CN100399518C - Etching system and etching solution processing method thereof - Google Patents

Abstract

The etching system comprises a processing tank with a silicon-containing etching solution, a cooling tank, a preheating tank, a first pipeline capable of conveying the etching solution from the processing tank to the cooling tank, a second pipeline capable of conveying the etching solution from the cooling tank to the preheating tank, and a third pipeline capable of conveying the etching solution from the preheating tank to the processing tank. The etching solution processing method of the invention firstly uses an etching solution to carry out an etching manufacturing process of a silicon-containing film, and then cools the etching solution to a first temperature to form a silicon saturated etching solution. Filtering and removing silicide particles with a size larger than a preset size in the silicon saturated etching solution, and then heating to a second temperature to form a non-saturated etching solution so as to carry out another etching manufacturing process. The second temperature is at least 10 ℃ higher than the first temperature.

Description

Etching system and method for treating etching solution thereof

technical field

The invention relates to an etching system and an etching liquid processing method thereof, in particular to an etching system with a stable silicon nitride/silicon oxide etching selectivity ratio and an etching liquid processing method thereof.

Background technique

1 to 3 illustrate the conventional STI manufacturing process performed on a wafer 10 . In the integrated circuit manufacturing process, a metal-oxide-semiconductor (MOS) manufacturing process often uses a shallow trench isolation manufacturing process to form electrical isolation between transistors. As shown in Figure 1, the shallow trench isolation manufacturing process first forms a pad oxide layer 14, a silicon nitride layer 16, and a photoresist layer 18 on a silicon substrate 12 in sequence, and then uses active region photo The mask transfers the pattern of active areas onto photoresist layer 18 .

Referring to FIG. 2 , the silicon nitride layer 16 and the silicon oxide layer 14 not covered by the photoresist layer 18 are then removed from the silicon substrate 12 by dry etching. After that, dry etching continues to etch down the silicon substrate 12 to form a shallow trench 20 in the silicon substrate 12 .

Referring to FIG. 3 , after the photoresist layer 18 is removed, a substrate oxide layer 22 is grown on the surface of the shallow trench 20 by a thermal oxidation process. Then silicon oxide is filled into the shallow trench 20 by chemical vapor deposition technology, and the surface of the wafer 10 is planarized by chemical mechanical polishing technology. Finally, the silicon nitride layer 16 is stripped from the silicon substrate 12 by a wet etching process, leaving the silicon oxide layer 14 and the silicon oxide in the shallow trench 20 . MOS transistors are formed in the active regions 24 on both sides of the shallow trenches 20 by a subsequent manufacturing process, and the silicon oxide in the shallow trenches 20 forms electrical isolation between the MOS transistors.

The existing STI manufacturing process uses heated phosphoric acid (H ₃ PO ₄ ) to strip the silicon nitride layer 16 . Since the subsequent manufacturing process of MOS transistors is greatly affected by the surface shape and cleanliness of the wafer 10 after stripping the silicon nitride layer 16 , how to control the etching selectivity ratio of silicon nitride and silicon oxide becomes extremely important. The etching selectivity ratio of silicon nitride and silicon oxide is mainly affected by parameters such as the type of etchant, reaction products, reaction temperature and reaction time, so these parameters must be properly controlled to achieve a good etching ratio.

FIG. 4 illustrates a conventional etching device 30 . As shown in FIG. 4 , the etching device 30 includes a processing tank 32 , a preheating tank 34 and an etching solution composed of phosphoric acid and deionized water. During the etching process, the etchant in the processing tank 32 is heated and maintained at a temperature between 150° C. and 160° C. to strip the silicon nitride layer 16 of the wafer 10 . The preheating tank 34 preheats the phosphoric acid from the service pipeline 40 to between 120° C. and 140° C., and then transports it to the treatment tank 32 through the pipeline 36 to supplement the etching solution discharged from the treatment tank 32 through the pipeline 38 .

5 and 6 show the change of the silicon concentration of the etching solution in the processing tank 32 . As shown in FIG. 5 , since the silicon nitride etching reaction will generate silicide, the silicon concentration of the silicide in the etching solution in the treatment tank 32 will increase with the number of etching reactions (ie, reaction time). When the silicon concentration of the etching solution continues to increase and becomes saturated (the silicon concentration is about 100 ppm), silicide particles will be produced. The generation of silicide particles will seriously affect the cleanliness of the surface of the wafer 10 after etching. For example, a silicide particle of 0.2 micron remains on the surface of the wafer 10, which can seriously cause integrated circuit failure for a 0.13 micron MOS manufacturing process.

