Alumina etching solution as well as preparation method and application thereof
By using a combination of phosphate etchant, pH buffer, surfactant and thiool corrosion inhibitor in the alumina etchant, fluorine-free etching is achieved, solving the problems of alumina removal and material corrosion, and providing High-efficiency and stable semiconductor wafer wet etching effect.
Patent Information
- Application Number
- CN202411211781.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-06
AI Technical Summary
During the etching process, existing alumina etchants are prone to corrosion on non-metallic low-k materials such as SiO2 and SiN, and it is difficult to completely remove the alumina barrier layer, resulting in chip short circuit or damage.
Alumina etching liquid is adopted, including amine phosphate etching agent, pH buffer, surfactant and thiool corrosion inhibitor. Through the coordinated cooperation of components, fluorine-free etching is achieved, and the alumina barrier layer is quickly removed without corrosion. Aluminum nitride and other dielectric layers.
The etching liquid can be used stably within 48 hours, has a large operating window and a high success rate. It also achieves better results in wet etching of semiconductor wafers, avoiding chip short circuits and material damage.
Smart Images
Figure BDA0005020491740000081 
Figure BDA0005020491740000091 
Figure BDA0005020491740000101
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of etching liquid, and in particular to an aluminum oxide etching liquid and a preparation method and application thereof. Background Art
[0002] In the advanced semiconductor manufacturing process, multiple exposure technology has been increasingly used to further reduce the line width to 10nm or even 7nm and below, thereby improving the integration of semiconductor chips. In the multiple exposure process, a fluorine-containing gas source is usually used as an etching gas to dry-etch the formed dielectric layer; the dielectric layer is usually easily etched. If there is no barrier layer, the etching gas will etch the metal wire layer under the dielectric layer, causing chip failure.
[0003] Aluminum oxide is often used as an etch stop layer (barrier layer) in dry etching in multiple exposure processes due to its excellent resistance to dry etching. After the dry etching process is completed, the aluminum oxide used as the etch stop layer needs to be removed in order to proceed to the next deposition process. If the etch stop layer is not removed cleanly, it will cause a chip short circuit.
[0004] Aluminum oxide etchants in the prior art are usually fluorine-containing etchants, such as ammonium fluoride and hydrofluoric acid; however, fluorine-containing etchants will cause serious corrosion to non-metallic low-k materials such as SiO2 and SiN while etching aluminum oxide. Prior art CN113785040A discloses a composition for etching aluminum oxide, which uses a fluorine-containing anion etchant to etch aluminum oxide, and uses 4-methylmorpholine oxide as a solubilizer; due to the use of a fluorine-containing anion etchant, it is easy to cause undesirable damage to the silicon-containing dielectric layer.
[0005] Therefore, there is an urgent need to develop a wet etching solution that can completely remove the aluminum oxide serving as an etching stop layer while not corroding the aluminum nitride underneath and other materials in contact with it.
[0006] In view of this, the present invention is proposed. Summary of the invention
[0007] One of the purposes of the present invention is to provide an aluminum oxide etching solution that can effectively remove aluminum oxide while hardly corroding aluminum nitride and the dielectric layer in contact with it, and has a large operating window.
[0008] The second object of the present invention is to provide a method for preparing an aluminum oxide etching solution, which has a simple process, high efficiency and high success rate.
[0009] The third object of the present invention is to provide an application of aluminum oxide etching solution, which can achieve better application effect.
[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:
[0011] In a first aspect, an aluminum oxide etching solution comprises the following components by mass percentage:
[0012] Phosphate amine etchant 0.50%-25.00%, pH buffer 0.50%-15.00%, surfactant 0.01%-10.00% and mercapto alcohol corrosion inhibitor 0.10%-10.00%, the balance is water;
[0013] The pH buffer includes at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium succinate, ammonium tartrate and ammonium citrate.
[0014] Further, the phosphoamine etchant includes at least one of aminotrimethylene phosphoric acid, ethylenediaminetetramethylene phosphoric acid, hexamethylenediaminetetramethylene phosphoric acid, diethylenetriaminepentamethylene phosphoric acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylphosphonic acid), dihexenepenta(methylene phosphoric acid), [[(2-hydroxyethyl)imino]bis(methylene)]bisphosphonic acid, aminotrimethylene phosphoric acid and aminodimethylene phosphoric acid.
