JP2015126003A - Method of manufacturing compound semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a compound semiconductor wafer capable of manufacturing the compound semiconductor wafer in which abnormalities are less likely to be generated on a surface of an active layer.SOLUTION: A method of manufacturing a compound semiconductor wafer includes: a step of cutting out a wafer from an ingot formed from a compound semiconductor; a step of performing lapping processing on the wafer; a first polishing step of arranging the wafer subjected to the lapping processing in an opening of a carrier formed of a material containing an epoxy resin, and performing chemical mechanical polishing on both surfaces of the wafer; removing substances adhered onto a surface contacted with the carrier of the wafer at the first polishing step, by etching; and a second polishing step of performing chemical mechanical polishing on one surface or both surfaces of the wafer after the step of removing the adhered substances.

Description

  The present invention relates to a method for manufacturing a compound semiconductor wafer.

  Compound semiconductors include various semiconductors such as Schottky gate field effect transistors (MESFETs), high mobility transistors (HEMTs), and heterojunction bipolar transistors (HBTs). It is used for the production of elements.

  A semiconductor element is formed by forming an active layer on a wafer having a mirror-finished surface by molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), or ion implantation. Produced.

  Wafers used for semiconductor elements are obtained by lapping and polishing a wafer cut out from an ingot formed of a compound semiconductor by a method such as chemical mechanical polishing (CMP), and polishing the surface of the wafer. It is produced by making it into a mirror surface.

  For example, in order to reduce the warpage of the substrate, a lapping process is performed in which a lapping process is performed on the wafer using a double-side polishing machine so that the lapping amount on the back surface of the wafer formed from the compound semiconductor is larger than the lapping amount on the front surface. A method of manufacturing a compound semiconductor wafer has been proposed (see, for example, Patent Document 1).

  In addition, a carrier for a double-side polishing machine using a glass fiber reinforced epoxy resin has been proposed in order to efficiently polish both sides of the wafer in the lapping step without causing metal contamination on the wafer (for example, Patent Document 2). reference).

JP 2009-182135 A JP 2006-303136 A

  However, since the peripheral surface of the wafer is rubbed with the carrier during the lapping process, the deposit of the epoxy resin which is a component of the carrier may adhere.

  The deposits adhering to the peripheral surface of the wafer cannot be removed by wet cleaning with alcohol or ultrapure water and remain on the wafer as they are. The remaining epoxy resin in the deposit may wrap around the growth surface of the wafer when the active layer is grown on the wafer, causing an abnormality on the surface of the active layer and causing a decrease in yield.

  Accordingly, an object of the present invention is to provide a method of manufacturing a compound semiconductor wafer that can manufacture a compound semiconductor wafer that is less likely to cause an abnormality on the surface of an active layer.

In order to achieve the above object, the present invention provides the following [1] to [5].
[1] A step of cutting a wafer from an ingot formed from a compound semiconductor;
A step of lapping the wafer;
A first polishing step in which the wafer subjected to the lapping treatment is disposed in an opening of a carrier formed of a material containing an epoxy resin, and chemical mechanical polishing is performed on both surfaces of the wafer;
Removing the deposits attached to the surface of the wafer in contact with the carrier in the first polishing step by etching;
A second polishing step of performing chemical mechanical polishing on one or both surfaces of the wafer after the step of removing the deposits;
A method for producing a compound semiconductor wafer comprising:
[2] The step of removing the deposit is performed by etching the wafer while rotating the wafer in the circumferential direction in an etching tank.
The manufacturing method of the compound semiconductor wafer as described in said [1].
[3] The step of removing the deposit uses an etchant in which ammonia water, hydrogen peroxide water and water are mixed.
The method for producing a compound semiconductor wafer according to [1] or [2].
[4] The step of removing the deposit uses an etchant in which sulfuric acid, hydrogen peroxide solution, and water are mixed.
The manufacturing method of the compound semiconductor wafer as described in said [1] or [2].
[5] The compound semiconductor is GaAs.
The method for producing a compound semiconductor wafer according to any one of [1] to [4].

  According to the present invention, it is possible to manufacture a compound semiconductor wafer that is less likely to cause an abnormality on the surface of the active layer.

