KR101048235B1 - Corrosion measuring device and corrosion measuring method using the same - Google Patents

Abstract

The present invention relates to a corrosion measuring apparatus and a method for measuring corrosion using the same, wherein the Ag / AgCl in a container containing a solution for Chemical Mechanical Polishing (CMP) or Electro Chemical Mechanical Polishing (ECMP) A reference electrode made of a reference electrode, a counter electrode made of platinum gauze, and a working electrode made of a specimen are immersed, and a voltage is applied to the counter electrode, the reference electrode, and the working electrode, respectively. The Triton X-100 used for the citric acid or cleaning solution used in the CMP is a copper layer, a titanium layer, and a copper --- using a corrosion measurement device that includes an electrochemical analyzer that measures the open circuit potential and the degree of corrosion of the specimen. To understand the effects on titanium patterns and to easily apply them to actual processes. will be.

Copper, Titanium, Chemical Corrosion, Galvanic Corrosion, Open Circuit Potential

Description

Corrosion measuring apparatus and corrosion measuring method using the same {APPARATUS FOR MEASURING CORROSION AND METHOD FOR MEASURING CORROSION USING THE SAME}

The present invention relates to a corrosion measurement apparatus and a corrosion measurement method using the same, and to detect defects that may occur in the process of cleaning the surface of the wafer after chemical mechanical polishing of a metal layer or a metal pattern formed on the wafer during a process used in a semiconductor integrated circuit. It is a technique to prevent.

In the semiconductor manufacturing process, multilayer metallization is one of the key technologies in the next generation of ultra-large scale integration (ULSI). Multilayer interconnects at the heart of this technology require planarization of interconnect patterns formed in high aspect ratio sections including contacts, vias, trenches, and other patterns. Reliable formation of such interconnect patterns is critical to achieving ULSI and continuing efforts to increase circuit density and quality at each substrate and die.

In the manufacture of integrated circuits and other electronic devices, a plurality of layers of conductors, semiconductors, and dielectric materials are attached or removed from the surface of the substrate. Thin layers of conductors, semiconductors, and dielectric materials can be attached by a number of attachment methods. Common methods of attachment in recent processes include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma chemical vapor deposition (PECVD), and electrochemical plating (ECP), also known as sputtering.

As the layers of material are continuously attached and removed, the top surface of the substrate becomes non-planar across the surface and hence planarization is required. An example of a non-planar process is the deposition of a copper film in an ECP process, in which, in particular for lines wider than 10 microns, copper topography follows the existing non-planar topography of the wafer surface. . This 'flattening' or 'polishing' of the surface is the process of removing material from the surface of the substrate to form a generally flat planar surface. Planarization is useful for removing undesired surface topography and surface defects such as rough surfaces, aggregated materials, crystal lattice damage, scratches and contaminating layers or materials. Planarization is also useful for forming a pattern on a substrate by providing a uniform surface for metallization and subsequent levels of processing and by removing excess adhesion material used to form the pattern.

Such a planarization process is referred to as chemical mechanical planarization or chemical mechanical polishing (CMP).

CMP uses a chemical composition, typically a slurry or other fluid medium, to selectively remove material from the substrate. In conventional CMP technology, the substrate carrier or polishing head is mounted on the carrier assembly and positioned to contact the polishing pad within the CMP apparatus. The carrier assembly provides a controllable pressure on the substrate, thereby pressing the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. The CMP apparatus causes polishing or frictional motion between the substrate surface and the polishing pad while dispersing the polishing composition, resulting in chemical and mechanical actions and the resulting removal of material from the substrate surface.

Another planarization technique is Electro Chemical Mechanical Polishing (ECMP). ECMP technology removes metal layers or metal patterns from the substrate surface by electrochemical dissolution while simultaneously polishing the substrate with less mechanical wear compared to conventional CMP processes. Electrochemical dissolution is carried out by applying a bias between the cathode and the substrate surface to remove the metal layer or metal pattern from the substrate surface to the surrounding electrolyte. Typically, the bias is applied to the substrate surface in a substrate support device such as a substrate carrier head by a ring of conductive contacts. By placing the substrate in contact with a conventional polishing pad and imparting relative motion therebetween, mechanical wear is achieved.

