Resin bond grindstone and method of manufacturing a semiconductor chip using the grindstone
The present invention provides a resin bond grindstone and method of manufacturing a semiconductor chip using the grindstone that provide a semiconductor device with high reliability even when a thickness of the semiconductor chip is thinned, and specifically provides followings: [1] A resin bond grindstone which comprises grains coated with at least one magnetic metal selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof, and a resin, where the grains coated with the magnetic metal are dispersed in the resin; and [2] A method of manufacturing a semiconductor chip including a step of grinding a semiconductor wafer using the resin bond grindstone as described in above item [1] and a step of dicing the ground semiconductor wafer.
1. Field of the Invention
The present invention relates to an abrasive resin bond grindstone to obtain a thin semiconductor wafer and a method of manufacturing a semiconductor chip using the grindstone.
2. Related Art
With reduction in size and weight of electronic devices in recent years, a smaller shape and thinner thickness have been required of the semiconductor devices. With such changes in shape of the semiconductor devices, semiconductor chips mounted on the semiconductor devices have also been required to decrease their thickness.
A semiconductor chip is generally obtained from a semiconductor wafer, and it is thus necessary to thin the semiconductor wafer to thin the semiconductor chip. However, when the semiconductor chip is manufactured using an originally thin semiconductor wafer, there is a risk that the semiconductor wafer sustains damage during the fabricating process of the wafer. In order to obtain a thin semiconductor chip while preventing such damage to the semiconductor wafer, it is generally performed forming a basic structure of a semiconductor chip on a semiconductor wafer in advance, and then thinning a thickness of the entire semiconductor wafer.
Actually, many basic structures of semiconductor chips are formed on one surface portion of a semiconductor wafer, and to thin a thickness of the semiconductor wafer, it is required to uniformly grind the other surface portion i.e. backside of the semiconductor wafer where basic structures of semiconductor chips are not formed.
Generally, the backside of the semiconductor wafer is ground using a grindstone in performing the grinding as described above. A representative example as the grindstone to grind a semiconductor wafer is a resin bond grindstone such that grains coated with metal such as nickel or copper are dispersed in a thermosetting resin (JP H08-71927).
A semiconductor wafer is ground using the resin bond grindstone to thin a thickness of the wafer, the ground semiconductor wafer then undergoes dicing, and thin semiconductor chips are thereby obtained. Using the thin semiconductor chips, it is possible to obtain thin semiconductor devices such as FBGA, TSOP and TQFP.
BRIEF SUMMARY OF THE INVENTIONHowever, there has been a problem that as a semiconductor chip is made thinner by the grinding, a thin semiconductor device installed with the semiconductor chip malfunctions easier.
It is an object of the invention to provide a resin bond grindstone and method of manufacturing a semiconductor chip using the grindstone that provide a semiconductor device with high reliability even when a thickness of the semiconductor chip is thinned.
As a result of keen examination to overcome the aforementioned problem, the inventors of the invention found that when metal contained in a resin bond grindstone is at least one selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof, an obtained semiconductor chip causes less malfunctions, and reached the invention.
In other words, the invention provides:
[1] a resin bond grindstone which comprises grains coated with at least one magnetic metal selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof, and a resin, where the grains coated with the magnetic metal are dispersed in the resin.
Further, the invention provides:
[2] a semiconductor wafer grinding apparatus which is an apparatus to grind a semiconductor wafer, and comprises:
a base to which a resin bond grindstone is fixed with an adhesive containing magnetic metal;
means for rotating at least one of the base and a semiconductor wafer; and
means for bringing the resin bond grindstone provided on the base and the semiconductor wafer into contact with each other,
where the resin bond grindstone is the grindstone as described in aforementioned item [1], and the magnetic metal contained in the adhesive is at least one selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof.
Furthermore, the invention provides:
[3] a method of manufacturing a semiconductor wafer with a thickness ranging from 50 to 300 μm, which includes a step of grinding the semiconductor wafer using the semiconductor wafer grinding apparatus as described in aforementioned item [2].
Still furthermore, the invention provides:
[4] a method of manufacturing a semiconductor chip, which includes a step of dicing a semiconductor wafer obtained by the manufacturing method as described in aforementioned item [3].
Moreover, the invention provides:
[5] a semiconductor device provided with a semiconductor chip obtained by the manufacturing method as described in aforementioned item [4].
Further, the invention provides:
[6] an adhesive for a resin bond grindstone where the adhesive contains magnetic metal that is at least one selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof.
According to the invention, it is possible to provide a resin bond grindstone that provides a semiconductor device with high reliability even when a thickness of a semiconductor chip is thinned.
