compositions includes at least, forming a plurality of One of the different compositions is a tantalum nitride composite layer (TaxU, in which the button element content (X) varies from about 0.5 to 1. 1) According to the scope of patent application No. 15, a stepwise resistance is formed. Barrier layer Page 519721 6. The method for applying for a patent material, wherein the above-mentioned step of forming the metal salt composite layer of the plurality of different compositions includes at least: wherein X1 is about χ2 is about χ2 to form a first composition of the nitride button layer (T ~ u is less than 1, and about greater than 0.5; forming a nitride button layer (TaN) of a second composition; and forming a nitride button layer () of a third composition, greater than 0 · 5, It is less than about 1. 17. The method for forming a gradient barrier material according to item 10 of the scope of patent application, further includes performing a thermal cycle process. 18. A method for forming a gradient barrier layer on a substrate The method comprises the steps of: forming a first button metal layer on the substrate; forming a first tantalum nitride composite layer (T3χΛ_χ1) of a plurality of different compositions on the first tantalum metal layer, where χ1 decreases gradually Between about 0 and 5; * ^ forming a nitride button layer on the first nitride button composite layer of the plurality of different compositions;-forming one of a plurality of different compositions Tax2IVx2) on the tantalum nitride metal layer Between; and the brother-rat group composite layer (where X 2 passes · At about 5-1 square is formed with a second metal of the second nitride layer on the plurality of tantalum is not a composite layer.