CN116159811A - Cleaning method for contamination of grid net in ion beam etching cavity - Google Patents

Abstract

The invention provides a cleaning method for a grid net in an ion beam etching cavity, which uses a process menu of ion beam etching to clean, sets positive voltage, positive current and negative voltage applied to a first layer of grid net, enables plasmas to pass through the first layer of grid net without forming directional ion beams, and utilizes the repulsive collision effect among plasmas to clean the pollution of the grid net. The cleaning method of the invention directly uses the ion beam to etch the process menu of the cavity without opening other physical operations such as cavity opening, thus achieving the purpose of cleaning IBE grid without opening the cavity, and having good cleaning effect and stable process parameters before and after cleaning.

Description

A method for cleaning the contamination of the grid in the ion beam etching chamber

technical field

The invention belongs to the technical field of semiconductors, and in particular relates to a cleaning method for contamination of grids in ion beam etching chambers.

Background technique

Ion beam etching (IBE) is a kind of dry etching, which is a kind of equipment that uses a certain energy ion beam to bombard the surface of the material to cause sputtering on the surface of the material, thereby achieving the etching effect.

The etching process flow is as follows:

The gas Ar, O2 _{, etc.} enter the discharge chamber of the quartz cavity → the high-frequency wave initiated by the RF coil ionizes Ar and _O2 to generate plasma → apply positive voltage (BMV) and positive current (BMI) to the first layer of grid to screen the intensity of ions → Applying a negative voltage (ACV) to the second grid attracts the positively charged plasma and makes the plasma form a directional positively charged ion beam, which passes through the second grid → reaches the third grid screen The ion beam potential is 0 and passes through the third grid → the positively charged ion beam is neutralized by the electrons emitted by the neutralizer to form an electrically neutral ion beam → the electrically neutral ion beam is on the wafer on the stage The bombardment is carried out and the by-products are sucked away by the vacuum system.

During the IBE etching process, due to the opening of the baffle, there is no barrier between the chamber and the grid at this time, and part of the by-products generated by etching will be sputtered to the grid and adhere to the grid. surface, causing grid contamination.

The degree of contamination will directly affect the accuracy of the process, causing some parameters to drift during the process or the repeatability of the process will become poor, and it will also shorten the service life of the grid. For example, the second layer of grid is more contaminated, which will cause uneven distribution of negative charges on the grid surface, and the traction effect on argon ions will vary greatly in different regions, causing some argon ions to fail to pass through the holes of the grid and impact on the grid. grid surface, reducing its service life.

At present, the common solution to grid contamination in the industry is periodic production maintenance (PM), which defines a grid life cycle. When the grid reaches the life cycle, the grid is disassembled and wiped and other recovery actions are performed. From the process point of view, the method to solve the process parameter drift caused by the grid contamination is to restore the stability of the machine parameters by running the control chip (dummy chip) several times when the grid has been contaminated, but this method cannot clear the grid. The contamination on the machine can only temporarily restore the stability of the machine parameters.

Contents of the invention

The purpose of the present invention is to provide a method for cleaning the contamination of the grid in the ion beam etching cavity. The cleaning method in the present invention does not need to use other physical operations such as opening the cavity, and directly uses the process menu to achieve the desired effect without opening the cavity. The purpose of cleaning the IBE grid.

The invention provides a method for cleaning the contamination of the grid in the ion beam etching chamber. The process menu of ion beam etching is used for cleaning, and the positive voltage and current applied to the first layer of grid and the positive current applied to the second grid are set. The negative voltage on the first layer of grid makes the plasma pass through the first layer of grid without forming a directional ion beam, and the contamination of the grid is cleaned by the repulsion and collision between the plasmas.

Preferably, the positive voltage applied to the first grid is 50-1000V.

Preferably, the negative voltage applied to the second grid is 10-1000V.

Preferably, the positive current applied to the first grid is 5mA-10A.

Preferably, the process gas in the cleaning process is one or more of argon, oxygen, nitrogen, fluorine-based gases and alcohol gases.

Preferably, the flow rate of each of the process gases is 5-1000 sccm.

