JP2009242941A - Semiconductor device production method and semiconductor production apparatus - Google Patents

Abstract

Metals are embedded without voids in wiring portions using nanoscale microstructures in a semiconductor device, and electrical defects are suppressed to improve the yield of the semiconductor device.
In a step of embedding a metal plating film in a via hole or trench provided in an insulating film formed on a semiconductor substrate, first, the volume of the initial plating solution, the amount of replenished plating solution, the number of processed wafers, Collect each data of flowing current value and discharged plating solution amount. Next, the accumulated charge amount of the plating process is calculated based on the acquired current value. Also, the volume of the total plating solution is calculated. Then, based on the acquired volume of the total plating solution, the amount of discharged plating solution, and the accumulated charge amount, the decomposition amount of the inhibitor contained in the plating solution is calculated. Only when the amount of decomposition products is equal to or less than a preset threshold value, the plating process of the semiconductor substrate is performed.
[Selection] Figure 6

Description

  The present invention relates to a semiconductor device manufacturing method and a semiconductor manufacturing device, and more particularly to a plating method and a plating apparatus in a metal wiring forming process of a semiconductor device.

  FIG. 9 is a schematic configuration diagram of a conventional electroplating apparatus. The electroplating apparatus includes a circulation line 101, a plating bath 102, a cathode 104, an anode 105, a wafer 106, a filter 107, an additive concentration measuring device 108, a CPU 109, and an additive supply device 110.

  And in the conventional electroplating, the metal is plated, replenishing an additive (patent document 1). In addition, the concentration of the additive is measured by a current-potential curve (Non-Patent Document 1).

  FIG. 10 is a flowchart of processing steps in a conventional plating method. As shown in FIG. 10, in the conventional processing steps, plating solution replenishment (S101), additive concentration measurement (S102), recipe start (S103), wafer placement (S104), plating processing (S105), wafer unloading (S106). ), Plating is performed through each step of the recipe end (S107).

  In the conventional plating method, during electroplating, the concentration of each of the brightener, smoothing agent, and inhibitor contained in the plating solution as an additive is measured, and if necessary, each component is replenished. Electroplating is performed while maintaining the concentration within a predetermined range.

As a specific method, a current-potential curve of a plating solution containing an additive is used, or a CV (Cyclic Voltammetry) electrode for obtaining a current-potential curve of the plating solution is disposed in the plating solution in the plating apparatus. Measurement of the concentration of the additive is performed.
JP 2001-152398 A Hitoshi Oyamada and 3 others “Electrodeposition time dependence of filler filling ability in electrolytic copper plating” Journal of Japan Institute of Electronics Packaging Technical Paper Vol. 7 No. 3 p261-265 (2004)

  In the conventional electroplating method and electroplating apparatus, it is difficult to measure and evaluate the concentration of all the inclusion components present in the plating solution including by-products generated during the plating process. Therefore, a metal cannot be embedded without voids in a wiring portion using a nanoscale microstructure in a semiconductor device.

  An object of the present invention is to make it possible to embed a metal without voids in a wiring portion using a nanoscale microstructure in a semiconductor device, to suppress electrical defects and to improve the yield of the semiconductor device.

  In the method of manufacturing a semiconductor device according to the present invention, in the step of embedding a metal plating film in a via hole or a trench provided in an insulating film formed on a semiconductor substrate, first, the initial plating solution volume, supplemented plating solution Collect each data of quantity, number of processed wafers, flowing current value and discharged plating solution amount. Next, the accumulated charge amount of the plating process is calculated based on the acquired current value. Also, the volume of the total plating solution is calculated. Then, based on the acquired volume of the total plating solution, the amount of discharged plating solution, and the accumulated charge amount, the decomposition amount of the inhibitor contained in the plating solution is calculated.

  In the method for manufacturing a semiconductor device described above, it is preferable that a predetermined amount of plating solution is discharged when the amount of the decomposition product exceeds a preset value.

