JP4618295B2 - Method for forming metal electrode of semiconductor device - Google Patents

Description

The present invention relates to a metal electrode forming method for a semiconductor device in which a metal film is formed by patterning a metal film by cutting .

In recent years, in a method for manufacturing a semiconductor device, there has been a demand for inexpensively forming a metal electrode for solder bonding or the like on a circuit surface formed on a semiconductor substrate.
In response to this requirement, for example, as a technique for forming a metal electrode without performing a photolithography process for patterning, in Patent Document 1, a base electrode is formed on one surface of a semiconductor substrate, and a protective film is formed on the base electrode. In a semiconductor device in which an opening is formed in the protective film and a metal electrode for connection is formed on the surface of the base electrode facing from the opening, the base electrode facing from the opening to the upper surface of the protective film A technique for forming a metal electrode by patterning a metal film formed on a base electrode and a protective film by cutting using the fact that a step is formed so that the surface of the metal electrode is retracted is disclosed.
JP 2006-186304 A

When the metal electrode pattern is formed by cutting as in the above-described technique, it is necessary to perform cutting with high accuracy such that the variation in the cutting amount with respect to the surface of the metal film is within 2 μm, for example, on the entire surface of the semiconductor substrate. There is.
Here, when the semiconductor substrate is suction-fixed on the suction stage, the back surface of the semiconductor substrate is deformed so as to be flat, so that the main surface has a large unevenness reflecting the original uneven shape of the back surface. .
Since the cutting process is performed along a plane parallel to the suction stage, when the semiconductor substrate has a thickness variation larger than the required accuracy of the cutting amount, for example, a variation of 3 μm or more, the cutting amount is partially included in the surface. There is a region that does not satisfy the required accuracy, resulting in a decrease in product yield.

Therefore, in the present invention, a metal electrode of a semiconductor device that forms a metal electrode by patterning a metal film by cutting that satisfies the required accuracy of the cutting amount on a semiconductor substrate having a thickness variation larger than the required accuracy of the cutting amount. The object is to realize a forming method .

In order to achieve the above object, according to the first aspect of the present invention, in the invention according to claim 1, a step of forming a base electrode electrically connected to the semiconductor element on the main surface of the semiconductor substrate, and covering the base electrode Forming a protective film, forming an opening for exposing the base electrode from the surface of the protective film toward the base electrode; and covering the surface of the base electrode facing the protective film and the opening. Forming a metal film, and adsorbing and fixing the semiconductor substrate on which the metal film is formed to an adsorption stage for adsorbing and fixing the semiconductor substrate, and then facing the main surface of the semiconductor substrate, A step of acquiring surface shape data of a surface portion of the semiconductor substrate covering the protective film of the semiconductor film of the semiconductor substrate sucked and fixed to the suction stage by a surface shape measuring means for measuring the shape; and the surface shape Based on the surface shape data acquired by the fixing means, the cutting surface set in parallel with the suction stage by the deformation means for deforming the semiconductor substrate fixed to the suction stage by applying displacement from the suction stage side. And a step of deforming so that a distance between the surface portion of the semiconductor substrate and the surface portion of the semiconductor substrate falls within a predetermined range, and measuring a surface shape of the surface portion of the deformed semiconductor substrate by the surface shape measuring means, A step of determining whether or not a distance between the deformed semiconductor substrate and a surface portion of the deformed semiconductor substrate is within a predetermined range; and a distance between the cutting surface and the deformed semiconductor substrate is within a predetermined range. When it is determined that there is a pattern, the metal film is patterned by a cutting process in which cutting is performed on the cutting surface while the deformed semiconductor substrate is suction fixed to the suction stage. Te and forming a metal electrode, the adsorption stage is formed by a single thin plate deformable material of the, is sucked and secured on the entire back surface of the semiconductor substrate, using the technical means of.
According to a second aspect of the present invention, in the metal electrode forming method according to the first aspect, a technical means is used in which the adsorption stage is a thin plate-shaped stainless steel.

According to the first aspect of the present invention, the base electrode electrically connected to the semiconductor element is formed on the main surface of the semiconductor substrate, the protective film is formed to cover the base electrode, and the base layer is formed from the surface of the protective film. An opening for exposing the base electrode is formed toward the electrode, a metal film is formed to cover the surface of the base electrode facing the protective film and the opening, and the metal film is formed by cutting that performs cutting on the cutting surface. A metal electrode can be formed by patterning.
  Here, after the semiconductor substrate on which the metal film is formed is adsorbed and fixed to the adsorption stage, the surface of the surface portion covering the protective film among the metal films of the semiconductor substrate adsorbed and fixed to the adsorption stage by the surface shape measuring means The distance between the cutting surface set in parallel with the suction stage and the surface portion of the semiconductor substrate by the deformation means that obtains shape data and deforms the semiconductor substrate by applying displacement from the suction stage side based on the surface shape data. Can be modified so as to be within a predetermined range. Then, the surface shape of the semiconductor substrate deformed by the surface shape measuring means is measured, and when it is determined that the distance between the cutting surface and the surface portion is within a predetermined range, the semiconductor substrate deformed by the deforming means is Cutting can be performed on the cutting surface while being fixed to the suction stage by suction.
  As a result, for the semiconductor substrate in which the unevenness of the front surface portion is increased by reflecting and fixing to the suction stage, the unevenness difference of the front surface portion is reduced, and the distance between the cutting surface and the front surface portion is set to a predetermined value. It can be within the range (required accuracy of cutting). For this reason, since the processing precision of cutting can be improved, the product yield in metal electrode formation can be improved.