BRIEF DESCRIPTION OF THE DRAWINGSThe above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one example is illustrated by way of example, in which;
A preferred embodiment of the invention will be described below.
Described first is a resin bond grindstone of the invention.
It is necessary to provide the resin bond grindstone of the invention with grains.
Examples of the grains include fine particles of diamond, alumina, boron nitride, silicon carbide, garnet or the like. The fine particles may be comprised of one material, or two or more materials.
The diamond may be a natural diamond or synthesized diamond. A method of obtaining the synthesized diamond is not limited particularly. Examples used as the synthesized diamond are a diamond obtained by high-temperature high-pressure method and diamonds obtained by well-known methods such as CVD.
Further, with respect to the fine particles of alumina, boron nitride, silicon carbide, garnet or the like, the particles obtained by any methods may be used, and are commercially available.
A particle size of the grains for use in the invention is generally in a range of #5 to #4000 mesh. The grains are not limited particularly in shape. For example, the grains may have a regular shape such as a sphere or an irregular shape. Further, in the grains, all the particles do not need to be primary particles, and may be secondary particles, i.e. agglomeration.
Next, the grains for use in the invention need to be coated with magnetic metal.
It is required that all or part of a surface of each of the grains is coated, and it is preferable that all the grains are coated.
The magnetic metal for use in the invention needs to be cobalt, iron, manganese, chromium, vanadium or alloys thereof. It is possible to use one kind or two or more kinds of the magnetic metals.
A semiconductor wafer can be ground using the resin bond grindstone with either of the magnetic metals, and high reliability is produced in a semiconductor device mounted with a thin semiconductor chip obtained from the semiconductor wafer.
As a method of coating the grains with the magnetic metal, for example, there are methods of stirring and suspending the grains and fine particles of the magnetic meal using a liquid binder such as water, organic solvent or the like, and then causing evaporation, thermal decomposition or the like of the liquid binder. Further, the magnetic metal may be coated on a surface of the grain by methods such as electroless plating. It is not required of the grains that all the primary particles are coated with the magnetic metal, and it is only required of the grains that for example, particles including secondary particles are substantially coated with the magnetic metal.
A thickness of a coating layer of the magnetic metal is preferably in a range of 3 to 50 μm, and more preferably in a range of 5 to 20 μm.
The grain coated with the magnetic metal may be further coated with glass.
Examples of the glass include lead glass, crystalline glass and the like.
As the crystalline glass, for example, there is one kind or two or more kinds selected from silicon dioxide, boron oxide, lead oxide, zinc oxide and the like.
As a method of coating grains coated with the magnetic metal further with the glass, for example, there is a method of stirring the grains coated with the magnetic metal, viscosity adding agent, fine powder of the glass and the like with a solvent such as water, methyl cellulose, polyvinyl alcohol or the like to prepare a paste-like composition, separating the composition with a filter having a pore diameter larger than the grain coated with the magnetic metal, and calcining the obtained fraction at temperatures between the softening point of the glass powder and the decomposition temperature of the grains, or the like.
The resin bond grindstone of the invention contains the grains 1, magnetic metals 2 and resin 3 as illustrated in a schematic cross-sectional view of
Examples of the resin for use in the invention are a thermosetting resin composition, a thermoplastic resin composition and the like.
As the thermosetting resin composition, for example, there are an epoxy resin composition, bismaleimide resin composition, silicone resin composition and the like.
It is possible to add as appropriate additives such as, for example, an inorganic filler having as a main component silicon dioxide or the like, hardener, accelerator, lubricant and coloring agent to the thermosetting resin composition in ranges of not impairing the object of the invention.
As the thermosetting resin composition, for example, there are super engineering plastic based resin compositions such as polysulfone, polyether sulfone, polyether ether ketone, polyimide, and liquid crystal polymer, and engineering plastic based resin compositions such as nylon, polycarbonate, and poly(butylene terephthalate).
It is possible to add as appropriate additives such as, for example, an inorganic filler having as a main component silicon dioxide or the like, lubricant, coloring agent and antioxidant to the thermoplastic resin composition in ranges of not impairing the object of the invention.
One kind or two or more kinds of resins can be used as the resin for use in the invention.
A method of manufacturing a resin bond grindstone of the invention will be described below.
As the method of manufacturing the resin bond grindstone, for example, when the resin is a thermosetting resin, a composition containing the thermosetting resin, grains coated with the magnetic metal, and when necessary, additives such as a hardener and accelerator is uniformly mixed with a mixing machine such as a kneader or roller, the composition is then molded in a desired form by process of casting, pressing, transfer molding or the like, and the resin bond grindstone of the invention is thereby obtained.
