Method for solving the corrosion residue of on-chip thin film resistance tungsten titanium

Abstract

The application discloses a method for solving the corrosion residue of on-chip thin film resistance tungsten titanium, and belongs to the field of semiconductor chip manufacturing. The method first etches most of tungsten titanium on a prepared silicon wafer with a metal and a thin film resistance interconnection by using hydrogen peroxide, which is equivalent to main etching. The thin film resistance has a tungsten titanium barrier layer. Then, wet organic cleaning is performed to remove the reaction byproducts on the surface of the remaining tungsten titanium. Finally, hydrogen peroxide is used to remove the remaining tungsten titanium, which is equivalent to over-etching. Compared with the prior art, the method has strong operability, and a conventional wet acid tank can meet the process requirements. The cost is relatively low, the chemical etching liquid and special gas used are common materials in semiconductor integrated circuit production lines, and the method has a wide application prospect and can be used to corrode the chromium silicon thin film resistance metal interconnection layer in the manufacturing process of an analog integrated circuit.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor chip manufacturing and relates to a method for solving the problem of tungsten-titanium corrosion residue in on-chip thin-film resistors. Background Technology

[0002] In today's era of rapid technological advancement, semiconductor integrated circuits undoubtedly occupy a central position in electronic technology, continuously driving innovation and progress in numerous fields. From smartphones to high-performance computers, from smart cars to industrial automation control systems, the performance and precision of semiconductor integrated circuits directly determine the overall operating efficiency and functional performance of these complex electronic devices.

[0003] With the continuous expansion and diversification of application scenarios, the requirements for resistive components in circuit systems are also undergoing profound changes. Traditional diffused resistors and injection resistors once played an important role in early semiconductor circuits, but due to inherent limitations in resistance accuracy, temperature stability, and compatibility with other advanced processes, they are no longer able to meet the increasingly complex and precise design requirements of modern electronic products. For example, in audio processing circuits, the accurate amplification and reproduction of weak audio signals requires resistors with extremely high precision and extremely low noise characteristics; in high-precision sensor interface circuits, the stability of the resistor directly affects the accuracy and reliability of sensor measurement data. Against this backdrop, high-precision thin-film resistors have emerged and have demonstrated unique advantages and broad application prospects in the field of analog integrated circuits.

[0004] Thin-film resistors, with their unique manufacturing process and material structure, enable more precise resistance value control, typically achieving higher accuracy levels than traditional resistors, with resistance error controlled within an extremely small range. Simultaneously, thin-film resistors exhibit excellent temperature stability, with relatively small resistance changes under different operating temperatures, ensuring stable circuit operation under various conditions. In the signal processing chain of analog integrated circuits, high-precision thin-film resistors effectively reduce signal distortion and improve signal transmission fidelity, providing a solid foundation for high-quality audio, video, and various sensor signal processing.

[0005] In the manufacturing process of thin-film resistors, a tungsten-titanium alloy barrier layer plays an indispensable role. This barrier layer is uniformly deposited onto the surface of the thin-film resistor through a precise deposition process. Its primary function is to act as a robust physical barrier, effectively preventing the intrusion of impurities, moisture, and other substances from the external environment that could damage the thin-film resistor. During semiconductor manufacturing, wafers undergo numerous complex processes, including photolithography, etching, ion implantation, and chemical vapor deposition, all of which carry the risk of introducing contaminants to varying degrees. The tungsten-titanium alloy barrier layer provides reliable protection for the thin-film resistor in these complex process environments, ensuring that its internal structure and electrical performance remain unaffected. Furthermore, this barrier layer enhances the adhesion between the thin-film resistor and the metal interconnect layer, guaranteeing a stable and reliable electrical connection during the metal-to-thin-film resistor interconnection process and preventing malfunctions such as poor contact or signal transmission interruptions caused by interface problems.