According to a third aspect of the present invention, in the method for forming a metal electrode of a semiconductor device according to the first or second aspect, in the step of forming the metal electrode, the metal film is formed inside the opening of the metal film. Then, a technical means is used in which a metal electrode is formed by patterning so as to leave only the remaining portion.

According to the third aspect of the present invention, in the step of forming the metal electrode, the metal electrode is formed by patterning so as to leave only the portion formed in the opening of the metal film. The metal electrode can be formed on the surface of the base electrode facing from the portion and the side surface of the protective film forming a step from the opening toward the surface of the base electrode.

According to a fourth aspect of the present invention, in the metal electrode forming method for a semiconductor device according to any one of the first to third aspects, the deformation means is provided in contact with the back surface of the suction stage, A technical means of applying displacement to the semiconductor substrate through the suction stage is used.

According to the fourth aspect of the present invention, the deformation means is provided in contact with the back surface of the suction stage, and the semiconductor substrate is displaced via the suction stage. It is possible to prevent stress from being generated and the semiconductor substrate from being locally deformed.

According to a fifth aspect of the present invention, in the metal electrode forming method for a semiconductor device according to any one of the first to fourth aspects, the deformation means includes a plurality of actuators each capable of controlling displacement. The technical means is used.

According to the invention described in claim 5 , since the deformation means includes a plurality of actuators each capable of controlling the displacement, it is possible to give different displacements according to the deformation state of the semiconductor substrate. The surface shape can be accurately controlled.

According to a sixth aspect of the present invention, in the method for forming a metal electrode of a semiconductor device according to the fifth aspect , the technical means that the actuator is a piezoelectric actuator using a piezoelectric element is used.

According to the invention described in claim 6 , since the actuator is a piezoelectric actuator using a piezoelectric element, the accuracy of displacement control can be increased. In addition, the piezoelectric actuator has less backlash and generates less heat during operation.

According to a seventh aspect of the present invention, in the metal electrode forming method for a semiconductor device according to the fifth or sixth aspect , the number of measurement points of the surface shape data by the surface shape measuring means is greater than the number of the actuators. The technical means is used.

According to the invention described in claim 7 , since the number of measurement points of the surface shape data by the surface shape measuring means is larger than the number of actuators, the displacement of the area between the actuators can also be measured. Accuracy can be improved.

According to an eighth aspect of the present invention, in the method for forming a metal electrode of a semiconductor device according to any one of the first to seventh aspects, the surface shape measuring means corresponds to the point of giving a displacement by the deformation means. A technical means of measuring at least the surface shape of the surface portion is used.

According to the eighth aspect of the invention, since the surface shape measuring means measures at least the surface shape of the surface portion corresponding to the point to be displaced by the deforming means, the portion with the largest deformation can be measured. , Surface shape measurement accuracy can be improved.

According to a ninth aspect of the invention, in the metal electrode forming method for a semiconductor device according to any one of the first to eighth aspects, the surface shape measuring means is scanned along a plane parallel to the cutting surface. The technical means is a laser displacement meter.

According to the ninth aspect of the invention, the surface shape measuring means is a laser displacement meter that is scanned along a plane parallel to the cutting surface, so that the surface shape can be accurately measured without contact. Measurement time can be shortened.

[First Embodiment]
A method for forming a metal electrode of a semiconductor device and a second embodiment of the semiconductor device according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory cross-sectional view of a semiconductor device in which a metal electrode is formed by the metal electrode formation method of the first embodiment. 2 to 4 are process diagrams of the metal electrode forming method according to the first embodiment. FIG. 5 is an explanatory diagram of the surface shape control device. FIG. 5A is a cross-sectional view, and FIG. 5B is an explanatory plan view seen from the semiconductor substrate side. FIG. 6 is an explanatory diagram showing an example of the surface shape control of the semiconductor substrate. 6A is a thickness profile of the semiconductor substrate at the time of adsorption, FIG. 6B is a profile of displacement given by the deformation device, and FIG. 6C is a displacement profile given by the deformation device. 2 is a thickness profile of a semiconductor substrate. FIG. 7 is a cross-sectional explanatory view of a semiconductor device in which metal electrodes are soldered.
In each figure, for the sake of explanation, a part is enlarged and a part is omitted.