  The semiconductor manufacturing apparatus according to the present invention performs a process of embedding a metal plating film in a via hole or a trench provided in an insulating film formed on a semiconductor substrate. The semiconductor manufacturing apparatus according to the present invention includes means for circulating the plating solution, means for supplying the plating solution, and means for discharging the plating solution. Also, means for collecting each data of initial plating solution volume, replenished plating solution amount, number of processed wafers, flowed current value and discharged plating solution amount, and accumulation of plating process based on the acquired current value The means for calculating the amount of charge, the means for calculating the volume of the total plating solution, and the decomposition of the inhibitor contained in the plating solution based on the obtained volume of the total plating solution, the amount of discharged plating solution and the cumulative amount of charge. Means for calculating the quantity.

  In the semiconductor manufacturing apparatus, the plating solution discharge means preferably discharges the plating solution when the amount of the decomposed product exceeds a preset value.

  According to the present invention, by calculating the amount of by-products generated by electroplating and controlling the amount of by-products, it is possible to improve the yield of semiconductor devices by preventing filling defects due to variations in the composition of the plating solution. it can.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a schematic configuration diagram of an electroplating apparatus according to the first embodiment. The electroplating apparatus includes a plating bath 21 having a partition 22. An anode 14 is disposed at the bottom of the plating bath 21. The cathode 10 disposed facing the anode 14 holds the wafer 11 with the surface to be processed facing the anode 14. Between the anode 14 and the cathode 10, a filter 13 and a diffusion plate 12 are disposed from the anode 14 side. Moreover, the electroplating apparatus of this embodiment is provided with the circulation line 3 and the sub circulation line 4 as a circulation path | route of plating solution. Here, the circulation line 3 is a circulation path for reflowing the plating solution derived from the upper end of the plating bath 21 between the diffusion plate 12 and the filter 13 through the plating solution reservoir 2 and the filter 7. The auxiliary circulation line 4 is a circulation path through which the plating solution led out from the bottom of the plating bath 21 flows again between the filter 13 and the anode 14 through the filter 8. A supply valve 9 for introducing a new plating solution into the circulation line 3 is provided on the upstream side of the plating solution reservoir 2 in the circulation line 3, and the circulation is provided on the upstream side of the filter 8 in the sub circulation line 4. A waste liquid valve 5 is provided for discharging the plating solution from the path. The control device 1 controls the open / closed state of the supply valve 9 and the open / closed state of the waste liquid valve 5 based on data to be described later acquired by the monitoring device 6. In the present embodiment, the control device 1 is configured to control various operations of the electroplating device.

  In FIG. 1, in the copper electroplating apparatus, the current between 1 A and 50 A is applied to the wafer 11 placed on the cathode 10 side while circulating the plating solution and rotating the wafer 11 at a rotation speed of 5 to 100 rpm. To form a plating film. During the plating process, the plating solution is circulated through the main circulation line 3 including the plating solution reservoir 2. A plating solution collected on the anode 14 side is circulated by a secondary circulation line (SAC: Separate Anode Chamber line) 4 on the anode 14 side. The plating solution used here mainly consists of copper sulfate and additives.

  Three types of additives are used as the additive. The three types are inhibitors, accelerators (glossy materials) and smoothing agents. This additive plays an important role when embedding copper in the microstructure. The role is briefly explained as follows.

  The inhibitor is a PEG (poly (ethylene glycol))-PPG (poly (propylene glycol)) polymer (polymer), which suppresses the growth of the copper film. The accelerator (brighter) is an organic substance containing sulfur and promotes the growth of the copper film. The smoothing agent is an amine-based organic compound, and suppresses the growth of the copper film at the portion where the electric field is concentrated on the wafer, and does not suppress the growth of the copper film at the portion where the electric field is not concentrated. Therefore, the smooth material has a function of improving the smoothness of the copper film.

  Thus, in order to embed a copper film in a nano-order fine structure such as a via, contact, or trench without voids or defects such as voids or seams, it is very important to control the composition of the plating solution. However, it has been found that when the electroplating process proceeds, the composition of the plating solution changes due to electrolysis or the like. In addition, the metal cannot be embedded in the nanoscale fine structure only by controlling the concentration of the above-described additive within a predetermined value range. This is because the three types of additives can be electrolyzed to form different ones (by-products) including molecular structures different from those of the three types of additives.