Referring to FIG. 4 , in order to avoid the generation of silicide particles, the existing etching device 30 continuously circulates and filters the etching solution in the processing tank 32 through a pipeline 42 and a filter 44 (filter) to remove the silicide particles therein. However, when the amount of silicide particles generated is excessive, the filter 44 is prone to failure due to silicide particle clogging. Therefore, after several times of etching reactions (i.e. before the silicon concentration reaches 100ppm), the etching solution in the treatment tank 32 must be completely discharged through the pipeline 38, and then a new etching solution (silicon concentration is zero) must be supplied by the preheating tank 34 ) to the treatment tank 32 to prevent the silicon concentration in the treatment tank 32 from becoming saturated and producing too many silicide particles. In this way, the silicon concentration change curve 52 of the etching solution in the processing tank 32 changes between zero and 100 ppm and presents a zigzag shape, as shown in FIG. 5 .

The etching selectivity ratio between silicon nitride and silicon oxide is greatly affected by the silicon concentration in the etchant. However, the silicon concentration of the etching solution in the processing tank 32 is not maintained at a constant value, but gradually changes from zero (when the etching solution is completely renewed) to the silicon saturation concentration. Therefore, the etching selectivity ratio between silicon nitride and silicon oxide also changes with the number of times the etchant is used, making it more difficult to control manufacturing process parameters such as etching time.

The current processing method in the industry is to completely update the etching solution (silicon concentration is zero), first use dummy wafer to carry out several trial production (dummy runs) to increase the silicon concentration of the etching solution to a predetermined value, and then The etching manufacturing process of the actual wafer is carried out. However, this treatment method obviously reduces the use efficiency of the etching solution. Furthermore, completely renewing the phosphoric acid etching solution obviously also increases the usage of phosphoric acid, resulting in an increase of etching cost. Please refer to FIG. 6 , another etching solution treatment method is to periodically discharge part of the phosphoric acid etching solution through the pipeline 38 and supply an equal amount of new phosphoric acid to the treatment tank 32 through the pipeline 36 . In this way, the silicon concentration variation curve 62 of the etching solution in the processing tank 32 has a small variation range. Compared with the silicon concentration in the treatment tank 32 which changes with the etching reaction time, the phosphoric acid in the preheating tank 34 is directly supplied by the service pipeline 40 without any source of silicon, so its silicon concentration is substantially zero. Therefore, when the etching solution in the processing tank 32 is fully renewed in this processing method, it is still necessary to carry out several trial productions with a control chip to increase the silicon concentration of the etching solution.

Contents of the invention

The main purpose of the present invention is to provide an etching system with a stable silicon nitride/silicon oxide etching selectivity ratio and an etching solution processing method thereof.

To achieve the above purpose, the present invention discloses an etching system with a stable silicon nitride/silicon oxide etching selectivity ratio and an etching solution processing method thereof. The etching system includes a processing tank with a silicon-containing etching solution, a cooling tank, a preheating tank, a first pipeline that can transport the etching solution from the processing tank to the cooling tank, and a first pipeline that can deliver the etching solution from the cooling tank A second pipeline for delivering the etching solution to the preheating tank and a third pipeline for delivering the etching solution from the preheating tank to the processing tank.

The etchant treatment method of the present invention first uses an etchant to perform an etching process for a silicon-containing film, and then cools the etchant to a first temperature to form a silicon-saturated etchant. After filtering and removing silicide particles larger than a predetermined size in the silicon-saturated etching solution, the silicon-saturated etching solution is heated to at least 10° C. to form an unsaturated etching solution. Afterwards, another etching process is performed using the unsaturated etchant.

Compared with the prior art, the etchant of the present invention has a smaller variation range of silicon concentration, and thus can stably control the etching selectivity ratio of silicon nitride/silicon oxide. Furthermore, the present invention does not need to frequently discharge the used etchant, thus greatly reducing the cost of the etching process.

