TW302511B - Method of forming aluminum plug by selective chemical vapor deposition - Google Patents

Abstract

A method of forming aluminum plug by selective chemical vapor deposition comprises of the following steps: (1) on one substrate forming one semiconductor component, and forming one insulator overlaying on its surface, in which the insulator has one contact opening for exposing conductive region of the semiconductor component; (2) in vacuum environment applying one thermal annealing treatment to the substrate; (3) using dimethylethylamine alane covalent compound as precursor, with substrate temperature not higher than 250 centigrade, by chemical vapor deposition forming one aluminum layer, selectively depositing on the conductive region in the contact opening, and not depositing on the insulator surface for implementing one aluminum plug.

Description

c / oo I A7 B7 5. Description of the invention (丨) The present invention relates to the process of metallization of integrated circuits (and in particular, it relates to a procedure using vacuum thermal annealing treatment (vacuum thermal annealing treatment) to improve chemical gas The selectivity of phase deposition is used to form a contact plug. In the integrated circuit manufacturing process, it is a widely used technique to deposit aluminum metal by sputtering to form the required interconnect. Since the sputtering process belongs to a physical vapor deposition (PVD) method, its step coverage capability is generally worse than that formed by the chemical vapor deposition (CVD) method, so it is used in sub-micron The manufacturing process of the size device will have the disadvantages of uneven thickness of the deposited metal and the formation of voids. When the depth of the holes is small, the metal cannot be effectively deposited on the bottom. For the sake of clarity, please refer to Figure 1 to illustrate the process of depositing aluminum metal by conventional sputtering methods. As shown in the figure, a required semiconductor element is formed on a substrate 10, and in order to simplify the illustration, only the conductive region 12 of the semiconductor element is shown in the figure, for example, a metal layer or a metal clad layer. An insulating layer 14 is formed on the substrate 10, which may be a thermal oxide layer, a borophosphosilicate glass (BPSG) layer 'or a tetraethoxysilane (TEOS) layer. A contact opening 16 is formed in the insulating layer 14 by lithography imaging and etching procedures, exposing the conductive region 12 of the semiconductor element. Then, a sputtering process is applied to deposit an aluminum metal layer 18, which is connected to the conductive region 12 through the contact opening 16 to form an interconnecting wire. However, when the conventional sputtering aluminum metal process is applied to further reduce the size of the device, because the contact opening 16 is reduced, the aluminum metal layer 18 will have uneven coverage due to the poor step coverage, resulting in uneven thickness and the formation of holes 15 The nature of the component. When the hole is deep and small, the metal cannot even cover the bottom layer. The standard of this paper is applicable to China National Standard (CNS) A4 (210X297mm) (please read the notes on the back before filling in this page) Printed by the Employees Consumer Cooperative of Zhongshang Bureau of Standardization, Ministry of Economic Affairs ¾ 0 5 66TWF.DOC / 00 | A7 B7 Employee Consumer Cooperation of the Central Bureau of Standards of the Ministry of Economic Affairs Du Yinju V. Description of Invention (>) Often, in order to improve this problem, a tungsten plug (tungsten plug) is selectively deposited by CVD method 17 In the contact opening 16, an aluminum metal layer 18 is deposited on the surface of the insulating layer 14 by a general method to form the structure shown in FIG. However, the above-mentioned tungsten contact plug process steps are complicated and the cost is relatively high. In addition, the conductivity of tungsten is only one third of that of aluminum. Therefore, many researchers have tried to develop a CVD method to deposit aluminum technology, which is suitable for 0.25. F below the size of the manufacturing process. In the past, it was used as a precursor for the deposition of aluminum metal by CVD....--· · · · _ _ One thing is diisobutyl silver (triisobutyl aluminum, TIB A), and dimethyl The dimethylaluminum hydride (DMAH), the former because of its low vapor pressure, requires a high temperature of about 160 to 170 ° C to be evaporated and vaporized, which is inconvenient in operation. Although the latter has a relatively high vapor pressure, its structure contains strong C-A1 covalent bonds, which makes it easy for the deposited aluminum metal layer to contain carbon heteroatoms, affecting its conductive properties. Gladfelter and MG Simmonds of the University of Minnesota in 1991 proposed the use of dimethylethylamine alane (dimethyl ethylamine alane, ^ ^ Dan λ Α) coordination compound as a precursor of chemical vapor deposition of aluminum, its chemical structure is as follows As shown in Figure 3, due to a coordinate covalent bond between the nitrogen atom and the aluminum atom, the bond energy is smaller than the general covalent bond, so the vapor pressure is higher, about 90. (: It can be vaporized and vaporized at a temperature, and the aluminum metal layer produced is pure in composition and contains few other heteroatoms. Based on this excellent characteristic, the applicant in this case had SSDM, P.634 and 1994 in 1994. In 1994, VMIC, P.362 published the use of DMEAA in the semiconductor integrated circuit process. However, its deposition selectivity has not been discussed. The purpose of the present invention is to propose 4 (please read the back (Notes to fill out this page) ", τ a The paper scale is applicable to the Chinese National Standard (CMS) Α4 specification (210X 297 mm)