[0015] Furthermore, the mass proportion of the phosphate amine etchant in the etching solution is 1.00%-20.00%.
[0016] Furthermore, the mass proportion of the pH buffer in the etching solution is 1.00%-10.00%.
[0017] Further, the surfactant includes a nonionic surfactant;
[0018] The mass proportion of the nonionic surfactant in the etching solution is 0.05%-5.00%.
[0019] Furthermore, the nonionic surfactant includes at least one of coconut oil fatty acyl diethanolamine, coconut oil fatty acyl diethanolamine phosphate, coconut acid monoethanolamide, fatty acid polyoxyethylene ester, methyl stearate polyoxyethylene ether, stearic acid polyoxyethylene ester, lauric acid polyoxyethylene ester and oleic acid polyoxyethylene ester.
[0020] Furthermore, the mercapto alcohol corrosion inhibitor includes at least one of dithiopropanol, dithiothreitol, dithioerythritol, 1-mercapto-2-propanol, 3-methylthiopropanol, 1,3-dimethylthio-2-propanol and 1,1'-thiodipropan-2-ol.
[0021] Furthermore, the mass proportion of the mercapto alcohol corrosion inhibitor in the etching solution is 0.50%-8.00%.
[0022] In a second aspect, a method for preparing the aluminum oxide etching solution described in any one of the above items comprises the following steps:
[0023] The components are mixed in proportion to obtain the aluminum oxide etching solution.
[0024] A third aspect provides an application of the aluminum oxide etching solution described in any one of the above items in wet etching of semiconductor wafers.
[0025] Compared with the prior art, the present invention has at least the following beneficial effects:
[0026] The aluminum oxide etching solution provided by the present invention is a fluorine-free aluminum oxide etching solution. With the coordinated cooperation of various components and their proportions, it can not only quickly remove the aluminum oxide serving as a barrier layer, but also will not etch aluminum nitride and the silicon-containing dielectric layer in contact with it; in addition, the etching solution of the present invention can be stably used for 48 hours or longer, and has a large operating window.
[0027] The method for preparing the aluminum oxide etching solution provided by the invention has simple process, high efficiency and high success rate.
[0028] The application of the aluminum oxide etching solution provided by the present invention can achieve better application effect in wet etching of semiconductor wafers. DETAILED DESCRIPTION
[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0030] According to a first aspect of the present invention, there is provided an aluminum oxide etching solution comprising the following components by mass percentage:
[0031] Phosphate amine etchant 0.50%-25.00%, pH buffer 0.50%-15.00%, surfactant 0.01%-10.00% and mercapto alcohol corrosion inhibitor 0.10%-10.00%, the balance is water;
[0032] The pH buffer includes at least one of diammonium phosphate, monoammonium phosphate, ammonium succinate, ammonium tartrate, and ammonium citrate.
[0033] In the present invention, the typical but non-limiting mass percentage of the phosphate amine etchant is, for example, 0.50%, 1.00%, 2.00%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, 9.00%, 10.00%, 12.00%, 14.00%, 16.00%, 18.00%, 20.00%, 21.00%, 22.00%, 23.00%, 24.00%, 25.00%; the typical but non-limiting mass percentage of the pH buffer is, for example, 0.50%, 1.00%, 3.00%, 5.00%, 7.00%, 9.00%, 11. 00%, 13.00%, 15.00%; typical but non-limiting mass percentages of surfactants are, for example, 0.01%, 0.05%, 0.10%, 0.50%, 1.00%, 2.00%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, 9.00%, 10.00%; typical but non-limiting mass percentages of mercapto alcohol corrosion inhibitors are, for example, 0.10%, 0.30%, 0.50%, 1.00%, 2.00%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, 9.00%, 10.00%.
[0034] The aluminum oxide etching solution provided by the present invention is a fluorine-free aluminum oxide etching solution. With the coordinated cooperation of various components and their proportions, it can not only quickly remove the aluminum oxide serving as a barrier layer, but also will not etch aluminum nitride and the silicon-containing dielectric layer in contact with it; in addition, the etching solution of the present invention can be stably used for 48 hours or longer, and has a large operating window.