Description of drawings

1 to 3 illustrate an existing shallow trench isolation manufacturing process performed on a wafer;

Fig. 4 illustrates an existing etching device;

Fig. 5 and Fig. 6 show the silicon concentration change of existing etching solution;

Figure 7 shows the relationship between the silicon concentration of the etching solution and the etching rate and the concentration of silicide particles;

Fig. 8 shows the relationship between the silicon saturation concentration (i.e. the solubility of silicon) and temperature of etching solution;

Figure 9 illustrates an etching system of the present invention; and

FIG. 10 shows the variation of the silicon concentration of the etching solution of the present invention.

simple notation

10 wafers 12 silicon substrates

14 pad oxide layer 16 silicon nitride layer

18 photoresist layer 20 shallow trench

22 Substrate oxide layer 24 Active area

30 etching system 32 processing tank

34 preheating tank 36 pipelines

38 pipelines 40 factory pipelines

42 pipeline 44 filter

52 curves 62 curves

72 curves 74 curves

76 curves 92 curves

100 etching system 102 processing tank

104 cooling tank 106 preheating tank

111 valve 112 pipeline

113 valve 114 pipeline

116 pipelines 118 factory pipelines

120 filter 122 inlet port

124 outlet port 131 valve

132 pipeline 133 valve

134 pipeline 141 valve

142 pipeline 143 valve

144 pipeline

Detailed ways

FIG. 7 shows the relationship between the silicon concentration of the etching solution, the etching rate and the concentration of silicide particles. Curve 72 is the etching rate curve of silicon nitride, curve 74 is the etching rate curve of silicon oxide, and curve 76 is the concentration change curve of silicide particles. As shown in FIG. 7 , the etching rate of silicon nitride is substantially not affected by the silicon concentration and is constant, about 90 angstroms/minute. In contrast, the etching rate of silicon oxide decreases with the increase of silicon concentration, and when the silicon concentration exceeds 100ppm, it is a certain value, about 0.2 Angstrom/minute. When the silicon concentration is greater than 100 ppm, the concentration of silicide particles in the etchant increases as the silicon concentration increases.

FIG. 8 shows the relationship between the silicon saturation concentration (that is, the solubility of silicon) of the etching solution and the temperature. As shown in FIG. 8 , when the temperature of the etching solution is 80° C., 120° C. and 160° C., the silicon saturation concentrations are about 20 ppm, 40 ppm and 120 ppm respectively. That is, increasing the temperature of the etching solution can increase the solubility of silicon. As known, lowering the temperature of the etching solution can promote the formation of silicon silicide particles (solid phase) in the etching solution and reduce the silicon concentration of the etching solution (liquid phase), and the solid phase silicide particles can be filtered from the etching solution by a filter remove.

FIG. 9 illustrates an etching system 100 of the present invention. As shown in Figure 9, the etching system 100 includes a processing tank 102 with a silicon-containing etching solution, a cooling tank 104, a preheating tank 106, and a device that can transport the etching solution from the processing tank 102 to the cooling tank 104. A pipeline 112 , a pipeline 114 for delivering the etching solution from the cooling tank 104 to the preheating tank 106 , and a pipeline 116 for delivering the etching solution from the preheating tank 106 to the processing tank 102 . In addition, the preheating tank 106 can also supply brand new etching solution through the factory pipeline 118 .

The cooling tank 104 cools the etching solution in the tank to a first temperature to make the silicon concentration of the etching solution saturated, wherein the first temperature is preferably between 80° C. and 120° C. The preheating tank 106 heats the etching solution in the tank to a second temperature to make the silicon concentration of the etching solution in a non-saturated state, wherein the second temperature is at least 10° C. higher than the first temperature. The preheating tank 106 heats the etchant from the cooling tank 104 and then transports it to the processing tank 102 through a pipeline 116 for wet etching process. The temperature of the etching solution in the processing bath 102 may be between 130° C. and 160° C. Preferably, the preheating tank 106 directly heats the etching solution in the tank to the temperature for etching reaction, and then transports it to the processing tank 102 through the pipeline 116 .

The etching system 100 of the present invention also includes a filter 120 having an inlet port 122 and an outlet port 124, a pipeline 132 that can transport the etching solution from the bottom of the cooling tank 104 to the inlet port 122, and a pipeline 132 that can be fed from the bottom of the cooling tank 104. The outlet port 124 delivers the etching solution to the pipeline 134 of the cooling tank 104 . The filter 120 can be a filter 120 with a plurality of pores, wherein the size of the pores can be less than 0.1 micron. The cooling tank 104 promotes the silicon in the etching solution to form solid-phase silicide particles by reducing the temperature of the etching solution, and the solid-phase silicide particles larger than 0.1 microns will not pass through the openings of the filter 120 when the etching solution passes through. It is filtered out from the etching solution.

