JP4755053B2 - Wiring correction method - Google Patents

Description

  The present invention relates to a wiring correction method for forming a connection hole for drawing a correction wiring for connecting a lower layer wiring and an upper layer wiring of a semiconductor device by focused ion beam processing.

  In recent years, when changing the circuit or characteristics of an LSI, before the revision of the design, there is a tendency to perform an operation check by performing wiring processing with a focused ion beam (FIB) on an actual sample. When wiring correction is performed by FIB processing, the sample surface is sputtered by irradiating the surface of the sample with a focused ion beam made of accelerated positron gallium ions. Then, a connection hole reaching the lower layer wiring as a target is excavated, and the focused hole is filled with tungsten by irradiating a focused ion beam while sparging tungsten gas on the surface of the sample, and the lower layer wiring is connected to the upper layer wiring. (Refer nonpatent literature 1).

However, recently, it is difficult to specify the formation position of the connection hole due to planarization processing of the LSI surface, formation of a dummy pattern, or the like. In other words, when performing connection hole drilling by FIB processing, the FIB is scanned over the sample surface, and secondary electrons or secondary ions generated from the sample surface are imaged and converted into an image, thereby forming an uneven shape on the sample surface. Was confirmed on the screen. Then, a convex portion due to a lower layer wiring serving as a target is set as a scanning region, and a connection hole is formed by irradiating the scanning region with FIB. However, planarization processing such as CMP (Chemical Mechanical Planarization) is performed. As a result, it was difficult to determine the uneven shape of the sample using FIB. For this reason, by forming the connection hole in a wide range, the error is offset and the connection hole exposing the lower layer wiring is formed.

  However, when a wide connection hole is formed, there arises a problem that the processing time for filling the connection hole with tungsten becomes very long. Recently, connection holes tend to become deeper due to the multi-layer structure of LSI, and it is very difficult to fill the connection holes with tungsten.

Therefore, recently, as shown in FIG. 9, a method of pulling out the correction wiring 101 along the side surface of the connection hole 100 has been adopted. According to this, it is not necessary to fill all the large connection holes, and the processing time can be shortened.
Yukio Maruta, Katsumi Isobe, “Scan Technical Journal”, Fujitsu VSI Co., Ltd., March 1, 2004, vol. 1 (Volume 11)

  However, when the correction wiring 101 is formed along the side surface of the connection hole 100, the correction wiring 101 becomes thinner than the intended thickness of the correction wiring 101 at the edge 102 of the connection hole as shown in FIG. 10. . When the correction wiring 101 becomes thin in this way, problems such as disconnection and high resistance of the wiring are caused. On the other hand, the inventors' experiments have shown that even if an attempt is made to increase the amount of tungsten DOSE around the edge 102 of the connection hole 100 to increase the thickness of the correction wiring 101, the intended sufficient thickness cannot be obtained. ing.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a wiring correction method capable of maintaining good coverage.

In order to solve the above problems, the invention according to claim 1, in the wiring correction method of forming by a focused ion beam processing the connection holes to draw the modified wiring for connecting the lower wiring and the upper wiring of the semiconductor device, the size A plurality of overlapping processing frames that are different from each other are set with their center positions being deviated from each other, and each of the processing frames is irradiated repeatedly with a focused ion beam, thereby correcting the side of the connection hole. An inclined surface is formed in the direction in which the wiring is drawn out.

  According to this configuration, since the inclined surface is formed in the direction in which the correction wiring is drawn out, the periphery of the edge of the connection hole becomes gentle. For this reason, since the coverage of the correction wiring around the edge can be improved, the correction wiring can be formed in a desired thickness.

  The invention according to claim 2 is the wiring correction method, wherein a plurality of overlapping processing frames having different sizes are set, and the processing frames are arranged in order from the smaller processing frame to the larger processing frame. The inclined surface is formed by repeatedly irradiating a focused ion beam.

