JPH02139163A - Working method for wafer - Google Patents

Abstract

PURPOSE:To adequately omit the stage of lapping, etching, etc., and to improve the yield of the resist coating/exposure stages performed in succession after a wafer working stage by shaping the surface of a wafer by grinding in a recessed face or projecting face with good controllability. CONSTITUTION:Two circular surface plates 2, 3 driven by rotating independently each other are arranged in opposition up and down by sliding so that the upper surface plate 4 coincides with the shaft center of the rotary shaft 5 of the lower surface plate 3, the shaft center of the rotary shaft 5 of the lower surface plate 3 is pivotally supported vertically, the shaft center of the rotary shaft 8 of the upper surface plate 2 is pivotally supported by inclining to the shaft center of the rotary shaft 5 of the lower surface plate 3 in the surface including the rotary shafts 5, 8 of the two surface plates 2, 3 and a grindstone 7 is fixed to the upper surface plate 2. Moreover, a wafer 6 is vacuum adsorbed to the lower surface plate 3, two surface plates 2, 3 are rotated in the opposite direction each other, and yet, at least one part of the surface plates is press-fitted to the other part of the surface plate with moving in the vertical direction and the surface of the wafer 6 is shaped by grinding the recessed face or projecting face with good controllability.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method of processing a semiconductor substrate such as a silicon wafer, and in particular, it involves making the back surface of a substrate on which no devices are formed concave and omitting some of the processing steps. For the purpose of The axis of the rotating shaft of the plate is vertically supported, and in a plane including the rotating axis of the two surface plates,
The axis of the rotating shaft of the upper surface plate is tilted and supported with respect to the axis of the rotating shaft of the lower surface plate, and a grindstone is fixed to the upper surface plate, and the lower surface plate The wafer is vacuum-adsorbed, the two surface plates are rotated in opposite directions, and
A method for processing a wafer, in which at least one surface plate is moved vertically and pressed against the other surface plate, and the surface of the wafer is ground and shaped into a concave or convex surface with good controllability;
Alternatively, the axis of the rotating shaft of the upper surface plate is vertically supported,
In a plane including the rotation axes of the two surface plates, the axis of the rotation axis of the lower surface plate is tilted and supported with respect to the axis of the rotation axis of the upper surface plate, and the surface of the wafer is This includes controllability (including a wafer processing method for grinding and shaping into a concave or convex surface).

[Industrial application field]

The present invention relates to a method for processing semiconductor substrates such as silicon wafers.

The development of electronics has been remarkable in recent years, and this development is largely due to technological innovations in semiconductor devices.

In particular, the large scale and high integration of integrated circuits using silicon semiconductors is progressing at an abnormally rapid pace. It has expanded four times over the years.

In line with this trend, various studies are being conducted on how to perform fine patterning in the so-called wafer process, which is a series of steps from silicon wafers to finished devices.

The conventional wafer processing step is the initial step of the entire subsequent wafer process, and is composed of a large number of steps.

Therefore, how efficiently a wafer can be processed into a desired shape is of great importance from the perspective of improving the overall yield of the wafer process.

-i, after the wafer processing step, resist coating and subsequent pattern exposure are performed.

When resist coating and exposure are performed in the atmosphere, at -C, the back side of the wafer on which no devices are formed is vacuum-suctioned to a support stand, and the wafer is vacuum chucked.

Therefore, the back surface of the wafer on which no devices are formed can be more stably supported if it is a concave surface.

Therefore, there is a strong desire to develop an efficient method for processing one side of a wafer into a concave surface with good controllability.

[Conventional technology]

FIG. 4 shows a conventional wafer processing process diagram.

In the figure, silicon wafers are the most common wafer, and for example, in compound semiconductors,
Since there is not much difference in the processing steps, the case of a silicon wafer will be shown as a representative example and explained below.

Slicing 41 is a process in which a cylindrical ingot is sliced into thin rings using a wire saw or an internal blade type cutter to create a wafer prototype.The thickness is approximately 750 μm, and the shape of the wafer is controlled in this process. It is extremely difficult to do so, and it is not currently possible.