  As a precaution, the additive concentration control process is performed by opening the supply valve 9 in the circulation line 3 and replenishing the plating solution with a new plating solution. Conventionally, the by-product has been considered to have no effect on the embedding properties or to have a small effect, and thus this method has been used. However, as a result of the study by the inventors of the present application, it has been found that in this method, a via filling defect occurs in the nanoscale structure as described above. However, it is difficult to measure the amount of by-products during the plating process. Therefore, in the electroplating apparatus shown in FIG. 1 devised by the inventors of the present application, the monitoring apparatus 6 has an initial plating solution volume, a replenished plating solution amount, the number of processed wafers, a flowing current value, and an applied voltage. Data such as value, processing time, number of revolutions, amount of liquid waste, etc. are collected, and the control device 1 uses the data to calculate and determine the amount of by-products generated by electrolysis (the amount of decomposed product). Here, the “replenished plating solution amount” is the amount of plating solution replenished based on the “first plating solution”, and the “waste solution amount” is discharged based on the “first plating solution”. Is the amount of the plating solution applied.

  The monitoring device 6 and the control device 1 are stored in, for example, a dedicated arithmetic circuit or hardware including a processor and a memory such as a RAM (Random Access Memory) and a ROM (Read Only Memory) and the memory. It can be realized by software operating on the processor. In the present embodiment, the monitoring device 6 and the control device 1 are realized as a computer and a program executed on the computer. In addition, the monitoring apparatus 6 may acquire with the various sensors which acquire each above-mentioned data directly, and may acquire indirectly from the operation state of an electroplating apparatus.

Here, a model used by the control device 1 for calculation of the decomposition product amount (by-product amount) will be described. In the present embodiment, as shown in FIG. 1, since one wafer is processed in one plating process, the number of plating processes matches the number of processed wafers. In this case, the model expression of the decomposition product amount N _bn contained in the plating solution after the n-th wafer processing is the decomposition product amount N _b0 present in the initial plating solution (the first plating solution), in the n-th wafer processing. When the decomposition product generation amount G _n , the total plating solution volume (outer volume) V ₂ , and the amount of waste liquid V _{1 at} each time, it can be expressed as the following equation (1).

In particular, the model formula uses the accumulated charge amount (integrated value of the current value) calculated from the current value applied to the processed wafer to determine the generation amount G _n in each plating process (for example, the number of wafers and the current value applied). And the amount of decomposition product remaining after each waste solution is calculated from the amount of the plating solution discharged with respect to the total plating solution volume. Then, the amount of decomposition product remaining between the waste liquids is integrated to determine the amount of decomposition product N _bn contained in the plating solution after the nth wafer processing. By adding the decomposition product amount generated during the subsequent plating treatment to the decomposition product amount N _bn , the decomposition product amount at the time of the plating treatment can be calculated. Note that the data (particularly the current value) used to calculate the decomposed product amount N _bn needs to be acquired at a sampling rate finer than at least 2 Hz. This is because it affects the calculation accuracy of the amount of by-products. For example, when the sampling rate becomes slower than 2 Hz, the calculation accuracy deteriorates by 3% or more. Further, in the above formula (1), the volume V ₂ and the amount of waste liquid V _{1 of} the total plating solution are set to constant values, but when the amount of waste liquid and the amount of replenisher are different each time, the respective values are used. The amount of decomposition product can be calculated.

  FIG. 2 is a diagram showing the calculated amount of by-products and the state of occurrence of electrically defective chips caused by seams and voids. In FIG. 2, the vertical axis corresponds to the amount of by-products (the amount of decomposed products). It can be seen from FIG. 2 that when a by-product exceeds a certain amount, defective chips are generated. That is, it has been newly found that by-products are generated because the plating solution is electrolyzed in the process of processing the wafer as described above, and defects such as seams and voids are generated depending on the amount of the by-products. In addition, such a by-product behavior indicates that the by-product has an inhibitory effect. The present inventors have discovered this new fact. In the electroplating apparatus of this embodiment, the maximum capacity that can be filled with the plating solution is 200L.