Further, for example, when the resin is a thermoplastic resin, a composition containing the thermoplastic resin, grains coated with the magnetic metal, and when necessary, additives such as an antioxidant is preliminarily mixed with a mixing machine such as a tumbler, and extruded in the form of a strand with a heat extruder, and the obtained strand is cut with a cutting machine or the like to prepare pellets for molding.
In addition, in manufacturing the pellets for molding, the pellets may be manufactured by a method of melting the thermoplastic resin, and adding grains coated with the magnetic metal and the like as appropriate to the melting thermoplastic resin.
For example, by heat-melting forming thus obtained molding pellets with an extruder or the like, the molding pellets can be formed in a desired shape, and it is possible to obtain the resin bond grindstone of the invention.
Described next is a semiconductor wafer grinding apparatus of the invention.
The semiconductor wafer grinding apparatus of the invention will specifically be described below with reference to
First, the semiconductor wafer grinding apparatus of the invention needs to have the base 5 to which the resin bond grindstone 4 is fixed with an adhesive 7 containing magnetic metal.
As specific examples of the adhesive 7, for example, there are an epoxy based adhesive, acryl based adhesive, silicone based adhesive and the like.
It is necessary for the adhesive 7 to contain magnetic metal. The magnetic metal needs to be cobalt, iron, manganese, chromium, vanadium and alloys thereof. One kind or two or more kinds of the magnetic metals can be used.
The magnetic metal for use in the adhesive 7 is preferably the same as the magnetic metal used in the grindstone.
The magnetic metal for use in the adhesive 7 is generally of fine particles, but not limited particularly in shape, and may be in a regular shape such as a sphere or in an irregular shape.
The adhesive 7 contains the magnetic metal in a range of 5 to 30 weight %, and preferably in a range of 10 to 20 weight %.
Further, the semiconductor wafer grinding apparatus of the invention needs to have means for rotating at least one of the base 5 and the semiconductor wafer.
In addition, in rotating both the base 5 and the semiconductor wafer 8, their rotation directions can be the same directions or opposite directions, but it is preferable that the base 5 and the wafer 8 rotate in opposite directions to each other.
As illustrated in
As such means, for example, there are means for pushing the base toward the direction of the resin bond grindstone, means for pushing the resin bond grindstone toward the direction of the base, means for pushing the resin bond grindstone and the base in opposite directions, and the like.
Described next is a method of manufacturing a semiconductor wafer including a process for grinding the semiconductor wafer with the semiconductor wafer grinding apparatus of the invention.
As illustrated in
The diameter of the base 5 generally ranges from 100 to 500 mm, and preferably from 200 to 400 mm.
The rotation speed of the base 5 is generally in a range of 1,000 to 8,000 rpm (rotations per minute) in grinding the backside of a semiconductor wafer using the semiconductor wafer grinding apparatus.
With the resin bond grindstone 4 and the semiconductor wafer 8 brought into contact with each other, the semiconductor wafer 8 is ground at speed generally ranging from 0.0001 to 0.1 mm/s.
Meanwhile, the semiconductor wafer 8 is installed in a device (not shown in the figure) provided with another rotation means, and is rotated on the perpendicular passed through the center of the semiconductor wafer 8 as the center axis. It is possible to grind the backside of the semiconductor wafer 8 by rotating both the backside of the semiconductor wafer 8 and the resin bond grindstone 4 attached to the semiconductor wafer grinding apparatus while bringing the wafer 8 and the grindstone 4 into contact with each other.
As the semiconductor wafer 8, for example, there are a silicon wafer, gallium arsenide wafer, gallium nitride wafer and the like.
The diameter of the semiconductor wafer generally ranges from 10 to 400 nm, and preferably from 100 to 300 mm.
Grinding may be performed separately in a rough grinding step and in a finish grinding step.
The rough grinding step is generally performed by rotating the base to which is fixed the resin bond grindstone of the invention containing grains coated with the magnetic metal with a particle size ranging from #300 to #500 mesh in a range of 2000 to 4000 rpm, preferably in a range of 2500 to 3500 rpm, while rotating the semiconductor wafer in a range of 100 to 500 rpm, preferably in a range of 200 to 300 rpm, and pushing the base to the direction of the semiconductor wafer at speed ranging from 1 to 10 μm/sec., preferably from 3 to 8 μm/sec.