[0006] However, a critical process step following the interconnection of the metal and thin-film resistors—removing the tungsten-titanium barrier layer from the surface of the thin-film resistor—has encountered a thorny technical challenge. Conventional methods use etchants to remove the tungsten-titanium barrier layer. However, the actual results of etching this layer are unsatisfactory. After the etchant reacts with the tungsten-titanium alloy, a noticeable white substance remains on the surface of the thin-film resistor, which analysis confirms as incompletely etched tungsten-titanium components. These residual tungsten-titanium components are not in the form of uniform, fine particles, but rather exhibit a relatively concentrated and irregular distribution, with a coverage area and thickness sufficient to significantly affect the subsequent performance of the thin-film resistor. More seriously, a series of complex reaction byproducts are also attached to the surface of these white tungsten-titanium residues. These byproducts are generated during the reaction between the etchant and the tungsten-titanium due to incomplete chemical reactions and the possible participation of other impurities. Their chemical composition and structure are complex and diverse, possibly containing incompletely oxidized tungsten-titanium compounds, intermediate products from the decomposition of the etchant, and new substances formed by combining with trace impurities in the surrounding environment. These reaction byproducts not only further deteriorate the cleanliness and uniformity of the thin-film resistor surface, but also, due to their unknown electrical properties, are highly likely to introduce additional electrical interference during subsequent circuit operation.

[0007] To address this issue, technicians attempted traditional etching processes. These processes typically involve adding other chemical reagents to the existing etching system to enhance the etching effect, alter the chemical equilibrium of the reaction, and promote further dissolution or decomposition of residual substances. However, in treating tungsten-titanium residues and their surface reaction byproducts, the etching process failed to achieve its intended effect. Despite multiple rounds of optimization and adjustment of the type and concentration of the etching reagents and the processing conditions, effective removal of tungsten-titanium residues remained unsuccessful. This predicament prevented the surface condition of the thin-film resistors from meeting the standards required for subsequent processes, thus creating a chain reaction throughout the entire semiconductor device manufacturing process. Therefore, effectively addressing the issue of tungsten-titanium residues on the surface of thin-film resistors and related problems has become a critical technological bottleneck that urgently needs to be overcome in the field of semiconductor integrated circuit manufacturing technology. This is of paramount importance for promoting technological progress and improving product quality across the entire industry. Summary of the Invention

[0008] The purpose of this invention is to solve the problem of incomplete tungsten-titanium residue on the surface of thin-film resistors in the prior art, and to provide a method for solving the problem of tungsten-titanium corrosion residue on on-chip thin-film resistors.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] This invention proposes a method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors, comprising:

[0011] The first etching is performed on the silicon wafer on which the prepared metal and thin-film resistor are interconnected; wherein the thin-film resistor has a tungsten titanium barrier layer;

[0012] The silicon wafer etched for the first time is cleaned to remove the reaction byproducts on the surface of the tungsten titanium barrier layer, resulting in a pretreated silicon wafer.

[0013] A second etching process is performed on the pretreated silicon wafer to remove residual tungsten titanium in the thin-film resistor.

[0014] Preferably, the prepared silicon wafer with metal-thin film resistor interconnects is obtained by using high-pressure water rinsing or organic solvent cleaning.

[0015] Preferably, the first etching on the prepared silicon wafer with metal-thin-film resistor interconnects specifically involves:

[0016] The silicon wafer is etched for the first time using hydrogen peroxide.

[0017] Preferably, the amount of hydrogen peroxide used is determined according to the size of the etching tank.

[0018] Preferably, the temperature for the first etching with hydrogen peroxide is 40℃~80℃, the volume of hydrogen peroxide is 16L~32L, and the etching time is 1min30s~2min30s; the etching thickness range of tungsten-titanium is...

[0019] Preferably, the cleaning of the silicon wafer after the first etching specifically involves:

[0020] Organic cleaning solvents were used to clean the silicon wafers after the first etching.

[0021] Preferably, the temperature for cleaning with organic cleaning solvent is 50℃~80℃, and the cleaning time is 25min~35min.

[0022] Preferably, the second etching of the pretreated silicon wafer specifically involves:

[0023] The pretreated silicon wafer is etched a second time using hydrogen peroxide.

[0024] Preferably, the temperature for the second etching with hydrogen peroxide is 40℃~80℃, the volume of hydrogen peroxide is 16L~32L, and the etching time with hydrogen peroxide is 30s~1min30s; the thickness range of the etched tungsten-titanium is...