  A semiconductor device 10 used for a power card or the like is formed using a semiconductor substrate 11 made of silicon or the like as a main body. On the main surface 11 a of the semiconductor substrate 11, a base electrode 12 that is an electrode of the element is formed of Al alloy such as pure Al, Al—Si, Al—Si—Cu, or the like.

A protective film 13 made of an insulating material is formed so as to cover the main surface 11a and a part of the base electrode 12. The protective film 13 is made of, for example, a polyimide resin having a thickness of 1 to 20 μm.
The protective film 13 is formed with an opening 13 a that opens from the surface toward the base electrode 12 and exposes the base electrode 12.
Here, a step is formed so that the surface 12 a of the base electrode 12 facing the opening 13 a with respect to the upper surface 13 d of the protective film 13 is retracted.

  A metal electrode 15 to which wiring is connected is formed covering the surface 12a of the base electrode 12 exposed by the opening 13a and the side surface 13c of the protective film 13 forming the step. The metal electrode 15 is formed of a Ti / Ni / Au film, a Ni / Au film, or the like laminated from the base electrode 12 side, and is electrically connected to the base electrode 12.

Next, a method for forming the metal electrode 15 will be described.
First, as shown in FIG. 2A, a semiconductor substrate 11 on which a semiconductor element (not shown) is formed is prepared, and a base electrode 12 patterned by a photolithography method and electrically connected to the semiconductor element is used as a main surface 11a. To form.

Next, a protective film 13 having a thickness of, for example, 10 μm made of polyimide resin is formed by spin coating or the like, and an opening 13a for exposing the base electrode 12 is opened from the surface toward the base electrode 12 by photolithography. To form. By using a resin-based material as the protective film 13, the thick underlying electrode 12 can be covered appropriately.
Here, a step is formed such that the surface 12 a of the base electrode 12 facing the opening 13 a is retracted with respect to the upper surface 13 b of the protective film 13.

  Subsequently, as shown in FIG. 2B, a metal film 14 is formed by plating, sputtering, or the like so as to cover the upper surface 13b and the side surface 13c of the base electrode 12 and the protective film 13. The metal film 14 may be a laminated film such as a Ti / Ni / Au film or a Ni / Au film, or may be a single-layer metal film.

  Subsequently, as shown in FIG. 2C, the semiconductor substrate 11 is placed on the suction surface 21a provided on the suction stage 21b of the surface shape control device 20 (FIG. 5) on the back surface 11b and fixed by suction. At this time, since the back surface 11b is flattened by the suction force generated on the suction surface 21a, the front surface portion 11c of the semiconductor substrate 11 has a surface shape with large unevenness reflecting the original uneven shape of the back surface 11b.

  Here, the surface portion 11 c indicates a portion of the metal film 14 that covers the upper surface 13 b of the protective film 13. The “surface shape” is an uneven profile of the surface portion 11c and corresponds to a profile of the distance between the surface portion 11c and a cut surface P described later. The surface shape can be converted into surface shape data by digitizing the surface shape of the semiconductor substrate 11 at the surface portion 11c, the surface roughness, or the like.

Here, the configuration of the surface shape control device 20 will be described with reference to FIGS.
The surface shape control device 20 includes a stage 21 on which the semiconductor substrate 11 is placed, a suction device 22 for sucking and fixing the semiconductor substrate 11, and a surface shape measuring device 23 for measuring the shape of the surface portion 11c of the semiconductor substrate 11. The semiconductor device 11 includes a deformation device 24 for deforming the semiconductor substrate 11 from the back surface 11b, and a control computer 25 for controlling these devices.

  The stage 21 is formed in a hollow shape having a hollow portion 21d between the suction stage 21b and the lower stage 21c. The suction stage 21b includes a suction surface 21a for sucking and fixing the semiconductor substrate 11, a vacuum pump, and the like. An adsorption hole 21e is formed to apply an adsorption force generated by depressurizing the hollow portion 21d using the adsorption device 22 to the semiconductor substrate 11.

The suction stage 21b is formed so as to be easily deformed in order to apply displacement to the semiconductor substrate 11 by a deformation device 24 described later. Here, the adsorption stage 21b is formed of a plate-like stainless steel having a thickness of 1 mm.
The lower stage 21 c is provided with a decompression hole 21 f for connecting the suction device 22 and a deformation device 24.

  In the present embodiment, a plurality of piezoelectric actuators 24 a are used as the deformation device 24. The piezoelectric actuators 24a are arranged in a grid at predetermined intervals, for example, 1 cm intervals, and are provided so as to abut on the back surface 21g of the suction stage 21b and generate upward displacement. 5A and 5B exemplify a case where a total of 16 piezoelectric actuators 24a, 4 in the vertical direction and 4 in the horizontal direction, are arranged for convenience. Each piezoelectric actuator 24a can be independently controlled by the control computer 25 and can generate different displacements. Here, the piezoelectric actuator 24a has high accuracy of displacement control, less backlash, and a small amount of heat generated during operation.