[0035] In a preferred embodiment, the phosphoamine etchant includes but is not limited to at least one of aminotrimethylene phosphoric acid, ethylenediaminetetramethylene phosphoric acid, hexamethylenediaminetetramethylene phosphoric acid, diethylenetriaminepentamethylene phosphoric acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylphosphonic acid), dihexenepenta(methylene phosphoric acid), [[(2-hydroxyethyl)imino]bis(methylene)]bisphosphonic acid, aminotrimethylene phosphoric acid and aminodimethylene phosphoric acid.
[0036] In the present invention, the role of the amine phosphate etchant is that phosphoric acid reacts with aluminum oxide and can complex the generated aluminum ions, which is beneficial to the forward etching reaction, thereby achieving the purpose of rapid etching of aluminum oxide; at the same time, the present invention uses a fluorine-free substance as an etchant and will not corrode non-metals.
[0037] In summary, the etchant selected in the present invention can specifically combine with aluminum atoms to achieve the purpose of etching aluminum oxide, while not causing corrosion to the silicon-containing dielectric layer, and there is no need to introduce a dielectric layer corrosion inhibitor.
[0038] In a preferred embodiment, the mass proportion of the phosphate amine etchant in the etching solution can be 1.00%-20.00%, which is more conducive to sufficient etching to effectively remove aluminum oxide; if the proportion of the phosphate amine etchant is too high, the aluminum oxide etching rate will be too fast, causing lateral corrosion; if the proportion of the phosphate amine etchant is too low, the aluminum oxide etching rate will be too slow and the etching effect will be poor, resulting in failure to meet process requirements.
[0039] In a preferred embodiment, the mass proportion of the pH buffer in the etching solution can be 1.00%-10.00%, which is more conducive to maintaining the pH stability of the etching solution and keeping the pH of the solution between 6.5-7.5.
[0040] It should be noted that excessive acidity or alkalinity will lead to accelerated etching rates of aluminum oxide and aluminum nitride, so it is necessary to maintain the pH stability of the etching solution; the specific pH buffer selected in the present invention and its mass ratio can keep the pH of the solution between 6.5-7.5, and can also remain stable under long-term heating.
[0041] In a preferred embodiment, the surfactant includes but is not limited to a non-ionic surfactant, and the mass proportion of the non-ionic surfactant in the etching solution may be 0.05%-5.00%.
[0042] In a preferred embodiment, the nonionic surfactant includes but is not limited to at least one of coconut oil fatty acyl diethanolamine, coconut oil fatty acyl diethanolamine phosphate, coconut acid monoethanolamide, fatty acid polyoxyethylene esters, methyl stearate polyoxyethylene ether, stearic acid polyoxyethylene ester, lauric acid polyoxyethylene ester and oleic acid polyoxyethylene ester.
[0043] The nonionic surfactant selected in the present invention and its appropriate mass proportion can more effectively reduce the surface tension of the etching solution, so that the etching solution can smoothly enter the fine through-holes, thereby ensuring effective etching to effectively remove aluminum oxide; if the proportion of the nonionic surfactant is too high, the etching solution will cause foaming, which will prevent the etching solution from entering the fine through-holes, resulting in poor etching effect; if the proportion of the nonionic surfactant is too low, the effect of reducing the surface tension cannot be fully exerted, making it difficult for the etching solution to enter the fine through-holes, resulting in poor etching effect.
[0044] In a preferred embodiment, the mercapto alcohol corrosion inhibitor includes but is not limited to at least one of dithiopropanol, dithiothreitol, dithioerythritol, 1-mercapto-2-propanol, 3-methylthiopropanol, 1,3-dimethylthio-2-propanol and 1,1'-thiodipropan-2-ol.
[0045] Since the etchant will etch aluminum nitride, in order to protect aluminum nitride, the present invention uses specific mercapto alcohol substances as corrosion inhibitors. The mechanism of action is that the mercapto group is adsorbed on the surface of aluminum nitride, and the hydroxyl group is combined through hydrogen bonds to form a protective film, which can effectively prevent the etchant from contacting aluminum nitride, thereby achieving the purpose of protecting aluminum nitride.