This ECMP technique is mainly used to polish copper. ECMP technology removes metal layers or metal patterns from the substrate surface by electrochemical dissolution while polishing the substrate with reduced mechanical friction compared to conventional CMP processes.

Removal of the metal layer or metal pattern is performed by applying a bias in the electrolyte solution to oxidize the surface of the metal layer or metal pattern and to polish the oxide layer.

Next, a cleaning process is performed to clean the surfaces contaminated by the polishing process.

In this process, metal layers or metal patterns, in particular copper, are very susceptible to oxidation, so defects are likely to occur. Therefore, research for preventing defects is required, but no clear research results have been shown.

In addition, since there are few studies on defects that may occur in the cleaning process after the electrochemical mechanical polishing process, there is a difficulty in controlling the ECMP process, and thus there is a problem in that the yield or productivity of semiconductors are deteriorated.

According to the present invention, the degree of corrosion generated during the cleaning of the metal layer or the metal pattern formed on the wafer after the chemical mechanical polishing or the electrochemical mechanical polishing process is divided into chemical corrosion and galvanic corrosion, and the results are applied to the actual process to produce efficiency. It is an object of the present invention to provide a corrosion measuring apparatus and a corrosion measuring method using the same.

Corrosion measuring apparatus according to the present invention is a container containing a solution, each of which is immersed in the solution, a reference electrode made of Ag / AgCl, a counter electrode made of platinum gauze and a working electrode made of a specimen (Working electrode) and an electrochemical analyzer for measuring the open circuit potential and the degree of corrosion of the specimen while applying a voltage to the counter electrode, the reference electrode and the working electrode, respectively.

Here, the solution is characterized in that the solution for chemical mechanical polishing (Chemical Mechanical Polishing) or electrochemical mechanical polishing (Electro Chemical Mechanical Polishing), the solution further comprises citric acid or Triton X-100, The specimen is characterized in that the cross-mounted in the order of a silicon substrate with a copper layer, a silicon substrate with a titanium layer and a silicon substrate with a copper-titanium pattern, characterized in that the specimen is 10 × 15 mm in size. The test piece is partitioned into a corrosion reaction part and an electrode connection part, and is characterized in that the liquid silicon is coated on the entire surface except the corrosion reaction part and the electrode connection part.

In addition, the corrosion measurement method according to the present invention comprises the steps of preparing a first specimen, a second specimen and a third specimen having a copper layer, a titanium layer, and a copper-titanium pattern respectively formed on three silicon substrates, and the above-described corrosion measurement Adding citric acid to the solution of the device and measuring the open circuit potential and the degree of corrosion of each of the specimens according to the concentration of the citric acid while cross-mounting the first specimen, the second specimen and the third specimen to the working electrode in order. The Triton X-100 was added to the first measuring step and the solution of the above-mentioned corrosion measuring apparatus, and the concentration of the Triton X-100 was cross-mounted on the working electrode in the order of the first specimen, the second specimen and the third specimen. The second measurement step and the first measurement result and the second measurement result for measuring the open circuit potential and the degree of corrosion of each specimen according to the chemical corrosion (Chemical Corrosion) and galvanic corrosion (Galvanic Corr osion).

Here, the copper-titanium pattern of the third specimen is formed in the form of a titanium barrier layer formed on both side walls of the line-type copper pattern, the total line width including the copper pattern and the titanium barrier layer is formed to a size of 10㎛ And a silver (Ag) electrode layer is further formed on the electrode connection portion of the copper-titanium pattern, and the concentration of citric acid is added at 0.1 to 3 wt% of the total weight of the solution. The concentration of the Triton X-100 is characterized by setting the sections below 1CMC (Critical Micelle Concentration), the sections 1 to 2 CMC and the sections above 2 CMC, respectively.

In addition, the working electrode specimen for the corrosion measurement apparatus according to the present invention includes a metal layer or a metal pattern formed on the silicon substrate, and the metal layer or the metal pattern is exposed, the exposed area is a corrosion reaction portion and the electrode connection, respectively It characterized in that it comprises a liquid silicon coated on the entire surface of the silicon substrate to be partitioned.

