Abstract
An electrodeposited nano-twins copper layer, a method of fabricating the same, and a substrate comprising the same are disclosed. According to the present invention, at least 50% in volume of the electrodeposited nano-twins copper layer comprises plural grains adjacent to each other, wherein the said grains are made of stacked twins, the angle of the stacking directions of the nano-twins between one grain and the neighboring grain is between 0 to 20 degrees. The electrodeposited nano-twins copper layer of the present invention is highly reliable with excellent electro-migration resistance, hardness, and Young's modulus. Its manufacturing method is also fully compatible to semiconductor process.
Claims
1. A method for preparing a nano-twins copper metal layer, comprising: (A) providing an electrodepositing device, wherein the electrodepositing device comprises an anode, a cathode, a plating solution, and an electrical power supply source, and the electrical power supply source is connected to the anode and the cathode; and (B) using the electrical power supply source to provide an electrical power to perform electrodeposition at a surface of the cathode to grow a nano-twins copper metal layer; wherein over 50% of a volume of the nano-twins copper metal layer comprises a plurality of crystal grains, each crystal grain is connected with one another, each crystal grain is formed as a result of a plurality of nano-twins stacking in a direction of a [111] crystal axis, and an angle included between neighboring crystal grains is 0 to 20; wherein the plating solution comprises a copper-based salt compound, an acid, and a chloride anion supply source; and wherein the method is used in a preparation of through silicon via (TSV), interconnect of a semiconductor chip, pin through hole of a packaging substrate, metal wire, or substrate circuit.
2. The method according to claim 1, wherein a [111] surface of the nano-twins is exposed on over 50% of a surface area of the nano-twins copper metal layer.
3. The method according to claim 1, wherein a diameter of the crystal grains is in a range of 0.01 m-500 m and a thickness of the crystal grains is in a range of 0.01 m-500 m.
4. The method according to claim 1, wherein a diameter of the crystal grains is in a range of 1 m-10 m and a thickness of the crystal grains is in a range of 0.1 m-200 m.
5. The method according to claim 1, wherein the plating solution further comprises a substance selected from a group consisting of gelatin, surfactant, lattice dressing agent, and a combination thereof.
6. The method according to claim 1, wherein the acid in the plating solution is sulfuric acid, methane sulfonic acid, or a combination thereof.
7. The method according to claim 1, wherein a concentration of the acid in the plating solution is 80-120 g/L.
8. The method according to claim 1, wherein in step (B), a current density for electrodeposition is 10-120 mA/cm.sup.2.
9. The method according to claim 1, wherein a growth rate of the nano-twins copper metal layer is 0.22 m/min-2.64 m/min.
10. The method according to claim 1, wherein in step (B), a growth rate of a twins metal is 1.5 m/min-2 m/min when a current density for electrodeposition is 80 mA/cm.sup.2.
11. The method according to claim 1, wherein in step (B), electrodeposition is carried out by direct current electrodeposition, pulse electrodeposition, or both interchangeably.
12. The method according to claim 1, wherein the cathode is a substrate with a seed layer on a surface of the substrate, or a metal substrate.
13. The method according to claim 12, wherein the substrate is selected from a group consisting of silicon substrate, glass substrate, quartz substrate, plastic substrate, printed circuit board, III-V group material substrate, and a combination thereof.
14. The method according to claim 1, wherein in step (B), when the electrodeposition is in progress, the cathode or the plating solution is spun at a rotational speed of 50 rpm-1500 rpm.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is a diagram showing an electrodepositing device according to Example 1 and 2 of the present invention;
(2) FIG. 2A shows a cross-sectional focused ion beam (FIB) photo of a nano-twins copper metal layer according to Example 1 of the present invention;
(3) FIG. 2B is an isometric representation of a nano-twins copper metal layer according to Example 1 of the present invention;
(4) FIG. 3 is an exemplary display of X-ray analysis result from a plan-view for a columnar crystal of nano-twins copper metal layer according to Example 1 of the present invention;
(5) FIG. 4 is an exemplary display of EBSD pattern for a columnar crystal of nano-twins copper metal layer according to Example 1 of the present invention;
(6) FIG. 5 shows a statistical analysis result for a crystal of nano-twins copper metal layer of FIG. 4 deviating from an angle to positive [111] direction according to Example 1 of the present invention.
(7) FIG. 6 is a cross-sectional focused ion beam (FIB) photo of a nano-twins copper metal layer prepared by direct current electroplating at 20 mA/cm.sup.2 according to Example 1 of the present invention.