[0046] In a preferred embodiment, the mass proportion of the mercapto alcohol corrosion inhibitor in the etching solution can be 0.50%-8.00%, which is more conducive to further protecting aluminum nitride from being corroded by the etchant.
[0047] The corrosion inhibitor selected in the present invention and its appropriate mass proportion are more conducive to fully adsorbing the mercapto group on the surface of aluminum nitride to effectively form a dense protective film, thereby effectively protecting the aluminum nitride from being corroded by the etchant; if the corrosion inhibitor proportion is too high, the excess corrosion inhibitor cannot be completely dissolved in the etching solution, resulting in affecting the final etching effect; if the corrosion inhibitor proportion is too low, it will cause the aluminum nitride etching rate to increase, and the aluminum nitride cannot be fully protected from being corroded by the etchant.
[0048] According to a second aspect of the present invention, there is provided a method for preparing the aluminum oxide etching solution described in any one of the above items, comprising the following steps:
[0049] The components are mixed in proportion to obtain an aluminum oxide etching solution.
[0050] The method for preparing the aluminum oxide etching solution provided by the invention has simple process, high efficiency and high success rate.
[0051] According to a third aspect of the present invention, there is provided a use of the aluminum oxide etching solution described in any one of the above items in wet etching of semiconductor wafers.
[0052] The application of the aluminum oxide etching solution provided by the present invention can achieve better application effect in wet etching of semiconductor wafers.
[0053] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.
[0054] Examples 1-13
[0055] Example 1-13 provides an aluminum oxide etching solution, and the components and their mass proportions are shown in Table 1;
[0056] The various components are mixed evenly according to a certain proportion to obtain an aluminum oxide etching solution.
[0057] Comparative Examples 1-8
[0058] Comparative Example 1-8 provides an aluminum oxide etching solution, and the components and their mass proportions are shown in Table 1;
[0059] The various components are mixed evenly according to a certain proportion to obtain an aluminum oxide etching solution.
[0060] Table 1
[0061]
[0062]
[0063] Test example
[0064] The performance of the aluminum oxide etching solutions obtained in the examples and comparative examples was tested, and the results are shown in Table 2.
[0065] Etching rate of AlO (aluminum oxide) The etching solution was placed in a reactor and heated to the experimental temperature. Then, an AlO wafer cut into 3 cm*3 cm was placed in the reactor and immersed at a constant temperature for 10 min, washed with water, and dried with nitrogen. The etching rate was then calculated by measuring the change in film thickness before and after etching using an ellipsometer.
[0066] Etching rate of AlN (aluminum nitride) The etching solution was placed in a reactor and heated to the experimental temperature. Then an AlN wafer cut into 3cm*3cm pieces was placed in the reactor and immersed at a constant temperature for 10 minutes. The wafer was washed with water and dried with nitrogen. The etching rate was then calculated by measuring the change in film thickness before and after etching using an ellipsometer.
[0067] Etching rate of PETEOS The etching solution was placed in a reactor and heated to the experimental temperature. Then a PETEOS wafer cut into 3 cm*cm pieces was placed in the reactor and soaked at a constant temperature for 10 minutes. The wafer was washed with water and dried with nitrogen. The etching rate was then calculated by measuring the change in film thickness before and after etching using an ellipsometer.
[0068] pH test: After the pH meter is calibrated, place the pH electrode in the etching solution at 25°C, wait for the reading to stabilize, and read the pH value.
[0069] Table 2
[0070]
[0071] It can be seen from Table 2 that the etching solutions of Examples 1-13 of the present invention can effectively remove the aluminum oxide barrier layer, and have substantially no corrosion to the AlN and PETEOS in contact.
[0072] The normal operating temperature of the etching solution is 40° C. From the etching rate data at different operating temperatures recorded in Example 1, it can be seen that different operating temperatures have a significant effect on the etching rates of AlO and AlN; the higher the operating temperature, the greater the etching rate of the etching solution on AlO and AlN.
[0073] Compared with the etching solution of Example 13, the etching solution of Comparative Example 1 lacks an etchant, which results in almost no etching of AlO.