The etching system 100 of the present invention may also include a pipeline 142 connected to the inlet port 122 and a pipeline 144 connected to the outlet port 124 . Since the pores of the filter 120 will be blocked by silicide particles, it must be cleaned frequently to remove the blocked silicide particles. When the present invention cleans the filter 120, a solution comprising hydrofluoric acid (such as dilute hydrofluoric acid) can be input from the pipeline 142 to dissolve the silicide particles on the filter 120, and the dissolved silicide particles will Output from the pipeline 144. Afterwards, the hydrofluoric acid remaining in the filter 120 is rinsed with deionized water. In addition, the filter 120 can also be cleaned by inputting a deionized water through the pipeline 144 to clean and remove the silicide particles on the filter 120 in a countercurrent manner, and the waste liquid is output from the pipeline 142 .

When cleaning the filter 120 , the valves 131 and 133 are closed to prevent the silicide particles on the filter 120 from flowing back into the cooling tank 104 . When the filter 120 filters the silicide particles in the cooling tank 104 , the valves 141 and 143 are closed. Furthermore, when the filter 120 is cleaned, the valve 113 can be temporarily closed to suspend the supply of etching solution to the preheating tank 106, and the preheating tank 106 can continuously supply the etching solution during the cleaning of the filter 120 due to the storage of a large amount of etching solution. to the treatment tank 102. After cleaning the filter 120 and filtering the silicide particles in the cooling tank 104 , the valve 113 is opened to supply the etching solution to the preheating tank 106 .

As the design criteria of the semiconductor manufacturing process shrinks, the size of particles allowed in the etchant also shrinks accordingly. Therefore, it is necessary to select the filter 120 with smaller openings (for example, openings below 0.1 micron). However, since smaller openings are prone to failure due to particle clogging, it is necessary to increase the frequency of cleaning or replacement of the filter to ensure that the filter can remove the particles in the etching solution. When the filter 120 of the present invention is being cleaned or replaced, the preheating tank 106 can still continuously supply the circulating and filtered etching solution to the processing tank 102 . That is to say, the present invention increases the cleaning frequency of the filter 120 without affecting the supply of etching solution, so the filter 120 with smaller openings can be selected to cope with future semiconductor manufacturing processes.

FIG. 10 shows the variation of the silicon concentration of the etching solution in the processing bath 102 . The present invention can indirectly control the silicon concentration of the etching solution in the processing tank 102 by controlling the temperature of the cooling tank 104 . The etchant in the cooling tank 104 is saturated with silicon, and the silicon concentration depends on the temperature of the cooling tank 104 . The preheating tank 106 simply heats the etching solution from the cooling tank 104 without injecting new etching solution through the service pipeline 118 without changing the silicon concentration of the etching solution. The silicon concentration of the etchant transported from the preheating tank 106 to the processing tank 102 is not zero, but maintains a constant value. Compared with the prior art, the silicon concentration of the etching solution added to the treatment tank 32 is zero, thus causing a larger concentration variation interval (as shown in the curve 62 of Figure 10 ), the present invention is due to the addition of the silicon concentration of the etching solution to the treatment tank 102. is not zero, so the silicon concentration change curve 92 has a smaller concentration change interval. The above-mentioned system can even continuously input and output the etching solution into and out of the processing tank 102 at a fixed flow rate, so that the variation curve of the silicon concentration becomes stable and less than the saturation concentration.

Furthermore, compared to the silicon concentration of the etching solution in the preheating tank 34 of the prior art is zero (please refer to Figures 4, 5 and 6) and the processing tank 32 must periodically discharge the used etching solution, the present invention is due to The cooling tank 104 can supply the recycled etchant to the preheating tank 106 , so the silicon concentration in the preheating tank 106 is not zero, so the processing tank 102 does not need to use waste control chips for trial production.

In addition, phosphoric acid is only used as a catalyst in the etching solution, and will not be consumed by the etching reaction. However, in the prior art, the used etching solution must be discharged, resulting in an increase in the cost of the etching manufacturing process and additional costs for treating the waste etching solution. Relatively, the present invention does not need to discharge the used etchant, which can greatly reduce the cost of the etching process.

