JPH01302727A - Manufacture of compound semiconductor mirror-like substrate - Google Patents

Abstract

PURPOSE:To allow the surface of a substrate to have a high-quality clealiness by polising the substrate with a rinsing fluid containing a dechlorination agent at the time of the last rinsing process in the polishing process. CONSTITUTION:After the polishing process, dripping of an abrasive fluid is stopped. At the same time, the polishing is conducted while supplying a rising fluid for a certain period of time. The rinsing fluid contains a chemical dechlorination agent such as sodium thiosulfate water solution (Na2 S2O3) to eliminate chlorine which is a base of HClO existing in a mirror-like abrasive fluid. By such a simple method, it is possible to make the surface of a GaAs substrate completely free of haze and to reduce the amount of grains attached to the substrate surface to 1/3 or less as compared with in the past.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing mirror-finished substrates such as Ga A3 for semiconductor devices.

(Prior art) For mirror polishing of Ga AS substrates (wafers), #30
A mechanochemical polishing method using a mirror polishing agent containing hypochlorous acid is performed on a lapped wafer that has been pre-polished using a lapping agent of about 0.00.

FIG. 1 is a schematic diagram of an 8% mirror polishing apparatus to which the present invention relates. In this method, a mirror polishing agent 3 (etching liquid) is dripped onto the cloth 1 from a dripping nozzle 4 while rotating a disk 2 on which a polishing cloth 1 is attached. This method performs etching and polishing at the same time.

The abrasives used in mechanochemical boring are mainly hypochlorous acid-based or chlorinated cyanuric acid-based agents, and depending on their composition, they can improve the processing accuracy of mirror-finished wafers, the cleanliness of their surfaces, etc. Since the quality of the polishing agent may be affected, the polishing agent may be prepared by oneself, but commercially available products are generally used (product name: 1N5EC-NIB, G-1
000 etc.).

This research @ mechanism using hypochlorous acid is hypochlorous acid (HCI).
GaAs is chemically etched by O) to form Ga20.・As2o3 is generated, and mirror polishing progresses by repeating a mechanism in which the products (Ga 20.-AS 203) generated on the surface are mechanically removed using a polishing cloth.

If the specified amount of mirror polishing was not completed by this polishing mechanism, the dripping of the polishing liquid was stopped, and at the same time, in order to wash away the polishing liquid remaining on the rotating disk, rinse polishing was performed for several tens of seconds with pure water. After that, stop the rotating disk. If the apparatus is stopped without performing the rinsing step at this time, the cleanliness of the surface of the substrate will be very poor, probably because a small amount of reaction products remain on the surface of the substrate.

Conventionally, the cleanliness of the substrate surface has been inspected visually under fluorescent lighting, but more stringent inspection methods have recently been used. The strict inspection method includes
In a dark room of 10 lux or less, use a condenser rung (3000l
ux or higher) from an oblique direction on the wafer surface.
An oblique light method is used in which a beam focused to 20 nmφ is irradiated and visually inspected.

According to this oblique light method, extremely small surface cloudiness (
The presence or absence of haze, fine particles, dirt, scratches, etc. can be observed. By the way, the cleanliness described below in this specification is limited to only surface cloudiness (haze) and attached fine particles, and the test results will be referred to as cleanliness.

Now, the problem with the conventional technology is that the cleanliness of the substrate surface due to the mirror surface in places is greatly influenced by the rinsing method in the final rinsing and polishing process, and with the conventional rinsing liquid, a small amount of haze remains. It is difficult to obtain a completely haze-free wafer. This shows how difficult it is to completely eliminate haze, as more or less minute haze is observed even in mirror-finished wafers produced by several domestic semiconductor material manufacturers.

y;ca Ga2O3.As 203, which is thought to be produced by the etching reaction between As and hypochlorous acid, is thought to dissolve in sodium hydroxide, so 1 to 5% by weight of NaOH was used in the rinse solution. However, there was almost no haze removal effect.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method that allows the substrate surface to have high quality cleanliness in the production of a mirror substrate of a compound semiconductor such as Ga AS.

[Structure of the Invention] (Means and Effects for Solving the Problems) The method for manufacturing a mirror-finished substrate of the present invention provides a method for manufacturing a mirror-finished substrate when polishing a compound semiconductor substrate using a polishing liquid made of hypochlorous acid. It is characterized in that during the final rinsing step, polishing is performed using a rinsing liquid containing a chlorine removal agent.