According to this configuration, irradiating a focused ion beam in the order of large processing boxes of small rework frame. That is, since the connection hole having the inclined surface can be formed by repeatedly scanning the inside of each processing frame with a constant irradiation amount, it is not necessary to change the irradiation amount stepwise in the region where the inclined surface is formed.

According to a third aspect of the present invention, in the wiring correction method, the number of the processing frames is set according to the depth of the connection hole or the relative distance from the minimum processing frame to the maximum processing frame.
According to this configuration, the number of processing frames is set according to the depth of the connection hole or the relative distance from the minimum processing frame to the maximum processing frame. For this reason, when forming a deep connection hole or a connection hole with a long relative distance, it is possible to increase the processing frame to form an inclined surface having no step or unevenness.

  ADVANTAGE OF THE INVENTION According to this invention, the wiring correction method which can keep a coverage favorable can be provided.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
First, the connection hole 1 for wiring correction formed by the manufacturing method of the present invention will be described. FIG. 1 is a schematic view of a semiconductor device 11 in which a connection hole 1 is formed and before a correction wiring is formed. 2 is a cross-sectional view of the connection hole 1 from which the correction wiring is drawn based on a SIM (Scanning Ion Microscope) image observed by the focused ion beam apparatus, and FIG. 3 is a partially enlarged view thereof. As shown in FIG. 1, the connection hole 1 is formed to draw out a correction wiring 5 (see FIG. 2) that connects the upper layer wiring 3 and the lower layer wiring 4 of the semiconductor device 11, and the side surfaces 1 a to 1 d are inclined. Yes. The connection hole 1 is formed in a rectangular cross section, and the lower layer wiring 4 is exposed on the bottom surface 1e as shown in FIG. As shown in FIG. 2, the correction wiring 5 has a width of several μm and is drawn out along side surfaces 1 a and 1 c as inclined surfaces of the connection hole 1. As shown in FIG.
Since a is inclined, the angle of the edge E of the connection hole 1 becomes gentle. For this reason, the lead-out corrected wiring 5 does not become thin around the edge E, but maintains a thickness of about 4000 to 6000 mm and a maximum of 1 μm.

  The connection hole 1 shown in FIG. 4 differs from the connection hole 1 shown in FIGS. 1 to 3 in that only the side surface 1a in the direction in which the correction wiring 5 is drawn out is an inclined surface. That is, only one side surface 1a of the connection hole 1 is an inclined surface, and the other side surfaces 1b to 1c are formed substantially vertically. In the case of this connection hole 1, the correction wiring 5 is drawn out along the inclined side surface 1 a.

The inventor's experiment shows that when the inclination angle θ (see FIG. 3) of these inclined surfaces is equal to or smaller than a certain angle, the correction wiring 5 can maintain a suitable thickness without being thinned around the edge E. Yes. When the angle exceeds a certain angle, the correction wiring 5 formed around the edge E becomes thin. These connection holes 1 are formed by a focused ion beam device 10. (* Although the constant angle is 48.4 ° as a result of the inventor's experimental device, it depends on the gas pressure and the direction of the gas nozzle.)
Next, a method for forming the connection hole 1 will be described. FIG. 5 is a schematic diagram of the focused ion beam apparatus 10. The focused ion beam device 10 includes an ion source 12, an electronic control system device 13, a stage 14, a detector 15, a gas nozzle 16, a controller 30, an input operation unit 34, and a display 35.

  In the ion source 12, liquid gallium is stored, and the liquid gallium is led out to the outside through a lead needle at the tip. The electronic control system device 13 includes an extraction electrode 20, a condenser lens 21, a blanking electrode 22, a movable diaphragm 23, a focus lens 24, and a deflection electrode 25. The extraction electrode 20 applies a voltage to the ion source 12 and extracts positively charged ions of liquid gallium from the lead-out needle.