In short, the etching solution processing method of the present invention first uses an etching solution to perform an etching process of a silicon-containing film, and then cools the etching solution to a temperature between 80° C. and 120° C. to form a silicon-saturated etching solution. After filtering and removing silicide particles larger than a predetermined size (for example, 0.1 micron) in the silicon-saturated etching solution, the silicon-saturated etching solution is heated to at least 10° C. to form an unsaturated etching solution. Afterwards, another etching process is performed using the unsaturated etchant.

Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention It shall prevail as defined in the appended claims.

Claims (15)

1. etch system comprises:

One treatment trough has one and contains silicon etching liquid;

One cooling bath, wherein the etching solution in this cooling bath is cooled to one first temperature, uses so that the silicon concentration of this etching solution is a saturation condition;

One first pipeline is used for carrying this etching solution to this cooling bath from this treatment trough;

One fore-warmer tank;

One second pipeline is used for carrying this etching solution to this fore-warmer tank from this cooling bath;

One the 3rd pipeline is used for carrying this etching solution to this treatment trough from this fore-warmer tank;

One filter has an arrival end and a port of export;

One the 4th pipeline is carried the arrival end of this etching solution to this filter in order to this cooling bath certainly; And

One the 5th pipeline carries this etching solution to this cooling bath in order to the port of export of this filter certainly.

2. etch system as claimed in claim 1, wherein this first temperature is between 80 ℃ to 120 ℃.

3. etch system as claimed in claim 1, wherein this fore-warmer tank is heated to one second temperature with this etching solution, uses so that the silicon concentration of this etching solution is a unsaturated state.

4. etch system as claimed in claim 3, wherein this second temperature is higher than at least 10 ℃ of this first temperature.

5. etch system as claimed in claim 1, wherein this filter has a plurality of perforates less than 0.1 micron, is used for removing the silicide particulate of this etching solution greater than this perforate.

6. etch system as claimed in claim 5, it comprises in addition:

One the 6th pipeline is connected in the arrival end of this filter concurrently with the 4th pipeline; And

One the 7th pipeline is connected in the port of export of this filter concurrently with the 5th pipeline;

Wherein the 6th pipeline is used to import a solution that comprises hydrofluoric acid dissolving the silicide particulate on this filter, and the 7th pipeline is used to export this solution.

7. etch system as claimed in claim 5, it also comprises:

One the 6th pipeline is connected in the arrival end of this filter concurrently with the 4th pipeline; And

One the 7th pipeline is connected in the port of export of this filter concurrently with the 5th pipeline;

Wherein the 7th pipeline is used to import a deionized water with the silicide particulate on this filter of cleaning removal, and the 6th pipeline is used to export this deionized water.

8. etch system as claimed in claim 1, wherein the etching solution temperature in this treatment trough equals the etching solution temperature in this fore-warmer tank.

9. etching solution processing method comprises:

Utilize an etching solution to carry out the etching manufacturing process of a silicon-containing film;

This etching solution to one of cooling first temperature in a cooling bath is to form the saturated etching solution of a silicon;

Filter in the saturated etching solution of this silicon in this cooling bath silicide particulate greater than a preliminary dimension, wherein filtering this silicide particulate is that the saturated etching solution of this silicon in this cooling bath is passed through a filter with a concurrent, and the saturated etching solution of this silicon after will filtering is back in this cooling bath;

After filtering the saturated etching solution of this silicon in this cooling bath is delivered to a fore-warmer tank, and in this fore-warmer tank saturated etching solution to one second temperature of this silicon of heating, to form a unsaturation etching solution; And

Utilize this unsaturation etching solution to carry out another etching manufacturing process.

10. etching solution processing method as claimed in claim 9, wherein this first temperature is between 80 ℃ to 120 ℃.

11. etching solution processing method as claimed in claim 9, wherein this second temperature is higher than at least 10 ℃ of this first temperature.

12. etching solution processing method as claimed in claim 9, wherein this filter has a plurality of perforates less than 0.1 micron to remove in the saturated etching solution of this silicon the silicide particulate greater than this perforate.

13. as the etching solution processing method of claim 12, it also comprises a deionized water with a reflux type by this filter, to remove the silicide particulate on this filter.

14. as the etching solution processing method of claim 12, it comprises that also the solution with a hydrofluoric acid containing passes through this filter with a concurrent, to remove the silicide particulate on this filter.

15. etching solution processing method as claimed in claim 9, wherein this etching manufacturing process is carried out under this second temperature.

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