Further, the finish grinding step is generally performed by rotating the base to which is fixed the resin bond grindstone of the invention containing grains coated with the magnetic metal with a particle size ranging from #3000 to #4000 mesh in a range of 2000 to 4000 rpm, preferably in a range of 2500 to 3500 rpm, while rotating the semiconductor wafer in a range of 100 to 500 rpm, preferably in a range of 200 to 300 rpm, and pushing the base to the direction of the semiconductor wafer at speed ranging from 0.1 to 1 μm/sec., preferably from 0.3 to 0.8 μm/sec.
In grinding the semiconductor wafer, the grinding can be performed while pouring pure water on the semiconductor wafer to remove ground wastes.
The pure water is not limited particularly, as long as the pure water is to be generally used in manufacturing the semiconductor wafer.
The flow rate of the pure water is generally in a range of 10 to 40 l/min, and preferably in a range of 20 to 30 l/min.
After finishing the grinding, by blowing a gas such as dry air without foreign substances to the semiconductor wafer, water remaining on the semiconductor wafer is removed.
The thickness of thus obtained semiconductor wafer ranges from 50 to 300 μm, preferably from 60 to 150 μm, and more preferably from 70 to 120 μm.
The semiconductor wafer with a thickness ranging from 50 to 300 μm provides a semiconductor device with high reliability.
A method of manufacturing a semiconductor chip and a semiconductor device with the semiconductor chip will be described below taking FBGA as an example as one embodiment, according to a flowchart exemplified in
The backside of the semiconductor wafer is processed in the rough grinding step, and the rough ground backside of the semiconductor wafer is processed in the finish grinding step.
Subsequently, the semiconductor wafer is diced in a dicing step to obtain a semiconductor chip.
The semiconductor chip is bonded on a board of FBGA, wiring with gold wire or the like is provided between the semiconductor chip and the board in a wire bonding step, and a sealing step is carried out by sealing the semiconductor chip mounted on the FBGA board with a semiconductor sealant resin, and performing post cure at a temperature in a range of 70 to 190° C. for 1 to 10 hours, preferably for 2 to 6 hours.
The semiconductor sealant resin is not limited particularly, and commercially available resins can be used. Used generally are, for example, an epoxy resin composition having as main components an epoxy resin, phenol based hardener, accelerator, filler such as silica and the like, and so on.
Next, solder ball is applied to an FBGA package in a reflow step, and the FBGA package is thus obtained.
By grinding a semiconductor wafer using the resin bond grindstone of the invention, it is possible to obtain various semiconductor devices such as TSOP and TGFP, through similar steps to the flowchart as shown in
At least one selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof contained in the resin bond grindstone of the invention is rubbed inside the semiconductor wafer from the backside of the semiconductor wafer in the grinding step. However, even in this case, when the thickness of the semiconductor wafer is in a range of 50 to 300 μm, preferably in a range of 60 to 150 μm, and more preferably in a range of 70 to 120 μm, on conditions for manufacturing a semiconductor device using a semiconductor chip obtained from the semiconductor wafer, cobalt and the like may be diffused and/or dissolved inside the semiconductor wafer, but does not reach a basic structural portion of the semiconductor chip formed on the surface of the semiconductor wafer.
Therefore, the semiconductor device obtained by using the semiconductor chip exhibits high reliability.
The embodiment of the invention will be described below more specifically using Examples, but the invention is not limited to contents of the following Examples.
EXAMPLE 1The resin bond grindstone is first described. Diamond grains with a particle size of #3000 mesh were coated on their outer circumstance with an alloy comprised of cobalt and iron by electroless plating to have a thickness of about 10 μm, and herein, are referred to as alloy coated abrasive grains A.
The alloy coated abrasive grains A, lead glass powder, methylcellulose, and a proper amount of pure water were added to obtain a paste-like composition. Then, the composition was filtered with a #3000 mesh filter, granular grains passed through the filter were sintered on conditions of 500° C. for 30 minutes, and alloy coated abrasive grains with glass coating were obtained.
A thermosetting resin composition obtained by adding the alloy coated abrasive grains with glass coating and a thermosetting resin in proper amounts was filled in a die with a desired shape. The thermosetting resin composition was press molded on conditions with the heating temperature of 250° C. and the pressure of 1,000 kg/cm2, and a resin bond grindstone was obtained. The resin bond grindstone is hereinafter referred to as resin bond grindstone A.
EXAMPLE 2 Referring to
Using the thermosetting resin composition as an adhesive, as shown in
After bonding, the adhesive was cured on conditions of 200° C. for 30 minutes while pressing a portion of the bonding, and the semiconductor wafer grinding apparatus was thereby obtained. The semiconductor wafer grinding apparatus is hereinafter referred to as semiconductor wafer grinding apparatus A.