Beveling 42 is a process of grinding with a grindstone in order to prevent the peripheral edge of the slicing 41 from being chipped.

Lapping 43 is a process in which one or both sides of the wafer is ground and shaped using a processing machine called a lapping device, so that the wafer of uneven thickness is sliced into rounds by slicing 41 and has dimensions with specified precision. .

Etching 44 is a process of chemically removing processing distortion caused by lapping 43, that is, a processing-affected layer consisting of a fractured layer, using a chemical.

Kenreki 45 is a wafer after etching 44,
Polished by sandwiching the free abrasive grains with a polishing cloth attached to a surface plate.
This is the process of finishing the surface or both surfaces of the wafer on which devices will be formed into a mirror finish.

Cleaning 46 is a process for removing impurities that have adhered to the wafer during the above processing steps, and includes, for example, RCA cleaning (immersion in an ammonia aqueous solution of hydrogen peroxide), pure water cleaning, alcohol replacement, and drying.

In the conventional processing steps described above, not only can no steps be omitted, but once the initial shape of the wafer is determined in the slicing step 41, that shape remains as a history until later.

That is, even if subsequent steps, especially post-lapping step 3 in which the wafer is ground and shaped, can reduce the thickness variation, the initial shape cannot be changed with good controllability.

[Problem to be solved by the invention]

FIG. 5 shows changes in shape due to lapping, with (A) showing the convex shape and FIG. 5(B) showing the concave shape.

That is, in the lapping process, if the wafer 51 has a convex shape as shown in FIG. Since the pressure is applied, the surface 53 directly below the top, ie, the center portion of the wafer, is largely scraped.

Therefore, the shape of the wafer 54 after lapping becomes an upwardly convex arched shape.

On the other hand, in the case where the wafer 55 has a concave shape as shown in Figure (B) in the slicing process, even if it is ground and shaped in the lapping process, the highest pressure is applied to the apex 56 at the end. , the surface 57 directly below the apex, that is, the peripheral portion of the wafer, is largely etched.

Therefore, the shape of the wafer 58 after lapping is an arched shape with an upwardly concave surface.

In other words, in lapping processing, the shape cannot be controlled during the slicing process, so even if grinding and shaping is performed in subsequent processes such as lapping, the shape determined in the slicing process will remain as a history. .

Therefore, there is a problem in that it is not possible to make the back side of the wafer, that is, the side to be vacuum chucked, into a concave surface with good controllability in resist coating, exposure, and the like, which are the next steps after the wafer processing step.

Therefore, it is particularly important to efficiently and controllably make the back side of the wafer, on which no devices are formed, a concave surface.

[Means to solve the problem] FIG. 1 shows a diagram explaining the principle of the present invention.

The problem mentioned above is that in the same figure, the shape of the wafer determined in the slicing process is difficult to reshape in subsequent processes. Circular surface plates 2.3 are shifted and arranged vertically to face each other so that the end 4 of the upper surface plate 2 coincides with the axis of the rotating shaft 5 of the lower surface plate 3. The axis of rotation of the upper surface plate 2 is vertically supported, and the rotation axis 8 of the upper surface plate 2 is supported vertically in the plane including the rotation axis 5.8 of the two surface plates 2.3.
The axial center of the lower surface plate 3 is tilted to the axis of the rotary shaft 5 of the lower surface plate 3, and the grindstone 7 is fixed to the upper surface plate 2.
The wafer 6 is vacuum-adsorbed onto the lower surface plate 3, and the two surface plates 2.3 are rotated in opposite directions to each other, and while at least one surface plate is moved in the vertical direction, the other surface plate is moved. A wafer processing method in which the surface of the wafer 6 is ground and shaped into a concave or convex surface with good controllability by being pressed against a plate, or a method in which the axial center of the rotating shaft 8 of the upper surface plate 2 is vertically supported;
In a plane including the rotation shafts 5.8 of the two surface plates 2.3, the axis of the rotation shaft 5 of the lower surface plate 3 is tilted with respect to the axis of the rotation shaft 8 of the upper surface plate 2. This can be achieved by a wafer processing method in which the surface of the wafer 6 is ground and shaped into a concave or convex surface with good controllability.