When an upward displacement is generated in the piezoelectric actuator 24a, the semiconductor substrate 11 can be deformed by applying an upward displacement to the semiconductor substrate 11 via the suction stage 21b. Here, since the piezoelectric actuator 24a applies displacement to the semiconductor substrate 11 via the suction stage 21b, it is possible to prevent the piezoelectric actuator 24a from locally generating stress in the semiconductor substrate 11 and preventing local deformation. it can.
Further, it is possible to apply a downward displacement to the semiconductor substrate 11 by using the negative pressure generated by the adsorption device 22.

  The deformation device 24 may be provided with its upper end joined to the back surface 21g of the suction stage 21b. When this configuration is used, play does not occur when an upward displacement is given to the semiconductor substrate 11, and a downward displacement can also be given to the semiconductor substrate 11 via the suction stage 21b.

The surface shape measuring device 23 is a device that measures the surface shape of the surface portion 11 c of the semiconductor substrate 11. In the present embodiment, a laser displacement meter is used as the surface shape measuring device 23. When a laser displacement meter is used, the surface shape can be accurately measured without contact, and the measurement time can be shortened.
The surface shape data of the surface portion 11 c measured by the surface shape measuring device 23 is output to the control computer 25.

  In the subsequent process, as shown in FIG. 3D, the surface shape of the surface portion 11 c of the semiconductor substrate 11 is measured by the surface shape measuring device 23. Here, measurement points are set in a lattice shape on the surface portion 11c of the semiconductor substrate 11, and the thickness of the semiconductor substrate 11 is measured by scanning the surface shape measuring device 23 along a plane parallel to the cutting surface P. The measurement data at each point is output to the control computer 25. Then, in the control computer 25, the surface shape data of the surface portion 11 c of the semiconductor substrate 11 is constructed by complementing between the measurement points based on the measurement data of each point.

Here, as shown by the straight line S in FIG. 5B, the surface shape measuring device 23 scans so that the measurement point includes at least the point of the surface portion 11c corresponding to the point to which the displacement is given by the deformation device 24. To do.
According to this, since the measurement point with the largest displacement can be measured, the measurement accuracy of the surface shape can be improved.
Further, the number of measurement points can be made larger than the number of piezoelectric actuators 24a. According to this, the displacement of the region between the piezoelectric actuators 24a can also be measured, and the number of measurement points that complement each other between the piezoelectric actuators 24a can be increased. Therefore, the measurement accuracy of the surface shape can be improved.

  An example of the surface shape data is shown in FIG. In FIG. 6A, the horizontal axis indicates the position of the semiconductor substrate 11 in the X-axis (FIG. 5B) direction, and the vertical axis indicates the thickness of the semiconductor substrate 11. FIG. 6A shows a profile of thickness in a region having a width of about 80 mm measured at intervals of 1 mm, including the points on the surface portion 11 c corresponding to the points to which displacement is given by the deformation device 24. Here, the unevenness difference of the surface portion 11c of the semiconductor substrate 11 is a maximum of 3.2 μm.

  Subsequently, as shown in FIG. 3 (E), a displacement is applied from the back surface 11b of the semiconductor substrate 11 by the deformation device 24, and the distance between the cutting surface P set parallel to the suction stage 21b and the surface portion 11c is varied. The semiconductor substrate 11 is deformed so as to be within the required accuracy in the cutting process described later, and the surface shape is controlled. That is, the semiconductor substrate 11 is deformed so that the unevenness of the surface portion 11c is within the required accuracy in the cutting process.

Specifically, based on the surface shape data constructed in the control computer 25, the control computer 25 causes each piezoelectric actuator of the deformation device 24 so that the unevenness of the surface portion 11c is within the required accuracy, for example, within 1 μm. By controlling the amount of displacement 24a, the semiconductor substrate 11 is displaced from the back surface 11b via the suction stage 12b.
Here, the relationship between the displacement of each piezoelectric actuator 24a of the deformation device 24 and the deformation amount of the semiconductor substrate 11 is obtained in advance by simulation or actual measurement.

An example of the control of the surface shape is shown in FIGS. In FIG. 6B, the horizontal axis indicates the position of the semiconductor substrate 11 in the X-axis direction, and the vertical axis indicates the displacement given by the deformation device 24. Here, A to H in the figure indicate the arrangement positions of the piezoelectric actuators, and the displacement profile is a linear complement of the displacement applied by the piezoelectric actuators A to H.
A positive value represents an upward displacement, and a negative value represents a downward displacement. The displacements in the piezoelectric actuators C, E, and F are displacements generated by pressure reduction by the suction device 22.