FIG. 1 is a flowchart for explaining a method of manufacturing a compound semiconductor wafer according to an embodiment of the present invention. FIG. 2 is a perspective view showing a main part of a double-side polishing machine used in the first polishing process. FIG. 3 is a plan view showing the carrier used in the first polishing step. FIG. 4 is a photograph showing the peripheral surface of the wafer after the first polishing process and before the etching process. FIG. 5 is a schematic diagram showing the relationship between the wafer and the carrier when the wafer is double-side polished. FIG. 6 is a photograph showing the peripheral surface of the wafer according to Example 1 after etching. FIG. 7 is an observation image showing the shape of the wafer according to Example 1 after etching. FIG. 8 is a photograph showing the peripheral surface of the wafer according to Example 2 after etching. FIG. 9 is a photograph showing the peripheral surface of the wafer according to Example 3 after etching. FIG. 10 is a photograph showing the peripheral surface of the wafer according to Example 4 after etching. FIG. 11 is an observation image showing the shape of the wafer according to Comparative Example 1 after etching.

[Summary of embodiment]
The method of manufacturing a compound semiconductor wafer according to the present embodiment includes a step of cutting a wafer from an ingot formed of a compound semiconductor, a step of lapping the wafer, and the wafer subjected to the lapping process using an epoxy resin. A first polishing step in which chemical mechanical polishing is performed on both surfaces of the wafer in a state where the wafer is disposed in an opening of a carrier formed of a material containing the material, and the wafer on which both surfaces have been polished in the first polishing step is etched. Then, a step of removing deposits adhering to the surface of the wafer in contact with the carrier in the first polishing step, and a second chemical mechanical polishing on one or both sides of the wafer etched in the etching step. Polishing step.

[Embodiment]
FIG. 1 is a flowchart for explaining a method of manufacturing a compound semiconductor wafer according to an embodiment of the present invention. Hereinafter, an example of a method of manufacturing a compound semiconductor wafer according to the present embodiment will be described in the order of steps with reference to FIG.

  First, in the step (S1) for producing an ingot shown in FIG. 1, an ingot formed from a GaAs single crystal which is an example of a compound semiconductor is produced by a pulling method, a boat method or the like.

  Next, in the step of cutting out the wafer (S2), the ingot formed from the GaAs single crystal is sliced (cut) into a plate shape, and the wafer is cut out from the ingot. The ingot is sliced using an inner peripheral cutting machine, a multi-wire saw or the like.

  Next, in a step (S3) of performing a lapping process, a lapping process for removing saw marks on the surface of the wafer is performed on both surfaces of the cut wafer using alumina abrasive grains having a particle size of # 800 to # 3000. This lapping process removes saw marks generated on the front surface of the wafer when the ingot is sliced to make the thickness of the wafer uniform, and increases the parallelism between the front surface and the back surface. In the lapping process, alumina abrasive grains having a particle size other than # 800 to # 3000, silicon carbide abrasive grains, or the like may be used.

  Next, in the first polishing step (S4), both surfaces of the wafer are polished. FIG. 2 is a perspective view showing a main part of a double-side polishing machine used in the first polishing process. FIG. 3 is a plan view showing the carrier used in the first polishing step. FIG. 4 is an enlarged photograph of the peripheral surface of the wafer after the first polishing process and before the etching process. FIG. 5 is a schematic diagram showing the relationship between the wafer and the carrier when the wafer is double-side polished.

This step is performed by mechanochemical polishing using a mixture of a hypochlorous acid aqueous solution and SiO ₂ as the polishing liquid and a cloth having a porous layer on the surface as the polishing cloth. Mechanochemical polishing is an example of chemical mechanical polishing.

  In this step, the polishing liquid and the polishing cloth are applied to the double-side polishing machine 1 to polish the wafer. This double-side polishing machine 1 has a carrier 10 in which a plurality of openings 11 in which wafers 20 are respectively arranged are formed. Reference numerals 40, 50, and 60 denote an internal gear, a sun gear, and a rotating shaft, respectively.