  The condenser lens 21 suppresses excessive diffusion of the ion beam emitted from the ion source 12. The blanking electrode 22 passes the ion beam as it is without applying a potential difference between the paired electrodes when irradiating the ion beam, and applies a potential difference when not irradiated to bend the trajectory of the ion beam. The semiconductor device 11 is not irradiated with an ion beam.

  The movable diaphragm 23 has a plurality of holes having different inner diameters, and each hole controls the amount of ions passing therethrough depending on the size of the inner diameter. The ion beam B that has passed through the hole of the movable diaphragm 23 is focused by the focus lens 24. Further, the deflection electrode 25 bends the trajectory of the ion beam B in an electric field generated by an applied voltage, and irradiates the ion beam B to a predetermined region on the surface of the semiconductor device 11. The controller 30 changes the electric field of the deflection electrode 25 and scans a predetermined area on the surface of the semiconductor device 11.

  The stage 14 includes a holder for holding the semiconductor device 11 and can be displaced in four-axis or five-axis directions (XYZ direction, tilt, rotation). A detector 15 and a gas nozzle 16 are arranged above the stage 14. The detector 15 detects secondary ions or secondary electrons generated from the semiconductor device 11 by ion beam irradiation. Then, the detection signal is output to the controller 30.

The gas nozzle 16 is connected to a gas supply source for CVD, and sprays a compound gas for forming the correction wiring 5 on the surface of the semiconductor device 11. In this embodiment, tungsten-based compound gases such as W (CO) ₆ and WF ₆ are used, but other compound gases such as Mo (CO) ₆ , Cr (CO) ₆ , Ni (CO) _{4 and the} like are used. A compound gas such as metal carbonyl, an alkyl metal such as Al (CH ₃ ) ₃ , Cd (C ₂ H ₅ ) _2, or a halogen-based gas such as TiI may be used. Then, the chemical reaction is performed by scanning the ion beam B while spraying the compound gas, and only tungsten (or other metal) that is a solid component is deposited on the surface of the semiconductor device 11. As a result, the correction wiring 5 made of tungsten is formed on the semiconductor device 11.

  The electronic control system device 13 is connected to the controller 30. The controller 30 includes an irradiation control circuit 31, a processing frame calculation circuit 32, an image processing circuit 33, and an input operation unit 34. The irradiation control circuit 31 applies a voltage to the extraction electrode 20, the blanking electrode 22, the deflection electrode 25, etc., and drives and controls the movable diaphragm 23. Further, the irradiation control circuit 31 controls a drive mechanism (not shown) that drives the stage 14 to displace the stage 14 in the 4-axis direction or the 5-axis direction. Further, the irradiation control circuit 31 is connected to the processing frame calculation circuit 32 and the input operation unit 34. The input operation unit 34 is a keyboard, mouse, or the like operated by an operator, and can perform input operations such as irradiation start, irradiation stop, and irradiation position designation.

The image processing circuit 33 images the distribution data based on the secondary electron or secondary ion distribution output from the detector 15 and outputs the surface image of the semiconductor device 11 to the display 35.
The machining frame calculation circuit 32 automatically calculates a plurality of machining frames F for forming the connection holes 1 shown in FIGS. 6A and 6B based on a signal from the input operation unit 34. To do.

The processing frame F formed by the processing frame calculation circuit 32 is an ion beam irradiation region for forming each of the connection holes 1 described above, and is formed in a predetermined number and having different sizes. A processing frame F shown in FIG. 6A is a processing frame F for forming the connection hole 1 of FIGS. Each processing frame F _i (i = 2, 3,... N) has a slit width W in the vertical direction (y direction) and the horizontal direction (x direction) relative to the processing frame F _i-1 immediately inside thereof. It is set twice as large. The slit width W is constant with respect to one connection hole 1 and is set to a sufficiently small length, such as one tenth of the length of the inclined surface. Each processing frame F is overlapped with the center position thereof aligned.