Subsequently, the surface shape of the deformed surface portion 11c of the semiconductor substrate 11 is measured by the surface shape measuring device 23, and whether the variation in the distance between the cutting surface P and the surface portion 11c is within the required accuracy range in the cutting process. The control computer 25 determines whether or not. Here, it is determined whether or not the unevenness of the surface portion 11c is within 1 μm.
In the present embodiment, as shown in FIG. 6C, the unevenness of the surface portion 11c is within 1 μm, and the variation in the distance between the cutting surface P and the surface portion 11c is within the required accuracy range in the cutting process. Could be controlled.

  When the control computer 25 determines that the variation in the distance between the cutting surface P and the surface portion 11c is within the range of the required accuracy in the cutting, subsequently, as shown in FIG. Then, cutting is performed from the surface of the metal film 14, and the metal film 14 is patterned to form the metal electrode 15. Here, the upper surface 13b of the protective film 13 is also cut to reveal a new upper surface 13d.

  In this embodiment, the relative speed between the cutting tool 31 and the semiconductor device 10 is set to 20 m / s, and the cutting pitch is set to 70 μm. The height accuracy of the cutting tool 31 with respect to the metal film 14 was set to 0.1 μm or less.

  By cutting the entire main surface 11a of the semiconductor substrate 11 under the above-described cutting conditions, the metal film 14 located on the upper surface 13b of the protective film 13 is removed, and the metal film 14 is formed only inside the opening 13a. The metal electrode 15 can be formed by patterning to leave. That is, the metal electrode 15 is formed so as to cover the surface 12a of the base electrode 12 exposed by the opening 13a and the side surface 13c of the protective film 13 forming the step.

  Then, as shown in FIG. 4G, the metal electrode 15 can be formed on the semiconductor substrate 11 by releasing the displacement of the piezoelectric actuator 24 a and removing the semiconductor substrate 11 from the stage 21.

  According to the above process, the metal film 14 located on the upper surface 13b of the protective film 13 is removed by cutting the entire main surface 11a of the semiconductor substrate 11, and the metal film 14 is only inside the opening 13a. The metal electrode 15 can be formed by patterning so as to leave. Since the metal electrode 15 is formed so as to cover the surface 12a of the base electrode 12 exposed by the opening 13a and the side surface 13c of the protective film 13 forming the step, the metal electrode 15 is formed only on the surface 12a of the base electrode 12. Compared with the case where it forms, the intensity | strength of the metal electrode 15 can be improved.

  Further, with respect to the semiconductor substrate 11 in which the unevenness difference of the front surface part 11c is reflected by reflecting the shape of the back surface 11b by being fixed to the adsorption stage 21b, the unevenness difference of the front surface part 11c is reduced, and the cutting surface P and the surface part The distance from 11c can be set within a predetermined range (required processing accuracy). Thereby, since the processing precision of a cutting process can be improved, the product yield in metal electrode formation can be improved.

The metal electrode 15 is connected to another member by a member such as solder or a wire. For example, as shown in FIG. 7, a configuration in which a heat sink 40 is joined to the metal electrode 15 as an emitter electrode via a solder 41 can be used.
Here, the solder 41 is in contact with the portion of the metal electrode 15 formed on the side surface 13 c of the protective film 13 that forms the step. Thereby, since the area where the solder 41 contacts the metal electrode 15 can be increased, the joining strength of the solder 41 can be improved.

[Effect of the first embodiment]
(1) The base electrode 12 electrically connected to the semiconductor element is formed on the main surface 11 a of the semiconductor substrate 11, the protective film 13 is formed to cover the base electrode 12, and the base electrode 12 is formed from the surface of the protective film 13. An opening 13a for exposing the base electrode 12 is formed, a metal film 14 is formed covering the surface of the base electrode 12 facing the protective film 13 and the opening 13a, and cutting is performed on the cutting surface P. By processing, the metal electrode 15 can be formed by patterning so as to leave only a portion of the metal film 14 formed inside the opening 13a.
At this time, after the semiconductor substrate 11 on which the metal film 14 is formed is sucked and fixed to the suction stage 21b, the protective film 13 of the metal film 14 of the semiconductor substrate 11 sucked and fixed to the suction stage 21b by the surface shape measuring device 23. The surface shape data of the surface portion 11c covering the surface is obtained, and based on the surface shape data, the semiconductor substrate 11 is set in parallel with the suction stage 21b by the deformation device 24 that deforms the semiconductor substrate 11 from the suction stage 21b side. The distance between the cut surface P and the surface portion 11c of the semiconductor substrate 11 can be changed so as to be within a predetermined range (required accuracy of cutting). Then, when the surface shape of the deformed semiconductor substrate 11 is measured by the surface shape measurement device 23 and the distance between the cutting surface P and the surface portion 11c is determined to be within a predetermined range, the deformation device 24 Cutting can be performed on the cutting surface P while the deformed semiconductor substrate 11 is suction fixed to the suction stage 21b.
As a result, for the semiconductor substrate 11 in which the unevenness difference of the front surface portion 11c is increased by reflecting and fixing to the suction stage 21b, the unevenness difference of the front surface portion 11c is reduced, and the cutting surface P and the surface The distance with the part 11c can be within a predetermined range. For this reason, since the processing precision of cutting can be improved, the product yield in metal electrode formation can be improved.