The metal layer or the metal pattern may be formed of copper or titanium, and the silver (Ag) electrode layer may be further formed on the metal layer or the metal pattern of the electrode connection part.

The electrochemical corrosion measuring apparatus according to the present invention enables to identify various electrochemical reactions that may occur during the cleaning process after the chemical mechanical polishing or the electrochemical mechanical polishing process in the semiconductor manufacturing process. Therefore, by analyzing the corrosion degree measurement results according to the present invention divided into chemical reactions and galvanic reactions and applying them to the actual process, it is possible to improve the production yield and productivity.

The present invention forms a copper layer, a titanium layer, and a copper-titanium pattern on a wafer, followed by a chemical mechanical polishing (CMP) process or an electrochemical mechanical polishing (ECMP) process. This process consists of measuring chemical and galvanic corrosion on the copper and titanium surfaces during subsequent cleaning.

Hereinafter, the corrosion measuring apparatus and the corrosion measuring method using the same according to the present invention will be described in detail.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

As described above, in the present invention, a total of three specimens are manufactured, and a three-pole electrochemical corrosion measuring apparatus is manufactured.

1 is a plan view showing a first specimen according to the present invention, Figure 2 is a plan view showing a second specimen according to the present invention.

1 illustrates a first specimen 150 having a copper layer 100 formed on a wafer (not shown), and FIG. 2 illustrates a second specimen 250 having a titanium layer 200 formed on a wafer.

Thus, the silicon wafer deposited with copper and titanium is cut out to a size of 10 x 15 mm. And all other parts except the part to be connected to the electrode and the portion to cause the electrochemical reaction into the solution is coated with liquid silicon (110, 210), respectively, which is cured at room temperature. At this time, it is preferable that the width of the electrode connection portion to be connected to the electrode is about 3 × 7 mm, and the corrosion reaction portion is coated with liquid silicon (110, 210) so as to have a size of 7 × 7 mm, respectively. Here, since the liquid silicon (110, 210) is present in a solid state at room temperature, the corrosion of the coating portion does not appear. Therefore, if the size according to the present invention is maintained, only a change in the predetermined size can be easily measured, thereby enabling quantitative analysis.

3 is a wafer layout diagram for manufacturing a third specimen according to the present invention.

3 is a layout illustrating a line to be cut to a size of 10 × 15 mm, which is the specimen size after forming a copper-titanium pattern on the wafer 300.

4A to 4F are cross-sectional views illustrating a method of manufacturing a third specimen according to the present invention.

Referring to FIG. 4A, a damascene process is used to form a copper-titanium pattern on the silicon substrate 400. To this end, oxide layers SiO ₂ and 410 are formed on the silicon substrate 400. At this time, the oxide film 410 is preferably formed to a thickness of 1㎛.

Referring to FIG. 4B, the region where the copper-titanium pattern is to be formed is partially etched by using a line-type mask on the oxide layer 410.

Referring to FIG. 4C, an oxide pattern 420 having a trench is formed by etching some of the etched regions to the height of the copper-titanium pattern to be formed.

Referring to FIG. 4D, the titanium layer 430 is formed on the surface of the oxide layer pattern 420 including the trench, and the copper seed layer 440 is formed on the titanium layer 430. At this time, the titanium layer 430 is formed to a thickness of 500 kPa, and the copper seed layer 440 is preferably formed to a thickness of 1000 kPa.

Referring to FIG. 4E, a copper layer 450 is deposited on the copper seed layer 440 to completely fill the trench. At this time, the copper layer 450 is preferably formed using an electroplating process.

Referring to FIG. 4F, a process of planarizing the upper portion of the copper layer 450 is performed to expose the oxide layer pattern 420. At this time, it is preferable that the planarization process uses a CMP process or an ECMP process.

In this process, a copper-titanium pattern 460 including a titanium pattern 435 and a copper pattern 455 is formed between the oxide layer patterns 420. At this time, the copper-titanium pattern 460 is preferably 10 × 15,000 ㎛.