Each processing frame F shown in FIG. 6B is a processing frame for forming the connection hole 1 in which one side 1a shown in FIG. 4 is inclined. Each processing frame F _i (i = 2, 3,... N) has the same length in the vertical direction (y direction), and the length in the horizontal direction (x direction) has a processing frame F _i immediately inside thereof. _The slit width W is larger than _-1 . These processing frames F are overlapped with their center positions biased so that one side (the left side in FIG. 6B) overlaps.

  When the operator previously sets the formation location of the connection hole 1, the shape of the connection hole 1, the length of the inclined surface of the connection hole 1, etc., the processing frame calculation circuit 32 is based on the designated formation location. The coordinates of one processing frame F1 are calculated. When the first processing frame F1 is designated, the processing frame arithmetic circuit 32 focuses on the second processing frame F2, the third processing frame F3,... Larger than the first processing frame F1, with the first processing frame F1 as the center. Calculate automatically. At this time, when the shape in which the side surfaces 1a to 1d are inclined as the shape of the connection hole 1 in FIG. 1 is selected as the shape of the connection hole 1, the processing frame calculation circuit 32 is as shown in FIG. The coordinates of each processing frame F with the correct center are calculated. When a model in which any one of the side surfaces 1a to 1d is inclined like the connection hole 1 in FIG. 4 is selected, the coordinates of each processing frame F shifted in center are set as shown in FIG. 6 (b). Calculate. When forming the processing frame F of FIG. 6B, the centers are shifted in the direction in which the inclined surface is formed.

When the processing frame F is calculated in this way, the processing frame calculation circuit 32 outputs the coordinates of each processing frame F to the irradiation control circuit 31. The irradiation control circuit 31 controls the electronic control system device 13 and the stage 14 to perform positioning, and irradiates the surface of the semiconductor device 11 with the ion beam B. Specifically, for example, the case of using the processing frames F1 to Fn in FIG. 6A will be described as an example. As shown in FIG. 7A, first, the inside of the first processing frame F1 is ion beam B. To scan the first processing frame F1.
When one of the scans is completed, the first processed hole 41 is formed.

  Next, the second processing frame F2 larger than the first processing frame F1 is set as an irradiation region, and the inside of the second processing frame F2 is irradiated with a beam. As a result, as shown in FIG. 7B, the first processing hole 41 is excavated deeper by performing the second beam irradiation. Further, a second machining hole 42 that is shallower than the first machining hole 41 is formed so as to surround the first machining hole 41.

  When the second processing hole 42 is formed, the third processing frame F3 is set as an irradiation area, and the inside of the third processing frame F3 is scanned once. Accordingly, as shown in FIG. 7C, the first machining hole 41 and the second machining hole 42 are cut deeper, and a third machining hole 43 is newly formed. In this way, one scan is sequentially repeated from the first processing frame F1 to the third processing frame F3 until the set DOSE amount. Since the slit width W is set to tens of tenths of the length of the inclined surface finally formed, the side surface 1a of the connection hole 1 by the first to third processed holes 41 to 43 is used. ˜1d is not formed in a staircase shape but continuously becomes an inclined surface. In this way, when the beam is irradiated from the first processing frame F1 to the Nth processing frame Fn, the connection holes 1 as shown in FIGS. 1 to 3 are formed. The procedure for forming the connection hole 1 with one side surface 1a inclined as shown in FIG. 4 is performed in the same manner.

Next, the processing procedure of this embodiment is demonstrated according to FIG.
The operator confirms the alignment mark of the semiconductor device 11 placed on the stage 14 on the display 35, and performs positioning by displacing the stage 14 by the input operation unit 34. Then, the SIM (Scanning Ion Microscope) displayed on the screen of the display 35 is displayed.
) On the image, the center position and size of the first processing frame F1 are set (step S1).