  FIG. 3 is a diagram showing the result of physical analysis of an electrically defective chip (which identifies a defective part and observes a cross section of the defective part). The diameter of the contact 35 is 60 nm to 70 nm, and the thickness of the interlayer insulating film 32 including the depth of the trench 34 and the contact 35 is 200 nm to 300 nm. In FIG. 3, an interlayer insulating film 31 that is a base layer of the interlayer insulating film 32 and a metal plating layer filled in the trench 33 provided in the interlayer insulating film 31 are shown together.

  In FIG. 3, the depth of the trench 34 is less than 100 nm. Therefore, the aspect ratio of the contact 35 is about 5 at the maximum. In the case of a contact diameter of 100 nm or less, embedding becomes difficult when the aspect ratio is 3 or more, and a void 41 is generated on the side wall of the trench 34 in an electrically defective chip as shown in FIG. Further, a seam 42 was generated at the contact 35 portion. In addition, even if the copper concentration in the plating solution was changed from 10 mg / liter to 100 mg / liter, the generation of the seam 42 and the void 41 could not be suppressed.

  Next, the mechanism of occurrence of the via filling failure will be described.

  FIG. 4 is a mechanism diagram showing changes in via filling characteristics with respect to changes in the plating solution. According to the study by the present inventors, in order to obtain good via embedding characteristics, it is important to control the by-product 52 generated when the inhibitor 51 is electrolyzed. Although the inhibitor 51 is consumed by electrolysis, it was confirmed that a phenomenon that a molecule having a molecular weight smaller than that of the original PEG-PPG polymer was generated at that time was confirmed. This low molecular weight molecule is the by-product 52 described above. As described above, the by-product 52 has a function of suppressing the growth of a copper film similar to the inhibitor 51. Further, since the by-product 52 has a low molecular weight, the diffusion coefficient is large, and the amount reaching the fine via bottom (the bottom of the contact 35 in FIG. 4) increases. As a result, via and contact embedding defects occur. That is, it is considered that a defect such as a seam is generated as a result of the suppression of metal film growth (bottom filling) from the via bottom because the by-product 52 reaches the via bottom early.

  Therefore, even if the amount of the three kinds of additives is controlled by replenishing a new plating solution, the by-product generated by such a mechanism cannot be controlled, and embedding defects cannot be suppressed. The fundamental solution is to discharge by-products from the plating solution to the outside, that is, to discharge the waste solution. Therefore, it is most important to control the amount of waste liquid. Therefore, in the electroplating apparatus according to the first embodiment, when the amount of the by-product calculated by the above equation (1) exceeds a predetermined amount, the waste valve 5 in the SAC line 4 is opened. Thus, a configuration for discharging the plating solution is adopted. In this configuration, since by-products are released to the outside by the release, the amount of by-products in the plating solution that causes voids and seams can be reduced.

  FIG. 5 is a diagram showing the amount of by-products calculated by the above formula (1) and the result of actually measuring the amount of by-products in the plating solution using liquid chromatography. It can be seen from FIG. 5 that the amount of by-products in the plating solution increases as the amount of by-products calculated increases. In this measurement, the specific molecular structure of the by-product to be detected could not be specified, so the liquid was sampled on the basis of the calculated by-product amount, and molecules having a molecular weight different from that of the inhibitor were subjected to liquid chromatography. It is measured by.

  In liquid chromatography, the refractive index intensity with respect to the retention time of the column is observed, but such molecules with different molecular weights are detected separately because they appear different retention times (measurement times) that the inhibitor can observe. be able to. In actual measurement, it was possible to observe a peak considered as a by-product other than the inhibitor in a longer time than the retention time (measurement time) at which the inhibitor can be observed. In this liquid chromatography, the size exclusion mode is used. In this mode, molecules with a low molecular weight enter the back of the column, making it difficult to exit the column and increasing the column retention time. In this measurement, since a peak is observed when the retention time is long, it suggests that the molecular weight of the detected by-product is smaller than the molecular weight of the inhibitor. The results shown are obtained.

(Second Embodiment)
Based on the first embodiment of the present invention, the second embodiment provides an embedding method free from defects such as voids and seams.