  The carrier 10 may be made of a material containing an epoxy resin, such as an epoxy resin reinforced with glass fiber, aramid fiber, or tetron fiber. By rotating and revolving the carrier 10 in the circumferential direction of the wafer 20 with the wafer 20 sandwiched between the polishing cloths by the double-side polishing machine 1, the wafer 20 rotates with the rotation of the carrier 10 and both surfaces of the wafer 20 are polished. Is done. The polished wafer has a mirror surface with a center line average roughness (Ra) in the range of 2 to 3 nm on both sides. Reference numerals 12 and 13 are a hole and an outer gear, respectively.

  When the wafer 20 is polished on both sides in the first polishing step, as shown in FIG. 4, the deposit 100 formed mainly from the epoxy resin adheres to a portion where the peripheral surface 21 and the carrier 10 are in contact with each other. As shown in FIG. 5, when the wafer 20 is polished, the peripheral surface 21 of the wafer 20 and the opening 11 of the carrier 10 rub against each other at the contact portion 30, so that the epoxy resin forming the carrier 10 is worn. It is thought to be due to.

  Next, in the step of etching the wafer (S5), the deposits attached to the peripheral surface of the wafer in the first polishing step are removed by etching.

  This step is performed while rotating the wafer in the circumferential direction in an etching tank storing an etchant. For the etching, for example, a mixed solution of ammonia water or sulfuric acid, hydrogen peroxide water, and ultrapure water is used as an etchant. The water used for the etchant includes pure water and the like.

  Next, in the second polishing step (S6), one side of the wafer is polished using a single-side polishing machine. This step is performed by mechanochemical polishing using a hypochlorous acid aqueous solution as a polishing liquid and a suede type polishing cloth as a polishing cloth. The polished wafer has a mirror surface with a centerline average roughness (Ra) in the range of 0.2 to 0.4 nm. Note that both surfaces of the wafer may be polished in the second polishing step.

  Next, in the step of cleaning the wafer (S7), the wafer is cleaned using an acid or alkali chemical solution and dried to complete a compound semiconductor wafer.

(Effect of embodiment)
According to the present embodiment, the following effects can be obtained.
(1) By etching the wafer after polishing both sides of the wafer, it is possible to remove deposits attached to the peripheral surface of the wafer when both sides are polished. Thereby, when forming an active layer in the completed compound semiconductor wafer, it can reduce that a deposit | attachment inhibits the growth of an active layer.
(2) By etching while rotating the wafer in the circumferential direction in the etching tank, the surface of the wafer can be uniformly etched. Thereby, while adhering matter adhering to the peripheral surface of the wafer can be removed, deformation of the wafer main surface can be suppressed.
(3) Etching using an etchant in which ammonia water or sulfuric acid, hydrogen peroxide water, and ultrapure water are mixed to the wafer after double-side polishing, and scraping the entire wafer to adhere to the peripheral surface of the wafer The attached deposits can be removed.

[Example]
Next, examples of the present invention will be described. 6 and 8 to 10 are photographs showing the peripheral surfaces of the wafers according to Examples 1 to 4 after etching, respectively. 7 and 11 are simulation images showing the shapes of the wafers according to Example 1 and Comparative Example 1 after etching, respectively.

(Production of wafers according to examples and comparative examples)
Table 1 shows the composition of the etchant used in the etching of Examples 1 to 4. The wafers according to Examples 1 to 4 and Comparative Example 1 were produced by the above-described steps S1 to S5. That is, first, a wafer was cut out from an ingot formed of a compound semiconductor, this wafer was lapped, and then both surfaces of the wafer were polished. Next, the wafer was etched for 1 minute using the etchants having the respective compositions shown in Table 1.

(Evaluation of Examples and Comparative Examples)
In Examples 1 to 4, after performing etching using each etchant, the peripheral surface of the wafer according to each Example is observed using a scanning electron microscope (SEM) and attached to the peripheral surface. It was determined whether the kimono remained.

  Moreover, about Example 1 and Comparative Example 1, the shape of the wafer main surface was observed, and the shape of the wafer main surface after etching was evaluated.

Example 1
In Example 1, etching is performed while rotating a wafer in the circumferential direction using an etchant having a mixing ratio of 2: 1: 5 ammonia water, hydrogen peroxide water, and ultrapure water.