(2) Since the metal electrode 15 is formed so as to cover the surface 12a of the base electrode 12 exposed by the opening 13a and the side surface 13c of the protective film 13 forming the step, the metal electrode 15 is formed only on the surface 12a of the base electrode 12. Compared with the case where the electrode 15 is formed, the strength of the metal electrode 15 can be improved. Moreover, when soldering to the metal electrode 15, since the wet area of a solder can be enlarged, joint strength can be improved.

(3) The piezoelectric actuator 24a of the deformation device 24 is provided in contact with the back surface 21g of the suction stage 21b, and displaces the semiconductor substrate 11 via the suction stage 21b. It can be prevented that stress is locally generated and the semiconductor substrate 11 is locally deformed.

(4) Since the deformation device 24 includes a plurality of piezoelectric actuators 24a each capable of controlling the displacement, different deformations can be given depending on the deformation state of the semiconductor substrate 11, and the surface shape of the semiconductor substrate 11 can be changed. It can be controlled with high accuracy. The piezoelectric actuator 24a has high displacement control accuracy, low backlash, and a small amount of heat generated during operation.

(5) Since the number of measurement points of the surface shape data by the surface shape measuring device 23 is larger than the number of the piezoelectric actuators 24a, the displacement of the region between the piezoelectric actuators 24a can also be measured, thereby improving the measurement accuracy of the surface shape. Can be made.

(6) Since the surface shape measuring device 23 measures at least the surface shape of the surface portion 11c corresponding to the point to which the deformation device 24 gives displacement, the surface shape measuring device 23 can measure the most deformed portion. Accuracy can be improved.

(7) Since the surface shape measuring device 23 is a laser displacement meter scanned along a plane parallel to the cutting surface P, the surface shape can be accurately measured in a non-contact manner and the measurement time is shortened. be able to.

[Second Embodiment]
A method for forming a metal electrode of a semiconductor device and a second embodiment of the semiconductor device according to the present invention will be described with reference to the drawings. Here, a case where an Au electrode is used as an electrode for making contact between a power element such as a bipolar transistor or a lateral diffusion transistor (LDMOS) and an external substrate will be described as an example. 8 to 10 are cross-sectional explanatory views of the electrode forming method of the semiconductor device according to the second embodiment.
In addition, about the structure similar to 1st Embodiment, while using the same code | symbol, description is abbreviate | omitted.

A method for forming the metal electrode 15 will be described.
First, as shown in FIG. 8A, a semiconductor substrate 11 on which a power element (not shown) is formed is prepared, and a base electrode 12 patterned by photolithography and electrically connected to the semiconductor element is used as a main surface 11a. To form.

  Next, a protective film 53 made of silicon nitride (P-SiN) is formed on the upper surface of the base electrode 12, and an opening 53 a for exposing a part of the base electrode 12 is opened from the surface toward the base electrode 12. Form.

Next, as shown in FIG. 8B, a barrier / seed layer 56 that covers the surface of the protective film 53 and the base electrode 12 is formed by sputtering. In this embodiment, the barrier / seed layer 56 is formed by stacking a Cu film on a TiN film.
Then, the photoresist film 57 is patterned into a predetermined shape by photolithography and etching.

  Subsequently, as shown in FIG. 9C, the Au electrode film 54 is formed by electrolytic plating using the photoresist film 57 as a mask.

  Subsequently, as shown in FIG. 9D, after the photoresist film 57 is removed, the barrier / seed layer 56 exposed on the surface of the protective film 53 is removed by an etching method.

  Subsequently, as shown in FIG. 10E, the semiconductor substrate 11 is placed on the suction surface 21a provided on the suction stage 21b of the surface shape control device 20 (FIG. 5) on the back surface 11b, and is fixed by suction. At this time, since the back surface 11b is flattened by the suction force generated on the suction surface 21a, the front surface portion 11c of the semiconductor substrate 11 has a surface shape with large unevenness reflecting the original uneven shape of the back surface 11b. Here, the surface portion 11 c indicates a surface portion of the Au electrode film 54.

  In the subsequent step, as shown in FIG. 11F, the surface shape of the surface portion 11c of the semiconductor substrate 11 is measured by the surface shape measuring device 23. Here, measurement points are set in a lattice shape on the surface portion 11c of the semiconductor substrate 11, and the thickness of the semiconductor substrate 11 is measured by scanning the surface shape measuring device 23 along a plane parallel to the cutting surface P. The measurement data at each point is output to the control computer 25. Then, in the control computer 25, the surface shape data of the surface portion 11 c of the semiconductor substrate 11 is constructed by complementing between the measurement points based on the measurement data of each point.