[0025] Preferably, after the second etching, the presence or absence of tungsten-titanium residue is determined by testing whether the error between the thin film resistance value and the actual design value is less than 3%; if the error between the thin film resistance value and the actual design value is less than or equal to 3%, there is no tungsten-titanium residue; if the error between the thin film resistance value and the actual design value is greater than 3%, there is tungsten-titanium residue.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention proposes a method to address tungsten-titanium corrosion residue on on-chip thin-film resistors. Precise etching can control the connection between the metal and the thin-film resistor, reducing the risk of unnecessary short circuits or open circuits and optimizing the current transport path. For thin-film resistors with a tungsten-titanium barrier layer, this barrier layer itself prevents metal atoms from diffusing into the resistive layer and affecting the electrical performance of the resistor. The cleaning process removes reaction byproducts from the surface of the tungsten-titanium barrier layer. These byproducts may introduce additional impurities, affecting the conductivity and stability of the resistor. The cleaning step, as an intermediate step, ensures that each process step is performed on a relatively clean surface. This facilitates better compatibility of subsequent process steps with the current etching process and reduces process failures or performance degradation caused by surface contamination. A second etching process removes tungsten-titanium residue on the thin-film resistor. Tungsten-titanium residue may cause uneven local electric field distribution, increasing the risk of leakage. Removing these residues makes the resistor more stable under operating voltage, reduces leakage current, and thus improves the power efficiency and reliability of the entire circuit. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a diagram showing the residual tungsten-titanium after a single corrosion process according to the present invention.

[0030] Figure 2 This is a diagram showing the results of the multi-stage corrosion process without tungsten and titanium residue, as described in this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] The present invention will now be described in further detail with reference to the accompanying drawings:

[0037] This invention proposes a method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors, comprising the following steps:

[0038] Step 1: Perform the first etching using hydrogen peroxide on the prepared silicon wafer with the metal and thin-film resistor interconnects, such as... Figure 1 and Figure 2 As shown, the beige represents aluminum wire, the gray represents the substrate, and the light green represents the resistor. Figure 1 At the location circled in red, where the resistor overlaps with the aluminum wire, there are strip-shaped titanium-tungsten residues. Most of the tungsten-titanium was removed during the first etching process (80% tungsten-titanium was etched away). The thin-film resistor contains a tungsten-titanium barrier layer with a thickness ranging from [missing information].

[0039] In this process, high-pressure water jets or organic solvents are used to obtain the prepared silicon wafers with metal-thin film resistor interconnects, ensuring that the silicon wafer surface is clean and free of impurities.

[0040] The hydrogen peroxide used ranges from 16L to 32L, the reaction temperature from 40℃ to 80℃, and the first etching time with hydrogen peroxide is 1 min 30 s to 2 min 30 s; the etching thickness range for tungsten and titanium is as follows.

[0041] Step 2: Clean the silicon wafer after the first etching to remove the remaining reaction byproducts on the tungsten-titanium surface, and obtain the pretreated silicon wafer.

[0042] The silicon wafers etched for the first time are cleaned with organic cleaning solvents, with a volume of 16L to 32L. SYS9070, SYS700, EKC270, and other organic cleaning solutions can be used. Whether or not ultrasonic treatment is added depends on the specific conditions of the machine.

[0043] The temperature for cleaning with organic cleaning solvents is 50℃~80℃, and the cleaning time is 25min~35min.

[0044] Step 3: Use hydrogen peroxide to perform a second etching on the pretreated silicon wafer to remove the remaining tungsten titanium (etch away the remaining 20% ​​of tungsten titanium).

[0045] The hydrogen peroxide used ranges from 16L to 32L, the reaction temperature from 40℃ to 80℃, and the time for the second etching with hydrogen peroxide is from 30s to 1min30s; the etching thickness range for tungsten-titanium is...

[0046] Step 4: The presence of tungsten-titanium residue can be determined by microscopic examination or by testing whether the film resistance value deviates from the actual design value (whether the error is less than 3%). If the error between the film resistance value and the actual design value is less than or equal to 3%, there is no tungsten-titanium residue; if the error is greater than 3%, tungsten-titanium residue is present. Figure 2 The image shows the location where the resistor overlaps with the aluminum wire and the result of no titanium or tungsten residue on the resistor.

[0047] Using hydrogen peroxide for the first etching step has the following advantages:

[0048] 1) Hydrogen peroxide has a certain oxidizing property, and during the first etching step, it can selectively react with the tungsten-titanium barrier layer. Compared to the main material of the silicon wafer and thin-film resistor, hydrogen peroxide preferentially acts on the barrier layer. This selectivity helps to accurately remove part of the barrier layer material in the initial etching stage, while minimizing damage to the underlying thin-film resistor and silicon wafer. For example, in the complex structure of integrated circuits, there may be other sensitive electronic components or materials around the thin-film resistor. The selective etching of hydrogen peroxide ensures that these surrounding components are unaffected during the initial treatment of the barrier layer, maintaining the integrity of the entire structure.