[For production]

FIG. 1 shows a diagram explaining the principle of the present invention, and FIG. 2 shows the following:
A correlation diagram between the arrangement of two surface plates and grinding shaping in a surface grinding device is shown.

In FIG. 1, a surface grinding apparatus 1 used in the wafer processing method of the present invention is composed of two circular upper and lower surface plates 2 and 3 that are rotated independently of each other. 1 of a surface grinding device called an autorotating Down Feed system in which the end portion 4 of the surface plate 2 is arranged vertically and oppositely so that it coincides with the axis of the rotating shaft 5 of the surface plate 3 below.
It is a seed.

A wafer 6 to be ground and shaped is attracted to the lower surface plate 3 by a vacuum chuck.

On the other hand, a grindstone 7 is fixed to the upper surface plate 2.

Normal surface grinding is performed by pressing the upper and lower surface plates 2.3 into contact with each other while rotating the delimiting surface plates 2.3 in a state in which the axes of the rotating shafts 8.5 of the upper and lower surface plates 2.3 are parallel to each other.

However, a major feature of the present invention is that the axis of one of the two rotating shafts is tilted with respect to the other axis.

That is, in a plane including the rotational axes 5.8 of the two surface plates 2.3, the axial center of one of them is tilted with respect to the other axial center, and the angle of the inclination is adjusted to perform grinding and shaping. Then, the ground surface of the wafer 6 is made into a convex shape with good controllability,
It can be made into a concave shape.

In the surface grinding apparatus 1, how to arrange and configure the two upper and lower surface plates 2.3 to grind and shape the surface of the wafer into a convex surface or a concave surface as described above will be explained in the following. This can be clearly explained using Figure 2.

That is, in the same figure (A), the rotating shaft 5 of the lower surface plate 3
The axial center of the rotating shaft 8 of the upper surface plate 2 is tilted outward by supporting the axis vertically, or the axial center of the rotating shaft 8 of the upper surface plate 2 is vertically supported, By tilting the axis of the rotating shaft 5 of the lower surface plate 3 inward, the surface of the wafer 6 can be ground and shaped into a convex surface.

On the other hand, in the same figure (B), the axial center of the rotating shaft 5 of the lower surface plate 3 is vertically supported, and the axial center of the rotating shaft 8 of the upper surface plate 2 is tilted inward, or By vertically supporting the axis of the rotating shaft 8 of the surface plate 2 and tilting the axis of the rotating shaft 5 of the lower surface plate 3 outward, the surface of the wafer 6 can be ground and shaped into a concave surface. .

In this way, by adjusting the inclination of the axis of either one of the rotating shafts 5.8 of the two upper and lower surface plates 2.3, it is possible to grind and shape the surface of the wafer 6 to make it convex or concave with good controllability. It becomes possible.

When one surface of the wafer 6 is processed into a convex surface by the processing method of the present invention, lapping may be performed after that, and the back side of the concave surface described above in FIG. 5 may be used as a surface to be vacuum chucked.

On the other hand, when one surface of the wafer 6 is processed into a concave surface, the wafer 6 has the characteristic that it can be used as a surface for vacuum chuck without further lapping.

Furthermore, if the wafer that has been ground and shaped by the processing method of the present invention has no processing distortion, etching can be omitted.

Therefore, if necessary, lapping, etching, etc. in the conventional wafer processing steps can be omitted before proceeding to the next polishing step, making it possible to improve the efficiency of the wafer processing steps.

〔Example〕

Examples of the present invention will be described below with reference to the configuration diagram of the two upper and lower surface plates in Example 1 shown in FIG. This will be explained in detail using the relationship diagram.

Example 1: In the surface grinding apparatus 1 shown in FIG. 3(A), the upper surface plate 2 was a disk of 200++unφ, and a grindstone 7 having the same diameter was fixed thereto.

The whetstone 7 is made by heat-adhering diamond abrasive grains to a thickness of 0.5 mm on a 3III11 ceramic substrate using a synthetic resin binder.