(8) FIG. 7 is a cross-sectional focused ion beam (FIB) photo of a nano-twins copper metal layer prepared by direct current electroplating at 40 mA/cm.sup.2 according to Example 1 of the present invention;
(9) FIG. 8 is a cross-sectional focused ion beam (FIB) photo of a nano-twins copper metal layer prepared by direct current electroplating at 100 mA/cm.sup.2 according to Example 1 of the present invention;
(10) FIG. 9 is a cross-sectional focused ion beam (FIB) photo of a nano-twins copper metal layer prepared by direct current electroplating at 50 mA/cm.sup.2 according to Example 2 of the present invention;
(11) FIG. 10 shows a result of X-ray analysis from a plan view for a crystal grain of a nano-twins copper metal layer prepared by pulse electrodepositing according to Example 2 of the present invention;
(12) FIG. 11 is a perspective view showing a wire substrate according to Example 4 of the present invention;
(13) FIG. 12 is a display and graph of elemental analysis according to testing example of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
(14) Hereafter, examples will be provided to illustrate the embodiments of the present invention. Other advantages and effects of the invention will become more apparent from the disclosure of the present invention. Other various aspects also may be practiced or applied in the invention, and various modifications and variations can be made without departing from the spirit of the invention based on various concepts and applications.
(15) The figures presented herein are simplified diagrams showing examples of the current invention. It must be understood that the figures are only illustrative of the associated elements of the current invention, and are not intended to be the actual embodiments. The number, shape and other dimensions of the elements in the actual embodiments are chosen for specific design purposes, and their configuration and pattern may be more detailed.
Example 1
(16) An electrodepositing device 1 as shown in FIG. 1 is provided, the electrodepositing device 1 comprises an anode 11, a cathode 12, which are immersed in the plating solution 13 and are each connected to a direct current electrical power supply source 15 (Keithley 2400 is used herein). In the present case, the anode 11 is made from a material including metal copper, phosphorus copper or inert anode (for example, titanium-plated platinum); cathode 12 is made from a material including silicon substrate having its surface plated by copper seed layer, and can be made from a material selected from a group consisting of glass substrate having its surface plated by conductive layer and seed layer, conductive layer and seed layer plated surface glass substrate, quartz substrate, metal substrate, plastic substrate, or printed circuit board etc. The plating solution 13 comprises copper sulfate (copper ion concentration being 20-60 g/L), chloride anion (concentration being 10-100 ppm), and methane sulfonic acid (concentration being 80-120 g/L), and other surfactant or lattice modification agent (such as BASF Lugalvan 1-100 ml/L) can be added. The plating solution 13 of the present example can further comprises organic acid (for example, methane sulfonic acid), or gelatin etc., or a combination thereof for adjusting crystal grain composition and size.
(17) Next, a direct current having a 20-100 mA/cm.sup.2 electric current is used in electrodeposition, in which nano-twins are grown from the cathode 12 in the direction pointed by the arrow as shown in FIG. 1. A rotational speed of about 50 to 1500 rpm is applied on silicon chip or solution. During the growth process, the [111] surface of the twins and the planar surface of the nano-twins copper metal layer are roughly perpendicularly to the electric field orientation, and the twins copper is grown at about 1.76 m/min. The fully grown nano-twins copper metal layer comprises a plurality of crystal grains, wherein the crystal grins are formed by a plurality of twins copper. Since the nano-twins extend to reach the surface, [111] surface is still exposed on the surface. The thickness of the twins copper 14 achieved from electrodeposition is approximately 20 m. [111] crystal axis is an axis normal to the [111] surface.
(18) FIG. 2A is a cross-sectional focused ion beam (FIB) photo of the twins copper prepared with 80 mA/cm.sup.2 of the present example according to the current example, and FIG. 2B is an isometric representation of the nano-twins copper layer of the present example. According to FIGS. 2A and 2B, over 50% of volume of the nano-twins copper layer 14 prepared in the current example comprises a plurality of columnar crystal grains 16, and each crystal grain has a plurality of layer-shaped nano-twins copper (for example, neighboring black line and white line constitute a twins copper, and are stacked in a stacking direction 19 to form crystal grains 16), therefore, the whole nano-twins copper metal layer of the present invention comprises a significant number of nano-twins copper. The diameter D of these columnar crystal grains 16 can range from about 0.5 m to 8 m and the height L can range from about 2 m to 20 m, nano-twins plane 161 (level striation) and the [111] planar surface are parallel to each other, crystalline grain boundary 162 can be found between twins crystals, the [111] plane surface of copper is perpendicularly to the T direction of thickness, and the thickness T of the twins copper layer 14 is about 20 m. The angle included between stacking direction of neighboring crystals (which are almost identical to [111] crystal axis) ranges between 0 and 20.
(19) In the present embodiment, the thickness T of the twins copper layer 14 can be adjusted based on electrodeposition duration, which ranges about 0.1 m-500 m.
(20) As shown in FIG. 3, a result from X-ray analysis for a plan-view of nano-twins copper metal layer according to the present example is shown. X-ray is incidentally shot through the electrodeposited copper surface. As will be seen in FIG. 3, the electrodeposited layer crystal grain has a preferred orientation of [111] crystal axis (as shown by Cu(III) in FIG. 3). The Si(004) in the drawing is the diffraction peak of the silicon substrate. Other planar diffraction peaks of copper are not present, indicating that the copper prepared by the present example has [111] crystal axis.