Preferably, the cleaning time is 3-20 minutes.

Preferably, the contamination of the grid is one or more of Pt, SiO ₂ , Ru, MgO, SiN, TiN, C, Ag and Ta.

Preferably, the chamber pressure in the ion etching chamber is 0.05-10mT.

The present invention provides a method for cleaning the contamination of the grid in the ion beam etching chamber. The ion beam etching process menu is used for cleaning, and the positive voltage and current applied to the first layer of grid and the positive current applied to the second grid are set. The negative voltage on the second-layer grid makes the plasma pass through the first-layer grid without forming a directional ion beam, and the contamination on the grid is cleaned by using the repulsive collision effect between the plasmas. In the present invention, by setting the parameters in the three process menus of BMV, BMI and ACV, after the plasma passes through the first layer of grid, it cannot be pulled by the ion acceleration bias ACV on the second layer of grid, so that there are a large number of bands The positively charged plasma stays between the first layer and the second layer of grids, and the same positive charge will produce repulsion, which will increase the collision of argon ions per unit volume, reduce the free path, and part of the argon ions will hit the grid. The stain on the surface of the net can achieve the cleaning effect. A small amount of plasma passing through the second grid will also repel each other before reaching the third grid, and part of the argon ions will bombard the second and third grids to remove surface contamination. The cleaning method in the present invention does not need other physical operations such as opening the cavity, and directly uses the process menu of the ion beam etching cavity to achieve the purpose of cleaning the IBE grid without opening the cavity, and the cleaning effect is good, and the process parameters before and after cleaning are stable.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Figure 1 is a schematic diagram of the ion source work;

Fig. 2 is the schematic diagram of the principle of cleaning grid contamination of the present invention;

Among them, 1 is the RF coil, 2 is the quartz barrel, 3 is the first grid, 4 is the second grid, 5 is the third grid, and 6 is the neutralizer;

Fig. 3 is the change before and after the test menu etching 12 inch _SiO2 wafer in the embodiment 1 of the present invention;

Fig. 4 is the change chart of grid surface staining before and after cleaning of embodiment 1;

Fig. 5 is the change before and after the test menu etching 12 inch _SiO2 wafer in the comparative example 1 of the present invention;

Fig. 6 is a graph showing the change in contamination on the surface of the grid before and after cleaning in Comparative Example 1;

Fig. 7 is the change before and after the test menu etching 12 inch _SiO2 wafer in comparative example 2 of the present invention;

Fig. 8 is a graph showing the change of contamination on the surface of the grid before and after cleaning in Comparative Example 2.

Detailed ways

The present invention provides a method for cleaning the contamination of the grid in the ion beam etching chamber. The ion beam etching process menu is used for cleaning, and the positive voltage and current applied to the first layer of grid and the positive current applied to the second grid are set. The negative voltage on the second-layer grid makes the plasma pass through the first-layer grid without forming a directional ion beam, and the contamination on the grid is cleaned by using the repulsive collision effect between the plasmas.

The etching principle of ion beam etching is shown in Figure 1 (taking argon as an example):

Gases such as argon gas enter the quartz cavity, and filaments or RF coils generate high-frequency waves to ionize gases such as argon gas. The ionized argon ions reach the first grid (the grid close to the ion source is defined as the first grid, and the grid far away from the ion source is defined as the second and third grids).

Apply a positive voltage—ion energy (BMV) and positive current (BMI) to the grid on the first layer. Due to the repulsion between the positive voltage of the grid and the argon ions, only ions with energy greater than the repulsion force can pass through the grid, that is, through the BMV Perform a screen on the strength of the ions. BMI can be used to represent the ion beam flux. The applied BMI has a theoretical maximum value, that is, the maximum value at which ions passing through the first grid can be completely pulled by the second grid.

