In all the drawings for explaining present embodiments, those having the same functions are denoted by the same reference numerals, and repetition of explanations thereof will be omitted as much as possible. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First of all, sand particles which do not cause malfunction of semiconductor chips of the present invention will be described. The sand particles used in the present invention are sand particles not containing copper (Cu) or nickel (Ni), and concentration of copper and nickel contained in the constituent material of the sand particles is desirably not more than 1014 atoms·cm−3. As the above-mentioned particles, for example, fine particles of silicon (Si), silicon oxide, silicon nitride, alumina, silicon carbide, tungsten (W), molybdenum (Mo) and the like are mentioned. The particles may be composed of one or more kinds of them.
The above-described silicon, silicon oxide, or silicon nitride may be a natural product or a synthetic product and preferably contain 1014 atoms·cm−3 or more of boron (B) or phosphorous (P). No particular limitation is imposed on the method to obtain the synthetic product, and the synthetic product obtained at a high temperature and high pressure or by a known method such as the CVD method can be used.
The particles of alumina, silicon carbide, W, Mo and the like obtained by any methods can be used. Also these particles can be obtained as commercial products.
No particular limitation is imposed on the shape of the particles. For example, the particles may have regular shapes such as the spherical shape or may have irregular shapes. Also, not all the particles may be required to be the primary particles and they may be the secondary particle, i.e. agglomerates.
These sand particles are sprayed onto a grinding surface of a semiconductor wafer, so that impurities on the grinding surface can be removed. Consequently, semiconductor devices on which thinned semiconductor chips from the semiconductor wafer are mounted exhibit high reliability.
Next, equipment of removing impurities on a grinding surface of a semiconductor in the present invention will be described.
The equipment of removing impurities on a grinding surface of a semiconductor wafer in the present invention will be described in detail with reference to
First of all, the equipment of removing impurities on a grinding surface of a semiconductor wafer in the present invention has to be able to spray the sand particles of the present invention.
Then, as specific examples of the sand particles, for example, silicon, Silicon oxide, alumina and the like are mentioned.
The concentration of copper or nickel contained in the material of the sand particles has to be 1014 atoms·cm−3 or less. However, no particular limitation is imposed on the particle shape thereof, and the particles may have regular shapes such as the spherical shape or irregular shapes.
The equipment of removing impurities on a grinding surface of a semiconductor wafer of the present invention is required to have a means of rotating or moving at least one of the rotary table 3 and the swing arm 6. When the swing arm 6 is to be simultaneously moved while the rotary table 3 is moved, no particular limitation is imposed on the rotation direction of the rotary table 3 and the moving direction of the swing arm 6.
A process of manufacture of semiconductor including a step of removing an impurities layer 7 of the grinding surface of the thinned semiconductor wafer 1 by the equipment of removing impurities on a grinding surface of a semiconductor wafer will be described.
The diameter of the rotary table 3 of the equipment of removing impurities illustrated in
When the impurity layer 7 on the grinding surface of the thinned semiconductor wafer 1 is removed by using the equipment of removing impurities, a rotation speed of the rotary table 3 is normally in a range of 50 to 8000 rpm (revolutions/minute), preferably in a range of 100 to 3000 rpm. The rotation direction, the acceleration/deceleration in rotation speed and the rotation speed of the rotary table 3 can be varied at any time.
A moving speed of the swing arm 6 is normally in a range of 10 to 5000 mm/min and, preferably, in a range of 100 to 2000 mm/min, and the moving speed thereof from the center to the circumference of the rotary table 3 or from the circumference to the center of the rotary table 3 can be varied at any time.
When the number of rotations of the rotary table 3 is constant, the moving speed of the swing arm 6 is gradually reduced while the swing arm 6 moves from the center of the rotary table 3 toward the circumference. Inversely, the moving speed of the swing arm 6 is gradually increased while it moves from the circumference of the rotary table 3 to the center.
On the other hand, when the moving speed of the swing arm is constant, the number of rotations of the rotary table 3 is gradually increased while the swing arm 6 moves from the center of the rotary table 3 toward the circumference. Inversely, the number of rotations of the rotary table 3 is gradually reduced while the swing arm 6 moves from the circumference of the rotary table 3 toward the center.
Also, both the number of rotations of the rotary table 3 and the moving speed of the swing arm 6 can simultaneously be changed at any time.
The number of rotations of the rotary table 3 and the moving speed of the swing arm 6 are appropriately changed, so that the amount of the sand particles sprayed onto a unit area can be constant everywhere on surface of the rotary table 3.
As it can be understood from the results of
After the impurity removal, in order to remove foreign substances, surplus sand particles or the like remaining on the grinding surface of the thinned semiconductor wafer 1, clean dry air or nitrogen or the like is jetted from the compress air jet nozzle 5. The flow rate of the dry air or nitrogen or the like is normally in a range of 10 to 1000 1/min, and preferably in a range of 100 to 500 1/min. Meanwhile, the dry air or nitrogen jetted from the compress air jet nozzle 5 is jetted in an oblique direction to the thinned semiconductor wafer 1, so that the remaining foreign substances, surplus sand particles or the like remaining on the grinding surface can be efficiently removed.
Further, the removal of impurities by sandblast and removal of the foreign substances and surplus sand particles by the compress air jet nozzle 5 are repeated a plurality of times, so that the damage to the grinding surface of the semiconductor wafer 1 can be suppressed and the metal contamination removal efficiency can be improved.