  Further, the operator sets the shape of the connection hole 1 to be formed (step S2). For example, the side surfaces 1a to 1d to be inclined are set, and the shape of the connection hole 1 is determined. Further, the depth of the deepest position of the connection hole 1 (maximum depth) or the length of the inclined surface (slope length) is set. The slope length represents the relative distance from the first processing frame F1 to the Nth processing frame Fn.

  When each condition is set, the machining frame calculation circuit 32 calculates a variable other than the machining frame number N and the input set value (step S3). For example, when the maximum depth of the connection hole 1 is set in step S1, a DOSE amount (irradiation amount) necessary to form a hole of that depth is calculated, and the DOSE amount is calculated for one processing frame F. The number of processing frames F is calculated by dividing by the amount of DOSE (fixed value). Further, the slit width W is calculated by dividing the slope length by the number N of processing frames. Alternatively, when the slit width W is a fixed value, the slope length is divided by the slit width W to calculate the number N of processing frames.

  Further, the processing frame calculation circuit 32 sets the counter value n of the counter to an initial value “1” (step S4), and calculates the coordinates of the nth processing frame (step S5). At this time, the coordinates of the first processing frame F1 are calculated based on the center position and size of the first processing frame F1 set in step S1. When the coordinates of the first processing frame F1 are calculated, “1” is added to the counter value n (step S6), and it is determined whether or not the counter value n has reached the number N of processing frames (step S7). If it is determined that the counter value n is less than the processing frame number N (NO in step S7), the process returns to step S5 to calculate the coordinates of the second processing frame F2. When the shape of the connection hole 1 shown in FIG. 1 is selected, the coordinates of the machining frame that is increased by the slit width W with respect to each side of the first machining frame F1 are calculated.

  And step S5-step S7 are repeated and the coordinate of 3rd process frame F3, 4th process frame F4 ... is calculated. When the coordinates of the Nth processing frame Fn are calculated, the counter value n reaches the processing frame number N in step S8, and the processing processing of the processing frame F is terminated.

  When the coordinates of all the processing frames F are calculated in this way, the processing frame calculation circuit 32 outputs the coordinate data of each processing frame to the irradiation control circuit 31. The irradiation control circuit 31 drives and controls the electronic control system device 13 to control the amount of deflection of the ion beam B in the X-axis and Y-axis directions based on the set irradiation conditions and the coordinates of the processing frame F, so that small processing is performed. The inside of the large processing frame F is scanned in order from the frame F. Further, the detector 15 detects the distribution of secondary ions or secondary electrons generated from the surface of the semiconductor device 11 and outputs a SIM image of the surface of the semiconductor device 11 to the display 35.

  When the ion beam irradiation on all the processing frames F is completed, the connection holes 1 as shown in FIG. 1 or FIG. 4 are formed. After the connection hole 1 is formed, the irradiation control circuit 31 controls the gas nozzle 16 to spray the compound gas on the inclined side surfaces 1a and 1c (or the side surface 1a) and the bottom surface 1e of the formed connection hole 1. To do. Further, the irradiation control circuit 31 irradiates the ion beam B to the portion where the correction wiring 5 is drawn out while spraying the compound gas. As a result, the solid component is volumetrically deposited on the side surfaces 1a and 1c and the bottom surface 1e of the connection hole 1 by a chemical reaction. At this time, since the edge E of the connection hole 1 is gently formed, the coverage to the side surfaces 1a and 1c is improved, and the corrected wiring 5 having a desired thickness is also provided around the edge E as shown in FIG. Is formed.

According to the above embodiment, the following effects can be obtained.
(1) In the above embodiment, the inclined surface is formed by the focused ion beam processing in the connection hole 1 for drawing out the correction wiring 5 that connects the lower layer wiring 4 and the upper layer wiring 3 of the semiconductor device 11. For this reason, since the edge periphery has a gentle angle as compared with the connection hole 1 in which the inclined surface is not formed, the correction wiring around the edge is formed when the correction wiring 5 is formed by CVD using the focused ion beam apparatus 10. 5 is not thinned, and the corrected wiring 5 having a desired thickness can be formed. For this reason, disconnection and high resistance of wiring can be prevented.