The argon ions passing through the first grid layer reach between the first grid layer and the second grid layer. At this time, the repulsion of the BMV to the argon ions accelerates the movement to the second grid layer, and a grid is applied to the second layer grid. The negative voltage is the ion accelerating bias voltage (ACV). Due to the attraction effect of the negative voltage on the argon ions, the argon ions that originally moved irregularly are attracted to form a directional ion beam, so that the argon ions can pass through the second layer grid smoothly. The argon ions passing through the two-layer grid have a potential of 0 after reaching the third-layer ground grid, and neutralize with the electrons generated by the neutralizer after coming out of the third-layer grid, forming an electrically neutral ion beam. At this time, the baffle is opened , the ion beam bombards the wafer on the surface of the stage, so as to achieve the purpose of etching.

In this application, the principle of using the process menu to clean the grid contamination is shown in Figure 2:

Argon and other gases enter the quartz cavity, and the filament generates high-frequency waves to ionize the argon and other gases. The ionized argon ions reach the first grid (grid), apply positive voltage BMV and current BMI to the first grid, and perform intensity screening on the ions passing through the grid. At the same time, the applied BMI must be large enough, and the BMI value can exceed 2-20 times the theoretical maximum value, the purpose is to make the amount of ions passing through the first grid layer larger and more concise.

Apply a negative voltage ACV to the grid on the second layer. The value of ACV can be set as small as possible. The purpose of ACV is to apply a bias force to the ions and at the same time pull the ions through the grid on the first layer. When the ACV value is low , causing a large number of argon ions in the middle of the first grid and the second grid to be unable to be pulled. Due to their positive charges, these argon ions will produce repulsion, the collision of argon ions per unit volume will increase, the free path will decrease, and some argon ions will hit the contamination on the surface of the grid to achieve the cleaning effect.

A small amount of argon ions passing through the second layer of grid will also repel each other before reaching the third layer of grid, and some of the argon ions will bombard the second and third layer of grid to remove the surface contamination.

Specifically, in the present invention, the positive voltage BMV applied to the grid of the first layer is determined according to the contamination of the grid. Preferably, the value of the BMV should not be too high to ensure more When the plasma passes through the first grid, the BMV is preferably 50-1000V, more preferably 50-800V, most preferably 100-500V, such as 50V, 100V, 150V, 200V, 250V, 300V, 350V, 400V, 450V , 500V, 550V, 600V, 650V, 700V, 750V, 800V, 850V, 900V, 950V, 1000V, preferably a range value with any of the above values as the upper or lower limit.

The negative voltage applied on the second layer to the Internet, that is, the ion acceleration bias voltage ACV needs to be adjusted according to the set value of BMV. In the present invention, the ratio BMV/ACV of the BMV to ACV is 1 to 50, preferably 5 ~40, more preferably 10~30, follow the principle that the ACV value is as small as possible, and the ACV value is too high to form the risk of arcing (arcing), preferably, the ACV is preferably 10 ~ 1000V, more preferably 10 ~ 800V , more preferably 100-500V, such as 10V, 30V, 50V, 80V, 100V, 120V, 150V, 180V, 200V, 220V, 250V, 280V, 300V, 350V, 400V, 450V, 500V, 550V, 600V, 650V, 700V , 750V, 800V, 850V, 900V, 950V, 1000V, preferably a range value with any of the above-mentioned numerical values as the upper limit or the lower limit.

The value of the positive current BMI applied on the first grid is preferably 5mA-10A, more preferably 50mA-5A, most preferably 100mA-1A, such as 5mA, 50mA, 100mA, 200mA, 300mA, 400mA, 500mA, 550mA, 600mA, 650mA, 700mA, 800mA, 900mA, 1A, 1.5A, 2A, 2.5A, 3A, 3.5A, 4A, 4.5A, 5A, 5.5A, 6A, 6.5A, 7A, 7.5A, 8A, 8.5 A, 9A, 9.5A, and 10A are preferably range values with any of the above-mentioned numerical values as the upper limit or the lower limit.