For the wafer 6, a silicon ingot with a diameter of 6 inches was sliced into approximately 800 pm.
It was fixed to the surface plate 3 under 00wnφ by a vacuum chuck.

First, the end portions 4 of the upper surface plate 2 were disposed vertically opposite each other so as to be aligned with the axis of the rotating shaft 5 of the lower surface plate 3.

Next, the rotating shaft 5 of the lower surface plate 3 is vertically supported, and the axis of the rotating shaft 8 of the upper surface plate 2 is aligned inwardly with respect to the axis of the rotating shaft 5 of the lower surface plate 3. Tilt 0 degrees.

In this way, while rotating the two surface plates 2 and 3 in opposite directions at 3,000 revolutions/minute, the upper surface plate 2 was vertically rolled down.

In this way, the surface of the wafer 6 is made concave by 30
Grinding and shaping were performed for seconds.

Figure 3 (B) shows the tilt angle (±θ) and the amount of warpage (±δ).
Indicates the relationship between

According to the same figure (B), the inclination angle (±θ) of the axis of the rotating shaft
The relationship between the amount of warpage (±δ) on the surface of the wafer and the amount of warpage (±δ) is a good linear relationship.

That is, the axial center of the rotating shaft 5 of the lower surface plate 3 is vertically supported, and the axial center of the rotating shaft 8 of the upper surface plate 2 is aligned with respect to the axial center of the rotating shaft 5 of the lower surface plate 3. , the amount of curvature -δ when tilted inward by an angle of inclination -θ has a linear relationship.

In addition, when the axis of the rotating shaft 8 of the upper surface plate 2 is tilted outward by an inclination angle of 10θ with respect to the axis of the rotating shaft 5 of the lower surface plate 3, the warpage quantum δ is also a straight line. Become a relationship.

On the other hand, even if the axis of the rotating shaft 8 of the upper surface plate 2 is supported, and the axis of the rotating shaft 5 of the lower surface plate 3 is tilted inward or outward,
” A relationship similar to that described in 2 is obtained.

Therefore, it can be seen that by changing the inclination angle (±θ), the amount of warpage (±δ) can be changed with good controllability.

In Example 1, the axis of the rotating shaft 8 of the upper surface plate 2 is tilted inward at an angle of -0.03 degrees with respect to the axis of the rotating shaft 5 of the lower surface plate 3, and the wafer 60 surface, amount of warpage -
It was ground and shaped into a concave surface of 20 μm.

After that, a series of wafer processing including lapping, etching, polishing, and cleaning was performed.

As a result, by using the concave surface of the wafer 6 that has been ground and shaped by the surface grinding device 1 as the back side, that is, the side to be vacuum chucked, it can be used as is for the next process such as the resist coating and exposure process that follows the wafer processing. wafer processing was realized.

Example 2: In Example 1 described above, the wafer 6 is ground and shaped using the surface grinding device 1 so that it has a concave surface, and then lapping is omitted and a series of steps such as etching, polishing, and cleaning are performed. Performed wafer processing.

As a result, by using the concave surface obtained by grinding and shaping the surface of the wafer 6 with the surface grinding device 1 as the back side, the wafer can be processed so that it can be used as is for the resist coating/exposure process that follows the wafer A processing even if lapping is omitted. was realized.

Example 3: In Example 1 described above, the wafer 6 was ground and shaped using the surface grinding device 1 so as to have a concave surface, and then the wafer 6 was polished and etched without lapping and etching.
A series of wafer processing including cleaning was performed.

As a result, by using the concave surface of the wafer 6 that has been ground and shaped by the surface grinding device 1 as the back side, it is possible to process a wafer that can be used as is for the resist coating and exposure process that is performed subsequent to wafer processing, even if lapping and etching are omitted. I was able to make it happen.

Example 4: The specifications of the surface grinding device 1 are the same as in the first embodiment.

Also, the axis of the rotation shaft 8 of the upper surface plate 2 is vertically supported, and the axis of the rotation shaft 5 of the lower surface plate 3 is aligned with the axis of the rotation shaft 8 of the upper surface plate 2. The surface of the wafer 6 was ground and shaped into a convex surface with a warp of 52 μm.