  FIG. 6 is a flowchart of the plating process showing the second embodiment. When the recipe is started, first, the monitoring device 6 measures the concentrations of the three additives (S1). When the measured value exceeds the preset value range, the monitoring device 6 instructs the control device 1 to replenish the plating solution as NG. In response to the instruction, the control device 1 opens the supply valve 9 and replenishes a predetermined amount of plating solution (S1NG, S2). When the replenishment is completed, the monitoring device 6 again measures the concentration of the additive (S1). The plating solution is replenished repeatedly until the concentration of the additive falls within the above range, but the apparatus is stopped when the replenishment amount exceeds the value of the bath volume of the plating solution. When the concentration of the additive falls within the above range (S1OK), the monitoring device 6 performs the initial plating solution volume, the replenished plating solution amount, the number of processed wafers, the flowed current value, the applied voltage value, and the processing time. The device data such as the number of revolutions and the amount of discharged liquid is collected (S3). The control device 1 calculates the amount of by-products from these device data based on the formula (1) (S4). When the amount of by-products exceeds the preset value range, the control device 1 opens the waste liquid valve 5 and executes the waste liquid (S4NG, S5), and then collects data again to determine the amount of by-products. Calculate (S4). The waste liquid is repeatedly executed until the amount of by-products falls within a preset value range (S4NG, S5). When the amount of by-products falls within a preset value range, the control device 1 transports the wafer into the device (S6) and places the wafer on the cathode electrode. Thereafter, metal plating is performed (S7), the wafer is unloaded after the completion of plating (S8), and the recipe ends.

  Here, the important thing is that the concentration of the additive, which has been carried out outside the conventional recipe, and a process for judging the quality of this concentration are newly provided, and the concentration of the additive is a preset value. A mechanism and a process for adding a plating solution when it is out of range (S1NG) are provided. Furthermore, more importantly, after collecting the data of the apparatus, a new step for calculating the amount of by-products and determining the quality of this amount is provided, and the amount of by-products is outside the range of the preset value. This is the point where a mechanism and a process for implementing the waste liquid are provided in some cases (S4NG). Since these are implemented within the recipe, the monitored data can be calculated on the fly and the results fed back. The volume of the plating solution to be added and the volume of the plating solution to be discharged are controlled by the amount of by-products. Therefore, the calculation accuracy of the by-product amount is greatly improved.

  Although the description here is based on the recipe start (operation start) as a starting point, it goes without saying that the calculation accuracy does not greatly change even when the lot is reserved in the apparatus (track in).

(Third embodiment)
A third embodiment of the present invention will be described. The third embodiment of the present invention relates to an electroplating method in which an optimum amount of waste liquid is determined. Since the plating solution is expensive, the amount of waste solution is preferably as small as possible. Therefore, in the present embodiment, a method for determining an optimum amount of waste liquid based on the amount of wafers to be processed, that is, the amount of by-products to be generated, the volume of the entire plating solution tank, and the amount of waste liquid will be described.

  FIG. 7 is a diagram showing a result of simulating the amount of by-products in the plating solution with respect to the number of waste liquids. The calculation results when the initial by-product amount is “1” and 8% of the total plating solution is discarded and when 29% is discarded are shown. The waste liquid rate is determined by random numbers.

  It can be seen from FIG. 7 that the amount of by-products contained in the plating solution continues to increase because the by-product cannot be sufficiently released to the outside at a waste liquid rate of 8%. On the other hand, it can be seen that the increase in by-products is suppressed at a waste liquid rate of 29%. This shows that there is an optimum value for the waste liquid rate. Therefore, the result of obtaining the amount of increase of by-products with respect to the waste liquid rate from this calculation result is shown below.

  FIG. 8 is an explanatory diagram of an increase amount of by-products with respect to the waste liquid rate. In FIG. 8, the horizontal axis corresponds to the waste liquid rate, and the vertical axis corresponds to the amount of by-products.

  As can be seen from FIG. 8, the increase amount decreases as the waste liquid rate increases. Since the amount of the by-product is “1”, it can be seen that the waste liquid ratio for preventing the amount of the by-product from exceeding “1” is 34%. Therefore, in order not to increase the amount of by-products in the plating solution, it is necessary to waste 34% of the total plating solution amount at the time of waste solution. Of course, if the waste liquid ratio is made higher than 34%, it goes without saying that the amount of by-products in the plating liquid can be reduced as the number of waste liquids increases.