Next, the silicon substrate 400 is cut according to the layout of FIG. 3 to prepare a specimen for measuring the corrosion reaction.

5 is a plan view showing a third specimen according to the present invention.

5 is a third specimen 500 having a copper-titanium pattern 460 between the silicon oxide layer patterns 420. It is preferable to form the same size as the first and second specimens, and all regions except the electrode connection part and the corrosion reaction part are coated with the liquid silicon 470.

In addition, it is preferable to form a silver electrode 480 in the electrode connection part to prevent the problem of poor electrode connection due to the oxide film pattern 420.

6 is a schematic view showing a corrosion measurement apparatus according to the present invention.

Referring to FIG. 6, a three-electrode electrochemical corrosion measurement apparatus is shown. A solution 640 that can be used in CMP or ECMP is contained in a container 600, and Ag / AgCl is used as a reference electrode 610. The platinum gauze (Pt Mesh) is used as a counter electrode (630). Each of the specimens cross-mounted in the order of the silicon substrate having the copper layer, the silicon substrate having the titanium layer, and the silicon substrate having the copper-titanium pattern is a working electrode 620.

Next, the container 600 is manufactured in a fixed form so as not to move and the area in which the platinum electrode and the specimen are immersed in the solution is always kept constant. For each working electrode specimen, the area that is not required for the reaction is liquid silicone. It is preferably coated so as not to react. By adjusting the size of the corrosion reaction zone in this way, the quantitative analysis can be easily performed in a subsequent process.

 Next, an electrochemical analyzer 650 for measuring the open circuit potential and the degree of corrosion of the specimen while applying a voltage to the reference electrode 610, the working electrode 620, and the counter electrode 630 is provided. Here, each working electrode 620 is cross-mounted in the order of a silicon substrate having a copper layer, a silicon substrate having a titanium layer, and a silicon substrate having a copper-titanium pattern, and the electrochemical analyzer 650 is provided with the electrodes 610, respectively. The potential difference generated between the electrodes 610, 620, and 630 is measured while applying a voltage to the 620 and 630. As the potential difference increases, the degree of corrosion increases, so record and compare these results so that the analysis can be performed.

At this time, the voltage is preferably added to -1V to 1V. The electrochemical analyzer 650 measures a current that changes while applying a voltage, takes a log value thereof, and outputs a graph of current density and potential. Therefore, the degree of corrosion can be calculated using the slope of the graph output in this way. Corrosion degree can be expressed by the rate of corrosion, and the rate of corrosion can be obtained using the Tafel's equation, but the detailed calculation process is omitted here. .

7 is a graph of open circuit potential between copper, titanium and two metals with increasing citric acid concentration.

FIG. 7 is a graph illustrating an open circuit potential of copper (Cu), titanium (Ti) and two metals (Difference Between) with increasing citric acid concentration (wt%). As the concentration of citric acid increases, the open-circuit potential of copper and titanium also increases.

8 is a graph showing the degree of corrosion between copper, titanium, copper-titanium patterns and copper and copper-titanium patterns with increasing citric acid concentration.

FIG. 8 is a graph illustrating corrosion rates of copper (Cu), titanium (Ti), and copper-titanium patterns (Pattern) with increasing citric acid concentration (wt%) as a first measurement step. will be. Titanium (Ti) hardly reacts regardless of concentration, whereas copper (Cu) and copper-titanium pattern (Pattern) tend to increase the corrosion rate as the concentration of citric acid increases. At this time, the degree of corrosion is about the same area, and the difference between Cu and Pattern between the copper and the copper-titanium pattern may be regarded as the effect of galvanic corrosion.

Comparing the results of FIG. 8, it can be seen that as the concentration of citric acid increases, the degree of chemical corrosion increases in both copper (Cu) and copper-titanium pattern (Pattern), and the opening of copper (Cu) and titanium (Ti) in FIG. As the furnace potential increased, galvanic corrosion also increased with increasing concentration.

9 is a graph of open circuit potential between copper, titanium and two metals with increasing Triton X-100 concentration.