Printed by the Employee Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs 5. Description of the Invention (7) The research results of this aspect are used in conjunction with the process of selectively depositing aluminum contact plugs. According to the above object of the present invention, a method for forming an aluminum contact plug by selective chemical vapor deposition is proposed, which includes the following steps: forming a semiconductor element on a substrate, and forming an insulating layer covering the surface thereof, the insulating layer having A contact opening to expose the conductive area of the semiconductor device; subjecting the substrate to a thermal annealing process in a void environment; and using a dimethylethylamine aluminane complex as a precursor, at not more than 250 At a substrate temperature of ° C, an aluminum layer is formed by chemical vapor deposition, which is selectively deposited on the conductive region in the contact opening, but not deposited on the surface of the insulating layer, for making an aluminum contact bolt. According to a preferred embodiment of the present invention, wherein the above-mentioned thermal annealing treatment is heat treatment at about 450 ° C for about 30 minutes, the insulating layer used may be a thermal oxide layer or a phosphorosilicate glass layer. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is described below in conjunction with the attached drawings, which are described in detail as follows: Brief description of the drawings: Figure 1 It is a schematic cross-sectional view of a metal wire prepared by a conventional sputtering aluminum metal deposition process; FIG. 2 is a cross-sectional schematic view of a metal wire prepared by a conventional chemical vapor deposition tungsten contact plug process; FIG. 3 is the present The chemical structure diagram of the precursor DMEAA used in the invention; Figure 4 shows the relationship between the growth rate of the aluminum layer and the substrate temperature during deposition 5 (please read the precautions on the back before filling this page).

、 1T The size of this paper is in accordance with Chinese National Standard (CNS) Λ4 specification (210Χ 297mm) 0566TWF.DOC / 00 1 A7 ____B7 V. Description of invention (bucket)