  Subsequently, as shown in FIG. 11 (G), the displacement is applied from the back surface 11b of the semiconductor substrate 11 by the deformation device 24, and the variation in the distance between the cutting surface P set in parallel with the suction stage 21b and the surface portion 11c. The semiconductor substrate 11 is deformed so as to be within the required accuracy in the cutting process described later, and the surface shape is controlled. That is, the semiconductor substrate 11 is deformed so that the unevenness of the surface portion 11c is within the required accuracy in the cutting process.

  Specifically, based on the surface shape data constructed in the control computer 25, the control computer 25 causes each piezoelectric actuator of the deformation device 24 so that the unevenness of the surface portion 11c is within the required accuracy, for example, within 1 μm. By controlling the amount of displacement 24a, the semiconductor substrate 11 is displaced from the back surface 11b via the suction stage 12b.

  Subsequently, the surface shape of the deformed surface portion 11c of the semiconductor substrate 11 is measured by the surface shape measuring device 23, and whether the variation in the distance between the cutting surface P and the surface portion 11c is within the required accuracy range in the cutting process. The control computer 25 determines whether or not. Here, it is determined whether or not the unevenness of the surface portion 11c is within 1 μm.

  If the control computer 25 determines that the variation in the distance between the cutting surface P and the surface portion 11c is within the range of the required accuracy in the cutting process, then, as shown in FIG. The metal electrode 55 is formed by cutting from the surface of the Au electrode film 54.

  Then, as shown in FIG. 12I, the metal electrode 55 can be formed on the semiconductor substrate 11 by releasing the displacement of the piezoelectric actuator 24 a and removing the semiconductor substrate 11 from the stage 21.

According to the above-described process, the metal electrode 55 having a flat surface can be formed by cutting the entire main surface 11 a of the semiconductor substrate 11.
Further, with respect to the semiconductor substrate 11 in which the unevenness difference of the front surface portion 11c is reflected by reflecting the shape of the back surface 11b by being adsorbed and fixed to the adsorption stage 21b, the unevenness difference of the front surface portion 11c is reduced and the cutting surface P and the front surface portion are reduced. The distance from 11c can be set within a predetermined range (required processing accuracy). Thereby, since the processing precision of a cutting process can be improved, the product yield in metal electrode formation can be improved.

[Effects of Second Embodiment]
(1) By cutting the entire main surface 11a of the semiconductor substrate 11, the metal electrode 55 having a flat surface can be formed.
Further, with respect to the semiconductor substrate 11 in which the unevenness difference of the front surface portion 11c is reflected by reflecting the shape of the back surface 11b by being adsorbed and fixed to the adsorption stage 21b, the unevenness difference of the front surface portion 11c is reduced and the cutting surface P and the front surface portion are reduced. The distance from 11c can be set within a predetermined range (required processing accuracy). Thereby, since the processing precision of a cutting process can be improved, the product yield in metal electrode formation can be improved.

[Other Embodiments]
(1) In the above-described embodiment, the piezoelectric actuator 24a is used as the deforming device. However, the present invention is not limited to this, and can be applied as long as the displacement can be controlled. For example, an electromagnetic solenoid or a hydraulic actuator can be used. When this configuration is used, a displacement larger than that of the piezoelectric actuator 24a can be generated.

(2) In the above-described embodiment, the laser displacement meter is used as the surface shape measuring device 23. However, the present invention is not limited to this. For example, a gap that detects a distance by a surface roughness meter or a change in capacitance is used. A sensor or the like can also be used.
Moreover, the number and arrangement | positioning of the measurement point by the surface shape measuring apparatus 23 are arbitrary, and it is not necessary to arrange | position at equal intervals. For example, profile data acquired by continuous measurement can be used as in the case of using a surface roughness meter.

(3) A displacement may be applied by forming a through hole in the suction stage 21b and bringing the piezoelectric actuator 24a into direct contact. When this configuration is used, since the suction stage 21b is not interposed when the displacement is applied, the force required for the piezoelectric actuator 24a to generate the displacement can be reduced, so that a small piezoelectric actuator can be used. .

(4) In the embodiment described above, negative pressure is generated by reducing the atmospheric pressure of the hollow portion 21d by the adsorption device 22, but the hollow portion 21d is filled with a fluid such as water or oil. The negative pressure may be generated by discharging the gas to the outside of the hollow portion 21d. Even when this configuration is used, the semiconductor substrate 11 can be displaced downward by a negative pressure.