[0049] Because hydrogen peroxide has relatively mild chemical properties, it can achieve relatively fine etching when etching parameters (such as concentration, temperature, and time) are well controlled. This is crucial for high-precision thin-film resistor applications, as even minute structural changes in analog integrated circuits can affect resistor performance. Using hydrogen peroxide for the initial etching provides a good starting point for subsequent, more precise processing.

[0050] 2) In addition to removing some of the barrier layer material during the etching process, hydrogen peroxide can also clean the surface. It can oxidize and decompose some organic contaminants or slight oxide layers on the surface of the barrier layer. If these contaminants are not removed, they may affect the reaction in subsequent processes or introduce additional impurities.

[0051] The use of hydrogen peroxide for the second etching has the following advantages:

[0052] 1) After the first etching and cleaning, a small amount of tungsten-titanium residue will still remain. Hydrogen peroxide continues to exert its oxidizing properties during the second etching process, further corroding these residues. It can chemically react with the residual tungsten-titanium, converting it into soluble compounds or volatile substances, thereby effectively reducing the amount of tungsten-titanium residue on the surface of the thin-film resistor. This step-by-step removal method helps to more precisely control the material composition of the thin-film resistor surface, ensuring that the final resistor surface meets design requirements.

[0053] Hydrogen peroxide can be used to target newly exposed tungsten-titanium materials after the first etching process, or tungsten-titanium-reaction byproduct complexes remaining due to incomplete cleaning. It decomposes these substances through chemical reactions; for example, for some tungsten-titanium-oxide complexes, hydrogen peroxide can further oxidize the oxides, causing the entire complex structure to disintegrate, thereby removing these stubborn residues.

[0054] 2) A second etching with hydrogen peroxide can make the surface of the thin-film resistor smoother and more even. Residual tungsten and titanium can cause surface unevenness, which can affect subsequent processes (such as metal deposition) or electrical properties (such as uneven electric field distribution). A second etching with hydrogen peroxide can reduce this surface irregularity and improve the surface quality of the thin-film resistor.

[0055] Example 1

[0056] Step 1: Apply the prepared metal and thin-film resistor (with tungsten-titanium barrier layer) ) 80% of the tungsten titanium was etched away using hydrogen peroxide on the interconnected silicon wafers, with a thickness of (equivalent to main etching);

[0057] The silicon wafers were pretreated by cleaning with organic solvents to ensure that the surface of the silicon wafers was clean and free of impurities. The hydrogen peroxide used was pure hydrogen peroxide, and the amount of hydrogen peroxide used was 16L. The etching temperature of the hydrogen peroxide was 40℃ and the etching time was 1 minute and 30 seconds.

[0058] Step 2: Use SYS9070 cleaning solution to clean the silicon wafer after the first etching to remove the remaining reaction byproducts on the tungsten-titanium surface and obtain the pretreated silicon wafer.

[0059] The cleaning solution is a pure solution, the volume of the cleaning solution is 16L, the cleaning temperature is 50℃, and the cleaning time is 25min.

[0060] Step 3: Use hydrogen peroxide to remove the remaining 20% ​​of tungsten titanium, thickness (equivalent to over-etching);

[0061] The hydrogen peroxide used was pure hydrogen peroxide, the amount of hydrogen peroxide used was 16L, the etching temperature was 40℃, and the etching time was 30s.

[0062] Step 4: Check whether there is any tungsten or titanium residue by examining the film resistance value under a microscope or by testing whether there is an error between the film resistance value and the actual design value (an error of less than or equal to 3% can be used to determine whether there is any tungsten or titanium residue).

[0063] Example 2

[0064] Step 1: Apply the prepared metal and thin-film resistor (with tungsten-titanium barrier layer) ) 80% of the tungsten titanium was etched away using hydrogen peroxide on the interconnected silicon wafers, with a thickness of (equivalent to main etching);

[0065] The silicon wafers were pretreated by cleaning with organic solvents to ensure that the surface of the silicon wafers was clean and free of impurities. The hydrogen peroxide used was pure hydrogen peroxide, and the amount of hydrogen peroxide used was 24L. The etching temperature of the hydrogen peroxide was 60℃ and the etching time was 2min.

[0066] Step 2: Use SYS9070 cleaning solution to clean the silicon wafer after the first etching to remove the remaining reaction byproducts on the tungsten-titanium surface and obtain the pretreated silicon wafer.