In the present invention, the process gas used in the cleaning process is preferably one or more of argon, oxygen, nitrogen, fluorine-based gas and alcohol gas, and the fluorine-based gas is preferably carbon tetrafluoride , one or more of trifluoromethane, perfluorobutadiene, nitrogen trifluoride, hexafluoroethane and perfluoromethane; the alcohol gas is preferably methanol, ethanol, propanol, n-propanol and isopropanol One or more of pentanols. The flow rate of the process gas is preferably 50 to 1000 sccm, more preferably 100 to 900 sccm, such as 50 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, 800 sccm, 850 sccm, 900 sccm, 950 sccm, and 1000 sccm are preferably values in a range with any of the above numerical values as the upper limit or the lower limit. If the flow rate of the process gas is too small, the cleaning effect will not be good, and if the flow rate is too large, it will exceed the scope of the hardware.

In the present invention, the cleaning time is determined according to the contamination on the grid that needs to be removed, preferably 3 to 20 minutes to completely remove the IBE grid contamination, more preferably 5 to 15 minutes, such as 3 minutes, 5 minutes, 8min, 10min, 15min, and 20min are preferably range values with any of the above-mentioned numerical values as the upper limit or the lower limit. It should be noted that the process of cleaning the grid is the process of continuous bombardment of the grid by positive charges, so the time should not be too long, and cleaning for a long time will damage the service life of the grid.

In the present invention, the chamber pressure in the ion etching chamber during the cleaning process is preferably 0.05-10mT, more preferably 0.1-9mT, such as 0.05mT, 0.1mT, 0.5mT, 1mT, 2mT, 3mT, 4mT, 5mT, 6mT, 7mT, 8mT, 9mT, and 10mT are preferably range values with any of the above-mentioned numerical values as the upper limit or the lower limit. In the present invention, if the cavity pressure is too high, the uniformity of the subsequent process will be affected, resulting in an unstable etching rate, and the process parameters will fluctuate in a short period of time; if the cavity pressure is too low, there will be a risk of ignition failure.

In the present invention, in the cleaning process, the selection of the angle is determined according to the etching rate, and the angle is defined as the angle between the vertical line of the wafer surface and the vertical line of the ion source; the angle is preferably 0-80°, More preferably 10-70°, such as 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, preferably a range value with any of the above values as the upper or lower limit. In the case of the ion source opening the shutter, different angles may cause etching to the wafer on the stage.

In the present invention, the baffle between the chamber and the ion source can be selected to be opened or not opened during the cleaning process. When you choose to open the baffle, you need to place a wafer on the stage to avoid damage caused by ion beam bombardment; when you choose not to open the baffle, you do not need to place a wafer on the stage, and the contamination removed during the process will not enter In the chamber, the stability of the chamber environment is maintained.

The present invention provides a method for cleaning the contamination of the grid in the ion beam etching chamber. The ion beam etching process menu is used for cleaning, and the positive voltage and current applied to the first layer of grid and the positive current applied to the second grid are set. The negative voltage on the second-layer grid makes the plasma pass through the first-layer grid without forming a directional ion beam, and the contamination on the grid is cleaned by using the repulsive collision effect between the plasmas. In the present invention, by setting the parameters in the three process menus of BMV, BMI and ACV, after the plasma passes through the first layer of grid, it cannot be pulled by the ion acceleration bias ACV on the second layer of grid, so that there are a large number of bands The positively charged plasma stays between the first layer and the second layer of grids, and the same positive charge will produce repulsion, which will increase the collision of argon ions per unit volume, reduce the free path, and part of the argon ions will hit the grid. The stain on the surface of the net can achieve the cleaning effect. A small amount of plasma passing through the second grid will also repel each other before reaching the third grid, and part of the argon ions will bombard the second and third grids to remove surface contamination. The cleaning method in the present invention does not need other physical operations such as opening the cavity, and directly uses the process menu of the ion beam etching cavity to achieve the purpose of cleaning the IBE grid without opening the cavity, and the cleaning effect is good, and the process parameters before and after cleaning are stable.

In order to further illustrate the present invention, a method for cleaning the contamination of the ion beam etching cavity grid provided by the present invention will be described in detail below in conjunction with the examples, but it should not be construed as limiting the protection scope of the present invention.