Referring to FIG. 9, a graph of the open circuit potential of copper (Cu), titanium (Ti) and two metals (Difference between Ti and Cu) with increasing Triton X-100 concentration As a result, Triton X-100 has little effect on copper (Cu) and has a big effect on titanium (Ti).

10 is a graph of corrosion degree between copper, titanium, copper-titanium pattern and copper and copper-titanium pattern with increasing Triton X-100 concentration.

Referring to FIG. 10, the corrosion rate of copper (Cu), titanium (Ti), and copper-titanium pattern (Pattern) according to an increase of Triton X-100 concentration as a second measurement step (Corrosion Rate) A graph is shown. Unlike the results of FIG. 9, it can be seen that the copper-titanium pattern (Pattern) has a shape similar to that of the graph of titanium (Ti). This means that the area of titanium (Ti) is very small compared to copper (Cu) but is more severely corroded than copper, affecting the overall tendency of the copper-titanium pattern (Pattern).

This is due to the tendency of metals with lower open circuit potential to ionize more than the metals in contact, and Triton X-100 promotes this galvanic corrosion.

11 to 13 are schematic views showing the effect of Triton X-100 concentration on the degree of corrosion.

Figure 11 shows the effect of Triton X-100 on the degree of corrosion at Triton X-100 concentration below 1 CMC (critical micelle concentration), Figure 12 between 1 CMC and 2 CMC, and Figure 13 above 2 CMC. It is shown as.

Since Triton X-100 730 of FIG. 11 exists only as a monomer, it is easily attached to the surface of copper 720 and titanium 710 to prevent corrosion. Triton X-100 730 is hardly attached to the other oxide film 700. When the monomers are combined, the Triton X-100 730 is hardly adhered to the metal surface, and floats in the solution.

The Triton X-100 730 of FIG. 12 shows a surfactant present as a dimer, which also serves to prevent corrosion in copper 720, whereas corrosion is inferior to titanium 710. It can be seen that it does not play a role to prevent the problem.

In Figure 13, the micelle structures of the Triton X-100 (730), which form a solid spherical shape, are no longer attached to the metal surface and are moving in the solution.

As such, since the occurrence of corrosion is increased when the amount of the Triton X-100 added exceeds 2CMC, it is preferable to adjust the Triton X-100 concentration in the cleaning process to 2CMC or less.

14 and 15 are planar photographs showing the degree of corrosion according to whether Triton X-100 is included.

14 is a photograph when Triton X-100 is not included in the cleaning solution, and FIG. 15 is a photograph when Triton X-100 is not included.

The pattern shown here is a photograph taken after the above-described copper-titanium pattern is corroded. FIG. 14 shows a chemical corrosion effect, and FIG. 15 shows a galvanic corrosion effect. It can be seen that the Triton X-100 promoted galvanic corrosion by clearly showing damage in the pattern of FIG. 15.

As described above, as a first measurement step, the open circuit potential difference between the two metals becomes larger as a result of the open circuit potential measurement while increasing the concentration of citric acid in the solution for CMP. As a result, the degree of galvanic corrosion acceleration can be confirmed by subtracting chemical corrosion from the total corrosion.

Next, as a second measurement step, the effect of Triton X-100, a nonionic surfactant, on the specimen is investigated. Open-circuit measurement results show that copper decreases slightly with increasing surfactant, while titanium increases significantly. Each specimen changes its degree of corrosion depending on the concentration of the surfactant and its mechanism can be explained in terms of the change in the micelle structure with concentration. Finally, by comparing and analyzing the difference in corrosion of copper with or without Triton X-100 through optical micrographs and applying it to the actual process, it is possible to accurately control the CMP or ECMP process and increase the production efficiency. .

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments and can be manufactured in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1 is a plan view showing a first specimen according to the present invention.

2 is a plan view showing a second specimen according to the present invention.

Figure 3 is a wafer layout for producing a third specimen according to the present invention.

4A to 4F are cross-sectional views illustrating a method of manufacturing a third specimen according to the present invention.

5 is a plan view showing a third specimen according to the present invention.