[0067] The cleaning solution is a pure solution, the volume of the cleaning solution is 24L, the cleaning temperature is 65℃, and the cleaning time is 30min.

[0068] Step 3: Use hydrogen peroxide to remove the remaining 20% ​​of tungsten titanium, thickness (equivalent to over-etching);

[0069] The hydrogen peroxide used was pure hydrogen peroxide, with a volume of 24L. The etching temperature was 60℃, and the etching time was 1 minute.

[0070] Step 4: Check whether there is any tungsten or titanium residue by examining the film resistance value under a microscope or by testing whether there is an error between the film resistance value and the actual design value (an error of less than or equal to 3% can be used to determine whether there is any tungsten or titanium residue).

[0071] Example 3

[0072] Step 1: Apply the prepared metal and thin-film resistor (with tungsten-titanium barrier layer) ) 80% of the tungsten titanium was etched away using hydrogen peroxide on the interconnected silicon wafers, with a thickness of (equivalent to main etching);

[0073] The process involves pre-treating the silicon wafers with organic solvents to ensure a clean and impurity-free surface. The hydrogen peroxide used is pure hydrogen peroxide, with a volume of 32L. The etching temperature is 80℃, and the etching time is 2 minutes and 30 seconds.

[0074] Step 2: Use SYS9070 cleaning solution to clean the silicon wafer after the first etching to remove the remaining reaction byproducts on the tungsten-titanium surface and obtain the pretreated silicon wafer.

[0075] The cleaning solution is a pure solution, the volume of the cleaning solution is 32L, the cleaning temperature is 80℃, and the cleaning time is 35min.

[0076] Step 3: Use hydrogen peroxide to remove the remaining 20% ​​of tungsten titanium, thickness (equivalent to over-etching);

[0077] The hydrogen peroxide used was pure hydrogen peroxide, the amount of hydrogen peroxide used was 32L, the etching temperature was 80℃, and the etching time was 1 minute and 30 seconds.

[0078] Step 4: Check whether there is any tungsten or titanium residue by examining the film resistance value under a microscope or by testing whether there is an error between the film resistance value and the actual design value (an error of less than or equal to 3% can be used to determine whether there is any tungsten or titanium residue).

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors, characterized in that, include: The silicon wafer with the metal and thin-film resistor interconnects is first etched with hydrogen peroxide; wherein the thin-film resistor has a tungsten titanium barrier layer; the first etching removes part of the tungsten titanium barrier layer; the silicon wafer with the first etching is cleaned with an organic cleaning solvent to remove the reaction byproducts on the surface of the tungsten titanium barrier layer, and a pretreated silicon wafer is obtained. The pretreated silicon wafer is etched a second time using hydrogen peroxide to remove the tungsten-titanium residue from the thin-film resistors on the silicon wafer.

2. The method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors according to claim 1, characterized in that, The prepared silicon wafer with metal-thin film resistor interconnects is obtained by high-pressure water rinsing or cleaning with organic solvents.

3. The method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors according to claim 1, characterized in that, The amount of hydrogen peroxide used depends on the size of the etching tank.

4. The method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors according to claim 1, characterized in that, The temperature for the first etching with hydrogen peroxide is 40℃~80℃, the volume of hydrogen peroxide is 16L~32L, and the time for the first etching with hydrogen peroxide is 1min30s~2min30s. The thickness range of etched tungsten titanium is 800 Å to 1600 Å.

5. The method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors according to claim 1, characterized in that, The temperature for cleaning with organic cleaning solvents is 50℃~80℃, and the cleaning time is 25min~35min.

6. The method for resolving tungsten-titanium corrosion residue in on-chip thin-film resistors according to claim 1, characterized in that, The temperature for the second etching with hydrogen peroxide is 40℃~80℃, the volume of hydrogen peroxide is 16L~32L, and the time for the second etching with hydrogen peroxide is 30s~1min30s. The thickness range of etched tungsten titanium is 200 Å to 400 Å.

7. The method for resolving tungsten-titanium corrosion residues in on-chip thin-film resistors according to claim 1, characterized in that, After the second etching, the presence of tungsten-titanium residue is determined by testing whether the error between the thin film resistance value and the actual design value is less than 3%. If the error between the resistance value of the thin-film resistor and the actual design value is less than or equal to 3%, then there is no tungsten-titanium residue. If the resistance value of the thin-film resistor deviates from the actual design value by more than 3%, then tungsten-titanium residue is present.

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