RU2664882C1 - Device for chemical separation of semiconductor plates to crystals - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to devices for chemical liquid separation of semiconductor wafers onto crystals without the use of mechanical devices and electric power. Device for chemical separation of semiconductor wafers into crystals contains a working container, perforated elements and a removable set of masks, in which the arrangement of the grooves coincides with the arrangement of the regions of separation into crystals, the perforated elements – the base and the lid, the lid is seated on the base, and the diameter of the perforation hole and the distance from the lower plane of the cover to the upper plane of the semiconductor plate or the top plane of the removable masks does not exceed the minimum dimension of the crystal face.

EFFECT: invention provides an increase in the yield of suitable crystals, reduces energy consumption, raises the ergonomics of the device, makes it possible to form crystals of various shapes.

1 cl, 5 dwg

Description

The invention relates to the field of separation of semiconductor wafers into crystals.

In the manufacturing process of devices in microelectronics, semiconductor wafers are used on which repeating regions - crystals - are formed by lithography, deposition and etching of layers. The final operation of the technological route is the separation of the final structure of the semiconductor wafer into crystals. Such a plate has a maximum cost, since all technological operations, with the exception of separation into crystals, are carried out. Therefore, it is extremely important to obtain the maximum yield of suitable crystals from each plate. In cases where the crystal is a MEMS structure, that is, a structure in which a part of the material (for example, a deposited film) is not on the base, the probability of deformation upon separation increases several times.

An invention is known in which a structure for cutting a plate into crystals is described. The design includes a scribing element in the form of a blade that rotates and moves along the cut paths, as well as a container with a special solution that washes the blade [1].

The disadvantages of the invention include vibration that occurs during the cutting process. As a result of mechanical contact of the blade with the surface, critical mechanical stresses arise. For MEMS structures, including thin membranes, the use of this device leads to deformation. In addition, during operation, the wear of the cutting part of the blade reduces the performance and accuracy of scribing.

It is known the invention of cutting plates into crystals, which combines the mechanisms of coarse and precise adjustment of the position of the scribing device [2].

The disadvantages of the invention include mechanical contact with subsequent vibration during the cutting process, which reduces the yield of suitable crystals of MEMS structures.

The invention is known for dividing plates into crystals by using a scribing element [3].

A disadvantage of the invention is the mechanical contact of the scribing element with the regions of the cut paths of the plate. During operation, wear on the cutting edge of the blade reduces productivity and scribing accuracy. For MEMS structures, including thin membranes, the use of this device leads to deformation.

A device for cutting a plate into crystals using an adhesive tape and a laser beam [4].

The disadvantage of the analogue is the high radiation power that is required when cutting through the plate with a laser. This leads to strong heating of the local region of the plate. In some cases, this will result in molten metal. Consequently, metallization will be damaged, which will reduce the quality of the transmitted signal. Also, the metal can diffuse into the adjacent layer, which will lead to a change in the stoichiometric state of the materials, which means degradation of the device.

An analogue is known in which a device for dividing plates into crystals is described, which includes a bursting rod for pressure on a region with a previously formed relief [5].

The disadvantages of the invention include the need for preliminary machining of the substrate, which introduces mechanical stress. It is also difficult to control the position of the rupture rod during operation. Depending on the angle of inclination of the rod in the process of tensile pressure and preliminary mechanical stress, uncontrolled mechanical deformations, for example, cracks, which can propagate outside the region for separation into crystals, can occur. Therefore, a low yield of crystals is expected.

Known electroadhesive device for fixing products, mainly semiconductor wafers in installations for separating them into crystals [6].

The disadvantages of the invention include the use of electricity for the installation, in the process of reciprocating movements of the plate under the action of the voltage supplied to the piezoelectric elements. Another disadvantage of the device is the initial notching of the plate along the dividing strips, which introduces mechanical stresses.

The prototype is a device for the chemical separation of semiconductor wafers into crystals, containing a working capacity made in the form of two coaxial cylinders, the ends of which are connected by a cone with an angle of inclination of the walls of not more than 60 ° relative to the vertical axis, and the bottom of the lower cylinder is made in the form of a removable glass, the capacity is additionally equipped with a rod of cylindrical shape with a plug mounted with the possibility of reciprocating movement along the axis of the cylinders by means of a cyclically rotating shaft and cam mechanism, and a perforated cartridge mounted in the upper cylinder with the possibility of swinging, while the end face of the rod is perforated, and its diameter is equal to the inner diameter of the removable glass [7].

The disadvantages of the device include the complexity of manufacturing this design. Also inconvenience in work, because after separation of the plate, part of the crystals are collected in a narrow zone at the interface between the etchant and the neutral liquid, and then are pushed into the neutral liquid by the rod. Mechanical contact with the rod can lead to deformation of the brittle regions of crystals, in cases where the crystal is a MEMS structure.

In addition, the crystals are mixed in a neutral liquid. This may cause crystal surfaces to come into contact, as a result of which the neutral liquid will not wash away the etchant. Thus, additional material will be removed, that is, grinding will occur in some areas.

Also, the design does not provide a through motion (flow) of a neutral liquid due to the sealed design of the working tank. This reduces the rate of material removal during etching and reduces the uniformity of surface etching.

It should be noted that the structure will be divided into crystals in the case of a formed relief in the plate, that is, due to some jumpers. Otherwise, the plate will be altered entirely.

The objective of the present invention is to increase the yield of suitable crystals, reducing energy consumption, increasing the ergonomics of the device, enabling the formation of crystals of various shapes.