[0074] Compared with the etching solution of Example 13, the etching solutions of Comparative Examples 4, 5 and 6 use fluorine-containing etchants, which results in that although AlO can be etched, the etching rates for AlN and PETEOS are also significantly increased.
[0075] Compared with the etching solution of Example 13, the etching solution of Comparative Example 2 does not contain a pH buffer, which causes the pH of the solution to be acidic, resulting in a significant increase in the etching rate of AlO and AlN.
[0076] Compared with the etching solution of Example 13, the etching solution of Comparative Example 3 does not contain a corrosion inhibitor, which results in a significant increase in the etching rate of AlN.
[0077] Compared with the etching solution of Example 6, the etching solution of Comparative Example 7 uses other types of corrosion inhibitors, which results in poor corrosion inhibition effect on AlN.
[0078] The changes in pH and AlO etching rate of the etching solutions obtained in Example 6, Comparative Example 2 and Comparative Example 8 under long-term (24 h and 48 h) heating (40° C.) are shown in Table 3.
[0079] Table 3
[0080]
[0081] It can be seen from the data recorded in Table 3 that, compared with Example 6, no pH buffer is added in Comparative Example 2, or other types of pH buffers are used in Comparative Example 8, which will lead to poor pH stability of the etching solution and poor stability of the AlO etching rate. It can be seen that the performance of the etching solution is unstable, which is significantly inferior to the etching solution of Example 6 of the present invention.
[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. An aluminum oxide etching solution, characterized in that: It includes the following components by mass percentage: Phosphate amine etchant 0.50%-25.00%, pH buffer 0.50%-15.00%, surfactant 0.01%-10.00% and mercapto alcohol corrosion inhibitor 0.10%-10.00%, the balance is water; The pH buffer includes at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium succinate, ammonium tartrate and ammonium citrate.
2. The aluminum oxide etching solution according to claim 1, characterized in that: The phosphoamine etchant includes at least one of aminotrimethylene phosphoric acid, ethylenediaminetetramethylene phosphoric acid, hexamethylenediaminetetramethylene phosphoric acid, diethylenetriaminepentamethylene phosphoric acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylphosphonic acid), dihexenepenta(methylene phosphoric acid), [[(2-hydroxyethyl)imino]bis(methylene)]bisphosphonic acid, aminotrimethylene phosphoric acid and aminodimethylene phosphoric acid.
3. The aluminum oxide etching solution according to claim 2, characterized in that: The mass proportion of the phosphate amine etching agent in the etching solution is 1.00%-20.00%.
4. The aluminum oxide etching solution according to any one of claims 1 to 3, characterized in that: The mass proportion of the pH buffer in the etching solution is 1.00%-10.00%.
5. The aluminum oxide etching solution according to any one of claims 1 to 3, characterized in that: The surfactant includes a nonionic surfactant; The mass proportion of the nonionic surfactant in the etching solution is 0.05%-5.00%.
6. The aluminum oxide etching solution according to claim 5, characterized in that: The nonionic surfactant includes at least one of coconut oil fatty acyl diethanolamine, coconut oil fatty acyl diethanolamine phosphate, coconut acid monoethanolamide, fatty acid polyoxyethylene ester, stearic acid methyl ester polyoxyethylene ether, stearic acid polyoxyethylene ester, lauric acid polyoxyethylene ester and oleic acid polyoxyethylene ester.
7. The aluminum oxide etching solution according to claim 1, characterized in that: The mercapto alcohol corrosion inhibitor includes at least one of dimercaptopropanol, dithiothreitol, dithioerythritol, 1-mercapto-2-propanol, 3-methylthiopropanol, 1,3-dimethylthio-2-propanol and 1,1'-thiodipropan-2-ol.
8. The aluminum oxide etching solution according to claim 7, characterized in that: The mass proportion of the mercapto alcohol corrosion inhibitor in the etching solution is 0.50%-8.00%.
9. A method for preparing the aluminum oxide etching solution according to any one of claims 1 to 8, characterized in that: The following steps are involved: The components are mixed in proportion to obtain the aluminum oxide etching solution.
10. Use of the aluminum oxide etching solution according to any one of claims 1 to 8 in wet etching of semiconductor wafers.