(21) FIG. 4 shows the result of using electron backscatter diffraction (EBSD) as a means of analyzing the surface crystal orientation, which shows that all surface crystal grain orientation are centered around [111] orientation, which is the color blue. FIG. 5 shows the statistical study result for these crystal grains deviating from [111] orientation angle, it can be seen that the percentage of crystal grains whose angle deviating from the [111] orientation by within 10 (<10) is over 90%.
(22) Furthermore, the nano-twins copper metal layer having [111] preferred orientation of the present invention can also be obtained from other electric current density condition, as shown in the cross-sectional FIG photos of FIGS. 6-8, where the electric currents are each 20 mA/cm.sup.2, 40 mA/cm.sup.2, and 100 mA/cm.sup.2, it can also be seen in the diagram that the twins copper obtained by other electric current also has [111] preferred orientation.
(23) As seen in FIG. 6, FIG. 7, or FIG. 8, in the present invention, impure crystal grains 17 can be found between columnar crystal grains 16, and a surface of the nano-twins copper metal layer has some seed layers 18. The reason for such establishment is that the substrate surface would be covered by some seed layers 18 at the start of electrodeposition, therefore some seed layers 18 not composed by twins copper can be found on the formed nano-twins copper metal layer. Therefore, the nano-twins copper metal layer of the present invention is defined to have a characteristics of over 50% of volume comprises a plurality of crystal grains, each of the crystal grain is formed by the stacking of a plurality of nano-twins along [111] crystal axis orientation.
Example 2
(24) The combination of electrodepositing device and plating solution of the present example is the same as in Example 1, but pulse electrodeposition is used for plating instead of direct current power supply source. Silicon chip or solution is subject to rotation at a rate of about 0 to 1500 rpm. T.sub.on/T.sub.off is kept below 0.1/0.5 (sec), electric current density is kept at 50 mA/cm.sup.2, and twins copper is grown (plating 6000 cycles) from cathode moving toward the direction pointed by the arrow (as shown in FIG. 1). [111] plane of the twins is perpendicular to the orientation of electric field, and twins copper is grown at a rate of 0.183 m/min. The fully grown twins copper comprises a plurality of columnar crystal grains; the columnar crystal grain has a plurality of layer-shaped nano-twins copper, and the thickness of the nano-twins copper layer obtained after electrodeposition is about 10 m.
(25) FIG. 9 is a cross-sectional focused ion beam (FIB) photo of the nano-twins copper metal layer prepared in the current example. As shown in FIG. 9, over 50% of volume of the nano-twins copper metal layer prepared in the current example comprises a plurality of crystal grains, the diameter D of the crystal grain ranges from about 0.5 m to 8 m, the level striation is the nano-twins layer (for example, neighboring sets of black lines and white lines constitute a twins copper), the [111] plane of copper and twins plane are substantially cover 50% perpendicular to the orientation of thickness T, and the thickness T of crystal grain is about 10 m.
(26) Furthermore, as shown in FIG. 10, a result diagram displaying X-ray analysis of the nano-twins copper layer prepared by the present example is provided. The result shows that the nano-twins copper layer prepared by electrodepositon of the current example has a favorable [111] preferred orientation for which the intensity of diffraction of 280,000 counts is higher than the diffraction peak of the silicon chip, and for higher than Cu(222) diffraction peak, indicating that the twins copper layer prepared by the current example has a more favorable [111] preferred direction than that done by direct current.
Example 3
(27) The plating solution and method of the present example is the same as Example 1, but is different in an aspect that the current example has wire channel prepared by a semiconductor manufacturing process on the substrate surface, the micro through holes of the aspect ratio of 1:3, and that the nano-twins copper metal layer uses electrodeposition to fill holes and in turn forms interconnect.
Example 4
(28) As shown in FIG. 11, a circuit substrate is provided, which includes the same nano-twins copper metal layer prepared in Example 3. In other words, the nano-twins copper metal layer of the present example can be used in wires 3, and/or conductive throughhole 5. In addition, it can also be used in the three-dimensional integrated circuit, etc.
(29) And with regards to substrate material, the substrate can be silicon substrate, glass substrate, quartz substrate, metal substrate, printed circuit board, or III-V group material substrate.
Testing Example
(30) As shown in FIG. 12, an elemental analysis is conducted based on the nano-twins copper metal layer as prepared in Example 1. Testing conditions are shown in Table 1 below. By reference to the current figure, it can be observed that the nano-twins copper metal layer prepared from the electrodepositing method of the present invention would comprise a handful of impure grains, where these impure grains would include impure elements in addition to copper (for example, oxygen, sulfur, carbon, phosphorous, and others). However, the nano-twins copper metal layer would be devoid of these impure elements in the case of manufacture by sputtering.
(31) TABLE-US-00001 TABLE 1 Analytical Sputtering Sample Parameter Parameter Parameter Sample: 80 mA/cm.sup.2 PI: Ga PI: Cs Polarity: Negative Energy: 25 KeV Energy: 2 KeV Charge current: Charge current: 1.00 pA 45.00 pA Area: Area: 65.4 65.4 m.sup.2 250.1 250.1 m.sup.2