The problem is solved in that they form a device for the chemical separation of plates into crystals, which includes a working capacity, perforated elements, contains a removable set of masks in which the location of the grooves coincides with the location of the areas of separation into crystals, perforated elements - the base and the cover, the lid is fitted on the base, and the diameter of the perforation hole and the distance from the lower plane of the cover to the upper plane of the semiconductor wafer or the upper plane of the removable masks does not exceed mini the minimum size of the crystal face, and the distance from the lower plane of the semiconductor wafer to the upper plane of the base in the absence of a removable set of masks does not exceed the minimum size of the crystal face.

Compared with the prototype, the proposed design for the chemical separation of the plates into crystals is easier to manufacture. Simplicity of design and ergonomics reduce the likelihood of operator error during operation of the proposed device.

In the present invention, the separation of the semiconductor wafer into crystals occurs without mechanical contact between the cutting tool and the shared structure due to the replacement of the cutting tool with a liquid etchant. This provides increased yield of crystals.

It is possible to work both with the whole plate and with its individual parts through the use of a removable set of masks. Each mask contains a set of slots for working with both plates and parts of the plates. By varying the distance between the grooves of the masks, crystals of arbitrary shape are formed. Masks form close contact with the sample, covering a local area that cannot be etched. As a result, after the etching process, the crystals do not move.

The structure is fixed by means of threaded connections: bolt-cap-base and handle-cap-base. The device is transported by two handles. The length of the handles is selected depending on the depth of the bath.

This device allows you to work without the use of electricity, which reduces the cost of the final operation and the development of the semiconductor device as a whole.

The proposed design provides a through flow of the etchant fluid and the neutral medium, due to the perforation areas in the lid and in the base. Due to this, the etching rate is stabilized during the material removal process and the etching uniformity is increased. This allows you to remove the entire etchant and to avoid the removal of unplanned parts of the material.

During etching, a near-surface layer with an increased concentration of undesirable impurities forms at the bottom of the deep bath. The use of legs raises the base above the bottom of the bath, which provides protection against ingress of unwanted impurities, increases the stability of the structure, and also allows you to not disturb the circulation of the solution in the bath.

In FIG. 1 shows a model for a device for separating semiconductor wafers into crystals, where 1 is a perforated cover, 2 is a perforated base, 3 are legs, 4 is a removable set of masks, 5 is a semiconductor plate, 6 is a working capacity, 7 is a bolt, 8 is a handle , d is the diameter of the hole, m is the distance between the walls of the base, s is the largest side of the plate. In FIG. 2 shows a side view of a removable set of masks 4 for fixing the semiconductor wafer 5 in a stationary state during the chemical separation process, where n is the thickness of the removable masks, b is the distance between the grooves of the masks (matches the size of the crystal), and the length of the grooves in the mask (matches with the area of separation into crystals). In FIG. 3 illustrates a General view of the device without a removable set of masks 4 in the assembly process. In FIG. Figure 4 shows a crystal (part of a plate) of thickness Z, the length of the short side X, and the width Y (Y> X> Z). In FIG. 5 shows an image of a semiconductor wafer and the proposed construction for dividing it into crystals.

A device for the chemical separation of wafers into crystals is used as follows. A structure is made from a material that does not interact with the etchant. One of the options for the material of the product may be ftoroplast. The plate 5 is placed on a perforated base 2 with legs 3, fixing with a removable set of masks 4. The perforated cover 1 fixes the plate 5. The cover is connected to the base by threaded connections of bolts 7 and handles 8. The device is lowered into the bath with the etchant. The etchant enters the working tank 6. The fluid interacts with the sample through the cavity in the perforated base 2 and in the perforated cover 1. After dividing the plate into crystals, the device rises from the bath with the etchant. Then the device is placed in a bath with a neutral liquid to remove residual etchant. After that, the device rises from the bath with a neutral liquid. The next step is drying. The plate is spun in a centrifuge in an atmosphere of inert gas, such as nitrogen. With the final step, unscrew the bolts 7 and the handles 8, open the perforated cover 1 and remove the plate 5 (or crystals if the plate is divided into parts) with tweezers.

A specific example of execution. The crystal dimensions are X × Y × Z 4 mm × 8 mm × 0.6 μm. The diameter of the hole is d 4 mm. Thickness of removable masks n 2 mm. The distance between the grooves of the masks is 6 mm, the length of the grooves in the set of masks is 0.5 mm. The distance between the walls of the base m 160 mm. Plate diameter s 150 mm. The thickness of the perforated cover is 10 mm. As a result of liquid etching, the whole plate will become a set of square-shaped crystals with a side of 6 mm.

Thus, as a result of using the proposed design, the yield of suitable crystals is increased, energy consumption is reduced, the ergonomics of the device are increased, and the formation of crystals of various shapes is possible.

Information sources

1. US patent No. 6105567.

2. Taiwan Patent No. 200700336.

3. Chinese Patent No. 106206858.

4. Japanese Patent No. 2012-119468.

5. Chinese Patent No. 106024612.

6. RF patent No. 2047934.

7. RF patent No. 2022406 - prototype.

Claims (2)

1. A device for the chemical separation of semiconductor wafers into crystals, which includes a working capacity, perforated elements, characterized in that it contains a removable set of masks, in which the grooves coincide with the location of the areas of separation into crystals, perforated elements - the base and the cover, the lid is fitted to the base, and the diameter of the perforation hole and the distance from the lower plane of the lid to the upper plane of the semiconductor wafer or the upper plane of the removable masks does not exceed the minimum th the size of the crystal face. 2. A device for the chemical separation of semiconductor wafers into crystals according to claim 1, characterized in that it contains bolts for fastening and handles for transportation and fastening.

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