  In Example 1, as shown in FIG. 6, since no deposits were observed on the peripheral surface 21 of the wafer 20 after the etching, it was found that the deposits could be removed by etching after the first polishing step. .

  Further, in Example 1, it can be seen that the shape of the wafer shown in FIG. 7 after etching is less deformed than the wafer in Comparative Example 1 shown in FIG.

(Example 2)
In the second embodiment, etching is performed while rotating the wafer in the circumferential direction using an etchant having a mixing ratio of ammonia water, hydrogen peroxide water, and ultrapure water of 1: 1: 5. In Example 2, as shown in FIG. 8, no deposit was observed on the peripheral surface 21 of the wafer 20 after the etching.

(Example 3)
In Example 3, etching is performed while rotating a wafer in the circumferential direction using an etchant having a mixing ratio of sulfuric acid, hydrogen peroxide solution, and ultrapure water of 5: 1: 1. In Example 3, as shown in FIG. 9, no deposit was observed on the peripheral surface 21 of the wafer 20 after the etching.

Example 4
In Example 4, etching was performed while rotating the wafer in the circumferential direction using an etchant having a mixing ratio of sulfuric acid, hydrogen peroxide solution, and ultrapure water of 3: 1: 1. In Example 4, as shown in FIG. 10, no deposit was observed on the peripheral surface 21 of the wafer 20 after the etching.

(Comparative Example 1)
In Comparative Example 1, etching was performed without rotating a wafer using an etchant having a mixing ratio of ammonia water, hydrogen peroxide water, and ultrapure water of 2: 1: 5. In Comparative Example 1, as shown in FIG. 11, it can be seen that the main surface of the wafer 20 is undulated by etching, and the shape of the main surface of the wafer 20 is greatly deformed as compared with the wafer 20 of Example 1 shown in FIG. 7. .

  By observing the wafers according to Examples 1 to 4, by performing etching using an etchant in which ammonia water or sulfuric acid, hydrogen peroxide water, and ultrapure water are mixed with the wafer polished on both sides. It can be seen that the deposits adhered in the first polishing step can be removed.

  Further, it can be seen from the comparison between Example 1 and Comparative Example 1 that the deformation of the main surface of the wafer can be suppressed by etching the wafer while rotating it in the circumferential direction in the etching tank.

[Other embodiments]
The embodiments and examples of the present invention are not limited to the above-described embodiments and examples, and various modifications and implementations are possible without departing from the scope of the present invention. For example, the present invention can be applied to compound semiconductors such as AlGaAs, GaP, InP, GaN, AlN, and InN in addition to GaAs.

  In addition, the above-described method for manufacturing a compound semiconductor wafer may perform process deletion, addition, change, replacement, and the like within a range not changing the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Double-side polisher, 10 ... Carrier, 11 ... Opening part, 12 ... Hole, 13 ... Outer gear, 20 ... Wafer, 21 ... Peripheral surface, 30 ... Contact part, 40 ... Internal gear, 50 ... Sun gear, 60 ... Rotation Shaft, 100 ... deposit

Claims (5)

A step of cutting a wafer from an ingot formed from a compound semiconductor;
A step of lapping the wafer;
A first polishing step in which the wafer subjected to the lapping treatment is disposed in an opening of a carrier formed of a material containing an epoxy resin, and chemical mechanical polishing is performed on both surfaces of the wafer;
Removing the deposits attached to the surface of the wafer in contact with the carrier in the first polishing step by etching;
A second polishing step of performing chemical mechanical polishing on one or both surfaces of the wafer after the step of removing the deposits;
The manufacturing method of the compound semiconductor wafer containing this. The step of removing the deposit is performed by etching the wafer while rotating the wafer in the circumferential direction in an etching tank.
The manufacturing method of the compound semiconductor wafer of Claim 1. The step of removing the deposit uses an etchant in which ammonia water, hydrogen peroxide water and water are mixed.
The manufacturing method of the compound semiconductor wafer of Claim 1 or 2. The step of removing the deposit uses an etchant in which sulfuric acid, hydrogen peroxide solution, and water are mixed.
The manufacturing method of the compound semiconductor wafer of Claim 1 or 2. The compound semiconductor is GaAs.
The manufacturing method of the compound semiconductor wafer of any one of Claim 1 to 4.