  (2) In the above embodiment, the processing frame calculation circuit 32 of the focused ion beam apparatus 10 sets a plurality of processing frames F having different sizes. Moreover, the focused ion beam was irradiated to the inside of each processing frame F in order from the small processing frame F to the large processing frame F. That is, since the connection hole 1 having an inclined surface can be formed by scanning the inside of each processing frame F with a constant irradiation amount, the inclined surface is easier than forming the inclined surface by changing the irradiation amount in steps. Can be formed.

  (3) In the above embodiment, the processing frame number N is set based on the depth of the connection hole 1 or the relative distance (slope length) from the minimum first processing frame F1 to the maximum Nth processing frame Fn. I did it. For this reason, when forming the deep connection hole 1 or the connection hole 1 having a long slope length, an inclined surface having no step or unevenness is formed by increasing the number N of processing frames without increasing the slit width W. be able to.

  (4) In the said embodiment, the center of each process frame F was made the same, and the connection hole 1 (refer FIG. 1) in which all the side surfaces 1a-1d inclined was formed. For this reason, the shape of the connection hole 1 can be easily changed only by changing the overlapping state of the processing frames F.

  (5) In the above embodiment, the center of each processing frame F is biased to form the connection hole 1 (see FIG. 4) inclined only on one side surface 1a. For this reason, the connection hole 1 having a shape that does not adversely affect other wirings can be formed.

In addition, you may change the said embodiment as follows.
-In above-mentioned embodiment, although the process frame F was made into square or a rectangle, another polygonal shape may be sufficient.

In the above embodiment, the maximum depth and slope length of the connection hole 1 are set. However, the slit width W, the number N of processing frames, etc. are set in advance, and the maximum depth and slope length are not set. Also good.

In the above embodiment, the processing frame calculation circuit 32 automatically generates the coordinates of the processing frame F, but the operator may manually set the coordinates.
The configuration of the focused ion beam apparatus 10 is not limited to the configuration described above, and other configurations may be used.

The schematic diagram of the connection hole of this embodiment. Sectional drawing of the connection hole based on a SIM image. The enlarged view of the cross section of the connection hole. The schematic diagram of the connection hole of this embodiment. Explanatory drawing of the structure of the focused ion beam apparatus of this embodiment. (A) And (b) is explanatory drawing of each process frame. (A)-(c) is explanatory drawing of the process of forming each process frame. Explanatory drawing of the calculation procedure of the process frame of this embodiment. Sectional drawing of the conventional connection hole. The expanded sectional view of the conventional connection hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Connection hole 1a Side surface as inclined surface 1a-1d Side surface 3 Upper layer wiring 4 Lower layer wiring 5 Correction wiring 10 Focused ion beam apparatus 11 Semiconductor device F Processing frame F1 1st processing frame B ... Ion beam as a focused ion beam.

Claims (3)

In a wiring correction method for forming a connection hole for drawing a correction wiring for connecting a lower layer wiring and an upper layer wiring of a semiconductor device by focused ion beam processing,
A plurality of overlapping processing frames having different sizes are set with their center positions being deviated from each other, and by repeatedly irradiating a focused ion beam into each processing frame, among the side surfaces of the connection hole, A wiring correction method, wherein an inclined surface is formed in a direction in which the correction wiring is drawn out. In the wiring correction method according to claim 1,
Wiring correction method characterized by forming the inclined surface by irradiating the order of the processing boxes large from small again the processing frame, repeating a focused ion beam to the respective processing boxes inside. In the wiring correction method according to claim 1 or 2 ,
A wiring correction method, wherein the number of the processing frames is set according to a depth of the connection hole or a relative distance from the minimum processing frame to the maximum processing frame .

Images