Hafnium oxide etching solution and preparation method thereof

Abstract

The invention provides a hafnium oxide etching solution. The etching solution comprises the following components in percentage by weight: 78-94% of dihydric alcohol, 5-20% of alcohol ether, 0.5-1.5% of hydrofluoric acid and 0.05-0.15% of an inhibitor. According to the hafnium oxide etching solution, the etching selection ratio of hafnium oxide (HfO2) to indium gallium zinc oxide (IGZO) is 1: 1, and good etching uniformity is achieved.

Description

Technical Field

[0001] The invention belongs to the cross field of metal oxide etching and semiconductor storage technology, and specifically relates to a hafnium dioxide etching solution and a preparation method thereof. Background Art

[0002] Dynamic random access memory (DRAM) is a volatile, capacitor-based, destructive read form of memory. For a long time, DRAM memory cells were made of a single transistor and a single capacitor, the so-called 1T1C design. When writing to this memory cell, the transistor is turned on and charge is pushed into the capacitor (1) or removed from the capacitor (0); when reading, the charge is extracted and measured. This traditional system is super fast, cheap, and consumes very little power, but its challenge is how to meet the growing demand for high capacity, high performance, large bandwidth, low latency, and small memory cell size without increasing power consumption. The emergence of HBM is a breakthrough in DRAM's transition from 2D architecture to 3D architecture. It is a non-planar type with a 3D shape in the form of a cube / rectangle. The memory chips are stacked to form a cubic structure, which takes up less space, consumes less power, and has higher bandwidth. In the research process of 3D DRAM memory cells, various high-K materials have been used, such as Al2O3, HfO2, Ta2O5, etc., and good results have been achieved. By adjusting the equivalent oxide thickness (EOT) to control the threshold voltage (Vt), the data retention performance under short gate length is further optimized.

[0003] However, there is no dedicated selective etching solution for the HfO2 / IGZO structure. Therefore, a HfO2 and IGZO selective etching solution is developed to etch a specific HfO2 / IGZO structure, further promoting the development of 3D DRAM technology. Summary of the invention

[0004] The present invention is an invention for improving the above-mentioned problem, and its purpose is to provide a hafnium dioxide etching solution, wherein the etching solution comprises 78-94% of diol, 5-20% of alcohol ether, 0.5-1.5% of hydrofluoric acid, and 0.05-0.15% of inhibitor, accounting for 78-94% of the total weight of the etching solution.

[0005] Furthermore, the present invention relates to the above-mentioned diol being one or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,5-pentanediol.

[0006] Furthermore, the present invention relates to the above-mentioned alcohol ether is one or more of ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol isopropyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, and propylene glycol butyl ether.

[0007] Furthermore, the present invention relates to the above-mentioned hydrofluoric acid is electronic grade hydrofluoric acid with a content of 49%.

[0008] Furthermore, the present invention relates to the above-mentioned inhibitor being one of 5-isopropyl-o-cresol, 3-phenylphenol, 3-benzylphenol and 3-diethylaminophenol.

[0009] Furthermore, the present invention relates to the etching solution wherein the water content in the etching solution accounts for less than 1% of the total weight of the etching solution.

[0010] Furthermore, the invention relates to the etching solution having a pH value less than 7.

[0011] The present invention also provides a method for preparing a hafnium dioxide etching solution, comprising the following steps: S1. Weigh the diol, alcohol ether, hydrofluoric acid and inhibitor respectively according to the ratio described in claim 1; S2. Add the weighed diol, alcohol ether and inhibitor one by one in order, stirring for 5-10 minutes each time a component is added; S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2 while stirring.

[0012] Furthermore, the present invention relates to the above-mentioned preparation method, wherein the stirring rate in steps S2 and S3 is 100-300 r / min.

[0013] Furthermore, the present invention relates to the above-mentioned preparation method, wherein the hydrofluoric acid dropping rate in step S3 is one drop per 5-10 seconds.

[0014] The present invention has the following beneficial effects: The etching solution of the present invention is an organic weak acid solution, wherein the low-carbon alcohol ether can not only reduce the surface tension of the solution and improve the wettability, but also make the hydrofluoric acid better dispersed in the mixed organic matter. In addition, the preparation method of slowly dripping the hydrofluoric acid and stirring while dripping is combined with the low-carbon alcohol ether, and the hydrofluoric acid in the prepared etching solution is evenly dispersed and has good uniform etching ability. Most of the etching solution is composed of organic diols to replace water, which can reduce and maintain the water content in the etching solution to control F - Finally, the phenolic hydroxyl oxygen atom of the phenolic substance forms a delocalized bond with the benzene ring, which, combined with the oxygen atom ether bond of the alcohol ether, can selectively reduce the etching rate of hydrofluoric acid on IGZO, thereby improving the etching solution selectivity for HfO2 and IGZO. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution in the present application, the structure of the inventive etching will be listed below, and a brief introduction and description will be made through the drawings. Obviously, the drawings described below are only one embodiment of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 This is the cross-sectional morphology of the deep hole stacked structure sample of Example 1 before etching, with a total of 16 layers from top to bottom.