EXAMPLE 3 Referring to
Grinding was carried out by first roughly grinding the backside of the silicon wafer 8 with semiconductor chip portions for DRAM formed on the main surface portion in the semiconductor wafer grinding apparatus installed with the resin bond grindstone containing the alloy coated abrasive grains with glass coating with a particle size of #400 mesh, and further grinding in a silicon wafer grinding apparatus provided with the resin bond grindstone containing the alloy coated abrasive grains with glass coating with a particle size of #2000 mesh.
The thickness of the obtained silicon wafer was 100 μM.
A semiconductor chip was obtained by dicing the aforementioned silicon wafer. The semiconductor chip is hereinafter referred to as semiconductor chip A.
EXAMPLE 4Described below is a semiconductor device provided with the semiconductor chip A obtained in Example 3.
The semiconductor chip obtained in Example 3 was adhered to an FBGA board. The semiconductor chip and the board were bonded by wire bonding with gold wire, and then, transfer molded with a semiconductor sealant resin composition to perform post cure on conditions of 180° C. for 5 hours.
After the post cure, a solder ball applying step was carried out by performing reflow on condition of 250° C. to obtain a semiconductor device of DRAM having an FBGA package form.
The semiconductor device is hereinafter referred to as semiconductor device A.
A test to examine an occurrence rate of defective was carried out by keeping a given number of obtained semiconductor devices A on conditions with high temperature and high moisture for a given time, and counting a device such that data retention time fell below 64 msec. as a defective. With this occurrence rate set at 1, Table 1 shows relative results to following comparisons 1 and 2.
[Comparison 1]
A semiconductor wafer grinding apparatus was obtained in the same operation as in Example 2 except use of a commercially available adhesive containing copper and nickel as a substitute for the adhesive used in Example 2. The semiconductor wafer grinding apparatus is hereinafter referred to as semiconductor wafer grinding apparatus B.
Next, using the semiconductor wafer grinding apparatus B, a semiconductor device B of DRAM having an FBGA package form was obtained in the same operation as in Examples 3 and 4.
The same test as the test described in Example 4 was carried out using the semiconductor device B. Table 1 shows the relative results with the occurrence rate of defective in Example 4 set at 1.
[Comparison 2]
A semiconductor wafer grinding apparatus was obtained in the same operation as in Examples 1 and 2 except use of copper and nickel as a substitute for the alloy used in Example 1 and use of a commercially available adhesive containing copper and nickel as a substitute for the adhesive used in Example 2. The semiconductor wafer grinding apparatus is hereinafter referred to as semiconductor wafer grinding apparatus C.
Next, using the semiconductor wafer grinding apparatus C, a semiconductor device C of DRAM having an FBGA package form was obtained in the same operation as in Examples 3 and 4.
The same test as the test described in Example 4 was carried out using the semiconductor device C. Table 1 shows the relative results with the occurrence rate of defective in Example 4 set at 1.
The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.
This application is based on the Japanese Patent application No. 2004-344628 filed on Nov. 29, 2004, entire content of which is expressly incorporated by reference herein.
Claims
1. A resin bond grindstone comprising:
- grains coated with at least one magnetic metal selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof; and
- a resin,
- wherein the grains coated with the magnetic metal are dispersed in the resin.
2. A semiconductor wafer grinding apparatus which is an apparatus to grind a semiconductor wafer, comprising:
- a base to which a resin bond grindstone is fixed with an adhesive containing magnetic metal;
- means for rotating at least one of the base and a semiconductor wafer; and
- means for bringing the resin bond grindstone provided on the base and the semiconductor wafer into contact with each other,
- wherein the resin bond grindstone is the resin bond grindstone according to claim 1, and the magnetic metal contained in the adhesive is at least one selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof.
3. A method of manufacturing a semiconductor wafer with a thickness ranging from 50 to 300 μm, wherein the method includes a step of grinding the semiconductor wafer using the semiconductor wafer grinding apparatus according to claim 2.
4. A method of manufacturing a semiconductor chip, wherein the method includes a step of dicing a semiconductor wafer obtained by the method according to claim 3.
5. A semiconductor device provided with a semiconductor chip obtained by the method according to claim 4.
6. An adhesive for a resin bond grindstone, wherein the adhesive contains magnetic metal that is at least one selected from a group consisting of cobalt, iron, manganese, chromium, vanadium and alloys thereof.
Type: Application
Filed: Nov 29, 2005
Publication Date: Jun 1, 2006
Inventors: Kiyonori Oyu (Tokyo), Kazuyuki Hozawa (Tokyo), Shinichi Sakurada (Akita)
Application Number: 11/288,407
International Classification: B24B 7/30 (20060101); B24B 29/00 (20060101);