The thickness of the obtained semiconductor wafer 1 in this manner is in a range of 5 to 200 μm, preferably in a range of 30 to 100 μm, and more ideally, in a range of 50 to 70 μm.
When the thickness of the semiconductor wafer 1 is in the range a 5 to 200 μm, highly reliable semiconductor devices can be produced.
Next, a process of manufacture of a semiconductor chip and a semiconductor device having the semiconductor chip will be described in accordance with the flow chart exemplarily shown in
First of all, in order to thin the semiconductor wafer 1, rough grinding and fine grinding of the back surface of the semiconductor wafer 1 are performed, and further a dry polishing process is performed for removing the damaged layer of the grinding surface. After the dry polishing process of the semiconductor wafer 1, in order to remove an impurity layer adhering to the grinding surface, the impurity layer is removed by sandblast of the present invention.
Subsequently, the semiconductor wafer 1 is cut in dicing step, whereby semiconductor chips are obtained.
The semiconductor chip is attached onto a SiP substrate and wired to the substrate with Au wires or the like by wire bonding. The semiconductor chip mounted on the SiP substrate is sealed by a semiconductor sealing resin, and then is subjected to after-curing at 175° C. for five hours, thereby performing a sealing step.
Next, Solder balls are attached onto a SiP package in a step of reflow, so that the SiP package can be obtained.
As described above, according to the present embodiment, the semiconductor wafer 1 from which the impurities that cause malfunction of the semiconductor chip are removed can be obtained by removing impurities adhering to or remaining on the grinding surface of the semiconductor wafer by using the sand particles of the present invention by the equipment of removing impurities of the present invention.
Under the condition that the semiconductor device is manufactured by using the semiconductor chip obtained from the semiconductor wafer 1, the impurities on the grinding surface that cause malfunction of the semiconductor chip are removed, and therefore, there is no impurity that reach the basic structure part of the semiconductor chip formed on the surface of the semiconductor wafer 1.
Therefore, semiconductor devices obtained by using the semiconductor chip exhibit high reliability.
The embodiment of the present invention will be described in further detail with reference to examples below. However, the present invention is not limited to the contents of the examples below.
First of all, sand particles will be described. Silicon oxide particles (diameter: about 3 to 5 μm) having a copper concentration of 1014 atoms·cm−3 or less and a particle size of #3000 were used as the sand for sandblast.
Next, a process of manufacture of a semiconductor wafer and a semiconductor device chip will be described by using the equipment of removing impurities on a grinding surface of a semiconductor wafer, which is provided with the sand particles obtained from the first example.
A semiconductor wafer having semiconductor elements for FLASH memories formed on the surface thereof was roughly ground to 100 μm by using a diamond whetstone having a particle size of #300 and then was finely ground to 72 μm by using a diamond whetstone having a particle size of #2000. Then, the damage layer of the grinding surface was completely removed after grinding it by 2 μm by dry polishing. The thickness of the obtained semiconductor wafer was 70 μm.
Then, impurities adhering to the grinding surface of the thinned semiconductor wafer were removed by using the equipment of removing impurities on a grinding surface of a semiconductor wafer. Meanwhile thickness of the removed grinding layer was about 50 nm on average.
Semiconductor chips were obtained by dicing the semiconductor wafer.
Next, a semiconductor device having the semiconductor chip obtained in the second example will be described. After attaching the semiconductor chip obtained in the second example to a SiP substrate, the semiconductor chip and the SiP substrate were mutually connected by Au wires by wire bonding. Subsequently, they were subjected to a transfer molding with a semiconductor sealing resin and were subjected to after-curing under the condition at 175° C. and for five hours.
After the after-curing, a step of attaching solder balls was performed by performing reflow at 220° C. and a semiconductor device as a FLASH memory having a SiP package mode was obtained.
The semiconductor device obtained in this manner will be referred to as a semiconductor device A.
A certain number of the obtained semiconductor devices A were used, repeatedly erased and rewritten at a room temperature so that a fluctuation in the threshold voltage of the FLASH memories was measured before and after erasing and rewriting. When the fluctuation in the threshold voltage fluctuated over the allowable value of as a product, it was determined as a defective product, and a test of checking the yield was carried out under this condition. When the yield in this case is considered as 100%, and relative results of first and second comparative examples described as follows are shown in table 1.
Semiconductor devices were obtained by performing entirely the same operations as those of the second example and third example, except that the impurities on the grinding surface of the thinned semiconductor wafer were not removed in the second example. The semiconductor devices obtained in this process will be referred to as semiconductor devices B.
Semiconductor devices were obtained by performing entirely the same operations as the second embodiment and the third embodiment, except that a copper concentration of the sand particles was about 1016 atoms·cm−3 when the impurities on the grinding surface of the thinned semiconductor wafer were removed in the second example. The semiconductor devices obtained in this process will be referred to as the semiconductor devices C.
The invention made by the present inventor has been specifically described hereinabove based on the embodiments. However, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.
For example, although the case of application to a semiconductor device for SiP has been described in the above-described embodiment, no limitation is imposed thereon. For example, the invention can be applied to a semiconductor device for a memory, wherein a semiconductor chip for a memory circuit is mounted on a wiring circuit and a semiconductor chip for the control circuit to control the operation of the memory circuit is stacked on the semiconductor chip for the memory circuit and these semiconductor are sealed with a resin sealing body.
The present invention can be applied to the manufacturing industry of semiconductor devices.
Number | Date | Country | Kind |
---|---|---|---|
JP2006-262057 | Sep 2006 | JP | national |