[0017] Figure 2 This is the cross-sectional morphology of the deep hole stacked structure sample of Example 1 after etching. DETAILED DESCRIPTION

[0018] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0019] Example 1 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 88.1wt% 1,2-propylene glycol, 11.0wt% ethylene glycol methyl ether, 0.8wt% hydrofluoric acid and 0.1wt% 3-phenylphenol respectively according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,2-propylene glycol, ethylene glycol methyl ether and 3-phenylphenol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0020] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0021] Example 2 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 88.1wt% ethylene glycol, 11.0wt% ethylene glycol ethyl ether, 0.8wt% hydrofluoric acid and 0.1wt% 5-isopropyl o-cresol according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed ethylene glycol, ethylene glycol ethyl ether and 5-isopropyl o-cresol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0022] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0023] Example 3 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 88.1wt% 1,3-propylene glycol, 11.0wt% propylene glycol methyl ether, 0.8wt% hydrofluoric acid and 0.1wt% 3-benzylphenol respectively according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,3-propylene glycol, propylene glycol methyl ether and 3-benzylphenol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0024] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0025] Example 4 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 88.1wt% 1,4-butanediol, 11.0wt% propylene glycol butyl ether, 0.8wt% hydrofluoric acid and 0.1wt% 3-diethylaminophenol respectively according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,4-butanediol, propylene glycol butyl ether and 3-diethylaminophenol one by one in order. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0026] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0027] Example 5 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 88.1wt% 1,5-pentanediol, 11.0wt% ethylene glycol isopropyl ether, 0.8wt% hydrofluoric acid and 0.1wt% 5-isopropyl o-cresol according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,5-pentanediol, ethylene glycol isopropyl ether and 5-isopropyl o-cresol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0028] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0029] Example 6 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. According to the total weight of 100g of hafnium dioxide etching solution, 92.8wt% of ethylene glycol, 6.0wt% of propylene glycol methyl ether, 1.1wt% of hydrofluoric acid and 0.1wt% of 3-phenylphenol were weighed respectively; S2. Add the weighed ethylene glycol, propylene glycol methyl ether and 3-phenylphenol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0030] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0031] Example 7 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. According to the total weight of 100g of the hafnium dioxide etching solution, 92.8wt% of 1,2-propylene glycol, 6.0wt% of propylene glycol methyl ether, 1.1wt% of hydrofluoric acid and 0.1wt% of 5-isopropyl o-cresol were weighed respectively; S2. Add the weighed 1,2-propylene glycol, propylene glycol methyl ether and 5-isopropyl o-cresol one by one in sequence. Stir for 5-10 minutes each time a component is added at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0032] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0033] Example 8 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 92.8wt% 1,3-propylene glycol, 6.0wt% ethylene glycol propyl ether, 1.1wt% hydrofluoric acid and 0.1wt% 5-isopropyl o-cresol respectively according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,3-propylene glycol, ethylene glycol propyl ether and 5-isopropyl o-cresol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0034] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0035] Example 9 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. According to the total weight of 100g of hafnium dioxide etching solution, 79.8wt% 1,4-butanediol, 19.0wt% ethylene glycol butyl ether, 1.1wt% hydrofluoric acid and 0.1wt% 5-isopropyl o-cresol were weighed respectively; S2. Add the weighed 1,4-butanediol, ethylene glycol butyl ether and 5-isopropyl o-cresol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0036] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0037] Example 10 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. According to the total weight of 100g of the hafnium dioxide etching solution, 79.8wt% 1,5-pentanediol, 19.0wt% propylene glycol ethyl ether, 1.1wt% hydrofluoric acid and 0.1wt% 5-isopropyl o-cresol were weighed respectively; S2. Add the weighed 1,5-pentanediol, propylene glycol ethyl ether and 5-isopropyl o-cresol one by one in sequence. Stir each component for 5-10 minutes at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0038] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0039] Comparative Example 1 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 1.1wt% hydrofluoric acid based on the total weight of 100g of the hafnium dioxide etching solution, and the rest is deionized water; The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0040] Comparative Example 2 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 98.9wt% 1,2-propylene glycol and 1.1wt% hydrofluoric acid respectively based on the total weight of 100g of hafnium dioxide etching solution; S2. Slowly add the weighed hydrofluoric acid to 1,2-propylene glycol while stirring at a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0041] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0042] Comparative Example 3 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 92.9wt% 1,2-propylene glycol, 6.0wt% propylene glycol methyl ether, and 1.1wt% hydrofluoric acid according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,2-propylene glycol and propylene glycol methyl ether one by one in order. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0043] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0044] Comparative Example 4 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. Weigh 98.8wt% 1,2-propylene glycol, 1.1wt% hydrofluoric acid and 0.1wt% 5-isopropyl o-cresol according to the total weight of 100g of hafnium dioxide etching solution; S2. Add the weighed 1,2-propylene glycol and 5-isopropyl-o-cresol one by one in sequence. Stir for 5-10 minutes after adding each component at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0045] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0046] Comparative Example 5 The method for preparing the hafnium dioxide etching solution provided in this embodiment comprises the following steps: S1. According to the total weight of 100g of the hafnium dioxide etching solution, 95.8wt% of 1,2-propylene glycol, 3.0wt% of propylene glycol methyl ether, 1.1wt% of hydrofluoric acid and 0.1wt% of 5-isopropyl o-cresol were weighed respectively; S2. Add the weighed 1,2-propylene glycol, propylene glycol methyl ether and 5-isopropyl o-cresol one by one in sequence. Stir for 5-10 minutes each time a component is added at a stirring rate of 200 r / min. S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2, stirring while adding, with a stirring rate of 200 r / min and a hydrofluoric acid dropping rate of one drop per 5 seconds.