After that, a series of wafer processing including lapping, etching, polishing, and cleaning was performed.

As a result, by using the convex surface of the wafer 6 that has been ground and shaped by the surface grinding device 1 as the front side, it was possible to realize wafer processing that can be used as is for the resist coating and exposure process that is performed subsequent to wafer processing.

Example 5: In Example 4 described above, the wafer 6 is ground and shaped using the surface grinding device 1 so that it has a convex surface, and then etching is omitted and a series of steps such as lapping, polishing, and cleaning are performed. Performed wafer processing.

As a result, by using the convex surface of the wafer 6 that has been ground and shaped by the surface grinding device 1 as the front side, it is possible to realize wafer processing that can be used as is for the resist coating and exposure process that follows the wafer processing, even if etching is omitted. Ta.

As described in the above example, for the two upper and lower surface plates of a surface grinding device, the axis of the rotating shaft of either surface plate is supported perpendicularly, and the rotation of the other surface plate with respect to the axis is supported perpendicularly. It can be selected as appropriate whether the axis of the shaft is tilted inward or outward.

Further, various conditions such as the angle and direction of inclination, whether the surface of the wafer is convex or concave, and the amount of warpage depending on the size of the wafer can be appropriately selected with good controllability.

Furthermore, depending on the finished state of the grinding and shaping process performed by the surface grinding device, in other words, depending on the degree of processing distortion caused by the grinding and shaping process, lapping or etching (both lapping and etching) may occur in a series of subsequent wafer processing processes. can also be omitted.

〔Effect of the invention〕

As described above, according to the wafer processing method of the present invention, it is possible to make the surface of the wafer convex or concave, which could not be controlled arbitrarily with conventional processing methods.
Grinding and shaping can be done with good controllability.

Furthermore, in the conventional processing method, a series of wafer processing steps cannot be omitted, starting from slicing, and includes beveling, lapping, etching, polishing, and cleaning. Steps can be omitted as appropriate.

Therefore, the present invention greatly contributes to improving the yield of the resist coating/exposure process that is performed subsequent to the wafer processing process, and to streamlining and increasing the efficiency of the wafer processing process.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a correlation diagram between the arrangement of two surface plates and grinding shaping, Fig. 3 (A) and (B) are explanatory diagrams of one embodiment, and Fig. 4 is FIGS. 5A and 5B are cross-sectional views showing changes in shape during lapping processing. In the figure, 1 is a surface grinding device, 3 is a lower surface plate, 5.8 is a rotating shaft, and 7 is a grindstone. 2 is the upper surface plate, 4 is the edge, 6 is the wafer, Solid counterfeit money [A] 1lf11 to 11 within Y state
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Claims (1)

[Claims] 1) Two circular surface plates (2,
3), the end (4) of the upper surface plate (2) is the lower surface plate (3).
The lower surface plate (3) is vertically supported by vertically supporting the axis of the rotation shaft (5) of the lower surface plate (3), and the two In the plane that includes the rotating shafts (5, 8) of the plates (2, 3), the axis of the rotating shaft (8) of the upper surface plate (2) is aligned with the rotating shaft (5, 8) of the lower surface plate (3). The grinding wheel (7) is fixed to the upper surface plate (2), and the wafer (6) is vacuum-suctioned to the lower surface plate (3). and rotate the two surface plates (2, 3) in opposite directions,
and wafer processing, characterized in that at least one surface plate is moved in the vertical direction while being pressed against the other surface plate, and the surface of the wafer (6) is ground and shaped into a concave or convex surface with good controllability. Method. 2) The axis of the rotation shaft (8) of the upper surface plate (2) is vertically supported, and in a plane including the rotation shafts (5, 8) of the two surface plates (2, 3), The axial center of the rotating shaft (5) of the lower surface plate (3) is tilted and supported with respect to the axial center of the rotating shaft (8) of the upper surface plate (2), and the wafer (6) is 2. The method of processing a wafer according to claim 1, wherein the surface is shaped by grinding into a concave or convex surface with good controllability.