  In this embodiment, it is possible to determine the amount of waste liquid in advance in this way, and the value obtained here is held as a threshold value in the monitoring device 6 in FIG. 1, and the waste liquid rate is higher than this value. When it is lowered, it is possible to prevent the embedding failure by stopping the apparatus. In order to embed copper in a microstructure having a contact diameter of 100 nm or less as shown in FIG. 3 without defects such as voids and seams, at least 34% of the plating solution must be drained.

  Although the copper film is embedded in the above embodiment, it goes without saying that the same applies to other metal films such as silver and aluminum.

  As described above, according to the present invention, the yield of the semiconductor device can be improved by preventing the filling failure due to the composition variation of the plating solution.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the technical idea of the present invention. For example, in each of the above-described embodiments, the case where the present invention is applied to a semiconductor manufacturing apparatus including a circulation line and a sub-circulation line has been described. However, the present invention is a semiconductor manufacturing apparatus including only one circulation line as shown in FIG. It is also applicable to.

  The method for manufacturing a semiconductor device and the semiconductor manufacturing apparatus of the present invention have a function of obtaining the amount of by-product generated by calculation, and it is possible to control the amount of by-product to a constant value using this function, This is useful as a manufacturing technique for a wiring process of a semiconductor device in which metal is embedded in a nano-order fine structure. Moreover, it is applicable also to uses, such as a plating process in MEMS.

1 is a schematic configuration diagram of an electroplating apparatus according to a first embodiment of the present invention. Figure showing the relationship between the calculation result of the amount of by-products in the plating solution and the occurrence of defects Diagram showing the outline of via hole and trench filling failure Diagram showing the mechanism of poor filling of via holes and trenches The figure which shows the liquid chromatography measurement result based on the calculation result of the quantity of the by-product in the plating solution The flowchart which shows the process of the electroplating method in the 2nd Embodiment of this invention. The figure which shows the waste liquid rate simulation result in the 3rd Embodiment of this invention The figure which shows the waste-liquid rate determination method in the 3rd Embodiment of this invention. Schematic configuration diagram of conventional electroplating equipment Flow chart showing steps of a conventional electroplating method

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Plating solution reservoir 3 Circulation line 4 Sub circulation line 5 Waste liquid valve 6 Monitoring apparatus 7, 8 Filter 9 Supply valve 10 Cathode 11 Wafer 12 Diffusion plate 13 Filter 14 Anode

Claims (4)

In a method for manufacturing a semiconductor device, comprising a step of embedding a metal plating film in a via hole or a trench provided in an insulating film formed on a semiconductor substrate,
The step of embedding the metal plating film,
Collecting each data of initial plating solution volume, replenished plating solution amount, number of processed wafers, flowed current value and discharged plating solution amount;
Calculating a cumulative charge amount of the plating process based on the flowing current value;
Calculating the total plating solution volume;
Calculating a decomposition amount of the inhibitor contained in the plating solution based on the volume of the total plating solution, the discharged plating solution amount and the accumulated charge amount; and
A method for manufacturing a semiconductor device, comprising: Discharging a predetermined amount of plating solution when the amount of decomposed product exceeds a preset value;
Replenishing the plating solution;
The method of manufacturing a semiconductor device according to claim 1, further comprising: In a semiconductor manufacturing apparatus for performing a process of embedding a metal plating film in a via hole or a trench provided in an insulating film formed on a semiconductor substrate,
Means for circulating the plating solution;
Means for supplying a plating solution;
Means for discharging the plating solution;
Means for collecting each data of initial plating solution volume, replenished plating solution amount, number of processed wafers, flowed current value and discharged plating solution amount;
Means for calculating a cumulative charge amount of the plating process based on the flowing current value;
Means for calculating the volume of the total plating solution;
Based on the volume of the total plating solution, the amount of discharged plating solution and the accumulated charge amount, a means for calculating the amount of decomposition product of the inhibitor contained in the plating solution;
A semiconductor manufacturing apparatus comprising:   4. The semiconductor manufacturing apparatus according to claim 3, wherein the plating solution discharging means discharges a predetermined amount of the plating solution when the amount of the decomposition product exceeds a preset value.