Examples of the rinsing liquid containing a chlorine removing agent include a rinsing liquid in which sodium thiosulfate or sodium bisulfite is dissolved in pure water.

First, GaAs is extracted from hypochlorous acid (HCIO) in the polishing liquid.
), as shown in the reaction formula below, Ga2O3・As
20. It is thought that Ga 20. is generated on the GaAs surface. - As 203 is removed with a polishing cloth.

2 Ga As +6 HCI O −) Ga 203+As 20. ±6HC1 And when the mirror finishing is finished, in the rinsing process to stop the oxidation of HCl0, no matter what rinsing method is used, such as instant rinsing with a large amount of pure water, a mirror surface with high quality cleanliness can be achieved. Polished surfaces are not easily obtained. This is due to the fine particles of the product adsorbed on the mirror surface and the slightly attached H.
It was found that this was due to the progress of oxidation of Cl0.

The present invention improves this rinsing liquid, and the improved rinsing liquid removes sodium thiosulfate (N
a2S203) Contains a chemical dechlorinator such as an aqueous solution.

Note that HCl0 production from CI, and Na2S20. The chlorine removal by chlorine removal is thought to be based on the following reaction formula.

Production of HCl0 from CI2: C12±H20: HCI O+HClNa 2S2
Chlorine removal by 03 4 C12+Na 2S203+5820- 2 Na
CI +2 H2So4+6 HCI Due to this action, by using this rinsing liquid at the end of mirror polishing, Ga with high-quality cleanliness that could not be obtained conventionally.
As mirror-finished wafers can be easily obtained.

(Example) Examples will be described in detail below.

Ga AS substrate (a wafer is pasted with wax on an adhesive grate and fixed on a disk equipped with a polishing cloth. Then, a prepared commercially available polishing solution is dropped at a dropping rate of, for example, about 130 cc/nin). At the same time, the disk is rotated and a predetermined amount of polishing is performed.
After polishing by a predetermined amount of approximately 25 to 3 (lAzll), stop dropping the polishing liquid, and at the same time add rinsing liquid to approximately 617m.
Rinse polishing was performed for a certain period of time while supplying about 1 n. The rinsing liquid was made by dissolving Na 2 S 203 in pure water, and its concentration was 4 types: 0.5, 1, and 3.5% by weight.

The cleanliness of the obtained mirror substrate was inspected by the oblique light method. The haze test results are shown in Table 1.Na2S20.
The adhering particulate index is shown in Figure 2, with the case of pure water containing no particles being 100.

Table 1 From the results shown in Table 1, Na 2 S20. It can be seen that the rinsing effect is low when the concentration of +4 is less than 1% by weight, but when the concentration is more than 3% by weight, a remarkable rinsing effect appears and no haze is observed on the mirror surface. Also, from the results in Figure 2, the same (Na, S, 03 concentration is 3% by weight or more,
The index of adhering particles on the surface was 30, which was also confirmed to be significantly reduced. In the Na 25203 solution with a concentration of 3% by weight, which showed a remarkable effect in this example, chlorine removal was performed generally according to the reaction formula described above, but it is thought that a rather complicated reaction actually occurred.

In this example, the correlation between Na2s2o concentration and cleanliness was mainly described, but it goes without saying that it is the absolute amount that contributes to the chlorine removal reaction.

Further, although Na2S2O3 was used as the rinsing liquid shown in the examples, it was found that similar effects could be obtained by using other dechlorinating agents such as sodium hydrogen sulfite (NaH3O3).

[Effects of the Invention] According to the present invention, the rinsing liquid used at the end of the mirror surface juxtaposition process contains a chlorine removal agent such as Na 2 S20x, so the surface of the GaAs substrate can be completely haze-free by a simple method. In addition, the amount of fine particles adhering to the surface of the substrate was reduced to one-third or less compared to the conventional method, making a significant contribution to improving the yield of semiconductor devices.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a mirror polishing apparatus related to the present invention;
The figure is a graph explaining the effect of the method of the present invention. 1... Polishing cloth, 2... Disc, 3...
・Mirror polishing agent, 4...Dripping nozzle, 5...Substrate bonding plate, 6...Substrate (wafer). Patent applicant Toshiba Corporation Agent Patent attorney 1) Eiji

Claims (1)

[Claims] A mirror-finished substrate characterized in that, in polishing a compound semiconductor substrate using a polishing liquid made of primary hypochlorous acid, the polishing process is performed with a rinsing liquid containing a chlorine remover during the final rinsing step of the polishing process. manufacturing method.