It is a section explanatory view of the semiconductor device in which the metal electrode was formed by the metal electrode formation method of a 1st embodiment. It is process drawing of the metal electrode formation method of 1st Embodiment. It is process drawing of the metal electrode formation method of 1st Embodiment. It is process drawing of the metal electrode formation method of 1st Embodiment. It is explanatory drawing of a surface shape control apparatus. FIG. 5A is a cross-sectional view, and FIG. 5B is an explanatory plan view seen from the semiconductor substrate side. It is explanatory drawing which shows an example of the surface shape control of a semiconductor substrate. 6A is a thickness profile of the semiconductor substrate at the time of adsorption, FIG. 6B is a profile of displacement given by the deformation device, and FIG. 6C is a displacement profile given by the deformation device. 2 is a thickness profile of a semiconductor substrate. It is sectional explanatory drawing of the semiconductor device which performed soldering in the metal electrode. It is process drawing of the metal electrode formation method of 2nd Embodiment. It is process drawing of the metal electrode formation method of 2nd Embodiment. It is process drawing of the metal electrode formation method of 2nd Embodiment. It is process drawing of the metal electrode formation method of 2nd Embodiment. It is process drawing of the metal electrode formation method of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor device 11 Semiconductor substrate 11a Main surface
11c surface portion 12 ground electrode 13 protective film 13a opening 14 metal film 15 metal electrode 20 surface shape control device 21 stage 21a adsorption stage 23 surface shape measuring device (surface shape measuring means)
24 Deformation device (deformation means)
25 Control computer 31 Byte P Cutting surface

Claims (9)

Forming a base electrode electrically connected to the semiconductor element on the main surface of the semiconductor substrate;
Forming a protective film covering the base electrode, and forming an opening for exposing the base electrode from the surface of the protective film toward the base electrode;
Forming a metal film covering the surface of the base electrode facing the protective film and the opening; and
By a surface shape measuring means for measuring the surface shape of the semiconductor substrate disposed on the main surface of the semiconductor substrate after the semiconductor substrate on which the metal film is formed is sucked and fixed to the suction stage for sucking and fixing the semiconductor substrate. A step of acquiring surface shape data of a surface portion of the semiconductor substrate adsorbed and fixed to the adsorption stage and covering the protective film among the metal films;
Based on the surface shape data acquired by the surface shape measuring means, the semiconductor substrate fixed to the suction stage is set parallel to the suction stage by a deformation means for deforming the semiconductor substrate by displacement from the suction stage side. Deforming the cut surface and the surface portion of the semiconductor substrate so that the distance is within a predetermined range;
The surface shape measuring means measures the surface shape of the surface portion of the deformed semiconductor substrate, and determines whether the distance between the cutting surface and the surface portion of the deformed semiconductor substrate is within a predetermined range. And a process of
When it is determined that the distance between the cutting surface and the surface portion of the deformed semiconductor substrate is within a predetermined range, the deformed semiconductor substrate is fixed to the suction stage while being fixed to the suction stage. A process of cutting to form a metal electrode by patterning the metal film ,
The method of forming a metal electrode of a semiconductor device, wherein the suction stage is formed of a single thin plate-like material that is easily deformed and is fixed by suction to the entire back surface of the semiconductor substrate . In the metal electrode formation method of Claim 1,
The method of forming a metal electrode of a semiconductor device, wherein the suction stage is a thin plate-shaped stainless steel. In the metal electrode formation method of the semiconductor device of Claim 1 or Claim 2,
  A method of forming a metal electrode of a semiconductor device, wherein in the step of forming the metal electrode, the metal electrode is formed by patterning so as to leave only a portion of the metal film formed inside the opening. In the metal electrode formation method of the semiconductor device of any one of Claims 1-3,
The method for forming a metal electrode of a semiconductor device, wherein the deforming means is provided in contact with the back surface of the suction stage, and the semiconductor substrate is displaced through the suction stage. In the metal electrode formation method of the semiconductor device of any one of Claims 1-4,
The method for forming a metal electrode of a semiconductor device, wherein the deformation means includes a plurality of actuators each capable of controlling displacement. The metal electrode forming method for a semiconductor device according to claim 5,
The method for forming a metal electrode of a semiconductor device, wherein the actuator is a piezoelectric actuator using a piezoelectric element. In the metal electrode formation method of the semiconductor device of Claim 5 or Claim 6,
The method for forming a metal electrode of a semiconductor device, wherein the number of measurement points of the surface shape data by the surface shape measuring means is larger than the number of actuators. In the metal electrode formation method of the semiconductor device of any one of Claims 1-7,
The method for forming a metal electrode of a semiconductor device, wherein the surface shape measuring means measures at least a surface shape of the surface portion corresponding to a point given displacement by the deformation means. In the metal electrode formation method of the semiconductor device of any one of Claims 1-8,
The method for forming a metal electrode of a semiconductor device, wherein the surface shape measuring means is a laser displacement meter scanned along a plane parallel to the cutting surface.

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