Printed by the Ministry of Economic Affairs of the Central Bureau of Standards and Staff of the Consumer Cooperative Society. Figure 5 shows the Auger composition analysis chart of the aluminum layer deposited by the CVD method to indicate the purity of aluminum. Figure 6 shows the aluminum layer deposited by the CVD method on different materials Figure 7 shows the improvement of the aluminum layer deposited by the CVD method before and after a thermal annealing process in the selection of the jjg body; and Figure 8 is the aluminum produced by a preferred embodiment of the method of the present invention A schematic cross-sectional view of the contact plug. Discussion on the properties of the aluminum layer deposited by CVD method (1) Using DMEAA as a precursor for CVD deposition of aluminum layer, the relationship between the growth rate and the substrate temperature is plotted in Figure 4, which is shown in two reactions of lOOmTon • and 200mTOrr The curve under pressure has a similar trend, and the growth rate increases with the temperature of the substrate. After calculation, the activation energy of its surface reaction is about 0.75eV, which is equivalent to the coordination bond energy of aluminum-nitrogen. It is shown that when gJE ^ Mg_AA is the precursor of CVD deposition, breaking the aluminum-nitrogen bond is a fe step. 〃Because it has a smaller covalent bond energy than general precursors, it is more suitable for CVD applications. (2) The aluminum layer deposited by the above CVD method was used for Auger electron spectroscopy analysis to obtain the spectrogram shown in Figure 5 which shows that the aluminum layer contains almost no heteroatoms such as carbon or oxygen , The composition is quite pure. The measured resistance value is about 3.0 // Ω · cm, which is similar to the resistance value of the inscription layer formed by the general sputtering method. (3) Next, perform the above CVD procedure to form an aluminum layer on a substrate with a conductive layer and an insulating layer on the surface to form an aluminum layer, measured at different substrate temperatures. 6 The paper scale is applicable to China National Standards (CNS) A4 specifications ( 2 丨 OX297mm) (Please read the precautions on the back before filling in this page) Packing and Ordering 0566TWF.DOC / 001 A7 0566TWF.DOC / 001 A7 Printed by the Consumer Cooperative of the Central Bureau of Standards of the Ministry of Economy V. Invention Instructions (( ), The number of inscribed particles deposited on the surface of insulating layers of different materials, the result is plotted in Figure 6. The figure shows the number of inscribed particles measured on the surface of the four insulating materials, which are thermal oxidation Layer (Th-Οχ), tetraethoxylate sand yard (TEOS), borophosphosilicate glass (BPSG), and plasma strengthened oxygen and formation of cVD formation. Basically, the higher the substrate temperature during deposition, the more selective Poor, that is, at high temperatures, the aluminum layer is deposited on the surface of the conductive layer and the insulating layer on the substrate, and under lower temperature conditions, it is difficult to deposit on the insulating layer ^: ----- (4) Next, do the experiment described in the previous item again, but before applying the CVD procedure, An empty thermal annealing treatment, for example, at about 450. (: Heat treatment at a temperature of about 30 minutes, the result is plotted in Figure 7. Obviously, after the above empty thermal annealing treatment, the CVD process deposited aluminum in the insulating layer The selectivity on the surface can be improved. Among them, the effect of the pair / thermal oxygen layer is the best. The BPSG layer is second, and the PEOX is poor. The reason may be that the ρΕ〇χ layer is easy to absorb water, while the thermal oxidation layer is not The latter has less 〇Η bond, and the void thermal annealing treatment is more helpful to remove moisture, so aluminum is not deposited on its surface, but only deposited on the surface of the adjacent conductive layer. ^ The example is based on the above study As a result, it can be applied to the integrated circuit metallization process' to produce a structure of selectively depositing aluminum contact plugs. The following is a description of the detailed steps of the preferred embodiment in conjunction with Figure 8. First, as shown in Figure 8 As shown, a substrate 20 is provided, which is formed with required semiconductor devices. Here, only the conductive ridge 22 'of the semiconductor device is depicted as a metal layer or a metal silicide layer. On the substrate 20 = One The edge layer 24 is, for example, a thermal opening or a borophosphosilicate glass. A contact opening 26 is formed on the insulating layer 24 by lithography imaging and etching procedures. This paper size is suitable for Zhongnan Guohua. (CNS) Λ4 specification (210X297mm) ~ '------ (please read the precautions on the back before filling out this education) binding 3u ^ 5xt 0566TSV + .DOC / 001 Central Standard Falcon Bureau Employee Consumer Cooperative Printed Poly A7 Β7 V. Description of Invention U) The conductive region 22 of the semiconductor element. Secondly, the substrate 20 is subjected to an empty thermal annealing treatment, for example, a heat treatment at about 450 ° C for about 30 minutes. Afterwards, using DMEAA as a precursor, a chemical vapor deposition process is performed to deposit an aluminum layer 28, wherein the substrate temperature is controlled to not higher than 250 $ 'to obtain excellent deposition selectivity, that is, aluminum is only deposited in the contact opening On the conductive region 22 in 26 without being deposited on the surface of the insulating layer 24, an aluminum contact plug 28 structure as shown in FIG. 8 is made. Next, a conventional sputtering process can be performed to form the wire above the insulating layer 24. Since it is not a feature of the present invention, it will not be repeated here or drawn in the drawings. In summary, the method of the present invention uses DMEAA as a precursor of CVD. Because its aluminum-nitrogen coordination bond is easily broken, its vapor pressure is higher, and the evaporative gasification process conditions are more relaxed than those of the prior art. The high purity of the deposited aluminum layer 'resistance value is similar to that of the traditional sputtering method, and it will not affect the performance of the device. ----------- An empty dust annealing can greatly improve its effect on the conductive layer and the insulating layer. Therefore, it can be applied to the manufacture of aluminum contact plugs by selective chemical vapor deposition, which is very useful in the process of reducing the size of integrated circuits. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Anyone who is familiar with this skill can make some changes and retouching without departing from the spirit and scope of the present invention. The scope of protection of an invention shall be deemed as defined by the scope of the attached patent application. (Please read the precautions on the back before filling this page)

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X This paper wave scale is applicable to China National Standard (CNS) Λ4 specification (210X297mm)

Claims (1)

A8 B8 0566TWF.DOC / 0 01 C8 D8 VI. Patent application 1. The formation of an aluminum contact plug by selective chemical vapor deposition includes the following steps: forming a semiconductor element on a substrate and forming an insulating layer covering it On the surface, the insulating layer has a contact opening to expose the conductive region of the semiconductor device; subjecting the substrate to a thermal annealing process in a void environment; and using a dimethylethylamine aluminane coordination compound as a precursor At a substrate temperature not higher than 250 ° C, an aluminum layer is formed by chemical vapor deposition, which is selectively deposited on the conductive region in the contact opening without being deposited on the surface of the insulating layer For making an aluminum contact plug. 2. The method as described in item 1 of the patent application scope, wherein the thermal annealing treatment is heat treatment at a temperature of about 450 ° C for about 30 minutes. 3. The method as described in item 1 of the patent application scope, wherein the insulating layer is a thermal oxide layer. 4. The method as described in item 1 of the patent application scope, wherein the insulating layer is a glass layer. (Please read the precautions on the back before filling out this page). 1T Ministry of Economic Affairs Central Standard Falcon Bureau Employee Consumption Cooperation Printed This paper scale is applicable to China National Standard (CNS) Λ4 specification (210Χ 297 mm)