[0047] The prepared hafnium dioxide etching solution was used to etch HfO2 single wafer, IGZO single wafer and deep hole stacked structure sample at 25°C, the film thickness of HfO2 and IGZO single wafer before and after etching was recorded, the corresponding HfO2 and IGZO single wafer etching rates were calculated, and the HfO2 side etching amount in the deep hole stacked structure sample was recorded.

[0048] Table 1 Etching results of various embodiments and comparative examples

[0049] Note: The side etching amount max-min is the maximum value minus the minimum value of the side etching amount of 16 layers of HfO2 in the deep hole stacked structure sample.

[0050] Obviously, the above embodiments and comparative examples are only examples for clear demonstration, and are not limited to the above embodiments. For those skilled in the art, the above embodiments have many variations or combinations, and it is not necessary and impossible to cite all the embodiments here. Therefore, the changes or modifications based on the above embodiments are still within the protection scope of the present invention.

Claims

1. A hafnium dioxide etching solution, characterized in that: The etching solution comprises 78-94% of diol, 5-20% of alcohol ether, 0.5-1.5% of hydrofluoric acid and 0.05-0.15% of inhibitor, accounting for 78-94% of the total weight of the etching solution.

2. The hafnium dioxide etching solution according to claim 1, characterized in that: The diol in the etching solution is one or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,5-pentanediol.

3. The hafnium dioxide etching solution according to claim 1, characterized in that: The alcohol ether in the etching solution component is one or more of ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol isopropyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether and propylene glycol butyl ether.

4. The hafnium dioxide etching solution according to claim 1, characterized in that: The hydrofluoric acid is electronic grade hydrofluoric acid with a content of 49%.

5. The hafnium dioxide etching solution according to claim 1, characterized in that: The inhibitor in the etching solution is a combination of one or more of 5-isopropyl o-cresol, 3-phenylphenol, 3-benzylphenol and 3-diethylaminophenol.

6. The hafnium dioxide etching solution according to claim 1, characterized in that: The water content in the etching solution accounts for less than 1% of the total weight of the etching solution.

7. The hafnium dioxide etching solution according to claim 1, characterized in that: The pH of the etching solution is less than 7.

8. A method for preparing the hafnium dioxide etching solution according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Weigh the diol, alcohol ether, hydrofluoric acid and inhibitor respectively according to the ratio described in claim 1; S2. Add the weighed diol, alcohol ether and inhibitor one by one in order, stirring for 5-10 minutes each time a component is added; S3. Slowly add the weighed hydrofluoric acid to the mixed solution prepared in S2 while stirring.

9. The preparation method according to claim 8, characterized in that: The stirring rate in steps S2 and S3 is 100-300 r / min.

10. The preparation method according to claim 8, characterized in that: The hydrofluoric acid dropping rate in step S3 is one drop per 5-10 seconds.

Images