Example 1

Cleaning process menu parameter settings:

A The ion beam angle is 37°, the ion energy is 400V, the ion acceleration bias is 50V, the BMI is 4.68A, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas is argon, and the etching time is 600s.

The stability of the grid process after the process menu is cleaned is tested, and the process menu parameter settings for the test are as follows:

The ion beam angle is 35°, the ion energy is 600V, the ion acceleration bias is 800V, the BMI is 0.48A, the etching chamber pressure is 0.2mT, the gas flow rate is 18sccm, the gas is argon, and the etching time is 300s.

Figure 3 shows the cleaning results before and after etching a 12-inch SiO ₂ wafer with the test menu, and Figure 4 shows the changes in grid surface contamination.

It can be seen from Figures 3 to 4 that the removal of metal and SiO ₂ contamination on the surface of the Grid is relatively clean; and the process parameters are stable without significant changes.

Comparative example 1

Cleaning process menu settings:

B The ion beam angle is 37°, the ion energy is 400V, the ion acceleration bias is 400V, the BMI is 0.72A, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas is argon, and the etching time is 600s.

The stability of the grid process after the process menu is cleaned is tested, and the process menu parameter settings for the test are as follows:

The ion beam angle is 35°, the ion energy is 600V, the ion acceleration bias is 800V, the BMI is 0.48A, the etching chamber pressure is 0.2mT, the gas flow rate is 18sccm, the gas is argon, and the etching time is 300s.

The cleaning results are shown in Figures 5 and 6. It can be seen from Figures 5 and 6 that the metal and SiO ₂ contamination on the surface of the Grid is removed relatively cleanly; the etching rate has a small change.

In Comparative Example 1, although the BMI and ACV are relatively large, a certain ion beam is formed, which has a certain etching effect on the wafer. However, because the BMI is not particularly large, the cleaning of the grid is not so clean, resulting in certain process parameters. fluctuation.

Comparative example 2

B The ion beam angle is 37°, the ion energy is 400V, the ion acceleration bias is 400V, the BMI is 0.36A, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas is argon, and the etching time is 600s.

The stability of the grid process after the process menu is cleaned is tested, and the process menu parameter settings for the test are as follows:

The ion beam angle is 35°, the ion energy is 600V, the ion acceleration bias is 800V, the BMI is 0.48A, the etching chamber pressure is 0.2mT, the gas flow rate is 18sccm, the gas is argon, and the etching time is 300s.

The cleaning results are shown in Figures 7 and 8. It can be seen from Figures 7 and 8 that under the conditions of the BMV/ACV/BMI setting of Comparative Example 2, the BMI setting is not large enough, so the dissociated ions can be pulled The second layer of grids did not collide with the first layer and the second layer of grids, so the cleaning effect was not good. The metal and SiO ₂ contamination on the surface of the Grid was serious, and there was no obvious change before and after cleaning; the process parameters were comparatively Stable, no significant changes before and after cleaning.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (9)

1. A cleaning method for the grid net in the etching cavity of ion beam features that the process menu of ion beam etching is used to clean the grid net, the positive voltage, positive current and negative voltage are applied to the first grid net and the second grid net are set up to make the plasma pass through the first grid net without forming directional ion beam, so cleaning the contamination of grid net.

2. The cleaning method of claim 1, wherein the positive voltage applied to the first grid is 50-1000V.

3. The cleaning method according to claim 2, wherein the negative voltage applied to the second layer of grid is 10 to 1000V.

4. The method of claim 3, wherein the positive current applied to the first layer of mesh is between 5mA and 10A.

5. The method according to claim 1, wherein the process gas in the cleaning process is one or more of argon, oxygen, nitrogen, fluorine-based gas and alcohol gas.

6. The method of claim 5, wherein the flow rate of each of the process gases is 5-1000 sccm.

7. The method according to claim 1, wherein the time for the washing is 3 to 20 minutes.

8. The method of claim 1, wherein the contamination of the grid is Pt, siO ₂ One or more of Ru, mgO, siN, tiN, C, ag and Ta.

9. The cleaning method of claim 1, wherein the chamber pressure in the ion etching chamber is 0.05-10 mT.

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