6 is a schematic view showing a corrosion measurement apparatus according to the present invention.

7 is a graph of open circuit potential between copper, titanium and two metals with increasing citric acid concentration.

8 is a graph of corrosion degree between copper, titanium, copper-titanium pattern and copper and copper-titanium pattern with increasing citric acid concentration.

9 is a graph of open circuit potential between copper, titanium and two metals with increasing Triton X-100 concentration.

10 is a graph of corrosion degree between copper, titanium, copper-titanium pattern and copper and copper-titanium pattern with increasing Triton X-100 concentration.

11 to 13 are schematic views showing the effect of Triton X-100 concentration on the degree of corrosion.

14 and 15 are planar photographs showing the degree of corrosion in accordance with the inclusion of Triton X-100.

Claims (13)

A container containing a solution comprising citric acid or Triton X-100; A working electrode immersed in the solution and made of Ag / AgCl, a reference electrode made of Ag / AgCl, a counter electrode made of platinum gauze, and a specimen; And Including an electrochemical analyzer for measuring the open circuit potential and the corrosion degree of the specimen while applying a voltage to the counter electrode, the reference electrode and the working electrode, respectively, The specimen is divided into a corrosion reaction unit and an electrode connection unit, the liquid crystal coating on the front surface except the corrosion reaction unit and the electrode connection; Corrosion measuring apparatus characterized in that the. The method of claim 1, The solution is a corrosion measuring apparatus, characterized in that the solution for chemical mechanical polishing (Chemical Mechanical Polishing) or electrochemical mechanical polishing (Electro Chemical Mechanical Polishing). delete The method of claim 1, The specimen is And a silicon substrate having a copper layer, a silicon substrate having a titanium layer, and a silicon substrate having a copper-titanium pattern. delete (a) preparing a first specimen, a second specimen, and a third specimen, each having a copper layer, a titanium layer, and a copper-titanium pattern formed on three silicon substrates; (b) adding citric acid to the solution of the corrosion measuring apparatus according to claim 1, and cross-mounting the working electrode in the order of the first specimen, the second specimen and the third specimen of step (a) according to the concentration of the citric acid; A first measuring step of measuring an open circuit potential and a degree of corrosion of each specimen; (c) Triton X-100 is added to the solution of the corrosion measuring apparatus according to claim 1, and the Triton is cross-mounted in the order of the first specimen, the second specimen and the third specimen of step (a) to the working electrode. A second measurement step of measuring an open circuit potential and a degree of corrosion of each specimen according to the concentration of X-100; And (d) comparing the results of the first measurement step with the results of the second measurement step to measure chemical corrosion and galvanic corrosion. The method of claim 6, The copper-titanium pattern of the third specimen is formed in the form of a titanium barrier layer formed on both side walls of the line-type copper pattern, the total line width including the copper pattern and the titanium barrier layer is formed to a size of 10㎛. Corrosion measurement method. The method of claim 7, wherein Corrosion measuring method, characterized in that further forming a silver (Ag) electrode layer on the electrode connection portion of the copper-titanium pattern. The method of claim 6, The concentration of the citric acid is a corrosion measurement method, characterized in that added to 0.1 to 3 wt% of the total weight of the solution. The method of claim 6, The concentration of the Triton X-100 is measured by setting the section below 1CMC (Critical Micelle Concentration), 1 ~ 2 CMC section and more than 2 CMC section, respectively. A test piece used in the corrosion measuring apparatus of claim 1, comprising a metal layer or a metal pattern formed on an upper surface of a silicon substrate, and exposing the metal layer or the metal pattern, wherein the exposed area is divided into a corrosion reaction part and an electrode connection part, respectively. Work electrode specimen for a corrosion measurement device comprising a liquid silicon coated on the entire surface of the silicon substrate. The method of claim 11, The metal layer or metal pattern is a working electrode specimen for a corrosion measurement device, characterized in that formed of copper or titanium. The method of claim 11, The working electrode specimen for corrosion measurement apparatus, characterized in that the silver (Ag) electrode layer is further formed on the metal layer or the metal pattern of the electrode connection portion.

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